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Sample records for stability analysis model

  1. Stability Analysis for Car Following Model Based on Control Theory

    NASA Astrophysics Data System (ADS)

    Meng, Xiang-Pei; Li, Zhi-Peng; Ge, Hong-Xia

    2014-05-01

    Stability analysis is one of the key issues in car-following theory. The stability analysis with Lyapunov function for the two velocity difference car-following model (for short, TVDM) is conducted and the control method to suppress traffic congestion is introduced. Numerical simulations are given and results are consistent with the theoretical analysis.

  2. Stability analysis of the ribosome flow model.

    PubMed

    Margaliot, Michael; Tuller, Tamir

    2012-01-01

    Gene translation is a central process in all living organisms. Developing a better understanding of this complex process may have ramifications to almost every biomedical discipline. Recently, Reuveni et al. proposed a new computational model of this process called the ribosome flow model (RFM). In this study, we show that the dynamical behavior of the RFM is relatively simple. There exists a unique equilibrium point e and every trajectory converges to e. Furthermore, convergence is monotone in the sense that the distance to e can never increase. This qualitative behavior is maintained for any feasible set of parameter values, suggesting that the RFM is highly robust. Our analysis is based on a contraction principle and the theory of monotone dynamical systems. These analysis tools may prove useful in studying other properties of the RFM as well as additional intracellular biological processes. PMID:22732691

  3. Linear stability analysis of swirling turbulent flows with turbulence models

    NASA Astrophysics Data System (ADS)

    Gupta, Vikrant; Juniper, Matthew

    2013-11-01

    In this paper, we consider the growth of large scale coherent structures in turbulent flows by performing linear stability analysis around a mean flow. Turbulent flows are characterized by fine-scale stochastic perturbations. The momentum transfer caused by these perturbations affects the development of larger structures. Therefore, in a linear stability analysis, it is important to include the perturbations' influence. One way to do this is to include a turbulence model in the stability analysis. This is done in the literature by using eddy viscosity models (EVMs), which are first order turbulence models. We extend this approach by using second order turbulence models, in this case explicit algebraic Reynolds stress models (EARSMs). EARSMs are more versatile than EVMs, in that they can be applied to a wider range of flows, and could also be more accurate. We verify our EARSM-based analysis by applying it to a channel flow and then comparing the results with those from an EVM-based analysis. We then apply the EARSM-based stability analysis to swirling pipe flows and Taylor-Couette flows, which demonstrates the main benefit of EARSM-based analysis. This project is supported by EPSRC and Rolls-Royce through a Dorothy Hodgkin Research Fellowship.

  4. Surrogate models for efficient stability analysis of brake systems

    NASA Astrophysics Data System (ADS)

    Nechak, Lyes; Gillot, Frédéric; Besset, Sébastien; Sinou, Jean-Jacques

    2015-07-01

    This study assesses capacities of the global sensitivity analysis combined together with the kriging formalism to be useful in the robust stability analysis of brake systems, which is too costly when performed with the classical complex eigenvalues analysis (CEA) based on finite element models (FEMs). By considering a simplified brake system, the global sensitivity analysis is first shown very helpful for understanding the effects of design parameters on the brake system's stability. This is allowed by the so-called Sobol indices which discriminate design parameters with respect to their influence on the stability. Consequently, only uncertainty of influent parameters is taken into account in the following step, namely, the surrogate modelling based on kriging. The latter is then demonstrated to be an interesting alternative to FEMs since it allowed, with a lower cost, an accurate estimation of the system's proportions of instability corresponding to the influent parameters.

  5. Stability Analysis of a Spinning and Precessing Viscoelastic Rotor Model

    NASA Astrophysics Data System (ADS)

    Bose, S.; Nandi, A.; Neogy, S.

    2013-10-01

    The present work deals with stability analysis of a spinning and precessing gyroscopic systems, where the spin axis and precession axis intersect at right angle. The nutation speed is zero, the spin and precession speeds are considered to be uniform and the precession axis is located at one end of the shaft. The properties of the shaft material correspond to a four element type linear viscoelastic model. The shaft disk system is assumed to be axially and torsionally stiff. For analysis, a simple rotor has been considered with the rigid disk placed on a massless viscoelastic shaft at specified locations from one end of the shaft. The governing parametric equations for such a rotor are derived in the simultaneously spinning and precessing frame. A stability analysis is performed considering both two- and four-degree of freedom models. The stability borderlines are computed considering spin and precession speeds as parameters. It is shown that though viscoelastic material may appear attractive for its large material damping, for gyroscopic systems it may lead to unstable vibrations.

  6. Stability and Perturbation Analysis on a Model of Cell Chemotaxis

    NASA Astrophysics Data System (ADS)

    McCann, Colin; Skupsky, Ron; Losert, Wolfgang; Nossal, Ralph

    2006-03-01

    Many eukaryotic cells respond with directional movement to spatial and/or temporal gradients of small molecules that bind to cell surface receptors. The computational model of a chemotaxing cell developed in [1], which models cells such as neutrophils or Dictyostelium discoideum, is investigated with regard to stability and response to perturbations. A formal stability analysis finds that, when placed in an initial linear gradient, the model is most sensitive to perturbations at a 60-90 degree offset from the direction of the initial gradient. The model also responds most quickly and strongly to external point sources placed in that direction. These responses hold for all four of the model variants developed in [1]. This suggests that the observed `zigzag' behavior of real cell movement in a gradient may be influenced by the nature of the biochemical reactions that control a cell's chemotactic response. This research was funded in by the National Institutes of Health (NIH) and the National Institute of Standards and Technology (NIST). [1] Skupsky, R., W. Losert, and R.J. Nossal. 2005. ``Distinguishing modes of eukaryotic gradient sensing''. Biophys. J. 89:2806--2823

  7. A Coupled Aeroelastic Model for Launch Vehicle Stability Analysis

    NASA Technical Reports Server (NTRS)

    Orr, Jeb S.

    2010-01-01

    A technique for incorporating distributed aerodynamic normal forces and aeroelastic coupling effects into a stability analysis model of a launch vehicle is presented. The formulation augments the linear state-space launch vehicle plant dynamics that are compactly derived as a system of coupled linear differential equations representing small angular and translational perturbations of the rigid body, nozzle, and sloshing propellant coupled with normal vibration of a set of orthogonal modes. The interaction of generalized forces due to aeroelastic coupling and thrust can be expressed as a set of augmenting non-diagonal stiffness and damping matrices in modal coordinates with no penalty on system order. While the eigenvalues of the structural response in the presence of thrust and aeroelastic forcing can be predicted at a given flight condition independent of the remaining degrees of freedom, the coupled model provides confidence in closed-loop stability in the presence of rigid-body, slosh, and actuator dynamics. Simulation results are presented that characterize the coupled dynamic response of the Ares I launch vehicle and the impact of aeroelasticity on control system stability margins.

  8. Models and Stability Analysis of Boiling Water Reactors

    SciTech Connect

    John Dorning

    2002-04-15

    We have studied the nuclear-coupled thermal-hydraulic stability of boiling water reactors (BWRs) using a model that includes: space-time modal neutron kinetics based on spatial w-modes; single- and two-phase flow in parallel boiling channels; fuel rod heat conduction dynamics; and a simple model of the recirculation loop. The BR model is represented by a set of time-dependent nonlinear ordinary differential equations, and is studied as a dynamical system using the modern bifurcation theory and nonlinear dynamical systems analysis. We first determine the stability boundary (SB) - or Hopf bifurcation set- in the most relevant parameter plane, the inlet-subcooling-number/external-pressure-drop plane, for a fixed control rod induced external reactivity equal to the 100% rod line value; then we transform the SB to the practical power-flow map used by BWR operating engineers and regulatory agencies. Using this SB, we show that the normal operating point at 100% power is very stable, that stability of points on the 100% rod line decreases as the flow rate is reduced, and that operating points in the low-flow/high-power region are least stable. We also determine the SB that results when the modal kinetics is replaced by simple point reactor kinetics, and we thereby show that the first harmonic mode does not have a significant effect on the SB. However, we later show that it nevertheless has a significant effect on stability because it affects the basin of attraction of stable operating points. Using numerical simulations we show that, in the important low-flow/high-power region, the Hopf bifurcation that occurs as the SB is crossed is subcritical; hence, growing oscillations can result following small finite perturbations of stable steady-states on the 100% rod line at points in the low-flow/high-power region. Numerical simulations are also performed to calculate the decay ratios (DRs) and frequencies of oscillations for various points on the 100% rod line. It is determined that the U.S. NRC requirement of DR is not rigorously satisfied in the low-flow/high-power region; hence, this region should be avoided during normal startup and shutdown operations. The frequency of oscillation is shown to decrease as the flow rate is reduced. Moreover, the simulation frequency of 0.5Hz determined in the low-flow/high-power region is consistent with those observed during actual instability incidents. Additional numerical simulations show that in the low-flow/high-power region, for the same initial conditions, the use of point kinetics leads to damped oscillations, whereas the model that includes the modal neutron kinetics equations results in growing nonlinear oscillations.

  9. Stability analysis of an implicitly defined labor market model

    NASA Astrophysics Data System (ADS)

    Mendes, Diana A.; Mendes, Vivaldo M.

    2008-06-01

    Until very recently, the pervasive existence of models exhibiting well-defined backward dynamics but ill-defined forward dynamics in economics and finance has apparently posed no serious obstacles to the analysis of their dynamics and stability, despite the problems that may arise from possible erroneous conclusions regarding theoretical considerations and policy prescriptions from such models. A large number of papers have dealt with this problem in the past by assuming the existence of symmetry between forward and backward dynamics, even in the case when the map cannot be invertible either forward or backwards. However, this procedure has been seriously questioned over the last few years in a series of papers dealing with implicit difference equations and inverse limit spaces. This paper explores the search and matching labor market model developed by Bhattacharya and Bunzel [J. Bhattacharya, H. Bunzel, Chaotic Planning Solution in the Textbook Model of Equilibrium Labor Market Search and Matching, Mimeo, Iowa State University, 2002; J. Bhattacharya, H. Bunzel, Economics Bulletin 5 (19) (2003) 1-10], with the following objectives in mind: (i) to show that chaotic dynamics may still be present in the model for acceptable parameter values, (ii) to clarify some open questions related with the admissible dynamics in the forward looking setting, by providing a rigorous proof of the existence of cyclic and chaotic dynamics through the application of tools from symbolic dynamics and inverse limit theory.

  10. Stability analysis of the Euler discretization for SIR epidemic model

    SciTech Connect

    Suryanto, Agus

    2014-06-19

    In this paper we consider a discrete SIR epidemic model obtained by the Euler method. For that discrete model, existence of disease free equilibrium and endemic equilibrium is established. Sufficient conditions on the local asymptotical stability of both disease free equilibrium and endemic equilibrium are also derived. It is found that the local asymptotical stability of the existing equilibrium is achieved only for a small time step size h. If h is further increased and passes the critical value, then both equilibriums will lose their stability. Our numerical simulations show that a complex dynamical behavior such as bifurcation or chaos phenomenon will appear for relatively large h. Both analytical and numerical results show that the discrete SIR model has a richer dynamical behavior than its continuous counterpart.

  11. Stability analysis of a holographic dark energy model

    NASA Astrophysics Data System (ADS)

    Banerjee, Narayan; Roy, Nandan

    2015-08-01

    The stability of interacting holographic dark energy model is discussed. It is found that for some class of the rate of interaction between dark matter and dark energy, the system has a natural solution where the universe had been decelerating in the beginning but finally settles down to an accelerated phase of expansion.

  12. Slope Stability Analysis Using Radial Slices: A Mathematical Model

    NASA Astrophysics Data System (ADS)

    Kumar, Gyan Prakash; Das, Adarsha; Rai, Rajesh; Jaiswal, Ashok

    2015-10-01

    In this paper, a mathematical model has been formulated for calculating the factor of safety of a slope. Corresponding computer code has also been developed. Limit equilibrium method (moment equilibrium) has been adopted for calculating the net resulting driving and resisting forces. The probable slip circle region has been divided into radial slices for the simulation process. In this approach, the inter-slice shear forces are zero. Thus, the calculation process becomes simpler as compared to that with vertical slices. The slope stability analyses were done. Validation of the present program was done with existing limit equilibrium based methods. Various models were prepared and analysed with varying geometry and soil strength parameters. These models were also analysed with other limit equilibrium methods like Bishop, Janbu and Spencer method. The results were found to be in agreement with the results of other limit equilibrium methods for the same dump soil properties and slope parameters.

  13. Stability analysis of two-dimensional models of three-dimensional convection

    SciTech Connect

    Greenside, H.S.; Cross, M.C.

    1984-12-01

    Analytical and numerical methods are used to study the linear stability of spatially periodic solutions for various two-dimensional equations which model thermal convection in fluids. This analysis suggests new model equations that will be useful for investigating questions such as wave number selection, pattern formation, and the onset of turbulence in large aspect ratio Rayleigh-Benard systems. In particular, we construct a nonrelaxational model that has stability boundaries similar to those calculated for intermediate Prandtl number fluids.

  14. Stability analysis of a stochastic logistic model with infinite delay

    NASA Astrophysics Data System (ADS)

    Liu, Meng; Fan, Dejun; Wang, Ke

    2013-09-01

    This report is concerned with a stochastic logistic equation with infinite delay. We establish the sufficient conditions for global asymptotical stability of the zero solution and the positive equilibrium. Some classical results are improved and extended. Several numerical simulations are introduced to illustrate the main results.

  15. Floquet stability analysis of the longitudinal dynamics of two hovering model insects

    PubMed Central

    Wu, Jiang Hao; Sun, Mao

    2012-01-01

    Because of the periodically varying aerodynamic and inertial forces of the flapping wings, a hovering or constant-speed flying insect is a cyclically forcing system, and, generally, the flight is not in a fixed-point equilibrium, but in a cyclic-motion equilibrium. Current stability theory of insect flight is based on the averaged model and treats the flight as a fixed-point equilibrium. In the present study, we treated the flight as a cyclic-motion equilibrium and used the Floquet theory to analyse the longitudinal stability of insect flight. Two hovering model insects were considereda dronefly and a hawkmoth. The former had relatively high wingbeat frequency and small wing-mass to body-mass ratio, and hence very small amplitude of body oscillation; while the latter had relatively low wingbeat frequency and large wing-mass to body-mass ratio, and hence relatively large amplitude of body oscillation. For comparison, analysis using the averaged-model theory (fixed-point stability analysis) was also made. Results of both the cyclic-motion stability analysis and the fixed-point stability analysis were tested by numerical simulation using complete equations of motion coupled with the NavierStokes equations. The Floquet theory (cyclic-motion stability analysis) agreed well with the simulation for both the model dronefly and the model hawkmoth; but the averaged-model theory gave good results only for the dronefly. Thus, for an insect with relatively large body oscillation at wingbeat frequency, cyclic-motion stability analysis is required, and for their control analysis, the existing well-developed control theories for systems of fixed-point equilibrium are no longer applicable and new methods that take the cyclic variation of the flight dynamics into account are needed. PMID:22491980

  16. SAS applications for Tai's stability analysis and AMMI model in genotype x environmental interaction (GEI) effects.

    PubMed

    Thillainathan, M; Fernandez, G C

    2001-01-01

    A user-friendly graphical data analysis to perform stability analysis of genotype x environmental interactions, using Tai's stability model and additive main effects and multiplicative interaction (AMMI) biplots, are presented here. This practical approach integrates statistical and graphical analysis tools available in SAS systems and provides user-friendly applications to perform complete stability analyses without writing SAS program statements or using pull-down menu interfaces by running the SAS macros in the background. By using this macro approach, the agronomists and plant breeders can effectively perform stability analysis and spend more time in data exploration, interpretation of graphs, and output, rather than debugging their program errors. The necessary MACRO-CALL files can be downloaded from the author's home page at http://www.ag.unr.edu/gf. The nature and the distinctive features of the graphics produced by these applications are illustrated by using published data. PMID:11535655

  17. [Stability analysis of allelopathic effects of Panax notoginseng on main crops by AMMI model].

    PubMed

    Zhang, Zi-long; Hou, Jun-ling; Wang, Wen-quan

    2015-01-01

    This paper is aimed to study the differences of allelopathic effects of Panax notoginseng under different allelopathic chemicals resources and selection of appropriate rotation crops. The additive main effects and multiplicative interaction ( AMMI) model had been used to evaluate the stability of allelopathic effects of P. notoginseng on the varieties of corn, wheat and rice properly. The model could use not only to evaluate the stability of non-regional trial data but also explore the interaction between the rotation crop genotypes and donor substances more efficiently. Meanwhile, correspondence analysis can be used in the AMMI to evaluate genotype stability and donor substances. Ejingza No. 1 (g6) had stronger allelopathic effects with high stability, but Yunrui No. 1 (g9) which was appropriate rotation crop genotype, had weaker allelopathic effects with high stability. These findings will aid in choosing appropriate rotation crops and establishing proper rotation system. PMID:26080543

  18. Stability analysis of dynamic collaboration model with control signals on two lanes

    NASA Astrophysics Data System (ADS)

    Li, Zhipeng; Zhang, Run; Xu, Shangzhi; Qian, Yeqing; Xu, Juan

    2014-12-01

    In this paper, the influence of control signals on the stability of two-lane traffic flow is mainly studied by applying control theory with lane changing behaviors. We present the two-lane dynamic collaboration model with lateral friction and the expressions of feedback control signals. What is more, utilizing the delayed feedback control theory to the two-lane dynamic collaboration model with control signals, we investigate the stability of traffic flow theoretically and the stability conditions for both lanes are derived with finding that the forward and lateral feedback signals can improve the stability of traffic flow while the backward feedback signals cannot achieve it. Besides, direct simulations are conducted to verify the results of theoretical analysis, which shows that the feedback signals have a significant effect on the running state of two vehicle groups, and the results are same with the theoretical analysis.

  19. Analytical modeling of the input admittance of an electric drive for stability analysis purposes

    NASA Astrophysics Data System (ADS)

    Girinon, S.; Baumann, C.; Piquet, H.; Roux, N.

    2009-07-01

    Embedded electric HVDC distribution network are facing difficult issues on quality and stability concerns. In order to help to resolve those problems, this paper proposes to develop an analytical model of an electric drive. This self-contained model includes an inverter, its regulation loops and the PMSM. After comparing the model with its equivalent (abc) full model, the study focuses on frequency analysis. The association with an input filter helps in expressing stability of the whole assembly by means of Routh-Hurtwitz criterion.

  20. Stability Analysis of a Model of Atherosclerotic Plaque Growth

    PubMed Central

    Reddy, Sushruth; Seshaiyer, Padmanabhan

    2015-01-01

    Atherosclerosis, the formation of life-threatening plaques in blood vessels, is a form of cardiovascular disease. In this paper, we analyze a simplified model of plaque growth to derive physically meaningful results about the growth of plaques. In particular, the main results of this paper are two conditions, which express that the immune response increases as LDL cholesterol levels increase and that diffusion prevails over inflammation in a healthy artery. PMID:25883675

  1. Stability analysis of predator-prey model on the case of aerosol-cloud-precipitation interactions

    NASA Astrophysics Data System (ADS)

    Sulistyowati, Rita; Kurniadi, Rizal; Srigutomo, Wahyu

    2015-09-01

    A preliminary study has been performed on the analysis of the stability of predator-prey models in the case of aerosol-cloud-precipitation interactions which initiated by Koren-Feingold. The model consists of two coupled non-linear differential equations describing the development of a population of cloud drop concentration and cloud depth for precipitation. Stability analysis of the models was conducted to understand the stability behavior of systems interactions. In this paper, the analysis focused on the model without delay. The first step was done by determining the equilibrium point of the model equations which yielded 1 non-trivial equilibrium point and 4 trivial equilibrium point. Nontrivial equilibrium point (0,0) associated with the steady state or the absence of precipitation while the non-trivial equilibrium point shows the oscillation behavior in the formation of precipitation. The next step is linearizing the equation around the equilibrium point and calculating of eigenvalues of Jacobian matrix. Evaluation of the eigen values of characteristic equation determined the type of stability. There are saddle node, star point, unstable node, stable node and center. The results of numerical computations was simulated in the form of phase portrait to support the theoretical calculation. Phase portraits show the characteristic of populations growth of cloud depth and drop cloud. In the next research, this analysis will compared to delay model to determine the effect of time delay on the equilibrium point of the system.

  2. Stability analysis of predator-prey model on the case of aerosol-cloud-precipitation interactions

    NASA Astrophysics Data System (ADS)

    Sulistyowati, Rita; Kurniadi, Rizal; Srigutomo, Wahyu

    2015-09-01

    A preliminary study has been performed on the analysis of the stability of predator-prey models in the case of aerosol-cloud-precipitation interactions which initiated by Koren-Feingold. The model consists of two coupled non- linear differential equations describing the development of a population of cloud drop concentration and cloud depth for precipitation. Stability analysis of the models was conducted to understand the stability behavior of systems interactions. In this paper, the analysis focused on the model without delay. The first step was done by determining the equilibrium point of the model equations which yielded 1 non-trivial equilibrium point and 4 trivial equilibrium point. Nontrivial equilibrium point (0,0) associated with the steady state or the absence of precipitation while the non-trivial equilibrium point shows the oscillation behavior in the formation of precipitation. The next step is linearizing the equation around the equilibrium point and calculating of eigenvalues of Jacobian matrix. Evaluation of the eigen values of characteristic equation determined the type of stability. There are saddle node, star point, unstable node, stable node and center. The results of numerical computations was simulated in the form of phase portrait to support the theoretical calculation. Phase portraits show the characteristic of populations growth of cloud depth and drop cloud. In the next research, this analysis will compared to delay model to determine the effect of time delay on the equilibrium point of the system.

  3. Stability and Bifurcation Analysis of a Three-Species Food Chain Model with Delay

    NASA Astrophysics Data System (ADS)

    Pal, Nikhil; Samanta, Sudip; Biswas, Santanu; Alquran, Marwan; Al-Khaled, Kamel; Chattopadhyay, Joydev

    In the present paper, we study the effect of gestation delay on a tri-trophic food chain model with Holling type-II functional response. The essential mathematical features of the proposed model are analyzed with the help of equilibrium analysis, stability analysis, and bifurcation theory. Considering time-delay as the bifurcation parameter, the Hopf-bifurcation analysis is carried out around the coexisting equilibrium. The direction of Hopf-bifurcation and the stability of the bifurcating periodic solutions are determined by applying the normal form theory and center manifold theorem. We observe that if the magnitude of the delay is increased, the system loses stability and shows limit cycle oscillations through Hopf-bifurcation. The system also shows the chaotic dynamics via period-doubling bifurcation for further enhancement of time-delay. Our analytical findings are illustrated through numerical simulations.

  4. Analysis of stability and density waves of traffic flow model in an ITS environment

    NASA Astrophysics Data System (ADS)

    Li, Z.-P.; Liu, Y.-C.

    2006-10-01

    By introducing relative velocities of arbitrary number of cars ahead into the full velocity difference models (FVDM), we present a forward looking relative velocity model (FLRVM) of cooperative driving control system. To our knowledge, the model is an improvement over the similar extension in the forward looking optimal velocity models (FLOVM), because it is more reasonable and realistic in implement of incorporating intelligent transportation system in traffic. Then the stability criterion is investigated by the linear stability analysis with finding that new consideration theoretically lead to the improvement of the stability of traffic flow, and the validity of our theoretical analysis is confirmed by direct simulations. In addition, nonlinear analysis of the model shows that the three waves: triangular shock wave, soliton wave and kink-antikink wave appear respectively in stable, metastable and unstable regions. These correspond to the solutions of the Burgers equation, Korteweg-de Vries (KdV) equation and modified Korteweg-de Vries (mKdV) equation.

  5. Sensitivity analysis and calibration of a coupled hydrological/slope stability model (TRIGRS)

    NASA Astrophysics Data System (ADS)

    Zieher, Thomas; Rutzinger, Martin; Perzl, Frank; Meil, Gertraud

    2014-05-01

    Shallow landslides potentially endanger human living in mountain regions worldwide. In order to prevent impacts of such gravitational mass movements it is necessary to fully understand the processes involved. Shallow landslides are usually understood as gravitational mass movements of the translational, slope-parallel type comprising of a mixture of earth and debris with a maximum depth of 1-2 m. Depending on the degree of saturation the initial sliding can turn into a flow-like movement. Numerous approaches for modelling shallow landslide susceptibility with different degrees of complexity exist. Regardless of the modelling approach it is crucial to provide sufficient field data, mainly on regolith characteristics. As for the TRIGRS (Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability) model, numerous hydraulic and geotechnical parameters have to be known area-wide. Hence, as spatial interpolation of these input parameters is generally problematic in terms of accuracy, calibrating the model accordingly is a crucial step before conducting any simulations. This study presents a sensitivity analysis and the calibration of the coupled hydrological/slope stability model TRIGRS for a study area in Vorarlberg (Austria). The results of the sensitivity analysis show that in case of the stability model cohesion is the driving parameter while for the hydrological model it is the initial depth of the water table and the saturated hydraulic conductivity. The calibration of the stability model was carried out using a landslide inventory assuming completely saturated conditions. The use of geotechnical parameters extracted from literature for mapped soil types generally lead to unlikely stable conditions. In order to simulate mapped landslide initial areas correctly values for soil cohesion had to be adapted. However, the calibration of the stability model generally supports the assumption of saturated conditions. In absence of meteorological or hydrological data the hydrological model was calibrated using the landslide inventory aiming at saturated conditions for the respective landslide initial zones. Simulations conducted with the calibrated input parameters generally lead to conservatively unstable conditions. However, it has to be noted that the TRIGRS model does not account for effects of vegetation on slope hydrology and stability (e.g. interception or root cohesion). This work has been conducted within C3S-ISLS, which is funded by the Austrian Climate and Energy Fund, 5th ACRP Program. http://www.uibk.ac.at/geographie/lidar/c3s/c3s.html

  6. Analytical model and stability analysis of the leading edge spar of a passively morphing ornithopter wing.

    PubMed

    Wissa, Aimy; Calogero, Joseph; Wereley, Norman; Hubbard, James E; Frecker, Mary

    2015-01-01

    This paper presents the stability analysis of the leading edge spar of a flapping wing unmanned air vehicle with a compliant spine inserted in it. The compliant spine is a mechanism that was designed to be flexible during the upstroke and stiff during the downstroke. Inserting a variable stiffness mechanism into the leading edge spar affects its structural stability. The model for the spar-spine system was formulated in terms of the well-known Mathieu's equation, in which the compliant spine was modeled as a torsional spring with a sinusoidal stiffness function. Experimental data was used to validate the model and results show agreement within 11%. The structural stability of the leading edge spar-spine system was determined analytically and graphically using a phase plane plot and Strutt diagrams. Lastly, a torsional viscous damper was added to the leading edge spar-spine model to investigate the effect of damping on stability. Results show that for the un-damped case, the leading edge spar-spine response was stable and bounded; however, there were areas of instability that appear for a range of spine upstroke and downstroke stiffnesses. Results also show that there exist a damping ratio between 0.2 and 0.5, for which the leading edge spar-spine system was stable for all values of spine upstroke and downstroke stiffnesses. PMID:26502210

  7. Analysis and test evaluation of the dynamic response and stability of three advanced turboprop models

    NASA Technical Reports Server (NTRS)

    Bansal, P. N.; Arseneaux, P. J.; Smith, A. F.; Turnberg, J. E.; Brooks, B. M.

    1985-01-01

    Results of dynamic response and stability wind tunnel tests of three 62.2 cm (24.5 in) diameter models of the Prop-Fan, advanced turboprop, are presented. Measurements of dynamic response were made with the rotors mounted on an isolated nacelle, with varying tilt for nonuniform inflow. One model was also tested using a semi-span wing and fuselage configuration for response to realistic aircraft inflow. Stability tests were performed using tunnel turbulence or a nitrogen jet for excitation. Measurements are compared with predictions made using beam analysis methods for the model with straight blades, and finite element analysis methods for the models with swept blades. Correlations between measured and predicted rotating blade natural frequencies for all the models are very good. The IP dynamic response of the straight blade model is reasonably well predicted. The IP response of the swept blades is underpredicted and the wing induced response of the straight blade is overpredicted. Two models did not flutter, as predicted. One swept blade model encountered an instability at a higher RPM than predicted, showing predictions to be conservative.

  8. Aeromechanical stability analysis of a multirotor vehicle model representing a hybrid heavy lift airship (HHLA)

    NASA Technical Reports Server (NTRS)

    Venkatesan, C.; Friedmann, P. P.

    1984-01-01

    Hybrid Heavy Lift Airship (HHLA) is a proposed candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure to which four rotor systems, taken from existing helicopters are attached. Nonlinear equations of motion capable of modelling the dynamics of this coupled multi-rotor/support frame/vehicle system have been developed. Using these equations of motion the aeroelastic and aeromechanical stability analysis is performed aimed at identifying potential instabilities which could occur for this type of vehicle. The coupling between various blade, supporting structure and rigid body modes is identified. Furthermore, the effects of changes in buoyancy ratio (Buoyant lift/total weight) on the dynamic characteristics of the vehicle are studied. The dynamic effects found are of considerable importance for the design of such vehicles. The analytical model developed is also useful for studying the aeromechanical stability of single rotor and tandem rotor coupled rotor/fuselage systems.

  9. Perturbation and Stability Analysis of the Multi-Anticipative Intelligent Driver Model

    NASA Astrophysics Data System (ADS)

    Chen, Xi-Qun; Xie, Wei-Jun; Shi, Jing; Shi, Qi-Xin

    This paper discusses three kinds of IDM car-following models that consider both the multi-anticipative behaviors and the reaction delays of drivers. Here, the multi-anticipation comes from two ways: (1) the driver is capable of evaluating the dynamics of several preceding vehicles, and (2) the autonomous vehicles can obtain the velocity and distance information of several preceding vehicles via inter-vehicle communications. In this paper, we study the stability of homogeneous traffic flow. The linear stability analysis indicates that the stable region will generally be enlarged by the multi-anticipative behaviors and reduced by the reaction delays. The temporal amplification and the spatial divergence of velocities for local perturbation are also studied, where the results further prove this conclusion. Simulation results also show that the multi-anticipative behaviors near the bottleneck will lead to a quicker backwards propagation of oscillations.

  10. Characterizing Feedback Control Mechanisms in Nonlinear Microbial Models of Soil Organic Matter Decomposition by Stability Analysis

    NASA Astrophysics Data System (ADS)

    Georgiou, K.; Tang, J.; Riley, W. J.; Torn, M. S.

    2014-12-01

    Soil organic matter (SOM) decomposition is regulated by biotic and abiotic processes. Feedback interactions between such processes may act to dampen oscillatory responses to perturbations from equilibrium. Indeed, although biological oscillations have been observed in small-scale laboratory incubations, the overlying behavior at the plot-scale exhibits a relatively stable response to disturbances in input rates and temperature. Recent studies have demonstrated the ability of microbial models to capture nonlinear feedbacks in SOM decomposition that linear Century-type models are unable to reproduce, such as soil priming in response to increased carbon input. However, these microbial models often exhibit strong oscillatory behavior that is deemed unrealistic. The inherently nonlinear dynamics of SOM decomposition have important implications for global climate-carbon and carbon-concentration feedbacks. It is therefore imperative to represent these dynamics in Earth System Models (ESMs) by introducing sub-models that accurately represent microbial and abiotic processes. In the present study we explore, both analytically and numerically, four microbe-enabled model structures of varying levels of complexity. The most complex model combines microbial physiology, a non-linear mineral sorption isotherm, and enzyme dynamics. Based on detailed stability analysis of the nonlinear dynamics, we calculate the system modes as functions of model parameters. This dependence provides insight into the source of state oscillations. We find that feedback mechanisms that emerge from careful representation of enzyme and mineral interactions, with parameter values in a prescribed range, are critical for both maintaining system stability and capturing realistic responses to disturbances. Corroborating and expanding upon the results of recent studies, we explain the emergence of oscillatory responses and discuss the appropriate microbe-enabled model structure for inclusion in ESMs.

  11. Stability analysis of an e-SEIAR model with point-to-group worm propagation

    NASA Astrophysics Data System (ADS)

    Wang, Fangwei; Zhang, Yunkai; Wang, Changguang; Ma, Jianfeng

    2015-03-01

    Internet worms have drawn significant attention due to their enormous threats to the Internet. The main goal of this paper is to explore the interaction dynamics between a malicious worm and an benign worm, using a mathematical model, namely e-SEIAR. The e-SEIAR model takes two important network environment factors into consideration: point-to-group worm propagation mode and benign worms. Furthermore, some related dynamics properties are studied, along with the analysis of how to combat the worm prevalence based on the stability of equilibria. Simulation results show that the performance of our proposed models is effective in combating such worms, in terms of decreasing the number of hosts infected by the malicious worm and reducing the malicious worm propagation speed. Based on our simulations, we believe there is great potential for an effective method to use benign worms to combat malicious worms in some point-to-group applications.

  12. Evaluating network analysis and agent based modeling for investigating the stability of commercial air carrier schedules

    NASA Astrophysics Data System (ADS)

    Conway, Sheila Ruth

    For a number of years, the United States Federal Government has been formulating the Next Generation Air Transportation System plans for National Airspace System improvement. These improvements attempt to address air transportation holistically, but often address individual improvements in one arena such as ground or in-flight equipment. In fact, air transportation system designers have had only limited success using traditional Operations Research and parametric modeling approaches in their analyses of innovative operations. They need a systemic methodology for modeling of safety-critical infrastructure that is comprehensive, objective, and sufficiently concrete, yet simple enough to be deployed with reasonable investment. The methodology must also be amenable to quantitative analysis so issues of system safety and stability can be rigorously addressed. The literature suggests that both agent-based models and network analysis techniques may be useful for complex system development and analysis. The purpose of this research is to evaluate these two techniques as applied to analysis of commercial air carrier schedule (route) stability in daily operations, an important component of air transportation. Airline-like routing strategies are used to educe essential elements of applying the method. Two main models are developed, one investigating the network properties of the route structure, the other an Agent-based approach. The two methods are used to predict system properties at a macro-level. These findings are compared to observed route network performance measured by adherence to a schedule to provide validation of the results. Those interested in complex system modeling are provided some indication as to when either or both of the techniques would be applicable. For aviation policy makers, the results point to a toolset capable of providing insight into the system behavior during the formative phases of development and transformation with relatively low investment. Both Agent-Based Modeling and Network Analysis were found to be useful in this context, particularly when applied with an eye towards the system context, and concentrated effort on capturing the salient features of the system of interest.

  13. Global stability analysis of an SIR epidemic model with demographics and time delay on networks

    NASA Astrophysics Data System (ADS)

    Wang, Jianrong; Wang, Jianping; Liu, Maoxing; Li, Youwen

    2014-09-01

    In this paper, a susceptible-infected-recovery (SIR) epidemic model is governed with demographics and time delay on networks. Firstly, the basic reproduction number R0 is derived dependent on birth rate, death rate, recovery rate and transmission rate. The disease-free equilibrium of the model is stable when R0≤1 and unstable when R0>1. Secondly, based on a Jacobian matrix calculated along with the disease-free equilibrium, we find that the system does not occur Hopf branch under the disease-free equilibrium. Thirdly, the global asymptotic stability of a disease-free equilibrium and a unique endemic equilibrium are proved by structuring two Lyapunov functions. Finally, numerical simulations are performed to illustrate the analysis results.

  14. Stability analysis of carbon nanotube probes for an atomic force microscope via a continuum model

    NASA Astrophysics Data System (ADS)

    Wang, Q.; Varadan, V. K.

    2005-12-01

    A continuum model is employed in the stability analysis of carbon nanotubes (CNT) in the application in atomic force microscope (AFM) probes. Current experimental results have observed instability of CNT in the applications in AFM probes. However, a complete study and understanding of the instability of CNT has not yet been conducted so far. The research in the paper provides a complete mechanics analysis on the global and local buckling of both single-walled nanotubes (SWNT) and double-walled nanotubes (DWNT) via an elastic beam model. A cantilever beam model under a tilted compressive load for possible global buckling or local buckling instability of the CNT probe is employed, since a CNT probe interacts with the surface of a probe at an angle relative to the surface normal. A discrete beam model is employed to propose a mechanism of local buckling instability for beam structures. Based on this model, the development of kink instability of CNT is revealed and studied. A benchmark study on the size effect of the CNT on the critical axial force is carefully made for SWNT and DWNT probes. In addition, the global buckling load of CNT under horizontal axial force can be recovered from the current results on local instability by setting a zero tilted angle, and the predicted results are compared with those from a model considering the van der Waals effect to demonstrate the great feasibility of the proposed local instability model for global buckling analysis use. It is hoped this research may provide a benchmark study on a practical and novel design for effective AFM probes with CNT.

  15. Implementation of Bounding Surface Model into ABAQUS and Its Application to Wellbore Stability Analysis

    NASA Astrophysics Data System (ADS)

    Chen, S.; Al-Muntasheri, G.; Abousleiman, Y. N.

    2014-12-01

    The critical state concept based bounding surface model is one of the most widely used elastoplastic constitutive models for geomaterials, attributed mainly to its essential feature of allowing plastic deformation to occur for stress points within the bounding surface and thus the capability to represent the realistic non-recoverable behaviour of soils and rocks observed under the cyclic loading. This paper develops an implicit integration algorithm for the bounding surface model, using the standard return mapping approach (elastic predictor-plastic corrector), to obtain the updated stresses for the given strain increments. The formulation of the constitutive integration requires the derivation of a supplementary differential equation to describe the evolution of a key variable, i.e., the ratio between the image stress and the current stress quantities. It is essentially an extension of the integration scheme presented in an earlier work used for the simple bounding surface version of modified Cam Clay associated with a substantially simplified hardening rule. The integration algorithm for the bounding surface model is implemented into the finite element analysis commercial program, ABAQUS, through the material interface of UMAT (user defined material subroutine), and then used for the analysis of wellbore stability problem. The predictions from the ABAQUS simulations are generally in excellent agreement with the available analytical solutions, thus demonstrating the accuracy and robustness of the proposed integration scheme.

  16. Stability analysis, nonlinear pulsations and mass loss of models for 55 Cygni (HD 198478)

    NASA Astrophysics Data System (ADS)

    Yadav, Abhay Pratap; Glatzel, Wolfgang

    2016-01-01

    55 Cygni is a variable supergiant. Recent observational studies revealed that this star pulsates in pressure, gravity and strange modes. The pulsations seem to be associated with episodes of mass loss. In this paper we present a theoretical study of stellar models with parameters close to that of 55 Cygni. A linear nonadiabatic stability analysis with respect to radial perturbations is performed and the evolution of instabilities into the nonlinear regime is followed by numerical simulation. Our study indicates that the mass of 55 Cygni lies below 28 M?. As the final consequence of the instabilities the nonlinear simulations revealed finite amplitude pulsations with periods consistent with the observations. The nonlinear results also indicate a connection between pulsations and mass loss and allow for an estimate of the mean mass loss rate. It is consistent with the observed values.

  17. Stability analysis, non-linear pulsations and mass loss of models for 55 Cygni (HD 198478)

    NASA Astrophysics Data System (ADS)

    Yadav, Abhay Pratap; Glatzel, Wolfgang

    2016-04-01

    55 Cygni is a variable supergiant. Recent observational studies revealed that this star pulsates in pressure, gravity and strange modes. The pulsations seem to be associated with episodes of mass loss. In this paper we present a theoretical study of stellar models with parameters close to that of 55 Cygni. A linear non-adiabatic stability analysis with respect to radial perturbations is performed and the evolution of instabilities into the non-linear regime is followed by numerical simulation. Our study indicates that the mass of 55 Cygni lies below 28 M⊙. As the final consequence of the instabilities the non-linear simulations revealed finite amplitude pulsations with periods consistent with the observations. The non-linear results also indicate a connection between pulsations and mass loss and allow for an estimate of the mean mass-loss rate. It is consistent with the observed values.

  18. The Stability Analysis for an Extended Car Following Model Based on Control Theory

    NASA Astrophysics Data System (ADS)

    Ge, Hong-Xia; Meng, Xiang-Pei; Zhu, Ke-Qiang; Cheng, Rong-Jun

    2014-08-01

    A new method is proposed to study the stability of the car-following model considering traffic interruption probability. The stability condition for the extended car-following model is obtained by using the Lyapunov function and the condition for no traffic jam is also given based on the control theory. Numerical simulations are conducted to demonstrate and verify the analytical results. Moreover, numerical simulations show that the traffic interruption probability has an influence on driving behavior and confirm the effectiveness of the method on the stability of traffic flow.

  19. An Investment Model Analysis of Relationship Stability among Women Court-Mandated to Violence Interventions

    ERIC Educational Resources Information Center

    Rhatigan, Deborah L.; Moore, Todd M.; Stuart, Gregory L.

    2005-01-01

    This investigation examined relationship stability among 60 women court-mandated to violence interventions by applying a general model (i.e., Rusbult's 1980 Investment Model) to predict intentions to leave current relationships. As in past research, results showed that Investment Model predictions were supported such that court-mandated women who…

  20. The improvement of OPC accuracy and stability by the model parameters' analysis and optimization

    NASA Astrophysics Data System (ADS)

    Chung, No-Young; Choi, Woon-Hyuk; Lee, Sung-Ho; Kim, Sung-Il; Lee, Sun-Yong

    2007-10-01

    The OPC model is very critical in the sub 45nm device because the Critical Dimension Uniformity (CDU) is so tight to meet the device performance and the process window latitude for the production level. The OPC model is generally composed of an optical model and a resist model. Each of them has physical terms to be calculated without any wafer data and empirical terms to be fitted with real wafer data to make the optical modeling and the resist modeling. Empirical terms are usually related to the OPC accuracy, but are likely to be overestimated with the wafer data and so those terms can deteriorate OPC stability in case of being overestimated by a small cost function. Several physical terms have been used with ideal value in the optical property and even weren't be considered because those parameters didn't give a critical impact on the OPC accuracy, but these parameters become necessary to be applied to the OPC modeling at the low k1 process. Currently, real optic parameter instead of ideal optical parameter like the laser bandwidth, source map, pupil polarization including the phase and intensity difference start to be measured and those real measured value are used for the OPC modeling. These measured values can improve the model accuracy and stability. In the other hand these parameters can make the OPC model to overcorrect the process proximity errors without careful handling. The laser bandwidth, source map, pupil polarization, and focus centering for the optical modeling are analyzed and the sample data weight scheme and resist model terms are investigated, too. The image blurring by actual laser bandwidth in the exposure system is modeled and the modeling result shows that the extraction of the 2D patterns is necessary to get a reasonable result due to the 2D patterns' measurement noise in the SEM. The source map data from the exposure machine shows lots of horizontal and vertical intensity difference and this phenomenon must come from the measurement noise because this huge intensity difference can't be caused by the scanner system with respect to the X-Y intensity difference specification in the scanner. Therefore this source map should be well organized for the OPC modeling and a manipulated source map improves the horizontal and vertical mask bias and even OPC convergence. The focus parameter which is critical for the process window OPC and ORC should be matched to the tilted Bossung plot which is caused by uncorrectable aberration to predict the CD change in the through focus with a new devised method. Pupil polarization data can be applied into the OPC modeling and this parameter is also used for the unpolarized source and the polarized source and specially this parameter helps Apodization loss to be 0 and is evaluated for the effect into the modeling. With the analysis and optimization about the model parameters the robust model is achieved in the sub 45nm device node.

  1. Safe distance car-following model including backward-looking and its stability analysis

    NASA Astrophysics Data System (ADS)

    Yang, Da; Jin, Peter Jing; Pu, Yun; Ran, Bin

    2013-03-01

    The focus of this paper is the car-following behavior including backward-looking, simply called the bi-directional looking car-following behavior. This study is motivated by the potential changes of the physical properties of traffic flow caused by the fast developing intelligent transportation system (ITS), especially the new connected vehicle technology. Existing studies on this topic focused on general motors (GM) models and optimal velocity (OV) models. The safe distance car-following model, Gipps' model, which is more widely used in practice have not drawn too much attention in the bi-directional looking context. This paper explores the property of the bi-directional looking extension of Gipps' safe distance model. The stability condition of the proposed model is derived using the linear stability theory and is verified using numerical simulations. The impacts of the driver and vehicle characteristics appeared in the proposed model on the traffic flow stability are also investigated. It is found that taking into account the backward-looking effect in car-following has three types of effect on traffic flow: stabilizing, destabilizing and producing non-physical phenomenon. This conclusion is more sophisticated than the study results based on the OV bi-directional looking car-following models. Moreover, the drivers who have the smaller reaction time or the larger additional delay and think the other vehicles have larger maximum decelerations can stabilize traffic flow.

  2. Viscous Models of Liquid Bridges with Mode-Coupled Feedback Stress: Stability Analysis

    NASA Astrophysics Data System (ADS)

    Thiessen, David B.; Marston, Philip L.

    2000-11-01

    Linear viscous models with varying degrees of approximation are tested to describe liquid bridge dynamics in order to explore the stability of mode-coupled feedback stress. Stabilization of a liquid bridge against the Rayleigh-Plateau instability in effective zero gravity has been demonstrated by applying stress distributions with appropriate phasing to the liquid surface which couple into the lowest order unstable mode of the bridge [M. J. Marr-Lyon et al., Phys. Fluids 121, 986-995 (2000)]. In the experimental demonstrations to date, feedback stress has been applied in direct proportion to the measured mode amplitude. The effect of feedback delay in this case is destabilizing. This is a critical factor for certain technologies. The addition of mode velocity information to the feedback system should allow for greater stability in the presence of feedback delay. Simple models of liquid bridge dynamics are used to study the effects of parameters such as feedback gain and delay on the bridge stability.

  3. Linear stability analysis of self-excited vibrations in drilling using an infinite dimensional model

    NASA Astrophysics Data System (ADS)

    Aarsnes, Ulf Jakob F.; Aamo, Ole Morten

    2016-01-01

    This paper deals with predicting the occurrence of self-excited vibrations during drilling. Previous work postulates that these are due to the coupling between the distributed drill string system and the regenerative effect in the bit-rock interaction law. We use a previously developed distributed model and the linearized bit-rock interaction law to derive a graphical condition for stability based on the Nyquist stability criterion.

  4. Tailings dams stability analysis using numerical modelling of geotechnical and geophysical data

    NASA Astrophysics Data System (ADS)

    Mihai, S.; Zlagnean, M.; Oancea, I.; Petrescu, A.

    2009-04-01

    Methods for monitoring seepage and detecting internal erosion are essential for the safety evaluation of embankment dams. Internal erosion is one of the major reasons for embankment dam failures, and there are thousands of large tailings dams and waste-rock dumps in the world that may pe considered as hotspots for environmental impact. In this research the geophysical survey works were performed on Cetatuia 2 tailings dam. Electrical resistivity imaging (ERI) method was able to detect spatially anomalous zones inside the embankment dam. These anomalies are the results of internal erosion phenomena which may progressing inside the dam and is difficult to detect by conventional methods. Data aquired by geophysical survey together with their interpretations were used in the numerical model for slope stability assessment. The final results show us the structural weakness induced by the presence of internal erosion elements especially for seismic loading case. This research methodology may be also available for tailings dam monitoring purposes. Electrical Rezistivity Imaging (ERI) was performed on Cetatuia 2 dam at the Uranium Milling Plant Feldioara, in order to map areas with lateral and vertical changes in resistivity. The electrodes are connected to an automated computer operated switch box that selects the 4 electrodes to be used. A computer controls the switch box and the measuring device, and runs a program that selects the electrodes, makes the measurement, and stores the measurement. For inversion processing procedures was used Res2Din software. The measured resistivity were plotted by the pseudo section contouring method. There are five resistivity pseudosections obtained from the Cetatuia 2 tailings dam during the october 2007 measurements. Four transversal profiles trans1 to trans4 are perpendicular to the berms and the longitudinal one long1 is placed along dam's crest. The high resistivities near the berms surfaces corresponds to unsaturated fill materials and the low resistivities near the crest correspond to water saturated material. The resistivities values greater then 80 ohm.m may be explained by some error obtained for that inversion model. Profiles trans3 and trans4 were measured on perpendicular directions to berm alignment and show two distinct zones. The upward low resistivities zone correspond to water saturated materials especially from the compacted clay dam's core and the downward high resistivities zone belongs to unsaturated fill materials. The boundary between high and low resistivity at the depth of about 5 to 7 meters shows the groundwater level. The continuation of the high resistivity zones towards the end of the profile trans3, which is different from other profiles is probably due to the presence of dry coarse materials in shallow depth correspondingly to sandy clay. The sand fractions from the clay matrix may be affected by internal erosional phenomena, due to seepage currents that overpassed the material critical gradient. In this case the relative high resistivities values were considered as a presumptive erosional pattern. This profile was considered for the slope stability finite element modelling. The profile long1 which is placed along dam's crest is the longest profiles and extends up to nearly 420 m. The boundary between high and low resistivity at the depth of about 4 to 8 meters shows the groundwater across the dam core. The central part of the profile (about meter 200) shows the same relative high resistivities that occurred on transversal profile trans3. Resistivity data was used for building the 3D electrical resistivity model. The water saturated materials have locations very close to dam's crest (resistivity values usually lower then 10 ohm.m) and on both dam's arms. The groundwater levels were confirmed by the piezometric measurements. Electrical Rezistivity Imaging method had the possibility to show the most important disturbant elements that in certain conditions may weak the dam's state of safety. This study considered the SSR (Shear Strength Reduction) technique for slope stability numerical modelling. In the SSR finite element technique, elasto-plastic strength is assumed for dam's materials and shear strengths are progressively reduced until collapse occurs. Numerical modelling was performed on the most critical profile choosed through analysis of geophysical and geotechnical informational volume achieved by insitu or in laboratory tests. Finite element analysis were considered in two situations: first, before geophysical investigations and second considering the whole informational of data achieved. Both situations were analysed in static and pseudo-static conditions. The factor of safety before geophysical investigations is high enough to describe a stable state of stability even for the seismic load. The total displacement distributions were modified by the presence of internal erosional element giving a high state of instability, especially for the pseudo-static case. These analysis using the finite element method prove the importance of structural disturbance elements that may occure inside the dam body produced by internal erosional processes.

  5. Linearized blade row compression component model. Stability and frequency response analysis of a J85-3 compressor

    NASA Technical Reports Server (NTRS)

    Tesch, W. A.; Moszee, R. H.; Steenken, W. G.

    1976-01-01

    NASA developed stability and frequency response analysis techniques were applied to a dynamic blade row compression component stability model to provide a more economic approach to surge line and frequency response determination than that provided by time-dependent methods. This blade row model was linearized and the Jacobian matrix was formed. The clean-inlet-flow stability characteristics of the compressors of two J85-13 engines were predicted by applying the alternate Routh-Hurwitz stability criterion to the Jacobian matrix. The predicted surge line agreed with the clean-inlet-flow surge line predicted by the time-dependent method to a high degree except for one engine at 94% corrected speed. No satisfactory explanation of this discrepancy was found. The frequency response of the linearized system was determined by evaluating its Laplace transfer function. The results of the linearized-frequency-response analysis agree with the time-dependent results when the time-dependent inlet total-pressure and exit-flow function amplitude boundary conditions are less than 1 percent and 3 percent, respectively. The stability analysis technique was extended to a two-sector parallel compressor model with and without interstage crossflow and predictions were carried out for total-pressure distortion extents of 180 deg, 90 deg, 60 deg, and 30 deg.

  6. Nonlinear day-to-day traffic dynamics with driver experience delay: Modeling, stability and bifurcation analysis

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaomei; Orosz, Gbor

    2014-05-01

    In day-to-day traffic assignment problems travelers past experiences have important impact on their cost prediction which influences their route choice and consequently the arising flow patterns in the network. Many travelers execute the same trip in every few days, not daily, which leads to time delays in the system. In this paper, we propose a nonlinear, discrete-time model with driver experience delay. The linear stability of the stochastic user equilibrium is analyzed by studying the eigenvalues of the Jacobian matrix of the system while the nonlinear oscillations arising at the bifurcations are investigated by normal form calculations, numerical continuation and simulation. The methods are demonstrated on a two-route example. By applying rigorous analysis we show that the linearly unstable parameter domain as well as the period of arising oscillations increase with the delay. Moreover, delays and nonlinearities result in an extended domain of bistability where the stochastic user equilibrium coexists with stable and unstable oscillations. This study explains the influence of initial conditions on the dynamics of transportation networks and may provide guidance for network design and management.

  7. Stability analysis of the POD reduced order method for solving the bidomain model in cardiac electrophysiology.

    PubMed

    Corrado, Cesare; Lassoued, Jamila; Mahjoub, Moncef; Zemzemi, Njib

    2016-02-01

    In this paper we show the numerical stability of the Proper Orthogonal Decomposition (POD) reduced order method used in cardiac electrophysiology applications. The difficulty of proving the stability comes from the fact that we are interested in the bidomain model, which is a system of degenerate parabolic equations coupled to a system of ODEs representing the cell membrane electrical activity. The proof of the stability of this method is based on a priori estimates controlling the gap between the reduced order solution and the Galerkin finite element one. We present some numerical simulations confirming the theoretical results. We also combine the POD method with a time splitting scheme allowing a faster solving of the bidomain problem and show numerical results. Finally, we conduct numerical simulation in 2D illustrating the stability of the POD method in its sensitivity to the ionic model parameters. We also perform 3D simulation using a massively parallel code. We show the computational gain using the POD reduced order model. We also show that this method has a better scalability than the full finite element method. PMID:26723278

  8. Linear stability analysis of first-order delayed car-following models on a ring

    NASA Astrophysics Data System (ADS)

    Lassarre, Sylvain; Roussignol, Michel; Tordeux, Antoine

    2012-09-01

    The evolution of a line of vehicles on a ring is modeled by means of first-order car-following models. Three generic models describe the speed of a vehicle as a function of the spacing ahead and the speed of the predecessor. The first model is a basic one with no delay. The second is a delayed car-following model with a strictly positive parameter for the driver and vehicle reaction time. The last model includes a reaction time parameter with an anticipation process by which the delayed position of the predecessor is estimated. Explicit conditions for the linear stability of homogeneous configurations are calculated for each model. Two methods of calculus are compared: an exact one via Hopf bifurcations and an approximation by second-order models. The conditions describe stable areas for the parameters of the models that we interpret. The results notably show that the impact of the reaction time on the stability can be palliated by the anticipation process.

  9. Rock Cavern Stability Analysis Under Different Hydro-Geological Conditions Using the Coupled Hydro-Mechanical Model

    NASA Astrophysics Data System (ADS)

    Chen, H. M.; Zhao, Z. Y.; Choo, L. Q.; Sun, J. P.

    2016-02-01

    Rock cavern stability has a close relationship with the uncertain geological parameters, such as the in situ stress, the joint configurations, and the joint mechanical properties. Therefore, the stability of the rock cavern should be studied with variable geological conditions. In this paper, the coupled hydro-mechanical model, which is under the framework of the discontinuous deformation analysis, is developed to study the underground cavern stability when considering the hydraulic pressure after excavation. Variable geological conditions are taken into account to study their impacts on the seepage rate and the cavern stability, including the in situ stress ratio, joint spacing, and joint dip angle. In addition, the two cases with static hydraulic pressure and without hydraulic pressure are also considered for the comparison. The numerical simulations demonstrate that the coupled approach can capture the cavern behavior better than the other two approaches without the coupling effects.

  10. Stability analysis, modeling, simulation and experimental testing of an EMS Maglev system with structural flexibility

    NASA Astrophysics Data System (ADS)

    Hanasoge, Aravind M.

    Vehicle-guideway interaction studies of Magnetically Levitated (Maglev) vehicles indicate that structural flexibility can adversely affect the overall stability and performance of such systems. This is one of the reasons why guideways are generally made very rigid. This in turn leads to increased cost of the overall system since guideway construction forms a significant portion of the overall cost. In this dissertation, the influence of structural flexibility on the stability of Electromagnetic Suspension (EMS) Maglev systems is studied. It is shown how inherently unstable and flexible structure EMS Maglev systems can achieve guaranteed stability by using collocated actuators and sensors, along with de-centralized Proportional plus Derivative (PD) controllers. These results are valid even in the presence of Track/Guideway flexibility. A detailed dynamic model is developed for the EMS Maglev demonstration system (Test Bogie) currently under research and development at Old Dominion University (ODU). This model incorporates structural dynamics with flexible modes of vibration, non-linear electrodynamics, feedback controllers, discrete time implementation, noise filters and disturbance inputs. This model is validated via real time experimental testing. The model thus validated is used for simulation case studies involving levitation and lateral disturbance, lateral control, and centralized control.

  11. Stability analysis of a phase-field model of gravity-driven unsaturated flow through porous media.

    PubMed

    Cueto-Felgueroso, Luis; Juanes, Ruben

    2009-03-01

    The formation of preferential flow paths during infiltration of water into homogeneous, dry soil is an important phenomenon whose explanation and prediction have remained elusive under the standard theories of multiphase flow in porous media. We have recently proposed a macroscopic phase-field model of unsaturated flow in porous media, which explains why such fingering occurs [L. Cueto-Felgueroso and R. Juanes, Phys. Rev. Lett. 101, 244504 (2008)]. Here we present a linear stability analysis of the proposed model for constant-flux infiltration, which allows a quantitative description of the wetting front instability. The present analysis stresses the critical role of the initial water saturation and applied flux ratio in the asymptotic stability of the system, as well as in the transient growth of perturbations, which is consistent with the experimental evidence. The trends in the frequency and growth factor of the most unstable modes predicted by our analysis are also in quantitative agreement with experimental measurements. PMID:19392043

  12. Stability analysis of the mixed traffic flow of cars and trucks using heterogeneous optimal velocity car-following model

    NASA Astrophysics Data System (ADS)

    Yang, Da; Jin, Peter (Jing); Pu, Yun; Ran, Bin

    2014-02-01

    Real-world traffic flow usually contains a mixture of passenger vehicles (PV) and heavy vehicles (HV). In this paper, the four types of car-truck following combinations are considered: the car-following-car case, car-following-truck case, truck-following-car case and truck-following-truck case. The effect of different combinations on the stability of traffic flow is explored by converting the original Bandos optimal velocity (OV) model to a heterogeneous form. A new linear stability analysis method that can derive the stability criterion of the heterogeneous traffic flow mixed by cars and trucks is introduced. Moreover, the effect of the proportions of the four car-truck following combinations on traffic flow is examined through the trajectory analysis. It concludes that the linear stability of the car-truck mixed traffic flow is determined more by the proportions of the different car-truck following scenarios, rather than the numbers of the cars and trucks. Moreover, cars and trucks can both stabilize and destabilize traffic flow depending on the density of the traffic flow and the parameters of the heterogeneous OV model.

  13. Variational formulation and stability analysis of a three dimensional superelastic model for shape memory alloys

    NASA Astrophysics Data System (ADS)

    Alessi, Roberto; Pham, Kim

    2016-02-01

    This paper presents a variational framework for the three-dimensional macroscopic modelling of superelastic shape memory alloys in an isothermal setting. Phase transformation is accounted through a unique second order tensorial internal variable, acting as the transformation strain. Postulating the total strain energy density as the sum of a free energy and a dissipated energy, the model depends on two material scalar functions of the norm of the transformation strain and a material scalar constant. Appropriate calibration of these material functions allows to render a wide range of constitutive behaviours including stress-softening and stress-hardening. The quasi-static evolution problem of a domain is formulated in terms of two physical principles based on the total energy of the system: a stability criterion, which selects the local minima of the total energy, and an energy balance condition, which ensures the consistency of the evolution of the total energy with respect to the external loadings. The local phase transformation laws in terms of Kuhn-Tucker relations are deduced from the first-order stability condition and the energy balance condition. The response of the model is illustrated with a numerical traction-torsion test performed on a thin-walled cylinder. Evolutions of homogeneous states are given for proportional and non-proportional loadings. Influence of the stress-hardening/softening properties on the evolution of the transformation domain is emphasized. Finally, in view of an identification process, the issue of stability of homogeneous states in a multi-dimensional setting is answered based on the study of second-order derivative of the total energy. Explicit necessary and sufficient conditions of stability are provided.

  14. Stability analysis of a model gene network links aging, stress resistance, and negligible senescence

    PubMed Central

    Kogan, Valeria; Molodtsov, Ivan; Menshikov, Leonid I.; Reis, Robert J. Shmookler; Fedichev, Peter

    2015-01-01

    Several animal species are considered to exhibit what is called negligible senescence, i.e. they do not show signs of functional decline or any increase of mortality with age. Recent studies in naked mole rat and long-lived sea urchins showed that these species do not alter their gene-expression profiles with age as much as other organisms do. This is consistent with exceptional endurance of naked mole rat tissues to various genotoxic stresses. We conjectured, therefore, that the lifelong transcriptional stability of an organism may be a key determinant of longevity. We analyzed the stability of a simple genetic-network model and found that under most common circumstances, such a gene network is inherently unstable. Over a time it undergoes an exponential accumulation of gene-regulation deviations leading to death. However, should the repair systems be sufficiently effective, the gene network can stabilize so that gene damage remains constrained along with mortality of the organism. We investigate the relationship between stress-resistance and aging and suggest that the unstable regime may provide a mathematical basis for the Gompertz law of aging in many species. At the same time, this model accounts for the apparently age-independent mortality observed in some exceptionally long-lived animals. PMID:26316217

  15. Stability analysis of a multibody system model for coupled slosh-vehicle dynamics

    NASA Astrophysics Data System (ADS)

    Nichkawde, Chetan; Harish, P. M.; Ananthkrishnan, N.

    2004-08-01

    The coupled slosh-vehicle dynamics of a rigid body in planar atmospheric flight carrying a sloshing liquid is considered as a multibody system with the sloshing motion modelled as a simple pendulum. The coupled, non-linear equations for the four-degree-of-freedom multibody system are derived using the method of Lagrangian dynamics. Careful non-dimensionalization reveals two crucial parameters that determine the extent of coupling between the rigid body and slosh modes, and also two important frequency parameters. Using a two-parameter continuation method, critical combinations of these four parameters for which the coupled slosh-vehicle dynamics can become unstable are computed. Results are displayed in the form of neutral stability curves (stability boundaries) in parameter space, and an analytical expression incorporating the four parameters that represents the neutral stability curves is obtained. Reduced-order linearized models and key transfer functions are derived in an effort to understand the instability phenomenon. Physically, the sloshing motion is seen to induce a static instability, sometimes called tumbling, in the vehicle pitch dynamics, depending on the slosh mass fraction and the location of the slosh pendulum hinge point above the rigid vehicle center of mass.

  16. Stability analysis of a model gene network links aging, stress resistance, and negligible senescence.

    PubMed

    Kogan, Valeria; Molodtsov, Ivan; Menshikov, Leonid I; Shmookler Reis, Robert J; Fedichev, Peter

    2015-01-01

    Several animal species are considered to exhibit what is called negligible senescence, i.e. they do not show signs of functional decline or any increase of mortality with age. Recent studies in naked mole rat and long-lived sea urchins showed that these species do not alter their gene-expression profiles with age as much as other organisms do. This is consistent with exceptional endurance of naked mole rat tissues to various genotoxic stresses. We conjectured, therefore, that the lifelong transcriptional stability of an organism may be a key determinant of longevity. We analyzed the stability of a simple genetic-network model and found that under most common circumstances, such a gene network is inherently unstable. Over a time it undergoes an exponential accumulation of gene-regulation deviations leading to death. However, should the repair systems be sufficiently effective, the gene network can stabilize so that gene damage remains constrained along with mortality of the organism. We investigate the relationship between stress-resistance and aging and suggest that the unstable regime may provide a mathematical basis for the Gompertz "law" of aging in many species. At the same time, this model accounts for the apparently age-independent mortality observed in some exceptionally long-lived animals. PMID:26316217

  17. A Generalized Stability Analysis of the AMOC in Earth System Models: Implication for Decadal Variability and Abrupt Climate Change

    SciTech Connect

    Fedorov, Alexey V.; Fedorov, Alexey

    2015-01-14

    The central goal of this research project was to understand the mechanisms of decadal and multi-decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) as related to climate variability and abrupt climate change within a hierarchy of climate models ranging from realistic ocean models to comprehensive Earth system models. Generalized Stability Analysis, a method that quantifies the transient and asymptotic growth of perturbations in the system, is one of the main approaches used throughout this project. The topics we have explored range from physical mechanisms that control AMOC variability to the factors that determine AMOC predictability in the Earth system models, to the stability and variability of the AMOC in past climates.

  18. The stability of the extended model of hypothalamic-pituitary-adrenal axis examined by stoichiometric network analysis

    NASA Astrophysics Data System (ADS)

    Markovi?, V. M.; ?upi?, .; Ivanovi?, A.; Kolar-Ani?, Lj.

    2011-12-01

    Stoichiometric network analysis (SNA) represents a powerful mathematical tool for stability analysis of complex stoichiometric networks. Recently, the important improvement of the method has been made, according to which instability relations can be entirely expressed via reaction rates, instead of thus far used, in general case undefined, current rates. Such an improved SNA methodology was applied to the determination of exact instability conditions of the extended model of the hypothalamic-pituitary-adrenal (HPA) axis, a neuroendocrinological system, whose hormone concentrations exert complex oscillatory evolution. For emergence of oscillations, the Hopf bifurcation condition was utilized. Instability relations predicted by SNA showed good correlation with numerical simulation data of the HPA axis model.

  19. PrimeSupplier Cross-Program Impact Analysis and Supplier Stability Indicator Simulation Model

    NASA Technical Reports Server (NTRS)

    Calluzzi, Michael

    2009-01-01

    PrimeSupplier, a supplier cross-program and element-impact simulation model, with supplier solvency indicator (SSI), has been developed so that the shuttle program can see early indicators of supplier and product line stability, while identifying the various elements and/or programs that have a particular supplier or product designed into the system. The model calculates two categories of benchmarks to determine the SSI, with one category focusing on agency programmatic data and the other focusing on a supplier's financial liquidity. PrimeSupplier was developed to help NASA smoothly transition design, manufacturing, and repair operations from the Shuttle program to the Constellation program, without disruption in the industrial supply base.

  20. A simplified spatial model for BWR stability

    SciTech Connect

    Berman, Y.; Lederer, Y.; Meron, E.

    2012-07-01

    A spatial reduced order model for the study of BWR stability, based on the phenomenological model of March-Leuba et al., is presented. As one dimensional spatial dependence of the neutron flux, fuel temperature and void fraction is introduced, it is possible to describe both global and regional oscillations of the reactor power. Both linear stability analysis and numerical analysis were applied in order to describe the parameters which govern the model stability. The results were found qualitatively similar to past results. Doppler reactivity feedback was found essential for the explanation of the different regions of the flow-power stability map. (authors)

  1. Stability analysis of an HIV/AIDS epidemic model with treatment

    NASA Astrophysics Data System (ADS)

    Cai, Liming; Li, Xuezhi; Ghosh, Mini; Guo, Baozhu

    2009-07-01

    An HIV/AIDS epidemic model with treatment is investigated. The model allows for some infected individuals to move from the symptomatic phase to the asymptomatic phase by all sorts of treatment methods. We first establish the ODE treatment model with two infective stages. Mathematical analyses establish that the global dynamics of the spread of the HIV infectious disease are completely determined by the basic reproduction number [real]0. If [real]0<=1, the disease-free equilibrium is globally stable, whereas the unique infected equilibrium is globally asymptotically stable if [real]0>1. Then, we introduce a discrete time delay to the model to describe the time from the start of treatment in the symptomatic stage until treatment effects become visible. The effect of the time delay on the stability of the endemically infected equilibrium is investigated. Moreover, the delay model exhibits Hopf bifurcations by using the delay as a bifurcation parameter. Finally, numerical simulations are presented to illustrate the results.

  2. Bifurcation analysis and dynamic stability

    SciTech Connect

    Washburn, R.B. Jr.; Mehra, R.K.

    1980-01-01

    Using tools of bifurcation analysis, we examine the long-term behavior of implicit differential equations which are defined by simultaneous ordinary differential equations and implicit algebraic equations. The analysis shows how certain nonlinearities can make the long term behavior of such dynamic systems sensitive to very small amplitude uncertainties and noise. This sensitivity makes the long term behavior practically unpredictable. At the same time the analysis suggests simple stochastic models in case of such unpredictable behavior. Implicit differential equations are often used in modeling the dynamic behavior of electric power systems. Our analysis indicates essential limitations on the ability of such models to predict long term behavior of the system, and it suggests ways to improve the ability of these models to describe important features of long term behavior. This analysis of implicit differential equations has significant implications for the study of the long term dynamic stability of power systems. The analysis also sheds light on the origin and significance of multiple solutions of the load flow equations.

  3. Implementation of a Single-Stage-To-Orbit (SSTO) model for stability and control analysis

    NASA Technical Reports Server (NTRS)

    Ingalls, Stephen A.

    1995-01-01

    Three NASA centers: Marshall Space Flight Center (MSFC), Langley Research Center (LaRC), and Johnson Space Center (JSC) are currently involved in studying a family of single-stage- and two-stage-to-orbit (SSTO/TSTO) vehicles to serve as the next generation space transportation system (STS). A rocketed winged-body is the current focus. The configuration (WB001) is a vertically-launched, horizontally-landing system with circular cross-section. Preliminary aerodynamic data was generated by LaRC and is a combination of wind-tunnel data, empirical methods, and Aerodynamic Preliminary Analysis System-(APAS) generated values. JSC's efforts involve descent trajectory design, stability analysis, and flight control system synthesis. Analysis of WB001's static stability indicates instability in 'tuck' (C(sub mu) less than 0: Mach = 0.30, alpha greater than 3.25 deg; Mach = 0.60, alpha greater than 8.04), an unstable dihedral effects (C(sub l(beta)) greater than 0: Mach = 30,alpha less than 12 deg.; Mach = 0.60, alpha less than 10.00 deg.), and, most significantly, an unstable weathercock stability derivative, C(sub n(beta)), at all angles of attack and subsonic Mach numbers. Longitudinal trim solutions for Mach = 0.30 and 0.60 indicate flight path angle possibilities ranging from around 12 (M = 0.30) to slightly over 20 degrees at Mach = 0.60. Trim angles of attack increase from 6.24 at Mach 0.60 and 10,000 feet to 17.7 deg. at Mach 0.30, sea-level. Lateral trim was attempted for a design cross-wind of 25.0 knots. The current vehicle aerodynamic and geometric characteristics will only yield a lateral trim solution at impractical tip-fin deflections (approximately equal to 43 deg.) and bank angles (21 deg.). A study of the lateral control surfaces, tip-fin controllers for WB001, indicate increased surface area would help address these instabilities, particularly the deficiency in C(sub n(beta)), but obviously at the expense of increased vehicle weight. Growth factors of approximately 7 were determined using a design C(sub n(beta)) of 0.100/radian (approximate subsonic values for the orbiter).

  4. MAP Stability, Design and Analysis

    NASA Technical Reports Server (NTRS)

    Ericsson -Jackson, A.J.; Andrews, S. F.; ODonnell, J. R., Jr.; Markley, F. L.

    1998-01-01

    The Microwave Anisotropy Probe (MAP) is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. The design and analysis of the MAP attitude control system (ACS) have been refined since work previously reported. The full spacecraft and instrument flexible model was developed in NASTRAN, and the resulting flexible modes were plotted and reduced with the Modal Significance Analysis Package (MSAP). The reduced-order model was used to perform the linear stability analysis for each control mode, the results of which are presented in this paper. Although MAP is going to a relatively disturbance-free Lissajous orbit around the Earth-Sun L2 Lagrange point, a detailed disturbance-torque analysis is required because there are only a small number of opportunities for momentum unloading each year. Environmental torques, including solar pressure at L2, and aerodynamic and gravity gradient during phasing-loop orbits, were calculated and simulated. A simple model of fuel slosh was derived to model its effect on the motion of the spacecraft. In addition, a thruster mode linear impulse controller was developed to meet the accuracy requirements of the phasing loop burns. A dynamic attitude error limiter was added to improve the performance of the ACS during large attitude slews. The result of this analysis is a stable ACS subsystem that meets all of the mission's requirements.

  5. MAP stability, design, and analysis

    NASA Technical Reports Server (NTRS)

    Ericsson-Jackson, A. J.; Andrews, S. F.; O'Donnell, J. R., Jr.; Markley, F. L.

    1998-01-01

    The Microwave Anisotropy Probe (MAP) is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. The design and analysis of the MAP attitude control system (ACS) have been refined since work previously reported. The full spacecraft and instrument flexible model was developed in NASTRAN, and the resulting flexible modes were plotted and reduced with the Modal Significance Analysis Package (MSAP). The reduced-order model was used to perform the linear stability analysis for each control mode, the results of which are presented in this paper. Although MAP is going to a relatively disturbance-free Lissajous orbit around the Earth-Sun L(2) Lagrange point, a detailed disturbance-torque analysis is required because there are only a small number of opportunities for momentum unloading each year. Environmental torques, including solar pressure at L(2), aerodynamic and gravity gradient during phasing-loop orbits, were calculated and simulated. Thruster plume impingement torques that could affect the performance of the thruster modes were estimated and simulated, and a simple model of fuel slosh was derived to model its effect on the motion of the spacecraft. In addition, a thruster mode linear impulse controller was developed to meet the accuracy requirements of the phasing loop burns. A dynamic attitude error limiter was added to improve the performance of the ACS during large attitude slews. The result of this analysis is a stable ACS subsystem that meets all of the mission's requirements.

  6. Stability analysis and optimal control of an epidemic model with awareness programs by media.

    PubMed

    Misra, A K; Sharma, Anupama; Shukla, J B

    2015-12-01

    The impact of awareness campaigns and behavioral responses on epidemic outbreaks has been reported at times. However, to what extent does the provision of awareness and behavioral changes affect the epidemic trajectory is unknown, but important from the public health standpoint. To address this question, we formulate a mathematical model to study the effect of awareness campaigns by media on the outbreak of an epidemic. The awareness campaigns are treated as an intervention for the emergent disease. These awareness campaigns divide the whole populations into two subpopulation; aware and unaware, by inducing behavioral changes amongst them. The awareness campaigns are included explicitly as a separate dynamic variable in the modeling process. The model is analyzed qualitatively using stability theory of differential equations. We have also identified an optimal implementation rate of awareness campaigns so that disease can be controlled with minimal possible expenditure on awareness campaigns, using optimal control theory. The control setting is investigated analytically using optimal control theory, and the numerical solutions illustrating the optimal regimens under various assumptions are also shown. PMID:26551557

  7. Stochastic stability and instability of model ecosystems

    NASA Technical Reports Server (NTRS)

    Ladde, G. S.; Siljak, D. D.

    1975-01-01

    In this work, we initiate a stability study of multispecies communities in stochastic environment by using Ito's differential equations as community models. By applying the direct method of Liapunov, we obtain sufficient conditions for stability and instability in the mean of the equilibrium populations. The conditions are expressed in terms of the dominant diagonal property of community matrices, which is a suitable mechanism for resolving the central problem of 'complexity vs stability' in model ecosystems. As a by-product of this analysis we exhibit important structural properties of the stochastic density-dependent models, and establish tolerance of community stability to a broad class of nonlinear time-varying perturbations.

  8. Stability analysis of multi-group deterministic and stochastic epidemic models with vaccination rate

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Gang; Gao, Rui-Mei; Fan, Xiao-Ming; Han, Qi-Xing

    2014-09-01

    We discuss in this paper a deterministic multi-group MSIR epidemic model with a vaccination rate, the basic reproduction number ℛ0, a key parameter in epidemiology, is a threshold which determines the persistence or extinction of the disease. By using Lyapunov function techniques, we show if ℛ0 is greater than 1 and the deterministic model obeys some conditions, then the disease will prevail, the infective persists and the endemic state is asymptotically stable in a feasible region. If ℛ0 is less than or equal to 1, then the infective disappear so the disease dies out. In addition, stochastic noises around the endemic equilibrium will be added to the deterministic MSIR model in order that the deterministic model is extended to a system of stochastic ordinary differential equations. In the stochastic version, we carry out a detailed analysis on the asymptotic behavior of the stochastic model. In addition, regarding the value of ℛ0, when the stochastic system obeys some conditions and ℛ0 is greater than 1, we deduce the stochastic system is stochastically asymptotically stable. Finally, the deterministic and stochastic model dynamics are illustrated through computer simulations.

  9. Stability analysis for the flow of granular materials down an inclined plane using kinetic model. Quarterly report, January 1, 1993--March 31, 1993

    SciTech Connect

    Rajagopal, K.R.

    1993-07-01

    In the previous report the linearized stability equations for the flow of granular materials down an inclined plane, modeled by the kinetic constitutive theory [cf Richman & Marciniec (1990)] were derived. Here, we use the approximate solution of Richman & Marciniec (1990) as the base solution for the linearized stability analysis. The governing equations obtained are solved numerically to obtain the marginal stability curves which are presented in this report.

  10. Analysis of aeroelastic model stability augmentation systems. [for application to supersonic transport aircraft

    NASA Technical Reports Server (NTRS)

    Sevart, F. D.

    1971-01-01

    An analytical and mechanization study was conducted for two flutter stability augmentation systems. One concept uses only the wing trailing edge control surface. Another concept uses leading and trailing edge control surfaces operating simultaneously. The combined use of leading and trailing edge control surfaces should improve the surface coupling (controllability) with vertical bending and torsional structural modes and decrease the coupling between bending and torsional modes. The study was directed toward stability augmentation systems characteristics for the supersonic transport aircraft.

  11. Analysis and test evaluation of the dynamic stability of three advanced turboprop models at zero forward speed

    NASA Technical Reports Server (NTRS)

    Smith, Arthur F.

    1985-01-01

    Results of static stability wind tunnel tests of three 62.2 cm (24.5 in) diameter models of the Prop-Fan are presented. Measurements of blade stresses were made with the Prop-Fans mounted on an isolated nacelle in an open 5.5 m (18 ft) wind tunnel test section with no tunnel flow. The tests were conducted in the United Technology Research Center Large Subsonic Wind Tunnel. Stall flutter was determined by regions of high stress, which were compared with predictions of boundaries of zero total viscous damping. The structural analysis used beam methods for the model with straight blades and finite element methods for the models with swept blades. Increasing blade sweep tends to suppress stall flutter. Comparisons with similar test data acquired at NASA/Lewis are good. Correlations between measured and predicted critical speeds for all the models are good. The trend of increased stability with increased blade sweep is well predicted. Calculated flutter boundaries generaly coincide with tested boundaries. Stall flutter is predicted to occur in the third (torsion) mode. The straight blade test shows third mode response, while the swept blades respond in other modes.

  12. Stability analysis of free piston Stirling engines

    NASA Astrophysics Data System (ADS)

    Bégot, Sylvie; Layes, Guillaume; Lanzetta, François; Nika, Philippe

    2013-03-01

    This paper presents a stability analysis of a free piston Stirling engine. The model and the detailed calculation of pressures losses are exposed. Stability of the machine is studied by the observation of the eigenvalues of the model matrix. Model validation based on the comparison with NASA experimental results is described. The influence of operational and construction parameters on performance and stability issues is exposed. The results show that most parameters that are beneficial for machine power seem to induce irregular mechanical characteristics with load, suggesting that self-sustained oscillations could be difficult to maintain and control.

  13. Analysis of the stability of relative equilibriums of a prolate axisymmetric gyrostat by symbolic—numerical modeling

    NASA Astrophysics Data System (ADS)

    Banshchikov, A. V.; Chaikin, S. V.

    2015-09-01

    Applying Lyapunov's approach to the investigation of the stability of the motion according to first order approximation equations, the regions are singled out in the space of the inputed parameters where the stability, instability, or gyroscopic stabilization of relative equilibriums of a prolate axisymmetric orbital gyrostat with a constant gyrostatic moment vector are ensured. In particular, the result concerning instability and impossibility of gyroscopic stabilization of one in two existing equilibrium classes of the system have been formulated. The investigation was carried out using the LinModel software package and the symbolic—numerical modeling functions of the Mathematica Computer Algebra System.

  14. Evaluation of Reinforcement and Analysis of Stability of a High-Arch Dam Based on Geomechanical Model Testing

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Liu, Y. R.; Yang, Q.

    2015-03-01

    Reinforcement measures are often used in high-arch dams with complicated geological foundations. The geomechanical model test is an effective method to study the global stability of arch dams and to evaluate the reinforcement effects of foundation treatments. The block masonry technique was developed to simulate the jointed rock mass, tectonic discontinuities, and reinforcement measures. A tailor-made low-strength binder and small blocks were developed to simulate the strength and deformation of the jointed rock mass and discontinuities, respectively. We applied this technique to geomechanical model tests of the Dagangshan arch dam with and without foundation reinforcements. A rupture test was conducted, and the stress and displacement distribution of the dam and abutments were recorded; the failure mechanisms and processes were explored. The reinforcement effects of the foundation treatment were evaluated by comparing the test results of the models with and without foundation reinforcements. Our analysis indicates that foundation reinforcements can improve the stress distribution, decrease deformation, prevent slides, reduce fault movement, and improve the global stability of high-arch dams.

  15. Dynamic Simulation and Stability Analysis

    NASA Technical Reports Server (NTRS)

    Frisch, H. P.; Sanborn, J. A.

    1985-01-01

    Dynamic Interaction Simulation of Controls and Structure (DISCOS) program developed for dynamic simulation and stability analysis of passive and actively controlled spacecraft. In use of DISCOS, physical system undergoing analysis generally described as cluster of contiguous flexible structures (bodies) that comprise mechanical system, such as spacecraft.

  16. Development of NUFREQ-N, an analytical model for the stability analysis of nuclear coupled density-wave oscillations in boiling water nuclear reactors

    SciTech Connect

    Park, G.C.

    1983-01-01

    A state-of-the-art one-dimensional thermal-hydraulic model has been developed to be used for the linear analysis of nuclear-coupled density-wave oscillations in a boiling water nuclear reactor (BWR). The model accounts for phasic slip, distributed spacers, subcooled boiling, space/time-dependent power distributions and distributed heated wall dynamics. In addition to a parallel channel stability analysis, a detailed model was derived for the BWR loop analysis of both the natural and forced circulation modes of operation. In its final form, this model constitutes a multi-input, multi-output (MIMO) linear system, which features a general nodal neutron kinetics model. Kinetics parameters for use in the kinetics model have been obtained by utilizing self-consistent nodal data and power distributions. The stability characteristics of a typical BWR/4 has been investigated with the Nyquist criterion. The computer implementation of this mode, NUFREQ-N, was used for the parametric study of a typical BWR/4 and comparison were made with existing in-core and out-of-core data. Also, NUFREQ-N was used to analyze the expected stability characteristics of a typical BWR/4. The parametric results revealed important factors influencing BWR stability margin. It was found that NUFREQ-N generally agreed well with out-of-core data. This was especially true for the predicted power-to-flow transfer function, which is the most important transfer function in thermal-hydraulic stability analysis.

  17. Terrestrial Photogrammetry and Numerical Modelling for the Stability Analysis of Rock Slopes in High Mountain Areas: Aiguilles Marbres case

    NASA Astrophysics Data System (ADS)

    Curtaz, M.; Ferrero, A. M.; Roncella, R.; Segalini, A.; Umili, G.

    2014-03-01

    Several high-altitude slope instability phenomena, involving rock blocks of different volumes, have been observed in recent years. The increase in these phenomena could be correlated to climatic variations and to a general increase in temperature that has induced both ice melting with consequent water seepage and glacial lowering, with a consequent loss of support of the rock face. The degradation of the high-altitude thermal layer, which is known as "permafrost", can determine the formation of highly fractured rock slopes where instabilities can concentrate. The present research has developed a methodology to improve the understanding and assessment of rock slope stability conditions in high mountain environments where access is difficult. The observed instabilities are controlled by the presence of discontinuities that can determine block detachments. Consequently, a detailed survey of the rock faces is necessary, both in terms of topography and geological structure, and in order to locate the discontinuities on the slope to obtain a better geometric reconstruction and subsequent stability analysis of the blocky rock mass. Photogrammetric surveys performed at different times allow the geostructure of the rock mass to be determined and the rock block volumes and detachment mechanisms to be estimated, in order to assess the stability conditions and potential triggering mechanisms. Photogrammetric surveys facilitate both the characterisation of the rock mass and the monitoring of slope instabilities over time. The methodology has been applied in a case study pertaining to the North Face of Aiguilles Marbres in the Mont Blanc massif, which suffers from frequent instability phenomena. A slope failure that occurred in 2007 has been back-analysed using both the limit equilibrium method (LEM) and 3D distinct element modelling (DEM). The method has been supported and validated with traditional in situ surveys and measurements of the discontinuity orientation and other rock mass features.

  18. An Ex Vivo Model in Human Femoral Heads for Histopathological Study and Resonance Frequency Analysis of Dental Implant Primary Stability

    PubMed Central

    Hernndez-Corts, Pedro; Galindo-Moreno, Pablo; Catena, Andrs; Ortega-Oller, Inmaculada; Salas-Prez, Jos; Gmez-Snchez, Rafael; Aguilar, Mariano; Aguilar, David

    2014-01-01

    Objective. This study was designed to explore relationships of resonance frequency analysis (RFA)assessed implant stability (ISQ values) with bone morphometric parameters and bone quality in an ex vivo model of dental implants placed in human femoral heads and to evaluate the usefulness of this model for dental implant studies. Material and Methods. This ex vivo study included femoral heads from 17 patients undergoing surgery for femoral neck fracture due to osteoporosis (OP) (n = 7) or for total prosthesis joint replacement due to severe hip osteoarthrosis (OA) (n = 10). Sixty 4.5 13?mm Dentsply Astra implants were placed, followed by RFA. CD44 immunohistochemical analysis for osteocytes was also carried out. Results. As expected, the analysis yielded significant effects of femoral head type (OA versus OA) (P < 0.001), but not of the implants (P = 0.455) or of the interaction of the two factors (P = 0.848). Bonferroni post hoc comparisons showed a lower mean ISQ for implants in decalcified (50.33 2.92) heads than in fresh (66.93 1.10) or fixated (70.77 1.32) heads (both P < 0.001). The ISQ score (fresh) was significantly higher for those in OA (73.52 1.92) versus OP (67.13 1.09) heads. However, mixed linear analysis showed no significant association between ISQ scores and morphologic or histomorphometric results (P > 0.5 in all cases), and no significant differences in ISQ values were found as a function of the length or area of the cortical layer (both P > 0.08). Conclusion. Although RFA-determined ISQ values are not correlated with morphometric parameters, they can discriminate bone quality (OP versus OA). This ex vivo model is useful for dental implant studies. PMID:24995307

  19. Modeling and nonlinear hunting stability analysis of high-speed railway vehicle moving on curved tracks

    NASA Astrophysics Data System (ADS)

    Cheng, Yung-Chang; Lee, Sen-Yung; Chen, Hsing-Hao

    2009-07-01

    A heuristic nonlinear creep model is used to derive the nonlinear coupled differential equations of motion of a high-speed railway vehicle traveling on a curved track. The vehicle dynamics are modeled using a 21 degree-of-freedom (21-DOF) system which takes account of the lateral displacement and yaw angle of each wheelset, the lateral displacement, vertical displacement, roll angle and yaw angle of the truck frames, and the lateral displacement, vertical displacement, roll angle, pitch angle and yaw angle of the car body. To analyze the respective effects of the major system parameters on the vehicle dynamics, the 21-DOF system is reduced to 20-DOF, 14-DOF and 6-DOF models, respectively, by excluding designated subsets of the system parameters. The validity of the analytical models and the numerical solution procedure is confirmed by comparing the result obtained using the 6-DOF model for the critical velocity of a railway vehicle traveling on a tangent track with the solution presented in the literature. In general, the results obtained in this study show that the critical hunting speed derived using the 6-DOF or 14-DOF model is generally higher than that evaluated using the 20-DOF model. In addition, the critical hunting speed evaluated via the heuristic nonlinear creep model is lower than that derived using a linear creep model.

  20. Stability analysis of sleep apnea time series using identified models: a case study.

    PubMed

    Aguirre, Luis Antonio; Souza, Alvaro V P

    2004-04-01

    This paper investigates the use of identified nonlinear multivariable autonomous models in the classification of breathing patterns of a patient with sleep apnea. Details about the identification procedure are provided and the results reported for the case study at hand suggest that identified models could be useful in computer-based monitoring. PMID:15047435

  1. Stability analysis of the Biot/squirt models for wave propagation in saturated porous media

    NASA Astrophysics Data System (ADS)

    Liu, Jiawei; Yong, Wen-An

    2016-01-01

    This work is concerned with the Biot/squirt (BISQ) models for wave propagation in saturated porous media. We show that the models allow exponentially exploding solutions, as time goes to infinity, when the characteristic squirt-flow coefficient is negative or has a non-zero imaginary part. We also show that the squirt-flow coefficient does have non-zero imaginary parts for some experimental parameters or for low angular frequencies. Because the models are linear, the existence of such exploding solutions indicates instability of the BISQ models. This result, for the first time, provides a theoretical explanation of the well-known empirical observation that BISQ model is not reliable (not consistent with Gassmann's formula) at low frequencies. It calls on a reconsideration of the widely used BISQ theory. On the other hand, we demonstrate that the 3-D isotropic BISQ model is stable when the squirt-flow coefficient is positive. In particular, the original Biot model is unconditionally stable where the squirt-flow coefficient is 1.

  2. Global stability analysis of a delayed susceptible-infected-susceptible epidemic model.

    PubMed

    Paulhus, Calah; Wang, Xiang-Sheng

    2015-01-01

    We study a susceptible-infected-susceptible model with distributed delays. By constructing suitable Lyapunov functionals, we demonstrate that the global dynamics of this model is fully determined by the basic reproductive ratio R0. To be specific, we prove that if R0 ? 1, then the disease-free equilibrium is globally asymptotically stable. On the other hand, if R0>1, then the endemic equilibrium is globally asymptotically stable. It is remarkable that the model dynamics is independent of the probability of immunity lost. PMID:24978018

  3. Spectral stability of unitary network models

    NASA Astrophysics Data System (ADS)

    Asch, Joachim; Bourget, Olivier; Joye, Alain

    2015-08-01

    We review various unitary network models used in quantum computing, spectral analysis or condensed matter physics and establish relationships between them. We show that symmetric one-dimensional quantum walks are universal, as are CMV matrices. We prove spectral stability and propagation properties for general asymptotically uniform models by means of unitary Mourre theory.

  4. Dynamic simulation and stability analysis

    NASA Technical Reports Server (NTRS)

    Frisch, H. P.

    1979-01-01

    Dynamic Interaction Simulation of Controls and Structure (DISCOS) program was developed for dynamic simulation and stability analysis of passive and actively controlled spacecraft. Program is written in FORTRAN IV for batch execution and requires access to finite-element structures program as NASTRAN for flexible-body input data.

  5. The Existence and Stability Analysis of the Equilibria in Dengue Disease Infection Model

    NASA Astrophysics Data System (ADS)

    Anggriani, N.; Supriatna, A. K.; Soewono, E.

    2015-06-01

    In this paper we formulate an SIR (Susceptible - Infective - Recovered) model of Dengue fever transmission with constant recruitment. We found a threshold parameter K0, known as the Basic Reproduction Number (BRN). This model has two equilibria, disease-free equilibrium and endemic equilibrium. By constructing suitable Lyapunov function, we show that the disease- free equilibrium is globally asymptotic stable whenever BRN is less than one and when it is greater than one, the endemic equilibrium is globally asymptotic stable. Numerical result shows the dynamic of each compartment together with effect of multiple bio-agent intervention as a control to the dengue transmission.

  6. A Mathematical Model of Protectant and Curative Fungicide Application and its stability analysis

    NASA Astrophysics Data System (ADS)

    Anggriani, N.; Istifadah, N.; Hanifah, M.; Supriatna, A. K.

    2016-01-01

    In this paper we introduce a mathematical model for fungicide application with effect of protectant and curatives factor. We show the value of the Basic Reproduction Number (R0) of the fungal disease, which is computed from the largest eigen value of the next generation matrix of the model. The result show that in the region where R0 greater than one there is only one single stable endemic equilibrium. However, in region where R0 less than one some parameters affect the number of posibble equilibria. Some numerical simulation are also given to illustrate our analytical results.

  7. Stability analysis of 4-species A? aggregation model: A novel approach to obtaining physically meaningful rate constants.

    PubMed

    Ghag, G; Ghosh, P; Mauro, A; Rangachari, V; Vaidya, A

    2013-11-01

    Protein misfolding and concomitant aggregation towards amyloid formation is the underlying biochemical commonality among a wide range of human pathologies. Amyloid formation involves the conversion of proteins from their native monomeric states (intrinsically disordered or globular) to well-organized, fibrillar aggregates in a nucleation-dependent manner. Understanding the mechanism of aggregation is important not only to gain better insight into amyloid pathology but also to simulate and predict molecular pathways. One of the main impediments in doing so is the stochastic nature of interactions that impedes thorough experimental characterization and the development of meaningful insights. In this study, we have utilized a well-known intermediate state along the amyloid-? peptide aggregation pathway called protofibrils as a model system to investigate the molecular mechanisms by which they form fibrils using stability and perturbation analysis. Investigation of protofibril aggregation mechanism limits both the number of species to be modeled (monomers, and protofibrils), as well as the reactions to two (elongation by monomer addition, and protofibril-protofibril lateral association). Our new model is a reduced order four species model grounded in mass action kinetics. Our prior study required 3200 reactions, which makes determining the reaction parameters prohibitively difficult. Using this model, along with a linear perturbation argument, we rigorously determine stable ranges of rate constants for the reactions and ensure they are physically meaningful. This was accomplished by finding the ranges in which the perturbations dieout in a five-parameter sweep, which includes the monomer and protofibril equilibrium concentrations and three of the rate constants. The results presented are a proof-of-concept method in determining meaningful rate constants that can be used as a bonafide way for determining accurate rate constants for other models involving complex biological reactions such as amyloid aggregation. PMID:25018569

  8. Cosmological Models and Stability

    NASA Astrophysics Data System (ADS)

    Andersson, Lars

    Principles in the form of heuristic guidelines or generally accepted dogma play an important role in the development of physical theories. In particular, philosophical considerations and principles figure prominently in the work of Albert Einstein. As mentioned in the talk by Jiří Bičák at this conference, Einstein formulated the equivalence principle, an essential step on the road to general relativity, during his time in Prague 1911-1912. In this talk, I would like to discuss some aspects of cosmological models. As cosmology is an area of physics where "principles" such as the "cosmological principle" or the "Copernican principle" play a prominent role in motivating the class of models which form part of the current standard model, I will start by comparing the role of the equivalence principle to that of the principles used in cosmology. I will then briefly describe the standard model of cosmology to give a perspective on some mathematical problems and conjectures on cosmological models, which are discussed in the later part of this paper.

  9. Enhanced rotor modeling tailored for rub dynamic stability analysis and simulation

    NASA Technical Reports Server (NTRS)

    Davis, R. R.

    1989-01-01

    New methods are presented that allow straightforward application of complex nonlinearities to finite element based rotor dynamic analyses. The key features are: (1) the methods can be implemented with existing finite element or dynamic simulation programs, (2) formulation is general for simple application to a wide range of problems, and (3) implementation is simplified because nonlinear aspects are separated from the linear part of the model. The new techniques are illustrated with examples of inertial nonlinearity and torquewhirl which can be important in rubbing turbomachinery. The sample analyses provide new understanding of these nonlinearities which are discussed.

  10. Stability, Bifurcation and Chaos Analysis of Vector-Borne Disease Model with Application to Rift Valley Fever

    PubMed Central

    Pedro, Sansao A.; Abelman, Shirley; Ndjomatchoua, Frank T.; Sang, Rosemary; Tonnang, Henri E. Z.

    2014-01-01

    This paper investigates a RVF epidemic model by qualitative analysis and numerical simulations. Qualitative analysis have been used to explore the stability dynamics of the equilibrium points while visualization techniques such as bifurcation diagrams, Poincar maps, maxima return maps and largest Lyapunov exponents are numerically computed to confirm further complexity of these dynamics induced by the seasonal forcing on the mosquitoes oviposition rates. The obtained results show that ordinary differential equation models with external forcing can have rich dynamic behaviour, ranging from bifurcation to strange attractors which may explain the observed fluctuations found in RVF empiric outbreak data, as well as the non deterministic nature of RVF inter-epidemic activities. Furthermore, the coexistence of the endemic equilibrium is subjected to existence of certain number of infected Aedes mosquitoes, suggesting that Aedes have potential to initiate RVF epidemics through transovarial transmission and to sustain low levels of the disease during post epidemic periods. Therefore we argue that locations that may serve as RVF virus reservoirs should be eliminated or kept under control to prevent multi-periodic outbreaks and consequent chains of infections. The epidemiological significance of this study is: (1) low levels of birth rate (in both Aedes and Culex) can trigger unpredictable outbreaks; (2) Aedes mosquitoes are more likely capable of inducing unpredictable behaviour compared to the Culex; (3) higher oviposition rates on mosquitoes do not in general imply manifestation of irregular behaviour on the dynamics of the disease. Finally, our model with external seasonal forcing on vector oviposition rates is able to mimic the linear increase in livestock seroprevalence during inter-epidemic period showing a constant exposure and presence of active transmission foci. This suggests that RVF outbreaks partly build upon RVF inter-epidemic activities. Therefore, active RVF surveillance in livestock is recommended. PMID:25271641

  11. Jacobi stability analysis of the Lorenz system

    NASA Astrophysics Data System (ADS)

    Harko, Tiberiu; Ho, Chor Yin; Leung, Chun Sing; Yip, Stan

    2015-06-01

    We perform the study of the stability of the Lorenz system by using the Jacobi stability analysis, or the Kosambi-Cartan-Chern (KCC) theory. The Lorenz model plays an important role for understanding hydrodynamic instabilities and the nature of the turbulence, also representing a nontrivial testing object for studying nonlinear effects. The KCC theory represents a powerful mathematical method for the analysis of dynamical systems. In this approach, we describe the evolution of the Lorenz system in geometric terms, by considering it as a geodesic in a Finsler space. By associating a nonlinear connection and a Berwald type connection, five geometrical invariants are obtained, with the second invariant giving the Jacobi stability of the system. The Jacobi (in)stability is a natural generalization of the (in)stability of the geodesic flow on a differentiable manifold endowed with a metric (Riemannian or Finslerian) to the non-metric setting. In order to apply the KCC theory, we reformulate the Lorenz system as a set of two second-order nonlinear differential equations. The geometric invariants associated to this system (nonlinear and Berwald connections), and the deviation curvature tensor, as well as its eigenvalues, are explicitly obtained. The Jacobi stability of the equilibrium points of the Lorenz system is studied, and the condition of the stability of the equilibrium points is obtained. Finally, we consider the time evolution of the components of the deviation vector near the equilibrium points.

  12. Stability analysis and optimal control of plant fungal epidemic: An explicit model with curative factor

    NASA Astrophysics Data System (ADS)

    Anggriani, N.; Putri, L. Nurul; Supriatna, A. K.

    2015-03-01

    Many plants could not escape from diseases caused by fungi. The use of fungicide can help to reduce the spread of the fungi but if it used continuously with the same dosage, the fungi would be invulnerable to fungicide eventually. Hence, it is critical to know the appropriate level of fungicide application and its impact on the dynamics of the plants. In this paper we use an explicit model of fungal outbreaks of plant by taking into account a curative factor including the dynamic of fungicides itself. Granting of fungicide on crops is useful to control the infected plants as well as protecting the vulnerable plants. Optimal control is used to find out how many doses of the appropriate fungicide should be used to cure infected plants. Optimal control is obtained by applying Pontryagin's Minimum Principle. We found that the presence of appropriate level of fungicide speeds up the reduction of infected plants as well as accelerates the growth of healthy plants.

  13. Cage stability analysis for SSME HPOTP bearings

    NASA Technical Reports Server (NTRS)

    Merriman, T. L.; Kannel, J. W.

    1988-01-01

    A numerical model of cage motion (CAGEDYN) was used to analyze the stability of bearing cages in the Space Shuttle main engine (SSME) high pressure oxygen turbopump (HPOTP). The stability of existing bearing geometries, as well as perturbations of these geometries, was analyzed for various operating conditions. Results of the analyses show that some combinations of operating parameters, exacerbated by the sparse lubrication that exist in the HPOTP bearings, can cause unstable cage oscillations. Frequencies of cage oscillations were predicted by the CAGEDYN numerical model by Fourier analysis of predicted cage motions. Under conditions that cause unstable cage motion, high frequency oscillations were predicted that could cause premature cage failures.

  14. Modeling of shallow stabilization ponds

    SciTech Connect

    Babarutsi, S.; Marchand, P.; Safieddine, T.

    1999-07-01

    A two-dimensional hydrodynamic model is used to simulate shallow stabilization ponds. The model computes the flow field and the concentration distribution of a conservative tracer in the entire area of a pond. The location and the size of the dead zones, the bypassing, and the recirculating areas are also determined by the model. The numerical results are in good agreement with the experimental data obtained in the laboratory.

  15. Unified power flow controller: Modeling, stability analysis, control strategy and control system design

    NASA Astrophysics Data System (ADS)

    Sreenivasachar, Kannan

    2001-07-01

    Unified power flow controller (UPFC) has been the most versatile Flexible AC Transmission System (FACTS) device due to its ability to control real and reactive power flow on transmission lines while controlling the voltage of the bus to which it is connected. UPFC being a multi-variable power system controller it is necessary to analyze its effect on power system operation. To study the performance of the UPFC in damping power oscillations using PSCAD-EMTDC software, a de-coupled control system has been designed for the shunt inverter to control the UPFC bus voltage and the DC link capacitor voltage. The series inverter of a UPFC controls the real power flow in the transmission line. One problem associated with using a high gain PI controller (used to achieve fast control of transmission line real power flow) for the series inverter of a UPFC to control the real power flow in a transmission line is the presence of low damping. This problem is solved in this research by using a fuzzy controller. A method to model a fuzzy controller in PSCAD-EMTDC software has also been described. Further, in order to facilitate proper operation between the series and the shunt inverter control system, a new real power coordination controller has been developed and its performance was evaluated. The other problem concerning the operation of a UPFC is with respect to transmission line reactive power flow control. Step changes to transmission line reactive power references have significant impact on the UPFC bus voltage. To reduce the adverse effect of step changes in transmission line reactive power references on the UPFC bus voltage, a new reactive power coordination controller has been designed. Transient response studies have been conducted using PSCAD-EMTDC software to show the improvement in power oscillation damping with UPFC. These simulations include the real and reactive power coordination controllers. Finally, a new control strategy has been proposed for UPFC. In this proposed control strategy, the shunt inverter controls the DC link capacitor voltage and the transmission line reactive power flow. The series inverter controls the transmission line real power flow and the UPFC bus voltage. PSCAD-EMTDC simulations have been conducted to show the viability of the control strategy in damping power oscillations.

  16. Stability analysis of an acoustically levitated disk.

    PubMed

    Hu, Junhui; Nakamura, Kentaro; Ueha, Sadayuki

    2003-02-01

    In this paper, a model is developed for the stability analysis of an acoustically levitated disk on the basis of analyzing eddy acoustic streaming and acoustic viscous stress. In the model, the effect of the acoustic streaming outside the boundary layer that is on the surface of the levitated disk is properly taken into account. Also, the calculation of sound field and acoustic viscous stress is limited to the range that has a dominant effect on the stability. By this method, we obtain a quite accurate solution of the stability coefficient. For the small horizontal shift of a large levitated disk, the model is verified by the good agreement between the experimental and theoretical results. By means of this model and relevant experiments, some factors that affect the stability of the levitated disk are investigated, and useful guidelines for design and application are obtained. It is found that the range from the edge to the outermost nodal circle of the disk-shaped vibrator has a large effect on the stability of the levitated disk. To stabilize the levitated disk by acoustic viscous force, the distance between the edge and the outermost nodal circle of the vibrator must be larger than a critical value, which is determined by the driving frequency and the sound velocity of the fluid between the levitated disk and the vibrator. When this condition is satisfied, increasing the distance between the edge and the outermost nodal circle leads to a decrease in the stability. It is also found that the property of the fluid between the levitated disk and the vibrator has a large effect on the stability. It is easier to stabilize the levitated disk in steam than in air, but more difficult to do so in carbon dioxide and hydrogen. In addition, theoretical results show that increasing the weight per unit area of the levitated object increases the stability for a given vibrator velocity. The distribution of the acoustic viscous stress and the dependence of the stability coefficient and the holding force on the horizontal shift of the levitated disk, which are obtained by this study, also are useful to a better understanding of the stability of the levitated disk. PMID:12625585

  17. Analysis of the Stability of Teacher-Level Growth Scores from the Student Growth Percentile Model. REL 2016-104

    ERIC Educational Resources Information Center

    Lash, Andrea; Makkonen, Reino; Tran, Loan; Huang, Min

    2016-01-01

    This study, undertaken at the request of the Nevada Department of Education, examined the stability over years of teacher-level growth scores from the Student Growth Percentile (SGP) model, which many states and districts have selected as a measure of effectiveness in their teacher evaluation systems. The authors conducted a generalizability study…

  18. Euler Technology Assessment - SPLITFLOW Code Applications for Stability and Control Analysis on an Advanced Fighter Model Employing Innovative Control Concepts

    NASA Technical Reports Server (NTRS)

    Jordan, Keith J.

    1998-01-01

    This report documents results from the NASA-Langley sponsored Euler Technology Assessment Study conducted by Lockheed-Martin Tactical Aircraft Systems (LMTAS). The purpose of the study was to evaluate the ability of the SPLITFLOW code using viscous and inviscid flow models to predict aerodynamic stability and control of an advanced fighter model. The inviscid flow model was found to perform well at incidence angles below approximately 15 deg, but not as well at higher angles of attack. The results using a turbulent, viscous flow model matched the trends of the wind tunnel data, but did not show significant improvement over the Euler solutions. Overall, the predictions were found to be useful for stability and control design purposes.

  19. Catchment scale validation of SMOS and ASCAT soil moisture products using hydrological modeling and temporal stability analysis

    NASA Astrophysics Data System (ADS)

    Rtzer, K.; Montzka, C.; Bogena, H.; Wagner, W.; Kerr, Y. H.; Kidd, R.; Vereecken, H.

    2014-11-01

    Since soil moisture is an important influencing factor of the hydrological cycle, knowledge of its spatio-temporal dynamics is crucial for climate and hydrological modeling. In recent years several soil moisture data products from satellite information have become available with global coverage and sub-monthly resolution. Since the remote sensing of soil moisture is an indirect measurement method and influenced by a large number of factors (e.g. atmospheric correction, vegetation, soil roughness, etc.), a comprehensive validation of the resulting soil moisture products is required. However, the coarse spatial resolution of these products hampers the comparison with point-scale in situ measurements. Therefore, upscaling of in situ to the scale of the satellite data is needed. We present the validation results of the soil moisture products of the years 2010-2012 retrieved from the Soil Moisture and Ocean Salinity (SMOS) and the Advanced Scatterometer (ASCAT) for the Rur and Erft catchments in western Germany. For the upscaling of in situ data obtained from three test sites of the Terrestrial Environmental Observatories (TERENO) initiative we used the hydrological model WaSiM ETH. Correlation of the SMOS product to modeled and upscaled soil moisture resulted in a mean correlation coefficient of 0.28 whereas for ASCAT a correlation coefficient of 0.50 was obtained. However, for specific regions the SMOS product showed similar correlation coefficients as the ASCAT product. While for ASCAT correlation was mainly dependent on topography and vegetation, SMOS was also influenced by radiofrequency interferences in our study area. Both products show dry biases as compared to the soil moisture reference. However, while SMOS showed relatively constant bias values, ASCAT bias is variable throughout the year. As an additional validation method we performed a temporal stability analysis of the retrieved spatio-temporal soil moisture data. Through investigation of mean relative differences of soil moisture for every pixel, their standard deviations and their rankings, we analyzed the temporal persistence of spatial patterns. Our results show high standard deviations for both SMOS and ASCAT soil moisture products as compared to modeled soil moisture, indicating a lower temporal persistence. The consistence of ranks of mean relative differences was low for SMOS and relative ASCAT soil moisture compared to modeled soil moisture, while ASCAT soil moisture, converted to absolute values, showed higher rank consistence.

  20. Liquid rocket spray combustion stability analysis

    NASA Technical Reports Server (NTRS)

    Litchford, Ron J.; Jeng, San-Mou

    1992-01-01

    A computational approach to the analysis of spray combustion stability in liquid rocket combustors is proposed which is based on the unsteady quasi-two-dimensional Euler equations with interphase source terms derived from a Lagrangian treatment of the combusting spray. Based on a preliminary evaluation, the computational methodology presented here is a promising research tool and a potential design/development aid for investigating the stability characteristics of liquid rocket engines. The method is characterized by low numerical noise; the Lagrangian treatment of the spray offers improved flexibility for the direct modeling of spray combustion.

  1. Thermal Stabilization of Proteins by Mono- and Oligosaccharides: Measurement and Analysis in the Context of an Excluded Volume Model.

    PubMed

    Beg, Ilyas; Minton, Allen P; Hassan, Imtaiyaz; Islam, Asimul; Ahmad, Faizan

    2015-06-16

    The reversible thermal denaturation of apo α-lactalbumin and lysozyme was monitored via measurement of changes in absorbance and ellipticity in the presence of varying concentrations of seven mono- and oligosaccharides: glucose, galactose, fructose, sucrose, trehalose, raffinose, and stachyose. The temperature dependence of the unfolding curves was quantitatively accounted for by a two-state model, according to which the free energy of unfolding is increased by an amount that is independent of temperature and depends linearly upon the concentration of added saccharide. The increment of added unfolding free energy per mole of added saccharide was found to depend approximately linearly upon the extent of oligomerization of the saccharide. The relative strength of stabilization of different saccharide oligomers could be accounted for by a simplified statistical-thermodynamic model attributing the stabilization effect to volume exclusion deriving from steric repulsion between protein and saccharide molecules. PMID:26000826

  2. Time domain modelling and stability analysis of an integral pulse frequency modulated dc to dc power converter

    NASA Technical Reports Server (NTRS)

    Iwens, R. P.; Yu, Y.; Triner, J. E.

    1975-01-01

    Using state variable representation a nonlinear, discrete-time system is derived that models the converter exactly. This system is linearized about its steady state solution, and converter stability, transient response and audio susceptibility are studied. The steady state solution of the converter is stable if and only if all the roots of the linearized system are absolutely less than unity. Excellent agreement with laboratory test data has been observed.

  3. Analysis and testing of aeroelastic model stability augmentation systems. [for supersonic transport aircraft wing and B-52 aircraft control system

    NASA Technical Reports Server (NTRS)

    Sevart, F. D.; Patel, S. M.

    1973-01-01

    Testing and evaluation of a stability augmentation system for aircraft flight control were performed. The flutter suppression system and synthesis conducted on a scale model of a supersonic wing for a transport aircraft are discussed. Mechanization and testing of the leading and trailing edge surface actuation systems are described. The ride control system analyses for a 375,000 pound gross weight B-52E aircraft are presented. Analyses of the B-52E aircraft maneuver load control system are included.

  4. Numerical Stability and Control Analysis Towards Falling-Leaf Prediction Capabilities of Splitflow for Two Generic High-Performance Aircraft Models

    NASA Technical Reports Server (NTRS)

    Charlton, Eric F.

    1998-01-01

    Aerodynamic analysis are performed using the Lockheed-Martin Tactical Aircraft Systems (LMTAS) Splitflow computational fluid dynamics code to investigate the computational prediction capabilities for vortex-dominated flow fields of two different tailless aircraft models at large angles of attack and sideslip. These computations are performed with the goal of providing useful stability and control data to designers of high performance aircraft. Appropriate metrics for accuracy, time, and ease of use are determined in consultations with both the LMTAS Advanced Design and Stability and Control groups. Results are obtained and compared to wind-tunnel data for all six components of forces and moments. Moment data is combined to form a "falling leaf" stability analysis. Finally, a handful of viscous simulations were also performed to further investigate nonlinearities and possible viscous effects in the differences between the accumulated inviscid computational and experimental data.

  5. Dynamic Analysis of Power System Voltage Stability.

    NASA Astrophysics Data System (ADS)

    Gebreselassie, Assefa

    This thesis investigates the effects of loads and voltage regulators on the dynamic voltage stability of power systems. The analysis focuses on the interactions of machine flux dynamics with loads and voltage control devices. The results are based on eigenvalue analysis of the linearized models and time simulation of the nonlinear models, using models from the Power System Toolbox, a Matlab -based package for the simulation and small signal analysis of nonlinear power systems. The voltage stability analysis results are developed using a single machine single load system with typical machine and network parameters and the NPCC 10-machine system. Dynamic models for generators, exciters and loads are used. The generator is modeled with a pair of poles and one damper circuit in both the d-axis and the q-axis. Saturation effects are included in the model. The IEEE Type DC1 DC commutator exciter model is used for all the exciters. Five different types of loads: constant impedance, constant current, constant power, a first order induction motor model (slip model) and a third order induction motor model (slip-flux model) are considered. The modes of instability and the stability limits of the different representation of loads are examined for two different operating modes of the exciters. The first, when all the exciters are on automatic control and the second when some exciters are on manual control. Modal participation factors are used to determine the characteristics of the critical modes. The characteristics of the unstable modes are verified by performing time simulation of the nonlinear models. Oscillatory and non-oscillatory instabilities are experienced by load buses when all the exciters are on automatic control and some exciters are on manual control respectively, for loads which are predominantly constant power and induction motors. It is concluded that the mode of instability does not depend on the type of loads but on the operating condition of the exciters. However, the severity of instability depends on the type of loads. Hence in dynamic voltage analysis, to arrive at a meaningful conclusion, the operating conditions of the exciters and the exact load composition should be taken into account.

  6. Massively Parallel Linear Stability Analysis with P_ARPACK for 3D Fluid Flow Modeled with MPSalsa

    SciTech Connect

    Lehoucq, R.B.; Salinger, A.G.

    1998-10-13

    We are interested in the stability of three-dimensional fluid flows to small dkturbances. One computational approach is to solve a sequence of large sparse generalized eigenvalue problems for the leading modes that arise from discretizating the differential equations modeling the flow. The modes of interest are the eigenvalues of largest real part and their associated eigenvectors. We discuss our work to develop an effi- cient and reliable eigensolver for use by the massively parallel simulation code MPSalsa. MPSalsa allows simulation of complex 3D fluid flow, heat transfer, and mass transfer with detailed bulk fluid and surface chemical reaction kinetics.

  7. The stability of colorectal cancer mathematical models

    NASA Astrophysics Data System (ADS)

    Khairudin, Nur Izzati; Abdullah, Farah Aini

    2013-04-01

    Colorectal cancer is one of the most common types of cancer. To better understand about the kinetics of cancer growth, mathematical models are used to provide insight into the progression of this natural process which enables physicians and oncologists to determine optimal radiation and chemotherapy schedules and develop a prognosis, both of which are indispensable for treating cancer. This thesis investigates the stability of colorectal cancer mathematical models. We found that continuous saturating feedback is the best available model of colorectal cancer growth. We also performed stability analysis. The result shows that cancer progress in sequence of genetic mutations or epigenetic which lead to a very large number of cells population until become unbounded. The cell population growth initiate and its saturating feedback is overcome when mutation changes causing the net per-capita growth rate of stem or transit cells exceed critical threshold.

  8. Development of NUFREQ-N, an analytical model for the stability analysis of nuclear coupled density-wave oscillations in boiling-water nuclear reactors

    SciTech Connect

    Park, G.C.; Podowski, M.; Becker, M.; Lahey, R.T., Jr.

    1983-07-01

    A state-of-the-art one-dimensional thermal-hydraulic model has been developed to be used for the linear analysis of nuclear-coupled density-wave oscillations in a boiling water nuclear reactor (BWR). The model accounts for phasic slip, distributed spacers, subcooled boiling, space/time-dependent power distributions and distributed heated wall dynamics. In addition to a parallel channel stability analysis, a detailed model was derived for the BWR loop analysis of both the natural and forced circulation modes of operation. In its final form, this model constitutes a multi-input, multi-output(MIMO) linear system, which features a general nodal neutron kinetics model. The computer implementation of this model, NUFREQ-N, was used for the parametric study of a typical BWR/4 and comparisons were made with existing in-core and out-of-core data. Also, NUFREQ-N was used to analyze the expected stability characteristics of a typical BWR/4.

  9. Dynamic model and stability analysis of a laser using a nonlinear Fabry-Perot etalon as a cavity mirror

    SciTech Connect

    Li, S.; Pons, R. . Dept. of Fisica); Zhang, Y. . Telecommunications Engineering Dept.)

    1994-08-01

    In this paper, the authors study a laser using a nonlinear Fabry-Perot etalon as a cavity mirror. First, using the semiclassical laser theory and the differential equation for the lossy nonlinear Fabry-Perot etalon, they develop dynamic equations describing this system for single-mode operation. In this model, the frequency-pulling effect, a finite response time of the nonlinear medium, and a finite-cavity round-trip time of the Fabry-Perot etalon are included. Second, based on this model, they analyze the stability of this laser and give some numerical results. The results show that (1) this system can exist in the stable state and in the unstable state; (2) there are not only saddle-node bifurcations but also Hopf bifurcations; (3) the detuning parameter will effect the characteristics of the bistability and the number and distribution of Hopf bifurcation points.

  10. The stability analysis of a general viral infection model with distributed delays and multi-staged infected progression

    NASA Astrophysics Data System (ADS)

    Wang, Jinliang; Liu, Shengqiang

    2015-01-01

    We investigate an in-host model with general incidence and removal rate, as well as distributed delays in virus infections and in productions. By employing Lyapunov functionals and LaSalle's invariance principle, we define and prove the basic reproductive number R0 as a threshold quantity for stability of equilibria. It is shown that if R0 > 1 , then the infected equilibrium is globally asymptotically stable, while if R0 ⩽ 1 , then the infection free equilibrium is globally asymptotically stable under some reasonable assumptions. Moreover, n + 1 distributed delays describe (i) the time between viral entry and the transcription of viral RNA, (ii) the n - 1 -stage time needed for activated infected cells between viral RNA transcription and viral release, and (iii) the time necessary for the newly produced viruses to be infectious (maturation), respectively. The model can describe the viral infection dynamics of many viruses such as HIV-1, HCV and HBV.

  11. Stability Analysis of ISS Medications

    NASA Technical Reports Server (NTRS)

    Wotring, V. E.

    2014-01-01

    It is known that medications degrade over time, and that extreme storage conditions will hasten their degradation. The temperature and humidity conditions of the ISS have been shown to be within the ideal ranges for medication storage, but the effects of other environmental factors, like elevated exposure to radiation, have not yet been evaluated. Current operational procedures ensure that ISS medications are re-stocked before expiration, but this may not be possible on long duration exploration missions. For this reason, medications that have experienced long duration storage on the ISS were returned to JSC for analysis to determine any unusual effects of aging in the low- Earth orbit environment. METHODS Medications were obtained by the JSC Pharmacy from commercial distributors and were re-packaged by JSC pharmacists to conserve up mass and volume. All medication doses were part of the ISS crew medical kit and were transported to the International Space Station (ISS) via NASA's Shuttle Transportation System (Space Shuttle). After 568 days of storage, the medications were removed from the supply chain and returned to Earth on a Dragon (SpaceX) capsule. Upon return to Earth, medications were transferred to temperature and humidity controlled environmental chambers until analysis. Nine medications were chosen on the basis of their availability for study. The medications included several of the most heavily used by US crewmembers: 2 sleep aids, 2 antihistamines/decongestants, 3 pain relievers, an antidiarrheal and an alertness medication. Each medication was available at a single time point; analysis of the same medication at multiple time points was not possible. Because the samples examined in this study were obtained opportunistically from medical supplies, there were no control samples available (i.e. samples aged for a similar period of time on the ground); a significant limitation of this study. Medications were analyzed using the HPLC/MS methods described in the United States Pharmacopeia (USP) to measure the amount of intact active ingredient, identify degradation products and measure their amounts. Some analyses were conducted by an independent analytical laboratory, but certain (Schedule) medications could not be shipped to their facility and were analyzed at JSC. RESULTS Nine medications were analyzed with respect to active pharmaceutical ingredient (API) and degradant amounts. Results were compared to the USP requirements for API and degradants/impurities content for every FDA-approved medication. One medication met USP requirements at 5 months after its expiration date. Four of the nine (44% of those tested) medications tested met USP requirements up to 8 months post-expiration. Another 3 medications (33% of those tested) met USP guidelines 2-3 months before expiration. One medication, a compound classed by the FDA as a dietary supplement and sometimes used as a sleep aid, failed to meet USP requirements at 11 months post-expiration. CONCLUSION Analysis of each medication at a single time point provides limited information on the stability of a medication stored in particular conditions; it is not possible to predict how long a medication may be safe and effective from these data. Notwithstanding, five of the nine medications tested (56%) met USP requirements for API and degradants/impurities at least 5 months past expiration dates. The single compound that failed to meet USP requirements is not regulated as strictly as prescription medications are during manufacture; it is unknown if this medication would have met the requirements prior to flight. Notably, it was the furthest beyond its expiration date. Only more comprehensive analysis of flight-aged samples compared to appropriate ground controls will permit determination of spaceflight effects on medication stability.

  12. Analysis and test evaluation of the dynamic response and stability of three advanced turboprop models at low forward speed

    NASA Technical Reports Server (NTRS)

    Smith, Arthur F.

    1985-01-01

    Results of wind tunnel tests at low forward speed for blade dynamic response and stability of three 62.2 cm (24.5 in) diameter models of the Prop-Fan, advanced turboprop, are presented. Measurements of dynamic response were made with the rotors mounted on an isolated nacelle, with varying tilt for nonuniform inflow. Low speed stall flutter tests were conducted at Mach numbers from 0.0 to 0.35. Measurements are compared to Eigen-solution flutter boundaries. Calculated 1P stress response agrees favorably with experiment. Predicted stall flutter boundaries correlate well with measured high stress regions. Stall flutter is significantly reduced by increased blade sweep. Susceptibility to stall flutter decreases rapidly with forward speed.

  13. Onset of natural terrain landslides modelled by linear stability analysis of creeping slopes with a two-state variable friction law

    NASA Astrophysics Data System (ADS)

    Chau, K. T.

    1999-12-01

    This paper further examines the possibility of modelling landslide as a consequence of the unstable slip in a steadily creeping slope when it is subject to perturbations, such as those induced by rainfall and earthquakes. In particular, the one-state variable friction law used in the landslide analysis by Chau is extended to a two-state variable friction law. According to this state variable friction law, the shear strength () along the slip surface depends on the creeping velocity (V) as well as the two state variables (1 and 2), which evolve with the ongoing slip. For translational slides, a system of three coupled non-linear first-order ordinary differential equations is formulated, and a linear stability analysis is applied to study the stability in the neighbourhood of the equilibrium solution of the system. By employing the stability classification of Reyn for three-dimensional space, it is found that equilibrium state (or critical point) of a slope may change from a stable spiral to a saddle spiral with unstable plane focus through a transitional state called converging vortex spiral (i.e. bifurcation occurs), as the non-linear parameters of the slip surface evolve with its environmental changes (such as those induced by rainfall or human activities). If the one-state variable friction law is used in landslide modelling, velocity strengthening (i.e. d 0, where stability of a creeping slope containing the same slip surface under gravitational pull. This conclusion, however, does not apply if a two-state variable friction law is employed to model the sliding along the slip surface. In particular, neither the region of stable creeping slopes in the non-linear parameter space can be inferred by that of velocity strengthening, nor the unstable region by that of velocity weakening.

  14. Analysis of cavern and well stability at the West Hackberry SPR site using a full-dome model.

    SciTech Connect

    Sobolik, Steven R.

    2015-08-01

    This report presents computational analyses that simulate the structural response of caverns at the Strategic Petroleum Reserve (SPR) West Hackberry site. The cavern field comprises 22 caverns. Five caverns (6, 7, 8, 9, 11) were acquired from industry and have unusual shapes and a history dating back to 1946. The other 17 caverns (101-117) were leached according to SPR standards in the mid-1980s and have tall cylindrical shapes. The history of the caverns and their shapes are simulated in a three-dimensional geomechanics model of the site that predicts deformations, strains, and stresses. Future leaching scenarios corresponding to oil drawdowns using fresh water are also simulated by increasing the volume of the caverns. Cavern pressures are varied in the model to capture operational practices in the field. The results of the finite element model are interpreted to provide information on the current and future status of subsidence, well integrity, and cavern stability. The most significant results in this report are relevant to Cavern 6. The cavern is shaped like a bowl with a large ceiling span and is in close proximity to Cavern 9. The analyses predict tensile stresses at the edge of the ceiling during repressurization of Cavern 6 following workover conditions. During a workover the cavern is at low pressure to service a well. The wellhead pressures are atmospheric. When the workover is complete, the cavern is repressurized. The resulting elastic stresses are sufficient to cause tension around the edge of the large ceiling span. With time, these stresses relax to a compressive state because of salt creep. However, the potential for salt fracture and propagation exists, particularly towards Cavern 9. With only 200 feet of salt between the caverns, the operational consequences must be examined if the two caverns become connected. A critical time may be during a workover of Cavern 9 in part because of the operational vulnerabilities, but also because dilatant damage is predicted under the ledge that forms the lower lobe in the cavern. The remaining caverns have no significant issues regarding cavern stability and may be safely enlarged during subsequent oil drawdowns. Predicted well strains and subsidence are significant and consequently future remedial actions may be necessary. These predicted well strains certainly suggest appropriate monitoring through a well-logging program. Subsidence is currently being monitored.

  15. Concrete gravity dam stability analysis

    SciTech Connect

    Morris, D.

    1992-09-01

    Under Federal Energy Regulatory Commission (FERC) guidelines, dam owners must evaluate the stability of their structures every five years. Because traditional approaches typically yield overly conservative stability estimates, EPRI sponsored the development of a computer code, CG-DAMS, to provide more-realistic assessments that reflect site-specific conditions. This finite-element code-which is available in mainframe, workstation, and personal computer versions-can be used to predict crack growth, shear, and stress under a variety of loads.

  16. Stability analysis and stabilization strategies for linear supply chains

    NASA Astrophysics Data System (ADS)

    Nagatani, Takashi; Helbing, Dirk

    2004-04-01

    Due to delays in the adaptation of production or delivery rates, supply chains can be dynamically unstable with respect to perturbations in the consumption rate, which is known as “bull-whip effect”. Here, we study several conceivable production strategies to stabilize supply chains, which is expressed by different specifications of the management function controlling the production speed in dependence of the stock levels. In particular, we will investigate, whether the reaction to stock levels of other producers or suppliers has a stabilizing effect. We will also demonstrate that the anticipation of future stock levels can stabilize the supply system, given the forecast horizon τ is long enough. To show this, we derive linear stability conditions and carry out simulations for different control strategies. The results indicate that the linear stability analysis is a helpful tool for the judgement of the stabilization effect, although unexpected deviations can occur in the non-linear regime. There are also signs of phase transitions and chaotic behavior, but this remains to be investigated more thoroughly in the future.

  17. Power System Transient Stability Analysis through a Homotopy Analysis Method

    SciTech Connect

    Wang, Shaobu; Du, Pengwei; Zhou, Ning

    2014-04-01

    As an important function of energy management systems (EMSs), online contingency analysis plays an important role in providing power system security warnings of instability. At present, N-1 contingency analysis still relies on time-consuming numerical integration. To save computational cost, the paper proposes a quasi-analytical method to evaluate transient stability through time domain periodic solutions’ frequency sensitivities against initial values. First, dynamic systems described in classical models are modified into damping free systems whose solutions are either periodic or expanded (non-convergent). Second, because the sensitivities experience sharp changes when periodic solutions vanish and turn into expanded solutions, transient stability is assessed using the sensitivity. Third, homotopy analysis is introduced to extract frequency information and evaluate the sensitivities only from initial values so that time consuming numerical integration is avoided. Finally, a simple case is presented to demonstrate application of the proposed method, and simulation results show that the proposed method is promising.

  18. Slope stability analysis of Valles Marineris, Mars

    NASA Astrophysics Data System (ADS)

    Vittorio De Blasio, Fabio; Battista Crosta, Giovanni; Castellanza, Riccardo; Utili, Stefano

    2013-04-01

    Valles Marineris (VM) in the equatorial area of Mars exhibits several gravitational failures which resulted in a series of large landslides up to several hundred cubic kilometers in volume. Questions arise as to forces at play and rock strength in the stability of the walls of VM. In this work we address the stability analysis of the walls of VM by considering the strength of the materials of the chasma walls and the causes of landslides. Using finite element calculations and the limit analysis upper bound method, we explore the range of cohesion and friction angle values associated to realistic failure geometries, and compare predictions with the classical Culmann's wedge model. Our analysis is based both on synthetic, simplified slope profiles and also on the real shape of the walls of VM taken from the MOLA topographic data. Validation of the calibrated cohesion and friction angle values is performed by comparing the computed unstable cross sectional areas with the observed pre- and post-failure profiles and estimated failure surface geometry. This offers a link between rock mass properties, slope geometry and volume of the observed failure. Pseudo-static seismic analyses generated another set of dimensionless charts. Our pseudo-static analyses show that low seismicity events induced by meteoroids impacts compatible with the size of craters could be a cause for some of the observed landslides if poor rock properties for VM is assumed.

  19. The stability of input structures in a supply-driven input-output model: A regional analysis

    SciTech Connect

    Allison, T.

    1994-06-01

    Disruptions in the supply of strategic resources or other crucial factor inputs often present significant problems for planners and policymakers. The problem may be particularly significant at the regional level where higher levels of product specialization mean supply restrictions are more likely to affect leading regional industries. To maintain economic stability in the event of a supply restriction, regional planners may therefore need to evaluate the importance of market versus non-market systems for allocating the remaining supply of the disrupted resource to the region`s leading consuming industries. This paper reports on research that has attempted to show that large short term changes on the supply side do not lead to substantial changes in input coefficients and do not therefore mean the abandonment of the concept of the production function as has been suggested (Oosterhaven, 1988). The supply-driven model was tested for six sectors of the economy of Washington State and found to yield new input coefficients whose values were in most cases close approximations of their original values, even with substantial changes in supply. Average coefficient changes from a 50% output reduction in these six sectors were in the vast majority of cases (297 from a total of 315) less than +2.0% of their original values, excluding coefficient changes for the restricted input. Given these small changes, the most important issue for the validity of the supply-driven input-output model may therefore be the empirical question of the extent to which these coefficient changes are acceptable as being within the limits of approximation.

  20. Application of small-signal modeling and measurement techniques to the stability analysis of an integrated switching-mode power system. [onboard Dynamics Explorer Satellite

    NASA Technical Reports Server (NTRS)

    Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.; Rodriguez, G. E.

    1980-01-01

    Small-signal modeling techniques are used in a system stability analysis of a breadboard version of a complete functional electrical power system. The system consists of a regulated switching dc-to-dc converter, a solar-cell-array simulator, a solar-array EMI filter, battery chargers and linear shunt regulators. Loss mechanisms in the converter power stage, including switching-time effects in the semiconductor elements, are incorporated into the modeling procedure to provide an accurate representation of the system without requiring frequency-domain measurements to determine the damping factor. The small-signal system model is validated by the use of special measurement techniques which are adapted to the poor signal-to-noise ratio encountered in switching-mode systems. The complete electrical power system with the solar-array EMI filter is shown to be stable over the intended range of operation.

  1. Stability analysis of cylindrical Vlasov equilibria

    SciTech Connect

    Short, R W

    1980-02-01

    A method is presented for the fully kinetic, nonlocal stability analysis of cylindrically symmetric equilibria. Applications to the lower hybrid drift instability and the modes associated with a finite-width relativistic E-layer are discussed.

  2. The radial growth phase of malignant melanoma: multi-phase modelling, numerical simulations and linear stability analysis

    PubMed Central

    Ciarletta, P.; Foret, L.; Ben Amar, M.

    2011-01-01

    Cutaneous melanoma is disproportionately lethal despite its relatively low incidence and its potential for cure in the early stages. The aim of this study is to foster understanding of the role of microstructure on the occurrence of morphological changes in diseased skin during melanoma evolution. The authors propose a biomechanical analysis of its radial growth phase, investigating the role of intercellular/stromal connections on the initial stages of epidermis invasion. The radial growth phase of a primary melanoma is modelled within the multi-phase theory of mixtures, reproducing the mechanical behaviour of the skin layers and of the epidermal–dermal junction. The theoretical analysis takes into account those cellular processes that have been experimentally observed to disrupt homeostasis in normal epidermis. Numerical simulations demonstrate that the loss of adhesiveness of the melanoma cells both to the basal laminae, caused by deregulation mechanisms of adherent junctions, and to adjacent keratynocytes, consequent to a downregulation of E-cadherin, are the fundamental biomechanical features for promoting tumour initiation. Finally, the authors provide the mathematical proof of a long wavelength instability of the tumour front during the early stages of melanoma invasion. These results open the perspective to correlate the early morphology of a growing melanoma with the biomechanical characteristics of its micro-environment. PMID:20656740

  3. Solar Dynamic Power System Stability Analysis and Control

    NASA Technical Reports Server (NTRS)

    Momoh, James A.; Wang, Yanchun

    1996-01-01

    The objective of this research is to conduct dynamic analysis, control design, and control performance test of solar power system. Solar power system consists of generation system and distribution network system. A bench mark system is used in this research, which includes a generator with excitation system and governor, an ac/dc converter, six DDCU's and forty-eight loads. A detailed model is used for modeling generator. Excitation system is represented by a third order model. DDCU is represented by a seventh order system. The load is modeled by the combination of constant power and constant impedance. Eigen-analysis and eigen-sensitivity analysis are used for system dynamic analysis. The effects of excitation system, governor, ac/dc converter control, and the type of load on system stability are discussed. In order to improve system transient stability, nonlinear ac/dc converter control is introduced. The direct linearization method is used for control design. The dynamic analysis results show that these controls affect system stability in different ways. The parameter coordination of controllers are recommended based on the dynamic analysis. It is concluded from the present studies that system stability is improved by the coordination of control parameters and the nonlinear ac/dc converter control stabilize system oscillation caused by the load change and system fault efficiently.

  4. The contribution of the acetabular labrum to hip joint stability: a quantitative analysis using a dynamic three-dimensional robot model.

    PubMed

    Bonner, Tara F; Colbrunn, Robb W; Bottros, John J; Mutnal, Amar B; Greeson, Clay B; Klika, Alison K; van den Bogert, Antonie J; Barsoum, Wael K

    2015-06-01

    The acetabular labrum provides mechanical stability to the hip joint in extreme positions where the femoral head is disposed to subluxation. We aimed to quantify the isolated labrum's stabilizing value. Five human cadaveric hips were mounted to a robotic manipulator, and subluxation potential tests were run with and without labrum. Three-dimensional (3D) kinematic data were quantified using the stability index (Colbrunn et al., 2013, "Impingement and Stability of Total Hip Arthroplasty Versus Femoral Head Resurfacing Using a Cadaveric Robotics Model," J. Orthop. Res., 31(7), pp. 1108-1115). Global and regional stability indices were significantly greater with labrum intact than after total labrectomy for both anterior and posterior provocative positions. In extreme positions, the labrum imparts significant overall mechanical resistance to hip subluxation. Regional stability contributions vary with joint orientation. PMID:25759977

  5. Stability analysis of zigzag boron nitride nanoribbons

    SciTech Connect

    Rai, Hari Mohan Late, Ravikiran; Saxena, Shailendra K.; Kumar, Rajesh; Sagdeo, Pankaj R.; Jaiswal, Neeraj K.; Srivastava, Pankaj

    2015-05-15

    We have explored the structural stability of bare and hydrogenated zigzag boron nitride nanoribbons (ZBNNRs). In order to investigate the structural stability, we calculate the cohesive energy for bare, one-edge and both edges H-terminated ZBNNRs with different widths. It is found that the ZBNNRs with width Nz=8 are energetically more favorable than the lower-width counterparts (Nz<8). Bare ZBNNRs have been found energetically most stable as compared to the edge terminated ribbons. Our analysis reveals that the structural stability is a function of ribbon-width and it is not affected significantly by the type of edge-passivation (one-edge or both-edges)

  6. Developments in Cylindrical Shell Stability Analysis

    NASA Technical Reports Server (NTRS)

    Knight, Norman F., Jr.; Starnes, James H., Jr.

    1998-01-01

    Today high-performance computing systems and new analytical and numerical techniques enable engineers to explore the use of advanced materials for shell design. This paper reviews some of the historical developments of shell buckling analysis and design. The paper concludes by identifying key research directions for reliable and robust methods development in shell stability analysis and design.

  7. Stability analysis of unsteady ablation fronts

    SciTech Connect

    Betti, R.; McCrory, R.L.; Verdon, C.P.

    1993-08-01

    The linear stability analysis of unsteady ablation fronts, is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

  8. Stability analysis of unsteady ablation fronts

    NASA Astrophysics Data System (ADS)

    Betti, R.; McCrory, R. L.; Verdon, C. P.

    1993-08-01

    The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

  9. Stability analysis of unsteady ablation fronts

    NASA Astrophysics Data System (ADS)

    Betti, R.; McCrory, R. L.; Verdon, C. P.

    1993-11-01

    The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code orchid.

  10. Stability analysis of unsteady ablation fronts

    SciTech Connect

    Betti, R.; McCrory, R.L.; Verdon, C.P. )

    1993-11-08

    The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

  11. Stability/Instability Analysis of Rotating Machinery

    NASA Technical Reports Server (NTRS)

    Powers, Richard W.

    1987-01-01

    Numerical index of stability calculated for nonlinear system. Technique for determining rotor stability or instability from analysis of measurements adapted for use with computer simulations of rotor motion. Involves calculation of log decrement or increment of vibration amplitude. Applicable to rotors mounted in loose bearings and to similar problems in which load-versus-deflection characteristics nonlinear. Developed for assessments of vibrational characteristics of turbopump rotors, technique also usable with such mechanisms as high-speed ball bearings.

  12. Voltage stability analysis in the new deregulated environment

    NASA Astrophysics Data System (ADS)

    Zhu, Tong

    Nowadays, a significant portion of the power industry is under deregulation. Under this new circumstance, network security analysis is more critical and more difficult. One of the most important issues in network security analysis is voltage stability analysis. Due to the expected higher utilization of equipment induced by competition in a power market that covers bigger power systems, this issue is increasingly acute after deregulation. In this dissertation, some selected topics of voltage stability analysis are covered. In the first part, after a brief review of general concepts of continuation power flow (CPF), investigations on various matrix analysis techniques to improve the speed of CPF calculation for large systems are reported. Based on these improvements, a new CPF algorithm is proposed. This new method is then tested by an inter-area transaction in a large inter-connected power system. In the second part, the Arnoldi algorithm, the best method to find a few minimum singular values for a large sparse matrix, is introduced into the modal analysis for the first time. This new modal analysis is applied to the estimation of the point of voltage collapse and contingency evaluation in voltage security assessment. Simulations show that the new method is very efficient. In the third part, after transient voltage stability component models are investigated systematically, a novel system model for transient voltage stability analysis, which is a logical-algebraic-differential-difference equation (LADDE), is offered. As an example, TCSC (Thyristor controlled series capacitors) is addressed as a transient voltage stabilizing controller. After a TCSC transient voltage stability model is outlined, a new TCSC controller is proposed to enhance both fault related and load increasing related transient voltage stability. Its ability is proven by the simulation.

  13. Convective instability in sedimentation: Linear stability analysis

    NASA Astrophysics Data System (ADS)

    Yu, Xiao; Hsu, Tian-Jian; Balachandar, S.

    2013-01-01

    ABSTRACTConvective sedimentation in a stably stratified saltwater is studied using the linear <span class="hlt">stability</span> <span class="hlt">analysis</span>. Convective sedimentation is known to occur due to the double-diffusive mechanism and the settling-driven mechanism. In this study, a semi-empirical closure of sediment diffusivity based on the long-range hydrodynamics effect is adopted. The sediment phase can act as either the slow- or fast-diffusing agent in the double-diffusive system for the given salt diffusivity. Moreover, the settling-driven effect is proportional to the square of the sediment diameter via Stoke settling law. We consider sediment concentration (grain size) in the upper freshwater layer to be in the range of 0.1 to 39.4 g/l (2 to 60 m), which is on top of a saltwater layer with salinity 35 ppt. Linear <span class="hlt">stability</span> <span class="hlt">analysis</span> allows us to identify the dominant mechanism that triggers the instability, the growth rate, and the resulting characteristic finger width. <span class="hlt">Model</span> results suggest that for fine sediment with grain diameter smaller than 10 m (settling velocity 0.09 mm/s), double-diffusive mechanism controls the instability and the resulting sediment finger size is of millimeter scale. For the given threshold of growth rate of O(0.01) s-1, the minimum sediment concentration is about 8-15 g/l. For grain size greater than or around 10 m, the settling-driven mechanism dominates and instabilities occur at sediment concentration as low as O(0.1) g/l with centimeter-scale fingers. Our findings may contribute to a better understanding on the observed rapid sediment removal in the plume of small mountainous rivers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/934697','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/934697"><span id="translatedtitle">Moduli <span class="hlt">stabilization</span> in stringy ISS <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nakayama, Yu; Nakayama, Yu; Yamazaki, Masahito; Yanagida, T.T.</p> <p>2007-09-28</p> <p>We present a stringy realization of the ISS metastable SUSY breaking <span class="hlt">model</span> with moduli <span class="hlt">stabilization</span>. The mass moduli of the ISS <span class="hlt">model</span> is <span class="hlt">stabilized</span> by gauging of a U(1) symmetry and its D-term potential. The SUSY is broken both by F-terms and D-terms. It is possible to obtain de Sitter vacua with a vanishingly small cosmological constant by an appropriate fine-tuning of flux parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020021569&hterms=1044&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D%2526%25231044','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020021569&hterms=1044&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D%2526%25231044"><span id="translatedtitle">The nu Andromedae System: <span class="hlt">Models</span> and <span class="hlt">Stability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stepinski, Tomasz F.; Malhotra, Renu; Black, David C.</p> <p>2000-01-01</p> <p>Radial velocity observations of the F8 V star nu Andromedae taken at Lick and at Whipple Observatories have revealed evidence of three periodicities in the line-of-sight velocity of the star. These periodicities have been interpreted as evidence for at least three low-mass companions (LMCs) revolving around nu Andromedae. The mass and orbital parameters inferred for these companions raise questions about the dynamical <span class="hlt">stability</span> of the system. We report here results from our independent <span class="hlt">analysis</span> of the published radial velocity data, as well as new unpublished data taken at Lick Observatory. Our results confirm the finding of three periods in the data. Our best fits to the data, on the assumption that these periods arise from the gravitational perturbations of companions in Keplerian orbits, are also generally in agreement but with some differences from the earlier findings. We find that the available data do not constrain well the orbital eccentricity of the middle companion in a three-companion <span class="hlt">model</span> of the data. We also find that in order for our best-fit <span class="hlt">model</span> to the Lick data to be dynamically stable over the lifetime of the star (approximately 2 billion years), the system must have a mean inclination to the plane of the sky greater than 13 deg. The corresponding minimum inclination for the best fit to the Whipple data set is 19 deg. These values imply that the maximum mass for the outer companion can be no greater than about 20 Jupiter masses. Our <span class="hlt">analysis</span> of the <span class="hlt">stability</span> of the putative systems also places constraints on the relative inclinations of the orbital planes of the companions. We comment on global versus local (i.e., method of steepest descent) means of finding best-fit orbits from radial velocity data sets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22278068','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22278068"><span id="translatedtitle">Magnetization <span class="hlt">stability</span> <span class="hlt">analysis</span> of the Stoner-Wohlfarth <span class="hlt">model</span> under a spin-polarized current with a tilted polarization</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang, Zhiyuan; Sun, Z. Z.</p> <p>2014-02-14</p> <p>The stationary-state solutions of magnetization dynamics under a spin-polarized current that was polarized in an arbitrary direction were investigated by solving the Landau-Lifshitz-Gilbert-Slonczewski equation for a single-domain magnet. Taking into consideration the uniaxial magnetic anisotropy, the equilibrium directions of the magnetization vectors were analytically obtained by solving an algebraic cubic equation. It was found that one to three pairs of magnetization equilibrium states existed, depending on the current intensity and the direction of the spin polarization. By numerically analyzing the <span class="hlt">stabilities</span> of these equilibrium states, the threshold switching current for the reversing the magnetic vector was obtained under different current polarization configurations, which may be useful for use in future spintronics devices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810008861','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810008861"><span id="translatedtitle">Advanced <span class="hlt">stability</span> <span class="hlt">analysis</span> for laminar flow control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Orszag, S. A.</p> <p>1981-01-01</p> <p>Five classes of problems are addressed: (1) the extension of the SALLY <span class="hlt">stability</span> <span class="hlt">analysis</span> code to the full eighth order compressible <span class="hlt">stability</span> equations for three dimensional boundary layer; (2) a comparison of methods for prediction of transition using SALLY for incompressible flows; (3) a study of instability and transition in rotating disk flows in which the effects of Coriolis forces and streamline curvature are included; (4) a new linear three dimensional instability mechanism that predicts Reynolds numbers for transition to turbulence in planar shear flows in good agreement with experiment; and (5) a study of the <span class="hlt">stability</span> of finite amplitude disturbances in axisymmetric pipe flow showing the <span class="hlt">stability</span> of this flow to all nonlinear axisymmetric disturbances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.H32C..02T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.H32C..02T"><span id="translatedtitle">Sand Bank Weakly Nonlinear <span class="hlt">Stability</span> <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tambroni, N.; Blondeaux, P.</p> <p>2006-12-01</p> <p>In the continental shelf, tidal currents often give rise to large scale periodic bed forms named sand banks. Sand banks are long ridges (length of the order of several tens of kilometers) with a spacing (crest to crest distance) up to 10 km and a height up to several tens of meters. Their crests are almost aligned with the tidal currents, forming small positive or negative angles. Although reliable <span class="hlt">models</span> based on linear <span class="hlt">stability</span> analyses exist to predict the main geometrical characteristics of the sand banks as they start to appear, little is known on the morphodynamic processes that shape and maintain these bed forms in equilibrium conditions. A weakly nonlinear <span class="hlt">analysis</span> is a powerful tool to investigate the equilibrium configuration attained by unstable bottom perturbations when the parameters of the problem are close to the critical values. However difficulties arise to apply a weakly nonlinear <span class="hlt">analysis</span> of sand bank dynamics because the linear approaches predict infinite wavelengths of the most unstable mode close to the critical conditions. Here we first revisit the linear approach of Hulscher et al. (1993, Cont. Shelf Res. 13). In particular the time development of small amplitude bottom perturbations forced by tidal currents is studied using a different parameterization of both the bed shear stress and the sediment transport predictor which provides vanishing values of the sediment transport rate when the bottom shear stress is smaller than a critical value and accounts for the deviation of the sediment transport rate from the depth averaged velocity. With these improvements, both clockwise and counterclockwise sand banks are predicted. Moreover the wavelength of the most unstable mode close to the critical conditions turns out to be finite. This result opens the possibility to carry out a weakly nonlinear <span class="hlt">stability</span> <span class="hlt">analysis</span>. Then the time development of the most unstable mode is studied for values of the parameters close to the marginal conditions. The <span class="hlt">analysis</span> provides estimates of the sand bank equilibrium amplitude and predicts equilibrium profiles characterized by crests sharper than the troughs, a feature often observed in field surveys.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910053355&hterms=classical+conditioning&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dclassical%2Bconditioning','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910053355&hterms=classical+conditioning&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dclassical%2Bconditioning"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of spacecraft power systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Halpin, S. M.; Grigsby, L. L.; Sheble, G. B.; Nelms, R. M.</p> <p>1990-01-01</p> <p>The problems in applying standard electric utility <span class="hlt">models</span>, analyses, and algorithms to the study of the <span class="hlt">stability</span> of spacecraft power conditioning and distribution systems are discussed. Both single-phase and three-phase systems are considered. Of particular concern are the load and generator <span class="hlt">models</span> that are used in terrestrial power system studies, as well as the standard assumptions of load and topological balance that lead to the use of the positive sequence network. The standard assumptions regarding relative speeds of subsystem dynamic responses that are made in the classical transient <span class="hlt">stability</span> algorithm, which forms the backbone of utility-based studies, are examined. The applicability of these assumptions to a spacecraft power system <span class="hlt">stability</span> study is discussed in detail. In addition to the classical indirect method, the applicability of Liapunov's direct methods to the <span class="hlt">stability</span> determination of spacecraft power systems is discussed. It is pointed out that while the proposed method uses a solution process similar to the classical algorithm, the <span class="hlt">models</span> used for the sources, loads, and networks are, in general, more accurate. Some preliminary results are given for a linear-graph, state-variable-based <span class="hlt">modeling</span> approach to the study of the <span class="hlt">stability</span> of space-based power distribution networks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22277659','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22277659"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> in tachyonic potential chameleon cosmology</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Farajollahi, H.; Salehi, A.; Tayebi, F.; Ravanpak, A. E-mail: a.salehi@guilan.ac.ir E-mail: aravanpak@guilan.ac.ir</p> <p>2011-05-01</p> <p>We study general properties of attractors for tachyonic potential chameleon scalar-field <span class="hlt">model</span> which possess cosmological scaling solutions. An analytic formulation is given to obtain fixed points with a discussion on their <span class="hlt">stability</span>. The <span class="hlt">model</span> predicts a dynamical equation of state parameter with phantom crossing behavior for an accelerating universe. We constrain the parameters of the <span class="hlt">model</span> by best fitting with the recent data-sets from supernovae and simulated data points for redshift drift experiment generated by Monte Carlo simulations.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6308353','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6308353"><span id="translatedtitle">HVDC <span class="hlt">models</span> used in <span class="hlt">stability</span> studies</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Johnson, B.K.</p> <p>1989-04-01</p> <p>A new generation of detailed <span class="hlt">models</span> for HVDC systems has recently been applied in power system <span class="hlt">stability</span> programs. These <span class="hlt">models</span> represent the high speed dynamics of the converter controllers as well as the L/R dynamics of the dc transmission. Older dc <span class="hlt">models</span> such as those described in reference which are based upon pseudo-steady state relationships are however still in general use. The latter <span class="hlt">models</span> remain popular since they require a minimum of data and significantly less computer resources than the detailed <span class="hlt">models</span>. The following questions therefore need to be answered concerning the two types of <span class="hlt">models</span>: (1) To what extent is simulation accuracy impacted by using the older HVDC <span class="hlt">model</span>. (2) Is the difference in precision significant compared to other uncertainties which are inherent in <span class="hlt">stability</span> calculations. This paper addresses these questions and also considers a third type of HVDC <span class="hlt">model</span> described in Appendix I which relieves some of the assumptions associated with the pseudo steady state <span class="hlt">models</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ShWav.tmp...26B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ShWav.tmp...26B"><span id="translatedtitle">Aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> of flexible overexpanded rocket nozzle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bekka, N.; Sellam, M.; Chpoun, A.</p> <p>2015-05-01</p> <p>The aim of this paper is to present a new aeroelastic <span class="hlt">stability</span> <span class="hlt">model</span> taking into account the viscous effects for a supersonic nozzle flow in overexpanded regimes. This <span class="hlt">model</span> is inspired by the Pekkari <span class="hlt">model</span> which was developed initially for perfect fluid flow. The new <span class="hlt">model</span> called the "Modified Pekkari <span class="hlt">Model</span>" (MPM) considers a more realistic wall pressure profile for the case of a free shock separation inside the supersonic nozzle using the free interaction theory of Chapman. To reach this objective, a code for structure computation coupled with aerodynamic excitation effects is developed that allows the <span class="hlt">analysis</span> of aeroelastic <span class="hlt">stability</span> for the overexpanded nozzles. The main results are presented in a comparative manner using existing <span class="hlt">models</span> (Pekkari <span class="hlt">model</span> and its extended version) and the modified Pekkari <span class="hlt">model</span> developed in this work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6203588','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6203588"><span id="translatedtitle">Automating <span class="hlt">stability</span> <span class="hlt">analysis</span> for concrete gravity dams</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Barrett, P.R. ); Morris, D.I.</p> <p>1993-06-01</p> <p>In an effort to get more realistic <span class="hlt">stability</span> results, dam owners-with FERC's encouragement-began using actual data collected at their structures in dam safety analyses in the mid-1980s. However, making use of the data was not always easy. The conventional cracked-base <span class="hlt">analysis</span> method cannot take into account the effects of the dam and foundation stiffnesses. General finite-element software programs for determining dam <span class="hlt">stability</span> using site-specific data were available, but required a great deal of manipulation, expertise, and time. In early 1987, representatives of utilities, consulting firms, FERC, and federal hydropower producers serving on an Electric Power Research Institute (EPRI) dam safety advisory committee agreed that a special computer code was needed to bridge the gap between traditional analytical practices and finite-element methods. Consequently, EPRI funded ANATECH Research Corp., a consulting engineer firm in San Diego, California, to develop CG-DAMS. This two-dimensional, finite-element computer code automates the <span class="hlt">stability</span> <span class="hlt">analysis</span> process. The menu-driven software prompts the user for input of a specific structure's geometry, loading (using input commands such as reservoir and tailwater elevations), and site-specific material properties in the dam and foundation. The results of the <span class="hlt">analysis</span> are illustrated in easy-to-use graphical and tabular formats, and can be used to predict crack growth, shear, and normal stresses under normal loading, flood loading, and seismic loading. Although CG-DAMS was designed to respond to FERC's dam <span class="hlt">stability</span> <span class="hlt">analysis</span> requirements, it can be useful to any dam owner wanting to make more realistic <span class="hlt">stability</span> assessments than the conventional cracked-base method that reflect site-specific conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2821677','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2821677"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of an Encapsulated Microbubble against Gas Diffusion</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Katiyar, Amit; Sarkar, Kausik</p> <p>2009-01-01</p> <p>Linear <span class="hlt">stability</span> <span class="hlt">analysis</span> is performed for a mathematical <span class="hlt">model</span> of diffusion of gases from an encapsulated microbubble. It is an Epstein-Plesset <span class="hlt">model</span> modified to account for encapsulation elasticity and finite gas permeability. Although, bubbles, containing gases other than air is considered, the final stable bubble, if any, contains only air, and <span class="hlt">stability</span> is achieved only when the surrounding medium is saturated or oversaturated with air. In absence of encapsulation elasticity, only a neutral <span class="hlt">stability</span> is achieved for zero surface tension, the other solution being unstable. For an elastic encapsulation, different equilibrium solutions are obtained depending on the saturation level and whether the surface tension is smaller or higher than the elasticity. For an elastic encapsulation, elasticity can <span class="hlt">stabilize</span> the bubble. However, imposing a non-negativity condition on the effective surface tension (consisting of reference surface tension and the elastic stress) leads to an equilibrium radius which is only neutrally stable. If the encapsulation can support net compressive stress, it achieves actual <span class="hlt">stability</span>. The linear <span class="hlt">stability</span> results are consistent with our recent numerical findings. Physical mechanisms for the <span class="hlt">stability</span> or instability of various equilibriums are provided. PMID:20005522</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20997064','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20997064"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of a Uniformly Heated Channel with Supercritical Water</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ortega Gomez, T.; Class, A.; Schulenberg, T.; Lahey, R.T. Jr.</p> <p>2006-07-01</p> <p>The thermal-hydraulic <span class="hlt">stability</span> of a uniformly heated channel at supercritical water pressure has been investigated to help understand the system instability phenomena which may occur in Supercritical Water Nuclear Reactors (SCWR). We have extended the <span class="hlt">modeling</span> approach often used for Boiling Water Nuclear Reactor (BWR) <span class="hlt">stability</span> <span class="hlt">analysis</span> to supercritical pressure operation conditions. We have shown that Ledinegg excursive instabilities and pressure-drop oscillations (PDO) will not occur in supercritical water systems. The linear <span class="hlt">stability</span> characteristics of a typical uniformly heated channel were computed by evaluating the eigenvalues of the <span class="hlt">model</span>. An <span class="hlt">analysis</span> of non-linear instability phenomena was also performed in the time domain and the dynamic bifurcations were evaluated. (authors)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AIPC.1404..284B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AIPC.1404..284B"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> in a <span class="hlt">Model</span> of 1,2-dichloroethane Biodegradation by Klebsiella Oxytoca va 8391Immobilized on Granulated Activated Carbon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Borisov, M.; Dimitrova, N.</p> <p>2011-11-01</p> <p>We consider an ecological <span class="hlt">model</span> for biodegradation of toxic substances in aquatic and atmospheric biotic systems. The <span class="hlt">model</span>, which is described by a nonlinear system of four ordinary differential equations, is known to be experimentally validated. We compute the equilibrium points of the <span class="hlt">model</span> and study their asymptotic <span class="hlt">stability</span>. The Maple package BifTools is used to calculate one- and two-parameter bifurcations of the equilibrium points.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910019313','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910019313"><span id="translatedtitle">ASTROP2 users manual: A program for aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> of propfans</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Narayanan, G. V.; Kaza, K. R. V.</p> <p>1991-01-01</p> <p>A user's manual is presented for the aeroelastic <span class="hlt">stability</span> and response of propulsion systems computer program called ASTROP2. The ASTROP2 code preforms aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> of rotating propfan blades. This <span class="hlt">analysis</span> uses a two-dimensional, unsteady cascade aerodynamics <span class="hlt">model</span> and a three-dimensional, normal-mode structural <span class="hlt">model</span>. Analytical <span class="hlt">stability</span> results from this code are compared with published experimental results of a rotating composite advanced turboprop <span class="hlt">model</span> and of nonrotating metallic wing <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19820005844&hterms=automobile&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dautomobile','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19820005844&hterms=automobile&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dautomobile"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of automobile driver steering control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Allen, R. W.</p> <p>1981-01-01</p> <p>In steering an automobile, the driver must basically control the direction of the car's trajectory (heading angle) and the lateral deviation of the car relative to a delineated pathway. A previously published linear control <span class="hlt">model</span> of driver steering behavior which is analyzed from a <span class="hlt">stability</span> point of view is considered. A simple approximate expression for a <span class="hlt">stability</span> parameter, phase margin, is derived in terms of various driver and vehicle control parameters, and boundaries for <span class="hlt">stability</span> are discussed. A field test study is reviewed that includes the measurement of driver steering control parameters. Phase margins derived for a range of vehicle characteristics are found to be generally consistent with known adaptive properties of the human operator. The implications of these results are discussed in terms of driver adaptive behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvA..89f3814G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvA..89f3814G"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of the spatiotemporal Lugiato-Lefever <span class="hlt">model</span> for Kerr optical frequency combs in the anomalous and normal dispersion regimes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Godey, Cyril; Balakireva, Irina V.; Coillet, Aurlien; Chembo, Yanne K.</p> <p>2014-06-01</p> <p>We propose a detailed <span class="hlt">stability</span> <span class="hlt">analysis</span> of the Lugiato-Lefever <span class="hlt">model</span> for Kerr optical frequency combs in whispering-gallery-mode resonators when they are pumped in either the anomalous- or normal-dispersion regime. We analyze the spatial bifurcation structure of the stationary states depending on two parameters that are experimentally tunable; namely, the pump power and the cavity detuning. Our study demonstrates that, in both the anomalous- and normal-dispersion cases, nontrivial equilibria play an important role in this bifurcation map because their associated eigenvalues undergo critical bifurcations that are actually foreshadowing the existence of localized and extended spatial dissipative structures. The corresponding bifurcation maps are evidence of a considerable richness from a dynamical standpoint. The case of anomalous dispersion is indeed the most interesting from the theoretical point of view because of the considerable variety of dynamical behavior that can be observed. For this case we study the emergence of super- and subcritical Turing patterns (or primary combs) in the system via modulational instability. We determine the areas where bright isolated cavity solitons emerge, and we show that soliton molecules can emerge as well. Very complex temporal patterns can actually be observed in the system, where solitons (or soliton complexes) coexist with or without mutual interactions. Our investigations also unveil the mechanism leading to the phenomenon of breathing solitons. Two routes to chaos in the system are identified; namely, a route via the destabilization of a primary comb, and another via the destabilization of solitons. For the case of normal dispersion, we unveil the mechanism leading to the emergence of weakly stable Turing patterns. We demonstrate that this weak <span class="hlt">stability</span> is justified by the distribution of stable and unstable fixed points in the parameter space (flat states). We show that dark cavity solitons can emerge in the system, and also show how these solitons can coexist in the resonator as long as they do not interact with each other. We find evidence of breather solitons in this normal dispersion regime as well. The Kerr frequency combs corresponding to all these spatial dissipative structures are analyzed in detail, along with their <span class="hlt">stability</span> properties. A discussion is led about the possibility to gain unifying comprehension of the observed spectra from the dynamical complexity of the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050010184','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050010184"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of the Slowed-Rotor Compound Helicopter Configuration</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, Wayne; Floros, Matthew W.</p> <p>2004-01-01</p> <p>The <span class="hlt">stability</span> and control of rotors at high advance ratio are considered. Teetering, articulated, gimbaled, and rigid hub types are considered for a compound helicopter (rotor and fixed wing). <span class="hlt">Stability</span> predictions obtained using an analytical rigid flapping blade <span class="hlt">analysis</span>, a rigid blade CAMRAD II <span class="hlt">model</span>, and an elastic blade CAMRAD II <span class="hlt">model</span> are compared. For the flapping blade <span class="hlt">analysis</span>, the teetering rotor is the most stable, 5howing no instabilities up to an advance ratio of 3 and a Lock number of 18. With an elastic blade <span class="hlt">model</span>, the teetering rotor is unstable at an advance ratio of 1.5. <span class="hlt">Analysis</span> of the trim controls and blade flapping shows that for small positive collective pitch, trim can be maintained without excessive control input or flapping angles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070035908','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070035908"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of the Slowed-Rotor Compound Helicopter Configuration</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Floros, Matthew W.; Johnson, Wayne</p> <p>2007-01-01</p> <p>The <span class="hlt">stability</span> and control of rotors at high advance ratio are considered. Teetering, articulated, gimbaled, and rigid hub types are considered for a compound helicopter (rotor and fixed wing). <span class="hlt">Stability</span> predictions obtained using an analytical rigid flapping blade <span class="hlt">analysis</span>, a rigid blade CAMRAD II <span class="hlt">model</span>, and an elastic blade CAMRAD II <span class="hlt">model</span> are compared. For the flapping blade <span class="hlt">analysis</span>, the teetering rotor is the most stable, showing no instabilities up to an advance ratio of 3 and a Lock number of 18. A notional elastic blade <span class="hlt">model</span> of a teetering rotor is unstable at an advance ratio of 1.5, independent of pitch frequency. <span class="hlt">Analysis</span> of the trim controls and blade flapping shows that for small positive collective pitch, trim can be maintained without excessive control input or flapping angles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1190...13N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1190...13N"><span id="translatedtitle"><span class="hlt">Analysis</span> of <span class="hlt">Stabilization</span> Mechanisms in Lifted Flames</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Navarro-Martinez, S.; Kronenburg, A.</p> <p>2009-12-01</p> <p>Flame <span class="hlt">stabilization</span> and the mechanisms that govern the dynamics at the flame base have been subject to numerous studies in recent years. Recent results using a combined Large Eddy Simulation-Conditional Moment Closure (LES-CMC) approach to <span class="hlt">model</span> the turbulent flow field and the turbulence-chemistry interactions has been successful in predicting flame ignition and <span class="hlt">stabilization</span> by auto-ignition, but LES-CMCs capability of the accurate <span class="hlt">modelling</span> of the competition between turbulent quenching and laminar and turbulent flame propagation at the anchor point has not been resolved. This paper will consolidate LES-CMC results by analysing a wide range of lifted flame geometries with different prevailing <span class="hlt">stabilization</span> mechanisms. The simulations allow a clear distinction of the prevailing <span class="hlt">stabilization</span> mechanisms for the different flames, LES-CMC accurately predicts the competition between turbulence and chemistry during the auto-ignition process, however, the dynamics of the extinction process and turbulent flame propagation are not well captured. The averaging process inherent in the CMC methods does not allow for an instant response of the transported conditionally averaged reactive species to the changes in the flow conditions and any response of the scalars will therefore be delayed. Stationary or quasi-stationary conditions, however, can be well predicted for all flame configurations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5086327','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5086327"><span id="translatedtitle">Aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> of a Darrieus wind turbine</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Popelka, D.</p> <p>1982-02-01</p> <p>An aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> has been developed for predicting flutter instabilities on vertical axis wind turbines. The analytical <span class="hlt">model</span> and mathematical formulation of the problem are described as well as the physical mechanism that creates flutter in Darrieus turbines. Theoretical results are compared with measured experimental data from flutter tests of the Sandia 2 Meter turbine. Based on this comparison, the <span class="hlt">analysis</span> appears to be an adequate design evaluation tool.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/619676','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/619676"><span id="translatedtitle">Thermodynamic <span class="hlt">modeling</span> of natural zeolite <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chipera, S.J.; Bish, D.L.</p> <p>1997-06-01</p> <p>Zeolites occur in a variety of geologic environments and are used in numerous agricultural, commercial, and environmental applications. It is desirable to understand their <span class="hlt">stability</span> both to predict future <span class="hlt">stability</span> and to evaluate the geochemical conditions resulting in their formation. The use of estimated thermodynamic data for measured zeolite compositions allows thermodynamic <span class="hlt">modeling</span> of <span class="hlt">stability</span> relationships among zeolites in different geologic environments (diagenetic, saline and alkaline lakes, acid rock hydrothermal, basic rock, deep sea sediments). This <span class="hlt">modeling</span> shows that the relative cation abundances in both the aqueous and solid phases, the aqueous silica activity, and temperature are important factors in determining the stable zeolite species. Siliceous zeolites (e.g., clinoptilolite, mordenite, erionite) present in saline and alkaline lakes or diagenetic deposits formed at elevated silica activities. Aluminous zeolites (e.g., natrolite, mesolite/scolecite, thomsonite) formed in basic rocks in association with reduced silica activities. Likewise, phillipsite formation is favored by reduced aqueous silica activities. The presence of erionite, chabazite, and phillipsite are indicative of environments with elevated potassium concentrations. Elevated temperature, calcic water conditions, and reduced silica activity help to enhance the laumontite and wairakite <span class="hlt">stability</span> fields. Analcime <span class="hlt">stability</span> increases with increased temperature and aqueous Na concentration, and/or with decreased silica activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=105275&keyword=Ball+AND+Analysis&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=55618553&CFTOKEN=88586685','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=105275&keyword=Ball+AND+Analysis&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=55618553&CFTOKEN=88586685"><span id="translatedtitle">DYNAMIC LANDSCAPES, <span class="hlt">STABILITY</span> AND ECOLOGICAL <span class="hlt">MODELING</span></span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The image of a ball rolling along a series of hills and valleys is an effective heuristic by which to communicate <span class="hlt">stability</span> concepts in ecology. However, the dynamics of this landscape <span class="hlt">model</span> have little to do with ecological systems. Other landscape representations, however, are ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25196012','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25196012"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> for a multi-camera photogrammetric system.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Habib, Ayman; Detchev, Ivan; Kwak, Eunju</p> <p>2014-01-01</p> <p>Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue, and describes the existing methods for performing <span class="hlt">stability</span> <span class="hlt">analysis</span> for a single camera. The paper then points out the lack of coverage of <span class="hlt">stability</span> <span class="hlt">analysis</span> for multi-camera systems, suggests a modification of the collinearity <span class="hlt">model</span> to be used for the calibration of an entire photogrammetric system, and proposes three methods for system <span class="hlt">stability</span> <span class="hlt">analysis</span>. The proposed methods explore the impact of the changes in interior orientation and relative orientation/mounting parameters on the reconstruction process. Rather than relying on ground truth in real datasets to check the system calibration <span class="hlt">stability</span>, the proposed methods are simulation-based. Experiment results are shown, where a multi-camera photogrammetric system was calibrated three times, and <span class="hlt">stability</span> <span class="hlt">analysis</span> was performed on the system calibration parameters from the three sessions. The proposed simulation-based methods provided results that were compatible with a real-data based approach for evaluating the impact of changes in the system calibration parameters on the three-dimensional reconstruction. PMID:25196012</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4178982','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4178982"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> for a Multi-Camera Photogrammetric System</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Habib, Ayman; Detchev, Ivan; Kwak, Eunju</p> <p>2014-01-01</p> <p>Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue, and describes the existing methods for performing <span class="hlt">stability</span> <span class="hlt">analysis</span> for a single camera. The paper then points out the lack of coverage of <span class="hlt">stability</span> <span class="hlt">analysis</span> for multi-camera systems, suggests a modification of the collinearity <span class="hlt">model</span> to be used for the calibration of an entire photogrammetric system, and proposes three methods for system <span class="hlt">stability</span> <span class="hlt">analysis</span>. The proposed methods explore the impact of the changes in interior orientation and relative orientation/mounting parameters on the reconstruction process. Rather than relying on ground truth in real datasets to check the system calibration <span class="hlt">stability</span>, the proposed methods are simulation-based. Experiment results are shown, where a multi-camera photogrammetric system was calibrated three times, and <span class="hlt">stability</span> <span class="hlt">analysis</span> was performed on the system calibration parameters from the three sessions. The proposed simulation-based methods provided results that were compatible with a real-data based approach for evaluating the impact of changes in the system calibration parameters on the three-dimensional reconstruction. PMID:25196012</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120011835','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120011835"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> for HIFiRE Experiments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Li, Fei; Choudhari, Meelan M.; Chang, Chau-Lyan; White, Jeffery A.; Kimmel, Roger; Adamczak, David; Borg, Matthew; Stanfield, Scott; Smith, Mark S.</p> <p>2012-01-01</p> <p>The HIFiRE-1 flight experiment provided a valuable database pertaining to boundary layer transition over a 7-degree half-angle, circular cone <span class="hlt">model</span> from supersonic to hypersonic Mach numbers, and a range of Reynolds numbers and angles of attack. This paper reports selected findings from the ongoing computational <span class="hlt">analysis</span> of the measured in-flight transition behavior. Transition during the ascent phase at nearly zero degree angle of attack is dominated by second mode instabilities except in the vicinity of the cone meridian where a roughness element was placed midway along the length of the cone. The growth of first mode instabilities is found to be weak at all trajectory points analyzed from the ascent phase. For times less than approximately 18.5 seconds into the flight, the peak amplification ratio for second mode disturbances is sufficiently small because of the lower Mach numbers at earlier times, so that the transition behavior inferred from the measurements is attributed to an unknown physical mechanism, potentially related to step discontinuities in surface height near the locations of a change in the surface material. Based on the time histories of temperature and/or heat flux at transducer locations within the aft portion of the cone, the onset of transition correlated with a linear N-factor, based on parabolized <span class="hlt">stability</span> equations, of approximately 13.5. Due to the large angles of attack during the re-entry phase, crossflow instability may play a significant role in transition. Computations also indicate the presence of pronounced crossflow separation over a significant portion of the trajectory segment that is relevant to transition <span class="hlt">analysis</span>. The transition behavior during this re-entry segment of HIFiRE-1 flight shares some common features with the predicted transition front along the elliptic cone shaped HIFiRE-5 flight article, which was designed to provide hypersonic transition data for a fully 3D geometric configuration. To compare and contrast the crossflow dominated transition over the HIFiRE-1 and HIFiRE-5 configurations, this paper also analyzes boundary layer instabilities over a subscale <span class="hlt">model</span> of the HIFiRE-5 flight configuration that was tested in the Mach 6 quiet tunnel facility at Purdue University.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4786283','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4786283"><span id="translatedtitle"><span class="hlt">Stability</span> of Ensemble <span class="hlt">Models</span> Predicts Productivity of Enzymatic Systems</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Theisen, Matthew K.; Lafontaine Rivera, Jimmy G.; Liao, James C.</p> <p>2016-01-01</p> <p><span class="hlt">Stability</span> in a metabolic system may not be obtained if incorrect amounts of enzymes are used. Without <span class="hlt">stability</span>, some metabolites may accumulate or deplete leading to the irreversible loss of the desired operating point. Even if initial enzyme amounts achieve a stable steady state, changes in enzyme amount due to stochastic variations or environmental changes may move the system to the unstable region and lose the steady-state or quasi-steady-state flux. This situation is distinct from the phenomenon characterized by typical sensitivity <span class="hlt">analysis</span>, which focuses on the smooth change before loss of <span class="hlt">stability</span>. Here we show that metabolic networks differ significantly in their intrinsic ability to attain <span class="hlt">stability</span> due to the network structure and kinetic forms, and that after achieving <span class="hlt">stability</span>, some enzymes are prone to cause instability upon changes in enzyme amounts. We use Ensemble <span class="hlt">Modelling</span> for Robustness <span class="hlt">Analysis</span> (EMRA) to analyze <span class="hlt">stability</span> in four cell-free enzymatic systems when enzyme amounts are changed. Loss of <span class="hlt">stability</span> in continuous systems can lead to lower production even when the system is tested experimentally in batch experiments. The predictions of instability by EMRA are supported by the lower productivity in batch experimental tests. The EMRA method incorporates properties of network structure, including stoichiometry and kinetic form, but does not require specific parameter values of the enzymes. PMID:26963521</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/566792','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/566792"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of White Oak Dam</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p></p> <p>1995-04-11</p> <p>White Oak Dam is located in the White Oak Creek watershed which provides the primary surface drainage for Oak Ridge National Laboratory. A <span class="hlt">stability</span> <span class="hlt">analysis</span> was made on the dam by Syed Ahmed in January 1994 which included an evaluation of the liquefaction potential of the embankment and foundation. This report evaluates the <span class="hlt">stability</span> of the dam and includes comments on the report prepared by Ahmed. Slope <span class="hlt">stability</span> analyses were performed on the dam and included cases for sudden drawdown, steady seepage, partial pool and earthquake. Results of the <span class="hlt">stability</span> analyses indicate that the dam is stable and failure of the structure would not occur for the cases considered. The report prepared by Ahmed leads to the same conclusions as stated above. Review of the report finds that it is complete, well documented and conservative in its selection of soil parameters. The evaluation of the liquefaction potential is also complete and this report is in agreement with the findings that the dam and foundation are not susceptible to liquefaction.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6375664','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6375664"><span id="translatedtitle">Xenon <span class="hlt">stability</span> <span class="hlt">analysis</span> using the generalized nyquist criterion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Choi, Yoocho; Park, Gooncherl; Chung, Changhyun ); Park, Jongkyun</p> <p>1990-06-01</p> <p>Xenon-induced spatial power oscillations caused by control rod movement may cause control problems in nuclear power plant operation. Many studies have been performed to assess the xenon <span class="hlt">stability</span> <span class="hlt">analysis</span> using the time-domain technique or the frequency-domain technique for the single-input/single-output (SISO) system. However, those methods are too complicated and thus too time consuming, or too simple to provide results according to control rod movement in a certain position. This study analyzes xenon axial <span class="hlt">stability</span> using the modal expansion technique in the frequency domain with the generalized Nyquist criterion, which is suitable for a multi-input/multi-output (MIMO) system. To examine this <span class="hlt">model</span>, an axial <span class="hlt">stability</span> <span class="hlt">analysis</span> has been performed for the pressurized water reactor core of YGN-1 in Korea. The studied design parameters are power level, control rod position, and core average burnup.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.134..190G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.134..190G"><span id="translatedtitle">Aggregation in ecosystem <span class="hlt">models</span> and <span class="hlt">model</span> <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giricheva, Evgeniya</p> <p>2015-05-01</p> <p>Using a multimodal approach to research ecosystems improves usage of available information on an object. This study presents several <span class="hlt">models</span> of the Bering Sea ecosystem. The ecosystem is considered as a closed object, that is, the influence of the environment is not provided. We then add the links with the external medium in the <span class="hlt">models</span>. The <span class="hlt">models</span> differ in terms of the degree and method of grouping components. Our method is based on the differences in habitat and food source of groups, which allows us to determine the grouping of species with a greater effect on system dynamics. In particular, we determine whether benthic fish aggregation or pelagic fish aggregation can change the consumption structure of some groups of species, and consequently, the behavior of the entire <span class="hlt">model</span> system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26402034','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26402034"><span id="translatedtitle">Robust and convenient <span class="hlt">analysis</span> of protein thermal and chemical <span class="hlt">stability</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Niklasson, Markus; Andresen, Cecilia; Helander, Sara; Roth, Marie G L; Zimdahl Kahlin, Anna; Lindqvist Appell, Malin; Mrtensson, Lars-Gran; Lundstrm, Patrik</p> <p>2015-12-01</p> <p>We present the software CDpal that is used to analyze thermal and chemical denaturation data to obtain information on protein <span class="hlt">stability</span>. The software uses standard assumptions and equations applied to two-state and various types of three-state denaturation <span class="hlt">models</span> in order to determine thermodynamic parameters. It can analyze denaturation monitored by both circular dichroism and fluorescence spectroscopy and is extremely flexible in terms of input format. Furthermore, it is intuitive and easy to use because of the graphical user interface and extensive documentation. As illustrated by the examples herein, CDpal should be a valuable tool for <span class="hlt">analysis</span> of protein <span class="hlt">stability</span>. PMID:26402034</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22356563','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22356563"><span id="translatedtitle">A consistent orbital <span class="hlt">stability</span> <span class="hlt">analysis</span> for the GJ 581 system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Joiner, David A.; Sul, Cesar; Kress, Monika E.; Dragomir, Diana; Kane, Stephen R.</p> <p>2014-06-20</p> <p>We apply a combination of N-body <span class="hlt">modeling</span> techniques and automated data fitting with Monte Carlo Markov Chain uncertainty <span class="hlt">analysis</span> of Keplerian orbital <span class="hlt">models</span> to RV data to determine long-term <span class="hlt">stability</span> of the planetary system GJ 581. We find that while there are <span class="hlt">stability</span> concerns with the four-planet <span class="hlt">model</span> as published by Forveille et al., when uncertainties in the system are accounted for, particularly stellar jitter, the hypothesis that the four-planet <span class="hlt">model</span> is gravitationally unstable is not statistically significant. Additionally, the system including proposed planet g by Vogt et al. also shows some <span class="hlt">stability</span> concerns when eccentricities are allowed to float in the orbital fit, yet when uncertainties are included in the <span class="hlt">analysis</span>, the system including planet g also cannot be proven to be unstable. We present revised reduced χ{sup 2} values for Keplerian astrocentric orbital fits assuming four-planet and five-planet <span class="hlt">models</span> for GJ 581 under the condition that best fits must be stable, and we find no distinguishable difference by including planet g in the <span class="hlt">model</span>. Additionally, we present revised orbital element estimates for each, assuming uncertainties due to stellar jitter under the constraint of the system being gravitationally stable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21136868','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21136868"><span id="translatedtitle"><span class="hlt">STABILITY</span> <span class="hlt">ANALYSIS</span> OF THE ITER TF CONDUCTOR</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Savoldi Richard, L.; Zanino, R.</p> <p>2008-03-16</p> <p>The <span class="hlt">stability</span> <span class="hlt">analysis</span> of the reference Nb{sub 3}Sn conductor for the International Thermonuclear Experimental Reactor (ITER) Toroidal Field (TF) coils is performed using the Mithrandir code. From the point of view of the temperature margin, the most critical conductor in the winding pack, as well as the most critical location along it, is identified by a Vincenta code <span class="hlt">analysis</span>, which also provides the initial and boundary conditions for the <span class="hlt">stability</span> study. With this approach, the 1D Mithrandir <span class="hlt">analysis</span> can be restricted to the most critical conductor, using a much finer grid than Vincenta, in order to capture the details of normal zone initiation and possible recovery to SC state. Two different disturbances are considered: one short in space and time (0.01 m, 1 ms), simulating a disturbance of mechanical nature, the other longer (3 m, 100 ms), corresponding to AC losses (plasma disruption). Both disturbances are applied to the superconducting cable at end-of-burn, in the reference ITER inductive operation scenario. The grid-independence of the results was verified first. Since the results are strongly influenced by the choice of the heat transfer coefficient between strands and helium, this effect has been also parametrically investigated. In all cases, the computed minimum quench energies turn out to be above the level of the expected disturbances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21421147','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21421147"><span id="translatedtitle"><span class="hlt">Stability</span> of the Einstein static universe in open cosmological <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Canonico, Rosangela; Parisi, Luca</p> <p>2010-09-15</p> <p>The <span class="hlt">stability</span> properties of the Einstein static solution of general relativity are altered when corrective terms arising from modification of the underlying gravitational theory appear in the cosmological equations. In this paper the existence and <span class="hlt">stability</span> of static solutions are considered in the framework of two recently proposed quantum gravity <span class="hlt">models</span>. The previously known <span class="hlt">analysis</span> of the Einstein static solutions in the semiclassical regime of loop quantum cosmology with modifications to the gravitational sector is extended to open cosmological <span class="hlt">models</span> where a static neutrally stable solution is found. A similar <span class="hlt">analysis</span> is also performed in the framework of Horava-Lifshitz gravity under detailed balance and projectability conditions. In the case of open cosmological <span class="hlt">models</span> the two solutions found can be either unstable or neutrally stable according to the admitted values of the parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950016557','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950016557"><span id="translatedtitle">Shapes and <span class="hlt">stability</span> of algebraic nuclear <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lopez-Moreno, Enrique; Castanos, Octavio</p> <p>1995-01-01</p> <p>A generalization of the procedure to study shapes and <span class="hlt">stability</span> of algebraic nuclear <span class="hlt">models</span> introduced by Gilmore is presented. One calculates the expectation value of the Hamiltonian with respect to the coherent states of the algebraic structure of the system. Then equilibrium configurations of the resulting energy surface, which depends in general on state variables and a set of parameters, are classified through the Catastrophe theory. For one- and two-body interactions in the Hamiltonian of the interacting Boson <span class="hlt">model</span>-1, the critical points are organized through the Cusp catastrophe. As an example, we apply this Separatrix to describe the energy surfaces associated to the Rutenium and Samarium isotopes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED377217.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED377217.pdf"><span id="translatedtitle">The <span class="hlt">Stability</span> of Post Hoc <span class="hlt">Model</span> Modifications in Covariance Structure <span class="hlt">Models</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hutchinson, Susan R.</p> <p></p> <p>The work of R. MacCallum et al. (1992) was extended by examining chance modifications through a Monte Carlo simulation. The <span class="hlt">stability</span> of post hoc <span class="hlt">model</span> modifications was examined under varying sample size, <span class="hlt">model</span> complexity, and severity of misspecification using 2- and 4-factor oblique confirmatory factor <span class="hlt">analysis</span> (CFA) <span class="hlt">models</span> with four and eight</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22375786','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22375786"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> and future singularity of the m{sup 2} R □{sup -2} R <span class="hlt">model</span> of non-local gravity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dirian, Yves; Mitsou, Ermis E-mail: ermis.mitsou@unige.ch</p> <p>2014-10-01</p> <p>We analyse the classical <span class="hlt">stability</span> of the <span class="hlt">model</span> proposed by Maggiore and Mancarella, where gravity is modified by a term ∼ m{sup 2} R □{sup -2} R to produce the late-time acceleration of the expansion of the universe. Our study takes into account all excitations of the metric that can potentially drive an instability. There are some subtleties in identifying these modes, as a non-local field theory contains dynamical fields which yet do not correspond to degrees of freedom. Since some of them are ghost-like, we clarify the impact of such modes on the <span class="hlt">stability</span> of the solutions of interest that are the flat space-time and cosmological solutions. We then find that flat space-time is unstable under scalar perturbations, but the instability manifests itself only at cosmological scales, i.e. out of the region of validity of this solution. It is therefore the <span class="hlt">stability</span> of the FLRW solution which is relevant there, in which case the scalar perturbations are known to be well-behaved by numerical studies. By finding the analytic solution for the late-time behaviour of the scale factor, which leads to a big rip singularity, we argue that the linear perturbations are bounded in the future because of the domination of Hubble friction. In particular, this effect damps the scalar ghost perturbations which were responsible for destabilizing Minkowski space-time. Thus, the <span class="hlt">model</span> remains phenomenologically viable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/979539','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/979539"><span id="translatedtitle">Theory and <span class="hlt">modelling</span> of nanocarbon phase <span class="hlt">stability</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Barnard, A. S.</p> <p>2006-01-01</p> <p>The transformation of nanodiamonds into carbon-onions (and vice versa) has been observed experimentally and has been <span class="hlt">modeled</span> computationally at various levels of sophistication. Also, several analytical theories have been derived to describe the size, temperature and pressure dependence of this phase transition. However, in most cases a pure carbon-onion or nanodiamond is not the final product. More often than not an intermediary is formed, known as a bucky-diamond, with a diamond-like core encased in an onion-like shell. This has prompted a number of studies investigating the relative <span class="hlt">stability</span> of nanodiamonds, bucky-diamonds, carbon-onions and fullerenes, in various size regimes. Presented here is a review outlining results of numerous theoretical studies examining the phase diagrams and phase <span class="hlt">stability</span> of carbon nanoparticles, to clarify the complicated relationship between fullerenic and diamond structures at the nanoscale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/9348740','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/9348740"><span id="translatedtitle">Closed-loop <span class="hlt">stability</span> of pharmacokinetic-pharmacodynamic <span class="hlt">models</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wada, D R</p> <p>1997-12-01</p> <p>In automatic feedback control of intravenous drug infusions, convergence to the setpoint is an important objective. This paper examines the <span class="hlt">stability</span> of pharmacokinetic-pharmacodynamic <span class="hlt">models</span> of patient response regulated with proportional integral feedback. The <span class="hlt">model</span> consists of three components: linear compartmental pharmacokinetics, a first-order lag, and sigmoidal static pharmacodynamics. The permitted pharmacokinetic <span class="hlt">models</span> obey the principle of detailed balance and admit drug administration into and sampling from the same compartment. Convergence to the setpoint occurs if the reset time of the controller is greater than the maximum possible time constant of the first-order lag. The convergence <span class="hlt">analysis</span> uses standard Popov <span class="hlt">stability</span> theory and takes advantage of the little known fact that many pharmacokinetic <span class="hlt">models</span> possess poles and zeros that alternate on the negative real axis. PMID:9348740</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JGR...10419993L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JGR...10419993L"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of the plasma sheet using Hall magnetohydrodynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, D.-Y.</p> <p>1999-09-01</p> <p>Linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of the plasma sheet configuration is performed using Hall magnetohydrodynamics, which is more appropriate than the strict ideal MHD for the stressed current sheet during the substorm growth phase. By adding the Hall term in Ohm's law we study the impact of the error involved in assuming perfect conductivity on the <span class="hlt">stability</span>. The ballooning-like mode with large perpendicular wavenumber is considered, and its basic eigenmode equations are derived. The ballooning instability is currently one of the strong candidates for causing the substorm onset. Numerical computations of the eigenmode equations are carried out for some <span class="hlt">model</span> equilibria. It is found that the Hall-MHD effect is not so significant in determining the ballooning <span class="hlt">stability</span>, as the result is not much different from that of ideal MHD: (1) The ballooning instability is rather easily triggered in the <span class="hlt">model</span> where the field lines are not too much stretched but the plasma beta still exceeds some critical value, which depends on the situation; (2) The ballooning mode, however, seems to be <span class="hlt">stabilized</span> in the very stretched field <span class="hlt">models</span> and is not destabilized by adding the Hall-MHD effect in such <span class="hlt">models</span>. The result implies that the ballooning <span class="hlt">stability</span> in the plasma sheet seems to be much more dependent on equilibrium properties such as the field shape than on the physical formulation. It is further suggested that extensive field <span class="hlt">modeling</span> and subsequent tests for the ballooning mode are a high priority in future in order to establish a firm connection between ballooning instability and the substorm onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/814594','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/814594"><span id="translatedtitle">Truck Roll <span class="hlt">Stability</span> Data Collection and <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stevens, SS</p> <p>2001-07-02</p> <p>The principal objective of this project was to collect and analyze vehicle and highway data that are relevant to the problem of truck rollover crashes, and in particular to the subset of rollover crashes that are caused by the driver error of entering a curve at a speed too great to allow safe completion of the turn. The data are of two sorts--vehicle dynamic performance data, and highway geometry data as revealed by vehicle behavior in normal driving. Vehicle dynamic performance data are relevant because the roll <span class="hlt">stability</span> of a tractor trailer depends both on inherent physical characteristics of the vehicle and on the weight and distribution of the particular cargo that is being carried. Highway geometric data are relevant because the set of crashes of primary interest to this study are caused by lateral acceleration demand in a curve that exceeds the instantaneous roll <span class="hlt">stability</span> of the vehicle. An <span class="hlt">analysis</span> of data quality requires an evaluation of the equipment used to collect the data because the reliability and accuracy of both the equipment and the data could profoundly affect the safety of the driver and other highway users. Therefore, a concomitant objective was an evaluation of the performance of the set of data-collection equipment on the truck and trailer. The objective concerning evaluation of the equipment was accomplished, but the results were not entirely positive. Significant engineering apparently remains to be done before a reliable system can be fielded. Problems were identified with the trailer to tractor fiber optic connector used for this test. In an over-the-road environment, the communication between the trailer instrumentation and the tractor must be dependable. In addition, the computer in the truck must be able to withstand the rigors of the road. The major objective--data collection and <span class="hlt">analysis</span>--was also accomplished. Using data collected by instruments on the truck, a ''bad-curve'' database can be generated. Using this database, instrumented vehicles would not need roadside beacons. The speed, acceleration, and roll <span class="hlt">stability</span> of the vehicle could be determined prior to entering a curve, and a warning issued, if appropriate, for curves that have been characterized in the database. Thus, the <span class="hlt">analysis</span> indicates that the data can be effectively used to provide a timely warning of rollover risk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhFl...16.3755H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhFl...16.3755H"><span id="translatedtitle">Nonparallel linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of unconfined vortices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herrada, M. A.; Barrero, A.</p> <p>2004-10-01</p> <p>Parabolized <span class="hlt">stability</span> equations [F. P. Bertolotti, Th. Herbert, and P. R. Spalart, J. Fluid. Mech. 242, 441 (1992)] have been used to study the <span class="hlt">stability</span> of a family of swirling jets at high Reynolds numbers whose velocity and pressure fields decay far from the axis as rm-2 and r2(m-2), respectively [M. Prez-Saborid, M. A. Herrada, A. Gmez-Barea, and A. Barrero, J. Fluid. Mech. 471, 51 (2002)]; r is the radial distance and m is a real number in the interval 0<m<2. Results show that the nonparallel effects of the basic flow play an important role in the development of both axisymmetric and nonaxisymmetric unstable perturbations upstream of the vortex breakdown station. A complementary local nonparallel <span class="hlt">analysis</span> shows the convective nature of these instabilities. Therefore, a criterion based on the transition from convective to absolute instabilities cannot be applied to predict the vortex breakdown of this kind of swirling jets. On the contrary, the failure of the quasicylindrical approximation used to compute the downstream evolution of the basic flow gives a clear breakdown criterion based on the catastrophic transition between slender and nonslender flows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10148534','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10148534"><span id="translatedtitle">BWR <span class="hlt">stability</span> <span class="hlt">analysis</span> at Brookhaven National Laboratory</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wulff, W.; Cheng, H.S.; Mallen, A.N.; Rohatgi, U.S.</p> <p>1991-12-31</p> <p>Following the unexpected, but safely terminated, power and flow oscillations in the LaSalle-2 Boiling Water Reactor (BWR) on March 9, 1988, the Nuclear Regulatory Commission (NRC) Offices of Nuclear Reactor Regulation (NRR) and of <span class="hlt">Analysis</span> and Evaluation of Operational Data (AEOD) requested that the Office of Nuclear Regulatory Research (RES) carry out BWR <span class="hlt">stability</span> analyses, centered around fourteen specific questions. Ten of the fourteen questions address BWR <span class="hlt">stability</span> issues in general and are dealt with in this paper. The other four questions address local, out-of-phase oscillations and matters of instrumentation; they fall outside the scope of the work reported here. It was the purpose of the work documented in this report to answer ten of the fourteen NRC-stipulated questions. Nine questions are answered by analyzing the LaSalle-2 instability and related BWR transients with the BNL Engineering Plant Analyzer (EPA) and by performing an uncertainty assessment of the EPA predictions. The tenth question is answered on the basis of first principles. The ten answers are summarized</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5281766','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5281766"><span id="translatedtitle">BWR <span class="hlt">stability</span> <span class="hlt">analysis</span> at Brookhaven National Laboratory</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wulff, W.; Cheng, H.S.; Mallen, A.N.; Rohatgi, U.S.</p> <p>1991-01-01</p> <p>Following the unexpected, but safely terminated, power and flow oscillations in the LaSalle-2 Boiling Water Reactor (BWR) on March 9, 1988, the Nuclear Regulatory Commission (NRC) Offices of Nuclear Reactor Regulation (NRR) and of <span class="hlt">Analysis</span> and Evaluation of Operational Data (AEOD) requested that the Office of Nuclear Regulatory Research (RES) carry out BWR <span class="hlt">stability</span> analyses, centered around fourteen specific questions. Ten of the fourteen questions address BWR <span class="hlt">stability</span> issues in general and are dealt with in this paper. The other four questions address local, out-of-phase oscillations and matters of instrumentation; they fall outside the scope of the work reported here. It was the purpose of the work documented in this report to answer ten of the fourteen NRC-stipulated questions. Nine questions are answered by analyzing the LaSalle-2 instability and related BWR transients with the BNL Engineering Plant Analyzer (EPA) and by performing an uncertainty assessment of the EPA predictions. The tenth question is answered on the basis of first principles. The ten answers are summarized</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/929704','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/929704"><span id="translatedtitle">Kahler <span class="hlt">stabilized</span>, modular invariant heterotic string <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gaillard, Mary K.; Gaillard, Mary K.; Nelson, Brent D.</p> <p>2007-03-19</p> <p>We review the theory and phenomenology of effective supergravity theories based on orbifold compactifications of the weakly-coupled heterotic string. In particular, we consider theories in which the four-dimensional theory displays target space modular invariance and where the dilatonic mode undergoes Kahler <span class="hlt">stabilization</span>. A self-contained exposition of effective Lagrangian approaches to gaugino condensation and heterotic string theory is presented, leading to the development of the <span class="hlt">models</span> of Bintruy, Gaillard and Wu. Various aspects of the phenomenology of this class of <span class="hlt">models</span> are considered. These include issues of supersymmetry breaking and superpartner spectra, the role of anomalous U(1) factors, issues of flavor and R-parity conservation, collider signatures, axion physics, and early universe cosmology. For the vast majority of phenomenological considerations the theories reviewed here compare quite favorably to other string-derived <span class="hlt">models</span> in the literature. Theoretical objections to the framework and directions for further research are identified and discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090019073','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090019073"><span id="translatedtitle">Bounded Linear <span class="hlt">Stability</span> Margin <span class="hlt">Analysis</span> of Nonlinear Hybrid Adaptive Control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nguyen, Nhan T.; Boskovic, Jovan D.</p> <p>2008-01-01</p> <p>This paper presents a bounded linear <span class="hlt">stability</span> <span class="hlt">analysis</span> for a hybrid adaptive control that blends both direct and indirect adaptive control. <span class="hlt">Stability</span> and convergence of nonlinear adaptive control are analyzed using an approximate linear equivalent system. A <span class="hlt">stability</span> margin <span class="hlt">analysis</span> shows that a large adaptive gain can lead to a reduced phase margin. This method can enable metrics-driven adaptive control whereby the adaptive gain is adjusted to meet <span class="hlt">stability</span> margin requirements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000PhyA..286..133M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhyA..286..133M"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> for systems of nonlinear Hill's equations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahmoud, Gamal M.; Bountis, Tassos; Ahmed, Sayed A.</p> <p>2000-10-01</p> <p>Systems of nonlinear differential equations with periodic coefficients, which include Hill's and Mathieu's equations as examples in the linear limit, are important from a practical point of view. Nonlinear Hill's equations <span class="hlt">model</span> a variety of dynamical systems of interest to physics and engineering, in which perturbations enter as periodic modulations of their linear frequencies. As is well known, the <span class="hlt">stability</span> properties of some fundamental periodic solutions of these systems is often an essential problem. The main purpose of this paper is to concentrate on one such class of nonlinear Hill's equations and study the <span class="hlt">stability</span> properties of some of their simplest periodic solutions analytically as well as numerically. To accomplish this task, we first use an extension of the generalized averaging method to approximate these solutions and then apply the technique of multiple scaling to perform the <span class="hlt">stability</span> <span class="hlt">analysis</span>. A three-particle system with free-free boundary conditions is studied as an example. The accuracy of our results is tested, within the limits of first-order perturbation theory, and is found to be well confirmed by numerical experiments. The <span class="hlt">stability</span> <span class="hlt">analysis</span> of these simple periodic solutions, though local in itself, can yield considerable information about more global properties of the dynamics, since it is in the vicinity of such solutions that the largest regions of regular or chaotic motion are usually observed, depending on whether the periodic solution is, respectively, stable or unstable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009LNCS.5508...14F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009LNCS.5508...14F"><span id="translatedtitle"><span class="hlt">Stability</span> of a Distributed Generation Network Using the Kuramoto <span class="hlt">Models</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fioriti, Vincenzo; Ruzzante, Silvia; Castorini, Elisa; Marchei, Elena; Rosato, Vittorio</p> <p></p> <p>We derive a Kuramoto-like equation from the Cardell-Ilic distributed electrical generation network and use the resulting <span class="hlt">model</span> to simulate the phase <span class="hlt">stability</span> and the synchronization of a small electrical grid. It is well-known that a major problem for distributed generation is the frequency <span class="hlt">stability</span>. This is a non linear problem and proper <span class="hlt">models</span> for <span class="hlt">analysis</span> are sorely lacking. In our <span class="hlt">model</span> nodes are arranged in a regular lattice; the strength of their couplings are randomly chosen and allowed to vary as square waves. Although the system undergoes several synchronization losses, nevertheless it is able to quickly resynchronize. Moreover, we show that the synchronization rising-time follows a power-law.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhRvE..88f2109Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhRvE..88f2109Z"><span id="translatedtitle"><span class="hlt">Stability</span> of earthquake clustering <span class="hlt">models</span>: Criticality and branching ratios</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhuang, Jiancang; Werner, Maximilian J.; Harte, David S.</p> <p>2013-12-01</p> <p>We study the <span class="hlt">stability</span> conditions of a class of branching processes prominent in the <span class="hlt">analysis</span> and <span class="hlt">modeling</span> of seismicity. This class includes the epidemic-type aftershock sequence (ETAS) <span class="hlt">model</span> as a special case, but more generally comprises <span class="hlt">models</span> in which the magnitude distribution of direct offspring depends on the magnitude of the progenitor, such as the branching aftershock sequence (BASS) <span class="hlt">model</span> and another recently proposed branching <span class="hlt">model</span> based on a dynamic scaling hypothesis. These <span class="hlt">stability</span> conditions are closely related to the concepts of the criticality parameter and the branching ratio. The criticality parameter summarizes the asymptotic behavior of the population after sufficiently many generations, determined by the maximum eigenvalue of the transition equations. The branching ratio is defined by the proportion of triggered events in all the events. Based on the results for the generalized case, we show that the branching ratio of the ETAS <span class="hlt">model</span> is identical to its criticality parameter because its magnitude density is separable from the full intensity. More generally, however, these two values differ and thus place separate conditions on <span class="hlt">model</span> <span class="hlt">stability</span>. As an illustration of the difference and of the importance of the <span class="hlt">stability</span> conditions, we employ a version of the BASS <span class="hlt">model</span>, reformulated to ensure the possibility of stationarity. In addition, we analyze the magnitude distributions of successive generations of the BASS <span class="hlt">model</span> via analytical and numerical methods, and find that the compound density differs substantially from a Gutenberg-Richter distribution, unless the process is essentially subcritical (branching ratio less than 1) or the magnitude dependence between the parent event and the direct offspring is weak.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1181205','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1181205"><span id="translatedtitle"><span class="hlt">Analysis</span> of the <span class="hlt">stability</span> of looped-out and stacked-in conformations of an adenine bulge in DNA using a continuum <span class="hlt">model</span> for solvent and ions.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zacharias, M; Sklenar, H</p> <p>1997-01-01</p> <p>A combination of conformational search, energy minimization, and energetic evaluation using a continuum solvent treatment has been employed to study the <span class="hlt">stability</span> of various conformations of the DNA fragment d(CGCAGAA)/d(TTCGCG) containing a single adenine bulge. The extra-helical (looped-out) bulge conformation derived from a published x-ray structure and intra-helical (stacked bulge base) <span class="hlt">model</span> structures partially based on nuclear magnetic resonance (NMR) data were used as start structures for the conformational search. Solvent-dependent contributions to the <span class="hlt">stability</span> of the conformations were calculated from the solvent exposed molecular surface area and by using the finite difference Poisson-Boltzmann approach. Three classes (I-III) of bulge conformations with calculated low energies can be distinguished. The lowest-energy conformations were found in class I, corresponding to structures with the bulge base stacked between flanking helices, and class II, composed of structures forming a triplet of the bulge base and a flanking base pair. All extra-helical bulge structures, forming class III, were found to be less stable compared with the lowest energy structures of class I and II. The results are consistent with NMR data on an adenine bulge in the same sequence context indicating an intra-helical or triplet bulge conformation in solution. Although the total energies and total electrostatic energies of the low-energy conformations show only relatively modest variations, the energetic contributions to the <span class="hlt">stability</span> were found to vary significantly among the classes of bulge structures. All intra-helical bulge structures are <span class="hlt">stabilized</span> by a more favorable Coulomb charge-charge interaction but destabilized by a larger electrostatic reaction field contribution compared with all extra-helical and most triplet bulge structures. Van der Waals packing interactions and nonpolar surface-area-dependent contributions appear to favor triplet class II structures and to a lesser degree also the intra-helical stacked bulge conformations. The large conformational variation found for class III conformers might add a favorable entropic contribution to the <span class="hlt">stability</span> of the extra-helical bulge form. PMID:9414214</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6555A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6555A"><span id="translatedtitle">Robustness for slope <span class="hlt">stability</span> <span class="hlt">modelling</span> under deep uncertainty</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Almeida, Susana; Holcombe, Liz; Pianosi, Francesca; Wagener, Thorsten</p> <p>2015-04-01</p> <p>Landslides can have large negative societal and economic impacts, such as loss of life and damage to infrastructure. However, the ability of slope <span class="hlt">stability</span> assessment to guide management is limited by high levels of uncertainty in <span class="hlt">model</span> predictions. Many of these uncertainties cannot be easily quantified, such as those linked to climate change and other future socio-economic conditions, restricting the usefulness of traditional decision <span class="hlt">analysis</span> tools. Deep uncertainty can be managed more effectively by developing robust, but not necessarily optimal, policies that are expected to perform adequately under a wide range of future conditions. Robust strategies are particularly valuable when the consequences of taking a wrong decision are high as is often the case of when managing natural hazard risks such as landslides. In our work a physically based numerical <span class="hlt">model</span> of hydrologically induced slope instability (the Combined Hydrology and <span class="hlt">Stability</span> <span class="hlt">Model</span> - CHASM) is applied together with robust decision making to evaluate the most important uncertainties (storm events, groundwater conditions, surface cover, slope geometry, material strata and geotechnical properties) affecting slope <span class="hlt">stability</span>. Specifically, impacts of climate change on long-term slope <span class="hlt">stability</span> are incorporated, accounting for the deep uncertainty in future climate projections. Our findings highlight the potential of robust decision making to aid decision support for landslide hazard reduction and risk management under conditions of deep uncertainty.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DPPGP8049S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DPPGP8049S"><span id="translatedtitle">Fully Parallel MHD <span class="hlt">Stability</span> <span class="hlt">Analysis</span> Tool</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Svidzinski, Vladimir; Galkin, Sergei; Kim, Jin-Soo; Liu, Yueqiang</p> <p>2014-10-01</p> <p>Progress on full parallelization of the plasma <span class="hlt">stability</span> code MARS will be reported. MARS calculates eigenmodes in 2D axisymmetric toroidal equilibria in MHD-kinetic plasma <span class="hlt">models</span>. It is a powerful tool for studying MHD and MHD-kinetic instabilities and it is widely used by fusion community. Parallel version of MARS is intended for simulations on local parallel clusters. It will be an efficient tool for simulation of MHD instabilities with low, intermediate and high toroidal mode numbers within both fluid and kinetic plasma <span class="hlt">models</span>, already implemented in MARS. Parallelization of the code includes parallelization of the construction of the matrix for the eigenvalue problem and parallelization of the inverse iterations algorithm, implemented in MARS for the solution of the formulated eigenvalue problem. Construction of the matrix is parallelized by distributing the load among processors assigned to different magnetic surfaces. Parallelization of the solution of the eigenvalue problem is made by repeating steps of the present MARS algorithm using parallel libraries and procedures. Initial results of the code parallelization will be reported. Work is supported by the U.S. DOE SBIR program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SSEle.113...28F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SSEle.113...28F"><span id="translatedtitle">Physics-based <span class="hlt">stability</span> <span class="hlt">analysis</span> of MOS transistors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferrara, A.; Steeneken, P. G.; Boksteen, B. K.; Heringa, A.; Scholten, A. J.; Schmitz, J.; Hueting, R. J. E.</p> <p>2015-11-01</p> <p>In this work, a physics-based <span class="hlt">model</span> is derived based on a linearization procedure for investigating the electrical, thermal and electro-thermal instability of power metal-oxide-semiconductor (MOS) transistors. The proposed <span class="hlt">model</span> can be easily interfaced with a circuit or device simulator to perform a failure <span class="hlt">analysis</span>, making it particularly useful for power transistors. Furthermore, it allows mapping the failure points on a three-dimensional (3D) space defined by the gate-width normalized drain current, drain voltage and junction temperature. This leads to the definition of the Safe Operating Volume (SOV), a powerful frame work for making failure predictions and determining the main root of instability (electrical, thermal or electro-thermal) in different bias and operating conditions. A comparison between the <span class="hlt">modeled</span> and the measured SOV of silicon-on-insulator (SOI) LDMOS transistors is reported to support the validity of the proposed <span class="hlt">stability</span> <span class="hlt">analysis</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/12852904','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/12852904"><span id="translatedtitle">Simplified <span class="hlt">model</span> and <span class="hlt">stabilization</span> of SSFP sequences.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Le Roux, Patrick</p> <p>2003-07-01</p> <p>Steady-state free precession (SSFP) is used today in a form similar to other rapid sequences like fast spin echo (FSE) where a large longitudinal magnetization is present at the beginning of the train of excitations. This results in a transient behavior which impedes any measurement before the steady state is established. Several solutions have been proposed to <span class="hlt">stabilize</span> the signals more quickly. Starting from a simplified <span class="hlt">model</span> of signal generation, and by a suitable change of reference frame, this paper justifies theoretically the linear ramp-up proposed by Nishimura and Vasanawala (p. 301, 8th Annual Proceedings of ISMRM, 2000, Denver). This linear ramp-up can be generalized into a one giving less oscillatory residues. The solution is efficient in the sense that it does not require nutation angles larger than the one used during the <span class="hlt">stabilized</span> period. Also, this solution is robust because it scales up or down nicely and is thus insensitive to B(1) variations. PMID:12852904</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008APS..DFD.HF009M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008APS..DFD.HF009M"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of an evaporating binary mixture</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Machrafi, Hatim; Rednikov, Alexey; Colinet, Pierre; Dauby, Pierre</p> <p>2008-11-01</p> <p>Rayleigh-Bénard-Marangoni instabilities in an evaporating binary mixture, consisting of a solvent and a solute of weak concentration, are studied theoretically. Local thermodynamic equilibrium is assumed at the flat gas-liquid interface. Solvent evaporation and air absorption in the liquid are neglected. At a certain height above the interface, the temperature and the concentration are fixed. One of the goals of the study is to track down the effects of this artifact on the results. Non-linear quasi-stationary basic profiles (due to evaporation) of the temperature and the solute concentration in the gas phase are considered, while the temperature distribution in the liquid is assumed to be linear and quasi-stationary. For the solute concentration in the liquid phase, two variants of the reference solution are studied, one just linear and quasi-stationary, whereas the other involves a fully transient non-linear profile. The latter is a more realistic option, given the relatively slow diffusion time in the liquid. A linear <span class="hlt">stability</span> <span class="hlt">analysis</span> is then carried out numerically, and illustrated for an aqueous solution of ethyl alcohol.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.5753A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.5753A"><span id="translatedtitle">Wellbore <span class="hlt">stability</span> <span class="hlt">analysis</span> during the production of a carbonate reservoir</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alves, J.-L.; Coehlo, L.; Baud, P.; Guevara Junior, N.</p> <p>2009-04-01</p> <p>Carbonate reservoirs represent a major part of the world oil and gas reserves. During production, the extraction of hydrocarbons reduces pore pressure and thus causes an increase in the effective stress and mechanical compaction in the reservoir. The compactive deformation and failure may be spatially extensive or localized to the vicinity of the wellbore, but in either case the consequences can be economically severe involving surface subsidence, well failure and various production problems. The <span class="hlt">analysis</span> of wellbore <span class="hlt">stability</span> and more generally of deformation and failure in carbonate environments hinges upon a relevant constitutive <span class="hlt">modeling</span> of carbonate rocks over a wide range of porosities. In this study, we performed a wellbore <span class="hlt">stability</span> <span class="hlt">analysis</span> for a lateral wellbore junction in three dimensions. The complex geometry for the wellbore junction was <span class="hlt">modeled</span> with tetrahedral finite elements considering a rate independent elastic-plastic isotropic material that presented linear behavior during elastic strain and associated flow rule. A finite element <span class="hlt">model</span> simulating drilling and production phases were done for field conditions from a deep water reservoir in Campos basin, offshore Brazil. In this context, several scenarios were studied considering true 3D orientation for both in situ stresses and geometry of the wellbore junction itself. We discussed the impact of constitutive <span class="hlt">modeling</span> on the wellbore <span class="hlt">stability</span>, based on new experimental data on two micritic porous carbonates. Series of conventional triaxial experiments were performed at room temperature in dry and wet conditions on samples of Comiso and Tavel limestones of respective porosity 17 and 16%. The wet samples were deformed in drained conditions with 10 MPa pore pressure. The initial yield stresses were identified as the critical stresses at the onset of shear-enhanced compaction, subsequent yield stresses were considered to depend on hardening given by the plastic volumetric strain. For both limestones, we found that water had a moderate effect on the yield stresses but influenced significantly the hardening behavior of the rocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6853993','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6853993"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of large electric power systems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Elwood, D.M.</p> <p>1993-01-01</p> <p>Modern electric power systems are large and complicated, and, in many regions of the world, the generation and transmission systems are operating near their limits. Ensuring the reliable operation of the power system requires engineers to study the response of the system to various disturbances. The responses to large disturbances are examined by numerically solving the nonlinear differential-algebraic equations describing the power system. The response to small disturbances is typically studied via eigenanalysis. The Electric Power Research Institute (EPRI) recently developed the Extended Transient/Mid-term <span class="hlt">Stability</span> Program (ETMSP) to study large disturbance <span class="hlt">stability</span> and the Small Signal <span class="hlt">Stability</span> Program Package (SSSP) to study small signal <span class="hlt">stability</span>. The primary objectives of the work described in this report were to (1) explore ways of speeding up ETMSP, especially on mid-term voltage <span class="hlt">stability</span> problems, (2) explore ways of speeding up the Multi-Area Small-Signal <span class="hlt">Stability</span> program (MASS), one of the codes in SSSP, and (3) explore ways of increasing the size of problem that can be solved by the Cray version of MASS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12..652H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12..652H"><span id="translatedtitle">Landslide <span class="hlt">stability</span> <span class="hlt">analysis</span> on basis of LIDAR data extraction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, Hui; Fernandez-Steeger, Tomas M.; Dong, Mei; Azzam, Rafig</p> <p>2010-05-01</p> <p>Currently, existing contradictory between remediation and acquisition from natural resource induces a series of divergences. With regard to open pit mining, legal regulation requires human to fill back the open pit area with water or recreate new landscape by other materials; on the other hand, human can not help excavating the mining area due to the shortage of power resource. However, to engineering geologists, one coincident problem which takes place not only in filling but also in mining operation should be paid more attention to, i.e. the slope <span class="hlt">stability</span> <span class="hlt">analysis</span> within these areas. There are a number of construction activities during remediation or mining process which can directly or indirectly cause slope failure. Lives can be endangered since local failure either while or after remediation; for mining process, slope failure in a bench, which carries a main haul road or is adjacent to human activity area, would be significant catastrophe to the whole mining program. The <span class="hlt">stability</span> of an individual bench or slope is controlled by several factors, which are geological condition, morphology, climate, excavation techniques and transportation approach. The task which takes the longest time is to collect the morphological data. Consequently, it is one of the most dangerous tasks due to the time consuming in mining field. LIDAR scanning for morphological data collecting can help to skip this obstacle since advantages of LIDAR techniques as follows: Dynamic range available on the market: from 3 m to beyond 1 km, Ruggedly designed for demanding field applications, Compact, easily hand-carried and deployed by a single operator. In 2009, scanning campaigns for 2 open pit quarry have been carried out. The aim for these LIDAR detections is to construct a detailed 3D quarry <span class="hlt">model</span> and analyze the bench <span class="hlt">stability</span> to support the filling planning. The 3D quarry surface was built up by using PolyWorks 10.1 on basis of LIDAR data. LIDAR data refining takes an important role during surface construction for further more precise <span class="hlt">analysis</span> purpose. 3D geological <span class="hlt">model</span> can be built based on the connection between surface <span class="hlt">model</span> and geological data like borehole data in GOCAD. Regarding the bench <span class="hlt">stability</span> <span class="hlt">analysis</span>, LEM (Limit Equilibrium Method) <span class="hlt">analysis</span> using Janbu and FEM (Finite Element Method) have been adopted during this analyzing task. A program was developed to convert GOCAD 2D section data directly into the FEM software. The meshed <span class="hlt">model</span> is then used for <span class="hlt">stability</span> <span class="hlt">analysis</span>. In one quarry, 3 cross sections have been extracted on basis of LIDAR original data (original 3 cross sections). To evaluate the advantages of LIDAR data for slope <span class="hlt">analysis</span>, the results of safety factor (SF) were compared to simplified slope <span class="hlt">models</span> as they are used normally. The comparison showed that variations of the SF reach up to 9%. Additionally, conservative evaluation demonstrated by SF results based on simplified <span class="hlt">model</span> is not adaptive for decision making of filling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000ApJ...535..190S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000ApJ...535..190S"><span id="translatedtitle">Singular Isothermal Disks. I. Linear <span class="hlt">Stability</span> <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shu, Frank H.; Laughlin, Gregory; Lizano, Susana; Galli, Daniele</p> <p>2000-05-01</p> <p>As part of a larger effort to understand how binary and single stars form from the collapse of magnetized molecular cloud cores, we perform a global <span class="hlt">stability</span> <span class="hlt">analysis</span> of isopedically magnetized, singular isothermal disks (SIDs). The work described here has precedents in earlier studies of disturbances in power-law disks by Zang in 1976, Toomre in 1977, Lynden-Bell & Lemos in 1993, Syer & Tremaine in 1996, and Goodman & Evans in 1999. We find the analytic criteria for the bifurcation of axisymmetric disks into nonaxisymmetric forms with azimuthal periodicities m=1 (eccentric displacements), 2 (oval distortions), 3 (triangular distortions), etc. These bifurcations, which occur at zero frequency, are the compressible and differentially rotating analogs of how the classical sequence of incompressible and uniformly rotating Maclaurin spheroids bifurcate (secularly, under dissipative forces) to become Dedekind ellipsoids with figure axes that remain fixed in space. Like Syer & Tremaine and Lynden-Bell & Lemos, we also find that zero-frequency logarithmic spirals are possible scale-free disturbances, but our interpretation of the existence of such steadily propagating wavetrains is different. We give a dynamical instability interpretation based on the onset of swing amplification by overreflection at the corotation circle of prograde spiral density waves the pattern speeds of which have nonzero and positive values. Our <span class="hlt">analysis</span> yields identical instability criteria as the global normal-modes treatment of Goodman & Evans, and we tentatively also identify dynamical barred-spiral instabilities as the ``breathing mode'' limit of two-armed ordinary-spiral instabilities. We prove a general ``reciprocity theorem,'' which states that the overreflection factors are identical for spiral density waves launched from cavities interior or exterior to Q-barriers that straddle the corotation circle. This globally valid result supports a unifying interpretation, advocated for many years by C. C. Lin and his colleagues (see, e.g., work by Bertin & Lin): the coexistence of spiral structure in galaxies arising from the instability of internal normal modes in the combined star/gas disk or from driving by external tidal influences associated with the chance passages of companion bodies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7472S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7472S"><span id="translatedtitle"><span class="hlt">Analysis</span> of slope <span class="hlt">stabilization</span> by soil bioengineering method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Switala, Barbara Maria; Wu, Wei</p> <p>2013-04-01</p> <p>The aim of the project is to create a numerical <span class="hlt">model</span> which will include the impact of vegetation on the slope <span class="hlt">stability</span> <span class="hlt">analysis</span>, considering both mechanical and hydrological factors. This will enrich the current knowledge about how roots reinforce the soil layers on the slope and how it influences the increase of shear strength of the soil. This has to be combined together with hydrological effects caused by evapotranspiration: modified soil moisture regime, dissipation of excess pore pressure and established matric suction. Coupled analyses (mechanical and hydrological) are rarely conducted, or only outdated <span class="hlt">models</span> are used, which leads to overestimation of the additional shear strength of soil. That is why there is a need to support this branch of landslide hazard assessment and develop a new <span class="hlt">model</span>. This research will help to raise awareness, that soil bioengineering methods of slope <span class="hlt">stabilization</span> can in some cases be more appropriate and less expensive than traditional methods. As an input to the <span class="hlt">model</span>, the appropriate slope geometry and soil properties have to be chosen. It is also important to consider different plant types and root properties, as well as different levels of groundwater table. To assess the effect of evapotranspiration it is necessary to know the geographical location of the slope and the weather conditions in the chosen region. The final output of the <span class="hlt">model</span>, which will help to quantitatively assess the impact of vegetation on the slope <span class="hlt">stability</span>, is the factor of safety (FOS) for vegetated slope for different types of soil and degrees of saturation. Results may then be compared with different conditions and factors of safety, calculated for the corresponding non-vegetated slope. It will be possible to specify the most favorable and unfavorable conditions. Moreover, the calculations provide also information on changes of cohesion, caused by mechanical and hydrological effects, as well as the change in the friction angle of soil.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6873395','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6873395"><span id="translatedtitle">CG-DAMS: Concrete gravity dam <span class="hlt">stability</span> <span class="hlt">analysis</span> software</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1993-01-01</p> <p>CG-DAMS is a finite element based program written specifically for the <span class="hlt">stability</span> <span class="hlt">analysis</span> of concrete gravity dams. The code automates the prediction and evaluation of cracking in the dam, along the dam-rock interface, and in the foundation using incremental nonlinear <span class="hlt">analysis</span> techniques based on the smeared crack'' approach. Its primary application is in the computation of dam-rock interface sliding <span class="hlt">stability</span> factors of safety. The automated procedure for crack propagation <span class="hlt">analysis</span> replaces the trial-and-error cracked-base <span class="hlt">analysis</span> method commonly used in gravity dam safety analyses. This Application manual of CG-DAMS illustrates, through sample problems, the many features of the software. Example problems illustrate the capabilities of both CG-DAMS-PC and CG-DAMS-ABAQUS. CG-DAMS-PC is a menu driven program that runs on 386/486 PCs under the DOS operating system (4 Megabytes RAM, 25 Megabytes of hard disk space). CG-DAMS-ABAQUS is a pre- and post-processor along with a concrete constitutive <span class="hlt">model</span> and distributed load module that interfaces with the ABAQUS general purpose finite element program. The PC program contains thermal <span class="hlt">analysis</span> capabilities, a rough crack constitutive <span class="hlt">model</span>, and an interface to the CRFLOOD software not available with the ABAQUS version. The CG-DAMS-ABAQUS program contains time marching dynamic <span class="hlt">analysis</span> capabilities not available with the PC program. Example analyses presented include static, pseudo dynamic, and time marching dynamic analyses. The manual also presents sensitivity evaluations on mesh size and foundation material strength. Comparisons are presented between CG-DAMS and gravity method calculations. Comparisons with other finite element software are included for the dynamic time history analyses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JCli...17.1004B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JCli...17.1004B"><span id="translatedtitle">Dynamic <span class="hlt">Stabilization</span> of Atmospheric Single Column <span class="hlt">Models</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bergman, John W.; Sardeshmukh, Prashant D.</p> <p>2004-03-01</p> <p>Single column <span class="hlt">models</span> (SCMs) provide an economical framework for assessing the sensitivity of atmospheric temperature and humidity to natural and imposed perturbations, and also for developing improved representations of diabatic processes in weather and climate <span class="hlt">models</span>. Their economy is achieved at the expense of ignoring interactions with the circulation dynamics; thus, advection by the large-scale flow is either prescribed or neglected. This artificial decoupling of the diabatic and adiabatic tendencies can often cause rapid error growth in SCM integrations, especially in the Tropics where large-scale vertical advection is important. As a result, SCMs can quickly develop highly unrealistic thermodynamic structures, making it pointless to study their subsequent evolution.This paper suggests one way around this fundamental difficulty through a simple coupling of the diabatic and adiabatic tendencies. In essence, the local vertical velocity at any instant is specified by a formula that links the local vertical temperature advection to the evolution of SCM-generated diabatic heating rates up to that instant. This vertical velocity is then used to determine vertical humidity advection, and also horizontal temperature and humidity advection under an additional assumption that the column is embedded in a uniform environment. The parameters in the formula are estimated in a separate set of calculations, from the approach to equilibrium of a linearized global primitive equation <span class="hlt">model</span> forced by steady heat sources. As a test, the parameterized dynamics are used to predict the linear <span class="hlt">model</span>'s local response to oscillating heat sources, and found to perform remarkably well over a wide range of space and time scales. In a second test, the parameterization is found to capture important aspects of a general circulation <span class="hlt">model</span>'s vertical advection and temperature tendencies and their lead lag relationships with diabatic heating fluctuations at convectively active locations in the Tropics.When implemented in the NCAR SCM, the dynamically coupled SCM shows a clear improvement over its uncoupled counterpart for tropical conditions observed during the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE). Coupling effectively <span class="hlt">stabilizes</span> the SCM. As a result, short-term prediction errors are substantially reduced, the ensemble spread is reduced in ensemble runs, and the SCM is able to maintain realistic thermodynamic structures in extended runs. Such a dynamically coupled SCM should therefore be more useful not only for isolating physical parameterization errors in weather and climate <span class="hlt">models</span>, but also for economical simulations of regional climate variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19860005824&hterms=friedmann+1985&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfriedmann%2B1985','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19860005824&hterms=friedmann+1985&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfriedmann%2B1985"><span id="translatedtitle">Influence of various unsteady aerodynamic <span class="hlt">models</span> on the aeromechanical <span class="hlt">stability</span> of a helicopter in ground resonance</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Friedmann, P. P.; Venkatesan, C.</p> <p>1985-01-01</p> <p>The aeromechanical <span class="hlt">stability</span> of a helicopter in ground resonance was analyzed, by incorporating five different aerodynamic <span class="hlt">models</span> in the coupled rotor/fuselage <span class="hlt">analysis</span>. The sensitivity of the results to changes in aerodynamic <span class="hlt">modelling</span> was carefully examined. The theoretical results were compared with experimental data and useful conclusions are drawn regarding the role of aerodynamic <span class="hlt">modeling</span> on this aeromechanical <span class="hlt">stability</span> problem. The aerodynamic <span class="hlt">model</span> which provided the best all around correlation with the experimental data was identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930091789','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930091789"><span id="translatedtitle"><span class="hlt">Analysis</span> and prediction of longitudinal <span class="hlt">stability</span> of airplanes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gilruth, R R; White, M D</p> <p>1941-01-01</p> <p>An <span class="hlt">analysis</span> has been made of the longitudinal <span class="hlt">stability</span> characteristics of 15 airplanes as determined in flight. In the correlation of satisfactory and unsatisfactory characteristics with determined values, the derivative that expresses the ratio of static-restoring moments to elevator-control moments was found to represent most nearly the <span class="hlt">stability</span> characteristics appreciated by the pilots. The <span class="hlt">analysis</span> was extended to study the effects of various design features on the observed <span class="hlt">stability</span> characteristics. Design charts and data are included that show the effects on longitudinal <span class="hlt">stability</span> of relative positions of wing and tail, fuselage size and location, engine nacelles, and horizontal-tail arrangements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999CMaPh.204..551L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999CMaPh.204..551L"><span id="translatedtitle">Nonlinear <span class="hlt">Stability</span> of Weak Detonation Wavesfor a Combustion <span class="hlt">Model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Tai-Ping; Yu, Shih-Hsien</p> <p></p> <p>We show that the weak detonation waves for a combustion <span class="hlt">model</span> of Rosales-Majda are nonlinearly stable. Because of the strongly nonlinear nature of the wave, usual <span class="hlt">stability</span> <span class="hlt">analysis</span> of weakly nonlinear nature does not apply. The chemical switch on-off is the main feature of nonlinearity. In particular, the propagation of the wave depends sensitively on the tail behaviour of the flow in front of it. Unlike the strong detonation waves, a weak detonation is supersonic and there is the separation of the gas waves from the reacting front. As a consequence, the reacting front needs to be traced.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT........43D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT........43D"><span id="translatedtitle">Theoretical foundations for finite-time transient <span class="hlt">stability</span> and sensitivity <span class="hlt">analysis</span> of power systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dasgupta, Sambarta</p> <p></p> <p>Transient <span class="hlt">stability</span> and sensitivity <span class="hlt">analysis</span> of power systems are problems of enormous academic and practical interest. These classical problems have received renewed interest, because of the advancement in sensor technology in the form of phasor measurement units (PMUs). The advancement in sensor technology has provided unique opportunity for the development of real-time <span class="hlt">stability</span> monitoring and sensitivity <span class="hlt">analysis</span> tools. Transient <span class="hlt">stability</span> problem in power system is inherently a problem of <span class="hlt">stability</span> <span class="hlt">analysis</span> of the non-equilibrium dynamics, because for a short time period following a fault or disturbance the system trajectory moves away from the equilibrium point. The real-time <span class="hlt">stability</span> decision has to be made over this short time period. However, the existing <span class="hlt">stability</span> definitions and hence <span class="hlt">analysis</span> tools for transient <span class="hlt">stability</span> are asymptotic in nature. In this thesis, we discover theoretical foundations for the short-term transient <span class="hlt">stability</span> <span class="hlt">analysis</span> of power systems, based on the theory of normally hyperbolic invariant manifolds and finite time Lyapunov exponents, adopted from geometric theory of dynamical systems. The theory of normally hyperbolic surfaces allows us to characterize the rate of expansion and contraction of co-dimension one material surfaces in the phase space. The expansion and contraction rates of these material surfaces can be computed in finite time. We prove that the expansion and contraction rates can be used as finite time transient <span class="hlt">stability</span> certificates. Furthermore, material surfaces with maximum expansion and contraction rate are identified with the <span class="hlt">stability</span> boundaries. These <span class="hlt">stability</span> boundaries are used for computation of <span class="hlt">stability</span> margin. We have used the theoretical framework for the development of <span class="hlt">model</span>-based and <span class="hlt">model</span>-free real-time <span class="hlt">stability</span> monitoring methods. Both the <span class="hlt">model</span>-based and <span class="hlt">model</span>-free approaches rely on the availability of high resolution time series data from the PMUs for <span class="hlt">stability</span> prediction. The problem of sensitivity <span class="hlt">analysis</span> of power system, subjected to changes or uncertainty in load parameters and network topology, is also studied using the theory of normally hyperbolic manifolds. The sensitivity <span class="hlt">analysis</span> is used for the identification and rank ordering of the critical interactions and parameters in the power network. The sensitivity <span class="hlt">analysis</span> is carried out both in finite time and in asymptotic. One of the distinguishing features of the asymptotic sensitivity <span class="hlt">analysis</span> is that the asymptotic dynamics of the system is assumed to be a periodic orbit. For asymptotic sensitivity <span class="hlt">analysis</span> we employ combination of tools from ergodic theory and geometric theory of dynamical systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22277689','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22277689"><span id="translatedtitle">Perturbative <span class="hlt">stability</span> of SFT-based cosmological <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Galli, Federico; Koshelev, Alexey S. E-mail: alexey.koshelev@vub.ac.be</p> <p>2011-05-01</p> <p>We review the appearance of multiple scalar fields in linearized SFT based cosmological <span class="hlt">models</span> with a single non-local scalar field. Some of these local fields are canonical real scalar fields and some are complex fields with unusual coupling. These systems only admit numerical or approximate <span class="hlt">analysis</span>. We introduce a modified potential for multiple scalar fields that makes the system exactly solvable in the cosmological context of Friedmann equations and at the same time preserves the asymptotic behavior expected from SFT. The main part of the paper consists of the <span class="hlt">analysis</span> of inhomogeneous cosmological perturbations in this system. We show numerically that perturbations corresponding to the new type of complex fields always vanish. As an example of application of this <span class="hlt">model</span> we consider an explicit construction of the phantom divide crossing and prove the perturbative <span class="hlt">stability</span> of this process at the linear order. The issue of ghosts and ways to resolve it are briefly discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21997361','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21997361"><span id="translatedtitle">A nonlinear <span class="hlt">stability</span> <span class="hlt">analysis</span> of vegetative turing pattern formation for an interaction-diffusion plant-surface water <span class="hlt">model</span> system in an arid flat environment.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kealy, Bonni J; Wollkind, David J</p> <p>2012-04-01</p> <p>The development of spontaneous stationary vegetative patterns in an arid flat environment is investigated by means of a weakly nonlinear diffusive instability <span class="hlt">analysis</span> applied to the appropriate <span class="hlt">model</span> system for this phenomenon. In particular, that process can be <span class="hlt">modeled</span> by a partial differential interaction-diffusion equation system for the plant biomass density and the surface water content defined on an unbounded flat spatial domain. The main results of this <span class="hlt">analysis</span> can be represented by closed-form plots in the rate of precipitation versus the specific rate of plant density loss parameter space. From these plots, regions corresponding to bare ground and vegetative patterns consisting of parallel stripes, labyrinth-like mazes, hexagonal arrays of gaps, irregular mosaics, and homogeneous distributions of vegetation, respectively, may be identified in this parameter space. Then those theoretical predictions are compared with both relevant observational evidence involving tiger and pearled bush patterns and existing numerical simulations of similar <span class="hlt">model</span> systems as well as placed in the context of the results from some recent nonlinear vegetative pattern formation studies. PMID:21997361</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/543659','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/543659"><span id="translatedtitle">White Oak Dam <span class="hlt">stability</span> <span class="hlt">analysis</span>. Volume I</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ahmed, S.B.</p> <p>1994-01-01</p> <p>A parametric study was conducted to evaluate the <span class="hlt">stability</span> of the White Oak Dam (WOD) embankment and foundation. Slope <span class="hlt">stability</span> analyses were performed for the upper and lower bound soil properties at three sections of the dam using the PCSTABL4 computer program. Minimum safety factors were calculated for the applicable seismic and static loading conditions. Liquefaction potential of the dam embankment and foundation solid during the seismic event was assessed by using simplified procedures. The WOD is classified as a low hazard facility and the Evaluation Basis Earthquake (EBE) is defined as an earthquake with a magnitude of m{sub b} = 5.6 and a Peak Ground Accelerator (PGA) of 0.13 g. This event is approximately equivalent to a Modified Mercalli Intensity of VI-VIII. The EBE is used to perform the seismic evaluation for slope <span class="hlt">stability</span> and liquefaction potential. Results of the <span class="hlt">stability</span> analyses and the liquefaction assessment lead to the conclusion that the White Oak Dam is safe and stable for the static and the seismic events defined in this study. Ogden Environmental, at the request of MMES, has checked and verified the calculations for the critical loading conditions and performed a peer review of this report. Ogden has determined that the WOD is stable under the defined static and seismic loading conditions and the embankment materials are in general not susceptible to liquefaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880062958&hterms=Simplification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSimplification','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880062958&hterms=Simplification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSimplification"><span id="translatedtitle"><span class="hlt">Modeling</span>, <span class="hlt">model</span> simplification and <span class="hlt">stability</span> robustness with aeroelastic vehicles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schmidt, David K.; Newman, Brett</p> <p>1988-01-01</p> <p>The linearization and simplification of a nonlinear, literal <span class="hlt">model</span> for flexible aircraft is highlighted. Areas of <span class="hlt">model</span> fidelity that are critical if the <span class="hlt">model</span> is to be used for control system synthesis are developed, and several simplification techniques that can deliver the necessary <span class="hlt">model</span> fidelity are discussed. These techniques include both numerical and analytical approaches. An analytical approach, based on first-order sensitivity theory is shown to lead not only to excellent numerical results, but also to closed-form analytical expressions for key system dynamic properties such as the pole/zero factors of the vehicle transfer-function matrix. The analytical results are expressed in terms of vehicle mass properties, vibrational characteristics, and rigid-body and aeroelastic <span class="hlt">stability</span> derivatives, thus leading to the underlying causes for critical dynamic characteristics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790017563','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790017563"><span id="translatedtitle">Study report on guidelines and test procedures for investigating <span class="hlt">stability</span> of nonlinear cardiovascular control system <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fitzjerrell, D. G.</p> <p>1974-01-01</p> <p>A general study of the <span class="hlt">stability</span> of nonlinear as compared to linear control systems is presented. The <span class="hlt">analysis</span> is general and, therefore, applies to other types of nonlinear biological control systems as well as the cardiovascular control system <span class="hlt">models</span>. Both inherent and numerical <span class="hlt">stability</span> are discussed for corresponding analytical and graphic methods and numerical methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110011791','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110011791"><span id="translatedtitle">CFD Based Computations of Flexible Helicopter Blades for <span class="hlt">Stability</span> <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Guruswamy, Guru P.</p> <p>2011-01-01</p> <p>As a collaborative effort among government aerospace research laboratories an advanced version of a widely used computational fluid dynamics code, OVERFLOW, was recently released. This latest version includes additions to <span class="hlt">model</span> flexible rotating multiple blades. In this paper, the OVERFLOW code is applied to improve the accuracy of airload computations from the linear lifting line theory that uses displacements from beam <span class="hlt">model</span>. Data transfers required at every revolution are managed through a Unix based script that runs jobs on large super-cluster computers. Results are demonstrated for the 4-bladed UH-60A helicopter. Deviations of computed data from flight data are evaluated. Fourier <span class="hlt">analysis</span> post-processing that is suitable for aeroelastic <span class="hlt">stability</span> computations are performed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997PhDT.......229L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997PhDT.......229L"><span id="translatedtitle">GE simplified boiling water reactor <span class="hlt">stability</span> <span class="hlt">analysis</span> in time domain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, Shanlai</p> <p>1997-12-01</p> <p>General Electric Simplified Boiling Water Reactor (SBWR) was designed as a next generation light water reactor. It uses natural circulation to remove the heat from the reactor core. Because of this unique in-vessel circulation feature, SBWR is expected to exhibit different <span class="hlt">stability</span> behaviors. The main emphasis of this thesis is to study the SBWR <span class="hlt">stability</span> behavior in the time domain. The best-estimate BWR accident/transient <span class="hlt">analysis</span> computer code, TRAC-BF1, is employed to analyze the SBWR <span class="hlt">stability</span> behavior. A detailed TRAC-BF1 SBWR <span class="hlt">model</span> has been developed, which has the capability to <span class="hlt">model</span> the in-vessel natural circulation and the reactor core kinetics. The <span class="hlt">model</span> is used to simulate three slow depressurization processes. The simulation results show that the reactor is stable under low pressure and nominal downcomer water level conditions. However, when the downcomer water level is raised to about 19.2 m above the bottom of the reactor vessel, an unstable power oscillation is observed. The identified power oscillation is further analyzed using TRAC-BF1 1-D kinetics and the new TRAC-BF1 3-D kinetics code developed in this thesis. The effects of different time step sizes and vessel <span class="hlt">model</span> nodalizations are examined. It is found that the power oscillation is in-phase and has a frequency of 0.3 HZ. In order to further explore the physical instabilty initiation mechanisms, a simplified dynamic <span class="hlt">model</span> consisting of six simple differential equations is developed. The simplified <span class="hlt">model</span> is able to predict the dominant physical phenomenon identified by the TRAC-BF1 <span class="hlt">analysis</span>. The results indicate that the system instability is possibly caused by the steam separator hydro-static head oscillation under the high water level condition. In order to explore the higher order spacial effect of power oscillation, a 3-D reactor core kinetics code is coupled with the TRAC-BF1 computer code in the PVM parallel processing environment. A new coupling scheme and a multiple time step marching technique are developed. The new TRAC-BF1 3-D code package is examined using LMW standard benchmark problem. It is then successfully used to study the possible SBWR power oscillation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3326025','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3326025"><span id="translatedtitle">Systematic <span class="hlt">Analysis</span> of <span class="hlt">Stability</span> Patterns in Plant Primary Metabolism</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Girbig, Dorothee; Grimbs, Sergio; Selbig, Joachim</p> <p>2012-01-01</p> <p>Metabolic networks are characterized by complex interactions and regulatory mechanisms between many individual components. These interactions determine whether a steady state is stable to perturbations. Structural kinetic <span class="hlt">modeling</span> (SKM) is a framework to analyze the <span class="hlt">stability</span> of metabolic steady states that allows the study of the system Jacobian without requiring detailed knowledge about individual rate equations. <span class="hlt">Stability</span> criteria can be derived by generating a large number of structural kinetic <span class="hlt">models</span> (SK-<span class="hlt">models</span>) with randomly sampled parameter sets and evaluating the resulting Jacobian matrices. Until now, SKM experiments applied univariate tests to detect the network components with the largest influence on <span class="hlt">stability</span>. In this work, we present an extended SKM approach relying on supervised machine learning to detect patterns of enzyme-metabolite interactions that act together in an orchestrated manner to ensure <span class="hlt">stability</span>. We demonstrate its application on a detailed SK-<span class="hlt">model</span> of the Calvin-Benson cycle and connected pathways. The identified <span class="hlt">stability</span> patterns are highly complex reflecting that changes in dynamic properties depend on concerted interactions between several network components. In total, we find more patterns that reliably ensure <span class="hlt">stability</span> than patterns ensuring instability. This shows that the design of this system is strongly targeted towards maintaining <span class="hlt">stability</span>. We also investigate the effect of allosteric regulators revealing that the tendency to <span class="hlt">stability</span> is significantly increased by including experimentally determined regulatory mechanisms that have not yet been integrated into existing kinetic <span class="hlt">models</span>. PMID:22514655</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19820044822&hterms=superresolution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsuperresolution','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19820044822&hterms=superresolution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsuperresolution"><span id="translatedtitle">Application of modern time series <span class="hlt">analysis</span> to high <span class="hlt">stability</span> oscillators</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Farrell, B. F.; Mattison, W. M.; Vessot, R. F. C.</p> <p>1980-01-01</p> <p>Techniques of modern time series <span class="hlt">analysis</span> useful for investigating the characteristics of high-<span class="hlt">stability</span> oscillators and identifying systematic perturbations are discussed with reference to an experiment in which the frequencies of superconducting cavity-<span class="hlt">stabilized</span> oscillators and hydrogen masers were compared. The techniques examined include transformation to stationarity, autocorrelation and cross-correlation, superresolution, and transfer function determination.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1214469A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1214469A"><span id="translatedtitle">Wellbore <span class="hlt">stability</span> <span class="hlt">analysis</span> in carbonate reservoir considering anisotropic behaviour</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alves, Jos; Guevara, Nestor; Coelho, Lucia; Baud, Patrick</p> <p>2010-05-01</p> <p>Carbonate reservoirs represent a major part of the world oil and gas reserves. In particular, recent discoveries in the pre-salt offshore Brazil place big challenges to exploration and production under high temperatures and pressures (HTHP). During production, the extraction of hydrocarbons reduces pore pressure and thus causes an increase in the effective stress and mechanical compaction in the reservoir. The compactive deformation and failure may be spatially extensive or localized to the vicinity of the wellbore, but in either case the consequences can be economically severe involving surface subsidence, well failure and various production problems. The <span class="hlt">analysis</span> of wellbore <span class="hlt">stability</span> and more generally of deformation and failure in carbonate environments hinges upon a relevant constitutive <span class="hlt">modeling</span> of carbonate rocks over a wide range of porosities, in particular, observed microstructure of samples suggests anisotropic behaviour. In this study, we performed a wellbore <span class="hlt">stability</span> <span class="hlt">analysis</span> for a lateral wellbore junction in three dimensions. The complex geometry for the wellbore junction was <span class="hlt">modeled</span> with tetrahedral finite elements considering a rate independent elastic-plastic isotropic material that presented linear behavior during elastic strain and associated flow rule. A finite element <span class="hlt">model</span> simulating drilling and production phases were done for field conditions from a deep water reservoir in Campos basin, offshore Brazil. In this context, several scenarios were studied considering true 3D orientation for both in situ stresses and geometry of the wellbore junction itself. We discussed the impact of constitutive <span class="hlt">modeling</span>, considering anisotropic ductile damage and pressure sensitiveness on the wellbore <span class="hlt">stability</span>. Parameter values for the <span class="hlt">analysis</span> were based based on experimental data on two micritic porous carbonates. Series of conventional triaxial experiments were performed at room temperature in dry and wet conditions on samples of Comiso and Tavel limestones of respective porosity 17 and 16%. The wet samples were deformed in drained conditions with 10 MPa pore pressure. The initial yield stresses were identified as the critical stresses at the onset of shear-enhanced compaction, subsequent yield stresses were considered to depend on hardening given by the plastic volumetric strain. For both limestones, we found that water had a moderate effect on the yield stresses but influenced significantly the hardening behavior of the rocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhPro..58..248J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhPro..58..248J"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of ITER Side Correction Coils</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jin, Fang; Xiaoyu, Chen; Wei, Zhou; Liangfeng, Liu; Yuntao, Song; Weiyue, Wu</p> <p></p> <p>The <span class="hlt">stability</span> of the Side Correction Coils (SCC) cable-in-conduit conductors (CICC) for the International Thermonuclear Experimental Reactor (ITER) has been analyzed by the formulas and the code Gandalf. This paper describes the 1-dimensional mathematical code Gandalf, uses the code to simulate the quench and the recovery status of ITER SCC CICC, discusses the dependence of the <span class="hlt">stability</span> margin on various operating parameters including operating current, operating temperature and mass flow rate, and analyzes the differences between the simulated values and the calculated values. The ITER SCC's quenching is also simulated to investigate its temperature distribution and temperature margin. Dependence of temperature margin on magnetic fields and operating temperature has been researched. The studies of ITER SCC provide a basis for the stable operation and optimization design of SCC CICC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930065908&hterms=Real+Analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DReal%2BAnalysis','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930065908&hterms=Real+Analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DReal%2BAnalysis"><span id="translatedtitle">Space Shuttle Main Engine real time <span class="hlt">stability</span> <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuo, F. Y.</p> <p>1993-01-01</p> <p>The Space Shuttle Main Engine (SSME) is a reusable, high performance, liquid rocket engine with variable thrust. The engine control system continuously monitors the engine parameters and issues propellant valve control signals in accordance with the thrust and mixture ratio commands. A real time engine simulation lab was installed at MSFC to verify flight software and to perform engine dynamic <span class="hlt">analysis</span>. A real time engine <span class="hlt">model</span> was developed on the AD100 computer system. This <span class="hlt">model</span> provides sufficient fidelity on the dynamics of major engine components and yet simplified enough to be executed in real time. The hardware-in-the-loop type simulation and <span class="hlt">analysis</span> becomes necessary as NASA is continuously improving the SSME technology, some with significant changes in the dynamics of the engine. The many issues of interfaces between new components and the engine can be better understood and be resolved prior to the firing of the engine. In this paper, the SSME real time simulation Lab at the MSFC, the SSME real time <span class="hlt">model</span>, SSME engine and control system <span class="hlt">stability</span> <span class="hlt">analysis</span>, both in real time and non-real time is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993jpmc.confQQ...K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993jpmc.confQQ...K"><span id="translatedtitle">Space Shuttle Main Engine real time <span class="hlt">stability</span> <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuo, F. Y.</p> <p>1993-06-01</p> <p>The Space Shuttle Main Engine (SSME) is a reusable, high performance, liquid rocket engine with variable thrust. The engine control system continuously monitors the engine parameters and issues propellant valve control signals in accordance with the thrust and mixture ratio commands. A real time engine simulation lab was installed at MSFC to verify flight software and to perform engine dynamic <span class="hlt">analysis</span>. A real time engine <span class="hlt">model</span> was developed on the AD100 computer system. This <span class="hlt">model</span> provides sufficient fidelity on the dynamics of major engine components and yet simplified enough to be executed in real time. The hardware-in-the-loop type simulation and <span class="hlt">analysis</span> becomes necessary as NASA is continuously improving the SSME technology, some with significant changes in the dynamics of the engine. The many issues of interfaces between new components and the engine can be better understood and be resolved prior to the firing of the engine. In this paper, the SSME real time simulation Lab at the MSFC, the SSME real time <span class="hlt">model</span>, SSME engine and control system <span class="hlt">stability</span> <span class="hlt">analysis</span>, both in real time and non-real time is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ThCFD..29..155M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ThCFD..29..155M"><span id="translatedtitle">A linear thermal <span class="hlt">stability</span> <span class="hlt">analysis</span> of discretized fluid equations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miyamoto, Yoshiaki; Ito, Junshi; Nishizawa, Seiya; Tomita, Hirofumi</p> <p>2015-06-01</p> <p>The effects of discretization on the equations, and their solutions, describing Rayleigh-Bnard convection are studied through linear <span class="hlt">stability</span> <span class="hlt">analysis</span> and numerical integration of the discretized equations. Linear <span class="hlt">stability</span> analyses of the discretized equations were conducted in the usual manner except that the assumed solution contained discretized components (e.g., spatial grid interval in the x direction, ). As the resolution became infinitely high (), the solutions approached those obtained from the continuous equations. The wavenumber of the maximum growth rate increased with increasing until the wavenumber reached a minimum resolvable resolution, . Therefore, the discretization of equations tends to reproduce higher-wavenumber structures than those predicted by the continuous equations. This behavior is counter intuitive and opposed to the expectation of leading to blurred simulated convection structures. However, when the <span class="hlt">analysis</span> is conducted for discretized equations that are not combined into a single equation, as is the case for practically solved numerical <span class="hlt">models</span>, the maximum growing wavenumber rather tends to decrease with increasing as intuitively expected. The degree of the decrease depends on the discretization accuracy of the first-order differentials. When the accuracy of the discretization scheme is of low order, the wavenumber monotonically decreases with increasing . On the other hand, when higher-order schemes are used for the discretization, the wavenumber does increase with increasing , a similar trend to that in the case of the single-discretized equation for smaller.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780012233','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780012233"><span id="translatedtitle">Static and dynamic <span class="hlt">stability</span> <span class="hlt">analysis</span> of the space shuttle vehicle-orbiter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chyu, W. J.; Cavin, R. K.; Erickson, L. L.</p> <p>1978-01-01</p> <p>The longitudinal static and dynamic <span class="hlt">stability</span> of a Space Shuttle Vehicle-Orbiter (SSV Orbiter) <span class="hlt">model</span> is analyzed using the FLEXSTAB computer program. Nonlinear effects are accounted for by application of a correction technique in the FLEXSTAB system; the technique incorporates experimental force and pressure data into the linear aerodynamic theory. A flexible Orbiter <span class="hlt">model</span> is treated in the static <span class="hlt">stability</span> <span class="hlt">analysis</span> for the flight conditions of Mach number 0.9 for rectilinear flight (1 g) and for a pull-up maneuver (2.5 g) at an altitude of 15.24 km. Static <span class="hlt">stability</span> parameters and structural deformations of the Orbiter are calculated at trim conditions for the dynamic <span class="hlt">stability</span> <span class="hlt">analysis</span>, and the characteristics of damping in pitch are investigated for a Mach number range of 0.3 to 1.2. The calculated results for both the static and dynamic <span class="hlt">stabilities</span> are compared with the available experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JCos...18.7978M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JCos...18.7978M"><span id="translatedtitle">Gravitational <span class="hlt">Stability</span> for a Vacuum Cosmic Space Crystalline <span class="hlt">Model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montemayor-Aldrete, J. A.; Morones-Ibarra, J. R.; Morales-Mori, A.</p> <p>2012-03-01</p> <p>Using a generalization of the Heisenberg?s uncertainty principle it is shown that the local gravitational <span class="hlt">stability</span> condition for an infinite tridimensional crystalline <span class="hlt">model</span> of the quantum vacuum cosmic space (which is existing from an infinite time before the occurrence of our local actual big bang event) implies to obtain an equation formally equivalent to the relation first used by Gamow to predict the present temperature of the microwave background from the matter density. The compatibility condition between the quantum and the relativistic approaches has been obtained without infinities arising from the quantum <span class="hlt">analysis</span> or singularities arising from the relativistic theory. The action, which leads to our theory, is the least action possible in a quantum scheme. The energy fluctuation involved in the gravitational <span class="hlt">stabilization</span> of vacuum space, inside the actual volume of our universe, is times the energy of the crystalline structure of vacuum space inside the present Universe volume. The same process of quantum gravitational <span class="hlt">stabilization</span> of such crystalline structure occurs everywhere (by pairs of cells of similar sizes under the action of tension-compression gravitational stresses very near to mechanic-gravitational equilibrium) in the infinite cosmic vacuum space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20935283','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20935283"><span id="translatedtitle">Critical <span class="hlt">analysis</span> of Goldberger-Wise <span class="hlt">stabilization</span> of the Randall-Sundrum braneworld scenario</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dey, Anindya; Maity, Debaprasad; SenGupta, Soumitra</p> <p>2007-05-15</p> <p>The Goldberger-Wise mechanism of <span class="hlt">stabilizing</span> modulus in the Randall-Sundrum braneworld, by introducing a bulk scalar field with quartic interaction terms localized at the 3-branes, has been extremely popular as a <span class="hlt">stabilizing</span> mechanism when the backreaction of the scalar field on the geometry is negligibly small. In this paper we reexamine the mechanism by an exact <span class="hlt">analysis</span> without resorting to the approximations adopted by Goldberger and Wise. An exact calculation of the <span class="hlt">stabilization</span> condition indicates the existence of closely spaced minimum and a maximum for the potential and also brings out some new features involved in the context of the <span class="hlt">stabilization</span> of such braneworld <span class="hlt">models</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS21A1664T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS21A1664T"><span id="translatedtitle">Ageostrophic linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of the Labrador Current</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thomsen, S.; Eden, C.</p> <p>2012-12-01</p> <p>The water mass transformation process in the Labrador Sea during winter plays an important role for the Atlantic meridional overturning circulation and the global climate system. The Labrador Sea Water (LSW) is exported within the deep Labrador Current (LC) after the convection process. LSW takes up large amounts of atmospheric tracer gases as CO2 and oxygen, and is thus one of the major agent for ventilation of the abyssal ocean. It is shown that enhanced eddy kinetic energy (EKE) along the LC shows up in a 1/12 ocean <span class="hlt">model</span> simulation during the transformation process. Moored in-situ measurements within the LC also show enhanced EKE levels during winter. This instability processes within the LC is important as it might alter the water mass properties of the (LSW) by frontal mixing processes during the water mass transformation and export within the LC. The frontal instability process, which lead to enhanced EKE along the LC during winter is investigated using ageostrophic linear <span class="hlt">stability</span> <span class="hlt">analysis</span>. Dense and weakly stratified water masses produced during the wintertime transformation process lead to weaker stratification and a strengthening of the lateral density gradients within the LC. Weak stratification and enhanced vertical shear result in low Richardson numbers and the growth rate of baroclinic waves increases significantly within the shelf break LC during winter. Rapid frontogenesis along the whole LC sets in resulting in enhance EKE. During the rest of the year strong stratification and weak vertical shear leads to larger Richardson numbers and smaller growth rates. Ageostrophic linear <span class="hlt">stability</span> <span class="hlt">analysis</span> shows that a geostrophic interior mode has similar wavelengths as the first wavelike disturbances in the <span class="hlt">model</span> simulations. A shallow mode with lateral scales O (1 km) is also predicted, which can be associated with mixed layer instabilities and submesoscale variability but remains unresolved by the <span class="hlt">model</span> simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000PhFl...12.2438F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhFl...12.2438F"><span id="translatedtitle"><span class="hlt">Stability</span> of a four-vortex aircraft wake <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fabre, David; Jacquin, Laurent</p> <p>2000-10-01</p> <p>The <span class="hlt">stability</span> of an aircraft wake <span class="hlt">model</span> composed of an external vortex pair (<span class="hlt">modeling</span> the wing tip vortices) and an internal vortex pair rotating in the opposite direction (<span class="hlt">modeling</span> the vortices generated by the fuselage and the horizontal tail) in a stationary configuration is investigated with the vortex filament <span class="hlt">stability</span> method used by Crow [AIAA J. 8, 2172 (1970)] and Crouch [J. Fluid Mech. 350, 311 (1997)]. It is shown that this configuration is unstable with respect to two-dimensional and three-dimensional disturbances. For long wavelength three-dimensional symmetric perturbations, the rapid growth observed in the numerical simulations of Rennich and Lele [J. Air. 36, 398 (1999)] is found. Moreover, the <span class="hlt">analysis</span> allows one to show that without an excitation of the long-wave mode, the system will naturally develop short wavelength instabilities localized within the inner vortices which do not affect the outer vortices. Inspection of the initial value problem shows that the long-wave modes can be efficiently initiated by the introduction of perturbations on the internal vortices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009Chaos..19b6107K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009Chaos..19b6107K"><span id="translatedtitle">Neuromechanical <span class="hlt">models</span> for insect locomotion: <span class="hlt">Stability</span>, maneuverability, and proprioceptive feedback</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kukillaya, R.; Proctor, J.; Holmes, P.</p> <p>2009-06-01</p> <p>We describe a hierarchy of <span class="hlt">models</span> for legged locomotion, emphasizing relationships among feedforward (preflexive) <span class="hlt">stability</span>, maneuverability, and reflexive feedback. We focus on a hexapedal geometry representative of insect locomotion in the ground plane that includes a neural central pattern generator circuit, nonlinear muscles, and a representative proprioceptive sensory pathway. Although these components of the <span class="hlt">model</span> are rather complex, neglect of leg mass yields a neuromechanical system with only three degrees of freedom, and numerical simulations coupled with a Poincaré map <span class="hlt">analysis</span> shows that the feedforward dynamics is strongly stable, apart from one relatively slow mode and a neutral mode in body yaw angle. These modes moderate high frequency perturbations, producing slow heading changes that can be corrected by a stride-to-stride steering strategy. We show that the <span class="hlt">model</span>'s response to a lateral impulsive perturbation closely matches that of a cockroach subject to a similar impulse. We also describe preliminary studies of proprioceptive leg force feedback, showing how a reflexive pathway can reinforce the preflexive <span class="hlt">stability</span> inherent in the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920022291','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920022291"><span id="translatedtitle">Sensitivity <span class="hlt">analysis</span> of hydrodynamic <span class="hlt">stability</span> operators</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schmid, Peter J.; Henningson, Dan S.; Khorrami, Mehdi R.; Malik, Mujeeb R.</p> <p>1992-01-01</p> <p>The eigenvalue sensitivity for hydrodynamic <span class="hlt">stability</span> operators is investigated. Classical matrix perturbation techniques as well as the concept of epsilon-pseudoeigenvalues are applied to show that parts of the spectrum are highly sensitive to small perturbations. Applications are drawn from incompressible plane Couette, trailing line vortex flow and compressible Blasius boundary layer flow. Parametric studies indicate a monotonically increasing effect of the Reynolds number on the sensitivity. The phenomenon of eigenvalue sensitivity is due to the non-normality of the operators and their discrete matrix analogs and may be associated with large transient growth of the corresponding initial value problem.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/85460','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/85460"><span id="translatedtitle">Global <span class="hlt">stability</span> <span class="hlt">analysis</span> of the steady and periodic cylinder wake</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Noack, B.R.; Eckelmann, H.</p> <p>1994-07-01</p> <p>A global, three-dimensional <span class="hlt">stability</span> <span class="hlt">analysis</span> of the steady and the periodic cylinder wake is carried out employing a low-dimensional Galerkin method. The steady flow is found to be asymptotically stable with respect to all perturbations for Re less than 54. The onset of periodicity is confirmed to be a supercritical Hopf bifurcation which can be <span class="hlt">modeled</span> by the Landau equations. The periodic solution is observed to be only neutrally stable for 54 less than Re less than 170. While two-dimensional perturbations of the vortex street rapidly decay, three-dimensional perturbations with long spanwise wavelengths neither grow nor decay. The periodic solution becomes unstable at Re = 170 by a perturbation with the spanwise wavelength of 1.8 diameters. This instability is shown to be a supercritical Hopf bifurcation in the spanwise coordinate and leads to a three-dimensional periodic flow. Finally the transition scenario for higher Reynolds numbers is discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22971606','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22971606"><span id="translatedtitle">Anterior shoulder <span class="hlt">stability</span>: Contributions of rotator cuff forces and the capsular ligaments in a cadaver <span class="hlt">model</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Blasier, R B; Guldberg, R E; Rothman, E D</p> <p>1992-05-01</p> <p>The purpose of this study was to quantify in a biomechanical <span class="hlt">model</span> the contributions to shoulder joint <span class="hlt">stability</span> that are made by tensions in the four tendons of the rotator cuff and by static resistance of defined portions of the capsular ligaments. A materials testing machine was used to directly determine anterior joint laxity by measurement of the force required to produce a standard anterior subluxation. Shoulders were tested in external or neutral humeral rotation. Data were analyzed by multiway <span class="hlt">analysis</span> of variance with regression <span class="hlt">analysis</span>. This <span class="hlt">model</span> simulated tensions in the rotator cuff musculature by applying static loads at the tendon insertion sites acting along the anatomic lines of action. A load in any of the cuff tendons resulted in a measurable and statistically significant contribution to anterior joint <span class="hlt">stability</span>. The contributions between different tendons were not significantly different and did not depend on the humeral rotation (neutral or external). In neutral humeral rotation the superior and middle glenohumeral ligaments together function equally with the inferior glenohumeral ligament as primary <span class="hlt">stabilizers</span> against anterior humeral translation. The posterior capsule is a secondary <span class="hlt">stabilizer</span>. The external rotation of the abducted humerus increases anterior <span class="hlt">stability</span> by more than doubling the <span class="hlt">stability</span> contribution from the inferior glenohumeral ligament. The <span class="hlt">stability</span> contribution from the posterior capsule is larger in external rotation than in neutral rotation but is still of secondary magnitude. In external rotation the <span class="hlt">stability</span> contribution of the anterior capsule, including the superior glenohumeral ligament and the middle glenohumeral ligament, becomes insignificant. The <span class="hlt">model</span> presented here simulates the combined effect of two major sources of shoulder <span class="hlt">stability</span>. This versatile <span class="hlt">model</span> permits the direct measurement of the contributions to anterior shoulder <span class="hlt">stability</span> that are made by tensions in the rotator cuff tendons and by static resistance of defined capsular zones. The use of multiple regression <span class="hlt">analysis</span>-a standard statistical technique but one relatively new to the orthopaedic literature-permits quantitative determination of the contribution of each independent variable to the dependent variable, shoulder <span class="hlt">stability</span>. PMID:22971606</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PUSP...37..109K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PUSP...37..109K"><span id="translatedtitle">Soap Bubble Elasticity: <span class="hlt">Analysis</span> and Correlation with Foam <span class="hlt">Stability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karakashev, S. I.; Tsekov, R.; Manev, E. D.; Nguyen, A. V.</p> <p>2010-05-01</p> <p>A correlation between the elastic modulus of soap bubble and the foam <span class="hlt">stability</span> was found. A <span class="hlt">model</span> system was chosen: a soap bubble <span class="hlt">stabilized</span> by simple nonionic surfactant tetraethylene glycol octyl ether (C8E4) and 10^-5 M NaCl. The Elastic moduli were determined by periodical expansion and shrinking of foam bubbles with frequency of 0.1 Hz and volumetric amplitude of 2 mm 3. The film tension was monitored via commercial profile <span class="hlt">analysis</span> tensiometer (Sinterface Technologies, GmbH). The elastic moduli of foam bubbles versus surfactant concentration in the range of 2x10^-3 - 10^-2 M were obtained. In addition, the theory of Lucassen and van den Tempel for the elastic modulus of single liquid/air interface at given frequency was exploited as well. The bulk diffusion coefficient of the surfactant molecules is unknown parameter through the adsorption frequency in this theory. Hence, a fitting procedure (with one free parameter) was conducted matching experimental and theoretical data. The value of the bulk diffusion coefficient of C8E4 obtained was 5.1x10^-11 m^2/s, which is an order of magnitude lower value than what is expected for. The foam was generated by shaking method and left to decay. A correlation between the elastic modulus and foam life time upon surfactant concentration was found.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1000873','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1000873"><span id="translatedtitle"><span class="hlt">Stability</span> of metallic thin film with free electron <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wu, Biao; Zhang, Zhenyu</p> <p>2008-01-01</p> <p>The <span class="hlt">stability</span> of metallic thin lms is studied with free electron <span class="hlt">model</span>, which is popularly known as <span class="hlt">model</span> of \\particle in a box". A detailed theoretical framework is presented, along with discussion on typical metals, such as Pb, Al, Ag, Na, and Be. This simple <span class="hlt">model</span> is found to be able to describe well the oscillation pattern of <span class="hlt">stability</span> for continuous metallic lms. In particular, it yields even-odd oscillations in the <span class="hlt">stability</span> of Pb(111) lm, consistent with both experimental observation and ab initio results. However, the free electron <span class="hlt">model</span> is too crude to predict at what thickness the lm is stable. The lm <span class="hlt">stability</span> is further examined with a <span class="hlt">model</span> of \\particle in a corrugated box", where a lattice potential is added along the vertical direction of the lm. The e ect of lattice potential is found not substantial.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AIPC.1400..206A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AIPC.1400..206A"><span id="translatedtitle">Structural <span class="hlt">Stability</span> of Mathematical <span class="hlt">Models</span> of National Economy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ashimov, Abdykappar A.; Sultanov, Bahyt T.; Borovskiy, Yuriy V.; Adilov, Zheksenbek M.; Ashimov, Askar A.</p> <p>2011-12-01</p> <p>In the paper we test robustness of particular dynamic systems in a compact regions of a plane and a weak structural <span class="hlt">stability</span> of one dynamic system of high order in a compact region of its phase space. The test was carried out based on the fundamental theory of dynamical systems on a plane and based on the conditions for weak structural <span class="hlt">stability</span> of high order dynamic systems. A numerical algorithm for testing the weak structural <span class="hlt">stability</span> of high order dynamic systems has been proposed. Based on this algorithm we assess the weak structural <span class="hlt">stability</span> of one computable general equilibrium <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1602..100A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1602..100A"><span id="translatedtitle">Kinematic <span class="hlt">analysis</span> of rope skipper's <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ab Ghani, Nor Atikah; Rambely, Azmin Sham</p> <p>2014-06-01</p> <p>There are various kinds of jumping that can be done while performing rope skipping activity. This activity was always associated with injury. But, if the rope skipper can perform the activity in a right way, it is believed that the injury might be reduced. The main purpose of this paper is to observe the <span class="hlt">stability</span> of rope skipper from a biomechanics perspective, which are the centre of mass, angle at the ankle, knee and hip joints and also the trajectory for the ipsilateral leg between the two types of skip which is one leg and two legs. Six healthy, physically active subject, two males and four females (age: 8.001.25 years, weight: 17.906.85 kg and height: 1.220.08 m) participated in this study. Kinematic data of repeated five cycles of rope skipping activity was captured by using Vicon Nexus system. Based on the data collected, skipping with two legs shows more stable behavior during preparation, flight and landing phases. It is concluded that landing on the balls of the feet, lowering the trajectory positions of the feet from the ground as well as flexion of each joint which would reduce the injury while landing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..MARA51009A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..MARA51009A"><span id="translatedtitle"><span class="hlt">Analysis</span> of emulsion <span class="hlt">stability</span> in acrylic dispersions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahuja, Suresh</p> <p>2012-02-01</p> <p>Emulsions either micro or nano permit transport or solubilization of hydrophobic substances within a water-based phase. Different methods have been introduced at laboratory and industrial scales: mechanical stirring, high-pressure homogenization, or ultrasonics. In digital imaging, toners may be formed by aggregating a colorant with a latex polymer formed by batch or semi-continuous emulsion polymerization. Latex emulsions are prepared by making a monomer emulsion with monomer like Beta-carboxy ethyl acrylate (?-CEA) and stirring at high speed with an anionic surfactant like branched sodium dodecyl benzene sulfonates , aqueous solution until an emulsion is formed. Initiator for emulsion polymerization is 2-2'- azobis isobutyramide dehydrate with chain transfer agent are used to make the latex. If the latex emulsion is unstable, the resulting latexes produce a toner with larger particle size, broader particle size distribution with relatively higher latex sedimentation, and broader molecular weight distribution. Oswald ripening and coalescence cause droplet size to increase and can result in destabilization of emulsions. Shear thinning and elasticity of emulsions are applied to determine emulsion <span class="hlt">stability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7148442','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7148442"><span id="translatedtitle">Transient <span class="hlt">stability</span> <span class="hlt">analysis</span> for Sohio Prudhoe Bay emergency power system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hoan, W.T.; Chow, M.</p> <p>1986-05-01</p> <p>Small isolated automatic power systems of the types similar to the emergency power system at Prudhoe Bay are susceptible to <span class="hlt">stability</span> problems. These power systems, having two or more generator sets operating in parallel with remarkably different mechanical and control characteristics, require transient <span class="hlt">stability</span> <span class="hlt">analysis</span>. The design of the Prudhoe Bay emergency power system is discussed, as are <span class="hlt">stability</span> problems such as severe transient overload, voltage drop, and frequency drop, which are likely to occur and can cause catastrophic shutdowns during the emergency conditions. The conclusions drawn are that 1) a load sequencing and load blocking control scheme must be provided to control the automatic loads at Prudhoe Bay, and 2) <span class="hlt">stability</span> <span class="hlt">analysis</span> should be considered essential in the planning and design phases of similar power systems so that compatible generator units and appropriate load control schemes can be selected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2755368','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2755368"><span id="translatedtitle"><span class="hlt">Stability</span> over time: Is behavior <span class="hlt">analysis</span> a trait psychology?</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vyse, Stuart</p> <p>2004-01-01</p> <p>Historically, behavior <span class="hlt">analysis</span> and trait psychology have had little in common; however, recent developments in behavior <span class="hlt">analysis</span> bring it closer to one of the core assumptions of the trait approach: the <span class="hlt">stability</span> of behavior over time and, to a lesser extent, environments. The introduction of the concept of behavioral momentum and, in particular, the development of molar theories have produced some common features and concerns. Behavior-analytic theories of <span class="hlt">stability</span> provide improved explanations of many everyday phenomena and make possible the expansion of behavior <span class="hlt">analysis</span> into areas that have been inadequately addressed. ImagesFigure 1 PMID:22478416</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......345S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......345S"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of offshore wind farm and marine current farm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shawon, Mohammad Hasanuzzaman</p> <p></p> <p>Renewable energy has been playing an important role to meet power demand and 'Green Energy' market is getting bigger platform all over the world in the last few years. Due to massive increase in the prices of fossil fuels along with global warming issues, energy harvesting from renewable energy sources has received considerable interest, nowadays, where extensive researches are going on to ensure optimum use of renewable sources. In order to meet the increasing demand of electricity and power, integration of renewable energy is getting highest priorities around the world. Wind is one of the most top growing renewable energy resources and wind power market penetration is expected to reach 3.35 percent by 2013 from its present market of about 240 GW. A wind energy system is the most environmental friendly, cost effective and safe among all renewable energy resources available. Another promising form of renewable energy is ocean energy which covers 70 % of the earth. Ocean energy can be tapped from waves, tides and thermal elements. Offshore Wind farm (OWF) has already become very popular for large scale wind power integration with the onshore grid. Recently, marine current farm (MCF) is also showing good potential to become mainstream energy sources and already successfully commissioned in United Kingdom. However, squirrel cage induction generator (SCIG) has the <span class="hlt">stability</span> problem similar to synchronous generator especially during fault location to restore the electromagnetic torque. Series dynamic braking resistor (SDBR) has been known as a useful mean to <span class="hlt">stabilize</span> fixed speed wind generator system. On the other hand, doubly fed induction generator (DFIG) has the capability of coupling the control of active and reactive power and to provide necessary reactive power demand during grid fault conditions. Series dynamic braking resistor (SDBR) can also be employed with DFIG to limit the rotor over current. An integration of wind and tidal energy represents a new-trend for large electric energy production using offshore wind generators and marine current generators, respectively. Thus DFIG based offshore wind farm can be an economic solution to <span class="hlt">stabilize</span> squirrel cage induction generator based marine current farm without installing any addition FACTS devices. This thesis first focuses on the <span class="hlt">stabilization</span> of fixed speed IG based marine current farm using SDBR. Also <span class="hlt">stabilization</span> of DFIG based variable speed wind farm utilizing SDBR is studied in this work. Finally a co-operative control strategy is proposed where DFIG is controlled in such a way that it can even provide necessary reactive power demand of induction generator, so that additional cost of FACTS devices can be avoided. In that way, the DFIGs of the offshore wind farm (OWF) will actively compensate the reactive power demand of adjacent IGs of the marine current farm (MCF) during grid fault. Detailed <span class="hlt">modeling</span> and control scheme for the proposed system are demonstrated considering some realistic scenarios. The power system small signal <span class="hlt">stability</span> <span class="hlt">analysis</span> is also carried out by eigenvalue <span class="hlt">analysis</span> for marine current generator topology, wind turbine generator topology and integrated topology. The relation between the modes and state variables are discussed in light of modal and sensitivity analyses. The results of theoretical analyses are verified by MATLAB/SIMULINK and laboratory standard power system simulator PSCAD/EMTDC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/485108','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/485108"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of thin-walled fiber reinforced members</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Basu, P.K.; Dey, A.</p> <p>1997-07-01</p> <p>Finite element and theoretical <span class="hlt">stability</span> analyses of thin-walled glass fiber reinforced structural members are undertaken to predict the critical load in various modes of buckling and to study the buckling behavior of such members as compared to those made of isotropic materials. The applicability of component plate <span class="hlt">analysis</span> is evaluated with respect to full three-dimensional <span class="hlt">analysis</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820024466','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820024466"><span id="translatedtitle">Aeroelastic <span class="hlt">Stability</span> of Rotor Blades Using Finite Element <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chopra, I.; Sivaneri, N.</p> <p>1982-01-01</p> <p>The flutter <span class="hlt">stability</span> of flap bending, lead-lag bending, and torsion of helicopter rotor blades in hover is investigated using a finite element formulation based on Hamilton's principle. The blade is divided into a number of finite elements. Quasi-steady strip theory is used to evaluate the aerodynamic loads. The nonlinear equations of motion are solved for steady-state blade deflections through an iterative procedure. The equations of motion are linearized assuming blade motion to be a small perturbation about the steady deflected shape. The normal mode method based on the coupled rotating natural modes is used to reduce the number of equations in the flutter <span class="hlt">analysis</span>. First the formulation is applied to single-load-path blades (articulated and hingeless blades). Numerical results show very good agreement with existing results obtained using the modal approach. The second part of the application concerns multiple-load-path blades, i.e. bearingless blades. Numerical results are presented for several analytical <span class="hlt">models</span> of the bearingless blade. Results are also obtained using an equivalent beam approach wherein a bearingless blade is <span class="hlt">modelled</span> as a single beam with equivalent properties. Results show the equivalent beam <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910025622&hterms=bifurcation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dbifurcation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910025622&hterms=bifurcation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dbifurcation"><span id="translatedtitle">Bifurcation <span class="hlt">analysis</span> of axial flow compressor <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mccaughan, F. E.</p> <p>1990-01-01</p> <p>With a one-mode truncation it is possible to reduce the Moore-Greitzer <span class="hlt">model</span> for compressor instability to a set of three ordinary differential equations. These are approached from the point of view of bifurcation theory. Most of the bifurcations emerge from a degenerate Takens-Bogdanov bifurcation point. The bifurcation sets are completed using the numerical branch tracking scheme AUTO. Despite the severity of the truncation, the agreement with experimental results is excellent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.455.1015S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.455.1015S"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of axial reflection symmetric spacetime</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharif, M.; Bhatti, M. Zaeem Ul Haq</p> <p>2016-01-01</p> <p>In this paper, we explore instability regions of non-static axial reflection symmetric spacetime with anisotropic source in the interior. We impose linear perturbation on the Einstein field equations and dynamical equations to establish the collapse equation. The effects of different physical factors like energy density and anisotropic stresses on the instability regions are studied under Newtonian and post-Newtonian limits. We conclude that stiffness parameter has a significant role in this <span class="hlt">analysis</span> while the reflection terms increase instability ranges of non-static axial collapse.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870011347','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870011347"><span id="translatedtitle">Remarks on the <span class="hlt">stability</span> <span class="hlt">analysis</span> of reactive flows</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scheurer, B.</p> <p>1987-01-01</p> <p>A simple <span class="hlt">model</span> of compressible reacting flow is studied. First, a dispersion relation is derived for the linearized problem making a distinction between frozen and equilibrium sound speed. Second, the <span class="hlt">stability</span> of the Von Neumann-Richtmyer scheme applied to this <span class="hlt">model</span> is studied. A natural generalization of the C.F.L. condition is found.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22050685','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22050685"><span id="translatedtitle">Review of computer-aided <span class="hlt">models</span> for predicting collagen <span class="hlt">stability</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Concu, Riccardo; Podda, Gianni; Gonzalez-Diaz, Humberto; Shen, Bairong</p> <p>2011-12-01</p> <p>Collagen is the most abundant protein in the whole human body and its instability is involved in many important diseases, such as Osteogenesis imperfecta, Ehlers-Danlos syndrome, and collagenopathy. The <span class="hlt">stability</span> of the collagen triple helix is strictly related to its amino acid sequence, especially the main Gly-X-Y motif. Many groups have used computational methods to investigate collagen's structure and the relationship between its <span class="hlt">stability</span> and structure. In this study, we initially reviewed the most important computational methods that have been applied in this field. We then assembled data on a large number of collagen-like peptides to build the first Markov chain <span class="hlt">model</span> for predicting the <span class="hlt">stability</span> of the collagen at different temperatures, simply by analyzing the amino acid sequence. We used the literature to assemble a set of 102 peptides and their relative melting temperatures were determined experimentally, indicating a great variance with the main motif of the collagen. This dataset was then split in two classes, stable and unstable, according to their melting temperatures and the dataset was then used to build artificial neural network (ANN) <span class="hlt">models</span> to predict collagen <span class="hlt">stability</span>. We built <span class="hlt">models</span> to predict <span class="hlt">stability</span> at temperatures of 38C, 35C, 30C, and 25C degrees, and all <span class="hlt">models</span> had an accuracy between 82% and 92%. Several cross-validation procedures were performed to validate the <span class="hlt">model</span>. This method facilitates fast and accurate predictions of collagen <span class="hlt">stability</span> at different temperatures. PMID:22050685</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1117..217B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1117..217B"><span id="translatedtitle"><span class="hlt">Analysis</span> of Human Body Bipedal <span class="hlt">Stability</span> for Neuromotor Disabilities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baritz, Mihaela; Cristea, Luciana; Rogozea, Liliana; Cotoros, Diana; Repanovici, Angela</p> <p>2009-04-01</p> <p>The <span class="hlt">analysis</span> of different biomechanical aspects of balance and equilibrium is presented in the first part of the paper. We analyzed the posture, balance and <span class="hlt">stability</span> of human body for a normal person and for a person with loco-motor or neuro-motor disabilities (in the second part). In the third part of the paper we presented the methodology and the experimental setup used to record the human body behavior in postural <span class="hlt">stability</span> for persons with neuro-motors disabilities. The results and the conclusions are presented in the final part of the paper and also in the future work meant to establish the computer <span class="hlt">analysis</span> for rehabilitation neuromotor disabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=45267&keyword=Papers+AND+RAM&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=44973008&CFTOKEN=34670071','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=45267&keyword=Papers+AND+RAM&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=44973008&CFTOKEN=34670071"><span id="translatedtitle">RELATION OF URBAN <span class="hlt">MODEL</span> PERFORMANCE TO <span class="hlt">STABILITY</span></span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The RAM <span class="hlt">model</span> performance in estimating SO2 concentrations in St. Louis, MO for 1976 has been discussed in several previous papers by the authors. In these studies the <span class="hlt">model</span> estimates were compared to the observed concentrations of SO2 at 13 sites in the St. Louis metropolitan ar...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1218..668R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1218..668R"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of the Iter CS Coil Conductors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richard, L. Savoldi; Bessette, D.; Zanino, R.</p> <p>2010-04-01</p> <p>The <span class="hlt">stability</span> <span class="hlt">analysis</span> of the International Thermonuclear Experimental Reactor (ITER) Central Solenoid (CS) coil Nb3Sn conductor is performed following a similar approach to that recently used for the ITER Toroidal Field and Poloidal Field conductors. The most critical conductors in the winding pack, as well as the most critical (minimum temperature margin) location along them, are identified by the application of the Vincenta code, which also provides the initial and boundary conditions in the reference case. The Mithrandir code is then applied to these conductors, using a much finer grid than affordable in the Vincenta <span class="hlt">analysis</span>, in order to capture the details of normal zone initiation and possible recovery to SC state when different square wave disturbances of length L in the range [0.01 m, 7 m] and duration ? the range [1 ms, 100 ms] are applied to the cable. The computed minimum quench energy is shown to be typically above (in one case borderline to) the expected disturbance. The sensitivity to parametric of the heat transfer coefficient between strands and helium is significant for some disturbances. The inclusion of an external circuit in the <span class="hlt">model</span>, providing self-consistent boundary conditions, does not influence the results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19760039518&hterms=Best+sellers&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBest%2Bsellers','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19760039518&hterms=Best+sellers&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBest%2Bsellers"><span id="translatedtitle">Climate <span class="hlt">stability</span> for a Sellers-type <span class="hlt">model</span>. [atmospheric diffusive energy balance <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ghil, M.</p> <p>1976-01-01</p> <p>We study a diffusive energy-balance climate <span class="hlt">model</span> governed by a nonlinear parabolic partial differential equation. Three positive steady-state solutions of this equation are found; they correspond to three possible climates of our planet: an interglacial (nearly identical to the present climate), a glacial, and a completely ice-covered earth. We consider also <span class="hlt">models</span> similar to the main one studied, and determine the number of their steady states. All the <span class="hlt">models</span> have albedo continuously varying with latitude and temperature, and entirely diffusive horizontal heat transfer. The diffusion is taken to be nonlinear as well as linear. We investigate the <span class="hlt">stability</span> under small perturbations of the main <span class="hlt">model</span>'s climates. A <span class="hlt">stability</span> criterion is derived, and its application shows that the 'present climate' and the 'deep freeze' are stable, whereas the <span class="hlt">model</span>'s glacial is unstable. A variational principle is introduced to confirm the results of this <span class="hlt">stability</span> <span class="hlt">analysis</span>. For a sufficient decrease in solar radiation (about 2%) the glacial and interglacial solutions disappear, leaving the ice-covered earth as the only possible climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012TRACE..23..377F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012TRACE..23..377F"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Absorption Chiller-Heaters by Applying Transfer Function</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujii, Tatsuo; Miyake, Satoshi; Oka, Masahiro; Mori, Kiyoyuki</p> <p></p> <p>A transfer function approach is found to be a practical method for ensuring stable operation of absorption chiller-heaters. The transfer function <span class="hlt">model</span> is based on a solution-circuit of the machine, which dominates the <span class="hlt">stability</span> of the operation. This <span class="hlt">model</span> includes a solution pump, a generator with an overflow weir, and a float valve. We found that the solution-circuit system is designed with the cascade control, which makes the system stable. In this construction, the float valve actuates a primary control loop, and the overflow weir actuates a secondary loop. The effects of the characteristic of the solution pump and the overflow weir are estimated by the degree of the <span class="hlt">stabilities</span>, which are the gain margin and the phase margin. We found that the characteristic of the solution pump strongly effects the <span class="hlt">stability</span> by enhancing the effect of the cascade control and improving the <span class="hlt">stability</span>. So it is essential for a better <span class="hlt">stability</span> <span class="hlt">analysis</span> <span class="hlt">model</span>. According to these results, the established <span class="hlt">model</span> is useful for quantitatively predicting the <span class="hlt">stabilities</span> of a chiller-heater in operation, and simultaneously reducing its size and improving the <span class="hlt">stability</span> of operation. We conclude that the methodology based on transfer function can provide compact and reliable absorption chiller-heaters.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23054629','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23054629"><span id="translatedtitle">Determination and validation of reference gene <span class="hlt">stability</span> for qPCR <span class="hlt">analysis</span> in polysaccharide hydrogel-based 3D chondrocytes and mesenchymal stem cell cultural <span class="hlt">models</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chooi, Wai Hon; Zhou, Ruijie; Yeo, Suan Siong; Zhang, Feng; Wang, Dong-An</p> <p>2013-06-01</p> <p>Gene expression study is widely used to obtain information of the cell activities and phenotypes. To quantify gene expression, measurement of the mRNA copy number is commonly done by quantitative RT-PCR (RT-qPCR). However, proper reference gene is needed for different tissues to normalize the expression level of different genes accurately. In this study, reference gene determination was done for three-dimensional (3D) artificial tissue constructs in hydrogel. Porcine synovium-derived mesenchymal stem cells (SMSCs) and rabbit chondrocytes were cultured in both alginate and agarose hydrogels to set up four different 3D culture systems to form the artificial tissue constructs. The gene expression levels of candidate genes were determined by RT-qPCR and then analyzed by geNorm, Bestkeeper, and Normfinder. For porcine SMSCs, PPIA, and TBP were selected for tissue in alginate scaffold whereas HPRT and TBP were selected for the agarose scaffold system. On the other hand, HPRT, PPIA, and RPL18 were the stable reference genes for rabbit chondrocytes in alginate scaffold while TBP, RPL5, and RPL18 were selected for rabbit chondrocytes in agarose scaffold. This study has further indicated that suitable reference genes are different for each tissue and study purpose. The reference genes are expressed in different <span class="hlt">stability</span> when a scaffold of different material is used. PMID:23054629</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010APS..DFD.EL003H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010APS..DFD.EL003H"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of the pulmonary liquid bilayer.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Halpern, David; Grotberg, James</p> <p>2010-11-01</p> <p>The lung consists of liquid-lined compliant airways that convey air to and from the alveoli where gas exchange takes place. Because the airways are coated with a bilayer consisting of a mucus layer on top of a periciliary fluid layer, a surface tension instability can generate flows within the bilayer and induce the formation of liquid plugs that block the passage of air. This is a problem for example with premature neonates whose lungs do not produce sufficient quantities of surfactant and suffer from respiratory distress syndrome. To study this instability a system of coupled nonlinear evolution equations are derived using lubrication theory for the thicknesses of the two liquid layers which are assumed to be Newtonian. A normal mode <span class="hlt">analysis</span> is used to investigate the initial growth of the disturbances, and reveals how the grow rate is affected by the ratio of viscosities ?, film thicknesses ? and surface tensions ? of the two layers which can change by disease. Numerical solutions of the evolution equations show that there is a critical bilayer thickness ?c above which closure occurs, and that a more viscous and thicker layer compared to the periciliary layer closes more slowly. However, ?cis weakly dependent on ?, ? and ?. We also examine the potential impact of wall shear stress and normal stress on cell damage. This work is funded by NIH HL85156.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006APS..DFD.EN001T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006APS..DFD.EN001T"><span id="translatedtitle">Linear <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Couette Flow with a Porous Wall</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tilton, Nils; Cortelezzi, Luca</p> <p>2006-11-01</p> <p>It is well known that plane Couette flow in a channel with perfectly smooth, impermeable walls is linearly stable for all Reynolds numbers. Little attention has been given in literature to the <span class="hlt">stability</span> of plane Couette flow when at least one of the walls is porous. In this study, we consider a channel delimited by an impermeable moving wall, which drives the flow, and a stationary, rigid, homogeneous, isotropic, porous block. We perform a three-dimensional linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of the fully developed laminar flow in both the channel and the porous block. We restrict the study to sufficiently small permeabilities in order to neglect inertial effects in the porous flow. We solve the coupled linear <span class="hlt">stability</span> problem, arising from the adjacent channel and porous flows, using a spectral collocation technique. The linear <span class="hlt">stability</span> <span class="hlt">analysis</span> takes account of the coupling between the two disturbance fields through boundary conditions recently derived by Ochoa-Tapia and Whitaker (Int. J. Heat Mass Transfer, 38, 1995). We find that Couette flow over a permeable wall is no longer absolutely stable. While the critical Reynolds number tends to infinity as the permeability tends to zero, it decreases drastically for higher permeabilities. We also find a new channel mode and new class of modes in the porous region. We compare and discuss these results in terms of the recently published results of a three-dimensional linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of a channel flow with porous walls (Tilton and Cortelezzi, Phys. Fluids 18, 051702, 2006).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/220153','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/220153"><span id="translatedtitle">Automated 3-D <span class="hlt">analysis</span> of Gravity Dam <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Barrett, P.R.; Boggs, H.</p> <p>1995-12-31</p> <p>The safety and <span class="hlt">stability</span> of nonfederal hydroelectric project dams in the U.S. is a responsibility of the Federal Energy Regulatory Commission (FERC). FERC requires dam owners to reevaluate their structure`s <span class="hlt">stability</span> every five years. In spite of the fact that FERC guidelines allow owners to use a variety of analytical approaches, millions of dollars are spent each year on safety modifications based on sometimes very conservative <span class="hlt">analysis</span> methods. <span class="hlt">Analysis</span> methods are often limited to hand calculations that assume a 2-D rigid body bending response of the dam or automated 2-D finite element analyses which can sometimes predict smaller safety factors than the rigid body analyses. Evaluation of dam <span class="hlt">stability</span> using 3-D finite element analyses can sometimes reduce the conservatism in evaluating a dam`s <span class="hlt">stability</span> even when conventional wisdom suggests that a 2-D <span class="hlt">analysis</span> is sufficient. Significant increases in <span class="hlt">stability</span> obtained from the 3-D analyses come primarily from the confining stresses from the dam abutments and the redistribution of load along the dam`s length. Even when the confining stresses are relatively small, large changes in sliding safety factors can be seen, since most dams, <span class="hlt">stability</span> is extremely sensitive to variations in dam-rock interface cracks. The confining stresses reduce the propagation of cracks. The length of crack controls the magnitude of uplift loads applied to the bottom of the dam which in turn potentially leads to longer crack lengths. Both crack length and magnitude of uplift load directly effect the sliding <span class="hlt">stability</span> factor of safety.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983IAUS..100..285D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983IAUS..100..285D"><span id="translatedtitle">The <span class="hlt">stability</span> of axisymmetric galaxy <span class="hlt">models</span> with anisotropic dispersions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Zeeuw, T.; Franx, M.; Meys, J.; Brink, K.; Habing, H.</p> <p></p> <p>Axisymmetric <span class="hlt">models</span> constructed by means of Schwarzschild's (1979) self-consistent method are discussed, with attention also given to the <span class="hlt">stability</span> of the <span class="hlt">models</span>. Use is made of van Albada's axisymmetric N-body program (van Albada and van Gorkum, 1977) in order to test the <span class="hlt">stability</span> of the equilibrium <span class="hlt">models</span> in the presence of axisymmetric perturbations. It is found that <span class="hlt">models</span> that have a local radial velocity dispersion below a certain critical value are unstable to such perturbations. It is suspected that a generalized <span class="hlt">stability</span> criterion for the local anisotropic velocity dispersion may exist, analogous to the result for infinitely thin disks. This <span class="hlt">stability</span> depends only on the orbits that constitute the <span class="hlt">model</span> and not on the fraction of retrograde stars in each orbit. The <span class="hlt">models</span> that are stable in the presence of axisymmetric perturbations may still be unstable to barlike perturbations. Since this instability depends on the total angular momentum of the <span class="hlt">model</span>, the fraction of retrograde stars is important. Using Vandervoort's (1982) refinement of the Ostriker-Peebles (Ostriker and Peebles, 1973) criterion, it is found that some of the <span class="hlt">models</span> should be stable even if all stars are direct but that other <span class="hlt">models</span> can be made stable only when a fraction of the stars is retrograde.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009RMRE...42..751A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009RMRE...42..751A"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> and the Stabilisation of Flexural Toppling Failure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amini, Mehdi; Majdi, Abbas; Aydan, Ömer</p> <p>2009-10-01</p> <p>Flexural toppling is a mode of failure that may occur in a wide range of layered rock strata in both rock slopes and large underground excavations. Whenever rock mass is composed of a set of parallel discontinuities dipping steeply against the excavated face plane, the rock mass will have the potential of flexural toppling failure as well. In such cases, the rock mass behaves like inclined superimposed cantilever beams that bend under their own weight while transferring the load to the underlying strata. If the bending stress exceeds the rock column’s tensile strength, flexural toppling failure will be initiated. Since the rock columns are “statically indeterminate,” thus, their factors of safety may not be determined solely by equations of equilibrium. The paper describes an analytical <span class="hlt">model</span> with a sequence of inclined superimposed cantilever rock columns with a potential of flexural topping failure. The <span class="hlt">model</span> is based on the principle of compatibility equations and leads to a new method by which the magnitudes and points of application of intercolumn forces are determined. On the basis of the proposed <span class="hlt">model</span>, a safety factor for each rock column can be computed independently. Hence, every rock column will have a unique factor of safety. The least factor of safety that exists in any rock column is selected as the rock mass representative safety factor based on which simple equations are proposed for a conservative rock mass <span class="hlt">stability</span> <span class="hlt">analysis</span> and design. As a result, some new relations are established in order to design the length, cross-sectional area and pattern of fully grouted rock bolts for the stabilisation of such rock mass. Finally, the newly proposed equations are compared with the results of existing experimental flexural toppling failure <span class="hlt">models</span> (base friction and centrifuge tests) for further verification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JApMa..70..162W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JApMa..70..162W"><span id="translatedtitle"><span class="hlt">Stability</span> of localized solutions under rigid loading in a heuristic buckling <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wadee, M. Khurram</p> <p>2005-02-01</p> <p>The <span class="hlt">stability</span> of static localized buckling solutions which bifurcate from the critical load for a strut on an elastic foundation is analysed under conditions of rigid loading (i.e. with prescribed end shortening) using a non-periodic modal <span class="hlt">analysis</span>. The characteristic of such deflection patterns is in marked contrast with <span class="hlt">stability</span> under the more straightforward case of dead loading (behaviour under prescribed load). The <span class="hlt">model</span> presented incorporates initial destabilization and subsequent restabilization of the response at the lowest order.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930018247','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930018247"><span id="translatedtitle"><span class="hlt">Stability</span> investigations of airfoil flow by global <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Morzynski, Marek; Thiele, Frank</p> <p>1992-01-01</p> <p>As the result of global, non-parallel flow <span class="hlt">stability</span> <span class="hlt">analysis</span> the single value of the disturbance growth-rate and respective frequency is obtained. This complex value characterizes the <span class="hlt">stability</span> of the whole flow configuration and is not referred to any particular flow pattern. The global <span class="hlt">analysis</span> assures that all the flow elements (wake, boundary and shear layer) are taken into account. The physical phenomena connected with the wake instability are properly reproduced by the global <span class="hlt">analysis</span>. This enhances the investigations of instability of any 2-D flows, including ones in which the boundary layer instability effects are known to be of dominating importance. Assuming fully 2-D disturbance form, the global linear <span class="hlt">stability</span> problem is formulated. The system of partial differential equations is solved for the eigenvalues and eigenvectors. The equations, written in the pure stream function formulation, are discretized via FDM using a curvilinear coordinate system. The complex eigenvalues and corresponding eigenvectors are evaluated by an iterative method. The investigations performed for various Reynolds numbers emphasize that the wake instability develops into the Karman vortex street. This phenomenon is shown to be connected with the first mode obtained from the non-parallel flow <span class="hlt">stability</span> <span class="hlt">analysis</span>. The higher modes are reflecting different physical phenomena as for example Tollmien-Schlichting waves, originating in the boundary layer and having the tendency to emerge as instabilities for the growing Reynolds number. The investigations are carried out for a circular cylinder, oblong ellipsis and airfoil. It is shown that the onset of the wake instability, the waves in the boundary layer, the shear layer instability are different solutions of the same eigenvalue problem, formulated using the non-parallel theory. The <span class="hlt">analysis</span> offers large potential possibilities as the generalization of methods used till now for the <span class="hlt">stability</span> <span class="hlt">analysis</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25811440','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25811440"><span id="translatedtitle"><span class="hlt">Stability</span> and optimization in structured population <span class="hlt">models</span> on graphs.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Colombo, Rinaldo M; Garavello, Mauro</p> <p>2015-04-01</p> <p>We prove existence and uniqueness of solutions, continuous dependence from the initial datum and <span class="hlt">stability</span> with respect to the boundary condition in a class of initial--boundary value problems for systems of balance laws. The particular choice of the boundary condition allows to comprehend <span class="hlt">models</span> with very different structures. In particular, we consider a juvenile-adult <span class="hlt">model</span>, the problem of the optimal mating ratio and a <span class="hlt">model</span> for the optimal management of biological resources. The <span class="hlt">stability</span> result obtained allows to tackle various optimal management/control problems, providing sufficient conditions for the existence of optimal choices/controls. PMID:25811440</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=%22EQUATIONS+of+motion%22&pg=2&id=EJ903747','ERIC'); return false;" href="http://eric.ed.gov/?q=%22EQUATIONS+of+motion%22&pg=2&id=EJ903747"><span id="translatedtitle"><span class="hlt">Stabilizing</span> a Bicycle: A <span class="hlt">Modeling</span> Project</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Pennings, Timothy J.; Williams, Blair R.</p> <p>2010-01-01</p> <p>This article is a project that takes students through the process of forming a mathematical <span class="hlt">model</span> of bicycle dynamics. Beginning with basic ideas from Newtonian mechanics (forces and torques), students use techniques from calculus and differential equations to develop the equations of rotational motion for a bicycle-rider system as it tips from…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=equations+AND+motion&pg=2&id=EJ903747','ERIC'); return false;" href="http://eric.ed.gov/?q=equations+AND+motion&pg=2&id=EJ903747"><span id="translatedtitle"><span class="hlt">Stabilizing</span> a Bicycle: A <span class="hlt">Modeling</span> Project</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Pennings, Timothy J.; Williams, Blair R.</p> <p>2010-01-01</p> <p>This article is a project that takes students through the process of forming a mathematical <span class="hlt">model</span> of bicycle dynamics. Beginning with basic ideas from Newtonian mechanics (forces and torques), students use techniques from calculus and differential equations to develop the equations of rotational motion for a bicycle-rider system as it tips from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090041645','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090041645"><span id="translatedtitle">A Robustly <span class="hlt">Stabilizing</span> <span class="hlt">Model</span> Predictive Control Algorithm</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ackmece, A. Behcet; Carson, John M., III</p> <p>2007-01-01</p> <p>A <span class="hlt">model</span> predictive control (MPC) algorithm that differs from prior MPC algorithms has been developed for controlling an uncertain nonlinear system. This algorithm guarantees the resolvability of an associated finite-horizon optimal-control problem in a receding-horizon implementation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=37566&keyword=microcomputer&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=49885066&CFTOKEN=16867813','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=37566&keyword=microcomputer&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=49885066&CFTOKEN=16867813"><span id="translatedtitle">GEOTECHNICAL <span class="hlt">ANALYSIS</span> FOR REVIEW OF DIKE <span class="hlt">STABILITY</span> (GARDS). TECHNICAL MANUAL</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The structure and capabilities of a user-friendly, interactive computer program developed for the <span class="hlt">stability</span> <span class="hlt">analysis</span> of dikes (GARDS) are described. The program was developed under the sponsorship of the U.S. Environmental Protection Agency and therefore emphasizes Hazardous Wast...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19770042914&hterms=slope+stability&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dslope%2Bstability','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19770042914&hterms=slope+stability&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dslope%2Bstability"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of a reinforced carbon carbon shell</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Agan, W. E.; Jordan, B. M.</p> <p>1977-01-01</p> <p>This paper presents the development of a <span class="hlt">stability</span> <span class="hlt">analysis</span> for the nose cap of the NASA Space Shuttle Orbiter. <span class="hlt">Stability</span> is evaluated by the differential stiffness <span class="hlt">analysis</span> of the NASTRAN finite-element computer code, addressing those nonstandard characteristics in the nose cap such as nonuniform curvature, asymmetrical and nonuniform loads, support fixity, and various combinations of membrane and bending stresses. A full-sized nose cap, thinner than production, was statically tested and <span class="hlt">stability</span> analyzed. The failing load level correlated to within 30%. The region and mode of buckling that occurred during test was accurately predicted by <span class="hlt">analysis</span>. The criterion for predicting instability is based on the behavior of the nonlinear deflections. The deflections are nonlinear elastic in that the stresses are well within the elastic range of the material, but the geometry-load relationship produces nonlinear deflections. The load-deflection relationship is well defined by differential stiffness <span class="hlt">analysis</span> up to the zero-slope portion of the curve, the point of neutral <span class="hlt">stability</span> or where the shell 'snaps through' just prior to general instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=310672','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=310672"><span id="translatedtitle">Bank <span class="hlt">stability</span> <span class="hlt">analysis</span> for fluvial erosion and mass failure</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>The central objective of this study was to highlight the differences in magnitude between mechanical and fluvial streambank erosional strength with the purpose of developing a more comprehensive bank <span class="hlt">stability</span> <span class="hlt">analysis</span>. Mechanical erosion and ultimately failure signifies the general movement or coll...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1299419','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1299419"><span id="translatedtitle"><span class="hlt">Analysis</span> of the <span class="hlt">stability</span> of hemoglobin S double strands.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mu, X Q; Makowski, L; Magdoff-Fairchild, B</p> <p>1998-01-01</p> <p>The deoxyhemoglobin S (deoxy-HbS) double strand is the fundamental building block of both the crystals of deoxy-HbS and the physiologically relevant fibers present within sickle cells. To use the atomic-resolution detail of the hemoglobin-hemoglobin interaction known from the crystallography of HbS as a basis for understanding the interactions in the fibers, it is necessary to define precisely the relationship between the straight double strands in the crystal and the twisted, helical double strands in the fibers. The intermolecular contact conferring the <span class="hlt">stability</span> of the double strand in both crystal and fiber is between the beta6 valine on one HbS molecule and residues near the EF corner of an adjacent molecule. <span class="hlt">Models</span> for the helical double strands were constructed by a geometric transformation from crystal to fiber that preserves this critical interaction, minimizes distortion, and makes the transformation as smooth as possible. From these <span class="hlt">models</span>, the energy of association was calculated over the range of all possible helical twists of the double strands and all possible distances of the double strands from the fiber axis. The calculated association energies reflect the fact that the axial interactions decrease as the distance between the double strand and the fiber axis increases, because of the increased length of the helical path taken by the double strand. The lateral interactions between HbS molecules in a double strand change relatively little between the crystal and possible helical double strands. If the twist of the fiber or the distance between the double strand and the fiber axis is too great, the lateral interaction is broken by intermolecular contacts in the region around the beta6 valine. Consequently, the geometry of the beta6 valine interaction and the residues surrounding it severely restricts the possible helical twist, radius, and handedness of helical aggregates constructed from the double strands. The limitations defined by this <span class="hlt">analysis</span> establish the structural basis for the right-handed twist observed in HbS fibers and demonstrates that for a subunit twist of 8 degrees, the fiber diameter cannot be more than approximately 300 A, consistent with electron microscope observations. The energy of interaction among HbS molecules in a double strand is very slowly varying with helical pitch, explaining the variable pitch observed in HbS fibers. The <span class="hlt">analysis</span> results in a <span class="hlt">model</span> for the HbS double strand, for use in the <span class="hlt">analysis</span> of interactions between double strands and for refinement of <span class="hlt">models</span> of the HbS fibers against x-ray diffraction data. PMID:9449367</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3850M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3850M"><span id="translatedtitle">Prediction of the biochar carbon <span class="hlt">stability</span> by thermal <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Méndez, Ana; Cely, Paola; Plaza, César; Paz-Ferreiro, Jorge; Gascó, Gabriel</p> <p>2015-04-01</p> <p>Thermal <span class="hlt">analysis</span> (DTA, DSC, TG and dTG) has been used for decades to characterize carbonaceous materials used as fuels (oil, coal). Our research group has used these techniques for the characterisation of different biochars in order to assess proportions of labile and recalcitrant organic matter and to study the evolution of soil organic matter in soils amended with biochar. Thermal <span class="hlt">analysis</span> could be used to determine the proximate <span class="hlt">analysis</span>, i.e., the percentage of humidity, volatile matter and fixed carbon or to calculate the thermostability index, previously identified as a reliable parameter for evaluating the level of <span class="hlt">stability</span> of organic matter in organic wastes and biochar. Relationship between the <span class="hlt">stability</span> of biochar, the raw material and the pyrolysis conditions could be established by thermal <span class="hlt">analysis</span> techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.V43B1427B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.V43B1427B"><span id="translatedtitle">Limitations of Deterministic <span class="hlt">Modelling</span> of Slope <span class="hlt">Stability</span> on Volcanic Edifices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burrell, R. V.; Pinkerton, H.; Binley, A.</p> <p>2004-12-01</p> <p>The conditions leading to the 18 May 1980 sector collapse of Mount St Helens have been the subject of a number of detailed investigations. Preservation of the initial failure plane(s) allowed Voight et al. (1983) and Donnadieu et al. (2001) to undertake back analyses and determine a range of possible failure conditions. While the <span class="hlt">models</span> proposed offer major insights into potential failure mechanisms, we will demonstrate that deterministic analyses are of limited usefulness because many of the <span class="hlt">model</span> parameters, such as cohesion, internal friction and pore pressure, are very poorly constrained. This creates problems of non-uniqueness in the solution. An alternative approach involves a series of Monte Carlo simulations to identify potential combinations of parameters that will produce the observed failure plane. Initial input ranges are specified for each parameter and the predetermined <span class="hlt">model</span> is run repeatedly, with the parameter values for each <span class="hlt">model</span> selected at random from within the input ranges. The interaction between parameters can be examined in detail, providing a better understanding of the potential failure conditions. This approach, which has been tested initially on a theoretical slope with predetermined failure conditions, highlights the fact that it is impossible to generate a unique <span class="hlt">model</span> that fits the data when the slope has poorly defined strength parameters. This has clear implications for the validity of commonly used deterministic approaches. This probabilistic back <span class="hlt">analysis</span> approach has been used to reanalyse the conditions that led to the May 18 collapse on Mount St Helens. Donnadieu, F., Merle, O., and Besson, J.C., 2001, Volcanic edifice <span class="hlt">stability</span> during cryptodome intrusion, Bulletin of Volcanology, vol 63, p61-72. Voight, B., Janda, R.J., Glicken, H., and Douglass, P.M., 1983, Nature and Mechanics of the Mount St-Helens Rockslide-Avalanche of 18 May 1980, Geotechnique, vol 33, p243-273.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920051784&hterms=oral&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Doral','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920051784&hterms=oral&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Doral"><span id="translatedtitle">Aeroelastic <span class="hlt">stability</span> analyses of two counter rotating propfan designs for a cruise missile <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mahajan, Aparajit J.; Lucero, John M.; Mehmed, Oral; Stefko, George L.</p> <p>1992-01-01</p> <p>A modal aeroelastic <span class="hlt">analysis</span> combining structural and aerodynamic <span class="hlt">models</span> is applied to counterrotating propfans to evaluate their structural integrity for wind-tunnel testing. The aeroelastic <span class="hlt">analysis</span> code is an extension of the 2D <span class="hlt">analysis</span> code called the Aeroelastic <span class="hlt">Stability</span> and Response of Propulsion Systems. Rotational speed and freestream Mach number are the parameters for calculating the <span class="hlt">stability</span> of the two blade designs with a modal method combining a finite-element structural <span class="hlt">model</span> with 2D steady and unsteady cascade aerodynamic <span class="hlt">models</span>. The <span class="hlt">model</span> demonstrates convergence to the least stable aeroelastic mode, describes the effects of a nonuniform inflow, and permits the modification of geometry and rotation. The <span class="hlt">analysis</span> shows that the propfan designs are suitable for the wind-tunnel test and confirms that the propfans should be flutter-free under the range of conditions of the testing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5816208','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5816208"><span id="translatedtitle">Laboratory and numerical discontinuum <span class="hlt">modeling</span> of wellbore <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rawlings, C.G.; Barton, N.R. ); Bandis, S.C. ); Addis, M.A. ); Gutierrez, M.S. . Rock Engineering and Reservoir Mechanics Division)</p> <p>1993-11-01</p> <p>Wellbore-<span class="hlt">stability</span> analyses based on intact wellbore walls can be too conservative because failed/fractured zones around wellbores relieve stress and give support. Wellbore-breakout analyses indicate that most drilled wells experience deformation beyond the rupture stage and that this deformation is acceptable for the drilling process. Validation of the methods available to predict wellbore <span class="hlt">stability</span> requires a comparison of theoretical <span class="hlt">models</span> with experimental simulations of wellbore behavior. This paper describes a series of scaled laboratory wellbore-<span class="hlt">stability</span> experiments carried out under various borehole inclinations and stress conditions. The goal was to investigate the influence of the fractured zone, stress anisotropy, well deviation, and well orientation on wellbore <span class="hlt">stability</span>. Classic log spiral fracture geometries were obtained around the wellbore, and the effect of the fractured zone on wellbore <span class="hlt">stability</span> was studied with a distinct-element program called the universal distinct-element code (UDEC). Results show the importance of taking into account the <span class="hlt">stability</span> of the fractured zone and subsequent wellbore breakout when wellbore <span class="hlt">stability</span> is considered.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960015896','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960015896"><span id="translatedtitle">Fluid Dynamic and <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of a Thin Liquid Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McMaster, Matthew S.</p> <p>1992-01-01</p> <p>Interest in thin sheet flows has recently been renewed due to their potential application in space radiators. Theoretical and experimental studies of the fluid dynamics and <span class="hlt">stability</span> of thin liquid sheet flows have been carried out in this thesis. A computer program was developed to determine the cross-sectional shape of the edge cylinder given the cross-sectional area of the edge cylinder. A <span class="hlt">stability</span> <span class="hlt">analysis</span> was performed on a non-planer liquid sheet. A study was conducted to determine the effects of air resistance on the sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001PhyD..156..139S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001PhyD..156..139S"><span id="translatedtitle">Mechanical <span class="hlt">models</span> for insect locomotion: <span class="hlt">stability</span> and parameter studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmitt, John; Holmes, Philip</p> <p>2001-08-01</p> <p>We extend the <span class="hlt">analysis</span> of simple <span class="hlt">models</span> for the dynamics of insect locomotion in the horizontal plane, developed in [Biol. Cybern. 83 (6) (2000) 501] and applied to cockroach running in [Biol. Cybern. 83 (6) (2000) 517]. The <span class="hlt">models</span> consist of a rigid body with a pair of effective legs (each representing the insect’s support tripod) placed intermittently in ground contact. The forces generated may be prescribed as functions of time, or developed by compression of a passive leg spring. We find periodic gaits in both cases, and show that prescribed (sinusoidal) forces always produce unstable gaits, unless they are allowed to rotate with the body during stride, in which case a (small) range of physically unrealistic stable gaits does exist. <span class="hlt">Stability</span> is much more robust in the passive spring case, in which angular momentum transfer at touchdown/liftoff can result in convergence to asymptotically straight motions with bounded yaw, fore-aft and lateral velocity oscillations. Using a non-dimensional formulation of the equations of motion, we also develop exact and approximate scaling relations that permit derivation of gait characteristics for a range of leg stiffnesses, lengths, touchdown angles, body masses and inertias, from a single gait family computed at ‘standard’ parameter values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6714107','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6714107"><span id="translatedtitle">Geotechnical <span class="hlt">analysis</span> for dike <span class="hlt">stability</span> (GARDS) (for microcomputers). Software</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ammon, D.C.; McCandless, R.; Cluxton, P.</p> <p>1986-12-01</p> <p>The structure and capabilities of a user-friendly, interactive computer program developed for the <span class="hlt">stability</span> <span class="hlt">analysis</span> of dikes (GARDS) are described. The GARDS program is designed to guide a geotechnical non-specialist (EPA regulatory personnel) through the customary steps of earth dike <span class="hlt">analysis</span> considering slope <span class="hlt">stability</span>, settlement, liquefaction, hydraulic flow and pressure conditions, and piping. The GARDS package is designed for use on the IBM-PC/XT microcomputer. User documentation consists of a combined Handbook/User's Manual (under development) which presents basic theory, program operational procedures, and example long hand and computer solutions for each <span class="hlt">analysis</span>...Software Description: The program is written in the FORTRAN program language for implementation on an IBM-PC AT, XT or compatible microcomputer using a DOS 2.1 or higher operating system. 512K bytes of core storage are required. Note: A hard disk is required; a color monitor is recommended.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JSV...333.5464B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JSV...333.5464B"><span id="translatedtitle">Experimental bifurcation <span class="hlt">analysis</span> of an impact oscillator-Determining <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bureau, Emil; Schilder, Frank; Elmegrd, Michael; Santos, Ilmar F.; Thomsen, Jon J.; Starke, Jens</p> <p>2014-10-01</p> <p>We propose and investigate three different methods for assessing <span class="hlt">stability</span> of dynamical equilibrium states during experimental bifurcation <span class="hlt">analysis</span>, using a control-based continuation method. The idea is to modify or turn off the control at an equilibrium state and study the resulting behavior. As a proof of concept the three methods are successfully implemented and tested for a harmonically forced impact oscillator with a hardening spring nonlinearity, and controlled by electromagnetic actuators. We show that under certain conditions it is possible to quantify the instability in terms of finite-time Lyapunov exponents. As a special case we study an isolated branch in the bifurcation diagram brought into existence by a 1:3 subharmonic resonance. On this isola it is only possible to determine <span class="hlt">stability</span> using one of the three methods, which is due to the fact that only this method guarantees that the equilibrium state can be restored after measuring <span class="hlt">stability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19870059230&hterms=analysis+work+group&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Danalysis%2Bwork%2Bgroup','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19870059230&hterms=analysis+work+group&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Danalysis%2Bwork%2Bgroup"><span id="translatedtitle">Linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of three-dimensional compressible boundary layers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Malik, Mujeeb R.; Orszag, Steven A.</p> <p>1987-01-01</p> <p>A compressible <span class="hlt">stability</span> <span class="hlt">analysis</span> computer code is developed. The code uses a matrix finite-difference method for local eigenvale solution when a good guess for the eigenvalue is available and is significantly more computationally efficient than the commonly used inital-value approach. The local eigenvalue search procedure also results in eigenfunctions and, at little extra work, group velocities. A globally convergent eigenvalue procedure is also developed that may be used when no guess for the eigenvalue is available. The global problem is formulated in such a way that no unstable spurious modes appear so that the method is suitable for use in a black-box <span class="hlt">stability</span> code. Sample <span class="hlt">stability</span> calculations are presented for the boundary layer profiles of an LFC swept wing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EPJC...63..461G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EPJC...63..461G"><span id="translatedtitle"><span class="hlt">Stability</span> of the scalar potential and symmetry breaking in the economical 3-3-1 <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giraldo, Yithsbey; Ponce, William A.; Snchez, Luis A.</p> <p>2009-10-01</p> <p>A detailed study of the criteria for <span class="hlt">stability</span> of the scalar potential and the proper electroweak symmetry breaking pattern in the economical 3-3-1 <span class="hlt">model</span>, is presented. For the <span class="hlt">analysis</span> we use and improve a method previously developed to study the scalar potential in the two-Higgs-doublet extension of the standard <span class="hlt">model</span>. A new theorem related to the <span class="hlt">stability</span> of the potential is stated. As a consequence of this study, the consistency of the economical 3-3-1 <span class="hlt">model</span> emerges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920017793','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920017793"><span id="translatedtitle">Effect of <span class="hlt">model</span> selection on combustor performance and <span class="hlt">stability</span> predictions using ROCCID</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Giuliani, James E.; Klem, Mark D.</p> <p>1992-01-01</p> <p>The ROCket Combustor Interactive Design (ROCCID) methodology is an interactive computer program that combines previously developed combustion <span class="hlt">analysis</span> <span class="hlt">models</span> to calculate the combustion performance and <span class="hlt">stability</span> of liquid rocket engines. Test data from 213 kN (48,000 lbf) Liquid Oxygen (LOX)/RP-1 combustor with an O-F-O (oxidizer-fuel-oxidizer) triplet injector were used to characterize the predictive capabilities of the ROCCID <span class="hlt">analysis</span> <span class="hlt">models</span> for this injector/propellant configuration. Thirteen combustion performance and <span class="hlt">stability</span> <span class="hlt">models</span> were incorporated into ROCCID, and ten of them, which have options for triplet injectors, were examined. Calculations using different combinations of <span class="hlt">analysis</span> <span class="hlt">models</span>, with little or no anchoring, were carried out on a test matrix of operating combinations matching those of the test program. Results of the computer analyses were compared to test data, and the ability of the <span class="hlt">model</span> combinations to correctly predict combustion <span class="hlt">stability</span> or instability was determined. For the best <span class="hlt">model</span> combination(s), sensitivity of the calculations to fuel drop size and mixing efficiency was examined. Error in the <span class="hlt">stability</span> calculations due to uncertainty in the pressure interaction index (N) was examined. The recommended <span class="hlt">model</span> combinations for this O-F-O triplet LOX/RP-1 configuration are proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/378008','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/378008"><span id="translatedtitle">A multivariate screening <span class="hlt">analysis</span> of W/O emulsions in high external electric fields as studied by means of dielectric time domain spectroscopy. 2: <span class="hlt">Model</span> emulsions <span class="hlt">stabilized</span> by interfacially active fractions from crude oils</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Foerdedal, H.; Midttun, O.; Sjoeblom, J.; Kvalheim, O.M.; Schildberg, Y.; Volle, J.L.</p> <p>1996-09-01</p> <p>The electrically induced coalescence of water-in-oil emulsions <span class="hlt">stabilized</span> by interfacially active fractions from crude oils has been studied by means of time domain dielectric spectroscopy at high electric fields. The experiments were designed with a 2{sup 7-3} reduced factorial design. Regression <span class="hlt">analysis</span> clearly shows that the choice of organic solvent and the amount of asphaltenes, as well as the interplay between these variables, are the most significant parameters for determining the <span class="hlt">stability</span> of these emulsions. It should be pointed out that the asphaltenes were the only surface active fraction tested. No interplay between, for instance, asphaltenes and resins was investigated. The nonlinearity found in the regression <span class="hlt">analysis</span> is explained by different aggregation states of asphaltenes in aliphatic and aromatic solvents. The influence of the variables upon the emulsion <span class="hlt">stability</span> is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1637...89B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1637...89B"><span id="translatedtitle">The beauty of simple adaptive control and new developments in nonlinear systems <span class="hlt">stability</span> <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barkana, Itzhak</p> <p>2014-12-01</p> <p>Although various adaptive control techniques have been around for a long time and in spite of successful proofs of <span class="hlt">stability</span> and even successful demonstrations of performance, the eventual use of adaptive control methodologies in practical real world systems has met a rather strong resistance from practitioners and has remained limited. Apparently, it is difficult to guarantee or even understand the conditions that can guarantee stable operations of adaptive control systems under realistic operational environments. Besides, it is difficult to measure the robustness of adaptive control system <span class="hlt">stability</span> and allow it to be compared with the common and widely used measure of phase margin and gain margin that is utilized by present, mainly LTI, controllers. Furthermore, customary <span class="hlt">stability</span> <span class="hlt">analysis</span> methods seem to imply that the mere <span class="hlt">stability</span> of adaptive systems may be adversely affected by any tiny deviation from the pretty idealistic and assumably required <span class="hlt">stability</span> conditions. This paper first revisits the fundamental qualities of customary direct adaptive control methodologies, in particular the classical <span class="hlt">Model</span> Reference Adaptive Control, and shows that some of their basic drawbacks have been addressed and eliminated within the so-called Simple Adaptive Control methodology. Moreover, recent developments in the <span class="hlt">stability</span> <span class="hlt">analysis</span> methods of nonlinear systems show that prior conditions that were customarily assumed to be needed for <span class="hlt">stability</span> are only apparent and can be eliminated. As a result, sufficient conditions that guarantee <span class="hlt">stability</span> are clearly stated and lead to similarly clear proofs of <span class="hlt">stability</span>. As many real-world applications show, once robust <span class="hlt">stability</span> of the adaptive systems can be guaranteed, the added value of using Add-On Adaptive Control along with classical Control design techniques is pushing the desired performance beyond any previous limits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22390805','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22390805"><span id="translatedtitle">The beauty of simple adaptive control and new developments in nonlinear systems <span class="hlt">stability</span> <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Barkana, Itzhak</p> <p>2014-12-10</p> <p>Although various adaptive control techniques have been around for a long time and in spite of successful proofs of <span class="hlt">stability</span> and even successful demonstrations of performance, the eventual use of adaptive control methodologies in practical real world systems has met a rather strong resistance from practitioners and has remained limited. Apparently, it is difficult to guarantee or even understand the conditions that can guarantee stable operations of adaptive control systems under realistic operational environments. Besides, it is difficult to measure the robustness of adaptive control system <span class="hlt">stability</span> and allow it to be compared with the common and widely used measure of phase margin and gain margin that is utilized by present, mainly LTI, controllers. Furthermore, customary <span class="hlt">stability</span> <span class="hlt">analysis</span> methods seem to imply that the mere <span class="hlt">stability</span> of adaptive systems may be adversely affected by any tiny deviation from the pretty idealistic and assumably required <span class="hlt">stability</span> conditions. This paper first revisits the fundamental qualities of customary direct adaptive control methodologies, in particular the classical <span class="hlt">Model</span> Reference Adaptive Control, and shows that some of their basic drawbacks have been addressed and eliminated within the so-called Simple Adaptive Control methodology. Moreover, recent developments in the <span class="hlt">stability</span> <span class="hlt">analysis</span> methods of nonlinear systems show that prior conditions that were customarily assumed to be needed for <span class="hlt">stability</span> are only apparent and can be eliminated. As a result, sufficient conditions that guarantee <span class="hlt">stability</span> are clearly stated and lead to similarly clear proofs of <span class="hlt">stability</span>. As many real-world applications show, once robust <span class="hlt">stability</span> of the adaptive systems can be guaranteed, the added value of using Add-On Adaptive Control along with classical Control design techniques is pushing the desired performance beyond any previous limits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980017945','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980017945"><span id="translatedtitle">The <span class="hlt">Stability</span> of Radiatively Cooling Jets I. Linear <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hardee, Philip E.; Stone, James M.</p> <p>1997-01-01</p> <p>The results of a spatial <span class="hlt">stability</span> <span class="hlt">analysis</span> of a two-dimensional slab jet, in which optically thin radiative cooling is dynamically important, are presented. We study both magnetized and unmagnetized jets at external Mach numbers of 5 and 20. We <span class="hlt">model</span> the cooling rate by using two different cooling curves: one appropriate to interstellar gas, and the other to photoionized gas of reduced metallicity. Thus, our results will be applicable to both protostellar (Herbig-Haro) jets and optical jets from active galactic nuclei. We present analytical solutions to the dispersion relations in useful limits and solve the dispersion relations numerically over a broad range of perturbation frequencies. We find that the growth rates and wavelengths of the unstable Kelvin-Helmholtz (K-H) modes are significantly different from the adiabatic limit, and that the form of the cooling function strongly affects the results. In particular, if the cooling curve is a steep function of temperature in the neighborhood of the equilibrium state, then the growth of K-H modes is reduced relative to the adiabatic jet. On the other hand, if the cooling curve is a shallow function of temperature, then the growth of K-H modes can be enhanced relative to the adiabatic jet by the increase in cooling relative to heating in overdense regions. Inclusion of a dynamically important magnetic field does not strongly modify the important differences between an adiabatic jet and a cooling jet, provided the jet is highly supermagnetosonic and not magnetic pressure-dominated. In the latter case, the unstable modes behave more like the transmagnetosonic magnetic pressure-dominated adiabatic limit. We also plot fluid displacement surfaces associated with the various waves in a cooling jet in order to predict the structures that might arise in the nonlinear regime. This <span class="hlt">analysis</span> predicts that low-frequency surface waves and the lowest order body modes will be the most effective at producing observable features in the jet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JFS....42..488L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JFS....42..488L"><span id="translatedtitle">Nonlinear aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> of wind turbine blade with bending-bending-twist coupling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Tingrui; Ren, Yongsheng; Yang, Xinghua</p> <p>2013-10-01</p> <p>In this study, the nonlinear aeroelastic <span class="hlt">stability</span> of wind turbine blade with bending-bending-twist coupling has been investigated for composite thin-walled structure with pretwist angle. The aerodynamic <span class="hlt">model</span> used here is the differential dynamic stall nonlinear ONERA <span class="hlt">model</span>. The nonlinear aeroelastic equations are reduced to ordinary equations by Galerkin method, with the aerodynamic force decomposition by strip theory. The nonlinear resulting equations are solved by a time-marching approach, and are linearized by small perturbation about the equilibrium point. The nonlinear aeroelastic <span class="hlt">stability</span> characteristics are investigated through eigenvalue <span class="hlt">analysis</span>, nonlinear time domain response, and linearized time domain response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750014250','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750014250"><span id="translatedtitle"><span class="hlt">Analysis</span> of a <span class="hlt">stability</span> valve system for extending the dynamic range of a supersonic inlet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Webb, J. A., Jr.; Dustin, M. O.</p> <p>1975-01-01</p> <p>A <span class="hlt">stability</span> valve system designed for a full-scale, flight, supersonic, mixed-compression inlet was <span class="hlt">modeled</span> dynamically by using analog computer techniques. The system uses poppet valves mounted in the inlet cowl to bypass airflow and augments the inlet shock position control system by preventing unstarts caused by high-frequency perturbations. The <span class="hlt">model</span> was used as a design aid to investigate the effects of varying both the physical configurations of the valve and the flight and wind tunnel conditions. Results of the <span class="hlt">analysis</span> indicate that the <span class="hlt">stability</span> valve will provide a bandpass operation of 1 hertz to 17 hertz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920046966&hterms=terahertz+test&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dterahertz%2Btest','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920046966&hterms=terahertz+test&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dterahertz%2Btest"><span id="translatedtitle">Thermal <span class="hlt">analysis</span> and test of SUNLITE reference cavity for laser frequency <span class="hlt">stabilization</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Amundsen, R. M.</p> <p>1992-01-01</p> <p>SUNLITE is a space-based experiment which uses a reference cavity to provide a stable frequency reference for a terahertz laser oscillator. Thermal <span class="hlt">stability</span> of the cavity is a key factor in attaining a stable narrow-linewidth laser beam. This paper describes the thermal <span class="hlt">stability</span> requirements on the cavity design and detailed thermal <span class="hlt">analysis</span> performed, as well as thermal testing that was performed on a prototype. Analytical thermal <span class="hlt">models</span> were correlated to the test data and additional <span class="hlt">modeling</span> of the current design is presented. Suggestions for improving similar high-precision thermal tests are given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20090009917&hterms=air+quality+control&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dair%2Bquality%2Bcontrol','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20090009917&hterms=air+quality+control&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dair%2Bquality%2Bcontrol"><span id="translatedtitle"><span class="hlt">Stability</span> and Control <span class="hlt">Analysis</span> of the F-15B Quiet Spike Aircraft</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McWherter, Shaun; Moua,Cheng; Gera, Joseph; Cox, Timothy H.</p> <p>2007-01-01</p> <p>The primary objective of the Quiet Spike flight research program was the aerodynamic and structural proof-of-concept of a telescoping, 24 ft, sonic-boom suppressing nose boom on a F-15B aircraft. The program goal was to collect flight data for <span class="hlt">model</span> validation up to 1.8 Mach. In the area of <span class="hlt">stability</span> and controls the primary concern was to assess the effect of the spike on the <span class="hlt">stability</span>, controllability and handling qualities of the aircraft. The primary goal of this test philosophy was maintaining safety of flight. Two main issues are discussed in this paper: the <span class="hlt">stability</span> and controls approach and <span class="hlt">analysis</span> in the presence of uncertain spike influenced aerodynamics on the F-15B aircraft flight dynamics; and the <span class="hlt">analysis</span> of F-15B flight dynamics implications due to spike induced air flow in the vicinity of air data and angle-of-attack sensors. Also addressed are flight test implications based on the <span class="hlt">analysis</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1615579G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1615579G"><span id="translatedtitle">Integrating plant-microbe interactions to understand soil C <span class="hlt">stabilization</span> with the MIcrobial-MIneral Carbon <span class="hlt">Stabilization</span> <span class="hlt">model</span> (MIMICS)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grandy, Stuart; Wieder, Will; Kallenbach, Cynthia; Tiemann, Lisa</p> <p>2014-05-01</p> <p>If soil organic matter is predominantly microbial biomass, plant inputs that build biomass should also increase SOM. This seems obvious, but the implications fundamentally change how we think about the relationships between plants, microbes and SOM. Plant residues that build microbial biomass are typically characterized by low C/N ratios and high lignin contents. However, plants with high lignin contents and high C/N ratios are believed to increase SOM, an entrenched idea that still strongly motivates agricultural soil management practices. Here we use a combination of meta-<span class="hlt">analysis</span> with a new microbial-explicit soil biogeochemistry <span class="hlt">model</span> to explore the relationships between plant litter chemistry, microbial communities, and SOM <span class="hlt">stabilization</span> in different soil types. We use the MIcrobial-MIneral Carbon <span class="hlt">Stabilization</span> (MIMICS) <span class="hlt">model</span>, newly built upon the Community Land <span class="hlt">Model</span> (CLM) platform, to enhance our understanding of biology in earth system processes. The turnover of litter and SOM in MIMICS are governed by the activity of r- and k-selected microbial groups and temperature sensitive Michaelis-Menten kinetics. Plant and microbial residues are <span class="hlt">stabilized</span> short-term by chemical recalcitrance or long-term by physical protection. Fast-turnover litter inputs increase SOM by >10% depending on temperature in clay soils, and it's only in sandy soils devoid of physical protection mechanisms that recalcitrant inputs build SOM. These results challenge centuries of lay knowledge as well as conventional ideas of SOM formation, but are they realistic? To test this, we conducted a meta-<span class="hlt">analysis</span> of the relationships between the chemistry of plant liter inputs and SOM concentrations. We find globally that the highest SOM concentrations are associated with plant inputs containing low C/N ratios. These results are confirmed by individual tracer studies pointing to greater <span class="hlt">stabilization</span> of low C/N ratio inputs, particularly in clay soils. Our <span class="hlt">model</span> and meta-<span class="hlt">analysis</span> results suggest that current ideas about plant-microbe-SOM relationships are unraveling. If so, our reconsideration of the mechanisms <span class="hlt">stabilizing</span> SOM will also challenge long-held views about how to optimize plant community management to increase SOM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10185866','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10185866"><span id="translatedtitle">Preliminary hazards <span class="hlt">analysis</span> of thermal scrap <span class="hlt">stabilization</span> system. Revision 1</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lewis, W.S.</p> <p>1994-08-23</p> <p>This preliminary <span class="hlt">analysis</span> examined the HA-21I glovebox and its supporting systems for potential process hazards. Upon further <span class="hlt">analysis</span>, the thermal <span class="hlt">stabilization</span> system has been installed in gloveboxes HC-21A and HC-21C. The use of HC-21C and HC-21A simplified the initial safety <span class="hlt">analysis</span>. In addition, these gloveboxes were cleaner and required less modification for operation than glovebox HA-21I. While this document refers to glovebox HA-21I for the hazards <span class="hlt">analysis</span> performed, glovebox HC-21C is sufficiently similar that the following <span class="hlt">analysis</span> is also valid for HC-21C. This hazards <span class="hlt">analysis</span> document is being re-released as revision 1 to include the updated flowsheet document (Appendix C) and the updated design basis (Appendix D). The revised Process Flow Schematic has also been included (Appendix E). This Current revision incorporates the recommendations provided from the original hazards <span class="hlt">analysis</span> as well. The System Design Description (SDD) has also been appended (Appendix H) to document the bases for Safety Classification of thermal <span class="hlt">stabilization</span> equipment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AdSpR..48..133S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AdSpR..48..133S"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of explicit guidance laws for space launch vehicles with varying thrust integrals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Song, Eun-Jung; Cho, Sang-bum; Park, Chang-Su; Roh, Woong-Rae; Joh, Miok</p> <p>2011-07-01</p> <p>In this study, a <span class="hlt">stability</span> <span class="hlt">analysis</span> of the explicit guidance laws for space launch vehicles is performed with consideration of varying thrust integrals. Among various forms of explicit guidance, linear tangent guidance in its general form is selected and six different acceleration profiles are considered for this numerical experiment. A linear system <span class="hlt">modeling</span> which includes all of the significant dynamic elements of a space launcher is performed to analyze the effect of the characteristics of thrust integrals on <span class="hlt">stability</span> margins. Numerical results show that in an aspect of guidance <span class="hlt">stability</span>, it is advantageous to have thrust integrals derived from increasing acceleration profiles, such as constant thrust case, which may be considered in the development of propulsion systems. Finally, time-domain simulation with the original nonlinear <span class="hlt">models</span> is performed to verify the approach and the result shows that the nonlinear dynamics of the system is conserved well in the linear <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100038437','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100038437"><span id="translatedtitle">Bounded Linear <span class="hlt">Stability</span> <span class="hlt">Analysis</span> - A Time Delay Margin Estimation Approach for Adaptive Control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nguyen, Nhan T.; Ishihara, Abraham K.; Krishnakumar, Kalmanje Srinlvas; Bakhtiari-Nejad, Maryam</p> <p>2009-01-01</p> <p>This paper presents a method for estimating time delay margin for <span class="hlt">model</span>-reference adaptive control of systems with almost linear structured uncertainty. The bounded linear <span class="hlt">stability</span> <span class="hlt">analysis</span> method seeks to represent the conventional <span class="hlt">model</span>-reference adaptive law by a locally bounded linear approximation within a small time window using the comparison lemma. The locally bounded linear approximation of the combined adaptive system is cast in a form of an input-time-delay differential equation over a small time window. The time delay margin of this system represents a local <span class="hlt">stability</span> measure and is computed analytically by a matrix measure method, which provides a simple analytical technique for estimating an upper bound of time delay margin. Based on simulation results for a scalar <span class="hlt">model</span>-reference adaptive control system, both the bounded linear <span class="hlt">stability</span> method and the matrix measure method are seen to provide a reasonably accurate and yet not too conservative time delay margin estimation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11268840','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11268840"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of the biodegradation of mixed wastes in a continuous bioreactor with cell recycle.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ajbar, A</p> <p>2001-04-01</p> <p>The <span class="hlt">stability</span> characteristics of a continuous bioreactor with cell recycle for biodegradation of mixed wastes are investigated. The system involves a pure culture of Pseudomonas putida and media containing phenol and glucose as carbon and energy sources. The <span class="hlt">model</span> growth kinetics for the two substitutable substrates were experimentally validated in a previous study. The <span class="hlt">stability</span> <span class="hlt">analysis</span> carried out using elementary principles of bifurcation theory shows rich dynamics characteristics of the reactor <span class="hlt">model</span>, including steady-state multiplicity and hysteresis. The effect of the bioreactor operating parameters on the <span class="hlt">stability</span> behavior of the <span class="hlt">model</span> is discussed. Practical criteria are also derived for the safe operation of the unit and to prevent the occurrence of wash-out conditions. PMID:11268840</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvD..92j4017P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvD..92j4017P"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of exponential solutions in Lovelock cosmologies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pavluchenko, Sergey A.</p> <p>2015-11-01</p> <p>In this paper we perform <span class="hlt">stability</span> <span class="hlt">analysis</span> for exponential solutions in Einstein-Gauss-Bonnet and cubic Einstein-Lovelock gravity. We report our findings, provide areas on parameter space, and discuss similarities and differences between cases. <span class="hlt">Analysis</span> suggests that only several cases out of numerous found solutions have stable specific perturbation. Overall, all solutions fall into three groupsthe above mentioned group with at least one stable specific perturbation; another group with at least one unstable perturbation, which makes these solutions unstable; and the largest group with marginal or neutral <span class="hlt">stability</span>. In particular, for the cases with three-dimensional isotropic subspace which could give rise to successful compactification, only one general case and one additional partial solution in the cubic Lovelock case could have stable perturbation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20090026339&hterms=nonequilibrium+conditions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dnonequilibrium%2Bconditions','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20090026339&hterms=nonequilibrium+conditions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dnonequilibrium%2Bconditions"><span id="translatedtitle">Orbiter Boundary Layer Transition <span class="hlt">Stability</span> <span class="hlt">Modeling</span> at Flight Entry Conditions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bartkowicz, Matt; Johnson, Heath; Candler, Graham; Campbell, Charles H.</p> <p>2009-01-01</p> <p>State of the art boundary layer <span class="hlt">stability</span> <span class="hlt">modeling</span> capabilities are increasingly seeing application to entry flight vehicles. With the advent of user friendly and robust implementations of two-dimensional chemical nonequilibrium <span class="hlt">stability</span> <span class="hlt">modeling</span> with the STABL/PSE-CHEM software, the need for flight data to calibrate such analyses capabilities becomes more critical. Recent efforts to perform entry flight testing with the Orbiter geometry related to entry aerothermodynamics and boundary layer transition is allowing for a heightened focus on the Orbiter configuration. A significant advancement in the state of the art can likely be achieved by establishing a basis of understanding for the occurrence of boundary layer transition on the Orbiter due to discrete protruding gap fillers and the nominal distributed roughness of the actual thermal protection system. Recent success in demonstrating centerline two-dimensional <span class="hlt">stability</span> <span class="hlt">modeling</span> on the centerline of the Orbiter at flight entry conditions provides a starting point for additional investigations. The more detailed paper will include smooth Orbiter configuration boundary layer <span class="hlt">stability</span> results for several typical orbiter entry conditions. In addition, the numerical <span class="hlt">modeling</span> approach for establishing the mean laminar flow will be reviewed and the method for determining boundary layer disturbance growth will be overviewed. In addition, if actual Orbiter TPS surface data obtained via digital surface scans become available, it may be possible to investigate the effects of an as-flown flight configuration on boundary layer transition compared to a smooth CAD reference.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AIPC.1558..564H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AIPC.1558..564H"><span id="translatedtitle"><span class="hlt">Stability</span> of a general SEIV epidemic <span class="hlt">model</span> with time delay</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hikal, M. M.; El-Sheikh, M. M. A.</p> <p>2013-10-01</p> <p>An SEIV epidemic <span class="hlt">model</span> with a general nonlinear incidence rate, vaccination and time delay in treatment is considered. Sufficient conditions for the time delay to keep the <span class="hlt">stability</span> of the endemic equilibria are given. A numerical simulations is given to illustrate our results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25501529','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25501529"><span id="translatedtitle">On <span class="hlt">stability</span> issues in deriving multivariable regression <span class="hlt">models</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sauerbrei, Willi; Buchholz, Anika; Boulesteix, Anne-Laure; Binder, Harald</p> <p>2015-07-01</p> <p>In many areas of science where empirical data are analyzed, a task is often to identify important variables with influence on an outcome. Most often this is done by using a variable selection strategy in the context of a multivariable regression <span class="hlt">model</span>. Using a study on ozone effects in children (n = 496, 24 covariates), we will discuss aspects relevant for deriving a suitable <span class="hlt">model</span>. With an emphasis on <span class="hlt">model</span> <span class="hlt">stability</span>, we will explore and illustrate differences between predictive <span class="hlt">models</span> and explanatory <span class="hlt">models</span>, the key role of stopping criteria, and the value of bootstrap resampling (with and without replacement). Bootstrap resampling will be used to assess variable selection <span class="hlt">stability</span>, to derive a predictor that incorporates <span class="hlt">model</span> uncertainty, check for influential points, and visualize the variable selection process. For the latter two tasks we adapt and extend recent approaches, such as <span class="hlt">stability</span> paths, to serve our purposes. Based on earlier experiences and on results from the example, we will argue for simpler <span class="hlt">models</span> and that predictions are usually very similar, irrespective of the selection method used. Important differences exist for the corresponding variances, and the <span class="hlt">model</span> uncertainty concept helps to protect against serious underestimation of the variance of a predictor-derived data dependently. Results of <span class="hlt">stability</span> investigations illustrate severe difficulties in the task of deriving a suitable explanatory <span class="hlt">model</span>. It seems possible to identify a small number of variables with an important and probably true influence on the outcome, but too often several variables are included whose selection may be a result of chance or may depend on a small number of observations. PMID:25501529</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997Chaos...7..590L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997Chaos...7..590L"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of fixed points via chaos control</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lcher, M.; Johnson, G. A.; Hunt, E. R.</p> <p>1997-12-01</p> <p>This paper reviews recent advances in the application of chaos control techniques to the <span class="hlt">stability</span> <span class="hlt">analysis</span> of two-dimensional dynamical systems. We demonstrate how the system's response to one or multiple feedback controllers can be utilized to calculate the characteristic multipliers associated with an unstable periodic orbit. The experimental results, obtained for a single and two coupled diode resonators, agree well with the presented theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060008696','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060008696"><span id="translatedtitle">A Three-Dimensional Unsteady CFD <span class="hlt">Model</span> of Compressor <span class="hlt">Stability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chima, Rodrick V.</p> <p>2006-01-01</p> <p>A three-dimensional unsteady CFD code called CSTALL has been developed and used to investigate compressor <span class="hlt">stability</span>. The code solved the Euler equations through the entire annulus and all blade rows. Blade row turning, losses, and deviation were <span class="hlt">modeled</span> using body force terms which required input data at stations between blade rows. The input data was calculated using a separate Navier-Stokes turbomachinery <span class="hlt">analysis</span> code run at one operating point near stall, and was scaled to other operating points using overall characteristic maps. No information about the stalled characteristic was used. CSTALL was run in a 2-D throughflow mode for very fast calculations of operating maps and estimation of stall points. Calculated pressure ratio characteristics for NASA stage 35 agreed well with experimental data, and results with inlet radial distortion showed the expected loss of range. CSTALL was also run in a 3-D mode to investigate inlet circumferential distortion. Calculated operating maps for stage 35 with 120 degree distortion screens showed a loss in range and pressure rise. Unsteady calculations showed rotating stall with two part-span stall cells. The paper describes the body force formulation in detail, examines the computed results, and concludes with observations about the code.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6633203','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6633203"><span id="translatedtitle"><span class="hlt">Stability</span> and accuracy of differencing methods for viscoplastic <span class="hlt">models</span> in wavecodes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Silling, S.A. )</p> <p>1993-01-01</p> <p>The numerical <span class="hlt">stability</span> and truncation error of a family of differencing schemes for viscoplastic constitutive relations in wavecodes is investigated. A von Neumann <span class="hlt">stability</span> <span class="hlt">analysis</span> is performed for a one-dimensional <span class="hlt">model</span> problem. This <span class="hlt">analysis</span> identifies two differencing methods that have no restriction on the time step size beyond the usual Courant-Friedrichs-Lewy condition. One of these methods is first-order accurate, and the other is second-order accurate. Implementation of one of these methods in the three-dimensional wavecode CTH is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5966023','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5966023"><span id="translatedtitle"><span class="hlt">Stability</span> and accuracy of differencing schemes for viscoplastic <span class="hlt">models</span> in wavecodes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Silling, S.A.</p> <p>1991-03-01</p> <p>The numerical <span class="hlt">stability</span> and truncation error of a family of differencing schemes for viscoplastic constitutive relations in wavecodes is investigated. A von Neumann <span class="hlt">stability</span> <span class="hlt">analysis</span> is performed for a one-dimensional <span class="hlt">model</span> problem. This <span class="hlt">analysis</span> identifies two differencing methods which have no restriction on the time step size beyond the usual Courant-Friedrichs-Lewy condition. One of these methods is first-order accurate, and the other is second-order accurate. Implementation of one of these methods in the three-dimensional wavecode CTH is discussed. 6 refs., 1 fig., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009Cryo...49..687N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009Cryo...49..687N"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of ITER Poloidal Field Coils conductors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nicollet, S.; Bessette, D.; Ciazynski, D.; Duchateau, J. L.; Lacroix, B.; Rajainmki, H.</p> <p>2009-12-01</p> <p>The <span class="hlt">stability</span> <span class="hlt">analysis</span> [1] of the Poloidal Field Coils of the ITER Project, specially the PF5, PF3 and PF2 coils for scenario #2, normal mode has been performed using the Gandalf [2] code. The conductor <span class="hlt">stability</span> is assessed in the most severe operating conditions, at the minimal temperature margin time of the 4th pulse. It consists in determining the maximal deposited energy (perturbation in mJ/cm 3 of superconducting strands) which can be absorbed without runaway. This study is performed for three initial different designs: Cu-nonCu ratio of 2.3, 1.6 and 4.4 for PF5, and Cu-nonCu ratio of 2.3, 1.6 and 6.9 for PF3 and PF2. The results are presented as well as a discussion about the phenomena, important parameters and uncertainties. For each type of perturbation, the calculated <span class="hlt">stability</span> limits are quite similar from one design to another. The low Cu-nonCu ratios do not show significant <span class="hlt">stability</span> degradation compared to the original ITER design with high ratios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4226630','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4226630"><span id="translatedtitle">The Predictive Performance and <span class="hlt">Stability</span> of Six Species Distribution <span class="hlt">Models</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Huang, Min-Yi; Fan, Wei-Yi; Wang, Zhi-Gao</p> <p>2014-01-01</p> <p>Background Predicting species’ potential geographical range by species distribution <span class="hlt">models</span> (SDMs) is central to understand their ecological requirements. However, the effects of using different <span class="hlt">modeling</span> techniques need further investigation. In order to improve the prediction effect, we need to assess the predictive performance and <span class="hlt">stability</span> of different SDMs. Methodology We collected the distribution data of five common tree species (Pinus massoniana, Betula platyphylla, Quercus wutaishanica, Quercus mongolica and Quercus variabilis) and simulated their potential distribution area using 13 environmental variables and six widely used SDMs: BIOCLIM, DOMAIN, MAHAL, RF, MAXENT, and SVM. Each <span class="hlt">model</span> run was repeated 100 times (trials). We compared the predictive performance by testing the consistency between observations and simulated distributions and assessed the <span class="hlt">stability</span> by the standard deviation, coefficient of variation, and the 99% confidence interval of Kappa and AUC values. Results The mean values of AUC and Kappa from MAHAL, RF, MAXENT, and SVM trials were similar and significantly higher than those from BIOCLIM and DOMAIN trials (p<0.05), while the associated standard deviations and coefficients of variation were larger for BIOCLIM and DOMAIN trials (p<0.05), and the 99% confidence intervals for AUC and Kappa values were narrower for MAHAL, RF, MAXENT, and SVM. Compared to BIOCLIM and DOMAIN, other SDMs (MAHAL, RF, MAXENT, and SVM) had higher prediction accuracy, smaller confidence intervals, and were more stable and less affected by the random variable (randomly selected pseudo-absence points). Conclusions According to the prediction performance and <span class="hlt">stability</span> of SDMs, we can divide these six SDMs into two categories: a high performance and <span class="hlt">stability</span> group including MAHAL, RF, MAXENT, and SVM, and a low performance and <span class="hlt">stability</span> group consisting of BIOCLIM, and DOMAIN. We highlight that choosing appropriate SDMs to address a specific problem is an important part of the <span class="hlt">modeling</span> process. PMID:25383906</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012CompM..50..695C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012CompM..50..695C"><span id="translatedtitle">Computational <span class="hlt">analysis</span> of noise reduction devices in axial fans with <span class="hlt">stabilized</span> finite element formulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Corsini, A.; Rispoli, F.; Sheard, A. G.; Tezduyar, T. E.</p> <p>2012-12-01</p> <p>The paper illustrates how a computational fluid mechanic technique, based on <span class="hlt">stabilized</span> finite element formulations, can be used in <span class="hlt">analysis</span> of noise reduction devices in axial fans. Among the noise control alternatives, the study focuses on the use of end-plates fitted at the blade tips to control the leakage flow and the related aeroacoustic sources. The end-plate shape is configured to govern the momentum transfer to the swirling flow at the blade tip. This flow control mechanism has been found to have a positive link to the fan aeroacoustics. The complex physics of the swirling flow at the tip, developing under the influence of the end-plate, is governed by the rolling up of the jet-like leakage flow. The RANS <span class="hlt">modelling</span> used in the computations is based on the streamline-upwind/Petrov-Galerkin and pressure-<span class="hlt">stabilizing</span>/Petrov-Galerkin methods, supplemented with the DRDJ <span class="hlt">stabilization</span>. Judicious determination of the <span class="hlt">stabilization</span> parameters involved is also a part of our computational technique and is described for each component of the <span class="hlt">stabilized</span> formulation. We describe the flow physics underlying the design of the noise control device and illustrate the aerodynamic performance. Then we investigate the numerical performance of the formulation by analysing the inner workings of the <span class="hlt">stabilization</span> operators and of their interaction with the turbulence <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750010242','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750010242"><span id="translatedtitle">Space shuttle maneuvering engine reusable thrust chamber program. Task 11: <span class="hlt">Stability</span> analyses and acoustic <span class="hlt">model</span> testing data dump</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oberg, C. L.</p> <p>1974-01-01</p> <p>The combustion <span class="hlt">stability</span> characteristics of engines applicable to the Space Shuttle Orbit Maneuvering System and the adequacy of acoustic cavities as a means of assuring <span class="hlt">stability</span> in these engines were investigated. The study comprised full-scale <span class="hlt">stability</span> rating tests, bench-scale acoustic <span class="hlt">model</span> tests and <span class="hlt">analysis</span>. Two series of <span class="hlt">stability</span> rating tests were made. Acoustic <span class="hlt">model</span> tests were made to determine the resonance characteristics and effects of acoustic cavities. Analytical studies were done to aid design of the cavity configurations to be tested and, also, to aid evaluation of the effectiveness of acoustic cavities from available test results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JChPh.120.6274L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JChPh.120.6274L"><span id="translatedtitle">Thermodynamic <span class="hlt">stability</span> and kinetic foldability of a lattice protein <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Jie; Wang, Jun; Zhang, Jian; Wang, Wei</p> <p>2004-04-01</p> <p>By using serial mutations, i.e., a residue replaced by 19 kinds of naturally occurring residues, the <span class="hlt">stability</span> of native conformation and folding behavior of mutated sequences are studied. The 3×3×3 lattice protein <span class="hlt">model</span> with two kinds of interaction potentials between the residues, namely the original Miyazawa and Jernigan (MJ) potentials and the modified MJ potentials (MMJ), is used. Effects of various sites in the mutated sequences on the <span class="hlt">stability</span> and foldability are characterized through the Z-score and the folding time. It is found that the sites can be divided into three types, namely the hydrophobic-type (H-type), the hydrophilic-type (P-type) and the neutral-type (N-type). These three types of sites relate to the hydrophobic core, the hydrophilic surface and the parts between them. The <span class="hlt">stability</span> of the native conformation for the serial mutated sequences increases (or decreases) as the increasing in the hydrophobicity of the mutated residues for the H-type sites (or the P-type sites), while varies randomly for the N-type sites. However, the foldability of the mutated sequences is not always consistent with the thermodynamic <span class="hlt">stability</span>, and their relationship depends on the site types. Since the hydrophobic tendency of the MJ potentials is strong, the ratio between the number of the H-type sites and the number of the P-type sites is found to be 1:2. Differently, for the MJJ potentials it is found that such a ratio is about 1:1 which is relevant to that of real proteins. This suggests that the modification of the MJ potentials is rational in the aspect of thermodynamic <span class="hlt">stability</span>. The folding of <span class="hlt">model</span> proteins with the MMJ potentials is fast. However, the relationship between the foldability and the thermodynamic <span class="hlt">stability</span> of the mutated sequences is complex.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ChOE...29..719E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ChOE...29..719E"><span id="translatedtitle">Numerical <span class="hlt">modeling</span> of the <span class="hlt">stability</span> of horizontal multidrain oil wells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elyasi, Ayub; Goshtasbi, Kamran</p> <p>2015-10-01</p> <p>The <span class="hlt">stability</span> of the horizontal multidrain wells is a crucial issue and several factors are involved in this matter, including in-situ stresses, magnitude and distribution as well as the mainbore trajectories. In this paper, this issue is evaluated by assuming different circumstances for the above mentioned factors, based on finite difference threedimensional <span class="hlt">modeling</span> by using the finite difference numerical software, FLAC3D. The <span class="hlt">stability</span> of the mainbore and lateral branches is analyzed based on the Normalized Yielded Zone Area (NYZA) criterion, i.e. the ratio of the surrounding yielded cross-sectional area to the initial area of the well. Optimum mud pressures are obtained in the mainbore and lateral branches in different mainbore trajectories under three in-situ stress regimes. In addition, the <span class="hlt">stability</span> of the junction where the lateral branches are bifurcated from the mainbore is assessed in those situations. The optimum trajectory of the mainbore, in which the junction has obtained the most stable condition, is selected in each stress regime. It was concluded that in the Normal Faulting (NF) stress regime, the mainbore and junction <span class="hlt">stability</span> varies in relation to the mainbore trajectories, inversely. However, in the other two stress regimes, i.e. Strike Slip (SS) and Reverse Faulting (RF), the variations of the mainbore and junction <span class="hlt">stability</span> are in the same trend with respect to the mainbore trajectory deviations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/541933','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/541933"><span id="translatedtitle">M-theory <span class="hlt">model</span>-building and proton <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ellis, J.; Faraggi, A.E.; Nanopoulos, D.V. ||</p> <p>1997-09-01</p> <p>The authors study the problem of baryon <span class="hlt">stability</span> in M theory, starting from realistic four-dimensional string <span class="hlt">models</span> constructed using the free-fermion formulation of the weakly-coupled heterotic string. Suitable variants of these <span class="hlt">models</span> manifest an enhanced custodial gauge symmetry that forbids to all orders the appearance of dangerous dimension-five baryon-decay operators. The authors exhibit the underlying geometric (bosonic) interpretation of these <span class="hlt">models</span>, which have a Z{sub 2} x Z{sub 2} orbifold structure similar, but not identical, to the class of Calabi-Yau threefold compactifications of M and F theory investigated by Voisin and Borcea. A related generalization of their work may provide a solution to the problem of proton <span class="hlt">stability</span> in M theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15016012','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15016012"><span id="translatedtitle">Progress Toward the <span class="hlt">Analysis</span> of the Kinetic <span class="hlt">Stabilizer</span> Concept</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Post, R F; Byers, J A; Cohen, R H; Fowler, T K; Ryutov, D D; Tung, L S</p> <p>2005-02-08</p> <p>The Kinetic <span class="hlt">Stabilizer</span> (K-S) concept [1] represents a means for <span class="hlt">stabilizing</span> axisymmetric mirror and tandem-mirror (T-M) magnetic fusion systems against MHD interchange instability modes. Magnetic fusion research has given us examples of axisymmetric mirror confinement devices in which radial transport rates approach the classical ''Spitzer'' level, i.e. situations in which turbulence if present at all, is at too low a level to adversely affect the radial transport [2,3,4]. If such a low-turbulence condition could be achieved in a T-M system it could lead to a fusion power system that would be simpler, smaller, and easier to develop than one based on closed-field confinement, e.g., the tokamak, where the transport is known to be dominated by turbulence. However, since conventional axisymmetric mirror systems suffer from the MHD interchange instability, the key to exploiting this new opportunity is to find a practical way to <span class="hlt">stabilize</span> this mode. The K-S represents one avenue to achieving this goal. The starting point for the K-S concept is a theoretical <span class="hlt">analysis</span> by Ryutov [5]. He showed that a MHD-unstable plasma contained in an axisymmetric mirror cell can be MHD-<span class="hlt">stabilized</span> by the presence of a low-density plasma on the expanding field lines outside the mirrors. If this plasma communicates well electrically with the plasma in the then this exterior plasma can <span class="hlt">stabilize</span> the interior, confined, plasma. This <span class="hlt">stabilization</span> technique was conclusively demonstrated in the Gas Dynamic Trap (GDT) experiment [6] at Novosibirsk, Russia, at mirror-cell plasma beta values of 40 percent. The GDT operates in a high collisionality regime. Thus the effluent plasma leaking through the mirrors, though much lower in density than that of the confined plasma, is still high enough to satisfy the <span class="hlt">stabilization</span> criterion. This would not, however, be the case in a fusion T-M with axisymmetric plug and central cell fields. In such a case the effluent plasma would be far too low in density to <span class="hlt">stabilize</span> the plasmas in the plug cells and the central cell. The K-S resolves this dilemma by employing ion beams injected up the magnetic gradient in the ''expander'' region outside the outermost mirror in such a way that as they are compressed, stagnated, and reflected they form a ''<span class="hlt">stabilizer</span>'' plasma in the expander. Preliminary calculations [1] showed that the power required to maintain the <span class="hlt">stabilizer</span> beams would be orders of magnitude less than the fusion power generated. This report reviews those calculations and describes additional theoretical and computational work in progress, aimed at confirming and extending the <span class="hlt">analysis</span> of the K-S concept as applied to axisymmetric tandem mirror systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6377M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6377M"><span id="translatedtitle">Parallel processing for efficient 3D slope <span class="hlt">stability</span> <span class="hlt">modelling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marchesini, Ivan; Mergili, Martin; Alvioli, Massimiliano; Metz, Markus; Schneider-Muntau, Barbara; Rossi, Mauro; Guzzetti, Fausto</p> <p>2014-05-01</p> <p>We test the performance of the GIS-based, three-dimensional slope <span class="hlt">stability</span> <span class="hlt">model</span> r.slope.<span class="hlt">stability</span>. The <span class="hlt">model</span> was developed as a C- and python-based raster module of the GRASS GIS software. It considers the three-dimensional geometry of the sliding surface, adopting a modification of the <span class="hlt">model</span> proposed by Hovland (1977), and revised and extended by Xie and co-workers (2006). Given a terrain elevation map and a set of relevant thematic layers, the <span class="hlt">model</span> evaluates the <span class="hlt">stability</span> of slopes for a large number of randomly selected potential slip surfaces, ellipsoidal or truncated in shape. Any single raster cell may be intersected by multiple sliding surfaces, each associated with a value of the factor of safety, FS. For each pixel, the minimum value of FS and the depth of the associated slip surface are stored. This information is used to obtain a spatial overview of the potentially unstable slopes in the study area. We test the <span class="hlt">model</span> in the Collazzone area, Umbria, central Italy, an area known to be susceptible to landslides of different type and size. Availability of a comprehensive and detailed landslide inventory map allowed for a critical evaluation of the <span class="hlt">model</span> results. The r.slope.<span class="hlt">stability</span> code automatically splits the study area into a defined number of tiles, with proper overlap in order to provide the same statistical significance for the entire study area. The tiles are then processed in parallel by a given number of processors, exploiting a multi-purpose computing environment at CNR IRPI, Perugia. The map of the FS is obtained collecting the individual results, taking the minimum values on the overlapping cells. This procedure significantly reduces the processing time. We show how the gain in terms of processing time depends on the tile dimensions and on the number of cores.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPIE.7386E..1ZD','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPIE.7386E..1ZD"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of the mode-locking dynamics in a laser cavity with a passive polarizer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ding, Edwin; Kutz, J. Nathan</p> <p>2009-06-01</p> <p>A low-dimensional <span class="hlt">model</span> is constructed via a variational formulation which characterizes the mode-locking dynamics in a laser cavity with a passive polarizer. The theoretical <span class="hlt">model</span> accounts explicitly for the effects of the passive polarizer with a Jones matrix. In combination with the nonlinear interaction of the orthogonally polarized electromagnetic fields, the evolution of the mode-locked state reduces to the nonlinear interaction of the amplitude, width and phase chirp. This <span class="hlt">model</span> allows for an explicit analytic prediction of the steady-state mode-locked state (fixed point) and its corresponding <span class="hlt">stability</span>. The <span class="hlt">stability</span> <span class="hlt">analysis</span> requires a center manifold reduction which reveals that the solution decays to the mode-locked state on a timescale dependent on the gain bandwidth and the net cavity gain. Quantitative and qualitative agreement is achieved between the full governing <span class="hlt">model</span> and the low-dimensional <span class="hlt">model</span>, thus providing for an excellent design tool for characterizing and optimizing mode-locking performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JSV...259...31C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JSV...259...31C"><span id="translatedtitle">Dynamic Response and <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of AN Automatic Ball Balancer for a Flexible Rotor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chung, J.; Jang, I.</p> <p>2003-01-01</p> <p>Dynamic <span class="hlt">stability</span> and time responses are studied for an automatic ball balancer of a rotor with a flexible shaft. The Stodola-Green rotor <span class="hlt">model</span>, of which the shaft is flexible, is selected for <span class="hlt">analysis</span>. This rotor <span class="hlt">model</span> is able to include the influence of rigid-body rotations due to the shaft flexibility on dynamic responses. Applying Lagrange's equation to the rotor with the ball balancer, the non-linear equations of motion are derived. Based on the linearized equations, the <span class="hlt">stability</span> of the ball balancer around the balanced equilibrium position is analyzed. On the other hand, the time responses computed from the non-linear equations are investigated. This study shows that the automatic ball balancer can achieve the balancing of a rotor with a flexible shaft if the system parameters of the balancer satisfy the <span class="hlt">stability</span> conditions for the balanced equilibrium position.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4682966','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4682966"><span id="translatedtitle"><span class="hlt">Analysis</span> of Biobanked Serum from a Mycobacterium avium subsp paratuberculosis Bovine Infection <span class="hlt">Model</span> Confirms the Remarkable <span class="hlt">Stability</span> of Circulating miRNA Profiles and Defines a Bovine Serum miRNA Repertoire</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Riepema, Karel; Bakker, Douwe; Gordon, Stephen V.</p> <p>2015-01-01</p> <p>Johne’s Disease (JD) is a chronic enteritis of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). Current disease control strategies are hampered by the lack of sensitive and specific diagnostic modalities. Therefore, novel diagnostic and prognostic tools are needed, and circulating microRNAs (miRNAs) may hold potential in this area. The aims of this study were twofold: (i) to address the <span class="hlt">stability</span> of miRNA in bovine sera from biobanked samples, and (ii) to assess the potential of miRNAs as biomarkers for JD disease progression. To address these aims we used bovine sera from an experimental MAP infection <span class="hlt">model</span> that had been stored at -20°C for over a decade, allowing us to also assess the <span class="hlt">stability</span> of miRNA profiles in biobanked serum samples through comparison with fresh sera. Approximately 100–200 intact miRNAs were identified in each sample with 83 of these being consistently detected across all 57 samples. The miRNA profile of the biobanked sera stored at -20°C for over 10 years was highly similar to the profile of <1 year-old sera stored at -80°C, with an overlap of 73 shared miRNAs. IsomiR <span class="hlt">analysis</span> also indicated a distinct bovine serum-specific isomiR profile as compared to previously reported bovine macrophage miRNA profiles. To explore the prognostic potential of miRNA profiles cattle defined as seropositive for anti-MAP antibodies (n = 5) were compared against seronegative cattle (n = 7). No significant differential expressed miRNAs were detected at either the early (6 months) or late (43, 46 and 49 months) intervals (FDR≤0.05, fold-change≥1.5) across seropositive or seronegative animals. However, comparing pre-infection sera to the early and late time-points identified increased miR-29a and miR-92b abundance (2-fold) that may be due to blood-cell population changes over time (P<0.001). In conclusion our study has demonstrated that bovine circulating miRNAs retain their integrity under long-term sub-optimal storage temperatures opening the way for increased miRNA analyses from biobanked samples for a range of infectious and non-infectious diseases. PMID:26675426</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22369863','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22369863"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of inflation with an SU(2) gauge field</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Maeda, Kei-ichi; Yamamoto, Kei E-mail: K.Yamamoto@damtp.cam.ac.uk</p> <p>2013-12-01</p> <p>We study anisotropic cosmologies of a scalar field interacting with an SU(2) gauge field via a gauge-kinetic coupling. We analyze Bianchi class A <span class="hlt">models</span>, which include Bianchi type I, II, VI{sub 0}, VII{sub 0}, VIII and IX. The linear <span class="hlt">stability</span> of isotropic inflationary solution with background magnetic field is shown, which generalizes the known results for U(1) gauge fields. We also study anisotropic inflationary solutions, all of which turn out to be unstable. Then nonlinear <span class="hlt">stability</span> for the isotropic inflationary solution is examined by numerically investigating the dependence of the late-time behaviour on the initial conditions. We present a number of novel features that may well affect physical predictions and viability of the <span class="hlt">models</span>. First, in the absence of spatial curvature, strong initial anisotropy leads to a rapid oscillation of gauge field, thwarting convergence to the inflationary attractor. Secondly, the inclusion of spatial curvature destabilizes the oscillatory attractor and the global <span class="hlt">stability</span> of the isotropic inflation with gauge field is restored. Finally, based on the numerical evidence combined with the knowledge of the eigenvalues for various inflationary solutions, we give a generic lower-bound for the duration of transient anisotropic inflation, which is inversely proportional to the slow-roll parameter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23061836','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23061836"><span id="translatedtitle">Theoretical study of vapor-liquid homogeneous nucleation using <span class="hlt">stability</span> <span class="hlt">analysis</span> of a macroscopic phase.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carren-Caldern, Bernardo</p> <p>2012-10-14</p> <p><span class="hlt">Stability</span> <span class="hlt">analysis</span> is generally used to verify that the solution to phase equilibrium calculations corresponds to a stable state (minimum of the free energy). In this work, tangent plane distance <span class="hlt">analysis</span> for <span class="hlt">stability</span> of macroscopic mixtures is also used for analyzing the nucleation process, reconciling thus this <span class="hlt">analysis</span> with classical nucleation theories. In the context of the revised nucleation theory, the driving force and the nucleation work are expressed as a function of the Lagrange multiplier corresponding to the mole fraction constraint from the minimization problem of <span class="hlt">stability</span> <span class="hlt">analysis</span>. Using a van der Waals fluid applied to a ternary mixture, Lagrange multiplier properties are illustrated. In particular, it is shown how the Lagrange multiplier value is equal to one on the binodal and spinodal curves at the same time as the driving force of nucleation vanishes on these curves. Finally, it is shown that, on the spinodal curve, the nucleation work from the revised and generalized nucleation theories are characterized by two different local minima from <span class="hlt">stability</span> <span class="hlt">analysis</span>, irrespective of any interfacial tension <span class="hlt">models</span>. PMID:23061836</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/435391','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/435391"><span id="translatedtitle">A versatile FACTS device <span class="hlt">model</span> for powerflow and <span class="hlt">stability</span> simulations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Arabi, S.; Kundur, P.</p> <p>1996-11-01</p> <p>While early FACTs devices consisted mainly of thyristor-controlled/switched RLC/transformer components, the newer generation is based on the self-commutated voltage-sourced converter. The variety of devices and applications, and the changing nature of the technology, call for versatile <span class="hlt">modelling</span> capabilities at different levels of detail. This paper describes a <span class="hlt">model</span> conceived as a coordinated and interconnected set of controllable shunt and series elements. For each device, functional characteristics, typical settings and controls, and simulation examples are presented. The <span class="hlt">model</span> is capable of representing virtually any FACTS device for powerflow and all types of <span class="hlt">stability</span> simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JSV...307..495M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JSV...307..495M"><span id="translatedtitle">Dynamic <span class="hlt">stability</span> index and vibration <span class="hlt">analysis</span> of a flexible Stewart platform</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mukherjee, Parthajit; Dasgupta, Bhaskar; Mallik, A. K.</p> <p>2007-11-01</p> <p>This article proposes a dynamic <span class="hlt">stability</span> index of a flexible manipulator. The method is illustrated by considering the 6-UPS Stewart platform as an example. First, the <span class="hlt">analysis</span> of dynamics and vibration of a 6-UPS Stewart platform is presented. The dynamic formulation follows the Newton-Euler approach. Leg stiffness, force and torque due to viscous friction at the joints, inertia and gravity effects are considered in the <span class="hlt">model</span>. Finally, the response of the platform, subjected to base excitations at different frequencies, has been studied and the dynamic <span class="hlt">stability</span> index developed has been validated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910050519&hterms=external+environment+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dexternal%2Benvironment%2Banalysis','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910050519&hterms=external+environment+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dexternal%2Benvironment%2Banalysis"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of position and force control problems for robot arms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wen, John T.; Murphy, Steve</p> <p>1990-01-01</p> <p>A <span class="hlt">stability</span> <span class="hlt">analysis</span> for robot manipulators under the influence of external forces is presented. Several control objectives are considered: rejecting the external force as a source of disturbance, complying to the external force as a generalized mass-spring-damper system, and actively controlling the external force when a dynamic <span class="hlt">model</span> for the environment is available. An explanation of instability is given for the case in which the environment has flexibility and the gains are inappropriately chosen. When the environment is stiff in the force control subspace, robust <span class="hlt">stability</span> can be achieved via the integral force feedback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4638359','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4638359"><span id="translatedtitle">Game Theoretical <span class="hlt">Analysis</span> on Cooperation <span class="hlt">Stability</span> and Incentive Effectiveness in Community Networks</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liu, Yi; Qian, Depei; Zhang, Han; Cai, Jihong</p> <p>2015-01-01</p> <p>Community networks, the distinguishing feature of which is membership admittance, appear on P2P networks, social networks, and conventional Web networks. Joining the network costs money, time or network bandwidth, but the individuals get access to special resources owned by the community in return. The prosperity and <span class="hlt">stability</span> of the community are determined by both the policy of admittance and the attraction of the privileges gained by joining. However, some misbehaving users can get the dedicated resources with some illicit and low-cost approaches, which introduce instability into the community, a phenomenon that will destroy the membership policy. In this paper, we analyze on the <span class="hlt">stability</span> using game theory on such a phenomenon. We propose a game-theoretical <span class="hlt">model</span> of <span class="hlt">stability</span> <span class="hlt">analysis</span> in community networks and provide conditions for a stable community. We then extend the <span class="hlt">model</span> to analyze the effectiveness of different incentive policies, which could be used when the community cannot maintain its members in certain situations. Then we verify those <span class="hlt">models</span> through a simulation. Finally, we discuss several ways to promote community network’s <span class="hlt">stability</span> by adjusting the network’s properties and give some proposal on the designs of these types of networks from the points of game theory and <span class="hlt">stability</span>. PMID:26551649</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030064141','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030064141"><span id="translatedtitle"><span class="hlt">Modeling</span> and Simulation of a Helicopter Slung Load <span class="hlt">Stabilization</span> Device</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cicolani, Luigi S.; Ehlers, George E.</p> <p>2002-01-01</p> <p>This paper addresses the problem of simulation and <span class="hlt">stabilization</span> of the yaw motions of a cargo container slung load. The study configuration is a UH-60 helicopter carrying a 6ft x 6 ft x 8 ft CONEX container. This load is limited to 60 KIAS in operations and flight testing indicates that it starts spinning in hover and that spin rate increases with airspeed. The simulation reproduced the load yaw motions seen in the flight data after augmenting the load <span class="hlt">model</span> with terms representing unsteady load yaw moment effects acting to reinforce load oscillations, and augmenting the hook <span class="hlt">model</span> to include yaw resistance at the hook. The use of a vertical fin to <span class="hlt">stabilize</span> the load is considered. Results indicate that the CONEX airspeed can be extended to 110 kts using a 3x5 ft fin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19790063665&hterms=climate+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dclimate%2Benergy','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19790063665&hterms=climate+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dclimate%2Benergy"><span id="translatedtitle">A <span class="hlt">stability</span> theorem for energy-balance climate <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cahalan, R. F.; North, G. R.</p> <p>1979-01-01</p> <p>The paper treats the <span class="hlt">stability</span> of steady-state solutions of some simple, latitude-dependent, energy-balance climate <span class="hlt">models</span>. For north-south symmetric solutions of <span class="hlt">models</span> with an ice-cap-type albedo feedback, and for the sum of horizontal transport and infrared radiation given by a linear operator, it is possible to prove a 'slope <span class="hlt">stability</span>' theorem, i.e., if the local slope of the steady-state iceline latitude versus solar constant curve is positive (negative) the steady-state solution is stable (unstable). Certain rather weak restrictions on the albedo function and on the heat transport are required for the proof, and their physical basis is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhyD..194....1L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhyD..194....1L"><span id="translatedtitle">A <span class="hlt">stability</span> index for detonation waves in Majdas <span class="hlt">model</span> for reacting flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lyng, Gregory; Zumbrun, Kevin</p> <p>2004-07-01</p> <p>Using Evans function techniques, we develop a <span class="hlt">stability</span> index for weak and strong detonation waves analogous to that developed for shock waves in [SIAM J. Math. Anal. 32 (2001) 929; Commun. Pure Appl. Math. 51 (7) (1998) 797], yielding useful necessary conditions for <span class="hlt">stability</span>. Here, we carry out the <span class="hlt">analysis</span> in the context of the Majda <span class="hlt">model</span>, a simplified <span class="hlt">model</span> for reacting flow; the method is extended to the full Navier-Stokes equations of reacting flow in [G. Lyng, One dimensional <span class="hlt">stability</span> of detonation waves, Doctoral Thesis, Indiana University, 2002; G. Lyng, K. Zumbrun, <span class="hlt">Stability</span> of detonation waves, Preprint, 2003]. The resulting <span class="hlt">stability</span> condition is satisfied for all nondegenerate, i.e., spatially exponentially decaying, weak and strong detonations of the Majda <span class="hlt">model</span> in agreement with numerical experiments of [SIAM J. Sci. Statist. Comput. 7u (1986) 1059] and analytical results of [Commun. Math. Phys. 204 (3) (1999) 551; Commun. Math. Phys. 202 (3) (1999) 547] for a related <span class="hlt">model</span> of Majda and Rosales. We discuss also the role in the ZND limit of degenerate, subalgebraically decaying weak detonation and (for a modified, bump-type ignition function) deflagration profiles, as discussed in [SIAM J. Math. Anal. 24 (1993) 968; SIAM J. Appl. Math. 55 (1995) 175] for the full equations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvD..92i5010B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvD..92i5010B"><span id="translatedtitle">Higgs-radion mixing in <span class="hlt">stabilized</span> brane world <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boos, Edward E.; Bunichev, Viacheslav E.; Perfilov, Maxim A.; Smolyakov, Mikhail N.; Volobuev, Igor P.</p> <p>2015-11-01</p> <p>We consider a quartic interaction of the Higgs and Goldberger-Wise fields, which connects the mechanism of the extra dimension size <span class="hlt">stabilization</span> with spontaneous symmetry breaking on our brane and gives rise to a coupling of the Higgs field to the radion and its KK tower. We estimate a possible influence of this coupling on the Higgs-radion mixing and study restrictions on <span class="hlt">model</span> parameters from the LHC data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740003696','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740003696"><span id="translatedtitle"><span class="hlt">Analysis</span> and testing of <span class="hlt">stability</span> augmentation systems. [for supersonic transport aircraft wing and B-52 aircraft control system</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sevart, F. D.; Patel, S. M.; Wattman, W. J.</p> <p>1972-01-01</p> <p>Testing and evaluation of <span class="hlt">stability</span> augmentation systems for aircraft flight control were conducted. The flutter suppression system <span class="hlt">analysis</span> of a scale supersonic transport wing <span class="hlt">model</span> is described. Mechanization of the flutter suppression system is reported. The ride control synthesis for the B-52 aeroelastic <span class="hlt">model</span> is discussed. <span class="hlt">Model</span> analyses were conducted using equations of motion generated from generalized mass and stiffness data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/152981','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/152981"><span id="translatedtitle">Control sensitivity indices for <span class="hlt">stability</span> <span class="hlt">analysis</span> of HVdc systems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nayak, O.B.; Gole, A.M.; Chapman, D.G.; Davies, J.B.</p> <p>1995-10-01</p> <p>This paper presents a new concept called the ``Control Sensitivity Index`` of CSI, for the <span class="hlt">stability</span> <span class="hlt">analysis</span> of HVdc converters connected to weak ac systems. The CSI for a particular control mode can be defined as the ratio of incremental changes in the two system variables that are most relevant to that control mode. The index provides valuable information on the <span class="hlt">stability</span> of the system and, unlike other approaches, aids in the design of the controller. It also plays an important role in defining non-linear gains for the controller. This paper offers a generalized formulation of CSI and demonstrates its application through an <span class="hlt">analysis</span> of the CSI for three modes of HVdc control. The conclusions drawn from the <span class="hlt">analysis</span> are confirmed by a detailed electromagnetic transients simulation of the ac/dc system. The paper concludes that the CSI can be used to improve the controller design and, for an inverter in a weak ac system, the conventional voltage control mode is more stable than the conventional {gamma} control mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26997661','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26997661"><span id="translatedtitle">Graph theory and <span class="hlt">stability</span> <span class="hlt">analysis</span> of protein complex interaction networks.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huang, Chien-Hung; Chen, Teng-Hung; Ng, Ka-Lok</p> <p>2016-04-01</p> <p>Protein complexes play an essential role in many biological processes. Complexes can interact with other complexes to form protein complex interaction network (PCIN) that involves in important cellular processes. There are relatively few studies on examining the interaction topology among protein complexes; and little is known about the <span class="hlt">stability</span> of PCIN under perturbations. We employed graph theoretical approach to reveal hidden properties and features of four species PCINs. Two main issues are addressed, (i) the global and local network topological properties, and (ii) the <span class="hlt">stability</span> of the networks under 12 types of perturbations. According to the topological parameter classification, we identified some critical protein complexes and validated that the topological <span class="hlt">analysis</span> approach could provide meaningful biological interpretations of the protein complex systems. Through the Kolmogorov-Smimov test, we showed that local topological parameters are good indicators to characterise the structure of PCINs. We further demonstrated the effectiveness of the current approach by performing the scalability and data normalization tests. To measure the robustness of PCINs, we proposed to consider eight topological-based perturbations, which are specifically applicable in scenarios of targeted, sustained attacks. We found that the degree-based, betweenness-based and brokering-coefficient-based perturbations have the largest effect on network <span class="hlt">stability</span>. PMID:26997661</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/984317','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/984317"><span id="translatedtitle">Thermal <span class="hlt">Stability</span> <span class="hlt">Analysis</span> for Superconducting Coupling Coil in MICE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wu, Hong; Wang, Li; Pan, Heng; Guo, XingLong; Green, M.A.</p> <p>2010-06-28</p> <p>The superconducting coupling coil to be used in the Muon Ionization Cooling Experiment (MICE) with inner radius of 750 mm, length of 285 mm and thickness of 110.4 mm will be cooled by a pair of 1.5 W at 4.2 K cryo-coolers. When the coupling coil is powered to 210 A, it will produce about 7.3 T peak magnetic field at the conductor and it will have a stored energy of 13 MJ. A key issue for safe operation of the coupling coil is the thermal <span class="hlt">stability</span> of the coil during a charge and discharge. The magnet and its cooling system are designed for a rapid discharge where the magnet is to be discharged in 5400 seconds. The numerical simulation for the thermal <span class="hlt">stability</span> of the MICE coupling coil has been done using ANSYS. The <span class="hlt">analysis</span> results show that the superconducting coupling coil has a good <span class="hlt">stability</span> and can be charged and discharged safely.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005APS..DFD.EQ009T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005APS..DFD.EQ009T"><span id="translatedtitle">Linear <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of a Channel Flow with Porous Walls</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tilton, Nils</p> <p>2005-11-01</p> <p>This study is motivated by the extensive use of wall-transpiration in numerical studies related to inhibition and control of wall-turbulence. In general, wall-transpiration has been implemented by providing the wall-normal velocity and imposing a no-slip condition on the wall-tangential velocity. Physically, however, the pores cannot be infinitesimally small and, consequently, it is important to address how the presence of the pores affects the slip velocity at the wall and the <span class="hlt">stability</span> of the boundary layer. Moreover, our work is motivated by the existence of only few studies on the linear <span class="hlt">stability</span> of channels with porous walls. Our study considers a parallel-plate channel with porous walls such that a longitudinal pressure gradient induces a laminar flow in both the open channel region and the porous walls. Simplified counterparts to the Orr-Sommerfeld and Squire equations are derived for the porous regions that are valid for small permeablities. The linear <span class="hlt">stability</span> <span class="hlt">analysis</span> takes account of the coupling between the three disturbance fields through boundary conditions recently derived by Ochoa-Tapia and Whitaker (Int. J. Heat Mass Transfer, Vol. 38, 1995, pp 2635-2646). The resulting Orr-Sommerfeld spectrum and eigenfunctions reduce to those for Poiseuille flow as the permeability of the walls tends to zero, but are altered for greater values. We discuss symmetrical flows where parameters at both porous walls are identical as well as skewed flows where parameters at the two walls differ.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptLE..78...26X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptLE..78...26X"><span id="translatedtitle">Architectural <span class="hlt">stability</span> <span class="hlt">analysis</span> of the rotary-laser scanning technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xue, Bin; Yang, Xiaoxia; Zhu, Jigui</p> <p>2016-03-01</p> <p>The rotary-laser scanning technique is an important method in scale measurements due to its high accuracy and large measurement range. This paper first introduces a newly designed measurement station which is able to provide two-dimensional measurement information including the azimuth and elevation by using the rotary-laser scanning technique, then presents the architectural <span class="hlt">stability</span> <span class="hlt">analysis</span> of this technique by detailed theoretical derivations. Based on the designed station, a validation using both experiment and simulation is presented in order to verify the analytic conclusion. The results show that the architectural <span class="hlt">stability</span> of the rotary-laser scanning technique is only affected by the two scanning angles' difference. And the difference which brings the best architectural <span class="hlt">stability</span> can be calculated by using pre-calibrated parameters of the two laser planes. This research gives us an insight into the rotary-laser scanning technique. Moreover, the measurement accuracy of the rotary-laser scanning technique can be further improved based on the results of the study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22369940','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22369940"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of restricted non-static axial symmetry</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sharif, M.; Bhatti, M. Zaeem Ul Haq E-mail: mzaeem.math@gmail.com</p> <p>2013-11-01</p> <p>This paper aims to investigate the instability of very restricted class of non-static axially symmetric spacetime with anisotropic matter configuration. The perturbation scheme is established for the Einstein field equations and conservation laws. The instability range in the Newtonian and post-Newtonian regions are explored by constructing the collapse equation in this scenario. It is found that the adiabatic index plays an important role in the <span class="hlt">stability</span> <span class="hlt">analysis</span> which depends upon the physical parameters i.e., energy density and anisotropic pressure of the fluid distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT........77M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT........77M"><span id="translatedtitle">A continuum <span class="hlt">model</span> for flocking: Obstacle avoidance, equilibrium, and <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mecholsky, Nicholas Alexander</p> <p></p> <p>The <span class="hlt">modeling</span> and investigation of the dynamics and configurations of animal groups is a subject of growing attention. In this dissertation, we present a partial-differential-equation based continuum <span class="hlt">model</span> of flocking and use it to investigate several properties of group dynamics and equilibrium. We analyze the reaction of a flock to an obstacle or an attacking predator. We show that the flock response is in the form of density disturbances that resemble Mach cones whose configuration is determined by the anisotropic propagation of waves through the flock. We investigate the effect of a flock 'pressure' and pairwise repulsion on an equilibrium density distribution. We investigate both linear and nonlinear pressures, look at the convergence to a 'cold' (T ? 0) equilibrium solution, and find regions of parameter space where different <span class="hlt">models</span> produce the same equilibrium. Finally, we analyze the <span class="hlt">stability</span> of an equilibrium density distribution to long-wavelength perturbations. Analytic results for the <span class="hlt">stability</span> of a constant density solution as well as <span class="hlt">stability</span> regimes for constant density solutions to the equilibrium equations are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JDE...257.3102C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JDE...257.3102C"><span id="translatedtitle"><span class="hlt">Stability</span> of spiky solution of Keller-Segel's minimal chemotaxis <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Xinfu; Hao, Jianghao; Wang, Xuefeng; Wu, Yaping; Zhang, Yajing</p> <p>2014-11-01</p> <p>A huge volume of research has been done for the simplest chemotaxis <span class="hlt">model</span> (Keller-Segel's minimal <span class="hlt">model</span>) and its variants, yet, some of the basic issues remain unresolved until now. For example, it is known that the minimal <span class="hlt">model</span> has spiky steady states that can be used to <span class="hlt">model</span> the important cell aggregation phenomenon, but the <span class="hlt">stability</span> of monotone spiky steady states was not shown. In this paper, we derive, first formally and then rigorously, the asymptotic expansion of these monotone steady states, and then we use this fine information on the spike to prove its local asymptotic <span class="hlt">stability</span>. Moreover, we obtain the uniqueness of such steady states. We expect that the new ideas and techniques for rigorous asymptotic expansion and spectrum <span class="hlt">analysis</span> presented in this paper will be useful in attacking and hence stimulating research on other more sophisticated chemotaxis <span class="hlt">models</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000063376','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000063376"><span id="translatedtitle">Fuzzy Current-Mode Control and <span class="hlt">Stability</span> <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kopasakis, George</p> <p>2000-01-01</p> <p>In this paper a current-mode control (CMC) methodology is developed for a buck converter by using a fuzzy logic controller. Conventional CMC methodologies are based on lead-lag compensation with voltage and inductor current feedback. In this paper the converter lead-lag compensation will be substituted with a fuzzy controller. A small-signal <span class="hlt">model</span> of the fuzzy controller will also be developed in order to examine the <span class="hlt">stability</span> properties of this buck converter control system. The paper develops an analytical approach, introducing fuzzy control into the area of CMC.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23127841','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23127841"><span id="translatedtitle">Qualitative <span class="hlt">analysis</span> of the <span class="hlt">stability</span> of a continuous vermicomposting system.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hu, Enzhu; Liu, Hong</p> <p>2012-12-01</p> <p>A mathematical <span class="hlt">model</span> was established to describe ecological relationships in a continuous vermicomposting system. The distributions of organic matter, microbes and earthworms on non-dimensional specific growth rates were simulated. The range of specific growth rates were visualized utilizing three-dimensional reconstruction technology. The <span class="hlt">stability</span> of a vermicomposting system was not influenced by the initial concentrations of microbes and earthworms, only their species. The coordinates of the stable point depended on the dilution rate and initial amount of organic matter. The method described could be help for establishing a stable continuous vermicomposting system. PMID:23127841</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150005708','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150005708"><span id="translatedtitle">Robust <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of the Space Launch System Control Design: A Singular Value Approach</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pei, Jing; Newsome, Jerry R.</p> <p>2015-01-01</p> <p>Classical <span class="hlt">stability</span> <span class="hlt">analysis</span> consists of breaking the feedback loops one at a time and determining separately how much gain or phase variations would destabilize the stable nominal feedback system. For typical launch vehicle control design, classical control techniques are generally employed. In addition to <span class="hlt">stability</span> margins, frequency domain Monte Carlo methods are used to evaluate the robustness of the design. However, such techniques were developed for Single-Input-Single-Output (SISO) systems and do not take into consideration the off-diagonal terms in the transfer function matrix of Multi-Input-Multi-Output (MIMO) systems. Robust <span class="hlt">stability</span> <span class="hlt">analysis</span> techniques such as H(sub infinity) and mu are applicable to MIMO systems but have not been adopted as standard practices within the launch vehicle controls community. This paper took advantage of a simple singular-value-based MIMO <span class="hlt">stability</span> margin evaluation method based on work done by Mukhopadhyay and Newsom and applied it to the SLS high-fidelity dynamics <span class="hlt">model</span>. The method computes a simultaneous multi-loop gain and phase margin that could be related back to classical margins. The results presented in this paper suggest that for the SLS system, traditional SISO <span class="hlt">stability</span> margins are similar to the MIMO margins. This additional level of verification provides confidence in the robustness of the control design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JSV...330.6006S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JSV...330.6006S"><span id="translatedtitle">Study of nonlinear system <span class="hlt">stability</span> using eigenvalue <span class="hlt">analysis</span>: Gyroscopic motion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shabana, Ahmed A.; Zaher, Mohamed H.; Recuero, Antonio M.; Rathod, Cheta</p> <p>2011-11-01</p> <p>General computational multibody system (MBS) algorithms allow for the linearization of the highly nonlinear equations of motion at different points in time in order to obtain the eigenvalue solution. This eigenvalue solution of the linearized equations is often used to shed light on the system <span class="hlt">stability</span> at different configurations that correspond to different time points. Different MBS algorithms, however, employ different sets of orientation coordinates, such as Euler angles and Euler parameters, which lead to different forms of the dynamic equations of motion. As a consequence, the forms of the linearized equations and the eigenvalue solution obtained strongly depend on the set of orientation coordinates used. This paper addresses this fundamental issue by examining the effect of the use of different orientation parameters on the linearized equations of a gyroscope. The nonlinear equations of motion of the gyroscope are formulated using two different sets of orientation parameters: Euler angles and Euler parameters. In order to obtain a set of linearized equations that can be used to define the eigenvalue solution, the algebraic equations that describe the MBS constraints are systematically eliminated leading to a nonlinear form of the equations of motion expressed in terms of the system degrees of freedom. Because in MBS applications the generalized forces can be highly nonlinear and can depend on the velocities, a state space formulation is used to solve the eigenvalue problem. It is shown in this paper that the independent state equations formulated using Euler angles and Euler parameters lead to different eigenvalue solutions. This solution is also different from the solution obtained using a form of the Newton-Euler matrix equation expressed in terms of the angular accelerations and angular velocities. A time-domain solution of the linearized equations is also presented in order to compare between the solutions obtained using two different sets of orientation parameters and also to shed light on the important issue of using the eigenvalue <span class="hlt">analysis</span> in the study of MBS <span class="hlt">stability</span>. The validity of using the eigenvalue <span class="hlt">analysis</span> based on the linearization of the nonlinear equations of motion in the study of the <span class="hlt">stability</span> of railroad vehicle systems, which have known critical speeds, is examined. It is shown that such an eigenvalue <span class="hlt">analysis</span> can lead to wrong conclusions regarding the <span class="hlt">stability</span> of nonlinear systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JCli...18..501L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JCli...18..501L"><span id="translatedtitle">Thermohaline Circulation <span class="hlt">Stability</span>: A Box <span class="hlt">Model</span> Study. Part I: Uncoupled <span class="hlt">Model</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lucarini, Valerio; Stone, Peter H.</p> <p>2005-02-01</p> <p>A thorough <span class="hlt">analysis</span> of the <span class="hlt">stability</span> of the uncoupled Rooth interhemispheric three-box <span class="hlt">model</span> of thermohaline circulation (THC) is presented. The <span class="hlt">model</span> consists of a northern high-latitude box, a tropical box, and a southern high-latitude box, which correspond to the northern, tropical, and southern Atlantic Ocean, respectively. Restoring boundary conditions are adopted for the temperature variables, and flux boundary conditions are adopted for the salinity variables. This paper examines how the strength of THC changes when the system undergoes forcings that are analogous to those of global warming conditions by applying the equilibrium state perturbations to the moisture and heat fluxes into the three boxes. In each class of experiments, using suitably defined metrics, the authors determine the boundary dividing the set of forcing scenarios that lead the system to equilibria characterized by a THC pattern similar to the present one from those that drive the system to equilibria with a reversed THC. Fast increases in the moisture flux into the northern high-latitude box are more effective than slow increases in leading the THC to a breakdown, while the increases of moisture flux into the southern high-latitude box strongly inhibit the breakdown and can prevent it, as in the case of slow increases in the Northern Hemisphere. High rates of heat flux increase in the Northern Hemisphere destabilize the system more effectively than low ones; increases in the heat fluxes in the Southern Hemisphere tend to <span class="hlt">stabilize</span> the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983JSV....88..369R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983JSV....88..369R"><span id="translatedtitle">Whirling and <span class="hlt">stability</span> of flywheel systems, part I: Derivation of combined and lumped parameter <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramanujam, G.; Bert, C. W.</p> <p>1983-06-01</p> <p>The objective of this paper is to provide a theoretical foundation to predict many aspects of dynamic behavior of flywheel systems when spin-tested with a quill shaft support and driven by an air turbine. Theoretical analyses for the following are presented: (1) determination of natural frequencies (or for brevity critical speeds of various orders), (2) Routh-type <span class="hlt">stability</span> <span class="hlt">analysis</span> to determine the <span class="hlt">stability</span> limits (i.e., the speed range within which small perturbations attenuate rather than cause catastrophic failure), and (3) forced whirling <span class="hlt">analysis</span> to estimate the response of major components of the system to flywheel mass eccentricity and initial tilt. For the first and third kinds of analyses, two different mathematical <span class="hlt">models</span> of the generic system are investigated. One is a seven-degree-of-freedom lumped parameter <span class="hlt">analysis</span>, while the other is a combined distributed and lumped parameter <span class="hlt">analysis</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/477355','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/477355"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of thermocapillary convection in rectangular cavities</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xu, J.; Zebib, A.</p> <p>1996-12-31</p> <p>This paper presents <span class="hlt">stability</span> <span class="hlt">analysis</span> on thermocapillary convection of acetone (Pr = 4.4) in rectangular cavities using direct numerical simulation. Influence of the Reynolds number (Re) and cavity aspect ratio (Ar) on motion is investigated. Results are exhibited for streamline and isotherm patterns at different values of Re and Ar. Neutral <span class="hlt">stability</span> curves for transition to time-dependent convection are delineated for this Pr = 4.4 fluid in the Re-Ar plane, and compared with the results for fluids with Pr = 10.0, 6.78 and 1.0. Several interesting features of these diagrams are discussed. One important conclusion the authors have from the comparison is that Ar{sub cr} increases as Pr decreases. Thus, it appears that large values of both Ar and Re are necessary to induce thermocapillary oscillations for small Pr fluids such as liquid metals. On the other hand, energy <span class="hlt">analysis</span> is performed for the oscillatory flow in the neighborhood of critical points in order to gain insight of mechanisms leading to instability. Results are provided for flows near both critical points with Ar = 3.0.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19890065226&hterms=Real+Analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DReal%2BAnalysis','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19890065226&hterms=Real+Analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DReal%2BAnalysis"><span id="translatedtitle">Computational <span class="hlt">analysis</span> of a <span class="hlt">stability</span> robustness margin for structured real-parameter perturbations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wedell, Evan; Chuang, C.-H.; Wie, Bong</p> <p>1989-01-01</p> <p>An efficient computational method is presented for <span class="hlt">stability</span> robustness <span class="hlt">analysis</span> with structured real-parameter perturbations. A generic <span class="hlt">model</span> of a class of uncertain dynamical systems is used as an example. The parameter uncertainty is characterized by a real scalar, epsilon. Multilinearity of the closed-loop characteristic polynomial is exploited to permit application of the mapping theorem to calculate the <span class="hlt">stability</span> robustness margin. It is found that sensitive geometry of the <span class="hlt">stability</span> boundary in the epsilon, omega-plane renders problematic the calculation of the minimum epsilon as a function of omega. This difficulty is avoided by calculating the minimum distance to the image of the uncertainty domain over omega as a function of epsilon. It is also shown that a certain class of uncertain dynamical systems has the required multilinearity property and are thus amenable to the proposed technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910045598&hterms=external+environment+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dexternal%2Benvironment%2Banalysis','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910045598&hterms=external+environment+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dexternal%2Benvironment%2Banalysis"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of position and force control problems for robot arms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wen, John T.; Murphy, Steve</p> <p>1990-01-01</p> <p><span class="hlt">Stability</span> issues involving the control of a robot arm under the influence of external forces are discussed. Several different scenarios are considered: position control with the external force as an unmodeled disturbance, compliant control for a bounded external force in some subspace, and compliant control for a force due to the interaction with an environment whose dynamical behavior can be <span class="hlt">modeled</span>. In each of these cases, a <span class="hlt">stability</span> <span class="hlt">analysis</span> using the Lyapunov method is presented. An explanation of instability is put forth for the case in which the environment has flexibility and the gains are inappropriately chosen. When the environment is stiff in the force control subspace, robust <span class="hlt">stability</span> can be achieved with the integral force feedback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25025089','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25025089"><span id="translatedtitle">Ant colony optimization <span class="hlt">analysis</span> on overall <span class="hlt">stability</span> of high arch dam basis of field monitoring.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lin, Peng; Liu, Xiaoli; Chen, Hong-Xin; Kim, Jinxie</p> <p>2014-01-01</p> <p>A dam ant colony optimization (D-ACO) <span class="hlt">analysis</span> of the overall <span class="hlt">stability</span> of high arch dams on complicated foundations is presented in this paper. A modified ant colony optimization (ACO) <span class="hlt">model</span> is proposed for obtaining dam concrete and rock mechanical parameters. A typical dam parameter feedback problem is proposed for nonlinear back-<span class="hlt">analysis</span> numerical <span class="hlt">model</span> based on field monitoring deformation and ACO. The basic principle of the proposed <span class="hlt">model</span> is the establishment of the objective function of optimizing real concrete and rock mechanical parameter. The feedback <span class="hlt">analysis</span> is then implemented with a modified ant colony algorithm. The algorithm performance is satisfactory, and the accuracy is verified. The m groups of feedback parameters, used to run a nonlinear FEM code, and the displacement and stress distribution are discussed. A feedback <span class="hlt">analysis</span> of the deformation of the Lijiaxia arch dam and based on the modified ant colony optimization method is also conducted. By considering various material parameters obtained using different <span class="hlt">analysis</span> methods, comparative analyses were conducted on dam displacements, stress distribution characteristics, and overall dam <span class="hlt">stability</span>. The comparison results show that the proposal <span class="hlt">model</span> can effectively solve for feedback multiple parameters of dam concrete and rock material and basically satisfy assessment requirements for geotechnical structural engineering discipline. PMID:25025089</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4083295','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4083295"><span id="translatedtitle">Ant Colony Optimization <span class="hlt">Analysis</span> on Overall <span class="hlt">Stability</span> of High Arch Dam Basis of Field Monitoring</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liu, Xiaoli; Chen, Hong-Xin; Kim, Jinxie</p> <p>2014-01-01</p> <p>A dam ant colony optimization (D-ACO) <span class="hlt">analysis</span> of the overall <span class="hlt">stability</span> of high arch dams on complicated foundations is presented in this paper. A modified ant colony optimization (ACO) <span class="hlt">model</span> is proposed for obtaining dam concrete and rock mechanical parameters. A typical dam parameter feedback problem is proposed for nonlinear back-<span class="hlt">analysis</span> numerical <span class="hlt">model</span> based on field monitoring deformation and ACO. The basic principle of the proposed <span class="hlt">model</span> is the establishment of the objective function of optimizing real concrete and rock mechanical parameter. The feedback <span class="hlt">analysis</span> is then implemented with a modified ant colony algorithm. The algorithm performance is satisfactory, and the accuracy is verified. The m groups of feedback parameters, used to run a nonlinear FEM code, and the displacement and stress distribution are discussed. A feedback <span class="hlt">analysis</span> of the deformation of the Lijiaxia arch dam and based on the modified ant colony optimization method is also conducted. By considering various material parameters obtained using different <span class="hlt">analysis</span> methods, comparative analyses were conducted on dam displacements, stress distribution characteristics, and overall dam <span class="hlt">stability</span>. The comparison results show that the proposal <span class="hlt">model</span> can effectively solve for feedback multiple parameters of dam concrete and rock material and basically satisfy assessment requirements for geotechnical structural engineering discipline. PMID:25025089</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JIEIB.tmp...27C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JIEIB.tmp...27C"><span id="translatedtitle">Optimal <span class="hlt">Stabilization</span> of Social Welfare under Small Variation of Operating Condition with Bifurcation <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chanda, Sandip; De, Abhinandan</p> <p>2015-07-01</p> <p>A social welfare optimization technique has been proposed in this paper with a developed state space based <span class="hlt">model</span> and bifurcation <span class="hlt">analysis</span> to offer substantial <span class="hlt">stability</span> margin even in most inadvertent states of power system networks. The restoration of the power market dynamic price equilibrium has been negotiated in this paper, by forming Jacobian of the sensitivity matrix to regulate the state variables for the standardization of the quality of solution in worst possible contingencies of the network and even with co-option of intermittent renewable energy sources. The <span class="hlt">model</span> has been tested in IEEE 30 bus system and illustrious particle swarm optimization has assisted the fusion of the proposed <span class="hlt">model</span> and methodology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CNSNS..26..265Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CNSNS..26..265Y"><span id="translatedtitle">Wavelet <span class="hlt">modeling</span> and prediction of the <span class="hlt">stability</span> of states: the Roman Empire and the European Union</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yaroshenko, Tatyana Y.; Krysko, Dmitri V.; Dobriyan, Vitalii; Zhigalov, Maksim V.; Vos, Hendrik; Vandenabeele, Peter; Krysko, Vadim A.</p> <p>2015-09-01</p> <p>How can the <span class="hlt">stability</span> of a state be quantitatively determined and its future <span class="hlt">stability</span> predicted? The rise and collapse of empires and states is very complex, and it is exceedingly difficult to understand and predict it. Existing theories are usually formulated as verbal <span class="hlt">models</span> and, consequently, do not yield sharply defined, quantitative prediction that can be unambiguously validated with data. Here we describe a <span class="hlt">model</span> that determines whether the state is in a stable or chaotic condition and predicts its future condition. The central <span class="hlt">model</span>, which we test, is that growth and collapse of states is reflected by the changes of their territories, populations and budgets. The <span class="hlt">model</span> was simulated within the historical societies of the Roman Empire (400 BC to 400 AD) and the European Union (1957-2007) by using wavelets and <span class="hlt">analysis</span> of the sign change of the spectrum of Lyapunov exponents. The <span class="hlt">model</span> matches well with the historical events. During wars and crises, the state becomes unstable; this is reflected in the wavelet <span class="hlt">analysis</span> by a significant increase in the frequency ω (t) and wavelet coefficients W (ω, t) and the sign of the largest Lyapunov exponent becomes positive, indicating chaos. We successfully reconstructed and forecasted time series in the Roman Empire and the European Union by applying artificial neural network. The proposed <span class="hlt">model</span> helps to quantitatively determine and forecast the <span class="hlt">stability</span> of a state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4043158','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4043158"><span id="translatedtitle">Nonlinear flight dynamics and <span class="hlt">stability</span> of hovering <span class="hlt">model</span> insects</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liang, Bin; Sun, Mao</p> <p>2013-01-01</p> <p>Current analyses on insect dynamic flight <span class="hlt">stability</span> are based on linear theory and limited to small disturbance motions. However, insects' aerial environment is filled with swirling eddies and wind gusts, and large disturbances are common. Here, we numerically solve the equations of motion coupled with the Navier–Stokes equations to simulate the large disturbance motions and analyse the nonlinear flight dynamics of hovering <span class="hlt">model</span> insects. We consider two representative <span class="hlt">model</span> insects, a <span class="hlt">model</span> hawkmoth (large size, low wingbeat frequency) and a <span class="hlt">model</span> dronefly (small size, high wingbeat frequency). For small and large initial disturbances, the disturbance motion grows with time, and the insects tumble and never return to the equilibrium state; the hovering flight is inherently (passively) unstable. The instability is caused by a pitch moment produced by forward/backward motion and/or a roll moment produced by side motion of the insect. PMID:23697714</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AcAau..93..162N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AcAau..93..162N"><span id="translatedtitle">On the <span class="hlt">stability</span> and bifurcation <span class="hlt">analysis</span> of dual-spin spacecraft</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nazari, Morad; Butcher, Eric A.</p> <p>2014-01-01</p> <p>The dynamics of dual-spin spacecraft under effects of energy dissipation are considered in this paper, where the damper masses in the platform (P) and the rotor (R) cause energy loss in the system. The Floquet theory is employed to obtain <span class="hlt">stability</span> charts for different relative spin rates of the subsystem R with respect to the subsystem P. Based on the general <span class="hlt">model</span> for the system with nutation dampers on both P and R, <span class="hlt">models</span> are presented for a system whose nutation damper exists only in P as well as a system without nutation damper. The results obtained from the Floquet theory agree with the energy sink <span class="hlt">analysis</span> in the literature. The bifurcation <span class="hlt">analysis</span> based on the movement of loci of the Floquet multipliers as the system passes through the flutter <span class="hlt">stability</span> boundary indicates that the system experiences the secondary Hopf (Neimark-Sacker) bifurcation. The investigations show that for spacecraft whose nutation damper exists only in one of the subsystems, there is no need to apply Floquet theory, and the Routh-Hurwitz criteria provides necessary and sufficient conditions for <span class="hlt">stability</span>. Furthermore, for the case that only P has damping, the Lyapunov <span class="hlt">stability</span> criteria agree with Routh-Hurwitz criteria.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......443S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......443S"><span id="translatedtitle">Thermal <span class="hlt">Stability</span> of Nanocrystalline Alloys by Solute Additions and A Thermodynamic <span class="hlt">Modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saber, Mostafa</p> <p></p> <p>Nanocrystalline alloys show superior properties due to their exceptional microstructure. Thermal <span class="hlt">stability</span> of these materials is a critical aspect. It is well known that grain boundaries in nanocrystalline microstructures cause a significant increase in the total free energy of the system. A driving force provided to reduce this excess free energy can cause grain growth. The presence of a solute addition within a nanocrystalline alloy can lead to the thermal <span class="hlt">stability</span>. Kinetic and thermodynamic <span class="hlt">stabilization</span> are the two basic mechanisms with which <span class="hlt">stability</span> of a nanoscale grain size can be achieved at high temperatures. The basis of this thesis is to study the effect of solute addition on thermal <span class="hlt">stability</span> of nanocrystalline alloys. The objective is to determine the effect of Zr addition on the thermal <span class="hlt">stability</span> of mechanically alloyed nanocrysatillne Fe-Cr and Fe-Ni alloys. In Fe-Cr-Zr alloy system, nanoscale grain size <span class="hlt">stabilization</span> was maintained up to 900 C by adding 2 at% Zr. Kinetic pinning by intermetallic particles in the nanoscale range was identified as a primary mechanism of thermal <span class="hlt">stabilization</span>. In addition to the grain size strengthening, intermetallic particles also contribute to strengthening mechanisms. The <span class="hlt">analysis</span> of microhardness, XRD data, and measured grain sizes from TEM micrographs suggested that both thermodynamic and kinetic mechanisms are possible mechanisms. It was found that alpha ? gamma phase transformation in Fe-Cr-Zr system does not influence the grain size <span class="hlt">stabilization</span>. In the Fe-Ni-Zr alloy system, it was shown that the grain growth in Fe-8Ni-1Zr alloy is much less than that of pure Fe and Fe-8Ni alloy at elevated temperatures. The microstructure of the ternary Fe-8Ni-1Zr alloy remains in the nanoscale range up to 700 C. Using an in-situ TEM study, it was determined that drastic grain growth occurs when the alpha ? gamma phase transformation occurs. Accordingly, there can be a synergistic relationship between grain growth and alpha ? gamma phase transformation in Fe-Ni-Zr alloys. In addition to the experimental study of thermal <span class="hlt">stabilization</span> of nanocrystalline Fe-Cr-Zr or Fe-Ni-Zr alloys, the thesis presented here developed a new predictive <span class="hlt">model</span>, applicable to strongly segregating solutes, for thermodynamic <span class="hlt">stabilization</span> of binary alloys. This <span class="hlt">model</span> can serve as a benchmark for selecting solute and evaluating the possible contribution of <span class="hlt">stabilization</span>. Following a regular solution <span class="hlt">model</span>, both the chemical and elastic strain energy contributions are combined to obtain the mixing enthalpy. The total Gibbs free energy of mixing is then minimized with respect to simultaneous variations in the grain boundary volume fraction and the solute concentration in the grain boundary and the grain interior. The Lagrange multiplier method was used to obtained numerical solutions. Application are given for the temperature dependence of the grain size and the grain boundary solute excess for selected binary system where experimental results imply that thermodynamic <span class="hlt">stabilization</span> could be operative. This thesis also extends the binary <span class="hlt">model</span> to a new <span class="hlt">model</span> for thermodynamic <span class="hlt">stabilization</span> of ternary nanocrystalline alloys. It is applicable to strongly segregating size-misfit solutes and uses input data available in the literature. In a same manner as the binary <span class="hlt">model</span>, this <span class="hlt">model</span> is based on a regular solution approach such that the chemical and elastic strain energy contributions are incorporated into the mixing enthalpy DeltaHmix, and the mixing entropy DeltaSmix is obtained using the ideal solution approximation. The Gibbs mixing free energy Delta Gmix is then minimized with respect to simultaneous variations in grain growth and solute segregation parameters. The Lagrange multiplier method is similarly used to obtain numerical solutions for the minimum Delta Gmix. The temperature dependence of the nanocrystalline grain size and interfacial solute excess can be obtained for selected ternary systems. As an example, <span class="hlt">model</span> predictions are compared to experimental results for Fe-Cr-Zr and Fe-Ni-Zr </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPhCS.557a2133P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhCS.557a2133P"><span id="translatedtitle"><span class="hlt">Stability</span> and spring constant investigation for micromachined inductive suspensions: theoretical <span class="hlt">analysis</span> vs. experimental results</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Poletkin, K.; Lu, Z.; den Hartogh, B.; Wallrabe, U.; Badilita, V.</p> <p>2014-11-01</p> <p>We present a linear analytical <span class="hlt">model</span> coupled with experimental <span class="hlt">analysis</span> to discuss <span class="hlt">stability</span> of a levitated proof mass (PM) in a micromachined inductive suspension (MIS), which has been previously introduced and characterized. The <span class="hlt">model</span> is a function of the MIS geometry, describes the dynamics of a levitated disk-shaped PM near the equilibrium point, and predicts conditions for stable levitation. The experimental setup directly measures the lateral component of the Lorentz force, which has a <span class="hlt">stabilization</span> role in the MIS structure, as well as the vertical levitation force. The experimental setup is further used to derive mechanical parameters such as stiffness values relative to lateral, vertical and angular displacements, proven to be in excellent agreement with the values predicted by the analytical <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920013948','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920013948"><span id="translatedtitle">Aeroelastic <span class="hlt">stability</span> analyses of two counter rotating propfan designs for a cruise missile <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mahajan, Aparajit J.; Lucero, John M.; Mehmed, Oral; Stefko, George L.</p> <p>1992-01-01</p> <p>Aeroelastic <span class="hlt">stability</span> analyses were performed to insure structural integrity of two counterrotating propfan blade designs for a NAVY/Air Force/NASA cruise missile <span class="hlt">model</span> wind tunnel test. This <span class="hlt">analysis</span> predicted if the propfan designs would be flutter free at the operating conditions of the wind tunnel test. Calculated <span class="hlt">stability</span> results are presented for the two blade designs with rotational speed and Mach number as the parameters. A aeroelastic <span class="hlt">analysis</span> code ASTROP2 (Aeroelastic <span class="hlt">Stability</span> and Response of Propulsion Systems - 2 Dimensional <span class="hlt">Analysis</span>), developed at LeRC, was used in this project. The aeroelastic <span class="hlt">analysis</span> is a modal method and uses the combination of a finite element structural <span class="hlt">model</span> and two dimensional steady and unsteady cascade aerodynamic <span class="hlt">models</span>. This code was developed to analyze single rotation propfans but was modified and applied to counterrotating propfans for the present work. Modifications were made to transform the geometry and rotation of the aft rotor to the same reference frame as the forward rotor, to input a non-uniform inflow into the rotor being analyzed, and to automatically converge to the least stable aeroelastic mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090034255','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090034255"><span id="translatedtitle"><span class="hlt">Stability</span> and Control <span class="hlt">Analysis</span> of the F-15B Quiet SpikeTM Aircraft</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McWherter, Shaun C.; Moua, Cheng M.; Gera, Joseph; Cox, Timothy H.</p> <p>2009-01-01</p> <p>The primary purpose of the Quiet Spike(TradeMark) flight research program was to analyze the aerodynamic, structural, and mechanical proof-of-concept of a large multi-stage telescoping nose spike installed on the National Aeronautics and Space Administration Dryden Flight Research Center (Edwards, California) F-15B airplane. This report describes the preflight <span class="hlt">stability</span> and control <span class="hlt">analysis</span> performed to assess the effect of the spike on the <span class="hlt">stability</span>, controllability, and handling qualities of the airplane; and to develop an envelope expansion approach to maintain safety of flight. The overall flight test objective was to collect flight data to validate the spike structural dynamics and loads <span class="hlt">model</span> up to Mach 1.8. Other objectives included validating the mechanical feasibility of a morphing fuselage at operational conditions and determining the near-field shock wave characterization. The two main issues relevant to the <span class="hlt">stability</span> and control objectives were the effects of the spike-influenced aerodynamics on the F-15B airplane flight dynamics, and the air data and angle-of-attack sensors. The <span class="hlt">analysis</span> covered the sensitivity of the <span class="hlt">stability</span> margins, and the handling qualities due to aerodynamic variation and the maneuvering limitations of the F-15B Quiet Spike configuration. The results of the <span class="hlt">analysis</span> and the implications for the flight test program are also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JCos...17.7313M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JCos...17.7313M"><span id="translatedtitle">Gravitational <span class="hlt">Stability</span> for a Vacuum Cosmic Space Crystalline <span class="hlt">Model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montemayor-Varela, J.; Morones-Ibarra, J.; Morales-Mori, A.; Mendez-Allende, A.; Montmayer-Varela, A.; del Castillo-Mussot, M.; Vazquez, G.</p> <p>2011-11-01</p> <p>Using a generalization of the Heisenberg's uncertainty principle it is shown that the local gravitational <span class="hlt">stability</span> condition for an infinite tridimensional crystalline m o d e l o f t h e quantum vacuum cosmic space (which is existing from an infinite time before the occurrence of our local actual big bang event) implies to obtain an equation formally equivalent to the relation first used by Gamow to predict the present temperature of the microwave background from the matter density. The compatibility condition between the quantum and the relativistic approaches has been obtained without infinities arising from the quantum <span class="hlt">analysis</span> or singularities arising from the relativistic theory. The action, which leads to our theory, is the least action possible in a quantum scheme. The energy fluctuation involved in the gravitational <span class="hlt">stabilization</span> of vacuum space, inside the actual volume of our universe, is 10-40 times the energy of the crystalline structure of vacuum space inside the present Universe volume. The same process of quantum gravitational <span class="hlt">stabilization</span> occurs everywhere (by pairs of cells with tension- compression gravitational stresses) in the infinite cosmic vacuum space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3337434','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3337434"><span id="translatedtitle">Genome-wide <span class="hlt">analysis</span> of long noncoding RNA <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Clark, Michael B.; Johnston, Rebecca L.; Inostroza-Ponta, Mario; Fox, Archa H.; Fortini, Ellen; Moscato, Pablo; Dinger, Marcel E.; Mattick, John S.</p> <p>2012-01-01</p> <p>Transcriptomic analyses have identified tens of thousands of intergenic, intronic, and cis-antisense long noncoding RNAs (lncRNAs) that are expressed from mammalian genomes. Despite progress in functional characterization, little is known about the post-transcriptional regulation of lncRNAs and their half-lives. Although many are easily detectable by a variety of techniques, it has been assumed that lncRNAs are generally unstable, but this has not been examined genome-wide. Utilizing a custom noncoding RNA array, we determined the half-lives of ?800 lncRNAs and ?12,000 mRNAs in the mouse Neuro-2a cell line. We find only a minority of lncRNAs are unstable. LncRNA half-lives vary over a wide range, comparable to, although on average less than, that of mRNAs, suggestive of complex metabolism and widespread functionality. Combining half-lives with comprehensive lncRNA annotations identified hundreds of unstable (half-life < 2 h) intergenic, cis-antisense, and intronic lncRNAs, as well as lncRNAs showing extreme <span class="hlt">stability</span> (half-life > 16 h). <span class="hlt">Analysis</span> of lncRNA features revealed that intergenic and cis-antisense RNAs are more stable than those derived from introns, as are spliced lncRNAs compared to unspliced (single exon) transcripts. Subcellular localization of lncRNAs indicated widespread trafficking to different cellular locations, with nuclear-localized lncRNAs more likely to be unstable. Surprisingly, one of the least stable lncRNAs is the well-characterized paraspeckle RNA Neat1, suggesting Neat1 instability contributes to the dynamic nature of this subnuclear domain. We have created an online interactive resource (http://<span class="hlt">stability</span>.matticklab.com) that allows easy navigation of lncRNA and mRNA <span class="hlt">stability</span> profiles and provides a comprehensive annotation of ?7200 mouse lncRNAs. PMID:22406755</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhRvE..69e1608G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhRvE..69e1608G"><span id="translatedtitle">Linear morphological <span class="hlt">stability</span> <span class="hlt">analysis</span> of the solid-liquid interface in rapidsolidification of a binary system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galenko, P. K.; Danilov, D. A.</p> <p>2004-05-01</p> <p>The interface <span class="hlt">stability</span> against small perturbations of the planar solid-liquid interface is considered analytically in linear approximation. Following the analytical procedure of Trivedi and Kurz [<article> R. Trivedi and W. Kurz, Acta Metall. 34, 1663 (1986) </article>], which is advancing the original treatment of morphological <span class="hlt">stability</span> by Mullins and Sekerka [<article> W. W. Mullins and R. F. Sekerka, J. Appl. Phys. 35, 444 (1964) </article>] to the case of rapid solidification, we extend the <span class="hlt">model</span> by introducing the local nonequilibrium in the solute diffusion field around the interface. A solution to the heat- and mass-transport problem around the perturbed interface is given in the presence of the local nonequilibrium solute diffusion. Using the developing local nonequilibrium <span class="hlt">model</span> of solidification, the self-consistent <span class="hlt">analysis</span> of linear morphological <span class="hlt">stability</span> is presented with the attribution to the marginal (neutral) and absolute morphological <span class="hlt">stability</span> of a rapidly moving interface. Special consideration of the interface <span class="hlt">stability</span> for the cases of solidification in negative and positive thermal gradients is given. A quantitative comparison of the <span class="hlt">model</span> predictions for the absolute morphological <span class="hlt">stability</span> is presented with regard to experimental results of Hoglund and Aziz [<proc> D. E. Hoglund and M. J. Aziz, in <booktitle>Kinetics of Phase Transformations</booktitle>, edited by <editor>M.O. Thompson</editor>, <editor>M. J. Aziz</editor>, and <editor>G. B. Stephenson</editor>, <series>MRS Symposia Proceedings</series> No. 205 (<publisher>Materials Research Society</publisher>, Pittsburgh, 1991), p. 325 </proc>] on critical solute concentration for the interface breakdown during rapid solidification of Si-Sn alloys.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013StGM...35....3A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013StGM...35....3A"><span id="translatedtitle">Slope <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Waste Dump in Sandstone Open Pit Osielec</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adamczyk, Justyna; Ca?a, Marek; Flisiak, Jerzy; Kolano, Malwina; Kowalski, Micha?</p> <p>2013-03-01</p> <p>This paper presents the slope <span class="hlt">stability</span> <span class="hlt">analysis</span> for the current as well as projected (final) geometry of waste dump Sandstone Open Pit "Osielec". For the <span class="hlt">stability</span> <span class="hlt">analysis</span> six sections were selected. Then, the final geometry of the waste dump was designed and the <span class="hlt">stability</span> <span class="hlt">analysis</span> was conducted. On the basis of the <span class="hlt">analysis</span> results the opportunities to improve the <span class="hlt">stability</span> of the object were identified. The next issue addressed in the paper was to determine the proportion of the mixture containing mining and processing wastes, for which the waste dump remains stable. <span class="hlt">Stability</span> calculations were carried out using Janbu method, which belongs to the limit equilibrium methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21736312','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21736312"><span id="translatedtitle">Foamability and foam <span class="hlt">stability</span> of molecular reconstituted <span class="hlt">model</span> sparkling wines.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Coelho, Elisabete; Rocha, Slvia M; Coimbra, Manuel A</p> <p>2011-08-24</p> <p>The present work aims at identifying the contribution of the different wine components to the foaming properties of wines. Twelve fractions were isolated from wine, and foam aptitude of each fraction was measured individually at the concentration at which it was recovered, using wine <span class="hlt">model</span> solutions. For these concentrations, the maximum foam height (HM) was 8.4-11.7 cm, foam height on <span class="hlt">stability</span> was 6.9-7.5 cm, and foam <span class="hlt">stability</span> (TS) was 3.0-6.5 s. Moreover, foam measurements were also performed using 2-, 5-, and 10-fold concentrations of these compounds in wine. The HM increased linearly with the concentration of mannoproteins having low content of protein (MP1), and TS increased exponentially. The fractions that individually showed higher foaming properties were mixed in binary and ternary combinations, demonstrating that MP1 when mixed with low molecular weight hydrophobic compounds strengthens the air/water interface of these solutions, a characteristic that is on the basis of sparkling wines' foamability and foam <span class="hlt">stability</span>. PMID:21736312</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840009069','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840009069"><span id="translatedtitle">Bifurcation <span class="hlt">analysis</span> of aircraft pitching motions near the <span class="hlt">stability</span> boundary</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hui, W. H.; Tobak, M.</p> <p>1984-01-01</p> <p>Bifuraction theory is used to analyze the nonlinear dynamic <span class="hlt">stability</span> characteristics of an aircraft subject to single degree of freedom pitching-motion perturbations about a large mean angle of attack. The requisite aerodynamic information in the equations of motion is represented in a form equivalent to the response to finite-amplitude pitching oscillations about the mean angle of attack. This information is deduced from the case of infinitesimal-amplitude oscillations. The bifurcation theory <span class="hlt">analysis</span> reveals that when the mean angle of attack is increased beyond a critical value at which the aerodynamic damping vanishes, new solutions representing finite-amplitude periodic motions bifurcate from the previously stable steady motion. The sign of a simple criterion, cast in terms of aerodynamic properties, determines whether the bifurcating solutions are stable (supercritical) or unstable (subcritical). For flat-plate airfoils flying at supersonic/hypersonic speed, the bifurcation is subcritical, implying either that exchanges of <span class="hlt">stability</span> between steady and periodic motion are accompanied by hysteresis phenomena, or that potentially large aperiodic departures from steady motion may develop.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013amos.confE..34H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013amos.confE..34H"><span id="translatedtitle"><span class="hlt">Analysis</span> of Faint Glints from <span class="hlt">Stabilized</span> GEO Satellites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hall, D.; Kervin, P.</p> <p>2013-09-01</p> <p>Ground-based telescopes routinely acquire temporal brightness measurements of satellites in geo-stationary and geo-synchronous orbit that provide valuable characterization information. For instance, GEO satellites that are not <span class="hlt">stabilized</span> tend to rotate, and produce brightnesses that vary in time with frequencies corresponding to rotation rates. Temporal brightness patterns can also be exploited to characterize <span class="hlt">stabilized</span> GEO satellites. For example, many operational GEO satellites have solar panels that glint when they reflect sunlight towards an observer in a mirror-like fashion. These well-known solar panel glints can be remarkably bright, often exceeding several stellar magnitudes in amplitude. Measured brightnesses and times of these glints can be exploited to estimate the size, segmentation, and alignment of the solar array, valuable information about the satellite's power generation and consumption capabilities. However, satellites can produce other glints in addition to those originating from solar panels. These glints can be much fainter, with amplitudes as small as 0.2 magnitudes. Several observations of GEO satellites show several such glints occurring during the span of a single night. Furthermore, many of these recur from night to night when observed from a single ground-based site, but with subtle, incremental changes in both peak times and brightnesses. These fainter glints must originate from reflective elements mounted on the satellite's main bus, solar panel structure, or other peripheral structures that might be stationary or moving with respect to the main bus. Our <span class="hlt">analysis</span> indicates that such glints can be exploited for GEO satellite characterization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030062997','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030062997"><span id="translatedtitle">AIR <span class="hlt">Model</span> Preflight <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tai, H.; Wilson, J. W.; Maiden, D. L.</p> <p>2003-01-01</p> <p>The atmospheric ionizing radiation (AIR) ER-2 preflight <span class="hlt">analysis</span>, one of the first attempts to obtain a relatively complete measurement set of the high-altitude radiation level environment, is described in this paper. The primary thrust is to characterize the atmospheric radiation and to define dose levels at high-altitude flight. A secondary thrust is to develop and validate dosimetric techniques and monitoring devices for protecting aircrews. With a few chosen routes, we can measure the experimental results and validate the AIR <span class="hlt">model</span> predictions. Eventually, as more measurements are made, we gain more understanding about the hazardous radiation environment and acquire more confidence in the prediction <span class="hlt">models</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100009809','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100009809"><span id="translatedtitle">Absolute <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of a Phase Plane Controlled Spacecraft</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jang, Jiann-Woei; Plummer, Michael; Bedrossian, Nazareth; Hall, Charles; Jackson, Mark; Spanos, Pol</p> <p>2010-01-01</p> <p>Many aerospace attitude control systems utilize phase plane control schemes that include nonlinear elements such as dead zone and ideal relay. To evaluate phase plane control robustness, <span class="hlt">stability</span> margin prediction methods must be developed. Absolute <span class="hlt">stability</span> is extended to predict <span class="hlt">stability</span> margins and to define an abort condition. A constrained optimization approach is also used to design flex filters for roll control. The design goal is to optimize vehicle tracking performance while maintaining adequate <span class="hlt">stability</span> margins. Absolute <span class="hlt">stability</span> is shown to provide satisfactory <span class="hlt">stability</span> constraints for the optimization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMNH13D..04S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMNH13D..04S"><span id="translatedtitle">SOSlope 3D: implementing root reinforcement and preferential flow in slope <span class="hlt">stability</span> <span class="hlt">modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schwarz, M.; Cohen, D.</p> <p>2013-12-01</p> <p>The quantification of root reinforcement represents a key issue in different area of engineering (slope <span class="hlt">stability</span>, soil protection, silviculture/tree <span class="hlt">stability</span>, hydraulic). Between all the effects of plants (direct and indirect) on the physical and chemical soil processes, the mechanical effect of roots is considered particularly important for slope <span class="hlt">stability</span>. The study of root reinforcement is faced with the high complexity of interactions of processes and factors at different spatio-temporal scales. In particular, the hierarchical spatial heterogeneity of vegetation and its effects on soil processes represent a big challenge for quantitative up-scaling methods. The objective of this contribution is to contextualize the complexity of the root-soil interactions in view of slope <span class="hlt">stability</span> problems, to review the recent scientific contributions in the quantification of root reinforcement, and to discuss the practical meaning of recent research results. In the presentation of an up-scaling framework for the implementation of root reinforcement and preferential flow in slope <span class="hlt">stability</span> <span class="hlt">analysis</span>, the following arguments will be discussed: tensile force and pullout force of single roots, apparent elasticity of single roots, strain loading approach for the characterization of root bundle mechanics, meaning of root diameter distribution on root reinforcement, spatial heterogeneity of root distribution, hydro-mechanical and rheological properties of rooted soil under tension and compression, and triggering mechanism of shallow landslides. The above-mentioned factors and processes build up the modules implemented in a numerical <span class="hlt">model</span> for slope <span class="hlt">stability</span> calculations, the SOSlope <span class="hlt">model</span>. The SOSlope <span class="hlt">model</span> is characterized by the use of a spring-block framework (with 1x1 m cell grid), a strain step loading approach for the redistribution of forces, and the implementation of a spatial distribution of root at the hill slope scale. The results of simulations performed with the SOSlope <span class="hlt">model</span> serve as background for the discussion on the role of root reinforcement for protection forests management and bioengineering applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JDE...170..344K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JDE...170..344K"><span id="translatedtitle"><span class="hlt">Stability</span> of a Resonant System of Conservation Laws <span class="hlt">Modeling</span> Polymer Flow with Gravitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klingenberg, Christian; Risebro, Nils Henrik</p> <p>2001-03-01</p> <p>We prove L1 uniqueness and <span class="hlt">stability</span> for a resonant 22 system of conservation laws that arise as a <span class="hlt">model</span> for two phase polymer flow in porous media. The <span class="hlt">analysis</span> uses the equivalence of the Eulerian and Lagrangian formulation of this system, and the results are first established for an auxiliary scalar equation. Our methods are based on front tracking approximations for the auxiliary equation, and the Krukov entropy condition for scalar conservation laws.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/984647','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/984647"><span id="translatedtitle"><span class="hlt">Analysis</span> of cavern <span class="hlt">stability</span> at the Bryan Mound SPR site.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ehgartner, Brian L.; Sobolik, Steven Ronald</p> <p>2009-04-01</p> <p>This report presents computational analyses that simulate the structural response of caverns at the Strategic Petroleum Reserve Bryan Mound site. The cavern field comprises 20 caverns. Five caverns (1, 2, 4, and 5; 3 was later plugged and abandoned) were acquired from industry and have unusual shapes and a history dating back to 1946. The other 16 caverns (101-116) were leached according to SPR standards in the mid-1980s and have tall cylindrical shapes. The history of the caverns and their shapes are simulated in a 3-D geomechanics <span class="hlt">model</span> of the site that predicts deformations, strains, and stresses. Future leaching scenarios due to oil drawdowns using fresh water are also simulated by increasing the volume of the caverns. Cavern pressures are varied in the <span class="hlt">model</span> to capture operational practices in the field. The results of the finite element <span class="hlt">model</span> are interpreted to provide information on the current and future status of subsidence, well integrity, and cavern <span class="hlt">stability</span>. The most significant result in this report is relevant to caverns 1, 2, and 5. The caverns have non-cylindrical shapes and have potential regions where the surrounding salt may be damaged during workover procedures. During a workover the normal cavern operating pressure is lowered to service a well. At this point the wellhead pressures are atmospheric. When the workover is complete, the cavern is repressurized. The resulting elastic stresses are sufficient to cause tension and large deviatoric stresses at several locations. With time, these stresses relax to a compressive state due to salt creep. However, the potential for salt damage and fracturing exists. The analyses predict tensile stresses at locations with sharp-edges in the wall geometry, or in the case of cavern 5, in the neck region between the upper and lower lobes of the cavern. The effects do not appear to be large-scale, however, so the only major impact is the potential for stress-induced salt falls in cavern 5, potentially leading to hanging string damage. Caverns 1 and 2 have no significant issues regarding leachings due to drawdowns; cavern 5 may require a targeted leaching of the neck region to improve cavern <span class="hlt">stability</span> and lessen hanging string failure potential. The remaining caverns have no significant issues regarding cavern <span class="hlt">stability</span> and may be safely enlarged during subsequent oil drawdowns. Well strains are significant and consequently future remedial actions may be necessary. Well strains certainly suggest the need for appropriate monitoring through a well-logging program. Subsidence is currently being monitored; there are no issues identified regarding damage from surface subsidence or horizontal strain to surface facilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.jstor.org/stable/info/1941283','USGSPUBS'); return false;" href="http://www.jstor.org/stable/info/1941283"><span id="translatedtitle">Assessment of sampling <span class="hlt">stability</span> in ecological applications of discriminant <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Williams, B.K.; Titus, K.</p> <p>1988-01-01</p> <p>A simulation study was undertaken to assess the sampling <span class="hlt">stability</span> of the variable loadings in linear discriminant function <span class="hlt">analysis</span>. A factorial design was used for the factors of multivariate dimensionality, dispersion structure, configuration of group means, and sample size. A total of 32,400 discriminant analyses were conducted, based on data from simulated populations with appropriate underlying statistical distributions. A review of 60 published studies and 142 individual analyses indicated that sample sizes in ecological studies often have met that requirement. However, individual group sample sizes frequently were very unequal, and checks of assumptions usually were not reported. The authors recommend that ecologists obtain group sample sizes that are at least three times as large as the number of variables measured.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930030760&hterms=wisdom&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwisdom','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930030760&hterms=wisdom&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwisdom"><span id="translatedtitle">Symplectic maps for the n-body problem - <span class="hlt">Stability</span> <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wisdom, Jack; Holman, Matthew</p> <p>1992-01-01</p> <p>The <span class="hlt">stability</span> of new symplectic n-body maps is examined from the point of view of nonlinear dynamics. The resonances responsible for the principal artifacts are identified. These are resonances between the stepsize and the difference of mean motions between pairs of planets. For larger stepsizes resonant perturbations are evident in the variation of the energy of the system corresponding to these stepsize resonances. It is shown that the principal instability of the method can be predicted and corresponds to the overlap of the stepsize resonances. It is noted that the <span class="hlt">analysis</span> suggests that other artifacts will occur. For example, the overlap of a stepsize resonance with a resonance of the actual system may also give a region of chaotic behavior that is an artifact. It is pointed out that the fact that the principal artifacts corresponds to a particular set of stepsize resonances suggests that it may be possible to perturbatively remove the effect when the stepsize resonances are nonoverlapping.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5746419','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5746419"><span id="translatedtitle">Coupled three-dimensional aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> of bladed disks</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gerolymos, G.A. )</p> <p>1993-10-01</p> <p>In the present work an algorithm for the coupled aeromechanical computation of three-dimensional compressor cascades vibrating in a traveling-wave mode is presented and applied to the determination of aeroelastic <span class="hlt">stability</span> of a transonic fan rotor. The initial vibratory modes are computed using a finite-element structural <span class="hlt">analysis</span> code. The unsteady flow field response to blade vibration is estimated by numerical integration of the three-dimensional unsteady Euler equations. Coupling relations are formulated in the frequency domain, using a mode-modification technique, based on modal projection. The vibratory mode is updated at the end of the aerodynamic simulation of each period, and the updated mode is used for the simulation of the next period. A number of results illustrate the method's potential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6278409','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6278409"><span id="translatedtitle"><span class="hlt">Analysis</span> of boiling-water nuclear-reactor-<span class="hlt">stability</span> margin</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Balaram, J.; Shen, C.N.; Lahey, R.T. Jr.; Becker, M.</p> <p>1983-05-01</p> <p>The phenomenon of nuclear-coupled density-wave oscillations in Boiling Water Nuclear Reactors (BWR) must be analyzed to demonstrate acceptable operational characteristics. Specifically, the <span class="hlt">stability</span> margin required for acceptable system performance must be quantified. This is important not only from the design viewpoint but also from the requirement of establishing licensing acceptance criteria for a BWR. In this report the currently used licensing criterion based on the so called decay ratio of the system is analyzed. This criterion is based on a single-input single-output (SISO) <span class="hlt">analysis</span> of the system and thus does not take into account the multi-input, multi-output (MIMO) nature of a BWR system. The deficiencies of the current criterion are discussed, and an interim acceptance criterion is purposed. MIMO-related problems are identified and not how the proposed interim criteria can evolve to deal with these concerns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20010003456&hterms=Rivera&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3DRivera','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20010003456&hterms=Rivera&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3DRivera"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of the Planetary System Orbiting Upsilon Andromedae</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lissauer, Jack J.; Rivera, Eugenio J.; DeVincenzi, Donald (Technical Monitor)</p> <p>2000-01-01</p> <p>We present results of long-term numerical orbital integrations designed to test the <span class="hlt">stability</span> of the three-planet system orbiting Upsilon Andromedae and short-term integrations to test whether mutual perturbations among the planets can be used to determine planetary masses. Our initial conditions are based on the latest fits to the radial velocity data obtained by the planet-search group at Lick Observatory. The new fits result in significantly more stable systems than did the initially announced planetary parameters. An analytic <span class="hlt">analysis</span> of the star and the two outer planets shows that this subsystem is Hill stable up to five. Our integrations involving all three planets show that the system is stable for at least 100 Myr for up to four. In our simulations, we still see a secular resonance between the outer two planets and in some cases large oscillations in the eccentricity of the inner planet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhFl...25h4109B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhFl...25h4109B"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> and numerical simulation of simplified solid rocket motors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boyer, G.; Casalis, G.; Estivalèzes, J.-L.</p> <p>2013-08-01</p> <p>This paper investigates the Parietal Vortex Shedding (PVS) instability that significantly influences the Pressure Oscillations of the long and segmented solid rocket motors. The eigenmodes resulting from the <span class="hlt">stability</span> <span class="hlt">analysis</span> of a simplified configuration, namely, a cylindrical duct with sidewall injection, are presented. They are computed taking into account the presence of a wall injection defect, which is shown to induce hydrodynamic instabilities at discrete frequencies. These instabilities exhibit eigenfunctions in good agreement with the measured PVS vortical structures. They are successfully compared in terms of temporal evolution and frequencies to the unsteady hydrodynamic fluctuations computed by numerical simulations. In addition, this study has shown that the hydrodynamic instabilities associated with the PVS are the driving force of the flow dynamics, since they are responsible for the emergence of pressure waves propagating at the same frequency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1651...18A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1651...18A"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of three species food chain with competition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abadi, Savitri, D.</p> <p>2015-03-01</p> <p>We study a food chain system that consists of 1 prey and 2 predators populations. The prey population grows logistically while the predators apply different Holling functional responses. The first predator preys on the prey following Holling type II functional response and the second predator preys on both the prey and the first predator following Holling type II and III functional responses, respectively. The study starts with the <span class="hlt">stability</span> <span class="hlt">analysis</span> of critical points of the systems. Then, by using normal form and centre manifold method the information about other nontrivial solutions due to bifurcation including possible limit cycles appearance is obtained. The results are confirmed by numerical simulation using MatCont and biological interpretation of the results are also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJAME..20..299K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJAME..20..299K"><span id="translatedtitle">The Least Squares Stochastic Finite Element Method in Structural <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Steel Skeletal Structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kamiński, M.; Szafran, J.</p> <p>2015-05-01</p> <p>The main purpose of this work is to verify the influence of the weighting procedure in the Least Squares Method on the probabilistic moments resulting from the <span class="hlt">stability</span> <span class="hlt">analysis</span> of steel skeletal structures. We discuss this issue also in the context of the geometrical nonlinearity appearing in the Stochastic Finite Element Method equations for the <span class="hlt">stability</span> <span class="hlt">analysis</span> and preservation of the Gaussian probability density function employed to <span class="hlt">model</span> the Young modulus of a structural steel in this problem. The weighting procedure itself (with both triangular and Dirac-type) shows rather marginal influence on all probabilistic coefficients under consideration. This hybrid stochastic computational technique consisting of the FEM and computer algebra systems (ROBOT and MAPLE packages) may be used for analogous nonlinear analyses in structural reliability assessment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JIEI...10...71D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JIEI...10...71D"><span id="translatedtitle">On the <span class="hlt">stability</span> of equilibrium for a reformulated foreign trade <span class="hlt">model</span> of three countries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dassios, Ioannis K.; Kalogeropoulos, Grigoris</p> <p>2014-06-01</p> <p>In this paper, we study the <span class="hlt">stability</span> of equilibrium for a foreign trade <span class="hlt">model</span> consisting of three countries. As the gravity equation has been proven an excellent tool of <span class="hlt">analysis</span> and adequately stable over time and space all over the world, we further enhance the problem to three masses. We use the basic Structure of Heckscher-Ohlin-Samuelson <span class="hlt">model</span>. The national income equals consumption outlays plus investment plus exports minus imports. The proposed reformulation of the problem focus on two basic concepts: (1) the delay inherited in our economic variables and (2) the interaction effect along the three economies involved. <span class="hlt">Stability</span> and stabilizability conditions are investigated while numerical examples provide further insight and better understanding. Finally, a generalization of the gravity equation is somehow obtained for the <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhRvD..85b4014C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhRvD..85b4014C"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> and area spectrum of three-dimensional Lifshitz black holes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cuadros-Melgar, Bertha; de Oliveira, Jeferson; Pellicer, C. E.</p> <p>2012-01-01</p> <p>In this work, we probe the <span class="hlt">stability</span> of a z=3 three-dimensional Lifshitz black hole by using scalar and spinorial perturbations. We found an analytical expression for the quasinormal frequencies of the scalar probe field, which perfectly agree with the behavior of the quasinormal modes obtained numerically. The results for the numerical <span class="hlt">analysis</span> of the spinorial perturbations reinforce the conclusion of the scalar <span class="hlt">analysis</span>, i.e., the <span class="hlt">model</span> is stable under scalar and spinor perturbations. As an application we found the area spectrum of the Lifshitz black hole, which turns out to be equally spaced.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3632304','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3632304"><span id="translatedtitle"><span class="hlt">Analysis</span> of alpha hemoglobin <span class="hlt">stabilizing</span> protein overexpression in murine ?-thalassemia</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Nasimuzzaman, Md; Khandros, Eugene; Wang, Xiaomei; Kong, Yi; Zhao, Huifen; Weiss, David; Rivella, Stefano; Weiss, Mitchell J.; Persons, Derek A.</p> <p>2013-01-01</p> <p>Excess free ?-globin is cytotoxic and contributes to the pathophysiology of ?-thalassemia. Alpha hemoglobin <span class="hlt">stabilizing</span> protein (AHSP) is a molecular chaperone that binds free ?-globin to promote its folding and inhibit its ability to produce damaging reactive oxygen species. Reduced AHSP levels correlate with increased severity of ?-thalassemia in some human cohorts, but causal mechanistic relationships are not established for these associations. We used transgenic and lentiviral gene transfer methods to investigate whether supraphysiologic AHSP levels could mitigate the severity of ?-thalassemia intermedia by providing an increased sink for the excess pool of ?-globin chains. We tested wild-type AHSP and two mutant versions with amino acid substitutions that confer 3- or 13-fold higher affinity for ?-globin. Erythroid overexpression of these AHSP proteins up to 11-fold beyond endogenous levels had no major effects on hematologic parameters in ?-thalassemic animals. Our results demonstrate that endogenous AHSP is not limiting for ?-globin detoxification in a murine <span class="hlt">model</span> of ?-thalassemia. PMID:20815047</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780023101','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780023101"><span id="translatedtitle"><span class="hlt">Analysis</span> of <span class="hlt">stability</span> contributions of high dihedral V-tails</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Freeman, C. E.; Yeager, W. T., Jr.</p> <p>1978-01-01</p> <p>An investigation was undertaken to determine the effectiveness of four analytical methods (empirical, modified empirical, vortex-lattice, and an inviscid, three dimensional, potential flow, wing body program) to estimate the lateral and longitudinal static <span class="hlt">stability</span> characteristics of an isolated V-tail wind tunnel <span class="hlt">model</span>. The experimental tests were conducted in the V/STOL tunnel at a Mach number of 0.18. Angle-of-attack data were obtained from -12 deg to 8 deg at 0 deg sideslip. Sideslip sweeps from -5 deg to 10 deg were made at angles of attack of 4 deg, 0 deg and -4 deg. The V-tail dihedral angles were 45 deg, 50 deg, 55 deg, and 60 deg.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995JSV...188...39A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995JSV...188...39A"><span id="translatedtitle">Snoring: Linear <span class="hlt">Stability</span> <span class="hlt">Analysis</span> and In-Vitroexperiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aurgan, Y.; Depollier, C.</p> <p>1995-11-01</p> <p>A theoretical and experimental study is presented of the aeroelastic instability of the human soft palate, which can explain the occurrence of snoring. The soft palate is <span class="hlt">modelled</span> by a beam clamped at its leading edge and free at its trailing edge. The continuous and discrete cases are investigated. Only the two first modes of vibration of the soft palate are taken into account. The flow is incompressible, inviscid and one dimensional. Structural damping and flow nonstationarities can be considered. Theory shows that the soft palate loses its <span class="hlt">stability</span> by flutter and that this instability is mainly controlled by a single dimensionless parameter which can be easily interpreted from a medical point of view. An experimental apparatus which produces sounds very close to human snoring is described. Agreement between theory and experiments is good.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27015076','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27015076"><span id="translatedtitle">Computational <span class="hlt">Modeling</span> and Finite Element <span class="hlt">Analysis</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Goel, Vijay K; Nyman, Edward</p> <p>2016-04-01</p> <p>Computational <span class="hlt">modeling</span> with finite element <span class="hlt">analysis</span> (FEA) is an integral component of medical device design and development. Researchers assess dimensions and <span class="hlt">stability</span> of the experimental device; test load sharing, stresses, and strains; and analyze failures and modifications. The most important step in FEA is validation of the <span class="hlt">model</span>. Testing should include decompression and <span class="hlt">stabilization</span> procedures simulated in the finite element <span class="hlt">model</span> (FEM). Prerequisites of quality FEA include a solid understanding of morphology and material properties of the <span class="hlt">model</span>, a firm grasp of the effects of loads on body structures, and the work of a skilled bioengineer who can translate the ideas of surgeons into an appropriate FEM. With today's modern techniques-computed tomography/magnetic resonance imaging, etc.-the bioengineer moves from scan to FEM in just weeks. PMID:27015076</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/956682','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/956682"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of implicit time discretizations for the Compton-scattering Fokker-Planck equation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Densmore, Jeffery D; Warsa, James S; Lowrie, Robert B; Morel, Jim E</p> <p>2008-01-01</p> <p>The Fokker-Planck equation is a widely used approximation for <span class="hlt">modeling</span> the Compton scattering of photons in high energy density applications. In this paper, we perform a <span class="hlt">stability</span> <span class="hlt">analysis</span> of three implicit time discretizations for the Compton-Scattering Fokker-Planck equation. Specifically, we examine (i) a Semi-Implicit (SI) scheme that employs backward-Euler differencing but evaluates temperature-dependent coefficients at their beginning-of-time-step values, (ii) a Fully Implicit (FI) discretization that instead evaluates temperature-dependent coefficients at their end-of-time-step values, and (iii) a Linearized Implicit (LI) scheme, which is developed by linearizing the temperature dependence of the FI discretization within each time step. Our <span class="hlt">stability</span> <span class="hlt">analysis</span> shows that the FI and LI schemes are unconditionally stable and cannot generate oscillatory solutions regardless of time-step size, whereas the SI discretization can suffer from instabilities and nonphysical oscillations for sufficiently large time steps. With the results of this <span class="hlt">analysis</span>, we present time-step limits for the SI scheme that prevent undesirable behavior. We test the validity of our <span class="hlt">stability</span> <span class="hlt">analysis</span> and time-step limits with a set of numerical examples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JCoPh.228.5933D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JCoPh.228.5933D"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of implicit time discretizations for the Compton-scattering Fokker-Planck equation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Densmore, Jeffery D.; Warsa, James S.; Lowrie, Robert B.; Morel, Jim E.</p> <p>2009-09-01</p> <p>The Fokker-Planck equation is a widely used approximation for <span class="hlt">modeling</span> the Compton scattering of photons in high energy density applications. In this paper, we perform a <span class="hlt">stability</span> <span class="hlt">analysis</span> of three implicit time discretizations for the Compton-Scattering Fokker-Planck equation. Specifically, we examine (i) a Semi-Implicit (SI) scheme that employs backward-Euler differencing but evaluates temperature-dependent coefficients at their beginning-of-time-step values, (ii) a Fully Implicit (FI) discretization that instead evaluates temperature-dependent coefficients at their end-of-time-step values, and (iii) a Linearized Implicit (LI) scheme, which is developed by linearizing the temperature dependence of the FI discretization within each time step. Our <span class="hlt">stability</span> <span class="hlt">analysis</span> shows that the FI and LI schemes are unconditionally stable and cannot generate oscillatory solutions regardless of time-step size, whereas the SI discretization can suffer from instabilities and nonphysical oscillations for sufficiently large time steps. With the results of this <span class="hlt">analysis</span>, we present time-step limits for the SI scheme that prevent undesirable behavior. We test the validity of our <span class="hlt">stability</span> <span class="hlt">analysis</span> and time-step limits with a set of numerical examples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7026669','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7026669"><span id="translatedtitle"><span class="hlt">Stability</span> criteria for the LSDM (Livermore Statistical Dynamic <span class="hlt">Model</span>)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Taylor, K.E.</p> <p>1986-10-01</p> <p>One criterion for stable integration of zonally averaged primitive equation <span class="hlt">models</span> is normally given by the Courant-Fridericks-Lewy condition applied to the fastest (horizontally) progagating waves. In practice this means that the horizontally propagating acoustic wave (Lamb wave) limits the length of the time step that can be used in the integration: ..delta..t < ..delta..x/c, where c is the phase speed of the Lamb wave. In the Livermore Statistical Dynamic <span class="hlt">Model</span> (LSDM) there are other simulated processes that may place more stringent constraints on the length of the time-step. In the attached notes, I have derived the <span class="hlt">stability</span> criteria for the LSDM. I have found that to a good approximation (within 15%), the length of time-step must be less than ..delta..t/sub c/ where 1/..delta..t/sub c/ = (1 + ..gamma../2) (1/tau/sub s/ + 1/tau/sub r/) + ..gamma../2 1/tau/sub e/.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998PhDT.......380C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998PhDT.......380C"><span id="translatedtitle">Power system <span class="hlt">stability</span> enhancement employing controllers based on a versatile <span class="hlt">modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chung, Chi Yung</p> <p></p> <p>Rapid advances in power electronics have made it both practicable and economic to design powerful thyristor-controlled devices, such as Flexible AC Transmission Systems (FACTS), for <span class="hlt">stability</span> enhancements. The discrepancies of existing <span class="hlt">modeling</span> approaches have limited the feasibility of handling these devices or designing its damping controller. In this thesis, a versatile and generalized approach to <span class="hlt">model</span> standard power system components is proposed. The more systematic and realistic representation, accompanied by the development of powerful eigenvalue-<span class="hlt">analysis</span> techniques, facilitates the study of small signal <span class="hlt">stability</span> (monotonic and oscillatory) of the power systems. In monotonic <span class="hlt">stability</span> study, the effect of exciter and governor is critically reviewed based on the exploitation of eigenvalues, modal and sensitivity analyses over a wide range of operating conditions. In oscillatory <span class="hlt">stability</span> study, a common FACTS device, the static var compensator (SVC), is used to improve system damping. This study reveals the inadequacy of many conventional methodologies in SVC design since they have ignored (or cannot handle) some important factors such as SVC mode instability and robustness of the power system. Two approaches, combined sensitivities and Hinfinity algorithms, are introduced to solve these limitations. Finally, an extended Hinfinity algorithm, which is applied to PSS design and successfully solves certain limitations of the existing H infinity based PSS design, is also presented. Although these studies are developed on selected controller devices or typical systems for convenience of discussion, extension to more complex systems can be dealt with in a similar way because of the versatility of the proposed <span class="hlt">modeling</span> methodology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013HESSD..10.2287C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013HESSD..10.2287C"><span id="translatedtitle">A coupled distributed hydrological-<span class="hlt">stability</span> <span class="hlt">analysis</span> on a terraced slope of Valtellina (northern Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Camera, C.; Apuani, T.; Masetti, M.</p> <p>2013-02-01</p> <p>The aim of this work was to understand and reproduce the hydrological dynamics of a slope, which was terraced using dry-stone retaining walls and its response to these processes in terms of <span class="hlt">stability</span> at the slope scale. The slope studied is located in Valtellina (northern Italy), near the village of Tresenda, and in the last 30 yr has experienced several soil slip/debris flow events. In 1983 alone, such events caused the death of 18 people. Direct observation of the events of 1983 enabled the principal triggering cause of these events to be recognized in the formation of an overpressure at the base of a dry-stone wall, which caused its failure. To perform the analyses it is necessary to include the presence of dry-stone walls, considering the importance they have in influencing hydrological and geotechnical processes at the slope scale. This requires a very high resolution DEM (1 m 1 m because the walls are from 0.60 m to 1.0 m wide) that has been appositely derived. A hydrogeological raster-based <span class="hlt">model</span>, which takes into account both the unsaturated and saturated flux components, was applied. This was able to identify preferential infiltration zones and was rather precise in the prediction of maximum groundwater levels, providing valid input for the distributed <span class="hlt">stability</span> <span class="hlt">analysis</span>. Results of the hydrogeological <span class="hlt">model</span> were used for the successive <span class="hlt">stability</span> <span class="hlt">analysis</span>. Sections of terrace were identified from the downslope base of a retaining wall to the top of the next downslope retaining wall. Within each section a global method of equilibrium was applied to determine its safety factor. The <span class="hlt">stability</span> <span class="hlt">model</span> showed a general tendency to overestimate the amount of unstable areas. An investigation of the causes of this unexpected behavior was, therefore, also performed in order to progressively improve the reliability of the <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900020495','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900020495"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of multiple-robot control systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wen, John T.; Kreutz, Kenneth</p> <p>1989-01-01</p> <p>In a space telerobotic service scenario, cooperative motion and force control of multiple robot arms are of fundamental importance. Three paradigms to study this problem are proposed. They are distinguished by the set of variables used for control design. They are joint torques, arm tip force vectors, and an accelerated generalized coordinate set. Control issues related to each case are discussed. The latter two choices require complete <span class="hlt">model</span> information, which presents practical <span class="hlt">modeling</span>, computational, and robustness problems. Therefore, focus is on the joint torque control case to develop relatively <span class="hlt">model</span> independent motion and internal force control laws. The rigid body assumption allows the motion and force control problems to be independently addressed. By using an energy motivated Lyapunov function, a simple proportional derivative plus gravity compensation type of motion control law is always shown to be <span class="hlt">stabilizing</span>. The asymptotic convergence of the tracing error to zero requires the use of a generalized coordinate with the contact constraints taken into account. If a non-generalized coordinate is used, only convergence to a steady state manifold can be concluded. For the force control, both feedforward and feedback schemes are analyzed. The feedback control, if proper care has been taken, exhibits better robustness and transient performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......217L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......217L"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of a natural circulation lead-cooled fast reactor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, Qiyue</p> <p></p> <p>This dissertation is aimed at nuclear-coupled thermal hydraulics <span class="hlt">stability</span> <span class="hlt">analysis</span> of a natural circulation lead cooled fast reactor design. The <span class="hlt">stability</span> concerns arise from the fact that natural circulation operation makes the system susceptible to flow instabilities similar to those observed in boiling water reactors. In order to capture the regional effects, modal expansion method which incorporates higher azimuthal modes is used to <span class="hlt">model</span> the neutronics part of the system. A reduced order <span class="hlt">model</span> is used in this work for the thermal-hydraulics. Consistent with the number of heat exchangers (HXs), the reactor core is divided into four equal quadrants. Each quadrant has its corresponding external segments such as riser, plenum, pipes and HX forming an equivalent 1-D closed loop. The local pressure loss along the loop is represented by a lumped friction factor. The heat transfer process in the HX is represented by a <span class="hlt">model</span> for the coolant temperature at the core inlet that depends on the coolant temperature at the core outlet and the coolant velocity. Additionally, time lag effects are incorporated into this HX <span class="hlt">model</span> due to the finite coolant speed. A conventional <span class="hlt">model</span> is used for the fuel pin heat conduction to couple the neutronics and thermal-hydraulics. The feedback mechanisms include Doppler, axial/radial thermal expansion and coolant density effects. These effects are represented by a linear variation of the macroscopic cross sections with the fuel temperature. The weighted residual method is used to convert the governing PDEs to ODEs. Retaining the first and second modes, leads to six ODEs for neutronics, and five ODEs for the thermal-hydraulics in each quadrant. Three <span class="hlt">models</span> are developed. These are: 1) natural circulation <span class="hlt">model</span> with a closed coolant flow path but without coupled neutronics, 2) forced circulation <span class="hlt">model</span> with constant external pressure drop across the heated channels but without coupled neutronics, 3) coupled system including neutronics with higher modes and thermal-hydraulics. In the second <span class="hlt">model</span>, the HX and the external flow path are not incorporated and therefore no time delays are considered, and a constant heat source term is assumed. There is no difference among four equivalent loops, and the system is finally described by a set of ODEs. The thermal hydraulics in the first and third <span class="hlt">models</span> is represented by sets of ODEs with time lags, namely, DDEs, due to external pipes and the HX <span class="hlt">model</span>. <span class="hlt">Models</span> 1 and 2 use a constant heat source term rather than coupled neutronics as is the case in <span class="hlt">model</span> 3. In <span class="hlt">model</span> 3, the four equivalent loops are linked via modal neutronics. They are represented by twenty-six (six for neutronics; twenty for thermal-hydraulics / five for each loop) equations. Two approaches, one in time domain and the other in frequency domain, are used for <span class="hlt">stability</span> analyses. For <span class="hlt">model</span> number 1, based on the characteristic of DDEs, a MATLAB package is used to carry out the <span class="hlt">stability</span> <span class="hlt">analysis</span>. Results of the frequency domain <span class="hlt">analysis</span> are presented in core-height---friction-factor space, dividing the space into stable and unstable regions. Results are also verified in time-domain. For <span class="hlt">model</span> number 2, eigenvalues of the Jacobian matrix are evaluated for the frequency domain <span class="hlt">stability</span> <span class="hlt">analysis</span>. Scenarios including pulse stimulation on coolant velocity, and different friction factors are simulated in the time domain. The third <span class="hlt">model</span> is studied only in the time domain. Eight different scenarios are simulated. These include system response after different perturbations such as positive or negative reactivity insertion in one or more quadrants. Results show that SUPERSTAR design is very robust, and that the nominal operation points have considerable safety margins. Results also identify regions in design and operation parameter spaces where the reactor becomes less stable or even unstable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhBio...8f6006C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhBio...8f6006C"><span id="translatedtitle">Quantitative <span class="hlt">analysis</span> of the ion-dependent folding <span class="hlt">stability</span> of DNA triplexes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Gengsheng; Chen, Shi-Jie</p> <p>2011-12-01</p> <p>A DNA triplex is formed through binding of a third strand to the major groove of a duplex. Due to the high charge density of a DNA triplex, metal ions are critical for its <span class="hlt">stability</span>. We recently developed the tightly bound ion (TBI) <span class="hlt">model</span> for ion-nucleic acids interactions. The <span class="hlt">model</span> accounts for the potential correlation and fluctuations of the ion distribution. We now apply the TBI <span class="hlt">model</span> to analyze the ion dependence of the thermodynamic <span class="hlt">stability</span> for DNA triplexes. We focus on two experimentally studied systems: a 24-base DNA triplex and a pair of interacting 14-base triplexes. Our theoretical calculations for the number of bound ions indicate that the TBI <span class="hlt">model</span> provides improved predictions for the number of bound ions than the classical Poisson-Boltzmann (PB) equation. The improvement is more significant for a triplex, which has a higher charge density than a duplex. This is possibly due to the higher ion concentration around the triplex and hence a stronger ion correlation effect for a triplex. In addition, our <span class="hlt">analysis</span> for the free energy landscape for a pair of 14-mer triplexes immersed in an ionic solution shows that divalent ions could induce an attractive force between the triplexes. Furthermore, we investigate how the protonated cytosines in the triplexes affect the <span class="hlt">stability</span> of the triplex helices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......477A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......477A"><span id="translatedtitle"><span class="hlt">Analysis</span> of a Major Electric Grid -- <span class="hlt">Stability</span> and Adaptive Protection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alanzi, Sultan</p> <p></p> <p>Protective systems of the electric grid are designed to detect and mitigate the effects of faults and other disturbances that may occur. Distance relays are used extensively for the detection of faults on transmission lines. Out-of-step relays are used for generator protection to detect loss of synchronism conditions that result from disturbances on the electric grid. Also, when a disturbance occurs and generators may tend to lose synchronism with each other, it is beneficial to separate the overall system into several independent systems that can remain stable. Unfortunately there have been cases, such as the 2003 Northeast blackout where the operation of protective relays, namely the zone 3 distance relay used for transmission line protection, contributed to the cascading effect of the blackout. It is the objective of this dissertation to propose adaptive relays for both distance protection of transmission lines and out-of-step protection of generators. By being adaptive, the relays are made aware of the system operating conditions and can adjust its settings accordingly. Inputs to the adaptive logic can come from system or environmental conditions. As a result of this effort, a new distance relay operating characteristic is proposed, referred to as a mushroom relay, which is a combination of a quadrilateral relay and a Mho relay. Also, a new criterion for determining if a power swing following a disturbance is stable or unstable is proposed. Distance protection of transmission lines is very important when discussing system responses to faults and disturbances. Distance relays are very common worldwide and although they offer great protection, there are limitations that need to be addressed. Parallel line operations (infeed effect) and the loadability limits are among the limitations that lead to improper response of relays. An Adaptive Distance Relays (ADR) offer great benefits to the protection scheme as their settings can be changed in accordance with prefault system conditions. This dissertation introduces a combination of quadrilateral and mho characteristics to create a distance relay with a mushroom shape in R-X diagrams. This new relay offers larger protective reach with a lower limitation on loadability. When major disturbances occur, the power balance between load and generation might be disturbed causing the generators to lose synchronism (to be out-of-step) with each other. Out-of-step protection against power swings is essential to provide supervising signals for distance relays to mitigate the effects of the disturbance. A new R-X criterion is proposed to identify out-of-step conditions for large and complex power systems, such as KEG. A proposed Adaptive Out-of-Step Relay (AOSR) will monitor power system conditions and adjust the relay reach accordingly for better power swing classification. When unstable swings are detected, controllable tripping signals are initiated and system separation will create small subsystems or islands of the power system. These smaller systems will be created to achieve a balance of load and available generation. The electric power system chosen to study and to illustrate the criteria for the proposed adaptive relays was that of the country of Kuwait. The small oil-rich country of Kuwait has been dealing with an electric energy crisis that started summer 2006. With a dry dessert climate and intensely hot summers, the 3.6 million residents of Kuwait depend on continuously operated A/C units for living. This is the major reason why the peak load in a summer month reaches almost 11,000 MW while the peak load in a winter month does not exceed 5,000 MW. The Kuwait Electric Grid (KEG) is <span class="hlt">modelled</span> and analyzed using Power Analytics' software known as PaladinRTM DesignBase(TM). Performance studies produce data to examine distance and out-of-step protection. Power Flow (PF), Short Circuit <span class="hlt">Analysis</span> (SCA), and Transient <span class="hlt">Stability</span> <span class="hlt">Analysis</span> (TSA) are used to verify the <span class="hlt">model</span> of KEG. These studies are the starting point when studying any large power system in order to investigate how the system operates during normal conditions and during abnormal conditions due to disturbances. Simulations showed that KEG is highly stressed, as major disturbances would cause instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT.......195C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.......195C"><span id="translatedtitle">Extensions to the time lag <span class="hlt">models</span> for practical application to rocket engine <span class="hlt">stability</span> design</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Casiano, Matthew J.</p> <p></p> <p>The combustion instability problem in liquid-propellant rocket engines (LREs) has remained a tremendous challenge since their discovery in the 1930s. Improvements are usually made in solving the combustion instability problem primarily using computational fluid dynamics (CFD) and also by testing demonstrator engines. Another approach is to use analytical <span class="hlt">models</span>. Analytical <span class="hlt">models</span> can be used such that design, redesign, or improvement of an engine system is feasible in a relatively short period of time. Improvements to the analytical <span class="hlt">models</span> can greatly aid in design efforts. A thorough literature review is first conducted on liquid-propellant rocket engine (LRE) throttling. Throttling is usually studied in terms of vehicle descent or ballistic missile control however there are many other cases where throttling is important. It was found that combustion instabilities are one of a few major issues that occur during deep throttling (other major issues are heat transfer concerns, performance loss, and pump dynamics). In the past and again recently, gas injected into liquid propellants has shown to be a viable solution to throttle engines and to eliminate some forms of combustion instability. This review uncovered a clever solution that was used to eliminate a chug instability in the Common Extensible Cryogenic Engine (CECE), a modified RL10 engine. A separate review was also conducted on classic time lag combustion instability <span class="hlt">models</span>. Several new <span class="hlt">stability</span> <span class="hlt">models</span> are developed by incorporating important features to the classic and contemporary <span class="hlt">models</span>, which are commonly used in the aerospace rocket industry. The first two <span class="hlt">models</span> are extensions of the original Crocco and Cheng concentrated combustion <span class="hlt">model</span> with feed system contributions. A third new <span class="hlt">model</span> is an extension to the Wenzel and Szuch double-time lag <span class="hlt">model</span> also with feed system contributions. The first new <span class="hlt">model</span> incorporates the appropriate injector acoustic boundary condition which is neglected in contemporary <span class="hlt">models</span>. This new feature shows that the injector boundary can play a significant role for combustion <span class="hlt">stability</span>, especially for gaseous injection systems or a system with an injector orifice on the order of the size of the chamber. The second new <span class="hlt">model</span> additionally accounts for resistive effects. Advanced signal <span class="hlt">analysis</span> techniques are used to extract frequency-dependent damping from a gas generator component data set. The damping values are then used in the new <span class="hlt">stability</span> <span class="hlt">model</span> to more accurately represent the chamber response of the component. The results show a more realistic representation of <span class="hlt">stability</span> margin by incorporating the appropriate damping effects into the chamber response from data. The original Crocco <span class="hlt">model</span>, a contemporary <span class="hlt">model</span>, and the two new <span class="hlt">models</span> are all compared and contrasted to a marginally stable test case showing their applicability. The <span class="hlt">model</span> that incorporates resistive aspects shows the best comparison to the test data. Parametrics are also examined to show the influence of the new features and their applicability. The new features allow a more accurate representation of <span class="hlt">stability</span> margin to be obtained. The third new <span class="hlt">model</span> is an extension to the Wenzel and Szuch double-time lag chug <span class="hlt">model</span>. The feed system chug <span class="hlt">model</span> is extended to account for generic propellant flow rates. This <span class="hlt">model</span> is also extended to incorporate aspects due to oxygen boiling and helium injection in the feed system. The solutions to the classic <span class="hlt">models</span>, for the single-time lag and the double-time lag <span class="hlt">models</span>, are often plotted on a practical engine operating map, however the <span class="hlt">models</span> have presented some difficulties for numerical algorithms for several reasons. Closed-form solutions for use on these practical operating maps are formulated and developed. These <span class="hlt">models</span> are incorporated in a graphical user interface tool and the new <span class="hlt">model</span> is compared to an extensive data set. It correctly predicts the <span class="hlt">stability</span> behavior at various operating conditions incorporating the influence of injected helium and boiling oxygen in the feed system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PhDT.......134P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PhDT.......134P"><span id="translatedtitle">Mode switching and linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of resonant acoustic flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Panickar, Praveen</p> <p></p> <p>Resonant acoustic flows occur in a wide variety of practical, aerospace-related applications and are a rich source of complex flow-physics. The primary concern associated with these types of flows is the high-amplitude fluctuating pressures associated with the resonant tones that could lead to sonic fatigue failure of sensitive components in the vicinity of such flows. However, before attempting to devise methods to suppress the resonant tones, it is imperative to understand the physics governing these flows in the hope that such an understanding will lead to more robust and effective suppression techniques. To this end, an in-depth study of various resonant acoustic flows was undertaken in this thesis, the main aim being to bring about a better understanding of such flows by revealing physically relevant information. Starting with the resonant acoustic mechanism in underexpanded jets from two-dimensional nozzles, it was shown that, for a variety of flow situations (geometries, shock-cell structures and orientations) in such jets, the nonlinear interaction density acted as a faithful precursor to a, hitherto unpredictable, spanwise instability mode switch. Following this, a study of the occurrence of, previously undocumented and theoretically unexpected, helical instabilities in subsonic impinging jets was undertaken. Using metrics from linear <span class="hlt">stability</span> <span class="hlt">analysis</span>, it was shown that the presence of the helical modes was justified. The results from this study on impinging jets are directly applicable to modern Stationary Take-Off and Vertical Landing (STOVL) aircraft that have twin, closely spaced exhausts. Finally, a novel technique that yielded dramatic suppression of resonant acoustic tones using high frequency excitation, in subsonic flows over open cavities, was investigated. Linear <span class="hlt">stability</span> calculations of the experimentally measured baseline and excited velocity profiles showed that the instability of the high frequency excitation corresponded to a spatially decaying mode, which in turn lead to the resonance suppression associated with this mechanism. The experimental results showed good agreement with linear <span class="hlt">stability</span> calculations for the measured mean velocity profiles. It is hoped that the work presented in this thesis will further the understanding of resonant acoustic flows and provide insights that can lead to better control techniques in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24789569','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24789569"><span id="translatedtitle"><span class="hlt">Stabilizing</span> control for a pulsatile cardiovascular mathematical <span class="hlt">model</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de los Reyes, Aurelio A; Jung, Eunok; Kappel, Franz</p> <p>2014-06-01</p> <p>In this paper, we develop a pulsatile <span class="hlt">model</span> for the cardiovascular system which describes the reaction of this system to a submaximal constant workload imposed on a person at a bicycle ergometer test after a period of rest. Furthermore, the <span class="hlt">model</span> should allow to use measurements for the pulsatile pressure in fingertips which provide information on the diastolic and the systolic pressure for parameter estimation. Based on the assumption that the baroreceptor loop is the essential control loop in this case, we design a <span class="hlt">stabilizing</span> feedback control for the pulsatile <span class="hlt">model</span> which is obtained by solving a linear-quadratic regulator problem for the linearization of a non-pulsatile counterpart of the pulsatile <span class="hlt">model</span>. We also investigate the behavior of the <span class="hlt">model</span> with respect to changes in the weight of the term in the cost functional for the linear-quadratic regulator problem which penalizes the deviation of the momentary pressure in the aorta from the pressure at the stationary situation which should be obtained. PMID:24789569</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21607968','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21607968"><span id="translatedtitle">Proton <span class="hlt">stability</span> and light Z' inspired by string derived <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Faraggi, Alon E.; Mehta, Viraf M.</p> <p>2011-10-15</p> <p>Proton <span class="hlt">stability</span> is one of the most perplexing puzzles in particle physics. While the renormalizable standard <span class="hlt">model</span> forbids proton decay mediating operators due to accidental global symmetries, many of its extensions introduce such dimension four, five and six operators. Furthermore, it is, in general, expected that quantum gravity only respects local gauge, or discreet, symmetries. String theory provides the arena to study particle physics in a consistent framework of perturbative quantum gravity. An appealing proposition, in this context, is that the dangerous operators are suppressed by an Abelian gauge symmetry, which is broken near the TeV scale. A viable U(1) symmetry should also be anomaly free, be family universal, and allow the generation of fermion masses via the Higgs mechanism. We discuss such U(1) symmetries that arise in quasirealistic free fermionic heterotic-string derived <span class="hlt">models</span>. Ensuring that the U(1) symmetry is anomaly free at the low scale requires that the standard <span class="hlt">model</span> spectrum is augmented by additional states that are compatible with the charge assignments in the string <span class="hlt">models</span>. We construct such string-inspired <span class="hlt">models</span> and discuss some of their phenomenological implications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1014152','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1014152"><span id="translatedtitle">SDI CFD <span class="hlt">MODELING</span> <span class="hlt">ANALYSIS</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lee, S.</p> <p>2011-05-05</p> <p>The Savannah River Remediation (SRR) Organization requested that Savannah River National Laboratory (SRNL) develop a Computational Fluid Dynamics (CFD) method to mix and blend the miscible contents of the blend tanks to ensure the contents are properly blended before they are transferred from the blend tank; such as, Tank 50H, to the Salt Waste Processing Facility (SWPF) feed tank. The work described here consists of two <span class="hlt">modeling</span> areas. They are the mixing <span class="hlt">modeling</span> <span class="hlt">analysis</span> during miscible liquid blending operation, and the flow pattern <span class="hlt">analysis</span> during transfer operation of the blended liquid. The transient CFD governing equations consisting of three momentum equations, one mass balance, two turbulence transport equations for kinetic energy and dissipation rate, and one species transport were solved by an iterative technique until the species concentrations of tank fluid were in equilibrium. The steady-state flow solutions for the entire tank fluid were used for flow pattern <span class="hlt">analysis</span>, for velocity scaling <span class="hlt">analysis</span>, and the initial conditions for transient blending calculations. A series of the <span class="hlt">modeling</span> calculations were performed to estimate the blending times for various jet flow conditions, and to investigate the impact of the cooling coils on the blending time of the tank contents. The <span class="hlt">modeling</span> results were benchmarked against the pilot scale test results. All of the flow and mixing <span class="hlt">models</span> were performed with the nozzles installed at the mid-elevation, and parallel to the tank wall. From the CFD <span class="hlt">modeling</span> calculations, the main results are summarized as follows: (1) The benchmark analyses for the CFD flow velocity and blending <span class="hlt">models</span> demonstrate their consistency with Engineering Development Laboratory (EDL) and literature test results in terms of local velocity measurements and experimental observations. Thus, an application of the established criterion to SRS full scale tank will provide a better, physically-based estimate of the required mixing time, and elevation of transfer pump for minimum sludge disturbance. (2) An empirical equation for a tank with no cooling coils agrees reasonably with the current <span class="hlt">modeling</span> results for the dual jet. (3) From the sensitivity study of the cooling coils, it was found that the tank mixing time for the coiled tank was about two times longer than that of the tank fluid with no coils under the 1/10th scale, while the coiled tank required only 50% longer than the one without coils under the full scale Tank 50H. In addition, the time difference is reduced when the pumping U{sub o}d{sub o} value is increased for a given tank. (4) The blending time for T-shape dual jet pump is about 20% longer than that of 15{sup o} upward V-shape pump under the 1/10th pilot-scale tank, while the time difference between the two pumps is about 12% for the full-scale Tank 50H. These results are consistent with the literature information. (5) A transfer pump with a solid-plate suction screen operating at 130 gpm can be located 9.5 inches above settled sludge for 2 in screen height in a 85 ft waste tank without disturbing any sludge. Detailed results are summarized in Table 13. Final pump performance calculations were made by using the established CW pump design, and operating conditions to satisfy the two requirements of minimum sludge disturbance, and adequate blending of tank contents. The final calculation results show that the blending times for the coiled and uncoiled tanks coupled with the CW pump design are 159 and 83 minutes, respectively. All the results are provided in Table 16.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26275044','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26275044"><span id="translatedtitle">Kinetic <span class="hlt">Analysis</span> of Haloacetonitrile <span class="hlt">Stability</span> in Drinking Waters.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yu, Yun; Reckhow, David A</p> <p>2015-09-15</p> <p>Haloacetonitriles (HANs) are an important class of drinking water disinfection byproducts (DBPs) that are reactive and can undergo considerable transformation on time scales relevant to system distribution (i.e., from a few hours to a week or more). The <span class="hlt">stability</span> of seven mono-, di-, and trihaloacetonitriles was examined under a variety of conditions including different pH levels and disinfectant doses that are typical of drinking water distribution systems. Results indicated that hydroxide, hypochlorite, and their protonated forms could react with HANs via nucleophilic attack on the nitrile carbon, forming the corresponding haloacetamides (HAMs) and haloacetic acids (HAAs) as major reaction intermediates and end products. Other stable intermediate products, such as the N-chloro-haloacetamides (N-chloro-HAMs), may form during the course of HAN chlorination. A scheme of pathways for the HAN reactions was proposed, and the rate constants for individual reactions were estimated. Under slightly basic conditions, hydroxide and hypochlorite are primary reactants and their associated second-order reaction rate constants were estimated to be 6 to 9 orders of magnitude higher than those of their protonated conjugates (i.e., neutral water and hypochlorous acid), which are much weaker but more predominant nucleophiles at neutral and acidic pHs. Developed using the estimated reaction rate constants, the linear free energy relationships (LFERs) summarized the nucleophilic nature of HAN reactions and demonstrated an activating effect of the electron withdrawing halogens on nitrile reactivity, leading to decreasing HAN <span class="hlt">stability</span> with increasing degree of halogenation of the substituents, while subsequent shift from chlorine to bromine atoms has a contrary <span class="hlt">stabilizing</span> effect on HANs. The chemical kinetic <span class="hlt">model</span> together with the reaction rate constants that were determined in this work can be used for quantitative predictions of HAN concentrations depending on pH and free chlorine contact times (CTs), which can be applied as an informative tool by drinking water treatment and system management engineers to better control these emerging nitrogenous DBPs, and can also be significant in making regulatory decisions. PMID:26275044</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790023859','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790023859"><span id="translatedtitle">A multiloop generalization of the circle criterion for <span class="hlt">stability</span> margin <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Safonov, M. G.; Athans, M.</p> <p>1979-01-01</p> <p>In order to provide a theoretical tool suited for characterizing the <span class="hlt">stability</span> margins of multiloop feedback systems, multiloop input-output <span class="hlt">stability</span> results generalizing the circle <span class="hlt">stability</span> criterion are considered. Generalized conic sectors with 'centers' and 'radii' determined by linear dynamical operators are employed to specify the <span class="hlt">stability</span> margins as a frequency dependent convex set of <span class="hlt">modeling</span> errors (including nonlinearities, gain variations and phase variations) which the system must be able to tolerate in each feedback loop without instability. The resulting <span class="hlt">stability</span> criterion gives sufficient conditions for closed loop <span class="hlt">stability</span> in the presence of frequency dependent <span class="hlt">modeling</span> errors, even when the <span class="hlt">modeling</span> errors occur simultaneously in all loops. The <span class="hlt">stability</span> conditions yield an easily interpreted scalar measure of the amount by which a multiloop system exceeds, or falls short of, its <span class="hlt">stability</span> margin specifications.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20921005','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20921005"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> and controller synthesis for hybrid dynamical systems.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heemels, W P M H; De Schutter, B; Lunze, J; Lazar, M</p> <p>2010-11-13</p> <p>Wherever continuous and discrete dynamics interact, hybrid systems arise. This is especially the case in many technological systems in which logic decision-making and embedded control actions are combined with continuous physical processes. Also for many mechanical, biological, electrical and economical systems the use of hybrid <span class="hlt">models</span> is essential to adequately describe their behaviour. To capture the evolution of these systems, mathematical <span class="hlt">models</span> are needed that combine in one way or another the dynamics of the continuous parts of the system with the dynamics of the logic and discrete parts. These mathematical <span class="hlt">models</span> come in all kinds of variations, but basically consist of some form of differential or difference equations on the one hand and automata or other discrete-event <span class="hlt">models</span> on the other hand. The collection of <span class="hlt">analysis</span> and synthesis techniques based on these <span class="hlt">models</span> forms the research area of hybrid systems theory, which plays an important role in the multi-disciplinary design of many technological systems that surround us. This paper presents an overview from the perspective of the control community on <span class="hlt">modelling</span>, <span class="hlt">analysis</span> and control design for hybrid dynamical systems and surveys the major research lines in this appealing and lively research area. PMID:20921005</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.8637T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.8637T"><span id="translatedtitle">Laboratory and <span class="hlt">modelling</span> studies on the atmospheric <span class="hlt">stability</span> of levoglucosan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tilgner, Andreas; Hoffmann, Dirk; Iinuma, Yoshiteru; Herrmann, Hartmut</p> <p>2010-05-01</p> <p>Aerosol particles are known to influence important atmospheric processes such as cloud formation and the solar radiation budget. Therefore, much effort is spend to characterise and locate the sources of atmospheric particles. Source apportionment studies using molecular tracer compounds are a common approach to distinguish between different sources. The anhydromonosaccharide levoglucosan (1,6-anhydro-?-D-glucopyranose) is an widely used and very specific tracer compound for particle emissions from natural and anthropogenic biomass combustion processes. Levoglucosan is formed in large quantities during the pyrolysis of cellulose at temperatures above 300 C. Even if levoglucosan is widely used in source apportionment studies only few studies investigated the atmospheric <span class="hlt">stability</span> of this tracer compound so far. Furthermore, oxidation processes by free radicals in aqueous particles are not yet considered as a potential sink reaction for this highly water soluble compound. Therefore, detailed kinetic studies on the reactivity of levoglucosan towards three important atmospheric free radicals (OH, NO3 and SO4-) in aqueous solutions were performed for the first time using the laser flash photolysis technique. Laboratory studies on the <span class="hlt">stability</span> of levoglucosan were done both in the presence and absence of other water soluble reaction partners. The results obtained in the different experiments will be presented, compared and discussed. Furthermore, the experimental data were implemented into the parcel <span class="hlt">model</span> SPACCIM (Spectral Aerosol Cloud Chemistry Interaction <span class="hlt">Model</span>; Wolke et al., 2005) in order to study the degradation fluxes of levoglucosan in cloud droplets and aqueous particles considering a detailed microphysics and multiphase chemistry. The <span class="hlt">model</span> calculations, performed under different conditions (summer, winter, with cloud passages, without cloud passages, different relative humidity and iron contents), show that levoglucosan can be oxidised readily by OH radicals in the tropospheric aqueous phase. Mean degradation fluxes of about 7.2 ng m-3 h-1 in summer and 4.7 ng m-3 h-1 in winter were calculated. The detailed results of the <span class="hlt">model</span> calculations will be presented and the influence of the different <span class="hlt">model</span> scenarios on the calculated degradation fluxes discussed. <span class="hlt">Model</span> calculations demonstrate that under certain atmospheric conditions the oxidation of levoglucosan can be as fast as that of other atmospherically relevant organic compounds and it may not be as stable as previously thought in the atmosphere particularly under high relative humidity conditions. References: Wolke, R.; Sehili, A. M.; Simmel, M.; Knoth, O.; Tilgner, A.; Herrmann, H. SPACCIM: A parcel <span class="hlt">model</span> with detailed microphysics and complex multiphase chemistry. Atmos. Environ. 2005, 39, 4375-4388.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/959096','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/959096"><span id="translatedtitle"><span class="hlt">Analysis</span> of cavern <span class="hlt">stability</span> at the West Hackberry SPR site.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ehgartner, Brian L.; Sobolik, Steven Ronald</p> <p>2009-05-01</p> <p>This report presents computational analyses that simulate the structural response of caverns at the Strategic Petroleum Reserve (SPR) West Hackberry site. The cavern field comprises 22 caverns. Five caverns (6, 7, 8, 9, 11) were acquired from industry and have unusual shapes and a history dating back to 1946. The other 17 caverns (101-117) were leached according to SPR standards in the mid-1980s and have tall cylindrical shapes. The history of the caverns and their shapes are simulated in a three-dimensional geomechanics <span class="hlt">model</span> of the site that predicts deformations, strains, and stresses. Future leaching scenarios corresponding to oil drawdowns using fresh water are also simulated by increasing the volume of the caverns. Cavern pressures are varied in the <span class="hlt">model</span> to capture operational practices in the field. The results of the finite element <span class="hlt">model</span> are interpreted to provide information on the current and future status of subsidence, well integrity, and cavern <span class="hlt">stability</span>. The most significant results in this report are relevant to Cavern 6. The cavern is shaped like a bowl with a large ceiling span and is in close proximity to Cavern 9. The analyses predict tensile stresses at the edge of the ceiling during repressuization of Cavern 6 following workover conditions. During a workover the cavern is at low pressure to service a well. The wellhead pressures are atmospheric. When the workover is complete, the cavern is repressurized. The resulting elastic stresses are sufficient to cause tension around the edge of the large ceiling span. With time, these stresses relax to a compressive state because of salt creep. However, the potential for salt fracture and propagation exists, particularly towards Cavern 9. With only 200 ft of salt between the caverns, the operational consequences must be examined if the two caverns become connected. A critical time may be during a workover of Cavern 9 in part because of the operational vulnerabilities, but also because dilatant damage is predicted under the ledge that forms the lower lobe in the cavern. The remaining caverns have no significant issues regarding cavern <span class="hlt">stability</span> and may be safely enlarged during subsequent oil drawdowns. Predicted well strains and subsidence are significant and consequently future remedial actions may be necessary. These predicted well strains certainly suggest appropriate monitoring through a well-logging program. Subsidence is currently being monitored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25177932','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25177932"><span id="translatedtitle">Adaptability and <span class="hlt">stability</span> <span class="hlt">analysis</span> of the juice yield of yellow passion fruit varieties.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Oliveira, E J; Freitas, J P X; Jesus, O N</p> <p>2014-01-01</p> <p>This study analyzed the genotype x environment interaction (GE) for the juice productivity (JuProd) of 12 yellow passion fruit varieties (Passiflora edulis Sims. f. flavicarpa Deg.) using additive main effects and multiplicative interaction (AMMI) <span class="hlt">model</span> and auxiliary parameters. The experiments were conducted in eight environments of Bahia State, Brazil, using a randomized block design with three replications. <span class="hlt">Analysis</span> of variance showed significant effects (P ? 0.01) for environments, genotypes, and GE interaction. The first two interaction principal component axes (IPCAs) explained 81.00% of the sum of squares of the GE interaction. The AMMI1 and AMMI2 <span class="hlt">models</span> showed that varieties 09 and 11 were the most stable. Other parameters, namely, the AMMI <span class="hlt">stability</span> value (ASV), yield <span class="hlt">stability</span> (YSI), sustainability, and <span class="hlt">stability</span> index (StI), indicated that other varieties were more stable. These varying results were certainly a consequence of methodological differences. In contrast, the ranking of varieties for each of the <span class="hlt">stability</span> parameters showed significant positive correlations (P ? 0.05) between IPCA1 x (ASV, YSI), JuProd x (StI, YSI), YSI x ASV, and StI x YSI. Cluster <span class="hlt">analysis</span> based on the genotypic profile of the effects of the GE interaction identified three groups that correlated with the distribution of varieties in the AMMI1 biplot. However, the classification of stable genotypes was limited because the association with the productivity was not included in the <span class="hlt">analysis</span>. Variety 08 showed the most stable and productive behavior, ranking above average in half of the environments, and it should be recommended for use. PMID:25177932</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004APS..DPPHP1030P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004APS..DPPHP1030P"><span id="translatedtitle">Transport <span class="hlt">Analysis</span> of the Kinetically <span class="hlt">Stabilized</span> Tandem Mirror</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pratt, J.; Kim, J.-H.; Horton, W.; Wong, H. V.; Fowler, T. K.</p> <p>2004-11-01</p> <p>We undertake a transport study for the Kinetically <span class="hlt">Stabilized</span> Tandem Mirror (KSTM), an attractive magnetic confinement device for achieving a steady-state fusion burning experiment. For an MHD stable system, we investigate three different radial transport <span class="hlt">models</span> with Bohm, gyroBohm, and ETG scaling. Numerical coefficients in the <span class="hlt">models</span> are consistent with tokamak and stellarator databases, thus providing a conservative transport estimate. The well-known confinement improvement at high ? and steep ?-gradient is taken into account. The plug mirrors create an ambipolar potential that controls end losses, whereas radial losses are driven by drift wave turbulence, which also lowers the electron temperature via the ETG effect. We solve the radial transport equations using Pastukhov-type power and particle losses, with mirror ratio R=9 and with large density ratio between plug and central cell regions in order to achieve an ion potential ?i ? 2.3 Te = 6 Ti for high axial confinement. Profiles and total energy confinement times are calculated for a proof-of-principle experiment (L=7 m,B=0.28 T, R=1 m) and for a test reactor facility (L = 30 m to 80 m, B=3 T, R= 1 m). Work supported by DOE grant DE-FG02-04ER5474.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/175938','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/175938"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of a backfilled room-and-pillar mine</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tesarik, D.R.; Seymour, J.B.; Yanske, T.R.; McKibbin, R.W.</p> <p>1995-12-31</p> <p>Displacement and stress changes in cemented backfill and ore pillars at the Buick Mine, near Boss, MO, were monitored by engineers from the US Bureau of Mines and The Doe Run Co., St. Louis, MO. A test area in this room-and-pillar mine was backfilled to provide support when remnant ore pillars were mined. Objectives of this research were to evaluate the effect of backfill on mine <span class="hlt">stability</span>, observe backfill conditions during pillar removal, and calibrate a numerical <span class="hlt">model</span> to be used to design other areas of the mine. Relative vertical displacements in the backfill were measured with embedment strain gauges and vertical extensometers. Other types of instruments used were earth pressure cells (to identify loading trends in the backfill), borehole extensometers (to measure relative displacement changes in the mine roof and support pillars), and biaxial stressmeters (to measure stress changes in several support pillars and abutments). Two- and three-dimensional numeric codes were used to <span class="hlt">model</span> the study area. With information from these codes and the installed instruments, two failed pillars were identified and rock mass properties were estimated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26ES...29a2003F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26ES...29a2003F"><span id="translatedtitle">Prediction of landslide run-out distance based on slope <span class="hlt">stability</span> <span class="hlt">analysis</span> and center of mass approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Firmansyah; Feranie, S.; Tohari, Adrin; Latief, F. D. E.</p> <p>2016-01-01</p> <p>Mitigation of landslide hazard requires the knowledge of landslide run-out distance. This paper presents the application of slope <span class="hlt">stability</span> <span class="hlt">analysis</span> and center of mass approach to predict the run-out distance of a rotational landslide <span class="hlt">model</span> with different soil types. The Morgenstern-Price method was used to estimate the potential sliding zone and volume of landslide material. The center of mass approach used a simple Coulomb friction <span class="hlt">model</span> to determine the run-out distance. Results of the slope <span class="hlt">stability</span> <span class="hlt">analysis</span> showed that the soil unit weight can influence the depth of sliding zone, and the volume of unstable material. The slope <span class="hlt">model</span> of silty sand and gravel would have the largest volume of unstable mass. From the Coulomb friction <span class="hlt">analysis</span>, this slope <span class="hlt">model</span> has higher run-out distance and velocity than other slope <span class="hlt">models</span>. Thus, the run-out distance will be influenced by soil type and the dimension of unstable soil mass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6725441','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6725441"><span id="translatedtitle">In situ vitrification: application <span class="hlt">analysis</span> for <span class="hlt">stabilization</span> of transuranic waste</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Oma, K.H.; Farnsworth, R.K.; Rusin, J.M.</p> <p>1982-09-01</p> <p>The in situ vitrification process builds upon the electric melter technology previously developed for high-level waste immobilization. In situ vitrification converts buried wastes and contaminated soil to an extremely durable glass and crystalline waste form by melting the materials, in place, using joule heating. Once the waste materials have been solidified, the high integrity waste form should not cause future ground subsidence. Environmental transport of the waste due to water or wind erosion, and plant or animal intrusion, is minimized. Environmental studies are currently being conducted to determine whether additional <span class="hlt">stabilization</span> is required for certain in-ground transuranic waste sites. An applications <span class="hlt">analysis</span> has been performed to identify several in situ vitrification process limitations which may exist at transuranic waste sites. Based on the process limit <span class="hlt">analysis</span>, in situ vitrification is well suited for solidification of most in-ground transuranic wastes. The process is best suited for liquid disposal sites. A site-specific performance <span class="hlt">analysis</span>, based on safety, health, environmental, and economic assessments, will be required to determine for which sites in situ vitrification is an acceptable disposal technique. Process economics of in situ vitrification compare favorably with other in-situ solidification processes and are an order of magnitude less than the costs for exhumation and disposal in a repository. Leachability of the vitrified product compares closely with that of Pyrex glass and is significantly better than granite, marble, or bottle glass. Total release to the environment from a vitrified waste site is estimated to be less than 10/sup -5/ parts per year. 32 figures, 30 tables.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006IJTPE.126..776W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006IJTPE.126..776W"><span id="translatedtitle">Modal Voltage <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Multi-infeed HVDC System Considering its Control Systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Guohong; Minakawa, Tamotsu; Hayashi, Toshiyuki</p> <p></p> <p>This work presents a method for investigating the voltage <span class="hlt">stability</span> of multi-infeed HVDC systems, which is based on the eigenvalue decomposition technique known as modal <span class="hlt">analysis</span>. In this method, the eigenvalue of linearized steady-state system power-voltage equations are computed to evaluate the long-term voltage <span class="hlt">stability</span>. The contributions of this work to modal <span class="hlt">analysis</span> method are control systems of HVDC system, such as an Automatic Power Regulator (APR) and an Automatic (DC) Current Regulator (ACR) on its rectifier side and a changeover between an Automatic (DC) Voltage Regulator (AVR) and an Automatic extinction advance angle Regulator (A?R) modes on its inverter side, were taken into account, and the formularization for modal <span class="hlt">analysis</span> considering not only these control systems of HVDC system but also generator and load characteristics was fulfilled and presented in this paper. The application results from an AC/DC <span class="hlt">model</span> power system with dual HVDC systems verified the efficiency of the proposed method and quantitatively illustrated the influence of control systems of HVDC system on AC/DC system long-term voltage <span class="hlt">stability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25068534','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25068534"><span id="translatedtitle">Towards understanding the <span class="hlt">stabilization</span> process in vermicomposting using PARAFAC <span class="hlt">analysis</span> of fluorescence spectra.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lv, Baoyi; Xing, Meiyan; Zhao, Chunhui; Yang, Jian; Xiang, Liang</p> <p>2014-12-01</p> <p>In this study, fluorescence excitation-emission matrix (EEM) combined with parallel factor <span class="hlt">analysis</span> (PARAFAC) was employed to trace the behavior of water extractable organic matter and assess the <span class="hlt">stabilization</span> process during vermicomposting of sewage sludge and cattle dung. Experiments using different mixing ratios of sewage sludge and cattle dung were conducted using Eisenia fetida. The results showed that vermicomposting reduced the DOC, DOC/DON ratio and ammonia, while increased the nitrate content. A three-component <span class="hlt">model</span> containing two humic-like materials (components 1 and 2) and a protein-like material (component 3) was successfully developed using PARAFAC <span class="hlt">analysis</span>. Moreover, the initial waste composition had a significant effect on the distribution of each component and the addition of cattle dung improved the <span class="hlt">stability</span> of sewage sludge in vermicomposting. The PARAFAC results also indicated that protein-like materials were degraded and humic acid-like compounds were evolved during vermicomposting. Pearson correlation <span class="hlt">analysis</span> showed that components 2 and 3 are more suitable to assess vermicompost maturity than component 1. In all, EEM-PARAFAC can be used to track organic transformation and assess biological <span class="hlt">stability</span> during the vermicomposting process. PMID:25068534</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhyD..241..472M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhyD..241..472M"><span id="translatedtitle">Continuum <span class="hlt">modeling</span> of the equilibrium and <span class="hlt">stability</span> of animal flocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mecholsky, Nicholas A.; Ott, Edward; Antonsen, Thomas M.; Guzdar, Parvez</p> <p>2012-03-01</p> <p>Groups of animals often tend to arrange themselves in flocks that have characteristic spatial attributes and temporal dynamics. Using a dynamic continuum <span class="hlt">model</span> for a flock of individuals, we find equilibria of finite spatial extent where the density goes continuously to zero at a well-defined flock edge, and we discuss conditions on the <span class="hlt">model</span> that allow for such solutions. We also demonstrate conditions under which, as the flock size increases, the interior density in our equilibria tends to an approximately uniform value. Motivated by observations of starling flocks that are relatively thin in a direction transverse to the direction of flight, we investigate the <span class="hlt">stability</span> of infinite, planar-sheet flock equilibria. We find that long-wavelength perturbations along the sheet are unstable for the class of <span class="hlt">models</span> that we investigate. This has the conjectured consequence that sheet-like flocks of arbitrarily large transverse extent relative to their thickness do not occur. However, we also show that our <span class="hlt">model</span> admits approximately sheet-like, pancake-shaped, three-dimensional ellipsoidal equilibria with definite aspect ratios (transverse length-scale to flock thickness) determined by anisotropic perceptual/response characteristics of the flocking individuals, and we argue that these pancake-like equilibria are stable to the previously mentioned sheet instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1168..953M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1168..953M"><span id="translatedtitle">A Note on Local <span class="hlt">Stability</span> Conditions for Two Types of Monetary <span class="hlt">Models</span> with Recursive Utility</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miyazaki, Kenji; Utsunomiya, Hitoshi</p> <p>2009-09-01</p> <p>This note explores local <span class="hlt">stability</span> conditions for money-in-utility-function (MIUF) and transaction-costs (TC) <span class="hlt">models</span> with recursive utility. Although Chen et al. [Chen, B.-L., M. Hsu, and C.-H. Lin, 2008, Inflation and growth: impatience and a qualitative equivalent, Journal of Money, Credit, and Banking, Vol. 40, No. 6, 1310-1323] investigated the relationship between inflation and growth in MIUF and TC <span class="hlt">models</span> with recursive utility, they conducted only a comparative static <span class="hlt">analysis</span> in a steady state. By establishing sufficient conditions for local <span class="hlt">stability</span>, this note proves that impatience should be increasing in consumption and real balances. Increasing impatience, although less plausible from an empirical point of view, receives more support from a theoretical viewpoint.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880050709&hterms=math+models&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmath%2Bmodels','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880050709&hterms=math+models&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmath%2Bmodels"><span id="translatedtitle">A study of aeroelastic <span class="hlt">stability</span> for the <span class="hlt">model</span> support system of the National Transonic Facility</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Strganac, Thomas W.</p> <p>1988-01-01</p> <p>Oscillations of wind-tunnel <span class="hlt">models</span> have been observed during testing in the National Transonic Facility. These oscillations have been the subject of an extensive investigation. As a part of this effort, a study of the aeroelastic <span class="hlt">stability</span> of the <span class="hlt">model</span> support structure has been performed. This structure is mathematically <span class="hlt">modelled</span> as a wing and conventional flutter <span class="hlt">analysis</span> is performed. The math <span class="hlt">model</span> implemented both experimentally and numerically obtained modal characteristics. A technique for illustrating the flutter boundary for wind tunnels is demonstrated. Results indicate that the classical flutter boundary is well above the operating envelope of the facility. However, the <span class="hlt">analysis</span> indicates a damping-dependent instability is present which is inherent in the design. One possible modification in the design has been evaluated which eliminates the predicted instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/460454','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/460454"><span id="translatedtitle">Analytical mass leaching <span class="hlt">model</span> for contaminated soil and soil <span class="hlt">stabilized</span> waste</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shackelford, C.D.; Glade, M.J.</p> <p>1997-03-01</p> <p>An analytical <span class="hlt">model</span> for evaluating mass leaching from contaminated soil or soil <span class="hlt">stabilized</span> waste is presented. The <span class="hlt">model</span> is based on mass transport due to advection, dispersion, and retardation and can be used to evaluate the suitability and/or efficiency of soil washing solutions based on the results of column leaching studies. The <span class="hlt">model</span> differs from more traditional <span class="hlt">models</span> for column leaching studies in that the <span class="hlt">analysis</span> is based on the cumulative mass of leachate instead of leachate concentration. A cumulative mass basis for leaching eliminates the requirement for determination of instantaneous effluent concentrations in the more traditional column leaching approach thereby allowing for the collection of relatively large effluent volumes. The cumulative masses of three heavy metals -- Cd, Pb, and Zn -- leached from two specimens of soil mixed with fly ash are analyzed with the mass leaching <span class="hlt">model</span> to illustrate application and limitation of the <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/6844380','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/6844380"><span id="translatedtitle">[Efficacy testing of <span class="hlt">stabilizing</span> agents in epinephrine <span class="hlt">model</span> solutions. 19: <span class="hlt">Stability</span> of drugs and preparations].</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wollmann, H; Raether, G</p> <p>1983-01-01</p> <p>The efficiency of 54 <span class="hlt">stabilizers</span> was tested on epinephrine solutions using a selection-combination method. The addition of only one antioxidant produces but slight improvements in <span class="hlt">stability</span>. Maximal additive activity is achieved by the combination of two antioxidants. Superadditive effects (which are necessary for considerable prolongation of the time of applicability of aqueous epinephrine solutions) are obtained by the combination of antioxidants of different modes of action and a discolouration-protective agent or a synergist. On this basis, the authors developed an efficient <span class="hlt">stabilizing</span> procedure for pharmaceutical preparations containing active principles sensitive to oxidation. The relationship between the concentration of the <span class="hlt">stabilizer</span> and the <span class="hlt">stabilizing</span> effect is demonstrated by examples. PMID:6844380</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CNSNS..27...30K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CNSNS..27...30K"><span id="translatedtitle">Epidemic spreading and global <span class="hlt">stability</span> of an SIS <span class="hlt">model</span> with an infective vector on complex networks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kang, Huiyan; Fu, Xinchu</p> <p>2015-10-01</p> <p>In this paper, we present a new SIS <span class="hlt">model</span> with delay on scale-free networks. The <span class="hlt">model</span> is suitable to describe some epidemics which are not only transmitted by a vector but also spread between individuals by direct contacts. In view of the biological relevance and real spreading process, we introduce a delay to denote average incubation period of disease in a vector. By mathematical <span class="hlt">analysis</span>, we obtain the epidemic threshold and prove the global <span class="hlt">stability</span> of equilibria. The simulation shows the delay will effect the epidemic spreading. Finally, we investigate and compare two major immunization strategies, uniform immunization and targeted immunization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960047496','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960047496"><span id="translatedtitle">ASTROP2 Users Manual: A Program for Aeroelastic <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Propfans</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Reddy, T. S. R.; Lucero, John M.</p> <p>1996-01-01</p> <p>This manual describes the input data required for using the second version of the ASTROP2 (Aeroelastic <span class="hlt">STability</span> and Response Of Propulsion systems - 2 dimensional <span class="hlt">analysis</span>) computer code. In ASTROP2, version 2.0, the program is divided into two modules: 2DSTRIP, which calculates the structural dynamic information; and 2DASTROP, which calculates the unsteady aerodynamic force coefficients from which the aeroelastic <span class="hlt">stability</span> can be determined. In the original version of ASTROP2, these two aspects were performed in a single program. The improvements to version 2.0 include an option to account for counter rotation, improved numerical integration, accommodation for non-uniform inflow distribution, and an iterative scheme to flutter frequency convergence. ASTROP2 can be used for flutter <span class="hlt">analysis</span> of multi-bladed structures such as those found in compressors, turbines, counter rotating propellers or propfans. The <span class="hlt">analysis</span> combines a two-dimensional, unsteady cascade aerodynamics <span class="hlt">model</span> and a three dimensional, normal mode structural <span class="hlt">model</span> using strip theory. The flutter <span class="hlt">analysis</span> is formulated in the frequency domain resulting in an eigenvalue determinant. The flutter frequency and damping can be inferred from the eigenvalues.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6457M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6457M"><span id="translatedtitle">GIS-based <span class="hlt">modelling</span> of deep-seated slope <span class="hlt">stability</span> in complex geology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mergili, Martin; Marchesini, Ivan; Schneider-Muntau, Barbara; Cardinali, Mauro; Fiorucci, Federica; Valigi, Daniela; Santangelo, Michele; Bucci, Francesco; Guzzetti, Fausto</p> <p>2014-05-01</p> <p>We use the <span class="hlt">model</span> r.slope.<span class="hlt">stability</span> to explore the chances and challenges of physically-based <span class="hlt">modelling</span> of deep-seated slope <span class="hlt">stability</span> in complex geology over broad areas and not on individual slopes. The <span class="hlt">model</span> is developed as a C and python-based raster module within the GRASS GIS software. It makes use of a modification of the three-dimensional sliding surface <span class="hlt">model</span> proposed by Hovland (1977) and revised and extended by Xie and co-workers (2006). Given a digital elevation <span class="hlt">model</span> and a set of thematic layers (lithological classes and related geotechnical parameters), the <span class="hlt">model</span> evaluates the slope <span class="hlt">stability</span> for a large number of randomly selected potential slip surfaces, ellipsoidal in shape. The bottoms of soil or bedrock layers can also be considered as potential slip surfaces by truncating the ellipsoids. Any single raster cell may be intersected by multiple sliding surfaces, each associated with a computed safety factor. For each pixel, the lowest value of the safety factor and the depth of the associated slip surface are stored. This information can be used to obtain a spatial overview of the potentially unstable regions in the study area. The r.slope.<span class="hlt">stability</span> <span class="hlt">model</span> can be executed both in a soil class-based mode, where the input data are mainly structured according to horizontally defined soil classes, and in a layer-based mode, where the data are structured according to a potentially large number of layers. Here, we test the <span class="hlt">model</span> for the layer-based mode, allowing for the <span class="hlt">analysis</span> of relatively complex geologic structures. We test the <span class="hlt">model</span> in the Collazzone area, Umbria, central Italy, which is susceptible to landslides of different types. According to field observations in this area, morpho-structural settings (i.e., the orientation and dip of the geological layers) play a crucial role for the distribution of the deep-seated landslides. We have prepared a lithological <span class="hlt">model</span> based on aerial photointerpretation, field survey and surface information on the strike and dip directions of each layer. We have further investigated the geotechnical parameters (cohesion and internal friction angle) associated to the layers using direct shear tests. We execute r.slope.<span class="hlt">stability</span> for various assumptions of the geotechnical parameters, ellipsoid geometry and seepage direction. In this way, we obtain the spatial probability of slope failures which is validated using a pre-existing landslide inventory map, using an ROC plot. Acknowledging the challenges related to the high natural variability of geotechnical parameters in space, the results satisfactorily reproduce the observed distribution of deep-seated landslides in the study area. The assumed direction of seepage (slope-parallel vs. layer-parallel) strongly influences the <span class="hlt">model</span> results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910046036&hterms=differential+equations&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddifferential%2Bequations','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910046036&hterms=differential+equations&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddifferential%2Bequations"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of multigrid acceleration methods for the solution of partial differential equations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fay, John F.</p> <p>1990-01-01</p> <p>A calculation is made of the <span class="hlt">stability</span> of various relaxation schemes for the numerical solution of partial differential equations. A multigrid acceleration method is introduced, and its effects on <span class="hlt">stability</span> are explored. A detailed <span class="hlt">stability</span> <span class="hlt">analysis</span> of a simple case is carried out and verified by numerical experiment. It is shown that the use of multigrids can speed convergence by several orders of magnitude without adversely affecting <span class="hlt">stability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5350672','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5350672"><span id="translatedtitle">Boiling water reactor <span class="hlt">stability</span> <span class="hlt">analysis</span> in the time domain</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Borkowski, J.A.</p> <p>1991-01-01</p> <p>Boiling water nuclear reactors may experience density wave instabilities. These instabilities cause the density, and consequently the mass flow rate, to oscillate in the shrouded fuel bundles. This effect causes the nuclear power generation to oscillate due to the tight coupling of flow to power, especially under gravity-driven circulation. In order to predict the amplitude of the power oscillation, a time domain transient <span class="hlt">analysis</span> tool may be employed. The <span class="hlt">modeling</span> tool must have sufficient hydrodynamic detail to <span class="hlt">model</span> natural circulation in two-phase flow as well as the coupled nuclear feedback. TRAC/BF1 is a <span class="hlt">modeling</span> code with such capabilities. A dynamic system <span class="hlt">model</span> has been developed for a typical boiling water reactor. Using this tool it has been demonstrated that density waxes may be <span class="hlt">modeled</span> in this fashion and that their resultant hydrodynamic and nuclear behavior correspond well to simple theory. Several cases have been analyzed using this <span class="hlt">model</span>, the goal being to determine the coupling between the channel hydrodynamics and the nuclear power. From that study it has been concluded that two-phase friction controls the extent of the oscillation and that the existing conventional methodologies of implementing two-phase friction into <span class="hlt">analysis</span> codes of this type can lead to significant deviation in results from case to case. It has also been determined that higher dimensional nuclear feedback <span class="hlt">models</span> reduce the extent of the oscillation. It has also been confirmed from a nonlinear dynamic standpoint that the birth of this oscillation may be described as a Hopf Bifurcation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ChPhB..22i8401Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ChPhB..22i8401Z"><span id="translatedtitle">Dynamical investigation and parameter <span class="hlt">stability</span> region <span class="hlt">analysis</span> of a flywheel energy storage system in charging mode</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Wei-Ya; Li, Yong-Li; Chang, Xiao-Yong; Wang, Nan</p> <p>2013-09-01</p> <p>In this paper, the dynamic behavior <span class="hlt">analysis</span> of the electromechanical coupling characteristics of a flywheel energy storage system (FESS) with a permanent magnet (PM) brushless direct-current (DC) motor (BLDCM) is studied. The Hopf bifurcation theory and nonlinear methods are used to investigate the generation process and mechanism of the coupled dynamic behavior for the average current controlled FESS in the charging mode. First, the universal nonlinear dynamic <span class="hlt">model</span> of the FESS based on the BLDCM is derived. Then, for a 0.01 kWh/1.6 kW FESS platform in the Key Laboratory of the Smart Grid at Tianjin University, the phase trajectory of the FESS from a stable state towards chaos is presented using numerical and stroboscopic methods, and all dynamic behaviors of the system in this process are captured. The characteristics of the low-frequency oscillation and the mechanism of the Hopf bifurcation are investigated based on the Routh <span class="hlt">stability</span> criterion and nonlinear dynamic theory. It is shown that the Hopf bifurcation is directly due to the loss of control over the inductor current, which is caused by the system control parameters exceeding certain ranges. This coupling nonlinear process of the FESS affects the <span class="hlt">stability</span> of the motor running and the efficiency of energy transfer. In this paper, we investigate into the effects of control parameter change on the <span class="hlt">stability</span> and the <span class="hlt">stability</span> regions of these parameters based on the averaged-<span class="hlt">model</span> approach. Furthermore, the effect of the quantization error in the digital control system is considered to modify the <span class="hlt">stability</span> regions of the control parameters. Finally, these theoretical results are verified through platform experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PEPI..246...41A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PEPI..246...41A"><span id="translatedtitle">A new free-surface <span class="hlt">stabilization</span> algorithm for geodynamical <span class="hlt">modelling</span>: Theory and numerical tests</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andrés-Martínez, Miguel; Morgan, Jason P.; Pérez-Gussinyé, Marta; Rüpke, Lars</p> <p>2015-09-01</p> <p>The surface of the solid Earth is effectively stress free in its subaerial portions, and hydrostatic beneath the oceans. Unfortunately, this type of boundary condition is difficult to treat computationally, and for computational convenience, numerical <span class="hlt">models</span> have often used simpler approximations that do not involve a normal stress-loaded, shear-stress free top surface that is free to move. Viscous flow <span class="hlt">models</span> with a computational free surface typically confront <span class="hlt">stability</span> problems when the time step is bigger than the viscous relaxation time. The small time step required for <span class="hlt">stability</span> (< 2 Kyr) makes this type of <span class="hlt">model</span> computationally intensive, so there remains a need to develop strategies that mitigate the <span class="hlt">stability</span> problem by making larger (at least ∼10 Kyr) time steps stable and accurate. Here we present a new free-surface <span class="hlt">stabilization</span> algorithm for finite element codes which solves the <span class="hlt">stability</span> problem by adding to the Stokes formulation an intrinsic penalization term equivalent to a portion of the future load at the surface nodes. Our algorithm is straightforward to implement and can be used with both Eulerian or Lagrangian grids. It includes α and β parameters to respectively control both the vertical and the horizontal slope-dependent penalization terms, and uses Uzawa-like iterations to solve the resulting system at a cost comparable to a non-stress free surface formulation. Four tests were carried out in order to study the accuracy and the <span class="hlt">stability</span> of the algorithm: (1) a decaying first-order sinusoidal topography test, (2) a decaying high-order sinusoidal topography test, (3) a Rayleigh-Taylor instability test, and (4) a steep-slope test. For these tests, we investigate which α and β parameters give the best results in terms of both accuracy and <span class="hlt">stability</span>. We also compare the accuracy and the <span class="hlt">stability</span> of our algorithm with a similar implicit approach recently developed by Kaus et al. (2010). We find that our algorithm is slightly more accurate and stable for steep slopes, and also conclude that, for longer time steps, the optimal α controlling factor for both approaches is ∼2/3, instead of the 1/2 Crank-Nicolson parameter inferred from a linearized accuracy <span class="hlt">analysis</span>. This more-implicit value coincides with the velocity factor for a Galerkin time discretization applied to our penalization term using linear shape functions in time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22252969','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22252969"><span id="translatedtitle">Low frequency azimuthal <span class="hlt">stability</span> of the ionization region of the Hall thruster discharge. I. Local <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Escobar, D.; Ahedo, E.</p> <p>2014-04-15</p> <p>Results based on a local linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of the Hall thruster discharge are presented. A one-dimensional azimuthal framework is used including three species: neutrals, singly charged ions, and electrons. A simplified linear <span class="hlt">model</span> is developed with the aim of deriving analytical expressions to characterize the <span class="hlt">stability</span> of the ionization region. The results from the local <span class="hlt">analysis</span> presented here indicate the existence of an instability that gives rise to an azimuthal oscillation in the +E × B direction with a long wavelength. According to the <span class="hlt">model</span>, the instability seems to appear only in regions where the ionization and the electric field make it possible to have positive gradients of plasma density and ion velocity at the same time. A more complex <span class="hlt">model</span> is also solved numerically to validate the analytical results. Additionally, parametric variations are carried out with respect to the main parameters of the <span class="hlt">model</span> to identify the trends of the instability. As the temperature increases and the neutral-to-plasma density ratio decreases, the growth rate of the instability decreases down to a limit where azimuthal perturbations are no longer unstable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930005608','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930005608"><span id="translatedtitle">BLSTA: A boundary layer code for <span class="hlt">stability</span> <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wie, Yong-Sun</p> <p>1992-01-01</p> <p>A computer program is developed to solve the compressible, laminar boundary-layer equations for two-dimensional flow, axisymmetric flow, and quasi-three-dimensional flows including the flow along the plane of symmetry, flow along the leading-edge attachment line, and swept-wing flows with a conical flow approximation. The finite-difference numerical procedure used to solve the governing equations is second-order accurate. The flow over a wide range of speed, from subsonic to hypersonic speed with perfect gas assumption, can be calculated. Various wall boundary conditions, such as wall suction or blowing and hot or cold walls, can be applied. The results indicate that this boundary-layer code gives velocity and temperature profiles which are accurate, smooth, and continuous through the first and second normal derivatives. The code presented herein can be coupled with a <span class="hlt">stability</span> <span class="hlt">analysis</span> code and used to predict the onset of the boundary-layer transition which enables the assessment of the laminar flow control techniques. A user's manual is also included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4134820','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4134820"><span id="translatedtitle">Slope <span class="hlt">Stability</span> <span class="hlt">Analysis</span> Using Limit Equilibrium Method in Nonlinear Criterion</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lin, Hang; Zhong, Wenwen; Xiong, Wei; Tang, Wenyu</p> <p>2014-01-01</p> <p>In slope <span class="hlt">stability</span> <span class="hlt">analysis</span>, the limit equilibrium method is usually used to calculate the safety factor of slope based on Mohr-Coulomb criterion. However, Mohr-Coulomb criterion is restricted to the description of rock mass. To overcome its shortcomings, this paper combined Hoek-Brown criterion and limit equilibrium method and proposed an equation for calculating the safety factor of slope with limit equilibrium method in Hoek-Brown criterion through equivalent cohesive strength and the friction angle. Moreover, this paper investigates the impact of Hoek-Brown parameters on the safety factor of slope, which reveals that there is linear relation between equivalent cohesive strength and weakening factor D. However, there are nonlinear relations between equivalent cohesive strength and Geological Strength Index (GSI), the uniaxial compressive strength of intact rock σci, and the parameter of intact rock mi. There is nonlinear relation between the friction angle and all Hoek-Brown parameters. With the increase of D, the safety factor of slope F decreases linearly; with the increase of GSI, F increases nonlinearly; when σci is relatively small, the relation between F and σci is nonlinear, but when σci is relatively large, the relation is linear; with the increase of mi, F decreases first and then increases. PMID:25147838</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/489297','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/489297"><span id="translatedtitle">Crack <span class="hlt">stability</span> <span class="hlt">analysis</span> of low alloy steel primary coolant pipe</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tanaka, T.; Kameyama, M.; Urabe, Y.</p> <p>1997-04-01</p> <p>At present, cast duplex stainless steel has been used for the primary coolant piping of PWRs in Japan and joints of dissimilar material have been applied for welding to reactor vessels and steam generators. For the primary coolant piping of the next APWR plants, application of low alloy steel that results in designing main loops with the same material is being studied. It means that there is no need to weld low alloy steel with stainless steel and that makes it possible to reduce the welding length. Attenuation of Ultra Sonic Wave Intensity is lower for low alloy steel than for stainless steel and they have advantageous inspection characteristics. In addition to that, the thermal expansion rate is smaller for low alloy steel than for stainless steel. In consideration of the above features of low alloy steel, the overall reliability of primary coolant piping is expected to be improved. Therefore, for the evaluation of crack <span class="hlt">stability</span> of low alloy steel piping to be applied for primary loops, elastic-plastic future mechanics <span class="hlt">analysis</span> was performed by means of a three-dimensioned FEM. The evaluation results for the low alloy steel pipings show that cracks will not grow into unstable fractures under maximum design load conditions, even when such a circumferential crack is assumed to be 6 times the size of the wall thickness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/138771','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/138771"><span id="translatedtitle">Implications of <span class="hlt">stability</span> <span class="hlt">analysis</span> for heat transfer at Yucca Mountain</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ross, B.; Yiqiang Zhang; Ning Lu</p> <p>1993-03-01</p> <p>An analytical solution has been obtained to the <span class="hlt">stability</span> problem for an infinite horizontal layer of gas with Its humidity constrained to 100%. Latent heat transfer makes convective heat transfer much more Important for this moist gas than for a dry gas. The critical Rayleigh number for the onset of convective flow in the moist gas, with a lower no-flow boundary at 97{degrees}C and an upper no-flow boundary at 27{degrees}C, is 0.18, much less than the value of 4m{sup 2} for a dry gas. Although the heat source at Yucca Mountain will be finite in extent, the solution for an infinite horizontal layer still gives a useful criterion for the qualitative importance of convective heat transfer. The critical Rayleigh number of 0.18 corresponds to a permeability of 4 {times} 10{sup {minus}12} m{sup 2} if other parameters ate given values measured at Yucca Mountain. This value falls roughly in the middle of the range of measured permeabilities. The <span class="hlt">analysis</span> also gives a time constant for the onset of convection, which at twice the critical Rayleigh number is 1000 yr. Thus convection will probably make an important contribution, to host transfer at Yucca Mountain if the rock permeability falls in the upper portion of the range of measurements to date, but only at times after a few hundred or thousand years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19810025327&hterms=differential+equation+applied&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddifferential%2Bequation%2Bapplied','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19810025327&hterms=differential+equation+applied&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddifferential%2Bequation%2Bapplied"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of numerical boundary conditions and implicit difference approximations for hyperbolic equations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Beam, R. M.; Warming, R. F.; Yee, H. C.</p> <p>1981-01-01</p> <p>Implicit, noniterative, finite difference schemes were recently developed by several authors for multidimensional systems of nonlinear hyperbolic partial differential equations. When applied to linear <span class="hlt">model</span> equations with periodic boundary conditions those schemes are unconditionally stable (A-stable). As applied in practice the algorithms often face a severe time step restriction. A major source of the difficulty is the treatment of the numerical boundary conditions. One conjecture was that unconditional <span class="hlt">stability</span> requires implicit numerical boundary conditions. An apparent counter example was the space time extrapolation considered by Gustafsson, Kreiss, and Sunstrom. Spatial (implicit) and space time (explicit) extrapolation using normal mode <span class="hlt">analysis</span> for a finite and infinite number of spatial mesh intervals are examined. The results indicate that for unconditional <span class="hlt">stability</span> with a finite number of spatial mesh intervals, the numerical boundary conditions must be implicit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPhCS.548a2064E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhCS.548a2064E"><span id="translatedtitle">Hydrodynamic <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Particle-Laden Solid Rocket Motors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elliott, T. S.; Majdalani, J.</p> <p>2014-11-01</p> <p>Fluid-wall interactions within solid rocket motors can result in parietal vortex shedding giving rise to hydrodynamic instabilities, or unsteady waves, that translate into pressure oscillations. The oscillations can result in vibrations observed by the rocket, rocket subsystems, or payload, which can lead to changes in flight characteristics, design failure, or other undesirable effects. For many years particles have been embedded in solid rocket propellants with the understanding that their presence increases specific impulse and suppresses fluctuations in the flowfield. This study utilizes a two dimensional framework to understand and quantify the aforementioned two-phase flowfield inside a motor case with a cylindrical grain perforation. This is accomplished through the use of linearized Navier-Stokes equations with the Stokes drag equation and application of the biglobal ansatz. Obtaining the biglobal equations for <span class="hlt">analysis</span> requires quantification of the mean flowfield within the solid rocket motor. To that end, the extended Taylor-Culick form will be utilized to represent the gaseous phase of the mean flowfield while the self-similar form will be employed for the particle phase. Advancing the mean flowfield by quantifying the particle mass concentration with a semi-analytical solution the finalized mean flowfield is combined with the biglobal equations resulting in a system of eight partial differential equations. This system is solved using an eigensolver within the framework yielding the entire spectrum of eigenvalues, frequency and growth rate components, at once. This work will detail the parametric <span class="hlt">analysis</span> performed to demonstrate the <span class="hlt">stabilizing</span> and destabilizing effects of particles within solid rocket combustion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=214702','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=214702"><span id="translatedtitle">Rank <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Surface and Profile Soil Moisture</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Although several studies have examined the spatial and rank <span class="hlt">stability</span> of soil moisture at the surface layer (0-5cm) with the purpose of estimating large scale mean soil moisture, the integration of the rank <span class="hlt">stability</span> of profile (0-60cm) soil moisture has not been fully considered. This research comb...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25689104','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25689104"><span id="translatedtitle"><span class="hlt">Stability</span> properties of surfactant-free thin films at different ionic strengths: measurements and <span class="hlt">modeling</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lech, Frederik J; Wierenga, Peter A; Gruppen, Harry; Meinders, Marcel B J</p> <p>2015-03-10</p> <p>Foam lamellae are the smallest structural elements in foam. Such lamellae can experimentally be studied by <span class="hlt">analysis</span> of thin liquid films in glass cells. These thin liquid films usually have to be <span class="hlt">stabilized</span> against rupture by surface active substances, such as proteins or low molecular weight surfactants. However, horizontal thin liquid films of pure water with a radius of 100 ?m also show remarkable <span class="hlt">stability</span> when created in closed Sheludko cells. To understand thin film <span class="hlt">stability</span> of surfactant-free films, the drainage behavior and rupture times of films of water and NaCl solutions were determined. The drainage was <span class="hlt">modeled</span> with an extended Derjaguin-Landau-Verwey-Overbeek (DLVO) <span class="hlt">model</span>, which combines DLVO and hydrophobic contributions. Good correspondence between experiment and theory is observed, when hydrophobic interactions are included, with fitted values for surface potential (?(0,water)) of -60 5 mV, hydrophobic strength (B(hb,water)) of 0.22 0.02 mJ/m(2), and a range of the hydrophobic interaction (?(hb, water)) of 15 1 nm in thin liquid films. In addition, Vrij's rupture criterion was successfully applied to <span class="hlt">model</span> the <span class="hlt">stability</span> regions and rupture times of the films. The films of pure water are stable over long time scales (hours) and drain to a final thickness >40 nm if the concentration of electrolytes is low (resistivity 18.2 MQ). With increasing amounts of ions (NaCl) the thin films drain to <40 nm thickness and the rupture <span class="hlt">stability</span> of the films is reduced from hours to seconds. PMID:25689104</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4223625','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4223625"><span id="translatedtitle">Primary posterior <span class="hlt">stabilized</span> total knee arthroplasty: <span class="hlt">analysis</span> of different instrumentation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2014-01-01</p> <p>Background Intercondylar femoral bone removal during posterior <span class="hlt">stabilized</span> (PS) total knee arthroplasty (TKA) makes many cruciate substituting implant designs less appealing than cruciate retaining implants. Bone stock conservation is considered fundamental in the prevision of future revision surgeries. The purpose of this study was to compare the quantity of intercondylar bone removable during PS housing preparation using three contemporary PS TKA instrumentations. Method We compared different box cutting jigs which were utilized for the PS housing of three popular PS knee prostheses. The bone removal area from every PS box cutting jig was three-dimensionally measured. Results Independently from the implant size, the cutting jig for a specific PS TKA always resected significantly less bone than the others: this difference was statistically significant, especially for small- to medium-sized total knee femoral components. Conclusion This study does not establish a clinical relevance of removing more or less bone at primary TKA, but suggests that if a PS design is indicated, it is preferable to select a <span class="hlt">model</span> which possibly resects less distal femoral bone. PMID:25037275</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1232133','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1232133"><span id="translatedtitle"><span class="hlt">Model</span> <span class="hlt">Analysis</span> ToolKit</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p></p> <p>2015-05-15</p> <p>MATK provides basic functionality to facilitate <span class="hlt">model</span> <span class="hlt">analysis</span> within the Python computational environment. <span class="hlt">Model</span> <span class="hlt">analysis</span> setup within MATK includes: - define parameters - define observations - define <span class="hlt">model</span> (python function) - define samplesets (sets of parameter combinations) Currently supported functionality includes: - forward <span class="hlt">model</span> runs - Latin-Hypercube sampling of parameters - multi-dimensional parameter studies - parallel execution of parameter samples - <span class="hlt">model</span> calibration using internal Levenberg-Marquardt algorithm - <span class="hlt">model</span> calibration using lmfit package - <span class="hlt">model</span> calibration using levmar package - Markov Chain Monte Carlo using pymc package MATK facilitates <span class="hlt">model</span> <span class="hlt">analysis</span> using: - scipy - calibration (scipy.optimize) - rpy2 - Python interface to R</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050229353','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050229353"><span id="translatedtitle">Operations and <span class="hlt">Modeling</span> <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ebeling, Charles</p> <p>2005-01-01</p> <p>The Reliability and Maintainability <span class="hlt">Analysis</span> Tool (RMAT) provides NASA the capability to estimate reliability and maintainability (R&M) parameters and operational support requirements for proposed space vehicles based upon relationships established from both aircraft and Shuttle R&M data. RMAT has matured both in its underlying database and in its level of sophistication in extrapolating this historical data to satisfy proposed mission requirements, maintenance concepts and policies, and type of vehicle (i.e. ranging from aircraft like to shuttle like). However, a companion analyses tool, the Logistics Cost <span class="hlt">Model</span> (LCM) has not reached the same level of maturity as RMAT due, in large part, to nonexistent or outdated cost estimating relationships and underlying cost databases, and it's almost exclusive dependence on Shuttle operations and logistics cost input parameters. As a result, the full capability of the RMAT/LCM suite of <span class="hlt">analysis</span> tools to take a conceptual vehicle and derive its operations and support requirements along with the resulting operating and support costs has not been realized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9307E..1SB','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9307E..1SB"><span id="translatedtitle">Implementation of a capsular bag <span class="hlt">model</span> to enable sufficient lens <span class="hlt">stabilization</span> within a mechanical eye <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bayer, Natascha; Rank, Elisabet; Traxler, Lukas; Beckert, Erik; Drauschke, Andreas</p> <p>2015-03-01</p> <p>Cataract still remains the leading cause of blindness affecting 20 million people worldwide. To restore the patients vision the natural lens is removed and replaced by an intraocular lens (IOL). In modern cataract surgery the posterior capsular bag is maintained to prevent inflammation and to enable <span class="hlt">stabilization</span> of the implant. Refractive changes following cataract surgery are attributable to lens misalignments occurring due to postoperative shifts and tilts of the artificial lens. Mechanical eye <span class="hlt">models</span> allow a preoperative investigation of the impact of such misalignments and are crucial to improve the quality of the patients' sense of sight. Furthermore, the success of sophisticated IOLs that correct high order aberrations is depending on a critical evaluation of the lens position. A new type of an IOL holder is designed and implemented into a preexisting mechanical eye <span class="hlt">model</span>. A physiological representation of the capsular bag is realized with an integrated film element to guarantee lens <span class="hlt">stabilization</span> and centering. The positioning sensitivity of the IOL is evaluated by performing shifts and tilts in reference to the optical axis. The modulation transfer function is used to measure the optical quality at each position. Lens <span class="hlt">stability</span> tests within the holder itself are performed by determining the modulation transfer function before and after measurement sequence. Mechanical <span class="hlt">stability</span> and reproducible measurement results are guaranteed with the novel capsular bag <span class="hlt">model</span> that allows a precise interpretation of postoperative lens misalignments. The integrated film element offers additional <span class="hlt">stabilization</span> during measurement routine without damaging the haptics or deteriorating the optical performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950056095&hterms=dynamic+stall+model&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddynamic%2Bstall%2Bmodel','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950056095&hterms=dynamic+stall+model&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddynamic%2Bstall%2Bmodel"><span id="translatedtitle">Dynamic-stall and structural-<span class="hlt">modeling</span> effects on helicopter blade <span class="hlt">stability</span> with experimental correlation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barwey, D.; Gaonkar, Gopal H.</p> <p>1994-01-01</p> <p>The effects of blade and root-flexure elasticity and dynamic stall on the <span class="hlt">stability</span> of hingeless rotor blades are investigated. The dynamic stall description is based on the ONERA <span class="hlt">models</span> of lift, drag, and pitching moment. The structural <span class="hlt">analysis</span> is based on three blade <span class="hlt">models</span> that range from a rigid flap-lag <span class="hlt">model</span> to two elastic flap-lag-torsion <span class="hlt">models</span>, which differ in representing root-flexure elasticity. The predictions are correlated with the measured lag damping of an experimental isolated three-blade rotor; the correlation covers rotor operations from near-zero-thrust conditions in hover to highly stalled, high-thrust conditions in foward flight. That correlation shows sensitivity of lag-damping predictions to structural refinements in blade and root-flexure <span class="hlt">modeling</span>. Moreover, this sensitivity increases with increasing control pitch angle and advance ratio. For high-advance-ratio and high-thrust conditions, inclusion of dynamic stall generally improves the correlation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/479396','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/479396"><span id="translatedtitle">Electrical transient <span class="hlt">stability</span> and underfrequency load shedding <span class="hlt">analysis</span> for a large pump station</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shilling, S.R.</p> <p>1997-01-01</p> <p>Electrical transients from faults, loss of generation, and load swings can disrupt pump station operations. Isolated stations with no utility tie, and those with weak utility ties, are especially at risk. Relative to this problem, the following four main issues are addressed: (1) analyze the methods that use high-speed underfrequency load shedding to maintain system <span class="hlt">stability</span> and preserve station operations; (2) analyze combustion gas turbine generator and diesel generator transient responses, as they pertain to the electrical engineer; (3) discuss system component <span class="hlt">modeling</span> and the use of low voltage circuit switching devices to shed loads; (4) compare two computer <span class="hlt">analysis</span> program outputs for underfrequency load shedding responses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/392610','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/392610"><span id="translatedtitle">Electrical transient <span class="hlt">stability</span> and underfrequency load shedding <span class="hlt">analysis</span> for a large pump station</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shilling, S.R.</p> <p>1995-12-31</p> <p>Electrical transients from faults, loss of generation, and load swings can disrupt pump station operations. Isolated stations with no utility tie and those with weak utility ties are especially at risk. Relative to this problem, the following four main issues are addressed: (1) Analyze the methods that use high-speed underfrequency load shedding to maintain system <span class="hlt">stability</span> and preserve station operations. (2) Analyze combustion gas turbine generator and diesel generator transient responses, as they pertain to the Electrical Engineer. (3) Discuss system component <span class="hlt">modeling</span> and the use of low voltage circuit switching devices to shed loads. (4) Compare two computer <span class="hlt">analysis</span> program outputs for underfrequency load shedding responses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730016177','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730016177"><span id="translatedtitle">Modal <span class="hlt">analysis</span> for Liapunov <span class="hlt">stability</span> of rotating elastic bodies. Ph.D. Thesis. Final Report</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Colin, A. D.</p> <p>1973-01-01</p> <p>This study consisted of four parallel efforts: (1) modal analyses of elastic continua for Liapunov <span class="hlt">stability</span> <span class="hlt">analysis</span> of flexible spacecraft; (2) development of general purpose simulation equations for arbitrary spacecraft; (3) evaluation of alternative mathematical <span class="hlt">models</span> for elastic components of spacecraft; and (4) examination of the influence of vehicle flexibility on spacecraft attitude control system performance. A complete record is given of achievements under tasks (1) and (3), in the form of technical appendices, and a summary description of progress under tasks two and four.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/283981','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/283981"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of the instantaneous Bethe-Salpeter equation and the consequences for meson spectroscopy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Parramore, J.; Jean, H.; Piekarewicz, J.</p> <p>1996-05-01</p> <p>We investigate the light and heavy meson spectra in the context of the instantaneous approximation to the Bethe-Salpeter equation (Salpeter{close_quote}s equation). We use a static kernel consisting of a one-gluon-exchange component and a confining contribution. Salpeter{close_quote}s equation is known to be formally equivalent to a random-phase-approximation equation; as such, it can develop imaginary eigenvalues. Thus our study cannot be complete without first discussing the <span class="hlt">stability</span> of Salpeter{close_quote}s equation. The <span class="hlt">stability</span> <span class="hlt">analysis</span> limits the form of the kernel and reveals that a Lorentz scalar confining interaction in the Salpeter equation leads to instabilities (imaginary eigenvalues), whereas one transforming as the time component of a vector does not. Moreover, the <span class="hlt">stability</span> <span class="hlt">analysis</span> sets an upper limit on the size of the one-gluon-exchange component; the value for the critical coupling is determined through a solution of the {open_quote}{open_quote}semirelativistic{close_quote}{close_quote} Coulomb problem. These limits place important constraints on the interaction and suggest that a more sophisticated <span class="hlt">model</span> is needed to describe the light and heavy quarkonia. {copyright} {ital 1996 The American Physical Society.}</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/14103','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/14103"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Large-Scale Incompressible Flow Calculations on Massively Parallel Computers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>LEHOUCQ,RICHARD B.; ROMERO,LOUIS; SALINGER,ANDREW G.</p> <p>1999-10-25</p> <p>A set of linear and nonlinear <span class="hlt">stability</span> <span class="hlt">analysis</span> tools have been developed to analyze steady state incompressible flows in 3D geometries. The algorithms have been implemented to be scalable to hundreds of parallel processors. The linear <span class="hlt">stability</span> of steady state flows are determined by calculating the rightmost eigenvalues of the associated generalize eigenvalue problem. Nonlinear <span class="hlt">stability</span> is studied by bifurcation <span class="hlt">analysis</span> techniques. The boundaries between desirable and undesirable operating conditions are determined for buoyant flow in the rotating disk CVD reactor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009CNSNS..14..351N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009CNSNS..14..351N"><span id="translatedtitle">Bifurcation <span class="hlt">analysis</span> of parametrically excited bipolar disorder <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nana, Laurent</p> <p>2009-02-01</p> <p>Bipolar II disorder is characterized by alternating hypomanic and major depressive episode. We <span class="hlt">model</span> the periodic mood variations of a bipolar II patient with a negatively damped harmonic oscillator. The medications administrated to the patient are <span class="hlt">modeled</span> via a forcing function that is capable of <span class="hlt">stabilizing</span> the mood variations and of varying their amplitude. We analyze analytically, using perturbation method, the amplitude and <span class="hlt">stability</span> of limit cycles and check this <span class="hlt">analysis</span> with numerical simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920032730&hterms=Bertolotti&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBertolotti','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920032730&hterms=Bertolotti&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBertolotti"><span id="translatedtitle"><span class="hlt">Analysis</span> of the linear <span class="hlt">stability</span> of compressible boundary layers using the PSE. [parabolic <span class="hlt">stability</span> equations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bertolotti, F. P.; Herbert, TH.</p> <p>1991-01-01</p> <p>The application of linearized parabolic <span class="hlt">stability</span> equations (PSE) to compressible flow is considered. The effect of mean-flow nonparallelism is found to be weak on 2D waves and strong on 3D waves. Results for a single choice of free-stream parameters that corresponds to the atmospheric conditions at 15,000 m above sea level are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011SPIE.7752E..0HW','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011SPIE.7752E..0HW"><span id="translatedtitle">The study of landscape <span class="hlt">stability</span> in Yuli County by principal component <span class="hlt">analysis</span> method based on RS and GIS technology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Qianfeng; Zhou, Kefa; Sun, Li; Chen, Limou; Ou, Yang; Li, Guangyu; Qin, Yanfang; Wang, Jinlin</p> <p>2011-02-01</p> <p>In order to evaluate quantitatively the landscape <span class="hlt">stability</span> of arid areas, a study area was selected in Yuli county of the middle and lower reaches of Tarim river. Remote sensing image data are the main data sources, the image data are processed by the support of RS and GIS technology. The study extracted 11 indices of landscape <span class="hlt">stability</span> by FRAGSTATS software, and the standard matrix of these indices data are got using Z-Score method, then the comprehensive evaluation <span class="hlt">model</span> of landscape <span class="hlt">stability</span> is constructed by principal component <span class="hlt">analysis</span> method. The study results showed that the range of comprehensive evaluation scores of Yuli's ecological landscape <span class="hlt">stability</span> is 1.736, which indicated there is a great variation in ecological landscape <span class="hlt">stability</span> of study area. The <span class="hlt">stability</span> declines as the following order: forest land - water area- grass land- cultivated land - buildup land -unused land. The landscape <span class="hlt">stability</span> is always the key scientific issues which should be solved urgently, the study on landscape <span class="hlt">stability</span> has important theoretical and practical significance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995MsT..........5S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995MsT..........5S"><span id="translatedtitle">Performance <span class="hlt">analysis</span> of a GPS Interferometric attitude determination system for a gravity gradient <span class="hlt">stabilized</span> spacecraft</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stoll, John C.</p> <p>1995-05-01</p> <p>The performance of an unaided attitude determination system based on GPS interferometry is examined using linear covariance <span class="hlt">analysis</span>. The <span class="hlt">modelled</span> system includes four GPS antennae onboard a gravity gradient <span class="hlt">stabilized</span> spacecraft, specifically the Air Force's RADCAL satellite. The principal error sources are identified and <span class="hlt">modelled</span>. The optimal system's sensitivities to these error sources are examined through an error budget and by varying system parameters. The effects of two satellite selection algorithms, Geometric and Attitude Dilution of Precision (GDOP and ADOP, respectively) are examined. The attitude performance of two optimal-suboptimal filters is also presented. Based on this <span class="hlt">analysis</span>, the limiting factors in attitude accuracy are the knowledge of the relative antenna locations, the electrical path lengths from the antennae to the receiver, and the multipath environment. The performance of the system is found to be fairly insensitive to torque errors, orbital inclination, and the two satellite geometry figures-of-merit tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012NucFu..52g4003W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012NucFu..52g4003W"><span id="translatedtitle">Control-oriented <span class="hlt">modelling</span> for neoclassical tearing mode <span class="hlt">stabilization</span> via minimum-seeking techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wehner, W.; Schuster, E.</p> <p>2012-07-01</p> <p>Suppression of magnetic islands driven by the neoclassical tearing mode (NTM) is necessary for efficient and sustained operation of tokamak fusion reactors. Compensating for the lack of bootstrap current, due to the pressure profile flattening in the magnetic island, by a localized electron cyclotron current drive (ECCD) has been proved experimentally as an effective method to <span class="hlt">stabilize</span> NTMs. The effectiveness of this method is limited in practice by the uncertainties in the width of the island, the relative position between the island and the beam, and the ECCD power threshold for NTM <span class="hlt">stabilization</span>. Heuristic search and suppress algorithms have been proposed and shown effective in improving the alignment of the ECCD beam with the island, using only an estimate of the island width. Making use of this estimate, real-time, non-<span class="hlt">model</span>-based, extremum-seeking optimization algorithms have also been proposed not only for beam steering but also for power modulation in order to minimize the island-beam misalignment and the time required for NTM <span class="hlt">stabilization</span>. A control-oriented dynamic <span class="hlt">model</span> for the effect of ECCD on the magnetic island is proposed in this work to enable both control design and performance <span class="hlt">analysis</span> of these minimum-seeking type of controllers. The <span class="hlt">model</span> expands previous work by including the impact of beam modulation parameters such as the island-beam phase mismatch and the beam duty-cycle on the island width dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....9117V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....9117V"><span id="translatedtitle">Establishing the hydrological influence of vegetation on slope <span class="hlt">stability</span>: a <span class="hlt">modelling</span> approach in eco-engineering</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van Beek, L. P. H.; Bogaard, T. A.; van Asch, Th. W.</p> <p>2003-04-01</p> <p>Contrary to the beneficial mechanical effect of root reinforcement, the hydrological influence of vegetation are neither exclusively positive or negative with regards to slope <span class="hlt">stability</span>. The net effect of vegetation on the hillslope scale is consequently difficult to establish and experimental data to test relevant hypotheses at the hillslope scale are thinly sown. Notwithstanding the limited amount of field data, eco-engineers, planners and decision makers need reliable information to evaluate the possible hydrological effects of changes in the vegetation cover or management strategies. Physically-based <span class="hlt">modelling</span> can provide a solution to this problem by rigorous evaluation of the influence of the various hydrological processes that are related to vegetation. The proposed approach establishes the hydrological influence of vegetation on slope <span class="hlt">stability</span> by means of a sensitivity <span class="hlt">analysis</span>. The input for the sensitivity <span class="hlt">analysis</span> is specified by an idealised slope. This slope is based on several existing slopes subject to landsliding and considers a range of typical soil, slope and vegetation conditions. This allows for the identification of those conditions under which vegetation may have a positive, hydrological influence on slope <span class="hlt">stability</span> by attenuation of the hydrological response after potentially triggering events. However, uncertainty is introduced by the <span class="hlt">models</span> themselves since they are merely approximations of reality. Moreover, the natural variability in input data and the way in which these data are treated will affect the reliability of the <span class="hlt">model</span> outcome. These effects of uncertainty on the <span class="hlt">model</span> outcome must be assessed before it can be applied with confidence in the decision making process. In order to study the effects of uncertainty, several transient 2-D hydrological <span class="hlt">models</span> of varying complexity have been applied to the idealised slope (water balance approach and FEM). Data from the idealised slope have been used to specify conditions that range from transient and spatially distributed to steady-state and lumped. This results in a range of complexity and detail at which the hydrological influence of vegetation is <span class="hlt">modelled</span>. The results are used to define what level of <span class="hlt">model</span> complexity is warranted by readily available data and to establish to which extent uncertainty affects the reliability of the <span class="hlt">model</span> outcome. This hydrological <span class="hlt">modelling</span> approach in eco-engineering is part of the EU-funded ECOSLOPES project which studies the effects of vegetation on the mechanical and hydrological aspects on slope <span class="hlt">stability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6764669','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6764669"><span id="translatedtitle"><span class="hlt">Analysis</span> of relationship between <span class="hlt">stability</span> and flow parameters in a BWR</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Upadhyaya, B.R.; Kitamura, M.</p> <p>1980-01-01</p> <p>Results of quantitative <span class="hlt">analysis</span> of mutual relationship between the BWR <span class="hlt">stability</span> and channel steam velocity are presented. The <span class="hlt">stability</span> parameter, defined by the damping ratio, and the steam velocity are estimated by <span class="hlt">analysis</span> of neutron noise data from local power range monitor (LPRM) detector signals. These parameters are treated as varying randomly as a function of time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=197122','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=197122"><span id="translatedtitle">LONG-TERM <span class="hlt">STABILITY</span> OF FOOD PATTERNS IDENTIFIED BY USE OF FACTOR <span class="hlt">ANALYSIS</span> AMONG SWEDISH WOMEN</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Limited data exist on the reproducibility of food patterns measured using factor <span class="hlt">analysis</span>, as well as the <span class="hlt">stability</span> of patterns over time. Our primary objective was to explore the long-term <span class="hlt">stability</span> of food patterns derived using confirmatory factor <span class="hlt">analysis</span> among 33,840 women participating in the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title40-vol32/pdf/CFR-2010-title40-vol32-sec1065-190.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title40-vol32/pdf/CFR-2010-title40-vol32-sec1065-190.pdf"><span id="translatedtitle">40 CFR 1065.190 - PM-<span class="hlt">stabilization</span> and weighing environments for gravimetric <span class="hlt">analysis</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-07-01</p> <p>... 40 Protection of Environment 32 2010-07-01 2010-07-01 false PM-<span class="hlt">stabilization</span> and weighing environments for gravimetric <span class="hlt">analysis</span>. 1065.190 Section 1065.190 Protection of Environment ENVIRONMENTAL... § 1065.190 PM-<span class="hlt">stabilization</span> and weighing environments for gravimetric <span class="hlt">analysis</span>. (a) This...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930091902','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930091902"><span id="translatedtitle"><span class="hlt">Analysis</span> of wind-tunnel <span class="hlt">stability</span> and control tests in terms of flying qualities of full-scale airplanes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kayten, Gerald G</p> <p>1945-01-01</p> <p>The <span class="hlt">analysis</span> of results of wind-tunnel <span class="hlt">stability</span> and control tests of powered airplane <span class="hlt">models</span> in terms of the flying qualities of full-scale airplanes is advocated. In order to indicated the topics upon which comments are considered desirable in the report of a wind-tunnel <span class="hlt">stability</span> and control investigation and to demonstrate the nature of the suggested <span class="hlt">analysis</span>, the present NACA flying-qualities requirements are discussed in relation to wind-tunnel tests. General procedures for the estimation of flying qualities from wind-tunnel tests are outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1232133-model-analysis-toolkit','SCIGOV-ESTSC'); return false;" href="http://www.osti.gov/scitech/biblio/1232133-model-analysis-toolkit"><span id="translatedtitle"><span class="hlt">Model</span> <span class="hlt">Analysis</span> ToolKit</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech/">Energy Science and Technology Software Center (ESTSC)</a></p> <p></p> <p>2015-05-15</p> <p>MATK provides basic functionality to facilitate <span class="hlt">model</span> <span class="hlt">analysis</span> within the Python computational environment. <span class="hlt">Model</span> <span class="hlt">analysis</span> setup within MATK includes: - define parameters - define observations - define <span class="hlt">model</span> (python function) - define samplesets (sets of parameter combinations) Currently supported functionality includes: - forward <span class="hlt">model</span> runs - Latin-Hypercube sampling of parameters - multi-dimensional parameter studies - parallel execution of parameter samples - <span class="hlt">model</span> calibration using internal Levenberg-Marquardt algorithm - <span class="hlt">model</span> calibration using lmfit package - modelmore » calibration using levmar package - Markov Chain Monte Carlo using pymc package MATK facilitates <span class="hlt">model</span> <span class="hlt">analysis</span> using: - scipy - calibration (scipy.optimize) - rpy2 - Python interface to R« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25410686','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25410686"><span id="translatedtitle">On the linear <span class="hlt">stability</span> of blood flow through <span class="hlt">model</span> capillary networks.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Davis, Jeffrey M</p> <p>2014-12-01</p> <p>Under the approximation that blood behaves as a continuum, a numerical implementation is presented to analyze the linear <span class="hlt">stability</span> of capillary blood flow through <span class="hlt">model</span> tree and honeycomb networks that are based on the microvascular structures of biological tissues. The tree network is comprised of a cascade of diverging bifurcations, in which a parent vessel bifurcates into two descendent vessels, while the honeycomb network also contains converging bifurcations, in which two parent vessels merge into one descendent vessel. At diverging bifurcations, a cell partitioning law is required to account for the nonuniform distribution of red blood cells as a function of the flow rate of blood into each descendent vessel. A linearization of the governing equations produces a system of delay differential equations involving the discharge hematocrit entering each network vessel and leads to a nonlinear eigenvalue problem. All eigenvalues in a specified region of the complex plane are captured using a transformation based on contour integrals to construct a linear eigenvalue problem with identical eigenvalues, which are then determined using a standard QR algorithm. The predicted value of the dimensionless exponent in the cell partitioning law at the instability threshold corresponds to a supercritical Hopf bifurcation in numerical simulations of the equations governing unsteady blood flow. Excellent agreement is found between the predictions of the linear <span class="hlt">stability</span> <span class="hlt">analysis</span> and nonlinear simulations. The relaxation of the assumption of plug flow made in previous <span class="hlt">stability</span> analyses typically has a small, quantitative effect on the <span class="hlt">stability</span> results that depends on the specific network structure. This implementation of the <span class="hlt">stability</span> <span class="hlt">analysis</span> can be applied to large networks with arbitrary structure provided only that the connectivity among the network segments is known. PMID:25410686</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20050205815&hterms=Tube&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DTube','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20050205815&hterms=Tube&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DTube"><span id="translatedtitle">Experimentation and <span class="hlt">Modeling</span> of Jet A Thermal <span class="hlt">Stability</span> in a Heated Tube</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Khodabandeh, Julia W.</p> <p>2005-01-01</p> <p>High performance aircraft typically use hydrocarbon fuel to regeneratively cool the airframe and engine components. As the coolant temperatures increase, the fuel may react with dissolved oxygen forming deposits that limit the regenerative cooling system performance. This study investigates the deposition of Jet A using a thermal <span class="hlt">stability</span> experiment and computational fluid dynamics (CFD) <span class="hlt">modeling</span>. The experimental portion of this study is performed with a high Reynolds number thermal <span class="hlt">stability</span> (HiRets) tester in which fuel passes though an electrically heated tube and the fuel outlet temperature is held constant. If the thermal <span class="hlt">stability</span> temperature of the fuel is exceeded, deposits form and adhere to the inside of the tube creating an insulating layer between the tube and the fuel. The HiRets tester measures the tube outer wall temperatures near the fuel outlet to report the effect of deposition occurring inside the tube. Final deposits are also estimated with a carbon burn off <span class="hlt">analysis</span>. The CFD <span class="hlt">model</span> was developed and used to simulate the fluid dynamics, heat transfer, chemistry, and transport of the deposit precursors. The <span class="hlt">model</span> is calibrated to the experiment temperature results and carbon burn-off deposition results. The <span class="hlt">model</span> results show that the dominant factor in deposition is the heated wall temperature and that most of the deposits are formed in the laminar sublayer. The <span class="hlt">models</span> predicted a 7.0E-6 kilograms per square meter-sec deposition rate, which compared well to the carbon burn-off <span class="hlt">analysis</span> deposition rate of 1.0E-6 kilograms per square meter-sec.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=126617&keyword=transformer&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=58627613&CFTOKEN=62276985','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=126617&keyword=transformer&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=58627613&CFTOKEN=62276985"><span id="translatedtitle">APPLICATIONS <span class="hlt">ANALYSIS</span> REPORT: CHEMFIX TECHNOLOGIES, INC. - SOLIDIFICATION/<span class="hlt">STABILIZATION</span> PROCESS</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>In support of the U.S. Environmental Protection Agency's (EPA) Superfund Innovative Technology Evaluation (SITE) Program, this report evaluates the Chemfix Technologies, Inc. (Chemfix), solidification/<span class="hlt">stabilization</span> technology for on-site treatment of hazardous waste. The Chemfix ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/420360','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/420360"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of a variable-speed wind turbine</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bir, G.S.; Wright, A.D.; Butterfield, C.P.</p> <p>1996-10-01</p> <p>This paper examines the elastomechanical <span class="hlt">stability</span> of a four-bladed wind turbine over a specific rotor speed range. <span class="hlt">Stability</span> modes, frequencies, and dampings are extracted using a specialized modal processor developed at NREL that post-processes the response data generated by the ADAMS simulation code. The processor can analyze a turbine with an arbitrary number of rotor blades and offers a novel capability of isolating <span class="hlt">stability</span> modes that become locked at a single frequency. Results indicate that over a certain rotor speed range, the tower lateral mode and the rotor regressive in-plane mode coalesce, resulting in a self-excited instability. Additional results show the effect of tower and nacelle parameters on the <span class="hlt">stability</span> boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014FlDyR..46f1401C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014FlDyR..46f1401C"><span id="translatedtitle">Vortex <span class="hlt">stability</span> in a multi-layer quasi-geostrophic <span class="hlt">model</span>: application to Mediterranean Water eddies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carton, Xavier; Sokolovskiy, Mikhail; Mnesguen, Claire; Aguiar, Ana; Meunier, Thomas</p> <p>2014-12-01</p> <p>The <span class="hlt">stability</span> of circular vortices to normal mode perturbations is studied in a multi-layer quasi-geostrophic <span class="hlt">model</span>. The stratification is fitted on the Gulf of Cadiz where many Mediterranean Water (MW) eddies are generated. Observations of MW eddies are used to determine the parameters of the reference experiment; sensitivity tests are conducted around this basic case. The objective of the study is two-fold: (a) determine the growth rates and nonlinear evolutions of unstable perturbations for different three-dimensional (3D) velocity structures of the vortices, (b) check if the different structure of our idealized vortices, mimicking MW cyclones and anticyclones, can induce different <span class="hlt">stability</span> properties in a <span class="hlt">model</span> that conserves parity symmetry, and apply these results to observed MW eddies. The linear <span class="hlt">stability</span> <span class="hlt">analysis</span> reveals that, among many 3D distributions of velocity, the observed eddies are close to maximal <span class="hlt">stability</span>, with instability time scales longer than 100 days (these time scales would be less than 10 days for vertically more sheared eddies). The elliptical deformation is most unstable for realistic eddies (the antisymmetric one dominates for small eddies and the triangular one for large eddies); the antisymmetric mode is stronger for cyclones than for anticyclones. Nonlinear evolutions of eddies with radii of about 30 km, and elliptically perturbed, lead to their re-organization into 3D tripoles; smaller eddies are stable and larger eddies break into 3D dipoles. Horizontally more sheared eddies are more unstable and sustain more asymmetric instabilities. In summary, few differences were found between cyclone and anticyclone <span class="hlt">stability</span>, except for strong horizontal velocity shears.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986PhyA..139..412V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986PhyA..139..412V"><span id="translatedtitle">Limits of <span class="hlt">stability</span> of the extended water <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Royen, Eddy; Meijer, Paul H. E.</p> <p>1986-12-01</p> <p>In this paper we report the metastable states of the extended water <span class="hlt">model</span>. The framework of the computations is explained in detail; the constrained or “observed” variables are determined as function of the nonobserved order parameters, or cluster variables, and the susceptibility is expressed in terms of the Hessian of the free energy with respect to these constrained variables. Since the Hessian is of the fourth order in this <span class="hlt">model</span>, there are different possibilities for it to be zero, each associated with different spinodal. The <span class="hlt">analysis</span> of this problem was done and examples are given. The procedure used is compared with Gibbs original work on the equilibrium of heterogeneous substances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23433548','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23433548"><span id="translatedtitle">Robust <span class="hlt">stability</span> <span class="hlt">analysis</span> of genetic regulatory network with time delays.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Pin-Lin</p> <p>2013-05-01</p> <p>The robust asymptotic <span class="hlt">stability</span> problem of genetic regulatory networks with time delays is investigated by Lyapunov functional approach and linear matrix inequality techniques (LMIs). <span class="hlt">Stability</span> criteria for the delayed genetic regulatory networks are expressed as a set of LMIs, yielding much less conservative analytic results. New criteria with reduced conservatism are obtained and they involve less matrix parameters than the existing ones. Finally, three numerical examples are presented to illustrate effectiveness and less conservative results. PMID:23433548</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvB..91p5433C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvB..91p5433C"><span id="translatedtitle">Relative <span class="hlt">stability</span> and local curvature <span class="hlt">analysis</span> in carbon nanotori</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chuang, Chern; Guan, Jie; Witalka, David; Zhu, Zhen; Jin, Bih-Yaw; Tomnek, David</p> <p>2015-04-01</p> <p>We introduce a concise formalism to characterize nanometer-sized tori based on carbon nanotubes and to determine their <span class="hlt">stability</span> by combining ab initio density functional calculations with a continuum elasticity theory approach that requires only shape information. We find that the high strain energy in nanotori containing only hexagonal rings is significantly reduced in nanotori containing also other polygons. Our approach allows to determine local curvature and link it to local strain energy, which is correlated with local <span class="hlt">stability</span> and chemical reactivity.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/7237386','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/7237386"><span id="translatedtitle">(Research <span class="hlt">stability</span> <span class="hlt">analysis</span> of fluidized-bed equations)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1991-01-01</p> <p>In previous reports we have outlined the equations governing the flow of a mixture of a fluid infused with solid particles, the equations governing the state of uniform fluidization and the equation governing the linearized <span class="hlt">stability</span> of the state of uniform fluidization. We have also discussed how material function {beta}{sub 01}, the pressure like term, i.e., the spherical part of the stress tensor for the solid constituent, could play a <span class="hlt">stabilizing</span> role. We have carried out the optimization study for the <span class="hlt">stability</span> equations and have obtained bounds for this material function {beta}{sub 01}, which will ensure the <span class="hlt">stability</span> of the state of uniform fluidization for a range of values for the other material parameters. Here, we provide few preliminary results which show the effect of different material parameters on the <span class="hlt">stability</span> of the state of uniform fluidization. Figures (1) through (10) show the variation of the root of the characteristic equation with the wave number, {sigma}. Negative values for the root implies that the flow is stabe and positive values that the flow is unstable. For the sake of completeness, we provide the section on <span class="hlt">stability</span> which can also be found in our previous report.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013CompM..51..949B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013CompM..51..949B"><span id="translatedtitle">Improvement of <span class="hlt">stability</span> conditions, accuracy and uniqueness of penalty approach in contact <span class="hlt">modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bednarek, Tomasz; Kowalczyk, Piotr</p> <p>2013-06-01</p> <p>The main objective of this paper is to improve <span class="hlt">stability</span> conditions, uniqueness and convergence of numerical <span class="hlt">analysis</span> of metal forming processes with contact constraints enforced by the penalty method. A commonly known drawback of this approach is the choice of penalty factor values. When assumed too low, they result in inaccurate fulfillment of the constraints while when assumed too high, they lead to ill-conditioning of the equations system which affects <span class="hlt">stability</span> and uniqueness of the solution. The proposed modification of the penalty algorithm consists in adaptive estimation of the penalty factor values for the particular system of finite element equations and for the assumed allowed inaccuracy in fulfillment of the contact constraints. The algorithm is tested on realistic examples of sheet metal forming. The finite element code based on flow approach formulation (for rigid-plastic and rigid-viscoplastic material <span class="hlt">model</span>) has been used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MPLB...2950097Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MPLB...2950097Z"><span id="translatedtitle">Traffic <span class="hlt">stability</span> of a car-following <span class="hlt">model</span> considering driver’s desired velocity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Geng; Sun, Di-Hua; Liu, Wei-Ning; Liu, Hui</p> <p>2015-07-01</p> <p>In this paper, a new car-following <span class="hlt">model</span> is proposed by considering driver’s desired velocity according to Transportation Cyber Physical Systems. The effect of driver’s desired velocity on traffic flow has been investigated through linear <span class="hlt">stability</span> theory and nonlinear reductive perturbation method. The linear <span class="hlt">stability</span> condition shows that driver’s desired velocity effect can enlarge the stable region of traffic flow. From nonlinear <span class="hlt">analysis</span>, the Burgers equation and mKdV equation are derived to describe the evolution properties of traffic density waves in the stable and unstable regions respectively. Numerical simulation is carried out to verify the analytical results, which reveals that traffic congestion can be suppressed efficiently by taking driver’s desired velocity effect into account.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730021264','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730021264"><span id="translatedtitle">An experimental investigation of vortex <span class="hlt">stability</span>, tip shapes, compressibility, and noise for hovering <span class="hlt">model</span> rotors</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tangler, J. L.; Wohlfeld, R. M.; Miley, S. J.</p> <p>1973-01-01</p> <p>Schlieren methods of flow visualization and hot-wire anemometry for velocity measurements were used to investigate the wakes generated by hovering <span class="hlt">model</span> propellers and rotors. The research program was directed toward investigating (1) the <span class="hlt">stability</span> of the tip vortex, (2) the effects produced by various tip shapes on performance and tip vortex characteristics, and (3) the shock formation and noise characteristics associated with various tip shapes. A free-wake <span class="hlt">analysis</span> was also conducted for comparison with the vortex <span class="hlt">stability</span> experimental results. Schlieren photographs showing wake asymmetry, interaction, and instability are presented along with a discussion of the effects produced by the number of blades, collective pitch, and tip speed. Two hot-wire anemometer techniques, used to measure the maximum circumferential velocity in the tip vortex, are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/10131323','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/10131323"><span id="translatedtitle">CG-DAMS: Concrete gravity dam <span class="hlt">stability</span> <span class="hlt">analysis</span> software. Application manual, final report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1993-01-01</p> <p>CG-DAMS is a finite element based program written specifically for the <span class="hlt">stability</span> <span class="hlt">analysis</span> of concrete gravity dams. The code automates the prediction and evaluation of cracking in the dam, along the dam-rock interface, and in the foundation using incremental nonlinear <span class="hlt">analysis</span> techniques based on the ``smeared crack`` approach. Its primary application is in the computation of dam-rock interface sliding <span class="hlt">stability</span> factors of safety. The automated procedure for crack propagation <span class="hlt">analysis</span> replaces the trial-and-error cracked-base <span class="hlt">analysis</span> method commonly used in gravity dam safety analyses. This Application manual of CG-DAMS illustrates, through sample problems, the many features of the software. Example problems illustrate the capabilities of both CG-DAMS-PC and CG-DAMS-ABAQUS. CG-DAMS-PC is a menu driven program that runs on 386/486 PCs under the DOS operating system (4 Megabytes RAM, 25 Megabytes of hard disk space). CG-DAMS-ABAQUS is a pre- and post-processor along with a concrete constitutive <span class="hlt">model</span> and distributed load module that interfaces with the ABAQUS general purpose finite element program. The PC program contains thermal <span class="hlt">analysis</span> capabilities, a rough crack constitutive <span class="hlt">model</span>, and an interface to the CRFLOOD software not available with the ABAQUS version. The CG-DAMS-ABAQUS program contains time marching dynamic <span class="hlt">analysis</span> capabilities not available with the PC program. Example analyses presented include static, pseudo dynamic, and time marching dynamic analyses. The manual also presents sensitivity evaluations on mesh size and foundation material strength. Comparisons are presented between CG-DAMS and gravity method calculations. Comparisons with other finite element software are included for the dynamic time history analyses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000APS..DPPMP1141R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000APS..DPPMP1141R"><span id="translatedtitle"><span class="hlt">Modeling</span> of Neoclassical Tearing Mode <span class="hlt">Stability</span> for NSTX</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rosenberg, A.; Gates, D.; Pletzer, A.; Hegna, C.; Kruger, S.</p> <p>2000-10-01</p> <p>Neoclassical tearing modes (NTMs) can lead to disruption and loss of confinement. Previous <span class="hlt">analysis</span> of these modes used large aspect ratio, low ? approximations to determine the effect of NTMs on tokamak plasmas. A more accurate tool is needed to predict the onset of these instabilities. As a follow-up to recent theoretical work, a code has been written which computes the tearing mode island growth rate for arbitrary tokamak geometry. It calls PEST-3 to compute ?^', the resistive MHD matching parameter. The code also calls routines in NIMROD for D_nc, DI and D_R, which are the bootstrap current driven term and the ideal and resistive interchange mode criterion, respectively. In addition to these components, the NIMROD routines calculate ?_s-H, a new correction to the Pfirsch-Schlter term. Finite parallel transport effects were added and threshold island widths for several NSTX equilibria were determined. Another program takes the output of PEST-3 and allows the user to specify the rational surface, island width, and amount of detail near the perturbed surface to visualize the total helical flux. The results of this work will determine the <span class="hlt">stability</span> of NTMs in an ST plasma with greater accuracy than previously achieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002CPL...358..383F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002CPL...358..383F"><span id="translatedtitle">Computer-aided molecular <span class="hlt">modeling</span> techniques for predicting the <span class="hlt">stability</span> of drug cyclodextrin inclusion complexes in aqueous solutions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faucci, Maria Teresa; Melani, Fabrizio; Mura, Paola</p> <p>2002-06-01</p> <p>Molecular <span class="hlt">modeling</span> was used to investigate factors influencing complex formation between cyclodextrins and guest molecules and predict their <span class="hlt">stability</span> through a theoretical <span class="hlt">model</span> based on the search for a correlation between experimental <span class="hlt">stability</span> constants ( Ks) and some theoretical parameters describing complexation (docking energy, host-guest contact surfaces, intermolecular interaction fields) calculated from complex structures at a minimum conformational energy, obtained through stochastic methods based on molecular dynamic simulations. Naproxen, ibuprofen, ketoprofen and ibuproxam were used as <span class="hlt">model</span> drug molecules. Multiple Regression <span class="hlt">Analysis</span> allowed identification of the significant factors for the complex <span class="hlt">stability</span>. A mathematical <span class="hlt">model</span> ( r=0.897) related log Ks with complex docking energy and lipophilic molecular fields of cyclodextrin and drug.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JPhCS.259a2034G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JPhCS.259a2034G"><span id="translatedtitle"><span class="hlt">Stability</span> of gravity-scalar systems for domain-wall <span class="hlt">models</span> with a soft wall</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>George, Damien P.</p> <p>2010-11-01</p> <p>We show that it is possible to create an RS soft-wall <span class="hlt">model</span>, a <span class="hlt">model</span> with a compact extra dimension, without using fundamental branes. All that is required are bulk scalar fields minimally coupled to gravity. Of crucial importance is the <span class="hlt">stability</span> of the size of the extra dimension. Without branes, one cannot easily implement the Goldberger-Wise mechanism, and instead it must be shown that the scalar configuration is stable in its own right. We use the superpotential approach for generating solutions, the so called 'fake supergravity' scenario, and show that configurations generated in such a way are always free of tachyonic modes. Furthermore, we show that the <span class="hlt">model</span> is also free of zero modes (in the spin-0 sector) if all the scalars have odd parity. We discuss the hierarchy problem in soft-wall <span class="hlt">models</span>, and applications of our <span class="hlt">analysis</span> to the AdS/QCD correspondence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=240497','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=240497"><span id="translatedtitle">Incorporating seepage processes into a streambank <span class="hlt">stability</span> <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Seepage processes are usually neglected in bank <span class="hlt">stability</span> analyses although they can become a prominent failure mechanism under certain field conditions. This study incorporated the effects of seepage (i.e., seepage gradient forces and seepage erosion undercutting) into the Bank <span class="hlt">Stability</span> and Toe Er...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1412013O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1412013O"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">Analysis</span> of CO2-Brine Immiscible Displacement</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ott, H.; Berg, S.</p> <p>2012-04-01</p> <p>The viscous <span class="hlt">stability</span> of the primary drainage process is of major interest for the injection of carbon dioxide (CO2) in saline aquifers, since it determines the spread of the CO2 plume in the target aquifer and consequently the initial utilization of the pore space for CO2 storage. In order to analyze the <span class="hlt">stability</span> of the displacement process, the relative permeability saturation functions must be known; these are usually derived by experiments under conditions representative for the field. It is therefore very important to characterize the flood front <span class="hlt">stability</span>, not only on the field scale but also on the experimental scale, in order to judge the validity of the experimental results as a precondition for reliable field simulations. Here we investigate the onset of viscous fingering, thereby studying under what conditions CO2-brine displacement remains stable. We discuss the role of relative permeability and the <span class="hlt">stabilizing</span> effect of capillary pressure at different length scales by means of numerical simulations. The results allow us to assess different definitions of the mobility ratio and establish criteria for judging the <span class="hlt">stability</span> of the displacement process. We further show that in cases where gravitational forces are important, the gravity tongue dominates the fingering pattern, and unstable situations can occur where <span class="hlt">stability</span> would be predicted, by considering viscous and capillary forces only. The application of our findings is not limited to CO2-brine displacement. The criteria for <span class="hlt">stability</span> can be applied to most two-phase flow problems in reservoir engineering in general ranging from water flooding to low interfacial tension surfactant flooding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JCli...18..514L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JCli...18..514L"><span id="translatedtitle">Thermohaline Circulation <span class="hlt">Stability</span>: A Box <span class="hlt">Model</span> Study. Part II: Coupled Atmosphere-Ocean <span class="hlt">Model</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lucarini, Valerio; Stone, Peter H.</p> <p>2005-02-01</p> <p>A thorough <span class="hlt">analysis</span> of the <span class="hlt">stability</span> of a coupled version of an interhemispheric three-box <span class="hlt">model</span> of thermohaline circulation (THC) is presented. This study follows a similarly structured <span class="hlt">analysis</span> of an uncoupled version of the same <span class="hlt">model</span> presented in Part I of this paper. The <span class="hlt">model</span> consists of a northern high-latitude box, a tropical box, and a southern high-latitude box, which can be thought of as corresponding to the northern, tropical, and southern Atlantic Ocean, respectively. This paper examines how the strength of THC changes when the system undergoes forcings representing global warming conditions.Since a coupled <span class="hlt">model</span> is used, a direct representation of the radiative forcing is possible because the main atmospheric physical processes responsible for freshwater and heat fluxes are formulated separately. Each perturbation to the initial equilibrium is characterized by the total radiative forcing realized, by the rate of increase, and by the north-south asymmetry. Although only weakly asymmetric or symmetric radiative forcings are representative of physically reasonable conditions, general asymmetric forcings are considered in order to get a more complete picture of the mathematical properties of the system. The choice of suitably defined metrics makes it possible to determine the boundary dividing the set of radiative forcing scenarios that lead the system to equilibria characterized by a THC pattern similar to the present one, from those that drive the system to equilibria where the THC is reversed. This paper also considers different choices for the atmospheric transport parameterizations and for the ratio between the high-latitude and tropical radiative forcing. It is generally found that fast forcings are more effective than slow forcings in disrupting the present THC pattern, forcings that are stronger in the northern box are also more effective in destabilizing the system, and very slow forcings do not destabilize the system whatever their asymmetry, unless the radiative forcings are very asymmetric and the atmospheric transport is a relatively weak function of the meridional temperature gradient. In this latter case some relevant hysteresis graphs of the system are presented. The changes in the strength of the THC are primarily forced by changes in the latent heat transport in the hemisphere because of its sensitivity to temperature, which arises from the Clausius-Clapeyron relation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/12786239','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/12786239"><span id="translatedtitle">Bifurcation and <span class="hlt">stability</span> <span class="hlt">analysis</span> of rotating chemical spirals in circular domains: boundary-induced meandering and <span class="hlt">stabilization</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Br, Markus; Bangia, Anil K; Kevrekidis, Ioannis G</p> <p>2003-05-01</p> <p>Recent experimental and <span class="hlt">model</span> studies have revealed that the domain size may strongly influence the dynamics of rotating spirals in two-dimensional pattern forming chemical reactions. Hartmann et al. [Phys. Rev. Lett. 76, 1384 (1996)], report a frequency increase of spirals in circular domains with diameters substantially smaller than the spiral wavelength in a large domain for the catalytic NO+CO reaction on a microstructured platinum surface. Accompanying simulations with a simple reaction-diffusion system reproduced the behavior. Here, we supplement these studies by a numerical bifurcation and <span class="hlt">stability</span> <span class="hlt">analysis</span> of rotating spirals in a simple activator-inhibitor <span class="hlt">model</span>. The problem is solved in a co-rotating frame of reference. No-flux conditions are imposed at the boundary of the circular domain. At large domain sizes, eigenvalues and eigenvectors very close to those corresponding to infinite medium translational invariance are observed. Upon decrease of domain size, we observe a simultaneous change in the rotation frequency and a deviation of these eigenvalues from being neutrally stable (zero real part). The latter phenomenon indicates that the translation symmetry of the spiral solution is appreciably broken due to the interaction with the (now nearby) wall. Various dynamical regimes are found: first, the spiral simply tries to avoid the boundary and its tip moves towards the center of the circular domain corresponding to a negative real part of the "translational" eigenvalues. This effect is noticeable at a domain radius of R<R(cr,1). The spiral subsequently exhibits an oscillatory instability: the tip trajectory displays a meandering motion, which may be characterized as boundary-induced spiral meandering. A systematic study of the spiral rotation as a function of a control parameter and the domain size reveals that the meandering instability in large domains becomes suppressed, and the spiral rotation becomes rigid, at a critical radius R(cr,0). Boundary-induced meandering arises below a second critical radius R(cr,2)<R(cr,0). PMID:12786239</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..MARG45010H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..MARG45010H"><span id="translatedtitle">Electrochemical <span class="hlt">Stability</span> of <span class="hlt">Model</span> Polymer Electrolyte/Electrode Interfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hallinan, Daniel; Yang, Guang</p> <p>2015-03-01</p> <p>Polymer electrolytes are promising materials for high energy density rechargeable batteries. However, typical polymer electrolytes are not electrochemically stable at the charging voltage of advanced positive electrode materials. Although not yet reported in literature, decomposition is expected to adversely affect the performance and lifetime of polymer-electrolyte-based batteries. In an attempt to better understand polymer electrolyte oxidation and design stable polymer electrolyte/positive electrode interfaces, we are studying electron transfer across <span class="hlt">model</span> interfaces comprising gold nanoparticles and organic protecting ligands assembled into monolayer films. Gold nanoparticles provide large interfacial surface area yielding a measurable electrochemical signal. They are inert and hence non-reactive with most polymer electrolytes and lithium salts. The surface can be easily modified with ligands of different chemistry and molecular weight. In our study, poly(ethylene oxide) (PEO) will serve as the polymer electrolyte and lithium bis(trifluoromethanesulfonyl) imide salt (LiTFSI) will be the lithium salt. The effect of ligand type and molecular weight on both optical and electrical properties of the gold nanoparticle film will be presented. Finally, the electrochemical <span class="hlt">stability</span> of the electrode/electrolyte interface and its dependence on interfacial properties will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998JApMe..37.1055M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998JApMe..37.1055M"><span id="translatedtitle">Applied <span class="hlt">Modeling</span> of Surface Fluxes under Different <span class="hlt">Stability</span> Regimes.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mohan, Manju; Siddiqui, T. A.</p> <p>1998-10-01</p> <p>In this study various surface layer parameters, fluxes, and eddy diffusivity profiles have been estimated by making use of routine meteorological data for both unstable and stable conditions. Several empirical relationships for estimating turbulence parameters are tested with data. The estimation schemes are discussed at length for both <span class="hlt">stability</span> conditions. Routine meteorological observations have been used for the computations of net radiation, sensible heat flux, friction velocity, scaling temperature in the surface layer, Monin-Obukhov length, and eddy diffusivity profiles. These parameters are important and are used for the estimation of input parameters for air quality <span class="hlt">models</span> for predicting ground-level concentrations. Special emphasis has been given to stable conditions by using recent formulations for turbulence parameters and their verification with data. Two recent schemes have been compared. About 153 h of data have been selected from the field experiments sponsored by the Electric Power Research Institute around the Kincaid Power Plant in 1980-81 for the validation of net radiation, friction velocity, and Monin-Obukhov length. Several statistical techniques have been used to assess the performance of the schemes. Based on the statistical measures, the chosen parameterization schemes are judged to perform well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AIPC.1479.1720O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AIPC.1479.1720O"><span id="translatedtitle">Joint regression <span class="hlt">analysis</span> and AMMI <span class="hlt">model</span> applied to oat improvement</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oliveira, A.; Oliveira, T. A.; Mejza, S.</p> <p>2012-09-01</p> <p>In our work we present an application of some biometrical methods useful in genotype <span class="hlt">stability</span> evaluation, namely AMMI <span class="hlt">model</span>, Joint Regression <span class="hlt">Analysis</span> (JRA) and multiple comparison tests. A genotype <span class="hlt">stability</span> <span class="hlt">analysis</span> of oat (Avena Sativa L.) grain yield was carried out using data of the Portuguese Plant Breeding Board, sample of the 22 different genotypes during the years 2002, 2003 and 2004 in six locations. In Ferreira et al. (2006) the authors state the relevance of the regression <span class="hlt">models</span> and of the Additive Main Effects and Multiplicative Interactions (AMMI) <span class="hlt">model</span>, to study and to estimate phenotypic <span class="hlt">stability</span> effects. As computational techniques we use the Zigzag algorithm to estimate the regression coefficients and the agricolae-package available in R software for AMMI <span class="hlt">model</span> <span class="hlt">analysis</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999LNES...78..147V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999LNES...78..147V"><span id="translatedtitle">A combined conceptual <span class="hlt">model</span> for the effects of fissure-induced infiltration on slope <span class="hlt">stability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van Beek, L. P. H.; van Asch, Th. W. J.</p> <p></p> <p>In humid and subhumid Mediterranean environments the disruption of the vegetation cover by in particular shallow landslides limits the area in which erodible material is exposed to overland flow. On short temporal scales the hydrological system that allows for the generation of critical pore pressures or soil moisture conditions on the potential shear surface determines the occurrence of these landslides. Hence the relative contribution of landsliding to land degradation processes can be quantified in terms of its magnitude and frequency through a semiphysical hillslope <span class="hlt">model</span> that links the relevant hydrological processes to a <span class="hlt">stability</span> <span class="hlt">analysis</span>. For the development of such a combined <span class="hlt">model</span> for hydrology and slope <span class="hlt">stability</span> a conceptualization of the process system is needed. Through the implementation of the resulting <span class="hlt">model</span> in a GIS environment the effect of topography, to which the occurrence of landslides is intrinsically linked, can be incorporated. In addition, the spatial variation of hydrological and geomechanical parameters can be incorporated in the <span class="hlt">model</span>. This is important since the occurrence and extent of shallow landslides is directly dependent on the net rainfall input in the hydrological system, as defined by the land cover of the area. In this paper a conceptual <span class="hlt">model</span> is presented that combines a description of the hydrology with an assessment of the slope <span class="hlt">stability</span>. The conceptual framework of this <span class="hlt">model</span> is based on field observations in the Alcoy area (SE Spain). In this area shallow landslides occur on steep, unsaturated slopes in marly deposits of Miocene age, at the boundary between regolith and bedrock (1-2 m depth). Given the low matric permeability of the marl it has been assumed that preferential flow along distinct sets of fissures by-passing slower matric percolation might account for the observed response time of landslides to rainfall events. The fissures in the regolith are either relict primary bedrock structures (discontinuities) or are formed by weathering, creep and shear; they are supplied with water by subsurface flow through the more permeable rootzone. With the combined slope <span class="hlt">stability</span> <span class="hlt">model</span>, which is programmed in the meta-language embedded in the PCRaster GIS package, a sensitivity <span class="hlt">analysis</span> has been performed to assess the impact of fissure flow on the occurrence of landslides in a small catchment of 1.2 km2 near Alcoy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011SPIE.8001E..0VC','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011SPIE.8001E..0VC"><span id="translatedtitle">Laser frequency <span class="hlt">stability</span>: a simple approach for a quantitative <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cabral, Alexandre; Abreu, Manuel; Rebordo, Jos M.</p> <p>2011-05-01</p> <p>The characterization of the laser linewidth and laser frequency <span class="hlt">stability</span> is critically important for the evaluation of a metrology system performance when the working principle is based in interferometric processes. In particular, the midterm <span class="hlt">stability</span> range, corresponding to noise in the hundreds of hertz to kilohertz bandwidth, affects strongly the measurement final accuracy when working at measurement rates at the ksample/s level. In this case, it is of crucial importance to know the uncertainty associated to the measurement of the laser instantaneous frequency and what is the variance of this value within the measurement period. In this paper we present a simple method to measure the frequency noise and obtain the Allan variance statistics for an External Cavity Diode Laser (ECDL) used in a Frequency Sweeping Interferometry (FSI) scheme for long distance high accuracy measurements. For this type of lasers, the main contributors affecting the midterm <span class="hlt">stability</span> are the current and technical noise, including thermal and mechanical fluctuations, optical feedback, as well as the feedback <span class="hlt">stabilization</span> techniques employed to reduce acoustic disturbances. The proposed method is based in the principle of delayed interferometry, where the variation of the laser center frequency is characterized for measurement conditions in the kilohertz range. The final accuracy of the metrology system is evaluated in accordance with the laser <span class="hlt">stability</span> characteristics obtained by this method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5383507','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5383507"><span id="translatedtitle">Equilibrium and <span class="hlt">stability</span> of bioeconomic <span class="hlt">models</span> of renewable resources under diverse harvesting regimes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Castro Ospina, J.M.</p> <p>1984-01-01</p> <p>A review is presented of some bioeconomic mathematical <span class="hlt">models</span> that incorporate constant harvesting. This is followed by a complete qualitative and quantitative <span class="hlt">analysis</span> of competition and predator-prey Lotka-Volterra bioeconomic <span class="hlt">models</span>. The trivial and non-trivial equilibrium points of these systems are analyzed and the Routh-Hurwitz criteria are used to determine the necessary and sufficient conditions for <span class="hlt">stability</span> in relation to the effort parameter eta. Some numerical examples that illustrate the corresponding qualitative <span class="hlt">stability</span> <span class="hlt">analysis</span> for the open access and bioeconomic equilibria for the competition and predator-prey systems are given. In the numerical examples analyzed, three different open access and bioeconomic equilibria were found. The non-trivial equilibrium points are unstable and infeasible. A critical level of effort was also derived for the predator-prey numerical example and corresponding management policies were formulated. When only the predator is harvested, it can be shown that the system under <span class="hlt">analysis</span> undergoes a critical bifurcation at the point E/sub c/.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730023223','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730023223"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> and trend study of a balloon tethered in a wind, with experimental comparisons</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Redd, L. T.; Bland, S. R.; Bennett, R. M.</p> <p>1973-01-01</p> <p>A <span class="hlt">stability</span> <span class="hlt">analysis</span> and trend study for a balloon tethered in a steady wind are presented. The linearized, <span class="hlt">stability</span>-derivative type <span class="hlt">analysis</span> includes balloon aerodynamics, buoyancy, mass (including apparent mass), and static forces resulting from the tether cable. The <span class="hlt">analysis</span> has been applied to a balloon 7.64 m in length, and the results are compared with those from tow tests of this balloon. This comparison shows that the <span class="hlt">analysis</span> gives reasonable predictions for the damping, frequencies, modes of motion, and <span class="hlt">stability</span> boundaries exhibited by the balloon. A trend study for the 7.64-m balloon was made to illustrate how the <span class="hlt">stability</span> boundaries are affected by changes in individual <span class="hlt">stability</span> parameters. The trends indicated in this study may also be applicable to many other tethered-balloon systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012IJART...1b...5E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012IJART...1b...5E"><span id="translatedtitle">Strength <span class="hlt">Analysis</span> of Coconut Fiber <span class="hlt">Stabilized</span> Earth for Farm Structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Enokela, O. S.; P. O, Alada</p> <p>2012-07-01</p> <p>Investigation of the strength characteristic of soil from alluvial deposit of River Benue in makurdi <span class="hlt">stabilized</span> with coconut fiber as a <span class="hlt">stabilizer</span> was carried as local building material for farm structure. Processed coconut fibers were mixed with the soil at four different mix ratios of 1% fiber, 2% fiber, 3% fiber and 4% fiber by percentage weight with 0% fiber as control. Compaction test and compressive strength were carried out on the various <span class="hlt">stabilizing</span> ratio. From the compaction test, the correlation between the maximum dry density and optimum moisture content is a second order polynomial with a coefficient of 63% obtained at1.91kg/m3and 20.0% respectively while the compressive strength test shows an optimum failure load of 8.62N/mm2 at 2%fibre:100% soil mix ratio at 2.16 maximum dry density.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19292501','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19292501"><span id="translatedtitle">Kinetic aspects of emulsion <span class="hlt">stabilization</span> by surfactants: a microfluidic <span class="hlt">analysis</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Baret, Jean-Christophe; Kleinschmidt, Felix; El Harrak, Abdeslam; Griffiths, Andrew D</p> <p>2009-06-01</p> <p>In classical emulsification processes, surfactants play two roles: first, they reduce the interfacial tension, facilitating droplet deformation and rupture, and second, they reduce droplet coalescence. Here, we use a microfluidic emulsification system to completely uncouple these two processes, allowing <span class="hlt">stabilization</span> against coalescence to be studied quantitatively and independently of droplet formation. We demonstrate that, in addition to the classical effect of <span class="hlt">stabilization</span> by an increase of surfactant concentration, the dynamics of adsorption of surfactant at the water-oil interface is a key element for droplet <span class="hlt">stabilization</span>. Microfluidic emulsification devices can therefore be tailored to improve emulsification while decreasing the concentration of surfactant by increasing the time before the droplets first come into contact. PMID:19292501</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020034623&hterms=mohan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmohan','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020034623&hterms=mohan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmohan"><span id="translatedtitle">Linear <span class="hlt">Stability</span> Regime <span class="hlt">Analysis</span> of the Compressible Reacting Mixing Layer</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Day, M. J.; Reynolds, William C.; Mansour, N. N.; Rai, Man Mohan (Technical Monitor)</p> <p>1995-01-01</p> <p>Previous investigations have shown that a compressible reacting mixing layer can develop two peaks in the mean density weighted vorticity profile. Linear <span class="hlt">stability</span> analyses show that at these peaks two distinct 'outer' instability modes appear in addition to the more common central mode, which exists unaccompanied in incompressible nonreacting flows. The present study parametrically analyzes the effects of compressibility, heat release, stoichiometry, and density ratio on the amplification rate and obliquity of each <span class="hlt">stability</span> mode. The mean profiles used in the spatial <span class="hlt">stability</span> calculation are generated by self-similar solutions of the compressible boundary layer equations combined with the assumption of infinitely fast chemistry. It is shown that the influence of stoichiometry and density ratio on the peaks of the density weighted vorticity profile determines which modes will dominate. Of particular interest are the conditions where two modes are equally amplified, causing the mixing layer to develop into a 'colayer' structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=2786&keyword=dictionary&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=55115772&CFTOKEN=76333884','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=2786&keyword=dictionary&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=55115772&CFTOKEN=76333884"><span id="translatedtitle">EXPOSURE <span class="hlt">ANALYSIS</span> <span class="hlt">MODELING</span> SYSTEM (EXAMS)</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The Exposure <span class="hlt">Analysis</span> <span class="hlt">Modeling</span> System (EXAMS), first published in 1982 (EPA-600/3-82-023), provides interactive computer software for formulating aquatic ecosystem <span class="hlt">models</span> and rapidly evaluating the fate, transport, and exposure concentrations of synthetic organic chemicals--pesti...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SCPMA..57.2194Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SCPMA..57.2194Y"><span id="translatedtitle">The <span class="hlt">stability</span> <span class="hlt">analysis</span> of rolling motion of hypersonic vehicles and its validations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ye, YouDa; Zhao, ZhongLiang; Tian, Hao; Zhang, XianFeng</p> <p>2014-12-01</p> <p>The <span class="hlt">stability</span> of the rolling motion of near space hypersonic vehicles with rudder control is studied using method of qualitative <span class="hlt">analysis</span> of nonlinear differential equations, and the <span class="hlt">stability</span> criteria of the deflected rolling motions are improved. The outcomes can serve as the basis for further study regarding the influence of pitching and lateral motion on the <span class="hlt">stability</span> of rolling motion. To validate the theoretical results, numerical simulations were done for the rolling motion of two hypersonic vehicles with typical configurations. Also, wind tunnel experiments for four aircraft <span class="hlt">models</span> with typical configurations have been done. The results show that: 1) there exist two dynamic patterns of the rolling motion under statically stable condition. The first one is point attractor, for which the motion of aircraft returns to the original state. The second is periodic attractor, for which the aircraft rolls periodically. 2) Under statically unstable condition, there exist three dynamic patterns of rolling motion, namely, the point attractor, periodic attractor around deflected state of rolling motion, and double periodic attractors or chaotic attractors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997APS..DPPoTP213R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997APS..DPPoTP213R"><span id="translatedtitle">MHD <span class="hlt">Stability</span> <span class="hlt">Analysis</span> of Reversed Shear Discharges in Alcator C-Mod</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramos, J. J.; Hubbard, A.; in, Y.; Porkolab, M.; Snipes, J.; Wolfe, S. M.; Bondeson, A.; Martynov, A.</p> <p>1997-11-01</p> <p>Reversed magnetic shear experiments have been carried out in Alcator C-mod by applying early ICRF heating during the current ramp-up phase. A detailed MHD <span class="hlt">stability</span> <span class="hlt">analysis</span> of these configurations is presented here. The purpose of this work is to find a theoretical explanation for the observed bursts of MHD activity as detected by the ECE and magnetic diagnostics. MHD equilibrium <span class="hlt">models</span> of the experimental plasmas are generated with the EFIT code, and their linear <span class="hlt">stability</span> is investigated with the KINX code for ideal modes and the MARS code for resistive modes. MHD <span class="hlt">stability</span> results are sensitive to equilibrium details that cannot be resolved with the available diagnostics of pressure and current profiles, therefore different possible equilibrium reconstructions must be considered. Resistive single tearing modes with resonant surfaces in the cold plasma region near the edge seem to provide the best interpretation of experimental data. However, if the edge current density gradient is sufficiently large, ideal surface kink instabilities can also be excited.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011GeoJI.185..911B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011GeoJI.185..911B"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> for acoustic wave propagation in tilted TI media by finite differences</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bakker, Peter M.; Duveneck, Eric</p> <p>2011-05-01</p> <p>Several papers in recent years have reported instabilities in P-wave <span class="hlt">modelling</span>, based on an acoustic approximation, for inhomogeneous transversely isotropic media with tilted symmetry axis (TTI media). In particular, instabilities tend to occur if the axis of symmetry varies rapidly in combination with strong contrasts of medium parameters, which is typically the case at the foot of a steeply dipping salt flank. In a recent paper, we have proposed and demonstrated a P-wave <span class="hlt">modelling</span> approach for TTI media, based on rotated stress and strain tensors, in which the wave equations reduce to a coupled set of two second-order partial differential equations for two scalar stress components: a normal component along the variable axis of symmetry and a lateral component of stress in the plane perpendicular to that axis. Spatially constant density is assumed in this approach. A numerical discretization scheme was proposed which uses discrete second-derivative operators for the non-mixed second-order derivatives in the wave equations, and combined first-derivative operators for the mixed second-order derivatives. This paper provides a complete and rigorous <span class="hlt">stability</span> <span class="hlt">analysis</span>, assuming a uniformly sampled grid. Although the spatial discretization operator for the TTI acoustic wave equation is not self-adjoint, this operator still defines a complete basis of eigenfunctions of the solution space, provided that the solution space is somewhat restricted at locations where the medium is elliptically anisotropic. First, a <span class="hlt">stability</span> <span class="hlt">analysis</span> is given for a discretization scheme, which is purely based on first-derivative operators. It is shown that the coefficients of the central difference operators should satisfy certain conditions. In view of numerical artefacts, such a discretization scheme is not attractive, and the non-mixed second-order derivatives of the wave equation are discretized directly by second-derivative operators. It is shown that this modification preserves <span class="hlt">stability</span>, provided that the central difference operators of the second-order derivatives dominate over the twice applied operators of the first-order derivatives. In practice, it turns out that this is almost the case. <span class="hlt">Stability</span> of the desired discretization scheme is enforced by slightly weighting down the mixed second-order derivatives in the wave equation. This has a minor, practically negligible, effect on the kinematics of wave propagation. Finally, it is shown that non-reflecting boundary conditions, enforced by applying a taper at the boundaries of the grid, do not harm the <span class="hlt">stability</span> of the discretization scheme.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhFl...28b2104K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhFl...28b2104K"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of non-inertial thin film flow over a heterogeneously heated porous substrate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumawat, Tara Chand; Tiwari, Naveen</p> <p>2016-02-01</p> <p>The dynamics and linear <span class="hlt">stability</span> of a gravity drive thin film flowing over non-uniformly heated porous substrate are studied. A governing equation for the evolution of film-thickness is derived within the lubrication approximation. Darcy-Brinkman equation is used to <span class="hlt">model</span> flow in the porous medium along with a tangential stress-jump condition at the interface of the porous layer and the fluid film. A temperature profile is imposed at the solid wall to <span class="hlt">model</span> an embedded heater beneath the porous layer. At the upstream edge of the heater, an opposing thermocapillary stress at the liquid-air interface leads to the formation of a thermocapillary ridge. The ridge becomes unstable beyond a critical Marangoni number leading to the formation of rivulets that are periodic in the spanwise direction. Increase in the values of parameters such as Darcy number, stress jump coefficient, and porosity is shown to have <span class="hlt">stabilizing</span> effect on the film dynamics. The critical Marangoni number is shown to increase monotonically with Darcy number for various values of porosity. At large values of stress-jump coefficient, a non-monotonic variation in critical Marangoni number versus Darcy number is shown. A correlation is developed numerically for the ratio of critical Marangoni number at large Darcy number to that for a non-porous substrate as a function of porosity and thickness of the porous substrate. A transient growth <span class="hlt">analysis</span> is carried out followed by non-linear <span class="hlt">stability</span> <span class="hlt">analysis</span>. The non-modal growth is found to be negligible thus indicating that the eigenvalues are physically determinant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860005835','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860005835"><span id="translatedtitle">F-111 natural laminar flow glove flight test data <span class="hlt">analysis</span> and boundary layer <span class="hlt">stability</span> <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Runyan, L. J.; Navran, B. H.; Rozendaal, R. A.</p> <p>1984-01-01</p> <p>An <span class="hlt">analysis</span> of 34 selected flight test data cases from a NASA flight program incorporating a natural laminar flow airfoil into partial wing gloves on the F-111 TACT airplane is given. This <span class="hlt">analysis</span> determined the measured location of transition from laminar to turbulent flow. The report also contains the results of a boundary layer <span class="hlt">stability</span> <span class="hlt">analysis</span> of 25 of the selected cases in which the crossflow (C-F) and Tollmien-Schlichting (T-S) disturbance amplification factors are correlated with the measured transition location. The chord Reynolds numbers for these cases ranges from about 23 million to 29 million, the Mach numbers ranged from 0.80 to 0.85, and the glove leading-edge sweep angles ranged from 9 deg to 25 deg. Results indicate that the maximum extent of laminar flow varies from 56% chord to 9-deg sweep on the upper surface, and from 51% chord at 16-deg sweep to 6% chord at 25-deg sweep on the lower. The results of the boundary layer <span class="hlt">stability</span> <span class="hlt">analysis</span> indicate that when both C-F and T-S disturbances are amplified, an interaction takes place which reduces the maximum amplification factor of either type of disturbance that can be tolerated without causing transition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EL.....8541001K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EL.....8541001K"><span id="translatedtitle">Modulus <span class="hlt">stabilization</span> of the generalized Randall-Sundrum <span class="hlt">model</span> with a bulk scalar field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koley, R.; Mitra, J.; Gupta, S. Sen</p> <p>2009-02-01</p> <p>We study the <span class="hlt">stabilization</span> of the inter-brane spacing modulus of generalized warped brane <span class="hlt">models</span> with a nonzero brane cosmological constant. Employing the Goldberger-Wise <span class="hlt">stabilization</span> prescription of braneworld <span class="hlt">models</span> with a bulk scalar field, we show that the <span class="hlt">stabilized</span> value of the modulus generally depends on the value of the brane cosmological constant. Our result further reveals that the <span class="hlt">stabilized</span> modulus value corresponding to a vanishingly small cosmological constant can only resolve the gauge hierarchy problem simultaneously. This in turn vindicates the original Randall-Sundrum <span class="hlt">model</span>, where the 3-brane cosmological constant was chosen to be zero.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23270595','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23270595"><span id="translatedtitle">Assessment of implant <span class="hlt">stability</span> of patients with and without radiotherapy using resonance frequency <span class="hlt">analysis</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Karayazgan-Saracoglu, Banu; Atay, Arzu; Zulfikar, Haluk; Erpardo, Yuksel</p> <p>2015-02-01</p> <p>The purpose of this study was to clinically monitor the <span class="hlt">stability</span> of dental implants in patients with and without a history of radiotherapy, using resonance frequency <span class="hlt">analysis</span> over 1 year. The <span class="hlt">stability</span> of patients with 80 implants was monitored with resonance frequency <span class="hlt">analysis</span> (Osstell Mentor) over 1 year. Data were assessed with Mann-Whitney U test and correlation <span class="hlt">analysis</span>. Irradiated maxillary implants showed statistically lower values than the mandibular implants at a significant level (P < .05). PMID:23270595</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/645573','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/645573"><span id="translatedtitle">Advanced techniques for the <span class="hlt">analysis</span> of crisis <span class="hlt">stability</span>, deterrence, and latency</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Canavan, G.H.</p> <p>1997-12-01</p> <p>Studies on crisis <span class="hlt">stability</span>, deterrence, and latency are presented in chronological order, which also reflects their logical order of development, captures the main features of <span class="hlt">stability</span> <span class="hlt">analysis</span>; relates first strike, crisis, and arms control <span class="hlt">stability</span> as seen from US and Russian perspective; and addresses questions such as whether uncertainty in damage preference or defense deployment can be destabilizing. It illustrates the problems with alternative metrics, latency and reconstitution, and deep unilateral and proportional force reductions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/808391','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/808391"><span id="translatedtitle"><span class="hlt">Modeling</span> of Neoclassical Tearing Mode <span class="hlt">Stability</span> for Generalized Toroidal Geometry</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>A.L. Rosenberg; D.A. Gates; A. Pletzer; J.E. Menard; S.E. Kruger; C.C. Hegna; F. Paoletti; S. Sabbagh</p> <p>2002-08-21</p> <p>Neoclassical tearing modes (NTMs) can lead to disruption and loss of confinement. Previous <span class="hlt">analysis</span> of these modes used large aspect ratio, low beta (plasma pressure/magnetic pressure) approximations to determine the effect of NTMs on tokamak plasmas. A more accurate tool is needed to predict the onset of these instabilities. As a follow-up to recent theoretical work, a code has been written which computes the tearing mode island growth rate for arbitrary tokamak geometry. It calls PEST-3 [A. Pletzer et al., J. Comput. Phys. 115, 530 (1994)] to compute delta prime, the resistive magnetohydrodynamic (MHD) matching parameter. The code also calls the FLUXGRID routines in NIMROD [A.H. Glasser et al., Plasma Phys. Controlled Fusion 41, A747 (1999)] for Dnc, DI and DR [C.C. Hegna, Phys. Plasmas 6, 3980 (1999); A.H. Glasser et al., Phys. Fluids 18, 875 (1975)], which are the bootstrap current driven term and the ideal and resistive interchange mode criterion, respectively. In addition to these components, the NIMROD routines calculate alphas-H, a new correction to the Pfirsch-Schlter term. Finite parallel transport effects were added and a National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] equilibrium was analyzed. Another program takes the output of PEST-3 and allows the user to specify the rational surface, island width, and amount of detail near the perturbed surface to visualize the total helical flux. The results of this work will determine the <span class="hlt">stability</span> of NTMs in an spherical torus (ST) [Y.-K.M. Peng et al., Nucl. Fusion 26, 769 (1986)] plasma with greater accuracy than previously achieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002PhPl....9.4567R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002PhPl....9.4567R"><span id="translatedtitle"><span class="hlt">Modeling</span> of neoclassical tearing mode <span class="hlt">stability</span> for generalized toroidal geometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rosenberg, A. L.; Gates, D. A.; Pletzer, A.; Menard, J. E.; Kruger, S. E.; Hegna, C. C.; Paoletti, F.; Sabbagh, S.</p> <p>2002-11-01</p> <p>Neoclassical tearing modes (NTMs) can lead to disruption and loss of confinement. Previous <span class="hlt">analysis</span> of these modes used large aspect ratio, low ? (plasma pressure/magnetic pressure) approximations to determine the effect of NTMs on tokamak plasmas. A more accurate tool is needed to predict the onset of these instabilities. As a follow-up to recent theoretical work, a code has been written which computes the tearing mode island growth rate for arbitrary tokamak geometry. It calls PEST-3 [A. Pletzer et al., J. Comput. Phys. 115, 530 (1994)] to compute ?', the resistive magnetohydrodynamic (MHD) matching parameter. The code also calls the FLUXGRID routines in NIMROD [A. H. Glasser et al., Plasma Phys. Controlled Fusion 41, A747 (1999)] for Dnc, DI, and DR [C. C. Hegna, Phys. Plasmas 6, 3980 (1999); A. H. Glasser et al., Phys. Fluids 18, 875 (1975)], which are the bootstrap current driven term and the ideal and resistive interchange mode criterion, respectively. In addition to these components, the NIMROD routines calculate ?s-H, a new correction to the Pfirsch-Schlter term. Finite parallel transport effects were added and a National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] equilibrium was analyzed. Another program takes the output of PEST-3 and allows the user to specify the rational surface, island width, and amount of detail near the perturbed surface to visualize the total helical flux. The results of this work will determine the <span class="hlt">stability</span> of NTMs in a spherical torus (ST) [Y.-K. M. Peng et al., Nucl. Fusion 26, 769 (1986)] plasma with greater accuracy than previously achieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5997675','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5997675"><span id="translatedtitle">Coalbed methane <span class="hlt">modeling</span> <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Covatch, G.L.; Layne, A.W.; Salamy, S.P.</p> <p>1985-12-01</p> <p>Systems analyses or the Department of Energy's (DOE) Coalbed Methane Project (CMP) were performed at the Morgantown Energy Technology Center (METC). In the analyses, both reservoir and stimulation <span class="hlt">models</span> were evaluated using data from US Steel's Oak Grove Coal Degasification Field. In the first part of the study two reservoir <span class="hlt">models</span> designed for predicting methane and water production from coalbeds, WELL2D and ARRAY, were evaluated. WELL2D is a two-dimensional, single-well, radial flow <span class="hlt">model</span>; ARRAY is a two-dimensional, multiwell production <span class="hlt">model</span>. In the evaluation, the <span class="hlt">models</span> were used to history match the actual production of the individual wells. The resultant information was then factored into a full-field simulation of the Oak Grove Field. This report summarizes the technical approaches used in the two <span class="hlt">models</span>, their installation onto the DOE/METC computer system, and gives the results from their evaluation. In the second part of the study, three stimulation <span class="hlt">models</span> were evaluated to determine their applicability to the CMP. The stimulation <span class="hlt">models</span>, OSUFRAC (generalized hydraulic fracture), ORUFRAC1 (stress contrast hydraulic fracture <span class="hlt">model</span>), and TUFRAC (hydraulic fracture proppant placement <span class="hlt">model</span>), were designed for hydraulic fracturing of homogeneous reservoirs. A summary of the technical approach used in each <span class="hlt">model</span> and the results of the analyses are presented. 11 refs., 27 figs., 12 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/543660','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/543660"><span id="translatedtitle">White Oak Dam <span class="hlt">stability</span> <span class="hlt">analysis</span>. Appendix. Volume II</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ahmed, S.B.</p> <p>1994-01-01</p> <p>A parametric study was conducted to evaluate the <span class="hlt">stability</span> of the White Oak Dam (WOD) embankment and foundation. Slope <span class="hlt">stability</span> analyses were performed for the upper and lower bound soil properties at three sections of the dam using the PCSTABL4 computer program. Minimum safety factors were calculated for the applicable seismic and static loading conditions. Liquefaction potential of the dam embankment and foundation solid during the seismic event was assessed by using simplified procedures. The WOD is classified as a low hazard facility and the Evaluation Basis Earthquake (EBE) is defined as an earthquake with a magnitude of m{sub b} = 5.6 and a Peak Ground Accelerator (PGA) of 0.13 g. This event is approximately equivalent to a Modified Mercalli Intensity of VI-VIII. The EBE is used to perform the seismic evaluation for slope <span class="hlt">stability</span> and liquefaction potential. Results of the <span class="hlt">stability</span> analyses and the liquefaction assessment lead to the conclusion that the White Oak Dam is safe and stable for the static and the seismic events defined in this study. Ogden Environmental, at the request of MMES, has checked and verified the calculations for the critical loading conditions and performed a peer review of this report. Ogden has determined that the WOD is stable under the defined static and seismic loading conditions and the embankment materials are in general not susceptible to liquefaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25687597','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25687597"><span id="translatedtitle"><span class="hlt">Modelling</span> aerobic <span class="hlt">stabilization</span> of domestic and industrial sludge using a multi-component biomass <span class="hlt">model</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Katipoglu-Yazan, Tugce</p> <p>2015-01-01</p> <p>The objective of the study was to investigate the achievable limits of aerobic sludge <span class="hlt">stabilization</span> applied on waste-activated sludge generated in domestic, tannery, and pharmaceutical wastewater treatment plants. <span class="hlt">Stabilization</span> study involved monitoring of conventional parameters and <span class="hlt">model</span> evaluation of oxygen uptake rate and particulate components of waste sludge. Multi-component biomass approach was adopted based on death-regeneration mechanism. The results showed that sludge <span class="hlt">stabilization</span> efficiency ranged between 25% and 30%, which was closely related to the fate of different particulate fractions of biomass, that is, viable biomass, hydrolysable particulates, and microbial metabolic products. <span class="hlt">Model</span> calibration exercises yield in rate coefficient ranges of 0.18-0.32/day for biomass decay and 0.60-0.65/day for hydrolysis of non-biomass components. Degradation rates of particulate metabolic products were estimated as 0.035, 0.04, and 0.01/day for domestic, tannery, and pharmaceutical sludge, respectively. Relatively low degradation rates compared to conventional biological treatment processes confirmed reduced microbial activity in the course of aerobic <span class="hlt">stabilization</span>. PMID:25687597</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850021648','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850021648"><span id="translatedtitle">Nonlinear global <span class="hlt">stability</span> <span class="hlt">analysis</span> of compressor stall phenomena</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Razavi, H.</p> <p>1985-01-01</p> <p>Compressor stall phenomena are analyzed from the point of view of nonlinear control theory, based on bifurcation-catastrophe techniques. This new approach appears promising and offers insight into such well-known compressor instability problems as surge and rotating stall and suggests strategies for recovery. Three interlocking dynamic nonlinear state space <span class="hlt">models</span> are developed. It is shown that the problem of rotating stall can be viewed as an induced bifurcation of solution of the unstalled <span class="hlt">model</span>. Hysteresis effects are shown to exist in the stall/recovery process. Surge cycles are observed for some critical parameter values. The oscillatory behavior is seen to be due to development of limit cycles, generated by Hopf bifurcation of solutions. More specifically, it is observed that at certain critical values of parameters, a family of stable limit cycles with growning and then diminishing amplitudes is generated, then giving rise to an unstable family of limit cycles. This unstable family in turn bifurcates into other unstable families. To further illustrate the utility of the methodology, some partial computation of domains is carried out, and parameter sensitivity <span class="hlt">analysis</span> is performed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CompM..56..879H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CompM..56..879H"><span id="translatedtitle"><span class="hlt">Stabilized</span> plane and axisymmetric Lobatto finite element <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, Y. C.; Sze, K. Y.; Zhou, Y. X.</p> <p>2015-11-01</p> <p>High order elements are renowned for their high accuracy and convergence. Among them, Lobatto spectral finite elements are commonly used in explicit dynamic analyses as their mass matrices when evaluated by the Lobatto integration rule are diagonal. While there are numerous advanced first and second order elements, advanced high order elements are rarely seen. In this paper, generic <span class="hlt">stabilization</span> schemes are devised for the reduced integrated plane and axisymmetric elements. Static and explicit dynamic tests are considered for evaluating the relatively merits of the <span class="hlt">stabilized</span> and conventional elements. The displacement errors of the <span class="hlt">stabilized</span> elements are less than those of the conventional Lobatto elements. When the material is nearly incompressible, the <span class="hlt">stabilized</span> elements are also more accurate in terms of the energy error norm. This advantage is of practical importance for bio-tissue and hydrated soil analyses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhA...48w5501M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhA...48w5501M"><span id="translatedtitle">Equilibrium and <span class="hlt">stability</span> properties of detonation waves in the hydrodynamic limit of a kinetic <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marques, Wilson, Jr.; Jacinta Soares, Ana; Pandolfi Bianchi, Miriam; Kremer, Gilberto M.</p> <p>2015-06-01</p> <p>A shock wave structure problem, like the one which can be formulated for the planar detonation wave, is analyzed here for a binary mixture of ideal gases undergoing the symmetric reaction {{A}1}+{{A}1}\\rightleftharpoons {{A}2}+{{A}2}. The problem is studied at the hydrodynamic Euler limit of a kinetic <span class="hlt">model</span> of the reactive Boltzmann equation. The chemical rate law is deduced in this frame with a second-order reaction rate, in a chemical regime such that the gas flow is not far away from the chemical equilibrium. The caloric and the thermal equations of state for the specific internal energy and temperature are employed to close the system of balance laws. With respect to other approaches known in the kinetic literature for detonation problems with a reversible reaction, this paper aims to improve some aspects of the wave solution. Within the mathematical <span class="hlt">analysis</span> of the detonation <span class="hlt">model</span>, the equation of the equilibrium Hugoniot curve of the final states is explicitly derived for the first time and used to define the correct location of the equilibrium Chapman-Jouguet point in the Hugoniot diagram. The parametric space is widened to investigate the response of the detonation solution to the activation energy of the chemical reaction. Finally, the mathematical formulation of the linear <span class="hlt">stability</span> problem is given for the wave detonation structure via a normal-mode approach, when bidimensional disturbances perturb the steady solution. The <span class="hlt">stability</span> equations with their boundary conditions and the radiation condition of the considered <span class="hlt">model</span> are explicitly derived for small transversal deviations of the shock wave location. The paper shows how a second-order chemical kinetics description, derived at the microscopic level, and an analytic deduction of the equilibrium Hugoniot curve, lead to an accurate picture of the steady detonation with reversible reaction, as well as to a proper bidimensional linear <span class="hlt">stability</span> <span class="hlt">analysis</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/875346','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/875346"><span id="translatedtitle">ESF SOUTH PORTAL BOX-CUT/HIGHWALL <span class="hlt">STABILITY</span> <span class="hlt">ANALYSIS</span> (SCPB:N/A)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Saeed Bonabian</p> <p>1996-03-28</p> <p>The main purpose and objective of this <span class="hlt">analysis</span> is to design a Box-Cut at the ESF South Portal to accommodate the Tunnel Boring Machine's (TBM) exit at the conclusion of the ESF Main Loop construction. The <span class="hlt">stability</span> of the Highwall and the sidewalls at the Box-Cut are assessed using analytical methods by numerical <span class="hlt">modeling</span> techniques. A ground reinforcement system for the South Ramp Box-Cut slopes will be recommended. This report summarizes the results of the analyses and provides the details of the recommended ground reinforcement system for the Box-Cut slopes at the South Portal. The reinforcement design details are then incorporated into design output documents for implementation in the field. Method of excavation for the Box-Cut is also discussed and a recommendation is provided in this <span class="hlt">analysis</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/923384','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/923384"><span id="translatedtitle">DIAGNOSIS, <span class="hlt">ANALYSIS</span>, AND RESOLUTION OF THERMAL <span class="hlt">STABILITY</span> ISSUES WITH HOM COUPLERS ON PROTOTYPE CEBAF SRF CAVITIES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Charles Reece; Edward Daly; G. Davis; William Hicks; Timothy Rothgeb; H. Phillips; Joseph Preble; Haipeng Wang; Genfa Wu</p> <p>2008-02-12</p> <p>During initial testing of the prototype cavities incorporated into the developmental cryomodule Renascence severe thermal <span class="hlt">stability</span> issues were encountered during CW operation. Additional diagnostic instrumentation was added. This enabled identification of an unanticipated thermal impedance between the HOM coupler probe feedthrough assembly and the cavity beamtube. Subsequent detailed FE <span class="hlt">analysis</span> successfully <span class="hlt">modeled</span> the situation and indicated the need for alternate cooling path for the couplers on those cavities. HOM damping was measured to be adequate employing only two of the four HOM couplers. The two pickup probes on the couplers at the input power coupler side of each cavity were removed, the remaining HOM probe feedthroughs were heat stationed to two-phase helium supply piping, and a novel heat sink was added to station both the inner and outer conductors of the remaining HOM rf cables. The characterization measurements, <span class="hlt">analysis</span>, modifications, and resulting performance are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110005488','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110005488"><span id="translatedtitle">A Quasi-Steady Flexible Launch Vehicle <span class="hlt">Stability</span> <span class="hlt">Analysis</span> Using Steady CFD with Unsteady Aerodynamic Enhancement</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bartels, Robert E.</p> <p>2011-01-01</p> <p>Launch vehicles frequently experience a reduced <span class="hlt">stability</span> margin through the transonic Mach number range. This reduced <span class="hlt">stability</span> margin is caused by an undamping of the aerodynamics in one of the lower frequency flexible or rigid body modes. <span class="hlt">Analysis</span> of the behavior of a flexible vehicle is routinely performed with quasi-steady aerodynamic lineloads derived from steady rigid computational fluid dynamics (CFD). However, a quasi-steady aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> can be unconservative at the critical Mach numbers where experiment or unsteady computational aeroelastic (CAE) <span class="hlt">analysis</span> show a reduced or even negative aerodynamic damping. This paper will present a method of enhancing the quasi-steady aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> of a launch vehicle with unsteady aerodynamics. The enhanced formulation uses unsteady CFD to compute the response of selected lower frequency modes. The response is contained in a time history of the vehicle lineloads. A proper orthogonal decomposition of the unsteady aerodynamic lineload response is used to reduce the scale of data volume and system identification is used to derive the aerodynamic stiffness, damping and mass matrices. The results of the enhanced quasi-static aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> are compared with the damping and frequency computed from unsteady CAE <span class="hlt">analysis</span> and from a quasi-steady <span class="hlt">analysis</span>. The results show that incorporating unsteady aerodynamics in this way brings the enhanced quasi-steady aeroelastic <span class="hlt">stability</span> <span class="hlt">analysis</span> into close agreement with the unsteady CAE <span class="hlt">analysis</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.205..636S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.205..636S"><span id="translatedtitle"><span class="hlt">Stability</span> of the rate, state and temperature dependent friction <span class="hlt">model</span> and its applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh, Arun K.; Singh, Trilok N.</p> <p>2016-04-01</p> <p>In this paper, we study <span class="hlt">stability</span> of the rate, state and temperature friction (RSTF) <span class="hlt">model</span>. The Segall and Rice approach is used to <span class="hlt">model</span> heat transfer at the sliding interface with its surroundings. The effect of pore pressure is not considered in the <span class="hlt">model</span> to avoid the complex expression for critical stiffness. Linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of the spring-mass sliding system is carried out with the ageing law under the quasistatic conditions in order to determine the critical stiffness above which sliding behaviour changes from unstable to stable or vice versa. Our numerical simulations establish that critical stiffness of the heated surface may increase or decrease from corresponding to the critical stiffness of the unheated surface depending on the relative values of two contradictory parameters related with velocity effect and temperature effect. Parametric studies are also carried out to understand shear velocity and temperature of the sliding surface dependence of steady friction. The RSTF <span class="hlt">model</span> is also used to study the gravity induced failure of a creeping rock slope and the results are justified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JPhCS..43..103G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JPhCS..43..103G"><span id="translatedtitle">Critical current and cryogenic <span class="hlt">stability</span> <span class="hlt">modelling</span> of filamentary MgB2 conductors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Glowacki, B. A.; Majoros, M.; Tanaka, K.; Kitaguchi, H.; Kumakura, H.; Okada, M.; Hirakawa, M.; Yamada, H.; Hancock, M. H.; Bay, N.</p> <p>2006-06-01</p> <p>The <span class="hlt">modelling</span> of a single filament, 6 filaments and 19 filaments MgB2 conductors was performed for two limiting cases: a) isothermal conditions considering Jc(B) dependence, b) considering heating effects but with Jc magnetic field independent. As a starting point of the <span class="hlt">modelling</span> in case a) we used experimental dependence of Jc(B, 4.2 K) for the best wire. Then Poisson equation for magnetic vector potential was solved by finite element method and self-field critical current densities of the wires with different diameter were calculated. There is no significant dependence of Jc in range of electric fields E = 1 - 10 V/cm. The isothermal <span class="hlt">modelling</span> with Jc independent on magnetic field, case b), gave the results more close to the experimental ones. From the <span class="hlt">modelling</span> of the heating effects we conclude that the cryogenic <span class="hlt">stability</span> of the used Cu/SUS316/MgB2, Fe/MgB2 and Cu/MgCu2/MgB2 wires is adequate. The <span class="hlt">stabilizing</span> copper layer can take all the current up to the onset of film boiling of LHe where the current starts to decrease with increasing electric field, i.e. at this point the differential resistivity of the Cu/SUS316/MgB2 wire starts to become negative (indicating the onset of instability). <span class="hlt">Analysis</span> of mechanically induced defects limiting the Jc in 6 filaments conductor is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24303904','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24303904"><span id="translatedtitle"><span class="hlt">Stability</span> and invariant manifolds of a generalized Beddington host-parasitoid <span class="hlt">model</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kapçak, Sinan; Ufuktepe, Ünal; Elaydi, Saber</p> <p>2013-01-01</p> <p>We will investigate the <span class="hlt">stability</span> and invariant manifolds of a new discrete host-parasitoid <span class="hlt">model</span>. It is a generalization of the Beddington-Nicholson-Bailey <span class="hlt">model</span>. Our study establishes analytically, for the first time, the <span class="hlt">stability</span> of the coexistence fixed point. PMID:24303904</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4131858','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4131858"><span id="translatedtitle">Mechanical <span class="hlt">Analysis</span> of the Effects of Cephalic Trim on Lower Lateral Cartilage <span class="hlt">Stability</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Oliaei, Sepehr; Manuel, Cyrus; Protsenko, Dmitriy; Hamamoto, Ashley; Chark, Davin; Wong, Brian</p> <p>2014-01-01</p> <p>Objective To determine how mechanical <span class="hlt">stability</span> changes in the lower lateral cartilage (LLC) after varying degrees of cephalic resection in a porcine cartilage nasal tip <span class="hlt">model</span>. Methods Alar cartilage was harvested from fresh porcine crania (n=14) and sectioned to precisely emulate a human LLC in size and dimension. Flexural mechanical <span class="hlt">analysis</span> was performed both before and after cephalic trims of 0 (control), 4, and 6 mm. Cantilever deformation tests were performed on the LLC <span class="hlt">models</span> at 3 locations (4, 6, and 8 mm from the midline), and the integrated reaction force was measured. An equivalent elastic modulus of the crura was calculated assuming that the geometry of the LLC <span class="hlt">model</span> approximated a modified single cantilever beam. A 3-dimensional finite element <span class="hlt">model</span> was used to <span class="hlt">model</span> the stress distribution of the prescribed loading conditions for each of the 3 types of LLC widths. Results A statistically significant decrease (P=.02) in the equivalent elastic modulus of the LLC <span class="hlt">model</span> was noted at the most lateral point at 8 mm and only when 4 mm of the strut remained (P=05). The finite element <span class="hlt">model</span> revealed that the greatest internal stresses was at the tip of the nose when tissue was flexed 8 mm from the midline. Conclusion Our results provide the mechanical basis for suggested clinical guidelines stating that a residual strut of less than 6 mm can lead to suboptimal cosmetic results owing to poor structural support of the overlying skin soft-tissue envelope by an overly resected LLC. PMID:22250265</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16672287','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16672287"><span id="translatedtitle"><span class="hlt">Stability</span> in a mathematical <span class="hlt">model</span> of neurite elongation.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>McLean, Douglas R; Graham, Bruce P</p> <p>2006-06-01</p> <p>We have developed a continuum partial differential equation <span class="hlt">model</span> of tubulin-driven neurite elongation and solved the steady problem. For non-zero values of the decay coefficient, the authors identified three different regimes of steady neurite growth, small, moderate and large, dependent on the strength of the tubulin flux into the neurite at the soma. Solution of the fully time-dependent moving boundary problem is, however, hampered by its analytical intractibility. A linear instability <span class="hlt">analysis</span>, novel to moving boundary problems in this context, is possible and reduces to finding the zeros of an eigen-condition function. One of the system parameters is small and this permits solutions to the eigen-condition equation in terms of asymptotic series in each growth regime. Linear instability is demonstrated to be absent from the neurite growth <span class="hlt">model</span> and a Newton-Raphson root-finding algorithm is then shown to corroborate the asymptotic results for some selected examples. By numerically integrating the fully non-linear time-dependent system, we show how the steady solutions are non-linearly stable in each of the three growth regimes with decay and oscillatory behaviour being as predicted by the linear eigenvalue <span class="hlt">analysis</span>. PMID:16672287</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70028974','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70028974"><span id="translatedtitle"><span class="hlt">Stability</span> of landsat-4 thematic mapper outgassing <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Micijevic, E.; Chander, G.</p> <p>2006-01-01</p> <p>Oscillations in radiometric gains of the short wave infrared (SWIR) bands in Landsat-4 (L4) and Landsat-5 (L5) Thematic Mappers (TMs) are observed through an <span class="hlt">analysis</span> of detector responses to the Internal Calibrator (IC) pulses. The oscillations are believed to be caused by an interference effect due to a contaminant film buildup on the window of the cryogenically cooled dewar that houses these detectors. This process of contamination, referred to as outgassing effects, has been well characterized using an optical thin-film <span class="hlt">model</span> that relates detector responses to the accumulated film thickness and its growth rate. The current <span class="hlt">models</span> for L4 TM are based on average detector responses to the second brightest IC lamp and have been derived from three data sets acquired during different times throughout the instrument's lifetime. Unlike in L5 TM outgassing characterization, it was found that the L4 TM responses to all three IC lamps can be used to provide accurate characterization and correction for outgassing effects. The <span class="hlt">analysis</span> of single detector responses revealed an up to five percent difference in the estimated oscillating periods and also indicated a gradual variation of contaminant growth rate over the focal plane.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Stability+AND+analysis+AND+seed+AND+yield+AND+quality+AND+traits+AND+soybean+AND+%7bGlycine+AND+max+AND+L.+AND+Merrill%7d&pg=5&id=EJ870017','ERIC'); return false;" href="http://eric.ed.gov/?q=Stability+AND+analysis+AND+seed+AND+yield+AND+quality+AND+traits+AND+soybean+AND+%7bGlycine+AND+max+AND+L.+AND+Merrill%7d&pg=5&id=EJ870017"><span id="translatedtitle">Does Premarital Cohabitation Predict Subsequent Marital <span class="hlt">Stability</span> and Marital Quality? A Meta-<span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Jose, Anita; O'Leary, K. Daniel; Moyer, Anne</p> <p>2010-01-01</p> <p>Cohabitation with a romantic partner has become common in recent decades. This meta-<span class="hlt">analysis</span> examined the link between premarital cohabitation and marital <span class="hlt">stability</span> (k = 16) and marital quality (k = 12). Cohabitation had a significant negative association with both marital <span class="hlt">stability</span> and marital quality. The negative predictive effect on marital…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Stability+AND+analysis+AND+seed+AND+yield+AND+quality+AND+traits+AND+soybean+AND+%7bGlycine+AND+max+AND+L.+AND+Merrill%7d&pg=4&id=EJ961320','ERIC'); return false;" href="http://eric.ed.gov/?q=Stability+AND+analysis+AND+seed+AND+yield+AND+quality+AND+traits+AND+soybean+AND+%7bGlycine+AND+max+AND+L.+AND+Merrill%7d&pg=4&id=EJ961320"><span id="translatedtitle"><span class="hlt">Stability</span> and Change in Work Values: A Meta-<span class="hlt">Analysis</span> of Longitudinal Studies</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Jin, Jing; Rounds, James</p> <p>2012-01-01</p> <p>A meta-<span class="hlt">analysis</span> of longitudinal studies was conducted to investigate <span class="hlt">stability</span> and change in work values across the life span. Both rank-order <span class="hlt">stability</span> and mean-level change were investigated using an integrative classification for intrinsic, extrinsic, social and status work values (Ross, Schwartz, & Surkis, 1999). Results of rank-order…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=generation+AND+x&pg=3&id=EJ961320','ERIC'); return false;" href="http://eric.ed.gov/?q=generation+AND+x&pg=3&id=EJ961320"><span id="translatedtitle"><span class="hlt">Stability</span> and Change in Work Values: A Meta-<span class="hlt">Analysis</span> of Longitudinal Studies</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Jin, Jing; Rounds, James</p> <p>2012-01-01</p> <p>A meta-<span class="hlt">analysis</span> of longitudinal studies was conducted to investigate <span class="hlt">stability</span> and change in work values across the life span. Both rank-order <span class="hlt">stability</span> and mean-level change were investigated using an integrative classification for intrinsic, extrinsic, social and status work values (Ross, Schwartz, & Surkis, 1999). Results of rank-order</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Daniel+AND+K&pg=5&id=EJ870017','ERIC'); return false;" href="http://eric.ed.gov/?q=Daniel+AND+K&pg=5&id=EJ870017"><span id="translatedtitle">Does Premarital Cohabitation Predict Subsequent Marital <span class="hlt">Stability</span> and Marital Quality? A Meta-<span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Jose, Anita; O'Leary, K. Daniel; Moyer, Anne</p> <p>2010-01-01</p> <p>Cohabitation with a romantic partner has become common in recent decades. This meta-<span class="hlt">analysis</span> examined the link between premarital cohabitation and marital <span class="hlt">stability</span> (k = 16) and marital quality (k = 12). Cohabitation had a significant negative association with both marital <span class="hlt">stability</span> and marital quality. The negative predictive effect on marital</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1230224-canister-model-systems-analysis','SCIGOV-ESTSC'); return false;" href="http://www.osti.gov/scitech/biblio/1230224-canister-model-systems-analysis"><span id="translatedtitle">Canister <span class="hlt">Model</span>, Systems <span class="hlt">Analysis</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech/">Energy Science and Technology Software Center (ESTSC)</a></p> <p></p> <p>1993-09-29</p> <p>This packges provides a computer simulation of a systems <span class="hlt">model</span> for packaging nuclear waste and spent nuclear fuel in canisters. The canister <span class="hlt">model</span> calculates overall programmatic cost, number of canisters, and fuel and waste inventories for the Idaho Chemical Processing Plant (other initial conditions can be entered).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17358402','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17358402"><span id="translatedtitle"><span class="hlt">Stability</span> <span class="hlt">analysis</span> of dynamic ratcheting in elastoplastic systems.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Challamel, Nol; Lanos, Christophe; Hammouda, Abdelaziz; Redjel, Bachir</p> <p>2007-02-01</p> <p>This paper deals with the <span class="hlt">stability</span> and the dynamics of a harmonically excited elastic perfectly plastic asymmetrical oscillator. The hysteretical system is written as a nonsmooth, forced autonomous system. The dimension of the phase space can be reduced using adapted variables. It is shown that asymmetry of boundary conditions (forcing term) and material asymmetry lead to an equivalent system for this simple structural case. The forced vibration of such an oscillator is treated by a numerical approach by using time locating techniques. <span class="hlt">Stability</span> of the limit cycles is analytically investigated with a perturbation approach. The boundary between elastoplastic shakedown and dynamic ratcheting is given in closed form. It is shown that the divergence rate is strongly correlated to the internal asymmetry of the oscillator. PMID:17358402</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013evga.conf..179R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013evga.conf..179R"><span id="translatedtitle">Time Series <span class="hlt">Analysis</span> and <span class="hlt">Stability</span> of ICRF2 sources</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Raposo-Pulido, V.; Krsn, H.; Nilsson, T.; Heinkelmann, R.; Schuh, H.</p> <p>2013-08-01</p> <p>We have studied the precision and <span class="hlt">stability</span> of the positions of the radio sources observed in 3450 VLBI sessions from 1984 to 2011 using VieVS (Vienna VLBI Software). We first estimated time-series of the radio source coordinates. Each time series was then analyzed according to <span class="hlt">stability</span> and apparent proper motion of the source. The results were compared with the requirements for defining sources as specified by the IERS (Fey et al. 2009). Thus, with this study we aim to produce an updated list of radio sources useful for geodetic and astrometric VLBI as well as to assess the precision of them. Furthermore, we intend to provide an input to the realization of the next ICRF3.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21443424','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21443424"><span id="translatedtitle">Longitudinal structure of MHD perturbations at the boundary of convective <span class="hlt">stability</span> in the Kruskal-Oberman <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Arsenin, V. V.</p> <p>2010-10-15</p> <p>It is shown that, in contrast to the MHD <span class="hlt">model</span>, a perturbation at the boundary of convective <span class="hlt">stability</span> of a finite-pressure plasma in confinement systems without an averaged minB in the Kruskal-Oberman <span class="hlt">model</span> is not generally a purely flute one. The reasons for this discrepancy are clarified. The <span class="hlt">analysis</span> is carried out for axisymmetric configurations formed by a poloidal magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/348873','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/348873"><span id="translatedtitle">Advanced techniques for the <span class="hlt">analysis</span> of crisis <span class="hlt">stability</span>, deterrence, and latency</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Canavan, G.H.</p> <p>1998-12-31</p> <p>This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The principal results of studies on crisis <span class="hlt">stability</span>, deterrence, and latency are presented in their order of development. They capture the main features of <span class="hlt">stability</span> <span class="hlt">analysis</span>; relate first strike, crisis, and arms control <span class="hlt">stability</span> as seen from US and Russian perspective; and address whether different metrics, uncertain damage preferences, or the deployment of defenses can be destabilizing. The report explores differences between unilateral and proportional force reductions in the region of deep reductions where concern shifts from <span class="hlt">stability</span> to latency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/477358','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/477358"><span id="translatedtitle">Linear <span class="hlt">stability</span> <span class="hlt">analysis</span> of thermocapillary convection in a liquid bridge with encapsulation in inverse iterative algorithm</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Li, M.; Sun, Z.; Zeng, D.</p> <p>1996-12-31</p> <p>Linear <span class="hlt">stability</span> theory was applied in the present paper to analyze the <span class="hlt">stability</span> of the basic state solution of thermocapillary convection in a liquid bridge with liquid encapsulation. Discretizing the linearized disturbance equations by using finite-difference approximation, <span class="hlt">stability</span> <span class="hlt">analysis</span> is evolved to a complex generalized eigenvalue problem with a complicated band structure of matrix. The influence of dimensionless parameters on the <span class="hlt">stability</span> of the system is revealed through solving the complex generalized eigenvalue problem by inverse iteration. The results provide a theoretical and numerical foundation for crystal growth by float-zone method and for other engineering applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvE..91e2204E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvE..91e2204E"><span id="translatedtitle">Bubbles breaking the wall: Two-dimensional stress and <span class="hlt">stability</span> <span class="hlt">analysis</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eriksen, Jon Alm; Marks, Benjy; Sandnes, Bjrnar; Toussaint, Renaud</p> <p>2015-05-01</p> <p>Submerged granular material exhibits a wide range of behavior when the saturating fluid is slowly displaced by a gas phase. In confined systems, the moving interface between the invading gas and the fluid/grain mixture can cause beads to jam, and induce intermittency in the dynamics. Here, we study the <span class="hlt">stability</span> of layers of saturated jammed beads around stuck air bubbles, and the deformation mechanism leading to air channel formations in these layers. We describe a two-dimensional extension of a previous <span class="hlt">model</span> of the effective stress in the jammed packing. The effect of the tangential stress component on the yield stress is discussed, in particular how arching effects may impact the yield threshold. We further develop a linear <span class="hlt">stability</span> <span class="hlt">analysis</span>, to study undulations which develop under certain experimental conditions at the air-liquid interface. The linear <span class="hlt">analysis</span> gives estimates for the most unstable wavelengths for the initial growth of the perturbations. The estimates correspond well with peak to peak length measurements of the experimentally observed undulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CompM.tmp...15C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CompM.tmp...15C"><span id="translatedtitle"><span class="hlt">Stabilized</span> tetrahedral elements for crystal plasticity finite element <span class="hlt">analysis</span> overcoming volumetric locking</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheng, Jiahao; Shahba, Ahmad; Ghosh, Somnath</p> <p>2016-01-01</p> <p>Image-based CPFE <span class="hlt">modeling</span> involves computer generation of virtual polycrystalline microstructures from experimental data, followed by discretization into finite element meshes. Discretization is commonly accomplished using three-dimensional four-node tetrahedral or TET4 elements, which conform to the complex geometries. It has been commonly observed that TET4 elements suffer from severe volumetric locking when simulating deformation of incompressible or nearly incompressible materials. This paper develops and examines three locking-free <span class="hlt">stabilized</span> finite element formulations in the context of crystal plasticity finite element <span class="hlt">analysis</span>. They include a node-based uniform strain (NUS) element, a locally integrated B-bar (LIB) based element and a F-bar patch (FP) based element. All three formulations are based on the partitioning of TET4 element meshes and integrating over patches to obtain favorable incompressibility constraint ratios without adding large degrees of freedom. The results show that NUS formulation introduces unstable spurious energy modes, while the LIB and FP elements <span class="hlt">stabilize</span> the solutions and are preferred for reliable CPFE <span class="hlt">analysis</span>. The FP element is found to be computationally efficient over the LIB element.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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