An automated system for numerically rating document image quality
Cannon, M.; Kelly, P.; Iyengar, S.S.; Brener, N.
1997-04-01
As part of the Department of Energy document declassification program, the authors have developed a numerical rating system to predict the OCR error rate that they expect to encounter when processing a particular document. The rating algorithm produces a vector containing scores for different document image attributes such as speckle and touching characters. The OCR error rate for a document is computed from a weighted sum of the elements of the corresponding quality vector. The predicted OCR error rate will be used to screen documents that would not be handled properly with existing document processing products.
16 CFR 0.10 - Office of the Executive Director.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 16 Commercial Practices 1 2012-01-01 2012-01-01 false Office of the Executive Director. 0.10 Section 0.10 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE ORGANIZATION § 0.10 Office of the Executive Director. The Executive Director, under the direction of...
16 CFR 0.10 - Office of the Executive Director.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Office of the Executive Director. 0.10 Section 0.10 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE ORGANIZATION § 0.10 Office of the Executive Director. The Executive Director, under the direction of...
Evaluating the Controls on Magma Ascent Rates Through Numerical Modelling
NASA Astrophysics Data System (ADS)
Thomas, M. E.; Neuberg, J. W.
2015-12-01
The estimation of the magma ascent rate is a key factor in predicting styles of volcanic activity and relies on the understanding of how strongly the ascent rate is controlled by different magmatic parameters. The ability to link potential changes in such parameters to monitoring data is an essential step to be able to use these data as a predictive tool. We present the results of a suite of conduit flow models that assess the influence of individual model parameters such as the magmatic water content, temperature or bulk magma composition on the magma flow in the conduit during an extrusive dome eruption. By systematically varying these parameters we assess their relative importance to changes in ascent rate. The results indicate that potential changes to conduit geometry and excess pressure in the magma chamber are amongst the dominant controlling variables that effect ascent rate, but the single most important parameter is the volatile content (assumed in this case as only water). Modelling this parameter across a range of reported values causes changes in the calculated ascent velocities of up to 800%, triggering fluctuations in ascent rates that span the potential threshold between effusive and explosive eruptions.
Convergence rate for numerical computation of the lattice Green's function.
Ghazisaeidi, M; Trinkle, D R
2009-03-01
Flexible boundary-condition methods couple an isolated defect to bulk through the bulk lattice Green's function. Direct computation of the lattice Green's function requires projecting out the singular subspace of uniform displacements and forces for the infinite lattice. We calculate the convergence rates for elastically isotropic and anisotropic cases for three different techniques: relative displacement, elastic Green's function correction, and discontinuity correction. The discontinuity correction has the most rapid convergence for the general case. PMID:19392089
A numerical procedure for analysis of finite rate reacting flows
NASA Technical Reports Server (NTRS)
Shang, H. M.; Chen, Y. S.; Chen, Z. J.; Chen, C. P.; Wang, T. S.
1993-01-01
Combustion processes in rocket propulsion systems are characterized by the existence of multiple, vastly differing time and length scales, as well as flow-speeds at wide variation of Mach numbers. The chemical kinetics processes in the highly active reaction zone are characterized by much smaller scales compared to fluid convective and diffusive time scales. An operator splitting procedure for transient finite rate chemistry problems has been developed using a pressure based method, which can be applied to all speed flows without difficulties. The splitting of chemical kinetics terms formed the fluid-mechanical terms of the species equation ameliorated the difficulties associated with the disparate time scales and stiffness in the set of equations which describes highly exothermic combustion. A combined efficient ordinary differential equations (ODE) solver was used to integrate the effective chemical source terms over the residence time at each grid cell. One and two dimensional reacting flow situations were carried out to demonstrate and verify the current procedure. Different chemical kinetics with different degrees of nonlinearity have also been incorporated to test the robustness and generality of the proposed method.
The numerical response: rate of increase and food limitation in herbivores and predators.
Bayliss, Peter; Choquenot, David
2002-01-01
Two types of numerical response function have evolved since Solomon first introduced the term to generalize features of Lotka-Volterra predator-prey models: (i) the demographic numerical response, which links change in consumer demographic rates to food availability; and (ii) the isocline numerical response, which links consumer abundance per se to food availability. These numerical responses are interchangeable because both recognize negative feedback loops between consumer and food abundance resulting in population regulation. We review how demographic and isocline numerical responses have been used to enhance our understanding of population regulation of kangaroos and possums, and argue that their utility may be increased by explicitly accounting for non-equilibrium dynamics (due to environmental variability and/or biological interactions) and the existence of multiple limiting factors. Interferential numerical response functions may help bridge three major historical dichotomies in population ecology (equilibrium versus non-equilibrium dynamics, extrinsic versus intrinsic regulation and demographic versus isocline numerical responses). PMID:12396515
A numerical method for determining the strain rate intensity factor under plane strain conditions
NASA Astrophysics Data System (ADS)
Alexandrov, S.; Kuo, C.-Y.; Jeng, Y.-R.
2016-07-01
Using the classical model of rigid perfectly plastic solids, the strain rate intensity factor has been previously introduced as the coefficient of the leading singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. Since then, many strain rate intensity factors have been determined by means of analytical and semi-analytical solutions. However, no attempt has been made to develop a numerical method for calculating the strain rate intensity factor. This paper presents such a method for planar flow. The method is based on the theory of characteristics. First, the strain rate intensity factor is derived in characteristic coordinates. Then, a standard numerical slip-line technique is supplemented with a procedure to calculate the strain rate intensity factor. The distribution of the strain rate intensity factor along the friction surface in compression of a layer between two parallel plates is determined. A high accuracy of this numerical solution for the strain rate intensity factor is confirmed by comparison with an analytic solution. It is shown that the distribution of the strain rate intensity factor is in general discontinuous.
BCS theory has to be overhauled: Reassurance from numerical survival rate
NASA Astrophysics Data System (ADS)
Zheng, X. H.; Walmsley, D. G.
2016-07-01
The BCS theory has conceptual and numerical difficulties. We have previously overhauled it with a new scheme of phonon-mediated electron pairing that can be expressed analytically in terms of an empirical pairing survival rate factor, S(q) = 0 or 1/2, depending on phonon momentum, q. Now we evaluate S(q) numerically entirely from experimental data on normal state electrical resistivity and on superconducting tunnelling conductance. The empirical and numerical S(q) are reassuringly close in aluminium and lead and particularly so in two other cases, niobium and tantalum.
A method for generating numerical pilot opinion ratings using the optimal pilot model
NASA Technical Reports Server (NTRS)
Hess, R. A.
1976-01-01
A method for generating numerical pilot opinion ratings using the optimal pilot model is introduced. The method is contained in a rating hypothesis which states that the numerical rating which a human pilot assigns to a specific vehicle and task can be directly related to the numerical value of the index of performance resulting from the optimal pilot modeling procedure as applied to that vehicle and task. The hypothesis is tested using the data from four piloted simulations. The results indicate that the hypothesis is reasonable, but that the predictive capability of the method is a strong function of the accuracy of the pilot model itself. This accuracy is, in turn, dependent upon the parameters which define the optimal modeling problem. A procedure for specifying the parameters for the optimal pilot model in the absence of experimental data is suggested.
Assessing the numerical dissipation rate and viscosity in CFD simulations of fluid flows
NASA Astrophysics Data System (ADS)
Schranner, F. S.; Domaradzki, J. A.; Hickel, S.; Adams, N. A.
2014-11-01
We describe a method for quantifying the effective numerical dissipation rate and the effective numerical viscosity in Computational Fluid Dynamics simulations. Differently from the previous approach that was formulated in spectral space, the proposed method is developed in a physical-space representation and allows for determining numerical dissipation rates and viscosities locally, i.e., at the individual cell level or for arbitrary subdomains of the computational domain. The method is self-contained using only results produced by the Navier-Stokes solver being investigated. Since no extraneous information is required, the method is suitable for a straightforward quantification of the numerical dissipation as a post-processing step. We demonstrate the method's capabilities on the example of implicit large-eddy simulations of three-dimensional Taylor-Green vortex flows that exhibit laminar, transitional, and turbulent flow behavior at different stages of time evolution. For validation, we compare the numerical dissipation rate obtained using this method with exact reference data obtained with an accurate, spectral-space approach. Supported by Deutsche Forschungsgemeinschaft and Alexander von Humboldt Foundation.
NASA Astrophysics Data System (ADS)
Zhang, Sumei; Wang, Lihe
2013-07-01
This study proposes a pricing model through allowing for stochastic interest rate and stochastic volatility in the double exponential jump-diffusion setting. The characteristic function of the proposed model is then derived. Fast numerical solutions for European call and put options pricing based on characteristic function and fast Fourier transform (FFT) technique are developed. Simulations show that our numerical technique is accurate, fast and easy to implement, the proposed model is suitable for modeling long-time real-market changes. The model and the proposed option pricing method are useful for empirical analysis of asset returns and risk management in firms.
NASA Astrophysics Data System (ADS)
de Paiva, Eduardo
Concave beta sources of 106Ru/106Rh are used in radiotherapy to treat ophthalmic tumors. However, a problem that arises is the difficult determination of absorbed dose distributions around such sources mainly because of the small range of the electrons and the steep dose gradients. In this sense, numerical methods have been developed to calculate the dose distributions around the beta applicators. In this work a simple code in Fortran language is developed to estimate the dose rates along the central axis of 106Ru/106Rh curved plaques by numerical integration of the beta point source function and results are compared with other calculated data.
Numerical solution of the Penna model of biological aging with age-modified mutation rate.
Magdoń-Maksymowicz, M S; Maksymowicz, A Z
2009-06-01
In this paper we present results of numerical calculation of the Penna bit-string model of biological aging, modified for the case of a -dependent mutation rate m(a), where a is the parent's age. The mutation rate m(a) is the probability per bit of an extra bad mutation introduced in offspring inherited genome. We assume that m(a) increases with age a. As compared with the reference case of the standard Penna model based on a constant mutation rate m , the dynamics of the population growth shows distinct changes in age distribution of the population. Here we concentrate on mortality q(a), a fraction of items eliminated from the population when we go from age (a) to (a+1) in simulated transition from time (t) to next time (t+1). The experimentally observed q(a) dependence essentially follows the Gompertz exponential law for a above the minimum reproduction age. Deviation from the Gompertz law is however observed for the very old items, close to the maximal age. This effect may also result from an increase in mutation rate m with age a discussed in this paper. The numerical calculations are based on analytical solution of the Penna model, presented in a series of papers by Coe et al. [J. B. Coe, Y. Mao, and M. E. Cates, Phys. Rev. Lett. 89, 288103 (2002)]. Results of the numerical calculations are supported by the data obtained from computer simulation based on the solution by Coe et al. PMID:19658536
Scholl, M.A.
2000-01-01
Numerical simulations were used to examine the effects of heterogeneity in hydraulic conductivity (K) and intrinsic biodegradation rate on the accuracy of contaminant plume-scale biodegradation rates obtained from field data. The simulations were based on a steady-state BTEX contaminant plume-scale biodegradation under sulfate-reducing conditions, with the electron acceptor in excess. Biomass was either uniform or correlated with K to model spatially variable intrinsic biodegradation rates. A hydraulic conductivity data set from an alluvial aquifer was used to generate three sets of 10 realizations with different degrees of heterogeneity, and contaminant transport with biodegradation was simulated with BIOMOC. Biodegradation rates were calculated from the steady-state contaminant plumes using decreases in concentration with distance downgradient and a single flow velocity estimate, as is commonly done in site characterization to support the interpretation of natural attenuation. The observed rates were found to underestimate the actual rate specified in the heterogeneous model in all cases. The discrepancy between the observed rate and the 'true' rate depended on the ground water flow velocity estimate, and increased with increasing heterogeneity in the aquifer. For a lognormal K distribution with variance of 0.46, the estimate was no more than a factor of 1.4 slower than the true rate. For aquifer with 20% silt/clay lenses, the rate estimate was as much as nine times slower than the true rate. Homogeneous-permeability, uniform-degradation rate simulations were used to generate predictions of remediation time with the rates estimated from heterogeneous models. The homogeneous models were generally overestimated the extent of remediation or underestimated remediation time, due to delayed degradation of contaminants in the low-K areas. Results suggest that aquifer characterization for natural attenuation at contaminated sites should include assessment of the presence
Ritter, André
2014-10-20
The shifted angular spectrum method allows a reduction of the number of samples required for numerical off-axis propagation of scalar wave fields. In this work, a modification of the shifted angular spectrum method is presented. It allows a further reduction of the spatial sampling rate for certain wave fields. We calculate the benefit of this method for spherical waves. Additionally, a working implementation is presented showing the example of a spherical wave propagating through a circular aperture. PMID:25401659
NASA Astrophysics Data System (ADS)
Nielsen, K. L.; Niordson, C. F.
2014-02-01
A numerical model formulation of the higher order flow theory (rate-independent) by Fleck and Willis [2009. A mathematical basis for strain-gradient plasticity theory - part II: tensorial plastic multiplier. Journal of the Mechanics and Physics of Solids 57, 1045-1057.], that allows for elastic-plastic loading/unloading and the interaction of multiple plastic zones, is proposed. The predicted model response is compared to the corresponding rate-dependent version of visco-plastic origin, and coinciding results are obtained in the limit of small strain-rate sensitivity. First, (i) the evolution of a single plastic zone is analyzed to illustrate the agreement with earlier published results, whereafter examples of (ii) multiple plastic zone interaction, and (iii) elastic-plastic loading/unloading are presented. Here, the simple shear problem of an infinite slab constrained between rigid plates is considered, and the effect of strain gradients, strain hardening and rate sensitivity is brought out. For clarity of results, a 1D model is constructed following a procedure suitable for generalization to 2D and 3D.
On the efficient and reliable numerical solution of rate-and-state friction problems
NASA Astrophysics Data System (ADS)
Pipping, Elias; Kornhuber, Ralf; Rosenau, Matthias; Oncken, Onno
2016-03-01
We present a mathematically consistent numerical algorithm for the simulation of earthquake rupture with rate-and-state friction. Its main features are adaptive time stepping, a novel algebraic solution algorithm involving nonlinear multigrid and a fixed point iteration for the rate-and-state decoupling. The algorithm is applied to a laboratory scale subduction zone which allows us to compare our simulations with experimental results. Using physical parameters from the experiment, we find a good fit of recurrence time of slip events as well as their rupture width and peak slip. Computations in 3-D confirm efficiency and robustness of our algorithm.
A comparison of the efficiency of numerical methods for integrating chemical kinetic rate equations
NASA Technical Reports Server (NTRS)
Radhakrishnan, K.
1984-01-01
The efficiency of several algorithms used for numerical integration of stiff ordinary differential equations was compared. The methods examined included two general purpose codes EPISODE and LSODE and three codes (CHEMEQ, CREK1D and GCKP84) developed specifically to integrate chemical kinetic rate equations. The codes were applied to two test problems drawn from combustion kinetics. The comparisons show that LSODE is the fastest code available for the integration of combustion kinetic rate equations. It is shown that an iterative solution of the algebraic energy conservation equation to compute the temperature can be more efficient then evaluating the temperature by integrating its time-derivative.
Yao, Yijun; Shen, Rui; Pennel, Kelly G.; Suuberg, Eric M.
2013-01-01
In subsurface vapor intrusion, aerobic biodegradation has been considered as a major environmental factor that determines the soil gas concentration attenuation factors for contaminants such as petroleum hydrocarbons. The site investigation showed that oxygen could play an important role in this biodegradation rate, and this paper explores the influence of oxygen concentration in biodegradation reactions included in vapor intrusion (VI) models. Two different three dimensional (3-D) numerical models of vapor intrusion were explored for their sensitivity to the form of the biodegradation rate law. A second order biodegradation rate law, explicitly including oxygen concentration dependence, was introduced into one model. The results indicate that the aerobic/anoxic interface depth is determined by the ratio of contaminant source vapor to atmospheric oxygen concentration, and that the contaminant concentration profile in the aerobic zone was significantly influenced by the choice of rate law. PMID:24197079
Yao, Yijun; Shen, Rui; Pennel, Kelly G; Suuberg, Eric M
2013-12-01
In subsurface vapor intrusion, aerobic biodegradation has been considered as a major environmental factor that determines the soil gas concentration attenuation factors for contaminants such as petroleum hydrocarbons. The site investigation has shown that oxygen can play an important role in this biodegradation rate, and this paper explores the influence of oxygen concentration on biodegradation reactions included in vapor intrusion (VI) models. Two different three dimensional (3-D) numerical models of vapor intrusion were explored for their sensitivity to the form of the biodegradation rate law. A second order biodegradation rate law, explicitly including oxygen concentration dependence, was introduced into one model. The results indicate that the aerobic/anoxic interface depth is determined by the ratio of contaminant source vapor to atmospheric oxygen concentration, and that the contaminant concentration profile in the aerobic zone was significantly influenced by the choice of rate law. PMID:24197079
Experimental and numerical study on tensile strength of concrete under different strain rates.
Min, Fanlu; Yao, Zhanhu; Jiang, Teng
2014-01-01
The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at strain rates of 10(-7) s(-1) to 10(-4) s(-1) in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as effect of strain rates. PMID:24883355
Experimental and Numerical Study on Tensile Strength of Concrete under Different Strain Rates
Min, Fanlu; Yao, Zhanhu; Jiang, Teng
2014-01-01
The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at strain rates of 10−7 s−1 to 10−4 s−1 in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as effect of strain rates. PMID:24883355
NASA Astrophysics Data System (ADS)
Saksala, Timo
2015-07-01
In this paper, the embedded discontinuity approach is applied in finite element modeling of rock in compression and tension. For this end, a rate-dependent constitutive model based on (strong) embedded displacement discontinuity model is developed to describe the mode I, mode II and mixed mode fracture of rock. The constitutive model describes the bulk material as linear elastic until reaching the elastic limit. Beyond the elastic limit, the rate-dependent exponential softening law governs the evolution of the displacement jump. Rock heterogeneity is incorporated in the present approach by random description of the mineral texture of rock. Moreover, initial microcrack population always present in natural rocks is accounted for as randomly-oriented embedded discontinuities. In the numerical examples, the model properties are extensively studied in uniaxial compression. The effect of loading rate and confining pressure is also tested in the 2D (plane strain) numerical simulations. These simulations demonstrate that the model captures the salient features of rock in confined compression and uniaxial tension. The developed method has the computational efficiency of continuum plasticity models. However, it also has the advantage, over these models, of accounting for the orientation of introduced microcracks. This feature is crucial with respect to the fracture behavior of rock in compression as shown in this paper.
NASA Technical Reports Server (NTRS)
Gokoglu, S. A.; Kuczmarski, M.; Veitch, L.; Tsui, P.; Chait, A.
1990-01-01
The computational fluid dynamics (CFD) code FLUENT is adopted to simulate a cylindrical upflow reactor designed for chemical vapor deposition (CVD) on monofilaments. Equilibrium temperature profiles along the fiber and quartz reactor wall are experimentally measured and used as boundary conditions in numerical simulations. Two-dimensional axisymmetric flow and temperature fields are calculated for hydrogen and argon; the effect of free convection is assessed. The gas and surface chemistry is included for predicting silicon deposition from silane. The model predictions are compared with experimentally measured silicon CVD rates. Inferences are made for optimum conditions to obtain uniformity.
NASA Technical Reports Server (NTRS)
Raymond, William H.; Olson, William S.
1990-01-01
Delay in the spin-up of precipitation early in numerical atmospheric forecasts is a deficiency correctable by diabatic initialization combined with diabatic forcing. For either to be effective requires some knowledge of the magnitude and vertical placement of the latent heating fields. Until recently the best source of cloud and rain water data was the remotely sensed vertical integrated precipitation rate or liquid water content. Vertical placement of the condensation remains unknown. Some information about the vertical distribution of the heating rates and precipitating liquid water and ice can be obtained from retrieval techniques that use a physical model of precipitating clouds to refine and improve the interpretation of the remotely sensed data. A description of this procedure and an examination of its 3-D liquid water products, along with improved modeling methods that enhance or speed-up storm development is discussed.
A comparison of the efficiency of numerical methods for integrating chemical kinetic rate equations
NASA Technical Reports Server (NTRS)
Radhakrishnan, K.
1984-01-01
A comparison of the efficiency of several algorithms recently developed for the efficient numerical integration of stiff ordinary differential equations is presented. The methods examined include two general-purpose codes EPISODE and LSODE and three codes (CHEMEQ, CREK1D, and GCKP84) developed specifically to integrate chemical kinetic rate equations. The codes are applied to two test problems drawn from combustion kinetics. The comparisons show that LSODE is the fastest code currently available for the integration of combustion kinetic rate equations. An important finding is that an iterative solution of the algebraic energy conservation equation to compute the temperature can be more efficient than evaluating the temperature by integrating its time-derivative.
Estimation of geopotential from satellite-to-satellite range rate data: Numerical results
NASA Technical Reports Server (NTRS)
Thobe, Glenn E.; Bose, Sam C.
1987-01-01
A technique for high-resolution geopotential field estimation by recovering the harmonic coefficients from satellite-to-satellite range rate data is presented and tested against both a controlled analytical simulation of a one-day satellite mission (maximum degree and order 8) and then against a Cowell method simulation of a 32-day mission (maximum degree and order 180). Innovations include: (1) a new frequency-domain observation equation based on kinetic energy perturbations which avoids much of the complication of the usual Keplerian element perturbation approaches; (2) a new method for computing the normalized inclination functions which unlike previous methods is both efficient and numerically stable even for large harmonic degrees and orders; (3) the application of a mass storage FFT to the entire mission range rate history; (4) the exploitation of newly discovered symmetries in the block diagonal observation matrix which reduce each block to the product of (a) a real diagonal matrix factor, (b) a real trapezoidal factor with half the number of rows as before, and (c) a complex diagonal factor; (5) a block-by-block least-squares solution of the observation equation by means of a custom-designed Givens orthogonal rotation method which is both numerically stable and tailored to the trapezoidal matrix structure for fast execution.
Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.
2003-01-01
The use of multi-dimensional finite volume numerical techniques with finite thickness models for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the one-dimensional semi -infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody were investigated. An array of streamwise orientated heating striations were generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients due to the striation patterns two-dimensional heat transfer techniques were necessary to obtain accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates because it did not account for lateral heat conduction in the model.
Numerical simulation of hypersonic inlet flows with equilibrium or finite rate chemistry
NASA Technical Reports Server (NTRS)
Yu, Sheng-Tao; Hsieh, Kwang-Chung; Shuen, Jian-Shun; Mcbride, Bonnie J.
1988-01-01
An efficient numerical program incorporated with comprehensive high temperature gas property models has been developed to simulate hypersonic inlet flows. The computer program employs an implicit lower-upper time marching scheme to solve the two-dimensional Navier-Stokes equations with variable thermodynamic and transport properties. Both finite-rate and local-equilibrium approaches are adopted in the chemical reaction model for dissociation and ionization of the inlet air. In the finite rate approach, eleven species equations coupled with fluid dynamic equations are solved simultaneously. In the local-equilibrium approach, instead of solving species equations, an efficient chemical equilibrium package has been developed and incorporated into the flow code to obtain chemical compositions directly. Gas properties for the reaction products species are calculated by methods of statistical mechanics and fit to a polynomial form for C(p). In the present study, since the chemical reaction time is comparable to the flow residence time, the local-equilibrium model underpredicts the temperature in the shock layer. Significant differences of predicted chemical compositions in shock layer between finite rate and local-equilibrium approaches have been observed.
28 CFR 0.10 - Attorney General's Advisory Committee of U.S. Attorneys.
Code of Federal Regulations, 2010 CFR
2010-07-01
... the Associate Attorney General in formulating new programs for improvement of the criminal justice... U.S. Attorneys. 0.10 Section 0.10 Judicial Administration DEPARTMENT OF JUSTICE ORGANIZATION OF THE DEPARTMENT OF JUSTICE Office of the Attorney General § 0.10 Attorney General's Advisory Committee of...
28 CFR 0.10 - Attorney General's Advisory Committee of U.S. Attorneys.
Code of Federal Regulations, 2014 CFR
2014-07-01
... the Associate Attorney General in formulating new programs for improvement of the criminal justice... U.S. Attorneys. 0.10 Section 0.10 Judicial Administration DEPARTMENT OF JUSTICE ORGANIZATION OF THE DEPARTMENT OF JUSTICE Office of the Attorney General § 0.10 Attorney General's Advisory Committee of...
28 CFR 0.10 - Attorney General's Advisory Committee of U.S. Attorneys.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 28 Judicial Administration 1 2013-07-01 2013-07-01 false Attorney General's Advisory Committee of U.S. Attorneys. 0.10 Section 0.10 Judicial Administration DEPARTMENT OF JUSTICE ORGANIZATION OF THE DEPARTMENT OF JUSTICE Office of the Attorney General § 0.10 Attorney General's Advisory Committee of...
NASA Astrophysics Data System (ADS)
Lo, Po-Wei; Guo, Guang-Yu; Anders, Frithjof B.
2014-05-01
Motivated by the recent observation of the Kondo effect in graphene in transport experiments, we investigate the resistivity and dephasing rate in the Kondo regime due to magnetic impurities in graphene with different chemical potentials (μ). The Kondo effect due to either carbon vacancies or magnetic adatoms in graphene is described by the single-orbital pseudogap asymmetric Anderson impurity model which is solved by the accurate numerical renormalization group method. We find that although the Anderson impurity model considered here is a mixed-valence system, it can be driven into either the Kondo [μ >μc (critical value) >0], mixed-valency (μ ≈μc), or empty-orbital (μ <μc) regime by a gate voltage, giving rise to characteristic features in resistivity and dephasing rate in each regime. Specifically, in the case of μ <μc, the shapes of the resistivity (dephasing rate) curves for different μ are nearly identical. However, as temperature decreases, they start to increase to their maxima at a lower T /TK, but more rapidly [as (TK/T)3/2] than in normal metals [here, T (TK) denotes the (Kondo) temperature]. As T further decreases, after reaching the maximum, the dephasing rate drops more quickly than in normal metals, behaving as (T/TK)3 instead of (T/TK)2. Furthermore, the resistivity has a distinct peak above the saturation value near TK. In the case of μ >μc, in contrast, the resistivity curve has an additional broad shoulder above 10TK and the dephasing rate exhibits an interesting shoulder-peak shape. In the narrow boundary region (μ ≈μc), both the resistivity and dephasing rate curves are similar to the corresponding ones in normal metals. This explains the conventional Kondo-like resistivity from recent experiments on graphene with defects, although the distinct features in the resistivity in the other cases (μ <μc or μ >μc) were not seen in the experiments. The interesting features in the resistivity and dephasing rate are analyzed in
Numerical simulation of mud erosion rate in sand-mud alternate layer and comparison with experiment
NASA Astrophysics Data System (ADS)
Yoshida, T.; Yamaguchi, T.; Oyama, H.; Sato, T.
2015-12-01
For gas production from methane hydrates in sand-mud alternate layers, depressurization method is expected as feasible. After methane hydrate is dissociated, gas and water flow in pore space. There is a concern about the erosion of mud surface and it may result in flow blockage that disturbs the gas production. As a part of a Japanese National hydrate research program (MH21, funded by METI), we developed a numerical simulation of water-induced mud erosion in pore-scale sand-mud domains to model such mud erosion. The size of which is of the order of 100 micro meter. Water flow is simulated using a lattice Boltzmann method (LBM) and mud surface is treated as solid boundary with arbitrary shape, which changes with time. Periodic boundary condition is adopted at the domain boundaries, except for the surface of mud layers and the upper side. Shear stress acting on the mud surface is calculated using a momentum-exchange method. Mud layer is eroded when the shear stress exceeds a threshold coined a critical shear stress. In this study, we compared the simulated mud erosion rate with experimental data acquired from an experiment using artificial sand-mud core. As a result, the simulated erosion rate agrees well with that of the experiment.
Heinz, Sebastian; Mielke, Alexander
2016-04-28
We revisit the model for a two-well phase transformation in a linearly elastic body that was introduced and studied in Mielke et al. (2002 Arch. Ration. Mech. Anal. 162: , 137-177). This energetic rate-independent system is posed in terms of the elastic displacement and an internal variable that gives the phase portion of the second phase. We use a new approach based on mutual recovery sequences, which are adjusted to a suitable energy increment plus the associated dissipated energy and, thus, enable us to pass to the limit in the construction of energetic solutions. We give three distinct constructions of mutual recovery sequences which allow us (i) to generalize the existence result in Mielke et al. (2002), (ii) to establish the convergence of suitable numerical approximations via space-time discretization and (iii) to perform the evolutionary relaxation from the pure-state model to the relaxed-mixture model. All these results rely on weak converge and involve the H-measure as an essential tool. PMID:27002066
NASA Astrophysics Data System (ADS)
Mayeur, Jason R.; Mourad, Hashem M.; Luscher, Darby J.; Hunter, Abigail; Kenamond, Mark A.
2016-05-01
This paper details a numerical implementation of a single crystal plasticity model with dislocation transport for high strain rate applications. Our primary motivation for developing the model is to study the influence of dislocation transport and conservation on the mesoscale response of metallic crystals under extreme thermo-mechanical loading conditions (e.g. shocks). To this end we have developed a single crystal plasticity theory (Luscher et al (2015)) that incorporates finite deformation kinematics, internal stress fields caused by the presence of geometrically necessary dislocation gradients, advection equations to model dislocation density transport and conservation, and constitutive equations appropriate for shock loading (equation of state, drag-limited dislocation velocity, etc). In the following, we outline a coupled finite element–finite volume framework for implementing the model physics, and demonstrate its capabilities in simulating the response of a [1 0 0] copper single crystal during a plate impact test. Additionally, we explore the effect of varying certain model parameters (e.g. mesh density, finite volume update scheme) on the simulation results. Our results demonstrate that the model performs as intended and establishes a baseline of understanding that can be leveraged as we extend the model to incorporate additional and/or refined physics and move toward a multi-dimensional implementation.
Henry, Christophe; Minier, Jean-Pierre; Lefèvre, Grégory; Hurisse, Olivier
2011-04-19
test case. These new numerical results show that nonzero deposition rates are now obtained even in repulsive conditions, which confirms that surface roughness is a relevant aspect to introduce in general approaches to deposition. PMID:21405065
NASA Technical Reports Server (NTRS)
Oguzman, Ismail H.; Wang, Yang; Kolnik, Jan; Brennan, Kevin F.
1995-01-01
The hole initiated impact ionization rate in bulk silicon and GaAs is calculated using a numerical formulation of the impact ionization transition rate incorporated into an ensemble Monte Carlo simulation. The transition rate is calculated from Fermi's golden rule using a two-body screened Coulomb interaction including a wavevector dependent dielectric function. It is found that the effective threshold for hole initiated ionization is relatively soft in both materials, that the split-off band dominates the ionization process in GaAs. and that no clear dominance by any one band is observed in silicon, though the rate out of the light hole band is greatest.
NASA Technical Reports Server (NTRS)
Wang, Yang; Brennan, Kevin F.
1994-01-01
Ensemble Monte Carlo calculations of the electron interband impact ionization rate in bulk GaAs are presented using a wave-vector (k)-dependent formulation of the ionization transition rate. The transition rate is evaluated through the use of numerically generated wavefunctions determined via a k-p calculation within the first two conduction bands at numerous points within a finely spaced three-dimensional grid in k space. The transition rate is determined to be greatest for states within the second conduction band. Is is found that the interband impact ionization transition rate in bulk GaAs is best characterized as having an exceedingly soft threshold energy. As a consequence, the dead space, defined as the distance over which the ionization probability for a given carrier is assumed to be zero, is estimated to be much larger than that estimated using a harder threshold. These results have importance in the design of the multiquantum-well avalanche photodiodes.
NASA Technical Reports Server (NTRS)
Wang, Yang; Brennan, Kevin F.
1994-01-01
Ensemble Monte Carlo calculations of the electron interband impact ionization rate in bulk GaAs are presented using a wave-vector (k)-dependent formulation of the ionization transition rate. The transition rate is evaluated through use of numerically generated wavefunctions determined via a k-p calculation within the first two conduction bonds at numerous points within a finely spaced three-dimensional grid in k space. The transition rate is determined to be greatest for states within the second conduction band. It is found that the interband impact ionization transition rate in bulk GaAs is best characterized as having an exceedingly "soft" threshold energy. As a consequence, the dead space, defined as the distance over which the ionization probability for a given carrier is assumed to be zero, is estimated to be-much larger than that estimated using a "harder" threshold. These results have importance in the design of multiquantum-well avalanche photodiodes.
NASA Astrophysics Data System (ADS)
Zhu, W. C.; Niu, L. L.; Li, S. H.; Xu, Z. H.
2015-09-01
The tensile strength of rock subjected to dynamic loading constitutes many engineering applications such as rock drilling and blasting. The dynamic Brazilian test of rock specimens was conducted with the split Hopkinson pressure bar (SHPB) driven by pendulum hammer, in order to determine the indirect tensile strength of rock under an intermediate strain rate ranging from 5.2 to 12.9 s-1, which is achieved when the incident bar is impacted by pendulum hammer with different velocities. The incident wave excited by pendulum hammer is triangular in shape, featuring a long rising time, and it is considered to be helpful for achieving a constant strain rate in the rock specimen. The dynamic indirect tensile strength of rock increases with strain rate. Then, the numerical simulator RFPA-Dynamics, a well-recognized software for simulating the rock failure under dynamic loading, is validated by reproducing the Brazilian test of rock when the incident stress wave retrieved at the incident bar is input as the boundary condition, and then it is employed to study the Brazilian test of rock under the higher strain rate. Based on the numerical simulation, the strain-rate dependency of tensile strength and failure pattern of the Brazilian disc specimen under the intermediate strain rate are numerically simulated, and the associated failure mechanism is clarified. It is deemed that the material heterogeneity should be a reason for the strain-rate dependency of rock.
Pan, Wenxiao; Daily, Michael; Baker, Nathan A.
2015-05-07
Background: The calculation of diffusion-controlled ligand binding rates is important for understanding enzyme mechanisms as well as designing enzyme inhibitors. Methods: We demonstrate the accuracy and effectiveness of a Lagrangian particle-based method, smoothed particle hydrodynamics (SPH), to study diffusion in biomolecular systems by numerically solving the time-dependent Smoluchowski equation for continuum diffusion. Unlike previous studies, a reactive Robin boundary condition (BC), rather than the absolute absorbing (Dirichlet) BC, is considered on the reactive boundaries. This new BC treatment allows for the analysis of enzymes with “imperfect” reaction rates. Results: The numerical method is first verified in simple systems and thenmore » applied to the calculation of ligand binding to a mouse acetylcholinesterase (mAChE) monomer. Rates for inhibitor binding to mAChE are calculated at various ionic strengths and compared with experiment and other numerical methods. We find that imposition of the Robin BC improves agreement between calculated and experimental reaction rates. Conclusions: Although this initial application focuses on a single monomer system, our new method provides a framework to explore broader applications of SPH in larger-scale biomolecular complexes by taking advantage of its Lagrangian particle-based nature.« less
Pan, Wenxiao; Daily, Michael; Baker, Nathan A.
2015-05-07
Background: The calculation of diffusion-controlled ligand binding rates is important for understanding enzyme mechanisms as well as designing enzyme inhibitors. Methods: We demonstrate the accuracy and effectiveness of a Lagrangian particle-based method, smoothed particle hydrodynamics (SPH), to study diffusion in biomolecular systems by numerically solving the time-dependent Smoluchowski equation for continuum diffusion. Unlike previous studies, a reactive Robin boundary condition (BC), rather than the absolute absorbing (Dirichlet) BC, is considered on the reactive boundaries. This new BC treatment allows for the analysis of enzymes with “imperfect” reaction rates. Results: The numerical method is first verified in simple systems and then applied to the calculation of ligand binding to a mouse acetylcholinesterase (mAChE) monomer. Rates for inhibitor binding to mAChE are calculated at various ionic strengths and compared with experiment and other numerical methods. We find that imposition of the Robin BC improves agreement between calculated and experimental reaction rates. Conclusions: Although this initial application focuses on a single monomer system, our new method provides a framework to explore broader applications of SPH in larger-scale biomolecular complexes by taking advantage of its Lagrangian particle-based nature.
'Did not attends' in children 0-10: a scoping review.
Arai, L; Stapley, S; Roberts, H
2014-11-01
Patients who do not attend ('DNA') health appointments have been identified as a service problem incurring significant costs to the NHS. In order to explore the causes, effects and costs of child DNAs, we carried out a scoping study to map the literature and identify gaps in the research. Given the breadth of issues underpinning DNAs, a scoping study, including research studies, audits, policy documents and conference abstracts, was the most useful way to map the field. To foster public and patient participation, we sought advice from parents participating in the National Children's Bureau's Family Research Advisory Group. From a pool of 1997 items, we found few UK studies with non-attendance of 0-10 year olds as a primary focus, though many more incidentally reported DNA rates. Overall, four topics predominated: the conceptualization of DNAs; the correlates of non-attendance; initiatives to reduce non-attendance; and the relationship between non-attendance and safeguarding. The Family Research Advisory Group identified broadly similar issues, but with a stronger emphasis on communication and practical matters. While there may be circumstances where failing to attend appointments makes little or no difference to a child (or even benefits them) it is likely that there are children whose health or well-being are compromised as a result of failing to attend appointments. Both 'over' and 'under'-attendance can be a source of anxiety to health professionals. Areas where further work is needed include robust evaluation of the effectiveness, cost-effectiveness and maintenance of measures to reduce DNAs and a better understanding of the relationship of safeguarding to non-attendance. PMID:24134800
NASA Astrophysics Data System (ADS)
Illg, Christian; Haag, Michael; Teeny, Nicolas; Wirth, Jens; Fähnle, Manfred
2016-03-01
Scatterings of electrons at quasiparticles or photons are very important for many topics in solid-state physics, e.g., spintronics, magnonics or photonics, and therefore a correct numerical treatment of these scatterings is very important. For a quantum-mechanical description of these scatterings, Fermi's golden rule is used to calculate the transition rate from an initial state to a final state in a first-order time-dependent perturbation theory. One can calculate the total transition rate from all initial states to all final states with Boltzmann rate equations involving Brillouin zone integrations. The numerical treatment of these integrations on a finite grid is often done via a replacement of the Dirac delta distribution by a Gaussian. The Dirac delta distribution appears in Fermi's golden rule where it describes the energy conservation among the interacting particles. Since the Dirac delta distribution is a not a function it is not clear from a mathematical point of view that this procedure is justified. We show with physical and mathematical arguments that this numerical procedure is in general correct, and we comment on critical points.
Pan, Wenxiao; Daily, Michael D.; Baker, Nathan A.
2015-12-01
We demonstrate the accuracy and effectiveness of a Lagrangian particle-based method, smoothed particle hydrodynamics (SPH), to study diffusion in biomolecular systems by numerically solving the time-dependent Smoluchowski equation for continuum diffusion. The numerical method is first verified in simple systems and then applied to the calculation of ligand binding to an acetylcholinesterase monomer. Unlike previous studies, a reactive Robin boundary condition (BC), rather than the absolute absorbing (Dirichlet) boundary condition, is considered on the reactive boundaries. This new boundary condition treatment allows for the analysis of enzymes with "imperfect" reaction rates. Rates for inhibitor binding to mAChE are calculated at various ionic strengths and compared with experiment and other numerical methods. We find that imposition of the Robin BC improves agreement between calculated and experimental reaction rates. Although this initial application focuses on a single monomer system, our new method provides a framework to explore broader applications of SPH in larger-scale biomolecular complexes by taking advantage of its Lagrangian particle-based nature.
Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.
2006-01-01
The use of multi-dimensional finite volume heat conduction techniques for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the standard one-dimensional semi-infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the NASA Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody was investigated. An array of streamwise-orientated heating striations was generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients caused by striation patterns multi-dimensional heat transfer techniques were necessary to obtain more accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates compared to 2-D analysis because it did not account for lateral heat conduction in the model.
ERIC Educational Resources Information Center
Erickson, Ron; Ysseldyke, Jim; Thurlow, Martha
1997-01-01
Reviews present difficulties in the way that states report the participation of students with disabilities in their testing programs. Recommendations for policymakers include the following: identify students with disabilities in statewide assessment programs, standardize procedures for calculating participation rates, and improve lines of…
Marxen, Olaf; Magin, Thierry E.; Shaqfeh, Eric S.G.; Iaccarino, Gianluca
2013-12-15
A new numerical method is presented here that allows to consider chemically reacting gases during the direct numerical simulation of a hypersonic fluid flow. The method comprises the direct coupling of a solver for the fluid mechanical model and a library providing the physio-chemical model. The numerical method for the fluid mechanical model integrates the compressible Navier–Stokes equations using an explicit time advancement scheme and high-order finite differences. This Navier–Stokes code can be applied to the investigation of laminar-turbulent transition and boundary-layer instability. The numerical method for the physio-chemical model provides thermodynamic and transport properties for different gases as well as chemical production rates, while here we exclusively consider a five species air mixture. The new method is verified for a number of test cases at Mach 10, including the one-dimensional high-temperature flow downstream of a normal shock, a hypersonic chemical reacting boundary layer in local thermodynamic equilibrium and a hypersonic reacting boundary layer with finite-rate chemistry. We are able to confirm that the diffusion flux plays an important role for a high-temperature boundary layer in local thermodynamic equilibrium. Moreover, we demonstrate that the flow for a case previously considered as a benchmark for the investigation of non-equilibrium chemistry can be regarded as frozen. Finally, the new method is applied to investigate the effect of finite-rate chemistry on boundary layer instability by considering the downstream evolution of a small-amplitude wave and comparing results with those obtained for a frozen gas as well as a gas in local thermodynamic equilibrium.
Numerical study of strain-rate effect in cold rolls forming of steel
NASA Astrophysics Data System (ADS)
Falsafi, J.; Demirci, E.; Silberschmidt, V. V.
2013-07-01
Cold roll forming (CRF) is a well-known continuous manufacturing process, in which a flat strip is deformed by successive rotating pairs of tools, without changing the material thickness. In the past decades, to lessen the process-development efforts, finite-element simulations have been increasingly employed to improve the process design and predict the manufacturing-induced defects. One of the important aspects in design of the CRF process is consideration of resulting strains in the final product as the material passes through several complex forming stands. Sufficient knowledge of longitudinal strain in the workpiece is required to set various process parameters. Increasing a process speed in a roll forming operation can bring cost advantages, but the influence of the forming speed on the strain distribution should be explored. This study is focussed on a strain-rate effect in the CRF process of steel sheets. The strain-rate dependency of a plastic behaviour observed in most metals can affect the finished product's quality as well as process parameters. This paper investigates the influence of the strain rate on longitudinal strains induced in the roll forming operation by incorporating a phenomenological Johnson-Cook constitutive model, which allows studying the impact of the process speed on the output product. Taking advantage of 3D finite element analysis, a roll forming process was simulated using MCS.Marc, comprising a complete set of forming stations. Through the changing of the process speed, the strain rate impact on longitudinal peak strains and forming length was investigated. The results highlight the effect of the strain rate on edge thinning and subsequent undesirable distortions in the product.
NASA Astrophysics Data System (ADS)
Pitter, Richard L.; Zhang, Renyi
1991-06-01
Numerical models of trajectories of small aerosol spheres relative to oblate spheroids were used to determine ice crystal scavenging efficiencies. The models included the effects of aerodynamic flow about the ice particle, gravity, aerosol particle inertia and drag and electrostatic effects. Two electric configurations of the ice particle were investigated in detail. The first applied a net charge to the ice particle, of magnitude equal to the mean thunderstorm charge distribution, while the second applied a charge distribution, with no net charge, to the ice particle to model the electric multipole charge distribution. The results show that growing ice crystals with electric multipoles are better scavengers than single ice crystals with net thunderstorm charges, especially in the Greenfield gap (0.1 to 1.0 μm), and that larger single crystals are better scavengers than smaller single crystals. The results also show that the low density ice crystals are more effective scavengers with net charges than they are with charge distribution.
Numerical study of finite-rate supersonic combustion using parabolized equations
NASA Technical Reports Server (NTRS)
Chitsomboon, T.; Kumar, A.; Tiwari, S. N.
1987-01-01
A set of partial differential equations, describing the two-dimensional supersonic chemically-reacting flow of the hydrogen-air system, is formulated such that the equations are parabolic in the streamwise direction. A fully-implicit fully-coupled finite-difference algorithm is used to develop a computer code which solves the governing equations by marching in the streamwise direction. The combustion process is modeled by a two-step finite-rate chemistry whereas turbulence is simulated by an algebraic turbulence model. Results of two calculations of internal supersonic reacting flow show fairly good agreement with the results obtained by the more costly full Navier-Stokes procedure.
NASA Astrophysics Data System (ADS)
Sun, Yongle; Li, Q. M.; Withers, P. J.
2015-09-01
Realistic simulations are increasingly demanded to clarify the dynamic behaviour of foam materials, because, on one hand, the significant variability (e.g. 20% scatter band) of foam properties and the lack of reliable dynamic test methods for foams bring particular difficulty to accurately evaluate the strain-rate sensitivity in experiments; while on the other hand numerical models based on idealised cell structures (e.g. Kelvin and Voronoi) may not be sufficiently representative to capture the actual structural effect. To overcome these limitations, the strain-rate sensitivity of the compressive and tensile properties of closed-cell aluminium Alporas foam is investigated in this study by means of meso-scale realistic finite element (FE) simulations. The FE modelling method based on X-ray computed tomography (CT) image is introduced first, as well as its applications to foam materials. Then the compression and tension of Alporas foam at a wide variety of applied nominal strain-rates are simulated using FE model constructed from the actual cell geometry obtained from the CT image. The stain-rate sensitivity of compressive strength (collapse stress) and tensile strength (0.2% offset yield point) are evaluated when considering different cell-wall material properties. The numerical results show that the rate dependence of cell-wall material is the main cause of the strain-rate hardening of the compressive and tensile strengths at low and intermediate strain-rates. When the strain-rate is sufficiently high, shock compression is initiated, which significantly enhances the stress at the loading end and has complicated effect on the stress at the supporting end. The plastic tensile wave effect is evident at high strain-rates, but shock tension cannot develop in Alporas foam due to the softening associated with single fracture process zone occurring in tensile response. In all cases the micro inertia of individual cell walls subjected to localised deformation is found to
Numerical Modelling of Wire-EDM for Predicting Erosion Rate of Silicon
NASA Astrophysics Data System (ADS)
Joshi, Kamlesh; Sharma, Gaurav; Dongre, Ganesh; Joshi, Suhas Sitaram
2016-05-01
Recently, a lot of work is carried out in photovoltaic industry for slicing Si ingots using non-conventional technique like wire-EDM apart from conventional techniques like inner diameter saw and multi-wire saw. It is an emerging technology in field of Si wafer slicing and has a potential to be cost efficient. It reduces the kerf-loss and produces crack-free Si wafers. In general, the process of Si wafer cutting using wire-EDM is less understood due to its complex nature. In this work, the complex phenomena like formation of plasma channel, melting and erosion of Si material has been modelled mathematically. Further, the effect of input energy parameters like current, open voltage and pulse on-time on plasma and plasma-ingot interface temperature has been studied. The model is further extended along the length of the wire to evaluate the erosion depth and rate. The effect of process parameters on erosion depth and rate was validated experimentally. The model considers variation in material removal through the `plasma flushing efficiency'.
NASA Astrophysics Data System (ADS)
Khazaeli, Ali; Vatani, Ali; Tahouni, Nassim; Panjeshahi, Mohammad Hassan
2015-10-01
In flow batteries, electrolyte flow rate plays a crucial role on the minimizing mass transfer polarization which is at the compensation of higher pressure drop. In this work, a two-dimensional numerical method is applied to investigate the effect of electrolyte flow rate on cell voltage, maximum depth of discharge and pressure drop a six-cell stack of VRFB. The results show that during the discharge process, increasing electrolyte flow rate can raise the voltage of each cell up to 50 mV on average. Moreover, the maximum depth of discharge dramatically increases with electrolyte flow rate. On the other hand, the pressure drop also positively correlates with electrolyte flow rate. In order to investigate all these effects simultaneously, average energy and exergy efficiencies are introduced in this study for the transient process of VRFB. These efficiencies give insight into choosing an appropriate strategy for the electrolyte flow rate. Finally, the energy efficiency of electricity storage using VRFB is investigated and compared with other energy storage systems. The results illustrate that this kind of battery has at least 61% storage efficiency based on the second law of thermodynamics, which is considerably higher than that of their counterparts.
Maltsev, Victor A.; Vinogradova, Tatiana M.; Bogdanov, Konstantin Y.; Lakatta, Edward G.; Stern, Michael D.
2004-01-01
Recent studies employing Ca2+ indicators and confocal microscopy demonstrate substantial local Ca2+ release beneath the cell plasma membrane (subspace) of sinoatrial node cells (SANCs) occurring during diastolic depolarization. Pharmacological and biophysical experiments have suggested that the released Ca2+ interacts with the plasma membrane via the ion current (INaCa) produced by the Na+/Ca2+ exchanger and constitutes an important determinant of the pacemaker rate. This study provides a numerical validation of the functional importance of diastolic Ca2+ release for rate control. The subspace Ca2+ signals in rabbit SANCs were measured by laser confocal microscopy, averaged, and calibrated. The time course of the subspace [Ca2+] displayed both diastolic and systolic components. The diastolic component was mainly due to the local Ca2+ releases; it was numerically approximated and incorporated into a SANC cellular electrophysiology model. The model predicts that the diastolic Ca2+ release strongly interacts with plasma membrane via INaCa and thus controls the phase of the action potential upstroke and ultimately the final action potential rate. PMID:15041695
Numerical analysis of high strain rate failure of electro-magnetically loaded steel sheets
NASA Astrophysics Data System (ADS)
Erice, Borja; Mohr, Dirk
2015-09-01
Electro-magnetic forces provide a potentially power full means in designing dynamic experiments with active control of the loading conditions. This article deals with the development of computational models to simulate the thermo-mechanical response of electro-magnetically loaded metallic structures. The model assumes linear electromagnetic constitutive equations and time-independent electric induction to estimate the Joule heating and the Lorentz forces. The latter are then taken into account when evaluating stress equilibrium. A thermo-visco-plastic model with Johnson-Cook type of temperature and strain rate dependence and combined Swift-Voce hardening is used to evaluate the material's thermo-mechanical response. As a first application, the model is used to analyse the effect of electro-magnetic loading on the ductility of advanced high strength steels.
NASA Astrophysics Data System (ADS)
Neubauer, M.; Musolff, A.; Fleckenstein, J. H.
2013-12-01
Residence time distributions (RTD) of water in catchments are promising tools to characterize and model solute transport on a larger scale. In the last decade, much research has been conducted on the estimation and the application of RTD's. However, there are still some major issues to be addressed to complex derivation, parameterization and transient behavior. Through improved remote sensing data, the surface elevation can mostly be resolved in detail, while subsurface volumes and boundaries remain highly undetermined. Our objectives are to systematically evaluate the impact of different depths and geometries of the domain bottom and groundwater recharge rates on RTD's. The study site is a small (1.6 km2) headwater catchment located within the Harz Mountains, Germany. For this catchment long time series of climate, discharge and hydrochemistry are available while groundwater flow field and subsurface structure are less known. The site is intensively influenced by agricultural land use and exhibits strong seasonal dynamics of water flow and hydrochemistry due to the snowmelt. The modeling was performed using HydroGeoSphere, a coupled surface and subsurface model, which solves the Richards Equation for variable saturated soils. The Open Source software Paraview and R was chosen as postprocessors to perform and analyze forward particle tracking algorithms under steady state conditions. Ten depth and geometry scenarios of the domain bottom were created (5 horizontal bottom geometries - constant base and 5 variable bottom geometries - parallel to surface topography; both minimum depths ranging from 2 m to 50 m). The model's internal structure was discretized by two homogenous layers (averaged catchment representation) parallel to the input digital elevation model (2x2 m). The geometry scenarios were combined with fifteen steady state simulations for different groundwater recharge rate scenarios (0.1 mm up to 15 mm per day). Model results indicate a strong influence of
Numerical Simulation of Alongshore Variation of Sediment Transport Rate Downdrift of a Tidal Inlet
NASA Astrophysics Data System (ADS)
Keshtpoor, M.; Puleo, J. A.; Shi, F.
2013-12-01
Indian River Inlet is located at the midpoint of the Atlantic-facing Delaware coast and connects Delaware inland bays (Rehoboth Bay to the north and Indian River Bay due west) to the Atlantic Ocean. In late 1930's the US Army Corps of Engineers constructed twin jetties to provide a safe channel for navigational and recreational purposes. Offshore extended jetties interrupted the alongshore sediment transport that resulted in severe downdrift beach recession. The main concern is the retreat of the shoreline toward the inland infrastucture, such as State Route 1, within 1000 m downdrift of the inlet. In recent years the rate of sediment loss from the downdrift beach has increased and the sediment bypassing system was not able to mitigate the shoreline recession. Here, NearCOM, that couples a wave model, a nearshore circulation model, and a sediment transport model is applied to simulate the hydrodynamics and sediment transport under the impact of tide and wave forcing in the inlet adjacent area at the downdrift beach. The main goal is to understand the patterns of sediment transport and causes of erosion near the morphologically complex inlet. Simulations are carried out for the dominant wave cases with the high probability of occurrence. In addition, the offshore boundary is forced with conditions observed during Hurricane Felix to obtain the beach response to a severe wave case. The effect of applied wave cases on the alongshore variability of sediment transport will be discussed to address the causes of downdrift beach erosion.
Richardson, E.S.; Grout, R.W.; Chen, J.H.; Sankaran, R.
2010-03-15
The scalar mixing time scale, a key quantity in many turbulent combustion models, is investigated for reactive scalars in premixed combustion. Direct numerical simulations (DNS) of three-dimensional, turbulent Bunsen flames with reduced methane-air chemistry have been analyzed in the thin reaction zones regime. Previous conclusions from single step chemistry DNS studies are confirmed regarding the role of dilatation and turbulence-chemistry interactions on the progress variable dissipation rate. Compared to the progress variable, the mixing rates of intermediate species is found to be several times greater. The variation of species mixing rates are explained with reference to the structure of one-dimensional premixed laminar flames. According to this analysis, mixing rates are governed by the strong gradients which are imposed by flamelet structures at high Damkoehler numbers. This suggests a modeling approach to estimate the mixing rate of individual species which can be applied, for example, in transported probability density function simulations. Flame-turbulence interactions which modify the flamelet based representation are analyzed. (author)
NASA Technical Reports Server (NTRS)
Radhadrishnan, Krishnan
1993-01-01
A detailed analysis of the accuracy of several techniques recently developed for integrating stiff ordinary differential equations is presented. The techniques include two general-purpose codes EPISODE and LSODE developed for an arbitrary system of ordinary differential equations, and three specialized codes CHEMEQ, CREK1D, and GCKP4 developed specifically to solve chemical kinetic rate equations. The accuracy study is made by application of these codes to two practical combustion kinetics problems. Both problems describe adiabatic, homogeneous, gas-phase chemical reactions at constant pressure, and include all three combustion regimes: induction, heat release, and equilibration. To illustrate the error variation in the different combustion regimes the species are divided into three types (reactants, intermediates, and products), and error versus time plots are presented for each species type and the temperature. These plots show that CHEMEQ is the most accurate code during induction and early heat release. During late heat release and equilibration, however, the other codes are more accurate. A single global quantity, a mean integrated root-mean-square error, that measures the average error incurred in solving the complete problem is used to compare the accuracy of the codes. Among the codes examined, LSODE is the most accurate for solving chemical kinetics problems. It is also the most efficient code, in the sense that it requires the least computational work to attain a specified accuracy level. An important finding is that use of the algebraic enthalpy conservation equation to compute the temperature can be more accurate and efficient than integrating the temperature differential equation.
NASA Astrophysics Data System (ADS)
Shima, Shin-ichiro; Hasegawa, Koichi; Kusano, Kanya
2015-04-01
The influence of aerosol-cloud interactions on the steady state of marine stratocumulus is investigated through a series of numerical simulations of an idealized meteorological system in which aerosols are formed constantly. We constructed the system by modifying the set-up based on the RICO composite case defined in van Zanten et al. (2011). The super-droplet method (SDM) (Shima, 2008; Shima et al., 2009) is used for the simulation of cloud microphysical processes. The SDM is a particle-based and probabilistic method, with which the time evolution of aerosol/cloud/precipitation particles are calculated in a unified and accurate manner. For the simulation of atmospheric fluid dynamical processes, the cloud resolving model CReSS (Tsuboki, 2008) is used, in which the quasi-compressible approximation and the sound mode splitting method are applied. The steady states of the system are compared changing the aerosol nucleation rate and the initial number density of aerosols. It is observed that the system gradually evolves to reach its final steady state in a few days, which is irrelevant to the initial number density of aerosols. A transition of the final steady state from cumuli to strati occurs when the aerosol formation rate is increased. Chemical reactions in the gas phase and the liquid phase are not yet incorporated in the model, and the numerical simulations are performed in two dimensions. For these limitations, the results obtained are still preliminary.
NASA Astrophysics Data System (ADS)
Wehrer, Dr; Totsche, Dr
2009-04-01
Only the combination of physical models and experiments can elucidate the processes of reactive transport in porous media. Column scale experiments offer a great opportunity to identify and quantify processes of reactive transport. In contrast to batch experiments, approximately natural flow dynamics can be realized. However, due to the complexity of interactions and wide range of parameters the experiment can be insensitive to the wanted process and misinterpretation of the results is likely. In the proposed talk we want to give examples how numerical tools can be applied for thorough planning and evaluation of experiments. In a first phase, we performed systematical numerical experiments to optimize the experimental conditions, which allow the quantification of (de-)sorption kinetics under percolation conditions. For short term column experiments we found, that the application of flow interruptions along with two different flow velocities can be applied to avoid uniqueness problems with respect to identification of partitioning coefficient and mass transfer rate. By a sensitivity analysis the parameter space was divided into regions where physical reasonable parameter estimates can be expected and where equifinal solutions are likely. In a second phase we conducted column experiments to test this optimized experimental design for its suitability for the identification and quantification of rate-limited contaminant release. We used materials polluted with organic and inorganic contaminants originating from different soils, sites and materials (Coke oven sites, abandoned industrial sites, destruction debris, municipal waste incineration ash). Repacked soil columns were percolated under saturated and unsaturated conditions and were subjected to multiple flow interruptions and different flow velocities. The third phase consisted of data evaluation and process quantification applying numerical inversion of a physical transport model. The parameter sets were evaluated
Code of Federal Regulations, 2010 CFR
2010-04-01
... Investment Company Act for purposes of the Regulatory Flexibility Act. 270.0-10 Section 270.0-10 Commodity..., INVESTMENT COMPANY ACT OF 1940 § 270.0-10 Small entities under the Investment Company Act for purposes of the... defined for purposes of a particular rulemaking, the term small business or small organization...
NASA Astrophysics Data System (ADS)
Su, Ye; Shao, Wei; Vlček, Lukáš; Langhammer, Jakub
2015-04-01
Evapotranspiration drives the hydrological process through energy-driven water-phase changes between systems of soil-vegetation-atmosphere. Evapotranspiration performs a rather complex process attributable to the spatial and temporal variation of soil-vegetation-atmosphere system. For vegetation-covered land surfaces, the transpiration process is governed by the stomatal behavior and water uptake from the root zone, and evaporation is related with the interception of rainfall and radiation on the canopy and soil surface. This study is emphasized on describing the hydrological process and energy cycle in a basic hydrological response unit, a hillslope. The experimental hillslope is located in an experimental catchment of the Bohemian Forest Mountains' headwaters in the Czech Republic, where is mostly covered by dead Norway spruce forest (Picea abies) stands caused by balk beetle outbreak. High-frequency monitoring network of the hydro-climatic data, soil pore water pressure and soil temperature has been launched since 2012. To conceptualize the land-surface energy and water fluxes in a complex hillslope, a soil-vegetation-atmosphere transport (SVAT) model, coupled with a multi-phase soil physics process (i.e. the water, vapor and heat flow transport) is used. We selected an 8-week basis dataset from 2013 as a pilot for partitioning the evapotranspiration into three interactive components: transpiration (Et), canopy interception evaporation (Ei), and soil evaporation (Es), by using this numerical model. Within such model framework, the sensitive feedback of evapotranspiration rates to rainfall intensity, soil moisture, and solar radiation will be examined by conducting numerical experiments to better understand the mechanism of evapotranspiration process under various influencing factors. Such application study and followed numerical simulations provide a new path for quantifying the behaviors of the soil-vegetation-atmosphere system.
NASA Technical Reports Server (NTRS)
Gogos, George; Bowen, Brent D.; Nickerson, Jocelyn S.
2002-01-01
The NASA Nebraska Space Grant (NSGC) & EPSCoR programs have continued their effort to support outstanding research endeavors by funding the Numerical Simulation of the Combustion of Fuel Droplets study at the University of Nebraska at Lincoln (UNL). This team of researchers has developed a transient numerical model to study the combustion of suspended and moving droplets. The engines that propel missiles, jets, and many other devices are dependent upon combustion. Therefore, data concerning the combustion of fuel droplets is of immediate relevance to aviation and aeronautical personnel, especially those involved in flight operations. The experiments being conducted by Dr. Gogos and Dr. Nayagam s research teams, allow investigators to gather data for comparison with theoretical predictions of burning rates, flame structures, and extinction conditions. The consequent improved hndamental understanding droplet combustion may contribute to the clean and safe utilization of fossil hels (Williams, Dryer, Haggard & Nayagam, 1997, 72). The present state of knowledge on convective extinction of he1 droplets derives fiom experiments conducted under normal gravity conditions. However, any data obtained with suspended droplets under normal gravity are grossly affected by gravity. The need to obtain experimental data under microgravity conditions is therefore well justified and addresses one of the goals of NASA s Human Exploration and Development of Space (HEDS) microgravity combustion experiment.
Rafa, S. Molins; Trebotich, D.; Steefel, C. I.; Shen, C.
2012-02-01
The scale-dependence of geochemical reaction rates hinders their use in continuum scale models intended for the interpretation and prediction of chemical fate and transport in subsurface environments such as those considered for geologic sequestration of CO{sub 2}. Processes that take place at the pore scale, especially those involving mass transport limitations to reactive surfaces, may contribute to the discrepancy commonly observed between laboratory-determined and continuum-scale or field rates. Here, the dependence of mineral dissolution rates on the pore structure of the porous media is investigated by means of pore scale modeling of flow and multicomponent reactive transport. The pore scale model is comprised of high performance simulation tools and algorithms for incompressible flow and conservative transport combined with a general-purpose multicomponent geochemical reaction code. The model performs direct numerical simulation of reactive transport based on an operator-splitting approach to coupling transport and reactions. The approach is validated with a Poiseuille flow single-pore experiment and verified with an equivalent 1D continuum-scale model of a capillary tube packed with calcite spheres. Using the case of calcite dissolution as an example, the high resolution model is used to demonstrate that non-uniformity in the flow field at the pore scale has the effect of decreasing the overall reactivity of the system, even when systems with identical reactive surface area are considered. The effect becomes more pronounced as the heterogeneity of the reactive grain packing increases, particularly where the flow slows sufficiently such that the solution approaches equilibrium locally and the average rate becomes transport-limited.
NASA Astrophysics Data System (ADS)
Ismail-Zadeh, Alik; Le Mouël, Jean-Louis; Soloviev, Alexander; Tapponnier, Paul; Vorovieva, Inessa
2007-06-01
The Tibetan plateau and Himalayans have resulted from the continuous Indian and Eurasian plate convergence following their initial collision about 55 million years ago. Earthquakes in the region occur mainly in response to the crustal motion and stress localization associated with this convergence. To understand the basic features of the crustal motion and seismicity in the Tibet-Himalayan region, we develop a numerical model of block-and-fault dynamics. The model structure is composed of six major upper crustal blocks separated by fault planes. These blocks are assumed to be perfectly rigid and move as a consequence of the Indian plate push and of a flow of the lower crust. Deformations take place along the fault planes separating the blocks. The interaction of the blocks along the fault planes is visco-elastic as long as the ratio of the shear stress to the difference between the pore pressure and normal stress remains below a critical strength level. When the critical level is exceeded in some part of a fault plane, an earthquake (stress-drop) occurs causing also failures in adjacent parts of the fault plane. The stress-drop-affected parts of the fault plane enter in a state of creep immediately after the earthquake, and the creep lasts until the stress falls below a certain level. We develop several sets of numerical experiments to analyze the earthquake clustering, frequency-to-magnitude relationships, earthquake focal mechanisms, and fault slip rates in the model. Large events in the numerical experiments cluster on the fault segments associated with the Himalayan Frontal Thrust as well as at some internal faults of the Tibetan plateau. The clustering of earthquakes on a given fault is a consequence of the dynamics of the regional fault system rather than that of the fault only. We show that variations in the relationship of magnitude to frequency of the events are associated with changes in the motion of the upper crustal blocks and depend on the rheological
The success story at Birchwood: Operation below 0.10 lb/10{sup 6} Btu
Cohen, M.B.
1999-07-01
The Southern Energy, Inc. (SEI) Birchwood Power Facility is successfully operating on coal maintaining stack NO{sub x} emissions below 0.10 lb/10{sup 6} Btu (73 ppmvd at 3% O{sub 2}, 43 ng/J) on a 30-day rolling average. The cogeneration plant uses an integrated approach for controlling NO{sub x} including in-furnace reduction from a TFS 2000{trademark} firing system and post-combustion control from selective catalytic reduction (SCR). The plant began operation in November 1996, and continues to meet the State of Virginia's stringent environmental requirements under all operating conditions. This paper focuses upon recent performance and operation of the NO{sub x} control technologies. Operational data of the NO{sub x} emissions from the steam generator as well as those exiting the SCR are presented. In addition, the latest information from the Spring '99 outage is discussed.
Carreon, Leah Y.; Anderson, Paul A.; McDonough, Christine M.; Djurasovic, Mladen; Glassman, Steven D.
2010-01-01
Study Design Cross-sectional cohort Objective This study aims to provide an algorithm estimate SF-6D utilities using data from the NDI, neck pain and arm pain scores. Summary of Background Data Although cost-utility analysis is increasingly used to provide information about the relative value of alternative interventions, health state values or utilities are rarely available from clinical trial data. The Neck Disability Index (NDI) and numeric rating scales for neck and arm pain, are widely used disease-specific measures of symptoms, function and disability in patients with cervical degenerative disorders. The purpose of this study is to provide an algorithm to allow estimation of SF-6D utilities using data from the NDI, and numeric rating scales for neck and arm pain. Methods SF-36, NDI, neck and arm pain rating scale scores were prospectively collected pre-operatively, at 12 and 24 months post-operatively in 2080 patients undergoing cervical fusion for degenerative disorders. SF-6D utilities were computed and Spearman correlation coefficients were calculated for paired observations from multiple time points between NDI, neck and arm pain scores and SF-6D utility scores. SF-6D scores were estimated from the NDI, neck and arm pain scores using a linear regression model. Using a separate, independent dataset of 396 patients in which and NDI scores were available SF-6D was estimated for each subject and compared to their actual SF-6D. Results The mean age for those in the development sample, was 50.4 ± 11.0 years and 33% were male. In the validation sample the mean age was 53.1 ± 9.9 years and 35% were male. Correlations between the SF-6D and the NDI, neck and arm pain scores were statistically significant (p<0.0001) with correlation coefficients of 0.82, 0.62, and 0.50 respectively. The regression equation using NDI alone to predict SF-6D had an R2 of 0.66 and a root mean square error (RMSE) of 0.056. In the validation analysis, there was no statistically
ERIC Educational Resources Information Center
Betts, Lucy; Hartley, James
2012-01-01
Research with adults has shown that variations in verbal labels and numerical scale values on rating scales can affect the responses given. However, few studies have been conducted with children. The study aimed to examine potential differences in children's responses to Likert-type rating scales according to their anchor points and scale…
Hanson, Janice L.; Rosenberg, Adam A.; Lane, J. Lindsey
2013-01-01
Background: In medical education, evaluation of clinical performance is based almost universally on rating scales for defined aspects of performance and scores on examinations and checklists. Unfortunately, scores and grades do not capture progress and competence among learners in the complex tasks and roles required to practice medicine. While the literature suggests serious problems with the validity and reliability of ratings of clinical performance based on numerical scores, the critical issue is not that judgments about what is observed vary from rater to rater but that these judgments are lost when translated into numbers on a scale. As the Next Accreditation System of the Accreditation Council on Graduate Medical Education (ACGME) takes effect, medical educators have an opportunity to create new processes of evaluation to document and facilitate progress of medical learners in the required areas of competence. Proposal and initial experience: Narrative descriptions of learner performance in the clinical environment, gathered using a framework for observation that builds a shared understanding of competence among the faculty, promise to provide meaningful qualitative data closely linked to the work of physicians. With descriptions grouped in categories and matched to milestones, core faculty can place each learner along the milestones' continua of progress. This provides the foundation for meaningful feedback to facilitate the progress of each learner as well as documentation of progress toward competence. Implications: This narrative evaluation system addresses educational needs as well as the goals of the Next Accreditation System for explicitly documented progress. Educators at other levels of education and in other professions experience similar needs for authentic assessment and, with meaningful frameworks that describe roles and tasks, may also find useful a system built on descriptions of learner performance in actual work settings. Conclusions: We
Chen, Jackie; Sankaran, Ramanan; Hawkes, Evatt R
2009-05-01
The difficulty of experimental measurements of the scalar dissipation rate in turbulent flames has required researchers to estimate the true three-dimensional (3D) scalar dissipation rate from one-dimensional (1D) or two-dimensional (2D) gradient measurements. In doing so, some relationship must be assumed between the true values and their lower dimensional approximations. We develop these relationships by assuming a form for the statistics of the gradient vector orientation, which enables several new results to be obtained and the true 3D scalar dissipation PDF to be reconstructed from the lower-dimensional approximations. We use direct numerical simulations (DNS) of turbulent plane jet flames to examine the orientation statistics, and verify our assumptions and final results. We develop and validate new theoretical relationships between the lower-dimensional and true moments of the scalar dissipation PDF assuming a log-normal true PDF. We compare PDFs reconstructed from lower-dimensional gradient projections with the true values and find an excellent agreement for a 2D simulated measurement and also for a 1D simulated measurement perpendicular to the mean flow variations. Comparisons of PDFs of thermal dissipation from DNS with those obtained via reconstruction from 2D experimental measurements show a very close match, indicating this PDF is not unique to a particular flame configuration. We develop a technique to reconstruct the joint PDF of the scalar dissipation and any other scalar, such as chemical species or temperature. Reconstructed conditional means of the hydroxyl mass fraction are compared with the true values and an excellent agreement is obtained.
Naegeli, April N; Flood, Emuella; Tucker, Jennifer; Devlen, Jennifer; Edson-Heredia, Emily
2015-06-01
Plaque psoriasis (PP) and psoriatic arthritis (PsA) are autoinflammatory chronic conditions associated with skin involvement. Pruritus, or itching, is a prevalent and bothersome symptom in patients with PP and is associated with reduced health-related quality of life. The Worst Itch Numeric Rating Scale (WI-NRS) has been developed as a simple, single item with which to assess the patient-reported severity of this symptom at its most intense during the previous 24-hour period. Qualitative research was undertaken to assess the content validity of the WI-NRS. Patients with moderate to severe PP and patients with PsA were recruited from clinical sites in the USA. The qualitative research entailed two-part interviews, which began with concept elicitation to gain understanding of patients' experiences of itching, followed by cognitive debriefing of the WI-NRS to assess the instrument's understandability, clarity, and degree of appropriateness from the patient's perspective. Twelve patients with PP and 22 with PsA participated in the study. Patients reported that itching was an important and relevant symptom of their psoriatic disease. The WI-NRS was reported to be complete and easy to understand; the recall period was considered appropriate, the response scale was familiar, and, overall, the instrument was found to be appropriate for assessing itching severity. Patient responses support the content validity of the WI-NRS. The psychometric properties of the tool will be evaluated in future studies. PMID:25515935
Code of Federal Regulations, 2012 CFR
2012-04-01
... 17 Commodity and Securities Exchanges 3 2012-04-01 2012-04-01 false Small entities under the Securities Exchange Act for purposes of the Regulatory Flexibility Act. 240.0-10 Section 240.0-10 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION (CONTINUED) GENERAL RULES AND REGULATIONS, SECURITIES EXCHANGE ACT OF 1934 Rules...
NASA Astrophysics Data System (ADS)
Liu, Zhaojiang; Huang, Lei; Wan, Qi; Li, Xu; Guang, Ma; Li, Ping
2014-12-01
La0.75Mg0.25Ni3.5Si0.10 hydrogen storage alloy was prepared by vacuum induction melting furnace and subsequently heated treatment at 940°C for 8 h and cooled to room temperature in the oven. The electrochemical properties of La0.75Mg0.25Ni3.5Si0.10 compound were measured by LAND CT2001A battery test system. The morphologies of the samples were characterized by scanning electron microscopy (SEM). The surface state of samples was analyzed by X-ray photoelectron spectroscopy (XPS). It was found that the charge-discharge rate plays the key impact on the cycling stability of the alloy. During the cycle test, the prepared La0.75Mg0.25Ni3.5Si0.10 compound presented an excellent capacity retention at the charge-discharge of 1 C while the capacity of sample declined rapidly at 0.2 C. The excellent cycling stability performance of La0.75Mg0.25Ni3.5Si0.10 electrode at 1 C could be attributed to the less powder and less oxidation of surface effective active elements. The pulverization inevitably leads to the separation of the part of the cracking alloy and the electrode, resulting in reduction of the effective active substance and increasing attenuation of the capacity per cycle. In addition, on the analysis of the different cut-off potential effects on the electrode, it was found that the La0.75Mg0.25Ni3.5Si0.10 electrode shows good comprehensive electrochemical properties at 1 C cut-off 0.6-0.7 V. During charging, heavy overcharge will not be conducive to cycling stability performance during the charging test.
NASA Astrophysics Data System (ADS)
Kim, Chang-Goo; Kim, Woong-Tae; Ostriker, Eve C.
2011-12-01
We use vertically resolved numerical hydrodynamic simulations to study star formation and the interstellar medium (ISM) in galactic disks. We focus on outer-disk regions where diffuse H I dominates, with gas surface densities Σ = 3-20 M⊙ pc-2 and star-plus-dark matter volume densities ρsd = 0.003-0.5 M⊙ pc-3. Star formation occurs in very dense, self-gravitating clouds that form by mergers of smaller cold cloudlets. Turbulence, driven by momentum feedback from supernova events, destroys bound clouds and puffs up the disk vertically. Time-dependent radiative heating (FUV from recent star formation) offsets gas cooling. We use our simulations to test a new theory for self-regulated star formation. Consistent with this theory, the disks evolve to a state of vertical dynamical equilibrium and thermal equilibrium with both warm and cold phases. The range of star formation surface densities and midplane thermal pressures is ΣSFR ∼ 10-4 to 10-2 M⊙ kpc-2 yr-1 and P th/k B ∼ 102 to 104 cm-3 K. In agreement with observations, turbulent velocity dispersions are ~7 km s-1 and the ratio of the total (effective) to thermal pressure is Ptot/Pth ∼ 4-5, across this whole range (provided shielding is similar to the solar neighborhood). We show that ΣSFR is not well correlated with Σ alone, but rather with Σ ρsd1/2, because the vertical gravity from stars and dark matter dominates in outer disks. We also find that ΣSFR has a strong, nearly linear correlation with Ptot, which itself is within ~13% of the dynamical equilibrium estimate Ptot, DE. The quantitative relationships we find between &SigmaSFR and the turbulent and thermal pressures show that star formation is highly efficient for energy and momentum production, in contrast to the low efficiency of mass consumption. Star formation rates adjust until the ISM's energy and momentum losses are replenished by feedback within a dynamical time.
Muneeswaran, M.; Giridharan, N. V.; Bhuvaneswari, S.; Senguttuvan, G.
2014-04-24
Multiferroic Bi{sub 0.90}La{sub 0.10}Fe{sub 0.90}Co{sub 0.10}O{sub 3} ceramics have been synthesized via soft chemical co-precipitation method. From the X-ray diffraction analysis, ceramic powder sintered at 600°C was found to be single phase belonging to the rhombohedral structure with R3c space group confirmed by Rietveld analysis. Further, dielectric, Leakage and magnetic studies were performed at room temperature.
NASA Astrophysics Data System (ADS)
Pal, Vijayeta; Kumar, A.; Thakur, O. P.; Dwivedi, R. K.
2016-05-01
In the present work, a solid solution of lead free 0.90[(Bi0.96La0.04)0.5Na0.5TiO3]-0.10(Ba0.90Ca0.10TiO3] (abbreviated as 0.90BLNT-0.10BCT) piezoceramics has been synthesized by semi-wet technique. X-ray diffraction pattern confirms the phase formation. Rietveld refinement of XRD data demonstrates the coexistence of rhombhohedral (R3c) + tetragonal (P4mm) phase at room temperature. Raman spectrum is also support the above analysis. A large enhancement in bipolar strain of 0.12 % and calculated normalized strain, d*33 (defined as Smax/Emax) ~ 265 pm/V at 40kV/cm has been observed for this composition as compared to pure BLNT specimen, which make possible it as a potential lead-free candidates for piezoelectric applications.
13C(n,α0)10Be cross section measurement with sCVD diamond detector
NASA Astrophysics Data System (ADS)
Kavrigin, P.; Griesmayer, E.; Belloni, F.; Plompen, A. J. M.; Schillebeeckx, P.; Weiss, C.
2016-06-01
This paper presents 13C(n, α0)10Be cross section measurements performed at the Van de Graaff facility of the Joint Research Centre Geel. The 13C(n, α0)10Be cross section was measured relative to the 12C(n, α0)9Be cross section at 14.3 MeV and 17.0 MeV neutron energies. The measurements were performed with an sCVD (single-crystal chemical vapor deposition) diamond detector which acted as sample and as sensor simultaneously. A novel analysis technique was applied, which is based on the pulse-shape analysis of the detector's ionization current. This technique resulted in an efficient separation of background events and consequently in a well-determined selection of the nuclear reaction channels 12C(n, α0)9Be and 13C(n, α0)10Be.
Piva, Sara R.; Gil, Alexandra B.; Moore, Charity G.; Fitzgerald, G. Kelley
2016-01-01
Objective To assess internal and external responsiveness of the Activity of Daily Living Scale of the Knee Outcome Survey and Numeric Pain Rating Scale on patients with patellofemoral pain. Design One group pre-post design. Subjects A total of 60 individuals with patellofemoral pain (33 women; mean age 29.9 (standard deviation 9.6) years). Methods The Activity of Daily Living Scale and the Numeric Pain Rating Scale were assessed before and after 8 weeks of physical therapy program. Patients completed a global rating of change scale at the end of therapy. The standardized effect size, Guyatt responsiveness index, and the minimum clinical important difference were calculated. Results Standardized effect size of the Activity of Daily Living Scale was 0.63, Guyatt responsiveness index was 1.4, area under the curve was 0.83 (95% confidence interval: 0.72, 0.94), and the minimum clinical important difference corresponded to an increase of 7.1 percentile points. Standardized effect size of the Numeric Pain Rating Scale was 0.72, Guyatt responsiveness index was 2.2, area under the curve was 0.80 (95% confidence interval: 0.70, 0.92), and the minimum clinical important difference corresponded to a decrease of 1.16 points. Conclusion Information from this study may be helpful to therapists when evaluating the effectiveness of rehabilitation intervention on physical function and pain, and to power future clinical trials on patients with patellofemoral pain. PMID:19229444
Li, Yanli; Zhou, Maoqing; Zheng, Tingcai; Yao, Bo; Peng, Yingquan
2013-12-28
Based on drift-diffusion theory, a numerical model of the doping of a single energy level trap in the emission layer of an organic light emitting device (OLED) was developed, and the effects of doping of this single energy level trap on the distribution of the charge density, the recombination rate density, and the electric field in single- and double-layer OLEDs were studied numerically. The results show that by doping the n-type (p-type) emission layer with single energy electron (hole) traps, the distribution of the recombination rate density can be tuned and shifted, which is useful for improvement of the device performance by reduced electrode quenching or for realization of desirable special functions, e.g., emission spectrum tuning in multiple dye-doped white OLEDs.
Nuclear data for neutron and proton interactions with 12C in the energy range 0-10 GeV.
Pearlstein, S
1993-08-01
Nuclear model codes and nuclear systematics are used to give a first approximation to data for nucleons interacting with a 12C target over the range 0-10 GeV. Where there are experiments, the trial values are replaced by an eye guide through the measurements. The evaluated data have been placed in computerized form and are available for distribution. PMID:8392503
Sansinena, M; Santos, M V; Zaritzky, N; Chirife, J
2012-05-01
Slush nitrogen (SN(2)) is a mixture of solid nitrogen and liquid nitrogen, with an average temperature of -207 °C. To investigate whether plunging a French plastic straw (commonly used for sperm cryopreservation) in SN(2) substantially increases cooling rates with respect to liquid nitrogen (LN(2)), a numerical simulation of the heat conduction equation with convective boundary condition was used to predict cooling rates. Calculations performed using heat transfer coefficients in the range of film boiling confirmed the main benefit of plunging a straw in slush over LN(2) did not arise from their temperature difference (-207 vs. -196 °C), but rather from an increase in the external heat transfer coefficient. Numerical simulations using high heat transfer (h) coefficients (assumed to prevail in SN(2)) suggested that plunging in SN(2) would increase cooling rates of French straw. This increase of cooling rates was attributed to a less or null film boiling responsible for low heat transfer coefficients in liquid nitrogen when the straw is placed in the solid-liquid mixture or slush. In addition, predicted cooling rates of French straws in SN(2) tended to level-off for high h values, suggesting heat transfer was dictated by heat conduction within the liquid filled plastic straw. PMID:22225685
Xu, Aihua; Sun, Chenglin
2012-06-01
A Cu0.10Zn0.90Al1.90Fe0.10O4 spinel catalyst prepared by the sol-gel method was tested for catalytic wet air oxidation (CWAO) of phenol. The catalyst showed high activity for phenol degradation. During successive test at 170 degrees C, 100% phenol conversion and 95% chemical oxygen demand (COD) removal were observed. Results from scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) indicated that the catalyst structure remained unchanged during reaction. From the analysis of temperature programmed reduction (TPR), diffuse reflectance UV-Vis spectra (DR UV-Vis) and activity assay at basic solution pH, it can be suggested that the highly dispersed copper ions on the catalyst surface were almost completely dissolved into the reaction solution, whereas the tetra-coordinated copper ions were not only stable against leaching but also active towards phenol degradation. PMID:22856307
NASA Technical Reports Server (NTRS)
Pratt, D. T.; Radhakrishnan, K.
1986-01-01
The design of a very fast, automatic black-box code for homogeneous, gas-phase chemical kinetics problems requires an understanding of the physical and numerical sources of computational inefficiency. Some major sources reviewed in this report are stiffness of the governing ordinary differential equations (ODE's) and its detection, choice of appropriate method (i.e., integration algorithm plus step-size control strategy), nonphysical initial conditions, and too frequent evaluation of thermochemical and kinetic properties. Specific techniques are recommended (and some advised against) for improving or overcoming the identified problem areas. It is argued that, because reactive species increase exponentially with time during induction, and all species exhibit asymptotic, exponential decay with time during equilibration, exponential-fitted integration algorithms are inherently more accurate for kinetics modeling than classical, polynomial-interpolant methods for the same computational work. But current codes using the exponential-fitted method lack the sophisticated stepsize-control logic of existing black-box ODE solver codes, such as EPISODE and LSODE. The ultimate chemical kinetics code does not exist yet, but the general characteristics of such a code are becoming apparent.
Honey, D.A.
1989-12-01
The collisional Boltzmann equation was solved numerically to obtain excitation rates for use in a CO{sub 2} laser design program. The program was written in Microsoft QuickBasic for use on the IBM Personal Computer or equivalent. Program validation involved comparisons of computed transport coefficients with experimental data and previous theoretical work. Four different numerical algorithms were evaluated in terms of accuracy and efficiency. L-U decomposition was identified as the preferred approach. The calculated transport coefficients were found to agree with empirical data within one to five percent. The program was integrated into a CO{sub 2} laser design program. Studies were then performed to evaluate the effects on predicted laser output power and energy density as parameters affecting electron kinetics were changed. Plotting routines were written for both programs.
NASA Astrophysics Data System (ADS)
Mohebi, M.; Jamasbi, N.; Flores, G. A.; Liu, Jing
A molecular dynamics model is presented to understand the structural formation of MR fluids by including the thermal motion of the particles. The simulation results indicate that the complexity of the lateral pattern as viewed in the direction of the applied field increases with the rate of the application of external magnetic field. We have also found that the maximum range for attractive interaction (escape distance) for two initially straight chains increases with temperature. These results are relevant to understand the mechanisms and conditions for the formation of labyrinthine and columnar patterns found in MR fluids.
NASA Technical Reports Server (NTRS)
Kolnik, Jan; Wang, Yang; Oguzman, Ismail H.; Brennan, Kevin F.
1994-01-01
The electron interband impact-ionization rate for both silicon and gallium arsenide is calculated using an ensemble Monte Carlo simulation with the expressed purpose of comparing different formulations of the interband ionization transition rate. Specifically, three different treatments of the transition rate are examined: the traditional Keldysh formula, a new k-dependent analytical formulation first derived by W. Quade, E. Scholl, and M. Rudan (1993), and a more exact, numerical method of Y. Wang and K. F. Brennan (1994). Although the completely numerical formulation contains no adjustable parameters and as such provides a very reliable result, it is highly computationally intensive. Alternatively, the Keldysh formular, although inherently simple and computationally efficient, fails to include the k dependence as well as the details of the energy band structure. The k-dependent analytical formulation of Quade and co-workers overcomes the limitations of both of these models but at the expense of some new parameterization. It is found that the k-dependent analytical method of Quade and co-workers produces very similar results to those obtained with the completely numerical model for some quantities. Specifically, both models predict that the effective threshold for impact ionization in GaAs and silicon is quite soft, that the majority of ionization events originate from the second conduction band in both materials, and that the transition rate is k dependent. Therefore, it is concluded that the k-dependent analytical model can qualitatively reproduce results similar to those obtained with the numerical model yet with far greater computational efficiency. Nevertheless, there exist some important drawbacks to the k-dependent analytical model of Quade and co-workers: These are that it does not accurately reproduce the quantum yield data for bulk silicon, it requires determination of a new parameter, related physically to the overlap intergrals of the Bloch state which
Gutheil, W G; Kettner, C A; Bachovchin, W W
1994-11-15
Kinlsq, a Matlab-based computer program for the least-squares fitting of parameters to kinetics data described by numerically integrated rate equations, is described, and three applications to the analysis of enzyme kinetics data are given. The first application was to the analysis of a simple bimolecular enzyme plus inhibitor binding curve. The kinlsq fit to these data was essentially identical to that obtained with the corresponding analytically integrated rate equation, validating kinlsq. The second application was to the fit of a numerically integrated Michaelis-Menten model to the progress curve for dipeptidyl peptidase IV-catalyzed hydrolysis of Ala-Pro-p-nitroanilide as a demonstration of the analysis of steady-state enzyme kinetics data. The results obtained with kinlsq were compared with the results obtained by fitting this time course with the integrated Michaelis-Menten equation, and with the results obtained by fitting the (S,dP/dt) transform of the data with the Michaelis-Menten equation. The third application was to the analysis of the inhibition of chymotrypsin by the slow, tight-binding inhibitor MeOSuc-Ala-Ala-Pro-boroPhe, data not readily amenable to other methods of analysis. These applications demonstrate how kinlsq can be used to fit rate constants, equilibrium constants, steady-state constants, and the stoichiometric relationships between components. PMID:7695087
Santos, M V; Sansinena, M; Zaritzky, N; Chirife, J
2012-01-01
In oocyte vitrification, plunging directly into liquid nitrogen favor film boiling and strong nitrogen vaporization. A survey of literature values of heat transfer coefficients (h) for film boiling of small metal objects with different geometries plunged in liquid nitrogen revealed values between 125 to 1000 W per per square m per K. These h values were used in a numerical simulation of cooling rates of two oocyte vitrification devices (open-pulled straw and Cryotop), plunged in liquid and slush nitrogen conditions. Heat conduction equation with convective boundary condition was considered a linear mathematical problem and was solved using the finite element method applying the variational formulation. COMSOL Multiphysics was used to simulate the cooling process of the systems. Predicted cooling rates for OPS and Cryotop when cooled at -196 degree C (liquid nitrogen) or -207 degree C (average for slush nitrogen) for heat transfer coefficients estimated to be representative of film boiling, indicated lowering the cooling temperature produces only a maximum 10 percent increase in cooling rates; confirming the main benefit of plunging in slush over liquid nitrogen does not arise from their temperature difference. Numerical simulations also demonstrated that a hypothetical four-fold increase in the cooling rate of vitrification devices when plunging in slush nitrogen would be explained by an increase in heat transfer coefficient. This improvement in heat transfer (i.e., high cooling rates) in slush nitrogen is attributed to less or null film boiling when a sample is placed in slush (mixture of liquid and solid nitrogen) because it first melts the solid nitrogen before causing the liquid to boil and form a film. PMID:22434120
NASA Astrophysics Data System (ADS)
Humeau, Anne; Buard, Benjamin; Mahé, Guillaume; Chapeau-Blondeau, François; Rousseau, David; Abraham, Pierre
2010-10-01
To contribute to the understanding of the complex dynamics in the cardiovascular system (CVS), the central CVS has previously been analyzed through multifractal analyses of heart rate variability (HRV) signals that were shown to bring useful contributions. Similar approaches for the peripheral CVS through the analysis of laser Doppler flowmetry (LDF) signals are comparatively very recent. In this direction, we propose here a study of the peripheral CVS through a multifractal analysis of LDF fluctuations, together with a comparison of the results with those obtained on HRV fluctuations simultaneously recorded. To perform these investigations concerning the biophysics of the CVS, first we have to address the problem of selecting a suitable methodology for multifractal analysis, allowing us to extract meaningful interpretations on biophysical signals. For this purpose, we test four existing methodologies of multifractal analysis. We also present a comparison of their applicability and interpretability when implemented on both simulated multifractal signals of reference and on experimental signals from the CVS. One essential outcome of the study is that the multifractal properties observed from both the LDF fluctuations (peripheral CVS) and the HRV fluctuations (central CVS) appear very close and similar over the studied range of scales relevant to physiology.
NASA Technical Reports Server (NTRS)
Puri, Ishwar K.
2004-01-01
Our goal has been to investigate the influence of both dilution and radiation on the extinction process of nonpremixed flames at low strain rates. Simulations have been performed by using a counterflow code and three radiation models have been included in it, namely, the optically thin, the narrowband, and discrete ordinate models. The counterflow flame code OPPDIFF was modified to account for heat transfer losses by radiation from the hot gases. The discrete ordinate method (DOM) approximation was first suggested by Chandrasekhar for solving problems in interstellar atmospheres. Carlson and Lathrop developed the method for solving multi-dimensional problem in neutron transport. Only recently has the method received attention in the field of heat transfer. Due to the applicability of the discrete ordinate method for thermal radiation problems involving flames, the narrowband code RADCAL was modified to calculate the radiative properties of the gases. A non-premixed counterflow flame was simulated with the discrete ordinate method for radiative emissions. In comparison with two other models, it was found that the heat losses were comparable with the optically thin and simple narrowband model. The optically thin model had the highest heat losses followed by the DOM model and the narrow-band model.
Herold, Maria; Ptak, Thomas; Bayer-Raich, Marti; Wendel, Thomas; Grathwohl, Peter
2009-04-15
A series of integral pumping tests (IPTs) has been conducted at a former gasworks site to quantify the contaminant mass flow rates and average concentration in groundwater along three control planes across the groundwater flow direction. The measured concentration-time series were analysed numerically with the help of the inversion code CSTREAM and a flow and transport model representing the highly heterogeneous aquifer. Since the control planes cover the entire downstream width of the potentially contaminated area, they allow conclusions to be drawn about the current location and spread of the contaminant plume. Previous evaluations of integral pumping tests could calculate three scenarios concerning the spread of the plume around the IPT well: (i) the plume is located to the right of the pumping well, (ii) to the left, or (iii) is distributed symmetrically around it. To create a more realistic picture of the plume position, a series of direct-push monitoring wells were installed along one control plane. The concentrations found in these wells were included in the numerical analysis to condition the numerical inversion results, and allowed the identification of a more pronounced plume centre and fringe, which supports the development of optimised remediation strategies. PMID:19167131
NASA Astrophysics Data System (ADS)
Herold, Maria; Ptak, Thomas; Bayer-Raich, Marti; Wendel, Thomas; Grathwohl, Peter
2009-04-01
A series of integral pumping tests (IPTs) has been conducted at a former gasworks site to quantify the contaminant mass flow rates and average concentration in groundwater along three control planes across the groundwater flow direction. The measured concentration-time series were analysed numerically with the help of the inversion code CSTREAM and a flow and transport model representing the highly heterogeneous aquifer. Since the control planes cover the entire downstream width of the potentially contaminated area, they allow conclusions to be drawn about the current location and spread of the contaminant plume. Previous evaluations of integral pumping tests could calculate three scenarios concerning the spread of the plume around the IPT well: (i) the plume is located to the right of the pumping well, (ii) to the left, or (iii) is distributed symmetrically around it. To create a more realistic picture of the plume position, a series of direct-push monitoring wells were installed along one control plane. The concentrations found in these wells were included in the numerical analysis to condition the numerical inversion results, and allowed the identification of a more pronounced plume centre and fringe, which supports the development of optimised remediation strategies.
NASA Astrophysics Data System (ADS)
Parsons, R. A.; Nimmo, F.; Kreslavsky, M.
2008-12-01
Using a stereo pair of HiRISE images of a crater slope incised by fourteen gullies at -37.86 N, 217.92 E we calculate relative elevation changes between pairs of hand-selected points. Using the method of Kreslavsky [1]. The background slope on which the gullies are located has a slope of 22 degrees. Out of the five gullies we analyzed, all show a steadily decreasing slope from an average of 30 ± 4 degrees at the alcove to 16 ± 2 degrees at the apron. These measurements are in agreement with previous gully slope measurements done at MOLA resolution in a different region [2]. The slope beyond the base of the gully aprons is 4±1 degrees. The depth of alcove incision in nine of the gullies is 17±8.5~m. We take advantage of this slope and incision data to determine the evolution of a one-dimensional gully profile over time with a 1D sediment transport model [3]. The shear stress applied to the channel bed by flowing water is τ = ρ g h sinθ where h is the channel depth, g is gravity, and h is the channel depth. The rate of transport is non-linearly related to τ/τrg where the reference stress for a gravel bed is τrg = 0.035 ( (s-1)ρ g Dg ) where s is the ratio of sediment to water density, ρ is 1000~m3, and Dg is the sediment grainsize. The two significant unknowns in applying the theory to Martian gullies are the sediment grainsize and channel depth. We ran simulations for various channel depths and grainsizes to get a range of water discharges and simulation times that result in alcoves 25~m deep. Erosion is rapid due to the high slopes; incision rates decrease with decreasing channel depth and increasing grainsize. For grains 20~cm in diameter and a conservatively low channel depth of 20~cm, alcove incision occurs over a 5~h period, discharging a volume of 8500 m3 of water. These discharges assume a 1~m wide channel and a constant, bank-full discharge over the duration of the simulation. Gullies are spaced about every 500~m along the slope. If liquid water
NASA Astrophysics Data System (ADS)
Liu, Y.; McGuire, J. J.; Behn, M. D.
2013-12-01
We use a three-dimensional strike-slip fault model in the framework of rate and state-dependent friction to investigate earthquake behavior and scaling relations on oceanic transform faults (OTFs). Gabbro friction data under hydrothermal conditions are mapped onto OTFs using temperatures from (1) a half-space cooling model, and (2) a thermal model that incorporates a visco-plastic rheology, non-Newtonian viscous flow and the effects of shear heating and hydrothermal circulation. Without introducing small-scale frictional heterogeneities on the fault, our model predicts that an OTF segment can transition between seismic and aseismic slip over many earthquake cycles, consistent with the multimode hypothesis for OTF ruptures. The average seismic coupling coefficient χ is strongly dependent on the ratio of seismogenic zone width W to earthquake nucleation size h*; χ increases by four orders of magnitude as W/h* increases from ~ 1 to 2. Specifically, the average χ = 0.15 +/- 0.05 derived from global OTF earthquake catalogs can be reached at W/h* ≈ 1.2-1.7. The modeled largest earthquake rupture area is less than the total seismogenic area and we predict a deficiency of large earthquakes on long transforms, which is also consistent with observations. Earthquake magnitude and distribution on the Gofar (East Pacific Rise) and Romanche (equatorial Mid-Atlantic) transforms are better predicted using the visco-plastic model than the half-space cooling model. We will also investigate how fault gouge porosity variation during an OTF earthquake nucleation phase may affect the seismic wave velocity structure, for which up to 3% drop was observed prior to the 2008 Mw6 Gofar earthquake.
Bonnefous, Y.C.; Gadgil, A.J.; Revzan, K.L.; Fisk, W.J.; Riley, W.J.
1993-01-01
A subslab aggregate layer can increase the radon entry rate into a building by up to a factor of 5. We use a previously tested numerical technique to investigate and confirm this phenomenon. Then we demonstrate that a sub-aggregate membrane has the potential to significantly reduce the increase in radon entry rate due to the aggregate layer, even when a gap exists between the perimeter of the membrane and the footer. Such membranes greatly reduce diffusion of radon from the soil into the aggregate and are impermeable to flow. Radon entry through the basement floor slab is limited to radon entry through the holes in the membrane. In addition, a sub-aggregate membrane is predicted to improve the performance of active sub-slab ventilation systems and makes passive systems more promising.
NASA Astrophysics Data System (ADS)
Trakic, A.; Jin, J.; Li, M. Y.; McClymont, D.; Weber, E.; Liu, F.; Crozier, S.
2013-11-01
While high-field magnetic resonance imaging promises improved image quality and faster scan time, it is affected by non-uniform flip angle distributions and unsafe specific absorption rate levels within the patient, as a result of the complicated radiofrequency (RF) field - tissue interactions. This numerical study explored the possibility of using a single mechanically rotating RF coil for RF shimming and specific absorption rate management applications at 7 T. In particular, this new approach (with three different RF coil element arrangements) was compared against both an 8-channel parallel coil array and a birdcage volume coil, with and without RF current optimisation. The evaluation was conducted using an in-house developed and validated finite-difference time-domain method in conjunction with a tissue-equivalent human head model. It was found that, without current optimisation, the rotating RF coil method produced a more uniform flip angle distribution and a lower maximum global and local specific absorption rate compared to the 8-channel parallel coil array and birdcage resonator. In addition, due to the large number of degrees of freedom in the form of rotated sensitivity profiles, the rotating RF coil approach exhibited good RF shimming and specific absorption rate management performance. This suggests that the proposed method can be useful in the development of techniques that address contemporary RF issues associated with high-field magnetic resonance imaging.
NASA Astrophysics Data System (ADS)
Johnson, Scott E.; Vernon, Ron H.; Upton, Phaedra
2004-10-01
The San José pluton in Baja California, México, comprises at least two well-defined, texturally distinct units. The northern unit was intruded by the central unit after the former had extensively crystallized at its margins. During intrusion of the central unit, the margin of the northern unit underwent brittle and crystal-plastic deformation, at least part of which occurred in the presence of residual melt. We infer that biotite grains in this rock readily deformed by slip and frictional sliding along (001) planes, which caused strain-rate and differential-stress gradients across their grain boundaries into the surrounding plagioclase framework causing it to fracture. These microfractures grew and coalesced, and became sites of localized ductile flow. Continued development of these microshear zones led to coalescence of biotite grains, mainly by mechanical entrainment, and ultimately to a pervasive mylonitic foliation. Thus, in a single deformation, these rocks passed through a brittle-ductile transition. The development of an anastomosing network of ductile microshear zones allowed the progressive partitioning of strain rates, probably over several orders of magnitude, between the microshear zones and intervening polymineralic aggregates. Numerical experiments were conducted to evaluate the process of biotite-assisted fracturing of the stress-supporting framework, and the progressive evolution of differential stress and strain rate. The results are consistent with experimental evidence that biotite is extremely weak in shear, and that phyllosilicate-bearing rocks may accommodate strain rates several orders of magnitude higher than the bulk strain rate. This study also supports previous suggestions that strain rates associated with the growth of crustal magma chambers may be several, to many, orders of magnitude greater than those normally associated with regional tectonic deformation.
Merritt, Michael L.
1995-01-01
To construct a digital simulation of a plume of brackish water in the surficial Biscayne aquifer of central Dade County, Florida, that originated from a flowing artesian well, it was necessary to quantify the rate of spillage and the consequent point-source loading of the aquifer. However, a flow-rate measurement (2,350 gallons per minute) made 2 months after drilling of the well in 1944 was inconsistent with later measurements (1,170 gallons per minute) in 1964, 1965, and 1969. Possible explanations were the: (1) drawdown of the aquifer over time; (2) raising of the altitude at which the water was discharged; (3) installation of 80 feet of 8-inch liner; (4) an increase in the density of the flowing water; and (5) gradual deterioration of the well casing. The first approach to reconciling the measured flow rates was to apply a form of the equation for constant-drawdown analysis often used to estimate aquifer transmissivity. Next, a numerical simulation analysis was made that pro- vided the means to account for friction loss in the well and recharge across vertically adjacent con- fining layers and from lateral boundaries. The numerical analysis required the construction of a generalized model of the subsurface from the surficial Biscayne aquifer to the cavernous, dolomitic Boulder Zone at a depth of 3,000 feet. Calibration of the generalized flow model required that the moddle confining unit of the Floridan aquifer system separating the artesian flow zone in the Upper Floridan aquifer from the Lower Floridan aquifer (the Boulder Zone) have a vertical hydraulic conductivity of at least 1 foot per day. The intermediate confining unit separating the flow zone from the surficial Biscayne aquifer was assigned a much lower hydraulic conductivity (0.01 foot per day or less). The model indicated that the observed mounding of Upper Floridan aquifer heads along the axis of the Florida Peninsula was related to the variable depth of the freshwater and brackish-water zone
Preparation of UC0.07-0.10N0.90-0.93 spheres for TRISO coated fuel particles
Collins, Jack Lee; Hunt, Rodney Dale; Johnson, Jared A; Silva, Chinthaka M; Lindemer, Terrence
2014-01-01
The U.S. Department of Energy is considering a new nuclear fuel, which should be much more impervious during a loss of coolant accident. The fuel would consist of tristructural isotropic coated particles with dense uranium nitride (UN) kernels. The objectives of this effort are to make uranium oxide microspheres with adequately dispersed carbon nanoparticles and to convert these microspheres into UN kernels. Recent improvements to internal gelation process were successfully applied to the production of uranium gel spheres with different concentrations of carbon black. After the spheres were washed, a simple, two-step heat profile was used to produce kernels with a chemical composition of UC0.07 0.10N0.90 0.93. The first step involved heating the microspheres to 2023 K in a vacuum, and in the second step, the microspheres were held at 1873 K for 6 hrs in nitrogen.
Lemaire, R; Menanteau, S
2016-01-01
This paper deals with the thorough characterization of a new experimental test bench designed to study the devolatilization and oxidation of pulverized fuel particles in a wide range of operating conditions. This lab-scale facility is composed of a fuel feeding system, the functioning of which has been optimized by computational fluid dynamics. It allows delivering a constant and time-independent mass flow rate of fuel particles which are pneumatically transported to the central injector of a hybrid McKenna burner using a carrier gas stream that can be inert or oxidant depending on the targeted application. A premixed propane/air laminar flat flame stabilized on the porous part of the burner is used to generate the hot gases insuring the heating of the central coal/carrier-gas jet with a thermal gradient similar to those found in industrial combustors (>10(5) K/s). In the present work, results issued from numerical simulations performed a priori to characterize the velocity and temperature fields in the reaction chamber have been analyzed and confronted with experimental measurements carried out by coupling particle image velocimetry, thermocouple and two-color pyrometry measurements so as to validate the order of magnitude of the heating rate delivered by such a new test bench. Finally, the main features of the flat flame reactor we developed have been discussed with respect to those of another laboratory-scale system designed to study coal devolatilization at a high heating rate. PMID:26827350
NASA Astrophysics Data System (ADS)
Lemaire, R.; Menanteau, S.
2016-01-01
This paper deals with the thorough characterization of a new experimental test bench designed to study the devolatilization and oxidation of pulverized fuel particles in a wide range of operating conditions. This lab-scale facility is composed of a fuel feeding system, the functioning of which has been optimized by computational fluid dynamics. It allows delivering a constant and time-independent mass flow rate of fuel particles which are pneumatically transported to the central injector of a hybrid McKenna burner using a carrier gas stream that can be inert or oxidant depending on the targeted application. A premixed propane/air laminar flat flame stabilized on the porous part of the burner is used to generate the hot gases insuring the heating of the central coal/carrier-gas jet with a thermal gradient similar to those found in industrial combustors (>105 K/s). In the present work, results issued from numerical simulations performed a priori to characterize the velocity and temperature fields in the reaction chamber have been analyzed and confronted with experimental measurements carried out by coupling particle image velocimetry, thermocouple and two-color pyrometry measurements so as to validate the order of magnitude of the heating rate delivered by such a new test bench. Finally, the main features of the flat flame reactor we developed have been discussed with respect to those of another laboratory-scale system designed to study coal devolatilization at a high heating rate.
Morphologies of ˜190,000 Galaxies at z = 0-10 Revealed with HST Legacy Data. I. Size Evolution
NASA Astrophysics Data System (ADS)
Shibuya, Takatoshi; Ouchi, Masami; Harikane, Yuichi
2015-08-01
We present the redshift evolution of the galaxy effective radius re obtained from the Hubble Space Telescope (HST) samples of ˜190,000 galaxies at z = 0-10. Our HST samples consist of 176,152 photo-z galaxies at z = 0-6 from the 3D-HST+CANDELS catalog and 10,454 Lyman break galaxies (LBGs) at z = 4-10 identified in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), HUDF 09/12, and HFF parallel fields, providing the largest data set to date for galaxy size evolution studies. We derive re with the same technique over the wide redshift range of z = 0-10, evaluating the optical-to-UV morphological K correction and the selection bias of photo-z galaxies+LBGs as well as the cosmological surface-brightness dimming effect. We find that re values at a given luminosity significantly decrease toward high z, regardless of statistics choices (e.g., {r}{{e}}\\propto {(1+z)}-1.10+/- 0.06 for median). For star-forming galaxies, there is no evolution of the power-law slope of the size-luminosity relation and the median Sérsic index (n˜ 1.5). Moreover, the re distribution is well represented by log-normal functions whose standard deviation {σ }{ln{r}{{e}}} does not show significant evolution within the range of {σ }{ln{r}{{e}}}˜ 0.45-0.75. We calculate the stellar-to-halo size ratio from our re measurements and the dark-matter halo masses estimated from the abundance-matching study, and we obtain a nearly constant value of {r}{{e}}/{r}{vir}=1.0%-3.5% at z = 0-8. The combination of the re-distribution shape+standard deviation, the constant {r}{{e}}/{r}{vir}, and n˜ 1.5 suggests a picture in which typical high-z star-forming galaxies have disk-like stellar components in a sense of dynamics and morphology over cosmic time of z˜ 0-6. If high-z star-forming galaxies are truly dominated by disks, the {r}{{e}}/{r}{vir} value and the disk-formation model indicate that the specific angular momentum of the disk normalized by the host halo is {j
Moldenhauer, F; Botto, M; Walport, M J
1988-01-01
The stability of CR1 (complement receptor type 1) on ageing erythrocytes in vivo was examined in a group of normal subjects who had been genotyped using a restriction fragment length polymorphism (detected using a cDNA probe for CR1) that correlates with the numerical expression of CR1 on normal erythrocytes (H = allele correlating with high expression, L = low). Erythrocytes were separated into 5 fractions of increasing age on discontinuous Percoll gradients. Mean CR1 numbers on erythrocytes fell from 636 molecules per cell in the first fraction to 384 in the fifth in the HH group and from 478 to 315 in the LL group. There was no difference in the rate of decline of CR1 numbers between the groups. A group of nine SLE patients was also studied in the same way; their genotypes were HH (four) and HL (five). Mean CR1 numbers amongst all of these patients fell from 477 to 232, a faster rate of decline than in a genotypically matched group of normal subjects. There was no difference in the prevalence of the different structural allotypes amongst 30 SLE patients compared with 21 normal subjects. These data provide further evidence that there are enhanced extracellular mechanisms for the removal of CR1 from erythrocytes of SLE patients and do not support the hypothesis that inherited variation in CR1 expression on erythrocytes increases disease susceptibility to SLE. PMID:2899464
Preparation of UC0.07-0.10N0.90-0.93 spheres for TRISO coated fuel particles
NASA Astrophysics Data System (ADS)
Hunt, R. D.; Silva, C. M.; Lindemer, T. B.; Johnson, J. A.; Collins, J. L.
2014-05-01
The US Department of Energy is considering a new nuclear fuel that would be less susceptible to ruptures during a loss-of-coolant accident. The fuel would consist of tristructural isotropic coated particles with dense uranium nitride (UN) kernels with diameters of 650 or 800 μm. The objectives of this effort are to make uranium oxide microspheres with adequately dispersed carbon nanoparticles and to convert these microspheres into UN spheres, which could be then sintered into kernels. Recent improvements to the internal gelation process were successfully applied to the production of uranium gel spheres with different concentrations of carbon black. After the spheres were washed and dried, a simple two-step heat profile was used to produce porous microspheres with a chemical composition of UC0.07-0.10N0.90-0.93. The first step involved heating the microspheres to 2023 K in a vacuum, and in the second step, the microspheres were held at 1873 K for 6 h in flowing nitrogen.
NASA Astrophysics Data System (ADS)
Thomasson, M. J.; Hoffmann, J. P.; Ferré, P. A.
2003-12-01
Recent studies conducted by the U.S. Geological Survey (USGS) have shown that deep temperature profiles, measured before and after controlled infiltration, can be used to determine infiltration rates within the unsaturated zone. In this investigation, we extend this method to deep-temperature profiles measured before and after streamflow events in two boreholes located in the channel of an ephemeral stream in southern Arizona to infer recharge rates from short-term flow events. The deep-temperature profiles were analyzed to determine vertical fluxes with the use of a one-dimensional, forward numerical computer model. Temperature profiles were collected in boreholes located in Rillito Creek, in Tucson, Arizona. The two sites are about 6 kilometers apart and were selected on the basis of their lithology and hydraulic characteristics. The lithology at the upstream site is primarily homogeneous coarse sand, and the water table is approximately 37 meters below land surface. The initial response of the water table lags the onset of streamflow by about 2 weeks, and the water-level changes are as much as a few meters depending on the magnitude of the streamflow. The lithology at the downstream site is primarily homogeneous sand, with the exception of a clay layer at 12 meters below land surface, and the water table is approximately 41 meters below land surface. The initial response of the water table at the downstream site is rapid, occurring within about a day of streamflow. The magnitude of the water table response, however, is typically less than a meter and usually on the order of a few centimeters. Basic hydrologic models were developed for each site using hydraulic and thermal properties inferred from borehole core samples and cuttings, and from laboratory-determined hydraulic parameters. Water-table elevations and stream stages were used to define hydrologic boundary conditions. Field-measured temperature profiles were used to calibrate the models. The basic
Order and disorder in Ca 2ND 0.90H 0.10-A structural and thermal study
NASA Astrophysics Data System (ADS)
Verbraeken, Maarten C.; Suard, Emmanuelle; Irvine, John T. S.
2011-08-01
The structure of calcium nitride hydride and its deuterided form has been re-examined at room temperature and studied at high temperature using neutron powder diffraction and thermal analysis. When synthesised at 600 °C, a mixture of both ordered and disordered Ca 2ND 0.90H 0.10 phases results. The disordered phase is the minor component and has a primitive rocksalt structure (spacegroup Fm3 m) with no ordering of D/N on the anion sites and the ordered phase is best described using the rhombohedral spacegroup R-3 m with D and N arranged in alternate layers in (111) planes. This mixture of ordered and disordered phases exists up to 580 °C, at which the loss of deuterium yields Ca 2ND 0.85 with the disappearance of the disordered phase. In the new ordered phase there exists a similar content of vacancies on both anion sites; to achieve this balance, a little N transfers onto the D site, whereas there is no indication of D transferring onto the N-sites. These observations are thought to indicate that the D/N ordering is difficult to achieve with fully occupied anion sites. It has previously been reported that Ca 2ND has an ordered cubic cell with alternating D and N sites in the [100] directions [1]; however, for the samples studied herein, there were clearly two coexisting phases with apparent broadening/splitting of the primitive peaks but not for the ordered peaks. The rhombohedral phase was in fact metrically cubic; however, all the observed peaks were consistent with the rhombohedral unit cell with no peaks requiring the larger ordered cubic unit cell to be utilised. Furthermore this rhombohedral cell displays the same form of N-D ordering as the Sr and Ba analogues, which are metrically rhombohedral.
NASA Astrophysics Data System (ADS)
Velinov, Peter; Asenovski, Simeon; Mateev, Lachezar
2013-04-01
Numerical calculations of galactic cosmic ray (GCR) ionization rate profiles are presented for the middle atmosphere and lower ionosphere altitudes (35-90 km) for the full GCR composition (protons, alpha particles, and groups of heavier nuclei: light L, medium M, heavy H, very heavy VH). This investigation is based on a model developed by Velinov et al. (1974) and Velinov and Mateev (2008), which is further improved in the present paper. Analytical expressions for energy interval contributions are provided. An approximation of the ionization function on three energy intervals is used and for the first time the charge decrease interval for electron capturing (Dorman 2004) is investigated quantitatively. Development in this field of research is important for better understanding the impact of space weather on the atmosphere. GCRs influence the ionization and electric parameters in the atmosphere and also the chemical processes (ozone creation and depletion in the stratosphere) in it. The model results show good agreement with experimental data (Brasseur and Solomon 1986, Rosenberg and Lanzerotti 1979, Van Allen 1952).
Numerical Boundary Condition Procedures
NASA Technical Reports Server (NTRS)
1981-01-01
Topics include numerical procedures for treating inflow and outflow boundaries, steady and unsteady discontinuous surfaces, far field boundaries, and multiblock grids. In addition, the effects of numerical boundary approximations on stability, accuracy, and convergence rate of the numerical solution are discussed.
Tandon, Manish; Singh, Anshuman; Saluja, Vandana; Dhankhar, Mandeep; Pandey, Chandra Kant; Jain, Priyanka
2016-01-01
Background: Pain scores are used for acute pain management. The assessment of pain by the patient as well as the caregiver can be influenced by a variety of factors. The numeric rating scale (NRS) is widely used due to its easy application. The NRS requires abstract thinking by a patient to assign a score to correctly reflect analgesic needs, and its interpretation is subject to bias. Objectives: The study was done to validate a 4-point objective pain score (OPS) for the evaluation of acute postoperative pain and its comparison with the NRS. Patient and Methods: A total of 1021 paired readings of the OPS and NRS of 93 patients who underwent laparotomy and used patient-controlled analgesia were evaluated. Acute pain service (APS) personnel recorded the OPS and NRS. Rescue analgesia was divided into two incremental levels (level 1-paracetamol 1 g for NRS 2 - 5 and OPS 3, Level 2-Fentanyl 25 mcg for NRS ≥ 6 and OPS 1 and 2). In cases of disagreement between the two scores, an independent consultant decided the rescue analgesia. Results: The NRS and OPS agreed across the range of pain. There were 25 disagreements in 8 patients. On 24 occasions, rescue analgesia was increased from level 1 to 2, and one occasion it was decreased from level 2 to 1. On all 25 occasions, the decision to supplement analgesia went in favor of the OPS over the NRS. Besides these 25 disagreements, there were 17 occasions in which observer bias was possible for level 2 rescue analgesia. Conclusions: The OPS is a good stand-alone pain score and is better than the NRS for defining mild and moderate pain. It may even be used to supplement NRS when it is indicative of mild or moderate pain. PMID:27110530
Hirtl, Rene; Schmid, Gernot
2013-09-21
A modern wireless intra-ocular pressure monitoring system, based on 13.56 MHz inductively coupled data transmission, was dosimetrically analyzed with respect to the specific absorption rate (SAR) induced inside the head and the eye due to the electromagnetic field exposure caused by the reader antenna of the transmission system. The analysis was based on numerical finite difference time domain computations using a high resolution anatomical eye model integrated in a modern commercially available anatomical model of a male head. Three different reader antenna configurations, a 7-turn elliptic (30 mm × 50 mm) antenna at 12 mm distance from the eye, a flexible circular antenna (60 mm diameter, 8 turns on 2 mm substrate) directly attached to the skin, and a circular 7-turn antenna (30 mm diameter at 12 mm distance to the eye) were analyzed, respectively. Possible influences of the eye-lid status (closed or opened) and the transponder antenna contained in a contact lens directly attached to the eye were taken into account. The results clearly demonstrated that for typical reader antenna currents required for proper data transmission, the SAR values remain far below the limits for localized exposure of the head, as defined by the International Commission for Non-Ionizing Radiation Protection. Particularly the induced SAR inside the eye was found to be substantially (orders of magnitudes for typical reader antenna currents in the order of 1 A turn) below values which have been reported to be critical with respect to thermally induced adverse health effects in eye tissues. PMID:24002053
Wysham, Nicholas G.; Miriovsky, Benjamin J.; Currow, David C.; Herndon, James E.; Samsa, Gregory P.; Wilcock, Andrew; Abernethy, Amy P.
2016-01-01
Context Measurement of dyspnea is important for clinical care and research. Objectives To characterize the relationship between the 0–10 Numerical Rating Scale (NRS) and four-level categorical Verbal Descriptor Scale (VDS) for dyspnea assessment. Methods This was a substudy of a double-blind randomized controlled trial comparing palliative oxygen to room air for relief of refractory breathlessness in patients with life-limiting illness. Dyspnea was assessed with both a 0–10 NRS and a four-level categorical VDS over the one-week trial. NRS and VDS responses were analyzed in cross section and longitudinally. Relationships between NRS and VDS responses were portrayed using descriptive statistics and visual representations. Results Two hundred twenty-six participants contributed responses. At baseline, mild and moderate levels of breathlessness were reported by 41.9% and 44.6% of participants, respectively. NRS scores demonstrated increasing mean and median levels for increasing VDS intensity, from a mean (SD) of 0.6 (±1.04) for VDS none category to 8.2 (1.4) for VDS severe category. The Spearman correlation coefficient was strong at 0.78 (P < 0.0001). Based on the distribution of NRS scores within VDS categories, we calculated test characteristics of two different cutpoint models. Both models yielded 75% correct translations from NRS to VDS; however, Model A was more sensitive for moderate or greater dyspnea, with fewer misses downcoded. Conclusion There is strong correlation between VDS and NRS measures for dyspnea. Proposed practical cutpoints for the relationship between the dyspnea VDS and NRS are 0 for none, 1–4 for mild, 5–8 for moderate, and 9–10 for severe. PMID:26004401
Are large concentration of atomic H storable in tritium-impregnated solid in H2 below 0.10 K
NASA Technical Reports Server (NTRS)
Rosen, G.; Webeler, R. W. H.
1979-01-01
The storage and release of atomic hydrogen produced by the beta decay of tritium contained in a crystalline solid H2 matrix at concentrations greater than 2% and temperatures below 0.80 K are investigated. The temperature of a sample chamber containing tritium-impregnated H2 and placed in the mixing chamber of a dilution refrigerator was measured as the chamber was heated and cooled in order to determine the rates of energy storage and release. It is found that for samples containing 1.2 wt.% tritium, after storage at 0.054 K for 40 h, an increase in sample temperature to a trigger point of 0.17 K leads to an energy release due to the destabilization of atomic H in H2 as predicted by the phenomenological rate process theory. For a tritium weight fraction of 2.5%, energy releases were triggered at 0.54 and 0.82 K after storage at 0.080 K, indicating the trapping of H atoms at the sites of T2 and HT molecules in the sample. The application of a 15 kG magnetic field is shown to increase the storage capacity of T2 traps while reducing that of HT traps, and to lower the trigger temperatures of both. Results suggest that the direct conversion of nuclear energy to chemical energy may become technically feasible in the future.
NASA Astrophysics Data System (ADS)
Šimek, M.; Ambrico, P. F.; Prukner, V.
2015-07-01
The evolution of individual v = 0-10 vibrational levels of N2(A3Σ\\text{u}+ ) metastable species produced by filamentary streamer discharge was investigated by the laser-induced fluorescence technique. Triggered single streamer filament was periodically produced in pure nitrogen at a pressure of 200 torr and metastable species were monitored during the streamer channel decay in the centre of the discharge gap. The observed dynamics of N2(A3Σ\\text{u}+ ) vibrational levels follow two very different scenarios: while higher (v > 6) vibronic levels decay exponentially in hundreds of nanoseconds, the populations of lower levels (v ≤ 6) definitely increase, first reaching a local maximum on a microsecond timescale and then decreasing afterwards. Population maxima of N2(A3Σ\\text{u}+ , v ≤ 6) levels occur after the streamer onset with a certain delay, which decreases with increasing vibrational number. Interpretation of experimental observation based on a 0D kinetic model of the post-discharge period takes into account the most important processes redistributing populations between the N2(A3Σ\\text{u}+ ), N2 ≤ft({{\\text{B}}3}{{\\Pi}\\text{g}}\\right) and N2≤ft({{\\text{C}}3}{{\\Pi}\\text{u}}\\right) vibronic levels. The model reproduces experimental observations fairly well, including observed maxima delays occurring due to the collisional cascade, which transfers metastable species from higher even/odd vibrational levels towards v = 0/v = 1 terminal levels through the Δv = 2 vibrational relaxation mechanism. A calibration procedure based on the rate of energy-pooling processes was used to determine absolute populations of the v = 0 and 1 levels from LIF data, and the model results were utilized to place on an absolute scale all the higher (v > 1) measured vibronic levels. Vibrational distributions obtained from calibrated LIF data at selected instants show a reasonable qualitative agreement with model predictions
NASA Technical Reports Server (NTRS)
Strand, Albert A.; Jackson, Darryl J.
1992-01-01
As the nation redefines priorities to deal with a rapidly changing world order, both government and industry require new approaches for oversight of management systems, particularly for high technology products. Declining defense budgets will lead to significant reductions in government contract management personnel. Concurrently, defense contractors are reducing administrative and overhead staffing to control costs. These combined pressures require bold approaches for the oversight of management systems. In the Spring of 1991, the DPRO and TRW created a Process Action Team (PAT) to jointly prepare a Performance Based Management (PBM) system titled Teamwork for Oversight of Processes and Systems (TOPS). The primary goal is implementation of a performance based management system based on objective data to review critical TRW processes with an emphasis on continuous improvement. The processes are: Finance and Business Systems, Engineering and Manufacturing Systems, Quality Assurance, and Software Systems. The team established a number of goals: delivery of quality products to contractual terms and conditions; ensure that TRW management systems meet government guidance and good business practices; use of objective data to measure critical processes; elimination of wasteful/duplicative reviews and audits; emphasis on teamwork--all efforts must be perceived to add value by both sides and decisions are made by consensus; and synergy and the creation of a strong working trust between TRW and the DPRO. TOPS permits the adjustment of oversight resources when conditions change or when TRW systems performance indicate either an increase or decrease in surveillance is appropriate. Monthly Contractor Performance Assessments (CPA) are derived from a summary of supporting system level and process-level ratings obtained from objective process-level data. Tiered, objective, data-driven metrics are highly successful in achieving a cooperative and effective method of measuring
NASA Astrophysics Data System (ADS)
Strand, Albert A.; Jackson, Darryl J.
As the nation redefines priorities to deal with a rapidly changing world order, both government and industry require new approaches for oversight of management systems, particularly for high technology products. Declining defense budgets will lead to significant reductions in government contract management personnel. Concurrently, defense contractors are reducing administrative and overhead staffing to control costs. These combined pressures require bold approaches for the oversight of management systems. In the Spring of 1991, the DPRO and TRW created a Process Action Team (PAT) to jointly prepare a Performance Based Management (PBM) system titled Teamwork for Oversight of Processes and Systems (TOPS). The primary goal is implementation of a performance based management system based on objective data to review critical TRW processes with an emphasis on continuous improvement. The processes are: Finance and Business Systems, Engineering and Manufacturing Systems, Quality Assurance, and Software Systems. The team established a number of goals: delivery of quality products to contractual terms and conditions; ensure that TRW management systems meet government guidance and good business practices; use of objective data to measure critical processes; elimination of wasteful/duplicative reviews and audits; emphasis on teamwork--all efforts must be perceived to add value by both sides and decisions are made by consensus; and synergy and the creation of a strong working trust between TRW and the DPRO. TOPS permits the adjustment of oversight resources when conditions change or when TRW systems performance indicate either an increase or decrease in surveillance is appropriate. Monthly Contractor Performance Assessments (CPA) are derived from a summary of supporting system level and process-level ratings obtained from objective process-level data. Tiered, objective, data-driven metrics are highly successful in achieving a cooperative and effective method of measuring
Glushkov, A. V.
2009-11-15
The arrival directions of primary cosmic ray particles with energies E{sub 0} {>=} 10{sup 19} eV and zenith angles {theta} {<=} 60{sup o} recorded on the Yakutsk array over the period 1974-2009 are analyzed. These events separated by different time intervals are shown to have different global anisotropies.
Local anisotropy of cosmic rays with E{sub 0} {>=} 10{sup 17} eV from Yakutsk EAS array data
Glushkov, A. V.
2010-07-15
The arrival directions of primary cosmic ray particles with energies E{sub 0} {>=} 10{sup 17} eV and zenith angles {theta} {<=} 60{sup o} recorded on the Yakutsk array over the period 1974-2009 are analyzed. These events are shown to have different anisotropies in different energy ranges.
NASA Astrophysics Data System (ADS)
Rathod, Maureen L.
Initially 3D FEM simulation of a simplified mixer was used to examine the effect of mixer configuration and operating conditions on dispersive mixing of a non-Newtonian fluid. Horizontal and vertical velocity magnitudes increased with increasing mixer speed, while maximum axial velocity and shear rate were greater with staggered paddles. In contrast, parallel paddles produced an area of efficient dispersive mixing between the center of the paddle and the barrel wall. This study was expanded to encompass the complete nine-paddle mixing section using power-law and Bird-Carreau fluid models. In the center of the mixer, simple shear flow was seen, corresponding with high [special character omitted]. Efficient dispersive mixing appeared near the barrel wall at all flow rates and near the barrel center with parallel paddles. Areas of backflow, improving fluid retention time, occurred with staggered paddles. The Bird-Carreau fluid showed greater influence of paddle motion under the same operating conditions due to the inelastic nature of the fluid. Shear-thinning behavior also resulted in greater maximum shear rate as shearing became easier with decreasing fluid viscosity. Shear rate distributions are frequently calculated, but extension rate calculations have not been made in a complex geometry since Debbaut and Crochet (1988) defined extension rate as the ratio of the third to the second invariant of the strain rate tensor. Extension rate was assumed to be negligible in most studies, but here extension rate is shown to be significant. It is possible to calculate maximum stable bubble diameter from capillary number if shear and extension rates in a flow field are known. Extension rate distributions were calculated for Newtonian and non-Newtonian fluids. High extension and shear rates were found in the intermeshing region. Extension is the major influence on critical capillary number and maximum stable bubble diameter, but when extension rate values are low shear rate has
Yudov, Yury V.
2006-07-01
The direct numerical simulation, extended to boundary - fitted coordinate, has been carried out for a fully-developed turbulent flow thermal hydraulics in a triangular rod bundle. The rod bundle is premised to be an infinite array. The spacer grid effects are ignored. The purpose of this work is to verify DNS methodology to be applied for deriving coefficients for inter-subchannel turbulent mixing and heat transfer on a rod. These coefficients are incorporated in subchannel analysis codes. To demonstrate the validity of this methodology, numerical calculation was performed for the bundle with the pitch to diameter ratio 1.2, at friction Reynolds number of 600 and Prandtl number of 1. The results for the hydraulic parameters are compared with published DNS data, and the results for the heat exchange coefficients -- with those obtained using semi-empirical correlations. (authors)
ERIC Educational Resources Information Center
Goold, Vernell C.
1977-01-01
Numerical control (a technique involving coded, numerical instructions for the automatic control and performance of a machine tool) does not replace fundamental machine tool training. It should be added to the training program to give the student an additional tool to accomplish production rates and accuracy that were not possible before. (HD)
Merritt, Michael L.
1997-01-01
Simulation modeling techniques can by used advantageously in estimating artesian flow rates of wells in the upper Floridan Aquifer or for estimating transmissivity based in measured flow rates. The generalized aquifer model was useful in testing conceptual models of the relation between the various aquifers and confining layers beneath the surface of Dade County.
NASA Technical Reports Server (NTRS)
Siemers, P. M., III; Henry, M. W.
1986-01-01
Pressure distribution test data obtained on a 0.10-scale model of the forward fuselage of the Space Shuttle Orbiter are presented without analysis. The tests were completed in the AEDC 16T Propulsion Wind Tunnel. The 0.10-scale model was tested at angles of attack from -2 deg to 18 deg and angles of side slip from -6 to 6 deg at Mach numbers from 0.25 to 1/5 deg. The tests were conducted in support of the development of the Shuttle Entry Air Data System (SEADS). In addition to modeling the 20 SEADS orifices, the wind-tunnel model was also instrumented with orifices to match Development Flight Instrumentation (DFI) port locations that existed on the Space Shuttle Orbiter Columbia (OV-102) during the Orbiter Flight Test program. This DFI simulation has provided a means of comparisons between reentry flight pressure data and wind-tunnel and computational data.
NASA Astrophysics Data System (ADS)
Zhang, Haojia; Yang, Qiuhong; Lu, Shenzhou; Huang, Dongdong; Wang, Yonggang; Wei, Zhiyi; Wang, Qing; Zhang, Yongdong
2013-02-01
A 5 at.% Yb3+ doped (La0.10Y0.90)2O3 transparent ceramic was fabricated with nano-powders and sintered in H2 atmosphere. Spectroscopic properties and laser performance of Yb:(La0.10Y0.90)2O3 ceramic were studied. The ceramic exhibits excellent spectroscopic properties, with broad absorption and emission bands, and its refractive index (n) is close to 2. The gain cross-section (σg) was calculated at different population inversion ratio (β) values. In addition, among Yb3+ doped YAG crystal, Y2O3 and (YLa)2O3 ceramic, (YLa)2O3 ceramic has the least pump intensity (Imin) of 1.25 KW cm-2. Furthermore, a diode-pumped C-W ceramic laser output has been demonstrated at 1075 nm with a slope-efficiency of 60.2%.
ERIC Educational Resources Information Center
Siegler, Robert S.; Braithwaite, David W.
2016-01-01
In this review, we attempt to integrate two crucial aspects of numerical development: learning the magnitudes of individual numbers and learning arithmetic. Numerical magnitude development involves gaining increasingly precise knowledge of increasing ranges and types of numbers: from non-symbolic to small symbolic numbers, from smaller to larger…
NASA Astrophysics Data System (ADS)
Christian, Stippich; Anton, Glasmacher Ulrich; Peter, Christian, Hackspacher
2014-05-01
The aim of the research is to quantify the long-term landscape evolution of the South Atlantic passive continental margin (SAPCM) in SE-Brazil and NW-Namibia. Excellent onshore outcrop conditions and complete rift to post-rift archives between Sao Paulo and Porto Alegre and in the transition from Namibia to Angola (onshore Walvis ridge) allow a high precision quantification of exhumation, and uplift rates, influencing physical parameters, long-term acting forces, and process-response systems. Research will integrate the published and partly published thermochronological data from Brazil and Namibia, and test lately published new concepts on causes of long-term landscape evolution at rifted margins. The climate-continental margin-mantle coupled process-response system is caused by the interaction between endogenous and exogenous forces, which are related to the mantle-process driven rift - drift - passive continental margin evolution of the South Atlantic, and the climate change since the Early/Late Cretaceous climate maximum. Special emphasis will be given to the influence of long-living transform faults such as the Florianopolis Fracture Zone (FFZ) on the long-term topography evolution of the SAPCM's. A long-term landscape evolution model with process rates will be achieved by thermo-kinematic 3-D modeling (software code PECUBE and FastCape). Testing model solutions obtained for a multidimensional parameter space against the real thermochronological and geomorphological data set, the most likely combinations of parameter rates, and values can be constrained. The data and models will allow separating the exogenous and endogenous forces and their process rates.
Horstman, D.H.; Folinsbee, L.J.; Ives, P.J.; Abdul-Salaam, S.; McDonnell, W.F. )
1990-11-01
The magnitudes of pulmonary responses we previously observed (1) following 6.6-h exposures to 0.12 ppm ozone (O3) suggested that responses would also occur with similar exposures at lower O3 concentrations. The objective of this study was to determine the extent of pulmonary function decrements, respiratory discomfort, and increased airway reactivity to methacholine induced by exposure to O3 below 0.12 ppm. Separate 6.6-h chamber exposures to 0.00, 0.08, 0.10, and 0.12 ppm O3 included six 50-min periods of moderate exercise (VE approximately equal to 39 L/min, HR approximately equal to 115 bpm, and VO2 approximately equal to 1.5 L/min). Each exercise period was followed by 10 min of rest. A 35-min lunch break was included midway through the exposure. Although not intended as an exact simulation, the overall duration, intensity, and metabolic requirements of the exercise performed were representative of a day of moderate to heavy work or play. Preexposure FEV1 averaged 4.39 L, and essentially no change (+0.03 L) occurred with exposure to 0.00 ppm O3. Significant decreases (p less than 0.01) of -0.31, -0.30, and -0.54 L were observed with exposures to 0.08, 0.10, and 0.12 ppm, respectively. The provocative dose of methacholine required to increase airway resistance by 100% (PD100) was 58 cumulative inhalation units (CIU) following exposure to 0.00 ppm and was significantly reduced (p less than 0.01) to 37 CIU at 0.08, 31 CIU at 0.10, and 26 CIU at 0.12 ppm O3; reductions in PD100 are considered indicative of increases in nonspecific airway responsiveness.
NASA Astrophysics Data System (ADS)
Luquot, L.; Gouze, P.; soler Sagarra, J.; Saaltink, M.; Martinez-Perez, L.; Carrera, J.
2015-12-01
The Heletz structure has been selected as a test site for a prospective CO2 reservoir and for the MUSTANG European project injection experiment based on the analysis of the available geological, geophysical and borehole data from various areas of Israel. The Heletz area is located in the Southern part of the Mediterranean Coastal Plain, about 7 km from the sea shore. The target layer is composed of sandstone, has a thickness of around 20 meters and is located at a depth of 1500 m. Flow-through laboratory experiments of CO2-rich brine were realized to evaluate the chemical processes occurring in the Heletz site. The Heletz sandstone rock is poorly consolidated and has a high porosity (around 23%) and connectivity. We performed four flow-through experiments at in situ storage conditions (T = 60ºC, P = 15 MPa, PCO2 =1.8 MPa). The flow rates injection were 0.05 and 0.30 mL.min-1. Two different brine solutions were used, both representative of the Heletz reservoir native water. The first one was a synthetic brine of the Heletz reservoir (closed to seawater). The second one was the first one equilibrated with gypsum. The results show an increase in permeability for all the percolation experiment whatever the flow rate and the brine solution. This is explained by the dissolution of ankerite, dolomite and feldspar. We observed that the permeability increase is higher and faster for high flow rate injection than for low flow rate. Precipitation of secondary phases is characterized such as gypsum during equilibrated-gypsum brine injection. Secondary clay minerals precipitation is also observed near feldspar dissolution. Modeling these experiments is a non-trivial task, as some chemical processes are local in space. Reactive transport models have been performed in order to understand and reproduce the observed processes. We have used a water mixing approach which uses the mass mixing fraction between mobile and/or immobile zones. The approach relies in the fact of not
Converse, D.R.
1985-01-01
Flow rates of 0.7 to 2.4 m/s were measured in the hot springs on the East Pacific Rise (21/sup 0/N). We estimate that the Southwest, National Geographic, and the OBS vents collectively discharge 2 x 10/sup 8/ watts and 150 kg H/sub 2/O/S. The lifetimes of hot springs can not exceed 40,000 years because of the limited heat supply. Mechanical or chemical clogging of the flow routes may shorten these lifetime significantly. We predict that less than 3% of the sulfide particles debouched by the hot springs settle near the vents.
Knight, Matthew M.; Schleicher, David G.; Schwieterman, Edward W.; Christensen, Samantha R.; Farnham, Tony L.
2012-11-01
We report on photometry and imaging of Comet 10P/Tempel 2 obtained at Lowell Observatory from 1983 through 2011. We measured a nucleus rotation period of 8.950 {+-} 0.002 hr from 16 nights of imaging acquired between 2010 September and 2011 January. This rotation period is longer than the period we previously measured in 1999, which was itself longer than the period measured in 1988, and demonstrates that Tempel 2 is continuing to spin down, presumably due to torques caused by asymmetric outgassing. A nearly linear jet was observed which varied little during a rotation cycle in both R and CN images acquired during the 1999 and 2010 apparitions. We measured the projected direction of this jet throughout the two apparitions and, under the assumption that the source region of the jet was near the comet's pole, determined a rotational pole direction of R.A./decl. = 151 Degree-Sign /+59 Degree-Sign from CN measurements and R.A./decl. = 173 Degree-Sign /+57 Degree-Sign from dust measurements (we estimate a circular uncertainty of 3 Degree-Sign for CN and 4 Degree-Sign for dust). Different combinations of effects likely bias both gas and dust solutions and we elected to average these solutions for a final pole direction of R.A./decl. = 162 Degree-Sign {+-} 11 Degree-Sign /+58 Degree-Sign {+-} 1 Degree-Sign . Photoelectric photometry was acquired on 3 nights in 1983, 2 nights in 1988, 19 nights in 1999/2000, and 10 nights in 2010/2011. The activity exhibited a steep 'turn-on' {approx}3 months prior to perihelion (the exact timing of which varies) and a relatively smooth decline after perihelion. The activity during the 1999 and 2010 apparitions was similar; limited data in 1983 and 1988 (along with IUE data from the literature) were systematically higher and the difference cannot be explained entirely by the smaller perihelion distance. We measured a 'typical' composition, in agreement with previous investigators. Monte Carlo numerical modeling with our pole solution best
NASA Astrophysics Data System (ADS)
Knight, Matthew M.; Schleicher, David G.; Farnham, Tony L.; Schwieterman, Edward W.; Christensen, Samantha R.
2012-11-01
We report on photometry and imaging of Comet 10P/Tempel 2 obtained at Lowell Observatory from 1983 through 2011. We measured a nucleus rotation period of 8.950 ± 0.002 hr from 16 nights of imaging acquired between 2010 September and 2011 January. This rotation period is longer than the period we previously measured in 1999, which was itself longer than the period measured in 1988, and demonstrates that Tempel 2 is continuing to spin down, presumably due to torques caused by asymmetric outgassing. A nearly linear jet was observed which varied little during a rotation cycle in both R and CN images acquired during the 1999 and 2010 apparitions. We measured the projected direction of this jet throughout the two apparitions and, under the assumption that the source region of the jet was near the comet's pole, determined a rotational pole direction of R.A./decl. = 151°/+59° from CN measurements and R.A./decl. = 173°/+57° from dust measurements (we estimate a circular uncertainty of 3° for CN and 4° for dust). Different combinations of effects likely bias both gas and dust solutions and we elected to average these solutions for a final pole direction of R.A./decl. = 162° ± 11°/+58° ± 1°. Photoelectric photometry was acquired on 3 nights in 1983, 2 nights in 1988, 19 nights in 1999/2000, and 10 nights in 2010/2011. The activity exhibited a steep "turn-on" ~3 months prior to perihelion (the exact timing of which varies) and a relatively smooth decline after perihelion. The activity during the 1999 and 2010 apparitions was similar; limited data in 1983 and 1988 (along with IUE data from the literature) were systematically higher and the difference cannot be explained entirely by the smaller perihelion distance. We measured a "typical" composition, in agreement with previous investigators. Monte Carlo numerical modeling with our pole solution best replicated the observed coma morphology for a source region located near a comet latitude of +80° and having a
Multiferroic properties of Pb0.90Sr0.10TiO3-CoFe2O4 nanostructured bilayered thin film
NASA Astrophysics Data System (ADS)
Bala, Kanchan; Kotnala, R. K.; Negi, N. S.
2015-05-01
Pb0.90Sr0.10TiO3-CoFe2O4(PST10-CFO) nanostructured bilayered thin film were grown on Si (100) substrate by using metallo-organic decomposition chemical route and spin coating technique. Results show that PST (pervoskite structure) and CFO (spinel) phase coexist in the bilayered thin films, annealed at 650°C for 2hr and no obvious impurity phase can be detected. The structural, surface morphology and micro structural properties were confirmed by X-Ray diffraction (XRD), atomic force microscope (AFM) respectively. Excellent ferroelectric behavior at different voltage was observed, with two platinum electrodes only at surface of the bilayer thin film. A room temperature ferromagnetic behavior was observed in the bilayered Pb0.90Sr0.10TiO3-CoFe2O4 nanostructured thin film. The saturation magnetization and variation in coercivity value of the bilayer thin film is lower than that of the pure CFO film in the presence of non ferromagnetic PST layer which is the attributed that the significant coupling between the two phases.
NASA Technical Reports Server (NTRS)
Capone, F. J.; Berrier, B. L.
1980-01-01
The Langley 16 foot transonic tunnel was used to investigate the afterbody/nozzle longitudinal aerodynamic characteristics of three different two dimensional nozzles and a base-line axisymmetric nozzle installed on a 0.10 scale model of the F-18 airplane. The effects of thrust vectoring and in-flight thrust reversing were also studied. Horizontal-tail deflections of 0 deg, -2 deg, and -5 deg were tested. Test data were obtained at static conditions and at Mach numbers from 0.60 to 1.20 over an angle-of-attack range from -2 deg to 10 deg. Nozzle pressure ratio was varied from jet off to about 10.
Glushkov, A.V.; Pravdin, M.I.
2005-07-01
Data from the Yakutsk extensive air shower array for the period 1974-2004 are used to analyze the energy spectrum and anisotropy of primary cosmic rays (PCRs) with energy E{sub 0} {>=} 10{sup 17} eV. The spectra from different regions of the sky are shown to differ in shape. Enhanced and reduced particle fluxes come from the disks of the Galaxy and the Supergalaxy (the Local Supercluster of galaxies) at E{sub 0} {>=} 5 x 10{sup 18} eV and E{sub 0} {<=} (2-3) x 10{sup 18} eV, respectively. This is interpreted as a manifestation of the possible interaction between extragalactic PCRs and the matter of these spatial structures.
Glushkov, A. V. Pravdin, M. I.
2006-12-15
The astrophysical characteristics of primary cosmic rays (PCRs) and the structure of extensive air showers (EASs) with energy E{sub 0} {>=} 10{sup 17} eV are simultaneously analyzed using the Yakutsk EAS array data acquired in the period 1974-2005. Enhanced and reduced particle fluxes are shown to come from the disk of the Supergalaxy (the Local Supercluster of galaxies) at E{sub 0} {>=} 5 x 10{sup 18} eV and E{sub 0} {<=} (2-3) x 10{sup 18}, respectively. The development of air showers with E{sub 0} {>=} (3-5) x 10{sup 18} eV differs significantly from that at lower energies. This is interpreted as a manifestation of the possible interaction between extragalactic PCRs and the matter of this spatial structure.
NASA Astrophysics Data System (ADS)
Mohan, C. R. K.; Dey, Ranajit; Patel, Shiv P.; Pandey, R. K.; Sharma, M. P.; Bajpai, P. K.
2016-04-01
The effects of 100 MeV O8+ ion beam irradiation on the structural and dielectric behavior of Ba0.90Sr0.10TiO3 ceramics have been analyzed. Ion irradiation does not change the crystalline structure, however the tetragonal distortion increases. The low frequency dielectric dispersion especially at high temperatures increases significantly after ion irradiation. The dielectric relaxation phenomenon has been probed through complex impedance and electric modulus approaches. The observed dielectric relaxation has distributed relaxation times and is a thermally activated process. Ion irradiation enhances the cationic disordering. The contributions of grains and grains boundaries towards impedance have been separated. It is inferred that the grain boundaries become more resistive due to ion irradiation and is associated to oxygen vacancies annihilation. Ion irradiation also decreases the bulk ferroelectric polarization demonstrating that the surface or near surface modifications may tune the bulk properties in polar dielectrics.
NASA Astrophysics Data System (ADS)
Dar, Mashkoor Ahmad; Dar, Hilal Ahmad; Varshney, Dinesh
2016-05-01
Structural and dielectric properties of polycrystalline YMnO3 (x = 0.0, 0.10 and 0.20) which was prepared by solid-state reaction route, have been investigated. The X-ray diffraction pattern reveals that all the samples are in single phase and show hexagonal structure with P63cm space group. The particle size decreases with increase in Sm doping while to that X-ray density increases with increasing x. The dielectric constant (ɛ') of Y1-xSmxMnO3 measured in the frequency range 10 Hz to 1MHz is much higher at lower frequencies (≤ 1KHz) and its value decreases with enhanced frequency. At very high frequencies, ɛ' becomes frequency independent and is attributed to Maxwell Wagner type of interfacial polarization model. A very high value of dielectric constant ˜18642 is observed for x = 10%. The dielectric loss (tan δ) decreases wit increase in Sm doping.
NASA Astrophysics Data System (ADS)
Choudhury, S.; Sain, S.; Mandal, M. K.; Pradhan, S. K.; Meikap, A. K.
2016-07-01
The results on the measurement of electric and dielectric behaviour and capacitance-voltage characteristics of Zn1-xMnxO (x=0 to 0.10) nanocrystalline semiconductors are reported. Direct current conductivity increases with the increase Mn concentration and its thermal behavior can be explained by adiabatic polaronic hopping model. The alternating current conductivity obeys a power law of temperature and frequency. The temperature exponent p strongly depends on Mn concentration. The temperature dependence of frequency exponent s suggests that the overlapping large polaron conduction model is the appropriate conduction mechanism for the investigated samples. The interfacial boundaries and grain contribution to the dielectric properties can be identified by the analysis of complex impedance. Relaxation behaviour of the samples can be explained from the analysis of the electric modulus. Formation of Schottky diode can be described from capacitance-voltage characteristic of the samples and different diode parameters can be extracted from it.
Horstman, D.H.; Folinsbee, L.J.; Ives, P.J.; Salaam, S.A.; McDonnell, W.F.
1990-01-01
The magnitudes of pulmonary responses the authors previously observed (1) following 6.6-h exposure to 0.12 ppm ozone (O{sub 3}) suggested that responses would also occur with similar exposures at lower O{sub 3} concentrations. The objective of the study was to determine the extent of pulmonary function decrements, respiratory discomfort, and increased airway reactivity to methacholine induced by exposure to O{sub 3} below 0.12 ppm. Separate 6.6-h chamber exposures to 0.00, 0.08, 0.10, and 0.12 ppm O3 included six 50-min periods of moderate exercise (VE = 39 L/min, HR = 115 bpm, and VO2 = 1.5 L/min). Each exercise period was followed by 10 min of rest. A 35-min lunch break was included midway through the exposure. Although not intended as an exact simulation, the overall duration, intensity, and metabolic requirements of the exercise performed were representative of a day of moderate to heavy work or play. Preexposure FEV, averaged 4.39 L, and essentially no change (+0.03 L) occurred with exposure to 0.00 ppm O{sub 3}. Significant decreases (p<0.01) of -0.31, -0.30, and -0.54 L were observed with exposures to 0.08, 0.10, and 0.12 ppm, respectively. The study concludes that exposure to O{sub 3} at levels often found in ambient air while engaged in activity representative of a typical day of moderate to heavy work or play induced clinically meaningful pulmonary responses.
NASA Astrophysics Data System (ADS)
Dubowski, J. J.; Roth, A. P.; Deleporte, E.; Peter, G.; Feng, Z. C.; Perkowitz, S.
1992-02-01
Low-temperature photoluminescence, photoluminescence excitation and Raman spectroscopy measurements of CdTeCd 0.90Mn 0.10Te multiple quantum well (MQW) structures grown by pulsed laser evaporation and epitaxy (PLEE) on (001) Cd 1- xZn xTe substrates are carried out. The samples are grown from fluxes of Cd-Te and Cd-Mn-Te provided by ablation of solid CdTe and Cd 0.93Mn 0.07Te targets with Nd:YAG and excimer XeCl lasers, respectively. The excitonic lines corresponding to the quantum well E 1-HH 1 transition are investigated. Comparison between the observed PL excitonic emissions and calculated energy levels using a Kronig-Penney model with the well width as a fitting parameter allowed us to determine the "optical" well widths of the samples and to compare them with those determined from secondary ion mass spectroscopy in-depth profiles. Raman spectra for non-resonance excitation at 501.7 nm are dominated by the CdTe-like longitudinal optical (LO) modes at 166 cm -1 and MnTe-like LO modes at 194 cm -1 from the Cd 0.90Mn 0.10Te barriers. Under resonance conditions, with excitation at 476.5 nm the CdTe LO, 2LO and 3LO modes from the wells near 170,340 and 510 cm -1 dominate the spectra. The results clearly indicate that the PLEE-grown MQWs have the characteristics of the best currently available material.
NASA Technical Reports Server (NTRS)
Oguzman, Ismail H.; Wang, Yang; Kolnik, Jan; Brennan, Kevin F.
1995-01-01
In this paper, calculations of the hole initiated interband impact ionization rate in bulk silicon and GaAs are presented based on an ensemble Monte Carlo simulation with the inclusion of a wave-vector-dependent numerical transition rate formulation. The ionization transition rate is determined for each of the three valence bands, heavy, light, and split-off, using Fermi's golden rule with a two-body, screened Coulomb interaction. The dielectric function used within the calculation is assumed to be wave-vector-dependent. Calculations of the field-dependent impact ionization rate as well as the quantum yield are presented. It is found from both the quantum yield results and examination of the hole distribution function that the effective threshold energy for hole initiated impact ionization is relatively soft, similar to that predicted for the corresponding electron initiated ionization events occur more frequently than either heavy or split-offf initiated ionization events in bulk silicon over the applied electric field strengths examined here, 250-500 kV/cm. Conversely,in GaAs, the vast majority of hole initated ionization events originate from holes within the split-off band.
ERIC Educational Resources Information Center
Sozio, Gerry
2009-01-01
Senior secondary students cover numerical integration techniques in their mathematics courses. In particular, students would be familiar with the "midpoint rule," the elementary "trapezoidal rule" and "Simpson's rule." This article derives these techniques by methods which secondary students may not be familiar with and an approach that…
NASA Technical Reports Server (NTRS)
Baker, John G.
2009-01-01
Recent advances in numerical relativity have fueled an explosion of progress in understanding the predictions of Einstein's theory of gravity, General Relativity, for the strong field dynamics, the gravitational radiation wave forms, and consequently the state of the remnant produced from the merger of compact binary objects. I will review recent results from the field, focusing on mergers of two black holes.
Structure, phase transition and impedance of Zn1- x Li x O (0.10 ≤ x ≤ 0.70) ceramic
NASA Astrophysics Data System (ADS)
Ahmadu, U.; Salaudeen, Islamiyat Temitope
2016-07-01
Structural transformations of Li-doped Zn1- x Li x O (0.10 ≤ x ≤ 0.70) which was synthesised by solid-state reaction were investigated. XRD carried out on powder specimens of the samples show that they are polycrystalline in nature with a hexagonal wurtzite structure having minor impurities. The result indicates the maximum limit of substitution of Zn atoms by Li is at x = 0.4. The lattice parameter a reduced from 3.01 to 2.99 Å, while c reduced from 5.21 to 5.19 Å. However, the Zn-O bond length reduced from 1.88 to 1.87 Å for the undoped, to x = 0.60 for the doped, respectively. The c/ a ratio is 1.73 and is almost constant for all samples. The grain size of the (100) peak of the undoped ZnO is 41.73 nm and that of x = 0.10 is 41.76 nm. For x = 0.2-0.70, the grain size is 41.72 nm indicating that the grain size is almost independent of doping. The SEM results indicate a variation of grain size from 2.18 to 5.15 µm for the undoped ZnO to x = 0.50, which shows increase in grain size and reduction in grain boundaries as doping increases. The results show that x = 0.50 has the highest grain size and the one with the highest transition temperature is x = 0.6. DTA results indicate the structural phase transition temperature of the doped ZnO ranged from ~371 to ~409 K and increased as the amount of Li increases. A single arc is observed in all the impedance plots of the ZnO together with the presence of a relaxation process which is non-Debye. The impedance data show reduced resistance with increase in lithium content. A general increase in dielectric constant with increase in lithium content is observed.
Structural and dynamic electromagnetic properties of Ni0.27 Cu0.10 Zn0.63 Alx Fe2-x O4
NASA Astrophysics Data System (ADS)
Hossen, M. Belal; Hossain, A. K. M. Akther
2015-08-01
The influence of Al substitution on the structural and electromagnetic properties of Ni0.27Cu0.10Zn0.63AlxFe2 - xO4; (where x = 0.0 to x = 0.16 with step = 0.02) prepared by the combustion technique, has been investigated. X-ray diffraction analysis confirms the presence of single phase cubic spinel structure without any secondary phase. The lattice constant, theoretical density, bulk density and average grain size decreases with increasing Al content. B-H loops have been traced for all the compositions and the various hysteresis parameters like saturation induction, coercivity, remanance, remanance ratio and power loss have been studied as a function of Al content. The saturation induction and the initial permeability increases with sintering temperature up to 1150 °C where the maximum bulk density is obtained, while for higher sintering temperature they decrease. The variation of complex initial permeability for Al substituted NiCuZn ferrites can be presented as a form of semicircle so called the Cole-Cole plot and the relaxation phenomena were explained with various shapes of the plots. The analysis of complex impedance spectra by an equivalent circuit model were used to separate the grain and grain boundary resistance of various Ni0.27 Cu0.10 Zn0.63 Alx Fe2 - x O4 . The impedance plot showed the first semicircle at high frequency which corresponds to grain effect and the second semicircle at lower frequency which corresponds to grain boundary (conduction phenomenon). Both grain and grain boundary resistance increases with increasing Al content and the relative increase of grain resistance is larger than the grain boundary resistance. The frequency dependent conductivity results support the double (Jonscher's modified) power law,σT (ω) = σ (o) +A1 ω n1 +A2 ω n2 , and the results showed evidence of three types of conduction process at room temperature: (i) low frequency conductivity is due to long-range ordering (frequency independent or its tendency
Investigation of Material Gain of In0.90Ga0.10As0.59P0.41/InP Lasing Nano-Heregostructure
NASA Astrophysics Data System (ADS)
Yadav, Rashmi; Lal, Pyare; Rahman, F.; Dalela, S.; Alvi, P. A.
2014-02-01
In this paper, we have proposed a step separate confinement heterostructure (SCH) based lasing nano-heterostructure In0.90Ga0.10As0.59P0.41/InP consisting of single quantum well (SQW) and investigated material gain theoretically within TE and TM polarization modes. In addition, the quasi Fermi levels in the conduction and valence bands along with other lasing characteristics like anti-guiding factor, refractive index change with carrier density and differential gain have also been investigated and reported. Moreover, the behavior of quasi Fermi levels in respective bands has also been correlated with the material gain. Strain dependent study on material gain and refractive index change has also been reported. Interestingly, strain has been reported to play a very important role in shifting the lasing wavelength of TE mode to TM mode. The results investigated in the work suggest that the proposed unstrained nano-heterostructure is very suitable as a source for optical fiber based communication systems due to its lasing wavelengths achieved at 1.35 μm within TM mode, while 1.40 μm within TE mode.
Electron-Ion Mixed Conduction of BaCe0.90Y0.10O3-δ Thin Film Generated by Ru Substitution
NASA Astrophysics Data System (ADS)
Ochi, Masanori; Tsuchiya, Takashi; Yamaguchi, Shohei; Suetsugu, Takaaki; Suzuki, Naoya; Kobayashi, Masaki; Minohara, Makoto; Horiba, Koji; Kumigashira, Hiroshi; Higuchi, Tohru
2016-03-01
The structural and electrical properties of a c-axis-oriented BaCe0.85Ru0.05Y0.10O3-δ (BCRY) thin film on an Al2O3(0001) substrate depending on film thickness have been studied. The lattice constant of the c-axis decreases with increasing film thickness. The electrical conductivity is higher in the thin film with a small lattice constant. The activation energy (EA) of the dry BCRY thin film with a high conductivity is 0.26 eV, which corresponds to half of that of the bulk ceramic. The BCRY thin film exhibits electron-ion mixed conduction with a small EA of 0.18 eV below 400 °C in H2O atmosphere. The Ce3+ state created by oxygen vacancies, which locates at the top of the valence band, plays an important role in the electron-ion mixed conduction or proton conduction of the BCRY thin film.
NASA Technical Reports Server (NTRS)
Siemers, P. M., III; Henry, M. W.
1986-01-01
Pressure distribution test data obtained on a 0.10-scale model of the forward fuselage of the Space Shuttle Orbiter are presented without analysis. The tests were completed in the Ames Unitary Wind Tunnel (UPWT). The UPWT tests were conducted in two different test sections operating in the continuous mode, the 8 x 7 feet and 9 x 7 feet test sections. Each test section has its own Mach number range, 1.6 to 2.5 and 2.5 to 3.5 for the 9 x 7 feet and 8 x 7 feet test section, respectively. The test Reynolds number ranged from 1.6 to 2.5 x 10 to the 6th power ft and 0.6 to 2.0 x 10 to the 6th power ft, respectively. The tests were conducted in support of the development of the Shuttle Entry Air Data System (SEADS). In addition to modeling the 20 SEADS orifices, the wind-tunnel model was also instrumented with orifices to match Development Flight Instrumentation (DFI) port locations that existed on the Space Shuttle Columbia (OV-102) during the Orbiter Flight test program. This DFI simulation has provided a means for comparisons between reentry flight pressure data and wind-tunnel and computational data.
NASA Technical Reports Server (NTRS)
Fomin, Y. A.; Kalmykov, G. B.; Khristiansen, M. V.; Motova, M. V.; Nechin, Y. A.; Prosin, V. V.; Zhukov, V. Y.; Efimov, N. N.; Grigoriev, V. M.; Nikiforova, E. S.
1985-01-01
The individual cascade curves of EAS with E sub 0 10 to the 17th power eV/I to 3/ were studied by detection of EAS Cherenkov light pulses. The scintillators located at the center of the Yakutsk EAS array within a 500-m radius circle were used to select the showers and to determine the main EAS parameters. The individual cascade curves N(t) were obtained using the EAS Cherenkov light pulses satisfying the following requirements: (1) the signal-to-noise ratio fm/delta sub n 15, (2) the EAS axis-detector distance tau sub 350 m, (3) the zenith angle theta 30 deg, (4) the probability for EAS to be detected by scintillators W 0.8. Condition (1) arises from the desire to reduce the amplitude distortion of Cherenkov pulses due to noise and determines the range of EAS sizes, N(t). The resolution times of the Cherenkov pulse shape detectors are tau sub 0 approx. 23 ns which results in distortion of a pulse during the process of the detection. The distortion of pulses due to the finiteness of tau sub 0 value was estimated. It is shown that the rise time of pulse becomes greater as tau sub 0.5/tau sub 0 ratio decreases.
Identifying the sources of ferromagnetism in sol-gel synthesized Zn1-xCoxO (0≤x≤0.10) nanoparticles
NASA Astrophysics Data System (ADS)
Beltrán, J. J.; Barrero, C. A.; Punnoose, A.
2016-08-01
We have carefully investigated the structural, optical and electronic properties and related them with changes in the magnetism of sol-gel synthesized Zn1-xCoxO (0≤x≤0.10) nanoparticles. Samples with x≤0.05 were free of spurious phases. Samples with x≤0.03 were found to be with only high spin Co2+ ions into ZnO structure, whereas sample with x=0.05, exhibited the presence of high spin Co2+ and low spin Co3+. We found that the intensity of the main EPR peak associated with Co2+ varies with the nominal Co content in a similar manner as the saturation magnetization and coercive field do. These results point out that the ferromagnetism in these samples should directly be correlated with the presence of divalent cobalt ions. Bound magnetic polaron (BMP) model and the charge transfer model are insufficient to explain the ferromagnetic properties of Zn1-xCoxO nanoparticles. The room temperature ferromagnetism (RTFM) may be originated from a combination of several factors such as the interaction of high spin Co2+ ions, perturbation/alteration and/or changes in the electronic structure of ZnO close to the valence band edge and grain boundary effects.
Stadnyk, Yu.; Horyn', A.; Romaka, V.V.; Gorelenko, Yu.; Romaka, L.P.; Hlil, E.K.; Fruchart, D.
2010-12-15
The n-TiNiSn ternary intermetallic semiconductor is doped by the V donor impurity and the crystalline structure of the obtained Ti{sub 1-x}V{sub x}NiSn solid solutions (x=0-0.10) is determined by X-ray diffraction. Temperature and concentration dependences of the resistivity and thermopower are investigated in 80-380 K range. As main results, the TiNiSn conductivity type is revealed insensitive to V doping and the thermopower factor substantially increases versus V content. First principle calculations based on DFT using FPLO and KKR-CPA methods are performed as well. Experimental data and electronic structure calculations are compared and discussed in terms of thermopower improvements. -- Graphical abstract: Both approaches experimental and calculations point to the same conclusions. Resisitivity, power factor and thermopower estimations indicate that doping of TiNiSn based compound by the V induces insulator-metal transition without change of the negative sign of S thermopower. Vanadium is revealed as donor impurity.
Shih, Ying-Ta; Shen, Wen-He; Lee, Kuo-Long; Pan, Wei
2014-01-15
The magnetization of Co{sub 0.10}Ni{sub 0.90}/Cu(001) films before and after surface oxidization at 300 K is presented. Before the oxidization, the magnetization of the films in the thickness of 11 to 20 monolayers (ML) is in the in-plane direction at the temperature ranging from 140 K to 300 K. After the oxidization, the magnetizations of the films are in the in-plane direction at the temperature above 200 K, but transit to magnetization demolishment, in-plane-and-out-of-plane co-existence, spin reorientation transition, and coercivity enhancement, for films of 11, 12, 13, and above 15 ML, respectively. The blocking temperature of this film is also 200 K, which implies the transitions might be driven by the ordering of the antiferromagnetic surface oxides. The various magnetizations provide a model system for manipulating the magnetization direction, as well as a spin valve device by combination of the oxidized films.
Kaneva, A V; Belykh, E S; Maystrenko, T A; Shadrin, D M; Pylina, Ya I; Velegzhaninov, I O
2015-01-01
Low doses of ionizing radiation and chemical toxic agent effects on biological systems on different organization levels have been studied by numerous researchers. But there is a clear lack of experimental data that allow one to reveal molecular and cellular adaptations of plants and animals from natural populations to adverse effects of environmental factors. The present study was aimed to assess genotoxic effects in earthworms Aporrectodea caliginosa Savigny and Lumbricus rubellus Hoffmeister sampled from the populations that during numerous generations inhabited the territories with a technogeneously enhanced content of natural origin radionuclides and heavy metals in soil. The levels ofthe DNA damage detected with alkaline and neutral versions of Comet-assay in invertebrates from contaminated territories were established not to differ from the spontaneous level found in the animals from the reference population. At the same time the rate of the DNA damage reparation induced in A. caliginosa sampled from the contaminated sites with additional acute γ-irradiation (4 Gy) was found to be considerably higher as compared with earthworms from the reference population. PMID:25962273
Sugimoto, Yu; Kitazumi, Yuki; Shirai, Osamu; Yamamoto, Masahiro; Kano, Kenji
2016-03-31
To understand electrostatic interactions in biomolecules, the bimolecular rate constants (k) between redox enzymes and charged substrates (in this study, redox mediators in the electrode reaction) were evaluated at various ionic strengths (I) for the mediated bioelectrocatalytic reaction. The k value between bilirubin oxidase (BOD) and positively charged mediators increased with I, while that between BOD and negatively charged mediators decreased with I. The opposite trend was observed for the reaction of glucose oxidase (GOD). In the case of noncharged mediators, the k value was independent of I for both BOD and GOD. These results reflect the electrostatic interactions between the enzymes and the mediators. Furthermore, we estimated k/k° (k° being the thermodynamic rate constant) by numerical simulation (finite element method) based on the Poisson-Boltzmann (PB) equation. By considering the charges of individual atoms involved in the amino acids around the substrate binding sites in the enzymes, the simulated k/k° values well reproduced the experimental data. In conclusion, k/k° can be predicted by PB-based simulation as long as the crystal structure of the enzyme and the substrate binding site are known. PMID:26956542
NASA Astrophysics Data System (ADS)
Oh, Se-Young; Kim, Wan-Ho; Yune, Hyoung-Soon; Kim, Hee-Bom; Kim, Seo-Min; Ahn, Chang-Nam; Shin, Ki-Soo
2002-07-01
, registration between two stitched regions and stitching itself in the boundary. It is found from the experiment that total DOF of DE (double exposure) is 0.5 um and the total EL of DE is 10.0% in this paper. At present, it is very difficult to ensure stable process margin for the sub-0.10 um patterning. But there is a promising technology called stitching with special optimization. In addition, this technology will be nominated as an eternal candidate process whenever our lithography is in the adversity at the limits of his days.
Zhao Xin; Han Shumin; Zhu Xilin; Liu Baozhong; Liu Yanqing
2012-06-15
Mg{sub 2}Ni+x wt% LaMg{sub 2}Ni (x=0, 10, 20, 30) composites have been prepared by ball milling Mg{sub 2}Ni and LaMg{sub 2}Ni hydrides. X-ray Diffraction indicates that the composites consist of LaH{sub 3} and Mg{sub 2}NiH{sub 4} phases. Mg{sub 2}NiH{sub 4} phase transforms between with Mg{sub 2}Ni phase during hydriding/dehydriding cycling, while the LaH{sub 3} phase exists still after dehydriding process. Backscatter Electron results reveal that the LaH{sub 3} phase, which is decomposed from hydrided LaMg{sub 2}Ni, distributes in Mg{sub 2}Ni alloy homogeneously after ball milling procedure. Hydriding/Dehydriding measurements indicate significant improvement in reversible hydrogen storage properties of the composites over Mg{sub 2}Ni at low temperature. At 473 K, the hydrogen storage capacity of Mg{sub 2}Ni+20 wt% LaMg{sub 2}Ni composite reaches 3.22 wt% and can reversely desorb hydrogen completely, while the pure Mg{sub 2}Ni hydride is hardly desorbs hydrogen at this temperature. The improvement in the hydrogen storage properties is attributed to the existence of LaH{sub 3} phase in the composites. - Graphical abstract: The Mg{sub 2}Ni + x wt% LaMg{sub 2}Ni (x=10, 20, 30) composites display enhancement on reversible hydrogen storage properties compared with that of pure Mg{sub 2}Ni. Highlights: Black-Right-Pointing-Pointer Tittle La is introduced into Mg{sub 2}Ni alloy without multiphase created. Black-Right-Pointing-Pointer La is introduced into Mg{sub 2}Ni by hydrogen decomposed ball-milling. Black-Right-Pointing-Pointer Reversible hydrogen storage properties at low temperature are improved. Black-Right-Pointing-Pointer Hydrogen storage capacity of composites is beyond 3 wt% at 473 K.
Sarveena, Chand, Jagdish; Verma, S.; Singh, M.; Kotnala, R. K.; Batoo, K. M.
2015-06-24
The structural and magnetic behavior of sol-gel autocombustion synthesized nanocrystalline Ni{sub 0.58}Zn{sub 0.42}Co{sub 0.10}Cu{sub 0.10}Fe{sub 1.8}O{sub 4} have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy and vibrating sample magnetometer(VSM). Sample of high purity and high homogeneity was obtained by calcination at low temperature (500°C) resulting in nanoparticles of average diameter ∼15nm as determined by XRD and further confirmed by TEM. X-ray diffraction (XRD) and selective area diffraction (SAED) confirmed the single phase of the sample. Mössbauer results are supported by magnetization data. Well defined sextets and appearance of hysteresis at room temperature indicate the existence of ferromagnetic coupling at room temperature finding material utility in magnetic storage data. The existence of iron in ferric state confirmed by isomer shift is a clear evidence of improved magnetic properties of the present system.
Numerical simulations in combustion
NASA Technical Reports Server (NTRS)
Chung, T. J.
1989-01-01
This paper reviews numerical simulations in reacting flows in general and combustion phenomena in particular. It is shown that use of implicit schemes and/or adaptive mesh strategies can improve convergence, stability, and accuracy of the solution. Difficulties increase as turbulence and multidimensions are considered, particularly when finite-rate chemistry governs the given combustion problem. Particular attention is given to the areas of solid-propellant combustion dynamics, turbulent diffusion flames, and spray droplet vaporization.
KRUGER AA; MATLACK KS; GONG W; BARDAKCI T; D'ANGELO NA; LUTZE W; CALLOW RA; BRANDYS M; KOT WK; PEGG IL
2011-12-29
This report documents melter and off-gas performance results obtained on the DM1200 HLW Pilot Melter during processing of AZ-101 HLW simulants. The tests reported herein are a subset of six tests from a larger series of tests described in the Test Plan for the work; results from the other tests have been reported separately. The solids contents of the melter feeds were based on the WTP baseline value for the solids content of the feeds from pretreatment which changed during these tests from 20% to 15% undissolved solids resulting in tests conducted at two feed solids contents. Based on the results of earlier tests with single outlet 'J' bubblers, initial tests were performed with a total bubbling rate of 651 pm. The first set of tests (Tests 1A-1E) addressed the effects of skewing this total air flow rate back and forth between the two installed bubblers in comparison to a fixed equal division of flow between them. The second set of tests (2A-2D) addressed the effects of bubbler depth. Subsequently, as the location, type and number of bubbling outlets were varied, the optimum bubbling rate for each was determined. A third (3A-3C) and fourth (8A-8C) set of tests evaluated the effects of alternative bubbler designs with two gas outlets per bubbler instead of one by placing four bubblers in positions simulating multiple-outlet bubblers. Data from the simulated multiple outlet bubblers were used to design bubblers with two outlets for an additional set of tests (9A-9C). Test 9 was also used to determine the effect of small sugar additions to the feed on ruthenium volatility. Another set of tests (10A-10D) evaluated the effects on production rate of spiking the feed with chloride and sulfate. Variables held constant to the extent possible included melt temperature, plenum temperature, cold cap coverage, the waste simulant composition, and the target glass composition. The feed rate was increased to the point that a constant, essentially complete, cold cap was achieved
McCarthy, Ben; Pederson, Larry R.; Anderson, Harlan U.; Zhou, Xiao Dong; Singh, Prabhakar; Coffey, Greg W.; Thomsen, Ed C.
2007-10-01
Exposure of La0.9Sr0.1MnO3+δ to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700 to 1000oC were orders of magnitude higher than Makipirtti-Meng model estimations based on stepwise isothermal dilatometry results at high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900oC. Shrinkage was greatest when LSM-10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria is re-established, whereas the latter condition does not lead to excess vacancy concentrations.
Trolle, Ellen; Vandevijvere, Stefanie; Ruprich, Jiří; Ege, Majken; Dofková, Marcela; de Boer, Evelien; Ocké, Marga
2013-12-01
The aim of the present study was to validate thirty-eight picture series of six pictures each developed within the PANCAKE (Pilot study for the Assessment of Nutrient intake and food Consumption Among Kids in Europe) project for portion size estimation of foods consumed by infants, toddlers and children for future pan-European and national dietary surveys. Identical validation sessions were conducted in three European countries. In each country, forty-five foods were evaluated; thirty-eight foods were the same as the depicted foods, and seven foods were different, but meant to be quantified by the use of one of the thirty-eight picture series. Each single picture within a picture series was evaluated six times by means of predefined portions. Therefore, thirty-six pre-weighed portions of each food were evaluated by convenience samples of parents having children aged from 3 months to 10 years. The percentages of participants choosing the correct picture, the picture adjacent to the correct picture or a distant picture were calculated, and the performance of individual pictures within the series was assessed. For twenty foods, the picture series performed acceptably (mean difference between the estimated portion number and the served portion number less than 0.4 (SD < 1.1)). In addition, twelve foods were rated acceptable after adjustment for density differences. Some other series became acceptable after analyses at the country level. In conclusion, all picture series were acceptable for inclusion in the PANCAKE picture book. However, the picture series of baby food, salads and cakes either can only be used for foods that are very similar to those depicted or need to be substituted by another quantification tool. PMID:23803561
Malik, K.; Das, Diptasikha; Bandyopadhyay, S.; Banerjee, Aritra; Mandal, P.; Srihari, Velaga
2013-12-09
Thermal variation of structural property, linear thermal expansion coefficient (α), resistivity (ρ), thermopower (S), and power factor (PF) of polycrystalline Bi{sub 1-x}Sb{sub x} (x = 0.10 and 0.14) samples are reported. Temperature-dependent powder diffraction experiments indicate that samples do not undergo any structural phase transition. Rietveld refinement technique has been used to perform detailed structural analysis. Temperature dependence of α is found to be stronger for Bi{sub 0.90}Sb{sub 0.10}. Also, PF for direct band gap Bi{sub 0.90}Sb{sub 0.10} is higher as compared to that for indirect band gap Bi{sub 0.86}Sb{sub 0.14}. Role of electron-electron and electron-phonon scattering on ρ, S, and PF has been discussed.
Numerical simulation of emulsified fuel spray combustion with puffing and micro-explosion
Watanabe, Hirotatsu; Matsushita, Yohsuke; Aoki, Hideyuki; Miura, Takatoshi
2010-05-15
The purpose of this study was to develop numerical simulation of spray combustion of emulsified fuel with considering puffing and micro-explosion. First, a mathematical model for puffing was proposed. In the proposed puffing model, the rate of mass change of a droplet during puffing was expressed by the evaporation rate of dispersed water and the mass change rate due to fine droplets spouted from the droplet surface. The mass change rate due to fine droplets was related to the evaporation rate of the dispersed water and each liquid content. This model had only one experimental parameter. The essential feature of this model was that it was simple to apply to numerical simulation of spray combustion. First, the validity of the proposed puffing model was investigated with the experimental results for a single droplet. The calculated results for a single droplet with the experimental parameter varying from 5.0 to 10 were in good agreement with the experimental results. Moreover, numerical simulation of spray combustion of emulsified fuel was carried out. The occurrence of puffing and micro-explosion was determined by the inner droplet temperature. When micro-explosion occurred, a droplet changed to vapor rapidly. When the proposed puffing model was used in numerical simulation of spray combustion, the experimental parameter in the puffing model was determined for each droplet by random numbers within the range 5.0-10. The calculated results of spray combustion of emulsified fuel without considering puffing or micro-explosions were different from the experimental results even where combustion reactions were almost terminated. Meanwhile, the calculated results when considering puffing and micro-explosions were in good agreement with experimental results at the same location. (author)
Numerical Aerodynamic Simulation
NASA Technical Reports Server (NTRS)
1989-01-01
An overview of historical and current numerical aerodynamic simulation (NAS) is given. The capabilities and goals of the Numerical Aerodynamic Simulation Facility are outlined. Emphasis is given to numerical flow visualization and its applications to structural analysis of aircraft and spacecraft bodies. The uses of NAS in computational chemistry, engine design, and galactic evolution are mentioned.
NASA Astrophysics Data System (ADS)
Shalini, K.; Muneeswaran, M.; Giridharan, N. V.
2016-05-01
Ferroelectric Na0.5(Bi1-xPrx)0.5TiO3 (x=0.00, 0.10) ceramics have been synthesized through sol-gel method. The phase formation has been confirmed by X-ray diffraction analysis of ceramics annealed at 800°C. The relaxation mechanism is observed from variation of dielectric constant with respect to temperature and frequency. Substitution of Pr reduces vacancies and defects identified from leakage current measurements. Further, the polarization Vs electricfield (P-E) measurements have been performed at room temperature.
NASA Technical Reports Server (NTRS)
Esparza, V.; Thornton, D. E.
1976-01-01
Results are presented of a 0.10 scale orbiter forebody test with left and right mounted air data probes (ADP) as well as a flight test probe (nose boom). Left and right ADP data were obtained at Mach numbers of .3, .4, .5, .6, .7, .8, .85, .9, .95, .98, 1.05 and 1.1 through a Reynolds number range of 1.3 to 4.4 million. Nose boom data were obtained at Mach numbers of .3, .4, .5, .6, .7, .9 and .98.
NASA Astrophysics Data System (ADS)
Xie, Wei; Zou, Changwei; Xie, Mubiao; Bao, Dinghua
2016-05-01
(Bi1.90Eu0.10)(V1-zMoz)O5.5 (z = 0, 0.05, 0.10, 0.15 and 0.20) thin films with c-axis oriented were prepared on Pt(111)/Ti/SiO2/Si substrates by using chemical solution deposition method. The effect of Mo6+ concentration on the structure, luminescence properties and dielectric properties of the thin films were characterized systematically. X-ray diffraction data indicates that the thin films with low Mo6+-doping content can remain Bi2VO5.5 structure. When the Mo6+-doping content z reaches to 0.15, the thin films are a mixture of diphase with the main phase Bi2VO5.5 and secondary phase Bi2MoO6. Under UV irradiation, all the thin films emit a bright red or orange emission which origin from Eu3+. With increasing Mo6+-doping content z, the relative intensity of the Red and Orange emissions show obviously change. The value of Red/Orange ratio first decrease, and it reached minimum when z is 0.15, then it recover to the initial value. The variation trend of the Red/Orange ratio reflects the change of the lattice symmetry. Dielectric constant of the thin films increased with the increasing of the Mo6+ concentration while dielectric loss decreased. The decrease of the quantities of oxygen vacancies and the generation of Bi2MoO6 phase are responsible for the improvement of electric properties. These results explain that Eu3+ion can be used as an effective luminescent probe in (Bi1.90Eu0.10)(V1-zMoz)O5.5 (z = 0, 0.05, 0.10, 0.15 and 0.20) thin films, and the electric properties of the thin films can be improved by Mo6+ doping.
NASA Astrophysics Data System (ADS)
Cobb, J. L.; Markert, J. T.
1994-06-01
We report the results and analysis of DC magnetization studies of grain-aligned powders of the infinite-layer electron-doped compounds Sr 0.90La 0.10CuO 2. Magnetization data in the reversible temperature regime were analyzed to obtain the anisotropic superconducting parameters for this system. Three samples of Sr 0.90La 0.10CuO 2 were studied, presumably with very slightly diffrent La or O concentrations. Typically, the extracted values of the coherence lengths (ξ ∥=46 Å, ξ ⊥=30 Å), the penetration depths (λ ∥=290 nm, λ ⊥=450 nm), the mass anisotrophy ( ( {m ⊥}/{m ∥}) {1}/{2}≈1.5 ), and the lower and upper critical fields are appreciably less anisotropic than reported values for the electron-doped T‧ phase materials, possibly because the infinite-layer compound has a significantly shorter interplanar spacing (3.4 Å versus 6.0 Å). One notable sample, moreover, exhibits an inverse anisotropy (( ( {m ⊥}/{m ∥}) {1}/{2}≈0.6 ), further suggesting that this system behaves much like a three-dimensional metal.
Bala, Kanchan Kotnala, R. K.; Negi, N. S.
2015-05-15
Pb{sub 0.90}Sr{sub 0.10}TiO{sub 3}-CoFe{sub 2}O{sub 4}(PST10-CFO) nanostructured bilayered thin film were grown on Si (100) substrate by using metallo-organic decomposition chemical route and spin coating technique. Results show that PST (pervoskite structure) and CFO (spinel) phase coexist in the bilayered thin films, annealed at 650°C for 2hr and no obvious impurity phase can be detected. The structural, surface morphology and micro structural properties were confirmed by X-Ray diffraction (XRD), atomic force microscope (AFM) respectively. Excellent ferroelectric behavior at different voltage was observed, with two platinum electrodes only at surface of the bilayer thin film. A room temperature ferromagnetic behavior was observed in the bilayered Pb{sub 0.90}Sr{sub 0.10}TiO{sub 3}-CoFe{sub 2}O{sub 4} nanostructured thin film. The saturation magnetization and variation in coercivity value of the bilayer thin film is lower than that of the pure CFO film in the presence of non ferromagnetic PST layer which is the attributed that the significant coupling between the two phases.
NASA Astrophysics Data System (ADS)
Ochi, Masanori; Tsuchiya, Takashi; Yamaguchi, Shohei; Suetsugu, Takaaki; Suzuki, Naoya; Kobayashi, Masaki; Minohara, Makoto; Horiba, Koji; Kumigashira, Hiroshi; Higuchi, Tohru
2016-06-01
The a- and c-axes-oriented BaCe0.85Ru0.05Y0.10O3‑δ (BCRY) thin films have been deposited on Nb-SrTiO3(100) substrates by radio frequency (RF) magnetron sputtering. Such BCRY thin films have mixed valence states of Ce4+ and Ce3+. The activation energies (E A) for the conductivity of films thicker than 200 nm are 0.23–0.26 eV, which corresponds to half E A of bulk ceramics, below 400 °C. The BCRY thin films exhibit ion conduction at the bulk region and electron–ion mixed conduction at the surface region. Proton conduction is also observed in the surface state in addition to the mixed conduction. The Fermi levels (E F) locate at the middle position in the band gap region, although E F of the BaCe0.90Y0.10O3‑δ thin films locates on the valence band side. These results indicate that the Ru5+ ions and protons act as donor ions in BCRY thin films.
NASA Astrophysics Data System (ADS)
Reyes-Montero, A.; Pardo, L.; López-Juárez, R.; González, A. M.; Rea-López, S. O.; Cruz, M. P.; Villafuerte-Castrejón, M. E.
2015-06-01
The solid-state synthesis of Ba1-xCaxTi0.9Zr0.1O3 (x = 0.10, 0.15) (BCTZ) powder and the processing method of ceramics, by the use of reduced synthesis time and temperature (1250 °C for 2 h), are reported. Homogeneous and dense (≥95%) ceramic microstructures with sub-10 μm grain size were obtained under all sintering conditions. A comparative study of their ferro-piezoelectric properties as a function of sintering temperatures is presented. The study shows the role of the grain size effect for improving both piezoelectric and ferroelectric properties of these materials. With an increase of the sintering temperature, grain growth was promoted; therefore, higher ferro-piezoelectric values were obtained (at 1400 °C, for x = 0.10: d33 = 300 pC/N, {{d}31}=-150 pC/N, kp = 48% for x = 0.15: d33 = 410 pC/N, d31 =-154 pC/N, kp = 50%). In addition, a diffuse phase transition is observed in these BCTZ ceramics with a Curie temperature near 100 °C at 1 kHz.
NASA Astrophysics Data System (ADS)
Miah, Mohammad J.; Khan, M. N. I.; Hossain, A. K. M. Akther
2016-07-01
Multiferroic xBa0.95Sr0.05TiO3-(1-x)BiFe0.90Gd0.10O3 [xBST-(1-x)BFGO] (x = 0.00, 0.10 and 0.20) ceramics were prepared by the standard solid-state reaction technique. Crystal structure of the ceramics was determined by X-ray diffraction pattern. All the compositions exhibited rhombohedral crystal structure. The tolerance factor `t' varied from 0.847 to 0.864. The AC conductivity spectrum followed the Jonscher's power law. The Nyquist plots indicated that only grains have the contribution to the resistance in this material and the values of grain resistance (Rg) increased with BST content. The real part of complex initial permeability decreased with the increase in frequency and increased with increasing BST content. Magnetoelectric coefficient was determined for all compositions. The maximum value of magnetoelectric coefficient was found to be 1.467 mV.cm-1.Oe-1 for x = 0.20.
Jiang, Tong; Li, Qiang; Yan, Qingfeng; Luo, Nengneng; Zhang, Yiling; Chu, Xiangcheng
2014-11-15
Highlights: • PMN–PT–PZ ceramics with PZ content smaller than 0.10 mol% were synthesized. • T{sub rt} of the PMN–PT–PZ ceramics increased linearly with the increase of PZ constant. • A mutation of the ferroelectric and pyroelectric properties was observed near T{sub rt}. - Abstract: (1 − x)[Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3} (65/35)]–xPbZrO{sub 3} (PMN–PT–PZ) ceramics near morphotropic phase boundary with 0 ≤ x ≤ 0.10 were synthesized via the conventional solid-state reaction method. X-ray diffraction and variable temperature dielectric property characterization indicated that the rhombohedral to tetragonal phase transition temperature (T{sub rt}) increased linearly with the increase of PZ constant. The composition and temperature dependence of their ferroelectric and pyroelectric properties were also investigated. The results showed that there appeared mutation for remnant polarization, coercive field, as well as pyroelectric coefficient at the temperate range near T{sub rt}, which was ascribed to the reorientation of dipoles caused by the rhombohedral–tetragonal phase transition.
Numerical models of complex diapirs
NASA Astrophysics Data System (ADS)
Podladchikov, Yu.; Talbot, C.; Poliakov, A. N. B.
1993-12-01
Numerically modelled diapirs that rise into overburdens with viscous rheology produce a large variety of shapes. This work uses the finite-element method to study the development of diapirs that rise towards a surface on which a diapir-induced topography creeps flat or disperses ("erodes") at different rates. Slow erosion leads to diapirs with "mushroom" shapes, moderate erosion rate to "wine glass" diapirs and fast erosion to "beer glass"- and "column"-shaped diapirs. The introduction of a low-viscosity layer at the top of the overburden causes diapirs to develop into structures resembling a "Napoleon hat". These spread lateral sheets.
Numerical simulation of small perturbation transonic flows
NASA Technical Reports Server (NTRS)
Seebass, A. R.; Yu, N. J.
1976-01-01
The results of a systematic study of small perturbation transonic flows are presented. Both the flow over thin airfoils and the flow over wedges were investigated. Various numerical schemes were employed in the study. The prime goal of the research was to determine the efficiency of various numerical procedures by accurately evaluating the wave drag, both by computing the pressure integral around the body and by integrating the momentum loss across the shock. Numerical errors involved in the computations that affect the accuracy of drag evaluations were analyzed. The factors that effect numerical stability and the rate of convergence of the iterative schemes were also systematically studied.
Sahu, S. Roy, M.
2014-04-24
Polycrystalline ceramic samples of Bi{sub 4}V{sub 2−x}Y{sub x}O{sub 11} (x=0.0 and 0.10) have been synthesized by standard solid state reaction method. The formation of the compounds has been verified by room temperature (RT) X-ray diffraction. The frequency and temperature dependent dielectric constant of both the compounds have been measured. The dielectric studies indicate that the materials are highly lossy. The dc conductivity of the materials has been measured as a function of temperature from RT to 653K and their activation energies were calculated using Arrhenius relation σ = σ{sub o}exp(-Ea/kT). The specific heat and heat flow of both the compounds were determined as a function of temperature using Modulated Differential Scanning Calorimetry (MDSC)
NASA Astrophysics Data System (ADS)
Kim, Ju Sung; Ahn, Chang Won; Ullah, Amir; Chae, Song A.; Kim, Ill Won
2016-06-01
The Li, Ta, and Sb-substituted lead-free (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3 (KNLNTS) thin films were fabricated on Pt(111)/TiO2/SiO2/Si substrates using the radio frequency (RF) magnetron sputtering method. The KNLNTS thin films were annealed at 750 °C for 1 h in an oxygen ambient. The film with a thickness of 350 nm exhibited a typical ferroelectric P - E hysteresis loop without fatigue even after 1010 pulses. The KNLNTS thin film exhibited a relatively low leakage current density of ~10 -7 A/cm2 even up to an applied electric field of 142 kV/cm. A well-saturated piezoelectric hysteresis loop was obtained with a piezoelectric coefficient d 33 of 21 pm/V.
Substitutional disorder in Sr2-yEuyB2-2xSi2+3xAl2-xN8+x (x ≃ 0.12, y ≃ 0.10).
Funahashi, Shiro; Michiue, Yuichi; Takeda, Takashi; Xie, Rong-Jun; Hirosaki, Naoto
2014-05-01
A novel nitride, Sr2-yEuyB2-2xSi2+3xAl2-xN8+x (x ≃ 0.12, y ≃ 0.10) (distrontium europium diboron disilicon dialuminium octanitride), with the space group P62c, was synthesized from Sr3N2, EuN, Si3N4, AlN and BN under nitrogen gas pressure. The structure consists of a host framework with Sr/Eu atoms accommodated in the cavities. The host framework is constructed by the linkage of MN4 tetrahedra (M = Si, Al) and BN3 triangles, and contains substitutional disorder described by the alternative occupation of B2 or Si2N on the (0, 0, z) axis. The B2:Si2N ratio contained in an entire crystal is about 9:1. PMID:24816012
NASA Technical Reports Server (NTRS)
Polhamus, Edward C.; King, Thomas J., Jr.
1949-01-01
An investigation was made in the Langley high-speed 7- by 10-foot tunnel to determine the high-speed lateral and directional stability characteristics of a 0.10-scale model of the Grumman XF9F-2 airplane in the Mach number range from 0.40 to 0.85. The results indicate that static lateral and directional stability is present throughout the Mach number range investigated although in the Mach number range from 0.75 to 0.85 there is an appreciable decrease in rolling moment due to sideslip. Calculations of the dynamic stability indicate that according to current flying-quality requirements the damping of the lateral oscillation, although probably satisfactory for the sea-level condition, may not be satisfactory for the majority of the altitude conditions investigated
Moura, F.; Simoes, A. Z.; Cavalcante, L. S.; Zampieri, M.; Varela, J. A.; Longo, E.; Zaghete, M. A.; Simoes, M. L.
2008-01-21
Strain and vacancy clusters behavior of polycrystalline vanadium (V) and tungsten (W)-doped Ba[Zr{sub 0.10}Ti{sub 0.90}]O{sub 3}, (BZT:2%V) and (BZT:2%W) ceramics obtained by the mixed oxide method was evaluated. Substitution of V and W reduces the distortion of octahedral clusters, decreasing the Raman modes. Electron paramagnetic resonance data indicate that the addition of dopants leads to defects and symmetry changes in the BZT lattice. Remnant polarization and coercive field are affected by V and W substitution due the electron-relaxation mode. The unipolar strain E curves as a function of electric field reach its maximum value for BZT:2%V and BZT:2%W ceramics.
Lim, Hee Nam; Dong, Guangbin
2016-03-01
A general and practical catalytic method has been developed for the rapid synthesis of HCTD (heptacyclo[6.6.0.0(2,6).0(3,13).0(4,11).0(5,9).0(10,14)]tetradecanes) and various new 7,12-disubstituted HCTDs from norbornadienes. Compared to the known approaches, this new protocol avoids stoichiometric metals, utilizes commercially available reagents as catalysts, and affords higher yields and significantly improved selectivity. In addition, quadracyclane was discovered for the first time to undergo a similar endo,cis,endo cycloaddition to give HCTD in a good yield. Derivatization of HCTDs led to efficient preparation of a range of novel homo- and heterobifunctional scaffolds that hold potentials for biological and material applications. PMID:26862783
NASA Astrophysics Data System (ADS)
Saidi, M.; Chaouchi, A.; D'Astorg, S.; Rguiti, M.; Courtois, C.
2015-04-01
Polycrystalline of [(Na0.535K0.480)0.966Li0.058](Nb0.90Ta0.10)O3 samples were prepared using the high-temperature solid-state reaction technique. X-ray diffraction (XRD) analysis indicates the formation of a single-phase with orthorhombic structure. AC impedance plots were used as tool to analyze the electrical behavior of the sample as a function of frequency at different temperatures. The AC impedance studies revealed the presence of grain effect, from 425°C onwards. Complex impedance analysis indicated non-Debye type dielectric relaxation. The Nyquist plot showed the negative temperature coefficient of resistance (NTCR) characteristic of NKLNT. The AC conductivity results were used to correlate with the barrier hopping (CBH) model to evaluate the binding energy (Wm), the minimum hopping distance (Rmin), the density of states at Fermi level (N(Ef)), and the activation energy of the compound.
Rocket engine numerical simulation
NASA Technical Reports Server (NTRS)
Davidian, Ken
1993-01-01
The topics are presented in view graph form and include the following: a definition of the rocket engine numerical simulator (RENS); objectives; justification; approach; potential applications; potential users; RENS work flowchart; RENS prototype; and conclusions.
ERIC Educational Resources Information Center
Smith, David Eugene; Ginsburg, Jekuthiel
Counting, naming numbers, numerals, computation, and fractions are the topics covered in this pamphlet. Number lore and interesting number properties are noted; the derivation of some arithmetic terms is briefly discussed. (DT)
Freddie Fish. A Primary Environmental Study of Basic Numerals, Sets, Ordinals and Shapes.
ERIC Educational Resources Information Center
Kraynak, Ola
This teacher's guide and study guide are an environmental approach to mathematics education in the primary grades. The mathematical studies of the numerals 0-10, ordinals, number sets, and basic shapes - diamond, circle, square, rectangle, and triangle - are developed through the story of Freddie Fish and his search for clean water. The…
Sun, Hai Ling; Wu, Xiao; Chung, Tat Hang; Kwok, K W
2016-01-01
Luminescent materials with dynamic photoluminescence activity have aroused special interest because of their potential widespread applications. One proposed approach of directly and reversibly modulating the photoluminescence emissions is by means of introducing an external electric field in an in-situ and real-time way, which has only been focused on thin films. In this work, we demonstrate that real-time electric field-induced photoluminescence modulation can be realized in a bulk Ba0.85Ca0.15Ti0.90Zr0.10O3 ferroelectric ceramic doped with 0.2 mol% Pr(3+), owing to its remarkable polarization reversal and phase evolution near the morphotropic phase boundary. Along with in-situ X-ray diffraction analysis, our results reveal that an applied electric field induces not only typical polarization switching and minor crystal deformation, but also tetragonal-to-rhombohedral phase transformation of the ceramic. The electric field-induced phase transformation is irreversible and engenders dominant effect on photoluminescence emissions as a result of an increase in structural symmetry. After it is completed in a few cycles of electric field, the photoluminescence emissions become governed mainly by the polarization switching, and thus vary reversibly with the modulating electric field. Our results open a promising avenue towards the realization of bulk ceramic-based tunable photoluminescence activity with high repeatability, flexible controllability, and environmental-friendly chemical process. PMID:27339815
Sun, Hai Ling; Wu, Xiao; Chung, Tat Hang; Kwok, K. W.
2016-01-01
Luminescent materials with dynamic photoluminescence activity have aroused special interest because of their potential widespread applications. One proposed approach of directly and reversibly modulating the photoluminescence emissions is by means of introducing an external electric field in an in-situ and real-time way, which has only been focused on thin films. In this work, we demonstrate that real-time electric field-induced photoluminescence modulation can be realized in a bulk Ba0.85Ca0.15Ti0.90Zr0.10O3 ferroelectric ceramic doped with 0.2 mol% Pr3+, owing to its remarkable polarization reversal and phase evolution near the morphotropic phase boundary. Along with in-situ X-ray diffraction analysis, our results reveal that an applied electric field induces not only typical polarization switching and minor crystal deformation, but also tetragonal-to-rhombohedral phase transformation of the ceramic. The electric field-induced phase transformation is irreversible and engenders dominant effect on photoluminescence emissions as a result of an increase in structural symmetry. After it is completed in a few cycles of electric field, the photoluminescence emissions become governed mainly by the polarization switching, and thus vary reversibly with the modulating electric field. Our results open a promising avenue towards the realization of bulk ceramic-based tunable photoluminescence activity with high repeatability, flexible controllability, and environmental-friendly chemical process. PMID:27339815
NASA Astrophysics Data System (ADS)
Chao, Xiaolian; Wang, Juanjuan; Xie, Xueke; Liang, Pengfei; Yang, Zupei
2016-01-01
The objective of this work is to lower the sintering temperature of (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 (BCZT) ceramics without sacrificing their piezoelectric performance. Li2CO3 was used as sintering aid so that BCZT ceramics with low sintering temperature were fabricated by conventional solid-state sintering. The sintering temperature of the BCZT ceramics was greatly decreased from 1450°C to 1260°C by introducing Li2CO3. The ceramics with a Li2CO3 content of x = 0.02 demonstrated outstanding piezoelectric and dielectric properties: d 33 = 436 pC/N, k p = 56%, Q m = 86, ɛ r = 5185, tan δ = 0.017 and T c = 83°C. We explain the structural evolution in these ceramics through the growth mechanism of liquid-phase sintering, which includes 4 steps: (1) interface reaction in the initial state; (2) diffusion of Li2CO3 into BCZT grains; (3) densification by diffusion of CO2 through BCZT; and (4) improvement of properties by diffusion into the lattice of grain. As a result, Li2CO3 additive can effectively improve the piezoelectric properties of BCZT-based ceramics sintered at low temperatures.
Observation of bi-relaxor characteristic in multiferroic 0.70Bi0.90Ca0.10FeO3-0.30PbTiO3 ceramics
NASA Astrophysics Data System (ADS)
Tirupathi, Patri; Chandra, Amreesh
2013-09-01
The coexistence of bi-relaxor property, i.e. ferroelectric relaxor as well as spin glass type behaviour, is observed in disordered multiferroic ceramic 0.70Bi0.90Ca0.10FeO3-0.30PbTiO3. The real parts of dielectric permittivity and magnetic susceptibility show pronounced frequency dispersion near the corresponding phase transition temperatures, namely, Tc ≈ 550 K and TN ≈ 110 K, respectively. The relaxor behaviour observed in temperature-dependent dielectric constant measurement is confirmed by fitting of the Vogel-Fulcher equation. Similarly, magnetic spin glass behaviour is proven by power law fitting. The origin of such bi-relaxor in the present system can be attributed to the disorder and frustration among the uncompensated spins of the Fe-ion. This has been confirmed by analysing the x-ray photoelectron (XPS) spectrum of the sample under investigation. Using FESEM micrographs, the coexistence of nano-sized and bulk grains is shown. The importance of such coexistence is discussed and also presented in the paper.
NASA Astrophysics Data System (ADS)
Irmak, A. E.; Taşarkuyu, E.; Coşkun, A.; Acet, M.; Samancıoğlu, Y.; Aktürk, S.
2015-08-01
Structural, electrical, and magnetic properties of La0.65(Ca0.30Pb0.05)Mn0.90Cu0.10O3 compound were investigated. The compound, prepared by the sol-gel route, was pressed into pellets and one of them was sintered at 900 °C and the other at 1000 °C for 24 h. The aim of the study was to explore structural, electrical and magnetic properties of the compound. Temperature dependent X-ray powder diffraction studies on the sample sintered at 900 °C reveal an orthorhombic-Pbnm perovskite structure through the temperature range between 320 K and 86 K. Scanning electron microcopy and energy dispersive spectroscopy analyses showed grainy, homogeneous and stoichiometric structure. Magnetization and resistivity measurements reveal that the Curie temperatures, TC, and insulator-metal transition temperatures, TIM, coincide, but the samples sintered at 900 °C also exhibit thermal hysteresis both in magnetization and resistivity upon cooling and warming.
NASA Astrophysics Data System (ADS)
Sun, Hai Ling; Wu, Xiao; Chung, Tat Hang; Kwok, K. W.
2016-06-01
Luminescent materials with dynamic photoluminescence activity have aroused special interest because of their potential widespread applications. One proposed approach of directly and reversibly modulating the photoluminescence emissions is by means of introducing an external electric field in an in-situ and real-time way, which has only been focused on thin films. In this work, we demonstrate that real-time electric field-induced photoluminescence modulation can be realized in a bulk Ba0.85Ca0.15Ti0.90Zr0.10O3 ferroelectric ceramic doped with 0.2 mol% Pr3+, owing to its remarkable polarization reversal and phase evolution near the morphotropic phase boundary. Along with in-situ X-ray diffraction analysis, our results reveal that an applied electric field induces not only typical polarization switching and minor crystal deformation, but also tetragonal-to-rhombohedral phase transformation of the ceramic. The electric field-induced phase transformation is irreversible and engenders dominant effect on photoluminescence emissions as a result of an increase in structural symmetry. After it is completed in a few cycles of electric field, the photoluminescence emissions become governed mainly by the polarization switching, and thus vary reversibly with the modulating electric field. Our results open a promising avenue towards the realization of bulk ceramic-based tunable photoluminescence activity with high repeatability, flexible controllability, and environmental-friendly chemical process.
NASA Astrophysics Data System (ADS)
Amaral, J. B.; Araujo, R. M.; Pedra, P. P.; Meneses, C. T.; Duque, J. G. S.; dos S. Rezende, M. V.
2016-09-01
In this work, the effect of insertion of transition metal, TM (=Ni, Zn, Al and Fe), ions in Cu1-xTMxO samples (0
NASA Astrophysics Data System (ADS)
Chen, Renjie; Guo, Shuai; Wang, Jinzhi; Lee, Don; Yan, Aru
2011-04-01
Nanocomposite (Pr8.2Fe86.1-xCoxB5.7)0.99Zr0.01 (x = 0-10) ribbons consisting of Pr2(Fe,Co)14B and α-(Fe,Co) phases were prepared by a melt-spun technique. The microstructure and magnetic properties were studied. The results show that the Curie temperature increases drastically with increasing Co content. The optimal permanent magnetic properties are obtained at x = 2, and the value of Hci, Ms, Mr, and (BH)max are 6.52 kOe, 150.2 emu/g, 120.9 emu/g, and 22.34 MGOe, respectively. Typical magnetization behaviors of nanocomposite magnets are found in these ribbons. The significant remanence enhancement indicates that a strong intergrain exchange coupling exists in all ribbons studied in this work. By Co substitution, the intergrain exchange coupling is enhanced significantly. The study of microstructure shows that the larger grains of Pr2(Fe,Co)14B hard phase are surrounded by the smaller grains of α-(Fe,Co) soft phase with size about 10-20 nm in the ribbon with Co substitution. This kind of microstructure is in favor of exchange coupling between magnetically hard and soft phases and results in excellent magnetic properties.
Numerical analysis of bifurcations
Guckenheimer, J.
1996-06-01
This paper is a brief survey of numerical methods for computing bifurcations of generic families of dynamical systems. Emphasis is placed upon algorithms that reflect the structure of the underlying mathematical theory while retaining numerical efficiency. Significant improvements in the computational analysis of dynamical systems are to be expected from more reliance of geometric insight coming from dynamical systems theory. {copyright} {ital 1996 American Institute of Physics.}
Numerical Techniques in Acoustics
NASA Technical Reports Server (NTRS)
Baumeister, K. J. (Compiler)
1985-01-01
This is the compilation of abstracts of the Numerical Techniques in Acoustics Forum held at the ASME's Winter Annual Meeting. This forum was for informal presentation and information exchange of ongoing acoustic work in finite elements, finite difference, boundary elements and other numerical approaches. As part of this forum, it was intended to allow the participants time to raise questions on unresolved problems and to generate discussions on possible approaches and methods of solution.
Relationships between rating scales, question stem wording, and community responses to railway noise
NASA Astrophysics Data System (ADS)
Sato, Tetsumi; Yano, Takashi; Morihara, Takashi; Masden, Kirk
2004-10-01
Two series of social surveys on community responses to railway noise were carried out in Japan to evaluate the relationships between two verbal scales and a numeric scale, and those among four base descriptors. In the first survey, two types of questionnaires were prepared in which a 0-10- point numeric scale was used in combination with either a four-point or a five-point verbal scale. The key questions concerned annoyance, activity disturbance and related effects caused by railway noise. Community responses were compared on the basis of the dose-response relationships. Regarding the percentages of respondents who answered, "highly annoyed," it was found that there were no systematic differences between the two verbal scales. It was also found that the extent of noise annoyance rated on the four-point or five-point verbal scale corresponded with that rated on the 11-point numeric scale by percentages of scale steps. In the second survey, four types of questionnaires were prepared, each using one of the four base descriptors. Community responses to general noise annoyance among the four base descriptors were compared. No systematic differences were found among the four base descriptors.
Numerical ability predicts mortgage default.
Gerardi, Kristopher; Goette, Lorenz; Meier, Stephan
2013-07-01
Unprecedented levels of US subprime mortgage defaults precipitated a severe global financial crisis in late 2008, plunging much of the industrialized world into a deep recession. However, the fundamental reasons for why US mortgages defaulted at such spectacular rates remain largely unknown. This paper presents empirical evidence showing that the ability to perform basic mathematical calculations is negatively associated with the propensity to default on one's mortgage. We measure several aspects of financial literacy and cognitive ability in a survey of subprime mortgage borrowers who took out loans in 2006 and 2007, and match them to objective, detailed administrative data on mortgage characteristics and payment histories. The relationship between numerical ability and mortgage default is robust to controlling for a broad set of sociodemographic variables, and is not driven by other aspects of cognitive ability. We find no support for the hypothesis that numerical ability impacts mortgage outcomes through the choice of the mortgage contract. Rather, our results suggest that individuals with limited numerical ability default on their mortgage due to behavior unrelated to the initial choice of their mortgage. PMID:23798401
Numerical ability predicts mortgage default
Gerardi, Kristopher; Goette, Lorenz; Meier, Stephan
2013-01-01
Unprecedented levels of US subprime mortgage defaults precipitated a severe global financial crisis in late 2008, plunging much of the industrialized world into a deep recession. However, the fundamental reasons for why US mortgages defaulted at such spectacular rates remain largely unknown. This paper presents empirical evidence showing that the ability to perform basic mathematical calculations is negatively associated with the propensity to default on one’s mortgage. We measure several aspects of financial literacy and cognitive ability in a survey of subprime mortgage borrowers who took out loans in 2006 and 2007, and match them to objective, detailed administrative data on mortgage characteristics and payment histories. The relationship between numerical ability and mortgage default is robust to controlling for a broad set of sociodemographic variables, and is not driven by other aspects of cognitive ability. We find no support for the hypothesis that numerical ability impacts mortgage outcomes through the choice of the mortgage contract. Rather, our results suggest that individuals with limited numerical ability default on their mortgage due to behavior unrelated to the initial choice of their mortgage. PMID:23798401
Frontiers in Numerical Relativity
NASA Astrophysics Data System (ADS)
Evans, Charles R.; Finn, Lee S.; Hobill, David W.
2011-06-01
Preface; Participants; Introduction; 1. Supercomputing and numerical relativity: a look at the past, present and future David W. Hobill and Larry L. Smarr; 2. Computational relativity in two and three dimensions Stuart L. Shapiro and Saul A. Teukolsky; 3. Slowly moving maximally charged black holes Robert C. Ferrell and Douglas M. Eardley; 4. Kepler's third law in general relativity Steven Detweiler; 5. Black hole spacetimes: testing numerical relativity David H. Bernstein, David W. Hobill and Larry L. Smarr; 6. Three dimensional initial data of numerical relativity Ken-ichi Oohara and Takashi Nakamura; 7. Initial data for collisions of black holes and other gravitational miscellany James W. York, Jr.; 8. Analytic-numerical matching for gravitational waveform extraction Andrew M. Abrahams; 9. Supernovae, gravitational radiation and the quadrupole formula L. S. Finn; 10. Gravitational radiation from perturbations of stellar core collapse models Edward Seidel and Thomas Moore; 11. General relativistic implicit radiation hydrodynamics in polar sliced space-time Paul J. Schinder; 12. General relativistic radiation hydrodynamics in spherically symmetric spacetimes A. Mezzacappa and R. A. Matzner; 13. Constraint preserving transport for magnetohydrodynamics John F. Hawley and Charles R. Evans; 14. Enforcing the momentum constraints during axisymmetric spacelike simulations Charles R. Evans; 15. Experiences with an adaptive mesh refinement algorithm in numerical relativity Matthew W. Choptuik; 16. The multigrid technique Gregory B. Cook; 17. Finite element methods in numerical relativity P. J. Mann; 18. Pseudo-spectral methods applied to gravitational collapse Silvano Bonazzola and Jean-Alain Marck; 19. Methods in 3D numerical relativity Takashi Nakamura and Ken-ichi Oohara; 20. Nonaxisymmetric rotating gravitational collapse and gravitational radiation Richard F. Stark; 21. Nonaxisymmetric neutron star collisions: initial results using smooth particle hydrodynamics
Numerical calculations of strained premixed laminar flames
NASA Astrophysics Data System (ADS)
Darabiha, N.; Candel, S.; Marble, F. E.
The structure of a strained laminar flame in the vicinity of a stagnation point is examined numerically. The stagnation point is established by the counterflow of fresh mixture and hot products. This situation is described by standard reactive boundary layer equations. The numerical scheme used to solve the similar boundary layer equations put in F-V form (block-implicit) is an adaptation of the schemes proposed by Blottner (1979). The calculations are performed first on an uniform grid and then confirmed with an adaptive grid method due to Smooke (1982). Numerical calculations allow an exact description of the flame structure in physical and also reduced coordinates. Predictions of Libby and Williams (1982) for high and intermediate values of the strain rate based on activation energy asymptotics are confirmed. For low strain rates (ordinary unstrained laminar flame) the mass rate of reaction per unit flame area differs from that obtained by activation energy asymptotics.
Ahmad, Tokeer; Khatoon, Sarvari; Coolahan, Kelsey
2013-09-01
Graphical abstract: Monophasic and crystalline In{sub 2−x}Ni{sub x}O{sub 3} nanoparticles of size 8–15 nm have been synthesized solvothermally and showed red shift in energy band gap which decreases on increasing Ni{sup 2+} concentration in In{sub 2}O{sub 3} host lattice. - Highlights: • Monophasic Ni-doped In{sub 2}O{sub 3} nanoparticles by solvothermal method for first time. • Plausible reaction mechanism using thermogravimetric analysis. • High surface area with small particle size obtained. • Solid solutions exhibit paramagnetism with very weak antiferromagnetic interactions. - Abstract: In{sub 2−x}Ni{sub x}O{sub 3} (x = 0.05, 0.10 and 0.15) nanoparticles were successfully synthesized by solvothermal method by the thermal decomposition of oxalate precursor at 450 °C for the first time. X-ray diffraction studies showed the formation of highly crystalline and monophasic cubic structure of In{sub 2}O{sub 3} which is attributed to the formation of solid solution. These nanoparticles show good optical transmittance in the visible region. Optical measurements showed an energy band gap which decreases with increasing Ni concentration. The grain size decreases from 15 nm to 8 nm and surface area increases from 90 to 254 m{sup 2} g{sup −1} on increasing the Ni concentration. High dielectric constant and dielectric loss has been obtained which indicates the conducting nature of these solid solutions. Magnetic measurements showed that the samples are strong paramagnetic in nature with very weak antiferromagnetic interactions. No evidence of ferromagnetism is observed for these solid solutions at room temperature.
Bian, Jian Jiang Ding, Yao Min
2015-07-15
Highlights: • Structure, sinterability, and dielectric properties of CaWO{sub 4}–YLiF{sub 4} were studied. • CaWO{sub 4} can be densified (TD 97%) at 750 °C/2 h by YLiF{sub 4} doping. • Excellent microwave dielectric properties could be obtained. - Abstract: Structures and sintering behaviors of (1 − x) CaWO{sub 4}–xYLiF{sub 4} (0.02 ≤ x ≤ 0.10) ceramic have been investigated by X-ray powder diffraction (XRD), dilatometry, scanning electron microscopy (SEM) in this work. The microwave dielectric properties were measured with a network analyzer at the frequency of about 8–15 GHz. Limited solid solution could be formed within the compositional range of x < 0.1. The sintering temperature of CaWO{sub 4} could successfully be reduced to ∼750 °C/2 h by doping with small amount of YLiF{sub 4}. An optimized microwave dielectric properties with ϵ{sub r} = 10.5, Q × f = 73 000 GHz and τ{sub f} = −37.7 ppm/°C could be obtained after sintered at the 750 °C for 2 h for x = 0.04 compositions. XRD and back scattering SEM analysis indicated that the (1 − x) CaWO{sub 4}–xYLiF{sub 4} (x = 0.04) ceramic could be chemically compatible with Ag after sintering at 750 °C/2 h.
Toward Scientific Numerical Modeling
NASA Technical Reports Server (NTRS)
Kleb, Bil
2007-01-01
Ultimately, scientific numerical models need quantified output uncertainties so that modeling can evolve to better match reality. Documenting model input uncertainties and verifying that numerical models are translated into code correctly, however, are necessary first steps toward that goal. Without known input parameter uncertainties, model sensitivities are all one can determine, and without code verification, output uncertainties are simply not reliable. To address these two shortcomings, two proposals are offered: (1) an unobtrusive mechanism to document input parameter uncertainties in situ and (2) an adaptation of the Scientific Method to numerical model development and deployment. Because these two steps require changes in the computational simulation community to bear fruit, they are presented in terms of the Beckhard-Harris-Gleicher change model.
Zakynthinaki, Maria S.
2015-01-01
The objective of the present study was to formulate a simple and at the same time effective mathematical model of heart rate kinetics in response to movement (exercise). Based on an existing model, a system of two coupled differential equations which give the rate of change of heart rate and the rate of change of exercise intensity is used. The modifications introduced to the existing model are justified and discussed in detail, while models of blood lactate accumulation in respect to time and exercise intensity are also presented. The main modification is that the proposed model has now only one parameter which reflects the overall cardiovascular condition of the individual. The time elapsed after the beginning of the exercise, the intensity of the exercise, as well as blood lactate are also taken into account. Application of the model provides information regarding the individual’s cardiovascular condition and is able to detect possible changes in it, across the data recording periods. To demonstrate examples of successful numerical fit of the model, constant intensity experimental heart rate data sets of two individuals have been selected and numerical optimization was implemented. In addition, numerical simulations provided predictions for various exercise intensities and various cardiovascular condition levels. The proposed model can serve as a powerful tool for a complete means of heart rate analysis, not only in exercise physiology (for efficiently designing training sessions for healthy subjects) but also in the areas of cardiovascular health and rehabilitation (including application in population groups for which direct heart rate recordings at intense exercises are not possible or not allowed, such as elderly or pregnant women). PMID:25876164
Modelling heart rate kinetics.
Zakynthinaki, Maria S
2015-01-01
The objective of the present study was to formulate a simple and at the same time effective mathematical model of heart rate kinetics in response to movement (exercise). Based on an existing model, a system of two coupled differential equations which give the rate of change of heart rate and the rate of change of exercise intensity is used. The modifications introduced to the existing model are justified and discussed in detail, while models of blood lactate accumulation in respect to time and exercise intensity are also presented. The main modification is that the proposed model has now only one parameter which reflects the overall cardiovascular condition of the individual. The time elapsed after the beginning of the exercise, the intensity of the exercise, as well as blood lactate are also taken into account. Application of the model provides information regarding the individual's cardiovascular condition and is able to detect possible changes in it, across the data recording periods. To demonstrate examples of successful numerical fit of the model, constant intensity experimental heart rate data sets of two individuals have been selected and numerical optimization was implemented. In addition, numerical simulations provided predictions for various exercise intensities and various cardiovascular condition levels. The proposed model can serve as a powerful tool for a complete means of heart rate analysis, not only in exercise physiology (for efficiently designing training sessions for healthy subjects) but also in the areas of cardiovascular health and rehabilitation (including application in population groups for which direct heart rate recordings at intense exercises are not possible or not allowed, such as elderly or pregnant women). PMID:25876164
NASA Astrophysics Data System (ADS)
Miah, M. J.; Khan, M. N. I.; Akther Hossain, A. K. M.
2016-01-01
Polycrystalline (x)Ba0.95Sr0.05TiO3-(1-x)BiFe0.90Dy0.10O3 [(x)BST-(1-x)BFDO] ceramics were synthesized by the standard solid-state reaction method. Samples prepared from these powders were sintered at various temperatures (900-1000 °C). The crystal structure, microstructure, magnetic, dielectric, complex impedance and magnetoelectric properties of the (x)BST-(1-x)BFDO ceramics were systematically investigated. The X-ray diffraction pattern indicated that (x)BST-(1-x)BFDO ceramics showed a structural transition from rhombohedral to cubic phase. The average grain size increased to a maximum 2.86 μm for x=0.20 and then decreased. M-H plot showed weak ferromagnetism for x=0.00 to 0.30. The magnetization value increased for increasing BST substitution up to x=0.20 due to the modification of crystal structure and then decreased for further increasing due to the nonmagnetic behavior of BST. A significant remnant magnetization (0.086 emu/g) and a coercive magnetic field (103.62 Oe) were also obtained for this solid solution. The complex initial permeability increased with the increase of both BST content (up to x=0.20) and sintering temperatures. The room-temperature dielectric constant increased whereas dielectric loss decreased with increasing BST content because of reducing oxygen vacancies. Impedance spectroscopy analysis confirmed the conducting grains and highly resistive grain boundaries affecting the conductivity but the grains had major contribution in the conduction mechanism. Magnetoelectric voltage coefficient (αME) increased with the increase of BST content because of strong interaction between magnetic and ferroelectric domains. The highest value of αME=1.67 mV cm-1 Oe-1 was observed for x=0.20 solid solution sintered at Ts=1000 °C because of uniform grains in size and shape at this composition.
Hassnain Jaffari, G.; Mehmood, Zahid; Iqbal, Asad M.; Hasanain, S. K.; Ismat Shah, S.
2014-08-28
The dielectric response ε(T) of Ba{sub x}Sr{sub 1-x}TiO{sub 3} (x ≤ 0.1) for compositions at and below the critical composition for the ferroelectric transition has been studied. With progressive Ba substitution, the growth of ferroelectric correlations and the weakening of the Antiferrodistortive (AFD) and the quantum paraelectric (QPE) effects have been studied by monitoring the changes in both the in and out of phase parts of the dielectric response. For the compositions close to pure SrTiO{sub 3} (x = 0 and x = 0.02), the temperature dependence exhibits a continuous rise in the in-phase part and no ferroelectric peak, consistent with the QPE behavior. With increasing Ba substitution, the low temperature behavior of the in phase part ε{sup ′} progressively changes from a continuous rise to exhibit a weak maximum and finally to a well developed cusp. For higher Ba concentrations, the low temperature peak (T ∼ 50K), which corresponds to ferroelectric correlations, becomes increasingly sharper until at the critical composition, x = 0.10, the system shows a single well defined ferroelectric peak. However, the out of phase response of the x = 0.1 composition exhibited a succession of three BaTiO{sub 3} type ferroelectric transitions. For x≤0.04, the out of phase part shows evidence of an ordering around T ∼ 100K, which is the expected AFD ordering temperature. The deviations of the ε{sup ′}(T) data from the Curie-Weiss law have been analyzed within the frame work of two different theoretical models. It was determined that the dielectric behavior for lower concentrations of Ba (up to x ≤ 0.08) was explainable in terms of a model of non-interacting regions which are themselves homogeneously polarized and undergo a second order phase transition. For the phase boundary composition, i.e., x = 0.1, on the other hand, the data are explainable in terms of the Sherrington and Kirkpatrick model which includes the effects
Approaches to Numerical Relativity
NASA Astrophysics Data System (ADS)
d'Inverno, Ray
2005-07-01
Introduction Ray d'Inverno; Preface C. J. S. Clarke; Part I. Theoretical Approaches: 1. Numerical relativity on a transputer array Ray d'Inverno; 2. Some aspects of the characteristic initial value problem in numerical relativity Nigel Bishop; 3. The characteristic initial value problem in general relativity J. M. Stewart; 4. Algebraic approachs to the characteristic initial value problem in general relativity Jõrg Frauendiener; 5. On hyperboidal hypersurfaces Helmut Friedrich; 6. The initial value problem on null cones J. A. Vickers; 7. Introduction to dual-null dynamics S. A. Hayward; 8. On colliding plane wave space-times J. B. Griffiths; 9. Boundary conditions for the momentum constraint Niall O Murchadha; 10. On the choice of matter model in general relativity A. D. Rendall; 11. A mathematical approach to numerical relativity J. W. Barrett; 12. Making sense of the effects of rotation in general relativity J. C. Miller; 13. Stability of charged boson stars and catastrophe theory Franz E. Schunck, Fjodor V. Kusmartsev and Eckehard W. Mielke; Part II. Practical Approaches: 14. Numerical asymptotics R. Gómez and J. Winicour; 15. Instabilities in rapidly rotating polytropes Scott C. Smith and Joan M. Centrella; 16. Gravitational radiation from coalescing binary neutron stars Ken-Ichi Oohara and Takashi Nakamura; 17. 'Critical' behaviour in massless scalar field collapse M. W. Choptuik; 18. Goudunov-type methods applied to general relativistic gravitational collapse José Ma. Ibánez, José Ma. Martí, Juan A. Miralles and J. V. Romero; 19. Astrophysical sources of gravitational waves and neutrinos Silvano Bonazzola, Eric Gourgoulhon, Pawel Haensel and Jean-Alain Marck; 20. Gravitational radiation from triaxial core collapse Jean-Alain Marck and Silvano Bonazzola; 21. A vacuum fully relativistic 3D numerical code C. Bona and J. Massó; 22. Solution of elliptic equations in numerical relativity using multiquadrics M. R. Dubal, S. R. Oliveira and R. A. Matzner; 23
Pneumotachometer counts respiration rate of human subject
NASA Technical Reports Server (NTRS)
Graham, O.
1964-01-01
To monitor breaths per minute, two rate-to-analog converters are alternately used to read and count the respiratory rate from an impedance pneumograph sequentially displayed numerically on electroluminescent matrices.
Numerical Simulations of Thermobaric Explosions
Kuhl, A L; Bell, J B; Beckner, V E; Khasainov, B
2007-05-04
A Model of the energy evolution in thermobaric explosions is presented. It is based on the two-phase formulation: conservation laws for the gas and particle phases along with inter-phase interaction terms. It incorporates a Combustion Model based on the mass conservation laws for fuel, air and products; source/sink terms are treated in the fast-chemistry limit appropriate for such gas dynamic fields. The Model takes into account both the afterburning of the detonation products of the booster with air, and the combustion of the fuel (Al or TNT detonation products) with air. Numerical simulations were performed for 1.5-g thermobaric explosions in five different chambers (volumes ranging from 6.6 to 40 liters and length-to-diameter ratios from 1 to 12.5). Computed pressure waveforms were very similar to measured waveforms in all cases - thereby proving that the Model correctly predicts the energy evolution in such explosions. The computed global fuel consumption {mu}(t) behaved as an exponential life function. Its derivative {dot {mu}}(t) represents the global rate of fuel consumption. It depends on the rate of turbulent mixing which controls the rate of energy release in thermobaric explosions.
Ketkar, S.P.
1999-07-01
This new volume is written for both practicing engineers who want to refresh their knowledge in the fundamentals of numerical thermal analysis as well as for students of numerical heat transfer. it is a handy desktop reference that covers all the basics of finite difference, finite element, and control volume methods. In this volume, the author presents a unique hybrid method that combines the best features of finite element modeling and the computational efficiency of finite difference network solution techniques. It is a robust technique that is used in commercially available software. The contents include: heat conduction: fundamentals and governing equations; finite difference method; control volume method; finite element method; the hybrid method; and software selection.
Hybrid undulator numerical optimization
Hairetdinov, A.H.; Zukov, A.A.
1995-12-31
3D properties of the hybrid undulator scheme arc studied numerically using PANDIRA code. It is shown that there exist two well defined sets of undulator parameters which provide either maximum on-axis field amplitude or minimal higher harmonics amplitude of the basic undulator field. Thus the alternative between higher field amplitude or pure sinusoidal field exists. The behavior of the undulator field amplitude and harmonics structure for a large set of (undulator gap)/(undulator wavelength) values is demonstrated.
Numerical computation of Pop plot
Menikoff, Ralph
2015-03-23
The Pop plot — distance-of-run to detonation versus initial shock pressure — is a key characterization of shock initiation in a heterogeneous explosive. Reactive burn models for high explosives (HE) must reproduce the experimental Pop plot to have any chance of accurately predicting shock initiation phenomena. This report describes a methodology for automating the computation of a Pop plot for a specific explosive with a given HE model. Illustrative examples of the computation are shown for PBX 9502 with three burn models (SURF, WSD and Forest Fire) utilizing the xRage code, which is the Eulerian ASC hydrocode at LANL. Comparison of the numerical and experimental Pop plot can be the basis for a validation test or as an aid in calibrating the burn rate of an HE model. Issues with calibration are discussed.
NASA Astrophysics Data System (ADS)
Triwibowo, J.; Priyono, S.; Purawiardi, R. I.; Ratri, C. R.; Suwandi, E.
2016-02-01
Mn-doped LiFePO4 was synthesized through solid state process. Starting materials as LiOH.2H2O, Fe2O3, MnO2, H3PO4 and citric acid were technical grade materials. Synthesis process was conducted in two step heating process. The first heating process was purposed to remove organic materials at temperature of 320 °C for 10 hours in inert atmosphere. Subsequently, the second heating process was conducted at 800 °C for 8 hours also in inert atmosphere. Obtained phase was further observed by means of XRD. Morphology of the obtained powder was analyzed by SEM. The electrochemical performance was observed by cyclic voltammetry with the potential range 2 - 4.2 V under the scan rate mV/s. The rate capability of the obtained material was determined by charge-discharge test under various C-rates (0.5-10C) for potential range of 2 - 4.2 V.
Numerical Aerodynamic Simulation (NAS)
NASA Technical Reports Server (NTRS)
Peterson, V. L.; Ballhaus, W. F., Jr.; Bailey, F. R.
1983-01-01
The history of the Numerical Aerodynamic Simulation Program, which is designed to provide a leading-edge capability to computational aerodynamicists, is traced back to its origin in 1975. Factors motivating its development and examples of solutions to successively refined forms of the governing equations are presented. The NAS Processing System Network and each of its eight subsystems are described in terms of function and initial performance goals. A proposed usage allocation policy is discussed and some initial problems being readied for solution on the NAS system are identified.
Numerical Propulsion System Simulation
NASA Technical Reports Server (NTRS)
Naiman, Cynthia
2006-01-01
The NASA Glenn Research Center, in partnership with the aerospace industry, other government agencies, and academia, is leading the effort to develop an advanced multidisciplinary analysis environment for aerospace propulsion systems called the Numerical Propulsion System Simulation (NPSS). NPSS is a framework for performing analysis of complex systems. The initial development of NPSS focused on the analysis and design of airbreathing aircraft engines, but the resulting NPSS framework may be applied to any system, for example: aerospace, rockets, hypersonics, power and propulsion, fuel cells, ground based power, and even human system modeling. NPSS provides increased flexibility for the user, which reduces the total development time and cost. It is currently being extended to support the NASA Aeronautics Research Mission Directorate Fundamental Aeronautics Program and the Advanced Virtual Engine Test Cell (AVETeC). NPSS focuses on the integration of multiple disciplines such as aerodynamics, structure, and heat transfer with numerical zooming on component codes. Zooming is the coupling of analyses at various levels of detail. NPSS development includes capabilities to facilitate collaborative engineering. The NPSS will provide improved tools to develop custom components and to use capability for zooming to higher fidelity codes, coupling to multidiscipline codes, transmitting secure data, and distributing simulations across different platforms. These powerful capabilities extend NPSS from a zero-dimensional simulation tool to a multi-fidelity, multidiscipline system-level simulation tool for the full development life cycle.
Confidence in Numerical Simulations
Hemez, Francois M.
2015-02-23
This PowerPoint presentation offers a high-level discussion of uncertainty, confidence and credibility in scientific Modeling and Simulation (M&S). It begins by briefly evoking M&S trends in computational physics and engineering. The first thrust of the discussion is to emphasize that the role of M&S in decision-making is either to support reasoning by similarity or to “forecast,” that is, make predictions about the future or extrapolate to settings or environments that cannot be tested experimentally. The second thrust is to explain that M&S-aided decision-making is an exercise in uncertainty management. The three broad classes of uncertainty in computational physics and engineering are variability and randomness, numerical uncertainty and model-form uncertainty. The last part of the discussion addresses how scientists “think.” This thought process parallels the scientific method where by a hypothesis is formulated, often accompanied by simplifying assumptions, then, physical experiments and numerical simulations are performed to confirm or reject the hypothesis. “Confidence” derives, not just from the levels of training and experience of analysts, but also from the rigor with which these assessments are performed, documented and peer-reviewed.
Numerical study on microbubble-enhanced heating for various parameters in EUS-FUS
NASA Astrophysics Data System (ADS)
Okita, Kohei; Maezawa, Miyuki; Takagi, Shu; Matsumoto, Yoichiro
2012-11-01
Endoscopic ultrasonography guided focused ultrasound surgery (EUS-FUS) have been developed as a less-invasive treatment for pancreatic cancer. In the present study, microbubble-enhanced heating for various parameters in EUS-FUS is investigated numerically. Mass and momentum equations for bubbly mixture are solved to reproduce the propagation of ultrasound of 4.8MHz through the gel containing microbubbles as Sonazoid®. The dynamics of bubble is governed by the equation which considers the elasticity of both shell and surrounding media. Additionally, the heat equation with the time averaged heat source is solved to obtain a temperature distribution. The basic equations are discretized by the 6th-order finite difference method and developed based on FDTD method. The mixture and bubbles are coupled by Euler-Lagrange method. As the results, the temperature around the target increased due to the microbubble oscillation with increasing the initial void fraction fG0 from 10-5 to 10-4%. However, at fG0=10-3%, ultrasounds were too attenuated to heat the target. The heating region moved from the target to the transducer side. By comparing the results with and without shell, the shell of bubble induced the heating around focus. This is because the decrease of the attenuation due to the elasticity of the shell and the increase of the viscous dissipation rate due to the viscosity of the shell.
Stoenescu, M.L.; Smith, T.M.
1980-02-01
The collision integral terms in Boltzmann equation are reformulated numerically leading to the substitution of the multiple integrals with a multiplicative matrix of the two colliding species velocity distribution functions which varies with the differential collision cross section. A matrix of lower rank may be constructed when one of the distribution functions is specified, in which case the matrix elements represent kinetic transition probabilities in the velocity space and the multiplication of the time rate collision matrix with the unknown velocity distribution function expresses the time rate of change of the distribution. The collision matrix may be used to describe the time evolution of systems in nonequilibrium conditions, to evaluate the rate of momentum and energy transfer between given species, or to generate validity criteria for linearized kinetic equations.
Numerical approach for unstructured quantum key distribution.
Coles, Patrick J; Metodiev, Eric M; Lütkenhaus, Norbert
2016-01-01
Quantum key distribution (QKD) allows for communication with security guaranteed by quantum theory. The main theoretical problem in QKD is to calculate the secret key rate for a given protocol. Analytical formulas are known for protocols with symmetries, since symmetry simplifies the analysis. However, experimental imperfections break symmetries, hence the effect of imperfections on key rates is difficult to estimate. Furthermore, it is an interesting question whether (intentionally) asymmetric protocols could outperform symmetric ones. Here we develop a robust numerical approach for calculating the key rate for arbitrary discrete-variable QKD protocols. Ultimately this will allow researchers to study 'unstructured' protocols, that is, those that lack symmetry. Our approach relies on transforming the key rate calculation to the dual optimization problem, which markedly reduces the number of parameters and hence the calculation time. We illustrate our method by investigating some unstructured protocols for which the key rate was previously unknown. PMID:27198739
Numerical approach for unstructured quantum key distribution
NASA Astrophysics Data System (ADS)
Coles, Patrick J.; Metodiev, Eric M.; Lütkenhaus, Norbert
2016-05-01
Quantum key distribution (QKD) allows for communication with security guaranteed by quantum theory. The main theoretical problem in QKD is to calculate the secret key rate for a given protocol. Analytical formulas are known for protocols with symmetries, since symmetry simplifies the analysis. However, experimental imperfections break symmetries, hence the effect of imperfections on key rates is difficult to estimate. Furthermore, it is an interesting question whether (intentionally) asymmetric protocols could outperform symmetric ones. Here we develop a robust numerical approach for calculating the key rate for arbitrary discrete-variable QKD protocols. Ultimately this will allow researchers to study `unstructured' protocols, that is, those that lack symmetry. Our approach relies on transforming the key rate calculation to the dual optimization problem, which markedly reduces the number of parameters and hence the calculation time. We illustrate our method by investigating some unstructured protocols for which the key rate was previously unknown.
Numerical approach for unstructured quantum key distribution
Coles, Patrick J.; Metodiev, Eric M.; Lütkenhaus, Norbert
2016-01-01
Quantum key distribution (QKD) allows for communication with security guaranteed by quantum theory. The main theoretical problem in QKD is to calculate the secret key rate for a given protocol. Analytical formulas are known for protocols with symmetries, since symmetry simplifies the analysis. However, experimental imperfections break symmetries, hence the effect of imperfections on key rates is difficult to estimate. Furthermore, it is an interesting question whether (intentionally) asymmetric protocols could outperform symmetric ones. Here we develop a robust numerical approach for calculating the key rate for arbitrary discrete-variable QKD protocols. Ultimately this will allow researchers to study ‘unstructured' protocols, that is, those that lack symmetry. Our approach relies on transforming the key rate calculation to the dual optimization problem, which markedly reduces the number of parameters and hence the calculation time. We illustrate our method by investigating some unstructured protocols for which the key rate was previously unknown. PMID:27198739
Rythmos Numerical Integration Package
Coffey, Todd S.; Bartlett, Roscoe A.
2006-09-01
Rythmos numerically integrates transient differential equations. The differential equations can be explicit or implicit ordinary differential equations ofr formulated as fully implicit differential-algebraic equations. Methods include backward Euler, forward Euler, explicit Runge-Kutta, and implicit BDF at this time. Native support for operator split methods and strict modularity are strong design goals. Forward sensitivity computations will be included in the first release with adjoint sensitivities coming in the near future. Rythmos heavily relies on Thyra for linear algebra and nonlinear solver interfaces to AztecOO, Amesos, IFPack, and NOX in Tilinos. Rythmos is specially suited for stiff differential equations and thos applictions where operator split methods have a big advantage, e.g. Computational fluid dynamics, convection-diffusion equations, etc.
Rythmos Numerical Integration Package
2006-09-01
Rythmos numerically integrates transient differential equations. The differential equations can be explicit or implicit ordinary differential equations ofr formulated as fully implicit differential-algebraic equations. Methods include backward Euler, forward Euler, explicit Runge-Kutta, and implicit BDF at this time. Native support for operator split methods and strict modularity are strong design goals. Forward sensitivity computations will be included in the first release with adjoint sensitivities coming in the near future. Rythmos heavily relies on Thyra formore » linear algebra and nonlinear solver interfaces to AztecOO, Amesos, IFPack, and NOX in Tilinos. Rythmos is specially suited for stiff differential equations and thos applictions where operator split methods have a big advantage, e.g. Computational fluid dynamics, convection-diffusion equations, etc.« less
Numerical Modeling of Ablation Heat Transfer
NASA Technical Reports Server (NTRS)
Ewing, Mark E.; Laker, Travis S.; Walker, David T.
2013-01-01
A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.
Using PASCAL for numerical analysis
NASA Technical Reports Server (NTRS)
Volper, D.; Miller, T. C.
1978-01-01
The data structures and control structures of PASCAL enhance the coding ability of the programmer. Proposed extensions to the language further increase its usefulness in writing numeric programs and support packages for numeric programs.
Developmental Change in Numerical Estimation
ERIC Educational Resources Information Center
Slusser, Emily B.; Santiago, Rachel T.; Barth, Hilary C.
2013-01-01
Mental representations of numerical magnitude are commonly thought to undergo discontinuous change over development in the form of a "representational shift." This idea stems from an apparent categorical shift from logarithmic to linear patterns of numerical estimation on tasks that involve translating between numerical magnitudes and spatial…
MFIX documentation numerical technique
Syamlal, M.
1998-01-01
MFIX (Multiphase Flow with Interphase eXchanges) is a general-purpose hydrodynamic model for describing chemical reactions and heat transfer in dense or dilute fluid-solids flows, which typically occur in energy conversion and chemical processing reactors. The calculations give time-dependent information on pressure, temperature, composition, and velocity distributions in the reactors. The theoretical basis of the calculations is described in the MFIX Theory Guide. Installation of the code, setting up of a run, and post-processing of results are described in MFIX User`s manual. Work was started in April 1996 to increase the execution speed and accuracy of the code, which has resulted in MFIX 2.0. To improve the speed of the code the old algorithm was replaced by a more implicit algorithm. In different test cases conducted the new version runs 3 to 30 times faster than the old version. To increase the accuracy of the computations, second order accurate discretization schemes were included in MFIX 2.0. Bubbling fluidized bed simulations conducted with a second order scheme show that the predicted bubble shape is rounded, unlike the (unphysical) pointed shape predicted by the first order upwind scheme. This report describes the numerical technique used in MFIX 2.0.
Personalized numerical observer
NASA Astrophysics Data System (ADS)
Brankov, Jovan G.; Pretorius, P. Hendrik
2010-02-01
It is widely accepted that medical image quality should be assessed using task-based criteria, such as humanobserver (HO) performance in a lesion-detection (scoring) task. HO studies are time consuming and cost prohibitive to be used for image quality assessment during development of either reconstruction methods or imaging systems. Therefore, a numerical observer (NO), a HO surrogate, is highly desirable. In the past, we have proposed and successfully tested a NO based on a supervised-learning approach (namely a support vector machine) for cardiac gated SPECT image quality assessment. In the supervised-learning approach, the goal is to identify the relationship between measured image features and HO myocardium defect likelihood scores. Thus far we have treated multiple HO readers by simply averaging or pooling their respective scores. Due to observer variability, this may be suboptimal and less accurate. Therefore, in this work, we are setting our goal to predict individual observer scores independently in the hope to better capture some relevant lesion-detection mechanism of the human observers. This is even more important as there are many ways to get equivalent observer performance (measured by area under receiver operating curve), and simply predicting some joint (average or pooled) score alone is not likely to succeed.
Numerical Relativity and Astrophysics
NASA Astrophysics Data System (ADS)
Lehner, Luis; Pretorius, Frans
2014-08-01
Throughout the Universe many powerful events are driven by strong gravitational effects that require general relativity to fully describe them. These include compact binary mergers, black hole accretion, and stellar collapse, where velocities can approach the speed of light and extreme gravitational fields (ΦNewt/c2≃1) mediate the interactions. Many of these processes trigger emission across a broad range of the electromagnetic spectrum. Compact binaries further source strong gravitational wave emission that could directly be detected in the near future. This feat will open up a gravitational wave window into our Universe and revolutionize our understanding of it. Describing these phenomena requires general relativity, and—where dynamical effects strongly modify gravitational fields—the full Einstein equations coupled to matter sources. Numerical relativity is a field within general relativity concerned with studying such scenarios that cannot be accurately modeled via perturbative or analytical calculations. In this review, we examine results obtained within this discipline, with a focus on its impact in astrophysics.
Influence of Ar addition on ozone generation in a non-thermal plasma—a numerical investigation
NASA Astrophysics Data System (ADS)
Chen, Hsin Liang; Lee, How Ming; Chen, Shiaw Huei; Wei, Ta Chin; Been Chang, Moo
2010-10-01
A numerical model based on a dielectric barrier discharge is developed in this study to investigate the influence of Ar addition on ozone generation. The simulation results show good agreement with the experimental data, confirming the validity of the numerical model. The mechanisms regarding how the Ar addition affects ozone generation are investigated with the assistance of a numerical simulation by probing into the following two questions, (1) why the ozone concentration just slightly decreases in the low specific input energy (SIE, the ratio of discharge power to gas flow rate) region even if the inlet O2 concentration is substantially decreased and (2) why the variation of the increased rate of ozone concentration with SIE (i.e. the variation in the slope of ozone concentration versus SIE) is more significant for an O2/Ar mixture plasma. As SIE is relatively low, ozone decomposition through electron-impact and radical attack reactions is less significant because of low ozone concentration and gas temperature. Therefore, the ozone concentration depends mainly on the amount of oxygen atoms generated. The simulation results indicate that the amount of oxygen atoms generated per electronvolt for Ar concentrations of 0%, 10%, 30%, 50% and 80% are 0.178, 0.174, 0.169, 0.165 and 0.166, respectively, explaining why the ozone concentration does not decrease linearly with the inlet O2 concentration in the low SIE region. On the other hand, the simulation results show that increasing Ar concentration would lead to a lower reduced field and a higher gas temperature. The former would lead to an increase in the rate constant of e + O3 → e + O + O2 while the latter would result in a decrease in the rate constant of O + O2 + M → O3 + M and an increase in that of O3 + O → 2O2. The changes in the rate constants of these reactions would have a negative effect on ozone generation, which is the rationale for the second question.
Numerical methods used in fusion science numerical modeling
NASA Astrophysics Data System (ADS)
Yagi, M.
2015-04-01
The dynamics of burning plasma is very complicated physics, which is dominated by multi-scale and multi-physics phenomena. To understand such phenomena, numerical simulations are indispensable. Fundamentals of numerical methods used in fusion science numerical modeling are briefly discussed in this paper. In addition, the parallelization technique such as open multi processing (OpenMP) and message passing interface (MPI) parallel programing are introduced and the loop-level parallelization is shown as an example.
Rates inferred from the space debris catalog
Canavan, G.H.
1996-08-01
Collision and fragmentation rates are inferred from the AFSPC space debris catalog and compare with estimates from other treatments. The collision rate is evaluated without approximation. The fragmentation rate requires additional empirical assessments. The number of fragments per collision is low compared to analytic and numerical treatments, is peaked low, and falls rapidly with altitude.
Representation of Numerical and Non-Numerical Order in Children
ERIC Educational Resources Information Center
Berteletti, Ilaria; Lucangeli, Daniela; Zorzi, Marco
2012-01-01
The representation of numerical and non-numerical ordered sequences was investigated in children from preschool to grade 3. The child's conception of how sequence items map onto a spatial scale was tested using the Number-to-Position task (Siegler & Opfer, 2003) and new variants of the task designed to probe the representation of the alphabet…
Direct numerical simulation of hot jets
NASA Technical Reports Server (NTRS)
Jacob, Marc C.
1993-01-01
The ultimate motivation of this work is to investigate the stability of two dimensional heated jets and its implications for aerodynamic sound generation from data obtained with direct numerical simulations (DNS). As pointed out in our last report, these flows undergo two types of instabilities, convective or absolute, depending on their temperature. We also described the limits of earlier experimental and theoretical studies and explained why a numerical investigation could give us new insight into the physics of these instabilities. The aeroacoustical interest of these flows was also underlined. In order to reach this goal, we first need to succeed in the DNS of heated jets. Our past efforts have been focused on this issue which encountered several difficulties. Our numerical difficulties are directly related to the physical problem we want to investigate since these absolutely or almost absolutely unstable flows are by definition very sensitive to the smallest disturbances and are very likely to reach nonlinear saturation through a numerical feedback mechanism. As a result, it is very difficult to compute a steady laminar solution using a spatial DNS. A steady state was reached only for strongly co-flowed jets, but these flows are almost equivalent to two independent mixing layers. Thus they are far from absolute instability and have much lower growth rates.
Highly Parallel, High-Precision Numerical Integration
Bailey, David H.; Borwein, Jonathan M.
2005-04-22
This paper describes a scheme for rapidly computing numerical values of definite integrals to very high accuracy, ranging from ordinary machine precision to hundreds or thousands of digits, even for functions with singularities or infinite derivatives at endpoints. Such a scheme is of interest not only in computational physics and computational chemistry, but also in experimental mathematics, where high-precision numerical values of definite integrals can be used to numerically discover new identities. This paper discusses techniques for a parallel implementation of this scheme, then presents performance results for 1-D and 2-D test suites. Results are also given for a certain problem from mathematical physics, which features a difficult singularity, confirming a conjecture to 20,000 digit accuracy. The performance rate for this latter calculation on 1024 CPUs is 690 Gflop/s. We believe that this and one other 20,000-digit integral evaluation that we report are the highest-precision non-trivial numerical integrations performed to date.
Numerical Asymptotic Solutions Of Differential Equations
NASA Technical Reports Server (NTRS)
Thurston, Gaylen A.
1992-01-01
Numerical algorithms derived and compared with classical analytical methods. In method, expansions replaced with integrals evaluated numerically. Resulting numerical solutions retain linear independence, main advantage of asymptotic solutions.
16 CFR 0.10 - Office of the Executive Director.
Code of Federal Regulations, 2010 CFR
2010-01-01
..., financial management, information technology, and human resources. ... on strategic planning and assessing the management and resource implications of any proposed action... Chairman, is the chief operating official who develops and implements management and...
16 CFR 0.10 - Office of the Executive Director.
Code of Federal Regulations, 2014 CFR
2014-01-01
..., financial management, information technology, and human resources. ... on strategic planning and assessing the management and resource implications of any proposed action... Chairman, is the chief operating official who develops and implements management and...
16 CFR 0.10 - Office of the Executive Director.
Code of Federal Regulations, 2013 CFR
2013-01-01
..., financial management, information technology, and human resources. ... on strategic planning and assessing the management and resource implications of any proposed action... Chairman, is the chief operating official who develops and implements management and...
Ferrofluids: Modeling, numerical analysis, and scientific computation
NASA Astrophysics Data System (ADS)
Tomas, Ignacio
This dissertation presents some developments in the Numerical Analysis of Partial Differential Equations (PDEs) describing the behavior of ferrofluids. The most widely accepted PDE model for ferrofluids is the Micropolar model proposed by R.E. Rosensweig. The Micropolar Navier-Stokes Equations (MNSE) is a subsystem of PDEs within the Rosensweig model. Being a simplified version of the much bigger system of PDEs proposed by Rosensweig, the MNSE are a natural starting point of this thesis. The MNSE couple linear velocity u, angular velocity w, and pressure p. We propose and analyze a first-order semi-implicit fully-discrete scheme for the MNSE, which decouples the computation of the linear and angular velocities, is unconditionally stable and delivers optimal convergence rates under assumptions analogous to those used for the Navier-Stokes equations. Moving onto the much more complex Rosensweig's model, we provide a definition (approximation) for the effective magnetizing field h, and explain the assumptions behind this definition. Unlike previous definitions available in the literature, this new definition is able to accommodate the effect of external magnetic fields. Using this definition we setup the system of PDEs coupling linear velocity u, pressure p, angular velocity w, magnetization m, and magnetic potential ϕ We show that this system is energy-stable and devise a numerical scheme that mimics the same stability property. We prove that solutions of the numerical scheme always exist and, under certain simplifying assumptions, that the discrete solutions converge. A notable outcome of the analysis of the numerical scheme for the Rosensweig's model is the choice of finite element spaces that allow the construction of an energy-stable scheme. Finally, with the lessons learned from Rosensweig's model, we develop a diffuse-interface model describing the behavior of two-phase ferrofluid flows and present an energy-stable numerical scheme for this model. For a
Numerical data frame readout system used in testing telemetry systems
NASA Technical Reports Server (NTRS)
Cote, C. E.; Cressey, J. R.
1967-01-01
Digital telemetry systems are treated by a display system that offers direct readout as high data rates. The rates appear in numerical format and are adaptable to photographic recording techniques. The system can show bit dropouts at a memory output or locate a malfunction in a system.
Numerical calculation for cavitation flow of inducer
NASA Astrophysics Data System (ADS)
Ning, C.; Wang, Y.; Zhu, Z. T.; Xie, S. F.; Zhao, L. F.; Liu, Z. C.
2015-01-01
Inducer has significant effect on improving the cavitation characteristic of centrifugal pump. Several inducers were designed and modeled by Pro/E software. The mesh of flow field was done by ICEM and then was imported to ANSYS CFX to analyze the inducer's cavitation characteristic. Effects of the blade number on the performance of an inducer are investigated in the present paper. The inducers were designed on the basis of identical design flow rate and identical pressure elevation at nominal flow rate. The study focuses on the steady behavior of the inducers in cavitating conditions. Evolutions of performance, torque, mass flow rate, and amplitude of radial forces on the shaft according to the inlet pressure are considered. Furthermore, cavitation instabilities are analyzed in the study. The purpose of the present study is to investigate the pressure distribution and vapour volume fraction distribution through numerical simulations using the Navier-stokes solver with computational fluid dynamics (CFD) code.
Numerical simulation of dusty plasmas
Winske, D.
1995-09-01
The numerical simulation of physical processes in dusty plasmas is reviewed, with emphasis on recent results and unresolved issues. Three areas of research are discussed: grain charging, weak dust-plasma interactions, and strong dust-plasma interactions. For each area, we review the basic concepts that are tested by simulations, present some appropriate examples, and examine numerical issues associated with extending present work.
Numerical modeling of Hall thruster
Chable, S.; Rogier, F.
2005-05-16
A stationary plasma thruster is numerically studied using different levels. An one dimensional modeling is first analyzed and compared with experimental results. A simplified model of oscillations thruster is proposed and used to control the amplitude of oscillations. A two dimensional numerical method is discussed and applied to the computation of the flow in the exhaust.
Aerodynamic design using numerical optimization
NASA Technical Reports Server (NTRS)
Murman, E. M.; Chapman, G. T.
1983-01-01
The procedure of using numerical optimization methods coupled with computational fluid dynamic (CFD) codes for the development of an aerodynamic design is examined. Several approaches that replace wind tunnel tests, develop pressure distributions and derive designs, or fulfill preset design criteria are presented. The method of Aerodynamic Design by Numerical Optimization (ADNO) is described and illustrated with examples.
Computerized Numerical Control Curriculum Guide.
ERIC Educational Resources Information Center
Reneau, Fred; And Others
This guide is intended for use in a course in programming and operating a computerized numerical control system. Addressed in the course are various aspects of programming and planning, setting up, and operating machines with computerized numerical control, including selecting manual or computer-assigned programs and matching them with…
A Vocabulary for Numerical Control.
ERIC Educational Resources Information Center
Campbell, Clifton Paul
This glossary presents a standardized nomenclature for numerical control. It defines and describes some 286 technical words, terms, abbreviations, and acronyms which form a specialized vocabulary. The aim of this glossary is to provide a means for arriving at some common understanding of terminology for numerical control technology. Numerous…
Note on symmetric BCJ numerator
NASA Astrophysics Data System (ADS)
Fu, Chih-Hao; Du, Yi-Jian; Feng, Bo
2014-08-01
We present an algorithm that leads to BCJ numerators satisfying manifestly the three properties proposed by Broedel and Carrasco in [42]. We explicitly calculate the numerators at 4, 5 and 6-points and show that the relabeling property is generically satisfied.
Numerically controlled oscillator for the Fermilab booster
Crisp, J.L.; Ducar, R.J.
1989-04-01
In order to improve the stability of the Fermilab Booster low level rf system, a numerically controlled oscillator system is being constructed. Although the system has not been implemented to date, the design is outlined in this paper. The heart of the new system consists of a numerically synthesized frequency generator manufactured by the Sciteq Company. The 3 Ghz/sec rate and 30 to 53 MHz range of the Booster frequency program required the design of a CAMAC based, fast-cycling (1 MHz), 65K X 32 bit, digital function generator. A 1 MHz digital adder and 12 bit analog to digital converter will be used to correct small program errors by phase locking the oscillator to the beam. 6 refs., 1 fig.
A numerical method for predicting hypersonic flowfields
NASA Technical Reports Server (NTRS)
Maccormack, Robert W.; Candler, Graham V.
1989-01-01
The flow about a body traveling at hypersonic speed is energetic enough to cause the atmospheric gases to chemically react and reach states in thermal nonequilibrium. The prediction of hypersonic flowfields requires a numerical method capable of solving the conservation equations of fluid flow, the chemical rate equations for specie formation and dissociation, and the transfer of energy relations between translational and vibrational temperature states. Because the number of equations to be solved is large, the numerical method should also be as efficient as possible. The proposed paper presents a fully implicit method that fully couples the solution of the fluid flow equations with the gas physics and chemistry relations. The method flux splits the inviscid flow terms, central differences of the viscous terms, preserves element conservation in the strong chemistry source terms, and solves the resulting block matrix equation by Gauss Seidel line relaxation.
The distant type Ia supernova rate
Pain, R.; Fabbro, S.; Sullivan, M.; Ellis, R.S.; Aldering, G.; Astier, P.; Deustua, S.E.; Fruchter, A.S.; Goldhaber, G.; Goobar, A.; Groom, D.E.; Hardin, D.; Hook, I.M.; Howell, D.A.; Irwin, M.J.; Kim, A.G.; Kim, M.Y.; Knop, R.A.; Lee, J.C.; Perlmutter, S.; Ruiz-Lapuente, P.; Schahmaneche, K.; Schaefer, B.; Walton, N.A.
2002-05-20
We present a measurement of the rate of distant Type Ia supernovae derived using 4 large subsets of data from the Supernova Cosmology Project. Within this fiducial sample,which surveyed about 12 square degrees, thirty-eight supernovae were detected at redshifts 0.25--0.85. In a spatially flat cosmological model consistent with the results obtained by the Supernova Cosmology Project, we derive a rest-frame Type Ia supernova rate at a mean red shift z {approx_equal} 0.55 of 1.53 {sub -0.25}{sub -0.31}{sup 0.28}{sup 0.32} x 10{sup -4} h{sup 3} Mpc{sup -3} yr{sup -1} or 0.58{sub -0.09}{sub -0.09}{sup +0.10}{sup +0.10} h{sup 2} SNu(1 SNu = 1 supernova per century per 10{sup 10} L{sub B}sun), where the first uncertainty is statistical and the second includes systematic effects. The dependence of the rate on the assumed cosmological parameters is studied and the redshift dependence of the rate per unit comoving volume is contrasted with local estimates in the context of possible cosmic star formation histories and progenitor models.
The Distant Type Ia Supernova Rate
DOE R&D Accomplishments Database
Pain, R.; Fabbro, S.; Sullivan, M.; Ellis, R. S.; Aldering, G.; Astier, P.; Deustua, S. E.; Fruchter, A. S.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hardin, D.; Hook, I. M.; Howell, D. A.; Irwin, M. J.; Kim, A. G.; Kim, M. Y.; Knop, R. A.; Lee, J. C.; Perlmutter, S.; Ruiz-Lapuente, P.; Schahmaneche, K.; Schaefer, B.; Walton, N. A.
2002-05-28
We present a measurement of the rate of distant Type Ia supernovae derived using 4 large subsets of data from the Supernova Cosmology Project. Within this fiducial sample, which surveyed about 12 square degrees, thirty-eight supernovae were detected at redshifts 0.25--0.85. In a spatially flat cosmological model consistent with the results obtained by the Supernova Cosmology Project, we derive a rest-frame Type Ia supernova rate at a mean red shift z {approx_equal} 0.55 of 1.53 {sub -0.25}{sub -0.31}{sup 0.28}{sup 0.32} x 10{sup -4} h{sup 3} Mpc{sup -3} yr{sup -1} or 0.58{sub -0.09}{sub -0.09}{sup +0.10}{sup +0.10} h{sup 2} SNu(1 SNu = 1 supernova per century per 10{sup 10} L{sub B}sun), where the first uncertainty is statistical and the second includes systematic effects. The dependence of the rate on the assumed cosmological parameters is studied and the redshift dependence of the rate per unit comoving volume is contrasted with local estimates in the context of possible cosmic star formation histories and progenitor models.
NASA Technical Reports Server (NTRS)
Yee, H. C.; Rai, Man Mohan (Technical Monitor)
1994-01-01
This lecture attempts to illustrate the basic ideas of how the recent advances in nonlinear dynamical systems theory (dynamics) can provide new insights into the understanding of numerical algorithms used in solving nonlinear differential equations (DEs). Examples will be given of the use of dynamics to explain unusual phenomena that occur in numerics. The inadequacy of the use of linearized analysis for the understanding of long time behavior of nonlinear problems will be illustrated, and the role of dynamics in studying the nonlinear stability, accuracy, convergence property and efficiency of using time- dependent approaches to obtaining steady-state numerical solutions in computational fluid dynamics (CFD) will briefly be explained.
New fine structure cooling rate
NASA Technical Reports Server (NTRS)
Hoegy, W. R.
1976-01-01
One of the dominant electron cooling processes in the ionosphere is caused by electron impact induced fine structure transitions among the ground state levels of atomic oxygen. This fine structure cooling rate is based on theoretical cross sections. Recent advances in the numerical cross section determinations to include polarization effects and more accurate representations of the atomic target result in new lower values. These cross sections are employed in this paper to derive a new fine structure cooling rate which is between 40% and 60% of the currently used rate. A new generalized formula is presented for the cooling rate (from which the fine structure cooling rate is derived), valid for arbitrary mass and temperature difference of the colliding particles and arbitrary inelastic energy difference.
Numerical Simulation of Nix's Rotation
This is a numerical simulation of the orientation of Nix as seen from the center of the Pluto system. It has been sped up so that one orbit of Nix around Pluto takes 2 seconds instead of 25 days. L...
Numerical Optimization Using Computer Experiments
NASA Technical Reports Server (NTRS)
Trosset, Michael W.; Torczon, Virginia
1997-01-01
Engineering design optimization often gives rise to problems in which expensive objective functions are minimized by derivative-free methods. We propose a method for solving such problems that synthesizes ideas from the numerical optimization and computer experiment literatures. Our approach relies on kriging known function values to construct a sequence of surrogate models of the objective function that are used to guide a grid search for a minimizer. Results from numerical experiments on a standard test problem are presented.
Bidirectional Modulation of Numerical Magnitude.
Arshad, Qadeer; Nigmatullina, Yuliya; Nigmatullin, Ramil; Asavarut, Paladd; Goga, Usman; Khan, Sarah; Sander, Kaija; Siddiqui, Shuaib; Roberts, R E; Cohen Kadosh, Roi; Bronstein, Adolfo M; Malhotra, Paresh A
2016-05-01
Numerical cognition is critical for modern life; however, the precise neural mechanisms underpinning numerical magnitude allocation in humans remain obscure. Based upon previous reports demonstrating the close behavioral and neuro-anatomical relationship between number allocation and spatial attention, we hypothesized that these systems would be subject to similar control mechanisms, namely dynamic interhemispheric competition. We employed a physiological paradigm, combining visual and vestibular stimulation, to induce interhemispheric conflict and subsequent unihemispheric inhibition, as confirmed by transcranial direct current stimulation (tDCS). This allowed us to demonstrate the first systematic bidirectional modulation of numerical magnitude toward either higher or lower numbers, independently of either eye movements or spatial attention mediated biases. We incorporated both our findings and those from the most widely accepted theoretical framework for numerical cognition to present a novel unifying computational model that describes how numerical magnitude allocation is subject to dynamic interhemispheric competition. That is, numerical allocation is continually updated in a contextual manner based upon relative magnitude, with the right hemisphere responsible for smaller magnitudes and the left hemisphere for larger magnitudes. PMID:26879093
Numerical anomalies mimicking physical effects
NASA Astrophysics Data System (ADS)
Menikoff, R.
Numerical simulations of flows with shock waves typically use finite-difference shock-capturing algorithms. These algorithms give a shock a numerical width in order to generate the entropy increase that must occur across a shock wave. For algorithms in conservation form, steady-state shock waves are insensitive to the numerical dissipation because of the Hugoniot jump conditions. However, localized numerical errors occur when shock waves interact. Examples are the 'excess wall heating' in the Noh problem (shock reflected from rigid wall), errors when a shock impacts a material interface or an abrupt change in mesh spacing, and the start-up error from initializing a shock as a discontinuity. This class of anomalies can be explained by the entropy generation that occurs in the transient flow when a shock profile is formed or changed. The entropy error is localized spatially but under mesh refinement does not decrease in magnitude. Similar effects have been observed in shock tube experiments with partly dispersed shock waves. In this case, the shock has a physical width due to a relaxation process. An entropy anomaly from a transient shock interaction is inherent in the structure of the conservation equations for fluid flow. The anomaly can be expected to occur whenever heat conduction can be neglected and a shock wave has a non-zero width, whether the width is physical or numerical. Thus, the numerical anomaly from an artificial shock width mimics a real physical effect.
Bidirectional Modulation of Numerical Magnitude
Arshad, Qadeer; Nigmatullina, Yuliya; Nigmatullin, Ramil; Asavarut, Paladd; Goga, Usman; Khan, Sarah; Sander, Kaija; Siddiqui, Shuaib; Roberts, R. E.; Cohen Kadosh, Roi; Bronstein, Adolfo M.; Malhotra, Paresh A.
2016-01-01
Numerical cognition is critical for modern life; however, the precise neural mechanisms underpinning numerical magnitude allocation in humans remain obscure. Based upon previous reports demonstrating the close behavioral and neuro-anatomical relationship between number allocation and spatial attention, we hypothesized that these systems would be subject to similar control mechanisms, namely dynamic interhemispheric competition. We employed a physiological paradigm, combining visual and vestibular stimulation, to induce interhemispheric conflict and subsequent unihemispheric inhibition, as confirmed by transcranial direct current stimulation (tDCS). This allowed us to demonstrate the first systematic bidirectional modulation of numerical magnitude toward either higher or lower numbers, independently of either eye movements or spatial attention mediated biases. We incorporated both our findings and those from the most widely accepted theoretical framework for numerical cognition to present a novel unifying computational model that describes how numerical magnitude allocation is subject to dynamic interhemispheric competition. That is, numerical allocation is continually updated in a contextual manner based upon relative magnitude, with the right hemisphere responsible for smaller magnitudes and the left hemisphere for larger magnitudes. PMID:26879093
Experimental and Numerical Studies of Oceanic Overflow
NASA Astrophysics Data System (ADS)
Gibson, Thomas; Hohman, Fred; Morrison, Theresa; Reckinger, Shanon; Reckinger, Scott
2014-11-01
Oceanic overflows occur when dense water flows down a continental slope into less dense ambient water. The resulting density driven plumes occur naturally in various regions of the global ocean and affect the large-scale circulation. General circulation models currently rely on parameterizations for representing dense overflows due to resolution restrictions. The work presented here involves a direct qualitative and quantitative comparison between physical laboratory experiments and lab-scale numerical simulations. Laboratory experiments are conducted using a rotating square tank customized for idealized overflow and a high-resolution camera mounted on the table in the rotating reference frame for data collection. Corresponding numerical simulations are performed using the MIT general circulation model (MITgcm) run in the non-hydrostatic configuration. Resolution and numerical parameter studies are presented to ensure accuracy of the simulation. Laboratory and computational experiments are compared across a wide range of physical parameters, including Coriolis parameter, inflow density anomaly, and dense inflow volumetric flow rate. The results are analyzed using various calculated metrics, such as the plume velocity. Funding for this project is provided by the National Science Foundation.
48 CFR 1816.405-275 - Award fee evaluation rating.
Code of Federal Regulations, 2011 CFR
2011-10-01
... each adjectival rating category contained in FAR 16.401(e)(iv). (b) The following numerical scoring...). The numerical score for each factor is then multiplied by the weighting for that factor to determine... numerical score for that factor is 80, the weighted technical score is 48 (80 × 60 percent). The...
Numerical Simulation of Coherent Error Correction
NASA Astrophysics Data System (ADS)
Crow, Daniel; Joynt, Robert; Saffman, Mark
A major goal in quantum computation is the implementation of error correction to produce a logical qubit with an error rate lower than that of the underlying physical qubits. Recent experimental progress demonstrates physical qubits can achieve error rates sufficiently low for error correction, particularly for codes with relatively high thresholds such as the surface code and color code. Motivated by experimental capabilities of neutral atom systems, we use numerical simulation to investigate whether coherent error correction can be effectively used with the 7-qubit color code. The results indicate that coherent error correction does not work at the 10-qubit level in neutral atom array quantum computers. By adding more qubits there is a possibility of making the encoding circuits fault-tolerant which could improve performance.
Numerical MHD codes for modeling astrophysical flows
NASA Astrophysics Data System (ADS)
Koldoba, A. V.; Ustyugova, G. V.; Lii, P. S.; Comins, M. L.; Dyda, S.; Romanova, M. M.; Lovelace, R. V. E.
2016-05-01
We describe a Godunov-type magnetohydrodynamic (MHD) code based on the Miyoshi and Kusano (2005) solver which can be used to solve various astrophysical hydrodynamic and MHD problems. The energy equation is in the form of entropy conservation. The code has been implemented on several different coordinate systems: 2.5D axisymmetric cylindrical coordinates, 2D Cartesian coordinates, 2D plane polar coordinates, and fully 3D cylindrical coordinates. Viscosity and diffusivity are implemented in the code to control the accretion rate in the disk and the rate of penetration of the disk matter through the magnetic field lines. The code has been utilized for the numerical investigations of a number of different astrophysical problems, several examples of which are shown.
Submarine sand volcanos: experiments and numerical modelling
NASA Astrophysics Data System (ADS)
Philippe, P.; Ngoma, J.; Delenne, J.
2012-12-01
Fluid overpressure at the bottom of a soil layer may generate fracturation in preferential paths for a cohesive material. But the case of sandy soils is rather different: a significant internal flow is allowed within the material and can potentially induce hydro-mechanical instabilities whose most common example is fluidization. Many works have been devoted to fluidization but very few have the issue of initiation and development of a fluidized zone inside a granular bed, prior entire fluidization of the medium. In this contribution, we report experimental results and numerical simulations on a model system of immersed sand volcanos generated by a localized upward spring of liquid, injected at constant flow-rate at the bottom of a granular layer. Such a localized state of fluidization is relevant for some industrial processes (spouted bed, maintenance of navigable waterways,…) and for several geological issues (kimberlite volcano conduits, fluid venting, oil recovery in sandy soil, More precisely, what is presented here is a comparison between experiments, carried out by direct visualization throughout the medium, and numerical simulations, based on DEM modelling of the grains coupled to resolution of NS equations in the liquid phase (LBM). There is a very good agreement between the experimental phenomenology and the simulation results. When the flow-rate is increased, three regimes are successively observed: static bed, fluidized cavity that does not extend to the top of the layer, and finally fluidization over the entire height of layer that creates a fluidized chimney. A very strong hysteretic effect is present here with an extended range of stability for fluidized cavities when flow-rate is decreased back. This can be interpreted in terms force chains and arches. The influences of grain diameter, layer height and injection width are studied and interpreted using a model previously developed by Zoueshtiagh [1]. Finally, growing rate of the fluidized zone and
Numerical dosimetry dedicated to children RF exposure.
Wiart, Joe; Hadjem, Abdelhamid; Varsier, Nadège; Conil, Emmanuelle
2011-12-01
Children are more and more using wireless communication systems. This growth has strengthened public concern and has highlighted the need to assess the radio frequency (RF) exposure of children. In dosimetry, taking advantage of the improvement of High Performance Calculation systems, great efforts have been carried out to improve the numerical tools and human models used to assess the Specific Absorption Rate (SAR). This paper analyses progress in building child and foetus models for numerical dosimetry purpose. The simulation results, in terms of Specific Absorption Rate over 1 and 10 g of tissues, in specific organs such as brain and averaged over the whole body, are reported and analysed. The results show that compliance methods used nowadays to certify phones are valid for children. The studies also show that specific tissues such as peripheral brain tissues can have higher exposure with children than with adults. Studies performed with plane waves as sources and whole body children models show that the whole body SAR of children can be higher than the WBSAR of adults and that the compliance to ICNIRP reference levels does not guarantee the compliance to ICNIRP basic restrictions. Dealing with the foetus models and dielectric properties great efforts have been made. Preliminary results show that the foetus exposure is often lower than the mother exposure, with an important influencing parameter: the foetus position in the uterus. PMID:22005525
Numeral Incorporation in Japanese Sign Language
ERIC Educational Resources Information Center
Ktejik, Mish
2013-01-01
This article explores the morphological process of numeral incorporation in Japanese Sign Language. Numeral incorporation is defined and the available research on numeral incorporation in signed language is discussed. The numeral signs in Japanese Sign Language are then introduced and followed by an explanation of the numeral morphemes which are…
Numerical cognition: Adding it up.
LeFevre, Jo-Anne
2016-03-01
In this article, I provide a historical overview of the field of numerical cognition. I first situate the evolution and development of this field in the more general context of the cognitive revolution, which started in the mid-1950s. I then discuss the genesis of numerical cognition from 6 areas: psychophysics, information processing, neuropsychology, mathematics education, psychometrics, and cognitive development. This history is personal: I discuss some of my own work over the last 30 years and describe how each of the authors of the articles in this collection originally connected with the field. One important goal of the article is to highlight the major findings, both for experts and for those who are less familiar with research on numerical processing. In sum, I sketch a context within which to appreciate the neural, computational, and behavioural work that the other 4 authors summarise in their articles in this special section. (PsycINFO Database Record PMID:26913781
Numerical analysis of engine instability
NASA Astrophysics Data System (ADS)
Habiballah, M.; Dubois, I.
Following a literature review on numerical analyses of combustion instability, to give the state of the art in the area, the paper describes the ONERA methodology used to analyze the combustion instability in liquid propellant engines. Attention is also given to a model (named Phedre) which describes the unsteady turbulent two-phase reacting flow in a liquid rocket engine combustion chamber. The model formulation includes axial or radial propellant injection, baffles, and acoustic resonators modeling, and makes it possible to treat different engine types. A numerical analysis of a cryogenic engine stability is presented, and the results of the analysis are compared with results of tests of the Viking engine and the gas generator of the Vulcain engine, showing good qualitative agreement and some general trends between experiments and numerical analysis.
Numerical Package in Computer Supported Numeric Analysis Teaching
ERIC Educational Resources Information Center
Tezer, Murat
2007-01-01
At universities in the faculties of Engineering, Sciences, Business and Economics together with higher education in Computing, it is stated that because of the difficulty, calculators and computers can be used in Numerical Analysis (NA). In this study, the learning computer supported NA will be discussed together with important usage of the…
Numerical Modelling of Gelating Aerosols
Babovsky, Hans
2008-09-01
The numerical simulation of the gel phase transition of an aerosol system is an interesting and demanding task. Here, we follow an approach first discussed in [6, 8] which turns out as a useful numerical tool. We investigate several improvements and generalizations. In the center of interest are coagulation diffusion systems, where the aerosol dynamics is supplemented with diffusive spreading in physical space. This leads to a variety of scenarios (depending on the coagulation kernel and the diffusion model) for the spatial evolution of the gelation area.
Numerical methods in structural mechanics
NASA Astrophysics Data System (ADS)
Obraztsov, I. F.
The papers contained in this volume focus on numerical, numerical-analytical, and theoretical methods for dealing with strength, stability, and dynamics problems in the design of the structural elements of flight vehicles. Topics discussed include the solution of homogeneous boundary value problems for systems of ordinary differential equations modified by a difference factorization method, a study of the rupture strength of a welded joint between plates, singular solutions in mixed problems for a wedge and a half-strip, and a thermoelasticity problem for an open-profile cylindrical shell with a localized temperature field.
Numerical integration of subtraction terms
NASA Astrophysics Data System (ADS)
Seth, Satyajit; Weinzierl, Stefan
2016-06-01
Numerical approaches to higher-order calculations often employ subtraction terms, both for the real emission and the virtual corrections. These subtraction terms have to be added back. In this paper we show that at NLO the real subtraction terms, the virtual subtraction terms, the integral representations of the field renormalization constants and—in the case of initial-state partons—the integral representation for the collinear counterterm can be grouped together to give finite integrals, which can be evaluated numerically. This is useful for an extension towards next-to-next-to-leading order.
Numerical models of galactic dynamos
NASA Astrophysics Data System (ADS)
Elstner, Detlef
The state of the art for dynamo models in spiral galaxies is reviewed. The comparison of numerical models with special properties of observed magnetic fields yields constraints for the turbulent diffusivity and the α-effect. The derivation of the turbulence parameters from the vertical structure of the interstellar medium gives quite reasonable values for modelling the regular magnetic fields in galaxies with an α2Ω-dynamo. Considering the differences of the turbulence between spiral arms and interarm regions, the observed interarm magnetic fields are recovered in the numerical models due to the special properties of the α2Ω-dynamo.
The representation of numerical magnitude
Brannon, Elizabeth M
2006-01-01
The combined efforts of many fields are advancing our understanding of how number is represented. Researchers studying numerical reasoning in adult humans, developing humans and non-human animals are using a suite of behavioral and neurobiological methods to uncover similarities and differences in how each population enumerates and compares quantities to identify the neural substrates of numerical cognition. An important picture emerging from this research is that adult humans share with non-human animals a system for representing number as language-independent mental magnitudes and that this system emerges early in development. PMID:16546373
Numerical investigations of gaseous spherical diffusion flames
NASA Astrophysics Data System (ADS)
Lecoustre, Vivien R.
Spherical diffusion flames have several unique characteristics that make them attractive from experimental and theoretical perspectives. They can be modeled with one spatial dimension, which frees computational resources for detailed chemistry, transport, and radiative loss models. This dissertation is a numerical study of two classes of spherical diffusion flames: hydrogen micro-diffusion flames, emphasizing kinetic extinction, and ethylene diffusion flames, emphasizing sooting limits. The flames were modeled using a one-dimensional, time-accurate diffusion flame code with detailed chemistry and transport. Radiative losses from products were modeled using a detailed absorption/emission statistical narrow band model and the discrete ordinates method. During this work the code has been enhanced by the implementation of a soot formation/oxidation model using the method of moments. Hydrogen micro-diffusion flames were studied experimentally and numerically. The experiments involved gas jets of hydrogen. At their quenching limits, these flames had heat release rates of 0.46 and 0.25 W in air and in oxygen, respectively. These are the weakest flames ever observed. The modeling results confirmed the quenching limits and revealed high rates of reactant leakage near the limits. The effects of the burner size and mass flow rate were predicted to have a significant impact on the flame chemistry and species distribution profiles, favoring kinetic extinction. Spherical ethylene diffusion flames at their sooting limits were also examined. Seventeen normal and inverse spherical flames were considered. Initially sooty, these flames were experimentally observed to reach their sooting limits 2 s after ignition. Structure of the flames at 2 s was considered, with an emphasis on the relationships among local temperature, carbon to oxygen atom ratio (C/O), and scalar dissipation rate. A critical C/O ratio was identified, along with two different sooting limit regimes. Diffusion flames
ERIC Educational Resources Information Center
Dapre, P. A.
1977-01-01
A theory on the origin of Roman numerals proposes that the principal numbers can be stylized in terms of a square. It is speculated that the abacus or its equivalents, such as the counter or chequer-board, was used to count before the alphabet became common. (SW)
DEVELOPMENT OF NUMERICAL NUTRIENT CRITERIA
A major goal of the numeric nutrient criteria program is to develop waterbody-type technical guidance manuals for assessing trophic state. EPA has published guidance for lakes and for rivers. EPA Region 1 is publishing New England-specific guidance in 2001 for lakes, ponds and ...
NUMERICAL SIMULATION OF LARYNGEAL FLOW
In this study, we have investigated laryngeal air flows by numerically solving the corresponding Navier-Stokes equations expressed in a two-dimensional cylindrical coordinate system. The glottal aperture, defined by the geometry of the vocal folds was allowed to change with the v...
Numerical calculations of flow fields
NASA Technical Reports Server (NTRS)
Anderson, D.; Vogel, J. M.
1973-01-01
Numerical calculations were made of flow fields generated by various aerodynamic configurations. Data cover flow fields generated by a finitely thick lifting three dimensional wing with subsonic tips moving at supersonic speeds, cross flow instability associated with lifting delta wing configurations such as space shuttles, and flow fields produced by a lifting elliptic cone. Finite difference techniques were used to determine elliptic cone flow.
Conditional Convergence of Numerical Series
ERIC Educational Resources Information Center
Gomez, E.; Plaza, A.
2002-01-01
One of the most astonishing properties when studying numerical series is that the sum is not commutative, that is the sum may change when the order of its elements is altered. In this note an example is given of such a series. A well-known mathematical proof is given and a MATLAB[C] program used for different rearrangements of the series…
Elliptic systems and numerical transformations
NASA Technical Reports Server (NTRS)
Mastin, C. W.; Thompson, J. F.
1976-01-01
Properties of a transformation method, which was developed for solving fluid dynamic problems on general two dimensional regions, are discussed. These include construction error of the transformation and applications to mesh generation. An error and stability analysis for the numerical solution of a model parabolic problem is also presented.
Numerical simulation of asymmetric particle precipitation by pitch angle diffusion
NASA Astrophysics Data System (ADS)
Thorne, Richard M.; Abel, Robert W.; Summers, Danny
1996-11-01
A numerical simulation code is developed to evaluate the loss rate of particles trapped in a mirror magnetic field geometry with asymmetric loss cones. The one-dimensional model can accommodate particle diffusion at any prescribed rate and loss cones of any prescribed sizes, and it incorporates the important effect of atmospheric backscattering. Numerical solutions for the loss cone particle distribution function calculated for the case of equal loss cones provide an acceptable simulation of the well-known modified Bessel function solution. The code provides the first quantitative solutions for any specified rate of pitch angle scattering for the general case of arbitrary asymmetry in loss cone size. In the case of weak or moderate diffusion the ratio of particle precipitation fluxes into the two loss cones can provide a sensitive measurement of the rate of particle scattering, but to utilize this important diagnostic property, one must also have information on the fraction of particles that are backscattered from the atmosphere.
Numerical discrimination is mediated by neural coding variation.
Prather, Richard W
2014-12-01
One foundation of numerical cognition is that discrimination accuracy depends on the proportional difference between compared values, closely following the Weber-Fechner discrimination law. Performance in non-symbolic numerical discrimination is used to calculate individual Weber fraction, a measure of relative acuity of the approximate number system (ANS). Individual Weber fraction is linked to symbolic arithmetic skills and long-term educational and economic outcomes. The present findings suggest that numerical discrimination performance depends on both the proportional difference and absolute value, deviating from the Weber-Fechner law. The effect of absolute value is predicted via computational model based on the neural correlates of numerical perception. Specifically, that the neural coding "noise" varies across corresponding numerosities. A computational model using firing rate variation based on neural data demonstrates a significant interaction between ratio difference and absolute value in predicting numerical discriminability. We find that both behavioral and computational data show an interaction between ratio difference and absolute value on numerical discrimination accuracy. These results further suggest a reexamination of the mechanisms involved in non-symbolic numerical discrimination, how researchers may measure individual performance, and what outcomes performance may predict. PMID:25238315
Direct numerical simulation of turbulent aerosol coagulation
NASA Astrophysics Data System (ADS)
Reade, Walter Caswell
There are numerous systems-including both industrial applications and natural occurring phenomena-in which the collision/coagulation rates of aerosols are of significant interest. Two examples are the production of fine powders (such as titanium dioxide) and the formation of rain drops in the atmosphere. During the last decade, it has become apparent that dense aerosol particles behave much differently in a turbulent fluid than has been previously assumed. Particles with a response time on the order of the small-scale fluid time scale tend to collect in regions of low vorticity. The result is a particle concentration field that can be highly non-uniform. Sundaram and Collins (1997) recently demonstrated the effect that turbulence can have on the particle collision rate of a monodisperse system. The collision rates of finite-inertia particles can be as much as two orders of magnitude greater than particles that precisely follow the fluid streamlines. Sundaram and Collins derived a general collision expression that explicitly accounted for the two phenomena that affect the collision rate-changes in the particle concentration field and changes in the particle relative velocities. The result of Sundaram and Collins has generated further interest in the turbulent-aerosol problem. This thesis shows that, in addition to changing the rate that an aerosol size distribution might form, turbulence has the potential of dramatically changing the shape of the distribution. This result is demonstrated using direct numerical simulation of a turbulent-aerosol system over a wide range of particle parameters, and a moderate range of turbulence levels. Results show that particles with a small (but finite) initial inertia have the greatest potential of forming broad size distributions. The shape of the resulting size distribution is also affected by the initial size of the particles. Observations are explained using the statistics identified by Sundaram and Collins (1997). A major
A Numerical Study of Hypersonic Forebody/Inlet Integration Problem
NASA Technical Reports Server (NTRS)
Kumar, Ajay
1991-01-01
A numerical study of hypersonic forebody/inlet integration problem is presented in the form of the view-graphs. The following topics are covered: physical/chemical modeling; solution procedure; flow conditions; mass flow rate at inlet face; heating and skin friction loads; 3-D forebogy/inlet integration model; and sensitivity studies.
3D Numerical simulations of oblique subduction
NASA Astrophysics Data System (ADS)
Malatesta, C.; Gerya, T.; Scambelluri, M.; Crispini, L.; Federico, L.; Capponi, G.
2012-04-01
In the past 2D numerical studies (e.g. Gerya et al., 2002; Gorczyk et al., 2007; Malatesta et al., 2012) provided evidence that during intraoceanic subduction a serpentinite channel forms above the downgoing plate. This channel forms as a result of hydration of the mantle wedge by uprising slab-fluids. Rocks buried at high depths are finally exhumed within this buoyant low-viscosity medium. Convergence rate in these 2D models was described by a trench-normal component of velocity. Several present and past subduction zones worldwide are however driven by oblique convergence between the plates, where trench-normal motion of the subducting slab is coupled with trench-parallel displacement of the plates. Can the exhumation mechanism and the exhumation rates of high-pressure rocks be affected by the shear component of subduction? And how uprise of these rocks can vary along the plate margin? We tried to address these questions performing 3D numerical models that simulate an intraoceanic oblique subduction. The models are based on thermo-mechanical equations that are solved with finite differences method and marker-in-cell techniques combined with multigrid approach (Gerya, 2010). In most of the models a narrow oceanic basin (500 km-wide) surrounded by continental margins is depicted. The basin is floored by either layered or heterogeneous oceanic lithosphere with gabbro as discrete bodies in serpentinized peridotite and a basaltic layer on the top. A weak zone in the mantle is prescribed to control the location of subduction initiation and therefore the plate margins geometry. Finally, addition of a third dimension in the simulations allowed us to test the role of different plate margin geometries on oblique subduction dynamics. In particular in each model we modified the dip angle of the weak zone and its "lateral" geometry (e.g. continuous, segmented). We consider "continuous" weak zones either parallel or increasingly moving away from the continental margins
NASA Astrophysics Data System (ADS)
Sarlar, Kagan; Kucuk, Ilker
2015-01-01
The effect of Fe concentration on the glass forming ability (GFA) and magnetic properties in Co(40.2-x)Fe(20.1+x)Ni6.7B22.7Si5.3Nb5 (x=0-10) bulk metallic glasses were investigated. By suction casting method, the bulk metallic glasses with diameters up to 2 mm were produced. We try to find out which Fe concentration makes an influence on Co based system's magnetic properties and glass forming ability. The curves of thermal analysis, obtained using differential scanning calorimetry (DSC), show that the Co(40.2-x)Fe(20.1+x)Ni6.7B22.7Si5.3Nb5 (x=0-10) have a supercooled liquid region (∆Tx) of about 44 K. The saturation magnetizations (Js) for as-cast BMG alloys were in the range of 0.62 T-0.81 T.
High Rate Digital Demodulator ASIC
NASA Technical Reports Server (NTRS)
Ghuman, Parminder; Sheikh, Salman; Koubek, Steve; Hoy, Scott; Gray, Andrew
1998-01-01
The architecture of High Rate (600 Mega-bits per second) Digital Demodulator (HRDD) ASIC capable of demodulating BPSK and QPSK modulated data is presented in this paper. The advantages of all-digital processing include increased flexibility and reliability with reduced reproduction costs. Conventional serial digital processing would require high processing rates necessitating a hardware implementation in other than CMOS technology such as Gallium Arsenide (GaAs) which has high cost and power requirements. It is more desirable to use CMOS technology with its lower power requirements and higher gate density. However, digital demodulation of high data rates in CMOS requires parallel algorithms to process the sampled data at a rate lower than the data rate. The parallel processing algorithms described here were developed jointly by NASA's Goddard Space Flight Center (GSFC) and the Jet Propulsion Laboratory (JPL). The resulting all-digital receiver has the capability to demodulate BPSK, QPSK, OQPSK, and DQPSK at data rates in excess of 300 Mega-bits per second (Mbps) per channel. This paper will provide an overview of the parallel architecture and features of the HRDR ASIC. In addition, this paper will provide an over-view of the implementation of the hardware architectures used to create flexibility over conventional high rate analog or hybrid receivers. This flexibility includes a wide range of data rates, modulation schemes, and operating environments. In conclusion it will be shown how this high rate digital demodulator can be used with an off-the-shelf A/D and a flexible analog front end, both of which are numerically computer controlled, to produce a very flexible, low cost high rate digital receiver.
Numerical analysis of Stirling engine
NASA Astrophysics Data System (ADS)
Sekiya, Hiroshi
1992-11-01
A simulation model of the Stirling engine based on the third order method of analysis is presented. The fundamental equations are derived by applying conservation laws of physics to the machine model, the characteristic equations for heat transfer and gas flow are represented, and a numerical calculation technique using these equations is discussed. A numerical model of the system for balancing pressure in four cylinders is included in the simulation model. Calculations results from the model are compared with experimental results. A comparable study of engine performance using helium and hydrogen as working gas is conducted, clarifying the heat transfer and gas flow characteristics, and the effects of temperature conditions in the hot and cold engine sections on driving conditions. The design optimization of the heat exchanger is addressed.
Numerical investigation of stall flutter
Ekaterinaris, J.A.; Platzer, M.F.
1996-04-01
Unsteady, separated, high Reynolds number flow over an airfoil undergoing oscillatory motion is investigated numerically. The compressible form of the Reynolds-averaged governing equations is solved using a high-order, upwind biased numerical scheme. The turbulent flow region is computed using a one-equation turbulence model. The computed results show that the key to the accurate prediction of the unsteady loads at stall flutter conditions is the modeling of the transitional flow region at the leading edge. A simplified criterion for the transition onset is used. The transitional flow region is computed with a modified form of the turbulence model. The computed solution, where the transitional flow region is included, shows that the small laminar/transitional separation bubble forming during the pitch-up motion has a decisive effect on the near-wall flow and the development of the unsteady loads. Detailed comparisons of computed fully turbulent and transitional flow solutions with experimental data are presented.
Numerical simulations of hot spots
NASA Astrophysics Data System (ADS)
Norman, Michael L.
Numerical simulations of hot spots and their associated jets are examined with emphasis on their dynamical variability. Attention is given to two-dimensional simulations, which incorporate dynamically passive and important magnetic fields in the ideal MHD limit. Distributions of total and polarized radio brightness have been derived for comparison with observations. The move toward three-dimensional simulations is documented, and hydrodynamical models for multiple hot spots are discussed. It is suggested that useful insights can be obtained from two-dimensional slab jet simulation, which relax the axisymmetric constraints while allowing high numerical resolution. In particular the dentist-drill model of Scheuer (1982) for working-surface variability is substantiated, and it is shown to result from self-excited jet instabilities near the working surface.
Numerical simulation of electrochemical desalination.
Hlushkou, D; Knust, K N; Crooks, R M; Tallarek, U
2016-05-18
We present an effective numerical approach to simulate electrochemically mediated desalination of seawater. This new membraneless, energy efficient desalination method relies on the oxidation of chloride ions, which generates an ion depletion zone and local electric field gradient near the junction of a microchannel branch to redirect sea salt into the brine stream, consequently producing desalted water. The proposed numerical model is based on resolution of the 3D coupled Navier-Stokes, Nernst-Planck, and Poisson equations at non-uniform spatial grids. The model is implemented as a parallel code and can be employed to simulate mass-charge transport coupled with surface or volume reactions in 3D systems showing an arbitrarily complex geometrical configuration. PMID:27089841
Numerical simulation of electrochemical desalination
NASA Astrophysics Data System (ADS)
Hlushkou, D.; Knust, K. N.; Crooks, R. M.; Tallarek, U.
2016-05-01
We present an effective numerical approach to simulate electrochemically mediated desalination of seawater. This new membraneless, energy efficient desalination method relies on the oxidation of chloride ions, which generates an ion depletion zone and local electric field gradient near the junction of a microchannel branch to redirect sea salt into the brine stream, consequently producing desalted water. The proposed numerical model is based on resolution of the 3D coupled Navier–Stokes, Nernst–Planck, and Poisson equations at non-uniform spatial grids. The model is implemented as a parallel code and can be employed to simulate mass–charge transport coupled with surface or volume reactions in 3D systems showing an arbitrarily complex geometrical configuration.
Fresnel Integral Equations: Numerical Properties
Adams, R J; Champagne, N J II; Davis, B A
2003-07-22
A spatial-domain solution to the problem of electromagnetic scattering from a dielectric half-space is outlined. The resulting half-space operators are referred to as Fresnel surface integral operators. When used as preconditioners for nonplanar geometries, the Fresnel operators yield surface Fresnel integral equations (FIEs) which are stable with respect to dielectric constant, discretization, and frequency. Numerical properties of the formulations are discussed.
Cuba: Multidimensional numerical integration library
NASA Astrophysics Data System (ADS)
Hahn, Thomas
2016-08-01
The Cuba library offers four independent routines for multidimensional numerical integration: Vegas, Suave, Divonne, and Cuhre. The four algorithms work by very different methods, and can integrate vector integrands and have very similar Fortran, C/C++, and Mathematica interfaces. Their invocation is very similar, making it easy to cross-check by substituting one method by another. For further safeguarding, the output is supplemented by a chi-square probability which quantifies the reliability of the error estimate.
Numerical simulation of detonation failure in nitromethane
Kipp, M.E.; Nunziato, J.W.
1981-01-01
Detonation failure in the homogeneous liquid explosive nitromethane has been observed experimentally in a wide variety of confining geometries. However, numerical simulation of these failure situations with a wave propagation code has been essentially non-existent due to the large differences between the critical diameter and the length of the reaction zone - characteristic dimensions which differ by about two orders of magnitude. This inability to spatially resolve both the reaction zone and geometries of significant size has led us to propose a new numerical technique, based on the stability criterion for rate-type material models, in which only temporal resolution of the reaction zone is required. Using an improved model for nitromethane, we have carried out a series of two-dimensional calculations which illustrate the utility of the present approach in predicting a wide range of experimental observations. Of particular computational significance is the removal of the difficulty requiring spatial resolution of the reaction zone, so that problems of practical size can be analyzed with existing computer capabilities.
Numerical Simulation of Taylor Cone-Jet
NASA Astrophysics Data System (ADS)
Toledo, Ronne
The Taylor cone-jet is a particular type of electrohydrodynamic phenomenon where electrostatic stresses and surface tension effects shape the interface of the jet in a peculiar conical shape. A thin jet is issued from the cone apex that further breaks up into a fine aerosol. Due to its monodispersive properties, this fine aerosol has found a number of applications, ranging from mass spectrometry, colloidal space propulsion, combustion, nano-fabrication, coating/painting, and many others. In this study, a general non-dimensional analysis is performed to derive the governing equations and boundary conditions. In accordance with the observations of Gamero-Castano (2010), noting that droplet electric potential is insensitive to the flow rate conditions, a particular set of characteristic parameters is proposed, based on the terminal jet diameter. In order to solve the non-dimensional set of governing equations and boundary conditions, a numerical method combining the Boundary Element Method and the Finite Volume Method is developed. Results of electric current have shown good agreement with numerical and experimental data available in the literature. The main feature of the algorithm developed is related to the decoupling of the electrostatic from the hydrodynamic problem, allowing us to accurately prescribe the far field electric potential boundary conditions away from the hydrodynamic computational domain used to solve the hydrodynamics of the transition region near the cone apex.
Numerical simulation of conservation laws
NASA Technical Reports Server (NTRS)
Chang, Sin-Chung; To, Wai-Ming
1992-01-01
A new numerical framework for solving conservation laws is being developed. This new approach differs substantially from the well established methods, i.e., finite difference, finite volume, finite element and spectral methods, in both concept and methodology. The key features of the current scheme include: (1) direct discretization of the integral forms of conservation laws, (2) treating space and time on the same footing, (3) flux conservation in space and time, and (4) unified treatment of the convection and diffusion fluxes. The model equation considered in the initial study is the standard one dimensional unsteady constant-coefficient convection-diffusion equation. In a stability study, it is shown that the principal and spurious amplification factors of the current scheme, respectively, are structurally similar to those of the leapfrog/DuFort-Frankel scheme. As a result, the current scheme has no numerical diffusion in the special case of pure convection and is unconditionally stable in the special case of pure diffusion. Assuming smooth initial data, it will be shown theoretically and numerically that, by using an easily determined optimal time step, the accuracy of the current scheme may reach a level which is several orders of magnitude higher than that of the MacCormack scheme, with virtually identical operation count.
Requirements definition by numerical simulation
NASA Astrophysics Data System (ADS)
Hickman, James J.; Kostas, Chris; Tsang, Kang T.
1994-10-01
We are investigating the issues involved in requirements definition for narcotics interdiction: how much of a particular signature is possible, how does this amount change for different conditions, and what is the temporal relationship in various scenarios. Our approach has been to simulate numerically the conditions that arise during vapor or particulate transport. The advantages of this approach are that (1) a broad range of scenarios can be rapidly and inexpensively analyzed by simulation, and (2) simulations can display quantities that are difficult or impossible to measure. The drawback of this approach is that simulations cannot include all of the phenomena present in a real measurement, and therefore the fidelity of the simulation results is always an issue. To address this limitation, we will ultimately combine the results of numerical simulations with measurements of physical parameters for inclusion in the simulation. In this paper, we discuss these issues and how they apply to the current problems in narcotics interdictions, especially cargo containers. We also show the results of 1D and 3D numerical simulations, and compare these results with analytical solutions. The results indicate that this approach is viable. We also present data from 3D simulations of vapor transport in a loaded cargo container and some of the issues present in this ongoing work.
Numerical methods for turbulent flow
NASA Astrophysics Data System (ADS)
Turner, James C., Jr.
1988-09-01
It has generally become accepted that the Navier-Strokes equations predict the dynamic behavior of turbulent as well as laminar flows of a fluid at a point in space away form a discontinuity such as a shock wave. Turbulence is also closely related to the phenomena of non-uniqueness of solutions of the Navier-Strokes equations. These second order, nonlinear partial differential equations can be solved analytically for only a few simple flows. Turbulent flow fields are much to complex to lend themselves to these few analytical methods. Numerical methods, therefore, offer the only possibility of achieving a solution of turbulent flow equations. In spite of recent advances in computer technology, the direct solution, by discrete methods, of the Navier-Strokes equations for turbulent flow fields is today, and in the foreseeable future, impossible. Thus the only economically feasible way to solve practical turbulent flow problems numerically is to use statistically averaged equations governing mean-flow quantities. The objective is to study some recent developments relating to the use of numerical methods to study turbulent flow.
Numerical Studies of Impurities in Fusion Plasmas
DOE R&D Accomplishments Database
Hulse, R. A.
1982-09-01
The coupled partial differential equations used to describe the behavior of impurity ions in magnetically confined controlled fusion plasmas require numerical solution for cases of practical interest. Computer codes developed for impurity modeling at the Princeton Plasma Physics Laboratory are used as examples of the types of codes employed for this purpose. These codes solve for the impurity ionization state densities and associated radiation rates using atomic physics appropriate for these low-density, high-temperature plasmas. The simpler codes solve local equations in zero spatial dimensions while more complex cases require codes which explicitly include transport of the impurity ions simultaneously with the atomic processes of ionization and recombination. Typical applications are discussed and computational results are presented for selected cases of interest.
Numerical Simulations of Acoustically Driven, Burning Droplets
NASA Technical Reports Server (NTRS)
Kim, H.-C.; Karagozian, A. R.; Smith, O. I.; Urban, Dave (Technical Monitor)
1999-01-01
This computational study focuses on understanding and quantifying the effects of external acoustical perturbations on droplet combustion. A one-dimensional, axisymmetric representation of the essential diffusion and reaction processes occurring in the vicinity of the droplet stagnation point is used here in order to isolate the effects of the imposed acoustic disturbance. The simulation is performed using a third order accurate, essentially non-oscillatory (ENO) numerical scheme with a full methanol-air reaction mechanism. Consistent with recent microgravity and normal gravity combustion experiments, focus is placed on conditions where the droplet is situated at a velocity antinode in order for the droplet to experience the greatest effects of fluid mechanical straining of flame structures. The effects of imposed sound pressure level and frequency are explored here, and conditions leading to maximum burning rates are identified.
Numerical Analysis of Convection/Transpiration Cooling
NASA Technical Reports Server (NTRS)
Glass, David E.; Dilley, Arthur D.; Kelly, H. Neale
1999-01-01
An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.
Numerical Analysis of Convection/Transpiration Cooling
NASA Technical Reports Server (NTRS)
Glass, David E.; Dilley, Arthur D.; Kelly, H. Neale
1999-01-01
An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux, high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary, layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.
Entropy Splitting and Numerical Dissipation
NASA Technical Reports Server (NTRS)
Yee, H. C.; Vinokur, M.; Djomehri, M. J.
1999-01-01
A rigorous stability estimate for arbitrary order of accuracy of spatial central difference schemes for initial-boundary value problems of nonlinear symmetrizable systems of hyperbolic conservation laws was established recently by Olsson and Oliger (1994) and Olsson (1995) and was applied to the two-dimensional compressible Euler equations for a perfect gas by Gerritsen and Olsson (1996) and Gerritsen (1996). The basic building block in developing the stability estimate is a generalized energy approach based on a special splitting of the flux derivative via a convex entropy function and certain homogeneous properties. Due to some of the unique properties of the compressible Euler equations for a perfect gas, the splitting resulted in the sum of a conservative portion and a non-conservative portion of the flux derivative. hereafter referred to as the "Entropy Splitting." There are several potential desirable attributes and side benefits of the entropy splitting for the compressible Euler equations that were not fully explored in Gerritsen and Olsson. The paper has several objectives. The first is to investigate the choice of the arbitrary parameter that determines the amount of splitting and its dependence on the type of physics of current interest to computational fluid dynamics. The second is to investigate in what manner the splitting affects the nonlinear stability of the central schemes for long time integrations of unsteady flows such as in nonlinear aeroacoustics and turbulence dynamics. If numerical dissipation indeed is needed to stabilize the central scheme, can the splitting help minimize the numerical dissipation compared to its un-split cousin? Extensive numerical study on the vortex preservation capability of the splitting in conjunction with central schemes for long time integrations will be presented. The third is to study the effect of the non-conservative proportion of splitting in obtaining the correct shock location for high speed complex shock
Towards numerical prediction of cavitation erosion.
Fivel, Marc; Franc, Jean-Pierre; Chandra Roy, Samir
2015-10-01
This paper is intended to provide a potential basis for a numerical prediction of cavitation erosion damage. The proposed method can be divided into two steps. The first step consists in determining the loading conditions due to cavitation bubble collapses. It is shown that individual pits observed on highly polished metallic samples exposed to cavitation for a relatively small time can be considered as the signature of bubble collapse. By combining pitting tests with an inverse finite-element modelling (FEM) of the material response to a representative impact load, loading conditions can be derived for each individual bubble collapse in terms of stress amplitude (in gigapascals) and radial extent (in micrometres). This step requires characterizing as accurately as possible the properties of the material exposed to cavitation. This characterization should include the effect of strain rate, which is known to be high in cavitation erosion (typically of the order of several thousands s(-1)). Nanoindentation techniques as well as compressive tests at high strain rate using, for example, a split Hopkinson pressure bar test system may be used. The second step consists in developing an FEM approach to simulate the material response to the repetitive impact loads determined in step 1. This includes a detailed analysis of the hardening process (isotropic versus kinematic) in order to properly account for fatigue as well as the development of a suitable model of material damage and failure to account for mass loss. Although the whole method is not yet fully operational, promising results are presented that show that such a numerical method might be, in the long term, an alternative to correlative techniques used so far for cavitation erosion prediction. PMID:26442139
Direct numerical simulation of turbulent reacting flows
Chen, J.H.
1993-12-01
The development of turbulent combustion models that reflect some of the most important characteristics of turbulent reacting flows requires knowledge about the behavior of key quantities in well defined combustion regimes. In turbulent flames, the coupling between the turbulence and the chemistry is so strong in certain regimes that is is very difficult to isolate the role played by one individual phenomenon. Direct numerical simulation (DNS) is an extremely useful tool to study in detail the turbulence-chemistry interactions in certain well defined regimes. Globally, non-premixed flames are controlled by two limiting cases: the fast chemistry limit, where the turbulent fluctuations. In between these two limits, finite-rate chemical effects are important and the turbulence interacts strongly with the chemical processes. This regime is important because industrial burners operate in regimes in which, locally the flame undergoes extinction, or is at least in some nonequilibrium condition. Furthermore, these nonequilibrium conditions strongly influence the production of pollutants. To quantify the finite-rate chemistry effect, direct numerical simulations are performed to study the interaction between an initially laminar non-premixed flame and a three-dimensional field of homogeneous isotropic decaying turbulence. Emphasis is placed on the dynamics of extinction and on transient effects on the fine scale mixing process. Differential molecular diffusion among species is also examined with this approach, both for nonreacting and reacting situations. To address the problem of large-scale mixing and to examine the effects of mean shear, efforts are underway to perform large eddy simulations of round three-dimensional jets.
Statistical theory of asteroid escape rates.
Jaffé, Charles; Ross, Shane D; Lo, Martin W; Marsden, Jerrold; Farrelly, David; Uzer, T
2002-07-01
Transition states in phase space are identified and shown to regulate the rate of escape of asteroids temporarily captured in circumplanetary orbits. The transition states, similar to those occurring in chemical reaction dynamics, are then used to develop a statistical semianalytical theory for the rate of escape of asteroids temporarily captured by Mars. Theory and numerical simulations are found to agree to better than 1%. These calculations suggest that further development of transition state theory in celestial mechanics, as an alternative to large-scale numerical simulations, will be a fruitful approach to mass transport calculations. PMID:12097024
A method to enhance the data transfer rate of eutectic Sb-Te phase-change recording media
Yeh, T.-T.; Hsieh, T.-E.; Shieh, H.-P.D.
2005-07-15
This work describes the effect of nitrogen doping to eutectic Sb-Te phase-change materials in order to enhance the speed of the amorphous-to-crystalline phase transformation. When nitrogen at a sputtering gas flow ratio of N{sub 2}/Ar=3% was doped in the eutectic Ge-In-Sb-Te recording layer, the data transfer rate was increased up to 1.6 times. When thin GeN{sub x} nucleation promotion layers were further added in below and above the recording layer, an overall enhancement up to 3.3 times in data transfer rate was achieved. The nitrogen contents corresponding to the N{sub 2}/Ar flow ratios (N{sub 2}/Ar=0%-10%) were calibrated by electron spectroscopy for chemical analysis. Transmission electron microscopy revealed that nitrogen doping was able to promote the phase transformation by generating numerous nucleation sites uniformly distributed in the recording layer and hence increased the recrystallization speed.
Advanced Numerical Model for Irradiated Concrete
Giorla, Alain B.
2015-03-01
In this report, we establish a numerical model for concrete exposed to irradiation to address these three critical points. The model accounts for creep in the cement paste and its coupling with damage, temperature and relative humidity. The shift in failure mode with the loading rate is also properly represented. The numerical model for creep has been validated and calibrated against different experiments in the literature [Wittmann, 1970, Le Roy, 1995]. Results from a simplified model are shown to showcase the ability of numerical homogenization to simulate irradiation effects in concrete. In future works, the complete model will be applied to the analysis of the irradiation experiments of Elleuch et al. [1972] and Kelly et al. [1969]. This requires a careful examination of the experimental environmental conditions as in both cases certain critical information are missing, including the relative humidity history. A sensitivity analysis will be conducted to provide lower and upper bounds of the concrete expansion under irradiation, and check if the scatter in the simulated results matches the one found in experiments. The numerical and experimental results will be compared in terms of expansion and loss of mechanical stiffness and strength. Both effects should be captured accordingly by the model to validate it. Once the model has been validated on these two experiments, it can be applied to simulate concrete from nuclear power plants. To do so, the materials used in these concrete must be as well characterized as possible. The main parameters required are the mechanical properties of each constituent in the concrete (aggregates, cement paste), namely the elastic modulus, the creep properties, the tensile and compressive strength, the thermal expansion coefficient, and the drying shrinkage. These can be either measured experimentally, estimated from the initial composition in the case of cement paste, or back-calculated from mechanical tests on concrete. If some
Quantitative comparisons of numerical models of brittle wedge dynamics
NASA Astrophysics Data System (ADS)
Buiter, Susanne
2010-05-01
Numerical and laboratory models are often used to investigate the evolution of deformation processes at various scales in crust and lithosphere. In both approaches, the freedom in choice of simulation method, materials and their properties, and deformation laws could affect model outcomes. To assess the role of modelling method and to quantify the variability among models, we have performed a comparison of laboratory and numerical experiments. Here, we present results of 11 numerical codes, which use finite element, finite difference and distinct element techniques. We present three experiments that describe shortening of a sand-like, brittle wedge. The material properties of the numerical ‘sand', the model set-up and the boundary conditions are strictly prescribed and follow the analogue setup as closely as possible. Our first experiment translates a non-accreting wedge with a stable surface slope of 20 degrees. In agreement with critical wedge theory, all models maintain the same surface slope and do not deform. This experiment serves as a reference that allows for testing against analytical solutions for taper angle, root-mean-square velocity and gravitational rate of work. The next two experiments investigate an unstable wedge in a sandbox-like setup, which deforms by inward translation of a mobile wall. The models accommodate shortening by formation of forward and backward shear zones. We compare surface slope, rate of dissipation of energy, root-mean-square velocity, and the location, dip angle and spacing of shear zones. We show that we successfully simulate sandbox-style brittle behaviour using different numerical modelling techniques and that we obtain the same styles of deformation behaviour in numerical and laboratory experiments at similar levels of variability. The GeoMod2008 Numerical Team: Markus Albertz, Michelle Cooke, Tony Crook, David Egholm, Susan Ellis, Taras Gerya, Luke Hodkinson, Boris Kaus, Walter Landry, Bertrand Maillot, Yury Mishin
Numerical methods for molecular dynamics
Skeel, R.D.
1991-01-01
This report summarizes our research progress to date on the use of multigrid methods for three-dimensional elliptic partial differential equations, with particular emphasis on application to the Poisson-Boltzmann equation of molecular biophysics. This research is motivated by the need for fast and accurate numerical solution techniques for three-dimensional problems arising in physics and engineering. In many applications these problems must be solved repeatedly, and the extremely large number of discrete unknowns required to accurately approximate solutions to partial differential equations in three-dimensional regions necessitates the use of efficient solution methods. This situation makes clear the importance of developing methods which are of optimal order (or nearly so), meaning that the number of operations required to solve the discrete problem is on the order of the number of discrete unknowns. Multigrid methods are generally regarded as being in this class of methods, and are in fact provably optimal order for an increasingly large class of problems. The fundamental goal of this research is to develop a fast and accurate numerical technique, based on multi-level principles, for the solutions of the Poisson-Boltzmann equation of molecular biophysics and similar equations occurring in other applications. An outline of the report is as follows. We first present some background material, followed by a survey of the literature on the use of multigrid methods for solving problems similar to the Poisson-Boltzmann equation. A short description of the software we have developed so far is then given, and numerical results are discussed. Finally, our research plans for the coming year are presented.
Numerical methods for multibody systems
NASA Technical Reports Server (NTRS)
Glowinski, Roland; Nasser, Mahmoud G.
1994-01-01
This article gives a brief summary of some results obtained by Nasser on modeling and simulation of inequality problems in multibody dynamics. In particular, the augmented Lagrangian method discussed here is applied to a constrained motion problem with impulsive inequality constraints. A fundamental characteristic of the multibody dynamics problem is the lack of global convexity of its Lagrangian. The problem is transformed into a convex analysis problem by localization (piecewise linearization), where the augmented Lagrangian has been successfully used. A model test problem is considered and a set of numerical experiments is presented.
Results from Numerical General Relativity
NASA Technical Reports Server (NTRS)
Baker, John G.
2011-01-01
For several years numerical simulations have been revealing the details of general relativity's predictions for the dynamical interactions of merging black holes. I will review what has been learned of the rich phenomenology of these mergers and the resulting gravitational wave signatures. These wave forms provide a potentially observable record of the powerful astronomical events, a central target of gravitational wave astronomy. Asymmetric radiation can produce a thrust on the system which may accelerate the single black hole resulting from the merger to high relative velocity.
Numerical study of rock blasting
NASA Astrophysics Data System (ADS)
Stefanov, Yu. P.; Bakeev, R. A.; Yudin, A. S.; Kuznetsova, N. S.
2015-10-01
The paper presents numerical simulation results on fracture of a concrete block due to dynamic explosive loads applied to the walls of a blast hole. Considered in the study is the influence of the pulse shape and rock properties on the pattern of irreversible deformation and cracking. It is found that a fractured zone bounded by a plastically deformed contour always arises around the explosion site. Comparison of elastoplastic deformation and fracture induced in the concrete block by explosion pulses of different durations and amplitudes shows that shorter pulses with higher amplitudes and steeper rise times provide a higher blasting efficiency.
Radiation transport in numerical astrophysics
Lund, C.M.
1983-02-01
In this article, we discuss some of the numerical techniques developed by Jim Wilson and co-workers for the calculation of time-dependent radiation flow. Difference equations for multifrequency transport are given for both a discrete-angle representation of radiation transport and a Fick's law-like representation. These methods have the important property that they correctly describe both the streaming and diffusion limits of transport theory in problems where the mean free path divided by characteristic distances varies from much less than one to much greater than one. They are also stable for timesteps comparable to the changes in physical variables, rather than being limited by stability requirements.
Disruptive Innovation in Numerical Hydrodynamics
Waltz, Jacob I.
2012-09-06
We propose the research and development of a high-fidelity hydrodynamic algorithm for tetrahedral meshes that will lead to a disruptive innovation in the numerical modeling of Laboratory problems. Our proposed innovation has the potential to reduce turnaround time by orders of magnitude relative to Advanced Simulation and Computing (ASC) codes; reduce simulation setup costs by millions of dollars per year; and effectively leverage Graphics Processing Unit (GPU) and future Exascale computing hardware. If successful, this work will lead to a dramatic leap forward in the Laboratory's quest for a predictive simulation capability.
Gyrotactic trapping: A numerical study
NASA Astrophysics Data System (ADS)
Ghorai, S.
2016-04-01
Gyrotactic trapping is a mechanism proposed by Durham et al. ["Disruption of vertical motility by shear triggers formation of thin Phytoplankton layers," Science 323, 1067-1070 (2009)] to explain the formation of thin phytoplankton layer just below the ocean surface. This mechanism is examined numerically using a rational model based on the generalized Taylor dispersion theory. The crucial role of sedimentation speed in the thin layer formation is demonstrated. The effects of variation in different parameters on the thin layer formation are also investigated.
NASA Astrophysics Data System (ADS)
Ullah, Amir; Rahman, Muneeb-ur; Iqbal, Muhammad Javid; Ahn, Chang Won; Kim, Ill Won; Ullah, Aman
2016-06-01
The electrical properties of the 0.925(Bi0.5(Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 (0.925BNKT-0.075BST) ceramic were investigated by using AC impedance spectroscopy over a wide range of frequencies (10 -2 ~ 105 Hz). The X-ray diffraction patterns confirmed the formation of a single-phase compound. A single semicircular arc in the impedance spectrum indicates that the main contribution of the bulk resistance ( R b ) were due to grain effects, with Rb decreasing with increasing temperature. The conductivity of the ceramics increased with increasing temperature, and the activation energy resulting from the DC conductivity was 0.86 eV. The ceramic displayed a typical negative temperature coefficient of resistance (NTCR) behavior, like that of a semiconductor.
NASA Astrophysics Data System (ADS)
Błoch, K.
2015-09-01
This paper presents the results of studies into the structural and magnetic properties of the bulk amorphous alloy: (Fe0.61Co0.10Zr0.025Hf0.025Ti0.02W0.02B0.20)96Y4, fabricated in the form of rods of length: 20 mm, and diameters: 1 mm and 2 mm. The samples were produced using the suction-casting method. The amorphicity of the investigated alloy, in the as-quenched state, was verified using X-ray diffractometry and Mössbauer spectroscopy. Studies of the magnetic susceptibility disaccommodation and the approach to magnetic saturation facilitated the conclusion that the investigated alloy, obtained in the form of rods of 2 mm diameter, can be characterized by a higher packing density of atoms; this was further confirmed by the results of Mössbauer spectroscopy.
Numerical study of the small scale structures in Boussinesq convection
NASA Technical Reports Server (NTRS)
Weinan, E.; Shu, Chi-Wang
1992-01-01
Two-dimensional Boussinesq convection is studied numerically using two different methods: a filtered pseudospectral method and a high order accurate Essentially Nonoscillatory (ENO) scheme. The issue whether finite time singularity occurs for initially smooth flows is investigated. The numerical results suggest that the collapse of the bubble cap is unlikely to occur in resolved calculations. The strain rate corresponding to the intensification of the density gradient across the front saturates at the bubble cap. We also found that the cascade of energy to small scales is dominated by the formulation of thin and sharp fronts across which density jumps.
Formulation of numerical procedures for dynamic analysis of spinning structures
NASA Technical Reports Server (NTRS)
Gupta, K. K.
1986-01-01
The paper presents the descriptions of recently developed numerical algorithms that prove to be useful for the solution of the free vibration problem of spinning structures. First, a generalized procedure for the computation of nodal centrifugal forces in a finite element owing to any specified spin rate is derived in detail. This is followed by a description of an improved eigenproblem solution procedure that proves to be economical for the free vibration analysis of spinning structures. Numerical results are also presented which indicate the efficacy of the currently developed procedures.
NASA Astrophysics Data System (ADS)
Anjali Devi, S. P.; Suriyakumar, P.
2013-09-01
The nonlinear, steady, mixed convective, two-dimensional laminar hydromagnetic boundary layer flow of copper-water and alumina-water nanofluids over an inclined flat plate with an angle of inclination α in the presence of uniform transverse magnetic field is investigated in this work. The governing nonlinear partial differential equations of the problem are transformed into nonlinear ordinary differential equations by utilizing suitable similarity transformations and the resulting nonlinear ordinary differential equations are solved numerically using MATLAB. Numerical results for dimensionless velocity and temperature of the nanofluid flows are obtained and computations for the various values of Magnetic interaction parameter, angle of inclination, volume fraction, Prandtl number and mixed convection parameter. The range of volume fraction of nanofluids and the angle of inclination under study are as follows: 0.00 ≤ φ ≤ 0.10 and 0° ≤ α ≤ 60°. The results are displayed graphically to show the interesting aspects of the nanofluids.
Mechanical characterization of brain tissue in simple shear at dynamic strain rates.
Rashid, Badar; Destrade, Michel; Gilchrist, Michael D
2013-12-01
During severe impact conditions, brain tissue experiences a rapid and complex deformation, which can be seen as a mixture of compression, tension and shear. Diffuse axonal injury (DAI) occurs in animals and humans when both the strains and strain rates exceed 10% and 10/s, respectively. Knowing the mechanical properties of brain tissue in shear at these strains and strain rates is thus of particular importance, as they can be used in finite element simulations to predict the occurrence of brain injuries under different impact conditions. However, very few studies in the literature provide this information. In this research, an experimental setup was developed to perform simple shear tests on porcine brain tissue at strain rates ≤120/s. The maximum measured shear stress at strain rates of 30, 60, 90 and 120/s was 1.15±0.25kPa, 1.34±0.19kPa, 2.19±0.225kPa and 2.52±0.27kPa, (mean±SD), respectively at the maximum amount of shear, K=1. Good agreement of experimental, theoretical (Ogden and Mooney-Rivlin models) and numerical shear stresses was achieved (p=0.7866-0.9935). Specimen thickness effects (2.0-10.0mm thick specimens) were also analyzed numerically and we found that there is no significant difference (p=0.9954) in the shear stress magnitudes, indicating a homogeneous deformation of the specimens during simple shear tests. Stress relaxation tests in simple shear were also conducted at different strain magnitudes (10-60% strain) with the average rise time of 14ms. This allowed us to estimate elastic and viscoelastic parameters (initial shear modulus, μ=4942.0Pa, and Prony parameters: g1=0.520, g2=0.3057, τ1=0.0264s, and τ2=0.011s) that can be used in FE software to analyze the non-linear viscoelastic behavior of brain tissue. This study provides new insight into the behavior in finite shear of brain tissue under dynamic impact conditions, which will assist in developing effective brain injury criteria and adopting efficient countermeasures against
Technology Transfer Automated Retrieval System (TEKTRAN)
A field experiment was conducted at the Arkansas Valley Research Center (AVRC) in 2005 to test the effects of irrigation type and scheduling and fertilizer rate on corn yield and soil salinity. Four N (0, 60, 120, and 180 lb N/acre) and four manure (0, 10, 20, and 30 t/acre) application rates were ...
Numerical study of homogeneous nanodroplet growth.
Quang, Tran Si Bui; Leong, Fong Yew; Mirsaidov, Utkur M
2015-01-15
We investigate the axisymmetric homogeneous growth of 10-100 nm water nanodroplets on a substrate surface. The main mechanism of droplet growth is attributed to the accumulation of laterally diffusing water monomers, formed by the absorption of water vapour in the environment onto the substrate. Under assumptions of quasi-steady thermodynamic equilibrium, the nanodroplet evolves according to the augmented Young-Laplace equation. Using continuum theory, we model the dynamics of nanodroplet growth including the coupled effects of disjoining pressure, contact angle and monomer diffusion. Our numerical results show that the initial droplet growth is dominated by monomer diffusion, and the steady late growth rate of droplet radius follows a power law of 1/3, which is unaffected by the substrate disjoining pressure. Instead, the disjoining pressure modifies the growth rate of the droplet height, which then follows a power law of 1/4. We demonstrate how spatial depletion of monomers could lead to a growth arrest of the nanodroplet, as observed experimentally. This work has further implications on the growth kinetics, transport and phase transition of liquids at the nanoscale. PMID:25454424
Numerical modeling of fluidic flow meters
NASA Astrophysics Data System (ADS)
Choudhury, D.; Patel, B. R.
1992-05-01
The transient fluid flow in fluidic flow meters has been modeled using Creare.x's flow modeling computer program FLUENT/BFC that solves the Navier-Stokes equations in general curvilinear coordinates. The numerical predictions of fluid flow in a fluidic flow meter have been compared with the available experimental results for a particular design, termed the PC-4 design. Overall flow structures such as main jet bending, and primary and secondary vortices predicted by FLUENT/BFC are in excellent agreement with flow visualization results. The oscillation frequencies of the PC-4 design have been predicted for a range of flow rates encompassing laminar and turbulent flow and the results are in good agreement with experiments. The details of the flow field predictions reveal that an important factor that determines the onset of oscillations in the fluidic flow meter is the feedback jet momentum relative to the main jet momentum. The insights provided by the analysis of the PC-4 fluidic flow meter design have led to an improved design. The improved design has sustained oscillations at lower flow rates compared with the PC-4 design and has a larger rangeability.
Saturn's North Polar Hexagon Numerical Modeling Results
NASA Astrophysics Data System (ADS)
Morales-Juberias, R.; Sayanagi, K. M.; Dowling, T. E.
2008-12-01
In 1980, Voyager images revealed the presence of a circumpolar wave at 78 degrees planetographic latitude in the northern hemisphere of Saturn. It was notable for having a dominant planetary wavenumber-six zonal mode, and for being stationary with respect to Saturn's Kilometric Radiation rotation rate measured by Voyager. The center of this hexagonal feature was coincident with the center of a sharp eastward jet with a peak speed of 100 ms-1 and it had a meridional width of about 4 degrees. This hexagonal feature was confirmed in 1991 through ground-based observations, and it was observed again in 2006 with the Cassini VIMS instrument. The latest observations highlight the longevity of the hexagon and suggest that it extends at least several bars deep into the atmosphere. We use the Explicit Planetary Isentropic Code (EPIC) to perform high-resolution numerical simulations of this unique feature. We show that a wavenumber six instability mode arises naturally from initially barotropic jets when seeded with weak random turbulence. We also discuss the properties of the wave activity on the background vertical stability, zonal wind, planetary rotation rate and adjacent vortices. Computational resources were provided by the New Mexico Computing Applications Center and New Mexico Institute of Mining and Technology and the Comparative Planetology Laboratory at the University of Louisville.
Numerical Propulsion System Simulation Architecture
NASA Technical Reports Server (NTRS)
Naiman, Cynthia G.
2004-01-01
The Numerical Propulsion System Simulation (NPSS) is a framework for performing analysis of complex systems. Because the NPSS was developed using the object-oriented paradigm, the resulting architecture is an extensible and flexible framework that is currently being used by a diverse set of participants in government, academia, and the aerospace industry. NPSS is being used by over 15 different institutions to support rockets, hypersonics, power and propulsion, fuel cells, ground based power, and aerospace. Full system-level simulations as well as subsystems may be modeled using NPSS. The NPSS architecture enables the coupling of analyses at various levels of detail, which is called numerical zooming. The middleware used to enable zooming and distributed simulations is the Common Object Request Broker Architecture (CORBA). The NPSS Developer's Kit offers tools for the developer to generate CORBA-based components and wrap codes. The Developer's Kit enables distributed multi-fidelity and multi-discipline simulations, preserves proprietary and legacy codes, and facilitates addition of customized codes. The platforms supported are PC, Linux, HP, Sun, and SGI.
Numerical tests of stochastic tomography
NASA Astrophysics Data System (ADS)
Ru-Shan, Wu; Xiao-Bi, Xie
1991-05-01
The method of stochastic tomography proposed by Wu is tested numerically. This method reconstructs the heterospectra (power spectra of heterogeneities) at all depths of a non-uniform random medium using measured joint transverse-angular coherence functions (JTACF) of transmission fluctuations on an array. The inversion method is based on a constrained least-squares inversion implemented via the singular value decomposition. The inversion is also applicable to reconstructions using transverse coherence functions (TCF) or angular coherence functions (ACF); these are merely special cases of JTACF. Through the analysis of sampling functions and singular values, and through numerical examples of reconstruction using theoretically generated coherence functions, we compare the resolution and robustness of reconstructions using TCF, ACF and JTACF. The JTACF can `focus' the coherence analysis at different depths and therefore has a better depth resolution than TCF and ACF. In addition, the JTACF contains much more information than the sum of TCF and ACF, and has much better noise resistance properties than TCF and ACF. Inversion of JTACF can give a reliable reconstruction of heterospectra at different depths even for data with 20% noise contamination. This demonstrates the feasibility of stochastic tomography using JTACF.
Suppressing the numerical Cherenkov radiation in the Yee numerical scheme
NASA Astrophysics Data System (ADS)
Nuter, Rachel; Tikhonchuk, Vladimir
2016-01-01
The next generation of laser facilities will routinely produce relativistic particle beams from the interaction of intense laser pulses with solids and/or gases. Their modeling with Particle-In-Cell (PIC) codes needs dispersion-free Maxwell solvers in order to properly describe the interaction of electromagnetic waves with relativistic particles. A particular attention is devoted to the suppression of the numerical Cherenkov instability, responsible for the noise generation. It occurs when the electromagnetic wave is artificially slowed down because of the finite mesh size, thus allowing for the high energy particles to propagate with super-luminous velocities. In the present paper, we show how a slight increase of the light velocity in the Maxwell's equations enables to suppress this instability while keeping a good overall precision of calculations.
Numerical modeling of chemical vapor deposition (CVD) in a horizontal reactor
NASA Technical Reports Server (NTRS)
Sheikholeslami, M. Z.; Jasinski, T.; Fretz, K. W.
1988-01-01
In the present numerical prediction of the deposition rate of silicon from silane in a CVD process, the conservation equations for mass, momentum, energy, and chemical species are solved on a staggered grid using the SIMPLE algorithm, while the rate of chemical reactions in the gas phase and on the susceptor surface is obtained from an Arrhenius rate equation. Predicted deposition rates as a function of position along the susceptor with and without the gas phase chemical reaction are compared with the available experimental and numerical data; agreement is excellent except at the leading edge of the susceptor, where the deposition rate is overpredicted.
Kramers' rate for systems with multiplicative noise
NASA Astrophysics Data System (ADS)
Rosas, Alexandre; Pinto, Italo'Ivo Lima Dias; Lindenberg, Katja
2016-07-01
Kramers' rate for the passage of trajectories X (t ) over an energy barrier due to thermal or other fluctuations is usually associated with additive noise. We present a generalization of Kramers' rate for systems with multiplicative noise. We show that the expression commonly used in the literature for multiplicative noise is not correct, and we present results of numerical integrations of the Langevin equation for d X (t )/d t evolving in a quartic bistable potential which corroborate our claim.
Kramers' rate for systems with multiplicative noise.
Rosas, Alexandre; Pinto, Italo'Ivo Lima Dias; Lindenberg, Katja
2016-07-01
Kramers' rate for the passage of trajectories X(t) over an energy barrier due to thermal or other fluctuations is usually associated with additive noise. We present a generalization of Kramers' rate for systems with multiplicative noise. We show that the expression commonly used in the literature for multiplicative noise is not correct, and we present results of numerical integrations of the Langevin equation for dX(t)/dt evolving in a quartic bistable potential which corroborate our claim. PMID:27575071
Nucleation rate in monotectic alloys
NASA Astrophysics Data System (ADS)
Falk, F.
Cooling a melt of a monotectic system into the miscibility gap results in nucleation of fluid droplets in a fluid matrix prior to solidification. For homogeneous nucleation the temperature dependence of the nucleation rate is calculated. As material parameters the chemical potential of the species involved, the diffusion constant of the fluid, and the surface tension between adjacent phases are important. Since their temperature dependence is not well known from experiments, different theoretical models are used and their influence is discussed. The surface tension turns out to be the most crucial parameter in determining the nucleation rate. For AlIn numerical results are presented. In this system the undercooling with respect to homogeneous nucleation increases from zero at the critical point to 100 K at a composition near the monotectic point.
Numerical Modeling of Shear Bands and Dynamic Fracture in Metals
NASA Astrophysics Data System (ADS)
McAuliffe, Colin James
Understanding the failure of metals at high strain rate is of utmost importance in the design of a broad range of engineering systems. Numerical methods offer the ability to analyze such complex physics and aid the design of structural systems. The objective of this research will be to develop reliable finite element models for high strain rate failure modelling, incorporating shear bands and fracture. Shear band modelling is explored first, and the subsequent developments are extended to incorporate fracture. Mesh sensitivity, the spurious dependence of failure on the discretization, is a well known hurdle in achieving reliable numerical results for shear bands and fracture, or any other strain softening model. Mesh sensitivity is overcome by regularization, and while details of regularization techniques may differ, all are similar in that a length scale is introduced which serves as a localization limiter. This dissertation contains two main contributions, the first of which presents several developments in shear band modeling. The importance of using a monolithic nonlinear solver in combination with a PDE model accounting for thermal diffusion is demonstrated. In contrast, excluding one or both of these components leads to unreliable numerical results. The Pian-Sumihara stress interpolants are also employed in small and finite deformation and shown to significantly improve the computational cost of shear band modelling. This is partly due to the fact that fewer unknowns than an irreducible discretization result from the same mesh, and more significantly, the fact that convergence of numerical results upon mesh refinement is improved drastically. This means coarser meshes are adequate to resolve shear bands, alleviating some of the computational cost of numerical modelling, which are notoriously significant. Since extremely large deformations are present during shear banding, a mesh to mesh transfer algorithm is presented for the Pian Sumihara element and used as
Seafloor weathering buffering climate: numerical experiments
NASA Astrophysics Data System (ADS)
Farahat, N. X.; Archer, D. E.; Abbot, D. S.
2013-12-01
Continental silicate weathering is widely held to consume atmospheric CO2 at a rate controlled in part by temperature, resulting in a climate-weathering feedback [Walker et al., 1981]. It has been suggested that weathering of oceanic crust of warm mid-ocean ridge flanks also has a CO2 uptake rate that is controlled by climate [Sleep and Zahnle, 2001; Brady and Gislason, 1997]. Although this effect might not be significant on present-day Earth [Caldeira, 1995], seafloor weathering may be more pronounced during snowball states [Le Hir et al., 2008], during the Archean when seafloor spreading rates were faster [Sleep and Zahnle, 2001], and on waterworld planets [Abbot et al., 2012]. Previous studies of seafloor weathering have made significant contributions using qualitative, generally one-box, models, and the logical next step is to extend this work using a spatially resolved model. For example, experiments demonstrate that seafloor weathering reactions are temperature dependent, but it is not clear whether the deep ocean temperature affects the temperature at which the reactions occur, or if instead this temperature is set only by geothermal processes. Our goal is to develop a 2-D numerical model that can simulate hydrothermal circulation and resulting alteration of oceanic basalts, and can therefore address such questions. A model of diffusive and convective heat transfer in fluid-saturated porous media simulates hydrothermal circulation through porous oceanic basalt. Unsteady natural convection is solved for using a Darcy model of porous media flow that has been extensively benchmarked. Background hydrothermal circulation is coupled to mineral reaction kinetics of basaltic alteration and hydrothermal mineral precipitation. In order to quantify seafloor weathering as a climate-weathering feedback process, this model focuses on hydrothermal reactions that influence carbon uptake as well as ocean alkalinity: silicate rock dissolution, calcium and magnesium leaching
Revealing Educationally Critical Aspects of Rate
ERIC Educational Resources Information Center
Herbert, Sandra; Pierce, Robyn
2012-01-01
Rate (of change) is an important but complicated mathematical concept describing a ratio comparing two different numeric, measurable quantities. Research referring to students' difficulties with this concept spans more than 20 years. It suggests that problems experienced by some calculus students are likely a result of pre-existing limited or…
Numerical experiments in homogeneous turbulence
NASA Technical Reports Server (NTRS)
Rogallo, R. S.
1981-01-01
The direct simulation methods developed by Orszag and Patternson (1972) for isotropic turbulence were extended to homogeneous turbulence in an incompressible fluid subjected to uniform deformation or rotation. The results of simulations for irrotational strain (plane and axisymmetric), shear, rotation, and relaxation toward isotropy following axisymmetric strain are compared with linear theory and experimental data. Emphasis is placed on the shear flow because of its importance and because of the availability of accurate and detailed experimental data. The computed results are used to assess the accuracy of two popular models used in the closure of the Reynolds-stress equations. Data from a variety of the computed fields and the details of the numerical methods used in the simulation are also presented.
Numerical propagator through PIAA optics
NASA Astrophysics Data System (ADS)
Pueyo, Laurent; Shaklan, Stuart; Give'On, Amir; Krist, John
2009-08-01
In this communication we address two outstanding issues pertaining the modeling of PIAA coronagraphs, accurate numerical propagation of edge effects and fast propagation of mid spatial frequencies for wavefront control. In order to solve them, we first derive a quadratic approximation of the Huygens wavelets that allows us to develop an angular spectrum propagator for pupil remapping. Using this result we introduce an independent method to verify the ultimate contrast floor, due to edge propagation effects, of PIAA units currently being tested in various testbeds. We then delve into the details of a novel fast algorithm, based on the recognition that angular spectrum computations with a pre-apodised system are computationally light. When used for the propagation of mid spatial frequencies, such a fast propagator will ultimately allow us to develop robust wavefront control algorithms with DMs located before the pupil remapping mirrors.
Numerical classification of coding sequences
NASA Technical Reports Server (NTRS)
Collins, D. W.; Liu, C. C.; Jukes, T. H.
1992-01-01
DNA sequences coding for protein may be represented by counts of nucleotides or codons. A complete reading frame may be abbreviated by its base count, e.g. A76C158G121T74, or with the corresponding codon table, e.g. (AAA)0(AAC)1(AAG)9 ... (TTT)0. We propose that these numerical designations be used to augment current methods of sequence annotation. Because base counts and codon tables do not require revision as knowledge of function evolves, they are well-suited to act as cross-references, for example to identify redundant GenBank entries. These descriptors may be compared, in place of DNA sequences, to extract homologous genes from large databases. This approach permits rapid searching with good selectivity.
Numerical calculations of flow fields
NASA Technical Reports Server (NTRS)
Anderson, D. M.; Vogel, J. M.
1972-01-01
The solutions to the equations of motion for inviscid fluid flow around a pointed elliptic cone at incidence are presented. The numerical method used, MacCormack's second order preferential predictor-corrector finite difference approximation, is applied to the fluid flow equations derived in conservation-law form. The entropy boundary condition, hitherto unused for elliptic cone problems, is investigated and compared to reflection boundary condition solutions. The stagnation streamline movement of the inclined elliptic cone is noted and surface pressure coefficients are plotted. Also presented are solutions for an elliptic cone and a circular cone at zero incidence and a circular cone at a small angle of attack. Comparisons are made between these present solutions and previously published theory.
Numerical studies of frontal dynamics
NASA Technical Reports Server (NTRS)
Keyser, Daniel
1986-01-01
Efforts concentrated on the development of a two dimensional primitive equation (PE) model of frontogenesis that simultaneously incorporates the frontagenetical mechanisms of confluence and horizontal shear. Applying this model to study the effects of upper level frontogenesis, it appeared to be dominated by tilting effects associated with cross front variation of vertical motion, in which subsidence is maximized within and to the warm side of the frontal zone. Results suggest that aspects characteristic of three-dimensional baroclinic waves may be abstracted to a significant extent in a two dimensional framework. They also show that upper-level frontogenesis and tropopause folding can occur in the absence of three-dimensional curvature effects, commonly believed to be necessary for realistic upper-level frontogenesis. An implication of the dominant tilting effects is that they may have to be adequately resolved by numerical weather prediction models, thus requiring better horizontal and vertical resolution.
Comprehensive numerical modelling of tokamaks
Cohen, R.H.; Cohen, B.I.; Dubois, P.F.
1991-01-03
We outline a plan for the development of a comprehensive numerical model of tokamaks. The model would consist of a suite of independent, communicating packages describing the various aspects of tokamak performance (core and edge transport coefficients and profiles, heating, fueling, magnetic configuration, etc.) as well as extensive diagnostics. These codes, which may run on different computers, would be flexibly linked by a user-friendly shell which would allow run-time specification of packages and generation of pre- and post-processing functions, including workstation-based visualization of output. One package in particular, the calculation of core transport coefficients via gyrokinetic particle simulation, will become practical on the scale required for comprehensive modelling only with the advent of teraFLOP computers. Incremental effort at LLNL would be focused on gyrokinetic simulation and development of the shell.
Numerical Cosmic-Ray Hydrodynamics
NASA Astrophysics Data System (ADS)
Miniati, F.
2009-04-01
We present a numerical method for integrating the equations describing a system made of a fluid and cosmic-rays. We work out the modified characteristic equations that include the CR dynamical effects in smooth flows. We model the energy exchange between cosmic-rays and the fluid, due to diffusive processes in configuration and momentum space, with a flux conserving method. For a specified shock acceleration efficiency as a function of the upstream conditions and shock Mach number, we modify the Riemann solver to take into account the cosmic-ray mediation at shocks without resolving the cosmic-ray induced substructure. A self-consistent time-dependent shock solution is obtained by using our modified solver with Glimm's method. Godunov's method is applied in smooth parts of the flow.
Dynamical Casimir effect in superconducting circuits: A numerical approach
NASA Astrophysics Data System (ADS)
Lombardo, F. C.; Mazzitelli, F. D.; Soba, A.; Villar, P. I.
2016-03-01
We present a numerical analysis of the particle creation for a quantum field in the presence of time-dependent boundary conditions. Having in mind recent experiments involving superconducting circuits, we consider their description in terms of a scalar field in a one-dimensional cavity satisfying generalized boundary conditions that involve a time-dependent linear combination of the field and its spatial and time derivatives. We evaluate numerically the Bogoliubov transformation between i n - and o u t -states and find that the rate of particle production strongly depends on whether the spectrum of the unperturbed cavity is equidistant or not, and also on the amplitude of the temporal oscillations of the boundary conditions. We provide analytic justifications for the different regimes found numerically.
Numerical Simulations of the Geodynamo and Scaling Laws
NASA Astrophysics Data System (ADS)
Oruba, L.; Dormy, E.
2013-12-01
State of the art numerical models of the Geodynamo are still performed in a parameter regime extremely remote from the values relevant to the physics of the Earth core. In order to establish a connection between dynamo modeling and the geophysical motivation, it is necessary to use scaling laws. Such laws establish the dependency of essential quantities (such as the magnetic field strength) on measured or controlled quantities. They allow for a direct confrontation of advanced models with geophysical constraints. We will present a detailed analysis of scaling laws based on a wide database of 185 direct numerical simulations (courtesy of U. Christensen) and test various existing scaling laws. Our main concern is to stress the risks of a direct numerical fit free from physical insight. We show that different a priori hypothesis can yield contradictory dependences, in particular concerning the dependence of the magnetic field strength on the rotation rate as well as on the viscosity.
NUMERICAL SIMULATION OF NATURAL GAS-SWIRL BURNER
Ala Qubbaj
2005-03-01
A numerical simulation of a turbulent natural gas jet diffusion flame at a Reynolds number of 9000 in a swirling air stream is presented. The numerical computations were carried out using the commercially available software package CFDRC. The instantaneous chemistry model was used as the reaction model. The thermal, composition, flow (velocity), as well as stream function fields for both the baseline and air-swirling flames were numerically simulated in the near-burner region, where most of the mixing and reactions occur. The results were useful to interpret the effects of swirl in enhancing the mixing rates in the combustion zone as well as in stabilizing the flame. The results showed the generation of two recirculating regimes induced by the swirling air stream, which account for such effects. The present investigation will be used as a benchmark study of swirl flow combustion analysis as a step in developing an enhanced swirl-cascade burner technology.
Analysis of single ring infiltrometer test by direct numerical modeling
NASA Astrophysics Data System (ADS)
Réfloch, Aurore; Oxarango, Laurent; Rossier, Yvan; Gaudet, Jean Paul
2016-04-01
The well field of the Lyon metropolitan area provides drinking water to approximately 1,300,000 inhabitants. It is equipped with 12 infiltration basins. These basins have two main goals: sustaining the water table in times of peak demand for water, and preventing a possible contamination from the Rhône river by inverting groundwater flow direction. The water infiltration under the basins is thus crucial for the overall hydrogeologic behavior of the site. In order to characterize this phenomenon, a set of infiltrometer tests were performed to estimate the soil hydraulic properties. The soil is a coarse alluvial deposits. In order to deal with its sparse granulometric curve, a large single ring infiltrometer (1 meter in diameter) was used. A constant hydraulic head (=0.07 m) was imposed during the test. Two kinds of data are recorded: the amount of water infiltrated over time and the extension of the moisture stain around the ring. The main hydraulic properties are estimated using Richard's equation in a 2D axi-symmetric configuration. Simulations are performed using a finite element commercial software package (Comsol Multiphysics 5.1). According to simplified numerical models, an average homogeneous saturated permeability of the alluvial deposits is estimated at 5.0 10-6 m.s-1. However, such a simple model is not able to represent accurately the moisture stain at the soil surface. More complex models introduce anisotropy of permeability in the alluvium layer, with mono or bi-layer domain. In these cases, experimental and modeling results are consistent, both for the amount of water infiltrated over time and the extension of the moisture stain around the ring. The hydraulic anisotropy in the soil could be due to the stratified nature of alluvial deposits and to soil compaction during the construction of infiltration basins. Keywords: Single ring infiltrometer test, artificial aquifer recharge, numerical modeling.
Numerical simulation of an axial blood pump.
Chua, Leok Poh; Su, Boyang; Lim, Tau Meng; Zhou, Tongming
2007-07-01
The axial blood pump with a magnetically suspended impeller is superior to other artificial blood pumps because of its small size. In this article, the distributions of velocity, path line, pressure, and shear stress in the straightener, the rotor, and the diffuser of the axial blood pump, as well as the gap zone were obtained using the commercial software, Fluent (version 6.2). The main focus was on the flow field of the blood pump. The numerical results showed that the axial blood pump could produce 5.14 L/min of blood at 100 mm Hg through the outlet when rotating at 11,000 rpm. However, there was a leakage flow of 1.06 L/min in the gap between the rotor cylinder and the pump housing, and thus the overall flow rate the impeller could generate was 6.2 L/min. The numerical results showed that 75% of the scalar shear stresses (SSs) were less than 250 Pa, and 10% were higher than 500 Pa within the whole pump. The high SS region appeared around the blade tip where a large variation of velocity direction and magnitude was found, which might be due to the steep angle variation at the blade tip. Because the exposure time of the blood cell at the high SS region within the pump was relatively short, it might not cause serious damage to the blood cells, but the improvement of blade profile should be considered in the future design of the axial pump. PMID:17584481
Teaching Mathematics with Technology: Numerical Relationships.
ERIC Educational Resources Information Center
Bright, George W.
1989-01-01
Developing numerical relationships with calculators is emphasized. Calculators furnish some needed support for students as they investigate the value of fractions as the numerators or denominators change. An example with Logo programing for computers is also included. (MNS)
Numerical Simulation of Nanostructure Growth
NASA Technical Reports Server (NTRS)
Hwang, Helen H.; Bose, Deepak; Govindan, T. R.; Meyyappan, M.
2004-01-01
Nanoscale structures, such as nanowires and carbon nanotubes (CNTs), are often grown in gaseous or plasma environments. Successful growth of these structures is defined by achieving a specified crystallinity or chirality, size or diameter, alignment, etc., which in turn depend on gas mixture ratios. pressure, flow rate, substrate temperature, and other operating conditions. To date, there has not been a rigorous growth model that addresses the specific concerns of crystalline nanowire growth, while demonstrating the correct trends of the processing conditions on growth rates. Most crystal growth models are based on the Burton, Cabrera, and Frank (BCF) method, where adatoms are incorporated into a growing crystal at surface steps or spirals. When the supersaturation of the vapor is high, islands nucleate to form steps, and these steps subsequently spread (grow). The overall bulk growth rate is determined by solving for the evolving motion of the steps. Our approach is to use a phase field model to simulate the growth of finite sized nanowire crystals, linking the free energy equation with the diffusion equation of the adatoms. The phase field method solves for an order parameter that defines the evolving steps in a concentration field. This eliminates the need for explicit front tracking/location, or complicated shadowing routines, both of which can be computationally expensive, particularly in higher dimensions. We will present results demonstrating the effect of process conditions, such as substrate temperature, vapor supersaturation, etc. on the evolving morphologies and overall growth rates of the nanostructures.
Reconnection rates of magnetic fields
Park, W.; Monticello, D.A.; White, R.B.
1983-05-01
The Sweet-Parker and Petschek scalings of magnetic reconnection rate are modified to include the effect of the viscosity. The modified scalings show that the viscous effect can be important in high-..beta.. plasmas. The theoretical reconnection scalings are compared with numerical simulation results in a tokamak geometry for three different cases: a forced reconnection driven by external coils, the nonlinear m = 1 resistive internal kink, and the nonlinear m = 2 tearing mode. In the first two cases, the numerical reconnection rate agrees well with the modified Sweet-Parker scaling, when the viscosity is sufficiently large. When the viscosity is negligible, a steady state which was assumed in the derivation of the reconnection scalings is not reached and the current sheet in the reconnection layer either remains stable through sloshing motions of the plasma or breaks up to higher m modes. When the current sheet remains stable, a rough comparison with the Sweet-Parker scaling is obtained. In the nonlinear m = 2 tearing mode case where the instability is purely resistive, the reconnection occurs on the slower dissipation time scale (Psi/sub s/ approx. eta). In addition, experimental data of the nonlinear m = 1 resistive internal kink in tokamak discharges are analyzed and are found to give reasonable agreement with the modified Sweet-Parker scaling.
ERIC Educational Resources Information Center
Fried, John B.; Kovacs, Gabor J.
1982-01-01
Defining a numeric database as a computer-readable collection of data predominantly numeric in nature, this article reviews techniques and technologies having a positive influence on the growth of numeric databases, such as videotex, mini- and microcomputers, artificial intelligence, improved software, telecommunications, and office automation.…
Descriptive Report on Numerically Controlled Equipment.
ERIC Educational Resources Information Center
Campbell, Clifton P.
This report presents descriptive information on numerically controlled operational devises. The information is designed for the education and training community, manufacturers, supervisors, machine operators, and others who do not have an extensive technical background in numerical control. In the first of three chapters, numerical control…
The Language of Numerical Control: A Glossary.
ERIC Educational Resources Information Center
Campbell, Clifton Paul
Numerical control, a technique for automatically controlling equipment, is a system in which machine actions are determined by symbolic data recorded on a suitable media. This glossary of standardized nomenclature for numerical control defines and describes some 286 technical words and terms. Numerous entries are defined and described as they…
Interagency mechanical operations group numerical systems group
1997-09-01
This report consists of the minutes of the May 20-21, 1971 meeting of the Interagency Mechanical Operations Group (IMOG) Numerical Systems Group. This group looks at issues related to numerical control in the machining industry. Items discussed related to the use of CAD and CAM, EIA standards, data links, and numerical control.
Numerical homogenization on approach for stokesian suspensions.
Haines, B. M.; Berlyand, L. V.; Karpeev, D. A.
2012-01-20
In this technical report we investigate efficient methods for numerical simulation of active suspensions. The prototypical system is a suspension of swimming bacteria in a Newtonian fluid. Rheological and other macroscopic properties of such suspensions can differ dramatically from the same properties of the suspending fluid alone or of suspensions of similar but inactive particles. Elongated bacteria, such as E. coli or B. subtilis, swim along their principal axis, propelling themselves with the help of flagella, attached at the anterior of the organism and pushing it forward in the manner of a propeller. They interact hydrodynamically with the surrounding fluid and, because of their asymmetrical shape, have the propensity to align with the local flow. This, along with the dipolar nature of bacteria (the two forces a bacterium exerts on a fluid - one due to self-propulsion and the other opposing drag - have equal magnitude and point in opposite directions), causes nearby bacteria to tend to align, resulting in a intermittent local ordering on the mesoscopic scale, which is between the microscopic scale of an individual bacterium and the macroscopic scale of the suspension (e.g., its container). The local ordering is sometimes called a collective mode or collective swimming. Thanks to self-propulsion, collective modes inject momentum into the fluid in a coherent way. This enhances the local strain rate without changing the macroscopic stress applied at the boundary of the container. The macroscopic effective viscosity of the suspension is defined roughly as the ratio of the applied stress to the bulk strain rate. If local alignment and therefore local strain-rate enhancement, are significant, the effective viscosity can be appreciably lower than that of the corresponding passive suspension or even of the surrounding fluid alone. Indeed, a sevenfold decrease in the effective viscosity was observed in experiments with B. subtilis. More generally, local collective
Uncertainty evaluation in numerical modeling of complex devices
NASA Astrophysics Data System (ADS)
Cheng, X.; Monebhurrun, V.
2014-10-01
Numerical simulation is an efficient tool for exploring and understanding the physics of complex devices, e.g. mobile phones. For meaningful results, it is important to evaluate the uncertainty of the numerical simulation. Uncertainty quantification in specific absorption rate (SAR) calculation using a full computer-aided design (CAD) mobile phone model is a challenging task. Since a typical SAR numerical simulation is computationally expensive, the traditional Monte Carlo (MC) simulation method proves inadequate. The unscented transformation (UT) is an alternative and numerically efficient method herein investigated to evaluate the uncertainty in the SAR calculation using the realistic models of two commercially available mobile phones. The electromagnetic simulation process is modeled as a nonlinear mapping with the uncertainty in the inputs e.g. the relative permittivity values of the mobile phone material properties, inducing an uncertainty in the output, e.g. the peak spatial-average SAR value.The numerical simulation results demonstrate that UT may be a potential candidate for the uncertainty quantification in SAR calculations since only a few simulations are necessary to obtain results similar to those obtained after hundreds or thousands of MC simulations.
Design and numerical simulation of an optofluidic pressure sensor.
Ebnali-Heidari, Majid; Mansouri, Morteza; Mokhtarian, Saeed; Moravvej-Farshi, Mohammed Kazem
2012-06-01
We present a numerical design procedure for an all-optical compact sensor by means of integrating the optofluidic switch polymer interferometers to measure the microfluidic air pressure and flow rate. The design is based on a flexible air gap optical cavity that can generate an interference pattern when illuminated by a monochromatic light. The optical interference pattern directly depends on the pressure. In our numerical simulations, we take the effects of fluid flow rate, solid deformation, and the light interference into account. We use the beam propagation method for simulating the optics and the finite element method for simulating the mechanics. The significance of the proposed sensor lies with its low power consumption, compactness, low cost, and short length. This sensor can operate under pressure range of 0-60±6% Pa at a constant temperature of 20 °C. PMID:22695574
Numerical Investigation of Flow in a Centrifugal Compressor
NASA Astrophysics Data System (ADS)
Grishin, Yu. A.; Bakulin, V. N.
2015-09-01
With the use of the domestic software suite of computational hydrodynamics Flow Vision based on application of the method of control volumes, numerical simulation of air composition and delivery by a centrifugal compressor employed for supercharging a piston engine has been carried out. The head-flow characteristics of the compressor, as well as the 3D fields of flow velocity and pressure distributions in the elements of the compressor flow passage, including the interblade channels of the impeller, have been obtained for various regimes. In the regimes of diminished air flow rate, surging phenomena are identified, characterized by a return flow. The application of the technique of numerical experiment will make it possible from here on to carry out design optimization of the compressor flow passage profile and thus to improve its basic characteristics — the degree of pressure increase, compressed air flow rate, and the efficiency — as well as to reduce the costs of the development and production of compressors.
Numerical method for shear bands in ductile metal with inclusions
Plohr, Jee Yeon N; Plohr, Bradley J
2010-01-01
A numerical method for mesoscale simulation of high strain-rate loading of ductile metal containing inclusions is described. Because of small-scale inhomogeneities, such a composite material is prone to localized shear deformation (adiabatic shear bands). The modeling framework is the Generalized Method of Cells of Paley and Aboudi [Mech. Materials, vol. 14, pp. /27-139, 1992], which ensures that the micromechanical response of the material is reflected in the behavior of the composite at the mesoscale. To calculate the effective plastic strain rate when shear bands are present, the analytic and numerical analysis of shear bands by Glimm, Plohr, and Sharp [Mech. Materials, vol. 24, pp. 31-41, 1996] is adapted and extended.
Application of Numerical Optimization to Aluminum Alloy Wheel Casting
NASA Astrophysics Data System (ADS)
Duan, J.; Reilly, C.; Maijer, D. M.; Cockcroft, S. L.; Phillion, A. B.
2015-06-01
A method of numerically optimizing the cooling conditions in a low- pressure die casting process from the standpoint of maintaining good directional solidification, high cooling rates and reduced cycle times has been developed for the production of aluminumalloy wheels. The method focuses on the optimization of cooling channel timing and utilizes an open source numerical optimization algorithm coupled with an experimentally validated, ABAQUS-based, heat transfer model of the casting process. Key features of the method include: 1) carefully designed constraint functions to ensure directional solidification along the centerlineof the wheel; and 2) carefully formulated objective functions to maximize cooling rate. The method has been implemented on a prototype production die and the results have been tested with plant trial test.
Numerical Studies of Topological phases
NASA Astrophysics Data System (ADS)
Geraedts, Scott
The topological phases of matter have been a major part of condensed matter physics research since the discovery of the quantum Hall effect in the 1980s. Recently, much of this research has focused on the study of systems of free fermions, such as the integer quantum Hall effect, quantum spin Hall effect, and topological insulator. Though these free fermion systems can play host to a variety of interesting phenomena, the physics of interacting topological phases is even richer. Unfortunately, there is a shortage of theoretical tools that can be used to approach interacting problems. In this thesis I will discuss progress in using two different numerical techniques to study topological phases. Recently much research in topological phases has focused on phases made up of bosons. Unlike fermions, free bosons form a condensate and so interactions are vital if the bosons are to realize a topological phase. Since these phases are difficult to study, much of our understanding comes from exactly solvable models, such as Kitaev's toric code, as well as Levin-Wen and Walker-Wang models. We may want to study systems for which such exactly solvable models are not available. In this thesis I present a series of models which are not solvable exactly, but which can be studied in sign-free Monte Carlo simulations. The models work by binding charges to point topological defects. They can be used to realize bosonic interacting versions of the quantum Hall effect in 2D and topological insulator in 3D. Effective field theories of ''integer'' (non-fractionalized) versions of these phases were available in the literature, but our models also allow for the construction of fractional phases. We can measure a number of properties of the bulk and surface of these phases. Few interacting topological phases have been realized experimentally, but there is one very important exception: the fractional quantum Hall effect (FQHE). Though the fractional quantum Hall effect we discovered over 30
NASA Astrophysics Data System (ADS)
Chesnokov, Evgeni N.; Krasnoperov, Lev N.
2007-04-01
conclusion is particularly important for nucleation from supersaturated water vapor, since these processes for water molecules at and below the atmospheric pressure are in the low pressure limit, and the rate constants can be several orders of magnitude lower than the gas kinetic. In addition, the impact of the thermodynamic inconsistency of the previously developed partially reversible kinetic numerical models was assessed. At typical experimental conditions for water nucleation, S0=10 and Θ =10 (T=250K), the error in the particle nucleation rate introduced by the thermodynamic inconsistency exceeds one order of magnitude.
Numerical modelling of the solidification of ductile iron
NASA Astrophysics Data System (ADS)
Liu, J.; Elliott, R.
1998-01-01
Numerical calculations are presented describing the solidification of a ductile iron based on the Stefanescu macroscopic heat transfer-microscopic solidification kinetic model but using a different kinetic model than that used by Stefanescu. The results show that the kinetic model used influences the recalescence behaviour predicted by the modelling. Cooling curves calculated with the present model show reasonable agreement with experimentally measured cooling curves for four different cooling rates.
Numerical modeling of injection experiments at The Geysers
Pruess, Karsten; Enedy, Steve
1993-01-28
Data from injection experiments in the southeast Geysers are presented that show strong interference (both negative and positive) with a neighboring production well. Conceptual and numerical models are developed that explain the negative interference (decline of production rate) in terms of heat transfer limitations and water-vapor relative permeability effects. Recovery and overrecovery following injection shut-in are attributed to boiling of injected fluid, with heat of vaporization provided by the reservoir rocks.
Numerical analysis of a microwave torch with axial gas injection
Gritsinin, S. I.; Davydov, A. M.; Kossyi, I. A.; Kulumbaev, E. B.; Lelevkin, V. M.
2013-07-15
The characteristics of a microwave discharge in an argon jet injected axially into a coaxial channel with a shortened inner electrode are numerically analyzed using a self-consistent equilibrium gas-dynamic model. The specific features of the excitation and maintenance of the microwave discharge are determined, and the dependences of the discharge characteristics on the supplied electromagnetic power and gas flow rate are obtained. The calculated results are compared with experimental data.
Boltzmann Fluctuations in Numerical Simulations of Nonequilibrium Lattice Threshold Systems
Rundle, J.B.; Klein, W.; Gross, S.; Turcotte, D.L.
1995-08-21
Nonequilibrium threshold systems such as slider blocks are now used to model a variety of dynamical systems, including earthquake faults, driven neural networks, and sliding charge density waves. We show that for general mean field models driven at low rates fluctuations in the internal energy field are characterized by Boltzmann statistics. Numerical simulations confirm this prediction. Our results indicate that mean field models can be effectively treated as equilibrium systems.
Numerical modeling of injection experiments at The Geysers
Pruess, K. ); Enedy, S. )
1993-01-01
Data from injection experiments in the southeast Geysers are presented that show strong interference (both negative and positive) with a neighboring production well. Conceptual and numerical models are developed that explain the negative interference (decline of production rate) in terms of heat transfer limitations and water-vapor relative permeability effects. Recovery and over-recovery following injection shut-in are attributed to boiling of injected fluid, with heat of vaporization provided by the reservoir rocks.
Recent deformation rates on Venus
NASA Astrophysics Data System (ADS)
Grimm, Robert E.
1994-11-01
Constraints on the recent geological evolution of Venus may be provided by quantitative estimates of the rates of the principal resurfacing processes, volcanism and tectonism. This paper focuses on the latter, using impact craters as strain indicators. The total postimpact tectonic strain lies in the range 0.5-6.5%, which defines a recent mean strain rate of 10-18-10-17/s when divided by the mean surface age. Interpretation of the cratering record as one of pure production requires a decline in resurfacing rates at about 500 Ma (catastrophic resurfacing model). If distributed tectonic resurfacing contributed strongly before that time, as suggested by the widespread occurrence of tessera as inliers, the mean global strain rate must have been at least approximately 10-15/s, which is also typical of terrestrial active margins. Numerical calculations of the response of the lithosphere to inferred mantle convective forces were performed to test the hypothesis that a decrease in surface strain rate by at least two orders of magnitude could be caused by a steady decline in heat flow over the last billion years. Parameterized convection models predict that the mean global thermal gradient decreases by only about 5 K/km over this time; even with the exponential dependence of viscosity upon temperature, the surface strain rate drops by little more than one order of magnitude. Strongly unsteady cooling and very low thermal gradients today are necessary to satisfy the catastrophic model. An alternative, uniformitarian resurfacing hypothesis holds that Venus is resurfaced in quasi-random 'patches' several hundred kilometers in size that occur in response to changing mantle convection patterns.
Numerical Modeling of Nanoelectronic Devices
NASA Technical Reports Server (NTRS)
Klimeck, Gerhard; Oyafuso, Fabiano; Bowen, R. Chris; Boykin, Timothy
2003-01-01
Nanoelectronic Modeling 3-D (NEMO 3-D) is a computer program for numerical modeling of the electronic structure properties of a semiconductor device that is embodied in a crystal containing as many as 16 million atoms in an arbitrary configuration and that has overall dimensions of the order of tens of nanometers. The underlying mathematical model represents the quantummechanical behavior of the device resolved to the atomistic level of granularity. The system of electrons in the device is represented by a sparse Hamiltonian matrix that contains hundreds of millions of terms. NEMO 3-D solves the matrix equation on a Beowulf-class cluster computer, by use of a parallel-processing matrix vector multiplication algorithm coupled to a Lanczos and/or Rayleigh-Ritz algorithm that solves for eigenvalues. In a recent update of NEMO 3-D, a new strain treatment, parameterized for bulk material properties of GaAs and InAs, was developed for two tight-binding submodels. The utility of the NEMO 3-D was demonstrated in an atomistic analysis of the effects of disorder in alloys and, in particular, in bulk In(x)Ga(l-x)As and in In0.6Ga0.4As quantum dots.
Numerical Relativity meets Data Analysis
NASA Astrophysics Data System (ADS)
Schmidt, Patricia
2016-03-01
Gravitational waveforms (GW) from coalescing black hole binaries obtained by Numerical Relativity (NR) play a crucial role in the construction and validation of waveform models used as templates in GW matched filter searches and parameter estimation. In previous efforts, notably the NINJA and NINJA-2 collaborations, NR groups and data analysts worked closely together to use NR waveforms as mock GW signals to test the search and parameter estimation pipelines employed by LIGO. Recently, however, NR groups have been able to simulate hundreds of different binary black holes systems. It is desirable to directly use these waveforms in GW data analysis, for example to assess systematic errors in waveform models, to test general relativity or to appraise the limitations of aligned-spin searches among many other applications. In this talk, I will introduce recent developments that aim to fully integrate NR waveforms into the data analysis pipelines through a standardized interface. I will highlight a number of select applications for this new infrastructure.
Linking scales through numerical simulations
NASA Astrophysics Data System (ADS)
Lunati, I.
2012-12-01
Field-scale models of flow through porous media rely on a continuum description, which disregard pore-scale details and focus on macroscopic effects. As it is always the case, this choice is quite effective in reducing the number of model parameters, but this comes at expenses of an inherent loss of information and generality. Models based on Darcy's law, for instance, require spatial and temporal scale separation (locality and equilibrium). Although these conditions are generally met for single-phase flow, multiphase flow is far more complex: the interaction between nonlinearity of the interface behavior and the pore structure (disorder) creates a variety of flow regimes for which scale separation does not hold. In recent years, the increased computational power has led to a revival of pore-scale modeling in order to overcome this issue and describe the flow at the scale in which it physically occurs. If appropriate techniques are chosen, it is possible to use numerical simulations to complement experimental observations and advance our understanding of multiphase flow. By means of examples, we discuss the role played by these models in contributing to solve open problems and in devising alternatives to the standard description of flow through porous media.
Numerical Modeling of Ocean Circulation
NASA Astrophysics Data System (ADS)
Miller, Robert N.
2007-01-01
The modelling of ocean circulation is important not only for its own sake, but also in terms of the prediction of weather patterns and the effects of climate change. This book introduces the basic computational techniques necessary for all models of the ocean and atmosphere, and the conditions they must satisfy. It describes the workings of ocean models, the problems that must be solved in their construction, and how to evaluate computational results. Major emphasis is placed on examining ocean models critically, and determining what they do well and what they do poorly. Numerical analysis is introduced as needed, and exercises are included to illustrate major points. Developed from notes for a course taught in physical oceanography at the College of Oceanic and Atmospheric Sciences at Oregon State University, this book is ideal for graduate students of oceanography, geophysics, climatology and atmospheric science, and researchers in oceanography and atmospheric science. Features examples and critical examination of ocean modelling and results Demonstrates the strengths and weaknesses of different approaches Includes exercises to illustrate major points and supplement mathematical and physical details
Yahyaoui, N. E-mail: moncef-said@yahoo.fr; Sfina, N.; Said, M. E-mail: moncef-said@yahoo.fr; Lazzari, J.-L.; Bournel, A.
2014-01-21
We theoretically investigate germanium-tin alloy as a semiconductor for the design of near infrared optical modulators in which the Ge{sub 1−x}Sn{sub x} alloy is the active region. We have calculated the electronic band parameters for heterointerfaces between strained Ge{sub 1−x}Sn{sub x} and relaxed Si{sub 1−y}Ge{sub y}. Then, a type-I strain-compensated Si{sub 0.10}Ge{sub 0.90}/Si{sub 0.16}Ge{sub 0.84}/Ge{sub 0.94}Sn{sub 0.06} quantum well heterostructure optimized in terms of compositions and thicknesses is studied by solving Schrödinger equation without and under applied bias voltage. The strong absorption coefficient (>1.5 × 10{sup 4} cm{sup −1}) and the shift of the direct transition under large Stark effect at 3 V are useful characteristics for the design of optoelectronic devices based on compressively strained IV-IV heterostructures at near infrared wavelengths.
NASA Astrophysics Data System (ADS)
Zhang, Xiaoli; Wu, Meihua; Diao, Wenxin; Zhang, Bing; Hao, Jigong; Xu, Zhijun; Chu, Ruiqing
2015-10-01
In this study, a new lead-free luminescent electrostrictive material has been obtained by introducing trivalent Er3+ as the activator into 0.92(Bi0.5Na0.5)TiO3-0.08(Ba0.90Ca0.10)(Ti0.92Sn0.08)O3 (BNT-0.08BCST). A high, purely electrostrictive effect (the electrostrictive coefficient Q33 reaches up to 0.028 m4/C2) with exceptionally good fatigue resistance (up to 106 cycles) and thermostability (25-140 °C) is obtained in 0.2 mol%Er-modified BNT-0.08BCST ceramics. Besides the excellent electrostrictive properties, Er3+-modified BNT-0.08BCST samples exhibit a strong green-red upconversion emission, and the emission intensities are strongly dependent on the doping concentration, which reaches the optimal value as the doping concentration is 0.4 mol%. These results suggest that this kind of material may have potential application as a multifunctional device by integrating its excellent upconversion luminescence and electrostrictive properties.
Bhaskar, Ankam; Lin, Z.R.; Liu, Chia-Jyi
2013-11-15
Graphical abstract: - Highlights: • Resistivity of all the samples exhibits nonmetallic to metallic behavior in the low temperature region. • Ca{sub 3}Co{sub 3.85}Cu{sub 0.15}O{sub 9+δ} shows the highest dimensionless figure of merit. • The observed effective magnetic moments decrease with increasing Cu content. - Abstract: Ca{sub 3}Co{sub 4–x}Cu{sub x}O{sub 9+δ} (x = 0.00, 0.05, 0.07, 0.10 and 0.15) samples were prepared by conventional solid-state synthesis and their thermoelectric properties were systematically investigated. The thermopower of all the samples was positive, indicating that the predominant carriers are holes over the entire temperature range. Ca{sub 3}Co{sub 3.85}Cu{sub 0.15}O{sub 9+δ} had the highest power factor of 2.17 μW cm{sup −1} K{sup −2} at 141 K, representing an improvement of about 64.4% compared to undoped Ca{sub 3}Co{sub 4}O{sub 9+δ}. Magnetization measurements indicated that all the samples exhibit a low-spin state of cobalt ions. The observed effective magnetic moments decreased with increasing copper content.
Numerical Simulations of High Enthalpy Pulse Facilities
NASA Technical Reports Server (NTRS)
Wilson, Gregory J.; Edwards, Thomas A. (Technical Monitor)
1995-01-01
Axisymmetric flows within shock tubes and expansion tubes are simulated including the effects of finite rate chemistry and both laminar and turbulent boundary layers. The simulations demonstrate the usefulness of computational fluid dynamics for characterizing the flows in high enthalpy pulse facilities. The modeling and numerical requirements necessary to simulate these flows accurately are also discussed. Although there is a large body of analysis which explains and quantifies the boundary layer growth between the shock and the interface in a shock tube, there is a need for more detailed solutions. Phenomena such as thermochemical nonequilibrium. or turbulent transition behind the shock are excluded in the assumptions of Mirels' analysis. Additionally there is inadequate capability to predict the influence of the boundary layer on the expanded gas behind the interface. Quantifying the gas in this region is particularly important in expansion tubes because it is the location of the test gas. Unsteady simulations of the viscous flow in shock tubes are computationally expensive because they must follow features such as a shock wave over the length of the facility and simultaneously resolve the small length scales within the boundary layer. As a result, efficient numerical algorithms are required. The numerical approach of the present work is to solve the axisymmetric gas dynamic equations using an finite-volume formulation where the inviscid fluxes are computed with a upwind TVD scheme. Multiple species equations are included in the formulation so that finite-rate chemistry can be modeled. The simulations cluster grid points at the shock and interface and translate this clustered grid with these features to minimize numerical errors. The solutions are advanced at a CFL number of less than one based on the inviscid gas dynamics. To avoid limitations on the time step due to the viscous terms, these terms are treated implicitly. This requires a block tri
Numerical analysis of decoy state quantum key distribution protocols
Harrington, Jim W; Rice, Patrick R
2008-01-01
Decoy state protocols are a useful tool for many quantum key distribution systems implemented with weak coherent pulses, allowing significantly better secret bit rates and longer maximum distances. In this paper we present a method to numerically find optimal three-level protocols, and we examine how the secret bit rate and the optimized parameters are dependent on various system properties, such as session length, transmission loss, and visibility. Additionally, we show how to modify the decoy state analysis to handle partially distinguishable decoy states as well as uncertainty in the prepared intensities.
Numerical studies of transverse curvature effects on transonic flow stability
NASA Technical Reports Server (NTRS)
Macaraeg, M. G.; Daudpota, Q. I.
1992-01-01
A numerical study of transverse curvature effects on compressible flow temporal stability for transonic to low supersonic Mach numbers is presented for axisymmetric modes. The mean flows studied include a similar boundary-layer profile and a nonsimilar axisymmetric boundary-layer solution. The effect of neglecting curvature in the mean flow produces only small quantitative changes in the disturbance growth rate. For transonic Mach numbers (1-1.4) and aerodynamically relevant Reynolds numbers (5000-10,000 based on displacement thickness), the maximum growth rate is found to increase with curvature - the maximum occurring at a nondimensional radius (based on displacement thickness) between 30 and 100.
Numerical simulation of tulip flame dynamics
Cloutman, L.D.
1991-11-30
A finite difference reactive flow hydrodynamics program based on the full Navier-Stokes equations was used to simulate the combustion process in a homogeneous-charge, constant-volume combustion bomb in which an oddly shaped flame, known as a ``tulip flame`` in the literature, occurred. The ``tulip flame`` was readily reproduced in the numerical simulations, producing good agreement with the experimental flame shapes and positions at various times. The calculations provide sufficient detail about the dynamics of the experiment to provide some insight into the physical mechanisms responsible for the peculiar flame shape. Several factors seem to contribute to the tulip formation. The most important process is the baroclinic production of vorticity by the flame front, and this rate of production appears to be dramatically increased by the nonaxial flow generated when the initial semicircular flame front burns out along the sides of the chamber. The vorticity produces a pair of vortices behind the flame that advects the flame into the tulip shape. Boundary layer effects contribute to the details of the flame shape next to the walls of the chamber, but are otherwise not important. 24 refs.
Numerical simulation of tulip flame dynamics
Cloutman, L.D.
1991-11-30
A finite difference reactive flow hydrodynamics program based on the full Navier-Stokes equations was used to simulate the combustion process in a homogeneous-charge, constant-volume combustion bomb in which an oddly shaped flame, known as a tulip flame'' in the literature, occurred. The tulip flame'' was readily reproduced in the numerical simulations, producing good agreement with the experimental flame shapes and positions at various times. The calculations provide sufficient detail about the dynamics of the experiment to provide some insight into the physical mechanisms responsible for the peculiar flame shape. Several factors seem to contribute to the tulip formation. The most important process is the baroclinic production of vorticity by the flame front, and this rate of production appears to be dramatically increased by the nonaxial flow generated when the initial semicircular flame front burns out along the sides of the chamber. The vorticity produces a pair of vortices behind the flame that advects the flame into the tulip shape. Boundary layer effects contribute to the details of the flame shape next to the walls of the chamber, but are otherwise not important. 24 refs.
Numerical Modeling of Ocular Dysfunction in Space
NASA Technical Reports Server (NTRS)
Nelson, Emily S.; Mulugeta, Lealem; Vera, J.; Myers, J. G.; Raykin, J.; Feola, A. J.; Gleason, R.; Samuels, B.; Ethier, C. R.
2014-01-01
Upon introduction to microgravity, the near-loss of hydrostatic pressure causes a marked cephalic (headward) shift of fluid in an astronaut's body. The fluid shift, along with other factors of spaceflight, induces a cascade of interdependent physiological responses which occur at varying time scales. Long-duration missions carry an increased risk for the development of the Visual Impairment and Intracranial Pressure (VIIP) syndrome, a spectrum of ophthalmic changes including posterior globe flattening, choroidal folds, distension of the optic nerve sheath, kinking of the optic nerve and potentially permanent degradation of visual function. In the cases of VIIP found to date, the initial onset of symptoms occurred after several weeks to several months of spaceflight, by which time the gross bodily fluid distribution is well established. We are developing a suite of numerical models to simulate the effects of fluid shift on the cardiovascular, central nervous and ocular systems. These models calculate the modified mean volumes, flow rates and pressures that are characteristic of the altered quasi-homeostatic state in microgravity, including intracranial and intraocular pressures. The results of the lumped models provide initial and boundary data to a 3D finite element biomechanics simulation of the globe, optic nerve head and retrobulbar subarachnoid space. The integrated set of models will be used to investigate the evolution of the biomechanical stress state in the ocular tissues due to long-term exposure to microgravity.
Externally fed star formation: a numerical study
NASA Astrophysics Data System (ADS)
Mohammadpour, Motahareh; Stahler, Steven W.
2013-08-01
We investigate, through a series of numerical calculations, the evolution of dense cores that are accreting external gas up to and beyond the point of star formation. Our model clouds are spherical, unmagnetized configurations with fixed outer boundaries, across which gas enters subsonically. When we start with any near-equilibrium state, we find that the cloud's internal velocity also remains subsonic for an extended period, in agreement with observations. However, the velocity becomes supersonic shortly before the star forms. Consequently, the accretion rate building up the protostar is much greater than the benchmark value c_s^3/G, where cs is the sound speed in the dense core. This accretion spike would generate a higher luminosity than those seen in even the most embedded young stars. Moreover, we find that the region of supersonic infall surrounding the protostar races out to engulf much of the cloud, again in violation of the observations, which show infall to be spatially confined. Similar problematic results have been obtained by all other hydrodynamic simulations to date, regardless of the specific infall geometry or boundary conditions adopted. Low-mass star formation is evidently a quasi-static process, in which cloud gas moves inward subsonically until the birth of the star itself. We speculate that magnetic tension in the cloud's deep interior helps restrain the infall prior to this event.
Numerical Modeling of Suspension HVOF Spray
NASA Astrophysics Data System (ADS)
Jadidi, M.; Moghtadernejad, S.; Dolatabadi, A.
2016-02-01
A three-dimensional two-way coupled Eulerian-Lagrangian scheme is used to simulate suspension high-velocity oxy-fuel spraying process. The mass, momentum, energy, and species equations are solved together with the realizable k-ɛ turbulence model to simulate the gas phase. Suspension is assumed to be a mixture of solid particles [mullite powder (3Al2O3·2SiO2)], ethanol, and ethylene glycol. The process involves premixed combustion of oxygen-propylene, and non-premixed combustion of oxygen-ethanol and oxygen-ethylene glycol. One-step global reaction is used for each mentioned reaction together with eddy dissipation model to compute the reaction rate. To simulate the droplet breakup, Taylor Analogy Breakup model is applied. After the completion of droplet breakup, and solvent evaporation/combustion, the solid suspended particles are tracked through the domain to determine the characteristics of the coating particles. Numerical simulations are validated against the experimental results in the literature for the same operating conditions. Seven or possibly eight shock diamonds are captured outside the nozzle. In addition, a good agreement between the predicted particle temperature, velocity, and diameter, and the experiment is obtained. It is shown that as the standoff distance increases, the particle temperature and velocity reduce. Furthermore, a correlation is proposed to determine the spray cross-sectional diameter and estimate the particle trajectories as a function of standoff distance.
Direct numerical simulations of aeolian sand ripples
Durán, Orencio; Claudin, Philippe; Andreotti, Bruno
2014-01-01
Aeolian sand beds exhibit regular patterns of ripples resulting from the interaction between topography and sediment transport. Their characteristics have been so far related to reptation transport caused by the impacts on the ground of grains entrained by the wind into saltation. By means of direct numerical simulations of grains interacting with a wind flow, we show that the instability turns out to be driven by resonant grain trajectories, whose length is close to a ripple wavelength and whose splash leads to a mass displacement toward the ripple crests. The pattern selection results from a compromise between this destabilizing mechanism and a diffusive downslope transport which stabilizes small wavelengths. The initial wavelength is set by the ratio of the sediment flux and the erosion/deposition rate, a ratio which increases linearly with the wind velocity. We show that this scaling law, in agreement with experiments, originates from an interfacial layer separating the saltation zone from the static sand bed, where momentum transfers are dominated by midair collisions. Finally, we provide quantitative support for the use of the propagation of these ripples as a proxy for remote measurements of sediment transport. PMID:25331873
Direct numerical simulations of aeolian sand ripples.
Durán, Orencio; Claudin, Philippe; Andreotti, Bruno
2014-11-01
Aeolian sand beds exhibit regular patterns of ripples resulting from the interaction between topography and sediment transport. Their characteristics have been so far related to reptation transport caused by the impacts on the ground of grains entrained by the wind into saltation. By means of direct numerical simulations of grains interacting with a wind flow, we show that the instability turns out to be driven by resonant grain trajectories, whose length is close to a ripple wavelength and whose splash leads to a mass displacement toward the ripple crests. The pattern selection results from a compromise between this destabilizing mechanism and a diffusive downslope transport which stabilizes small wavelengths. The initial wavelength is set by the ratio of the sediment flux and the erosion/deposition rate, a ratio which increases linearly with the wind velocity. We show that this scaling law, in agreement with experiments, originates from an interfacial layer separating the saltation zone from the static sand bed, where momentum transfers are dominated by midair collisions. Finally, we provide quantitative support for the use of the propagation of these ripples as a proxy for remote measurements of sediment transport. PMID:25331873
Rating Movies and Rating the Raters Who Rate Them.
Zhou, Hua; Lange, Kenneth
2009-11-01
The movie distribution company Netflix has generated considerable buzz in the statistics community by offering a million dollar prize for improvements to its movie rating system. Among the statisticians and computer scientists who have disclosed their techniques, the emphasis has been on machine learning approaches. This article has the modest goal of discussing a simple model for movie rating and other forms of democratic rating. Because the model involves a large number of parameters, it is nontrivial to carry out maximum likelihood estimation. Here we derive a straightforward EM algorithm from the perspective of the more general MM algorithm. The algorithm is capable of finding the global maximum on a likelihood landscape littered with inferior modes. We apply two variants of the model to a dataset from the MovieLens archive and compare their results. Our model identifies quirky raters, redefines the raw rankings, and permits imputation of missing ratings. The model is intended to stimulate discussion and development of better theory rather than to win the prize. It has the added benefit of introducing readers to some of the issues connected with analyzing high-dimensional data. PMID:20802818
Rating Movies and Rating the Raters Who Rate Them
Zhou, Hua; Lange, Kenneth
2010-01-01
The movie distribution company Netflix has generated considerable buzz in the statistics community by offering a million dollar prize for improvements to its movie rating system. Among the statisticians and computer scientists who have disclosed their techniques, the emphasis has been on machine learning approaches. This article has the modest goal of discussing a simple model for movie rating and other forms of democratic rating. Because the model involves a large number of parameters, it is nontrivial to carry out maximum likelihood estimation. Here we derive a straightforward EM algorithm from the perspective of the more general MM algorithm. The algorithm is capable of finding the global maximum on a likelihood landscape littered with inferior modes. We apply two variants of the model to a dataset from the MovieLens archive and compare their results. Our model identifies quirky raters, redefines the raw rankings, and permits imputation of missing ratings. The model is intended to stimulate discussion and development of better theory rather than to win the prize. It has the added benefit of introducing readers to some of the issues connected with analyzing high-dimensional data. PMID:20802818
Numerical simulation of transitional flow
NASA Technical Reports Server (NTRS)
Biringen, Sedat
1986-01-01
The applicability of active control of transition by periodic suction-blowing is investigated via direct simulations of the Navier-Stokes equations. The time-evolution of finite-amplitude disturbances in plane channel flow is compared in detail with and without control. The analysis indicates that, for relatively small three-dimensional amplitudes, a two-dimensional control effectively reduces disturbance growth rates even for linearly unstable Reynolds numbers. After the flow goes through secondary instability, three-dimensional control seems necessary to stabilize the flow. An investigation of the temperature field suggests that passive temperature contamination is operative to reflect the flow dynamics during transition.
Playing Linear Numerical Board Games Promotes Low-Income Children's Numerical Development
ERIC Educational Resources Information Center
Siegler, Robert S.; Ramani, Geetha B.
2008-01-01
The numerical knowledge of children from low-income backgrounds trails behind that of peers from middle-income backgrounds even before the children enter school. This gap may reflect differing prior experience with informal numerical activities, such as numerical board games. Experiment 1 indicated that the numerical magnitude knowledge of…
Relativistic positioning systems: Numerical simulations
NASA Astrophysics Data System (ADS)
Puchades Colmenero, Neus
The position of users located on the Earth's surface or near it may be found with the classic positioning systems (CPS). Certain information broadcast by satellites of global navigation systems, as GPS and GALILEO, may be used for positioning. The CPS are based on the Newtonian formalism, although relativistic post-Newtonian corrections are done when they are necessary. This thesis contributes to the development of a different positioning approach, which is fully relativistic from the beginning. In the relativistic positioning systems (RPS), the space-time position of any user (ship, spacecraft, and so on) can be calculated with the help of four satellites, which broadcast their proper times by means of codified electromagnetic signals. In this thesis, we have simulated satellite 4-tuples of the GPS and GALILEO constellations. If a user receives the signals from four satellites simultaneously, the emission proper times read -after decoding- are the user "emission coordinates". In order to find the user "positioning coordinates", in an appropriate almost inertial reference system, there are two possibilities: (a) the explicit relation between positioning and emission coordinates (broadcast by the satellites) is analytically found or (b) numerical codes are designed to calculate the positioning coordinates from the emission ones. Method (a) is only viable in simple ideal cases, whereas (b) allows us to consider realistic situations. In this thesis, we have designed numerical codes with the essential aim of studying two appropriate RPS, which may be generalized. Sometimes, there are two real users placed in different positions, which receive the same proper times from the same satellites; then, we say that there is bifurcation, and additional data are needed to choose the real user position. In this thesis, bifurcation is studied in detail. We have analyzed in depth two RPS models; in both, it is considered that the satellites move in the Schwarzschild's space
Numerical simulations of Lake Vostok
NASA Astrophysics Data System (ADS)
Curchitser, E.; Tremblay, B.
2003-04-01
Numerical simulations of Lake Vostok We present a systematic approach towards a realistic hydrodynamic model of lake Vostok. The lake is characterized by the unusual combination of size (permitting significant geostrophic motion) and an overlying ice sheet several kilometers thick. A priori estimates of the circulation in the deep lake predict a mostly geostrophic circulation driven by horizontal temperature gradients produced by the pressure-dependent freezing point at the base of the (non-uniform) ice sheet. Further preliminary (remote) research has revealed the steep topography and the elliptical geometry of the lake. A three dimensional, primitive equation, free surface, model is used as a starting point for the Lake configuration. We show how the surface pressure gradient forces are modified to permit a simulation that includes the hydrostatic effects of the overlying ice sheet. A thermodynamic ice model is coupled with the circulation component to simulate the ice accretion/melting at the base of the ice sheet. A stretching of the terrain following vertical coordinate is used to resolve the boundary layer in the ice/water interface. Furthermore, the terrain-following coordinate evolves in time, and is used to track the evolution of the ice sheet due to ice accretion/melting. Both idealized and realistic ice sheet bottom topographies (from remote radar data) are used to drive the simulations. Steady state and time evolving simulations (i.e., constant and evolving ice sheet geometry) will be descirbed, as well as a comparison to an idealized box model (Tremblay, Clarke, and Hohman). The coastline and lake bathymetry used in the simulation are derived from radar data and are accurately represented in our model.
Accuracy of numerically produced compensators.
Thompson, H; Evans, M D; Fallone, B G
1999-01-01
A feasibility study is performed to assess the utility of a computer numerically controlled (CNC) mill to produce compensating filters for conventional clinical use and for the delivery of intensity-modulated beams. A computer aided machining (CAM) software is used to assist in the design and construction of such filters. Geometric measurements of stepped and wedged surfaces are made to examine the accuracy of surface milling. Molds are milled and filled with molten alloy to produce filters, and both the molds and filters are examined for consistency and accuracy. Results show that the deviation of the filter surfaces from design does not exceed 1.5%. The effective attenuation coefficient is measured for CadFree, a cadmium-free alloy, in a 6 MV photon beam. The effective attenuation coefficients at the depth of maximum dose (1.5 cm) and at 10 cm in solid water phantom are found to be 0.546 cm-1 and 0.522 cm-1, respectively. Further attenuation measurements are made with Cerrobend to assess the variations of the effective attenuation coefficient with field size and source-surface distance. The ability of the CNC mill to accurately produce surfaces is verified with dose profile measurements in a 6 MV photon beam. The test phantom is composed of a 10 degrees polystyrene wedge and a 30 degrees polystyrene wedge, presenting both a sharp discontinuity and sloped surfaces. Dose profiles, measured at the depth of compensation (10 cm) beneath the test phantom and beneath a flat phantom, are compared to those produced by a commercial treatment planning system. Agreement between measured and predicted profiles is within 2%, indicating the viability of the system for filter production. PMID:10100166
Numerical simulations of multifluid flows
NASA Astrophysics Data System (ADS)
Unverdi, Salih Ozen
1990-01-01
A method for full numerical simulations of unsteady, incompressible Navier-Stokes equations for multi-fluid systems is developed. Moving interfaces between dissimilar fluids are explicitly tracked and fluid properties are constructed on a stationary grid using the position of the interfaces. While the interfaces are explicitly tracked, they are not kept completely sharp but are given a finite thickness of the order of the mesh size to provide stability and smoothness. This thickness remains constant for all time but decreases with finer resolution of the stationary grid. A unique feature of the method is that the tracked interfaces carry the jump in properties across the interface and that, at each time step, the property fields are reconstructed by solving a Poisson equation. The advantage of this approach is that interfaces can interact in a natural way, since the gradients add or cancel as the grid distribution is constructed from the information carried by the tracked front. The emphasis is on the shape regimes of bubbles and bubble-bubble interactions in a stationary fluid. The circular, elliptical and skirted shape regimes and wake structures of two-dimensional bubbles are studied. Three-dimensional evolution of the interaction of two bubbles in a stationary fluid is investigated. Interaction of bubbles in a periodic array is also studied and it is found that a pair of bubbles in a free rise can interact in the absence of a toroidal wake below the upper bubble and that the interaction time is smaller as the viscosity of the outer fluid decreases. It is shown that the kinetic energy of the flow field decreases during this interaction. Sensitivity of the bubble interaction process to fluid properties is shown by different trajectories followed by bubbles in fluids of different viscosity. The Rayleigh-Taylor instability is also studied.
Simulating reionization in numerical cosmology
NASA Astrophysics Data System (ADS)
Sokasian, Aaron
2003-11-01
The incorporation of radiative transfer effects into cosmological hydrodynamical simulations is essential for understanding how the intergalactic medium (IGM) makes the transition from a neutral medium to one that is almost fully ionized. I present an approximate numerical method designed to study in a statistical sense how a cosmological density field is ionized by various sets of sources. The method requires relatively few time steps and can be employed with simulations of high resolution. First, I explore the reionization history of Helium II by z < 6 quasars. Comparisons between HeII opacities measured observationally and inferred from our analysis reveal that the uncertainties in the empirical luminosity function provide enough leeway to provide a satisfactory match. A property common to all the calculations is that the epoch of Helium II reionization must have occurred between 3≲
Numerical Modeling of Plasmas in which Nanoparticles Nucleate and Grow
NASA Astrophysics Data System (ADS)
Agarwal, Pulkit
Dusty plasmas refer to a broad category of plasmas. Plasmas such as argon-silane plasmas in which particles nucleate and grow are widely used in semiconductor processing and nanoparticle manufacturing. In such dusty plasmas, the plasma and the dust particles are strongly coupled to each other. This means that the presence of dust particles significantly affects the plasma properties and vice versa. Therefore such plasmas are highly complex and they involve several interesting phenomena like nucleation, growth, coagulation, charging and transport. Dusty plasma afterglow is equally complex and important. Especially, residual charge on dust particles carries special significance in several industrial and laboratory situations and it has not been well understood. A 1D numerical model was developed of a low-pressure capacitively-coupled plasma in which nanoparticles nucleate and grow. Polydispersity of particle size distributions can be important in such plasmas. Sectional method, which is well known in aerosol literature, was used to model the evolving particle size and charge distribution. The numerical model is transient and one-dimensional and self consistently accounts for nucleation, growth, coagulation, charging and transport of dust particles and their effect on plasma properties. Nucleation and surface growth rates were treated as input parameters. Results were presented in terms of particle size and charge distribution with an emphasis on importance of polydispersity in particle growth and dynamics. Results of numerical model were compared with experimental measurements of light scattering and light emission from plasma. Reasonable qualitative agreement was found with some discrepancies. Pulsed dusty plasma can be important for controlling particle production and/or unwanted particle deposition. In this case, it is important to understand the behavior of the particle cloud during the afterglow following plasma turn-off. Numerical model was modified to self
Numerical Models of Ophiolite Genesis and Obduction
NASA Astrophysics Data System (ADS)
Guilmette, C.; Beaumont, C.; Jamieson, R.
2013-12-01
Ophiolites are relics of oceanic lithosphere tectonically emplaced in continental settings. They are diagnostic features of continental suture zones, where they mark past plate boundaries. Even after having been studied for more than 40 years, the mechanisms involved in the genesis and subsequent obduction of ophiolites over continental margins are still debated. We present the results of 2D thermal-mechanical numerical models that successfully reproduce characteristics of natural examples like the Semail, Bay of Islands, Yarlung-Zangbo, and Coast Range ophiolites. The numerical models are upper mantle scale and use pressure-, temperature- and strain-dependent viscous-plastic rheologies. Both divergent and convergent velocity boundary conditions are used and tectonic boundary forces are monitored. The models start with the rifting of a stable continent, followed by development of an ocean ridge and accretion of oceanic lithosphere at a total rate of 3 cm/y. Once a specified ocean size/age is achieved, the velocity boundary conditions are reversed leading to convergence and the spontaneous inception of a suduction zone at the mid-ocean ridge. We present results for models including different ages of oceans (40 to 90 Ma) and different convergence velocities (5 to 15 cm/y). The interaction between the lower plate passive margin and the oceanic upper plate results in 5 different tectonic styles. These differ mainly by the presence or absence of oceanic spreading in the upper plate (back-arc basin), leading to supra-subduction zone ophiolites vs. MORB-type, and by the behaviour of the oceanic slab, e.g., slab rollback vs. breakoff. The evolution of effective slab pull is interpreted to be the major control on the resulting tectonic style. Low effective slab pull models (young oceans and fast convergence rates) fail to obduct an ophiolite. Strong effective slab pull models (old oceans and lower convergence rates) result in subduction zone retreat and spontaneous oceanic
Zdeněk Kopal: Numerical Analyst
NASA Astrophysics Data System (ADS)
Křížek, M.
2015-07-01
We give a brief overview of Zdeněk Kopal's life, his activities in the Czech Astronomical Society, his collaboration with Vladimír Vand, and his studies at Charles University, Cambridge, Harvard, and MIT. Then we survey Kopal's professional life. He published 26 monographs and 20 conference proceedings. We will concentrate on Kopal's extensive monograph Numerical Analysis (1955, 1961) that is widely accepted to be the first comprehensive textbook on numerical methods. It describes, for instance, methods for polynomial interpolation, numerical differentiation and integration, numerical solution of ordinary differential equations with initial or boundary conditions, and numerical solution of integral and integro-differential equations. Special emphasis will be laid on error analysis. Kopal himself applied numerical methods to celestial mechanics, in particular to the N-body problem. He also used Fourier analysis to investigate light curves of close binaries to discover their properties. This is, in fact, a problem from mathematical analysis.
Structural application and numerical calculation
Sih, G.C.; Ditommaso, A.
1984-01-01
Since cost effectiveness has always been one of the more important aspects of design, reinforced and/or prestressed concrete is being increasingly used in many other areas, such as in the construction of floating marine structures, storage tanks, and nuclear vessel containments. A subject of major concern is how the localized segregation of the constituents in concrete would affect its global behaviour. The degree of nonhomogenity due to material property and damage by yielding and/or cracking depends on the size scale and loading rate under consideration. Hence, a wider knowledge of concrete behaviour on a large scale is desirable, and it is hoped that this volume, in which the application of Linear Elastic Fracture Mechanics is also fully discussed, will go some way to achieving this.
Numerical tools for atomistic simulations.
Fang, H.; Gullett, Philip Michael; Slepoy, Alexander; Horstemeyer, Mark F.; Baskes, Michael I.; Wagner, Gregory John; Li, Mo
2004-01-01
The final report for a Laboratory Directed Research and Development project entitled 'Parallel Atomistic Computing for Failure Analysis of Micromachines' is presented. In this project, atomistic algorithms for parallel computers were developed to assist in quantification of microstructure-property relations related to weapon micro-components. With these and other serial computing tools, we are performing atomistic simulations of various sizes, geometries, materials, and boundary conditions. These tools provide the capability to handle the different size-scale effects required to predict failure. Nonlocal continuum models have been proposed to address this problem; however, they are phenomenological in nature and are difficult to validate for micro-scale components. Our goal is to separately quantify damage nucleation, growth, and coalescence mechanisms to provide a basis for macro-scale continuum models that will be used for micromachine design. Because micro-component experiments are difficult, a systematic computational study that employs Monte Carlo methods, molecular statics, and molecular dynamics (EAM and MEAM) simulations to compute continuum quantities will provide mechanism-property relations associated with the following parameters: specimen size, number of grains, crystal orientation, strain rates, temperature, defect nearest neighbor distance, void/crack size, chemical state, and stress state. This study will quantify sizescale effects from nanometers to microns in terms of damage progression and thus potentially allow for optimized micro-machine designs that are more reliable and have higher fidelity in terms of strength. In order to accomplish this task, several atomistic methods needed to be developed and evaluated to cover the range of defects, strain rates, temperatures, and sizes that a material may see in micro-machines. Therefore we are providing a complete set of tools for large scale atomistic simulations that include pre-processing of
Numerical Simulations of Granular Processes
NASA Astrophysics Data System (ADS)
Richardson, Derek C.; Michel, Patrick; Schwartz, Stephen R.; Ballouz, Ronald-Louis; Yu, Yang; Matsumura, Soko
2014-11-01
Spacecraft images and indirect observations including thermal inertia measurements indicate most small bodies have surface regolith. Evidence of granular flow is also apparent in the images. This material motion occurs in very low gravity, therefore in a completely different gravitational environment than on the Earth. Understanding and modeling these motions can aid in the interpretation of imaged surface features that may exhibit signatures of constituent material properties. Also, upcoming sample-return missions to small bodies, and possible future manned missions, will involve interaction with the surface regolith, so it is important to develop tools to predict the surface response. We have added new capabilities to the parallelized N-body gravity tree code pkdgrav [1,2] that permit the simulation of granular dynamics, including multi-contact physics and friction forces, using the soft-sphere discrete-element method [3]. The numerical approach has been validated through comparison with laboratory experiments (e.g., [3,4]). Ongoing and recently completed projects include: impacts into granular materials using different projectile shapes [5]; possible tidal resurfacing of asteroid Apophis during its 2029 encounter [6]; the Brazil-nut effect in low gravity [7]; and avalanche modeling.Acknowledgements: DCR acknowledges NASA (grants NNX08AM39G, NNX10AQ01G, NNX12AG29G) and NSF (AST1009579). PM acknowledges the French agency CNES. SRS works on the NEOShield Project funded under the European Commission’s FP7 program agreement No. 282703. SM acknowledges support from the Center for Theory and Computation at U Maryland and the Dundee Fellowship at U Dundee. Most simulations were performed using the YORP cluster in the Dept. of Astronomy at U Maryland and on the Deepthought High-Performance Computing Cluster at U Maryland.References: [1] Richardson, D.C. et al. 2000, Icarus 143, 45; [2] Stadel, J. 2001, Ph.D. Thesis, U Washington; [3] Schwartz, S.R. et al. 2012, Gran
NASA Astrophysics Data System (ADS)
Lemaire, J. L.; Eidelsberg, M.; Heays, A. N.; Gavilan, L.; Federman, S. R.; Stark, G.; Lyons, J. R.; de Oliveira, N.; Joyeux, D.
2016-08-01
Our knowledge of astronomical environments containing CO depends on accurate molecular data to reproduce and interpret observations. The constant improvement in UV space instrumentation, both in sensitivity and resolution, requires increasingly detailed laboratory data. Following a long-term experimental campaign at the SOLEIL Synchrotron facility, we have acquired complete datasets on the CO isotopologues in the vacuum ultraviolet. Absorption spectra were recorded using the Fourier-transform spectrometer installed on the DESIRS beamline, providing a resolving power R > 106 in the 8–12 eV range. Such resolution allows the analysis of individual line positions and strengths in electronic transitions and the location of perturbations. We continue our previous work on A–X bands of 12C16O and 13C16O, reporting here measurements for the 13C18O isotopologue. Gas column densities in the differentially-pumped system were calibrated using the B {}1{{{Σ }}}+–X {}1{{{Σ }}}+({v}\\prime =0,v\\prime\\prime =0) band. Absorption bands are analyzed by synthesizing line and band profiles and fitting them to measured spectra. New results for A {}1{{\\Pi }}({v}\\prime =0{--}10)–X {}1{{{Σ }}}+(v\\prime\\prime =0) bands include precise line assignments, term values, band-integrated oscillator strengths as well as individual ro-vibrational oscillator strengths and Hönl–London corrections. For ({v}\\prime =1) our results are compared with earlier studies. The interpretation of mixed perturbing bands, complementing an earlier study, is also presented as well as precise line assignments and term values for the B {}1{{{Σ }}}+–X {}1{{{Σ }}}+(0–0) band calibrator, and the nearby B–X (1–0) and C {}1{{{Σ }}}+–X {}1{{{Σ }}}+(0–0) bands.
Fujita, A.; Matsunami, D.; Yako, H.
2014-03-24
Tuning of phase-transition characteristics in La(Fe{sub x}Si{sub 1−x}){sub 13} was conducted in view of the correlation between microscopic itinerant electron natures and macroscopic thermodynamic (magnetocaloric) quantities. To realize a small hysteresis loss Q{sub H} accompanied by a large magnetic entropy change ΔS{sub M} in La(Fe{sub x}Si{sub 1−x}){sub 13}, two types of modulation based on itinerant electron characteristics, namely, the Fermi-level shift and the magnetovolume effect were combined by complex partial substitution of Al and Pr. Ab-initio calculations predict the reduction of a transition hysteresis owing to the Fermi-level shift after partial substitution of Al. On the other hand, the chemical pressure arisen from partial substitution of Pr enhances ΔS{sub M} through magnetovolume effect. The selective enhancement of ΔS{sub M} apart from Q{sub H} by the magnetovolume effect is well explained by the phenomenological Landau model. Consequently, ΔS{sub M} of La{sub 0.8}Pr{sub 0.2}(Fe{sub 0.88}Si{sub 0.10}Al{sub 0.02}){sub 13} is −18 J/kg K under a magnetic field change of 0–1.2 T, while the maximum value of Q{sub H} becomes 1/6 of that for La(Fe{sub 0.88}Si{sub 0.12}){sub 13}.
Numerical simulation of 3D breaking waves
NASA Astrophysics Data System (ADS)
Fraunie, Philippe; Golay, Frederic
2015-04-01
Numerical methods dealing with two phase flows basically can be classified in two ways : the "interface tracking" methods when the two phases are resolved separately including boundary conditions fixed at the interface and the "interface capturing" methods when a single flow is considered with variable density. Physical and numerical properties of the two approaches are discussed, based on some numerical experiments performed concerning 3D breaking waves. Acknowledgements : This research was supported by the Modtercom program of Region PACA.
Numerical Algorithm for Delta of Asian Option
Zhang, Boxiang; Yu, Yang; Wang, Weiguo
2015-01-01
We study the numerical solution of the Greeks of Asian options. In particular, we derive a close form solution of Δ of Asian geometric option and use this analytical form as a control to numerically calculate Δ of Asian arithmetic option, which is known to have no explicit close form solution. We implement our proposed numerical method and compare the standard error with other classical variance reduction methods. Our method provides an efficient solution to the hedging strategy with Asian options. PMID:26266271
Numerical Algorithm for Delta of Asian Option.
Zhang, Boxiang; Yu, Yang; Wang, Weiguo
2015-01-01
We study the numerical solution of the Greeks of Asian options. In particular, we derive a close form solution of Δ of Asian geometric option and use this analytical form as a control to numerically calculate Δ of Asian arithmetic option, which is known to have no explicit close form solution. We implement our proposed numerical method and compare the standard error with other classical variance reduction methods. Our method provides an efficient solution to the hedging strategy with Asian options. PMID:26266271
The Geometric Grids of the Hieratic Numeral.
NASA Astrophysics Data System (ADS)
Aboulfotouh, Hossam M. K.
The paper discusses the geometrical designs of the hieratic numeral signs. It shows the regular-grid-patterns of squares upon which, the shapes of the already decoded hieratic numeral-signs, have been designed. Also, it shows the design of some hieratic numeral signs, based on subdividing the circle; and the hieratic signs of modular notation. It might reveal the basic geometrical level of understanding of anonymous ancient Egyptians who designed them some four thousand years ago.
Spurious Numerical Solutions Of Differential Equations
NASA Technical Reports Server (NTRS)
Lafon, A.; Yee, H. C.
1995-01-01
Paper presents detailed study of spurious steady-state numerical solutions of differential equations that contain nonlinear source terms. Main objectives of this study are (1) to investigate how well numerical steady-state solutions of model nonlinear reaction/convection boundary-value problem mimic true steady-state solutions and (2) to relate findings of this investigation to implications for interpretation of numerical results from computational-fluid-dynamics algorithms and computer codes used to simulate reacting flows.
Nonlinear dynamics and numerical uncertainties in CFD
NASA Technical Reports Server (NTRS)
Yee, H. C.; Sweby, P. K.
1996-01-01
The application of nonlinear dynamics to improve the understanding of numerical uncertainties in computational fluid dynamics (CFD) is reviewed. Elementary examples in the use of dynamics to explain the nonlinear phenomena and spurious behavior that occur in numerics are given. The role of dynamics in the understanding of long time behavior of numerical integrations and the nonlinear stability, convergence, and reliability of using time-marching, approaches for obtaining steady-state numerical solutions in CFD is explained. The study is complemented with spurious behavior observed in CFD computations.
Probabilistic numerics and uncertainty in computations
Hennig, Philipp; Osborne, Michael A.; Girolami, Mark
2015-01-01
We deliver a call to arms for probabilistic numerical methods: algorithms for numerical tasks, including linear algebra, integration, optimization and solving differential equations, that return uncertainties in their calculations. Such uncertainties, arising from the loss of precision induced by numerical calculation with limited time or hardware, are important for much contemporary science and industry. Within applications such as climate science and astrophysics, the need to make decisions on the basis of computations with large and complex data have led to a renewed focus on the management of numerical uncertainty. We describe how several seminal classic numerical methods can be interpreted naturally as probabilistic inference. We then show that the probabilistic view suggests new algorithms that can flexibly be adapted to suit application specifics, while delivering improved empirical performance. We provide concrete illustrations of the benefits of probabilistic numeric algorithms on real scientific problems from astrometry and astronomical imaging, while highlighting open problems with these new algorithms. Finally, we describe how probabilistic numerical methods provide a coherent framework for identifying the uncertainty in calculations performed with a combination of numerical algorithms (e.g. both numerical optimizers and differential equation solvers), potentially allowing the diagnosis (and control) of error sources in computations. PMID:26346321
Numerical investigation of fluid flow in a chandler loop.
Touma, Hisham; Sahin, Iskender; Gaamangwe, Tidimogo; Gorbet, Maud B; Peterson, Sean D
2014-07-01
The Chandler loop is an artificial circulatory platform for in vitro hemodynamic experiments. In most experiments, the working fluid is subjected to a strain rate field via rotation of the Chandler loop, which, in turn, induces biochemical responses of the suspended cells. For low rotation rates, the strain rate field can be approximated using laminar flow in a straight tube. However, as the rotation rate increases, the effect of the tube curvature causes significant deviation from the laminar straight tube approximation. In this manuscript, we investigate the flow and associated strain rate field of an incompressible Newtonian fluid in a Chandler loop as a function of the governing nondimensional parameters. Analytical estimates of the strain rate from a perturbation solution for pressure driven steady flow in a curved tube suggest that the strain rate should increase with Dean number, which is proportional to the tangential velocity of the rotating tube, and the radius to radius of curvature ratio of the loop. Parametrically varying the rotation rate, tube geometry, and fill ratio of the loop show that strain rate can actually decrease with Dean number. We show that this is due to the nonlinear relationship between the tube rotation rate and height difference between the two menisci in the rotating tube, which provides the driving pressure gradient. An alternative Dean number is presented to naturally incorporate the fill ratio and collapse the numerical data. Using this modified Dean number, we propose an empirical formula for predicting the average fluid strain rate magnitude that is valid over a much wider parameter range than the more restrictive straight tube-based prediction. PMID:24686927
The Validity of Reading Comprehension Rate: Reading Speed, Comprehension, and Comprehension Rates
ERIC Educational Resources Information Center
Skinner, Christopher H.; Williams, Jacqueline L.; Morrow, Jennifer Ann; Hale, Andre D.; Neddenriep, Christine E.; Hawkins, Renee O.
2009-01-01
This article describes a secondary analysis of a brief reading comprehension rate measure, percent comprehension questions correct per minute spent reading (%C/M). This measure includes reading speed (seconds to read) in the denominator and percentage of comprehension questions answered correctly in the numerator. Participants were 22 4th-, 29…
Fertility Clinic Success Rates
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... page: //medlineplus.gov/ency/article/007305.htm Glomerular filtration rate To use the sharing features on this page, please enable JavaScript. Glomerular filtration rate (GFR) is a test used to check ...
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Rocket Engine Numerical Simulator (RENS)
NASA Technical Reports Server (NTRS)
Davidian, Kenneth O.
1997-01-01
Work is being done at three universities to help today's NASA engineers use the knowledge and experience of their Apolloera predecessors in designing liquid rocket engines. Ground-breaking work is being done in important subject areas to create a prototype of the most important functions for the Rocket Engine Numerical Simulator (RENS). The goal of RENS is to develop an interactive, realtime application that engineers can utilize for comprehensive preliminary propulsion system design functions. RENS will employ computer science and artificial intelligence research in knowledge acquisition, computer code parallelization and objectification, expert system architecture design, and object-oriented programming. In 1995, a 3year grant from the NASA Lewis Research Center was awarded to Dr. Douglas Moreman and Dr. John Dyer of Southern University at Baton Rouge, Louisiana, to begin acquiring knowledge in liquid rocket propulsion systems. Resources of the University of West Florida in Pensacola were enlisted to begin the process of enlisting knowledge from senior NASA engineers who are recognized experts in liquid rocket engine propulsion systems. Dr. John Coffey of the University of West Florida is utilizing his expertise in interviewing and concept mapping techniques to encode, classify, and integrate information obtained through personal interviews. The expertise extracted from the NASA engineers has been put into concept maps with supporting textual, audio, graphic, and video material. A fundamental concept map was delivered by the end of the first year of work and the development of maps containing increasing amounts of information is continuing. Find out more information about this work at the Southern University/University of West Florida. In 1996, the Southern University/University of West Florida team conducted a 4day group interview with a panel of five experts to discuss failures of the RL10 rocket engine in conjunction with the Centaur launch vehicle. The
Theoretical and numerical predictions of hypervelocity impact-generated plasma
Li, Jianqiao; Song, Weidong Ning, Jianguo
2014-08-15
The hypervelocity impact generated plasmas (HVIGP) in thermodynamic non-equilibrium state were theoretically analyzed, and a physical model was presented to explore the relationship between plasma ionization degree and internal energy of the system by a group of equations including a chemical reaction equilibrium equation, a chemical reaction rate equation, and an energy conservation equation. A series of AUTODYN 3D (a widely used software in dynamic numerical simulations and developed by Century Dynamic Inc.) numerical simulations of the impacts of hypervelocity Al projectile on its targets at different incident angles were performed. The internal energy and the material density obtained from the numerical simulations were then used to calculate the ionization degree and the electron temperature. Based on a self-developed 2D smooth particle hydrodynamic (SPH) code and the theoretical model, the plasmas generated by 6 hypervelocity impacts were directly simulated and their total charges were calculated. The numerical results are in good agreements with the experimental results as well as the empirical formulas, demonstrating that the theoretical model is justified by the AUTODYN 3D and self-developed 2D SPH simulations and applicable to predict HVIGPs. The study is of significance for astrophysical and cosmonautic researches and safety.
Sequential analysis of the numerical Stroop effect reveals response suppression.
Cohen Kadosh, Roi; Gevers, Wim; Notebaert, Wim
2011-09-01
Automatic processing of irrelevant stimulus dimensions has been demonstrated in a variety of tasks. Previous studies have shown that conflict between relevant and irrelevant dimensions can be reduced when a feature of the irrelevant dimension is repeated. The specific level at which the automatic process is suppressed (e.g., perceptual repetition, response repetition), however, is less understood. In the current experiment we used the numerical Stroop paradigm, in which the processing of irrelevant numerical values of 2 digits interferes with the processing of their physical size, to pinpoint the precise level of the suppression. Using a sequential analysis, we dissociated perceptual repetition from response repetition of the relevant and irrelevant dimension. Our analyses of reaction times, error rates, and diffusion modeling revealed that the congruity effect is significantly reduced or even absent when the response sequence of the irrelevant dimension, rather than the numerical value or the physical size, is repeated. These results suggest that automatic activation of the irrelevant dimension is suppressed at the response level. The current results shed light on the level of interaction between numerical magnitude and physical size as well as the effect of variability of responses and stimuli on automatic processing. PMID:21500951
Numerical analysis of volcanic SO{sub 2} plume transport
Uno, Itsushi
1996-12-31
Mt. Sakurajima volcano (1060m) located southern part of Kyushu island, Japan, emitted a huge amount of volcanic gas (e.g., 1000-2000 SO{sub 2}-ton/day) and has a strong impact in the environmental SO{sub 2} concentration. This volcanic SO{sub 2} plume transport process over the Kyushu island was simulated by a random walk model based on the wind and turbulence fields simulated by a mesoscale numerical model using four-dimensional data assimilation (FDDA). Continuous four days of numerical simulation was the period covering from May 7 to May 10, 1987. Grided global analysis by ECMWF and the special pilot-balloon observation data were used in the FDDA. Mesoscale numerical model with FDDA simulated well the general wind fields during the passage of high pressure system, and the complicated local wind circulation within the planetary boundary layer (PBL). Simulated surface wind variation was quantitatively compared with the observation data, and showed the good agreements. Numerical results of plume transport process were compared with SO{sub 2} surface and 3-D airborne measurements. It was revealed that simulated three-dimensional plume behavior explained well the observed SO{sub 2} variation, and the day-time development of PBL played an important role for the transport of the volcanic SO{sub 2} aloft to the surface level. Transformation rate from SO{sub 2} to sulfate was also determined from the trajectory by the random walk calculation.
Numerical tests of nucleation theories for the Ising models
NASA Astrophysics Data System (ADS)
Ryu, Seunghwa; Cai, Wei
2010-07-01
The classical nucleation theory (CNT) is tested systematically by computer simulations of the two-dimensional (2D) and three-dimensional (3D) Ising models with a Glauber-type spin flip dynamics. While previous studies suggested potential problems with CNT, our numerical results show that the fundamental assumption of CNT is correct. In particular, the Becker-Döring theory accurately predicts the nucleation rate if the correct droplet free energy function is provided as input. This validates the coarse graining of the system into a one dimensional Markov chain with the largest droplet size as the reaction coordinate. Furthermore, in the 2D Ising model, the droplet free energy predicted by CNT matches numerical results very well, after a logarithmic correction term from Langer’s field theory and a constant correction term are added. But significant discrepancies are found between the numerical results and existing theories on the magnitude of the logarithmic correction term in the 3D Ising model. Our analysis underscores the importance of correctly accounting for the temperature dependence of surface energy when comparing numerical results and nucleation theories.
Numerical estimation of cavitation intensity
NASA Astrophysics Data System (ADS)
Krumenacker, L.; Fortes-Patella, R.; Archer, A.
2014-03-01
Cavitation may appear in turbomachinery and in hydraulic orifices, venturis or valves, leading to performance losses, vibrations and material erosion. This study propose a new method to predict the cavitation intensity of the flow, based on a post-processing of unsteady CFD calculations. The paper presents the analyses of cavitating structures' evolution at two different scales: • A macroscopic one in which the growth of cavitating structures is calculated using an URANS software based on a homogeneous model. Simulations of cavitating flows are computed using a barotropic law considering presence of air and interfacial tension, and Reboud's correction on the turbulence model. • Then a small one where a Rayleigh-Plesset software calculates the acoustic energy generated by the implosion of the vapor/gas bubbles with input parameters from macroscopic scale. The volume damage rate of the material during incubation time is supposed to be a part of the cumulated acoustic energy received by the solid wall. The proposed analysis method is applied to calculations on hydrofoil and orifice geometries. Comparisons between model results and experimental works concerning flow characteristic (size of cavity, pressure,velocity) as well as pitting (erosion area, relative cavitation intensity) are presented.
NASA Technical Reports Server (NTRS)
Pearsons, K. S.; Bennett, R. L.
1974-01-01
The handbook was compiled to provide information in a concise form, describing the multitude of noise rating schemes. It is hoped that by describing the noise rating methods in a single volume the user will have better access to the definitions, application and calculation procedures of the current noise rating methods.
Electrohydraulic forming of dual phase steels; numerical and experimental work
NASA Astrophysics Data System (ADS)
Hassannejadasl, Amir; Green, Daniel E.; Golovashchenko, Sergey F.
2013-12-01
Electrohydraulic Forming (EHF) is a high velocity forming process, in which the strain-rate in the sheet metal can reach very high values depending on the prescribed input energy, the chamber geometry, the die geometry, instrumentation efficiency and the mechanical properties of the sheet material. In EHF, a high voltage discharge between electrodes that are submerged in a water-filled chamber generates a plasma channel that leads to propagation of a shockwave through the water that forms the sheet, with or without a die, in less than a millisecond. EHF generates a complex pressure pulse history that is extremely challenging to simulate. In this work, three-dimensional finite element simulations of DP590 sheet were completed in free-forming (EHFF) and die-forming (EHDF) conditions using ABAQUS/Explicit and a combination of Eulerian and Lagrangian elements. The Johnson-Cook constitutive plasticity model was selected and the parameters were calibrated based on uniaxial tensile test data at different strain-rates. A comprehensive numerical study was carried out with a view to understanding the differences between EHFF and EHDF in terms of the history of the deformation profile of the specimen, the strain-rate history, the loading path and through-thickness stresses. Higher strain-rates and more complex strain-paths were predicted in EHDF compared to EHFF due to dynamic sheet/die interaction. Good correlation between the experimental and numerical results demonstrated the ability of numerical models to accurately predict the history of the deformation profile in both EHDF and EHFF conditions.
Numerical Modeling of the Stability of Face-Centered Cubic Metals with High Vacancy Concentration
Brian P. Somerday; M. I. Baskes
1998-12-01
The objective of this research is to assess the possibility of forming an atomically porous structure in a low-density metal, e.g., Al with vacancies up to 0.20/lattice site; and to examine the effects of hydrogen and vacancy concentration on the stability of an atomically porous structure that has been experimentally produced in nickel. The approach involves numerical modeling using the Embedded-Atom Method (EAM). High vacancy concentrations cause the Al lattice to disorder at 300K. In contrast, Ni retains the face-centered-cubic structure at 300K for vacancy concentrations up to 0.15 Vac/lattice site. Unexpectedly, the lattice with 0.15 Vac/lattice site is more stable than the lattice with 0.10 or 0.20 Vac/lattice site. The Ni systems with 0.10 and 0.15 Vac/lattice site exhibit domains consisting of uniform lattice rotations. The Ni lattice with 0.15 Vac/lattice site is more stable with an initial distribution of random vacancies compared to ordered vacancies. The equilibrium lattice structures of Ni a d Al containing vacancies and H are less ordered to structures with vacancies only at 300K.
Numerical simulation of seasonal groundwater pumping
NASA Astrophysics Data System (ADS)
Filimonova, Elena; Baldenkov, Mikhail
2015-04-01
Increasing scarcity and contamination of water recourses require innovative water management strategies such as combined water system. The combined water system is a complex technology comprising two separate wells, major catchment-zone well and compensation pumping well, located inside a single stream basin. The major well is supplied by the well's catchment zone or surface flow, thus depleting the stream flow. The pumping rate of a major well is determined by the difference between the current stream flow and the minimum permissible stream flow. The deficiency of the stream flow in dry seasons can be compensated for by the short-term pumping of groundwater. The compensation pumping rate is determined by the difference between water demand and the permissible water withdrawal of the major well. The source for the compensation well is the aquifer storage. The estimation of streamflow depletion caused by compensation pumping is major question to evaluate the efficiency of the combined water system. Short-term groundwater pumping can use aquifer storage instead of catchment-zone water until the drawdown reaches the edge of the stream. Traditionally pumping simulation calculates in two-step procedure. Natural conditions, an aquifer system is in an approximate dynamic equilibrium, describe by steady-state model. A steady-state solution provides an initial heads, a set of flows through boundaries, and used as initial state for transient solutions, when pumping is imposed on an aquifer system. The transient solutions provide the total change in flows through the boundaries. A difference between the transient and steady-state solutions estimates the capture and the streamflow depletion. Numerical modeling of cyclical compensation pumping has special features: the periodic solution, the seasonal changes through the boundaries and the importance even small drawdown of stream level. When seasonality is a modeling feature, traditional approach leads to mistaken values of
MHD micropumping of power-law fluids: A numerical solution
NASA Astrophysics Data System (ADS)
Moghaddam, Saied
2013-02-01
The performance of MHD micropumps is studied numerically assuming that the viscosity of the fluid is shear-dependent. Using power-law model to represent the fluid of interest, the effect of power-law exponent, N, is investigated on the volumetric flow rate in a rectangular channel. Assuming that the flow is laminar, incompressible, two-dimensional, but (approximately) unidirectional, finite difference method (FDM) is used to solve the governing equations. It is found that shear-thinning fluids provide a larger flow rate as compared to Newtonian fluids provided that the Hartmann number is above a critical value. There exists also an optimum Hartmann number (which is larger than the critical Hartmann number) at which the flow rate is maximum. The power-law exponent, N, strongly affects the optimum geometry depending on the Hartmann number being smaller or larger than the critical Hartmann number.
Numerical Magnitude Representations Influence Arithmetic Learning
ERIC Educational Resources Information Center
Booth, Julie L.; Siegler, Robert S.
2008-01-01
This study examined whether the quality of first graders' (mean age = 7.2 years) numerical magnitude representations is correlated with, predictive of, and causally related to their arithmetic learning. The children's pretest numerical magnitude representations were found to be correlated with their pretest arithmetic knowledge and to be…
Pure Left Neglect for Arabic Numerals
ERIC Educational Resources Information Center
Priftis, Konstantinos; Albanese, Silvia; Meneghello, Francesca; Pitteri, Marco
2013-01-01
Arabic numerals are diffused and language-free representations of number magnitude. To be effectively processed, the digits composing Arabic numerals must be spatially arranged along a left-to-right axis. We studied one patient (AK) to show that left neglect, after right hemisphere damage, can selectively impair the computation of the spatial…
An Integrative Theory of Numerical Development
ERIC Educational Resources Information Center
Siegler, Robert; Lortie-Forgues, Hugues
2014-01-01
Understanding of numerical development is growing rapidly, but the volume and diversity of findings can make it difficult to perceive any coherence in the process. The integrative theory of numerical development posits that a coherent theme is present, however--progressive broadening of the set of numbers whose magnitudes can be accurately…
Numerical Integration: One Step at a Time
ERIC Educational Resources Information Center
Yang, Yajun; Gordon, Sheldon P.
2016-01-01
This article looks at the effects that adding a single extra subdivision has on the level of accuracy of some common numerical integration routines. Instead of automatically doubling the number of subdivisions for a numerical integration rule, we investigate what happens with a systematic method of judiciously selecting one extra subdivision for…
Numerical experiments on the theta pinch
NASA Technical Reports Server (NTRS)
Volosevich, P. P.; Zukakishyili, G. G.
1979-01-01
Numerical calculation of theta pinch problems are presented. Physical processes in theta pinch systems are considered in a one dimensional, two temperature magnetohydrodynamic, approximation with allowance for end losses by longitudinal heat conductivity. The numerical calculations are compared with results of earlier experiments.
Nonclassicality thresholds for multiqubit states: Numerical analysis
Gruca, Jacek; Zukowski, Marek; Laskowski, Wieslaw; Kiesel, Nikolai; Wieczorek, Witlef; Weinfurter, Harald; Schmid, Christian
2010-07-15
States that strongly violate Bell's inequalities are required in many quantum-informational protocols as, for example, in cryptography, secret sharing, and the reduction of communication complexity. We investigate families of such states with a numerical method which allows us to reveal nonclassicality even without direct knowledge of Bell's inequalities for the given problem. An extensive set of numerical results is presented and discussed.
NUMERICAL NOISE PM SIMULATION IN CMAQ
We have found that numerical noise in the latest release of CMAQ using the yamo advection scheme when compiled on Linux cluster with pgf90 (5.0 or 6.0). We recommend to use -C option to eliminate the numerical noise.
Handbook on Numerically Controlled Operational Devices.
ERIC Educational Resources Information Center
Campbell, Clifton P.
This handbook presents an organized set of descriptive information on numerically controlled operational devices. The information is intended for those involved in industry and technical education and to contribute to the knowledge of numerical control technology. It is also intended for supervisors, manufacturers, machine operators, and others…
Intersensory Redundancy Accelerates Preverbal Numerical Competence
ERIC Educational Resources Information Center
Jordan, Kerry E.; Suanda, Sumarga H.; Brannon, Elizabeth M.
2008-01-01
Intersensory redundancy can facilitate animal and human behavior in areas as diverse as rhythm discrimination, signal detection, orienting responses, maternal call learning, and associative learning. In the realm of numerical development, infants show similar sensitivity to numerical differences in both the visual and auditory modalities. Using a…
Numerical Investigation of Slag Behavior for RSRM
NASA Technical Reports Server (NTRS)
Liaw, P.; Chen, Y.-S.; Shang, H.; Shih, M.; Doran, D.; Stewart, E.
1996-01-01
It is known that the flow field of the redesigned solid rocket motor (RSRM) is very complicated due to the complex characteristics of turbulent multi-phase flow, chemical reaction, particle combustion, evaporation, breakup and agglomeration etc. It requires multi-phase calculations, chemical reaction simulation, and particle combustion, evaporation, and breakup models to obtain a better understanding of thermophysics for the RSRM design using numerical methods. Also, the slag buildup due to the molten particles is another factor affecting the performance of the RSRM. To achieve this goal, the volume of fluid (VOF) method is used to capture the free surface motion so as to simulate the accumulation of the molten particles (slag) of the RSRM. A finite rate chemistry model is used to simulate the chemical reaction effects. For multi-phase calculations, the Hermsen combustion model is used for the aluminum particle combustion analysis and the Taylor Analogy Breakup (TAB) model is used for the particle breakup analysis. An interphase mas-exchange model introduced by Spalding is used for the evaporation calculation. The particle trajectories are calculated using a one-step implicit method for several groups of particle sizes by which the drag forces and heat fluxes are then coupled with the gas phase equations. The preliminary results predicted a reasonable physical simulation of the particle effects using a simple two dimensional solid rocket motor configuration. It shows that the AL/AL2O3 particle sizes are reduced due to the combustion, evaporation, and breakup. The flow field is disturbed by the particles. Mach number distributions in the nozzle are deformed due to the effect of particle concentrations away from the center line.
Numerical simulation of baroclinic Jovian vortices
NASA Astrophysics Data System (ADS)
Achterberg, R. K.; Ingersoll, A. P.
1994-02-01
We examine the evolution of baroclinic vortices in a time-dependent, nonlinear numerical model of a Jovian atmosphere. The model uses a normal-mode expansion in the vertical, using the barotropic and first two baroclinic modes. Results for the stability of baroclinic vortices on an f plane in the absence of a mean zonal flow are similar to results of Earth vortex models, although the presence of a fluid interior on the Jovian planets shifts the stability boundaries to smaller length scales. The presence of a barotropic mean zonal flow in the interior stabilizes vortices against instability and significantly modifies the finite amplitude form of baroclinic instabilities. The effect of a zonal flow on a form of barotropic instability produces periodic oscillations in the latitude and longitude of the vortex as observed at the level of the cloud tops. This instability may explain some, but not all, observations of longitudinal oscillations of vortices on the outer planets. Oscillations in aspect ratio and orientation of stable vortices in a zonal shear flow are observed in this baroclinic model, as in simpler two-dimensional models. Such oscillations are also observed in the atmospheres of Jupiter and Neptune. The meridional propagation and decay of vortices on a beta plane is inhibited by the presence of a mean zonal flow. The direction of propagation of a vortex relative to the mean zonal flow depends upon the sign of the meridional potential vorticity gradient; combined with observations of vortex drift rates, this may provide a constraint on model assumption for the flow in the deep interior of the Jovian planets.
Rates and progenitors of type Ia supernovae
Wood-Vasey, William Michael
2004-08-16
analyzing the true sensitivity of a multi-epoch supernova search and finds a Type Ia supernova rate from z {approx} 0.01-0.1 of r{sub V} = 4.26{sub -1.93 -0.10}{sup +1.39 +0.10} h{sup 3} x 10{sup -4} SNe Ia/yr/Mpc{sup 3} from a preliminary analysis of a subsample of the SNfactory prototype search. Several unusual supernovae were found in the course of the SNfactory prototype search. One in particular, SN 2002ic, was the first SN Ia to exhibit convincing evidence for a circumstellar medium and offers valuable insight into the progenitors of Type Ia supernovae.
Zhou, Huan-Xiang
2012-01-01
Some of the rate theories that are most useful for modeling biological processes are reviewed. By delving into some of the details and subtleties in the development of the theories, the review will hopefully help the reader gain a more than superficial perspective. Examples are presented to illustrate how rate theories can be used to generate insight at the microscopic level into biomolecular behaviors. Attempt is made to clear up a number of misconceptions in the literature regarding popular rate theories, including the appearance of Planck’s constant in the transition-state theory and the Smoluchowski result as an upper limit for protein-protein and protein-DNA association rate constants. Future work in combining the implementation of rate theories through computer simulations with experimental probes of rate processes, and in modeling effects of intracellular environments so theories can be used for generating rate constants for systems biology studies is particularly exciting. PMID:20691138
Cox, T.J.; Runkel, R.L.
2008-01-01
Past applications of one-dimensional advection, dispersion, and transient storage zone models have almost exclusively relied on a central differencing, Eulerian numerical approximation to the nonconservative form of the fundamental equation. However, there are scenarios where this approach generates unacceptable error. A new numerical scheme for this type of modeling is presented here that is based on tracking Lagrangian control volumes across a fixed (Eulerian) grid. Numerical tests are used to provide a direct comparison of the new scheme versus nonconservative Eulerian numerical methods, in terms of both accuracy and mass conservation. Key characteristics of systems for which the Lagrangian scheme performs better than the Eulerian scheme include: nonuniform flow fields, steep gradient plume fronts, and pulse and steady point source loadings in advection-dominated systems. A new analytical derivation is presented that provides insight into the loss of mass conservation in the nonconservative Eulerian scheme. This derivation shows that loss of mass conservation in the vicinity of spatial flow changes is directly proportional to the lateral inflow rate and the change in stream concentration due to the inflow. While the nonconservative Eulerian scheme has clearly worked well for past published applications, it is important for users to be aware of the scheme's limitations. ?? 2008 ASCE.
Numerical simulations of cryogenic cavitating flows
NASA Astrophysics Data System (ADS)
Kim, Hyunji; Kim, Hyeongjun; Min, Daeho; Kim, Chongam
2015-12-01
The present study deals with a numerical method for cryogenic cavitating flows. Recently, we have developed an accurate and efficient baseline numerical scheme for all-speed water-gas two-phase flows. By extending such progress, we modify the numerical dissipations to be properly scaled so that it does not show any deficiencies in low Mach number regions. For dealing with cryogenic two-phase flows, previous EOS-dependent shock discontinuity sensing term is replaced with a newly designed EOS-free one. To validate the proposed numerical method, cryogenic cavitating flows around hydrofoil are computed and the pressure and temperature depression effect in cryogenic cavitation are demonstrated. Compared with Hord's experimental data, computed results are turned out to be satisfactory. Afterwards, numerical simulations of flow around KARI turbopump inducer in liquid rocket are carried out under various flow conditions with water and cryogenic fluids, and the difference in inducer flow physics depending on the working fluids are examined.
A numerical method for cardiac mechanoelectric simulations.
Pathmanathan, Pras; Whiteley, Jonathan P
2009-05-01
Much effort has been devoted to developing numerical techniques for solving the equations that describe cardiac electrophysiology, namely the monodomain equations and bidomain equations. Only a limited selection of publications, however, address the development of numerical techniques for mechanoelectric simulations where cardiac electrophysiology is coupled with deformation of cardiac tissue. One problem commonly encountered in mechanoelectric simulations is instability of the coupled numerical scheme. In this study, we develop a stable numerical scheme for mechanoelectric simulations. A number of convergence tests are carried out using this stable technique for simulations where deformations are of the magnitude typically observed in a beating heart. These convergence tests demonstrate that accurate computation of tissue deformation requires a nodal spacing of around 1 mm in the mesh used to calculate tissue deformation. This is a much finer computational grid than has previously been acknowledged, and has implications for the computational efficiency of the resulting numerical scheme. PMID:19263223
Confidence bands for measured economically optimal nitrogen rates
Technology Transfer Automated Retrieval System (TEKTRAN)
While numerous researchers have computed economically optimal N rate (EONR) values from measured yield – N rate data, nearly all have neglected to compute or estimate the statistical reliability of these EONR values. In this study, a simple method for computing EONR and its confidence bands is descr...
Rate-based ABR flow control using two timescale SPSA
NASA Astrophysics Data System (ADS)
Bhatnagar, Shalabh; Fu, Michael C.; Marcus, Steven I.
1999-08-01
In this paper, a two timescale simultaneous perturbation stochastic approximation algorithm is developed and applied to closed loop rate based available bit rate flow control. The relevant convergence results are stated and explained. Numerical experiments demonstrate fast convergence even in the presence of significant delays and a large number of parameterized policy levels.
Did Unilateral Divorce Laws Raise Divorce Rates in Western Europe?
ERIC Educational Resources Information Center
Kneip, Thorsten; Bauer, Gerrit
2009-01-01
The increase in European divorce rates over the past decades was accompanied by several changes in divorce laws. Yet for European countries, research on the effects of divorce law on the divorce rate is scarce. Most of the existing studies are based on data from North America and provide numerous, but inconsistent, results. We use fixed-effects…
Numerical and experimental study of rotating jet flows
NASA Astrophysics Data System (ADS)
Shin, Seungwon; Che, Zhizhao; Kahouadji, Lyes; Matar, Omar; Chergui, Jalel; Juric, Damir
2015-11-01
Rotating jets are investigated through experimental measurements and numerical simulations. The experiments are performed on a rotating jet rig and the effects of a range of parameters controlling the liquid jet are investigated, e.g. jet flow rate, rotation speed, jet diameter, etc. Different regimes of the jet morphology are identified, and the dependence on several dimensionless numbers is studied, e.g. Reynolds number, Weber number, etc. The breakup process of droplets is visualized through high speed imaging. Full three-dimensional direct numerical simulations are performed using BLUE, a massively parallel two-phase flow code. The novel interface algorithms in BLUE track the gas-liquid interface through a wide dynamic range including ligament formation, break up and rupture. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
Numerical Estimation of the Curvature of Biological Surfaces
NASA Technical Reports Server (NTRS)
Todd, P. H.
1985-01-01
Many biological systems may profitably be studied as surface phenomena. A model consisting of isotropic growth of a curved surface from a flat sheet is assumed. With such a model, the Gaussian curvature of the final surface determines whether growth rate of the surface is subharmonic or superharmonic. These properties correspond to notions of convexity and concavity, and thus to local excess growth and local deficiency of growth. In biological models where the major factors controlling surface growth are intrinsic to the surface, researchers thus gained from geometrical study information on the differential growth undergone by the surface. These ideas were applied to an analysis of the folding of the cerebral cortex, a geometrically rather complex surface growth. A numerical surface curvature technique based on an approximation to the Dupin indicatrix of the surface was developed. A metric for comparing curvature estimates is introduced, and considerable numerical testing indicated the reliability of this technique.
Numerical study of unsteady processes in a Faraday MHD generator
NASA Astrophysics Data System (ADS)
Vinogradova, G. N.; Panchenko, V. P.
1981-07-01
A numerical study is presented on the unsteady processes occurring in a Faraday MHD generator with a high power-conversion efficiency. A supersonic MHD generator operating with an equilibrium plasma and designed to convert energy in a system using a thermonuclear reactor is considered, and the steady operating modes are established for cases when an ohmic load is connected, disconnected, or reduced. A magnetic field is assumed to be generated by a suitable profiling of the external magnetic field, and the working medium is modeled by an ideal gas. Partial differential equations are solved numerically by using a central difference predictor-corrector scheme. The study can be applied to problems (e.g., transient times, nominal parameter maximal values and rates of change, methods of regulating the generator and switching it on and off) arising during the design of MHD generators.
Holloway, Ian D; Ansari, Daniel
2009-05-01
Although it is often assumed that abilities that reflect basic numerical understanding, such as numerical comparison, are related to children's mathematical abilities, this relationship has not been tested rigorously. In addition, the extent to which symbolic and nonsymbolic number processing play differential roles in this relationship is not yet understood. To address these questions, we collected mathematics achievement measures from 6- to 8-year-olds as well as reaction times from a numerical comparison task. Using the reaction times, we calculated the size of the numerical distance effect exhibited by each child. In a correlational analysis, we found that the individual differences in the distance effect were related to mathematics achievement but not to reading achievement. This relationship was found to be specific to symbolic numerical comparison. Implications for the role of basic numerical competency and the role of accessing numerical magnitude information from Arabic numerals for the development of mathematical skills and their impairment are discussed. PMID:18513738
Leukocyte margination at arteriole shear rate
Takeishi, Naoki; Imai, Yohsuke; Nakaaki, Keita; Yamaguchi, Takami; Ishikawa, Takuji
2014-01-01
Abstract We numerically investigated margination of leukocytes at arteriole shear rate in straight circular channels with diameters ranging from 10 to 22 μm. Our results demonstrated that passing motion of RBCs effectively induces leukocyte margination not only in small channels but also in large channels. A longer time is needed for margination to occur in a larger channel, but once a leukocyte has marginated, passing motion of RBCs occurs continuously independent of the channel diameter, and leukocyte margination is sustained for a long duration. We also show that leukocytes rarely approach the wall surface to within a microvillus length at arteriole shear rate. PMID:24907300
Experimental determination of chlorite dissolution rates
Rochelle, C.A.; Bateman, K.; MacGregor, R.; Pearce, J.M.; Wetton, P.D.; Savage, D.
1995-12-31
Current concepts of the geological disposal of low- and intermediate-level radioactive wastes in the UK envisage the construction of a mined facility (incorporating cementitious engineered barriers) in chlorite-bearing rocks. To model accurately the fluid-rock reactions within the disturbed zone surrounding a repository requires functions that describe mineral dissolution kinetics under pH conditions that vary from near neutral to highly alkaline. Therefore, an experimental study to determine the dissolution rates of Fe-rich chlorite has been undertaken as part of the Nirex Safety Assessment Research Program. Four experiments have been carried out at 25 C and four at 70 C, both sets using a range of NaCl/NaOH solutions of differing pH (of nominal pH 9.0, 10.3, 11.6 and 13.0 [at 25 C]). Dissolution rates have been calculated and were found to increase with increasing pH and temperature. However, increased pH resulted in non-stoichiometric dissolution possibly due to preferential dissolution of part of the chlorite structure relative to another, or reprecipitation of some elements as thin hydroxide or oxyhydroxide surface coatings on the chlorite. These results also show that chlorite dissolution is appreciably slower than that of albite and quartz at both 25 and 70 C, but slightly faster than that of muscovite at 70 C.
Numerical Studies of High-Z Plasma in the HyperV Plasma Guns
NASA Astrophysics Data System (ADS)
Wu, Linchun; Messer, Sarah; Witherspoon, F. Douglas; Welch, Dale; Thoma, Carsten; Phillips, Mike; Bogatu, I. Nick; Galkin, Sergei; Macfarlane, Joe; Golovkin, Igor
2010-11-01
Numerical studies of railguns and coaxial guns at HyperV Technologies Corp. include simulations of hypervelocity plasma transport in the gun, plasma expansion out of the nozzle, and two or more jets merging in vacuum. Plasma detachment, merging jets temperature and charge state evolution are examined in these processes. High-Z materials, such as argon and xenon, are used throughout these simulations. The plasma moves with an initial velocity of 0-10 km/s (80-100 km/s for jet merging), the initial number density ranges from 10^15cm-3 to 10^18cm-3, and the merging jets are several centimeters in radius. The LSP code is used to perform the simulations using improved fluid algorithms and equation-of-state models from Voss and atomic data from Prism.
Numerical simulation and modeling of combustion in scramjets
NASA Astrophysics Data System (ADS)
Clark, Ryan James
In the last fifteen years the development of a viable scramjet has quickly approached the following long term goals: responsive sub-orbital space access; long-range, prompt global strike; and high-speed transportation. Nonetheless, there are significant challenges that need to be resolved. These challenges include high skin friction drag and high heat transfer rates, inherent to vehicles in sustained, hypersonic flight. Another challenge is sustaining combustion. Numerical simulation and modeling was performed to provide insight into reducing skin friction drag and sustaining combustion. Numerical simulation was used to investigate boundary layer combustion, which has been shown to reduce skin friction drag. The objective of the numerical simulations was to quantify the effect of fuel injection parameters on boundary layer combustion and ultimately on the change in the skin friction coefficient and heat transfer rate. A qualitative analysis of the results suggest that the reduction in the skin friction coefficient depends on multiple parameters and potentially an interaction between parameters. Sustained combustion can be achieved through a stabilized detonation wave. Additionally, stabilizing a detonation wave will yield rapid combustion. This will allow for a shorter and lighter-weight engine system, resulting in less required combustor cooling. A stabilized detonation wave was numerically modeled for various inlet and geometric cases. The effect of fuel concentration, inlet Mach number, and geometric configuration on the stability of a detonation wave was quantified. Correlations were established between fuel concentration, inlet speed, geometric configuration and parameters characterizing the detonation wave. A linear relationship was quantified between the fuel concentration and the parameters characterizing the detonation wave.
Technology Transfer Automated Retrieval System (TEKTRAN)
In-situ determination of ice formation and thawing in soils is difficult despite its importance for many environmental processes. A sensible heat balance (SHB) method using a sequence of heat pulse probes has been shown to accurately measure water evaporation in subsurface soil, and it has the poten...
Concepts for radically increasing the numerical convergence rate of the Euler equations
NASA Technical Reports Server (NTRS)
Nixon, David; Tzuoo, Keh-Lih; Caruso, Steven C.; Farshchi, Mohammad; Klopfer, Goetz H.; Ayoub, Alfred
1987-01-01
Integral equation and finite difference methods have been developed for solving transonic flow problems using linearized forms of the transonic small disturbance and Euler equations. A key element is the use of a strained coordinate system in which the shock remains fixed. Additional criteria are developed to determine the free parameters in the coordinate straining; these free parameters are functions of the shock location. An integral equation analysis showed that the shock is located by ensuring that no expansion shocks exist in the solution. The expansion shock appears as oscillations in the solution near the sonic line, and the correct shock location is determined by removing these oscillations. A second objective was to study the ability of the Euler equation to model separated flow.
Riley, William J.; Gaudinski, Julia B.; Torn, Margaret S.; JoslinJr., John D.; Hanson, Paul J
2009-01-01
Carbon (C) fluxes through roots are the most uncertain of all C exchanges between the atmosphere, plants, and soil. Yet the three dominant methods to characterize root C fluxes (minirhizotron, sequential coring, and isotopes) yield significantly different estimates of temperate forest root mortality turnover times. We contend that these discrepancies result from limitations in interpreting these very distinct types of observations. In this study we used a whole-ecosystem 14C label to develop, parameterize, and test a model (Radix1.0) of fine-root mortality and decomposition. Radix simulates two live roots pools (one with structural and non-structural C components), two dead root pools, non-normally distributed root mortality turnover times, a stored C pool, seasonal growth and respiration patterns, a best-fit to measurements approach to estimate model parameters, and Monte Carlo uncertainty analysis. We applied Radix at a temperate forest in Oak Ridge Tennessee using 14C measurements from two root size classes (<0.5 mm and 0.5−2.0 mm) and three soil depth increments (O horizon, 0−15, and 30−60 cm). Predicted root lifetimes were 0.1-0.9 y and 11-14 y for fast and slow live root pools respectively, and 0.1-4 y and 11-14 y for fast and slow dead root pool decomposition turnover times, respectively. We estimated that C fluxes through fine roots <2 mm diameter are ~40, 220, and 90 g C m-2 y 1 in the O horizon, 0−15 cm, and 30−60 cm depth intervals, respectively. We conclude that accurate characterization of C flows through fine roots required a model with two live fine-root pools, two dead fine-root pools, and root respiration. Further, root turnover times on the order of a decade imply different response times in biomass and growth than are currently predicted by models with a single annual turnover pool.
Numerical study of supersonic combustion using a finite rate chemistry model
NASA Technical Reports Server (NTRS)
Chitsomboon, T.; Tiwari, S. N.; Kumar, A.; Drummond, J. P.
1986-01-01
The governing equations of two-dimensional chemically reacting flows are presented together with a global two-step chemistry model for H2-air combustion. The explicit unsplit MacCormack finite difference algorithm is used to advance the discrete system of the governing equations in time until convergence is attained. The source terms in the species equations are evaluated implicitly to alleviate stiffness associated with fast reactions. With implicit source terms, the species equations give rise to a block-diagonal system which can be solved very efficiently on vector-processing computers. A supersonic reacting flow in an inlet-combustor configuration is calculated for the case where H2 is injected into the flow from the side walls and the strut. Results of the calculation are compared against the results obtained by using a complete reaction model.
Riley, W.J.; Gaudinski, J.B.; Torn, M.S.; Joslin, J.D.; Hanson, P.J.
2009-09-01
We used an inadvertent whole-ecosystem {sup 14}C label at a temperate forest in Oak Ridge, Tennessee, USA to develop a model (Radix1.0) of fine-root dynamics. Radix simulates two live-root pools, two dead-root pools, non-normally distributed root mortality turnover times, a stored carbon (C) pool, and seasonal growth and respiration patterns. We applied Radix to analyze measurements from two root size classes (< 0.5 and 0.5-2.0 mm diameter) and three soil-depth increments (O horizon, 0-15 cm and 30-60 cm). Predicted live-root turnover times were < 1 yr and 10 yr for short- and long-lived pools, respectively. Dead-root pools had decomposition turnover times of 2 yr and 10 yr. Realistic characterization of C flows through fine roots requires a model with two live fine-root populations, two dead fine-root pools, and root respiration. These are the first fine-root turnover time estimates that take into account respiration, storage, seasonal growth patterns, and non-normal turnover time distributions. The presence of a root population with decadal turnover times implies a lower amount of belowground net primary production used to grow fine-root tissue than is currently predicted by models with a single annual turnover pool.
Solutions of two-factor models with variable interest rates
NASA Astrophysics Data System (ADS)
Li, Jinglu; Clemons, C. B.; Young, G. W.; Zhu, J.
2008-12-01
The focus of this work is on numerical solutions to two-factor option pricing partial differential equations with variable interest rates. Two interest rate models, the Vasicek model and the Cox-Ingersoll-Ross model (CIR), are considered. Emphasis is placed on the definition and implementation of boundary conditions for different portfolio models, and on appropriate truncation of the computational domain. An exact solution to the Vasicek model and an exact solution for the price of bonds convertible to stock at expiration under a stochastic interest rate are derived. The exact solutions are used to evaluate the accuracy of the numerical simulation schemes. For the numerical simulations the pricing solution is analyzed as the market completeness decreases from the ideal complete level to one with higher volatility of the interest rate and a slower mean-reverting environment. Simulations indicate that the CIR model yields more reasonable results than the Vasicek model in a less complete market.
Numeral-Incorporating Roots in Numeral Systems: A Comparative Analysis of Two Sign Languages
ERIC Educational Resources Information Center
Fuentes, Mariana; Massone, Maria Ignacia; Fernandez-Viader, Maria del Pilar; Makotrinsky, Alejandro; Pulgarin, Francisca
2010-01-01
Numeral-incorporating roots in the numeral systems of Argentine Sign Language (LSA) and Catalan Sign Language (LSC), as well as the main features of the number systems of both languages, are described and compared. Informants discussed the use of numerals and roots in both languages (in most cases in natural contexts). Ten informants took part in…
An Introduction to Numerical Control. Problems for Numerical Control Part Programming.
ERIC Educational Resources Information Center
Campbell, Clifton P.
This combination text and workbook is intended to introduce industrial arts students to numerical control part programming. Discussed in the first section are the impact of numerical control, training efforts, numerical control in established programs, related information for drafting, and the Cartesian Coordinate System and dimensioning…
Observed Barium Emission Rates
NASA Technical Reports Server (NTRS)
Stenbaek-Nielsen, H. C.; Wescott, E. M.; Hallinan, T. J.
1993-01-01
The barium releases from the CRRES satellite have provided an opportunity for verifying theoretically calculated barium ion and neutral emission rates. Spectra of the five Caribbean releases in the summer of 1991 were taken with a spectrograph on board a U.S. Air Force jet aircraft. Because the line of sight release densities are not known, only relative rates could be obtained. The observed relative rates agree well with the theoretically calculated rates and, together with other observations, confirm the earlier detailed theoretical emission rates. The calculated emission rates can thus with good accuracy be used with photometric observations. It has been postulated that charge exchange between neutral barium and oxygen ions represents a significant source for ionization. If so. it should be associated with emissions at 4957.15 A and 5013.00 A, but these emissions were not detected.
Reliability of Complex Nonlinear Numerical Simulations
NASA Technical Reports Server (NTRS)
Yee, H. C.
2004-01-01
This work describes some of the procedure to ensure a higher level of confidence in the predictability and reliability (PAR) of numerical simulation of multiscale complex nonlinear problems. The focus is on relating PAR of numerical simulations with complex nonlinear phenomena of numerics. To isolate sources of numerical uncertainties, the possible discrepancy between the chosen partial differential equation (PDE) model and the real physics and/or experimental data is set aside. The discussion is restricted to how well numerical schemes can mimic the solution behavior of the underlying PDE model for finite time steps and grid spacings. The situation is complicated by the fact that the available theory for the understanding of nonlinear behavior of numerics is not at a stage to fully analyze the nonlinear Euler and Navier-Stokes equations. The discussion is based on the knowledge gained for nonlinear model problems with known analytical solutions to identify and explain the possible sources and remedies of numerical uncertainties in practical computations. Examples relevant to turbulent flow computations are included.
On Numerical Methods For Hypersonic Turbulent Flows
NASA Astrophysics Data System (ADS)
Yee, H. C.; Sjogreen, B.; Shu, C. W.; Wang, W.; Magin, T.; Hadjadj, A.
2011-05-01
Proper control of numerical dissipation in numerical methods beyond the standard shock-capturing dissipation at discontinuities is an essential element for accurate and stable simulation of hypersonic turbulent flows, including combustion, and thermal and chemical nonequilibrium flows. Unlike rapidly developing shock interaction flows, turbulence computations involve long time integrations. Improper control of numerical dissipation from one time step to another would be compounded over time, resulting in the smearing of turbulent fluctuations to an unrecognizable form. Hypersonic turbulent flows around re- entry space vehicles involve mixed steady strong shocks and turbulence with unsteady shocklets that pose added computational challenges. Stiffness of the source terms and material mixing in combustion pose yet other types of numerical challenges. A low dissipative high order well- balanced scheme, which can preserve certain non-trivial steady solutions of the governing equations exactly, may help minimize some of these difficulties. For stiff reactions it is well known that the wrong propagation speed of discontinuities occurs due to the under-resolved numerical solutions in both space and time. Schemes to improve the wrong propagation speed of discontinuities for systems of stiff reacting flows remain a challenge for algorithm development. Some of the recent algorithm developments for direct numerical simulations (DNS) and large eddy simulations (LES) for the subject physics, including the aforementioned numerical challenges, will be discussed.
Mean Element Propagations Using Numerical Averaging
NASA Technical Reports Server (NTRS)
Ely, Todd A.
2009-01-01
The long-term evolution characteristics (and stability) of an orbit are best characterized using a mean element propagation of the perturbed two body variational equations of motion. The averaging process eliminates short period terms leaving only secular and long period effects. In this study, a non-traditional approach is taken that averages the variational equations using adaptive numerical techniques and then numerically integrating the resulting EOMs. Doing this avoids the Fourier series expansions and truncations required by the traditional analytic methods. The resultant numerical techniques can be easily adapted to propagations at most solar system bodies.
Waste glass melter numerical and physical modeling
Eyler, L.L.; Peters, R.D.; Lessor, D.L.; Lowery, P.S.; Elliott, M.L.
1991-10-01
Results of physical and numerical simulation modeling of high-level liquid waste vitrification melters are presented. Physical modeling uses simulant fluids in laboratory testing. Visualization results provide insight into convective melt flow patterns from which information is derived to support performance estimation of operating melters and data to support numerical simulation. Numerical simulation results of several melter configurations are presented. These are in support of programs to evaluate melter operation characteristics and performance. Included are investigations into power skewing and alternating current electric field phase angle in a dual electrode pair reference design and bi-modal convective stability in an advanced design. 9 refs., 9 figs., 1 tab.
An algebraic approach to BCJ numerators
NASA Astrophysics Data System (ADS)
Fu, Chih-Hao; Du, Yi-Jian; Feng, Bo
2013-03-01
One important discovery in recent years is that the total amplitude of gauge theory can be written as BCJ form where kinematic numerators satisfy Jacobi identity. Although the existence of such kinematic numerators is no doubt, the simple and explicit construction is still an important problem. As a small step, in this note we provide an algebraic approach to construct these kinematic numerators. Under our Feynman-diagram-like construction, the Jacobi identity is manifestly satisfied. The corresponding color ordered amplitudes satisfy off-shell KK-relation and off-shell BCJ relation similar to the color ordered scalar theory. Using our construction, the dual DDM form is also established.
Coincidental match of numerical simulation and physics
NASA Astrophysics Data System (ADS)
Pierre, B.; Gudmundsson, J. S.
2010-08-01
Consequences of rapid pressure transients in pipelines range from increased fatigue to leakages and to complete ruptures of pipeline. Therefore, accurate predictions of rapid pressure transients in pipelines using numerical simulations are critical. State of the art modelling of pressure transient in general, and water hammer in particular include unsteady friction in addition to the steady frictional pressure drop, and numerical simulations rely on the method of characteristics. Comparison of rapid pressure transient calculations by the method of characteristics and a selected high resolution finite volume method highlights issues related to modelling of pressure waves and illustrates that matches between numerical simulations and physics are purely coincidental.
Numerical modeling of combustion dynamics in a lean premixed combustor
Cannon, S.M.; Smith, C.E.
1998-07-01
The objective of this study was to evaluate the ability of a time-accurate, 2-D axi-symmetric CFD model to accurately predict combustion dynamics in a premixed pipe combustor driven by mixture feed variation. Independently measured data, including the magnitude and frequency of combustor pressure, were used to evaluate the model. The Smagorinsky, RGN k-{var{underscore}epsilon}, and molecular viscosity models were used to describe the subgrid turbulence, and a one-step, finite-rate reaction to equilibrium products model was used to describe the subgrid chemistry. Swirl source terms were included within the premix passage's computational domain and allowed the model to retain known boundary conditions at the choked flow inlet and the constant pressure exit. To ensure pressure waves were accurately captured, 1-D numerical analyses were first performed to assess the effects of boundary conditions, temporal and spatial differencing, time step, and grid size. It was found that the selected numerical details produced little numerical dissipation of the pressure waves. Then, 2-D axisymmetric analyses were performed in which the inlet temperature was varied. It was found that increases in the inlet temperature (keeping a constant mass flow rate) had a large effect on the unsteady combustor behavior since reaction and advection rates were increased. The correct trend of decreasing rms pressures with increasing inlet temperature was predicted. This agreement in rms pressure behavior supports the ability of the CFD model to accurately capture unsteady heat release and its coupling with resonant acoustic waves in multi-dimensional combustor systems. The effect of subgrid turbulence model was small for the unstable cases studied here.
NPP ATMS Snowfall Rate Product
NASA Technical Reports Server (NTRS)
Meng, Huan; Ferraro, Ralph; Kongoli, Cezar; Wang, Nai-Yu; Dong, Jun; Zavodsky, Bradley; Yan, Banghua
2015-01-01
Passive microwave measurements at certain high frequencies are sensitive to the scattering effect of snow particles and can be utilized to retrieve snowfall properties. Some of the microwave sensors with snowfall sensitive channels are Advanced Microwave Sounding Unit (AMSU), Microwave Humidity Sounder (MHS) and Advance Technology Microwave Sounder (ATMS). ATMS is the follow-on sensor to AMSU and MHS. Currently, an AMSU and MHS based land snowfall rate (SFR) product is running operationally at NOAA/NESDIS. Based on the AMSU/MHS SFR, an ATMS SFR algorithm has been developed recently. The algorithm performs retrieval in three steps: snowfall detection, retrieval of cloud properties, and estimation of snow particle terminal velocity and snowfall rate. The snowfall detection component utilizes principal component analysis and a logistic regression model. The model employs a combination of temperature and water vapor sounding channels to detect the scattering signal from falling snow and derive the probability of snowfall (Kongoli et al., 2015). In addition, a set of NWP model based filters is also employed to improve the accuracy of snowfall detection. Cloud properties are retrieved using an inversion method with an iteration algorithm and a two-stream radiative transfer model (Yan et al., 2008). A method developed by Heymsfield and Westbrook (2010) is adopted to calculate snow particle terminal velocity. Finally, snowfall rate is computed by numerically solving a complex integral. NCEP CMORPH analysis has shown that integration of ATMS SFR has improved the performance of CMORPH-Snow. The ATMS SFR product is also being assessed at several NWS Weather Forecast Offices for its usefulness in weather forecast.
Numerical Simulation of Two-Phase Critical Flow with the Phase Change in the Nozzle Tube
NASA Astrophysics Data System (ADS)
Ishigaki, Masahiro; Watanabe, Tadashi; Nakamura, Hideo
Two-phase critical flow in the nozzle tube is analyzed numerically by the best estimate code TRACE and the CFD code FLUENT, and the performance of the mass flow rate estimation by the numerical codes is discussed. For the best estimate analysis by the TRACE code, the critical flow option is turned on. The mixture model is used with the cavitation model and the evaporation-condensation model for the numerical simulation by the FLUENT code. Two test cases of the two-phase critical flow are analyzed. One case is the critical flashing flow in a convergent-divergent nozzle (Super Moby Dick experiment), and the other case is the break nozzle flow for a steam generator tube rupture experiment of pressurized water reactors at Large Scale Test Facility of Japan Atomic Energy Agency. The calculation results of the mass flow rates by the numerical simulations show good agreements with the experimental results.
Thrombosis modeling in intracranial aneurysms: a lattice Boltzmann numerical algorithm
NASA Astrophysics Data System (ADS)
Ouared, R.; Chopard, B.; Stahl, B.; Rüfenacht, D. A.; Yilmaz, H.; Courbebaisse, G.
2008-07-01
The lattice Boltzmann numerical method is applied to model blood flow (plasma and platelets) and clotting in intracranial aneurysms at a mesoscopic level. The dynamics of blood clotting (thrombosis) is governed by mechanical variations of shear stress near wall that influence platelets-wall interactions. Thrombosis starts and grows below a shear rate threshold, and stops above it. Within this assumption, it is possible to account qualitatively well for partial, full or no occlusion of the aneurysm, and to explain why spontaneous thrombosis is more likely to occur in giant aneurysms than in small or medium sized aneurysms.
Numerical simulation of film-cooled ablative rocket nozzles
NASA Technical Reports Server (NTRS)
Landrum, D. B.; Beard, R. M.
1996-01-01
The objective of this research effort was to evaluate the impact of incorporating an additional cooling port downstream between the injector and nozzle throat in the NASA Fast Track chamber. A numerical model of the chamber was developed for the analysis. The analysis did not model ablation but instead correlated the initial ablation rate with the initial nozzle wall temperature distribution. The results of this study provide guidance in the development of a potentially lighter, second generation ablative rocket nozzle which maintains desired performance levels.
Simple numerical method for predicting steady compressible flows
NASA Technical Reports Server (NTRS)
Vonlavante, Ernst; Nelson, N. Duane
1986-01-01
A numerical method for solving the isenthalpic form of the governing equations for compressible viscous and inviscid flows was developed. The method was based on the concept of flux vector splitting in its implicit form. The method was tested on several demanding inviscid and viscous configurations. Two different forms of the implicit operator were investigated. The time marching to steady state was accelerated by the implementation of the multigrid procedure. Its various forms very effectively increased the rate of convergence of the present scheme. High quality steady state results were obtained in most of the test cases; these required only short computational times due to the relative efficiency of the basic method.
Projected discrete ordinates methods for numerical transport problems
Larsen, E.W.
1985-01-01
A class of Projected Discrete-Ordinates (PDO) methods is described for obtaining iterative solutions of discrete-ordinates problems with convergence rates comparable to those observed using Diffusion Synthetic Acceleration (DSA). The spatially discretized PDO solutions are generally not equal to the DSA solutions, but unlike DSA, which requires great care in the use of spatial discretizations to preserve stability, the PDO solutions remain stable and rapidly convergent with essentially arbitrary spatial discretizations. Numerical results are presented which illustrate the rapid convergence and the accuracy of solutions obtained using PDO methods with commonplace differencing methods.
Numerical simulation of carbon arc discharge for nanoparticle synthesis
Kundrapu, M.; Keidar, M.
2012-07-15
Arc discharge with catalyst-filled carbon anode in helium background was used for the synthesis of carbon nanoparticles. In this paper, we present the results of numerical simulation of carbon arc discharges with arc current varying from 10 A to 100 A in a background gas pressure of 68 kPa. Anode sublimation rate and current voltage characteristics are compared with experiments. Distribution of temperature and species density, which is important for the estimation of the growth of nanoparticles, is obtained. The probable location of nanoparticle growth region is identified based on the temperature range for the formation of catalyst clusters.
A numerical and experimental study of confined swirling jets
NASA Technical Reports Server (NTRS)
Nikjooy, M.; Mongia, H. C.; Samuelsen, G. S.; Mcdonell, V. G.
1989-01-01
A numerical and experimental study of a confined strong swirling flow is presented. Detailed velocity measurements are made using a two-component laser Doppler velocimeter (LDV) technique. Computations are performed using a differential second-moment (DSM) closure. The effect of inlet dissipation rate on calculated mean and turbulence fields is investigated. Various model constants are employed in the pressure-strain model to demonstrate their influences on the predicted results. Finally, comparison of the DSM calculations with the algebraic second-monent (ASM) closure results shows that the DSM is better suited for complex swirling flow analysis.
Preliminary numerical analysis of improved gas chromatograph model
NASA Technical Reports Server (NTRS)
Woodrow, P. T.
1973-01-01
A mathematical model for the gas chromatograph was developed which incorporates the heretofore neglected transport mechanisms of intraparticle diffusion and rates of adsorption. Because a closed-form analytical solution to the model does not appear realizable, techniques for the numerical solution of the model equations are being investigated. Criteria were developed for using a finite terminal boundary condition in place of an infinite boundary condition used in analytical solution techniques. The class of weighted residual methods known as orthogonal collocation is presently being investigated and appears promising.
Numerical Modeling of Unsteady Thermofluid Dynamics in Cryogenic Systems
NASA Technical Reports Server (NTRS)
Majumdar, Alok
2003-01-01
A finite volume based network analysis procedure has been applied to model unsteady flow without and with heat transfer. Liquid has been modeled as compressible fluid where the compressibility factor is computed from the equation of state for a real fluid. The modeling approach recognizes that the pressure oscillation is linked with the variation of the compressibility factor; therefore, the speed of sound does not explicitly appear in the governing equations. The numerical results of chilldown process also suggest that the flow and heat transfer are strongly coupled. This is evident by observing that the mass flow rate during 90-second chilldown process increases by factor of ten.
Metabolic rate measurement system
NASA Technical Reports Server (NTRS)
Koester, K.; Crosier, W.
1980-01-01
The Metabolic Rate Measurement System (MRMS) is an uncomplicated and accurate apparatus for measuring oxygen consumption and carbon dioxide production of a test subject. From this one can determine the subject's metabolic rate for a variety of conditions, such as resting or light exercise. MRMS utilizes an LSI/11-03 microcomputer to monitor and control the experimental apparatus.
ERIC Educational Resources Information Center
Cunningham, Kevin
2007-01-01
This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…
Technology Transfer Automated Retrieval System (TEKTRAN)
Controlled-rate cooling is one of several techniques available for the long-term storage of plants in liquid nitrogen. In this technique samples are slowly cooled to an intermediate temperature and then plunged in liquid nitrogen. Controlled rate cooling is based on osmotic regulation of cell conte...
Scaling metabolic rate fluctuations.
Labra, Fabio A; Marquet, Pablo A; Bozinovic, Francisco
2007-06-26
Complex ecological and economic systems show fluctuations in macroscopic quantities such as exchange rates, size of companies or populations that follow non-Gaussian tent-shaped probability distributions of growth rates with power-law decay, which suggests that fluctuations in complex systems may be governed by universal mechanisms, independent of particular details and idiosyncrasies. We propose here that metabolic rate within individual organisms may be considered as an example of an emergent property of a complex system and test the hypothesis that the probability distribution of fluctuations in the metabolic rate of individuals has a "universal" form regardless of body size or taxonomic affiliation. We examined data from 71 individuals belonging to 25 vertebrate species (birds, mammals, and lizards). We report three main results. First, for all these individuals and species, the distribution of metabolic rate fluctuations follows a tent-shaped distribution with power-law decay. Second, the standard deviation of metabolic rate fluctuations decays as a power-law function of both average metabolic rate and body mass, with exponents -0.352 and -1/4 respectively. Finally, we find that the distributions of metabolic rate fluctuations for different organisms can all be rescaled to a single parent distribution, supporting the existence of general principles underlying the structure and functioning of individual organisms. PMID:17578913
Shore, B.W.
1981-01-30
The equations of motion are discussed which describe time dependent population flows in an N-level system, reviewing the relationship between incoherent (rate) equations, coherent (Schrodinger) equations, and more general partially coherent (Bloch) equations. Approximations are discussed which replace the elaborate Bloch equations by simpler rate equations whose coefficients incorporate long-time consequences of coherence.
The Numeric Solution of Eigenvalue Problems.
ERIC Educational Resources Information Center
Bauer, H.; Roth, K.
1980-01-01
Presents the mathematical background for solving eigenvalue problems, with illustrations of the applications in computer programing. The numerical matrix treatment is presented, with a demonstration of the simple HMO theory. (CS)
Numerical noise in ocean and estuarine models
Walters, R.; Carey, G.F.
1984-01-01
Approximate methods for solving the shallow water equations may lead to solutions exhibiting large fictitious, numerically-induced oscillations. The analysis of the discrete dispersion relation and modal solutions of small wavelengths provides a powerful technique for assessing the sensitivity of alternative numerical schemes to irregular data which may lead to such oscillatory numerical noise. For those schemes where phase speed vanishes at a finite wavenumber or there are multiple roots for wavenumber, oscillation modes can exist which are uncoupled from the dynamics of the problem. The discrete modal analysis approach is used here to identify two classes of spurious oscillation modes associated respectively with the two different asymptotic limits corresponding to estuarine and large scale ocean models. The analysis provides further insight into recent numerical results for models which include large spatial scales and Coriolis acceleration. ?? 1984.
Numerical models for high beta magnetohydrodynamic flow
Brackbill, J.U.
1987-01-01
The fundamentals of numerical magnetohydrodynamics for highly conducting, high-beta plasmas are outlined. The discussions emphasize the physical properties of the flow, and how elementary concepts in numerical analysis can be applied to the construction of finite difference approximations that capture these features. The linear and nonlinear stability of explicit and implicit differencing in time is examined, the origin and effect of numerical diffusion in the calculation of convective transport is described, and a technique for maintaining solenoidality in the magnetic field is developed. Many of the points are illustrated by numerical examples. The techniques described are applicable to the time-dependent, high-beta flows normally encountered in magnetically confined plasmas, plasma switches, and space and astrophysical plasmas. 40 refs.
NUMERICAL MODELS FOR PREDICTING WATERSHED ACIDIFICATION
Three numerical models of watershed acidification, including the MAGIC II, ETD, and ILWAS models, are reviewed, and a comparative study is made of the specific process formulations that are incorporated in the models to represent hydrological, geochemical, and biogeochemical proc...
Numerical approach to Zeeman line radiative transfer
NASA Astrophysics Data System (ADS)
Takeda, Yoichi
1991-10-01
An accelerated lambda iteration (ALI) method, a version of the operator perturbation technique, is formulated for applications to Zeeman line formation problems in the presence of magnetic fields. This approach has proven to be quite an effective and flexible numerical device, being applicable to extensive problems (e.g., LTE one-way integration problem, noncoherent scattering etc.). In addition to its general formulation, a specialized practical version is also proposed which is limited to scattering (or multi-level) problems under the assumption of complete frequency redistribution (CRD), but requiring much less computing time. In order to examine the computational efficiency of this ALI method, numerical examples are presented concerning line formation in a magnetic field for several simple cases (LTE Milne-Eddington model, noncoherent CRD scattering, angle-dependent coherent scattering), showing a reasonably rapid convergence with notable numerical stability. Comparisons with other recent numerical techniques confirm the distinguished superiority of the present method.
Quaternionic Numerical Ranges of Normal Quaternion Matrices
Feng Lianggui
2009-09-09
By the Jordan canonical block-entry form introduced in this paper, a practical method of determining the convexity and an estimation of the location on the quaternionic numerical range are given for a normal quaternion matrix.
Symbolic-numeric interface: A review
NASA Technical Reports Server (NTRS)
Ng, E. W.
1980-01-01
A survey of the use of a combination of symbolic and numerical calculations is presented. Symbolic calculations primarily refer to the computer processing of procedures from classical algebra, analysis, and calculus. Numerical calculations refer to both numerical mathematics research and scientific computation. This survey is intended to point out a large number of problem areas where a cooperation of symbolic and numerical methods is likely to bear many fruits. These areas include such classical operations as differentiation and integration, such diverse activities as function approximations and qualitative analysis, and such contemporary topics as finite element calculations and computation complexity. It is contended that other less obvious topics such as the fast Fourier transform, linear algebra, nonlinear analysis and error analysis would also benefit from a synergistic approach.
Object-oriented numerical computing C++
NASA Technical Reports Server (NTRS)
Vanrosendale, John
1994-01-01
An object oriented language is one allowing users to create a set of related types and then intermix and manipulate values of these related types. This paper discusses object oriented numerical computing using C++.
Numerical Stimulation of Multicomponent Chromatography Using Spreadsheets.
ERIC Educational Resources Information Center
Frey, Douglas D.
1990-01-01
Illustrated is the use of spreadsheet programs for implementing finite difference numerical simulations of chromatography as an instructional tool in a separations course. Discussed are differential equations, discretization and integration, spreadsheet development, computer requirements, and typical simulation results. (CW)
Value-Engineering Review for Numerical Control
NASA Technical Reports Server (NTRS)
Warner, J. L.
1984-01-01
Selecting parts for conversion from conventional machining to numerical control, value-engineering review performed for every part to identify potential changes to part design that result in increased production efficiency.