13 CFR 305.6 - Allowable methods of procurement for construction services.

Code of Federal Regulations, 2013 CFR

2013-01-01

... design/build, construction management at risk and force account. If an alternate method is used, the... for construction services. 305.6 Section 305.6 Business Credit and Assistance ECONOMIC DEVELOPMENT... Approved Projects § 305.6 Allowable methods of procurement for construction services. (a) Recipients may...

13 CFR 305.6 - Allowable methods of procurement for construction services.

Code of Federal Regulations, 2012 CFR

2012-01-01

... design/build, construction management at risk and force account. If an alternate method is used, the... for construction services. 305.6 Section 305.6 Business Credit and Assistance ECONOMIC DEVELOPMENT... Approved Projects § 305.6 Allowable methods of procurement for construction services. (a) Recipients may...

13 CFR 305.6 - Allowable methods of procurement for construction services.

Code of Federal Regulations, 2014 CFR

2014-01-01

... design/build, construction management at risk and force account. If an alternate method is used, the... for construction services. 305.6 Section 305.6 Business Credit and Assistance ECONOMIC DEVELOPMENT... Approved Projects § 305.6 Allowable methods of procurement for construction services. (a) Recipients may...

Roll Damping Derivatives from Generalized Lifting-Surface Theory and Wind Tunnel Forced-Oscillation Tests

NASA Technical Reports Server (NTRS)

Pototzky, Anthony S; Murphy, Patrick C.

2014-01-01

Improving aerodynamic models for adverse loss-of-control conditions in flight is an area being researched under the NASA Aviation Safety Program. Aerodynamic models appropriate for loss of control conditions require a more general mathematical representation to predict nonlinear unsteady behaviors. As more general aerodynamic models are studied that include nonlinear higher order effects, the possibility of measurements that confound aerodynamic and structural responses are probable. In this study an initial step is taken to look at including structural flexibility in analysis of rigid-body forced-oscillation testing that accounts for dynamic rig, sting and balance flexibility. Because of the significant testing required and associated costs in a general study, it makes sense to capitalize on low cost analytical methods where possible, especially where structural flexibility can be accounted for by a low cost method. This paper provides an initial look at using linear lifting surface theory applied to rigid-body aircraft roll forced-oscillation tests.

New Approaches in Force-Limited Vibration Testing of Flight Hardware

NASA Technical Reports Server (NTRS)

Kolaini, Ali R.; Kern, Dennis L.

2012-01-01

To qualify flight hardware for random vibration environments the following methods are used to limit the loads in the aerospace industry: (1) Response limiting and notching (2) Simple TDOF model (3) Semi-empirical force limits (4) Apparent mass, etc. and (5) Impedance method. In all these methods attempts are made to remove conservatism due to the mismatch in impedances between the test and the flight configurations of the hardware that are being qualified. Assumption is the hardware interfaces have correlated responses. A new method that takes into account the un-correlated hardware interface responses are described in this presentation.

The Cost of a Military Person-Year. A Method for Computing Savings from Force Reductions

DTIC Science & Technology

2007-01-01

personnel FASAB Federal Accounting Standards Advisory Board FASB Financial Accounting Standards Board FERS Federal Employee Retirement System FG federal...an average prescribed SMCR of only $61,393, which is clearly problematic: Using the Comptroller’s own methods as mandated by DoD financial man... financial commitment the Figure 4.2 Probability-Adjusted Present Values of Retirement Benefits for Current Members by YOS RAND MG598-4.2 1,400 $ th o u

The Ontology of Determination: From Descartes to Spinoza.

PubMed

Sangiacomo, Andrea

2015-12-01

This paper argues that Spinoza's notions of "conatus" and "power of acting" are derived by means of generalization from the notions of "force of motion" and "force of determination" that Spinoza discussed in his Principles of Cartesian Philosophy to account for interactions among bodies (impacts) on the basis of their degrees of contrariety. I argue that in the Ethics, Spinoza's ontology entails that interactions must always be accounted for in terms of degrees of "agreement or disagreement in nature" among interacting things. The notion of "power of acting" is used to express the extent to which a thing's conatus is aided or restrained by external causes on the basis of its degree of agreement or disagreement in nature with them. "Power of acting" generalizes the same approach and method of resolution at the basis of the notion of "force of determination" in order to account for causal interactions not only among the simplest bodies but also among more complex individuals.

Partition coefficients of methylated DNA bases obtained from free energy calculations with molecular electron density derived atomic charges.

PubMed

Lara, A; Riquelme, M; Vöhringer-Martinez, E

2018-05-11

Partition coefficients serve in various areas as pharmacology and environmental sciences to predict the hydrophobicity of different substances. Recently, they have also been used to address the accuracy of force fields for various organic compounds and specifically the methylated DNA bases. In this study, atomic charges were derived by different partitioning methods (Hirshfeld and Minimal Basis Iterative Stockholder) directly from the electron density obtained by electronic structure calculations in a vacuum, with an implicit solvation model or with explicit solvation taking the dynamics of the solute and the solvent into account. To test the ability of these charges to describe electrostatic interactions in force fields for condensed phases, the original atomic charges of the AMBER99 force field were replaced with the new atomic charges and combined with different solvent models to obtain the hydration and chloroform solvation free energies by molecular dynamics simulations. Chloroform-water partition coefficients derived from the obtained free energies were compared to experimental and previously reported values obtained with the GAFF or the AMBER-99 force field. The results show that good agreement with experimental data is obtained when the polarization of the electron density by the solvent has been taken into account, and when the energy needed to polarize the electron density of the solute has been considered in the transfer free energy. These results were further confirmed by hydration free energies of polar and aromatic amino acid side chain analogs. Comparison of the two partitioning methods, Hirshfeld-I and Minimal Basis Iterative Stockholder (MBIS), revealed some deficiencies in the Hirshfeld-I method related to the unstable isolated anionic nitrogen pro-atom used in the method. Hydration free energies and partitioning coefficients obtained with atomic charges from the MBIS partitioning method accounting for polarization by the implicit solvation model are in good agreement with the experimental values. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Tapping mode imaging with an interfacial force microscope

NASA Astrophysics Data System (ADS)

Warren, O. L.; Graham, J. F.; Norton, P. R.

1997-11-01

In their present embodiment, sensors used in interfacial force microscopy do not have the necessary mechanical bandwidth to be employed as free-running tapping mode devices. We describe an extremely stable method of obtaining tapping mode images using feedback on the sensor. Our method is immune to small dc drifts in the force signal, and the prospect of diminishing the risk of damaging fragile samples is realized. The feasibility of the technique is demonstrated by our imaging work on a Kevlar fiber-epoxy composite. We also present a model which accounts for the frequency dependence of the sensor in air when operating under closed loop control. A simplified force modulation model is investigated to explore the effect of contact on the closed loop response of the sensor.

Spectral analysis of structure functions and their scaling exponents in forced isotropic turbulence

NASA Astrophysics Data System (ADS)

Linkmann, Moritz; McComb, W. David; Yoffe, Samuel; Berera, Arjun

2014-11-01

The pseudospectral method, in conjunction with a new technique for obtaining scaling exponents ζn from the structure functions Sn (r) , is presented as an alternative to the extended self-similarity (ESS) method and the use of generalized structure functions. We propose plotting the ratio | Sn (r) /S3 (r) | against the separation r in accordance with a standard technique for analysing experimental data. This method differs from the ESS technique, which plots the generalized structure functions Gn (r) against G3 (r) , where G3 (r) ~ r . Using our method for the particular case of S2 (r) we obtain the new result that the exponent ζ2 decreases as the Taylor-Reynolds number increases, with ζ2 --> 0 . 679 +/- 0 . 013 as Rλ --> ∞ . This supports the idea of finite-viscosity corrections to the K41 prediction for S2, and is the opposite of the result obtained by ESS. The pseudospectral method permits the forcing to be taken into account exactly through the calculation of the energy input in real space from the work spectrum of the stirring forces. The combination of the viscous and the forcing corrections as calculated by the pseudospectral method is shown to account for the deviation of S3 from Kolmogorov's ``four-fifths''-law at all scales. This work has made use of the resources provided by the UK supercomputing service HECToR, made available through the Edinburgh Compute and Data Facility (ECDF). A. B. is supported by STFC, S. R. Y. and M. F. L. are funded by EPSRC.

FINCAP Analysis: A Method for Financial Capability Analysis of Air Force Contractors

DTIC Science & Technology

1979-03-01

obtained directly from the companies or through the SEC Pu’lications contractor (in hard copy or microfiche): Disclosure, Inc., 4827 Rugby Avenue...contracts- labor union wage agreements - material prices - escalation clauses in contracts - contractor accounting methods - level of capacity utilization

[Supercomputer investigation of the protein-ligand system low-energy minima].

PubMed

Oferkin, I V; Sulimov, A V; Katkova, E V; Kutov, D K; Grigoriev, F V; Kondakova, O A; Sulimov, V B

2015-01-01

The accuracy of the protein-ligand binding energy calculations and ligand positioning is strongly influenced by the choice of the docking target function. This work demonstrates the evaluation of the five different target functions used in docking: functions based on MMFF94 force field and functions based on PM7 quantum-chemical method accounting or without accounting the implicit solvent model (PCM, COSMO or SGB). For these purposes the ligand positions corresponding to the minima of the target function and the experimentally known ligand positions in the protein active site (crystal ligand positions) were compared. Each function was examined on the same test-set of 16 protein-ligand complexes. The new parallelized docking program FLM based on Monte Carlo search algorithm was developed to perform the comprehensive low-energy minima search and to calculate the protein-ligand binding energy. This study demonstrates that the docking target function based on the MMFF94 force field can be used to detect the crystal or near crystal positions of the ligand by the finding the low-energy local minima spectrum of the target function. The importance of solvent accounting in the docking process for the accurate ligand positioning is also shown. The accuracy of the ligand positioning as well as the correlation between the calculated and experimentally determined protein-ligand binding energies are improved when the MMFF94 force field is substituted by the new PM7 method with implicit solvent accounting.

Extracting Leading Nonlinear Modes of Changing Climate From Global SST Time Series

NASA Astrophysics Data System (ADS)

Mukhin, D.; Gavrilov, A.; Loskutov, E. M.; Feigin, A. M.; Kurths, J.

2017-12-01

Data-driven modeling of climate requires adequate principal variables extracted from observed high-dimensional data. For constructing such variables it is needed to find spatial-temporal patterns explaining a substantial part of the variability and comprising all dynamically related time series from the data. The difficulties of this task rise from the nonlinearity and non-stationarity of the climate dynamical system. The nonlinearity leads to insufficiency of linear methods of data decomposition for separating different processes entangled in the observed time series. On the other hand, various forcings, both anthropogenic and natural, make the dynamics non-stationary, and we should be able to describe the response of the system to such forcings in order to separate the modes explaining the internal variability. The method we present is aimed to overcome both these problems. The method is based on the Nonlinear Dynamical Mode (NDM) decomposition [1,2], but takes into account external forcing signals. An each mode depends on hidden, unknown a priori, time series which, together with external forcing time series, are mapped onto data space. Finding both the hidden signals and the mapping allows us to study the evolution of the modes' structure in changing external conditions and to compare the roles of the internal variability and forcing in the observed behavior. The method is used for extracting of the principal modes of SST variability on inter-annual and multidecadal time scales accounting the external forcings such as CO2, variations of the solar activity and volcanic activity. The structure of the revealed teleconnection patterns as well as their forecast under different CO2 emission scenarios are discussed.[1] Mukhin, D., Gavrilov, A., Feigin, A., Loskutov, E., & Kurths, J. (2015). Principal nonlinear dynamical modes of climate variability. Scientific Reports, 5, 15510. [2] Gavrilov, A., Mukhin, D., Loskutov, E., Volodin, E., Feigin, A., & Kurths, J. (2016). Method for reconstructing nonlinear modes with adaptive structure from multidimensional data. Chaos: An Interdisciplinary Journal of Nonlinear Science, 26(12), 123101.

Delinquent Medical Service Accounts at David Grant Air Force Medical Center Need Additional Management Oversight

DTIC Science & Technology

2015-09-24

No. DODIG-2015-179 S E P T E M B E R 2 4 , 2 0 1 5 Delinquent Medical Service Accounts at David Grant Air Force Medical Center Need Additional...us at www.dodig.mil Results in Brief Delinquent Medical Service Accounts at David Grant Air Force...Force Medical Center (DGMC) properly managed delinquent accounts over 180 days by effectively transferring the debt to the appropriate debt collection

A Numerical Method for Incompressible Flow with Heat Transfer

NASA Technical Reports Server (NTRS)

Sa, Jong-Youb; Kwak, Dochan

1997-01-01

A numerical method for the convective heat transfer problem is developed for low speed flow at mild temperatures. A simplified energy equation is added to the incompressible Navier-Stokes formulation by using Boussinesq approximation to account for the buoyancy force. A pseudocompressibility method is used to solve the resulting set of equations for steady-state solutions in conjunction with an approximate factorization scheme. A Neumann-type pressure boundary condition is devised to account for the interaction between pressure and temperature terms, especially near a heated or cooled solid boundary. It is shown that the present method is capable of predicting the temperature field in an incompressible flow.

3D Viscous Free-Surface Flow around a Combatant Ship Hull

NASA Astrophysics Data System (ADS)

Pacuraru, Florin; Lungu, Adrian; Maria, Viorel

2009-09-01

The prediction of the total drag experienced by an advancing ship is a complicated problem which requires a thorough understanding of the hydrodynamic forces acting on the hull, the physical processes from which these forces arise and their mutual interaction. A general numerical method to predict the hydrodynamic performance of a twin-propeller combatant ship hull is presented in the paper. For practical reasons, the technique couples a body forces method and a RANS-based finite volume solver to account for the interactions between the hull and the appendages mounted on it: propellers, rudders, shaft lines, bossings and brackets. The chimera approach has been found the most versatile way for grid generation of hull and appendages.

Semiempirical method for prediction of aerodynamic forces and moments on a steadily spinning light airplane

NASA Technical Reports Server (NTRS)

Pamadi, Bandu N.; Taylor, Lawrence W., Jr.

1987-01-01

A semi-empirical method is presented for the estimation of aerodynamic forces and moments acting on a steadily spinning (rotating) light airplane. The airplane is divided into wing, body, and tail surfaces. The effect of power is ignored. The strip theory is employed for each component of the spinning airplane to determine its contribution to the total aerodynamic coefficients. Then, increments to some of the coefficients which account for centrifugal effect are estimated. The results are compared to spin tunnel rotary balance test data.

An enhanced nonlinear damping approach accounting for system constraints in active mass dampers

NASA Astrophysics Data System (ADS)

Venanzi, Ilaria; Ierimonti, Laura; Ubertini, Filippo

2015-11-01

Active mass dampers are a viable solution for mitigating wind-induced vibrations in high-rise buildings and improve occupants' comfort. Such devices suffer particularly when they reach force saturation of the actuators and maximum extension of their stroke, which may occur in case of severe loading conditions (e.g. wind gust and earthquake). Exceeding actuators' physical limits can impair the control performance of the system or even lead to devices damage, with consequent need for repair or substitution of part of the control system. Controllers for active mass dampers should account for their technological limits. Prior work of the authors was devoted to stroke issues and led to the definition of a nonlinear damping approach, very easy to implement in practice. It consisted of a modified skyhook algorithm complemented with a nonlinear braking force to reverse the direction of the mass before reaching the stroke limit. This paper presents an enhanced version of this approach, also accounting for force saturation of the actuator and keeping the simplicity of implementation. This is achieved by modulating the control force by a nonlinear smooth function depending on the ratio between actuator's force and saturation limit. Results of a numerical investigation show that the proposed approach provides similar results to the method of the State Dependent Riccati Equation, a well-established technique for designing optimal controllers for constrained systems, yet very difficult to apply in practice.

A collision model for grain-resolving simulations of flows over dense, mobile, polydisperse granular sediment beds

DOE PAGES

Biegert, Edward; Vowinckel, Bernhard; Meiburg, Eckart

2017-03-21

We present a collision model for phase-resolved Direct Numerical Simulations of sediment transport that couple the fluid and particles by the Immersed Boundary Method. Typically, a contact model for these types of simulations comprises a lubrication force for particles in close proximity to another solid object, a normal contact force to prevent particles from overlapping, and a tangential contact force to account for friction. Our model extends the work of previous authors to improve upon the time integration scheme to obtain consistent results for particle-wall collisions. Furthermore, we account for polydisperse spherical particles and introduce new criteria to account formore » enduring contact, which occurs in many sediment transport situations. This is done without using arbitrary values for physically-defined parameters and by maintaining the full momentum balance of a particle in enduring contact. Lastly, we validate our model against several test cases for binary particle-wall collisions as well as the collective motion of a sediment bed sheared by a viscous flow, yielding satisfactory agreement with experimental data by various authors.« less

A collision model for grain-resolving simulations of flows over dense, mobile, polydisperse granular sediment beds

NASA Astrophysics Data System (ADS)

Biegert, Edward; Vowinckel, Bernhard; Meiburg, Eckart

2017-07-01

We present a collision model for phase-resolved Direct Numerical Simulations of sediment transport that couple the fluid and particles by the Immersed Boundary Method. Typically, a contact model for these types of simulations comprises a lubrication force for particles in close proximity to another solid object, a normal contact force to prevent particles from overlapping, and a tangential contact force to account for friction. Our model extends the work of previous authors to improve upon the time integration scheme to obtain consistent results for particle-wall collisions. Furthermore, we account for polydisperse spherical particles and introduce new criteria to account for enduring contact, which occurs in many sediment transport situations. This is done without using arbitrary values for physically-defined parameters and by maintaining the full momentum balance of a particle in enduring contact. We validate our model against several test cases for binary particle-wall collisions as well as the collective motion of a sediment bed sheared by a viscous flow, yielding satisfactory agreement with experimental data by various authors.

Calculation of force and power during bench throws using a Smith machine: the importance of considering the effect of counterweights.

PubMed

Kobayashi, Y; Narazaki, K; Akagi, R; Nakagaki, K; Kawamori, N; Ohta, K

2013-09-01

For achieving accurate and safe measurements of the force and power exerted on a load during resistance exercise, the Smith machine has been used instead of free weights. However, because some Smith machines possess counterweights, the equation for the calculation of force and power in this system should be different from the one used for free weights. The purpose of this investigation was to calculate force and power using an equation derived from a dynamic equation for a Smith machine with counterweights and to determine the differences in force and power calculated using 2 different equations. One equation was established ignoring the effect of the counterweights (Method 1). The other equation was derived from a dynamic equation for a barbell and counterweight system (Method 2). 9 female collegiate judo athletes performed bench throws using a Smith machine with a counterweight at 6 different loading conditions. Barbell displacement was recorded using a linear position transducer. The force and power were subsequently calculated by Methods 1 and 2. The results showed that the mean and peak power and force in Method 1 were significantly lower relative to those of Method 2 under all loading conditions. These results indicate that the mean and peak power and force during bench throwing using a Smith machine with counterweights would be underestimated when the calculations used to determine these parameters do not account for the effect of counterweights. © Georg Thieme Verlag KG Stuttgart · New York.

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

Determination of the viscous acoustic field for liquid drop positioning/forcing in an acoustic levitation chamber in microgravity

NASA Technical Reports Server (NTRS)

Lyell, Margaret J.

1992-01-01

The development of acoustic levitation systems has provided a technology with which to undertake droplet studies as well as do containerless processing experiments in a microgravity environment. Acoustic levitation chambers utilize radiation pressure forces to position/manipulate the drop. Oscillations can be induced via frequency modulation of the acoustic wave, with the modulated acoustic radiation vector acting as the driving force. To account for tangential as well as radial forcing, it is necessary that the viscous effects be included in the acoustic field. The method of composite expansions is employed in the determination of the acoustic field with viscous effects.

A new statistical approach to climate change detection and attribution

NASA Astrophysics Data System (ADS)

Ribes, Aurélien; Zwiers, Francis W.; Azaïs, Jean-Marc; Naveau, Philippe

2017-01-01

We propose here a new statistical approach to climate change detection and attribution that is based on additive decomposition and simple hypothesis testing. Most current statistical methods for detection and attribution rely on linear regression models where the observations are regressed onto expected response patterns to different external forcings. These methods do not use physical information provided by climate models regarding the expected response magnitudes to constrain the estimated responses to the forcings. Climate modelling uncertainty is difficult to take into account with regression based methods and is almost never treated explicitly. As an alternative to this approach, our statistical model is only based on the additivity assumption; the proposed method does not regress observations onto expected response patterns. We introduce estimation and testing procedures based on likelihood maximization, and show that climate modelling uncertainty can easily be accounted for. Some discussion is provided on how to practically estimate the climate modelling uncertainty based on an ensemble of opportunity. Our approach is based on the " models are statistically indistinguishable from the truth" paradigm, where the difference between any given model and the truth has the same distribution as the difference between any pair of models, but other choices might also be considered. The properties of this approach are illustrated and discussed based on synthetic data. Lastly, the method is applied to the linear trend in global mean temperature over the period 1951-2010. Consistent with the last IPCC assessment report, we find that most of the observed warming over this period (+0.65 K) is attributable to anthropogenic forcings (+0.67 ± 0.12 K, 90 % confidence range), with a very limited contribution from natural forcings (-0.01± 0.02 K).

Studying Climate Response to Forcing by the Nonlinear Dynamical Mode Decomposition

NASA Astrophysics Data System (ADS)

Mukhin, Dmitry; Gavrilov, Andrey; Loskutov, Evgeny; Feigin, Alexander

2017-04-01

An analysis of global climate response to external forcing, both anthropogenic (mainly, CO2 and aerosol) and natural (solar and volcanic), is needed for adequate predictions of global climate change. Being complex dynamical system, the climate reacts to external perturbations exciting feedbacks (both positive and negative) making the response non-trivial and poorly predictable. Thus an extraction of internal modes of climate system, investigation of their interaction with external forcings and further modeling and forecast of their dynamics, are all the problems providing the success of climate modeling. In the report the new method for principal mode extraction from climate data is presented. The method is based on the Nonlinear Dynamical Mode (NDM) expansion [1,2], but takes into account a number of external forcings applied to the system. Each NDM is represented by hidden time series governing the observed variability, which, together with external forcing time series, are mapped onto data space. While forcing time series are considered to be known, the hidden unknown signals underlying the internal climate dynamics are extracted from observed data by the suggested method. In particular, it gives us an opportunity to study the evolution of principal system's mode structure in changing external conditions and separate the internal climate variability from trends forced by external perturbations. Furthermore, the modes so obtained can be extrapolated beyond the observational time series, and long-term prognosis of modes' structure including characteristics of interconnections and responses to external perturbations, can be carried out. In this work the method is used for reconstructing and studying the principal modes of climate variability on inter-annual and decadal time scales accounting the external forcings such as anthropogenic emissions, variations of the solar activity and volcanic activity. The structure of the obtained modes as well as their response to external factors, e.g. forecast their change in 21 century under different CO2 emission scenarios, are discussed. [1] Mukhin, D., Gavrilov, A., Feigin, A., Loskutov, E., & Kurths, J. (2015). Principal nonlinear dynamical modes of climate variability. Scientific Reports, 5, 15510. http://doi.org/10.1038/srep15510 [2] Gavrilov, A., Mukhin, D., Loskutov, E., Volodin, E., Feigin, A., & Kurths, J. (2016). Method for reconstructing nonlinear modes with adaptive structure from multidimensional data. Chaos: An Interdisciplinary Journal of Nonlinear Science, 26(12), 123101. http://doi.org/10.1063/1.4968852

Foot-ankle complex injury risk curves using calcaneus bone mineral density data.

PubMed

Yoganandan, Narayan; Chirvi, Sajal; Voo, Liming; DeVogel, Nicholas; Pintar, Frank A; Banerjee, Anjishnu

2017-08-01

Biomechanical data from post mortem human subject (PMHS) experiments are used to derive human injury probability curves and develop injury criteria. This process has been used in previous and current automotive crashworthiness studies, Federal safety standards, and dummy design and development. Human bone strength decreases as the individuals reach their elderly age. Injury risk curves using the primary predictor variable (e.g., force) should therefore account for such strength reduction when the test data are collected from PMHS specimens of different ages (age at the time of death). This demographic variable is meant to be a surrogate for fracture, often representing bone strength as other parameters have not been routinely gathered in previous experiments. However, bone mineral densities (BMD) can be gathered from tested specimens (presented in this manuscript). The objective of this study is to investigate different approaches of accounting for BMD in the development of human injury risk curves. Using simulated underbody blast (UBB) loading experiments conducted with the PMHS lower leg-foot-ankle complexes, a comparison is made between the two methods: treating BMD as a covariate and pre-scaling test data based on BMD. Twelve PMHS lower leg-foot-ankle specimens were subjected to UBB loads. Calcaneus BMD was obtained from quantitative computed tomography (QCT) images. Fracture forces were recorded using a load cell. They were treated as uncensored data in the survival analysis model which used the Weibull distribution in both methods. The width of the normalized confidence interval (NCIS) was obtained using the mean and ± 95% confidence limit curves. The mean peak forces of 3.9kN and 8.6kN were associated with the 5% and 50% probability of injury for the covariate method of deriving the risk curve for the reference age of 45 years. The mean forces of 5.4 kN and 9.2kN were associated with the 5% and 50% probability of injury for the pre-scaled method. The NCIS magnitudes were greater in the covariate-based risk curves (0.52-1.00) than in the risk curves based on the pre-scaled method (0.24-0.66). The pre-scaling method resulted in a generally greater injury force and a tighter injury risk curve confidence interval. Although not directly applicable to the foot-ankle fractures, when compared with the use of spine BMD from QCT scans to pre-scale the force, the calcaneus BMD scaled data produced greater force at the same risk level in general. Pre-scaling the force data using BMD is an alternate, and likely a more accurate, method instead of using covariate to account for the age-related bone strength change in deriving risk curves from biomechanical experiments using PMHS. Because of the proximity of the calcaneus bone to the impacting load, it is suggested to use and determine the BMD of the foot-ankle bone in future UBB and other loading conditions to derive human injury probability curves for the foot-ankle complex. Copyright © 2017. Published by Elsevier Ltd.

How Does the Air Force Create Effective Accountability for Initial Spares?

DTIC Science & Technology

1990-05-01

effective accountability for initial spares? AUTHOR: Pamela J. Henson, Civilian, USAF The accountability for acquisition cost , schedule, and...in place to allow the Program Manager to effectively manage this cost element. Initial spares have traditionally been managed in Air Force Logistics...at Maxwell Air Force Base. Pamela became the Chief, Cost Analysis Division at HQ Air Force Logistics Command in 1987, where she received the Civilian

Force of resistance to pipeline pulling in plane and volumetrically curved wells

NASA Astrophysics Data System (ADS)

Toropov, V. S.; Toropov, S. Yu; Toropov, E. S.

2018-05-01

A method has been developed for calculating the component of the pulling force of a pipeline, arising from the well curvature in one or several planes, with the assumption that the pipeline is ballasted by filling with water or otherwise until zero buoyancy in the drilling mud is reached. This paper shows that when calculating this force, one can neglect the effect of sections with zero curvature. In the other case, if buoyancy of the pipeline is other than zero, the resistance force in the curvilinear sections should be calculated taking into account the difference between the normal components of the buoyancy force and weight. In the paper, it is proved that without taking into account resistance forces from the viscosity of the drilling mud, if buoyancy of the pipeline is zero, the total resistance force is independent of the length of the pipe and is determined by the angle equal to the sum of the entry angle and the exit angle of the pipeline to the day surface. For the case of the well curvature in several planes, it is proposed to perform the calculation of such volumetrically curved well by the central angle of the well profile. Analytical dependences are obtained that allow calculating the pulling force for well profiles with a variable curvature radius, i.e. at different angles of deviation between the drill pipes along the well profile.

Objective classification of historical tropical cyclone intensity

NASA Astrophysics Data System (ADS)

Chenoweth, Michael

2007-03-01

Preinstrumental records of historical tropical cyclone activity require objective methods for accurately categorizing tropical cyclone intensity. Here wind force terms and damage reports from newspaper accounts in the Lesser Antilles and Jamaica for the period 1795-1879 are compared with wind speed estimates calculated from barometric pressure data. A total of 95 separate barometric pressure readings and colocated simultaneous wind force descriptors and wind-induced damage reports are compared. The wind speed estimates from barometric pressure data are taken as the most reliable and serve as a standard to compare against other data. Wind-induced damage reports are used to produce an estimated wind speed range using a modified Fujita scale. Wind force terms are compared with the barometric pressure data to determine if a gale, as used in the contemporary newspapers, is consistent with the modern definition of a gale. Results indicate that the modern definition of a gale (the threshold point separating the classification of a tropical depression from a tropical storm) is equivalent to that in contemporary newspaper accounts. Barometric pressure values are consistent with both reported wind force terms and wind damage on land when the location, speed and direction of movement of the tropical cyclone are determined. Damage reports and derived wind force estimates are consistent with other published results. Biases in ships' logbooks are confirmed and wind force terms of gale strength or greater are identified. These results offer a bridge between the earlier noninstrumental records of tropical cyclones and modern records thereby offering a method of consistently classifying storms in the Caribbean region into tropical depressions, tropical storms, nonmajor and major hurricanes.

A Parametric Approach to Numerical Modeling of TKR Contact Forces

PubMed Central

Lundberg, Hannah J.; Foucher, Kharma C.; Wimmer, Markus A.

2009-01-01

In vivo knee contact forces are difficult to determine using numerical methods because there are more unknown forces than equilibrium equations available. We developed parametric methods for computing contact forces across the knee joint during the stance phase of level walking. Three-dimensional contact forces were calculated at two points of contact between the tibia and the femur, one on the lateral aspect of the tibial plateau, and one on the medial side. Muscle activations were parametrically varied over their physiologic range resulting in a solution space of contact forces. The obtained solution space was reasonably small and the resulting force pattern compared well to a previous model from the literature for kinematics and external kinetics from the same patient. Peak forces of the parametric model and the previous model were similar for the first half of the stance phase, but differed for the second half. The previous model did not take into account the transverse external moment about the knee and could not calculate muscle activation levels. Ultimately, the parametric model will result in more accurate contact force inputs for total knee simulators, as current inputs are not generally based on kinematics and kinetics inputs from TKR patients. PMID:19155015

40 CFR 35.936-14 - Force account work.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 1 2011-07-01 2011-07-01 false Force account work. 35.936-14 Section... ASSISTANCE STATE AND LOCAL ASSISTANCE Grants for Construction of Treatment Works-Clean Water Act § 35.936-14 Force account work. (a) A grantee must secure the project officer's prior written approval for use of...

Effects of hierarchical structures and insulating liquid media on adhesion

NASA Astrophysics Data System (ADS)

Yang, Weixu; Wang, Xiaoli; Li, Hanqing; Song, Xintao

2017-11-01

Effects of hierarchical structures and insulating liquid media on adhesion are investigated through a numerical adhesive contact model established in this paper, in which hierarchical structures are considered by introducing the height distribution into the surface gap equation, and media are taken into account through the Hamaker constant in Lifshitz-Hamaker approach. Computational methods such as inexact Newton method, bi-conjugate stabilized (Bi-CGSTAB) method and fast Fourier transform (FFT) technique are employed to obtain the adhesive force. It is shown that hierarchical structured surface exhibits excellent anti-adhesive properties compared with flat, micro or nano structured surfaces. Adhesion force is more dependent on the sizes of nanostructures than those of microstructures, and the optimal ranges of nanostructure pitch and maximum height for small adhesion force are presented. Insulating liquid media effectively decrease the adhesive interaction and 1-bromonaphthalene exhibits the smallest adhesion force among the five selected media. In addition, effects of hierarchical structures with optimal sizes on reducing adhesion are more obvious than those of the selected insulating liquid media.

Limit cycles of a flexible shaft with hydrodynamic journal bearings in unstable regimes

NASA Technical Reports Server (NTRS)

Brown, R. D.; Black, H. F.

1980-01-01

A symmetric 3 mass rotor supported on hydrodynamic bearings is described. An approximate method of representing finite bearings is used to calculate bearing forces. As the method sums forces from a number of independent circular lobes lemon 3 and 4 lobe bearings are taken into account. The calculations are based on an axial groove bearing. Linear analysis precedes nonlinear simulation of some unstable conditions. The demonstration of small limit cycles suggests that necessarily flexible rotors e.g., helicopter tail rotors, may be practical without either tilt pad bearings or external dampers.

An Analysis of the Cost Accounting System for the Depot Maintenance Service, Air Force Industrial Fund.

DTIC Science & Technology

1987-09-01

AN A NALYSIS OF THE COST ACCOUNTING SYSTEM FOR THE DEPOT 1/1 MRINTENANCE SERVI..(U) MIR FORCE INST OF TECH IIGHT-PTTERSON RFB OH SCHOOL OF SYST.. 0 L...I "VV h S~ ~~i FiLE COV, THSI CIO ~OF AN ANALYSIS OF THE COST ACCOUNTING SYSTEM FOR THE DEPOT MAINTENANCE SERVICE, AIR FORCE INDUSTRIAL FUND...Patterson Air Force Base, Ohio ~ p~UOW~~ ’ I ~ 1 12 02 0 AFIT/GLM/LSY/87S-83 AN ANALYSIS OF THE COST ACCOUNTING SYSTEM FOR THE DEPOT MAINTENANCE SERVICE, AIR

Force feedback in a piezoelectric linear actuator for neurosurgery.

PubMed

De Lorenzo, Danilo; De Momi, Elena; Dyagilev, Ilya; Manganelli, Rudy; Formaglio, Alessandro; Prattichizzo, Domenico; Shoham, Moshe; Ferrigno, Giancarlo

2011-09-01

Force feedback in robotic minimally invasive surgery allows the human operator to manipulate tissues as if his/her hands were in contact with the patient organs. A force sensor mounted on the probe raises problems with sterilization of the overall surgical tool. Also, the use of off-axis gauges introduces a moment that increases the friction force on the bearing, which can easily mask off the signal, given the small force to be measured. This work aims at designing and testing two methods for estimating the resistance to the advancement (force) experienced by a standard probe for brain biopsies within a brain-like material. The further goal is to provide a neurosurgeon using a master-slave tele-operated driver with direct feedback on the tissue mechanical characteristics. Two possible sensing methods, in-axis strain gauge force sensor and position-position error (control-based method), were implemented and tested, both aimed at device miniaturization. The analysis carried out was aimed at fulfilment of the psychophysics requirements for force detection and delay tolerance, also taking into account safety, which is directly related to the last two issues. Controller parameters definition is addressed and consideration is given to development of the device with integration of a haptic interface. Results show better performance of the control-based method (RMSE < 0.1 N), which is also best for reliability, sterilizability, and material dimensions for the application addressed. The control-based method developed for force estimation is compatible with the neurosurgical application and is also capable of measuring tissue resistance without any additional sensors. Force feedback in minimally invasive surgery allows the human operator to manipulate tissues as if his/her hands were in contact with the patient organs. Copyright © 2011 John Wiley & Sons, Ltd.

Nonstationary time series prediction combined with slow feature analysis

NASA Astrophysics Data System (ADS)

Wang, G.; Chen, X.

2015-01-01

Almost all climate time series have some degree of nonstationarity due to external driving forces perturbations of the observed system. Therefore, these external driving forces should be taken into account when reconstructing the climate dynamics. This paper presents a new technique of combining the driving force of a time series obtained using the Slow Feature Analysis (SFA) approach, then introducing the driving force into a predictive model to predict non-stationary time series. In essence, the main idea of the technique is to consider the driving forces as state variables and incorporate them into the prediction model. To test the method, experiments using a modified logistic time series and winter ozone data in Arosa, Switzerland, were conducted. The results showed improved and effective prediction skill.

Comparison of human gastrocnemius forces predicted by Hill-type muscle models and estimated from ultrasound images

PubMed Central

Biewener, Andrew A.; Wakeling, James M.

2017-01-01

ABSTRACT Hill-type models are ubiquitous in the field of biomechanics, providing estimates of a muscle's force as a function of its activation state and its assumed force–length and force–velocity properties. However, despite their routine use, the accuracy with which Hill-type models predict the forces generated by muscles during submaximal, dynamic tasks remains largely unknown. This study compared human gastrocnemius forces predicted by Hill-type models with the forces estimated from ultrasound-based measures of tendon length changes and stiffness during cycling, over a range of loads and cadences. We tested both a traditional model, with one contractile element, and a differential model, with two contractile elements that accounted for independent contributions of slow and fast muscle fibres. Both models were driven by subject-specific, ultrasound-based measures of fascicle lengths, velocities and pennation angles and by activation patterns of slow and fast muscle fibres derived from surface electromyographic recordings. The models predicted, on average, 54% of the time-varying gastrocnemius forces estimated from the ultrasound-based methods. However, differences between predicted and estimated forces were smaller under low speed–high activation conditions, with models able to predict nearly 80% of the gastrocnemius force over a complete pedal cycle. Additionally, the predictions from the Hill-type muscle models tested here showed that a similar pattern of force production could be achieved for most conditions with and without accounting for the independent contributions of different muscle fibre types. PMID:28202584

Comparison of human gastrocnemius forces predicted by Hill-type muscle models and estimated from ultrasound images.

PubMed

Dick, Taylor J M; Biewener, Andrew A; Wakeling, James M

2017-05-01

Hill-type models are ubiquitous in the field of biomechanics, providing estimates of a muscle's force as a function of its activation state and its assumed force-length and force-velocity properties. However, despite their routine use, the accuracy with which Hill-type models predict the forces generated by muscles during submaximal, dynamic tasks remains largely unknown. This study compared human gastrocnemius forces predicted by Hill-type models with the forces estimated from ultrasound-based measures of tendon length changes and stiffness during cycling, over a range of loads and cadences. We tested both a traditional model, with one contractile element, and a differential model, with two contractile elements that accounted for independent contributions of slow and fast muscle fibres. Both models were driven by subject-specific, ultrasound-based measures of fascicle lengths, velocities and pennation angles and by activation patterns of slow and fast muscle fibres derived from surface electromyographic recordings. The models predicted, on average, 54% of the time-varying gastrocnemius forces estimated from the ultrasound-based methods. However, differences between predicted and estimated forces were smaller under low speed-high activation conditions, with models able to predict nearly 80% of the gastrocnemius force over a complete pedal cycle. Additionally, the predictions from the Hill-type muscle models tested here showed that a similar pattern of force production could be achieved for most conditions with and without accounting for the independent contributions of different muscle fibre types. © 2017. Published by The Company of Biologists Ltd.

Accountability: The Most Underappreciated Aspect of Command

DTIC Science & Technology

2012-02-15

1994). Webster, John. "Air Force Hush Job Skips Accountability." The Spokesman-Review. May 25, 1995. http://www.spokesman.com/stories/1995/may/25...air-force- hush -job-skips- accountability/ (accessed December 9, 2011). Wynne, Michael W., Secretary of the Air Force. "Resignation Letter." June 6...used against you in a trial by court-martial except…for perjury, false swearing, or for a false official statement.” 79 John Webster, “Air Force Hush

Path suppression of strongly collapsing bubbles at finite and low Reynolds numbers.

PubMed

Rechiman, Ludmila M; Dellavale, Damián; Bonetto, Fabián J

2013-06-01

We study, numerically and experimentally, three different methods to suppress the trajectories of strongly collapsing and sonoluminescent bubbles in a highly viscous sulfuric acid solution. A new numerical scheme based on the window method is proposed to account for the history force acting on a spherical bubble with variable radius. We could quantify the history force, which is not negligible in comparison with the primary Bjerknes force in this type of problem, and results are in agreement with the classical primary Bjerknes force trapping threshold analysis. Moreover, the present numerical implementation reproduces the spatial behavior associated with the positional and path instability of sonoluminescent argon bubbles in strongly gassed and highly degassed sulfuric acid solutions. Finally, the model allows us to demonstrate that spatially stationary bubbles driven by biharmonic excitation could be obtained with a different mode from the one used in previous reported experiments.

Determination of the dynamical behaviour of biological materials during impact using a pendulum device

NASA Astrophysics Data System (ADS)

Van Zeebroeck, M.; Tijskens, E.; Van Liedekerke, P.; Deli, V.; De Baerdemaeker, J.; Ramon, H.

2003-09-01

A pendulum device has been developed to measure contact force, displacement and displacement rate of an impactor during its impact on the sample. Displacement, classically measured by double integration of an accelerometer, was determined in an alternative way using a more accurate incremental optical encoder. The parameters of the Kuwabara-Kono contact force model for impact of spheres have been estimated using an optimization method, taking the experimentally measured displacement, displacement rate and contact force into account. The accuracy of the method was verified using a rubber ball. Contact force parameters for the Kuwabara-Kono model have been estimated with success for three biological materials, i.e., apples, tomatoes and potatoes. The variability in the parameter estimations for the biological materials was quite high and can be explained by geometric differences (radius of curvature) and by biological variation of mechanical tissue properties.

Transducer-actuator systems and methods for performing on-machine measurements and automatic part alignment

DOEpatents

Barkman, William E.; Dow, Thomas A.; Garrard, Kenneth P.; Marston, Zachary

2016-07-12

Systems and methods for performing on-machine measurements and automatic part alignment, including: a measurement component operable for determining the position of a part on a machine; and an actuation component operable for adjusting the position of the part by contacting the part with a predetermined force responsive to the determined position of the part. The measurement component consists of a transducer. The actuation component consists of a linear actuator. Optionally, the measurement component and the actuation component consist of a single linear actuator operable for contacting the part with a first lighter force for determining the position of the part and with a second harder force for adjusting the position of the part. The actuation component is utilized in a substantially horizontal configuration and the effects of gravitational drop of the part are accounted for in the force applied and the timing of the contact.

CO2 forcing induces semi-direct effects with consequences for climate feedback interpretations

NASA Astrophysics Data System (ADS)

Andrews, Timothy; Forster, Piers M.

2008-02-01

Climate forcing and feedbacks are diagnosed from seven slab-ocean GCMs for 2 × CO2 using a regression method. Results are compared to those using conventional methodologies to derive a semi-direct forcing due to tropospheric adjustment, analogous to the semi-direct effect of absorbing aerosols. All models show a cloud semi-direct effect, indicating a rapid cloud response to CO2; cloud typically decreases, enhancing the warming. Similarly there is evidence of semi-direct effects from water-vapour, lapse-rate, ice and snow. Previous estimates of climate feedbacks are unlikely to have taken these semi-direct effects into account and so misinterpret processes as feedbacks that depend only on the forcing, but not the global surface temperature. We show that the actual cloud feedback is smaller than what previous methods suggest and that a significant part of the cloud response and the large spread between previous model estimates of cloud feedback is due to the semi-direct forcing.

Method of analysis for compressible flow through mixed-flow centrifugal impellers of arbitrary design

NASA Technical Reports Server (NTRS)

Hamrick, Joseph T; Ginsburg, Ambrose; Osborn, Walter M

1952-01-01

A method is presented for analysis of the compressible flow between the hub and the shroud of mixed-flow impellers of arbitrary design. Axial symmetry was assumed, but the forces in the meridional (hub to shroud) plane, which are derived from tangential pressure gradients, were taken into account. The method was applied to an experimental mixed-flow impeller. The analysis of the flow in the meridional plane of the impeller showed that the rotational forces, the blade curvature, and the hub-shroud profile can introduce severe velocity gradients along the hub and the shroud surfaces. Choked flow at the impeller inlet as determined by the analysis was verified by experimental results.

Securing Healthcare’s Quantified-Self Data: A Comparative Analysis Versus Personal Financial Account Aggregators Based on Porter’s Five Forces Framework for Competitive Force

DTIC Science & Technology

2016-09-01

HEALTHCARE’S QUANTIFIED-SELF DATA: A COMPARATIVE ANALYSIS VERSUS PERSONAL FINANCIAL ACCOUNT AGGREGATORS BASED ON PORTER’S FIVE FORCES FRAMEWORK FOR...TITLE AND SUBTITLE SECURING HEALTHCARE’S QUANTIFIED-SELF DATA: A COMPARATIVE ANALYSIS VERSUS PERSONAL FINANCIAL ACCOUNT AGGREGATORS BASED ON...Distribution is unlimited. SECURING HEALTHCARE’S QUANTIFIED-SELF DATA: A COMPARATIVE ANALYSIS VERSUS PERSONAL FINANCIAL ACCOUNT AGGREGATORS BASED ON

Sensitivity Analysis for Coupled Aero-structural Systems

NASA Technical Reports Server (NTRS)

Giunta, Anthony A.

1999-01-01

A novel method has been developed for calculating gradients of aerodynamic force and moment coefficients for an aeroelastic aircraft model. This method uses the Global Sensitivity Equations (GSE) to account for the aero-structural coupling, and a reduced-order modal analysis approach to condense the coupling bandwidth between the aerodynamic and structural models. Parallel computing is applied to reduce the computational expense of the numerous high fidelity aerodynamic analyses needed for the coupled aero-structural system. Good agreement is obtained between aerodynamic force and moment gradients computed with the GSE/modal analysis approach and the same quantities computed using brute-force, computationally expensive, finite difference approximations. A comparison between the computational expense of the GSE/modal analysis method and a pure finite difference approach is presented. These results show that the GSE/modal analysis approach is the more computationally efficient technique if sensitivity analysis is to be performed for two or more aircraft design parameters.

Analysis of an arched outer-race ball bearing considering centrifugal forces.

NASA Technical Reports Server (NTRS)

Hamrock, B. J.; Anderson, W. J.

1972-01-01

Thrust-load analysis of a 150-mm angular contact ball bearing, taking into account centrifugal forces but omitting gyroscopics, elastohydrodynamics, and thermal effects. A Newton-Raphson method of iteration is used to evaluate the radial and axial projection of the distance between the ball center and the outer raceway groove curvature center. Fatigue life of the bearing is evaluated. Results for life, contact loads, and angles are given for a conventional bearing and two arched bearings.

Theoretical study of the flow in a fluid damper containing high viscosity silicone oil: Effects of shear-thinning and viscoelasticity

NASA Astrophysics Data System (ADS)

Syrakos, Alexandros; Dimakopoulos, Yannis; Tsamopoulos, John

2018-03-01

The flow inside a fluid damper where a piston reciprocates sinusoidally inside an outer casing containing high-viscosity silicone oil is simulated using a finite volume method, at various excitation frequencies. The oil is modeled by the Carreau-Yasuda (CY) and Phan-Thien and Tanner (PTT) constitutive equations. Both models account for shear-thinning, but only the PTT model accounts for elasticity. The CY and other generalised Newtonian models have been previously used in theoretical studies of fluid dampers, but the present study is the first to perform full two-dimensional (axisymmetric) simulations employing a viscoelastic constitutive equation. It is found that the CY and PTT predictions are similar when the excitation frequency is low, but at medium and higher frequencies, the CY model fails to describe important phenomena that are predicted by the PTT model and observed in experimental studies found in the literature, such as the hysteresis of the force-displacement and force-velocity loops. Elastic effects are quantified by applying a decomposition of the damper force into elastic and viscous components, inspired from large amplitude oscillatory shear theory. The CY model also overestimates the damper force relative to the PTT model because it underpredicts the flow development length inside the piston-cylinder gap. It is thus concluded that (a) fluid elasticity must be accounted for and (b) theoretical approaches that rely on the assumption of one-dimensional flow in the piston-cylinder gap are of limited accuracy, even if they account for fluid viscoelasticity. The consequences of using lower-viscosity silicone oil are also briefly examined.

Compilation of FY 1997 Air Force General Funds Consolidated Financial Statements at the Defense Finance and Accounting Service Denver Center.

DTIC Science & Technology

1998-10-05

Consolidated Financial Statements to the Air Force Audit Agency. The Defense Finance and Accounting Service Denver Center maintained accounting records and prepared the FY 1997 financial statements for the Air Force. More than $343 billion in total assets was reported at year’s end in these statements, and total revenues for the year exceeded $64 billion. The Air Force Audit Agency disclaimed an opinion on these statements. Additionally, although the Office of Management and Budget does not require budgetary resource reporting until FY 1998, the Air Force

A fictitious domain approach for the simulation of dense suspensions

NASA Astrophysics Data System (ADS)

Gallier, Stany; Lemaire, Elisabeth; Lobry, Laurent; Peters, François

2014-01-01

Low Reynolds number concentrated suspensions do exhibit an intricate physics which can be partly unraveled by the use of numerical simulation. To this end, a Lagrange multiplier-free fictitious domain approach is described in this work. Unlike some methods recently proposed, the present approach is fully Eulerian and therefore does not need any transfer between the Eulerian background grid and some Lagrangian nodes attached to particles. Lubrication forces between particles play an important role in the suspension rheology and have been properly accounted for in the model. A robust and effective lubrication scheme is outlined which consists in transposing the classical approach used in Stokesian Dynamics to our present direct numerical simulation. This lubrication model has also been adapted to account for solid boundaries such as walls. Contact forces between particles are modeled using a classical Discrete Element Method (DEM), a widely used method in granular matter physics. Comprehensive validations are presented on various one-particle, two-particle or three-particle configurations in a linear shear flow as well as some O(103) and O(104) particle simulations.

Cases on Successful E-Learning Practices in the Developed and Developing World: Methods for the Global Information Economy

ERIC Educational Resources Information Center

Olaniran, Bolanle A., Ed.

2010-01-01

E-learning has become a significant aspect of training and education in the worldwide information economy as an attempt to create and facilitate a competent global work force. "Cases on Successful E-Learning Practices in the Developed and Developing World: Methods for the Global Information Economy" provides eclectic accounts of case…

Air Force Personnel Can Improve Compliance With the Berry Amendment and Buy American Act

DTIC Science & Technology

2016-02-24

accountability , integrity, and efficiency; advises the Secretary of Defense and Congress; and informs the public. Vision Our vision is to be a model...of personnel from the DoD OIG’s Quantitative Methods Division. Prior Coverage During the last 5 years, the Government Accountability Office (GAO... disclosures . The designated ombudsman is the DoD Hotline Director. For more information on your rights and remedies against retaliation, visit www.dodig.mil

Motion synthesis and force distribution analysis for a biped robot.

PubMed

Trojnacki, Maciej T; Zielińska, Teresa

2011-01-01

In this paper, the method of generating biped robot motion using recorded human gait is presented. The recorded data were modified taking into account the velocity available for robot drives. Data includes only selected joint angles, therefore the missing values were obtained considering the dynamic postural stability of the robot, which means obtaining an adequate motion trajectory of the so-called Zero Moment Point (ZMT). Also, the method of determining the ground reaction forces' distribution during the biped robot's dynamic stable walk is described. The method was developed by the authors. Following the description of equations characterizing the dynamics of robot's motion, the values of the components of ground reaction forces were symbolically determined as well as the coordinates of the points of robot's feet contact with the ground. The theoretical considerations have been supported by computer simulation and animation of the robot's motion. This was done using Matlab/Simulink package and Simulink 3D Animation Toolbox, and it has proved the proposed method.

Load-bearing Characters Analysis of Large Diameter Rock-Socketed Filling Piles Based on Self-Balanced Method

NASA Astrophysics Data System (ADS)

tongqing, Wu; liang, Li; xinjian, Liu; Xu, nianchun; Tian, Mao

2018-03-01

Self-balanced method is carried out on the large diameter rock-socketed filling piles of high-pile wharf at Inland River, to explore the distribution laws of load-displacement curve, pile internal force, pile tip friction resistance and pile side friction resistance under load force. The results showed that: the tip resistance of S1 and S2 test piles accounted for 53.4% and 53.6% of the pile bearing capacity, respectively, while the total side friction resistance accounted for 46.6% and 46.4% of the pile bearing capacity, respectively; both the pile tip friction resistance and pile side friction resistance can be fully played, and reach to the design requirements. The reasonability of large diameter rock-socketed filling design is verified through test analysis, which can provide basis for the optimization of high-pile wharf structural type, thus reducing the wharf project cost, and also providing reference for the similar large diameter rock-socketed filling piles of high-pile wharf at Inland River.

Strength Calculation of Inclined Sections of Reinforced Concrete Elements under Transverse Bending

NASA Astrophysics Data System (ADS)

Filatov, V. B.

2017-11-01

The authors propose a design model to determine the strength of inclined sections of bent reinforced concrete elements without shear reinforcement for the action of transverse force taking into account the aggregate interlock forces in the inclined crack. The calculated dependences to find out the components of forces acting in an inclined section are presented. The calculated dependences are obtained from the consideration of equilibrium conditions of the block over the inclined crack. A comparative analysis of the experimental values of the failure loads of the inclined section and the theoretical values obtained for the proposed dependencies and normative calculation methods is performed. It is shown that the proposed design model makes it possible to take into account the effect the longitudinal reinforcement percentage has on the inclined section strength, the element cross section height without the introduction of empirical coefficients which contributes to an increase in the structural safety of design solutions including the safety of high-strength concrete elements.

Spring constant of a tuning-fork sensor for dynamic force microscopy

PubMed Central

Lange, Manfred; Schmuck, Merlin; Schmidt, Nico; Möller, Rolf

2012-01-01

Summary We present an overview of experimental and numerical methods to determine the spring constant of a quartz tuning fork in qPlus configuration. The simple calculation for a rectangular cantilever is compared to the values obtained by the analysis of the thermal excitation and by the direct mechanical measurement of the force versus displacement. To elucidate the difference, numerical simulations were performed taking account of the real geometry including the glue that is used to mount the tuning fork. PMID:23365793

Force-moment line element method for flexible slender bodies in Stokes flow.

PubMed

Jiang, H; Yang, B

2013-09-01

The hydrodynamics of flexible slender bodies in Stokes flow is studied by taking into account the fluid-structure interaction through both forces and coupled moments. The fluid subjected to line sources of forces and moments is described by using integral equations. Meanwhile, the flexible slender body is modeled using finite beam elements. The two sides are linked through interfacial continuity conditions. Upon discretization, it results in a higher-order line element method for efficient and accurate solution of slender-body hydrodynamics. Four examples are presented to demonstrate the validity and efficiency of the present method: (a) hydrodynamics of a flexible slender rod subjected to a torque at one end, (b) hydrodynamics of a flexible slender rod subjected to a bending moment at one end, (c) hydrodynamics of a flexible slender rod subjected to a cyclic force, and (d) hydrodynamics of a flexible slender rod with a magnetized head within a rotating magnetic field. Examples (a) and (b) may serve as benchmark solutions and examples (c) and (d) show how planar and spiral waves can be excited in a slender body.

Analysis of prestressed concrete slab-and-beam structures

NASA Astrophysics Data System (ADS)

Sapountzakis, E. J.; Katsikadelis, J. T.

In this paper a solution to the problem of prestressed concrete slab-and-beam structures including creep and shrinkage effect is presented. The adopted model takes into account the resulting inplane forces and deformations of the plate as well as the axial forces and deformations of the beam, due to combined response of the system. The analysis consists in isolating the beams from the plate by sections parallel to the lower outer surface of the plate. The forces at the interface, which produce lateral deflection and inplane deformation to the plate and lateral deflection and axial deformation to the beam, are established using continuity conditions at the interface. The influence of creep and shrinkage effect relative with the time of the casting and the time of the loading of the plate and the beams is taken into account. The estimation of the prestressing axial force of the beams is accomplished iteratively. Both instant (e.g. friction, slip of anchorage) and time dependent losses are encountered. The solution of the arising plate and beam problems, which are nonlinearly coupled, is achieved using the analog equation method (AEM). The adopted model, compared with those ignoring the inplane forces and deformations, describes better the actual response of the plate-beams system and permits the evaluation of the shear forces at the interfaces, the knowledge of which is very important in the design of prefabricated ribbed plates.

Modelling cell motility and chemotaxis with evolving surface finite elements

PubMed Central

Elliott, Charles M.; Stinner, Björn; Venkataraman, Chandrasekhar

2012-01-01

We present a mathematical and a computational framework for the modelling of cell motility. The cell membrane is represented by an evolving surface, with the movement of the cell determined by the interaction of various forces that act normal to the surface. We consider external forces such as those that may arise owing to inhomogeneities in the medium and a pressure that constrains the enclosed volume, as well as internal forces that arise from the reaction of the cells' surface to stretching and bending. We also consider a protrusive force associated with a reaction–diffusion system (RDS) posed on the cell membrane, with cell polarization modelled by this surface RDS. The computational method is based on an evolving surface finite-element method. The general method can account for the large deformations that arise in cell motility and allows the simulation of cell migration in three dimensions. We illustrate applications of the proposed modelling framework and numerical method by reporting on numerical simulations of a model for eukaryotic chemotaxis and a model for the persistent movement of keratocytes in two and three space dimensions. Movies of the simulated cells can be obtained from http://homepages.warwick.ac.uk/∼maskae/CV_Warwick/Chemotaxis.html. PMID:22675164

Investigation of the dependence of joint contact forces on musculotendon parameters using a codified workflow for image-based modelling.

PubMed

Modenese, Luca; Montefiori, Erica; Wang, Anqi; Wesarg, Stefan; Viceconti, Marco; Mazzà, Claudia

2018-05-17

The generation of subject-specific musculoskeletal models of the lower limb has become a feasible task thanks to improvements in medical imaging technology and musculoskeletal modelling software. Nevertheless, clinical use of these models in paediatric applications is still limited for what concerns the estimation of muscle and joint contact forces. Aiming to improve the current state of the art, a methodology to generate highly personalized subject-specific musculoskeletal models of the lower limb based on magnetic resonance imaging (MRI) scans was codified as a step-by-step procedure and applied to data from eight juvenile individuals. The generated musculoskeletal models were used to simulate 107 gait trials using stereophotogrammetric and force platform data as input. To ensure completeness of the modelling procedure, muscles' architecture needs to be estimated. Four methods to estimate muscles' maximum isometric force and two methods to estimate musculotendon parameters (optimal fiber length and tendon slack length) were assessed and compared, in order to quantify their influence on the models' output. Reported results represent the first comprehensive subject-specific model-based characterization of juvenile gait biomechanics, including profiles of joint kinematics and kinetics, muscle forces and joint contact forces. Our findings suggest that, when musculotendon parameters were linearly scaled from a reference model and the muscle force-length-velocity relationship was accounted for in the simulations, realistic knee contact forces could be estimated and these forces were not sensitive the method used to compute muscle maximum isometric force. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

The Methodology of Calculation of Cutting Forces When Machining Composite Materials

NASA Astrophysics Data System (ADS)

Rychkov, D. A.; Yanyushkin, A. S.

2016-08-01

Cutting of composite materials has specific features and is different from the processing of metals. When this characteristic intense wear of the cutting tool. An important criterion in the selection process parameters composite processing is the value of the cutting forces, which depends on many factors and is determined experimentally, it is not always appropriate. The study developed a method of determining the cutting forces when machining composite materials and the comparative evaluation of the calculated and actual values of cutting forces. The methodology for calculating cutting forces into account specific features of the cutting tool and the extent of wear, the strength properties of the processed material and cutting conditions. Experimental studies conducted with fiberglass milling cutter equipped with elements of hard metal VK3M. The discrepancy between the estimated and the actual values of the cutting force is not more than 10%.

Error analysis and assessment of unsteady forces acting on a flapping wing micro air vehicle: free flight versus wind-tunnel experimental methods.

PubMed

Caetano, J V; Percin, M; van Oudheusden, B W; Remes, B; de Wagter, C; de Croon, G C H E; de Visser, C C

2015-08-20

An accurate knowledge of the unsteady aerodynamic forces acting on a bio-inspired, flapping-wing micro air vehicle (FWMAV) is crucial in the design development and optimization cycle. Two different types of experimental approaches are often used: determination of forces from position data obtained from external optical tracking during free flight, or direct measurements of forces by attaching the FWMAV to a force transducer in a wind-tunnel. This study compares the quality of the forces obtained from both methods as applied to a 17.4 gram FWMAV capable of controlled flight. A comprehensive analysis of various error sources is performed. The effects of different factors, e.g., measurement errors, error propagation, numerical differentiation, filtering frequency selection, and structural eigenmode interference, are assessed. For the forces obtained from free flight experiments it is shown that a data acquisition frequency below 200 Hz and an accuracy in the position measurements lower than ± 0.2 mm may considerably hinder determination of the unsteady forces. In general, the force component parallel to the fuselage determined by the two methods compares well for identical flight conditions; however, a significant difference was observed for the forces along the stroke plane of the wings. This was found to originate from the restrictions applied by the clamp to the dynamic oscillations observed in free flight and from the structural resonance of the clamped FWMAV structure, which generates loads that cannot be distinguished from the external forces. Furthermore, the clamping position was found to have a pronounced influence on the eigenmodes of the structure, and this effect should be taken into account for accurate force measurements.

DEM Modeling of a Flexible Barrier Impacted by a Dry Granular Flow

NASA Astrophysics Data System (ADS)

Albaba, Adel; Lambert, Stéphane; Kneib, François; Chareyre, Bruno; Nicot, François

2017-11-01

Flexible barriers are widely used as protection structures against natural hazards in mountainous regions, in particular for containing granular materials such as debris flows, snow avalanches and rock slides. This article presents a discrete element method-based model developed in the aim of investigating the response of flexible barriers in such contexts. It allows for accounting for the peculiar mechanical and geometrical characteristics of both the granular flow and the barrier in a same framework, and with limited assumptions. The model, developed with YADE software, is described in detail, as well as its calibration. In particular, cables are modeled as continuous bodies. Besides, it naturally considers the sliding of rings along supporting cables. The model is then applied for a generic flexible barrier to demonstrate its capacities in accounting for the behavior of different components. A detailed analysis of the forces in the different components showed that energy dissipators (ED) had limited influence on total force applied to the barrier and retaining capacity, but greatly influenced the load transmission within the barrier and the force in anchors. A sensitivity analysis showed that the barrier's response significantly changes according to the choice of ED activation force and incoming flow conditions.

A Force Balanced Fragmentation Method for ab Initio Molecular Dynamic Simulation of Protein.

PubMed

Xu, Mingyuan; Zhu, Tong; Zhang, John Z H

2018-01-01

A force balanced generalized molecular fractionation with conjugate caps (FB-GMFCC) method is proposed for ab initio molecular dynamic simulation of proteins. In this approach, the energy of the protein is computed by a linear combination of the QM energies of individual residues and molecular fragments that account for the two-body interaction of hydrogen bond between backbone peptides. The atomic forces on the caped H atoms were corrected to conserve the total force of the protein. Using this approach, ab initio molecular dynamic simulation of an Ace-(ALA) 9 -NME linear peptide showed the conservation of the total energy of the system throughout the simulation. Further a more robust 110 ps ab initio molecular dynamic simulation was performed for a protein with 56 residues and 862 atoms in explicit water. Compared with the classical force field, the ab initio molecular dynamic simulations gave better description of the geometry of peptide bonds. Although further development is still needed, the current approach is highly efficient, trivially parallel, and can be applied to ab initio molecular dynamic simulation study of large proteins.

23 CFR 645.113 - Agreements and authorizations.

Code of Federal Regulations, 2010 CFR

2010-04-01

... work. When Federal participation is requested, the agreement shall incorporate this regulation by reference and designate the method to be used for performing the work (by contract or force account) and for... utility is on the basis of actual direct and related indirect costs accumulated in accordance with a work...

New formulation of the discrete element method

NASA Astrophysics Data System (ADS)

Rojek, Jerzy; Zubelewicz, Aleksander; Madan, Nikhil; Nosewicz, Szymon

2018-01-01

A new original formulation of the discrete element method based on the soft contact approach is presented in this work. The standard DEM has heen enhanced by the introduction of the additional (global) deformation mode caused by the stresses in the particles induced by the contact forces. Uniform stresses and strains are assumed for each particle. The stresses are calculated from the contact forces. The strains are obtained using an inverse constitutive relationship. The strains allow us to obtain deformed particle shapes. The deformed shapes (ellipses) are taken into account in contact detection and evaluation of the contact forces. A simple example of a uniaxial compression of a rectangular specimen, discreti.zed with equal sized particles is simulated to verify the DDEM algorithm. The numerical example shows that a particle deformation changes the particle interaction and the distribution of forces in the discrete element assembly. A quantitative study of micro-macro elastic properties proves the enhanced capabilities of the DDEM as compared to standard DEM.

Rotor systems research aircraft risk-reduction shake test

NASA Technical Reports Server (NTRS)

Wellman, J. Brent

1990-01-01

A shake test and an extensive analysis of results were performed to evaluate the possibility of and the method for dynamically calibrating the Rotor Systems Research Aircraft (RSRA). The RSRA airframe was subjected to known vibratory loads in several degrees of freedom and the responses of many aircraft transducers were recorded. Analysis of the transducer responses using the technique of dynamic force determination showed that the RSRA, when used as a dynamic measurement system, could predict, a posteriori, an excitation force in a single axis to an accuracy of about 5 percent and sometimes better. As the analysis was broadened to include multiple degrees of freedom for the excitation force, the predictive ability of the measurement system degraded to about 20 percent, with the error occasionally reaching 100 percent. The poor performance of the measurement system is explained by the nonlinear response of the RSRA to vibratory forces and the inadequacy of the particular method used in accounting for this nonlinearity.

Detectability of the impacts of ozone-depleting substances and greenhouse gases upon stratospheric ozone accounting for nonlinearities in historical forcings

NASA Astrophysics Data System (ADS)

Bandoro, Justin; Solomon, Susan; Santer, Benjamin D.; Kinnison, Douglas E.; Mills, Michael J.

2018-01-01

We perform a formal attribution study of upper- and lower-stratospheric ozone changes using observations together with simulations from the Whole Atmosphere Community Climate Model. Historical model simulations were used to estimate the zonal-mean response patterns (fingerprints) to combined forcing by ozone-depleting substances (ODSs) and well-mixed greenhouse gases (GHGs), as well as to the individual forcing by each factor. Trends in the similarity between the searched-for fingerprints and homogenized observations of stratospheric ozone were compared to trends in pattern similarity between the fingerprints and the internally and naturally generated variability inferred from long control runs. This yields estimated signal-to-noise (S/N) ratios for each of the three fingerprints (ODS, GHG, and ODS + GHG). In both the upper stratosphere (defined in this paper as 1 to 10 hPa) and lower stratosphere (40 to 100 hPa), the spatial fingerprints of the ODS + GHG and ODS-only patterns were consistently detectable not only during the era of maximum ozone depletion but also throughout the observational record (1984-2016). We also develop a fingerprint attribution method to account for forcings whose time evolutions are markedly nonlinear over the observational record. When the nonlinearity of the time evolution of the ODS and ODS + GHG signals is accounted for, we find that the S/N ratios obtained with the stratospheric ODS and ODS + GHG fingerprints are enhanced relative to standard linear trend analysis. Use of the nonlinear signal detection method also reduces the detection time - the estimate of the date at which ODS and GHG impacts on ozone can be formally identified. Furthermore, by explicitly considering nonlinear signal evolution, the complete observational record can be used in the S/N analysis, without applying piecewise linear regression and introducing arbitrary break points. The GHG-driven fingerprint of ozone changes was not statistically identifiable in either the upper- or lower-stratospheric SWOOSH data, irrespective of the signal detection method used. In the WACCM simulations of future climate change, the GHG signal is statistically identifiable between 2020 and 2030. Our findings demonstrate the importance of continued stratospheric ozone monitoring to improve estimates of the contributions of ODS and GHG forcing to global changes in stratospheric ozone.

48 CFR 915.404-4-71-5 - Fee schedules.

Code of Federal Regulations, 2010 CFR

2010-10-01

... until such Force account work exceeds, in the aggregate, 20 percent of the base. Excessive use of Force..., appropriate fee reductions for such excessive Force account labor shall be computed as follows: (1) Determine... following adjustments shall be made to the Schedule fee amounts for complexity levels, excessive...

48 CFR 915.404-4-71-5 - Fee schedules.

Code of Federal Regulations, 2011 CFR

2011-10-01

... until such Force account work exceeds, in the aggregate, 20 percent of the base. Excessive use of Force..., appropriate fee reductions for such excessive Force account labor shall be computed as follows: (1) Determine... following adjustments shall be made to the Schedule fee amounts for complexity levels, excessive...

48 CFR 915.404-4-71-5 - Fee schedules.

Code of Federal Regulations, 2013 CFR

2013-10-01

... until such Force account work exceeds, in the aggregate, 20 percent of the base. Excessive use of Force..., appropriate fee reductions for such excessive Force account labor shall be computed as follows: (1) Determine... following adjustments shall be made to the Schedule fee amounts for complexity levels, excessive...

48 CFR 915.404-4-71-5 - Fee schedules.

Code of Federal Regulations, 2012 CFR

2012-10-01

... until such Force account work exceeds, in the aggregate, 20 percent of the base. Excessive use of Force..., appropriate fee reductions for such excessive Force account labor shall be computed as follows: (1) Determine... following adjustments shall be made to the Schedule fee amounts for complexity levels, excessive...

48 CFR 915.404-4-71-5 - Fee schedules.

Code of Federal Regulations, 2014 CFR

2014-10-01

... until such Force account work exceeds, in the aggregate, 20 percent of the base. Excessive use of Force..., appropriate fee reductions for such excessive Force account labor shall be computed as follows: (1) Determine... following adjustments shall be made to the Schedule fee amounts for complexity levels, excessive...

Simulating condensation on microstructured surfaces using Lattice Boltzmann Method

NASA Astrophysics Data System (ADS)

Alexeev, Alexander; Vasyliv, Yaroslav

2017-11-01

We simulate a single component fluid condensing on 2D structured surfaces with different wettability. To simulate the two phase fluid, we use the athermal Lattice Boltzmann Method (LBM) driven by a pseudopotential force. The pseudopotential force results in a non-ideal equation of state (EOS) which permits liquid-vapor phase change. To account for thermal effects, the athermal LBM is coupled to a finite volume discretization of the temperature evolution equation obtained using a thermal energy rate balance for the specific internal energy. We use the developed model to probe the effect of surface structure and surface wettability on the condensation rate in order to identify microstructure topographies promoting condensation. Financial support is acknowledged from Kimberly-Clark.

5 CFR 2100.10 - Conditions of disclosure and accounting of certain disclosures.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 5 Administrative Personnel 3 2010-01-01 2010-01-01 false Conditions of disclosure and accounting of certain disclosures. 2100.10 Section 2100.10 Administrative Personnel ARMED FORCES RETIREMENT HOME ARMED FORCES RETIREMENT HOME PRIVACY ACT PROCEDURES § 2100.10 Conditions of disclosure and accounting of...

Trends and associated uncertainty in the global mean temperature record

NASA Astrophysics Data System (ADS)

Poppick, A. N.; Moyer, E. J.; Stein, M.

2016-12-01

Physical models suggest that the Earth's mean temperature warms in response to changing CO2 concentrations (and hence increased radiative forcing); given physical uncertainties in this relationship, the historical temperature record is a source of empirical information about global warming. A persistent thread in many analyses of the historical temperature record, however, is the reliance on methods that appear to deemphasize both physical and statistical assumptions. Examples include regression models that treat time rather than radiative forcing as the relevant covariate, and time series methods that account for natural variability in nonparametric rather than parametric ways. We show here that methods that deemphasize assumptions can limit the scope of analysis and can lead to misleading inferences, particularly in the setting considered where the data record is relatively short and the scale of temporal correlation is relatively long. A proposed model that is simple but physically informed provides a more reliable estimate of trends and allows a broader array of questions to be addressed. In accounting for uncertainty, we also illustrate how parametric statistical models that are attuned to the important characteristics of natural variability can be more reliable than ostensibly more flexible approaches.

A phenomenological force model of Li-ion battery packs for enhanced performance and health management

NASA Astrophysics Data System (ADS)

Oh, Ki-Yong; Epureanu, Bogdan I.

2017-10-01

A 1-D phenomenological force model of a Li-ion battery pack is proposed to enhance the control performance of Li-ion battery cells in pack conditions for efficient performance and health management. The force model accounts for multiple swelling sources under the operational environment of electric vehicles to predict swelling-induced forces in pack conditions, i.e. mechanically constrained. The proposed force model not only incorporates structural nonlinearities due to Li-ion intercalation swelling, but also separates the overall range of states of charge into three ranges to account for phase transitions. Moreover, an approach to study cell-to-cell variations in pack conditions is proposed with serial and parallel combinations of linear and nonlinear stiffness, which account for battery cells and other components in the battery pack. The model is shown not only to accurately estimate the reaction force caused by swelling as a function of the state of charge, battery temperature and environmental temperature, but also to account for cell-to-cell variations due to temperature variations, SOC differences, and local degradation in a wide range of operational conditions of electric vehicles. Considering that the force model of Li-ion battery packs can account for many possible situations in actual operation, the proposed approach and model offer potential utility for the enhancement of current battery management systems and power management strategies.

Estimating trends in the global mean temperature record

NASA Astrophysics Data System (ADS)

Poppick, Andrew; Moyer, Elisabeth J.; Stein, Michael L.

2017-06-01

Given uncertainties in physical theory and numerical climate simulations, the historical temperature record is often used as a source of empirical information about climate change. Many historical trend analyses appear to de-emphasize physical and statistical assumptions: examples include regression models that treat time rather than radiative forcing as the relevant covariate, and time series methods that account for internal variability in nonparametric rather than parametric ways. However, given a limited data record and the presence of internal variability, estimating radiatively forced temperature trends in the historical record necessarily requires some assumptions. Ostensibly empirical methods can also involve an inherent conflict in assumptions: they require data records that are short enough for naive trend models to be applicable, but long enough for long-timescale internal variability to be accounted for. In the context of global mean temperatures, empirical methods that appear to de-emphasize assumptions can therefore produce misleading inferences, because the trend over the twentieth century is complex and the scale of temporal correlation is long relative to the length of the data record. We illustrate here how a simple but physically motivated trend model can provide better-fitting and more broadly applicable trend estimates and can allow for a wider array of questions to be addressed. In particular, the model allows one to distinguish, within a single statistical framework, between uncertainties in the shorter-term vs. longer-term response to radiative forcing, with implications not only on historical trends but also on uncertainties in future projections. We also investigate the consequence on inferred uncertainties of the choice of a statistical description of internal variability. While nonparametric methods may seem to avoid making explicit assumptions, we demonstrate how even misspecified parametric statistical methods, if attuned to the important characteristics of internal variability, can result in more accurate uncertainty statements about trends.

Bond breaking in epoxy systems: A combined QM/MM approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barr, Stephen A.; Ecker, Allison M.; Berry, Rajiv J., E-mail: Rajiv.Berry@us.af.mil

2016-06-28

A novel method to combine quantum mechanics (QM) and molecular mechanics has been developed to accurately and efficiently account for covalent bond breaking in polymer systems under high strain without the use of predetermined break locations. Use of this method will provide a better fundamental understanding of the mechano-chemical origins of fracture in thermosets. Since classical force fields cannot accurately account for bond breaking, and QM is too demanding to simulate large systems, a hybrid approach is required. In the method presented here, strain is applied to the system using a classical force field, and all bond lengths are monitored.more » When a bond is stretched past a threshold value, a zone surrounding the bond is used in a QM energy minimization to determine which, if any, bonds break. The QM results are then used to reconstitute the system to continue the classical simulation at progressively larger strain until another QM calculation is triggered. In this way, a QM calculation is only computed when and where needed, allowing for efficient simulations. A robust QM method for energy minimization has been determined, as well as appropriate values for the QM zone size and the threshold bond length. Compute times do not differ dramatically from classical molecular mechanical simulations.« less

Electromagnetic forces in negative-refractive-index metamaterials: A first-principles study

NASA Astrophysics Data System (ADS)

Yannopapas, Vassilios; Galiatsatos, Pavlos G.

2008-04-01

According to the theory of Veselago, when a particle immersed within a metamaterial with negative refractive index is illuminated by plane wave, it experiences a reversed radiation force due to the antiparallel directions of the phase velocity and energy flow. By employing an ab initio method, we show that, in the limit of zero losses, the effect of reversed radiation pressure is generally true only for the specular beam. Waves generated by diffraction of the incident light at the surface of the slab of the metamaterial can produce a total force which is parallel to the radiation flow. However, when the actual losses of the materials are taken into account, the phenomenon of reversed radiation force is evident within the whole range of a negative refractive index band.

Task Force on Education Funding Equity, Accountability, and Partnerships. Final Report.

ERIC Educational Resources Information Center

Maryland State Dept. of Legislative Services, Annapolis.

In 1997, Maryland formed the Task Force on Education Funding Equity, Accountability, and Partnerships. The group made a comprehensive review of education funding and programs in grades K-12 to ensure that students throughout Maryland have an equal opportunity for academic success. The task force's final report features the membership roster, the…

Task Force on Education Funding Equity, Accountability, and Partnerships. Preliminary Report.

ERIC Educational Resources Information Center

Maryland State Dept. of Legislative Services, Annapolis.

In 1997, Maryland formed the Task Force on Education Funding Equity, Accountability, and Partnerships to ensure that students throughout Maryland have an equal opportunity for academic success. The Task Force's preliminary report features a comprehensive review of education funding and programs in grades K-12. The report presents membership and…

An economical method of analyzing transient motion of gas-lubricated rotor-bearing systems.

NASA Technical Reports Server (NTRS)

Falkenhagen, G. L.; Ayers, A. L.; Barsalou, L. C.

1973-01-01

A method of economically evaluating the hydrodynamic forces generated in a gas-lubricated tilting-pad bearing is presented. The numerical method consists of solving the case of the infinite width bearing and then converting this solution to the case of the finite bearing by accounting for end leakage. The approximate method is compared to the finite-difference solution of Reynolds equation and yields acceptable accuracy while running about one-hundred times faster. A mathematical model of a gas-lubricated tilting-pad vertical rotor systems is developed. The model is capable of analyzing a two-bearing-rotor system in which the rotor center of mass is not at midspan by accounting for gyroscopic moments. The numerical results from the model are compared to actual test data as well as analytical results of other investigators.

Measurement of Cohesion in Asteroid Regolith Materials

NASA Technical Reports Server (NTRS)

Kleinhenz, Julie E.; Gaier, James R.; Waters, Deborah L.; Harvey, Ralph; Zeszut, Zoe; Carreno, Brandon; Shober, Patrick

2017-01-01

A study has been initiated to examine cohesive forces in asteroid materials to contribute to a better understanding of low density bodies such as asteroids and Phobos, and assist in exploration missions involving interaction with their surface material. The test specimen used in this study was a lightly weathered CM2 meteorite which is spectroscopically similar to Type C (carbonaceous) asteroids, and thought to have representative surface chemistry. To account for sample heterogeneity, adhesion forces were measured between the CM2 sample and its five primary mineral phase components. These adhesive forces bound the range of cohesive force that can be expected for the bulk material. All materials were characterized using a variety of optical and spectroscopic methods. Adhesive forces on the order of 50 to 400 µN were measured using a torsion balance in an ultrahigh vacuum chamber. The mineral samples exhibited clearly different adhesive strengths in the following hierarchy: Serpentine > Siderite > Bronzite > Olivine ˜ Fe-Ni.

Temporal Considerations of Carbon Sequestration in LCA

Treesearch

James Salazar; Richard Bergman

2013-01-01

Accounting for carbon sequestration in LCA illustrates the limitations of a single global warming characterization factor. Typical cradle-to-grave LCA models all emissions from end-of-life processes and then characterizes these flows by IPCC GWP (100-yr) factors. A novel method estimates climate change impact by characterizing annual emissions with the IPCC GHG forcing...

7 CFR 654.14 - Duration of sponsor(s)' responsibility.

Code of Federal Regulations, 2010 CFR

2010-01-01

... performed by force account, division of work, or performance of work methods, the sponsor(s)' O&M responsibilities begin on the date the work or portion thereof is completed as determined by NRCS, except for completed work located on Federal lands which are subject to special-use permits. The O&M agreement shall...

Reducing numerical costs for core wide nuclear reactor CFD simulations by the Coarse-Grid-CFD

NASA Astrophysics Data System (ADS)

Viellieber, Mathias; Class, Andreas G.

2013-11-01

Traditionally complete nuclear reactor core simulations are performed with subchannel analysis codes, that rely on experimental and empirical input. The Coarse-Grid-CFD (CGCFD) intends to replace the experimental or empirical input with CFD data. The reactor core consists of repetitive flow patterns, allowing the general approach of creating a parametrized model for one segment and composing many of those to obtain the entire reactor simulation. The method is based on a detailed and well-resolved CFD simulation of one representative segment. From this simulation we extract so-called parametrized volumetric forces which close, an otherwise strongly under resolved, coarsely-meshed model of a complete reactor setup. While the formulation so far accounts for forces created internally in the fluid others e.g. obstruction and flow deviation through spacers and wire wraps, still need to be accounted for if the geometric details are not represented in the coarse mesh. These are modelled with an Anisotropic Porosity Formulation (APF). This work focuses on the application of the CGCFD to a complete reactor core setup and the accomplishment of the parametrization of the volumetric forces.

Collapse Features

NASA Image and Video Library

2010-09-15

The depressions in this image from NASA Mars Odyssey likely formed due to both volcanic and tectonic forces. Tectonic forces likely account for some of the depressions, while collapse into lava tubes and lava flow erosion account for the remainder.

Error Modeling and Experimental Study of a Flexible Joint 6-UPUR Parallel Six-Axis Force Sensor.

PubMed

Zhao, Yanzhi; Cao, Yachao; Zhang, Caifeng; Zhang, Dan; Zhang, Jie

2017-09-29

By combining a parallel mechanism with integrated flexible joints, a large measurement range and high accuracy sensor is realized. However, the main errors of the sensor involve not only assembly errors, but also deformation errors of its flexible leg. Based on a flexible joint 6-UPUR (a kind of mechanism configuration where U-universal joint, P-prismatic joint, R-revolute joint) parallel six-axis force sensor developed during the prephase, assembly and deformation error modeling and analysis of the resulting sensors with a large measurement range and high accuracy are made in this paper. First, an assembly error model is established based on the imaginary kinematic joint method and the Denavit-Hartenberg (D-H) method. Next, a stiffness model is built to solve the stiffness matrix. The deformation error model of the sensor is obtained. Then, the first order kinematic influence coefficient matrix when the synthetic error is taken into account is solved. Finally, measurement and calibration experiments of the sensor composed of the hardware and software system are performed. Forced deformation of the force-measuring platform is detected by using laser interferometry and analyzed to verify the correctness of the synthetic error model. In addition, the first order kinematic influence coefficient matrix in actual circumstances is calculated. By comparing the condition numbers and square norms of the coefficient matrices, the conclusion is drawn theoretically that it is very important to take into account the synthetic error for design stage of the sensor and helpful to improve performance of the sensor in order to meet needs of actual working environments.

Error Modeling and Experimental Study of a Flexible Joint 6-UPUR Parallel Six-Axis Force Sensor

PubMed Central

Zhao, Yanzhi; Cao, Yachao; Zhang, Caifeng; Zhang, Dan; Zhang, Jie

2017-01-01

By combining a parallel mechanism with integrated flexible joints, a large measurement range and high accuracy sensor is realized. However, the main errors of the sensor involve not only assembly errors, but also deformation errors of its flexible leg. Based on a flexible joint 6-UPUR (a kind of mechanism configuration where U-universal joint, P-prismatic joint, R-revolute joint) parallel six-axis force sensor developed during the prephase, assembly and deformation error modeling and analysis of the resulting sensors with a large measurement range and high accuracy are made in this paper. First, an assembly error model is established based on the imaginary kinematic joint method and the Denavit-Hartenberg (D-H) method. Next, a stiffness model is built to solve the stiffness matrix. The deformation error model of the sensor is obtained. Then, the first order kinematic influence coefficient matrix when the synthetic error is taken into account is solved. Finally, measurement and calibration experiments of the sensor composed of the hardware and software system are performed. Forced deformation of the force-measuring platform is detected by using laser interferometry and analyzed to verify the correctness of the synthetic error model. In addition, the first order kinematic influence coefficient matrix in actual circumstances is calculated. By comparing the condition numbers and square norms of the coefficient matrices, the conclusion is drawn theoretically that it is very important to take into account the synthetic error for design stage of the sensor and helpful to improve performance of the sensor in order to meet needs of actual working environments. PMID:28961209

Origins and Elaboration of the National Health Accounts, 1926-2006

PubMed Central

Fetter, Bruce

2006-01-01

The National Health Statistics Group (NHSG) has managed to keep the national health accounts (NHA) apolitical and highly respected. NHSG strategies have included the careful acquisition and presentation of statistics relating to health costs and payers; the use of scholarly journals to disseminate ideas to other government offices and, beyond them, to industry, labor, the professions, and universities; and the promotion of cooperation with related U.S., statistical agencies, provider groups, contractors, and international organizations. Responding to an increasingly complex system of third-party payers in the U.S. health system and controversies over methods, the NHA has continually evolved to meet the demands of health care decisionmakers. Historically, these dialogues have forced health accountants to refine their methods to ensure that their portrayal of spending and financing trends presents information that can inform the decisionmaking process in a non-partisan way. PMID:17290668

26 CFR 301.7654-1 - Coordination of U.S. and Guam individual income taxes.

Code of Federal Regulations, 2010 CFR

2010-04-01

... taxpayer shall be determined by taking into account any compensation of any member of the Armed Forces for... any member of the Armed Forces described in paragraph (a)(2) of this section which is paid to Guam... income of members of the Armed Forces shall not be taken into account. For purposes of this subparagraph...

A non-contact, thermal noise based method for the calibration of lateral deflection sensitivity in atomic force microscopy.

PubMed

Mullin, Nic; Hobbs, Jamie K

2014-11-01

Calibration of lateral forces and displacements has been a long standing problem in lateral force microscopies. Recently, it was shown by Wagner et al. that the thermal noise spectrum of the first torsional mode may be used to calibrate the deflection sensitivity of the detector. This method is quick, non-destructive and may be performed in situ in air or liquid. Here we make a full quantitative comparison of the lateral inverse optical lever sensitivity obtained by the lateral thermal noise method and the shape independent method developed by Anderson et al. We find that the thermal method provides accurate results for a wide variety of rectangular cantilevers, provided that the geometry of the cantilever is suitable for torsional stiffness calibration by the torsional Sader method, in-plane bending of the cantilever may be eliminated or accounted for and that any scaling of the lateral deflection signal between the measurement of the lateral thermal noise and the measurement of the lateral deflection is eliminated or corrected for. We also demonstrate that the thermal method may be used to characterize the linearity of the detector signal as a function of position, and find a deviation of less than 8% for the instrument used.

Flight Dynamics of Flexible Aircraft with Aeroelastic and Inertial Force Interactions

NASA Technical Reports Server (NTRS)

Nguyen, Nhan T.; Tuzcu, Ilhan

2009-01-01

This paper presents an integrated flight dynamic modeling method for flexible aircraft that captures coupled physics effects due to inertial forces, aeroelasticity, and propulsive forces that are normally present in flight. The present approach formulates the coupled flight dynamics using a structural dynamic modeling method that describes the elasticity of a flexible, twisted, swept wing using an equivalent beam-rod model. The structural dynamic model allows for three types of wing elastic motion: flapwise bending, chordwise bending, and torsion. Inertial force coupling with the wing elasticity is formulated to account for aircraft acceleration. The structural deflections create an effective aeroelastic angle of attack that affects the rigid-body motion of flexible aircraft. The aeroelastic effect contributes to aerodynamic damping forces that can influence aerodynamic stability. For wing-mounted engines, wing flexibility can cause the propulsive forces and moments to couple with the wing elastic motion. The integrated flight dynamics for a flexible aircraft are formulated by including generalized coordinate variables associated with the aeroelastic-propulsive forces and moments in the standard state-space form for six degree-of-freedom flight dynamics. A computational structural model for a generic transport aircraft has been created. The eigenvalue analysis is performed to compute aeroelastic frequencies and aerodynamic damping. The results will be used to construct an integrated flight dynamic model of a flexible generic transport aircraft.

Quantification of in-contact probe-sample electrostatic forces with dynamic atomic force microscopy.

PubMed

Balke, Nina; Jesse, Stephen; Carmichael, Ben; Okatan, M Baris; Kravchenko, Ivan I; Kalinin, Sergei V; Tselev, Alexander

2017-01-04

Atomic force microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. In combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V nm -1 at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.

Sequential reconstruction of driving-forces from nonlinear nonstationary dynamics

NASA Astrophysics Data System (ADS)

Güntürkün, Ulaş

2010-07-01

This paper describes a functional analysis-based method for the estimation of driving-forces from nonlinear dynamic systems. The driving-forces account for the perturbation inputs induced by the external environment or the secular variations in the internal variables of the system. The proposed algorithm is applicable to the problems for which there is too little or no prior knowledge to build a rigorous mathematical model of the unknown dynamics. We derive the estimator conditioned on the differentiability of the unknown system’s mapping, and smoothness of the driving-force. The proposed algorithm is an adaptive sequential realization of the blind prediction error method, where the basic idea is to predict the observables, and retrieve the driving-force from the prediction error. Our realization of this idea is embodied by predicting the observables one-step into the future using a bank of echo state networks (ESN) in an online fashion, and then extracting the raw estimates from the prediction error and smoothing these estimates in two adaptive filtering stages. The adaptive nature of the algorithm enables to retrieve both slowly and rapidly varying driving-forces accurately, which are illustrated by simulations. Logistic and Moran-Ricker maps are studied in controlled experiments, exemplifying chaotic state and stochastic measurement models. The algorithm is also applied to the estimation of a driving-force from another nonlinear dynamic system that is stochastic in both state and measurement equations. The results are judged by the posterior Cramer-Rao lower bounds. The method is finally put into test on a real-world application; extracting sun’s magnetic flux from the sunspot time series.

Gauge Bosons--The Ties That Bind.

ERIC Educational Resources Information Center

Hill, Christopher T.

1982-01-01

Discusses four basic forces/interactions in nature (strong force, weak force, electromagnetic force and gravity), associated with elementary particles. Focuses on "gauge bosons" (for example, photons), thought to account for strong, weak, and electromagnetic forces. (Author/JN)

Optimization of aerodynamic form of projectile for solving the problem of shooting range increasing

NASA Astrophysics Data System (ADS)

Lipanov, Alexey M.; Korolev, Stanislav A.; Rusyak, Ivan G.

2017-10-01

The article is devoted to the development of methods for solving the problem of external ballistics using a more complete system of motion equation taken into account the rotation and oscillation about the mass center and using aerodynamic coefficients of forces and moments which are calculated on the basis of modeling the hydrodynamics of flow around the projectile. Developed methods allows to study the basic ways of increasing the shooting range or artillery.

A structure adapted multipole method for electrostatic interactions in protein dynamics

NASA Astrophysics Data System (ADS)

Niedermeier, Christoph; Tavan, Paul

1994-07-01

We present an algorithm for rapid approximate evaluation of electrostatic interactions in molecular dynamics simulations of proteins. Traditional algorithms require computational work of the order O(N2) for a system of N particles. Truncation methods which try to avoid that effort entail untolerably large errors in forces, energies and other observables. Hierarchical multipole expansion algorithms, which can account for the electrostatics to numerical accuracy, scale with O(N log N) or even with O(N) if they become augmented by a sophisticated scheme for summing up forces. To further reduce the computational effort we propose an algorithm that also uses a hierarchical multipole scheme but considers only the first two multipole moments (i.e., charges and dipoles). Our strategy is based on the consideration that numerical accuracy may not be necessary to reproduce protein dynamics with sufficient correctness. As opposed to previous methods, our scheme for hierarchical decomposition is adjusted to structural and dynamical features of the particular protein considered rather than chosen rigidly as a cubic grid. As compared to truncation methods we manage to reduce errors in the computation of electrostatic forces by a factor of 10 with only marginal additional effort.

A two-step FEM-SEM approach for wave propagation analysis in cable structures

NASA Astrophysics Data System (ADS)

Zhang, Songhan; Shen, Ruili; Wang, Tao; De Roeck, Guido; Lombaert, Geert

2018-02-01

Vibration-based methods are among the most widely studied in structural health monitoring (SHM). It is well known, however, that the low-order modes, characterizing the global dynamic behaviour of structures, are relatively insensitive to local damage. Such local damage may be easier to detect by methods based on wave propagation which involve local high frequency behaviour. The present work considers the numerical analysis of wave propagation in cables. A two-step approach is proposed which allows taking into account the cable sag and the distribution of the axial forces in the wave propagation analysis. In the first step, the static deformation and internal forces are obtained by the finite element method (FEM), taking into account geometric nonlinear effects. In the second step, the results from the static analysis are used to define the initial state of the dynamic analysis which is performed by means of the spectral element method (SEM). The use of the SEM in the second step of the analysis allows for a significant reduction in computational costs as compared to a FE analysis. This methodology is first verified by means of a full FE analysis for a single stretched cable. Next, simulations are made to study the effects of damage in a single stretched cable and a cable-supported truss. The results of the simulations show how damage significantly affects the high frequency response, confirming the potential of wave propagation based methods for SHM.

Approximate analytic method for high-apogee twelve-hour orbits of artificial Earth's satellites

NASA Astrophysics Data System (ADS)

Vashkovyaka, M. A.; Zaslavskii, G. S.

2016-09-01

We propose an approach to the study of the evolution of high-apogee twelve-hour orbits of artificial Earth's satellites. We describe parameters of the motion model used for the artificial Earth's satellite such that the principal gravitational perturbations of the Moon and Sun, nonsphericity of the Earth, and perturbations from the light pressure force are approximately taken into account. To solve the system of averaged equations describing the evolution of the orbit parameters of an artificial satellite, we use both numeric and analytic methods. To select initial parameters of the twelve-hour orbit, we assume that the path of the satellite along the surface of the Earth is stable. Results obtained by the analytic method and by the numerical integration of the evolving system are compared. For intervals of several years, we obtain estimates of oscillation periods and amplitudes for orbital elements. To verify the results and estimate the precision of the method, we use the numerical integration of rigorous (not averaged) equations of motion of the artificial satellite: they take into account forces acting on the satellite substantially more completely and precisely. The described method can be applied not only to the investigation of orbit evolutions of artificial satellites of the Earth; it can be applied to the investigation of the orbit evolution for other planets of the Solar system provided that the corresponding research problem will arise in the future and the considered special class of resonance orbits of satellites will be used for that purpose.

Effects of Internal Waves on Sound Propagation in the Shallow Waters of the Continental Shelves

DTIC Science & Technology

2016-09-01

experiment area were largely generated by tidal forcing. Compared to simulations without internal waves , simulations accounting for the effects of...internal waves in the experiment area were largely generated by tidal forcing. Compared to simulations without internal waves , simulations accounting for...IN THE SHALLOW WATERS OF THE CONTINENTAL SHELVES ..................................4  1.  Internal Tides—Internal Waves Generated by Tidal Forcing

Mechanical behavior simulation of MEMS-based cantilever beam using COMSOL multiphysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Acheli, A., E-mail: aacheli@cdta.dz; Serhane, R.

This paper presents the studies of mechanical behavior of MEMS cantilever beam made of poly-silicon material, using the coupling of three application modes (plane strain, electrostatics and the moving mesh) of COMSOL Multi-physics software. The cantilevers playing a key role in Micro Electro-Mechanical Systems (MEMS) devices (switches, resonators, etc) working under potential shock. This is why they require actuation under predetermined conditions, such as electrostatic force or inertial force. In this paper, we present mechanical behavior of a cantilever actuated by an electrostatic force. In addition to the simplification of calculations, the weight of the cantilever was not taken intomore » account. Different parameters like beam displacement, electrostatics force and stress over the beam have been calculated by finite element method after having defining the geometry, the material of the cantilever model (fixed at one of ends but is free to move otherwise) and his operational space.« less

Modeling of crack bridging in a unidirectional metal matrix composite

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Kantzos, Pete; Telesman, Jack

1991-01-01

The effective fatigue crack driving force and crack opening profiles were determined analytically for fatigue tested unidirectional composite specimens exhibiting fiber bridging. The crack closure pressure due to bridging was modeled using two approaches; the fiber pressure model and the shear lag model. For both closure models, the Bueckner weight function method and the finite element method were used to calculate crack opening displacements and the crack driving force. The predicted near crack tip opening profile agreed well with the experimentally measured profiles for single edge notch SCS-6/Ti-15-3 metal matrix composite specimens. The numerically determined effective crack driving force, Delta K(sup eff), was calculated using both models to correlate the measure crack growth rate in the composite. The calculated Delta K(sup eff) from both models accounted for the crack bridging by showing a good agreement between the measured fatigue crack growth rates of the bridged composite and that of unreinforced, unbridged titanium matrix alloy specimens.

Modeling of crack bridging in a unidirectional metal matrix composite

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Kantzos, Pete; Telesman, Jack

1992-01-01

The effective fatigue crack driving force and crack opening profiles were determined analytically for fatigue tested unidirectional composite specimens exhibiting fiber bridging. The crack closure pressure due to bridging was modeled using two approaches: the fiber pressure model and the shear lag model. For both closure models, the Bueckner weight function method and the finite element method were used to calculate crack opening displacements and the crack driving force. The predicted near crack tip opening profile agreed well with the experimentally measured profiles for single edge notch SCS-6/Ti-15-3 metal matrix composite specimens. The numerically determined effective crack driving force, Delta K(eff), was calculated using both models to correlate the measure crack growth rate in the composite. The calculated Delta K(eff) from both models accounted for the crack bridging by showing a good agreement between the measured fatigue crack growth rates of the bridged composite and that of unreinforced, unbridged titanium matrix alloy specimens.

A theoretical method for the analysis and design of axisymmetric bodies. [flow distribution and incompressible fluids

NASA Technical Reports Server (NTRS)

Beatty, T. D.

1975-01-01

A theoretical method is presented for the computation of the flow field about an axisymmetric body operating in a viscous, incompressible fluid. A potential flow method was used to determine the inviscid flow field and to yield the boundary conditions for the boundary layer solutions. Boundary layer effects in the forces of displacement thickness and empirically modeled separation streamlines are accounted for in subsequent potential flow solutions. This procedure is repeated until the solutions converge. An empirical method was used to determine base drag allowing configuration drag to be computed.

23 CFR 645.115 - Construction.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 23 Highways 1 2014-04-01 2014-04-01 false Construction. 645.115 Section 645.115 Highways FEDERAL... Relocations, Adjustments, and Reimbursement § 645.115 Construction. (a) Part 635, subpart B, of this title, Force Account Construction (justification required for force account work), states that it is cost...

23 CFR 645.115 - Construction.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 23 Highways 1 2012-04-01 2012-04-01 false Construction. 645.115 Section 645.115 Highways FEDERAL... Relocations, Adjustments, and Reimbursement § 645.115 Construction. (a) Part 635, subpart B, of this title, Force Account Construction (justification required for force account work), states that it is cost...

23 CFR 645.115 - Construction.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 23 Highways 1 2013-04-01 2013-04-01 false Construction. 645.115 Section 645.115 Highways FEDERAL... Relocations, Adjustments, and Reimbursement § 645.115 Construction. (a) Part 635, subpart B, of this title, Force Account Construction (justification required for force account work), states that it is cost...

23 CFR 645.115 - Construction.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 23 Highways 1 2010-04-01 2010-04-01 false Construction. 645.115 Section 645.115 Highways FEDERAL... Relocations, Adjustments, and Reimbursement § 645.115 Construction. (a) Part 635, subpart B, of this title, Force Account Construction (justification required for force account work), states that it is cost...

23 CFR 645.115 - Construction.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 23 Highways 1 2011-04-01 2011-04-01 false Construction. 645.115 Section 645.115 Highways FEDERAL... Relocations, Adjustments, and Reimbursement § 645.115 Construction. (a) Part 635, subpart B, of this title, Force Account Construction (justification required for force account work), states that it is cost...

CFD-DEM Onset of Motion Analysis for Application to Bed Scour Risk Assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sitek, M. A.; Lottes, S. A.

This CFD study with DEM was done as a part of the Federal Highway Administration’s (FHWA’s) effort to improve scour design procedures. The Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model, available in CD-Adapco’s StarCCM+ software, was used to simulate multiphase systems, mainly those which combine fluids and solids. In this method the motion of discrete solids is accounted for by DEM, which applies Newton's laws of motion to every particle. The flow of the fluid is determined by the local averaged Navier–Stokes equations that can be solved using the traditional CFD approach. The interactions between the fluid phase and solidsmore » phase are modeled by use of Newton's third law. The inter-particle contact forces are included in the equations of motion. Soft-particle formulation is used, which allows particles to overlap. In this study DEM was used to model separate sediment grains and spherical particles laying on the bed with the aim to analyze their movement due to flow conditions. Critical shear stress causing the incipient movement of the sediment was established and compared to the available experimental data. An example of scour around a cylindrical pier is considered. Various depths of the scoured bed and flow conditions were taken into account to gain a better understanding of the erosion forces existing around bridge foundations. The decay of these forces with increasing scour depth was quantified with a ‘decay function’, which shows that particles become increasingly less likely to be set in motion by flow forces as a scour hole increases in depth. Computational and experimental examples of the scoured bed around a cylindrical pier are presented.« less

Sarma-based key-group method for rock slope reliability analyses

NASA Astrophysics Data System (ADS)

Yarahmadi Bafghi, A. R.; Verdel, T.

2005-08-01

The methods used in conducting static stability analyses have remained pertinent to this day for reasons of both simplicity and speed of execution. The most well-known of these methods for purposes of stability analysis of fractured rock masses is the key-block method (KBM).This paper proposes an extension to the KBM, called the key-group method (KGM), which combines not only individual key-blocks but also groups of collapsable blocks into an iterative and progressive analysis of the stability of discontinuous rock slopes. To take intra-group forces into account, the Sarma method has been implemented within the KGM in order to generate a Sarma-based KGM, abbreviated SKGM. We will discuss herein the hypothesis behind this new method, details regarding its implementation, and validation through comparison with results obtained from the distinct element method.Furthermore, as an alternative to deterministic methods, reliability analyses or probabilistic analyses have been proposed to take account of the uncertainty in analytical parameters and models. The FOSM and ASM probabilistic methods could be implemented within the KGM and SKGM framework in order to take account of the uncertainty due to physical and mechanical data (density, cohesion and angle of friction). We will then show how such reliability analyses can be introduced into SKGM to give rise to the probabilistic SKGM (PSKGM) and how it can be used for rock slope reliability analyses. Copyright

The drugs industry and peasant self-defence in a Peruvian cocaine enclave.

PubMed

van Dun, Mirella

2012-11-01

This article gives a detailed account of the cocaine industry and the related violence in the Peruvian Upper Huallaga. It is argued that in this cocaine producing region violence increased during state-led forced eradication operations of the coca plants. Most of the violent incidents were closely related to the diminishing cocaine industry, but they were also related to the actions of the state security forces. Instead of receiving support from the state's security apparatus, the population mobilized its own forces to fight the violence. As will be argued, the causes of violence in this cocaine enclave are part of a dynamic interaction amongst many factors - an interaction that is influenced by the local context, a partial state vacuum, and the social utility and the economic advantages of violence. One needs to be aware that motivations of those who engage in the violent behaviour can change over time, as underlying power structures are influenced by changes in local conditions. The study covers an in-depth account of events taking place in the Upper Huallaga during the years 2003-2007. The research material was collected by several ethnographical fieldwork methods. Copyright © 2012 Elsevier B.V. All rights reserved.

Workpiece Temperature Variations During Flat Peripheral Grinding

NASA Astrophysics Data System (ADS)

Smirnov, Vitalii A.; Repko, Aleksandr V.

2018-06-01

The paper presents the results of researches of temperature variations during flat peripheral grinding. It is shown that the temperature variations of the workpiece can reach 25...30% of the average values, which can lead to some thermal defects. A nonlinear two-dimensional thermophysical grinding model is suggested. It takes into account local changes in the cutting conditions: the fluctuation of the cut layer and the cutting force, the thermal impact of the cutting grains, and the presence of surface cavities in the intermittent wheel. For the numerical solution of the problem, the method of finite differences is adapted. Researches of the method stability and convergence are made, taking into account the specific nature of the problem. A high accuracy of the approximation of the boundary conditions and the nonlinear heat equation is provided. An experimental verification of the proposed thermophysical model was carried out with the use of installation for simultaneous measurement of the grinding force and temperature. It is shown that the discrepancy between the theoretical and experimental values of the grinding temperature does not exceed 5%. The proposed thermophysical model makes it possible to predict with high accuracy the temperature variations during grinding by the wheel periphery.

Prevalence Comparison of Past-year Mental Disorders and Suicidal Behaviours in the Canadian Armed Forces and the Canadian General Population

PubMed Central

Zamorski, Mark A.; Boulos, David; Garber, Bryan G.

2016-01-01

Objective: Military personnel in Canada and elsewhere have been found to have higher rates of certain mental disorders relative to their corresponding general populations. However, published Canadian data have only adjusted for age and sex differences between the populations. Additional differences in the sociodemographic composition, labour force characteristics, and childhood trauma exposure in the populations could be driving these prevalence differences. Our objective is to compare the prevalence of past-year mental disorders and suicidal behaviours in the Canadian Armed Forces Regular Force with the rates in a representative, matched sample of Canadians in the general population (CGP). Methods: Data sources were the 2013 Canadian Forces Mental Health Survey and the 2012 Canadian Community Health Survey–Mental Health. CGP sample was restricted to match the age range, employment status, and history of chronic conditions of Regular Force personnel. An iterative proportional fitting method was used to approximate the marginal distribution of sociodemographic and childhood trauma variables in both samples. Results: Relative to the matched CGP, Regular Force personnel had significantly higher rates of past-year major depressive episode, generalized anxiety disorder, and suicide ideation. However, lower rates of alcohol use disorder were seen in Regular Force personnel relative to the matched CGP sample. Conclusions: Factors other than differences in sociodemographic composition and history of childhood trauma account for the excess burden of mental disorders and suicidal behaviours in the Canadian Armed Forces. Explanations to explore in future research include occupational trauma, selection effects, and differences in the context of administration of the 2 surveys. PMID:27270741

The limited swelling of montmorillonite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helmy, A.K.

1998-11-01

The attraction forces responsible for the occurrence of limited swelling of montmorillonite having divalent counterions were evaluated from (a) the electrostatic attraction between the negative charges of one surface and the effective charges of the counterions of the other interlayer surface and (b) van der Waals attraction between the two interlayer surfaces. Both methods of calculation almost account for the force required to maintain limited swelling of the clay. It is found that a Hamaker constant of 2.25 {times} 10{sup {minus}13} erg in place of 2.72 {times} 10{sup {minus}13} erg and a counterion charge screening factor of 0.82[1 {minus} exp({minus}{kappa}{chi})]more » in place of [1 {minus} exp({minus}{kappa}{chi})] reproduce the true value of the attraction force.« less

Force transients and minimum cross-bridge models in muscular contraction

PubMed Central

Halvorson, Herbert R.

2010-01-01

Two- and three-state cross-bridge models are considered and examined with respect to their ability to predict three distinct phases of the force transients that occur in response to step change in muscle fiber length. Particular attention is paid to satisfying the Le Châtelier–Brown Principle. This analysis shows that the two-state model can account for phases 1 and 2 of a force transient, but is barely adequate to account for phase 3 (delayed force) unless a stretch results in a sudden increase in the number of cross-bridges in the detached state. The three-state model (A → B → C → A) makes it possible to account for all three phases if we assume that the A → B transition is fast (corresponding to phase 2), the B → C transition is of intermediate speed (corresponding to phase 3), and the C → A transition is slow; in such a scenario, states A and C can support or generate force (high force states) but state B cannot (detached, or low-force state). This model involves at least one ratchet mechanism. In this model, force can be generated by either of two transitions: B → A or B → C. To determine which of these is the major force-generating step that consumes ATP and transduces energy, we examine the effects of ATP, ADP, and phosphate (Pi) on force transients. In doing so, we demonstrate that the fast transition (phase 2) is associated with the nucleotide-binding step, and that the intermediate-speed transition (phase 3) is associated with the Pi-release step. To account for all the effects of ligands, it is necessary to expand the three-state model into a six-state model that includes three ligand-bound states. The slowest phase of a force transient (phase 4) cannot be explained by any of the models described unless an additional mechanism is introduced. Here we suggest a role of series compliance to account for this phase, and propose a model that correlates the slowest step of the cross-bridge cycle (transition C → A) to: phase 4 of step analysis, the rate constant ktr of the quick-release and restretch experiment, and the rate constant kact for force development time course following Ca2+ activation. PMID:18425593

Force transients and minimum cross-bridge models in muscular contraction.

PubMed

Kawai, Masataka; Halvorson, Herbert R

2007-01-01

Two- and three-state cross-bridge models are considered and examined with respect to their ability to predict three distinct phases of the force transients that occur in response to step change in muscle fiber length. Particular attention is paid to satisfying the Le Châtelier-Brown Principle. This analysis shows that the two-state model can account for phases 1 and 2 of a force transient, but is barely adequate to account for phase 3 (delayed force) unless a stretch results in a sudden increase in the number of cross-bridges in the detached state. The three-state model (A-->B-->C-->A) makes it possible to account for all three phases if we assume that the A-->B transition is fast (corresponding to phase 2), the B-->A transition is of intermediate speed (corresponding to phase 3), and the C-->A transition is slow; in such a scenario, states A and C can support or generate force (high force states) but state B cannot (detached, or low-force state). This model involves at least one ratchet mechanism. In this model, force can be generated by either of two transitions: B-->A or B-->C. To determine which of these is the major force-generating step that consumes ATP and transduces energy, we examine the effects of ATP, ADP, and phosphate (Pi) on force transients. In doing so, we demonstrate that the fast transition (phase 2) is associated with the nucleotide-binding step, and that the intermediate-speed transition (phase 3) is associated with the Pi-release step. To account for all the effects of ligands, it is necessary to expand the three-state model into a six-state model that includes three ligand-bound states. The slowest phase of a force transient (phase 4) cannot be explained by any of the models described unless an additional mechanism is introduced. Here we suggest a role of series compliance to account for this phase, and propose a model that correlates the slowest step of the cross-bridge cycle (transition C-->A) to: phase 4 of step analysis, the rate constant k(tr) of the quick-release and restretch experiment, and the rate constant k(act) for force development time course following Ca(2+) activation.

Metrics that differentiate the origins of osmolyte effects on protein stability: a test of the surface tension proposal.

PubMed

Auton, Matthew; Ferreon, Allan Chris M; Bolen, D Wayne

2006-09-01

Osmolytes that are naturally selected to protect organisms against environmental stresses are known to confer stability to proteins via preferential exclusion from protein surfaces. Solvophobicity, surface tension, excluded volume, water structure changes and electrostatic repulsion are all examples of forces proposed to account for preferential exclusion and the ramifications exclusion has on protein properties. What has been lacking is a systematic way of determining which force(s) is(are) responsible for osmolyte effects. Here, we propose the use of two experimental metrics for assessing the abilities of various proposed forces to account for osmolyte-mediated effects on protein properties. Metric 1 requires prediction of the experimentally determined ability of the osmolyte to bring about folding/unfolding resulting from the application of the force in question (i.e. prediction of the m-value of the protein in osmolyte). Metric 2 requires prediction of the experimentally determined ability of the osmolyte to contract or expand the Stokes radius of the denatured state resulting from the application of the force. These metrics are applied to test separate claims that solvophobicity/solvophilicity and surface tension are driving forces for osmolyte-induced effects on protein stability. The results show clearly that solvophobic/solvophilic forces readily account for protein stability and denatured state dimensional effects, while surface tension alone fails to do so. The agreement between experimental and predicted m-values involves both positive and negative m-values for three different proteins, and as many as six different osmolytes, illustrating that the tests are robust and discriminating. The ability of the two metrics to distinguish which forces account for the effects of osmolytes on protein properties and which do not, provides a powerful means of investigating the origins of osmolyte-protein effects.

Dynamic analysis of a hollow cylinder subject to a dual traveling force imposed on its inner surface

NASA Astrophysics Data System (ADS)

Lee, Sooyoung; Seok, Jongwon

2015-03-01

The dynamic behavior of a hollow cylinder under a dual traveling force applied to the inner surface is investigated in this study. The cylinder is constrained at both the top and bottom surfaces not to move in the length direction but free in other directions. And a dual force travels at a constant velocity along the length direction on the inner surface of the hollow cylinder. The resulting governing field equations and the associated boundary conditions are ruled by the general Hooke's law. Due to the nature of the field equations, proper adjoint system of equations and biorthogonality conditions were derived in a precise and detailed manner. To solve these field equations in this study, the method of separation of variable is used and the method of Fro¨benius is employed for the differential equations in the radial direction. Using the field equations, the eigenanalyses on both the original and its adjoint system were performed with great care, which results in the eigenfunction sets of both systems. The biorthogonality conditions were applied to the field equations to obtain the discretized equation for each mode. Using the solutions of the discretized equations that account for the boundary forcing terms, the critical speed for a dual traveling force for each mode could be computed.

Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balke, Nina; Jesse, Stephen; Yu, Pu

Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ~1–3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip–sample contact stiffness. The approachmore » has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. Furthermore, this analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.« less

Racial Targeting of Sexual Violence in Darfur

PubMed Central

Rymond-Richmond, Wenona; Palloni, Alberto

2009-01-01

Objectives. We used the Atrocities Documentation Survey to determine whether Sudanese government forces were involved in racially targeting sexual victimization toward ethnically African women in the Darfur region of western Sudan. Methods. The US State Department conducted the survey by interviewing a randomized multistage probability sample of 1136 Darfur refugees at 20 sites in Chad in 2004. For a subset of 932 respondents who had fled from village clusters that accounted for 15 or more respondents per cluster, we used hierarchical linear models to analyze village-level patterns of reported sexual violence. We statistically controlled for individual sexual victimization to remove bias. Results. Respondents reported being subjected to racial epithets associated with sexual victimization significantly more often during combined attacks by Sudanese government forces and Janjaweed militia forces than during separate attacks by either force. Conclusions. Combined attacks by Sudanese government forces and Janjaweed militia forces led to racial epithets being used more often during sexual victimization in Darfur. Our results suggest that the Sudanese government is participating in the use of sexual assault as a racially targeted weapon against ethnically African civilians. PMID:19542043

Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopy

DOE PAGES

Balke, Nina; Jesse, Stephen; Yu, Pu; ...

2016-09-15

Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ~1–3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip–sample contact stiffness. The approachmore » has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. Furthermore, this analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.« less

Excellence and Accountability. Report of the Governor's Task Force on Higher Education Reform.

ERIC Educational Resources Information Center

New Mexico State Commission on Postsecondary Education, Santa Fe.

A task force report recommends ways to promote educational reform in higher education in New Mexico. Forty recommendations address the following areas: institutional missions, academic excellence and accountability, community colleges, student financial aid, affirmative action, economic development, capital outlay, and funding issues. Specific…

36 CFR 64.11 - Project performance.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Project performance. 64.11... Project performance. The State or local applicant shall be responsible for insuring the project is carried... Force Account. Labor costs charged to a project for force account work will be based on payrolls...

36 CFR 64.11 - Project performance.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 36 Parks, Forests, and Public Property 1 2014-07-01 2014-07-01 false Project performance. 64.11... Project performance. The State or local applicant shall be responsible for insuring the project is carried... Force Account. Labor costs charged to a project for force account work will be based on payrolls...

36 CFR 64.11 - Project performance.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 36 Parks, Forests, and Public Property 1 2012-07-01 2012-07-01 false Project performance. 64.11... Project performance. The State or local applicant shall be responsible for insuring the project is carried... Force Account. Labor costs charged to a project for force account work will be based on payrolls...

Quantification of in-contact probe-sample electrostatic forces with dynamic atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balke, Nina Wisinger; Jesse, Stephen; Carmichael, Ben D.

Here, atomic force microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. Inmore » combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V nm –1 at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.« less

Quantification of In-Contact Probe-Sample Electrostatic Forces with Dynamic Atomic Force Microscopy.

PubMed

Balke, Nina; Jesse, Stephen; Carmichael, Ben; Okatan, M; Kravchenko, Ivan; Kalinin, Sergei; Tselev, Alexander

2016-12-13

Atomic Force Microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. In combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V/nm at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids. Copyright 2016 IOP Publishing Ltd.

Quantification of in-contact probe-sample electrostatic forces with dynamic atomic force microscopy

DOE PAGES

Balke, Nina Wisinger; Jesse, Stephen; Carmichael, Ben D.; ...

2017-01-04

Here, atomic force microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. Inmore » combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V nm –1 at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.« less

Variability of the contrail radiative forcing due to crystal shape

NASA Astrophysics Data System (ADS)

Markowicz, K. M.; Witek, M. L.

2011-12-01

The aim of this study is to examine the influence of particles' shape and particles' optical properties on the contrail radiative forcing. Contrail optical properties in the shortwave and longwave range are derived using a ray-tracing geometric method and the discrete dipole approximation method, respectively. Both methods present good correspondence of the single scattering albedo and the asymmetry parameter in a transition range (3-7μm). We compare optical properties defined following simple 10 crystals habits randomly oriented: hexagonal plates, hexagonal columns with different aspect ratio, and spherical. There are substantial differences in single scattering properties between ten crystal models investigated here (e.g. hexagonal columns and plates with different aspect ratios, spherical particles). The single scattering albedo and the asymmetry parameter both vary up to 0.1 between various crystal shapes. Radiative forcing calculations were performed using a model which includes an interface between the state-of-the-art radiative transfer model Fu-Liou and databases containing optical properties of the atmosphere and surface reflectance and emissivity. This interface allows to determine radiative fluxes in the atmosphere and to estimate the contrail radiative forcing for clear- and all-sky (including natural clouds) conditions for various crystal shapes. The Fu-Liou code is fast and therefore it is suitable for computing radiative forcing on a global scale. At the same time it has sufficiently good accuracy for such global applications. A noticeable weakness of the Fu-Liou code is that it does not take into account the 3D radiative effects, e.g. cloud shading and horizontal. Radiative transfer model calculations were performed at horizontal resolution of 5x5 degree and time resolution of 20 min during day and 3 h during night. In order to calculate a geographic distribution of the global and annual mean contrail radiative forcing, the contrail cover must be determined. Two cases are discussed here: a 1% homogeneous contrail cover and the contrail cover provided by Rädel and Shine (2008). In the second distribution case, a more realistic contrail cover is taken into account. This model combines the AERO2K flight inventory with meteorological data and normalizes it with respect to the contrail cover derived from satellite observations. Simulations performed by the Fu-Liou model show significant variability of the shortwave, longwave, and net radiative forcing with crystal shape. The nonspherical crystals have smaller net forcing in contrary to spherical particles. The differences in net radiative forcing between optical models reach up to 50%. The hexagonal column and hexagonal plate particles show the smallest net radiative forcing while the largest forcing is obtained for the spheres. The global and annual mean shortwave, longwave, and net contrail radiative forcing, average over all crystal models and assuming an optical depth of 0.3 at visible wavelengths, is -5.7, 16.8, and 11.1 mW/m2, respectively. A ratio of the radiative forcings' standard deviation to the mean value, derived using 10 different ice particle models, is about 0.2 for the shortwave, 0.14 for the longwave, and 0.23 for the net radiation.

A Method to Capture Macroslip at Bolted Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopkins, Ronald Neil; Heitman, Lili Anne Akin

2015-10-01

Relative motion at bolted connections can occur for large shock loads as the internal shear force in the bolted connection overcomes the frictional resistive force. This macroslip in a structure dissipates energy and reduces the response of the components above the bolted connection. There is a need to be able to capture macroslip behavior in a structural dynamics model. A linear model and many nonlinear models are not able to predict marcoslip effectively. The proposed method to capture macroslip is to use the multi-body dynamics code ADAMS to model joints with 3-D contact at the bolted interfaces. This model includesmore » both static and dynamic friction. The joints are preloaded and the pinning effect when a bolt shank impacts a through hole inside diameter is captured. Substructure representations of the components are included to account for component flexibility and dynamics. This method was applied to a simplified model of an aerospace structure and validation experiments were performed to test the adequacy of the method.« less

A Method to Capture Macroslip at Bolted Interfaces [PowerPoint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopkins, Ronald Neil; Heitman, Lili Anne Akin

2016-01-01

Relative motion at bolted connections can occur for large shock loads as the internal shear force in the bolted connection overcomes the frictional resistive force. This macroslip in a structure dissipates energy and reduces the response of the components above the bolted connection. There is a need to be able to capture macroslip behavior in a structural dynamics model. A linear model and many nonlinear models are not able to predict marcoslip effectively. The proposed method to capture macroslip is to use the multi-body dynamics code ADAMS to model joints with 3-D contact at the bolted interfaces. This model includesmore » both static and dynamic friction. The joints are preloaded and the pinning effect when a bolt shank impacts a through hole inside diameter is captured. Substructure representations of the components are included to account for component flexibility and dynamics. This method was applied to a simplified model of an aerospace structure and validation experiments were performed to test the adequacy of the method.« less

Medicare changes create accounting, reporting, and auditing problems. Task Force on Federal Health Care Legislation, American Institute of Certified Public Accountants.

PubMed

1984-11-01

Hospital auditors and financial officers must adjust and react to the changing financial healthcare environment brought about by PPS. A close review of accounting systems, reporting methods, auditing procedures, and internal control systems should be made to determine that assets are safe-guarded and financial information is presented in conformity with GAAP. This article identified new problems and suggested solutions. Old tasks may no longer be necessary. For example, retroactive adjustments are not as important as they used to be. Estimates for capital and outpatient costs may continue to be required, but elaborate cost-finding techniques may no longer be necessary to estimate retroactive adjustments for reimbursable items. We recommend that prior to beginning an audit of a hospital's financial statements, each hospital's financial officers and its auditors discuss the possible accounting, reporting, and auditing implications as a result of PPS.

Elucidating the DEP phenomena using a volumetric polarization approach with consideration of the electric double layer

PubMed Central

Brcka, Jozef; Faguet, Jacques; Zhang, Guigen

2017-01-01

Dielectrophoretic (DEP) phenomena have been explored to great success for various applications like particle sorting and separation. To elucidate the underlying mechanism and quantify the DEP force experienced by particles, the point-dipole and Maxwell Stress Tensor (MST) methods are commonly used. However, both methods exhibit their own limitations. For example, the point-dipole method is unable to fully capture the essence of particle-particle interactions and the MST method is not suitable for particles of non-homogeneous property. Moreover, both methods fare poorly when it comes to explaining DEP phenomena such as the dependence of crossover frequency on medium conductivity. To address these limitations, the authors have developed a new method, termed volumetric-integration method, with the aid of computational implementation, to reexamine the DEP phenomena, elucidate the governing mechanism, and quantify the DEP force. The effect of an electric double layer (EDL) on particles' crossover behavior is dealt with through consideration of the EDL structure along with surface ionic/molecular adsorption, unlike in other methods, where the EDL is accounted for through simply assigning a surface conductance value to the particles. For validation, by comparing with literature experimental data, the authors show that the new method can quantify the DEP force on not only homogeneous particles but also non-homogeneous ones, and predict particle-particle interactions fairly accurately. Moreover, the authors also show that the predicted dependence of crossover frequency on medium conductivity and particle size agrees very well with experimental measurements. PMID:28396710

Bias correction of surface downwelling longwave and shortwave radiation for the EWEMBI dataset

NASA Astrophysics Data System (ADS)

Lange, Stefan

2018-05-01

Many meteorological forcing datasets include bias-corrected surface downwelling longwave and shortwave radiation (rlds and rsds). Methods used for such bias corrections range from multi-year monthly mean value scaling to quantile mapping at the daily timescale. An additional downscaling is necessary if the data to be corrected have a higher spatial resolution than the observational data used to determine the biases. This was the case when EartH2Observe (E2OBS; Calton et al., 2016) rlds and rsds were bias-corrected using more coarsely resolved Surface Radiation Budget (SRB; Stackhouse Jr. et al., 2011) data for the production of the meteorological forcing dataset EWEMBI (Lange, 2016). This article systematically compares various parametric quantile mapping methods designed specifically for this purpose, including those used for the production of EWEMBI rlds and rsds. The methods vary in the timescale at which they operate, in their way of accounting for physical upper radiation limits, and in their approach to bridging the spatial resolution gap between E2OBS and SRB. It is shown how temporal and spatial variability deflation related to bilinear interpolation and other deterministic downscaling approaches can be overcome by downscaling the target statistics of quantile mapping from the SRB to the E2OBS grid such that the sub-SRB-grid-scale spatial variability present in the original E2OBS data is retained. Cross validations at the daily and monthly timescales reveal that it is worthwhile to take empirical estimates of physical upper limits into account when adjusting either radiation component and that, overall, bias correction at the daily timescale is more effective than bias correction at the monthly timescale if sampling errors are taken into account.

Flow phenomena on plates and airfoils of short span

NASA Technical Reports Server (NTRS)

Winter, H

1936-01-01

Investigations on the flow phenomena at plates and cambered models were carried out with the aid of force measurements, some pressure distribution measurements, and photographic observation. The experimental methods are described and the results given. Section III of this work gives a comprehensive account of the results and enables us to see how nearly the lift line and lift surface theories agree with the experimental results.

Indiana's New and (Somewhat) Improved K-12 School Finance System. School Choice Issues in the State

ERIC Educational Resources Information Center

Aud, Susan L.

2005-01-01

Education finance policy has become an urgent concern in many state legislatures. Demands for greater equity and accountability have forced states to review, and in many cases to revise, the method by which schools are funded. This study sheds light on Indiana's financing of public K-12 education by providing a clear explanation of the components…

Algebraic diagrammatic construction formalism with three-body interactions

NASA Astrophysics Data System (ADS)

Raimondi, Francesco; Barbieri, Carlo

2018-05-01

Background: Self-consistent Green's function theory has recently been extended to the basic formalism needed to account for three-body interactions [Carbone, Cipollone, Barbieri, Rios, and Polls, Phys. Rev. C 88, 054326 (2013), 10.1103/PhysRevC.88.054326]. The contribution of three-nucleon forces has so far been included in ab initio calculations on nuclear matter and finite nuclei only as averaged two-nucleon forces. Purpose: We derive the working equations for all possible two- and three-nucleon terms that enter the expansion of the self-energy up to the third order, thus including the interaction-irreducible (i.e., not averaged) diagrams with three-nucleon forces that have been previously neglected. Methods: We employ the algebraic diagrammatic construction up to the third order as an organization scheme for generating a nonperturbative self-energy, in which ring (particle-hole) and ladder (particle-particle) diagrams are resummed to all orders. Results: We derive expressions of the static and dynamic self-energy up to the third order, by taking into account the set of diagrams required when either the skeleton or nonskeleton expansions of the single-particle propagator are assumed. A hierarchy of importance among different diagrams is revealed, and a particular emphasis is given to a third-order diagram [see Fig. 2(c)] that is expected to play a significant role among those featuring an interaction-irreducible three-nucleon force. Conclusion: A consistent formalism to resum at infinite order correlations induced by three-nucleon forces in the self-consistent Green's function theory is now available and ready to be implemented in the many-body solvers.

Examining Officer and Citizen Accounts of Police Use-of-Force Incidents

ERIC Educational Resources Information Center

Rojek, Jeff; Alpert, Geoffrey P.; Smith, Hayden P.

2012-01-01

This study contributes to the body of knowledge of police-citizen contacts by investigating perceptions and behaviors during encounters that result in physical resistance and force. The authors use the accounts literature as a way to understand police-citizen interactions. The data include interviews with citizens who resisted or were accused of…

A Contribution to the Problem of Initiation of a Combustion Source in an Oil-Saturated Bed

NASA Astrophysics Data System (ADS)

Koznacheev, I. A.; Dobrego, K. V.

2013-11-01

The problem on in-situ self-ignition of an oil-saturated bed under the conditions of forced filtration of an oxygen-containing gas has been solved with analytical and numerical methods with account of the burnout of a deficient gas component. The influence of the burnout of this component and of convective removal of heat from the bed on the time of its self-ignition has been determined. Recommendations for the optimum regime of initiation of the self-ignition of the bed with account of variation of the blast flow rate and the oxygen content have been given.

Construction and control of a physiological articulatory model

NASA Astrophysics Data System (ADS)

Dang, Jianwu; Honda, Kiyoshi

2004-02-01

A physiological articulatory model has been constructed using a fast computation method, which replicates midsagittal regions of the speech organs to simulate articulatory movements during speech. This study aims to improve the accuracy of modeling by using the displacement-based finite-element method and to develop a new approach for controlling the model. A ``semicontinuum'' tongue tissue model was realized by a discrete truss structure with continuum viscoelastic cylinders. Contractile effects of the muscles were systemically examined based on model simulations. The results indicated that each muscle drives the tongue toward an equilibrium position (EP) corresponding to the magnitude of the activation forces. The EPs shifted monotonically as the activation force increased. The monotonic shift revealed a unique and invariant mapping, referred to as an EP map, between a spatial position of the articulators and the muscle forces. This study proposes a control method for the articulatory model based on the EP maps, in which co-contractions of agonist and antagonist muscles are taken into account. By utilizing the co-contraction, the tongue tip and tongue dorsum can be controlled to reach their targets independently. Model simulation showed that the co-contraction of agonist and antagonist muscles could increase the stability of a system in dynamic control.

Climatic Effects of Black Carbon Aerosols Over the Tibetan Plateau

NASA Astrophysics Data System (ADS)

He, Cenlin

Black carbon (BC), also known as soot, has been identified as the second most important anthropogenic emissions in terms of global climate forcing in the current atmosphere. Ample evidence has shown that BC deposition is an important driver of rapid snow melting and glacier retreat over the Tibetan Plateau, which holds the largest snow/ice mass outside polar regions. However, the climatic effects of BC over the Tibetan Plateau have not been thoroughly investigated in such a manner as to understand, quantify, and reduce large uncertainties in the estimate of radiative and hydrological effects. Thus, this Ph.D. study seeks to understand and improve key processes controlling BC life cycle in global and regional models and to quantify BC radiative effects over the Tibetan Plateau. First, the capability of a state-of-the-art global chemical transport model (CTM), GEOS-Chem, and the associated model uncertainties are systematically evaluated in simulating BC over the Tibetan Plateau, using in situ measurements of BC in surface air, BC in snow, and BC absorption optical depth. The effects of three key factors on the simulation are also delineated, including Asian anthropogenic emissions, BC aging process, and model resolution. Subsequently, a microphysics-based BC aging scheme that accounts for condensation, coagulation, and heterogeneous chemical oxidation processes is developed and examined in GEOS-Chem by comparing with aircraft measurements. Compared to the default aging scheme, the microphysical scheme reduces model-observation discrepancies by a factor of 3, particularly in the middle and upper troposphere. In addition, a theoretical BC aging-optics model is developed to account for three typical evolution stages, namely, freshly emitted aggregates, coated BC by soluble material, and BC particles undergoing further hygroscopic growth. The geometric-optics surface-wave (GOS) approach is employed to compute the BC single-scattering properties at each aging stage, which are subsequently compared with laboratory measurements. Results show large variations in BC optical properties caused by coating morphology and aging stages. Furthermore, a comprehensive intercomparison of the GOS approach, the superposition T-matrix method, and laboratory measurements is performed for optical properties of BC with complex structures during aging. Moreover, a new snow albedo model is developed for widely-observed close-packed snow grains internally mixed with BC. Results indicate that albedo simulations that account for snow close packing match closer to observations. Close packing enhances BC-induced snow albedo reduction and associated surface radiative forcing by up to 15% (20%) for fresh (old) snow, which suggests that BC-snow albedo forcing is underestimated in previous modeling studies without accounting for close packing. Finally, the snow albedo forcing and direct radiative forcing (DRF) of BC in the Tibetan Plateau are estimated using GEOS-Chem in conjunction with a stochastic snow model and a radiative transfer model. This, for the first time, accounts for realistic non-spherical snow grain shape and stochastic multiple inclusions of BC within snow in assessing BC-snow interactions. The annual mean BC snow albedo forcing is 2.9 W m-2 over snow-covered Plateau regions. BC-snow internal mixing increases the albedo forcing by 40-60% compared with external mixing, whereas Koch snowflakes reduce the forcing by 20-40% relative to spherical snow grains. BC DRF at the top of the atmosphere is 2.3 W m-2 with uncertainties of -70% - +85% in the Plateau. The BC forcings are further attributed to emissions from different regions.

Electrostatics of proteins in dielectric solvent continua. II. Hamiltonian reaction field dynamics

NASA Astrophysics Data System (ADS)

Bauer, Sebastian; Tavan, Paul; Mathias, Gerald

2014-03-01

In Paper I of this work [S. Bauer, G. Mathias, and P. Tavan, J. Chem. Phys. 140, 104102 (2014)] we have presented a reaction field (RF) method, which accurately solves the Poisson equation for proteins embedded in dielectric solvent continua at a computational effort comparable to that of polarizable molecular mechanics (MM) force fields. Building upon these results, here we suggest a method for linearly scaling Hamiltonian RF/MM molecular dynamics (MD) simulations, which we call "Hamiltonian dielectric solvent" (HADES). First, we derive analytical expressions for the RF forces acting on the solute atoms. These forces properly account for all those conditions, which have to be self-consistently fulfilled by RF quantities introduced in Paper I. Next we provide details on the implementation, i.e., we show how our RF approach is combined with a fast multipole method and how the self-consistency iterations are accelerated by the use of the so-called direct inversion in the iterative subspace. Finally we demonstrate that the method and its implementation enable Hamiltonian, i.e., energy and momentum conserving HADES-MD, and compare in a sample application on Ac-Ala-NHMe the HADES-MD free energy landscape at 300 K with that obtained in Paper I by scanning of configurations and with one obtained from an explicit solvent simulation.

Charge-Spot Model for Electrostatic Forces in Simulation of Fine Particulates

NASA Technical Reports Server (NTRS)

Walton, Otis R.; Johnson, Scott M.

2010-01-01

The charge-spot technique for modeling the static electric forces acting between charged fine particles entails treating electric charges on individual particles as small sets of discrete point charges, located near their surfaces. This is in contrast to existing models, which assume a single charge per particle. The charge-spot technique more accurately describes the forces, torques, and moments that act on triboelectrically charged particles, especially image-charge forces acting near conducting surfaces. The discrete element method (DEM) simulation uses a truncation range to limit the number of near-neighbor charge spots via a shifted and truncated potential Coulomb interaction. The model can be readily adapted to account for induced dipoles in uncharged particles (and thus dielectrophoretic forces) by allowing two charge spots of opposite signs to be created in response to an external electric field. To account for virtual overlap during contacts, the model can be set to automatically scale down the effective charge in proportion to the amount of virtual overlap of the charge spots. This can be accomplished by mimicking the behavior of two real overlapping spherical charge clouds, or with other approximate forms. The charge-spot method much more closely resembles real non-uniform surface charge distributions that result from tribocharging than simpler approaches, which just assign a single total charge to a particle. With the charge-spot model, a single particle may have a zero net charge, but still have both positive and negative charge spots, which could produce substantial forces on the particle when it is close to other charges, when it is in an external electric field, or when near a conducting surface. Since the charge-spot model can contain any number of charges per particle, can be used with only one or two charge spots per particle for simulating charging from solar wind bombardment, or with several charge spots for simulating triboelectric charging. Adhesive image-charge forces acting on charged particles touching conducting surfaces can be up to 50 times stronger if the charge is located in discrete spots on the particle surface instead of being distributed uniformly over the surface of the particle, as is assumed by most other models. Besides being useful in modeling particulates in space and distant objects, this modeling technique is useful for electrophotography (used in copiers) and in simulating the effects of static charge in the pulmonary delivery of fine dry powders.

Are external knee load and EMG measures accurate indicators of internal knee contact forces during gait?

PubMed

Meyer, Andrew J; D'Lima, Darryl D; Besier, Thor F; Lloyd, David G; Colwell, Clifford W; Fregly, Benjamin J

2013-06-01

Mechanical loading is believed to be a critical factor in the development and treatment of knee osteoarthritis. However, the contact forces to which the knee articular surfaces are subjected during daily activities cannot be measured clinically. Thus, the ability to predict internal knee contact forces accurately using external measures (i.e., external knee loads and muscle electromyographic [EMG] signals) would be clinically valuable. We quantified how well external knee load and EMG measures predict internal knee contact forces during gait. A single subject with a force-measuring tibial prosthesis and post-operative valgus alignment performed four gait patterns (normal, medial thrust, walking pole, and trunk sway) to induce a wide range of external and internal knee joint loads. Linear regression analyses were performed to assess how much of the variability in internal contact forces was accounted for by variability in the external measures. Though the different gait patterns successfully induced significant changes in the external and internal quantities, changes in external measures were generally weak indicators of changes in total, medial, and lateral contact force. Our results suggest that when total contact force may be changing, caution should be exercised when inferring changes in knee contact forces based on observed changes in external knee load and EMG measures. Advances in musculoskeletal modeling methods may be needed for accurate estimation of in vivo knee contact forces. Copyright © 2012 Orthopaedic Research Society.

Numeric calculation of unsteady forces over thin pointed wings in sonic flow

NASA Technical Reports Server (NTRS)

Kimble, K. R.; Wu, J. M.

1975-01-01

A fast and reasonably accurate numerical procedure is proposed for the solution of a simplified unsteady transonic equation. The approach described takes into account many of the effects of the steady flow field. The resulting accuracy is within a few per cent and can be carried out on a computer in less than one minute per case (one frequency and one mode of oscillation). The problem concerns a rigid pointed wing which performs harmonic pitching oscillations of small amplitude in a steady uniform transonic flow. Wake influence is ignored and shocks must be weak. It is shown that the method is more flexible than the transonic box method proposed by Rodemich and Andrew (1965) in that it can easily account for variable local Mach number and rather arbitrary planform so long as the basic assumptions are fulfilled.

Financial Accounting for Local and State School Systems: 2014 Edition. NCES 2015-347

ERIC Educational Resources Information Center

Allison, Gregory S.

2015-01-01

The 2014 edition of "Financial Accounting for Local and State School Systems" updates the 2009 (see ED505993) and 2003 editions of the handbook. The 2003 edition was the work of the NCES National Forum on Education Statistics, Core Finance Data Task Force. That task force systematically rewrote nearly the entire text, incorporating new…

Implementing Nonlinear Buoyancy and Excitation Forces in the WEC-Sim Wave Energy Converter Modeling Tool: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawson, M.; Yu, Y. H.; Nelessen, A.

2014-05-01

Wave energy converters (WECs) are commonly designed and analyzed using numerical models that combine multi-body dynamics with hydrodynamic models based on the Cummins Equation and linearized hydrodynamic coefficients. These modeling methods are attractive design tools because they are computationally inexpensive and do not require the use of high performance computing resources necessitated by high-fidelity methods, such as Navier Stokes computational fluid dynamics. Modeling hydrodynamics using linear coefficients assumes that the device undergoes small motions and that the wetted surface area of the devices is approximately constant. WEC devices, however, are typically designed to undergo large motions in order to maximizemore » power extraction, calling into question the validity of assuming that linear hydrodynamic models accurately capture the relevant fluid-structure interactions. In this paper, we study how calculating buoyancy and Froude-Krylov forces from the instantaneous position of a WEC device (referred to as instantaneous buoyancy and Froude-Krylov forces from herein) changes WEC simulation results compared to simulations that use linear hydrodynamic coefficients. First, we describe the WEC-Sim tool used to perform simulations and how the ability to model instantaneous forces was incorporated into WEC-Sim. We then use a simplified one-body WEC device to validate the model and to demonstrate how accounting for these instantaneously calculated forces affects the accuracy of simulation results, such as device motions, hydrodynamic forces, and power generation.« less

An Empirical Polarizable Force Field Based on the Classical Drude Oscillator Model: Development History and Recent Applications

PubMed Central

2016-01-01

Molecular mechanics force fields that explicitly account for induced polarization represent the next generation of physical models for molecular dynamics simulations. Several methods exist for modeling induced polarization, and here we review the classical Drude oscillator model, in which electronic degrees of freedom are modeled by charged particles attached to the nuclei of their core atoms by harmonic springs. We describe the latest developments in Drude force field parametrization and application, primarily in the last 15 years. Emphasis is placed on the Drude-2013 polarizable force field for proteins, DNA, lipids, and carbohydrates. We discuss its parametrization protocol, development history, and recent simulations of biologically interesting systems, highlighting specific studies in which induced polarization plays a critical role in reproducing experimental observables and understanding physical behavior. As the Drude oscillator model is computationally tractable and available in a wide range of simulation packages, it is anticipated that use of these more complex physical models will lead to new and important discoveries of the physical forces driving a range of chemical and biological phenomena. PMID:26815602

SCISEAL: A CFD Code for Analysis of Fluid Dynamic Forces in Seals

NASA Technical Reports Server (NTRS)

Althavale, Mahesh M.; Ho, Yin-Hsing; Przekwas, Andre J.

1996-01-01

A 3D CFD code, SCISEAL, has been developed and validated. Its capabilities include cylindrical seals, and it is employed on labyrinth seals, rim seals, and disc cavities. State-of-the-art numerical methods include colocated grids, high-order differencing, and turbulence models which account for wall roughness. SCISEAL computes efficient solutions for complicated flow geometries and seal-specific capabilities (rotor loads, torques, etc.).

Motion control of a gantry crane with a container

NASA Astrophysics Data System (ADS)

Shugailo, T. S.; Yushkov, M. P.

2018-05-01

The transportation of a container by a gantry crane in a given time from one point of space to another is considered. The system is at rest at the end of the motion. A maximum admissible speed is taken into account. The control force is found using either the Pontryagin maximum principle or the generalized Gauss principle. The advantages of the second method over the first one is demonstrated.

Pulmonary blood flow redistribution by increased gravitational force

NASA Technical Reports Server (NTRS)

Hlastala, M. P.; Chornuk, M. A.; Self, D. A.; Kallas, H. J.; Burns, J. W.; Bernard, S.; Polissar, N. L.; Glenny, R. W.

1998-01-01

This study was undertaken to assess the influence of gravity on the distribution of pulmonary blood flow (PBF) using increased inertial force as a perturbation. PBF was studied in unanesthetized swine exposed to -Gx (dorsal-to-ventral direction, prone position), where G is the magnitude of the force of gravity at the surface of the Earth, on the Armstrong Laboratory Centrifuge at Brooks Air Force Base. PBF was measured using 15-micron fluorescent microspheres, a method with markedly enhanced spatial resolution. Each animal was exposed randomly to -1, -2, and -3 Gx. Pulmonary vascular pressures, cardiac output, heart rate, arterial blood gases, and PBF distribution were measured at each G level. Heterogeneity of PBF distribution as measured by the coefficient of variation of PBF distribution increased from 0.38 +/- 0.05 to 0.55 +/- 0.11 to 0.72 +/- 0.16 at -1, -2, and -3 Gx, respectively. At -1 Gx, PBF was greatest in the ventral and cranial and lowest in the dorsal and caudal regions of the lung. With increased -Gx, this gradient was augmented in both directions. Extrapolation of these values to 0 G predicts a slight dorsal (nondependent) region dominance of PBF and a coefficient of variation of 0.22 in microgravity. Analysis of variance revealed that a fixed component (vascular structure) accounted for 81% and nonstructure components (including gravity) accounted for the remaining 19% of the PBF variance across the entire experiment (all 3 gravitational levels). The results are inconsistent with the predictions of the zone model.

Incorporating water-release and lateral protein interactions in modeling equilibrium adsorption for ion-exchange chromatography.

PubMed

Thrash, Marvin E; Pinto, Neville G

2006-09-08

The equilibrium adsorption of two albumin proteins on a commercial ion exchanger has been studied using a colloidal model. The model accounts for electrostatic and van der Waals forces between proteins and the ion exchanger surface, the energy of interaction between adsorbed proteins, and the contribution of entropy from water-release accompanying protein adsorption. Protein-surface interactions were calculated using methods previously reported in the literature. Lateral interactions between adsorbed proteins were experimentally measured with microcalorimetry. Water-release was estimated by applying the preferential interaction approach to chromatographic retention data. The adsorption of ovalbumin and bovine serum albumin on an anion exchanger at solution pH>pI of protein was measured. The experimental isotherms have been modeled from the linear region to saturation, and the influence of three modulating alkali chlorides on capacity has been evaluated. The heat of adsorption is endothermic for all cases studied, despite the fact that the net charge on the protein is opposite that of the adsorbing surface. Strong repulsive forces between adsorbed proteins underlie the endothermic heat of adsorption, and these forces intensify with protein loading. It was found that the driving force for adsorption is the entropy increase due to the release of water from the protein and adsorbent surfaces. It is shown that the colloidal model predicts protein adsorption capacity in both the linear and non-linear isotherm regions, and can account for the effects of modulating salt.

Accounting for radiative forcing from albedo change in future global land-use scenarios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, Andrew D.; Calvin, Katherine V.; Collins, William D.

2015-08-01

We demonstrate the effectiveness of a new method for quantifying radiative forcing from land use and land cover change (LULCC) within an integrated assessment model, the Global Change Assessment Model (GCAM). The method relies on geographically differentiated estimates of radiative forcing from albedo change associated with major land cover transitions derived from the Community Earth System Model. We find that conversion of 1 km² of woody vegetation (forest and shrublands) to non-woody vegetation (crops and grassland) yields between 0 and –0.71 nW/m² of globally averaged radiative forcing determined by the vegetation characteristics, snow dynamics, and atmospheric radiation environment characteristic withinmore » each of 151 regions we consider globally. Across a set of scenarios designed to span a range of potential future LULCC, we find LULCC forcing ranging from –0.06 to –0.29 W/m² by 2070 depending on assumptions regarding future crop yield growth and whether climate policy favors afforestation or bioenergy crops. Inclusion of this previously uncounted forcing in the policy targets driving future climate mitigation efforts leads to changes in fossil fuel emissions on the order of 1.5 PgC/yr by 2070 for a climate forcing limit of 4.5 Wm –2, corresponding to a 12–67 % change in fossil fuel emissions depending on the scenario. Scenarios with significant afforestation must compensate for albedo-induced warming through additional emissions reductions, and scenarios with significant deforestation need not mitigate as aggressively due to albedo-induced cooling. In all scenarios considered, inclusion of albedo forcing in policy targets increases forest and shrub cover globally.« less

A Prototype JFACC: General George C. Kenney

DTIC Science & Technology

1994-06-01

Corps, as well as air forces from Australia and New Zealand . Many accounts of the Battles for Leyte and Luzon center around ground and naval forces...St Clair Streett USA Royal New Zealand Air Force (RNZAF) Royal Australian Air Force (RAAF) Air Command Organization SWPA June 15, 1944 Figure 5...Ground Task Force OPCON Operational Command POA Pacific Ocean Areas RAAF Royal Australian Air Force RNZAF Royal New Zealand Air Force SAP

Resistance to densification, tensile strength and capsule-filling performance of some pharmaceutical diluents.

PubMed

Nikolakakis, I; Aragon, O B; Malamataris, S

1998-07-01

The purpose of this study was to compare some indicators of capsule-filling performance, as measured by tapped density under different conditions, and elucidate possible quantitative relationships between variation of capsule fill-weight (%CV) and gravitational and inter-particle forces (attractive or frictional) derived from measurements of particle size, true density, low compression and tensile strength. Five common pharmaceutical diluents (lactose, maize starch, talc, Emcocel and Avicel) were investigated and two capsule-filling methods (pouring powder and dosator nozzle) were employed. It was found that for the pouring-type method the appropriateness of Hausner's ratio (HR), Carr's compressibility index (CC%) and Kawakita's constant (alpha) as indicators of capsule fill-weight variation decreases in the order alpha > CC% > HR; the appropriateness of these indicators also decreases with increasing cylinder size and with impact velocity during tapping. For the dosator-type method the appropriateness of the indicators decreases in the order HR > CC% > alpha, the opposite of that for the pouring-type method; the appropriateness of the indicators increases with decreasing cylinder size and impact velocity. The relationship between %CV and the ratio of inter-particle attractive to gravitational forces calculated from measurements of particle size and true density (Fvdw/Wp) was more significant for the pouring-type capsule-filling method. For the dosator-type method a significant relationship (1% level) was found between %CV and the product of Fvdw/Wp and a function expressing the increase, with packing density (p(f)), in the ratio of frictional to attractive inter-particle forces derived from compression (P) and tensile-strength (T) testing, d(log(P/T))/d(p(f)). The value of tapped density in predictions of capsule-filling performance is affected by the testing conditions in a manner depending on the filling method applied. For the pouring-type method predictions can be based on the ratio of attractive (inter-particle) to gravitational forces, whereas for the dosator-type method the contribution of frictional and attractive forces should, because of packing density change, also be taken into account.

Optimization of Low-Thrust Spiral Trajectories by Collocation

NASA Technical Reports Server (NTRS)

Falck, Robert D.; Dankanich, John W.

2012-01-01

As NASA examines potential missions in the post space shuttle era, there has been a renewed interest in low-thrust electric propulsion for both crewed and uncrewed missions. While much progress has been made in the field of software for the optimization of low-thrust trajectories, many of the tools utilize higher-fidelity methods which, while excellent, result in extremely high run-times and poor convergence when dealing with planetocentric spiraling trajectories deep within a gravity well. Conversely, faster tools like SEPSPOT provide a reasonable solution but typically fail to account for other forces such as third-body gravitation, aerodynamic drag, solar radiation pressure. SEPSPOT is further constrained by its solution method, which may require a very good guess to yield a converged optimal solution. Here the authors have developed an approach using collocation intended to provide solution times comparable to those given by SEPSPOT while allowing for greater robustness and extensible force models.

Elastic Green’s Function in Anisotropic Bimaterials Considering Interfacial Elasticity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juan, Pierre -Alexandre; Dingreville, Remi

Here, the two-dimensional elastic Green’s function is calculated for a general anisotropic elastic bimaterial containing a line dislocation and a concentrated force while accounting for the interfacial structure by means of a generalized interfacial elasticity paradigm. The introduction of the interface elasticity model gives rise to boundary conditions that are effectively equivalent to those of a weakly bounded interface. The equations of elastic equilibrium are solved by complex variable techniques and the method of analytical continuation. The solution is decomposed into the sum of the Green’s function corresponding to the perfectly bonded interface and a perturbation term corresponding to themore » complex coupling nature between the interface structure and a line dislocation/concentrated force. Such construct can be implemented into the boundary integral equations and the boundary element method for analysis of nano-layered structures and epitaxial systems where the interface structure plays an important role.« less

Elastic Green’s Function in Anisotropic Bimaterials Considering Interfacial Elasticity

DOE PAGES

Juan, Pierre -Alexandre; Dingreville, Remi

2017-09-13

Here, the two-dimensional elastic Green’s function is calculated for a general anisotropic elastic bimaterial containing a line dislocation and a concentrated force while accounting for the interfacial structure by means of a generalized interfacial elasticity paradigm. The introduction of the interface elasticity model gives rise to boundary conditions that are effectively equivalent to those of a weakly bounded interface. The equations of elastic equilibrium are solved by complex variable techniques and the method of analytical continuation. The solution is decomposed into the sum of the Green’s function corresponding to the perfectly bonded interface and a perturbation term corresponding to themore » complex coupling nature between the interface structure and a line dislocation/concentrated force. Such construct can be implemented into the boundary integral equations and the boundary element method for analysis of nano-layered structures and epitaxial systems where the interface structure plays an important role.« less

Accounting principles, revenue recognition, and the profitability of pharmacy benefit managers.

PubMed

McLean, Robert A; Garis, Robert I

2005-03-01

To contrast pharmacy benefit management (PBM) companies' measured profitability by using two accounting standards. The first accounting standard is that which, under Generally Accepted Accounting Principles (GAAP), PBMs are currently allowed to employ. The second accounting standard, seemingly more congruent with the PBM business model, treats the PBM as an agent of the plan sponsor. Financial Accounting Standards Board (FASB) Emerging Issues Task Force Issue 99-19, U.S. Securities and Exchange 10-K filings and financial accounting literature. Under GAAP record keeping, the PBM industry profitability appears modest. Using currently applied GAAP, the PBM treats all payment from the plan sponsor as revenue and all payment to the pharmacy as revenue. However, the PBM functions, in practice, as an entity that passes-through money collected from one party (the sponsor) to other parties (dispensing pharmacies). Therefore, it would seem that the nature of PBM cash flows would be more accurately recorded as a pass-through entity. When the PBM is evaluated using an accounting method that recognizes the pass-through nature of its business, the PBM profit margin increases dramatically. Current GAAP standards make traditional financial statement analysis of PBMs unrevealing, and may hide genuinely outstanding financial performance. Investors, regulators, pharmacies, and the FASB all have an interest in moving to clarify this accounting anomaly.

Bubble levitation and translation under single-bubble sonoluminescence conditions.

PubMed

Matula, Thomas J

2003-08-01

Bubble levitation in an acoustic standing wave is re-examined for conditions relevant to single-bubble sonoluminescence. Unlike a previous examination [Matula et al., J. Acoust. Soc. Am. 102, 1522-1527 (1997)], the stable parameter space [Pa,R0] is accounted for in this realization. Forces such as the added mass force and drag are included, and the results are compared with a simple force balance that equates the Bjerknes force to the buoyancy force. Under normal sonoluminescence conditions, the comparison is quite favorable. A more complete accounting of the forces shows that a stably levitated bubble does undergo periodic translational motion. The asymmetries associated with translational motion are hypothesized to generate instabilities in the spherical shape of the bubble. A reduction in gravity results in reduced translational motion. It is hypothesized that such conditions may lead to increased light output from sonoluminescing bubbles.

Mean and Fluctuating Force Distribution in a Random Array of Spheres

NASA Astrophysics Data System (ADS)

Akiki, Georges; Jackson, Thomas; Balachandar, Sivaramakrishnan

2015-11-01

This study presents a numerical study of the force distribution within a cluster of mono-disperse spherical particles. A direct forcing immersed boundary method is used to calculate the forces on individual particles for a volume fraction range of [0.1, 0.4] and a Reynolds number range of [10, 625]. The overall drag is compared to several drag laws found in the literature. As for the fluctuation of the hydrodynamic streamwise force among individual particles, it is shown to have a normal distribution with a standard deviation that varies with the volume fraction only. The standard deviation remains approximately 25% of the mean streamwise force on a single sphere. The force distribution shows a good correlation between the location of two to three nearest upstream and downstream neighbors and the magnitude of the forces. A detailed analysis of the pressure and shear forces contributions calculated on a ghost sphere in the vicinity of a single particle in a uniform flow reveals a mapping of those contributions. The combination of the mapping and number of nearest neighbors leads to a first order correction of the force distribution within a cluster which can be used in Lagrangian-Eulerian techniques. We also explore the possibility of a binary force model that systematically accounts for the effect of the nearest neighbors. This work was supported by the National Science Foundation (NSF OISE-0968313) under Partnership for International Research and Education (PIRE) in Multiphase Flows at the University of Florida.

32 CFR 536.104 - Current agreements in force.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 32 National Defense 3 2010-07-01 2010-07-01 true Current agreements in force. 536.104 Section 536.104 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS... agreements in force. Current listings of known agreements in force are also posted on the USARCS Web site...

Experimental and theoretical investigations on the validity of the geometrical optics model for calculating the stability of optical traps.

PubMed

Schut, T C; Hesselink, G; de Grooth, B G; Greve, J

1991-01-01

We have developed a computer program based on the geometrical optics approach proposed by Roosen to calculate the forces on dielectric spheres in focused laser beams. We have explicitly taken into account the polarization of the laser light and thd divergence of the laser beam. The model can be used to evaluate the stability of optical traps in a variety of different optical configurations. Our calculations explain the experimental observation by Ashkin that a stable single-beam optical trap, without the help of the gravitation force, can be obtained with a strongly divergent laser beam. Our calculations also predict a different trap stability in the directions orthogonal and parallel to the polarization direction of the incident light. Different experimental methods were used to test the predictions of the model for the gravity trap. A new method for measuring the radiation force along the beam axis in both the stable and instable regions is presented. Measurements of the radiation force on polystyrene spheres with diameters of 7.5 and 32 microns in a TEM00-mode laser beam showed a good qualitative correlation with the predictions and a slight quantitative difference. The validity of the geometrical approximations involved in the model will be discussed for spheres of different sizes and refractive indices.

A splitting integration scheme for the SPH simulation of concentrated particle suspensions

NASA Astrophysics Data System (ADS)

Bian, Xin; Ellero, Marco

2014-01-01

Simulating nearly contacting solid particles in suspension is a challenging task due to the diverging behavior of short-range lubrication forces, which pose a serious time-step limitation for explicit integration schemes. This general difficulty limits severely the total duration of simulations of concentrated suspensions. Inspired by the ideas developed in [S. Litvinov, M. Ellero, X.Y. Hu, N.A. Adams, J. Comput. Phys. 229 (2010) 5457-5464] for the simulation of highly dissipative fluids, we propose in this work a splitting integration scheme for the direct simulation of solid particles suspended in a Newtonian liquid. The scheme separates the contributions of different forces acting on the solid particles. In particular, intermediate- and long-range multi-body hydrodynamic forces, which are computed from the discretization of the Navier-Stokes equations using the smoothed particle hydrodynamics (SPH) method, are taken into account using an explicit integration; for short-range lubrication forces, velocities of pairwise interacting solid particles are updated implicitly by sweeping over all the neighboring pairs iteratively, until convergence in the solution is obtained. By using the splitting integration, simulations can be run stably and efficiently up to very large solid particle concentrations. Moreover, the proposed scheme is not limited to the SPH method presented here, but can be easily applied to other simulation techniques employed for particulate suspensions.

Rhombic micro-displacement amplifier for piezoelectric actuator and its linear and hybrid model

NASA Astrophysics Data System (ADS)

Chen, Jinglong; Zhang, Chunlin; Xu, Minglong; Zi, Yanyang; Zhang, Xinong

2015-01-01

This paper proposes rhombic micro-displacement amplifier (RMDA) for piezoelectric actuator (PA). First, the geometric amplification relations are analyzed and linear model is built to analyze the mechanical and electrical properties of this amplifier. Next, the accurate modeling method of amplifier is studied for important application of precise servo control. The classical Preisach model (CPM) is generally implemented using a numerical technique based on the first-order reversal curves (FORCs). The accuracy of CPM mainly depends on the number of FORCs. However, it is generally difficult to achieve enough number of FORCs in practice. So, Support Vector Machine (SVM) is employed in the work to circumvent the deficiency of the CPM. Then the hybrid model, which is based on discrete CPM and SVM is developed to account for hysteresis and dynamic effects. Finally, experimental validation is carried out. The analyzed result shows that this amplifier with the hybrid model is suitable for control application.

Initial bioadhesion on dental materials as a function of contact time, pH, surface wettability, and isoelectric point.

PubMed

Müller, Christine; Lüders, Anne; Hoth-Hannig, Wiebke; Hannig, Matthias; Ziegler, Christiane

2010-03-16

The adsorption of bovine serum albumin (BSA) on surfaces of dental enamel and of dental materials was investigated by scanning force spectroscopy. This method provides adhesion forces which can be measured as a function of contact time between protein and surface, pH, wettability, and isoelectric point of the surface. Whereas the chosen ceramic and composite materials resemble very well the adhesion on natural enamel, a much stronger adhesion was found for the more hydrophobic surfaces, that is, gold, titanium, poly(methyl methacrylate) (PMMA), and poly(tetrafluoroethylene) (PTFE). On hydrophilic surfaces, adhesion is mainly influenced by the electrostatic forces between protein and surface. However, the conformational change of BSA at pH values above pH 8 has to be taken into account. On the very hydrophobic PTFE surface, the special interface structure between PTFE and water plays an important role which governs BSA adhesion.

Analysis of Gas-Particle Flows through Multi-Scale Simulations

NASA Astrophysics Data System (ADS)

Gu, Yile

Multi-scale structures are inherent in gas-solid flows, which render the modeling efforts challenging. On one hand, detailed simulations where the fine structures are resolved and particle properties can be directly specified can account for complex flow behaviors, but they are too computationally expensive to apply for larger systems. On the other hand, coarse-grained simulations demand much less computations but they necessitate constitutive models which are often not readily available for given particle properties. The present study focuses on addressing this issue, as it seeks to provide a general framework through which one can obtain the required constitutive models from detailed simulations. To demonstrate the viability of this general framework in which closures can be proposed for different particle properties, we focus on the van der Waals force of interaction between particles. We start with Computational Fluid Dynamics (CFD) - Discrete Element Method (DEM) simulations where the fine structures are resolved and van der Waals force between particles can be directly specified, and obtain closures for stress and drag that are required for coarse-grained simulations. Specifically, we develop a new cohesion model that appropriately accounts for van der Waals force between particles to be used for CFD-DEM simulations. We then validate this cohesion model and the CFD-DEM approach by showing that it can qualitatively capture experimental results where the addition of small particles to gas fluidization reduces bubble sizes. Based on the DEM and CFD-DEM simulation results, we propose stress models that account for the van der Waals force between particles. Finally, we apply machine learning, specifically neural networks, to obtain a drag model that captures the effects from fine structures and inter-particle cohesion. We show that this novel approach using neural networks, which can be readily applied for other closures other than drag here, can take advantage of the large amount of data generated from simulations, and therefore offer superior modeling performance over traditional approaches.

Matrix method for acoustic levitation simulation.

PubMed

Andrade, Marco A B; Perez, Nicolas; Buiochi, Flavio; Adamowski, Julio C

2011-08-01

A matrix method is presented for simulating acoustic levitators. A typical acoustic levitator consists of an ultrasonic transducer and a reflector. The matrix method is used to determine the potential for acoustic radiation force that acts on a small sphere in the standing wave field produced by the levitator. The method is based on the Rayleigh integral and it takes into account the multiple reflections that occur between the transducer and the reflector. The potential for acoustic radiation force obtained by the matrix method is validated by comparing the matrix method results with those obtained by the finite element method when using an axisymmetric model of a single-axis acoustic levitator. After validation, the method is applied in the simulation of a noncontact manipulation system consisting of two 37.9-kHz Langevin-type transducers and a plane reflector. The manipulation system allows control of the horizontal position of a small levitated sphere from -6 mm to 6 mm, which is done by changing the phase difference between the two transducers. The horizontal position of the sphere predicted by the matrix method agrees with the horizontal positions measured experimentally with a charge-coupled device camera. The main advantage of the matrix method is that it allows simulation of non-symmetric acoustic levitators without requiring much computational effort.

Estimation of payload loads using rigid body interface accelerations. [in structural design of launch vehicle systems

NASA Technical Reports Server (NTRS)

Chen, J. C.; Garba, J. A.; Wada, B. K.

1978-01-01

In the design/analysis process of a payload structural system, the accelerations at the payload/launch vehicle interface obtained from a system analysis using a rigid payload are often used as the input forcing function to the elastic payload to obtain structural design loads. Such an analysis is at best an approximation since the elastic coupling effects are neglected. This paper develops a method wherein the launch vehicle/rigid payload interface accelerations are modified to account for the payload elasticity. The advantage of the proposed method, which is exact to the extent that the physical system can be described by a truncated set of generalized coordinates, is that the complete design/analysis process can be performed within the organization responsible for the payload design. The method requires the updating of the system normal modes to account for payload changes, but does not require a complete transient solution using the composite system model. An application to a real complex structure, the Viking Spacecraft System, is given.

Hull, Mechanical & Electrical (HM &E) Roadmap: Revolutionizing Naval Warfare and Achieving Energy Security

DTIC Science & Technology

2012-01-01

Further, recent economic studies have employed full-cost accounting methods ( Kaplan 2011) to estimate the costs force projection in the Persian...Type 45 Destroyer with an IPS and the Type 23 Frigate powered by the Combined Diesel- Electric and Gas Turbine (CODLAG) architecture provides an...Ammunition Ship and the Combined Diesel- Electric or Gas Turbine (CODLOG) (also known as hybrid gas- turbine -electric drive) aboard the USS MAKIN ISLAND

Numerical simulation of filtration of mine water from coal slurry particles

NASA Astrophysics Data System (ADS)

Dyachenko, E. N.; Dyachenko, N. N.

2017-11-01

The discrete element method is applied to model a technology for clarification of industrial waste water containing fine-dispersed solid impurities. The process is analyzed at the level of discrete particles and pores. The effect of filter porosity on the volume fraction of particles has been shown. The degree of clarification of mine water was also calculated depending on the coal slurry particle size, taking into account the adhesion force.

Paradoxies and axioms of science in the creativity of Clim Ivanovich Churyumov

NASA Astrophysics Data System (ADS)

Steklov, A. F.; Vidmachenko, A. P.; Zhilyaev, B. E.; Dashkiev, G. N.; Svyatogorov, O. A.

2017-09-01

Key ideas of K.I. Churyumov and authors of the article on the development of astronomical research in Ukraine, creation of Ukrainian Institute for Advanced Studies; concerning special directions of interaction of astronomical observatories and the Armed Forces of Ukraine during the period of hybrid wars and methods of solving certain tasks of astrobiology, life of people on the planet Earth taking into account monthly rhythms and climatic seasons.

Estimation of wing nonlinear aerodynamic characteristics at supersonic speeds

NASA Technical Reports Server (NTRS)

Carlson, H. W.; Mack, R. J.

1980-01-01

A computational system for estimation of nonlinear aerodynamic characteristics of wings at supersonic speeds was developed and was incorporated in a computer program. This corrected linearized theory method accounts for nonlinearities in the variation of basic pressure loadings with local surface slopes, predicts the degree of attainment of theoretical leading edge thrust, and provides an estimate of detached leading edge vortex loadings that result when the theoretical thrust forces are not fully realized.

Nonlinear Dynamics of Cantilever-Sample Interactions in Atomic Force Microscopy

NASA Technical Reports Server (NTRS)

Cantrell, John H.; Cantrell, Sean A.

2010-01-01

The interaction of the cantilever tip of an atomic force microscope (AFM) with the sample surface is obtained by treating the cantilever and sample as independent systems coupled by a nonlinear force acting between the cantilever tip and a volume element of the sample surface. The volume element is subjected to a restoring force from the remainder of the sample that provides dynamical equilibrium for the combined systems. The model accounts for the positions on the cantilever of the cantilever tip, laser probe, and excitation force (if any) via a basis set of set of orthogonal functions that may be generalized to account for arbitrary cantilever shapes. The basis set is extended to include nonlinear cantilever modes. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a matrix iteration procedure. The effects of oscillatory excitation forces applied either to the cantilever or to the sample surface (or to both) are obtained from the solution set and applied to the to the assessment of phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) modalities. The influence of bistable cantilever modes of on AFM signal generation is discussed. The effects on the cantilever-sample surface dynamics of subsurface features embedded in the sample that are perturbed by surface-generated oscillatory excitation forces and carried to the cantilever via wave propagation are accounted by the Bolef-Miller propagating wave model. Expressions pertaining to signal generation and image contrast in A-AFM are obtained and applied to amplitude modulation (intermittent contact) atomic force microscopy and resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM). The influence of phase accumulation in A-AFM on image contrast is discussed, as is the effect of hard contact and maximum nonlinearity regimes of A-AFM operation.

Soil water content assessment: critical issues concerning the operational application of the triangle method.

PubMed

Maltese, Antonino; Capodici, Fulvio; Ciraolo, Giuseppe; La Loggia, Goffredo

2015-03-19

Knowledge of soil water content plays a key role in water management efforts to improve irrigation efficiency. Among the indirect estimation methods of soil water content via Earth Observation data is the triangle method, used to analyze optical and thermal features because these are primarily controlled by water content within the near-surface evaporation layer and root zone in bare and vegetated soils. Although the soil-vegetation-atmosphere transfer theory describes the ongoing processes, theoretical models reveal limits for operational use. When applying simplified empirical formulations, meteorological forcing could be replaced with alternative variables when the above-canopy temperature is unknown, to mitigate the effects of calibration inaccuracies or to account for the temporal admittance of the soil. However, if applied over a limited area, a characterization of both dry and wet edges could not be properly achieved; thus, a multi-temporal analysis can be exploited to include outer extremes in soil water content. A diachronic empirical approach introduces the need to assume a constancy of other meteorological forcing variables that control thermal features. Airborne images were acquired on a Sicilian vineyard during most of an entire irrigation period (fruit-set to ripening stages, vintage 2008), during which in situ soil water content was measured to set up the triangle method. Within this framework, we tested the triangle method by employing alternative thermal forcing. The results were inaccurate when air temperature at airborne acquisition was employed. Sonic and aerodynamic air temperatures confirmed and partially explained the limits of simultaneous meteorological forcing, and the use of proxy variables improved model accuracy. The analysis indicates that high spatial resolution does not necessarily imply higher accuracies.

Soil Water Content Assessment: Critical Issues Concerning the Operational Application of the Triangle Method

PubMed Central

Maltese, Antonino; Capodici, Fulvio; Ciraolo, Giuseppe; La Loggia, Goffredo

2015-01-01

Knowledge of soil water content plays a key role in water management efforts to improve irrigation efficiency. Among the indirect estimation methods of soil water content via Earth Observation data is the triangle method, used to analyze optical and thermal features because these are primarily controlled by water content within the near-surface evaporation layer and root zone in bare and vegetated soils. Although the soil-vegetation-atmosphere transfer theory describes the ongoing processes, theoretical models reveal limits for operational use. When applying simplified empirical formulations, meteorological forcing could be replaced with alternative variables when the above-canopy temperature is unknown, to mitigate the effects of calibration inaccuracies or to account for the temporal admittance of the soil. However, if applied over a limited area, a characterization of both dry and wet edges could not be properly achieved; thus, a multi-temporal analysis can be exploited to include outer extremes in soil water content. A diachronic empirical approach introduces the need to assume a constancy of other meteorological forcing variables that control thermal features. Airborne images were acquired on a Sicilian vineyard during most of an entire irrigation period (fruit-set to ripening stages, vintage 2008), during which in situ soil water content was measured to set up the triangle method. Within this framework, we tested the triangle method by employing alternative thermal forcing. The results were inaccurate when air temperature at airborne acquisition was employed. Sonic and aerodynamic air temperatures confirmed and partially explained the limits of simultaneous meteorological forcing, and the use of proxy variables improved model accuracy. The analysis indicates that high spatial resolution does not necessarily imply higher accuracies. PMID:25808771

A Cost Model for Air Force Institute of Technology Programs.

DTIC Science & Technology

1979-09-01

Patterson AFB OH, September 1977. ADA 047662. 16. Horngren , Charles T. Cost Accounting , A Managerial Emphasis. Englewood Cliffs NJ: Prentice Hall, Inc...25 S . Categorical Breakdown of AFIT Cost Matrix ....... .................. . 26 6. Elemental Breakdown of AFIT Direct Cost Category...maximum use of existing data sources such as the Air Force Accounting System for Operations. Justification for Research In past years, cost studies

Nuclear Weapons: DOD Assessed the Need for Each Leg of the Strategic Triad and Considered Other Reductions to Nuclear Forces

DTIC Science & Technology

2016-09-01

NUCLEAR WEAPONS DOD Assessed the Need for Each Leg of the Strategic Triad and Considered Other Reductions to... Nuclear Forces Report to Congressional Requesters September 2016 GAO-16-740 United States Government Accountability Office United States...Government Accountability Office Highlights of GAO-16-740, a report to congressional requesters September 2016 NUCLEAR WEAPONS DOD Assessed

An algorithm for analytical solution of basic problems featuring elastostatic bodies with cavities and surface flaws

NASA Astrophysics Data System (ADS)

Penkov, V. B.; Levina, L. V.; Novikova, O. S.; Shulmin, A. S.

2018-03-01

Herein we propose a methodology for structuring a full parametric analytical solution to problems featuring elastostatic media based on state-of-the-art computing facilities that support computerized algebra. The methodology includes: direct and reverse application of P-Theorem; methods of accounting for physical properties of media; accounting for variable geometrical parameters of bodies, parameters of boundary states, independent parameters of volume forces, and remote stress factors. An efficient tool to address the task is the sustainable method of boundary states originally designed for the purposes of computerized algebra and based on the isomorphism of Hilbertian spaces of internal states and boundary states of bodies. We performed full parametric solutions of basic problems featuring a ball with a nonconcentric spherical cavity, a ball with a near-surface flaw, and an unlimited medium with two spherical cavities.

On deriving the Maxwell stress tensor method for calculating the optical force and torque on an object in harmonic electromagnetic fields

NASA Astrophysics Data System (ADS)

Ye, Qian; Lin, Haoze

2017-07-01

Though extensively used in calculating optical force and torque acting on a material object illuminated by laser, the Maxwell stress tensor (MST) method follows the electromagnetic linear and angular momentum balance that is usually derived in most textbooks for a continuous volume charge distribution in free space, if not resorting to the application of Noether’s theorem in electrodynamics. To cast the conservation laws into a physically appealing form involving the current densities of linear and angular momentum, on which the MST method is based, the divergence theorem is employed to transform a volume integral into a surface integral. When a material object of finite volume is put into the field, it brings about a discontinuity of field across its surface, due to the presence of induced surface charge and surface current. Ambiguity arises among students in whether the divergence theorem can still be directly used without any justification. By taking into account the effect of the induced surface charge and current, we present a simple pedagogical derivation for the MST method for calculating the optical force and torque on an object immersed in monochromatic optical field, without resorting to Noether’s theorem. Although the results turn out to be identical to those given in the standard textbooks, our derivation avoids the direct use of the divergence theorem on a discontinuous function.

Functional Scanning Probe Imaging of Nanostructured Solar Energy Materials.

PubMed

Giridharagopal, Rajiv; Cox, Phillip A; Ginger, David S

2016-09-20

From hybrid perovskites to semiconducting polymer/fullerene blends for organic photovoltaics, many new materials being explored for energy harvesting and storage exhibit performance characteristics that depend sensitively on their nanoscale morphology. At the same time, rapid advances in the capability and accessibility of scanning probe microscopy methods over the past decade have made it possible to study processing/structure/function relationships ranging from photocurrent collection to photocarrier lifetimes with resolutions on the scale of tens of nanometers or better. Importantly, such scanning probe methods offer the potential to combine measurements of local structure with local function, and they can be implemented to study materials in situ or devices in operando to better understand how materials evolve in time in response to an external stimulus or environmental perturbation. This Account highlights recent advances in the development and application of scanning probe microscopy methods that can help address such questions while filling key gaps between the capabilities of conventional electron microscopy and newer super-resolution optical methods. Focusing on semiconductor materials for solar energy applications, we highlight a range of electrical and optoelectronic scanning probe microscopy methods that exploit the local dynamics of an atomic force microscope tip to probe key properties of the solar cell material or device structure. We discuss how it is possible to extract relevant device properties using noncontact scanning probe methods as well as how these properties guide materials development. Specifically, we discuss intensity-modulated scanning Kelvin probe microscopy (IM-SKPM), time-resolved electrostatic force microscopy (trEFM), frequency-modulated electrostatic force microscopy (FM-EFM), and cantilever ringdown imaging. We explain these developments in the context of classic atomic force microscopy (AFM) methods that exploit the physics of cantilever motion and photocarrier generation to provide robust, nanoscale measurements of materials physics that are correlated with device operation. We predict that the multidimensional data sets made possible by these types of methods will become increasingly important as advances in data science expand capabilities and opportunities for image correlation and discovery.

Complex strain fields

NASA Astrophysics Data System (ADS)

Bradshaw, P.

Computational techniques for accounting for extra strain rates, abnormal distributions of delta-U/delta-y, fluctuating strain rates, and the effects of body forces in modeling shear flows are discussed. Consideration is given to simple shears where the extra strain rate does not affect turbulence, thin shear layers, moderately thin shear layers, and strongly distorted flows. Attention is given to formulations based on the exact transport equations for Reynolds stress as derived from the time-averaged Navier-Stokes equations. Extra strain rates arise from curvature, lateral divergence, and bulk compression, with Coriolis forces accounting for the first, intensification of the spanwise vorticity for the second, and compression or dilation of the shear layer producing the third. The curvature forces, e.g., buoyancy and Coriolis forces, are responsible for hurricanes and tornadoes.

Reflections on a Seminal Force in International Accounting

ERIC Educational Resources Information Center

Cascini, Karen T.

2007-01-01

Accounting is a manifestation of several important environmental factors within a country, including economic, educational and political, and, as such, is evolutionary in accordance with those changing social structures. Because of the major impact that international accounting has had on countries' internal accounting systems, it is important to…

Stress analysis of ribbon parachutes

NASA Technical Reports Server (NTRS)

Reynolds, D. T.; Mullins, W. M.

1975-01-01

An analytical method has been developed for determining the internal load distribution for ribbon parachutes subjected to known riser and aerodynamic forces. Finite elements with non-linear elastic properties represent the parachute structure. This method is an extension of the analysis previously developed by the authors and implemented in the digital computer program CANO. The present analysis accounts for the effect of vertical ribbons in the solution for canopy shape and stress distribution. Parametric results are presented which relate the canopy stress distribution to such factors as vertical ribbon strength, number of gores, and gore shape in a ribbon parachute.

Improved non-invasive method for aerosol particle charge measurement employing in-line digital holography

NASA Astrophysics Data System (ADS)

Tripathi, Anjan Kumar

Electrically charged particles are found in a wide range of applications ranging from electrostatic powder coating, mineral processing, and powder handling to rain-producing cloud formation in atmospheric turbulent flows. In turbulent flows, particle dynamics is influenced by the electric force due to particle charge generation. Quantifying particle charges in such systems will help in better predicting and controlling particle clustering, relative motion, collision, and growth. However, there is a lack of noninvasive techniques to measure particle charges. Recently, a non-invasive method for particle charge measurement using in-line Digital Holographic Particle Tracking Velocimetry (DHPTV) technique was developed in our lab, where charged particles to be measured were introduced to a uniform electric field, and their movement towards the oppositely charged electrode was deemed proportional to the amount of charge on the particles (Fan Yang, 2014 [1]). However, inherent speckle noise associated with reconstructed images was not adequately removed and therefore particle tracking data was contaminated. Furthermore, particle charge calculation based on particle deflection velocity neglected the particle drag force and rebound effect of the highly charged particles from the electrodes. We improved upon the existing particle charge measurement method by: 1) hologram post processing, 2) taking drag force into account in charge calculation, 3) considering rebound effect. The improved method was first fine-tuned through a calibration experiment. The complete method was then applied to two different experiments, namely conduction charging and enclosed fan-driven turbulence chamber, to measure particle charges. In all three experiments conducted, the particle charge was found to obey non-central t-location scale family of distribution. It was also noted that the charge distribution was insensitive to the change in voltage applied between the electrodes. The range of voltage applied where reliable particle charges can be measured was also quantified by taking into account the rebound effect of highly charged particles. Finally, in the enclosed chamber experiment, it was found that using carbon conductive coating on the inner walls of the chamber minimized the charge generation inside the chamber when glass bubble particles were used. The value of electric charges obtained in calibration experiment through the improved method was found to have the same order as reported in the existing work (Y.C Ahn et al. 2004 [2]), indicating that the method is indeed effective.

Adapting Covariance Propagation to Account for the Presence of Modeled and Unmodeled Maneuvers

NASA Technical Reports Server (NTRS)

Schiff, Conrad

2006-01-01

This paper explores techniques that can be used to adapt the standard linearized propagation of an orbital covariance matrix to the case where there is a maneuver and an associated execution uncertainty. A Monte Carlo technique is used to construct a final orbital covariance matrix for a 'prop-burn-prop' process that takes into account initial state uncertainty and execution uncertainties in the maneuver magnitude. This final orbital covariance matrix is regarded as 'truth' and comparisons are made with three methods using modified linearized covariance propagation. The first method accounts for the maneuver by modeling its nominal effect within the state transition matrix but excludes the execution uncertainty by omitting a process noise matrix from the computation. The second method does not model the maneuver but includes a process noise matrix to account for the uncertainty in its magnitude. The third method, which is essentially a hybrid of the first two, includes the nominal portion of the maneuver via the state transition matrix and uses a process noise matrix to account for the magnitude uncertainty. The first method is unable to produce the final orbit covariance except in the case of zero maneuver uncertainty. The second method yields good accuracy for the final covariance matrix but fails to model the final orbital state accurately. Agreement between the simulated covariance data produced by this method and the Monte Carlo truth data fell within 0.5-2.5 percent over a range of maneuver sizes that span two orders of magnitude (0.1-20 m/s). The third method, which yields a combination of good accuracy in the computation of the final covariance matrix and correct accounting for the presence of the maneuver in the nominal orbit, is the best method for applications involving the computation of times of closest approach and the corresponding probability of collision, PC. However, applications for the two other methods exist and are briefly discussed. Although the process model ("prop-burn-prop") that was studied is very simple - point-mass gravitational effects due to the Earth combined with an impulsive delta-V in the velocity direction for the maneuver - generalizations to more complex scenarios, including high fidelity force models, finite duration maneuvers, and maneuver pointing errors, are straightforward and are discussed in the conclusion.

Protein Dynamics from NMR: The Slowly Relaxing Local Structure Analysis Compared with Model-Free Analysis

PubMed Central

Meirovitch, Eva; Shapiro, Yury E.; Polimeno, Antonino; Freed, Jack H.

2009-01-01

15N-1H spin relaxation is a powerful method for deriving information on protein dynamics. The traditional method of data analysis is model-free (MF), where the global and local N-H motions are independent and the local geometry is simplified. The common MF analysis consists of fitting single-field data. The results are typically field-dependent, and multi-field data cannot be fit with standard fitting schemes. Cases where known functional dynamics has not been detected by MF were identified by us and others. Recently we applied to spin relaxation in proteins the Slowly Relaxing Local Structure (SRLS) approach which accounts rigorously for mode-mixing and general features of local geometry. SRLS was shown to yield MF in appropriate asymptotic limits. We found that the experimental spectral density corresponds quite well to the SRLS spectral density. The MF formulae are often used outside of their validity ranges, allowing small data sets to be force-fitted with good statistics but inaccurate best-fit parameters. This paper focuses on the mechanism of force-fitting and its implications. It is shown that MF force-fits the experimental data because mode-mixing, the rhombic symmetry of the local ordering and general features of local geometry are not accounted for. Combined multi-field multi-temperature data analyzed by MF may lead to the detection of incorrect phenomena, while conformational entropy derived from MF order parameters may be highly inaccurate. On the other hand, fitting to more appropriate models can yield consistent physically insightful information. This requires that the complexity of the theoretical spectral densities matches the integrity of the experimental data. As shown herein, the SRLS densities comply with this requirement. PMID:16821820

Repulsive tip tilting as the dominant mechanism for hydrogen bond-like features in atomic force microscopy imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Alex J.; Sakai, Yuki; Kim, Minjung

2016-05-09

Experimental atomic force microscopy (AFM) studies have reported distinct features in regions with little electron density for various organic systems. These unexpected features have been proposed to be a direct visualization of intermolecular hydrogen bonding. Here, we apply a computational method using ab initio real-space pseudopotentials along with a scheme to account for tip tilting to simulate AFM images of the 8-hydroxyquinoline dimer and related systems to develop an understanding of the imaging mechanism for hydrogen bonds. We find that contrast for the observed “hydrogen bond” feature comes not from the electrostatic character of the bonds themselves but rather frommore » repulsive tip tilting induced by neighboring electron-rich atoms.« less

Determination of muscle effort at the proximal femur rotation osteotomy

NASA Astrophysics Data System (ADS)

Sachenkov, O.; Hasanov, R.; Andreev, P.; Konoplev, Yu

2016-11-01

The paper formulates the problem of biomechanics of a new method for treatment of Legg-Calve-Perthes disease. Numerical calculations of the rotational flexion osteotomy have been carried out for a constructed mathematical model of the hip joint, taking into account the main set of muscles. The work presents the results of the calculations and their analysis. The results have been compared with the clinical data. The calculations of the reactive forces arising in the acetabulum and the proximal part of the femur allowed us to reveal that this reactive force changes both in value and direction. These data may be useful for assessing the stiffness of an external fixation device used in orthopedic intervention and for evaluating the compression in the joint.

Australian Defence Force surgical support to peacekeeping operations in East Timor.

PubMed

Chambers, Anthony J; Crozier, John A

2004-07-01

The Australian Defence Force (ADF) has provided surgical support to peacekeeping operations in East Timor since September 1999. The aim of the present paper is to document the wide range of surgical procedures performed by the ADF in East Timor from September 1999 to December 2002 on peacekeeping force personnel and the civilian population. Records of all surgical procedures performed by the ADF in East Timor from their arrival in September 1999 to December 2002 were retrospectively reviewed. Details of the type of procedures performed and anaesthetic administered, the age and sex of the patients and whether they were a member of peacekeeping forces or East Timorese civilian were recorded. There were 702 surgical procedures performed by the ADF in East Timor during this period, of which 401 (57%) were for peacekeeping force personnel and 301 (43%) were for East Timorese or other civilians. The most commonly performed procedures were for the management of non-battle wounds, accounting for 181 cases (26%). Battle-type wounds accounted for only 36 procedures (5%). Obstetric and gynaecology cases accounted for 30 procedures (4%). Fifty-six procedures (8%) were on children 12 years or younger. The wide range of surgical procedures performed by the ADF during peacekeeping operations in East Timor highlights the requirement for deployed surgeons to possess a broad range of clinical skills and has implications for their preparation and training. Battle-type wounds accounted for only a small proportion of procedures.

14 CFR 152.305 - Accounting records.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Accounting records. 152.305 Section 152.305 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIRPORTS...) Third party contract costs. (2) Force account costs. (3) Administrative costs. ...

14 CFR 152.305 - Accounting records.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Accounting records. 152.305 Section 152.305 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIRPORTS...) Third party contract costs. (2) Force account costs. (3) Administrative costs. ...

14 CFR 152.305 - Accounting records.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Accounting records. 152.305 Section 152.305 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIRPORTS...) Third party contract costs. (2) Force account costs. (3) Administrative costs. ...

14 CFR 152.305 - Accounting records.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Accounting records. 152.305 Section 152.305 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIRPORTS...) Third party contract costs. (2) Force account costs. (3) Administrative costs. ...

Force Structure: Better Information Needed to Support Air Force A-10 and Other Future Divestment Decisions

DTIC Science & Technology

2016-08-01

estimate should have a standardized structure that breaks costs into discrete elements with sufficient detail to ensure that cost elements are...FORCE STRUCTURE Better Information Needed to Support Air Force A-10 and Other Future Divestment Decisions Report...Accountability Office Highlights of GAO-16-816, a report to congressional committees August 2016 FORCE STRUCTURE Better Information Needed to Support

The effects of gravity on human walking: a new test of the dynamic similarity hypothesis using a predictive model.

PubMed

Raichlen, David A

2008-09-01

The dynamic similarity hypothesis (DSH) suggests that differences in animal locomotor biomechanics are due mostly to differences in size. According to the DSH, when the ratios of inertial to gravitational forces are equal between two animals that differ in size [e.g. at equal Froude numbers, where Froude = velocity2/(gravity x hip height)], their movements can be made similar by multiplying all time durations by one constant, all forces by a second constant and all linear distances by a third constant. The DSH has been generally supported by numerous comparative studies showing that as inertial forces differ (i.e. differences in the centripetal force acting on the animal due to variation in hip heights), animals walk with dynamic similarity. However, humans walking in simulated reduced gravity do not walk with dynamically similar kinematics. The simulated gravity experiments did not completely account for the effects of gravity on all body segments, and the importance of gravity in the DSH requires further examination. This study uses a kinematic model to predict the effects of gravity on human locomotion, taking into account both the effects of gravitational forces on the upper body and on the limbs. Results show that dynamic similarity is maintained in altered gravitational environments. Thus, the DSH does account for differences in the inertial forces governing locomotion (e.g. differences in hip height) as well as differences in the gravitational forces governing locomotion.

32 CFR 644.368 - Procedures and responsibilities for care, custody, accountability, and maintenance.

Code of Federal Regulations, 2010 CFR

2010-07-01

... their jurisdiction until final disposition is effected. (c) Department of the Air Force property. Pursuant to AFR 87-4, the Department of the Air Force is responsible for care and custody of excess Air Force real property. However, upon request by the Air Force DEs may assume custody if no costs are...

32 CFR 644.368 - Procedures and responsibilities for care, custody, accountability, and maintenance.

Code of Federal Regulations, 2013 CFR

2013-07-01

... property under their jurisdiction until final disposition is effected. (c) Department of the Air Force property. Pursuant to AFR 87-4, the Department of the Air Force is responsible for care and custody of excess Air Force real property. However, upon request by the Air Force DEs may assume custody if no costs...

32 CFR 644.368 - Procedures and responsibilities for care, custody, accountability, and maintenance.

Code of Federal Regulations, 2011 CFR

2011-07-01

... property under their jurisdiction until final disposition is effected. (c) Department of the Air Force property. Pursuant to AFR 87-4, the Department of the Air Force is responsible for care and custody of excess Air Force real property. However, upon request by the Air Force DEs may assume custody if no costs...

The influence of non-CO2 forcings on cumulative carbon emissions budgets

NASA Astrophysics Data System (ADS)

Tokarska, Katarzyna B.; Gillett, Nathan P.; Arora, Vivek K.; Lee, Warren G.; Zickfeld, Kirsten

2018-03-01

Carbon budgets provide a useful tool for policymakers to help meet the global climate targets, as they specify total allowable carbon emissions consistent with limiting warming to a given temperature threshold. Non-CO2 forcings have a net warming effect in the Representative Concentration Pathways (RCP) scenarios, leading to reductions in remaining carbon budgets based on CO2 forcing alone. Carbon budgets consistent with limiting warming to below 2.0 °C, with and without accounting for the effects of non-CO2 forcings, were assessed in inconsistent ways by the Intergovernmental Panel on Climate Change (IPCC), making the effects of non-CO2 forcings hard to identify. Here we use a consistent approach to compare 1.5 °C and 2.0 °C carbon budgets with and without accounting for the effects of non-CO2 forcings, using CO2-only and RCP8.5 simulations. The median allowable carbon budgets for 1.5 °C and 2.0 °C warming are reduced by 257 PgC and 418 PgC, respectively, and the uncertainty ranges on the budgets are reduced by more than a factor of two when accounting for the net warming effects of non-CO2 forcings. While our overall results are consistent with IPCC, we use a more robust methodology, and explain the narrower uncertainty ranges of carbon budgets when non-CO2 forcings are included. We demonstrate that most of the reduction in carbon budgets is a result of the direct warming effect of the non-CO2 forcings, with a secondary contribution from the influence of the non-CO2 forcings on the carbon cycle. Such carbon budgets are expected to play an increasingly important role in climate change mitigation, thus understanding the influence of non-CO2 forcings on these budgets and their uncertainties is critical.

Chapman-Enskog Analyses on the Gray Lattice Boltzmann Equation Method for Fluid Flow in Porous Media

NASA Astrophysics Data System (ADS)

Chen, Chen; Li, Like; Mei, Renwei; Klausner, James F.

2018-03-01

The gray lattice Boltzmann equation (GLBE) method has recently been used to simulate fluid flow in porous media. It employs a partial bounce-back of populations (through a fractional coefficient θ, which represents the fraction of populations being reflected by the solid phase) in the evolution equation to account for the linear drag of the medium. Several particular GLBE schemes have been proposed in the literature and these schemes are very easy to implement; but there exists uncertainty about the need for redefining the macroscopic velocity as there has been no systematic analysis to recover the Brinkman equation from the various GLBE schemes. Rigorous Chapman-Enskog analyses are carried out to show that the momentum equation recovered from these schemes can satisfy Brinkman equation to second order in ɛ only if θ = O( ɛ ) in which ɛ is the ratio of the lattice spacing to the characteristic length of physical dimension. The need for redefining macroscopic velocity is shown to be scheme-dependent. When a body force is encountered such as the gravitational force or that caused by a pressure gradient, different forms of forcing redefinitions are required for each GLBE scheme.

First principles calculation of current-induced forces in atomic gold contacts

NASA Astrophysics Data System (ADS)

Brandbyge, Mads; Stokbro, Kurt; Taylor, Jeremy; Mozos, Jose-Luis; Ordejon, Pablo

2002-03-01

We have recently developed an first principles method [1] for calculating the electronic structure, electronic transport, and forces acting on the atoms, for atomic scale systems connected to semi-infinite electrodes and with an applied voltage bias. Our method is based on the density functional theory (DFT) as implemented in the well tested SIESTA program [2]. We fully deal with the atomistic structure of the whole system, treating both the contact and the electrodes on the same footing. The effect of the finite bias (including selfconsistency and the solution of the electrostatic problem) is taken into account using nonequilibrium Green's functions. In this talk we show results for the forces acting on the contact atoms due to the nonequilibrium situation in the electronic subsystem, i.e. in the presence of an electronic current. We concentrate on one atom wide gold contacts/wires connected to bulk gold electrodes. References [1] Our implementation is called TranSIESTA and is described in M. Brandbyge, J. Taylor, K. Stokbro, J-L. Mozos, and P. Ordejon, cond-mat/0110650 [2] D. Sanchez-Portal, P. Ordejon, E. Artacho and J. Soler, Int. J. Quantum Chem. 65, 453 (1997).

Nonlinear vibration of a traveling belt with non-homogeneous boundaries

NASA Astrophysics Data System (ADS)

Ding, Hu; Lim, C. W.; Chen, Li-Qun

2018-06-01

Free and forced nonlinear vibrations of a traveling belt with non-homogeneous boundary conditions are studied. The axially moving materials in operation are always externally excited and produce strong vibrations. The moving materials with the homogeneous boundary condition are usually considered. In this paper, the non-homogeneous boundaries are introduced by the support wheels. Equilibrium deformation of the belt is produced by the non-homogeneous boundaries. In order to solve the equilibrium deformation, the differential and integral quadrature methods (DIQMs) are utilized to develop an iterative scheme. The influence of the equilibrium deformation on free and forced nonlinear vibrations of the belt is explored. The DIQMs are applied to solve the natural frequencies and forced resonance responses of transverse vibration around the equilibrium deformation. The Galerkin truncation method (GTM) is utilized to confirm the DIQMs' results. The numerical results demonstrate that the non-homogeneous boundary conditions cause the transverse vibration to deviate from the straight equilibrium, increase the natural frequencies, and lead to coexistence of square nonlinear terms and cubic nonlinear terms. Moreover, the influence of non-homogeneous boundaries can be exacerbated by the axial speed. Therefore, non-homogeneous boundary conditions of axially moving materials especially should be taken into account.

Numerical simulations for quantitative analysis of electrostatic interaction between atomic force microscopy probe and an embedded electrode within a thin dielectric: meshing optimization, sensitivity to potential distribution and impact of cantilever contribution

NASA Astrophysics Data System (ADS)

Azib, M.; Baudoin, F.; Binaud, N.; Villeneuve-Faure, C.; Bugarin, F.; Segonds, S.; Teyssedre, G.

2018-04-01

Recent experimental results demonstrated that an electrostatic force distance curve (EFDC) can be used for space charge probing in thin dielectric layers. A main advantage of the method is claimed to be its sensitivity to charge localization, which, however, needs to be substantiated by numerical simulations. In this paper, we have developed a model which permits us to compute an EFDC accurately by using the most sophisticated and accurate geometry for the atomic force microscopy probe. To avoid simplifications and in order to reproduce experimental conditions, the EFDC has been simulated for a system constituted of a polarized electrode embedded in a thin dielectric layer (SiN x ). The individual contributions of forces on the tip and on the cantilever have been analyzed separately to account for possible artefacts. The EFDC sensitivity to potential distribution is studied through the change in electrode shape, namely the width and the depth. Finally, the numerical results have been compared with experimental data.

Transient electrophoretic motion of a charged particle through a converging-diverging microchannel: effect of direct current-dielectrophoretic force.

PubMed

Ai, Ye; Joo, Sang W; Jiang, Yingtao; Xuan, Xiangchun; Qian, Shizhi

2009-07-01

Transient electrophoretic motion of a charged particle through a converging-diverging microchannel is studied by solving the coupled system of the Navier-Stokes equations for fluid flow and the Laplace equation for electrical field with an arbitrary Lagrangian-Eulerian finite-element method. A spatially non-uniform electric field is induced in the converging-diverging section, which gives rise to a direct current dielectrophoretic (DEP) force in addition to the electrostatic force acting on the charged particle. As a sequence, the symmetry of the particle velocity and trajectory with respect to the throat is broken. We demonstrate that the predicted particle trajectory shifts due to DEP show quantitative agreements with the existing experimental data. Although converging-diverging microchannels can be used for super fast electrophoresis due to the enhancement of the local electric field, it is shown that large particles may be blocked due to the induced DEP force, which thus must be taken into account in the study of electrophoresis in microfluidic devices where non-uniform electric fields are present.

Controlling the Adhesion of Superhydrophobic Surfaces Using Electrolyte Jet Machining Techniques

PubMed Central

Yang, Xiaolong; Liu, Xin; Lu, Yao; Zhou, Shining; Gao, Mingqian; Song, Jinlong; Xu, Wenji

2016-01-01

Patterns with controllable adhesion on superhydrophobic areas have various biomedical and chemical applications. Electrolyte jet machining technique (EJM), an electrochemical machining method, was firstly exploited in constructing dimples with various profiles on the superhydrophobic Al alloy surface using different processing parameters. Sliding angles of water droplets on those dimples firstly increased and then stabilized at a certain value with the increase of the processing time or the applied voltages of the EJM, indicating that surfaces with different adhesion force could be obtained by regulating the processing parameters. The contact angle hysteresis and the adhesion force that restricts the droplet from sliding off were investigated through experiments. The results show that the adhesion force could be well described using the classical Furmidge equation. On account of this controllable adhesion force, water droplets could either be firmly pinned to the surface, forming various patterns or slide off at designed tilting angles at specified positions on a superhydrophobic surface. Such dimples on superhydrophopbic surfaces can be applied in water harvesting, biochemical analysis and lab-on-chip devices. PMID:27046771

User's Manual for FOMOCO Utilities-Force and Moment Computation Tools for Overset Grids

NASA Technical Reports Server (NTRS)

Chan, William M.; Buning, Pieter G.

1996-01-01

In the numerical computations of flows around complex configurations, accurate calculations of force and moment coefficients for aerodynamic surfaces are required. When overset grid methods are used, the surfaces on which force and moment coefficients are sought typically consist of a collection of overlapping surface grids. Direct integration of flow quantities on the overlapping grids would result in the overlapped regions being counted more than once. The FOMOCO Utilities is a software package for computing flow coefficients (force, moment, and mass flow rate) on a collection of overset surfaces with accurate accounting of the overlapped zones. FOMOCO Utilities can be used in stand-alone mode or in conjunction with the Chimera overset grid compressible Navier-Stokes flow solver OVERFLOW. The software package consists of two modules corresponding to a two-step procedure: (1) hybrid surface grid generation (MIXSUR module), and (2) flow quantities integration (OVERINT module). Instructions on how to use this software package are described in this user's manual. Equations used in the flow coefficients calculation are given in Appendix A.

Small strain multiphase-field model accounting for configurational forces and mechanical jump conditions

NASA Astrophysics Data System (ADS)

Schneider, Daniel; Schoof, Ephraim; Tschukin, Oleg; Reiter, Andreas; Herrmann, Christoph; Schwab, Felix; Selzer, Michael; Nestler, Britta

2018-03-01

Computational models based on the phase-field method have become an essential tool in material science and physics in order to investigate materials with complex microstructures. The models typically operate on a mesoscopic length scale resolving structural changes of the material and provide valuable information about the evolution of microstructures and mechanical property relations. For many interesting and important phenomena, such as martensitic phase transformation, mechanical driving forces play an important role in the evolution of microstructures. In order to investigate such physical processes, an accurate calculation of the stresses and the strain energy in the transition region is indispensable. We recall a multiphase-field elasticity model based on the force balance and the Hadamard jump condition at the interface. We show the quantitative characteristics of the model by comparing the stresses, strains and configurational forces with theoretical predictions in two-phase cases and with results from sharp interface calculations in a multiphase case. As an application, we choose the martensitic phase transformation process in multigrain systems and demonstrate the influence of the local homogenization scheme within the transition regions on the resulting microstructures.

The Who, Whom, What, and How of Institutional Accountability.

ERIC Educational Resources Information Center

Prather, George

An accountability model for the California community colleges must be based on an extensive discussion of precisely who is being held accountable, to whom are they responsible, what are they responsible for, and how will such responsibility be enforced. In developing its model, the Assembly Bill 1725 Accountability Task Force of the California…

Ponderomotive forces in electrodynamics of moving media: The Minkowski and Abraham approaches

NASA Astrophysics Data System (ADS)

Nesterenko, V. V.; Nesterenko, A. V.

2016-09-01

In the general setting of the problem, the explicit compact formulae are derived for the ponderomotive forces in the macroscopic electrodynamics of moving media in the Minkowski and Abraham approaches. Taking account of the Minkowski constitutive relations and making use of a special representation for the Abraham energy-momentum tensor enable one to obtain a compact expression for the Abraham force in the case of arbitrary dependence of the medium velocity on spatial coordinates and the time and for nonstationary external electromagnetic field. We term the difference between the ponderomotive forces in the Abraham and Minkowski approaches as the Abraham force not only under consideration of media at rest but also in the case of moving media. The Lorentz force is found which is exerted by external electromagnetic field on the conduction current in a medium, the covariant Ohm law, and the constitutive Minkowski relations being taken into account. The physical argumentation is traced for the definition of the 4-vector of the ponderomotive force as the 4-divergence of the energy-momentum tensor of electromagnetic field in a medium.

Supersonic full-potential methods for missile body analysis

NASA Technical Reports Server (NTRS)

Pittman, James L.

1992-01-01

Accounts are presented of representative applications to missile bodies of arbitrary shape of methods based on the steady form of the full potential equation. The NCOREL and SIMP full-potential codes are compared, and their results are evaluated for the cases of an arrow wing and a wing-body configuration. Attention is given to the effect of cross-sectional and longitudinal geometries. Comparisons of surface pressure and longitudinal force and moment data for circular and elliptic bodies have shown that the full-potential methods yielded excellent results in attached-flow conditions. Results are presented for a conical star body, waveriders, the Shuttle Orbiter, and a highly swept wing-body cruising at Mach 4.

Layering of inertial confinement fusion targets in microgravity environments

NASA Astrophysics Data System (ADS)

Parks, P. B.; Fagaly, R. L.

1995-02-01

A critical concern in the fabrication of targets for inertial confinement fusion is ensuring that the hydrogenic (D2 or DT) fuel layer maintains spherical symmetry. Because of gravitationally induced sagging of the liquid prior to freezing, only relatively thin (less than 10 micrometers) layers of solid fuel can be produced by fast refreeze methods. One method to reduce the effective gravitational field environment is free-fall insertion into the target chamber. Another method to counterbalance the gravitational force is to use an applied magnetic field combined with a gradient field to induce a magnetic dipole force (F(sub m)) on the liquid fuel layer. For liquid deuterium, the required B dot product del(vector differential operator) B product to counterbalance the gravitational force (F(sub g)) is approximately 10 T(exp 2)/cm. In this paper, we examine the time-dependent dynamics of the liquid fuel layer in a reduced gravitational field environment. We employ an energy method which takes into account the sum of the free energy associated with the surface tension forces, net vertical force (F = F(sub m) - F(sub g) (in the case of magnetic field-assisted microgravity) or F(sub D) (the drag force in the case of free fall)), London-van der Waals forces, the kinetic energy of motion and viscous dissipation. By assuming that the motions are incompressible and irrotational, the volume integrals of the free energies over the deformed liquid fuel layer may be converted to surface integrals. With the surface expressed as the sum of Legendre polynomials, r(sub surface) = a + Sigma a(sub l)(t)P(sub l)(mu), the perturbed amplitude of the individual modes, a(sub l)(t) can be obtained. We show that the l = 1 vertical shift mode takes the longest to damp out, and may be problematic for free-fall insertion even for thin approximately 1 micrometer overfilled foam targets. For a given liquid fuel layer thickness delta, the equilibrium value of a(sub 1)/a (the concentricity of the inner fuel layer) is shown to be dependent on the net vertical force F and layer thickness, i.e., a(sub 1) approximately F delta(exp 5), but independent of the surface tension.

Development of a new physics-based internal coordinate mechanics force field and its application to protein loop modeling.

PubMed

Arnautova, Yelena A; Abagyan, Ruben A; Totrov, Maxim

2011-02-01

We report the development of internal coordinate mechanics force field (ICMFF), new force field parameterized using a combination of experimental data for crystals of small molecules and quantum mechanics calculations. The main features of ICMFF include: (a) parameterization for the dielectric constant relevant to the condensed state (ε = 2) instead of vacuum, (b) an improved description of hydrogen-bond interactions using duplicate sets of van der Waals parameters for heavy atom-hydrogen interactions, and (c) improved backbone covalent geometry and energetics achieved using novel backbone torsional potentials and inclusion of the bond angles at the C(α) atoms into the internal variable set. The performance of ICMFF was evaluated through loop modeling simulations for 4-13 residue loops. ICMFF was combined with a solvent-accessible surface area solvation model optimized using a large set of loop decoys. Conformational sampling was carried out using the biased probability Monte Carlo method. Average/median backbone root-mean-square deviations of the lowest energy conformations from the native structures were 0.25/0.21 Å for four residues loops, 0.84/0.46 Å for eight residue loops, and 1.16/0.73 Å for 12 residue loops. To our knowledge, these results are significantly better than or comparable with those reported to date for any loop modeling method that does not take crystal packing into account. Moreover, the accuracy of our method is on par with the best previously reported results obtained considering the crystal environment. We attribute this success to the high accuracy of the new ICM force field achieved by meticulous parameterization, to the optimized solvent model, and the efficiency of the search method. © 2010 Wiley-Liss, Inc.

Discovering Free Energy Basins for Macromolecular Systems via Guided Multiscale Simulation

PubMed Central

Sereda, Yuriy V.; Singharoy, Abhishek B.; Jarrold, Martin F.; Ortoleva, Peter J.

2012-01-01

An approach for the automated discovery of low free energy states of macromolecular systems is presented. The method does not involve delineating the entire free energy landscape but proceeds in a sequential free energy minimizing state discovery, i.e., it first discovers one low free energy state and then automatically seeks a distinct neighboring one. These states and the associated ensembles of atomistic configurations are characterized by coarse-grained variables capturing the large-scale structure of the system. A key facet of our approach is the identification of such coarse-grained variables. Evolution of these variables is governed by Langevin dynamics driven by thermal-average forces and mediated by diffusivities, both of which are constructed by an ensemble of short molecular dynamics runs. In the present approach, the thermal-average forces are modified to account for the entropy changes following from our knowledge of the free energy basins already discovered. Such forces guide the system away from the known free energy minima, over free energy barriers, and to a new one. The theory is demonstrated for lactoferrin, known to have multiple energy-minimizing structures. The approach is validated using experimental structures and traditional molecular dynamics. The method can be generalized to enable the interpretation of nanocharacterization data (e.g., ion mobility – mass spectrometry, atomic force microscopy, chemical labeling, and nanopore measurements). PMID:22423635

Convective Heat Transfer Scaling of Ignition Delay and Burning Rate with Heat Flux and Stretch Rate in the Equivalent Low Stretch Apparatus

NASA Technical Reports Server (NTRS)

Olson, Sandra

2011-01-01

To better evaluate the buoyant contributions to the convective cooling (or heating) inherent in normal-gravity material flammability test methods, we derive a convective heat transfer correlation that can be used to account for the forced convective stretch effects on the net radiant heat flux for both ignition delay time and burning rate. The Equivalent Low Stretch Apparatus (ELSA) uses an inverted cone heater to minimize buoyant effects while at the same time providing a forced stagnation flow on the sample, which ignites and burns as a ceiling fire. Ignition delay and burning rate data is correlated with incident heat flux and convective heat transfer and compared to results from other test methods and fuel geometries using similarity to determine the equivalent stretch rates and thus convective cooling (or heating) rates for those geometries. With this correlation methodology, buoyant effects inherent in normal gravity material flammability test methods can be estimated, to better apply the test results to low stretch environments relevant to spacecraft material selection.

Historical droughts in Mediterranean regions during the last 500 years: a data/model approach

NASA Astrophysics Data System (ADS)

Brewer, S.; Alleaume, S.; Guiot, J.; Nicault, A.

2007-06-01

We present here a new method for comparing the output of General Circulation Models (GCMs) with proxy-based reconstructions, using time series of reconstructed and simulated climate parameters. The method uses k-means clustering to allow comparison between different periods that have similar spatial patterns, and a fuzzy logic-based distance measure in order to take reconstruction errors into account. The method has been used to test two coupled ocean-atmosphere GCMs over the Mediterranean region for the last 500 years, using an index of drought stress, the Palmer Drought Severity Index. The results showed that, whilst no model exactly simulated the reconstructed changes, all simulations were an improvement over using the mean climate, and a good match was found after 1650 with a model run that took into account changes in volcanic forcing, solar irradiance, and greenhouse gases. A more detailed investigation of the output of this model showed the existence of a set of atmospheric circulation patterns linked to the patterns of drought stress: 1) a blocking pattern over northern Europe linked to dry conditions in the south prior to the Little Ice Age (LIA) and during the 20th century; 2) a NAO-positive like pattern with increased westerlies during the LIA; 3) a NAO-negative like period shown in the model prior to the LIA, but that occurs most frequently in the data during the LIA. The results of the comparison show the improvement in simulated climate as various forcings are included and help to understand the atmospheric changes that are linked to the observed reconstructed climate changes.

A novel method for calculating the dynamic capillary force and correcting the pressure error in micro-tube experiment.

PubMed

Wang, Shuoliang; Liu, Pengcheng; Zhao, Hui; Zhang, Yuan

2017-11-29

Micro-tube experiment has been implemented to understand the mechanisms of governing microcosmic fluid percolation and is extensively used in both fields of micro electromechanical engineering and petroleum engineering. The measured pressure difference across the microtube is not equal to the actual pressure difference across the microtube. Taking into account the additional pressure losses between the outlet of the micro tube and the outlet of the entire setup, we propose a new method for predicting the dynamic capillary pressure using the Level-set method. We first demonstrate it is a reliable method for describing microscopic flow by comparing the micro-model flow-test results against the predicted results using the Level-set method. In the proposed approach, Level-set method is applied to predict the pressure distribution along the microtube when the fluids flow along the microtube at a given flow rate; the microtube used in the calculation has the same size as the one used in the experiment. From the simulation results, the pressure difference across a curved interface (i.e., dynamic capillary pressure) can be directly obtained. We also show that dynamic capillary force should be properly evaluated in the micro-tube experiment in order to obtain the actual pressure difference across the microtube.

Competition between drag and Coulomb interactions in turbulent particle-laden flows using a coupled-fluid-Ewald-summation based approach

NASA Astrophysics Data System (ADS)

Yao, Yuan; Capecelatro, Jesse

2018-03-01

We present a numerical study on inertial electrically charged particles suspended in a turbulent carrier phase. Fluid-particle interactions are accounted for in an Eulerian-Lagrangian (EL) framework and coupled to a Fourier-based Ewald summation method, referred to as the particle-particle-particle-mesh (P3M ) method, to accurately capture short- and long-range electrostatic forces in a tractable manner. The EL P3M method is used to assess the competition between drag and Coulomb forces for a range of Stokes numbers and charge densities. Simulations of like- and oppositely charged particles suspended in a two-dimensional Taylor-Green vortex and three-dimensional homogeneous isotropic turbulence are reported. It is found that even in dilute suspensions, the short-range electric potential plays an important role in flows that admit preferential concentration. Suspensions of oppositely charged particles are observed to agglomerate in the form of chains and rings. Comparisons between the particle-mesh method typically employed in fluid-particle calculations and P3M are reported, in addition to one-point and two-point statistics to quantify the level of clustering as a function of Reynolds number, Stokes number, and nondimensional electric settling velocity.

Parallel hyperspectral compressive sensing method on GPU

NASA Astrophysics Data System (ADS)

Bernabé, Sergio; Martín, Gabriel; Nascimento, José M. P.

2015-10-01

Remote hyperspectral sensors collect large amounts of data per flight usually with low spatial resolution. It is known that the bandwidth connection between the satellite/airborne platform and the ground station is reduced, thus a compression onboard method is desirable to reduce the amount of data to be transmitted. This paper presents a parallel implementation of an compressive sensing method, called parallel hyperspectral coded aperture (P-HYCA), for graphics processing units (GPU) using the compute unified device architecture (CUDA). This method takes into account two main properties of hyperspectral dataset, namely the high correlation existing among the spectral bands and the generally low number of endmembers needed to explain the data, which largely reduces the number of measurements necessary to correctly reconstruct the original data. Experimental results conducted using synthetic and real hyperspectral datasets on two different GPU architectures by NVIDIA: GeForce GTX 590 and GeForce GTX TITAN, reveal that the use of GPUs can provide real-time compressive sensing performance. The achieved speedup is up to 20 times when compared with the processing time of HYCA running on one core of the Intel i7-2600 CPU (3.4GHz), with 16 Gbyte memory.

Significance of Strain in Formulation in Theory of Solid Mechanics

NASA Technical Reports Server (NTRS)

Patnaik, Surya N.; Coroneos, Rula M.; Hopkins, Dale A.

2003-01-01

The basic theory of solid mechanics was deemed complete circa 1860 when St. Venant provided the strain formulation or the field compatibility condition. The strain formulation was incomplete. The missing portion has been formulated and identified as the boundary compatibility condition (BCC). The BCC, derived through a variational formulation, has been verified through integral theorem and solution of problems. The BCC, unlike the field counterpart, do not trivialize when expressed in displacements. Navier s method and the stiffness formulation have to account for the extra conditions especially at the inter-element boundaries in a finite element model. Completion of the strain formulation has led to the revival of the direct force calculation methods: the Integrated Force Method (IFM) and its dual (IFMD) for finite element analysis, and the completed Beltrami-Michell formulation (CBMF) in elasticity. The benefits from the new methods in elasticity, in finite element analysis, and in design optimization are discussed. Existing solutions and computer codes may have to be adjusted for the compliance of the new conditions. Complacency because the discipline is over a century old and computer codes have been developed for half a century can lead to stagnation of the discipline.

Numerical prediction of pollutant dispersion and transport in an atmospheric boundary layer

NASA Astrophysics Data System (ADS)

Zeoli, Stéphanie; Bricteux, Laurent; Mech. Eng. Dpt. Team

2014-11-01

The ability to accurately predict concentration levels of air pollutant released from point sources is required in order to determine their environmental impact. A wall modeled large-eddy simulation (WMLES) of the ABL is performed using the OpenFoam based solver SOWFA (Churchfield and Lee, NREL). It uses Boussinesq approximation for buoyancy effects and takes into account Coriolis forces. A synthetic eddy method is proposed to properly model turbulence inlet velocity boundary conditions. This method will be compared with the standard pressure gradient forcing. WMLES are usually performed using a standard Smagorinsky model or its dynamic version. It is proposed here to investigate a subgrid scale (SGS) model with a better spectral behavior. To this end, a regularized variational multiscale (RVMs) model (Jeanmart and Winckelmans, 2007) is implemented together with standard wall function in order to preserve the dynamics of the large scales within the Ekman layer. The influence of the improved SGS model on the wind simulation and scalar transport will be discussed based on turbulence diagnostics.

An accurate real-time model of maglev planar motor based on compound Simpson numerical integration

NASA Astrophysics Data System (ADS)

Kou, Baoquan; Xing, Feng; Zhang, Lu; Zhou, Yiheng; Liu, Jiaqi

2017-05-01

To realize the high-speed and precise control of the maglev planar motor, a more accurate real-time electromagnetic model, which considers the influence of the coil corners, is proposed in this paper. Three coordinate systems for the stator, mover and corner coil are established. The coil is divided into two segments, the straight coil segment and the corner coil segment, in order to obtain a complete electromagnetic model. When only take the first harmonic of the flux density distribution of a Halbach magnet array into account, the integration method can be carried out towards the two segments according to Lorenz force law. The force and torque analysis formula of the straight coil segment can be derived directly from Newton-Leibniz formula, however, this is not applicable to the corner coil segment. Therefore, Compound Simpson numerical integration method is proposed in this paper to solve the corner segment. With the validation of simulation and experiment, the proposed model has high accuracy and can realize practical application easily.

Theoretical fluid dynamics

NASA Astrophysics Data System (ADS)

Shivamoggi, B. K.

This book is concerned with a discussion of the dynamical behavior of a fluid, and is addressed primarily to graduate students and researchers in theoretical physics and applied mathematics. A review of basic concepts and equations of fluid dynamics is presented, taking into account a fluid model of systems, the objective of fluid dynamics, the fluid state, description of the flow field, volume forces and surface forces, relative motion near a point, stress-strain relation, equations of fluid flows, surface tension, and a program for analysis of the governing equations. The dynamics of incompressible fluid flows is considered along with the dynamics of compressible fluid flows, the dynamics of viscous fluid flows, hydrodynamic stability, and dynamics of turbulence. Attention is given to the complex-variable method, three-dimensional irrotational flows, vortex flows, rotating flows, water waves, applications to aerodynamics, shock waves, potential flows, the hodograph method, flows at low and high Reynolds numbers, the Jeffrey-Hamel flow, and the capillary instability of a liquid jet.

Real-time modulated nanoparticle separation with an ultra-large dynamic range.

PubMed

Zeming, Kerwin Kwek; Thakor, Nitish V; Zhang, Yong; Chen, Chia-Hung

2016-01-07

Nanoparticles exhibit size-dependent properties which make size-selective purification of proteins, DNA or synthetic nanoparticles essential for bio-analytics, clinical medicine, nano-plasmonics and nano-material sciences. Current purification methods of centrifugation, column chromatography and continuous-flow techniques suffer from particle aggregation, multi-stage process, complex setups and necessary nanofabrication. These increase process costs and time, reduce efficiency and limit dynamic range. Here, we achieve an unprecedented real-time nanoparticle separation (51-1500 nm) using a large-pore (2 μm) deterministic lateral displacement (DLD) device. No external force fields or nanofabrication are required. Instead, we investigated innate long-range electrostatic influences on nanoparticles within a fluid medium at different NaCl ionic concentrations. In this study we account for the electrostatic forces beyond Debye length and showed that they cannot be assumed as negligible especially for precise nanoparticle separation methods such as DLD. Our findings have enabled us to develop a model to simultaneously quantify and modulate the electrostatic force interactions between nanoparticle and micropore. By simply controlling buffer solutions, we achieve dynamic nanoparticle size separation on a single device with a rapid response time (<20 s) and an enlarged dynamic range (>1200%), outperforming standard benchtop centrifuge systems. This novel method and model combines device simplicity, isolation precision and dynamic flexibility, opening opportunities for high-throughput applications in nano-separation for industrial and biological applications.

Tools and methods for experimental in-vivo measurement and biomechanical characterization of an Octopus vulgaris arm.

PubMed

Margheri, Laura; Mazzolai, Barbara; Cianchetti, Matteo; Dario, Paolo; Laschi, Cecilia

2009-01-01

This work illustrates new tools and methods for an in vivo and direct, but non-invasive, measurement of an octopus arm mechanical properties. The active elongation (longitudinal stretch) and the pulling force capability are measured on a specimen of Octopus vulgaris in order to quantitatively characterize the parameters describing the arm mechanics, for biomimetic design purposes. The novel approach consists of observing and measuring a living octopus with minimally invasive methods, which allow the animal to move with its complete ability. All tools are conceived in order to create a collaborative interaction with the animal for the acquisition of active measures. The data analysis is executed taking into account the presence of an intrinsic error due to the mobility of the subject and the aquatic environment. Using a system of two synchronized high-speed high-resolution cameras and purpose-made instruments, the maximum elongation of an arm and its rest length (when all muscles fibres are relaxed during propulsion movement) are measured and compared to define the longitudinal stretch, with the impressive average result of 194%. With a similar setup integrated with a force sensor, the pulling force capability is measured as a function of grasp point position along the arm. The measured parameters are used as real specifications for the design of an octopus-like arm with a biomimetic approach.

A variable acceleration calibration system

NASA Astrophysics Data System (ADS)

Johnson, Thomas H.

2011-12-01

A variable acceleration calibration system that applies loads using gravitational and centripetal acceleration serves as an alternative, efficient and cost effective method for calibrating internal wind tunnel force balances. Two proof-of-concept variable acceleration calibration systems are designed, fabricated and tested. The NASA UT-36 force balance served as the test balance for the calibration experiments. The variable acceleration calibration systems are shown to be capable of performing three component calibration experiments with an approximate applied load error on the order of 1% of the full scale calibration loads. Sources of error are indentified using experimental design methods and a propagation of uncertainty analysis. Three types of uncertainty are indentified for the systems and are attributed to prediction error, calibration error and pure error. Angular velocity uncertainty is shown to be the largest indentified source of prediction error. The calibration uncertainties using a production variable acceleration based system are shown to be potentially equivalent to current methods. The production quality system can be realized using lighter materials and a more precise instrumentation. Further research is needed to account for balance deflection, forcing effects due to vibration, and large tare loads. A gyroscope measurement technique is shown to be capable of resolving the balance deflection angle calculation. Long term research objectives include a demonstration of a six degree of freedom calibration, and a large capacity balance calibration.

Self-organizing magnetic beads for biomedical applications

NASA Astrophysics Data System (ADS)

Gusenbauer, Markus; Kovacs, Alexander; Reichel, Franz; Exl, Lukas; Bance, Simon; Özelt, Harald; Schrefl, Thomas

2012-03-01

In the field of biomedicine magnetic beads are used for drug delivery and to treat hyperthermia. Here we propose to use self-organized bead structures to isolate circulating tumor cells using lab-on-chip technologies. Typically blood flows past microposts functionalized with antibodies for circulating tumor cells. Creating these microposts with interacting magnetic beads makes it possible to tune the geometry in size, position and shape. We developed a simulation tool that combines micromagnetics and discrete particle dynamics, in order to design micropost arrays made of interacting beads. The simulation takes into account the viscous drag of the blood flow, magnetostatic interactions between the magnetic beads and gradient forces from external aligned magnets. We developed a particle-particle particle-mesh method for effective computation of the magnetic force and torque acting on the particles.

Numerical Investigation of the Effect of Some Parameters on Temperature Field and Kerf Width in Laser Cutting Process

NASA Astrophysics Data System (ADS)

Kheloufi, Karim; Amara, El Hachemi

A transient numerical model is developed to study the temperature field and the kerf shape during laser cutting process. The Fresnel absorption model is used to handle the absorption of the incident wave by the surface of the liquid metal and the enthalpy-porosity technique is employed to account for the latent heat during melting and solidification of the material. The VOF method is used to track the evolution of the shape of the kerf. Physical phenomena occurring at the liquid/gas interface, including friction force and pressure force exerted by the gas jet and the heat absorbed by the surface, are incorporated into the governing equations as source terms. Temperature and velocity distribution, and kerf shape are investigated.

A new atomic force microscope force ramp technique using digital force feedback control reveals mechanically weak protein unfolding events.

PubMed

Kawakami, M; Smith, D A

2008-12-10

We have developed a new force ramp modification of the atomic force microscope (AFM) which can control multiple unfolding events of a multi-modular protein using software-based digital force feedback control. With this feedback the force loading rate can be kept constant regardless the length of soft elastic linkage or number of unfolded polypeptide domains. An unfolding event is detected as a sudden drop in force, immediately after which the feedback control reduces the applied force to a low value of a few pN by lowering the force set point. Hence the remaining folded domains can relax and the subsequent force ramp is applied to relaxed protein domains identically in each case. We have applied this technique to determine the kinetic parameters x(u), which is the distance between the native state and transition state, and α(0), which is the unfolding rate constant at zero force, for the mechanical unfolding of a pentamer of I27 domains of titin. In each force ramp the unfolding probability depends on the number of folded domains remaining in the system and we had to take account of this effect in the analysis of unfolding force data. We obtained values of x(u) and α(0) to be 0.28 nm and 1.02 × 10(-3) s(-1), which are in good agreement with those obtained from conventional constant velocity experiments. This method reveals unfolding data at low forces that are not seen in constant velocity experiments and corrects for the change in stiffness that occurs with most mechanical systems throughout the unfolding process to allow constant force ramp experiments to be carried out. In addition, a mechanically weak structure was detected, which formed from the fully extended polypeptide chain during a force quench. This indicates that the new technique will allow studies of the folding kinetics of previously hidden, mechanically weak species.

Quantification of Cyclic Ground Reaction Force Histories During Daily Activity in Humans

NASA Technical Reports Server (NTRS)

Breit, G. A.; Whalen, R. T.; Wade, Charles E. (Technical Monitor)

1994-01-01

Theoretical models and experimental studies of bone remodeling suggest that bone density and structure are influenced by local cyclic skeletal tissue stress and strain histories. Estimation of long-term loading histories in humans is usually achieved by assessment of physical activity level by questionnaires, logbooks, and pedometers, since the majority of lower limb cyclic loading occurs during walking and running. These methods provide some indication of the mechanical loading history, but fail to consider the true magnitude of the lower limb skeletal forces generated by various daily activities. These techniques cannot account for individual gait characteristics, gait speed, and unpredictable high loading events that may influence bone mass significantly. We have developed portable instrumentation to measure and record the vertical component of the ground reaction force (GRFz) during normal daily activity. This equipment allows long-term quantitative monitoring of musculoskeletal loads, which in conjunction with bone mineral density assessments, promises to elucidate the relationship between skeletal stresses and bone remodeling.

Matrix methods applied to engineering rigid body mechanics

NASA Astrophysics Data System (ADS)

Crouch, T.

The purpose of this book is to present the solution of a range of rigorous body mechanics problems using a matrix formulation of vector algebra. Essential theory concerning kinematics and dynamics is formulated in terms of matrix algebra. The solution of kinematics and dynamics problems is discussed, taking into account the velocity and acceleration of a point moving in a circular path, the velocity and acceleration determination for a linkage, the angular velocity and angular acceleration of a roller in a taper-roller thrust race, Euler's theroem on the motion of rigid bodies, an automotive differential, a rotating epicyclic, the motion of a high speed rotor mounted in gimbals, and the vibration of a spinning projectile. Attention is given to the activity of a force, the work done by a conservative force, the work and potential in a conservative system, the equilibrium of a mechanism, bearing forces due to rotor misalignment, and the frequency of vibrations of a constrained rod.

Establishment of performance standards and a cut-score for the Canadian Forces firefighter physical fitness maintenance evaluation (FF PFME).

PubMed

Todd Rogers, W; Docherty, David; Petersen, Stewart

2014-01-01

The bookmark method for setting cut-scores was used to re-set the cut-score for the Canadian Forces Firefighter Physical Fitness Maintenance Evaluation (FF PFME). The time required to complete 10 tasks that together simulate a first-response firefighting emergency was accepted as a measure of work capacity. A panel of 25 Canadian Forces firefighter supervisors set cut-scores in three rounds. Each round involved independent evaluation of nine video work samples, where the times systematically increased from 400 seconds to 560 seconds. Results for Round 1 were discussed before moving to Round 2 and results for Round 2 were discussed before moving to Round 3. Accounting for the variability among panel members at the end of Round 3, a cut-score of 481 seconds (mean Round 3 plus 2 SEM) was recommended. Firefighters who complete the FF PFME in 481 seconds or less have the physical capacity to complete first-response firefighting work.

Biomolecular Force Field Parameterization via Atoms-in-Molecule Electron Density Partitioning.

PubMed

Cole, Daniel J; Vilseck, Jonah Z; Tirado-Rives, Julian; Payne, Mike C; Jorgensen, William L

2016-05-10

Molecular mechanics force fields, which are commonly used in biomolecular modeling and computer-aided drug design, typically treat nonbonded interactions using a limited library of empirical parameters that are developed for small molecules. This approach does not account for polarization in larger molecules or proteins, and the parametrization process is labor-intensive. Using linear-scaling density functional theory and atoms-in-molecule electron density partitioning, environment-specific charges and Lennard-Jones parameters are derived directly from quantum mechanical calculations for use in biomolecular modeling of organic and biomolecular systems. The proposed methods significantly reduce the number of empirical parameters needed to construct molecular mechanics force fields, naturally include polarization effects in charge and Lennard-Jones parameters, and scale well to systems comprised of thousands of atoms, including proteins. The feasibility and benefits of this approach are demonstrated by computing free energies of hydration, properties of pure liquids, and the relative binding free energies of indole and benzofuran to the L99A mutant of T4 lysozyme.

Sensitivity of the Eocene climate to CO2 and orbital variability

NASA Astrophysics Data System (ADS)

Keery, John S.; Holden, Philip B.; Edwards, Neil R.

2018-02-01

The early Eocene, from about 56 Ma, with high atmospheric CO2 levels, offers an analogue for the response of the Earth's climate system to anthropogenic fossil fuel burning. In this study, we present an ensemble of 50 Earth system model runs with an early Eocene palaeogeography and variation in the forcing values of atmospheric CO2 and the Earth's orbital parameters. Relationships between simple summary metrics of model outputs and the forcing parameters are identified by linear modelling, providing estimates of the relative magnitudes of the effects of atmospheric CO2 and each of the orbital parameters on important climatic features, including tropical-polar temperature difference, ocean-land temperature contrast, Asian, African and South (S.) American monsoon rains, and climate sensitivity. Our results indicate that although CO2 exerts a dominant control on most of the climatic features examined in this study, the orbital parameters also strongly influence important components of the ocean-atmosphere system in a greenhouse Earth. In our ensemble, atmospheric CO2 spans the range 280-3000 ppm, and this variation accounts for over 90 % of the effects on mean air temperature, southern winter high-latitude ocean-land temperature contrast and northern winter tropical-polar temperature difference. However, the variation of precession accounts for over 80 % of the influence of the forcing parameters on the Asian and African monsoon rainfall, and obliquity variation accounts for over 65 % of the effects on winter ocean-land temperature contrast in high northern latitudes and northern summer tropical-polar temperature difference. Our results indicate a bimodal climate sensitivity, with values of 4.36 and 2.54 °C, dependent on low or high states of atmospheric CO2 concentration, respectively, with a threshold at approximately 1000 ppm in this model, and due to a saturated vegetation-albedo feedback. Our method gives a quantitative ranking of the influence of each of the forcing parameters on key climatic model outputs, with additional spatial information from singular value decomposition providing insights into likely physical mechanisms. The results demonstrate the importance of orbital variation as an agent of change in climates of the past, and we demonstrate that emulators derived from our modelling output can be used as rapid and efficient surrogates of the full complexity model to provide estimates of climate conditions from any set of forcing parameters.

A second-order accurate immersed boundary-lattice Boltzmann method for particle-laden flows

NASA Astrophysics Data System (ADS)

Zhou, Qiang; Fan, Liang-Shih

2014-07-01

A new immersed boundary-lattice Boltzmann method (IB-LBM) is presented for fully resolved simulations of incompressible viscous flows laden with rigid particles. The immersed boundary method (IBM) recently developed by Breugem (2012) [19] is adopted in the present method, development including the retraction technique, the multi-direct forcing method and the direct account of the inertia of the fluid contained within the particles. The present IB-LBM is, however, formulated with further improvement with the implementation of the high-order Runge-Kutta schemes in the coupled fluid-particle interaction. The major challenge to implement high-order Runge-Kutta schemes in the LBM is that the flow information such as density and velocity cannot be directly obtained at a fractional time step from the LBM since the LBM only provides the flow information at an integer time step. This challenge can be, however, overcome as given in the present IB-LBM by extrapolating the flow field around particles from the known flow field at the previous integer time step. The newly calculated fluid-particle interactions from the previous fractional time steps of the current integer time step are also accounted for in the extrapolation. The IB-LBM with high-order Runge-Kutta schemes developed in this study is validated by several benchmark applications. It is demonstrated, for the first time, that the IB-LBM has the capacity to resolve the translational and rotational motion of particles with the second-order accuracy. The optimal retraction distances for spheres and tubes that help the method achieve the second-order accuracy are found to be around 0.30 and -0.47 times of the lattice spacing, respectively. Simulations of the Stokes flow through a simple cubic lattice of rotational spheres indicate that the lift force produced by the Magnus effect can be very significant in view of the magnitude of the drag force when the practical rotating speed of the spheres is encountered. This finding may lead to more comprehensive studies of the effect of the particle rotation on fluid-solid drag laws. It is also demonstrated that, when the third-order or the fourth-order Runge-Kutta scheme is used, the numerical stability of the present IB-LBM is better than that of all methods in the literature, including the previous IB-LBMs and also the methods with the combination of the IBM and the traditional incompressible Navier-Stokes solver.

Entrainment of coarse grains using a discrete particle model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valyrakis, Manousos, E-mail: Manousos.Valyrakis@glasgow.ac.uk; Arnold, Roger B. Jr.

2014-10-06

Conventional bedload transport models and incipient motion theories relying on a time-averaged boundary shear stress are incapable of accounting for the effects of fluctuating near-bed velocity in turbulent flow and are therefore prone to significant errors. Impulse, the product of an instantaneous force magnitude and its duration, has been recently proposed as an appropriate criterion for quantifying the effects of flow turbulence in removing coarse grains from the bed surface. Here, a discrete particle model (DPM) is used to examine the effects of impulse, representing a single idealized turbulent event, on particle entrainment. The results are classified according to themore » degree of grain movement into the following categories: motion prior to entrainment, initial dislodgement, and energetic displacement. The results indicate that in all three cases the degree of particle motion depends on both the force magnitude and the duration of its application and suggest that the effects of turbulence must be adequately accounted for in order to develop a more accurate method of determining incipient motion. DPM is capable of simulating the dynamics of grain entrainment and is an appropriate tool for further study of the fundamental mechanisms of sediment transport.« less

Biomechanics of Atlanto-Occipital and Atlanto-Axial Joint Injuries,

DTIC Science & Technology

1982-11-12

conditions, after physiological lordosis is taken into account, the main acting forces are: the weight of the head--force P21 the force of the muscles...position, the force Pv’ because of physiological lordosis , is directed away from the cen- tral axis of the vertebral shafts and can be considered using two...and the equivalent tension force in the transverse ligament of the atlas--R. We found out that under intermediate degree of physiological lordosis

Defining Responsibility in Maintaining Financial Accounting Systems.

DTIC Science & Technology

1995-01-01

acquisition and issuance of materials, original cost , location, etc., KAR 2 (Property and Inventory Accounting )." (3:10) The final methodology used in...PROFESSIONAL MILITARY COMPTROLLER SCHOOL IDEA PAPER TITLE DEFINING RESPONSIBILITY IN MAINTAINING FINANCIAL ACCOUNTING SYSTEMS AUTHOR . :.a EFANIE B...or the Department of the Air Force. DIC tiJ.[ In.,,- B . . . .. . PMCS IDEA PAPER TITLE: Defining Responsibility in Maintaining Financial Accounting

Using Enthalpy as a Prognostic Variable in Atmospheric Modelling with Variable Composition

DTIC Science & Technology

2016-04-14

the first place. It then becomes clear that specific enthalpy provides a viable alternative to account for the effects of composi- tional changes on...forces. It is also assumed that external forces acting on a molecule are proportional to its mass, mi , as is the case with the gravity or Coriolis ...relative humidity and is introduced into Equation (11) to account for the effects of water vapour on the gas constant R and, consequently, on the

The Perceived Effects on Weapon Systems Acquisition in Air Force Systems Command While Operating under a Continuing Resolution Authority

DTIC Science & Technology

1984-09-01

reviews program and financial reports. In addition, the GAO, the Defense Contract Audit Agency, and the Air Force Audit Agency regularly audit... account , for which a~gxpriations, funds, cc other authority were not available durinq the fiscal year 1983 [101.’ *P-1 line item: a prcrmtbudget line...intelligence, program mNauzent, contracting, and accounting and finance (which is also a staff position in the controller’s organization). The

The Report of the Working Group Concerning the Deterrence of and Response to Incidents of Sexual Assault at the U.S. Air Force Academy

DTIC Science & Technology

2003-06-01

counseling cadets on any personal problems cadets might have (from “boyfriend-girlfriend” problems to financial difficulties). To fulfill this... Accounting Office (GAO) issued a report on sexual harassment at all service academies in 1994.107 The GAO identified ongoing sexual harassment...hold cadets more accountable for their actions, consistent with the “marching orders” he received from the Chief of Staff of the Air Force.201 He

Tri-Service Champus Statistical Database Project (TCSDP): Champus Ambulatory Data Analysis. Detail Report

DTIC Science & Technology

1993-03-30

Navy was highest in all three measures, followed by the Air Force, and the Army was the lowest. No branch accounted for a large proportion of the...the largest proportion of workload and costs were in the category ’Outside Catchment Area’. The total government pay for outside catchment area category...services. MACDILL REG HOSP MACDILL AFB had the highest amount of total government pay in the Air Force’s billable MTF. It accounted for 4.13

A recurrence matrix solution for the dynamic response of aircraft in gusts

NASA Technical Reports Server (NTRS)

Houbolt, John C

1951-01-01

A systematic procedure developed for the calculation of the structural response of aircraft flying through a gust by use of difference equations in the solution of dynamic problems is first illustrated by means of a simple-damped-oscillator example. A detailed analysis is then given which leads to a recurrence matrix equation for the determination of the response of an airplane in a gust. The method takes into account wing bending and twisting deformations, fuselage deflection, vertical and pitching motion of the airplane, and some tail forces. The method is based on aerodynamic strip theory, but compressibility and three-dimensional aerodynamic effects can be taken into account approximately by means of over-all corrections. Either a sharp-edge gust or a gust of arbitrary shape in the spanwise or flight directions may be treated. In order to aid in the application of the method to any specific case, a suggested computational procedure is included. The possibilities of applying the method to a variety of transient aircraft problems, such as landing, are brought out. A brief review of matrix algebra, covering the extent to which it is used in the analysis, is also included. (author)

Nuclear spin relaxation in ligands outside of the first coordination sphere in a gadolinium (III) complex: Effects of intermolecular forces

NASA Astrophysics Data System (ADS)

Kruk, Danuta; Kowalewski, Jozef

2002-07-01

This article describes paramagnetic relaxation enhancement (PRE) in systems with high electron spin, S, where there is molecular interaction between a paramagnetic ion and a ligand outside of the first coordination sphere. The new feature of our treatment is an improved handling of the electron-spin relaxation, making use of the Redfield theory. Following a common approach, a well-defined second coordination sphere is assumed, and the PRE contribution from these more distant and shorter-lived ligands is treated in a way similar to that used for the first coordination sphere. This model is called "ordered second sphere," OSS. In addition, we develop here a formalism similar to that of Hwang and Freed [J. Chem. Phys. 63, 4017 (1975)], but accounting for the electron-spin relaxation effects. We denote this formalism "diffuse second sphere," DSS. The description of the dynamics of the intermolecular dipole-dipole interaction is based on the Smoluchowski equation, with a potential of mean force related to the radial distribution function. We have used a finite-difference method to calculate numerically a correlation function for translational motion, taking into account the intermolecular forces leading to an arbitrary radial distribution of the ligand protons. The OSS and DSS models, including the Redfield description of the electron-spin relaxation, were used to interpret the PRE in an aqueous solution of a slowly rotating gadolinium (III) complex (S=7/2) bound to a protein.

[Interaction of mental health and forced married migrants in Germany].

PubMed

Kizilhan, Jan

2015-11-01

The study examines the interaction of the forced married migrants and the frequency of the psychological illness. Forced-married and not forced-married migrants are compared concerning her psychological illness in psychosomatic clinics in Germany. Forced-married women reported significantly more about psychological illness and have undertaken on average at least four times a suicide attempt. Forced-married women suffer lifelong from this event and need, with taking into account cultural migration-specific aspects, special support in the psychosocial consultation and medical-therapeutic treatment. © Georg Thieme Verlag KG Stuttgart · New York.

Functional Scanning Probe Imaging of Nanostructured Solar Energy Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giridharagopal, Rajiv; Cox, Phillip A.; Ginger, David S.

From hybrid perovskites to semiconducting polymer/fullerene blends for organic photovoltaics, many new materials being explored for energy harvesting and storage exhibit performance characteristics that depend sensitively on their nanoscale morphology. At the same time, rapid advances in the capability and accessibility of scanning probe microscopy methods over the past decade have made it possible to study processing/structure/function relationships ranging from photocurrent collection to photocarrier lifetimes with resolutions on the scale of tens of nanometers or better. Importantly, such scanning probe methods offer the potential to combine measurements of local structure with local function, and they can be implemented to studymore » materials in situ or devices in operando to better understand how materials evolve in time in response to an external stimulus or environmental perturbation. This Account highlights recent advances in the development and application of scanning probe microscopy methods that can help address such questions while filling key gaps between the capabilities of conventional electron microscopy and newer super-resolution optical methods. Focusing on semiconductor materials for solar energy applications, we highlight a range of electrical and optoelectronic scanning probe microscopy methods that exploit the local dynamics of an atomic force microscope tip to probe key properties of the solar cell material or device structure. We discuss how it is possible to extract relevant device properties using noncontact scanning probe methods as well as how these properties guide materials development. Specifically, we discuss intensity-modulated scanning Kelvin probe microscopy (IM-SKPM), time-resolved electrostatic force microscopy (trEFM), frequency-modulated electrostatic force microscopy (FM-EFM), and cantilever ringdown imaging. We explain these developments in the context of classic atomic force microscopy (AFM) methods that exploit the physics of cantilever motion and photocarrier generation to provide robust, nanoscale measurements of materials physics that are correlated with device operation. We predict that the multidimensional data sets made possible by these types of methods will become increasingly important as advances in data science expand capabilities and opportunities for image correlation and discovery.« less

Functional Scanning Probe Imaging of Nanostructured Solar Energy Materials

DOE PAGES

Giridharagopal, Rajiv; Cox, Phillip A.; Ginger, David S.

2016-08-30

From hybrid perovskites to semiconducting polymer/fullerene blends for organic photovoltaics, many new materials being explored for energy harvesting and storage exhibit performance characteristics that depend sensitively on their nanoscale morphology. At the same time, rapid advances in the capability and accessibility of scanning probe microscopy methods over the past decade have made it possible to study processing/structure/function relationships ranging from photocurrent collection to photocarrier lifetimes with resolutions on the scale of tens of nanometers or better. Importantly, such scanning probe methods offer the potential to combine measurements of local structure with local function, and they can be implemented to studymore » materials in situ or devices in operando to better understand how materials evolve in time in response to an external stimulus or environmental perturbation. This Account highlights recent advances in the development and application of scanning probe microscopy methods that can help address such questions while filling key gaps between the capabilities of conventional electron microscopy and newer super-resolution optical methods. Focusing on semiconductor materials for solar energy applications, we highlight a range of electrical and optoelectronic scanning probe microscopy methods that exploit the local dynamics of an atomic force microscope tip to probe key properties of the solar cell material or device structure. We discuss how it is possible to extract relevant device properties using noncontact scanning probe methods as well as how these properties guide materials development. Specifically, we discuss intensity-modulated scanning Kelvin probe microscopy (IM-SKPM), time-resolved electrostatic force microscopy (trEFM), frequency-modulated electrostatic force microscopy (FM-EFM), and cantilever ringdown imaging. We explain these developments in the context of classic atomic force microscopy (AFM) methods that exploit the physics of cantilever motion and photocarrier generation to provide robust, nanoscale measurements of materials physics that are correlated with device operation. We predict that the multidimensional data sets made possible by these types of methods will become increasingly important as advances in data science expand capabilities and opportunities for image correlation and discovery.« less

Fast Bayesian approach for modal identification using forced vibration data considering the ambient effect

NASA Astrophysics Data System (ADS)

Ni, Yan-Chun; Zhang, Feng-Liang

2018-05-01

Modal identification based on vibration response measured from real structures is becoming more popular, especially after benefiting from the great improvement of the measurement technology. The results are reliable to estimate the dynamic performance, which fits the increasing requirement of different design configurations of the new structures. However, the high-quality vibration data collection technology calls for a more accurate modal identification method to improve the accuracy of the results. Through the whole measurement process of dynamic testing, there are many aspects that will cause the rise of uncertainty, such as measurement noise, alignment error and modeling error, since the test conditions are not directly controlled. Depending on these demands, a Bayesian statistical approach is developed in this work to estimate the modal parameters using the forced vibration response of structures, simultaneously considering the effect of the ambient vibration. This method makes use of the Fast Fourier Transform (FFT) of the data in a selected frequency band to identify the modal parameters of the mode dominating this frequency band and estimate the remaining uncertainty of the parameters correspondingly. In the existing modal identification methods for forced vibration, it is generally assumed that the forced vibration response dominates the measurement data and the influence of the ambient vibration response is ignored. However, ambient vibration will cause modeling error and affect the accuracy of the identified results. The influence is shown in the spectra as some phenomena that are difficult to explain and irrelevant to the mode to be identified. These issues all mean that careful choice of assumptions in the identification model and fundamental formulation to account for uncertainty are necessary. During the calculation, computational difficulties associated with calculating the posterior statistics are addressed. Finally, a fast computational algorithm is proposed so that the method can be practically implemented. Numerical verification with synthetic data and applicable investigation with full-scale field structures data are all carried out for the proposed method.

Contradictory Evidence on Wave Forcing of Tropical Upwelling in the Brewer-Dobson Circulation - A Suggested Resolution

NASA Technical Reports Server (NTRS)

Zhou, Tiehan; Geller, Marvin A.; Lin, Wuyin

2011-01-01

ERA-40 data are analyzed to demonstrate that wave forcing at lower latitudes plays a crucial role in driving the tropical upwelling portion of the Brewer-Dobson circulation. It is shown that subtropical wave forcing is correlated with tropical upwelling on both intraseasonal and interannual time scales when transient waves are taken into account, and that tropical wave forcing exerts its influence on tropical upwelling via its body force on the zonal mean flow.

The role of employee flexible spending accounts in health care financing.

PubMed

Schweitzer, M; Asch, D A

1996-08-01

Employee flexible spending accounts for health care represent one component of the current health care financing system that merits serious reform. These accounts create a system of undesirable incentives, force employees and employers to take complicated gambles, reduce tax revenues, and fail to meet their purported policy objectives. This paper describes shortcomings in these accounts from both a theoretical and an empirical perspective. Some proposed alternatives; including medical spending accounts and zero balance accounts, resolve many of these concerns but not all of them.

Effects of tongue force training on bulbar motor function in the female SOD1-G93A rat model of Amyotrophic Lateral Sclerosis

PubMed Central

Ma, Delin; Shuler, Jeffrey M.; Kumar, Aishwarya; Stanford, Quincy R.; Tungtur, Sudheer; Nishimune, Hiroshi; Stanford, John A.

2016-01-01

Background The use of exercise in Amyotrophic Lateral Sclerosis (ALS) is controversial. Although moderate exercise appears to be beneficial for limb muscles in ALS, the effects of exercise on bulbar muscles such as the tongue have not been studied. Objective The aim of this study was to determine the effects of tongue force training on bulbar motor function in the SOD1-G93A rat model of ALS. Methods We compared the effects of tongue force training on bulbar motor function and neuromuscular junction (NMJ) innervation in female SOD1-G93A rats and age-matched female wild-type controls. Half of each group underwent afternoon tongue force training sessions, while all rats were tested under minimal force conditions in the mornings. Results Tongue force did not differ between the SOD1-G93A rats and healthy controls during the morning testing sessions, nor was it affected by training. Surprisingly, decreases in tongue motility, the number of licks per session, and body weight were greater in the tongue force-trained SOD1-G93A rats. Forelimb grip force, survival, and denervation of the genioglossus muscle did not differ between the trained and untrained SOD1-G93A rats. Genioglossus innervation was correlated with changes in tongue force but not tongue motility in SOD1-G93A rats at end stage. Conclusions The results indicate a potential deleterious effect of tongue force training on tongue motility in female SOD1-G93A rats. The lack of relationship between genioglossus innervation and tongue motility suggest that factors other than lower motor neuron integrity likely accounted for this effect. PMID:27573800

The Changing Role of Women in the Rural Economy.

ERIC Educational Resources Information Center

O'Leary, Jeanne M.

Labor force participation of nonmetropolitan women rose in the 1970's but not in a consistent pattern. Their labor force participation rose 4.5% between 1973 and 1978, when they comprised 41% of the total nonmetropolitan labor force. Although women accounted for 89% of nonmetropolitan employment growth in the 1960's and 58% in the 1970's, their…

75 FR 78684 - Privacy Act of 1974; System of Records

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-16

... Department of the Air Force's notices for systems of records subject to the Privacy Act of 1974 (5 U.S.C... system: Air Force Active duty, Reserve and National Guard military personnel, government civilians, and... Regulations; 10 U.S.C. 8013, Secretary of the Air Force; 31 U.S.C. 3512, Executive agency accounting and other...

Control of thumb force using surface functional electrical stimulation and muscle load sharing

PubMed Central

2013-01-01

Background Stroke survivors often have difficulties in manipulating objects with their affected hand. Thumb control plays an important role in object manipulation. Surface functional electrical stimulation (FES) can assist movement. We aim to control the 2D thumb force by predicting the sum of individual muscle forces, described by a sigmoidal muscle recruitment curve and a single force direction. Methods Five able bodied subjects and five stroke subjects were strapped in a custom built setup. The forces perpendicular to the thumb in response to FES applied to three thumb muscles were measured. We evaluated the feasibility of using recruitment curve based force vector maps in predicting output forces. In addition, we developed a closed loop force controller. Load sharing between the three muscles was used to solve the redundancy problem having three actuators to control forces in two dimensions. The thumb force was controlled towards target forces of 0.5 N and 1.0 N in multiple directions within the individual’s thumb work space. Hereby, the possibilities to use these force vector maps and the load sharing approach in feed forward and feedback force control were explored. Results The force vector prediction of the obtained model had small RMS errors with respect to the actual measured force vectors (0.22±0.17 N for the healthy subjects; 0.17±0.13 N for the stroke subjects). The stroke subjects showed a limited work range due to limited force production of the individual muscles. Performance of feed forward control without feedback, was better in healthy subjects than in stroke subjects. However, when feedback control was added performances were similar between the two groups. Feedback force control lead, especially for the stroke subjects, to a reduction in stationary errors, which improved performance. Conclusions Thumb muscle responses to FES can be described by a single force direction and a sigmoidal recruitment curve. Force in desired direction can be generated through load sharing among redundant muscles. The force vector maps are subject specific and also suitable in feedforward and feedback control taking the individual’s available workspace into account. With feedback, more accurate control of muscle force can be achieved. PMID:24103414

Non-specific binding of Na+ and Mg2+ to RNA determined by force spectroscopy methods

PubMed Central

Bizarro, C. V.; Alemany, A.; Ritort, F.

2012-01-01

RNA duplex stability depends strongly on ionic conditions, and inside cells RNAs are exposed to both monovalent and multivalent ions. Despite recent advances, we do not have general methods to quantitatively account for the effects of monovalent and multivalent ions on RNA stability, and the thermodynamic parameters for secondary structure prediction have only been derived at 1M [Na+]. Here, by mechanically unfolding and folding a 20 bp RNA hairpin using optical tweezers, we study the RNA thermodynamics and kinetics at different monovalent and mixed monovalent/Mg2+ salt conditions. We measure the unfolding and folding rupture forces and apply Kramers theory to extract accurate information about the hairpin free energy landscape under tension at a wide range of ionic conditions. We obtain non-specific corrections for the free energy of formation of the RNA hairpin and measure how the distance of the transition state to the folded state changes with force and ionic strength. We experimentally validate the Tightly Bound Ion model and obtain values for the persistence length of ssRNA. Finally, we test the approximate rule by which the non-specific binding affinity of divalent cations at a given concentration is equivalent to that of monovalent cations taken at 100-fold concentration for small molecular constructs. PMID:22492710

Three-dimensional simulations of nanopowder compaction processes by granular dynamics method.

PubMed

Boltachev, G Sh; Lukyashin, K E; Shitov, V A; Volkov, N B

2013-07-01

In order to describe and to study the processes of cold compaction within the discrete element method a three-dimensional model of nanosized powder is developed. The elastic forces of repulsion, the tangential forces of "friction" (Cattaneo-Mindlin), and the dispersion forces of attraction (van der Waals-Hamaker), as well as the formation and destruction of hard bonds between the individual particles are taken into account. The monosized powders with the size of particles in the range 10-40 nm are simulated. The simulation results are compared to the experimental data of the alumina nanopowders compaction. It is shown that the model allows us to reproduce experimental data reliably and, in particular, describes the size effect in the compaction processes. A number of different external loading conditions is used in order to perform the theoretical and experimental researches. The uniaxial compaction (the closed-die compaction), the biaxial (radial) compaction, and the isotropic compaction (the cold isostatic pressing) are studied. The real and computed results are in a good agreement with each other. They reveal a weak sensitivity of the oxide nanopowders to the loading condition (compaction geometry). The application of the continuum theory of the plastically hardening porous body, which is usually used for the description of powders, is discussed.

Study of thermal and acoustic noise interferences in low stiffness atomic force microscope cantilevers and characterization of their dynamic properties.

PubMed

Boudaoud, Mokrane; Haddab, Yassine; Le Gorrec, Yann; Lutz, Philippe

2012-01-01

The atomic force microscope (AFM) is a powerful tool for the measurement of forces at the micro/nano scale when calibrated cantilevers are used. Besides many existing calibration techniques, the thermal calibration is one of the simplest and fastest methods for the dynamic characterization of an AFM cantilever. This method is efficient provided that the Brownian motion (thermal noise) is the most important source of excitation during the calibration process. Otherwise, the value of spring constant is underestimated. This paper investigates noise interference ranges in low stiffness AFM cantilevers taking into account thermal fluctuations and acoustic pressures as two main sources of noise. As a result, a preliminary knowledge about the conditions in which thermal fluctuations and acoustic pressures have closely the same effect on the AFM cantilever (noise interference) is provided with both theoretical and experimental arguments. Consequently, beyond the noise interference range, commercial low stiffness AFM cantilevers are calibrated in two ways: using the thermal noise (in a wide temperature range) and acoustic pressures generated by a loudspeaker. We then demonstrate that acoustic noises can also be used for an efficient characterization and calibration of low stiffness AFM cantilevers. The accuracy of the acoustic characterization is evaluated by comparison with results from the thermal calibration.

Three-dimensional simulations of nanopowder compaction processes by granular dynamics method

NASA Astrophysics Data System (ADS)

Boltachev, G. Sh.; Lukyashin, K. E.; Shitov, V. A.; Volkov, N. B.

2013-07-01

In order to describe and to study the processes of cold compaction within the discrete element method a three-dimensional model of nanosized powder is developed. The elastic forces of repulsion, the tangential forces of “friction” (Cattaneo-Mindlin), and the dispersion forces of attraction (van der Waals-Hamaker), as well as the formation and destruction of hard bonds between the individual particles are taken into account. The monosized powders with the size of particles in the range 10-40 nm are simulated. The simulation results are compared to the experimental data of the alumina nanopowders compaction. It is shown that the model allows us to reproduce experimental data reliably and, in particular, describes the size effect in the compaction processes. A number of different external loading conditions is used in order to perform the theoretical and experimental researches. The uniaxial compaction (the closed-die compaction), the biaxial (radial) compaction, and the isotropic compaction (the cold isostatic pressing) are studied. The real and computed results are in a good agreement with each other. They reveal a weak sensitivity of the oxide nanopowders to the loading condition (compaction geometry). The application of the continuum theory of the plastically hardening porous body, which is usually used for the description of powders, is discussed.

Forced-Choice Assessment of Work-Related Maladaptive Personality Traits: Preliminary Evidence From an Application of Thurstonian Item Response Modeling.

PubMed

Guenole, Nigel; Brown, Anna A; Cooper, Andrew J

2018-06-01

This article describes an investigation of whether Thurstonian item response modeling is a viable method for assessment of maladaptive traits. Forced-choice responses from 420 working adults to a broad-range personality inventory assessing six maladaptive traits were considered. The Thurstonian item response model's fit to the forced-choice data was adequate, while the fit of a counterpart item response model to responses to the same items but arranged in a single-stimulus design was poor. Monotrait heteromethod correlations indicated corresponding traits in the two formats overlapped substantially, although they did not measure equivalent constructs. A better goodness of fit and higher factor loadings for the Thurstonian item response model, coupled with a clearer conceptual alignment to the theoretical trait definitions, suggested that the single-stimulus item responses were influenced by biases that the independent clusters measurement model did not account for. Researchers may wish to consider forced-choice designs and appropriate item response modeling techniques such as Thurstonian item response modeling for personality questionnaire applications in industrial psychology, especially when assessing maladaptive traits. We recommend further investigation of this approach in actual selection situations and with different assessment instruments.

Higher Education Counts: Accountability Measures for the New Millennium. 2005 Report

ERIC Educational Resources Information Center

Connecticut Department of Higher Education (NJ1), 2005

2005-01-01

"Higher Education Counts" is the annual accountability report on Connecticut's state system of higher education, as required under Connecticut General Statutes Section 10a-6a. The report contains accountability measures developed through the Performance Measures Task Force and approved by the Board of Governors for Higher Education. The…

Model for Efficient and Effective Footnote Disclosure in Pedagogical and Practitioner Application

ERIC Educational Resources Information Center

Bullen, Maria L.; Kordecki, Gregory S.

2014-01-01

In the U.S. and in other countries, accounting graduates continue to enter diverse size work forces in industry, government, and in public accounting. Beyond income tax and consulting work, accounting professionals often require a specific association with financial statement services. These services involve not only detailed scheduled financial…

An Observational Assessment of Accountability Systems for Our "Handicapped" Students and Their Impact on Educators.

ERIC Educational Resources Information Center

Kunzweiler, Charles

1981-01-01

Present systems of accountability, which require excessive paperwork and force teachers into the "Directive Teaching Model," cause special education teachers to be accountable to the system rather than to self-actualization needs of students. Special education teachers must have the freedom and training to create "unique"…

Understanding the interplay of weak forces in [3,3]-sigmatropic rearrangement for stereospecific synthesis of diamines.

PubMed

So, Soon Mog; Mui, Leo; Kim, Hyunwoo; Chin, Jik

2012-08-21

Chiral diamines are important building blocks for constructing stereoselective catalysts, including transition metal based catalysts and organocatalysts that facilitate oxidation, reduction, hydrolysis, and C-C bond forming reactions. These molecules are also critical components in the synthesis of drugs, including antiviral agents such as Tamiflu and Relenza and anticancer agents such as oxaliplatin and nutlin-3. The diaza-Cope rearrangement reaction provides one of the most versatile methods for rapidly generating a wide variety of chiral diamines stereospecifically and under mild conditions. Weak forces such as hydrogen bonding, electronic, steric, oxyanionic, and conjugation effects can drive this equilibrium process to completion. In this Account, we examine the effect of these individual weak forces on the value of the equilibrium constant for the diaza-Cope rearrangement reaction using both computational and experimental methods. The availability of a wide variety of aldehydes and diamines allows for the facile synthesis of the diimines needed to study the weak forces. Furthermore, because the reaction generally takes place cleanly at ambient temperature, we can easily measure equilibrium constants for rearrangement of the diimines. We use the Hammett equation to further examine the electronic and oxyanionic effects. In addition, computations and experiments provide us with new insights into the origin and extent of stereospecificity for this rearrangement reaction. The diaza-Cope rearrangement, with its unusual interplay between weak forces and the equilibrium constant of the reaction, provides a rare opportunity to study the effects of the fundamental weak forces on a chemical reaction. Among these many weak forces that affect the diaza-Cope rearrangement, the anion effect is the strongest (10.9 kcal/mol) followed by the resonance-assisted hydrogen-bond effect (7.1 kcal/mol), the steric effect (5.7 kcal/mol), the conjugation effect (5.5 kcal/mol), and the electronic effect (3.2 kcal/mol). Based on both computation and experimental data, the effects of these weak forces are additive. Understanding the interplay of the weak forces in the [3,3]-sigmatropic reaction is interesting in its own right and also provides valuable insights for the synthesis of chiral diamine based drugs and catalysts in excellent yield and enantiopurity.

Bifurcation, chaos, and scan instability in dynamic atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cantrell, John H., E-mail: john.h.cantrell@nasa.gov; Cantrell, Sean A., E-mail: scantrell@nlsanalytics.com

The dynamical motion at any point on the cantilever of an atomic force microscope can be expressed quite generally as a superposition of simple harmonic oscillators corresponding to the vibrational modes allowed by the cantilever shape. Central to the dynamical equations is the representation of the cantilever-sample interaction force as a polynomial expansion with coefficients that account for the interaction force “stiffness,” the cantilever-to-sample energy transfer, and the displacement amplitude of cantilever oscillation. Renormalization of the cantilever beam model shows that for a given cantilever drive frequency cantilever dynamics can be accurately represented by a single nonlinear mass-spring model withmore » frequency-dependent stiffness and damping coefficients [S. A. Cantrell and J. H. Cantrell, J. Appl. Phys. 110, 094314 (2011)]. Application of the Melnikov method to the renormalized dynamical equation is shown to predict a cascade of period doubling bifurcations with increasing cantilever drive force that terminates in chaos. The threshold value of the drive force necessary to initiate bifurcation is shown to depend strongly on the cantilever setpoint and drive frequency, effective damping coefficient, nonlinearity of the cantilever-sample interaction force, and the displacement amplitude of cantilever oscillation. The model predicts the experimentally observed interruptions of the bifurcation cascade for cantilevers of sufficiently large stiffness. Operational factors leading to the loss of image quality in dynamic atomic force microscopy are addressed, and guidelines for optimizing scan stability are proposed using a quantitative analysis based on system dynamical parameters and choice of feedback loop parameter.« less

Aerodynamic vibrations of a maglev vehicle running on flexible guideways under oncoming wind actions

NASA Astrophysics Data System (ADS)

Yau, J. D.

2010-05-01

This paper intends to present a computational framework of aerodynamic analysis for a maglev (magnetically levitated) vehicle traveling over flexible guideways under oncoming wind loads. The guideway unit is simulated as a series of simple beams with identical span and the maglev vehicle as a rigid car body supported by levitation forces. To carry out the interaction dynamics of maglev vehicle/guideway system, this study adopts an onboard PID (proportional-integral-derivative) controller based on Ziegler-Nicholas (Z-N) method to control the levitation forces. Interaction of wind with high-speed train is a complicated situation arising from unsteady airflow around the train. In this study, the oncoming wind loads acting on the running maglev vehicle are generated in temporal/spatial domain using digital simulation techniques that can account for the moving effect of vehicle's speed and the spatial correlation of stochastic airflow velocity field. Considering the motion-dependent nature of levitation forces and the non-conservative characteristics of turbulent airflows, an iterative approach is used to compute the interaction response of the maglev vehicle/guideway coupling system under wind actions. For the purpose of numerical simulation, this paper employs Galerkin's method to convert the governing equations containing a maglev vehicle into a set of differential equations in generalized systems, and then solve the two sets of differential equations using an iterative approach with the Newmark method. From the present investigation, the aerodynamic forces may result in a significant amplification on acceleration amplitude of the running maglev vehicle at higher speeds. For this problem, a PID+LQR (linear quadratic regulator) controller is proposed to reduce the vehicle's acceleration response for the ride comfort of passengers.

The importance of cantilever dynamics in the interpretation of Kelvin probe force microscopy.

PubMed

Satzinger, Kevin J; Brown, Keith A; Westervelt, Robert M

2012-09-15

A realistic interpretation of the measured contact potential difference (CPD) in Kelvin probe force microscopy (KPFM) is crucial in order to extract meaningful information about the sample. Central to this interpretation is a method to include contributions from the macroscopic cantilever arm, as well as the cone and sharp tip of a KPFM probe. Here, three models of the electrostatic interaction between a KPFM probe and a sample are tested through an electrostatic simulation and compared with experiment. In contrast with previous studies that treat the KPFM cantilever as a rigid object, we allow the cantilever to bend and rotate; accounting for cantilever bending provides the closest agreement between theory and experiment. We demonstrate that cantilever dynamics play a major role in CPD measurements and provide a simulation technique to explore this phenomenon.

Strong quantum squeezing near the pull-in instability of a nonlinear beam

DOE PAGES

Passian, Ali; Siopsis, George

2016-08-04

Microscopic silicon-based suspended mechanical oscillators, constituting an extremely sensitive force probe, transducer, and actuator, are being increasingly employed in many developing microscopies, spectroscopies, and emerging optomechanical and chem-bio sensors. Here, we predict a significant squeezing in the quantum state of motion of an oscillator constrained as a beam and subject to an electrically induced nonlinearity. When we take into account the quantum noise, the underlying nonlinear dynamics is investigated in both the transient and stationary regimes of the driving force leading to the finding that strongly squeezed states are accessible in the vicinity of the pull-in instability of the oscillator.more » We discuss a possible application of this strong quantum squeezing as an optomechanical method for detecting broad-spectrum single or low-count photons, and further suggest other novel sensing actions.« less

First-principles simulations of electrostatic interactions between dust grains

NASA Astrophysics Data System (ADS)

Itou, H.; Amano, T.; Hoshino, M.

2014-12-01

We investigated the electrostatic interaction between two identical dust grains of an infinite mass immersed in homogeneous plasma by employing first-principles N-body simulations combined with the Ewald method. We specifically tested the possibility of an attractive force due to overlapping Debye spheres (ODSs), as was suggested by Resendes et al. [Phys. Lett. A 239, 181-186 (1998)]. Our simulation results demonstrate that the electrostatic interaction is repulsive and even stronger than the standard Yukawa potential. We showed that the measured electric field acting on the grain is highly consistent with a model electrostatic potential around a single isolated grain that takes into account a correction due to the orbital motion limited theory. Our result is qualitatively consistent with the counterargument suggested by Markes and Williams [Phys. Lett. A 278, 152-158 (2000)], indicating the absence of the ODS attractive force.

Dynamic analysis of elastic rubber tired car wheel breaking under variable normal load

NASA Astrophysics Data System (ADS)

Fedotov, A. I.; Zedgenizov, V. G.; Ovchinnikova, N. I.

2017-10-01

The purpose of the paper is to analyze the dynamics of the braking of the wheel under normal load variations. The paper uses a mathematical simulation method according to which the calculation model of an object as a mechanical system is associated with a dynamically equivalent schematic structure of the automatic control. Transfer function tool analyzing structural and technical characteristics of an object as well as force disturbances were used. It was proved that the analysis of dynamic characteristics of the wheel subjected to external force disturbances has to take into account amplitude and phase-frequency characteristics. Normal load variations impact car wheel braking subjected to disturbances. The closer slip to the critical point is, the higher the impact is. In the super-critical area, load variations cause fast wheel blocking.

Three-dimensional unsteady Euler equations solutions on dynamic grids

NASA Technical Reports Server (NTRS)

Belk, D. M.; Janus, J. M.; Whitfield, D. L.

1985-01-01

A method is presented for solving the three-dimensional unsteady Euler equations on dynamic grids based on flux vector splitting. The equations are cast in curvilinear coordinates and a finite volume discretization is used for handling arbitrary geometries. The discretized equations are solved using an explicit upwind second-order predictor corrector scheme that is stable for a CFL of 2. Characteristic variable boundary conditions are developed and used for unsteady impermeable surfaces and for the far-field boundary. Dynamic-grid results are presented for an oscillating air-foil and for a store separating from a reflection plate. For the cases considered of stores separating from a reflection plate, the unsteady aerodynamic forces on the store are significantly different from forces obtained by steady-state aerodynamics with the body inclination angle changed to account for plunge velocity.

An accurate ab initio quartic force field for ammonia

NASA Technical Reports Server (NTRS)

Martin, J. M. L.; Lee, Timothy J.; Taylor, Peter R.

1992-01-01

The quartic force field of ammonia is computed using basis sets of spdf/spd and spdfg/spdf quality and an augmented coupled cluster method. After correcting for Fermi resonance, the computed fundamentals and nu 4 overtones agree on average to better than 3/cm with the experimental ones except for nu 2. The discrepancy for nu 2 is principally due to higher-order anharmonicity effects. The computed omega 1, omega 3, and omega 4 confirm the recent experimental determination by Lehmann and Coy (1988) but are associated with smaller error bars. The discrepancy between the computed and experimental omega 2 is far outside the expected error range, which is also attributed to higher-order anharmonicity effects not accounted for in the experimental determination. Spectroscopic constants are predicted for a number of symmetric and asymmetric top isotopomers of NH3.

Results of the first complete static calibration of the RSRA rotor-load-measurement system

NASA Technical Reports Server (NTRS)

Acree, C. W., Jr.

1984-01-01

The compound Rotor System Research Aircraft (RSRA) is designed to make high-accuracy, simultaneous measurements of all rotor forces and moments in flight. Physical calibration of the rotor force- and moment-measurement system when installed in the aircraft is required to account for known errors and to ensure that measurement-system accuracy is traceable to the National Bureau of Standards. The first static calibration and associated analysis have been completed with good results. Hysteresis was a potential cause of static calibration errors, but was found to be negligible in flight compared to full-scale loads, and analytical methods have been devised to eliminate hysteresis effects on calibration data. Flight tests confirmed that the calibrated rotor-load-measurement system performs as expected in flight and that it can dependably make direct measurements of fuselage vertical drag in hover.

Density-Functional Theory with Dispersion-Correcting Potentials for Methane: Bridging the Efficiency and Accuracy Gap between High-Level Wave Function and Classical Molecular Mechanics Methods.

PubMed

Torres, Edmanuel; DiLabio, Gino A

2013-08-13

Large clusters of noncovalently bonded molecules can only be efficiently modeled by classical mechanics simulations. One prominent challenge associated with this approach is obtaining force-field parameters that accurately describe noncovalent interactions. High-level correlated wave function methods, such as CCSD(T), are capable of correctly predicting noncovalent interactions, and are widely used to produce reference data. However, high-level correlated methods are generally too computationally costly to generate the critical reference data required for good force-field parameter development. In this work we present an approach to generate Lennard-Jones force-field parameters to accurately account for noncovalent interactions. We propose the use of a computational step that is intermediate to CCSD(T) and classical molecular mechanics, that can bridge the accuracy and computational efficiency gap between them, and demonstrate the efficacy of our approach with methane clusters. On the basis of CCSD(T)-level binding energy data for a small set of methane clusters, we develop methane-specific, atom-centered, dispersion-correcting potentials (DCPs) for use with the PBE0 density-functional and 6-31+G(d,p) basis sets. We then use the PBE0-DCP approach to compute a detailed map of the interaction forces associated with the removal of a single methane molecule from a cluster of eight methane molecules and use this map to optimize the Lennard-Jones parameters for methane. The quality of the binding energies obtained by the Lennard-Jones parameters we obtained is assessed on a set of methane clusters containing from 2 to 40 molecules. Our Lennard-Jones parameters, used in combination with the intramolecular parameters of the CHARMM force field, are found to closely reproduce the results of our dispersion-corrected density-functional calculations. The approach outlined can be used to develop Lennard-Jones parameters for any kind of molecular system.

A numerical method for simulations of rigid fiber suspensions

NASA Astrophysics Data System (ADS)

Tornberg, Anna-Karin; Gustavsson, Katarina

2006-06-01

In this paper, we present a numerical method designed to simulate the challenging problem of the dynamics of slender fibers immersed in an incompressible fluid. Specifically, we consider microscopic, rigid fibers, that sediment due to gravity. Such fibers make up the micro-structure of many suspensions for which the macroscopic dynamics are not well understood. Our numerical algorithm is based on a non-local slender body approximation that yields a system of coupled integral equations, relating the forces exerted on the fibers to their velocities, which takes into account the hydrodynamic interactions of the fluid and the fibers. The system is closed by imposing the constraints of rigid body motions. The fact that the fibers are straight have been further exploited in the design of the numerical method, expanding the force on Legendre polynomials to take advantage of the specific mathematical structure of a finite-part integral operator, as well as introducing analytical quadrature in a manner possible only for straight fibers. We have carefully treated issues of accuracy, and present convergence results for all numerical parameters before we finally discuss the results from simulations including a larger number of fibers.

Specific and Non-Specific Protein Association in Solution: Computation of Solvent Effects and Prediction of First-Encounter Modes for Efficient Configurational Bias Monte Carlo Simulations

PubMed Central

Cardone, Antonio; Pant, Harish; Hassan, Sergio A.

2013-01-01

Weak and ultra-weak protein-protein association play a role in molecular recognition, and can drive spontaneous self-assembly and aggregation. Such interactions are difficult to detect experimentally, and are a challenge to the force field and sampling technique. A method is proposed to identify low-population protein-protein binding modes in aqueous solution. The method is designed to identify preferential first-encounter complexes from which the final complex(es) at equilibrium evolves. A continuum model is used to represent the effects of the solvent, which accounts for short- and long-range effects of water exclusion and for liquid-structure forces at protein/liquid interfaces. These effects control the behavior of proteins in close proximity and are optimized based on binding enthalpy data and simulations. An algorithm is described to construct a biasing function for self-adaptive configurational-bias Monte Carlo of a set of interacting proteins. The function allows mixing large and local changes in the spatial distribution of proteins, thereby enhancing sampling of relevant microstates. The method is applied to three binary systems. Generalization to multiprotein complexes is discussed. PMID:24044772

Review of Superelastic Differential Force Archwires for Producing Ideal Orthodontic Forces: an Advanced Technology Potentially Applicable to Orthognathic Surgery and Orthopedics.

PubMed

Kuntz, Michael L; Vadori, Ryan; Khan, M Ibraheem

2018-06-20

Gentle and continuous loads are preferred for optimum orthodontic tooth movement. Nitinol, an alloy of nickel and titanium developed for the aerospace industry, found its first clinical applications in orthodontics because it has ideal load-deflection behavior. The purpose of this review is to elucidate the criteria for effective orthodontic mechanics relative to emerging Nitinol technology. The specialized materials with variable stiffness that were originally developed for orthodontics are increasingly attractive for in the temporomandibular joint, orthognathic surgery, and orthopedics. The evolution of orthodontic archwires is driven by a need to achieve low load-deflection characteristics and Nitinol is the alloy of choice. Scientific knowledge of the biological response to orthodontic forces continues to grow, but definitive guidance on optimal force levels for individual teeth is elusive. Finite element models (FEM) that take into account periodontal ligament (PDL) stresses indicate differential force archwires are needed to realize optimal treatment. However, previous wire fabrication methods, including welding of different materials and selective resistive heating, are limited by poor mechanical performance and spatial resolution. Recently, a novel laser processing technique was developed for precisely programing relative levels of stiffness in a single archwire. FEM was used to estimate the optimal force for each tooth by calculating the 3D bone-PDL surface area. There remains a general consensus that light and continuous forces are desirable for orthodontic treatment. New developments in archwire materials and technology have provided the orthodontist with a complete spectrum of load-deflection rates and differential force options to express these forces with maximized archwire economy. These technologies also appear to have application to orthopedic implant devices.

Simplification of the Kalman filter for meteorological data assimilation

NASA Technical Reports Server (NTRS)

Dee, Dick P.

1991-01-01

The paper proposes a new statistical method of data assimilation that is based on a simplification of the Kalman filter equations. The forecast error covariance evolution is approximated simply by advecting the mass-error covariance field, deriving the remaining covariances geostrophically, and accounting for external model-error forcing only at the end of each forecast cycle. This greatly reduces the cost of computation of the forecast error covariance. In simulations with a linear, one-dimensional shallow-water model and data generated artificially, the performance of the simplified filter is compared with that of the Kalman filter and the optimal interpolation (OI) method. The simplified filter produces analyses that are nearly optimal, and represents a significant improvement over OI.

Oscillations of a sessile droplet in open air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korenchenko, A. E., E-mail: korenchenko@physics.susu.ac.ru; Beskachko, V. P.

2013-11-15

The open system consisting of a sessile drop, a neutral gas, and a substrate is analyzed by numerical methods. The mode with constant contact angle is considered. The model takes into account evaporation from drop surface, free and forced convection in gas, buoyancy, and Marangoni effect in the liquid phase. It was established that every considered mechanical and thermodynamical disturbance of the system leads to the drop surface oscillations, and thus a drop in an open air oscillates almost inevitably. The displacement of the liquid-gas interface due to oscillations is analyzed in terms of its impact on the accuracy ofmore » measurement of the surface tension by sessile drop method.« less

26 CFR 301.7654-1 - Coordination of U.S. and Guam individual income taxes.

Code of Federal Regulations, 2011 CFR

2011-04-01

... Armed Forces of the United States, the special procedure agreed upon with the Department of Defense in... taxpayer shall be determined by taking into account any compensation of any member of the Armed Forces for... any member of the Armed Forces described in paragraph (a)(2) of this section which is paid to Guam...

Non-perturbative theory of dispersion interactions

NASA Astrophysics Data System (ADS)

Boström, M.; Thiyam, P.; Persson, C.; Parsons, D. F.; Buhmann, S. Y.; Brevik, I.; Sernelius, Bo E.

2015-03-01

Some open questions exist with fluctuation-induced forces between extended dipoles. Conventional intuition derives from large-separation perturbative approximations to dispersion force theory. Here, we present a full non-perturbative theory. In addition, we discuss how one can take into account finite dipole size corrections. It is of fundamental value to investigate the limits of validity of the perturbative dispersion force theory.

Daylighting Strategies for U. S. Air Force Office Facilities: Economic Analysis of Building Energy Performance and Life-Cycle Cost Modeling with Monte Carlo Method

DTIC Science & Technology

2009-03-26

annually ( McHugh , et al., 1998). USAF has used daylighting as an energy savings strategy in earlier studies (Holtz, 1990); and is pursuing it to meet...using renewable energy to generate electricity ( McHugh , et al., 1998). For example, traditional utility systems that are straining to meet peak...1998) found that lighting accounts for 40-50% of commercial energy consumption and McHugh , Burns, and Hittle (1998) stated that electric lighting and

Oscillatory flow in a cone-and-plate bioreactor.

PubMed

Chung, C A; Tzou, M R; Ho, R W

2005-08-01

Motivated by biometric applications, we analyze oscillatory flow in a cone-and-plate geometry. The cone is rotated in a simple harmonic way on a stationary plate. Based on assuming that the angle between the cone and plate is small, we describe the flow analytically by a perturbation method in terms of two small parameters, the Womersley number and the Reynolds number, which account for the influences of the local acceleration and centripetal force, respectively. Working equations for the shear stresses induced both by laminar primary and secondary flows on the plate surface are presented.

Numerical simulation and prediction of coastal ocean circulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, P.

1992-01-01

Numerical simulation and prediction of coastal ocean circulation have been conducted in three cases. 1. A process-oriented modeling study is conducted to study the interaction of a western boundary current (WBC) with coastal water, and its responses to upstream topographic irregularities. It is hypothesized that the interaction of propagating WBC frontal waves and topographic Rossby waves are responsible for upstream variability. 2. A simulation of meanders and eddies in the Norwegian Coastal Current (NCC) for February and March of 1988 is conducted with a newly developed nested dynamic interactive model. The model employs a coarse-grid, large domain to account formore » non-local forcing and a fine-grid nested domain to resolve meanders and eddies. The model is forced by wind stresses, heat fluxes and atmospheric pressure corresponding Feb/March of 1988, and accounts for river/fjord discharges, open ocean inflow and outflow, and M[sub 2] tides. The simulation reproduced fairly well the observed circulation, tides, and salinity features in the North Sea, Norwegian Trench and NCC region in the large domain and fairly realistic meanders and eddies in the NCC in the nested region. 3. A methodology for practical coastal ocean hindcast/forecast is developed, taking advantage of the disparate time scales of various forcing and considering wind to be the dominant factor in affecting density fluctuation in the time scale of 1 to 10 days. The density field obtained from a prognostic simulation is analyzed by the empirical orthogonal function method (EOF), and correlated with the wind; these information are then used to drive a circulation model which excludes the density calculation. The method is applied to hindcast the circulation in the New York Bight for spring and summer season of 1988. The hindcast fields compare favorably with the results obtained from the prognostic circulation model.« less

Influence of polygonal wear of railway wheels on the wheel set axle stress

NASA Astrophysics Data System (ADS)

Wu, Xingwen; Chi, Maoru; Wu, Pingbo

2015-11-01

The coupled vehicle/track dynamic model with the flexible wheel set was developed to investigate the effects of polygonal wear on the dynamic stresses of the wheel set axle. In the model, the railway vehicle was modelled by the rigid multibody dynamics. The wheel set was established by the finite element method to analyse the high-frequency oscillation and dynamic stress of wheel set axle induced by the polygonal wear based on the modal stress recovery method. The slab track model was taken into account in which the rail was described by the Timoshenko beam and the three-dimensional solid finite element was employed to establish the concrete slab. Furthermore, the modal superposition method was adopted to calculate the dynamic response of the track. The wheel/rail normal forces and the tangent forces were, respectively, determined by the Hertz nonlinear contact theory and the Shen-Hedrick-Elkins model. Using the coupled vehicle/track dynamic model, the dynamic stresses of wheel set axle with consideration of the ideal polygonal wear and measured polygonal wear were investigated. The results show that the amplitude of wheel/rail normal forces and the dynamic stress of wheel set axle increase as the vehicle speeds rise. Moreover, the impact loads induced by the polygonal wear could excite the resonance of wheel set axle. In the resonance region, the amplitude of the dynamic stress for the wheel set axle would increase considerably comparing with the normal conditions.

A new class of actuator surface models for wind turbines

NASA Astrophysics Data System (ADS)

Yang, Xiaolei; Sotiropoulos, Fotis

2018-05-01

Actuator line model has been widely employed in wind turbine simulations. However, the standard actuator line model does not include a model for the turbine nacelle which can significantly impact turbine wake characteristics as shown in the literature. Another disadvantage of the standard actuator line model is that more geometrical features of turbine blades cannot be resolved on a finer mesh. To alleviate these disadvantages of the standard model, we develop a new class of actuator surface models for turbine blades and nacelle to take into account more geometrical details of turbine blades and include the effect of turbine nacelle. In the actuator surface model for blade, the aerodynamic forces calculated using the blade element method are distributed from the surface formed by the foil chords at different radial locations. In the actuator surface model for nacelle, the forces are distributed from the actual nacelle surface with the normal force component computed in the same way as in the direct forcing immersed boundary method and the tangential force component computed using a friction coefficient and a reference velocity of the incoming flow. The actuator surface model for nacelle is evaluated by simulating the flow over periodically placed nacelles. Both the actuator surface simulation and the wall-resolved large-eddy simulation are carried out. The comparison shows that the actuator surface model is able to give acceptable results especially at far wake locations on a very coarse mesh. It is noted that although this model is employed for the turbine nacelle in this work, it is also applicable to other bluff bodies. The capability of the actuator surface model in predicting turbine wakes is assessed by simulating the flow over the MEXICO (Model experiments in Controlled Conditions) turbine and a hydrokinetic turbine.

Effect of the tidal-seismic resonance

NASA Astrophysics Data System (ADS)

Tian, Y.; Zheng, Y.

2017-12-01

For a moon spiraling inward to its planet, the tidal force frequency of a moon is increasing. When the distance of the moon to the planet is close enough, the tidal force frequency can intrude into the frequency range of planet normal modes. Usually the football mode, also known as 0S2, has the lowest frequency. This mode is most likely to be excited and coupled first. When the tidal force has the same frequency with the normal modes, the resonance can happen. The existence of the topography or internal heterogeneities of the planet can have mode coupling. So the energy of gravity force with higher spatial frequencies can be transferred to the low spatial 0S2 mode. The resonant mode 0S2 can exert a negative torque to the rotating moon so its orbit decays. With our 3D numerical boundary element method which takes into account planet surface topography (i.e., Mars as example), we found that the closer the moon is to the planet, the greater falling rate of the moon would be. We applied our method to a planet with equal size of Mars and elastic constants in possible range. The vibration amplitude on the planet surface can reach to the scale of meters when as the moon drop down to about 1.04 radius of the planet to achieve resonance with the 0S2 mode. Our modeling showed that the influence of tidal force caused resonance could not be neglected in the process of moon falling. On the other hand, the resonance may also be able to speed up the accretion of the early forming planet by absorbing the dust of small asteroid nearby by the tidal-seismic resonance.

A second-order accurate immersed boundary-lattice Boltzmann method for particle-laden flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Qiang; Fan, Liang-Shih, E-mail: fan.1@osu.edu

A new immersed boundary-lattice Boltzmann method (IB-LBM) is presented for fully resolved simulations of incompressible viscous flows laden with rigid particles. The immersed boundary method (IBM) recently developed by Breugem (2012) [19] is adopted in the present method, development including the retraction technique, the multi-direct forcing method and the direct account of the inertia of the fluid contained within the particles. The present IB-LBM is, however, formulated with further improvement with the implementation of the high-order Runge–Kutta schemes in the coupled fluid–particle interaction. The major challenge to implement high-order Runge–Kutta schemes in the LBM is that the flow information suchmore » as density and velocity cannot be directly obtained at a fractional time step from the LBM since the LBM only provides the flow information at an integer time step. This challenge can be, however, overcome as given in the present IB-LBM by extrapolating the flow field around particles from the known flow field at the previous integer time step. The newly calculated fluid–particle interactions from the previous fractional time steps of the current integer time step are also accounted for in the extrapolation. The IB-LBM with high-order Runge–Kutta schemes developed in this study is validated by several benchmark applications. It is demonstrated, for the first time, that the IB-LBM has the capacity to resolve the translational and rotational motion of particles with the second-order accuracy. The optimal retraction distances for spheres and tubes that help the method achieve the second-order accuracy are found to be around 0.30 and −0.47 times of the lattice spacing, respectively. Simulations of the Stokes flow through a simple cubic lattice of rotational spheres indicate that the lift force produced by the Magnus effect can be very significant in view of the magnitude of the drag force when the practical rotating speed of the spheres is encountered. This finding may lead to more comprehensive studies of the effect of the particle rotation on fluid–solid drag laws. It is also demonstrated that, when the third-order or the fourth-order Runge–Kutta scheme is used, the numerical stability of the present IB-LBM is better than that of all methods in the literature, including the previous IB-LBMs and also the methods with the combination of the IBM and the traditional incompressible Navier–Stokes solver. - Highlights: • The IBM is embedded in the LBM using Runge–Kutta time schemes. • The effectiveness of the present IB-LBM is validated by benchmark applications. • For the first time, the IB-LBM achieves the second-order accuracy. • The numerical stability of the present IB-LBM is better than previous methods.« less

Understanding and Improving Depot Level Reparable Pricing for Air Force Systems

DTIC Science & Technology

1997-03-01

Horngren , “ Cost Accounting and Cost ...T. Horngren , “ Cost Accounting and Cost Management in a JIT Environment”, Journal of Cost Management, Winter, 1988. 16Margaret L. Gagne and Richard...Charles T. Horngren . “ Cost Accounting and Cost Management in a JIT Environment.” Journal of Cost Management (Winter, 1988). Gagne, Margaret L.

Graphene thickness dependent adhesion force and its correlation to surface roughness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pourzand, Hoorad; Tabib-Azar, Massood, E-mail: azar.m@utah.edu; Biomedical Engineering, University of Utah, Salt Lake City, Utah 84112

2014-04-28

In this paper, adhesion force of graphene layers on 300 nm silicon oxide is studied. A simple model for measuring adhesion force for a flat surface with sub-nanometer roughness was developed and is shown that small surface roughness decreases adhesion force while large roughness results in an effectively larger adhesion forces. We also show that surface roughness over scales comparable to the tip radius increase by nearly a factor of two, the effective adhesion force measured by the atomic force microscopy. Thus, we demonstrate that surface roughness is an important parameter that should be taken into account in analyzing the adhesionmore » force measurement results.« less

The prior conceptions about force and motion held by grade 8 students in educational opportunity expansion schools of Thailand

NASA Astrophysics Data System (ADS)

Buaraphan, Khajornsak

2018-01-01

According to the constructivist theory, students' prior conceptions play an important role in their process of knowledge construction and teachers must take those prior conceptions into account when designing learning activities. The interpretive study was conducted to explore grade 8 students' conceptions about force and motion. The research participants were 42 students (21 male, 21 female) from seven Educational Opportunity Expansion Schools in Nakhon Pathom province located at the central region of Thailand. In each school, two low, two medium and two high achievers were selected. The Interview-About-Instance (IAI) technique was used to collect data. All interviews were audio recorded and subsequently transcribed verbatim. The students' conceptions were interpreted into scientific conception (SC), partial scientific conception (PC) and alternative conception (AC). The frequency of each category was counted and calculated for percentage. The results revealed that the students held a variety of prior conceptions about force and motion ranged from SC, PC to AC. Each students, including the high achievers, held mixed conceptions of force and motion. Interesting, the two dominant ACs held by the students were: a) force-implies-motion or motion-implies-force, and b) force coming only from an active agent. The science teachers need to take these ACs into account when designing the learning activities to cope with them. The implications regarding teaching and learning about force and motion are also discussed.

Quasi-steady aerodynamic model of clap-and-fling flapping MAV and validation using free-flight data.

PubMed

Armanini, S F; Caetano, J V; Croon, G C H E de; Visser, C C de; Mulder, M

2016-06-30

Flapping-wing aerodynamic models that are accurate, computationally efficient and physically meaningful, are challenging to obtain. Such models are essential to design flapping-wing micro air vehicles and to develop advanced controllers enhancing the autonomy of such vehicles. In this work, a phenomenological model is developed for the time-resolved aerodynamic forces on clap-and-fling ornithopters. The model is based on quasi-steady theory and accounts for inertial, circulatory, added mass and viscous forces. It extends existing quasi-steady approaches by: including a fling circulation factor to account for unsteady wing-wing interaction, considering real platform-specific wing kinematics and different flight regimes. The model parameters are estimated from wind tunnel measurements conducted on a real test platform. Comparison to wind tunnel data shows that the model predicts the lift forces on the test platform accurately, and accounts for wing-wing interaction effectively. Additionally, validation tests with real free-flight data show that lift forces can be predicted with considerable accuracy in different flight regimes. The complete parameter-varying model represents a wide range of flight conditions, is computationally simple, physically meaningful and requires few measurements. It is therefore potentially useful for both control design and preliminary conceptual studies for developing new platforms.

Patient accounting: vital for financial survival.

PubMed

Puhala, J M; Barrett, M J

1987-09-01

The implementation of the prospective payment system has affected the financial stability of hospitals. It has forced them to take a closer look at their patient accounting function as it affects cash flow and patient service revenue. This article addresses several new issues relating to patient accounts processing that have created a need for more emphasis on the patient accounting function. Efficient operations and effective accounts receivable management may be the difference between the success or failure of a hospital in today's competitive environment.

Dynamics of cell shape and forces on micropatterned substrates predicted by a cellular Potts model.

PubMed

Albert, Philipp J; Schwarz, Ulrich S

2014-06-03

Micropatterned substrates are often used to standardize cell experiments and to quantitatively study the relation between cell shape and function. Moreover, they are increasingly used in combination with traction force microscopy on soft elastic substrates. To predict the dynamics and steady states of cell shape and forces without any a priori knowledge of how the cell will spread on a given micropattern, here we extend earlier formulations of the two-dimensional cellular Potts model. The third dimension is treated as an area reservoir for spreading. To account for local contour reinforcement by peripheral bundles, we augment the cellular Potts model by elements of the tension-elasticity model. We first parameterize our model and show that it accounts for momentum conservation. We then demonstrate that it is in good agreement with experimental data for shape, spreading dynamics, and traction force patterns of cells on micropatterned substrates. We finally predict shapes and forces for micropatterns that have not yet been experimentally studied. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Chaos, Fractals and Their Applications

NASA Astrophysics Data System (ADS)

Thompson, J. Michael T.

2016-12-01

This paper gives an up-to-date account of chaos and fractals, in a popular pictorial style for the general scientific reader. A brief historical account covers the development of the subject from Newton’s laws of motion to the astronomy of Poincaré and the weather forecasting of Lorenz. Emphasis is given to the important underlying concepts, embracing the fractal properties of coastlines and the logistics of population dynamics. A wide variety of applications include: NASA’s discovery and use of zero-fuel chaotic “superhighways” between the planets; erratic chaotic solutions generated by Euler’s method in mathematics; atomic force microscopy; spontaneous pattern formation in chemical and biological systems; impact mechanics in offshore engineering and the chatter of cutting tools; controlling chaotic heartbeats. Reference is made to a number of interactive simulations and movies accessible on the web.

Accounting for Intraligand Interactions in Flexible Ligand Docking with a PMF-Based Scoring Function.

PubMed

Lizunov, A Y; Gonchar, A L; Zaitseva, N I; Zosimov, V V

2015-10-26

We analyzed the frequency with which intraligand contacts occurred in a set of 1300 protein-ligand complexes [ Plewczynski et al. J. Comput. Chem. 2011 , 32 , 742 - 755 .]. Our analysis showed that flexible ligands often form intraligand hydrophobic contacts, while intraligand hydrogen bonds are rare. The test set was also thoroughly investigated and classified. We suggest a universal method for enhancement of a scoring function based on a potential of mean force (PMF-based score) by adding a term accounting for intraligand interactions. The method was implemented via in-house developed program, utilizing an Algo_score scoring function [ Ramensky et al. Proteins: Struct., Funct., Genet. 2007 , 69 , 349 - 357 .] based on the Tarasov-Muryshev PMF [ Muryshev et al. J. Comput.-Aided Mol. Des. 2003 , 17 , 597 - 605 .]. The enhancement of the scoring function was shown to significantly improve the docking and scoring quality for flexible ligands in the test set of 1300 protein-ligand complexes [ Plewczynski et al. J. Comput. Chem. 2011 , 32 , 742 - 755 .]. We then investigated the correlation of the docking results with two parameters of intraligand interactions estimation. These parameters are the weight of intraligand interactions and the minimum number of bonds between the ligand atoms required to take their interaction into account.

van der Waals forces in density functional theory: a review of the vdW-DF method.

PubMed

Berland, Kristian; Cooper, Valentino R; Lee, Kyuho; Schröder, Elsebeth; Thonhauser, T; Hyldgaard, Per; Lundqvist, Bengt I

2015-06-01

A density functional theory (DFT) that accounts for van der Waals (vdW) interactions in condensed matter, materials physics, chemistry, and biology is reviewed. The insights that led to the construction of the Rutgers-Chalmers van der Waals density functional (vdW-DF) are presented with the aim of giving a historical perspective, while also emphasizing more recent efforts which have sought to improve its accuracy. In addition to technical details, we discuss a range of recent applications that illustrate the necessity of including dispersion interactions in DFT. This review highlights the value of the vdW-DF method as a general-purpose method, not only for dispersion bound systems, but also in densely packed systems where these types of interactions are traditionally thought to be negligible.

Nonlinear vibration of viscoelastic beams described using fractional order derivatives

NASA Astrophysics Data System (ADS)

Lewandowski, Roman; Wielentejczyk, Przemysław

2017-07-01

The problem of non-linear, steady state vibration of beams, harmonically excited by harmonic forces is investigated in the paper. The viscoelastic material of the beams is described using the Zener rheological model with fractional derivatives. The constitutive equation, which contains derivatives of both stress and strain, significantly complicates the solution to the problem. The von Karman theory is applied to take into account geometric nonlinearities. Amplitude equations are obtained using the finite element method together with the harmonic balance method, and solved using the continuation method. The tangent matrix of the amplitude equations is determined in an explicit form. The stability of the steady-state solution is also examined. A parametric study is carried out to determine the influence of viscoelastic properties of the material on the beam's responses.

Prediction Interval Development for Wind-Tunnel Balance Check-Loading

NASA Technical Reports Server (NTRS)

Landman, Drew; Toro, Kenneth G.; Commo, Sean A.; Lynn, Keith C.

2014-01-01

Results from the Facility Analysis Verification and Operational Reliability project revealed a critical gap in capability in ground-based aeronautics research applications. Without a standardized process for check-loading the wind-tunnel balance or the model system, the quality of the aerodynamic force data collected varied significantly between facilities. A prediction interval is required in order to confirm a check-loading. The prediction interval provides an expected upper and lower bound on balance load prediction at a given confidence level. A method has been developed which accounts for sources of variability due to calibration and check-load application. The prediction interval method of calculation and a case study demonstrating its use is provided. Validation of the methods is demonstrated for the case study based on the probability of capture of confirmation points.

Dissection of the binding of hydrogen peroxide to trypsin using spectroscopic methods and molecular modeling

NASA Astrophysics Data System (ADS)

Song, Wei; Yu, Zehua; Hu, Xinxin; Liu, Rutao

2015-02-01

Studies on the effects of environmental pollutants to protein in vitro has become a global attention. Hydrogen peroxide (H2O2) is used as an effective food preservative and bleacher in industrial production. The toxicity of H2O2 to trypsin was investigated by multiple spectroscopic techniques and the molecular docking method at the molecular level. The intrinsic fluorescence of trypsin was proved to be quenched in a static process based on the results of fluorescence lifetime experiment. Hydrogen bonds interaction and van der Waals forces were the main force to generate the trypsin-H2O2 complex on account of the negative ΔH0 and ΔS0. The binding of H2O2 changed the conformational structures and internal microenvironment of trypsin illustrated by UV-vis absorption, fluorescence, synchronous fluorescence, three-dimensional (3D) fluorescence and circular dichroism (CD) results. However, the binding site was far away from the active site of trypsin and the trypsin activity was only slightly affected by H2O2, which was further explained by molecular docking investigations.

Study of Hydrokinetic Turbine Arrays with Large Eddy Simulation

NASA Astrophysics Data System (ADS)

Sale, Danny; Aliseda, Alberto

2014-11-01

Marine renewable energy is advancing towards commercialization, including electrical power generation from ocean, river, and tidal currents. The focus of this work is to develop numerical simulations capable of predicting the power generation potential of hydrokinetic turbine arrays-this includes analysis of unsteady and averaged flow fields, turbulence statistics, and unsteady loadings on turbine rotors and support structures due to interaction with rotor wakes and ambient turbulence. The governing equations of large-eddy-simulation (LES) are solved using a finite-volume method, and the presence of turbine blades are approximated by the actuator-line method in which hydrodynamic forces are projected to the flow field as a body force. The actuator-line approach captures helical wake formation including vortex shedding from individual blades, and the effects of drag and vorticity generation from the rough seabed surface are accounted for by wall-models. This LES framework was used to replicate a previous flume experiment consisting of three hydrokinetic turbines tested under various operating conditions and array layouts. Predictions of the power generation, velocity deficit and turbulence statistics in the wakes are compared between the LES and experimental datasets.

Non-gray gas radiation effect on mixed convection in lid driven square cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherifi, Mohammed, E-mail: production1998@yahoo.fr; Benbrik, Abderrahmane, E-mail: abenbrik@umbb.dz; Laouar-Meftah, Siham, E-mail: laouarmeftah@gmail.com

A numerical study is performed to investigate the effect of non-gray radiation on mixed convection in a vertical two sided lid driven square cavity filled with air-H{sub 2}O-CO{sub 2} gas mixture. The vertical moving walls of the enclosure are maintained at two different but uniform temperatures. The horizontal walls are thermally insulated and considered as adiabatic walls. The governing differential equations are solved by a finite-volume method and the SIMPLE algorithm was adopted to solve the pressure–velocity coupling. The radiative transfer equation (RTE) is solved by the discrete ordinates method (DOM). The spectral line weighted sum of gray gases modelmore » (SLW) is used to account for non-gray radiation properties. Simulations are performed in configurations where thermal and shear forces induce cooperating buoyancy forces. Streamlines, isotherms, and Nusselt number are analyzed for three different values of Richardson’s number (from 0.1 to 10) and by considering three different medium (transparent medium, gray medium using the Planck mean absorption coefficient, and non-gray medium assumption).« less

A Fast Surrogate-facilitated Data-driven Bayesian Approach to Uncertainty Quantification of a Regional Groundwater Flow Model with Structural Error

NASA Astrophysics Data System (ADS)

Xu, T.; Valocchi, A. J.; Ye, M.; Liang, F.

2016-12-01

Due to simplification and/or misrepresentation of the real aquifer system, numerical groundwater flow and solute transport models are usually subject to model structural error. During model calibration, the hydrogeological parameters may be overly adjusted to compensate for unknown structural error. This may result in biased predictions when models are used to forecast aquifer response to new forcing. In this study, we extend a fully Bayesian method [Xu and Valocchi, 2015] to calibrate a real-world, regional groundwater flow model. The method uses a data-driven error model to describe model structural error and jointly infers model parameters and structural error. In this study, Bayesian inference is facilitated using high performance computing and fast surrogate models. The surrogate models are constructed using machine learning techniques to emulate the response simulated by the computationally expensive groundwater model. We demonstrate in the real-world case study that explicitly accounting for model structural error yields parameter posterior distributions that are substantially different from those derived by the classical Bayesian calibration that does not account for model structural error. In addition, the Bayesian with error model method gives significantly more accurate prediction along with reasonable credible intervals.

Wearable Accelerometers in High Performance Jet Aircraft.

PubMed

Rice, G Merrill; VanBrunt, Thomas B; Snider, Dallas H; Hoyt, Robert E

2016-02-01

Wearable accelerometers have become ubiquitous in the fields of exercise physiology and ambulatory hospital settings. However, these devices have yet to be validated in extreme operational environments. The objective of this study was to correlate the gravitational forces (G forces) detected by wearable accelerometers with the G forces detected by high performance aircraft. We compared the in-flight G forces detected by the two commercially available portable accelerometers to the F/A-18 Carrier Aircraft Inertial Navigation System (CAINS-2) during 20 flights performed by the Navy's Flight Demonstration Squadron (Blue Angels). Postflight questionnaires were also used to assess the perception of distractibility during flight. Of the 20 flights analyzed, 10 complete in-flight comparisons were made, accounting for 25,700 s of correlation between the CAINS-2 and the two tested accelerometers. Both accelerometers had strong correlations with that of the F/A-18 Gz axis, averaging r = 0.92 and r = 0.93, respectively, over 10 flights. Comparison of both portable accelerometer's average vector magnitude to each other yielded an average correlation of r = 0.93. Both accelerometers were found to be minimally distracting. These results suggest the use of wearable accelerometers is a valid means of detecting G forces during high performance aircraft flight. Future studies using this surrogate method of detecting accelerative forces combined with physiological information may yield valuable in-flight normative data that heretofore has been technically difficult to obtain and hence holds the promise of opening the door for a new golden age of aeromedical research.

Employment perspectives of patients with ankylosing spondylitis.

PubMed

Chorus, A M J; Boonen, A; Miedema, H S; van der Linden, Sj

2002-08-01

To assess the labour market position of patients with ankylosing spondylitis (AS) in relation to disease duration and to identify potential factors in relation to withdrawal from the labour force. A cross sectional mail survey was conducted among 658 patients with AS. Participation in the labour force was defined as having a paid job. The independent effect of duration of disease was examined by an indirect method of standardisation. A broad variety of risk factors were examined separately and in a combined analysis, including sociodemographic factors, disease related variables, coping styles, and work related factors. Attributable and preventable fractions were calculated from the combined analyses to assess the relative importance of the contributing factors. Probability of participation in the labour force was similarly reduced in patients with AS with different durations of disease. Pacing to cope with limitations was the most relevant factor in increasing the risk of withdrawal from the labour force, accounting for 73% of withdrawals. Coping with limitations by often seeking creative solutions, high disease activity, increased age, and insufficient support from colleagues or management were also positively associated with withdrawal from the labour force. Technical or ergonomic adjustments of the workplace, working in large companies, and coping with dependency style through frequent acceptance were negatively associated. Of these factors, technical or ergonomic adjustment was the most relevant in terms of reducing the risk. Sociodemographic factors, disease related factors, coping styles, and work related factors contribute simultaneously to withdrawal from the labour force.

A Geography of Unmarried Cohabitation in the Americas1

PubMed Central

López-Gay, Antonio; Esteve, Albert; López-Colás, Julian; Permanyer, Iñaki; Turu, Anna; Kennedy, Sheela; Laplante, Benoît; Lesthaeghe, Ron

2014-01-01

BACKGROUND In the context of increasing cohabitation and growing demand for understanding the driving forces behind the cohabitation boom, most analyses have been carried out at a national level, not accounting for regional heterogeneity within countries. OBJECTIVE This paper presents the geography of unmarried cohabitation in the Americas. We offer a large-scale, cross-national perspective together with small-area estimates of cohabitation. We decided to produce this map because: (i) geography unveils spatial heterogeneity and challenges explanatory frameworks that may work at the international level but have low explanatory power in regard to intra-national variation. (ii) we argue that historical pockets of cohabitation can still be identified by examining the current geography of cohabitation. (iii) our map is a first step toward understanding whether the recent increase in cohabitation is an intensification of pre-existing traditions or whether it has different roots that also imply a new geography. METHODS Census microdata from 39 countries and 19,000 local units have been pulled together to map the prevalence of cohabitation among women. RESULTS The results show inter- and intra-national regional contrasts. The highest rates of cohabitation are found in areas of Central America, the Caribbean, Colombia and Peru. The lowest rates are mainly found in the United States and Mexico. In all countries the spatial autocorrelation statistics indicates substantial spatial heterogeneity. CONCLUSIONS Our results raise the question as to which forces have shaped these patterns and remind us that such forces need to be taken into account to understand recent patterns, particularly increases, in cohabitation. PMID:26161036

HEP Computing

Science.gov Websites

page.) How do I set up an ANL mailing list? How do I request an ANL collaborator account? How do I DayForce working you need to install the Citrix Receiver) How do I sign up for an account on the LCRC Blues

Sandia National Laboratories: National Security Missions: International

Science.gov Websites

Transportation Energy Energy Research Global Security WMD Counterterrorism & Response Global Threat Reduction Homeland Defense & Force Protection Homeland Security Cyber & Infrastructure Security Global Business Procurement Technical Assistance Program (PTAP) Current Suppliers iSupplier Account Accounts

Reservations about the conclusions of the interdivisional (APA Divisions 12 & 29) task force on evidence-based therapy relationships: what do we know, what don't we know?

PubMed

Kazantzis, Nikolaos; Cronin, Timothy J; Norton, Peter J; Lai, Jerry; Hofmann, Stefan G

2015-05-01

We offer a critical and constructive appraisal of the conclusions provided by the Interdivisional (American Psychological Association [APA] Divisions 12 & 29) Task Force on Evidence-Based Therapy Relationships. We highlight problems in overlapping terminology and definitions, as well as problems in the conduct of its meta-analyses (i.e., duplication of studies between reviews, inappropriate study inclusion, and use of measures of specific constructs for the calculation of effects for multiple relationship elements). On this basis, we express reservation about the conclusions offered by the APA Task Force. This special issue explores whether there are other therapeutic relationship elements that warrant consideration and further study. We were particularly interested in those elements that showed promise based on empirical or theoretical grounds, and in each article, we asked for an account of how the case formulation would guide the methods of adaptation for each individual client, and how the element would contribute to clinically relevant changes. © 2015 Wiley Periodicals, Inc.

Aeroelastic Response from Indicial Functions with a Finite Element Model of a Suspension Bridge

NASA Astrophysics Data System (ADS)

Mikkelsen, O.; Jakobsen, J. B.

2017-12-01

The present paper describes a comprehensive analysis of the aeroelastic bridge response in time-domain, with a finite element model of the structure. The main focus is on the analysis of flutter instability, accounting for the wind forces generated by the bridge motion, including twisting as well as vertical and horizontal translation, i.e. all three global degrees of freedom. The solution is obtained by direct integration of the equations of motion for the bridge-wind system, with motion-dependent forces approximated from flutter derivatives in terms of rational functions. For the streamlined bridge box-girder investigated, the motion dependent wind forces related to the along-wind response are found to have a limited influence on the flutter velocity. The flutter mode shapes in the time-domain and the frequency domain are consistent, and composed of the three lowest symmetrical vertical modes coupled with the first torsional symmetric mode. The method applied in this study provides detailed response estimates and contributes to an increased understanding of the complex aeroelastic behaviour of long-span bridges.

Contact angle change during evaporation of near-critical liquids

NASA Astrophysics Data System (ADS)

Nikolayev, Vadim; Hegseth, John; Beysens, Daniel

1998-11-01

An unexpected change of the dynamic contact angle was recently observed in a near-critical liquid-gas system in a space experiment. While the near-critical liquid completely wets a solid under equilibrium conditions, the apparent contact angle changed from 0^circ to about 120^circ during evaporation. We propose an explanation for this phenomenon by taking into account vapor recoil due to evaporation (motion of the vapor from the free liquid surface). This force is normal to the vapor-liquid interface and is directed towards the liquid. It increases sharply near the triple contact line. Near the critical point, where the surface tension force is very weak, the vapor recoil force can be important enough to change the apparent contact angle. A similar effect can also explain the drying of a heater during boiling at high heat flux. The drying greatly reduces the heat transfer to the liquid causing the heater to melt. This phenomenon is called ``boiling crisis", ``burnout" or ``Departure from Nuclear Boiling". We report the preliminary results of the numerical simulation of the liquid evaporation by the Boundary Element method.

Case reports: molar distalization with static repelling magnets. Part II.

PubMed

Steger, E R; Blechman, A M

1995-11-01

The following two nonextraction therapy case reports demonstrate four important points: (1) Static repelling magnets, with certain characteristic parameters, distalize molars rapidly without adverse effects that are clinically discernable. Beneficial properties such as considerably reduced patient compliance requirements for force application, reduced mobility and discomfort, and mostly bodily movement are demonstrated clinically. (2) Anchorage can be controlled by using conventional techniques of anchorage augmentation or force reduction. (3) Treatment can be satisfactorily completed and documented in accord with contemporary criteria, with conventional therapeutic methods, once the initial, most difficult, magnetic molar distalization is completed. (4) The mechanism of action that accounts for the bioeffects remains unclear. However, we hypothesize that observed reduction of mobility and discomfort during rapid movement, combined with basic research and other clinical data, are attributable to the simultaneous, synergistic property of the magnetic force field, which disrupts the local equilibrium and also the static magnetic bioeffect. Among others, one distinguishing and pertinent bioeffect may be an increased rate of osteogenesis and bone remodeling, which may be very dependent on correct dosage through a possible biologic window and the field geometry.

Persistence of unsafe practice in everyday work: an exploration of organizational and psychological factors constraining safety in the operating room.

PubMed

Espin, S; Lingard, L; Baker, G R; Regehr, G

2006-06-01

This paper explores the factors that influence the persistence of unsafe practice in an interprofessional team setting in health care, towards the development of a descriptive theoretical model for analyzing problematic practice routines. Using data collected during a mixed method interview study of 28 members of an operating room team, participants' approaches to unsafe practice were analyzed using the following three theoretical models from organizational and cognitive psychology: Reason's theory of "vulnerable system syndrome", Tucker and Edmondson's concept of first and second order problem solving, and Amalberti's model of practice migration. These three theoretical approaches provide a critical insight into key trends in the interview data, including team members' definition of error as the breaching of standards of practice, nurses' sense of scope of practice as a constraint on their reporting behaviours, and participants' reports of the forces influencing tacit agreements to work around safety regulations. However, the relational factors underlying unsafe practice routines are poorly accounted for in these theoretical approaches. Incorporating an additional theoretical construct such as "relational coordination" to account for the emotional human features of team practice would provide a more comprehensive theoretical approach for use in exploring unsafe practice routines and the forces that sustain them in healthcare team settings.

DEM modeling of failure mechanisms induced by excavations on the Moon

NASA Astrophysics Data System (ADS)

jiang, mingjing; shen, zhifu; Utili, Stefano

2013-04-01

2D Discrete Element Method (DEM) analyses were performed for excavations supported by retaining walls in lunar environment. The lunar terrain is made of a layer of sand (regolith) which differs from terrestrial sands for two main features: the presence of adhesive attractive forces due to van der Waals interactions and grains being very irregular in shape leading to high interlocking. A simplified contact model based on linear elasticity and perfect plasticity was employed. The contact model includes a moment - relative rotation law to account for high interlocking among grains and a normal adhesion law to account for the van der Waals interactions. Analyses of the excavations were run under both lunar and terrestrial environments. Under lunar environment, gravity is approximately one sixth than the value on Earth and adhesion forces between grains of lunar regolith due to van der Waals interactions are not negligible. From the DEM simulations it emerged that van der Waals interactions may significantly increase the bending moment and deflection of the retaining wall, and the ground displacements. Hence this study indicates that an unsafe estimate of the wall response to an excavation on the Moon would be obtained from physical experiments performed in a terrestrial environment, i.e., considering the effect of gravity but neglecting the van der Waals interactions.

Deficiencies in Journal Vouchers that Affected the FY 2009 Air Force General Fund Statement of Budgetary Resources

DTIC Science & Technology

2011-12-01

internal control over financial reporting to: • properly support reconciliations with specific accounting transactions and discontinue forcing...agreement of amounts to meet budgetary financial reporting requirements; • include adequate detailed evidence with journal vouchers so that audit trails...Finding A. Forced Journal Voucher Adjustments Weaken the Reliability of Financial Reporting 5 Reimbursable Activity Adjustments Need Detailed

U.S. Air Force Annual Financial Statement 2010

DTIC Science & Technology

2010-01-01

certain contract financing payments that are not reported elsewhere on Air Force’s Balance Sheet. The Air Force conducts business with commercial...the reporting entity has a contractual commitment for payment is $712.8 million. The Air Force is a party in numerous individual contracts that...promulgated by the Federal Accounting Standards Advisory Board; the Office of Management and Budget (OMB) Circular No. A-136, Financial Reporting

Are there interactive effects of physiological and radiative forcing produced by increased CO2 concentration on changes of land hydrological cycle?

NASA Astrophysics Data System (ADS)

Peng, Jing; Dan, Li; Dong, Wenjie

2014-01-01

Three coupled climate-carbon cycle models including CESM (Community Earth System Model), CanEsm (the Canadian Centre for Climate Modelling and Analysis Earth System Model) and BCC (Beijing Climate Center Climate System Model) were used to estimate whether changes in land hydrological cycle responded to the interactive effects of CO2-physiological forcing and CO2-radiative forcing. No signs could be indicated that the interactive effects of CO2-physiological forcing and CO2-radiative forcing on the hydrological variables (e.g. precipitation, evapotranspiration and runoff) were detected at global and regional scales. For each model, increases in precipitation, evapotranspiration and runoff (e.g. 0.37, 0.18 and 0.25 mm/year2) were simulated in response to CO2-radiative forcing (experiment M3). Decreases in precipitation and evapotranspiration (about - 0.02 and - 0.09 mm/year2) were captured if the CO2 physiological effect was only accounted for (experiment M2). In this experiment, a reverse sign in runoff (the increase of 0.08 mm/year2) in contrast to M3 is presented. All models simulated the same signs across Eastern Asia in response to the CO2 physiological forcing and radiative forcing: increases in precipitation and evapotranspiration only considering greenhouse effect; reductions in precipitation and evapotranspiration in response to CO2-physiological effect; and enhanced trends in runoff from all experiments. However, there was still a large uncertainty on the magnitude of the effect of transpiration on runoff (decreased transpiration accounting for 8% to 250% of the increased runoff) from the three models. Two models (CanEsm and BCC) attributed most of the increase in runoff to the decrease in transpiration if the CO2-physiological effect was only accounted for, whereas CESM exhibited that the decrease in transpiration could not totally explain the increase in runoff. The attribution of the CO2-physiological forcing to changes in stomatal conductance versus changes in vegetation structure (e.g. increased Leaf Area Index) is an issue to discuss, and among the three models, no agreement appeared.

The importance of the diurnal and annual cycle of air traffic for contrail radiative forcing.

PubMed

Stuber, Nicola; Forster, Piers; Rädel, Gaby; Shine, Keith

2006-06-15

Air traffic condensation trails, or contrails, are believed to have a net atmospheric warming effect, although one that is currently small compared to that induced by other sources of human emissions. However, the comparably large growth rate of air traffic requires an improved understanding of the resulting impact of aircraft radiative forcing on climate. Contrails have an effect on the Earth's energy balance similar to that of high thin ice clouds. Their trapping of outgoing longwave radiation emitted by the Earth and atmosphere (positive radiative forcing) is partly compensated by their reflection of incoming solar radiation (negative radiative forcing). On average, the longwave effect dominates and the net contrail radiative forcing is believed to be positive. Over daily and annual timescales, varying levels of air traffic, meteorological conditions, and solar insolation influence the net forcing effect of contrails. Here we determine the factors most important for contrail climate forcing using a sophisticated radiative transfer model for a site in southeast England, located in the entrance to the North Atlantic flight corridor. We find that night-time flights during winter (December to February) are responsible for most of the contrail radiative forcing. Night flights account for only 25 per cent of daily air traffic, but contribute 60 to 80 per cent of the contrail forcing. Further, winter flights account for only 22 per cent of annual air traffic, but contribute half of the annual mean forcing. These results suggest that flight rescheduling could help to minimize the climate impact of aviation.

Factors Influencing Interdisciplinary Team Member Agreement With Social Worker Assessments of Domestic Violence Incidents in the United States Air Force

DTIC Science & Technology

2002-08-01

General Accounting Office (GAO) noted, "the programs were little more than administrative mechanisms to formalize the existing structure" (Daley, 1999...p. 57). The USAF formalized the DoD Directive by establishing the Air Force Family Advocacy Program (FAP) later that year through Air Force...highly formalized authority structure has served the military well and allows for consistency despite frequent turnover of a mobile personnel force. The

Accelerating NBODY6 with graphics processing units

NASA Astrophysics Data System (ADS)

Nitadori, Keigo; Aarseth, Sverre J.

2012-07-01

We describe the use of graphics processing units (GPUs) for speeding up the code NBODY6 which is widely used for direct N-body simulations. Over the years, the N2 nature of the direct force calculation has proved a barrier for extending the particle number. Following an early introduction of force polynomials and individual time steps, the calculation cost was first reduced by the introduction of a neighbour scheme. After a decade of GRAPE computers which speeded up the force calculation further, we are now in the era of GPUs where relatively small hardware systems are highly cost effective. A significant gain in efficiency is achieved by employing the GPU to obtain the so-called regular force which typically involves some 99 per cent of the particles, while the remaining local forces are evaluated on the host. However, the latter operation is performed up to 20 times more frequently and may still account for a significant cost. This effort is reduced by parallel SSE/AVX procedures where each interaction term is calculated using mainly single precision. We also discuss further strategies connected with coordinate and velocity prediction required by the integration scheme. This leaves hard binaries and multiple close encounters which are treated by several regularization methods. The present NBODY6-GPU code is well balanced for simulations in the particle range 104-2 × 105 for a dual-GPU system attached to a standard PC.

Nanoscale hydrodynamics near solids

NASA Astrophysics Data System (ADS)

Camargo, Diego; de la Torre, J. A.; Duque-Zumajo, D.; Español, Pep; Delgado-Buscalioni, Rafael; Chejne, Farid

2018-02-01

Density Functional Theory (DFT) is a successful and well-established theory for the study of the structure of simple and complex fluids at equilibrium. The theory has been generalized to dynamical situations when the underlying dynamics is diffusive as in, for example, colloidal systems. However, there is no such a clear foundation for Dynamic DFT (DDFT) for the case of simple fluids in contact with solid walls. In this work, we derive DDFT for simple fluids by including not only the mass density field but also the momentum density field of the fluid. The standard projection operator method based on the Kawasaki-Gunton operator is used for deriving the equations for the average value of these fields. The solid is described as featureless under the assumption that all the internal degrees of freedom of the solid relax much faster than those of the fluid (solid elasticity is irrelevant). The fluid moves according to a set of non-local hydrodynamic equations that include explicitly the forces due to the solid. These forces are of two types, reversible forces emerging from the free energy density functional, and accounting for impenetrability of the solid, and irreversible forces that involve the velocity of both the fluid and the solid. These forces are localized in the vicinity of the solid surface. The resulting hydrodynamic equations should allow one to study dynamical regimes of simple fluids in contact with solid objects in isothermal situations.

Will Empowerment of USAF Program Managers Mitigate the Acquisitions Crisis

DTIC Science & Technology

2016-06-10

FAR Federal Acquisition Regulations GAO Government Accountability Office MDAP Major Defense Acquisition Program USAF United States Air Force ix...actually run the project. The Government Accountability Office (GAO),2 along with many other organizations, including Congress in their 2016 National...1 Government Accountability Office (GAO), GAO-06-110, Best Practices: Better Support of Weapons Systems Program Managers Needed to

Webinar Presentation: Linking Regional Aerosol Emission Changes with Multiple Impact Measures through Direct and Cloud-Related Forcing Estimates

EPA Pesticide Factsheets

This presentation, Linking Regional Aerosol Emission Changes with Multiple Impact Measures through Direct and Cloud-Related Forcing Estimates, was given at the STAR Black Carbon 2016 Webinar Series: Accounting for Impact, Emissions, and Uncertainty.

Inhomogeneous Forcing and Transient Climate Sensitivity

NASA Technical Reports Server (NTRS)

Shindell, Drew T.

2014-01-01

Understanding climate sensitivity is critical to projecting climate change in response to a given forcing scenario. Recent analyses have suggested that transient climate sensitivity is at the low end of the present model range taking into account the reduced warming rates during the past 10-15 years during which forcing has increased markedly. In contrast, comparisons of modelled feedback processes with observations indicate that the most realistic models have higher sensitivities. Here I analyse results from recent climate modelling intercomparison projects to demonstrate that transient climate sensitivity to historical aerosols and ozone is substantially greater than the transient climate sensitivity to CO2. This enhanced sensitivity is primarily caused by more of the forcing being located at Northern Hemisphere middle to high latitudes where it triggers more rapid land responses and stronger feedbacks. I find that accounting for this enhancement largely reconciles the two sets of results, and I conclude that the lowest end of the range of transient climate response to CO2 in present models and assessments (less than 1.3 C) is very unlikely.

Anthropometry as a predictor of high speed performance.

PubMed

Caruso, J F; Ramey, E; Hastings, L P; Monda, J K; Coday, M A; McLagan, J; Drummond, J

2009-07-01

To assess anthropometry as a predictor of high-speed performance, subjects performed four seated knee- and hip-extension workouts with their left leg on an inertial exercise trainer (Impulse Technologies, Newnan GA). Workouts, done exclusively in either the tonic or phasic contractile mode, entailed two one-minute sets separated by a 90-second rest period and yielded three performance variables: peak force, average force and work. Subjects provided the following anthropometric data: height, weight, body mass index, as well as total, upper and lower left leg lengths. Via multiple regression, anthropometry attempted to predict the variance per performance variable. Anthropometry explained a modest (R2=0.27-0.43) yet significant degree of variance from inertial exercise trainer workouts. Anthropometry was a better predictor of peak force variance from phasic workouts, while it accounted for a significant degree of average force and work variance solely from tonic workouts. Future research should identify variables that account for the unexplained variance from high-speed exercise performance.

Temporomandibular joint injury potential imposed by the low-velocity extension-flexion maneuver.

PubMed

Howard, R P; Hatsell, C P; Guzman, H M

1995-03-01

It has been proposed that significant temporomandibular joint injury can occur as a result of rapid extension-flexion motion of the neck (whip-lash). This motion, which is experienced by passengers in vehicles that undergo rear-end collisions, has been described as causing rapid protrusion and opening of the mandible. It has been speculated that this relative motion between the mandible and the cranium produces forces at the temporomandibular joint (TMJ) that injure the articular elements. The objective of this study was to measure these forces by an experimental method. Accelerometer sensor and high-speed cinematographic data were obtained from the kinematic responses of live human test subjects positioned as occupants in motor vehicles that underwent staged low-velocity rear-end collisions. Linear and moment forces generated at the TMJs were obtained from the resultant acceleration pulse at the craniomandibular complex, estimation of the mass properties of the mandible and its appended soft tissues, and the application of Newton's Second Law of motion. The maximum linear forces generated at the TMJ in a rear-end collision resulting in a velocity change of the test subject of 8 km/h (5 mph) were in the 7 to 10 N (1.6 to 2.2 lb) range. Moment forces at the joint peaked briefly at 0.55 N.m (4.81 lb-in). These force magnitudes generated at the TMJ constitute a minor fraction of the forces experienced at the joint during normal physiologic function. It is a conclusion of this study that injuries to the TMJ attributed to low-velocity "whiplash" cannot be accounted for by the joint forces produced by this maneuver.

Modeling methodology for a CMOS-MEMS electrostatic comb

NASA Astrophysics Data System (ADS)

Iyer, Sitaraman V.; Lakdawala, Hasnain; Mukherjee, Tamal; Fedder, Gary K.

2002-04-01

A methodology for combined modeling of capacitance and force 9in a multi-layer electrostatic comb is demonstrated in this paper. Conformal mapping-based analytical methods are limited to 2D symmetric cross-sections and cannot account for charge concentration effects at corners. Vertex capacitance can be more than 30% of the total capacitance in a single-layer 2 micrometers thick comb with 10 micrometers overlap. Furthermore, analytical equations are strictly valid only for perfectly symmetrical finger positions. Fringing and corner effects are likely to be more significant in a multi- layered CMOS-MEMS comb because of the presence of more edges and vertices. Vertical curling of CMOS-MEMS comb fingers may also lead to reduced capacitance and vertical forces. Gyroscopes are particularly sensitive to such undesirable forces, which therefore, need to be well-quantified. In order to address the above issues, a hybrid approach of superposing linear regression models over a set of core analytical models is implemented. Design of experiments is used to obtain data for capacitance and force using a commercial 3D boundary-element solver. Since accurate force values require significantly higher mesh refinement than accurate capacitance, we use numerical derivatives of capacitance values to compute the forces. The model is formulated such that the capacitance and force models use the same regression coefficients. The comb model thus obtained, fits the numerical capacitance data to within +/- 3% and force to within +/- 10%. The model is experimentally verified by measuring capacitance change in a specially designed test structure. The capacitance model matches measurements to within 10%. The comb model is implemented in an Analog Hardware Description Language (ADHL) for use in behavioral simulation of manufacturing variations in a CMOS-MEMS gyroscope.

Measuring Charter School Efficiency: An Early Appraisal

ERIC Educational Resources Information Center

Carpenter, Dick M., II; Noller, Scott L.

2010-01-01

In an era of increased accountability and challenging times for public finance, charter schools built on decentralization, grassroots accountability, and market forces may provide, in the spirit of "educational laboratories," lessons for increasing student achievement more efficiently through diverse and innovative management,…

The Use of Atomic Force Microscopy for 3D Analysis of Nucleic Acid Hybridization on Microarrays.

PubMed

Dubrovin, E V; Presnova, G V; Rubtsova, M Yu; Egorov, A M; Grigorenko, V G; Yaminsky, I V

2015-01-01

Oligonucleotide microarrays are considered today to be one of the most efficient methods of gene diagnostics. The capability of atomic force microscopy (AFM) to characterize the three-dimensional morphology of single molecules on a surface allows one to use it as an effective tool for the 3D analysis of a microarray for the detection of nucleic acids. The high resolution of AFM offers ways to decrease the detection threshold of target DNA and increase the signal-to-noise ratio. In this work, we suggest an approach to the evaluation of the results of hybridization of gold nanoparticle-labeled nucleic acids on silicon microarrays based on an AFM analysis of the surface both in air and in liquid which takes into account of their three-dimensional structure. We suggest a quantitative measure of the hybridization results which is based on the fraction of the surface area occupied by the nanoparticles.

An analytic method to account for drag in the Vinti Satellite theory

NASA Technical Reports Server (NTRS)

Watson, J. S.; Mistretta, G. D.; Bonavito, N. L.

1974-01-01

To retain separability in the Vinti theory of earth satellite motion when a nonconservative force such as air drag is considered, a set of variational equations for the orbital elements are introduced, and expressed as functions of the transverse, radial, and normal components of the nonconservative forces acting on the system. In this approach, the Hamiltonian is preserved in form, and remains the total energy, but the initial or boundary conditions and hence the Jacobi constants of the motion advance with time through the variational equations. In particular, the atmospheric density profile is written as a fitted exponential function of the eccentric anomaly, which adheres to tabular data at all altitudes and simultaneously reduced the variational equations to indefinite integrals with closed form evaluations. The values of the limits for any arbitrary time interval are obtained from the Vinti program.

Limbless undulatory propulsion on land.

PubMed

Guo, Z V; Mahadevan, L

2008-03-04

We analyze the lateral undulatory motion of a natural or artificial snake or other slender organism that "swims" on land by propagating retrograde flexural waves. The governing equations for the planar lateral undulation of a thin filament that interacts frictionally with its environment lead to an incomplete system. Closures accounting for the forces generated by the internal muscles and the interaction of the filament with its environment lead to a nonlinear boundary value problem, which we solve using a combination of analytical and numerical methods. We find that the primary determinant of the shape of the organism is its interaction with the external environment, whereas the speed of the organism is determined primarily by the internal muscular forces, consistent with prior qualitative observations. Our model also allows us to pose and solve a variety of optimization problems such as those associated with maximum speed and mechanical efficiency, thus defining the performance envelope of this mode of locomotion.

Comment on "Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcing" by S. Lovejoy and C. Varotsos (2016)

NASA Astrophysics Data System (ADS)

Rypdal, Kristoffer; Rypdal, Martin

2016-07-01

Lovejoy and Varotsos (2016) (L&V) analyse the temperature response to solar, volcanic, and solar plus volcanic forcing in the Zebiak-Cane (ZC) model, and to solar and solar plus volcanic forcing in the Goddard Institute for Space Studies (GISS) E2-R model. By using a simple wavelet filtering technique they conclude that the responses in the ZC model combine subadditively on timescales from 50 to 1000 years. Nonlinear response on shorter timescales is claimed by analysis of intermittencies in the forcing and the temperature signal for both models. The analysis of additivity in the ZC model suffers from a confusing presentation of results based on an invalid approximation, and from ignoring the effect of internal variability. We present tests without this approximation which are not able to detect nonlinearity in the response, even without accounting for internal variability. We also demonstrate that internal variability will appear as subadditivity if it is not accounted for. L&V's analysis of intermittencies is based on a mathematical result stating that the intermittencies of forcing and response are the same if the response is linear. We argue that there are at least three different factors that may invalidate the application of this result for these data. It is valid only for a power-law response function; it assumes power-law scaling of structure functions of forcing as well as temperature signal; and the internal variability, which is strong at least on the short timescales, will exert an influence on temperature intermittence which is independent of the forcing. We demonstrate by a synthetic example that the differences in intermittencies observed by L&V easily can be accounted for by these effects under the assumption of a linear response. Our conclusion is that the analysis performed by L&V does not present valid evidence for a detectable nonlinear response in the global temperature in these climate models.

System analysis of force feedback microscopy

NASA Astrophysics Data System (ADS)

Rodrigues, Mario S.; Costa, Luca; Chevrier, Joël; Comin, Fabio

2014-02-01

It was shown recently that the Force Feedback Microscope (FFM) can avoid the jump-to-contact in Atomic force Microscopy even when the cantilevers used are very soft, thus increasing force resolution. In this letter, we explore theoretical aspects of the associated real time control of the tip position. We take into account lever parameters such as the lever characteristics in its environment, spring constant, mass, dissipation coefficient, and the operating conditions such as controller gains and interaction force. We show how the controller parameters are determined so that the FFM functions at its best and estimate the bandwidth of the system under these conditions.

Electron fluctuation induced resonance broadening in nano electromechanical systems: the origin of shear force in vacuum.

PubMed

Siria, A; Barois, T; Vilella, K; Perisanu, S; Ayari, A; Guillot, D; Purcell, S T; Poncharal, P

2012-07-11

This article presents a study of the poorly understood "shear-force" used in an important class of near-field instruments that use mechanical resonance feedback detection. In the case of a metallic probe near a metallic surface in vacuum, we show that in the 10-60 nm range there is no such a thing as a shear-force in the sense of the nonconservative friction force. Fluctuations of the oscillator resonance frequency, likely induced by local charge variations, could account for the reported effects in the literature without introducing a dissipative force.

Is agritourism eco-friendly? A comparison between agritourisms and other farms in Italy using farm accountancy data network dataset.

PubMed

Mastronardi, Luigi; Giaccio, Vincenzo; Giannelli, Agostino; Scardera, Alfonso

2015-01-01

This paper presents the results of research regarding the environmental performances of Italian farms with agritourism compared with farms without agritourism. In Italy, agritourism is considered an agricultural activity and can only be performed by a farmer. Moreover, Italian national legislation forces the farmer to dedicate himself mainly to traditional farming, rather than to tourism activities. For this reason, environmental performances have been highlighted by analyzing only features and production systems of the farms. By utilizing the most frequent indicators used in studies regarding sustainability, the authors show how Italian agritourisms tend to develop more environmentally friendly agricultural methods, which have a positive impact on biodiversity, landscape and natural resources. The empirical analysis is based on the Italian FADN (Farm Accountancy Data Network) dataset. The European FADN was created to represent farms' technical and economic operation in the European Union and on which it drafts the agricultural and rural policies. The dichotomous structure of the dependent variable (presence or absence of agritourism at the farm) has a propensity for an assessment method based on Binary Response Model Regression.

Managing change in the nursing handover from traditional to bedside handover – a case study from Mauritius

PubMed Central

Kassean, Hemant K; Jagoo, Zaheda B

2005-01-01

Background The shift handover forms an important part of the communication process that takes place twice within the nurses' working day in the gynaecological ward. This paper addresses the topic of implementing a new system of bedside handover, which puts patients central to the whole process of managing care and also addresses some of the shortcomings of the traditional handover system. Methods A force field analysis in terms of the driving forces had shown that there was dissatisfaction with the traditional method of handover which had led to an increase in the number of critical incidents and complaints from patients, relatives and doctors. The restraining forces identified were a fear of accountability, lack of confidence and that this change would lead to more work. A 3 – step planned change model consisting of unfreezing, moving and refreezing was used to guide us through the change process. Resistance to change was managed by creating a climate of open communication where stakeholders were allowed to voice opinions, share concerns, insights, and ideas thereby actively participating in decision making. Results An evaluation had shown that this process was successfully implemented to the satisfaction of patients, and staff in general. Conclusion This successful change should encourage other nurses to become more proactive in identifying areas for change management in order to improve our health care system. PMID:15676078

SPIREs: A Finite-Difference Frequency-Domain electromagnetic solver for inhomogeneous magnetized plasma cylinders

NASA Astrophysics Data System (ADS)

Melazzi, D.; Curreli, D.; Manente, M.; Carlsson, J.; Pavarin, D.

2012-06-01

We present SPIREs (plaSma Padova Inhomogeneous Radial Electromagnetic solver), a Finite-Difference Frequency-Domain (FDFD) electromagnetic solver in one dimension for the rapid calculation of the electromagnetic fields and the deposited power of a large variety of cylindrical plasma problems. The two Maxwell wave equations have been discretized using a staggered Yee mesh along the radial direction of the cylinder, and Fourier transformed along the other two dimensions and in time. By means of this kind of discretization, we have found that mode-coupling of fast and slow branches can be fully resolved without singularity issues that flawed other well-established methods in the past. Fields are forced by an antenna placed at a given distance from the plasma. The plasma can be inhomogeneous, finite-temperature, collisional, magnetized and multi-species. Finite-temperature Maxwellian effects, comprising Landau and cyclotron damping, have been included by means of the plasma Z dispersion function. Finite Larmor radius effects have been neglected. Radial variations of the plasma parameters are taken into account, thus extending the range of applications to a large variety of inhomogeneous plasma systems. The method proved to be fast and reliable, with accuracy depending on the spatial grid size. Two physical examples are reported: fields in a forced vacuum waveguide with the antenna inside, and forced plasma oscillations in the helicon radiofrequency range.

Developing a Common Metric for Evaluating Police Performance in Deadly Force Situations

DTIC Science & Technology

2012-08-27

2005).“Police Inservice Deadly Force Training and Requalification in Washington State.” Law Enforcement Executive Forum, 5(2):67-86. NIJ Metric...OF: EXECUTIVE SUMMARY Background There is a critical lack of scientific evidence about whether deadly force management, accountability and training ...Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS training metrics develoment, deadly encounters

Spin-Orbit Torque and Spin Pumping in YIG/Pt with Interfacial Insertion Layers (Postprint)

DTIC Science & Technology

2018-05-03

Distribution Statement A. Approved for public release: distribution unlimited. © 2018 AMERICAN INSTITUTE OF PHYSICS (STINFO COPY) AIR FORCE RESEARCH ...SPONSORING/MONITORING AGENCY ACRONYM(S) Air Force Research Laboratory Materials and Manufacturing Directorate Wright-Patterson Air Force Base, OH... observe a large enhancement of Gilbert damping with the insertion of Py that cannot be accounted for solely by spin pumping, revealing significant spin

Regularity Aspects in Inverse Musculoskeletal Biomechanics

NASA Astrophysics Data System (ADS)

Lund, Marie; Stâhl, Fredrik; Gulliksson, Mârten

2008-09-01

Inverse simulations of musculoskeletal models computes the internal forces such as muscle and joint reaction forces, which are hard to measure, using the more easily measured motion and external forces as input data. Because of the difficulties of measuring muscle forces and joint reactions, simulations are hard to validate. One way of reducing errors for the simulations is to ensure that the mathematical problem is well-posed. This paper presents a study of regularity aspects for an inverse simulation method, often called forward dynamics or dynamical optimization, that takes into account both measurement errors and muscle dynamics. Regularity is examined for a test problem around the optimum using the approximated quadratic problem. The results shows improved rank by including a regularization term in the objective that handles the mechanical over-determinancy. Using the 3-element Hill muscle model the chosen regularization term is the norm of the activation. To make the problem full-rank only the excitation bounds should be included in the constraints. However, this results in small negative values of the activation which indicates that muscles are pushing and not pulling, which is unrealistic but the error maybe small enough to be accepted for specific applications. These results are a start to ensure better results of inverse musculoskeletal simulations from a numerical point of view.

Kinetic and kinematic analysis of stamping impacts during simulated rucking in rugby union.

PubMed

Oudshoorn, Bodil Y; Driscoll, Heather F; Dunn, Marcus; James, David

2018-04-01

Laceration injuries account for up to 23% of injuries in rugby union. They are frequently caused by studded footwear as a result of a player stamping onto another player during the ruck. Little is known about the kinetics and kinematics of rugby stamping impacts; current test methods assessing laceration injury risk of stud designs therefore lack informed test parameters. In this study, twelve participants stamped on an anthropomorphic test device in a one-on-one simulated ruck setting. Velocity and inclination angle of the foot prior to impact was determined from high-speed video footage. Total stamping force and individual stud force were measured using pressure sensors. Mean foot inbound velocity was 4.3 m ∙ s -1 (range 2.1-6.3 m ∙ s -1 ). Mean peak total force was 1246 N and mean peak stud force was 214 N. The total mean effective mass during stamping was 6.6 kg (range: 1.6-13.5 kg) and stud effective mass was 1.2 kg (range: 0.5-2.9 kg). These results provide representative test parameters for mechanical test devices designed to assess laceration injury risk of studded footwear for rugby union.

Use of Tekscan K-Scan Sensors for Retropatellar Pressure Measurement Avoiding Errors during Implantation and the Effects of Shear Forces on the Measurement Precision

PubMed Central

Wilharm, A.; Hurschler, Ch.; Dermitas, T.; Bohnsack, M.

2013-01-01

Pressure-sensitive K-Scan 4000 sensors (Tekscan, USA) provide new possibilities for the dynamic measurement of force and pressure in biomechanical investigations. We examined the sensors to determine in particular whether they are also suitable for reliable measurements of retropatellar forces and pressures. Insertion approaches were also investigated and a lateral parapatellar arthrotomy supplemented by parapatellar sutures proved to be the most reliable method. The ten human cadaver knees were tested in a knee-simulating machine at a torque of 30 and 40 Nm. Each test cycle involved a dynamic extension from 120° flexion. All recorded parameters showed a decrease of 1-2% per measurement cycle. Although we supplemented the sensors with a Teflon film, the decrease, which was likely caused by shear force, was significant. We evaluated 12 cycles and observed a linear decrease in parameters up to 17.2% (coefficient of regression 0.69–0.99). In our opinion, the linear decrease can be considered a systematic error and can therefore be quantified and accounted for in subsequent experiments. That will ensure reliable retropatellar usage of Tekscan sensors and distinguish the effects of knee joint surgeries from sensor wear-related effects. PMID:24369018

Accountability in the ontario cancer services system: a qualitative study of system leaders' perspectives.

PubMed

Bytautas, Jessica; Dobrow, Mark; Sullivan, Terrence; Brown, Adalsteinn

2014-09-01

Cancer Care Ontario (CCO), the provincial cancer agency, operates under a model of accountable governance that has been hailed as exemplary. We explored cancer system leaders' views on the balance and perceived efficacy of approaches to accountability in this context. Semi-structured interviews were conducted with 19 participants (MOHLTC=5, CCO=14). Adopting a qualitative descriptive approach, we coded data for four policy instruments used in approaches to accountability. Financial incentives are a key lever used by both parties to effect change. Cancer-specific regulations were somewhat weak, but agency-wide directives were a necessary nuisance that had great force. The effect of public reporting on mobilizing consumer sovereignty was questioned; however, transparency for its own sake was highly valued. Professionalism and stewardship, with an emphasis on trust-based partnerships and clinical engagement, were critical to CCO's success. These approaches were seen to work together, but what made each have force was reliance on professionalism and stewardship. Copyright © 2014 Longwoods Publishing.

The Development of A Performance Measurement Concept for the Royal Australian Air Force

DTIC Science & Technology

1992-09-01

knowledge of management accounting and performance measurement techniques. As the RAAF currently has no cost management and performance measurement system...provides a review of the current literature on management accounting for performance measurement, specifically referring to the problems of using...traditional management accounting methodologies as a basis for formulating performance measures. Chapter III explains the methodology used to conduct the

Joint Intelligence Analysis Complex: DOD Needs to Fully Incorporate Best Practices into Future Cost Estimates

DTIC Science & Technology

2016-11-01

Report to Congressional Requesters November 2016 GAO-17-29 United States Government Accountability Office United States Government... Accountability Office Highlights of GAO-17-29, a report to congressional requesters November 2016 JOINT INTELLIGENCE ANALYSIS COMPLEX DOD...of scope, according to DOD and Air Force officials. However, without fully accounting for life- cycle costs, management may have difficulty

A revised version of the transfer matrix method to analyze one-dimensional structures

NASA Technical Reports Server (NTRS)

Nitzsche, F.

1983-01-01

A new and general method to analyze both free and forced vibration characteristics of one-dimensional structures is discussed in this paper. This scheme links for the first time the classical transfer matrix method with the recently developed integrating matrix technique to integrate systems of differential equations. Two alternative approaches to the problem are presented. The first is based upon the lumped parameter model to account for the inertia properties of the structure. The second releases that constraint allowing a more precise description of the physical system. The free vibration of a straight uniform beam under different support conditions is analyzed to test the accuracy of the two models. Finally some results for the free vibration of a 12th order system representing a curved, rotating beam prove that the present method is conveniently extended to more complicated structural dynamics problems.

Modeling the electrophoretic separation of short biological molecules in nanofluidic devices

NASA Astrophysics Data System (ADS)

Fayad, Ghassan; Hadjiconstantinou, Nicolas

2010-11-01

Via comparisons with Brownian Dynamics simulations of the worm-like-chain and rigid-rod models, and the experimental results of Fu et al. [Phys. Rev. Lett., 97, 018103 (2006)], we demonstrate that, for the purposes of low-to-medium field electrophoretic separation in periodic nanofilter arrays, sufficiently short biomolecules can be modeled as point particles, with their orientational degrees of freedom accounted for using partition coefficients. This observation is used in the present work to build a particularly simple and efficient Brownian Dynamics simulation method. Particular attention is paid to the model's ability to quantitatively capture experimental results using realistic values of all physical parameters. A variance-reduction method is developed for efficiently simulating arbitrarily small forcing electric fields.

Hydrodynamic Contributions to Amoeboid Cell Motility

NASA Astrophysics Data System (ADS)

Lewis, Owen; Guy, Robert

2011-11-01

Understanding the methods by which cells move is a fundamental problem in modern biology. Recent evidence has shown that the fluid dynamics of cytoplasm can play a vital role in cellular motility. The slime mold Physarum polycephalum provides an excellent model organism for the study of amoeboid motion. In this research, we use both analytic and computational models to investigate intracellular fluid flow in a simple model of Physarum. In both models, of we are specifically interested in stresses generated by cytoplasmic flow which act in the direction of cellular motility. In our numerical model, the Immersed Boundary Method is used to account for such stresses. We investigate the relationship between contraction waves, low waves and locomotive forces, and attempt characterize conditions necessary to generate directed motion.

Detrended partial cross-correlation analysis of two nonstationary time series influenced by common external forces

NASA Astrophysics Data System (ADS)

Qian, Xi-Yuan; Liu, Ya-Min; Jiang, Zhi-Qiang; Podobnik, Boris; Zhou, Wei-Xing; Stanley, H. Eugene

2015-06-01

When common factors strongly influence two power-law cross-correlated time series recorded in complex natural or social systems, using detrended cross-correlation analysis (DCCA) without considering these common factors will bias the results. We use detrended partial cross-correlation analysis (DPXA) to uncover the intrinsic power-law cross correlations between two simultaneously recorded time series in the presence of nonstationarity after removing the effects of other time series acting as common forces. The DPXA method is a generalization of the detrended cross-correlation analysis that takes into account partial correlation analysis. We demonstrate the method by using bivariate fractional Brownian motions contaminated with a fractional Brownian motion. We find that the DPXA is able to recover the analytical cross Hurst indices, and thus the multiscale DPXA coefficients are a viable alternative to the conventional cross-correlation coefficient. We demonstrate the advantage of the DPXA coefficients over the DCCA coefficients by analyzing contaminated bivariate fractional Brownian motions. We calculate the DPXA coefficients and use them to extract the intrinsic cross correlation between crude oil and gold futures by taking into consideration the impact of the U.S. dollar index. We develop the multifractal DPXA (MF-DPXA) method in order to generalize the DPXA method and investigate multifractal time series. We analyze multifractal binomial measures masked with strong white noises and find that the MF-DPXA method quantifies the hidden multifractal nature while the multifractal DCCA method fails.

High-speed trains subject to abrupt braking

NASA Astrophysics Data System (ADS)

Tran, Minh Thi; Ang, Kok Keng; Luong, Van Hai; Dai, Jian

2016-12-01

The dynamic response of high-speed train subject to braking is investigated using the moving element method. Possible sliding of wheels over the rails is accounted for. The train is modelled as a 15-DOF system comprising of a car body, two bogies and four wheels interconnected by spring-damping units. The rail is modelled as a Euler-Bernoulli beam resting on a two-parameter elastic damped foundation. The interaction between the moving train and track-foundation is accounted for through the normal and tangential wheel-rail contact forces. The effects of braking torque, wheel-rail contact condition, initial train speed and severity of railhead roughness on the dynamic response of the high-speed train are investigated. For a given initial train speed and track irregularity, the study revealed that there is an optimal braking torque that would result in the smallest braking distance with no occurrence of wheel sliding, representing a good compromise between train instability and safety.

Analysis of the injection of a heated turbulent jet into a cross flow

NASA Technical Reports Server (NTRS)

Campbell, J. F.; Schetz, J. A.

1973-01-01

The development of a theoretical model is investigated of the incompressible jet injection process. The discharge of a turbulent jet into a cross flow was mathematically modeled by using an integral method which accounts for natural fluid mechanisms such as turbulence, entrainment, buoyancy, and heat transfer. The analytical results are supported by experimental data and demonstrate the usefulness of the theory for estimating the trajectory and flow properties of the jet for a variety of injection conditions. The capability of predicting jet flow properties, as well as two- and three-dimensional jet paths, was enhanced by obtaining the jet cross-sectional area during the solution of the conservation equations. Realistic estimates of temperature in the jet fluid were acquired by accounting for heat losses in the jet flow due to forced convection and to entrainment of free-stream fluid into the jet.

Probing static disorder in Arrhenius kinetics by single-molecule force spectroscopy.

PubMed

Kuo, Tzu-Ling; Garcia-Manyes, Sergi; Li, Jingyuan; Barel, Itay; Lu, Hui; Berne, Bruce J; Urbakh, Michael; Klafter, Joseph; Fernández, Julio M

2010-06-22

The widely used Arrhenius equation describes the kinetics of simple two-state reactions, with the implicit assumption of a single transition state with a well-defined activation energy barrier DeltaE, as the rate-limiting step. However, it has become increasingly clear that the saddle point of the free-energy surface in most reactions is populated by ensembles of conformations, leading to nonexponential kinetics. Here we present a theory that generalizes the Arrhenius equation to include static disorder of conformational degrees of freedom as a function of an external perturbation to fully account for a diverse set of transition states. The effect of a perturbation on static disorder is best examined at the single-molecule level. Here we use force-clamp spectroscopy to study the nonexponential kinetics of single ubiquitin proteins unfolding under force. We find that the measured variance in DeltaE shows both force-dependent and independent components, where the force-dependent component scales with F(2), in excellent agreement with our theory. Our study illustrates a novel adaptation of the classical Arrhenius equation that accounts for the microscopic origins of nonexponential kinetics, which are essential in understanding the rapidly growing body of single-molecule data.

Dynamic Simulation of Random Packing of Polydispersive Fine Particles

NASA Astrophysics Data System (ADS)

Ferraz, Carlos Handrey Araujo; Marques, Samuel Apolinário

2018-02-01

In this paper, we perform molecular dynamic (MD) simulations to study the two-dimensional packing process of both monosized and random size particles with radii ranging from 1.0 to 7.0 μm. The initial positions as well as the radii of five thousand fine particles were defined inside a rectangular box by using a random number generator. Both the translational and rotational movements of each particle were considered in the simulations. In order to deal with interacting fine particles, we take into account both the contact forces and the long-range dispersive forces. We account for normal and static/sliding tangential friction forces between particles and between particle and wall by means of a linear model approach, while the long-range dispersive forces are computed by using a Lennard-Jones-like potential. The packing processes were studied assuming different long-range interaction strengths. We carry out statistical calculations of the different quantities studied such as packing density, mean coordination number, kinetic energy, and radial distribution function as the system evolves over time. We find that the long-range dispersive forces can strongly influence the packing process dynamics as they might form large particle clusters, depending on the intensity of the long-range interaction strength.

Identification of barriers to the recruitment & retention of women intermodal transportation workers.

DOT National Transportation Integrated Search

2011-12-01

The Bureau of Labor Statistics reports that as of 2009, women comprised 46.8 percent of : the total United States labor force. The female workforce is projected to account for 46.9 percent : of the total labor force in 2018 and is expected to contrib...

Selected Contemporary Work Force Reports: A Synthesis and Critique. Information Series No. 354.

ERIC Educational Resources Information Center

Weber, James M.

Demographic and social changes, increasing economic interdependence, and educational reform movements are causing major changes in vocational education. Essential work force skills and the standards to account for their achievement are being debated. The 1980s'"Excellence Movement" focused on strengthening academic requirements,…

Indonesia: Internal Conditions, the Global Economy, and Regional Development.

ERIC Educational Resources Information Center

Leitner, Helga; Sheppard, Eric S.

1987-01-01

Describes recent trends in the economic and regional development of Indonesia and examines the internal and external forces influencing the process. Shows how these forces account for the rise of a strong centralized state. Discusses Indonesia's current problems. Includes tables, maps, and graphs of economic investment figures, world trade, and…

77 FR 42485 - Notice Is Given of the Names of Members of the Performance Review Board for the Department of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-19

..., Director, Defense Finance and Accounting Service. 10. Mr. Williams, Principle Deputy Director for Air Force..., all career status Air Force Tier 3 SES members not included in the above list are eligible to serve on...

Joining Forces: A Response to Kathy Rentz from the European Perspective

ERIC Educational Resources Information Center

Louhiala-Salminen, Leena

2010-01-01

In this article, the author responds to Kathy Rentz. She happily joins forces for pedagogically defensible teaching conditions and gives a brief "activist" account from the European perspective. However, rather than "European," she emphasizes that for the most part, this response looks at business communication teachers'…

Estimation of the behavior factor of existing RC-MRF buildings

NASA Astrophysics Data System (ADS)

Vona, Marco; Mastroberti, Monica

2018-01-01

In recent years, several research groups have studied a new generation of analysis methods for seismic response assessment of existing buildings. Nevertheless, many important developments are still needed in order to define more reliable and effective assessment procedures. Moreover, regarding existing buildings, it should be highlighted that due to the low knowledge level, the linear elastic analysis is the only analysis method allowed. The same codes (such as NTC2008, EC8) consider the linear dynamic analysis with behavior factor as the reference method for the evaluation of seismic demand. This type of analysis is based on a linear-elastic structural model subject to a design spectrum, obtained by reducing the elastic spectrum through a behavior factor. The behavior factor (reduction factor or q factor in some codes) is used to reduce the elastic spectrum ordinate or the forces obtained from a linear analysis in order to take into account the non-linear structural capacities. The behavior factors should be defined based on several parameters that influence the seismic nonlinear capacity, such as mechanical materials characteristics, structural system, irregularity and design procedures. In practical applications, there is still an evident lack of detailed rules and accurate behavior factor values adequate for existing buildings. In this work, some investigations of the seismic capacity of the main existing RC-MRF building types have been carried out. In order to make a correct evaluation of the seismic force demand, actual behavior factor values coherent with force based seismic safety assessment procedure have been proposed and compared with the values reported in the Italian seismic code, NTC08.

Analytical investigation for Lorentz forces effect on nanofluid Marangoni boundary layer hydrothermal behavior using HAM

NASA Astrophysics Data System (ADS)

Sheikholeslami, M.; Ganji, D. D.

2017-12-01

In this paper, semi analytical approach is applied to investigate nanofluid Marangoni convection in presence of magnetic field. Koo-Kleinstreuer-Li model is taken into account to simulate nanofluid properties. Homotopy analysis method is utilized to solve the final ordinary equations which are obtained from similarity transformation. Roles of Hartmann number and nanofluid volume fraction are presented graphically. Results show that temperature augments with rise of nanofluid volume fraction. Impact of nanofluid volume fraction on normal velocity is more than tangential velocity. Temperature gradient enhances with rise of magnetic number.

Horizontal Gene Transfer and the History of Life

PubMed Central

Daubin, Vincent; Szöllősi, Gergely J.

2016-01-01

Microbes acquire DNA from a variety of sources. The last decades, which have seen the development of genome sequencing, have revealed that horizontal gene transfer has been a major evolutionary force that has constantly reshaped genomes throughout evolution. However, because the history of life must ultimately be deduced from gene phylogenies, the lack of methods to account for horizontal gene transfer has thrown into confusion the very concept of the tree of life. As a result, many questions remain open, but emerging methodological developments promise to use information conveyed by horizontal gene transfer that remains unexploited today. PMID:26801681

Improvement of automatic control system for high-speed current collectors

NASA Astrophysics Data System (ADS)

Sidorov, O. A.; Goryunov, V. N.; Golubkov, A. S.

2018-01-01

The article considers the ways of regulation of pantographs to provide quality and reliability of current collection at high speeds. To assess impact of regulation was proposed integral criterion of the quality of current collection, taking into account efficiency and reliability of operation of the pantograph. The study was carried out using mathematical model of interaction of pantograph and catenary system, allowing to assess contact force and intensity of arcing at the contact zone at different movement speeds. The simulation results allowed us to estimate the efficiency of different methods of regulation of pantographs and determine the best option.

A weather-driven model of malaria transmission

PubMed Central

Hoshen, Moshe B; Morse, Andrew P

2004-01-01

Background Climate is a major driving force behind malaria transmission and climate data are often used to account for the spatial, seasonal and interannual variation in malaria transmission. Methods This paper describes a mathematical-biological model of the parasite dynamics, comprising both the weather-dependent within-vector stages and the weather-independent within-host stages. Results Numerical evaluations of the model in both time and space show that it qualitatively reconstructs the prevalence of infection. Conclusion A process-based modelling structure has been developed that may be suitable for the simulation of malaria forecasts based on seasonal weather forecasts. PMID:15350206

Numerical Simulation of Flow in the Chamber of the Water-Argon Plasma Generator

NASA Astrophysics Data System (ADS)

Hlbočan, Peter; Varchola, Michal; Knížat, Branislav; Mlkvik, Marek; Olšiak, Róbert

2012-12-01

The paper describes the CFD simulation of the flow of gas and plasma in a plasma generator with a hybrid stabilization of the electric arc. The momentum equations of the model also take Lorentz forces into account. In the energy equation, Joule heat is introduced as an energy source. The introduction of boundary conditions is also explained, as along with plasma transport properties and a method of solution. The paper presents selected results of pressure and velocity fields in the chamber of the plasma generator.

van der Waals forces in density functional theory: a review of the vdW-DF method

DOE PAGES

Berland, Kristian; Cooper, Valentino R.; Lee, Kyuho; ...

2015-05-15

We review a density functional theory (DFT) that accounts for van der Waals (vdW) interactions in condensed matter, materials physics, chemistry, and biology. The insights that led to the construction of the Rutgers–Chalmers van der Waals density functional (vdW-DF) are presented with the aim of giving a historical perspective, while also emphasizing more recent efforts which have sought to improve its accuracy. In addition to technical details, we discuss a range of recent applications that illustrate the necessity of including dispersion interactions in DFT. This review highlights the value of the vdW-DF method as a general-purpose method, not only formore » dispersion bound systems, but also in densely packed systems where these types of interactions are traditionally thought to be negligible.« less

Time-domain representation of frequency-dependent foundation impedance functions

USGS Publications Warehouse

Safak, E.

2006-01-01

Foundation impedance functions provide a simple means to account for soil-structure interaction (SSI) when studying seismic response of structures. Impedance functions represent the dynamic stiffness of the soil media surrounding the foundation. The fact that impedance functions are frequency dependent makes it difficult to incorporate SSI in standard time-history analysis software. This paper introduces a simple method to convert frequency-dependent impedance functions into time-domain filters. The method is based on the least-squares approximation of impedance functions by ratios of two complex polynomials. Such ratios are equivalent, in the time-domain, to discrete-time recursive filters, which are simple finite-difference equations giving the relationship between foundation forces and displacements. These filters can easily be incorporated into standard time-history analysis programs. Three examples are presented to show the applications of the method.

14 CFR 151.55 - Accounting and audit.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) Costs of force account construction. (5) Engineering costs of plans and designs. (6) Engineering costs... allowability of all incurred costs of the project. The sponsor shall segregate and group project costs so that it can furnish, on due notice, cost information in the following cost classifications: (1) Purchase...

14 CFR 151.55 - Accounting and audit.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) Costs of force account construction. (5) Engineering costs of plans and designs. (6) Engineering costs... allowability of all incurred costs of the project. The sponsor shall segregate and group project costs so that it can furnish, on due notice, cost information in the following cost classifications: (1) Purchase...

14 CFR 151.55 - Accounting and audit.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) Costs of force account construction. (5) Engineering costs of plans and designs. (6) Engineering costs... allowability of all incurred costs of the project. The sponsor shall segregate and group project costs so that it can furnish, on due notice, cost information in the following cost classifications: (1) Purchase...

14 CFR 151.55 - Accounting and audit.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) Costs of force account construction. (5) Engineering costs of plans and designs. (6) Engineering costs... allowability of all incurred costs of the project. The sponsor shall segregate and group project costs so that it can furnish, on due notice, cost information in the following cost classifications: (1) Purchase...

32 CFR 54.6 - Procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) Diving pay. (viii) Proficiency pay or special duty assignment pay. (ix) Career sea pay. (2) To determine..., U.S. Army Finance and Accounting Center, ATTN: FINCL-G, Indianapolis, IN 46249-0160, (317) 542-2155... 44199, (216) 522-5301. Air Force—Commander, Air Force Accounting and Finance Center, ATTN: JA, Denver...

Modification and optimization of the united-residue (UNRES) potential-energy function for canonical simulations. I. Temperature dependence of the effective energy function and tests of the optimization method with single training proteins

PubMed Central

Liwo, Adam; Khalili, Mey; Czaplewski, Cezary; Kalinowski, Sebastian; Ołdziej, Stanisław; Wachucik, Katarzyna; Scheraga, Harold A.

2011-01-01

We report the modification and parameterization of the united-residue (UNRES) force field for energy-based protein-structure prediction and protein-folding simulations. We tested the approach on three training proteins separately: 1E0L (β), 1GAB (α), and 1E0G (α + β). Heretofore, the UNRES force field had been designed and parameterized to locate native-like structures of proteins as global minima of their effective potential-energy surfaces, which largely neglected the conformational entropy because decoys composed of only lowest-energy conformations were used to optimize the force field. Recently, we developed a mesoscopic dynamics procedure for UNRES, and applied it with success to simulate protein folding pathways. How ever, the force field turned out to be largely biased towards α-helical structures in canonical simulations because the conformational entropy had been neglected in the parameterization. We applied the hierarchical optimization method developed in our earlier work to optimize the force field, in which the conformational space of a training protein is divided into levels each corresponding to a certain degree of native-likeness. The levels are ordered according to increasing native-likeness; level 0 corresponds to structures with no native-like elements and the highest level corresponds to the fully native-like structures. The aim of optimization is to achieve the order of the free energies of levels, decreasing as their native-likeness increases. The procedure is iterative, and decoys of the training protein(s) generated with the energy-function parameters of the preceding iteration are used to optimize the force field in a current iteration. We applied the multiplexing replica exchange molecular dynamics (MREMD) method, recently implemented in UNRES, to generate decoys; with this modification, conformational entropy is taken into account. Moreover, we optimized the free-energy gaps between levels at temperatures corresponding to a predominance of folded or unfolded structures, as well as to structures at the putative folding-transition temperature, changing the sign of the gaps at the transition temperature. This enabled us to obtain force fields characterized by a single peak in the heat capacity at the transition temperature. Furthermore, we introduced temperature dependence to the UNRES force field; this is consistent with the fact that it is a free-energy and not a potential-energy function. PMID:17201450

Competing effects of particle and medium inertia on particle diffusion in viscoelastic materials, and their ramifications for passive microrheology.

PubMed

Indei, Tsutomu; Schieber, Jay D; Córdoba, Andrés

2012-04-01

We analyze the appropriate form for the generalized Stokes-Einstein relation (GSER) for viscoelastic solids and fluids when bead inertia and medium inertia are taken into account, which we call the inertial GSER. It was previously shown for Maxwell fluids that the Basset (or Boussinesq) force arising from medium inertia can act purely dissipatively at high frequencies, where elasticity of the medium is dominant. In order to elucidate the cause of this counterintuitive result, we consider Brownian motion in a purely elastic solid where ordinary Stokes-type dissipation is not possible. The fluctuation-dissipation theorem requires the presence of a dissipative mechanism for the particle to experience fluctuating Brownian forces in a purely elastic solid. We show that the mechanism for such dissipation arises from the radiation of elastic waves toward the system boundaries. The frictional force associated with this mechanism is the Basset force, and it exists only when medium inertia is taken into consideration in the analysis of such a system. We consider first a one-dimensional harmonic lattice where all terms in the generalized Langevin equation--i.e., the elastic term, the memory kernel, and Brownian forces-can be found analytically from projection-operator methods. We show that the dissipation is purely from radiation of elastic waves. A similar analysis is made on a particle in a continuum, three-dimensional purely elastic solid, where the memory kernel is determined from continuum mechanics. Again, dissipation arises only from radiation of elastic shear waves toward infinite boundaries when medium inertia is taken into account. If the medium is a viscoelastic solid, Stokes-type dissipation is possible in addition to radiational dissipation so that the wave decays at the penetration depth. Inertial motion of the bead couples with the elasticity of the viscoelastic material, resulting in a possible resonant oscillation of the mean-square displacement (MSD) of the bead. On the other hand, medium inertia (the Basset force) tends to attenuate the oscillations by the dissipation mechanism described above. Thus competition between bead inertia and medium inertia determines whether or not the MSD oscillates. We find that, if the medium density is larger than 4/7 of the bead density, the Basset damping will suppress oscillations in the MSD; this criterion is sufficient but not necessary to present oscillations.

An Efficient Algorithm for Perturbed Orbit Integration Combining Analytical Continuation and Modified Chebyshev Picard Iteration

NASA Astrophysics Data System (ADS)

Elgohary, T.; Kim, D.; Turner, J.; Junkins, J.

2014-09-01

Several methods exist for integrating the motion in high order gravity fields. Some recent methods use an approximate starting orbit, and an efficient method is needed for generating warm starts that account for specific low order gravity approximations. By introducing two scalar Lagrange-like invariants and employing Leibniz product rule, the perturbed motion is integrated by a novel recursive formulation. The Lagrange-like invariants allow exact arbitrary order time derivatives. Restricting attention to the perturbations due to the zonal harmonics J2 through J6, we illustrate an idea. The recursively generated vector-valued time derivatives for the trajectory are used to develop a continuation series-based solution for propagating position and velocity. Numerical comparisons indicate performance improvements of ~ 70X over existing explicit Runge-Kutta methods while maintaining mm accuracy for the orbit predictions. The Modified Chebyshev Picard Iteration (MCPI) is an iterative path approximation method to solve nonlinear ordinary differential equations. The MCPI utilizes Picard iteration with orthogonal Chebyshev polynomial basis functions to recursively update the states. The key advantages of the MCPI are as follows: 1) Large segments of a trajectory can be approximated by evaluating the forcing function at multiple nodes along the current approximation during each iteration. 2) It can readily handle general gravity perturbations as well as non-conservative forces. 3) Parallel applications are possible. The Picard sequence converges to the solution over large time intervals when the forces are continuous and differentiable. According to the accuracy of the starting solutions, however, the MCPI may require significant number of iterations and function evaluations compared to other integrators. In this work, we provide an efficient methodology to establish good starting solutions from the continuation series method; this warm start improves the performance of the MCPI significantly and will likely be useful for other applications where efficiently computed approximate orbit solutions are needed.

GAO's Views on the Default Task Force's Recommendations for Reducing Default Costs in the Guaranteed Student Loan Program. Testimony before the Subcommittee on Postsecondary Education, Committee on Education and Labor, House of Representatives.

ERIC Educational Resources Information Center

Gainer, William J.

This General Accounting Office (GAO) testimony before the Subcommittee on Postsecondary Education, Committee on Education and Labor, House of Representatives, concerns the findings of the task force that addressed the increasing costs of student loan defaults. The task force report is considered, generally, to provide additional incentives and…

Supply Rate and Equilibrium Inventory of Air Force Enlisted Personnel: A Simultaneous Model of the Accession and Retention Markets Incorporating Force Level Constraints. Final Report for Period July 1969-June 1976.

ERIC Educational Resources Information Center

DeVany, Arthur S.; And Others

This research was designed to develop and test a model of the Air Force manpower market. The study indicates that previous manpower supply studies failed to account for simultaneous determination of enlistments and retentions and misinterpreted regressions as supply equations. They are, instead, reduced form equations resulting from joint…

Dynamics of Longitudinal Impact in the Variable Cross-Section Rods

NASA Astrophysics Data System (ADS)

Stepanov, R.; Romenskyi, D.; Tsarenko, S.

2018-03-01

Dynamics of longitudinal impact in rods of variable cross-section is considered. Rods of various configurations are used as elements of power pulse systems. There is no single method to the construction of a mathematical model of longitudinal impact on rods. The creation of a general method for constructing a mathematical model of longitudinal impact for rods of variable cross-section is the goal of the article. An elastic rod is considered with a cross-sectional area varying in powers of law from the longitudinal coordinate. The solution of the wave equation is obtained using the Fourier method. Special functions are introduced on the basis of recurrence relations for Bessel functions for solving boundary value problems. The expression for the square of the norm is obtained taking into account the orthogonality property of the eigen functions with weight. For example, the impact of an inelastic mass along the wide end of a conical rod is considered. The expressions for the displacements, forces and stresses of the rod sections are obtained for the cases of sudden velocity communication and the application of force. The proposed mathematical model makes it possible to carry out investigations of the stress-strain state in rods of variable and constant cross-section for various conditions of dynamic effects.

Food Adulteration in Switzerland: From 'Ravioli' over 'Springbok' to 'Disco Sushi'.

PubMed

Hubner, Philipp

2016-01-01

The driving force behind food adulteration is monetary profit and this has remained unchanged for at least the last hundred years. Food adulterations were and still are difficult to uncover because they occur mostly in an unpredictable and unexpected way. Very often food falsifiers take advantage of modern technology in such a way that food adulterations are difficult or sometimes even impossible to detect. Targets for food adulteration were and still are highly priced food items such as spirits, meat, seafood and olive oil. Although difficult to detect, food adulterations were in the past strong driving forces for the development of adequate detection methods in the official food control laboratories and for the enforcement of the food law. A very prominent example in this context is the 'Ravioli scandal' in Switzerland in the late 1970s which showed that cheap second-class meat could be processed into products without being discovered for long time. As a consequence the official food control laboratories in Switzerland were reinforced with more laboratory equipment and technical staff. With the introduction of new detection principles such as DNA-based analytical methods new kinds of food adulteration could and can be uncovered. Analytical methods have their limits and in some cases of food fraud there are no analytical means to detect them. In such cases the examination of trade by checking of accounts is the method of choice.

Fire-induced albedo change and surface radiative forcing in sub-Saharan Africa savanna ecosystems: Implications for the energy balance

NASA Astrophysics Data System (ADS)

Dintwe, Kebonye; Okin, Gregory S.; Xue, Yongkang

2017-06-01

Surface albedo is a critical parameter that controls surface energy balance. In dryland ecosystems, fires play a significant role in decreasing surface albedo, resulting in positive radiative forcing. Here we investigate the long-term effect of fire on surface albedo. We devised a method to calculate short-, medium-, and long-term effect of fire-induced radiative forcing and their relative effects on energy balance. We used Moderate Resolution Imaging Spectroradiometer (MODIS) data in our analysis, covering different vegetation classes in sub-Saharan Africa (SSA). Our analysis indicated that mean short-term fire-induced albedo change in SSA was -0.022, -0.035, and -0.041 for savannas, shrubland, and grasslands, respectively. At regional scale, mean fire-induced albedo change in savannas was -0.018 and -0.024 for northern sub-Saharan of Africa and the southern hemisphere Africa, respectively. The short-term mean fire-induced radiative forcing in burned areas in sub-Saharan Africa (SSA) was 5.41 W m-2, which contributed continental and global radiative forcings of 0.25 and 0.058 W m-2, respectively. The impact of fire in surface albedo has long-lasting effects that varies with vegetation type. The long-term energetic effects of fire-induced albedo change and associated radiative forcing were, on average, more than 19 times greater across SSA than the short-term effects, suggesting that fires exerted far more radiative forcing than previously thought. Taking into account the actual duration of fire's effect on surface albedo, we conclude that the contribution of SSA fires, globally and throughout the year, is 0.12 W m-2. These findings provide crucial information on possible impact of fire on regional climate variability.

United States Air Force Statistical Digest, Fiscal Year 1954. Ninth Edition

DTIC Science & Technology

1954-09-30

expenditure frOm the Treasury. In Budget_ Treasury Regulation 1, appropriation accounts include not only accounts to which money is directly...services received or assets acquired for vhich payment has been oade. Synonymous with disbursements less expenditure refunds. (AFM 170-3) FUND A sum of money ...during a given period reqUiring future payment of money . PROJECT ACCOUNr CLASSIFICATION In appropriation and fund accounting, an approved system of

High-speed adaptive contact-mode atomic force microscopy imaging with near-minimum-force

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Juan; Zou, Qingze, E-mail: qzzou@rci.rutgers.edu

In this paper, an adaptive contact-mode imaging approach is proposed to replace the traditional contact-mode imaging by addressing the major concerns in both the speed and the force exerted to the sample. The speed of the traditional contact-mode imaging is largely limited by the need to maintain precision tracking of the sample topography over the entire imaged sample surface, while large image distortion and excessive probe-sample interaction force occur during high-speed imaging. In this work, first, the image distortion caused by the topography tracking error is accounted for in the topography quantification. Second, the quantified sample topography is utilized inmore » a gradient-based optimization method to adjust the cantilever deflection set-point for each scanline closely around the minimal level needed for maintaining stable probe-sample contact, and a data-driven iterative feedforward control that utilizes a prediction of the next-line topography is integrated to the topography feeedback loop to enhance the sample topography tracking. The proposed approach is demonstrated and evaluated through imaging a calibration sample of square pitches at both high speeds (e.g., scan rate of 75 Hz and 130 Hz) and large sizes (e.g., scan size of 30 μm and 80 μm). The experimental results show that compared to the traditional constant-force contact-mode imaging, the imaging speed can be increased by over 30 folds (with the scanning speed at 13 mm/s), and the probe-sample interaction force can be reduced by more than 15% while maintaining the same image quality.« less

High-speed adaptive contact-mode atomic force microscopy imaging with near-minimum-force.

PubMed

Ren, Juan; Zou, Qingze

2014-07-01

In this paper, an adaptive contact-mode imaging approach is proposed to replace the traditional contact-mode imaging by addressing the major concerns in both the speed and the force exerted to the sample. The speed of the traditional contact-mode imaging is largely limited by the need to maintain precision tracking of the sample topography over the entire imaged sample surface, while large image distortion and excessive probe-sample interaction force occur during high-speed imaging. In this work, first, the image distortion caused by the topography tracking error is accounted for in the topography quantification. Second, the quantified sample topography is utilized in a gradient-based optimization method to adjust the cantilever deflection set-point for each scanline closely around the minimal level needed for maintaining stable probe-sample contact, and a data-driven iterative feedforward control that utilizes a prediction of the next-line topography is integrated to the topography feeedback loop to enhance the sample topography tracking. The proposed approach is demonstrated and evaluated through imaging a calibration sample of square pitches at both high speeds (e.g., scan rate of 75 Hz and 130 Hz) and large sizes (e.g., scan size of 30 μm and 80 μm). The experimental results show that compared to the traditional constant-force contact-mode imaging, the imaging speed can be increased by over 30 folds (with the scanning speed at 13 mm/s), and the probe-sample interaction force can be reduced by more than 15% while maintaining the same image quality.

Potentials of mean force for biomolecular simulations: Theory and test on alanine dipeptide

NASA Astrophysics Data System (ADS)

Pellegrini, Matteo; Grønbech-Jensen, Niels; Doniach, Sebastian

1996-06-01

We describe a technique for generating potentials of mean force (PMF) between solutes in an aqueous solution. We first generate solute-solvent correlation functions (CF) using Monte Carlo (MC) simulations in which we place a single atom solute in a periodic boundary box containing a few hundred water molecules. We then make use of the Kirkwood superposition approximation, where the 3-body correlation function is approximated as the product of 2-body CFs, to describe the mean water density around two solutes. Computing the force generated on the solutes by this average water density allows us to compute potentials of mean force between the two solutes. For charged solutes an additional approximation involving dielectric screening is made, by setting the dielectric constant of water to ɛ=80. These potentials account, in an approximate manner, for the average effect of water on the atoms. Following the work of Pettitt and Karplus [Chem. Phys. Lett. 121, 194 (1985)], we approximate the n-body potential of mean force as a sum of the pairwise potentials of mean force. This allows us to run simulations of biomolecules without introducing explicit water, hence gaining several orders of magnitude in efficiency with respect to standard molecular dynamics techniques. We demonstrate the validity of this technique by first comparing the PMFs for methane-methane and sodium-chloride generated with this procedure, with those calculated with a standard Monte Carlo simulation with explicit water. We then compare the results of the free energy profiles between the equilibria of alanine dipeptide generated by the two methods.

Contribution of trochanteric soft tissues to fall force estimates, the factor of risk, and prediction of hip fracture risk.

PubMed

Bouxsein, Mary L; Szulc, Pawel; Munoz, Fracoise; Thrall, Erica; Sornay-Rendu, Elizabeth; Delmas, Pierre D

2007-06-01

We compared trochanteric soft tissue thickness, femoral aBMD, and the ratio of fall force to femoral strength (i.e., factor of risk) in 21 postmenopausal women with incident hip fracture and 42 age-matched controls. Reduced trochanteric soft tissue thickness, low femoral aBMD, and increased ratio of fall force to femoral strength (i.e., factor of risk) were associated with increased risk of hip fracture. The contribution of trochanteric soft tissue thickness to hip fracture risk is incompletely understood. A biomechanical approach to assessing hip fracture risk that compares forces applied to the hip during a sideways fall to femoral strength may by improved by incorporating the force-attenuating effects of trochanteric soft tissues. We determined the relationship between femoral areal BMD (aBMD) and femoral failure load in 49 human cadaveric specimens, 53-99 yr of age. We compared femoral aBMD, trochanteric soft tissue thickness, and the ratio of fall forces to bone strength (i.e., the factor of risk for hip fracture, phi), before and after accounting for the force-attenuating properties of trochanteric soft tissue in 21 postmenopausal women with incident hip fracture and 42 age-matched controls. Femoral aBMD correlated strongly with femoral failure load (r2 = 0.73-0.83). Age, height, and weight did not differ; however, women with hip fracture had lower total femur aBMD (OR = 2.06; 95% CI, 1.19-3.56) and trochanteric soft tissue thickness (OR = 1.82; 95% CI, 1.01, 3.31). Incorporation of trochanteric soft tissue thickness measurements reduced the estimates of fall forces by approximately 50%. After accounting for force-attenuating properties of trochanteric soft tissue, the ratio of fall forces to femoral strength was 50% higher in cases than controls (0.92 +/- 0.44 versus 0.65 +/- 0.50, respectively; p = 0.04). It is possible to compute a biomechanically based estimate of hip fracture risk by combining estimates of femoral strength based on an empirical relationship between femoral aBMD and bone strength in cadaveric femora, along with estimates of loads applied to the hip during a sideways fall that account for thickness of trochanteric soft tissues. Our findings suggest that trochanteric soft tissue thickness may influence hip fracture risk by attenuating forces applied to the femur during a sideways fall and provide rationale for developing improved measurements of trochanteric soft tissue and for studying a larger cohort to determine whether trochanteric soft tissue thickness contributes to hip fracture risk independently of aBMD.

Accountability: A Watchword for University Administration in Nigeria

ERIC Educational Resources Information Center

Sofoluwe, Abayomi Olumade; Oduwaiye, Rhoda Olape; Ogundele, Michael Olarewaju; Kayode, David Jimoh

2015-01-01

The term accountability means different things to different people in different organizations. In the educational setting, the term is seen as liability to one's accomplishment in the educational system. The ever increasing needs of the universities and the dwindling resources available to them have forced university management and other…

Breaking the Ice: Career Development Activities for Accounting Students

ERIC Educational Resources Information Center

Kilpatrick, Bob G.; Wilburn, Nancy L.

2010-01-01

This paper describes two co-curricular career development activities, mock interviews and speed networking that we provide for accounting majors at our university. The driving force behind both activities was to increase comfort levels for students when interacting with professionals and to enhance their job interview and networking skills.…

Theoretical modeling of large molecular systems. Advances in the local self consistent field method for mixed quantum mechanics/molecular mechanics calculations.

PubMed

Monari, Antonio; Rivail, Jean-Louis; Assfeld, Xavier

2013-02-19

Molecular mechanics methods can efficiently compute the macroscopic properties of a large molecular system but cannot represent the electronic changes that occur during a chemical reaction or an electronic transition. Quantum mechanical methods can accurately simulate these processes, but they require considerably greater computational resources. Because electronic changes typically occur in a limited part of the system, such as the solute in a molecular solution or the substrate within the active site of enzymatic reactions, researchers can limit the quantum computation to this part of the system. Researchers take into account the influence of the surroundings by embedding this quantum computation into a calculation of the whole system described at the molecular mechanical level, a strategy known as the mixed quantum mechanics/molecular mechanics (QM/MM) approach. The accuracy of this embedding varies according to the types of interactions included, whether they are purely mechanical or classically electrostatic. This embedding can also introduce the induced polarization of the surroundings. The difficulty in QM/MM calculations comes from the splitting of the system into two parts, which requires severing the chemical bonds that link the quantum mechanical subsystem to the classical subsystem. Typically, researchers replace the quantoclassical atoms, those at the boundary between the subsystems, with a monovalent link atom. For example, researchers might add a hydrogen atom when a C-C bond is cut. This Account describes another approach, the Local Self Consistent Field (LSCF), which was developed in our laboratory. LSCF links the quantum mechanical portion of the molecule to the classical portion using a strictly localized bond orbital extracted from a small model molecule for each bond. In this scenario, the quantoclassical atom has an apparent nuclear charge of +1. To achieve correct bond lengths and force constants, we must take into account the inner shell of the atom: for an sp(3) carbon atom, we consider the two core 1s electrons and treat that carbon as an atom with three electrons. This results in an LSCF+3 model. Similarly, a nitrogen atom with a lone pair of electrons available for conjugation is treated as an atom with five electrons (LSCF+5). This approach is particularly well suited to splitting peptide bonds and other bonds that include carbon or nitrogen atoms. To embed the induced polarization within the calculation, researchers must use a polarizable force field. However, because the parameters of the usual force fields include an average of the induction effects, researchers typically can obtain satisfactory results without explicitly introducing the polarization. When considering electronic transitions, researchers must take into account the changes in the electronic polarization. One approach is to simulate the electronic cloud of the surroundings by a continuum whose dielectric constant is equal to the square of the refractive index. This Electronic Response of the Surroundings (ERS) methodology allows researchers to model the changes in induced polarization easily. We illustrate this approach by modeling the electronic absorption of tryptophan in human serum albumin (HSA).

A dynamic mechanical analysis technique for porous media

PubMed Central

Pattison, Adam J; McGarry, Matthew; Weaver, John B; Paulsen, Keith D

2015-01-01

Dynamic mechanical analysis (DMA) is a common way to measure the mechanical properties of materials as functions of frequency. Traditionally, a viscoelastic mechanical model is applied and current DMA techniques fit an analytical approximation to measured dynamic motion data by neglecting inertial forces and adding empirical correction factors to account for transverse boundary displacements. Here, a finite element (FE) approach to processing DMA data was developed to estimate poroelastic material properties. Frequency-dependent inertial forces, which are significant in soft media and often neglected in DMA, were included in the FE model. The technique applies a constitutive relation to the DMA measurements and exploits a non-linear inversion to estimate the material properties in the model that best fit the model response to the DMA data. A viscoelastic version of this approach was developed to validate the approach by comparing complex modulus estimates to the direct DMA results. Both analytical and FE poroelastic models were also developed to explore their behavior in the DMA testing environment. All of the models were applied to tofu as a representative soft poroelastic material that is a common phantom in elastography imaging studies. Five samples of three different stiffnesses were tested from 1 – 14 Hz with rough platens placed on the top and bottom surfaces of the material specimen under test to restrict transverse displacements and promote fluid-solid interaction. The viscoelastic models were identical in the static case, and nearly the same at frequency with inertial forces accounting for some of the discrepancy. The poroelastic analytical method was not sufficient when the relevant physical boundary constraints were applied, whereas the poroelastic FE approach produced high quality estimates of shear modulus and hydraulic conductivity. These results illustrated appropriate shear modulus contrast between tofu samples and yielded a consistent contrast in hydraulic conductivity as well. PMID:25248170

Self-force as a cosmic censor in the Kerr overspinning problem

NASA Astrophysics Data System (ADS)

Colleoni, Marta; Barack, Leor; Shah, Abhay G.; van de Meent, Maarten

2015-10-01

It is known that a near-extremal Kerr black hole can be spun up beyond its extremal limit by capturing a test particle. Here we show that overspinning is always averted once backreaction from the particle's own gravity is properly taken into account. We focus on nonspinning, uncharged, massive particles thrown in along the equatorial plane and work in the first-order self-force approximation (i.e., we include all relevant corrections to the particle's acceleration through linear order in the ratio, assumed small, between the particle's energy and the black hole's mass). Our calculation is a numerical implementation of a recent analysis by two of us [Phys. Rev. D 91, 104024 (2015)], in which a necessary and sufficient "censorship" condition was formulated for the capture scenario, involving certain self-force quantities calculated on the one-parameter family of unstable circular geodesics in the extremal limit. The self-force information accounts both for radiative losses and for the finite-mass correction to the critical value of the impact parameter. Here we obtain the required self-force data and present strong evidence to suggest that captured particles never drive the black hole beyond its extremal limit. We show, however, that, within our first-order self-force approximation, it is possible to reach the extremal limit with a suitable choice of initial orbital parameters. To rule out such a possibility would require (currently unavailable) information about higher-order self-force corrections.

Transient Characteristics of Free Piston Vuilleurnier Cycle Heat Pumps

NASA Astrophysics Data System (ADS)

Matsue, Junji; Fujimoto, Norioki; Shirai, Hiroyuki

A dynamic analysis of a free piston Vuilleumier cycle heat pump was performed using a time-stepping integration method to investigate transient characteristics under power controlling. The nonlinear relationship between displacement and force for pistons was taken into account for the motion of reciprocating components. The force for pistons is mainly caused by the pressure change of working gas varying with piston displacements; moreover nonlinear viscous dissipative force due to the oscillating flow of working gas in heat exchangers and discontinuous damping force caused by solid friction at piston seals and rod seals are included. The displacements of pistons and pressure changes in the Vuilleumier cycle heat pump were integrated by an ideal isothermal thermodynamic relationship. It was assumed that the flow friction was proportional to the kinematic pressure of working gas, and that the solid friction at the seals was due to the functions of the working gas pressure and the tension of seal springs. In order to investigate the transient characteristics of a proposed free piston Vuilleumier cycle heat pump machine when hot-side working gas temperatures and alternate force were changed, some calculations were performed and discussed. These calculation results make clear transient characteristics at starting and power controlling. It was further found that only a small amount of starter power is required in particular conditions. During controlling, the machine becomes unstable when there is ar elatively large reduction in cooling or heating power. Therefore, an auxiliary device is additionally needed to obtain stable operation, such as al inear motor.

An updated model for nitrate uptake modelling in plants. I. Functional component: cross-combination of flow–force interpretation of nitrate uptake isotherms, and environmental and in planta regulation of nitrate influx

PubMed Central

Le Deunff, Erwan; Malagoli, Philippe

2014-01-01

Background and Aims In spite of major breakthroughs in the last three decades in the identification of root nitrate uptake transporters in plants and the associated regulation of nitrate transport activities, a simplified and operational modelling approach for nitrate uptake is still lacking. This is due mainly to the difficulty in linking the various regulations of nitrate transport that act at different levels of time and on different spatial scales. Methods A cross-combination of a Flow–Force approach applied to nitrate influx isotherms and experimentally determined environmental and in planta regulation is used to model nitrate in oilseed rape, Brassica napus. In contrast to ‘Enzyme–Substrate’ interpretations, a Flow–Force modelling approach considers the root as a single catalytic structure and does not infer hypothetical cellular processes among nitrate transporter activities across cellular layers in the mature roots. In addition, this approach accounts for the driving force on ion transport based on the gradient of electrochemical potential, which is more appropriate from a thermodynamic viewpoint. Key Results and Conclusions Use of a Flow–Force formalism on nitrate influx isotherms leads to the development of a new conceptual mechanistic basis to model more accurately N uptake by a winter oilseed rape crop under field conditions during the whole growth cycle. This forms the functional component of a proposed new structure–function mechanistic model of N uptake. PMID:24638820

Dynamical simulation priors for human motion tracking.

PubMed

Vondrak, Marek; Sigal, Leonid; Jenkins, Odest Chadwicke

2013-01-01

We propose a simulation-based dynamical motion prior for tracking human motion from video in presence of physical ground-person interactions. Most tracking approaches to date have focused on efficient inference algorithms and/or learning of prior kinematic motion models; however, few can explicitly account for the physical plausibility of recovered motion. Here, we aim to recover physically plausible motion of a single articulated human subject. Toward this end, we propose a full-body 3D physical simulation-based prior that explicitly incorporates a model of human dynamics into the Bayesian filtering framework. We consider the motion of the subject to be generated by a feedback “control loop” in which Newtonian physics approximates the rigid-body motion dynamics of the human and the environment through the application and integration of interaction forces, motor forces, and gravity. Interaction forces prevent physically impossible hypotheses, enable more appropriate reactions to the environment (e.g., ground contacts), and are produced from detected human-environment collisions. Motor forces actuate the body, ensure that proposed pose transitions are physically feasible, and are generated using a motion controller. For efficient inference in the resulting high-dimensional state space, we utilize an exemplar-based control strategy that reduces the effective search space of motor forces. As a result, we are able to recover physically plausible motion of human subjects from monocular and multiview video. We show, both quantitatively and qualitatively, that our approach performs favorably with respect to Bayesian filtering methods with standard motion priors.

Plato and the Police: Dogs, Guardians, and Why Accountability Is the Wrong Answer

ERIC Educational Resources Information Center

Deane, Samantha; Shuffelton, Amy

2016-01-01

Attention to significant commonalities between the position of teachers and police officers, we suggest, illuminates problematic aspects of their position within a democracy. Demographically, both the teaching force and the police force are disproportionately white, yet the commonalities extend beyond race. We suspect too little attention has been…

Peacekeeping, a New Challenge for Burkina Faso’s Armed Forces

DTIC Science & Technology

2013-03-01

and trends. It takes into account the competitors , the internal and external threats and the opportunities. “Defining the vision is the first step...forces deployed in the peace mission in Sudan. BURKBATT uses Toyota 4x4 pickups as light tactical vehicles. They are less expensive and were adopted

Extension of volcanic forcing data back to 100 BC using the Analog method

NASA Astrophysics Data System (ADS)

Wagner, Sebastian; Zorita, Eduardo

2013-04-01

Present reconstructions of volcanic forcing to be used for climate simulations so far extend back until 500 AD for stratospheric aerosol sulphate injection (Gao et al., 2008), and back until 800 AD for aerosol optical depth and effective radius (Crowley et al. 2012; ICI5 data set). Here, we aim to extent the volcanic data set of Crowley et al. (2012) back to 100 BC. This data sets originally starts in 800 AD, for aerosol optical depth and effective radius. The method we apply is the Analog method, using information in the already existing reconstruction and extending it back in time by using information of long volcanic sulphate contained in Greenland and Antarctic Ice cores published in previous studies. The reconstruction of the volcanic forcing in first millennium is based on the search of analogs in the second millennium. The pool of analogs includes the ICI5 data set for the period 800-2000 AD. The basic philosophy is to find volcanic events with the same or similar magnitude in terms of volcanic sulphate deposition in Greenland and Antarctic ice cores. For the Northern Hemisphere the estimated maximum total stratospheric sulphate loading from Zielinski (1995) is used. For the Southern Hemisphere the Plummer et al. (2012) data set and the Ferris et al. (2011) data set are used in terms of sulphate deposition. To ensure that the volcanic event was large enough in magnitude, a certain threshold is applied to the analog selection. The extension, i.e. the analog search, is carried out separately for the four different latitudinal bands of the ICI5 data set. The method can be applied when better records than the Zielinski et al. (1995), record for the Northern Hemisphere become available. The analogs are selected based on the comparison between the information contained in the ice cores in the pre-800 AD period and post-800 AD period. For each event in the pre-800 AD period (the target), the most similar event (the analog) in the post-800 AD pool in terms of ice-core sulphate is identified. The forcing data (effective radius and aerosol optical depth) of the ICI5 data set for that analog event is then used as a surrogate for the target event. In the case that the analog does not exactly match the amplitude of the pre-800 AD event a scaling correction factor is applied, taking into account the relative difference of ice-core sulphate between the analog and the target. Although the method does not take into account the specific structure of each volcanic event, the basic patterns are reproduced reasonably well for a validation period in the second millennium AD. The largest uncertainties relate to the dating of each volcanic event, including the season of the eruption, the synchronization of hemispheric versus global eruptions and the translation of the ice core volcanic sulphate concentrations into stratospheric aerosol loadings. However, these uncertainties will essentially remain using different methods based on the sulphate information contained in Antarctic and Greenland ice cores.

Energetic costs of producing muscle work and force in a cyclical human bouncing task

PubMed Central

Kuo, Arthur D.

2011-01-01

Muscles expend energy to perform active work during locomotion, but they may also expend significant energy to produce force, for example when tendons perform much of the work passively. The relative contributions of work and force to overall energy expenditure are unknown. We therefore measured the mechanics and energetics of a cyclical bouncing task, designed to control for work and force. We hypothesized that near bouncing resonance, little work would be performed actively by muscle, but the cyclical production of force would cost substantial metabolic energy. Human subjects (n = 9) bounced vertically about the ankles at inversely proportional frequencies (1–4 Hz) and amplitudes (15–4 mm), such that the overall rate of work performed on the body remained approximately constant (0.30 ± 0.06 W/kg), but the forces varied considerably. We used parameter identification to estimate series elasticity of the triceps surae tendon, as well as the work performed actively by muscle and passively by tendon. Net metabolic energy expenditure for bouncing at 1 Hz was 1.15 ± 0.31 W/kg, attributable mainly to active muscle work with an efficiency of 24 ± 3%. But at 3 Hz (near resonance), most of the work was performed passively, so that active muscle work could account for only 40% of the net metabolic rate of 0.76 ± 0.28 W/kg. Near resonance, a cost for cyclical force that increased with both amplitude and frequency of force accounted for at least as much of the total energy expenditure as a cost for work. Series elasticity reduces the need for active work, but energy must still be expended for force production. PMID:21212245

Physically-based modeling of drag force caused by natural woody vegetation

NASA Astrophysics Data System (ADS)

Järvelä, J.; Aberle, J.

2014-12-01

Riparian areas and floodplains are characterized by woody vegetation, which is an essential feature to be accounted for in many hydro-environmental models. For applications including flood protection, river restoration and modelling of sediment processes, there is a need to improve the reliability of flow resistance estimates. Conventional methods such as the use of lumped resistance coefficients or simplistic cylinder-based drag force equations can result in significant errors, as these methods do not adequately address the effect of foliage and reconfiguration of flexible plant parts under flow action. To tackle the problem, physically-based methods relying on objective and measurable vegetation properties are advantageous for describing complex vegetation. We have conducted flume and towing tank investigations with living and artificial plants, both in arrays and with isolated plants, providing new insight into advanced parameterization of natural vegetation. The stem, leaf and total areas of the trees confirmed to be suitable characteristic dimensions for estimating flow resistance. Consequently, we propose the use of leaf area index and leaf-to-stem-area ratio to achieve better drag force estimates. Novel remote sensing techniques including laser scanning have become available for effective collection of the required data. The benefits of the proposed parameterization have been clearly demonstrated in our newest experimental studies, but it remains to be investigated to what extent the parameter values are species-specific and how they depend on local habitat conditions. The purpose of this contribution is to summarize developments in the estimation of vegetative drag force based on physically-based approaches as the latest research results are somewhat dispersed. In particular, concerning woody vegetation we seek to discuss three issues: 1) parameterization of reconfiguration with the Vogel exponent; 2) advantage of parameterizing plants with the leaf area index and leaf-to-stem-area ratio, and 3) effect of plant scale (size from twigs to mature trees). To analyze these issues we use experimental data from the authors' research teams as well as from other researchers. The results are expected to be useful for the design of future experimental campaigns and developing drag force models.

On the Analysis of Multistep-Out-of-Grid Method for Celestial Mechanics Tasks

NASA Astrophysics Data System (ADS)

Olifer, L.; Choliy, V.

2016-09-01

Occasionally, there is a necessity in high-accurate prediction of celestial body trajectory. The most common way to do that is to solve Kepler's equation analytically or to use Runge-Kutta or Adams integrators to solve equation of motion numerically. For low-orbit satellites, there is a critical need in accounting geopotential and another forces which influence motion. As the result, the right side of equation of motion becomes much bigger, and classical integrators will not be quite effective. On the other hand, there is a multistep-out-of-grid (MOG) method which combines Runge-Kutta and Adams methods. The MOG method is based on using m on-grid values of the solution and n × m off-grid derivative estimations. Such method could provide stable integrators of maximum possible order, O (hm+mn+n-1). The main subject of this research was to implement and analyze the MOG method for solving satellite equation of motion with taking into account Earth geopotential model (ex. EGM2008 (Pavlis at al., 2008)) and with possibility to add other perturbations such as atmospheric drag or solar radiation pressure. Simulations were made for satellites on low orbit and with various eccentricities (from 0.1 to 0.9). Results of the MOG integrator were compared with results of Runge-Kutta and Adams integrators. It was shown that the MOG method has better accuracy than classical ones of the same order and less right-hand value estimations when is working on high orders. That gives it some advantage over "classical" methods.

Error estimates for (semi-)empirical dispersion terms and large biomacromolecules.

PubMed

Korth, Martin

2013-10-14

The first-principles modeling of biomaterials has made tremendous advances over the last few years with the ongoing growth of computing power and impressive developments in the application of density functional theory (DFT) codes to large systems. One important step forward was the development of dispersion corrections for DFT methods, which account for the otherwise neglected dispersive van der Waals (vdW) interactions. Approaches at different levels of theory exist, with the most often used (semi-)empirical ones based on pair-wise interatomic C6R(-6) terms. Similar terms are now also used in connection with semiempirical QM (SQM) methods and density functional tight binding methods (SCC-DFTB). Their basic structure equals the attractive term in Lennard-Jones potentials, common to most force field approaches, but they usually use some type of cutoff function to make the mixing of the (long-range) dispersion term with the already existing (short-range) dispersion and exchange-repulsion effects from the electronic structure theory methods possible. All these dispersion approximations were found to perform accurately for smaller systems, but error estimates for larger systems are very rare and completely missing for really large biomolecules. We derive such estimates for the dispersion terms of DFT, SQM and MM methods using error statistics for smaller systems and dispersion contribution estimates for the PDBbind database of protein-ligand interactions. We find that dispersion terms will usually not be a limiting factor for reaching chemical accuracy, though some force fields and large ligand sizes are problematic.

The response of stationary planetary waves to tropospheric forcing

NASA Technical Reports Server (NTRS)

Alpert, J. C.; Geller, M. A.; Avery, S. K.

1983-01-01

The lower boundary forcing of airflow over topography, and the internal forcing that results from the geographical distribution of diabatic heating, are studied in light of a steady state, linear, quasi-geostrophic model of stationary waves on a sphere. The lower boundary vertical motions forced by airflow over topography depend on whether the horizontal deflection of airflow around topographic features is taken into account, the level of the wind profile at which flow over topography is assumed to take place, and the topographic data set that was used in the forcing formulation. The lower boundary forcing is taken to be given by the observed stationary planetary wave in lower boundary geopotential height, and the internal forcing is computed using the planetary wave propagation equation on the observed wave structure.

Financial Audit: Financial Reporting and Internal Controls at the Air Force Systems Command

DTIC Science & Technology

1991-01-01

As part of GAO’S audits of the Air Force’s financial management and operations for fiscal years 1988 and 1989, GAO evaluated the Air Force Systems Command’s internal accounting controls and financial reporting systems. For fiscal year 1988 and 1989, the Systems Command received about $26.7 billion and $32.4 billion, respectively, in appropriated funds. This report discusses the results of our audits of the Systems Command.

Force Structure: Preliminary Observations on Army Plans to Implement and Fund Modular Forces

DTIC Science & Technology

2005-03-16

affect the size and composition of the modular force as well as its cost. First, the Army’s Campaign Plan calls for a potential decision by fiscal year...upgrading existing active brigades, or other support and command elements; and • accounted for construction of temporary , relocatable facilities...Kevin Handley, Joah Iannotta, Harry Jobes, Joseph Kirschbaum, Eric Theus, Jason Venner , and J. Andrew Walker.Page 11 GAO-05-443T (350683) GAO’s

Importance of upper-limb inertia in calculating concentric bench press force.

PubMed

Rambaud, Olivier; Rahmani, Abderrahmane; Moyen, Bernard; Bourdin, Muriel

2008-03-01

The purpose of this study was to investigate the influence of upper-limb inertia on the force-velocity relationship and maximal power during concentric bench press exercise. Reference peak force values (Fpeakp) measured with a force plate positioned below the bench were compared to those measured simultaneously with a kinematic device fixed on the barbell by taking (Fpeakt) or not taking (Fpeakb) upper-limb inertia into account. Thirteen men (27.8 +/- 4.1 years, 184.6 +/- 5.5 cm, 99.5 +/- 18.6 kg) performed all-out concentric bench press exercise against 8 loads ranging between 7 and 74 kg. The results showed that for each load, Fpeakb was significantly less than Fpeakp (P < 0.0001), whereas no significant difference was found between Fpeakp and Fpeakt. The values of maximal force (F0), maximal velocity (V0), optimal velocity (Vopt), and maximal power (Pmax), extrapolated from the force- and power-velocity relationships determined with the kinematic device, were significantly underestimated when upper-limb inertia was ignored. The results underline the importance of taking account of the total inertia of the moving system to ensure precise evaluation of upper-limb muscular characteristics in all-out concentric bench press exercise with a kinematic device. A major application of this study would be to develop precise upper-limb muscular characteristic evaluation in laboratory and field conditions by using a simple and cheap kinematic device.

Estimation of snow albedo reduction by light absorbing impurities using Monte Carlo radiative transfer model

NASA Astrophysics Data System (ADS)

Sengupta, D.; Gao, L.; Wilcox, E. M.; Beres, N. D.; Moosmüller, H.; Khlystov, A.

2017-12-01

Radiative forcing and climate change greatly depends on earth's surface albedo and its temporal and spatial variation. The surface albedo varies greatly depending on the surface characteristics ranging from 5-10% for calm ocean waters to 80% for some snow-covered areas. Clean and fresh snow surfaces have the highest albedo and are most sensitive to contamination with light absorbing impurities that can greatly reduce surface albedo and change overall radiative forcing estimates. Accurate estimation of snow albedo as well as understanding of feedbacks on climate from changes in snow-covered areas is important for radiative forcing, snow energy balance, predicting seasonal snowmelt, and run off rates. Such information is essential to inform timely decision making of stakeholders and policy makers. Light absorbing particles deposited onto the snow surface can greatly alter snow albedo and have been identified as a major contributor to regional climate forcing if seasonal snow cover is involved. However, uncertainty associated with quantification of albedo reduction by these light absorbing particles is high. Here, we use Mie theory (under the assumption of spherical snow grains) to reconstruct the single scattering parameters of snow (i.e., single scattering albedo ῶ and asymmetry parameter g) from observation-based size distribution information and retrieved refractive index values. The single scattering parameters of impurities are extracted with the same approach from datasets obtained during laboratory combustion of biomass samples. Instead of using plane-parallel approximation methods to account for multiple scattering, we have used the simple "Monte Carlo ray/photon tracing approach" to calculate the snow albedo. This simple approach considers multiple scattering to be the "collection" of single scattering events. Using this approach, we vary the effective snow grain size and impurity concentrations to explore the evolution of snow albedo over a wide wavelength range (300 nm - 2000 nm). Results will be compared with the SNICAR model to better understand the differences in snow albedo computation between plane-parallel methods and the statistical Monte Carlo methods.

An advanced dissymmetric rolling model for online regulation

NASA Astrophysics Data System (ADS)

Cao, Trong-Son

2017-10-01

Roll-bite model is employed to predict the rolling force, torque as well as to estimate the forward slip for preset or online regulation at industrial rolling mills. The rolling process is often dissymmetric in terms of work-rolls rotation speeds and diameters as well as the friction conditions at upper and lower contact surfaces between work-rolls and the strip. The roll-bite model thus must be able to account for these dissymmetries and in the same time has to be accurate and fast enough for online applications. In the present study, a new method, namely Adapted Discretization Slab Method (ADSM) is proposed to obtain a robust roll-bite model, which can take into account the aforementioned dissymmetries and has a very short response time, lower than one millisecond. This model is based on the slab method, with an adaptive discretization and a global Newton-Raphson procedure to improve the convergence speed. The model was validated by comparing with other dissymmetric models proposed in the literature, as well as Finite Element simulations and industrial pilot trials. Furthermore, back-calculation tool was also constructed for friction management for both offline and online applications. With very short CPU time, the ADSM-based model is thus attractive for all online applications, both for cold and hot rolling.

Analysis of rotational and sliding collapse modes of masonry arches via Durand-Claye's method

NASA Astrophysics Data System (ADS)

Barsotti, Riccardo; Aita, Danila; Bennati, Stefano

2017-11-01

In this paper the mechanical behavior of circular and pointed masonry arches subject to their own weight is examined in order to determine their collapse modes. Different arch's shapes and thicknesses are considered; the influence of the friction coefficient on the arch collapse is analyzed as well. The safety level of arches is investigated by suitably reworking in semi-analytical form the stability area graphical method proposed by a renowned 19th century French scholar, Durand-Claye. Our analysis enables accounting for any given eccentricity of the thrust at the crown; furthermore, also the strength of masonry is taken into account. According to Durand-Claye's method, the arch is safe if along any given joint both the bending moment and the shear force do not exceed some given limit values. It is shown that attainment of a limit condition according to Durand-Claye corresponds to the onset of a collapse mechanism characterized by either relative rotation or sliding between masonry units. All possible symmetric collapse modes for an arch are thoroughly described. As it was expected, pointed and circular arches show different collapse behaviors. Limit values of arch thickness and friction coefficient are assessed. The results obtained are compared with those given by Michon in 1857.

Nonlinear analysis of thermally and electrically actuated functionally graded material microbeam.

PubMed

Li, Yingli; Meguid, S A; Fu, Yiming; Xu, Daolin

2014-02-08

In this paper, we provide a unified and self-consistent treatment of a functionally graded material (FGM) microbeam with varying thermal conductivity subjected to non-uniform or uniform temperature field. Specifically, it is our objective to determine the effect of the microscopic size of the beam, the electrostatic gap, the temperature field and material property on the pull-in voltage of the microbeam under different boundary conditions. The non-uniform temperature field is obtained by integrating the steady-state heat conduction equation. The governing equations account for the microbeam size by introducing an internal material length-scale parameter that is based on the modified couple stress theory. Furthermore, it takes into account Casimir and van der Waals forces, and the associated electrostatic force with the first-order fringing field effects. The resulting nonlinear differential equations were converted to a coupled system of algebraic equations using the differential quadrature method. The outcome of our work shows the dramatic effect and dependence of the pull-in voltage of the FGM microbeam upon the temperature field, its gradient for a given boundary condition. Specifically, both uniform and non-uniform thermal loading can actuate the FGM microbeam even without an applied voltage. Our work also reveals that the non-uniform temperature field is more effective than the uniform temperature field in actuating a FGM cantilever-type microbeam. For the clamped-clamped case, care must be taken to account for the effective use of thermal loading in the design of microbeams. It is also observed that uniform thermal loading will lead to a reduction in the pull-in voltage of a FGM microbeam for all the three boundary conditions considered.

Satellite-derived potential evapotranspiration for distributed hydrologic runoff modeling

NASA Astrophysics Data System (ADS)

Spies, R. R.; Franz, K. J.; Bowman, A.; Hogue, T. S.; Kim, J.

2012-12-01

Distributed models have the ability of incorporating spatially variable data, especially high resolution forcing inputs such as precipitation, temperature and evapotranspiration in hydrologic modeling. Use of distributed hydrologic models for operational streamflow prediction has been partially hindered by a lack of readily available, spatially explicit input observations. Potential evapotranspiration (PET), for example, is currently accounted for through PET input grids that are based on monthly climatological values. The goal of this study is to assess the use of satellite-based PET estimates that represent the temporal and spatial variability, as input to the National Weather Service (NWS) Hydrology Laboratory Research Distributed Hydrologic Model (HL-RDHM). Daily PET grids are generated for six watersheds in the upper Mississippi River basin using a method that applies only MODIS satellite-based observations and the Priestly Taylor formula (MODIS-PET). The use of MODIS-PET grids will be tested against the use of the current climatological PET grids for simulating basin discharge. Gridded surface temperature forcing data are derived by applying the inverse distance weighting spatial prediction method to point-based station observations from the Automated Surface Observing System (ASOS) and Automated Weather Observing System (AWOS). Precipitation data are obtained from the Climate Prediction Center's (CPC) Climatology-Calibrated Precipitation Analysis (CCPA). A-priori gridded parameters for the Sacramento Soil Moisture Accounting Model (SAC-SMA), Snow-17 model, and routing model are initially obtained from the Office of Hydrologic Development and further calibrated using an automated approach. The potential of the MODIS-PET to be used in an operational distributed modeling system will be assessed with the long-term goal of promoting research to operations transfers and advancing the science of hydrologic forecasting.

Advanced development of the boundary element method for elastic and inelastic thermal stress analysis. Ph.D. Thesis, 1987 Final Report

NASA Technical Reports Server (NTRS)

Henry, Donald P., Jr.

1991-01-01

The focus of this dissertation is on advanced development of the boundary element method for elastic and inelastic thermal stress analysis. New formulations for the treatment of body forces and nonlinear effects are derived. These formulations, which are based on particular integral theory, eliminate the need for volume integrals or extra surface integrals to account for these effects. The formulations are presented for axisymmetric, two and three dimensional analysis. Also in this dissertation, two dimensional and axisymmetric formulations for elastic and inelastic, inhomogeneous stress analysis are introduced. The derivatives account for inhomogeneities due to spatially dependent material parameters, and thermally induced inhomogeneities. The nonlinear formulation of the present work are based on an incremental initial stress approach. Two inelastic solutions algorithms are implemented: an iterative; and a variable stiffness type approach. The Von Mises yield criterion with variable hardening and the associated flow rules are adopted in these algorithms. All formulations are implemented in a general purpose, multi-region computer code with the capability of local definition of boundary conditions. Quadratic, isoparametric shape functions are used to model the geometry and field variables of the boundary (and domain) of the problem. The multi-region implementation permits a body to be modeled in substructured parts, thus dramatically reducing the cost of analysis. Furthermore, it allows a body consisting of regions of different (homogeneous) material to be studied. To test the program, results obtained for simple test cases are checked against their analytic solutions. Thereafter, a range of problems of practical interest are analyzed. In addition to displacement and traction loads, problems with body forces due to self-weight, centrifugal, and thermal loads are considered.

Accounting for multiple sources of uncertainty in impact assessments: The example of the BRACE study

NASA Astrophysics Data System (ADS)

O'Neill, B. C.

2015-12-01

Assessing climate change impacts often requires the use of multiple scenarios, types of models, and data sources, leading to a large number of potential sources of uncertainty. For example, a single study might require a choice of a forcing scenario, climate model, bias correction and/or downscaling method, societal development scenario, model (typically several) for quantifying elements of societal development such as economic and population growth, biophysical model (such as for crop yields or hydrology), and societal impact model (e.g. economic or health model). Some sources of uncertainty are reduced or eliminated by the framing of the question. For example, it may be useful to ask what an impact outcome would be conditional on a given societal development pathway, forcing scenario, or policy. However many sources of uncertainty remain, and it is rare for all or even most of these sources to be accounted for. I use the example of a recent integrated project on the Benefits of Reduced Anthropogenic Climate changE (BRACE) to explore useful approaches to uncertainty across multiple components of an impact assessment. BRACE comprises 23 papers that assess the differences in impacts between two alternative climate futures: those associated with Representative Concentration Pathways (RCPs) 4.5 and 8.5. It quantifies difference in impacts in terms of extreme events, health, agriculture, tropical cyclones, and sea level rise. Methodologically, it includes climate modeling, statistical analysis, integrated assessment modeling, and sector-specific impact modeling. It employs alternative scenarios of both radiative forcing and societal development, but generally uses a single climate model (CESM), partially accounting for climate uncertainty by drawing heavily on large initial condition ensembles. Strengths and weaknesses of the approach to uncertainty in BRACE are assessed. Options under consideration for improving the approach include the use of perturbed physics ensembles of CESM, employing results from multiple climate models, and combining the results from single impact models with statistical representations of uncertainty across multiple models. A key consideration is the relationship between the question being addressed and the uncertainty approach.

Systematic Design of a Magnetically Levitated Brushless DC Motor for a Reversible Rotary Intra-Aortic Blood Pump.

PubMed

Wang, Yaxin; Logan, Thomas G; Smith, P Alex; Hsu, Po-Lin; Cohn, William E; Xu, Liping; McMahon, Richard A

2017-10-01

The IntraVAD is a miniature intra-aortic ventricular assist device (VAD) designed to work in series with the compromised left ventricle. A reverse-rotation control (RRc) mode has been developed to increase myocardial perfusion and reduce ventricular volume. The RRc mode includes forward rotation in systole and reverse rotation in diastole, which requires the IntraVAD to periodically reverse its rotational direction in synchrony with the cardiac cycle. This periodic reversal leads to changes in pressure force over the impeller, which makes the entire system less stable. To eliminate the mechanical wear of a contact bearing and provide active control over the axial position of the rotor, a miniature magnetically levitated bearing (i.e., the PM-Coil module) composed of two concentric permanent magnetic (PM) rings and a pair of coils-one on each side-was proposed to provide passive radial and active axial rotor stabilization. In the early design stage, the numerical finite element method (FEM) was used to optimize the geometry of the brushless DC (BLDC) motor and the maglev module, but constructing a new model each time certain design parameters were adjusted required substantial computation time. Because the design criteria for the module had to be modified to account for the magnetic force produced by the motor and for the hemodynamic changes associated with pump operation, a simplified analytic expression was derived for the expected magnetic forces. Suitable bearings could then be designed capable of overcoming these forces without repeating the complicated FEM simulation for the motor. Using this method at the initial design stage can inform the design of the miniature maglev BLDC motor for the proposed pulsatile axial-flow VAD. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Electrolytes in a nanometer slab-confinement: Ion-specific structure and solvation forces

NASA Astrophysics Data System (ADS)

Kalcher, Immanuel; Schulz, Julius C. F.; Dzubiella, Joachim

2010-10-01

We study the liquid structure and solvation forces of dense monovalent electrolytes (LiCl, NaCl, CsCl, and NaI) in a nanometer slab-confinement by explicit-water molecular dynamics (MD) simulations, implicit-water Monte Carlo (MC) simulations, and modified Poisson-Boltzmann (PB) theories. In order to consistently coarse-grain and to account for specific hydration effects in the implicit methods, realistic ion-ion and ion-surface pair potentials have been derived from infinite-dilution MD simulations. The electrolyte structure calculated from MC simulations is in good agreement with the corresponding MD simulations, thereby validating the coarse-graining approach. The agreement improves if a realistic, MD-derived dielectric constant is employed, which partially corrects for (water-mediated) many-body effects. Further analysis of the ionic structure and solvation pressure demonstrates that nonlocal extensions to PB (NPB) perform well for a wide parameter range when compared to MC simulations, whereas all local extensions mostly fail. A Barker-Henderson mapping of the ions onto a charged, asymmetric, and nonadditive binary hard-sphere mixture shows that the strength of structural correlations is strongly related to the magnitude and sign of the salt-specific nonadditivity. Furthermore, a grand canonical NPB analysis shows that the Donnan effect is dominated by steric correlations, whereas solvation forces and overcharging effects are mainly governed by ion-surface interactions. However, steric corrections to solvation forces are strongly repulsive for high concentrations and low surface charges, while overcharging can also be triggered by steric interactions in strongly correlated systems. Generally, we find that ion-surface and ion-ion correlations are strongly coupled and that coarse-grained methods should include both, the latter nonlocally and nonadditive (as given by our specific ionic diameters), when studying electrolytes in highly inhomogeneous situations.

Effect of added mass on the interaction of bubbles in a low-Reynolds-number shear flow.

PubMed

Lavrenteva, Olga; Prakash, Jai; Nir, Avinoam

2016-02-01

Equal size air bubbles that are entrapped by a Taylor vortex of the secondary flow in a Couette device, thereby defying buoyancy, slowly form a stable ordered ring with equal separation distances between all neighbors. We present two models of the process dynamics based on force balance on a bubble in the presence of other bubbles positioned on the same streamline in a simple shear flow. The forces taken into account are the viscous resistance, the added mass force, and the inertia-induced repulsing force between two bubbles in a low-Reynolds-number shear flow obtained in Prakash et al. [J. Prakash et al., Phys. Rev. E 87, 043002 (2013)]. The first model of the process assumes that each bubble interacts solely with its nearest neighbors. The second model takes into account pairwise interactions among all the bubbles in the ring. The performed dynamic simulations were compared to the experimental results reported in Prakash et al. [J. Prakash et al., Phys. Rev. E 87, 043002 (2013)] and to the results of quasistationary models (ignoring the added mass effect) suggested in that paper. It is demonstrated that taking into account the effect of added mass, the models describe the major effect of the bubbles' ordering, provide good estimation of the relaxation time, and also predict nonmonotonic behavior of the separation distance between the bubbles, which exhibit over- and undershooting of equilibrium separations. The latter effects were observed in experiments, but are not predicted by the quasistationary models.

Frame Rate Considerations for Real-Time Abdominal Acoustic Radiation Force Impulse Imaging

PubMed Central

Fahey, Brian J.; Palmeri, Mark L.; Trahey, Gregg E.

2008-01-01

With the advent of real-time Acoustic Radiation Force Impulse (ARFI) imaging, elevated frame rates are both desirable and relevant from a clinical perspective. However, fundamental limitations on frame rates are imposed by thermal safety concerns related to incident radiation force pulses. Abdominal ARFI imaging utilizes a curvilinear scanning geometry that results in markedly different tissue heating patterns than those previously studied for linear arrays or mechanically-translated concave transducers. Finite Element Method (FEM) models were used to simulate these tissue heating patterns and to analyze the impact of tissue heating on frame rates available for abdominal ARFI imaging. A perfusion model was implemented to account for cooling effects due to blood flow and frame rate limitations were evaluated in the presence of normal, reduced and negligible tissue perfusions. Conventional ARFI acquisition techniques were also compared to ARFI imaging with parallel receive tracking in terms of thermal efficiency. Additionally, thermocouple measurements of transducer face temperature increases were acquired to assess the frame rate limitations imposed by cumulative heating of the imaging array. Frame rates sufficient for many abdominal imaging applications were found to be safely achievable utilizing available ARFI imaging techniques. PMID:17521042

Direct Numerical Simulation of Wetting and Spreading Behavior on Heterogeneous and Roughened Substrates

NASA Technical Reports Server (NTRS)

Schwartz, Leonard W.

1999-01-01

A method of calculation is presented that allows the simulation of the time-dependent three-dimensional motion of thin liquid layers on solid substrates for systems with finite equilibrium contact angles. The contact angle is a prescribed function of position on the substrate. Similar mathematical models are constructed for substrates with a pattern of roughness. Evolution equations are given, using the lubrication approximation, that include viscous, capillary and disjoining forces. Motion to and from dry substrate regions is made possible by use of a thin energetically-stable wetting layer. We simulate motion on heterogeneous substrates with periodic arrays of high contact-angle patches. Two different problems are treated for heterogenous substrates. The first is spontaneous motion driven only by wetting forces. If the contact-angle difference is sufficiently high, the droplet can find several different stable positions, depending on the previous history of the motion. A second simulation treats a forced cyclical motion. Energy dissipation per cycle for a heterogeneous substrate is found to be larger than for a uniform substrate with the same total energy. The Landau-Levich solution for plate removal from a liquid bath is extended to account for a pattern of roughness on the plate.

Machine learning predictions of molecular properties: Accurate many-body potentials and nonlocality in chemical space

DOE PAGES

Hansen, Katja; Biegler, Franziska; Ramakrishnan, Raghunathan; ...

2015-06-04

Simultaneously accurate and efficient prediction of molecular properties throughout chemical compound space is a critical ingredient toward rational compound design in chemical and pharmaceutical industries. Aiming toward this goal, we develop and apply a systematic hierarchy of efficient empirical methods to estimate atomization and total energies of molecules. These methods range from a simple sum over atoms, to addition of bond energies, to pairwise interatomic force fields, reaching to the more sophisticated machine learning approaches that are capable of describing collective interactions between many atoms or bonds. In the case of equilibrium molecular geometries, even simple pairwise force fields demonstratemore » prediction accuracy comparable to benchmark energies calculated using density functional theory with hybrid exchange-correlation functionals; however, accounting for the collective many-body interactions proves to be essential for approaching the “holy grail” of chemical accuracy of 1 kcal/mol for both equilibrium and out-of-equilibrium geometries. This remarkable accuracy is achieved by a vectorized representation of molecules (so-called Bag of Bonds model) that exhibits strong nonlocality in chemical space. The same representation allows us to predict accurate electronic properties of molecules, such as their polarizability and molecular frontier orbital energies.« less

The accuracy of ab initio calculations without ab initio calculations for charged systems: Kriging predictions of atomistic properties for ions in aqueous solutions

NASA Astrophysics Data System (ADS)

Di Pasquale, Nicodemo; Davie, Stuart J.; Popelier, Paul L. A.

2018-06-01

Using the machine learning method kriging, we predict the energies of atoms in ion-water clusters, consisting of either Cl- or Na+ surrounded by a number of water molecules (i.e., without Na+Cl- interaction). These atomic energies are calculated following the topological energy partitioning method called Interacting Quantum Atoms (IQAs). Kriging predicts atomic properties (in this case IQA energies) by a model that has been trained over a small set of geometries with known property values. The results presented here are part of the development of an advanced type of force field, called FFLUX, which offers quantum mechanical information to molecular dynamics simulations without the limiting computational cost of ab initio calculations. The results reported for the prediction of the IQA components of the energy in the test set exhibit an accuracy of a few kJ/mol, corresponding to an average error of less than 5%, even when a large cluster of water molecules surrounding an ion is considered. Ions represent an important chemical system and this work shows that they can be correctly taken into account in the framework of the FFLUX force field.

Free Vibration Analysis of DWCNTs Using CDM and Rayleigh-Schmidt Based on Nonlocal Euler-Bernoulli Beam Theory

PubMed Central

2014-01-01

The free vibration response of double-walled carbon nanotubes (DWCNTs) is investigated. The DWCNTs are modelled as two beams, interacting between them through the van der Waals forces, and the nonlocal Euler-Bernoulli beam theory is used. The governing equations of motion are derived using a variational approach and the free frequencies of vibrations are obtained employing two different approaches. In the first method, the two double-walled carbon nanotubes are discretized by means of the so-called “cell discretization method” (CDM) in which each nanotube is reduced to a set of rigid bars linked together by elastic cells. The resulting discrete system takes into account nonlocal effects, constraint elasticities, and the van der Waals forces. The second proposed approach, belonging to the semianalytical methods, is an optimized version of the classical Rayleigh quotient, as proposed originally by Schmidt. The resulting conditions are solved numerically. Numerical examples end the paper, in which the two approaches give lower-upper bounds to the true values, and some comparisons with existing results are offered. Comparisons of the present numerical results with those from the open literature show an excellent agreement. PMID:24715807

Machine Learning Predictions of Molecular Properties: Accurate Many-Body Potentials and Nonlocality in Chemical Space

PubMed Central

2015-01-01

Simultaneously accurate and efficient prediction of molecular properties throughout chemical compound space is a critical ingredient toward rational compound design in chemical and pharmaceutical industries. Aiming toward this goal, we develop and apply a systematic hierarchy of efficient empirical methods to estimate atomization and total energies of molecules. These methods range from a simple sum over atoms, to addition of bond energies, to pairwise interatomic force fields, reaching to the more sophisticated machine learning approaches that are capable of describing collective interactions between many atoms or bonds. In the case of equilibrium molecular geometries, even simple pairwise force fields demonstrate prediction accuracy comparable to benchmark energies calculated using density functional theory with hybrid exchange-correlation functionals; however, accounting for the collective many-body interactions proves to be essential for approaching the “holy grail” of chemical accuracy of 1 kcal/mol for both equilibrium and out-of-equilibrium geometries. This remarkable accuracy is achieved by a vectorized representation of molecules (so-called Bag of Bonds model) that exhibits strong nonlocality in chemical space. In addition, the same representation allows us to predict accurate electronic properties of molecules, such as their polarizability and molecular frontier orbital energies. PMID:26113956

Contribution to harmonic balance calculations of self-sustained periodic oscillations with focus on single-reed instruments.

PubMed

Farner, Snorre; Vergez, Christophe; Kergomard, Jean; Lizée, Aude

2006-03-01

The harmonic balance method (HBM) was originally developed for finding periodic solutions of electronical and mechanical systems under a periodic force, but has been adapted to self-sustained musical instruments. Unlike time-domain methods, this frequency-domain method does not capture transients and so is not adapted for sound synthesis. However, its independence of time makes it very useful for studying any periodic solution, whether stable or unstable, without care of particular initial conditions in time. A computer program for solving general problems involving nonlinearly coupled exciter and resonator, HARMBAL, has been developed based on the HBM. The method as well as convergence improvements and continuation facilities are thoroughly presented and discussed in the present paper. Applications of the method are demonstrated, especially on problems with severe difficulties of convergence: the Helmholtz motion (square signals) of single-reed instruments when no losses are taken into account, the reed being modeled as a simple spring.

A compressible multiphase framework for simulating supersonic atomization

NASA Astrophysics Data System (ADS)

Regele, Jonathan D.; Garrick, Daniel P.; Hosseinzadeh-Nik, Zahra; Aslani, Mohamad; Owkes, Mark

2016-11-01

The study of atomization in supersonic combustors is critical in designing efficient and high performance scramjets. Numerical methods incorporating surface tension effects have largely focused on the incompressible regime as most atomization applications occur at low Mach numbers. Simulating surface tension effects in high speed compressible flow requires robust numerical methods that can handle discontinuities caused by both material interfaces and shocks. A shock capturing/diffused interface method is developed to simulate high-speed compressible gas-liquid flows with surface tension effects using the five-equation model. This includes developments that account for the interfacial pressure jump that occurs in the presence of surface tension. A simple and efficient method for computing local interface curvature is developed and an acoustic non-dimensional scaling for the surface tension force is proposed. The method successfully captures a variety of droplet breakup modes over a range of Weber numbers and demonstrates the impact of surface tension in countering droplet deformation in both subsonic and supersonic cross flows.

Indentation quantification for in-liquid nanomechanical measurement of soft material using an atomic force microscope: rate-dependent elastic modulus of live cells.

PubMed

Ren, Juan; Yu, Shiyan; Gao, Nan; Zou, Qingze

2013-11-01

In this paper, a control-based approach to replace the conventional method to achieve accurate indentation quantification is proposed for nanomechanical measurement of live cells using atomic force microscope. Accurate indentation quantification is central to probe-based nanomechanical property measurement. The conventional method for in-liquid nanomechanical measurement of live cells, however, fails to accurately quantify the indentation as effects of the relative probe acceleration and the hydrodynamic force are not addressed. As a result, significant errors and uncertainties are induced in the nanomechanical properties measured. In this paper, a control-based approach is proposed to account for these adverse effects by tracking the same excitation force profile on both a live cell and a hard reference sample through the use of an advanced control technique, and by quantifying the indentation from the difference of the cantilever base displacement in these two measurements. The proposed control-based approach not only eliminates the relative probe acceleration effect with no need to calibrate the parameters involved, but it also reduces the hydrodynamic force effect significantly when the force load rate becomes high. We further hypothesize that, by using the proposed control-based approach, the rate-dependent elastic modulus of live human epithelial cells under different stress conditions can be reliably quantified to predict the elasticity evolution of cell membranes, and hence can be used to predict cellular behaviors. By implementing the proposed approach, the elastic modulus of HeLa cells before and after the stress process were quantified as the force load rate was changed over three orders of magnitude from 0.1 to 100 Hz, where the amplitude of the applied force and the indentation were at 0.4-2 nN and 250-450 nm, respectively. The measured elastic modulus of HeLa cells showed a clear power-law dependence on the load rate, both before and after the stress process. Moreover, the elastic modulus of HeLa cells was substantially reduced by two to five times due to the stress process. Thus, our measurements demonstrate that the control-based protocol is effective in quantifying and characterizing the evolution of nanomechanical properties during the stress process of live cells.

Voluntary EMG-to-force estimation with a multi-scale physiological muscle model

PubMed Central

2013-01-01

Background EMG-to-force estimation based on muscle models, for voluntary contraction has many applications in human motion analysis. The so-called Hill model is recognized as a standard model for this practical use. However, it is a phenomenological model whereby muscle activation, force-length and force-velocity properties are considered independently. Perreault reported Hill modeling errors were large for different firing frequencies, level of activation and speed of contraction. It may be due to the lack of coupling between activation and force-velocity properties. In this paper, we discuss EMG-force estimation with a multi-scale physiology based model, which has a link to underlying crossbridge dynamics. Differently from the Hill model, the proposed method provides dual dynamics of recruitment and calcium activation. Methods The ankle torque was measured for the plantar flexion along with EMG measurements of the medial gastrocnemius (GAS) and soleus (SOL). In addition to Hill representation of the passive elements, three models of the contractile parts have been compared. Using common EMG signals during isometric contraction in four able-bodied subjects, torque was estimated by the linear Hill model, the nonlinear Hill model and the multi-scale physiological model that refers to Huxley theory. The comparison was made in normalized scale versus the case in maximum voluntary contraction. Results The estimation results obtained with the multi-scale model showed the best performances both in fast-short and slow-long term contraction in randomized tests for all the four subjects. The RMS errors were improved with the nonlinear Hill model compared to linear Hill, however it showed limitations to account for the different speed of contractions. Average error was 16.9% with the linear Hill model, 9.3% with the modified Hill model. In contrast, the error in the multi-scale model was 6.1% while maintaining a uniform estimation performance in both fast and slow contractions schemes. Conclusions We introduced a novel approach that allows EMG-force estimation based on a multi-scale physiology model integrating Hill approach for the passive elements and microscopic cross-bridge representations for the contractile element. The experimental evaluation highlights estimation improvements especially a larger range of contraction conditions with integration of the neural activation frequency property and force-velocity relationship through cross-bridge dynamics consideration. PMID:24007560

New weight factor for Brownian force exerted on micro/nano-particles in air flow

NASA Astrophysics Data System (ADS)

Zhang, Peijie; Lin, Jianzhong; Ku, Xiaoke

2018-05-01

In order to effectively describe the effect of Brownian force exerted on the micro/nano-particles in air flow, a new weight factor, which is defined as the ratio of the characteristic velocity of the Brownian motion to the macroscopic velocity, is proposed and applied to the particle settlement under gravity. Results show that the weight factor can quantitatively evaluate the effect of Brownian force on the particle motion. Moreover, the value of the weight factor can also be used to judge the particle motion pattern and determine whether the Brownian force should be taken into account.

Radial forces in a misaligned radial face seal

NASA Technical Reports Server (NTRS)

Etsion, I.

1978-01-01

Radial forces on the primary seal ring of a flat misaligned seal are analyzed, taking into account the radial variation in seal clearance. An analytical solution for both hydrostatic and hydrodynamic effects is presented that covers the whole range from zero to full angular misalignment. The net radial force on the primary seal ring is always directed so as to produce a radial eccentricity which generates inward pumping. Although the radial force is usually very small, in some cases it may be one of the reasons for excessive leakage through both the primary and secondary seals of a radial face seal.

Radial forces in a misaligned radial face seal

NASA Technical Reports Server (NTRS)

Etsion, I.

1977-01-01

Radial forces on the primary seal ring of a flat misaligned seal are analyzed, taking into account the radial variation in seal clearance. An analytical solution for both hydrostatic and hydrodynamic effects is presented that covers the whole range from zero to full angular misalignment. The net radial force on the primary seal ring is always directed so as to produce a radial eccentricity which generates inward pumping. Although the radial force is usually very small, in some cases it may be one of the reasons for excessive leakage through both the primary and secondary seals of a radial face seal.

Influence of an Interdisciplinary Re-employment Programme Among Unemployed Persons with Mental Health Problems on Health, Social Participation and Paid Employment.

PubMed

Carlier, Bouwine E; Schuring, Merel; Burdorf, Alex

2018-03-01

Purpose To evaluate the influence of an interdisciplinary re-employment programme on labour force participation and perceived health among unemployed persons with common mental health problems. In addition, the influence of entering paid employment on self-rated physical health and mental health was investigated. Methods In this quasi-experimental study with 2 years follow up, 869 persons were enrolled after referral to an interdisciplinary re-employment programme (n = 380) or regular re-employment programme (n = 489). The propensity score technique was used to account for observed differences between the intervention and control group. The intervention programme was provided by an interdisciplinary team, consisting of mental health care professionals as well as employment specialists. Mental health problems were addressed through cognitive counselling and individual tailored job-search support was provided by an employment professional. Primary outcome measures were paid employment and voluntary work. Secondary outcome measures were self-rated mental and physical health, measured by the Short Form 12 Health Survey, and anxiety and depressive symptoms, measured by the Kessler Psychological Distress Scale. Changes in labour force participation and health were examined with repeated-measures logistic regression analyses by the generalized estimating equations method. Results The interdisciplinary re-employment programme did not have a positive influence on entering employment or physical or mental health among unemployed persons with mental health problems. After 2 years, 10% of the participants of the intervention programme worked fulltime, compared to 4% of the participants of the usual programmes (adjusted OR 1.65). The observed differences in labour force participation were not statistically significant. However, among persons who entered paid employment, physical health improved (+16%) and anxiety and depressive symptoms decreased (-15%), whereas health remained unchanged among persons who continued to be unemployed. Conclusions Policies to improve population health should take into account that promoting paid employment may be an effective intervention to improve health. It is recommended to invest in interdisciplinary re-employment programmes with a first place and train approach.

Developing a New Quantitative Account of Backward Masking

ERIC Educational Resources Information Center

Francis, Gregory

2003-01-01

A new general explanation for u-shaped backward masking is analyzed and found to predict shifts in the interstimulus interval (ISI) that produces strongest masking. This predicted shift is then compared to six sets of masking data. The resulting comparisons force the general explanation to make certain assumptions to account for the data. In this…

New Times, New Stakes: Moments of Transit, Accountability, and Classroom Practice

ERIC Educational Resources Information Center

Helfenbein, Robert J., Jr.

2004-01-01

In order to understand the relationship between high-stakes testing and its synonymous projection on history as the "age of accountability," Stuart Hall's Policing the Crisis (Hall, Critcher, Jefferson, Clarke, & Roberts, 1978) provides an interesting parallel depiction of the response of the dominant forces in the power structure to…

Assessment and Accountability: Report from the Prichard Committee for Academic Excellence, Task Force on Improving Kentucky Schools.

ERIC Educational Resources Information Center

Prichard Committee for Academic Excellence, Lexington, KY.

As part of a Kentucky effort to improve public education and to increase taxpayer confidence in expanded educational funding, a citizen committee examined and made recommendations on approaches to school accountability and assessment, particularly student testing in the Kentucky Instructional Results Information System (KIRIS). The recommendations…

The Case for Participatory Evaluation in an Era of Accountability

ERIC Educational Resources Information Center

Chouinard, Jill Anne

2013-01-01

Evaluation occurs within a specific context and is influenced by the economic, political, historical, and social forces that shape that context. The culture of evaluation is thus very much embedded in the culture of accountability that currently prevails in public sector institutions, policies, and program. As such, our understanding of the…

Teaching in the Age of Accountability: Restrained by School Culture?

ERIC Educational Resources Information Center

Aasebø, Turid Skarre; Midtsundstad, Jorunn H.; Willbergh, Ilmi

2017-01-01

In this paper, we explore how "teaching communication" in the classroom is connected to school culture. In the age of accountability, the outcome focus force to the forefront, a "blame game" which either blames students' achievements on the teachers and teacher education, or the students and their socio-economic background. We…

Making Evaluation Work for You: Ideas for Deriving Multiple Benefits from Evaluation

ERIC Educational Resources Information Center

Jayaratne, K. S. U.

2016-01-01

Increased demand for accountability has forced Extension educators to evaluate their programs and document program impacts. Due to this situation, some Extension educators may view evaluation simply as the task, imposed on them by administrators, of collecting outcome and impact data for accountability. They do not perceive evaluation as a useful…

Interactive Whiteboard Use: The Catalyst of Student Achievement

ERIC Educational Resources Information Center

Lamberth, Tenneille Terrell

2012-01-01

The No Child Left Behind (NCLB) Act of 2001 forced school districts to become more accountable by requiring all students to read on grade level by the year 2014. However, President Obama's educational policy shift is allowing states to develop their own accountability and improvement system. This study examined fourth and eighth grade math…

Accounting for Systems Analysts in the 21st Century

ERIC Educational Resources Information Center

Giordano, Thomas; McAleer, Brenda; Szakas, Joseph S.

2010-01-01

Computer Information System (CIS) majors are required to successfully complete an introductory accounting course. Given the current forces in the financial world, the appropriateness of this course warrants scrutiny as to whether it properly serves the student, and the degree to which it continues to meet the IS 2002 outcomes. The current business…

Politics, Control, and the Future of School Accountability.

ERIC Educational Resources Information Center

Moe, Terry M.

This paper examines the forces that affect school accountability. It presents the discussion in the context of the classic agency model, which is built around a principal-agent relationship. In these types of relationships, a principal attains certain goals through an agent, who acts on her behalf. Although ubiquitous in society, these kinds of…

Modeling of nanoscale liquid mixture transport by density functional hydrodynamics

NASA Astrophysics Data System (ADS)

Dinariev, Oleg Yu.; Evseev, Nikolay V.

2017-06-01

Modeling of multiphase compositional hydrodynamics at nanoscale is performed by means of density functional hydrodynamics (DFH). DFH is the method based on density functional theory and continuum mechanics. This method has been developed by the authors over 20 years and used for modeling in various multiphase hydrodynamic applications. In this paper, DFH was further extended to encompass phenomena inherent in liquids at nanoscale. The new DFH extension is based on the introduction of external potentials for chemical components. These potentials are localized in the vicinity of solid surfaces and take account of the van der Waals forces. A set of numerical examples, including disjoining pressure, film precursors, anomalous rheology, liquid in contact with heterogeneous surface, capillary condensation, and forward and reverse osmosis, is presented to demonstrate modeling capabilities.

Hydrodynamic Contributions to Amoeboid Cell Motility

NASA Astrophysics Data System (ADS)

Lewis, Owen; Guy, Robert

2012-11-01

Understanding the methods by which cells move is a fundamental problem in modern biology. Recent evidence has shown that the fluid dynamics of cytoplasm can play a vital role in cellular motility. The slime mold Physarum polycephalum provides an excellent model organism for the study of amoeboid motion. In this research, we use a simply analytic model in conjuction with computational experiments to investigate intracellular fluid flow in a simple model of Physarum. Of particlar interest are stresses generated by cytoplasmic flow which may be used to aid in cellular motility. In our numerical model, the Immersed Boundary Method is used to account for such stresses. We investigate the relationship between contraction waves, flow waves, adhesion, and locomotive forces in an attempt to characterize conditions necessary to generate directed motion.

Biological communities in San Francisco Bay track large-scale climate forcing over the North Pacific

NASA Astrophysics Data System (ADS)

Cloern, James E.; Hieb, Kathryn A.; Jacobson, Teresa; Sansó, Bruno; Di Lorenzo, Emanuele; Stacey, Mark T.; Largier, John L.; Meiring, Wendy; Peterson, William T.; Powell, Thomas M.; Winder, Monika; Jassby, Alan D.

2010-11-01

Long-term observations show that fish and plankton populations in the ocean fluctuate in synchrony with large-scale climate patterns, but similar evidence is lacking for estuaries because of shorter observational records. Marine fish and invertebrates have been sampled in San Francisco Bay since 1980 and exhibit large, unexplained population changes including record-high abundances of common species after 1999. Our analysis shows that populations of demersal fish, crabs and shrimp covary with the Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO), both of which reversed signs in 1999. A time series model forced by the atmospheric driver of NPGO accounts for two-thirds of the variability in the first principal component of species abundances, and generalized linear models forced by PDO and NPGO account for most of the annual variability of individual species. We infer that synchronous shifts in climate patterns and community variability in San Francisco Bay are related to changes in oceanic wind forcing that modify coastal currents, upwelling intensity, surface temperature, and their influence on recruitment of marine species that utilize estuaries as nursery habitat. Ecological forecasts of estuarine responses to climate change must therefore consider how altered patterns of atmospheric forcing across ocean basins influence coastal oceanography as well as watershed hydrology.

Handwriting analysis indicates spontaneous dyskinesias in neuroleptic naïve adolescents at high risk for psychosis.

PubMed

Dean, Derek J; Teulings, Hans-Leo; Caligiuri, Michael; Mittal, Vijay A

2013-11-21

Growing evidence suggests that movement abnormalities are a core feature of psychosis. One marker of movement abnormality, dyskinesia, is a result of impaired neuromodulation of dopamine in fronto-striatal pathways. The traditional methods for identifying movement abnormalities include observer-based reports and force stability gauges. The drawbacks of these methods are long training times for raters, experimenter bias, large site differences in instrumental apparatus, and suboptimal reliability. Taking these drawbacks into account has guided the development of better standardized and more efficient procedures to examine movement abnormalities through handwriting analysis software and tablet. Individuals at risk for psychosis showed significantly more dysfluent pen movements (a proximal measure for dyskinesia) in a handwriting task. Handwriting kinematics offers a great advance over previous methods of assessing dyskinesia, which could clearly be beneficial for understanding the etiology of psychosis.

Handwriting Analysis Indicates Spontaneous Dyskinesias in Neuroleptic Naïve Adolescents at High Risk for Psychosis

PubMed Central

Dean, Derek J.; Teulings, Hans-Leo; Caligiuri, Michael; Mittal, Vijay A.

2013-01-01

Growing evidence suggests that movement abnormalities are a core feature of psychosis. One marker of movement abnormality, dyskinesia, is a result of impaired neuromodulation of dopamine in fronto-striatal pathways. The traditional methods for identifying movement abnormalities include observer-based reports and force stability gauges. The drawbacks of these methods are long training times for raters, experimenter bias, large site differences in instrumental apparatus, and suboptimal reliability. Taking these drawbacks into account has guided the development of better standardized and more efficient procedures to examine movement abnormalities through handwriting analysis software and tablet. Individuals at risk for psychosis showed significantly more dysfluent pen movements (a proximal measure for dyskinesia) in a handwriting task. Handwriting kinematics offers a great advance over previous methods of assessing dyskinesia, which could clearly be beneficial for understanding the etiology of psychosis. PMID:24300590

Influence of Muscle-Tendon Wrapping on Calculations of Joint Reaction Forces in the Equine Distal Forelimb

PubMed Central

Merritt, Jonathan S.; Davies, Helen M. S.; Burvill, Colin; Pandy, Marcus G.

2008-01-01

The equine distal forelimb is a common location of injuries related to mechanical overload. In this study, a two-dimensional model of the musculoskeletal system of the region was developed and applied to kinematic and kinetic data from walking and trotting horses. The forces in major tendons and joint reaction forces were calculated. The components of the joint reaction forces caused by wrapping of tendons around sesamoid bones were found to be of similar magnitude to the reaction forces between the long bones at each joint. This finding highlighted the importance of taking into account muscle-tendon wrapping when evaluating joint loading in the equine distal forelimb. PMID:18509485

Effective tension and fluctuations in active membranes.

PubMed

Loubet, Bastien; Seifert, Udo; Lomholt, Michael Andersen

2012-03-01

We calculate the fluctuation spectrum of the shape of a lipid vesicle or cell exposed to a nonthermal source of noise. In particular, we take constraints on the membrane area and the volume of fluid that it encapsulates into account when obtaining expressions for the dependency of the membrane tension on the noise. We then investigate three possible origins of the nonthermal noise taken from the literature: A direct force, which models an external medium pushing on the membrane, a curvature force, which models a fluctuating spontaneous curvature, and a permeation force coming from an active transport of fluid through the membrane. For the direct force and curvature force cases, we compare our results to existing experiments on active membranes.

Subharmonic Oscillations and Chaos in Dynamic Atomic Force Microscopy

NASA Technical Reports Server (NTRS)

Cantrell, John H.; Cantrell, Sean A.

2015-01-01

The increasing use of dynamic atomic force microscopy (d-AFM) for nanoscale materials characterization calls for a deeper understanding of the cantilever dynamics influencing scan stability, predictability, and image quality. Model development is critical to such understanding. Renormalization of the equations governing d- AFM provides a simple interpretation of cantilever dynamics as a single spring and mass system with frequency dependent cantilever stiffness and damping parameters. The renormalized model is sufficiently robust to predict the experimentally observed splitting of the free-space cantilever resonance into multiple resonances upon cantilever-sample contact. Central to the model is the representation of the cantilever sample interaction force as a polynomial expansion with coefficients F(sub ij) (i,j = 0, 1, 2) that account for the effective interaction stiffness parameter, the cantilever-to-sample energy transfer, and the amplitude of cantilever oscillation. Application of the Melnikov method to the model equation is shown to predict a homoclinic bifurcation of the Smale horseshoe type leading to a cascade of period doublings with increasing drive displacement amplitude culminating in chaos and loss of image quality. The threshold value of the drive displacement amplitude necessary to initiate subharmonic generation depends on the acoustic drive frequency, the effective damping coefficient, and the nonlinearity of the cantilever-sample interaction force. For parameter values leading to displacement amplitudes below threshold for homoclinic bifurcation other bifurcation scenarios can occur, some of which lead to chaos.

Portuguese Armed Forces in the International Security and Assistance Force in Afghanistan: Psychological Support for the Command of Kabul International Airport

DTIC Science & Technology

2006-04-01

all other results are higher than the reference population averages. One should not neglect the bias of the results due to the “ social desirability...scales applied in this paper, the hypothesis of a bias ( social desirability) is also to be taken into account, in spite of the fact that the force...the main adjustment factors are: • Social competences (interpersonal relationship capability and team integration); • Family support; • Emotional

Environmental Impact Analysis Process. Environmental Assessment Air Force Small Launch Vehicle, Vandenberg Air Force Base, Edwards Air Force Base, and San Nicolas Island, CA

DTIC Science & Technology

1991-05-01

a historical breeding area, may be related to summer flooding in 1984, 1985, and 1987, which rendered the habitat unsuitable to the least terns...animal fetishes (de Cessac, 1951; Meighan and Eberhart, 1953; Heizer , 1957, 1960a and 1960b; Rozaire, 1959; Reinman and Townsend, 1960; Reinman...interest, and there are several published accounts of her life ( Heizer and Elsasser, n.d.). 2-168 Several archaeological surveys have been

Interval oscillation criteria for second-order forced impulsive delay differential equations with damping term.

PubMed

Thandapani, Ethiraju; Kannan, Manju; Pinelas, Sandra

2016-01-01

In this paper, we present some sufficient conditions for the oscillation of all solutions of a second order forced impulsive delay differential equation with damping term. Three factors-impulse, delay and damping that affect the interval qualitative properties of solutions of equations are taken into account together. The results obtained in this paper extend and generalize some of the the known results for forced impulsive differential equations. An example is provided to illustrate the main result.

Perspectives: Reforming American Higher Education--Implications for a Vibrant Work Force and a Healthy Democracy

ERIC Educational Resources Information Center

Kolb, Charles

2011-01-01

The forces of globalization are finally hitting American postsecondary education. For nearly three decades, since the 1983 publication of "A Nation At Risk" launched a sustained focus on the mediocre, if not failing, K-12 system, American postsecondary education has avoided the accountability spotlight. Postsecondary policy debates have focused…

Changes in the Structure of Children's Isometric Force Variability with Practice

ERIC Educational Resources Information Center

Deutsch, Katherine M.; Newell, Karl M.

2004-01-01

This study examined the effect of age and practice on the structure of children's force variability to test the information processing hypothesis that a reduction of sensorimotor system noise accounts in large part for age-related reductions in perceptual-motor performance variability. In the study, 6-year-olds, 10-year-olds, and young adults…

[Forced Oscillations of DNA Bases].

PubMed

Yakushevich, L V; Krasnobaeva, L A

2016-01-01

This paper presents the results of the studying of forced angular oscillations of the DNA bases with the help of the mathematical model consisting of two coupled nonlinear differential equations that take into account the effects of dissipation and the influence of an external periodic field. The calculation results are illustrated for sequence of gene encoding interferon alpha 17 (IFNA 17).

Comments on John Willinsky's Learning to Divide the World: Education at Empire's End

ERIC Educational Resources Information Center

Wang, Tsung Juang

2006-01-01

John Willinsky's view that imperialism and its legacy remain the driving force that divides the world into "superior" and "inferior" cultures fails to take into account other forces that also encourage peoples of different cultures to emphasize the differences between themselves. He is correct in noting that imperialism led to much injustice and…

Understanding electric field-enhanced transport for the measurement of nanoparticles and their assembly on surfaces

NASA Astrophysics Data System (ADS)

Tsai, De-Hao

The goal of this dissertation is to understand the synthesis, characterization, and integration of nanoparticles and nanoparticle-based devices by electric field-enhanced transport of nanoparticles. Chapter I describes the factors used for determining particle trajectories and found that electric fields provide the directional electrostatic force to overcome other non-directional influences on particle trajectories. This idea is widely applied in the nanoparticle classification, characterization, and assembly onto substrate surfaces as investigated in the following chapters. Chapter 2 presents a new assembly method to position metal nanoparticles delivered from the gas phase onto surfaces using the electrostatic force generated by biased p-n junction patterned substrates. Aligned deposition patterns of metal nanoparticles were observed, and the patterning selectivity quantified. A simple model accounting for the generated electric field, and the electrostatic, van der Waals, and image forces was used to explain the observed results. Chapter 2.2 describes a data set for particle size resolved deposition, from which a Brownian dynamics model for the process can be evaluated. Brownian motion and fluid convection of nanoparticles, as well as the interactions between the charged nanoparticles and the patterned substrate, including electrostatic force, image force and van der Waals force, are accounted for in the simulation. Using both experiment and simulation the effects of the particle size, electric field intensity, and the convective flow on coverage selectivity have been investigated. Coverage selectivity is most sensitive to electric field, which is controlled by the applied reverse bias voltage across the p-n junction. A non-dimensional analysis of the competition between the electrostatic and diffusion force is found to provide a means to collapse a wide range of process operating conditions and an effective indicator or process performance. Directed assembly of size-selected nanoparticles has been applied in the study of nanoparticle enhanced fluorescence (NEF) bio-sensing devices. Chapter 3 presents results of a systematic examination of funct onalized gold nanoparticles by electrospray-differential mobility analysis (ES-DMA). Formation of selfassembled monolayers (SAMs) of alkylthiol molecules and singly stranded DNA (ssDNA) on the Au-NP surface was detected from a change in particle mobility, which could be modeled to extract the surface packing density. A gas-phase temperature-programmed desorption (TPD) kinetic study of SAMs on the Au-NP found the data to be consistent with a second order Arrhenius based rate law, yielding an Arrhenius-factor of 1x1011s -1 and an activation energy ˜105 kJ/mol. This study suggests that the ES-DMA can be added to the tool set of characterization methods being employed and developed to study the structure and properties of coated nanoparticles. Chapter 3.2 demonstrates this ES-DMA as a new method to investigate colloidal aggregation and the parameters that govern it. Nanoparticle suspensions were characterized by sampling a Au nanoparticle (Au-NP) colloidal solution via electrospray (ES), followed by differential ion-mobility analysis (DMA) to determine the mobility distribution, and thus the aggregate distribution. By sampling at various times, the degree of flocculation and the flocculation rate are determined and found to be inversely proportional to the ionic strength and proportional to the residence time. A stability ratio at different ionic strengths, the critical concentration, and surface potential or surface charge density of Au-NPs are obtained from these data. This method should be a generically useful tool to probe the early stages of colloidal aggregation. Study of ES-DMA is extended to include the characterizations of a variety of materials. Biologically interested materials such as viruses and antibodies could also be characterized. These results show ES-DMA provides a general way to characterize the colloidal materials as well as aerosolized particles.

Probing surface charge potentials of clay basal planes and edges by direct force measurements.

PubMed

Zhao, Hongying; Bhattacharjee, Subir; Chow, Ross; Wallace, Dean; Masliyah, Jacob H; Xu, Zhenghe

2008-11-18

The dispersion and gelation of clay suspensions have major impact on a number of industries, such as ceramic and composite materials processing, paper making, cement production, and consumer product formulation. To fundamentally understand controlling mechanisms of clay dispersion and gelation, it is necessary to study anisotropic surface charge properties and colloidal interactions of clay particles. In this study, a colloidal probe technique was employed to study the interaction forces between a silica probe and clay basal plane/edge surfaces. A muscovite mica was used as a representative of 2:1 phyllosilicate clay minerals. The muscovite basal plane was prepared by cleavage, while the edge surface was obtained by a microtome cutting technique. Direct force measurements demonstrated the anisotropic surface charge properties of the basal plane and edge surface. For the basal plane, the long-range forces were monotonically repulsive within pH 6-10 and the measured forces were pH-independent, thereby confirming that clay basal planes have permanent surface charge from isomorphic substitution of lattice elements. The measured interaction forces were fitted well with the classical DLVO theory. The surface potentials of muscovite basal plane derived from the measured force profiles were in good agreement with those reported in the literature. In the case of edge surfaces, the measured forces were monotonically repulsive at pH 10, decreasing with pH, and changed to be attractive at pH 5.6, strongly suggesting that the charge on the clay edge surfaces is pH-dependent. The measured force profiles could not be reasonably fitted with the classical DLVO theory, even with very small surface potential values, unless the surface roughness was considered. The surface element integration (SEI) method was used to calculate the DLVO forces to account for the surface roughness. The surface potentials of the muscovite edges were derived by fitting the measured force profiles with the surface element integrated DLVO model. The point of zero charge of the muscovite edge surface was estimated to be pH 7-8.

Numerical analysis of multicomponent responses of surface-hole transient electromagnetic method

NASA Astrophysics Data System (ADS)

Meng, Qing-Xin; Hu, Xiang-Yun; Pan, He-Ping; Zhou, Feng

2017-03-01

We calculate the multicomponent responses of surface-hole transient electromagnetic method. The methods and models are unsuitable as geoelectric models of conductive surrounding rocks because they are based on regular local targets. We also propose a calculation and analysis scheme based on numerical simulations of the subsurface transient electromagnetic fields. In the modeling of the electromagnetic fields, the forward modeling simulations are performed by using the finite-difference time-domain method and the discrete image method, which combines the Gaver-Stehfest inverse Laplace transform with the Prony method to solve the initial electromagnetic fields. The precision in the iterative computations is ensured by using the transmission boundary conditions. For the response analysis, we customize geoelectric models consisting of near-borehole targets and conductive wall rocks and implement forward modeling simulations. The observed electric fields are converted into induced electromotive force responses using multicomponent observation devices. By comparing the transient electric fields and multicomponent responses under different conditions, we suggest that the multicomponent-induced electromotive force responses are related to the horizontal and vertical gradient variations of the transient electric field at different times. The characteristics of the response are determined by the varying the subsurface transient electromagnetic fields, i.e., diffusion, attenuation and distortion, under different conditions as well as the electromagnetic fields at the observation positions. The calculation and analysis scheme of the response consider the surrounding rocks and the anomalous field of the local targets. It therefore can account for the geological data better than conventional transient field response analysis of local targets.

United States Air Force Computer-Aided Acquisition and Logistics Support (CALS) Evolution of Computer Integrated Manufacturing (CIM) Technologies

DTIC Science & Technology

1988-11-01

Manufacturing System 22 4. Similar Parts Based Shape or Manufactuting Process 24 5. Projected Annual Unit Robot Sales and Installed Base Through 1992 30 6. U.S...effort needed to perform personnel, product design, marketing , and advertising, and finance tasks of the firm. Level III controls the resource...planning and accounting functions of the firm. Systems at this level support purchasing, accounts payable, accounts receivable, master scheduling and sales

Tracking Air Force Pallets Using RFID Technology: A Concept Study.

DTIC Science & Technology

1995-09-01

cost savings in terms of overall mission impact ( Horngren , 1994: 704-705). To illustrate the far-reaching control advantages of RF/ED, 3-3 the...estimate of $1,500,000 accounts only for the base pay labor costs directly associated with the physical process of opening and gathering information on...The total figure of $15,625,000 accounts only for estimated shipping costs of reordered assets. It does not account for the additional burden on the in

Estimating Supply-Chain Burdens in Support of Acquisition Decisions

DTIC Science & Technology

2013-03-20

Çì~íÉ=pÅÜççä= Abstract Acquisition decisions drive supply-chain requirements that incur financial costs and other critical impacts. To account ...their rates are fully burdened with respect to the cost of transport assets and any force protection, if necessary. However, DoD accounting systems and...Board (DSB) report (2008) highlighted the failure of DoD management processes to properly account for the enterprise- wide costs of fuel. Before 2009

Structural vibration and acoustic radiation of coupled propeller-shafting and submarine hull system due to propeller forces

NASA Astrophysics Data System (ADS)

Qu, Yegao; Su, Jinpeng; Hua, Hongxing; Meng, Guang

2017-08-01

This paper investigates the structural and acoustic responses of a coupled propeller-shafting and submarine pressure hull system under different propeller force excitations. The entire system, which consists of a rigid propeller, a main shaft, two bearings and an orthogonally stiffened pressure hull, is submerged in a heavy fluid. The shaft is elastically connected to the pressure hull by a radial bearing and a thrust bearing. The theoretical model of the structural system is formulated based on a modified variational method, in which the propeller, the main shaft and the bearings are treated as a lumped mass, an elastic beam and spatially distributed spring-damper systems, respectively. The rings and stringers in the pressure hull are modeled as discrete structural elements. The acoustic field generated by the hull is calculated using a spectral Kirchhoff-Helmholtz integral formulation. A strongly coupled structure-acoustic interaction analysis is employed to achieve reasonable solutions for the coupled system. The displacement of the pressure hull and the sound pressure of the fluid are expanded in the form of a double mixed series using Fourier series and Chebyshev orthogonal polynomials, providing a flexible way for the present method to account for the individual contributions of circumferential wave modes to the vibration and acoustic responses of the pressure hull in an analytical manner. The contributions of different circumferential wave modes of the pressure hull to the structural and acoustic responses of the coupled system under axial, transversal and vertical propeller forces are investigated. Computed results are compared with those solutions obtained from the coupled finite element/boundary element method. Effects of the ring and the bearing stiffness on the acoustic responses of the coupled system are discussed.

A finite-volume HLLC-based scheme for compressible interfacial flows with surface tension

NASA Astrophysics Data System (ADS)

Garrick, Daniel P.; Owkes, Mark; Regele, Jonathan D.

2017-06-01

Shock waves are often used in experiments to create a shear flow across liquid droplets to study secondary atomization. Similar behavior occurs inside of supersonic combustors (scramjets) under startup conditions, but it is challenging to study these conditions experimentally. In order to investigate this phenomenon further, a numerical approach is developed to simulate compressible multiphase flows under the effects of surface tension forces. The flow field is solved via the compressible multicomponent Euler equations (i.e., the five equation model) discretized with the finite volume method on a uniform Cartesian grid. The solver utilizes a total variation diminishing (TVD) third-order Runge-Kutta method for time-marching and second order TVD spatial reconstruction. Surface tension is incorporated using the Continuum Surface Force (CSF) model. Fluxes are upwinded with a modified Harten-Lax-van Leer Contact (HLLC) approximate Riemann solver. An interface compression scheme is employed to counter numerical diffusion of the interface. The present work includes modifications to both the HLLC solver and the interface compression scheme to account for capillary force terms and the associated pressure jump across the gas-liquid interface. A simple method for numerically computing the interface curvature is developed and an acoustic scaling of the surface tension coefficient is proposed for the non-dimensionalization of the model. The model captures the surface tension induced pressure jump exactly if the exact curvature is known and is further verified with an oscillating elliptical droplet and Mach 1.47 and 3 shock-droplet interaction problems. The general characteristics of secondary atomization at a range of Weber numbers are also captured in a series of simulations.

A finite-volume HLLC-based scheme for compressible interfacial flows with surface tension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garrick, Daniel P.; Owkes, Mark; Regele, Jonathan D., E-mail: jregele@iastate.edu

Shock waves are often used in experiments to create a shear flow across liquid droplets to study secondary atomization. Similar behavior occurs inside of supersonic combustors (scramjets) under startup conditions, but it is challenging to study these conditions experimentally. In order to investigate this phenomenon further, a numerical approach is developed to simulate compressible multiphase flows under the effects of surface tension forces. The flow field is solved via the compressible multicomponent Euler equations (i.e., the five equation model) discretized with the finite volume method on a uniform Cartesian grid. The solver utilizes a total variation diminishing (TVD) third-order Runge–Kuttamore » method for time-marching and second order TVD spatial reconstruction. Surface tension is incorporated using the Continuum Surface Force (CSF) model. Fluxes are upwinded with a modified Harten–Lax–van Leer Contact (HLLC) approximate Riemann solver. An interface compression scheme is employed to counter numerical diffusion of the interface. The present work includes modifications to both the HLLC solver and the interface compression scheme to account for capillary force terms and the associated pressure jump across the gas–liquid interface. A simple method for numerically computing the interface curvature is developed and an acoustic scaling of the surface tension coefficient is proposed for the non-dimensionalization of the model. The model captures the surface tension induced pressure jump exactly if the exact curvature is known and is further verified with an oscillating elliptical droplet and Mach 1.47 and 3 shock-droplet interaction problems. The general characteristics of secondary atomization at a range of Weber numbers are also captured in a series of simulations.« less

Tales of biographical disintegration: how parents make sense of their sons' suicides.

PubMed

Owens, Christabel; Lambert, Helen; Lloyd, Keith; Donovan, Jenny

2008-03-01

Suicide research relies heavily on accounts provided by bereaved relatives, using a method known as the psychological autopsy. Psychological autopsy studies are invariably quantitative in design and their findings reinforce the medical model of suicide, emphasising the role of mental illness. They largely ignore the meanings that narrators attach to events, the nature of the sense-making task and the influences bearing upon it. This study drew on psychological autopsy data but used qualitative analytic methods. Fourteen semi-structured interviews with the parents of young men aged 18-30 who had taken their own lives form the basis for this paper. Some parents represent their sons as victims who were cruelly destroyed by external forces, while others portray them as agents of their own destruction. Either way, their narratives are dominated by moral rather than medical categories and by questions of personal accountability. We show how the parents use the interview to perform a complex reconstructive task, striving to piece together both their son's and their own shattered biographies and repair damage to their moral identities. We argue that their stories represent survival tools, enabling them not only to make sense of the past but also to face their own future.

Deficits in Lower Limb Muscle Reflex Contraction Latency and Peak Force Are Associated With Impairments in Postural Control and Gross Motor Skills of Children With Developmental Coordination Disorder: A Cross-Sectional Study.

PubMed

Fong, Shirley S M; Ng, Shamay S M; Guo, X; Wang, Yuling; Chung, Raymond C K; Stat, Grad; Ki, W Y; Macfarlane, Duncan J

2015-10-01

This cross-sectional, exploratory study aimed to compare neuromuscular performance, balance and motor skills proficiencies of typically developing children and those with developmental coordination disorder (DCD) and to determine associations of these neuromuscular factors with balance and motor skills performances in children with DCD.One hundred thirty children with DCD and 117 typically developing children participated in the study. Medial hamstring and gastrocnemius muscle activation onset latencies in response to an unexpected posterior-to-anterior trunk perturbation were assessed by electromyography and accelerometer. Hamstring and gastrocnemius muscle peak force and time to peak force were quantified by dynamometer, and balance and motor skills performances were evaluated with the Movement Assessment Battery for Children (MABC).Independent t tests revealed that children with DCD had longer hamstring and gastrocnemius muscle activation onset latencies (P < 0.001) and lower isometric peak forces (P < 0.001), but not times to peak forces (P > 0.025), than the controls. Multiple regression analysis accounting for basic demographics showed that gastrocnemius peak force was independently associated with the MABC balance subscore and ball skills subscore, accounting for 5.7% (P = 0.003) and 8.5% (P = 0.001) of the variance, respectively. Gastrocnemius muscle activation onset latency also explained 11.4% (P < 0.001) of the variance in the MABC ball skills subscore.Children with DCD had delayed leg muscle activation onset times and lower isometric peak forces. Gastrocnemius peak force was associated with balance and ball skills performances, whereas timing of gastrocnemius muscle activation was a determinant of ball skill performance in the DCD population.

Analytical Investigation of Elastic Thin-Walled Cylinder and Truncated Cone Shell Intersection Under Internal Pressure.

PubMed

Zamani, J; Soltani, B; Aghaei, M

2014-10-01

An elastic solution of cylinder-truncated cone shell intersection under internal pressure is presented. The edge solution theory that has been used in this study takes bending moments and shearing forces into account in the thin-walled shell of revolution element. The general solution of the cone equations is based on power series method. The effect of cone apex angle on the stress distribution in conical and cylindrical parts of structure is investigated. In addition, the effect of the intersection and boundary locations on the circumferential and longitudinal stresses is evaluated and it is shown that how quantitatively they are essential.

High negative charge of a dust particle in a hot cathode discharge.

PubMed

Arnas, C; Mikikian, M; Doveil, F

1999-12-01

Dust particle levitation experiments in a plasma produced by a hot filament discharge, operating at low argon pressure, are presented. The basic characteristics of a dust grain trapped in a plate sheath edge in these experimental conditions are reported. Taking into account the sheath potential profiles measured with a differential emissive probe diagnostic, the forces applied to an isolated dust grain can be determined. Two different experimental methods yield approximately the same value for the dust charge. The observed high negative charge is mainly due to the contribution of the primary electrons emitted by the filaments as predicted by a simple model.

Euler Flow Computations on Non-Matching Unstructured Meshes

NASA Technical Reports Server (NTRS)

Gumaste, Udayan

1999-01-01

Advanced fluid solvers to predict aerodynamic performance-coupled treatment of multiple fields are described. The interaction between the fluid and structural components in the bladed regions of the engine is investigated with respect to known blade failures caused by either flutter or forced vibrations. Methods are developed to describe aeroelastic phenomena for internal flows in turbomachinery by accounting for the increased geometric complexity, mutual interaction between adjacent structural components and presence of thermal and geometric loading. The computer code developed solves the full three dimensional aeroelastic problem of-stage. The results obtained show that flow computations can be performed on non-matching finite-volume unstructured meshes with second order spatial accuracy.

Earthquake response analysis of 11-story RC building that suffered damage in 2011 East Japan Earthquake

NASA Astrophysics Data System (ADS)

Shibata, Akenori; Masuno, Hidemasa

2017-10-01

An eleven-story RC apartment building suffered medium damage in the 2011 East Japan earthquake and was retrofitted for re-use. Strong motion records were obtained near the building. This paper discusses the inelastic earthquake response analysis of the building using the equivalent single-degree-of-freedom (1-DOF) system to account for the features of damage. The method of converting the building frame into 1-DOF system with tri-linear reducing-stiffness restoring force characteristics was given. The inelastic response analysis of the building against the earthquake using the inelastic 1-DOF equivalent system could interpret well the level of actual damage.

Enhancing microscopic cascading contributions to higher-order nonlinear-optical responses through forced geometric constraints

NASA Astrophysics Data System (ADS)

Dawson, Nathan J.; Andrews, James H.; Crescimanno, Michael

2012-10-01

We review a model that was developed to take into account all possible microscopic cascading schemes in a single species system out to the fifth order using a self-consistent field approach. This model was designed to study the effects of boundaries in mesoscopic systems with constrained boundaries. These geometric constraints on the macroscopic structure show how the higher-ordered susceptibilities are manipulated by increasing the surface to volume ratio, while the microscopic structure influences the local field from all other molecules in the system. In addition to the review, we discuss methods of modeling real systems of molecules, where efforts are currently underway.

Effects of wave-induced forcing on a circulation model of the North Sea

NASA Astrophysics Data System (ADS)

Staneva, Joanna; Alari, Victor; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian

2017-04-01

The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution NEMO model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force and the sea-state dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25-27 October 2013), and about a month later, the storm Xaver (5-7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20-30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water level and current predictions.

Effects of wave-induced forcing on a circulation model of the North Sea

NASA Astrophysics Data System (ADS)

Staneva, Joanna; Alari, Victor; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian

2017-01-01

The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution Nucleus for European Modelling of the Ocean (NEMO) model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force, the sea-state-dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water-level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state-dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25-27 October 2013), and about a month later, the storm Xaver (5-7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20-30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water-level and current predictions.

A viable method to predict acoustic streaming in presence of cavitation.

PubMed

Louisnard, O

2017-03-01

The steady liquid flow observed under ultrasonic emitters generating acoustic cavitation can be successfully predicted by a standard turbulent flow calculation. The flow is driven by the classical averaged volumetric force density calculated from the acoustic field, but the inertial term in Navier-Stokes equations must be kept, and a turbulent solution must be sought. The acoustic field must be computed with a realistic model, properly accounting for dissipation by the cavitation bubbles [Louisnard, Ultrason. Sonochem., 19, (2012) 56-65]. Comparison with 20kHz experiments, involving the combination of acoustic streaming and a perpendicular forced flow in a duct, shows reasonably good agreement. Moreover, the persistence of the cavitation effects on the wall facing the emitter, in spite of the deflection of the streaming jet, is correctly reproduced by the model. It is also shown that predictions based either on linear acoustics with the correct turbulent solution, or with Louisnard's model with Eckart-Nyborg's theory yields unrealistic results. Copyright © 2016 Elsevier B.V. All rights reserved.

Active space debris charging for contactless electrostatic disposal maneuvers

NASA Astrophysics Data System (ADS)

Schaub, Hanspeter; Sternovsky, Zoltán

2014-01-01

The remote charging of a passive object using an electron beam enables touchless re-orbiting of large space debris from geosynchronous orbit (GEO) using electrostatic forces. The advantage of this method is that it can operate with a separation distance of multiple craft radii, thus reducing the risk of collision. The charging of the tug-debris system to high potentials is achieved by active charge transfer using a directed electron beam. Optimal potential distributions using isolated- and coupled-sphere models are discussed. A simple charging model takes into account the primary electron beam current, ultra-violet radiation induced photoelectron emission, collection of plasma particles, secondary electron emission and the recapture of emitted particles. The results show that through active charging in a GEO space environment high potentials can be both achieved and maintained with about a 75% transfer efficiency. Further, the maximum electrostatic tractor force is shown to be insensitive to beam current levels. This latter later result is important when considering debris with unknown properties.

Assessment of the Local Residual Stresses of 7050-T7452 Aluminum Alloy in Microzones by the Instrumented Indentation with the Berkovich Indenter

NASA Astrophysics Data System (ADS)

He, M.; Huang, C. H.; Wang, X. X.; Yang, F.; Zhang, N.; Li, F. G.

2017-10-01

The local residual stresses in microzones are investigated by the instrumented indentation method with the Berkovich indenter. The parameters required for determination of residual stresses are obtained from indentation load-penetration depth curves constructed during instrumented indentation tests on flat square 7050-T7452 aluminum alloy specimens with a central hole containing the compressive residual stresses generated by the cold extrusion process. The force balance system with account of the tensile and compressive residual stresses is used to explain the phenomenon of different contact areas produced by the same indentation load. The effect of strain-hardening exponent on the residual stress is tuned-off by application of the representative stress σ_{0.033} in the average contact pressure assessment using the Π theorem, while the yield stress value is obtained from the constitutive function. Finally, the residual stresses are calculated according to the proposed equations of the force balance system, and their feasibility is corroborated by the XRD measurements.

Techniques of Force and Pressure Measurement in the Small Joints of the Wrist.

PubMed

Schreck, Michael J; Kelly, Meghan; Canham, Colin D; Elfar, John C

2018-01-01

The alteration of forces across joints can result in instability and subsequent disability. Previous methods of force measurements such as pressure-sensitive films, load cells, and pressure-sensing transducers have been utilized to estimate biomechanical forces across joints and more recent studies have utilized a nondestructive method that allows for assessment of joint forces under ligamentous restraints. A comprehensive review of the literature was performed to explore the numerous biomechanical methods utilized to estimate intra-articular forces. Methods of biomechanical force measurements in joints are reviewed. Methods such as pressure-sensitive films, load cells, and pressure-sensing transducers require significant intra-articular disruption and thus may result in inaccurate measurements, especially in small joints such as those within the wrist and hand. Non-destructive methods of joint force measurements either utilizing distraction-based joint reaction force methods or finite element analysis may offer a more accurate assessment; however, given their recent inception, further studies are needed to improve and validate their use.

Traceable Dynamic Calibration of Force Transducers by Primary Means

PubMed Central

Vlajic, Nicholas; Chijioke, Ako

2018-01-01

We describe an apparatus for traceable, dynamic calibration of force transducers using harmonic excitation, and report calibration measurements of force transducers using this apparatus. In this system, the force applied to the transducer is produced by the acceleration of an attached mass, and is determined according to Newton’s second law, F = ma. The acceleration is measured by primary means, using laser interferometry. The capabilities of this system are demonstrated by performing dynamic calibrations of two shear-web-type force transducers up to a frequency of 2 kHz, with an expanded uncertainty below 1.2 %. We give an accounting of all significant sources of uncertainty, including a detailed consideration of the effects of dynamic tilting (rocking), which is a leading source of uncertainty in such harmonic force calibration systems. PMID:29887643