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1

Application of Statistical Continuum Mechanics to Guide Processing ...  

Science Conference Proceedings (OSTI)

Multi scale modeling including statistical continuum mechanics is used to predict microstructure evolution during processing. We also developed statistical ...

2

2.4 CONTINUUM MECHANICS (SOLIDS) In this introduction to continuum mechanics we consider the basic equations describing the physical  

E-Print Network (OSTI)

243 §2.4 CONTINUUM MECHANICS (SOLIDS) In this introduction to continuum mechanics we consider to simplify the constitutive equations for elasticity. We begin our study of continuum mechanics

California at Santa Cruz, University of

3

Atomistic and continuum modeling of mechanical properties of collagen: Elasticity, fracture, and self-assembly  

E-Print Network (OSTI)

efforts to refine the Standard Model and understanding of atomic properties. #12;Contents 1 Once Upon

Entekhabi, Dara

4

Concepts of Hyperbolicity and Relativistic Continuum Mechanics  

E-Print Network (OSTI)

After a short introduction to the characteristic geometry underlying weakly hyperbolic systems of partial differential equations we review the notion of symmetric hyperbolicity of first-order systems and that of regular hyperbolicity of second-order systems. Numerous examples are provided, mainly taken from nonrelativistic and relativistic continuum mechanics.

Robert Beig

2004-11-18T23:59:59.000Z

5

Joint spacing criterion for equivalent continuum model  

Science Conference Proceedings (OSTI)

Currently, the Yucca Mountain Site Characterization Project is investigating the feasibility of the disposal of high-level radioactive waste in the unsaturated Topopah Spring formation. The Topopah Spring formation is a heavily fractured, predominantly vertically jointed, welded tuff, and the potential disposal area is cut by the Ghost Dance fault and bounded by several other faults structures. The joints in the tuff and the faults may have an impact on the emplacement drift or borehole stability, as well as on the movement of fluids through the rock mass. The design of the repository drifts and layout, the waste emplacement scheme, and the thermomechanical performance of the rock mass will be analyzed using various numerical models. These models may be based on different assumptions regarding the representation of the fracture behavior under given applied stresses, and will range from discrete models where individual mechanically active fractures are treated distinctly, to continuum models where the joint behavior is smeared over a representative volume. There is always the question of applicability of a model with respect to a given material domain to be analyzed. For the mechanical analysis of the rock mass response around a repository drift, the applicability of an equivalent continuum model is dependent on the joint spacing in the rock mass. Considering the joint spacings that may be encountered at the potential repository site, a ratio of joint spacing to the planned drift diameter may be adopted as a criterion for evaluating the applicability of the Compliant Joint Model (CJM) in the Yucca Mountain Site Characterization Project. In this paper, this criterion is established by reviewing basic continuum concepts and numerical approximation implications used to build the CJM and by examining rock mass conditions that may be encountered at the potential Yucca Mountain repository site.

Tsai, F.C.

1995-12-31T23:59:59.000Z

6

From continuum Fokker-Planck models to discrete kinetic models  

E-Print Network (OSTI)

ABSTRACT Two theoretical formalisms are widely used in modeling mechanochemical systems such as protein motors: continuum Fokker-Planck models and discrete kinetic models. Both have advantages and disadvantages. Here we present a ‘‘finite volume’ ’ procedure to solve Fokker-Planck equations. The procedure relates the continuum equations to a discrete mechanochemical kinetic model while retaining many of the features of the continuum formulation. The resulting numerical algorithm is a generalization of the algorithm developed previously by Fricks, Wang, and Elston through relaxing the local linearization approximation of the potential functions, and a more accurate treatment of chemical transitions. The new algorithm dramatically reduces the number of numerical cells required for a prescribed accuracy. The kinetic models constructed in this fashion retain some features of the continuum potentials, so that the algorithm provides a systematic and consistent treatment of mechanical-chemical responses such as load-velocity relations, which are difficult to capture with a priori kinetic models. Several numerical examples are given to illustrate the performance of the method.

Jianhua Xing; Hongyun Wang; George Oster

2005-01-01T23:59:59.000Z

7

Continuum modeling of two-phase flows  

SciTech Connect

Continuum modeling of two-phase flows can essentially be achieved in two ways. The first approach, the so-called continuum theory of mixtures, ignores the details of the flow occurring on the microscopic level, while the second one is the result of some averaging procedure. Although they both lead, as expected, to the same set of basic equations, they differ strongly in their spirit when closure equations have to be found. In the present report, we have attempted to give a brief critical review of both approaches, to compare them and to discuss some of the major difficulties which arise. It is shown that the application of the continuum theory of mixtures is, in most cases, questionable and that the only appropriate way of finding closure equations, besides correlating experimental results, consists in a useful investigation of the microscopic flow pattern associated with an adequate averaging technique.

Bataille, J.; Kestin, J.

1981-12-01T23:59:59.000Z

8

The use of the teleparallelism connection in continuum mechanics  

E-Print Network (OSTI)

The geometry of parallelizable manifolds (i.e., teleparallelism) is summarized in the language of local frame fields. Some problems in continuum mechanics that relate to the couple-stresses that are produced in the bending and twisting of prismatic beams and wires are then discussed. It is then shown that by going to a higher-dimensional analogue of the geometry that one used for one-dimensional deformable objects, one is basically using the methods of teleparallelism in the context of the Cosserat approach to deformable bodies.

Delphenich, D H

2013-01-01T23:59:59.000Z

9

Molecular surface-free continuum model for electrodiffusion processes  

E-Print Network (OSTI)

Molecular surface-free continuum model for electrod-of introduc- ing a molecular surface and the painful task ofreaction kinet- ics, and molecular surface de?ned as an

Lu, Benzhuo; McCammon, J. Andrew

2008-01-01T23:59:59.000Z

10

The Effect of Nonlinearity in Hybrid KMC-Continuum models  

E-Print Network (OSTI)

Recently there has been interest in developing efficient ways to model heterogeneous surface reactions with hybrid computational models that couple a KMC model for a surface to a finite difference model for bulk diffusion in a continuous domain. We consider two representative problems that validate a hybrid method and also show that this method captures the combined effects of nonlinearity and stochasticity. We first validate a simple deposition/dissolution model with a linear rate showing that the KMC-continuum hybrid agrees with both a fully deterministic model and its analytical solution. We then study a deposition/dissolution model including competitive adsorption, which leads to a nonlinear rate, and show that, in this case, the KMC-continuum hybrid and fully deterministic simulations do not agree. However, we are able to identify the difference as a natural result of the stochasticity coming from the KMC surface process. Because KMC captures inherent fluctuations, we consider it to be more realistic tha...

Balter, Ariel; Tartakovsky, Alexandre M

2011-01-01T23:59:59.000Z

11

A study of discrete and continuum joint modeling techniques  

SciTech Connect

This paper presents the results of a numerical and experimental study in which finite element and discrete element techniques were used to analyze a layered polycarbonate plate model subjected to uniaxial compression. Also, the two analysis techniques were used to compute the response of an eight meter diameter drift in jointed-rock. The drift was subjected to in-situ and far-field induced thermal stresses. The finite element analyses used a continuum rock model to represent the jointed-rock. A comparison of the analyses showed that the finite element continuum joint model consistently predicted less joint slippage than did the discrete element analyses, although far-field displacements compared well.

Jung, J.; Brown, S.R.

1992-05-01T23:59:59.000Z

12

Crack Growth in Solid Oxide Fuel Cell Materials: From Discrete to Continuum Damage Modeling  

Science Conference Proceedings (OSTI)

This paper addresses the cracking problem of glass and ceramic materials used in solid oxide fuel cells (SOFCs). Analyses of an internal crack and of an interface crack between dissimilar materials were conducted using a modified boundary layer modeling approach. In this approach, fracture is allowed to occur in a small process window situated at an initial crack tip. Elastic displacement crack-tip fields are prescribed as remote boundary conditions. Crack propagation was first modeled discretely. Next, a continuum damage mechanics (CDM) model for brittle materials was developed to capture damage and crack growth in the process window. In particular, the damage model was applied to a glass-ceramic material that had been developed in-house for sealing purposes. Discrete and continuum damage solutions were then compared. Finally, the CDM model was used to determine the crack propagation direction as a function of a mode mixity measure.

Nguyen, Ba Nghiep; Koeppel, Brian J.; Ahzi, Said; Khaleel, Mohammad A.; Singh, Prabhakar

2006-04-01T23:59:59.000Z

13

Atomistic-to-Continuum Multiscale Modeling with Long-Range Electrostatic Interactions in Ionic Solids  

E-Print Network (OSTI)

We present a multiscale atomistic-to-continuum method for ionic crystals with defects. Defects often play a central role in ionic and electronic solids, not only to limit reliability, but more importantly to enable the functionalities that make these materials of critical importance. Examples include solid electrolytes that conduct current through the motion of charged point defects, and complex oxide ferroelectrics that display multifunctionality through the motion of domain wall defects. Therefore, it is important to understand the structure of defects and their response to electrical and mechanical fields. A central hurdle, however, is that interactions in ionic solids include both short-range atomic interactions as well as long-range electrostatic interactions. Existing atomistic-to-continuum multi-scale methods, such as the Quasicontinuum method, are applicable only when the atomic interactions are short-range. In addition, empirical reductions of quantum mechanics to density functional models are unable...

Marshall, Jason

2013-01-01T23:59:59.000Z

14

Application of the Creep Continuum Damage Mechanics Unified ...  

Science Conference Proceedings (OSTI)

How to Control Strength and Grain Structure of 304L Stainless Steel during Forging · Improved ... Process Modeling and Reduction of Copper Loss in Smelting Slag ... Use of Polymeric Residues from the Footwear Industry in Layers of Asphalt ...

15

Implicit continuum mechanics approach to heat conduction in granular materials  

SciTech Connect

In this paper, we derive a properly frame-invariant implicit constitutive relationship for the heat flux vector for a granular medium (or a density-gradient-type fluid). The heat flux vector is commonly modeled by Fourier’s law of heat conduction, and for complex materials such as nonlinear fluids, porous media, or granular materials, the coefficient of thermal conductivity is generalized by assuming that it would depend on a host of material and kinematic parameters such as temperature, shear rate, porosity, concentration, etc. In this paper, we extend the approach of Massoudi [Massoudi, M. Math. Methods Appl. Sci. 2006, 29, 1585; Massoudi, M. Math. Methods Appl. Sci. 2006, 29, 1599], who provided explicit constitutive relations for the heat flux vector for flowing granular materials; in order to do so, we use the implicit scheme suggested by Fox [Fox, N. Int. J. Eng. Sci. 1969, 7, 437], who obtained implicit relations in thermoelasticity.

Massoudi, M.; Mehrabadi, M.

2010-01-01T23:59:59.000Z

16

Bounding the electrostatic free energies associated with linear continuum models of molecular solvation  

Science Conference Proceedings (OSTI)

The importance of electrostatic interactions in molecular biology has driven extensive research toward the development of accurate and efficient theoretical and computational models. Linear continuum electrostatic theory has been surprisingly successful

Jaydeep P. Bardhan; Matthew G. Knepley; Mihai Anitescu

2009-01-01T23:59:59.000Z

17

Progress toward bridging from atomistic to continuum modeling to predict nuclear waste glass dissolution.  

SciTech Connect

This report summarizes research performed for the Nuclear Energy Advanced Modeling and Simulation (NEAMS) Subcontinuum and Upscaling Task. The work conducted focused on developing a roadmap to include molecular scale, mechanistic information in continuum-scale models of nuclear waste glass dissolution. This information is derived from molecular-scale modeling efforts that are validated through comparison with experimental data. In addition to developing a master plan to incorporate a subcontinuum mechanistic understanding of glass dissolution into continuum models, methods were developed to generate constitutive dissolution rate expressions from quantum calculations, force field models were selected to generate multicomponent glass structures and gel layers, classical molecular modeling was used to study diffusion through nanopores analogous to those in the interfacial gel layer, and a micro-continuum model (K{mu}C) was developed to study coupled diffusion and reaction at the glass-gel-solution interface.

Zapol, Peter (Argonne National Laboratory, Argonne, IL); Bourg, Ian (Lawrence Berkeley National Laboratories, Berkeley, CA); Criscenti, Louise Jacqueline; Steefel, Carl I. (Lawrence Berkeley National Laboratories, Berkeley, CA); Schultz, Peter Andrew

2011-10-01T23:59:59.000Z

18

Modeling flow and transport in unsaturated fractured rock: An evaluation of the continuum approach  

Science Conference Proceedings (OSTI)

Because the continuum approach is relatively simple and straightforward to implement, it has been commonly used in modeling flow and transport in unsaturated fractured rock. However, the usefulness of this approach can be questioned in terms of its adequacy for representing fingering flow and transport in unsaturated fractured rock. The continuum approach thus needs to be evaluated carefully by comparing simulation results with field observations directly related to unsaturated flow and transport processes. This paper reports on such an evaluation, based on a combination of model calibration and prediction, using data from an infiltration test carried out in a densely fractured rock within the unsaturated zone of Yucca Mountain, Nevada. Comparisons between experimental and modeling results show that the continuum approach may be able to capture important features of flow and transport processes observed from the test. The modeling results also show that matrix diffusion may have a significant effect on the overall transport behavior in unsaturated fractured rocks, which can be used to estimate effective fracture-matrix interface areas based on tracer transport data. While more theoretical, numerical, and experimental studies are needed to provide a conclusive evaluation, this study suggests that the continuum approach is useful for modeling flow and transport in unsaturated, densely fractured rock.

Liu, Hui-Hai; Haukwa, Charles B.; Ahlers, C. Fredrik; Bodvarsson, Gudmundur S.; Flint, Alan L.; Guertal, William B.

2002-09-01T23:59:59.000Z

19

THMC Modeling of EGS Reservoirs - Continuum through Discontinuum...  

Open Energy Info (EERE)

Derek Elsworth of PSU Other Principal Investigators Joshua Taron, PSU; Eric Sonnenthal, LBNL Targets Milestones - Develop coupled THMC models capable of accommodating (i) rupture...

20

Resonant Continuum Modes in the Eady Model with Rigid Lid  

Science Conference Proceedings (OSTI)

The Eady model with rigid upper lid is considered. The resonant, linearly amplifying solution that exists in the situation of neutral normal modes when an infinitely thin potential vorticity (PV) perturbation is located precisely at the steering ...

Johannes Jenkner; Martin Ehrendorfer

2006-02-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Final Report for DOE Grant DE-FG02-03ER25579; Development of High-Order Accurate Interface Tracking Algorithms and Improved Constitutive Models for Problems in Continuum Mechanics with Applications to Jetting  

Science Conference Proceedings (OSTI)

Much of the work conducted under the auspices of DE-FG02-03ER25579 was characterized by an exceptionally close collaboration with researchers at the Lawrence Berkeley National Laboratory (LBNL). For example, Andy Nonaka, one of Professor Miller's graduate students in the Department of Applied Science at U. C. Davis (UCD) wrote his PhD thesis in an area of interest to researchers in the Applied Numerical Algorithms Group (ANAG), which is a part of the National Energy Research Supercomputer Center (NERSC) at LBNL. Dr. Nonaka collaborated closely with these researchers and subsequently published the results of this collaboration jointly with them, one article in a peer reviewed journal article and one paper in the proceedings of a conference. Dr. Nonaka is now a research scientist in the Center for Computational Sciences and Engineering (CCSE), which is also part of the National Energy Research Supercomputer Center (NERSC) at LBNL. This collaboration with researchers at LBNL also included having one of Professor Puckett's graduate students in the Graduate Group in Applied Mathematics (GGAM) at UCD, Sarah Williams, spend the summer working with Dr. Ann Almgren, who is a staff scientist in CCSE. As a result of this visit Sarah decided work on a problem suggested by the head of CCSE, Dr. John Bell, for her PhD thesis. Having finished all of the coursework and examinations required for a PhD, Sarah stayed at LBNL to work on her thesis under the guidance of Dr. Bell. Sarah finished her PhD thesis in June of 2007. Writing a PhD thesis while working at one of the University of California (UC) managed DOE laboratories is long established tradition at UC and Professor Puckett has always encouraged his students to consider doing this. Another one of Professor Puckett's graduate students in the GGAM at UCD, Christopher Algieri, was partially supported with funds from DE-FG02-03ER25579 while he wrote his MS thesis in which he analyzed and extended work originally published by Dr. Phillip Colella, the head of ANAG, and some of his colleagues. Chris Algieri is now employed as a staff member in Dr. Bill Collins' Climate Science Department in the Earth Sciences Division at LBNL working with computational models of climate change. Finally, it should be noted that the work conducted by Professor Puckett and his students Sarah Williams and Chris Algieri and described in this final report for DOE grant # DE-FC02-03ER25579 is closely related to work performed by Professor Puckett and his students under the auspices of Professor Puckett's DOE SciDAC grant DE-FC02-01ER25473 An Algorithmic and Software Framework for Applied Partial Differential Equations: A DOE SciDAC Integrated Software Infrastructure Center (ISIC). Dr. Colella was the lead PI for this SciDAC grant, which was comprised of several research groups from DOE national laboratories and five university PI's from five different universities. In theory Professor Puckett tried to use funds from the SciDAC grant to support work directly involved in implementing algorithms developed by members of his research group at UCD as software that might be of use to Puckett's SciDAC CoPIs. (For example, see the work reported in Section 2.2.2 of this final report.) However, since there is considerable lead time spent developing such algorithms before they are ready to become `software' and research plans and goals change as the research progresses, Professor Puckett supported each member of his research group partially with funds from the SciDAC APDEC ISIC DE-FC02-01ER25473 and partially with funds from this DOE MICS grant DE-FC02-03ER25579. This has necessarily resulted in a significant overlap of project areas that were funded by both grants. In particular, both Sarah Williams and Chris Algieri were supported partially with funds from grant # DE-FG02-03ER25579, for which this is the final report, and in part with funds from Professor Puckett's DOE SciDAC grant # DE-FC02-01ER25473. For example, Sarah Williams received support from DE-FC02- 01ER25473 and DE-FC02-03ER25579, both while at UCD taking cla

Puckett, Elbridge Gerry [U.C. Davis, Department of Mathematics; Miller, Gregory Hale [.C. Davis, Department of Chemical Engineering

2012-10-14T23:59:59.000Z

22

Coupling atomistic and continuum hydrodynamics through a mesoscopic model: application to liquid water  

E-Print Network (OSTI)

We have conducted a triple-scale simulation of liquid water by concurrently coupling atomistic, mesoscopic, and continuum models of the liquid. The presented triple-scale hydrodynamic solver for molecular liquids enables the insertion of large molecules into the atomistic domain through a mesoscopic region. We show that the triple-scale scheme is robust against the details of the mesoscopic model owing to the conservation of linear momentum by the adaptive resolution forces. Our multiscale approach is designed for molecular simulations of open domains with relatively large molecules, either in the grand canonical ensemble or under non-equilibrium conditions.

Rafael Delgado-Buscalioni; Kurt Kremer; Matej Praprotnik

2009-08-04T23:59:59.000Z

23

NIST: Atomic Spectros. - Spectral Continuum Radiation  

Science Conference Proceedings (OSTI)

Atomic Spectroscopy: home page. 21. Spectral Continuum Radiation. Hydrogenic Species. Precise quantum-mechanical ...

24

Electric and magnetic response to the continuum for A=7 isobars in a dicluster model  

E-Print Network (OSTI)

Mirror isobars $^7$Li and $^7$Be are investigated in a dicluster model. The magnetic dipole moments and the magnetic dipole response to the continuum are calculated in this framework. The magnetic contribution is found to be small with respect to electric dipole and quadrupole excitations even at astrophysical energies, at a variance with the case of deuteron. Energy weighted molecular sum rules are evaluated and a formula for the molecular magnetic dipole sum rule is found which matches the numerical calculations. Cross-sections for photo-dissociation and radiative capture as well as the S-factor for reactions of astrophysical significance are calculated with good agreement with known experimental data.

A. Mason; R. Chatterjee; L. Fortunato; A. Vitturi

2008-06-25T23:59:59.000Z

25

Analytical free energy second derivatives with respect to nuclear coordinates: Complete formulation for electrostatic continuum solvation models  

Science Conference Proceedings (OSTI)

We present the theory and the implementation of analytical free energy second derivatives with respect to nuclear displacements for a molecular solute described within the framework of the polarizable continuum model. The formulation applies to a cavity with an accurately modeled molecular shape and it permits a complete consideration of all aspects of the solvation model. In particular

B. Mennucci; R. Cammi; J. Tomasi

1999-01-01T23:59:59.000Z

26

Continuum Power Spectrum Components in X-Ray Sources: Detailed Modelling and Search for Coherent Periodicities  

E-Print Network (OSTI)

This paper summarises two recently developed techniques in power spectral analysis and their application to a sample of X-ray light curves of accreting collapsed objects in active galactic nuclei and X-ray binaries. The first technique is designed to carry out detailed model fitting of continuum power spectrum components arising from noise variability by using maximum likelihood methods. The technique is applied to the light curves of a number of highly variable AGNs observed with EXOSAT. Substantially steeper logarithmic power spectrum slopes are obtained than previously estimated with standard methods. The second technique was devised in order to reveal coherent periodicities in the presence of ``coloured" (i.e. non--white) noise variability components from the source. To this aim the power spectra are searched for significant narrow peaks superposed on the ``coloured" continuum components. We present the results of a search for an orbital modulation in the light curves of a sample of 25 low mass X--ray binaries (LMXRBs), for which the orbital period is either unknown or detected only at optical wavelengths. This led to the discovery of a significant X--ray orbital modulation at the few percent level in the burster MXB1636-539.

L. Stella; E. Arlandi; G. Tagliaferri; G. L. Israel

1994-11-13T23:59:59.000Z

27

On the Nonpolar Hydration Free Energy of Proteins: Surface Area and Continuum Solvent Models for the Solute-Solvent  

E-Print Network (OSTI)

On the Nonpolar Hydration Free Energy of Proteins: Surface Area and Continuum Solvent Models solvent hydration free energy models are an important component of most modern computational methods aimed. The nonpolar component of the hydration free energy, consisting of a repulsive cavity term and an attractive

28

A comparison of staggered solution schemes for coupled particle---continuum systems modeled with the Arlequin method  

Science Conference Proceedings (OSTI)

This contribution aims at a systematic investigation of staggered solution schemes for the computation of coupled domains having different resolutions in space, a problem frequently arising in multi-scale modeling of materials. To couple a standard finite ... Keywords: Atomistic---continuum coupling, Bridging domain method, Domain decomposition, Lagrange multipliers, Multiscale modeling

S. Pfaller; G. Possart; P. Steinmann; M. Rahimi; F. Müller-Plathe; M. C. Böhm

2012-05-01T23:59:59.000Z

29

On the ability of Order Statistics to distinguish different models for continuum gamma decay  

SciTech Connect

A simulation procedure to calculate some important parameters to the application of Order Statistics in the analysis of continuum gamma decay is presented.

Sandoval, J. J.; Cristancho, F. [Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia); Centro Internacional de Fisica, Bogota (Colombia)

2007-10-26T23:59:59.000Z

30

Geometrical Field Representation of Solid, Fluid, and Gas as Continuum in Rational Mechanics  

E-Print Network (OSTI)

Based on the points-set transformation concept about the motion transformation in continuum, the macro classical strain is expressed by the additive addition of the intrinsic stretching of material element and its intrinsic local rotation. For zero classical strain (no macro deformation observed on its configuration surface, suitable container is required for liquid and gas to make up macro invariant configuration), the results show that: (1) For solid, the local rotation angular is zero. The material element has no intrinsic stretching. (2) For liquid, the local rotation will not change the basic gauge tensor. The material element has intrinsic plane stretching on the rotation plane. (3) For gas state, the intrinsic local rotation will amplify the basic gauge tensor. The material element has intrinsic stretching along the rotation direction. Hence, under the condition of no macro classical strain be observed, the material element has three different physical states: solid (no intrinsic stretching), fluid (plane intrinsic stretching), and gas (directional intrinsic stretching). Furthermore, for the three states, the free conditions are defined by zero intrinsic stretching. Referring to this free condition, the constitutive equations for the materials at multiple states are established.

Jianhua Xiao

2009-11-07T23:59:59.000Z

31

Discontinuous Modelling of Crack Propagation in a Gradient-Enhanced Continuum  

E-Print Network (OSTI)

. Baz?ant, Nonlocal damage theory, ASCE Journal of Engi- neering Mechanics, 113, (1987), 1512–1533. [2] M. G. D. Geers, R. de Borst, W. A. M. Brekelmans, R. H. J. Peerlings, Strain- based transient-gradient damage model for failure analyses, Computer Methods...

Simone, A; Wells, G N; Sluys, L J

32

Defining and testing a granular continuum element  

Science Conference Proceedings (OSTI)

Continuum mechanics relies on the fundamental notion of amesoscopic volume "element" in which properties averaged over discreteparticles obey deterministic relationships. Recent work on granularmaterials suggests a continuum law may be inapplicable, revealinginhomogeneities at the particle level, such as force chains and slow cagebreaking. Here, we analyze large-scale Discrete-Element Method (DEM)simulations of different granular flows and show that a "granularelement" can indeed be defined at the scale of dynamical correlations,roughly three to five particle diameters. Its rheology is rather subtle,combining liquid-like dependence on deformation rate and solid-likedependence on strain. Our results confirm some aspects of classicalplasticity theory (e.g., coaxiality of stress and deformation rate),while contradicting others (i.e., incipient yield), and can guide thedevelopment of more realistic continuum models.

Rycroft, Chris H.; Kamrin, Ken; Bazant, Martin Z.

2007-12-03T23:59:59.000Z

33

DCPT v1.0 - New particle tracker for modeling transport in dual-continuum - User's Manual  

E-Print Network (OSTI)

Dual-Continuum Media User's Manual Lehua Pan, Hui Hai Liu,report serves as a user's manual of DCPT V1.0. It includes

Pan, Lehua; Liu, Hui Hai; Cushey, Mark; Bodvarsson, Gudmundur

2001-01-01T23:59:59.000Z

34

Coupling pore-scale networks to continuum-scale models of porous media  

Science Conference Proceedings (OSTI)

Network modeling is a useful tool for investigating pore-scale behavior and in some cases for determining macroscopic information such as permeability, relative permeability, and capillary pressure. Physically representative network models are particularly ... Keywords: Coupling, Fractured porous media, Multiscale modeling, Network modeling, Pore-scale modeling

Matthew T. Balhoff; Karsten E. Thompson; Martin Hjortsø

2007-03-01T23:59:59.000Z

35

Equilibrium Conformations of Concentric-tube Continuum Robots  

Science Conference Proceedings (OSTI)

Robots consisting of several concentric, preshaped, elastic tubes can work dexterously in narrow, constrained, and/or winding spaces, as are commonly found in minimally invasive surgery. Previous models of these â??active cannulasâ? assume ... Keywords: active cannula, concentric tube robot, continuum robot, elastica, flexible arms, kinematics, mechanics, medical robots, snake-like robot, variational calculus

D. Caleb Rucker; Robert J. Webster, III; Gregory S. Chirikjian; Noah J. Cowan

2010-09-01T23:59:59.000Z

36

NREL: Continuum Magazine - View: Continuum  

NLE Websites -- All DOE Office Websites (Extended Search)

plan to roll out more models in the coming year. NREL research and development helps manufacturers optimize vehicle efficiency and performance, as well as the interface with...

37

Mechanical model for ductility loss  

Science Conference Proceedings (OSTI)

A mechanical model was constructed to probe into the mechanism of ductility loss. Fracture criterion based on critical localized deformation was undertaken. Two microstructure variables were considered in the model. Namely, the strength ratio of grain boundary affected area to the matrix, ..cap omega.., and the linear fraction, x, of grain boundary affected area. A parametrical study was carried out. The study shows that the ductility is very sensitive to those microstructure parameters. The functional dependence of ductility to temperature as well as strain-rate, suggested by the model, is demonstrated to be consistent with the observation.

Hu, W.L.

1980-02-11T23:59:59.000Z

38

The circular continuum of agencies, libraries, and users: a model of e-government in practice  

Science Conference Proceedings (OSTI)

When e-government first became a viable solution to the dissemination of government information, experts believed that the rise of direct government-to-citizen (G2C) services would improve government transparency and foster civic engagement. It soon ... Keywords: digital government, electronic government, models

Natalie Greene Taylor; Paul T. Jaeger; Ursula Gorham; John Carlo Bertot; Ruth Lincoln; Elizabeth Larson

2012-10-01T23:59:59.000Z

39

Calculation of the Gibbs Free Energy of Solvation and Dissociation of HCl in Water via Monte Carlo Simulations and Continuum Solvation Models  

Science Conference Proceedings (OSTI)

The free energy of solvation and dissociation of hydrogen chloride in water is calculated through a combined molecular simulation quantum chemical approach at four temperatures between T = 300 and 450 K. The free energy is first decomposed into the sum of two components: the Gibbs free energy of transfer of molecular HCl from the vapor to the aqueous liquid phase and the standard-state free energy of acid dissociation of HCl in aqueous solution. The former quantity is calculated using Gibbs ensemble Monte Carlo simulations using either Kohn-Sham density functional theory or a molecular mechanics force field to determine the system’s potential energy. The latter free energy contribution is computed using a continuum solvation model utilizing either experimental reference data or micro-solvated clusters. The predicted combined solvation and dissociation free energies agree very well with available experimental data. CJM was supported by the US Department of Energy,Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

McGrath, Matthew; Kuo, I-F W.; Ngouana, Brice F.; Ghogomu, Julius N.; Mundy, Christopher J.; Marenich, Aleksandr; Cramer, Christopher J.; Truhlar, Donald G.; Siepmann, Joern I.

2013-08-28T23:59:59.000Z

40

DENSE MULTIPHASE FLOW SIMULATION: CONTINUUM MODEL FOR POLY-DISPERSED SYSTEMS USING KINETIC THEORY  

SciTech Connect

The overall objective of the project was to verify the applicability of the FCMOM approach to the kinetic equations describing the particle flow dynamics. For monodispersed systems the fundamental equation governing the particle flow dynamics is the Boltzmann equation. During the project, the FCMOM was successfully applied to several homogeneous and in-homogeneous problems in different flow regimes, demonstrating that the FCMOM has the potential to be used to solve efficiently the Boltzmann equation. However, some relevant issues still need to be resolved, i.e. the homogeneous cooling problem (inelastic particles cases) and the transition between different regimes. In this report, the results obtained in homogeneous conditions are discussed first. Then a discussion of the validation results for in-homogeneous conditions is provided. And finally, a discussion will be provided about the transition between different regimes. Alongside the work on development of FCMOM approach studies were undertaken in order to provide insights into anisotropy or particles kinetics in riser hydrodynamics. This report includes results of studies of multiphase flow with unequal granular temperatures and analysis of momentum re-distribution in risers due to particle-particle and fluid-particle interactions. The study of multiphase flow with unequal granular temperatures entailed both simulation and experimental studies of two particles sizes in a riser and, a brief discussion of what was accomplished will be provided. And finally, a discussion of the analysis done on momentum re-distribution of gas-particles flow in risers will be provided. In particular a discussion of the remaining work needed in order to improve accuracy and predictability of riser hydrodynamics based on two-fluid models and how they can be used to model segregation in risers.

Moses Bogere

2011-08-31T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Modeling the Mechanics of the Cytoskeleton  

E-Print Network (OSTI)

Mechanics . . . . . . . . . . . . . . . . . . . . . . .t contribute to the network’s mechanics have been removed.R.D. Kamm, Cytoskeletal Mechanics, models and measurements,

Bai, Mo

2012-01-01T23:59:59.000Z

42

STATISTICAL MECHANICS MODELING OF MESOSCALE DEFORMATION IN METALS  

SciTech Connect

The research under this project focused on a theoretical and computational modeling of dislocation dynamics of mesoscale deformation of metal single crystals. Specifically, the work aimed to implement a continuum statistical theory of dislocations to understand strain hardening and cell structure formation under monotonic loading. These aspects of crystal deformation are manifestations of the evolution of the underlying dislocation system under mechanical loading. The project had three research tasks: 1) Investigating the statistical characteristics of dislocation systems in deformed crystals. 2) Formulating kinetic equations of dislocations and coupling these kinetics equations and crystal mechanics. 3) Computational solution of coupled crystal mechanics and dislocation kinetics. Comparison of dislocation dynamics predictions with experimental results in the area of statistical properties of dislocations and their field was also a part of the proposed effort. In the first research task, the dislocation dynamics simulation method was used to investigate the spatial, orientation, velocity, and temporal statistics of dynamical dislocation systems, and on the use of the results from this investigation to complete the kinetic description of dislocations. The second task focused on completing the formulation of a kinetic theory of dislocations that respects the discrete nature of crystallographic slip and the physics of dislocation motion and dislocation interaction in the crystal. Part of this effort also targeted the theoretical basis for establishing the connection between discrete and continuum representation of dislocations and the analysis of discrete dislocation simulation results within the continuum framework. This part of the research enables the enrichment of the kinetic description with information representing the discrete dislocation systems behavior. The third task focused on the development of physics-inspired numerical methods of solution of the coupled dislocation kinetics and crystal mechanics framework. To a large extent, this task has also been successfully started. We have developed a custom finite-element approach with mesh points being a subset of the underlying crystal structure. When used to predict the evolution of the dislocation system, the planar motion of dislocations is naturally captured for all slip systems, thus minimizing numerical errors and providing simple ways to investigate cross slip and dislocation reactions. Preliminary results in this direction show that we are closer than ever in building a predictive framework for dislocation dynamics and mesoscale plasticity based on the first principles of dislocation dynamics. The rest of the report gives and overview of the research performed under this project and highlights the key results and open questions left for future investigations.

Anter El-Azab

2013-04-08T23:59:59.000Z

43

On the Mechanical Response of Chopped Glass/Urethane Resin Composite: Data and Model  

SciTech Connect

This report presents data on the creep response of a polymeric composite that is a candidate material for automotive applications. The above data were used to establish the basis for the mechanical characterization of the material's response over a wide range of stresses and temperatures, as well as under cyclic loading and due to exposure to distilled water. A constitutive model based upon fundamental principles of irreversible thermodynamics and continuum mechanics was employed to encompass the above mentioned database and to predict the response under more complex inputs. These latter tests verified the validity of the model.

Elahi, M.; Weitsman, Y.J.

1999-11-01T23:59:59.000Z

44

The H2O2+OH ? HO2+H2O reaction in aqueous solution from a charge-dependent continuum model of solvation  

Science Conference Proceedings (OSTI)

We applied our recently developed protocol of the conductor-like continuum model of solvation to describe the title reaction in aqueous solution. The model has the unique feature of the molecular cavity being dependent on the atomic charges in the solute, and can be extended naturally to transition states and reaction pathways. It was used to calculate the reaction energetics and reaction rate in solution for the title reaction. The rate of reaction calculated using canonical variational transition state theory CVT in the context of the equilibrium solvation path (ESP) approximation, and including correction for tunneling through the small curvature approximation (SCT) was found to be 3.6 106 M-1 s-1, in very good agreement with experiment, These results suggest that the present protocol of the conductor-like continuum model of solvation with the charge-dependent cavity definition captures accurately the solvation effects at transition states and allows for quantitative estimates of reaction rates in solutions. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

Ginovska, Bojana; Camaioni, Donald M.; Dupuis, Michel

2008-07-07T23:59:59.000Z

45

Assessing continuum postulates in simulations of granular flow  

Science Conference Proceedings (OSTI)

Continuum mechanics relies on the fundamental notion of a mesoscopic volume"element" in which properties averaged over discrete particles obey deterministic relationships. Recent work on granular materials suggests a continuum law may be inapplicable, revealing inhomogeneities at the particle level, such as force chains and slow cage breaking. Here, we analyze large-scale three-dimensional Discrete-Element Method (DEM) simulations of different granular flows and show that an approximate"granular element" defined at the scale of observed dynamical correlations (roughly three to five particle diameters) has a reasonable continuum interpretation. By viewing all the simulations as an ensemble of granular elements which deform and move with the flow, we can track material evolution at a local level. Our results confirm some of the hypotheses of classical plasticity theory while contradicting others and suggest a subtle physical picture of granular failure, combining liquid-like dependence on deformation rate and solid-like dependence on strain. Our computational methods and results can be used to guide the development of more realistic continuum models, based on observed local relationships betweenaverage variables.

Rycroft, Chris; Kamrin, Ken; Bazant, Martin

2008-08-26T23:59:59.000Z

46

Floquet bound states in the continuum  

E-Print Network (OSTI)

Quantum mechanics predicts that certain stationary potentials can sustain bound states with an energy buried in the continuous spectrum of scattered states, the so-called bound states in the continuum (BIC). Originally regarded as mathematical curiosities, BIC have found an increasing interest in recent years, particularly in quantum and classical transport of matter and optical waves in mesoscopic and photonic systems where the underlying potential can be judiciously tailored. Most of our knowledge of BIC is so far restricted to static potentials. Here we introduce a new kind of BIC, referred to as Floquet BIC, which corresponds to a normalizable Floquet state of a time-periodic Hamiltonian with a quasienergy embedded into the spectrum of Floquet scattered states. We discuss the appearance of Floquet BIC states in a tight-binding lattice model driven by an ac field in the proximity of the dynamic localization regime

Stefano Longhi; Giuseppe Della Valle

2013-10-18T23:59:59.000Z

47

Continuum computational methods to study chemical problems in solution  

Science Conference Proceedings (OSTI)

Computational methods using the continuum approximation to describe chemical problems in solution are reviewed. The various computational strategies thus far proposed for the basic model

J. Tomasi

1995-01-01T23:59:59.000Z

48

Modeling of multiple three phase contact lines of liquid droplets on geometrically patterned surfaces: continuum and mesoscopic analysis  

E-Print Network (OSTI)

By solving the Young Laplace equation of capillary hydrostatics one can accurately determine equilibrium shapes of droplets on relatively smooth solid surfaces. The solution, however of the Young Laplace equation becomes tricky when a droplet is sitting on a geometrically patterned surface and multiple, and unknown a priori, three phase contact lines have not been accounted for, since air pockets are trapped beneath the liquid droplet. In this work, we propose an augmented Young-Laplace equation, in which a unified formulation for the liquid/vapor and liquid/solid interfaces is adopted, incorporating microscale interactions. This way, we bypass the implementation of the Young's contact angle boundary condition at each three phase contact line. We demonstrate the method's efficiency by computing equilibrium wetting states of entire droplets sitting on geometrically structured surfaces, and compare the results with those of the mesoscopic Lattice Boltzmann simulations. The application of well-established parameter continuation techniques enables the tracing of stable and unstable equilibrium solutions if necessary for the determination of energy barriers separating co-existing stable wettign states. Since energy barriers determine whether a surface facilitates or inhibits certain wetting transitions, their computation is important for many technical applications. Our continuum-level analysis can readily be applied to patterned surfaces with increased and unstructured geometric complexity, having a significant computational advantage, as compared to the computationally demanding mesoscopic simulations that are usually employed for the same task.

Nikolaos T. Chamakos; Michail E. Kavousanakis; Athanasios G. Papathanasiou

2013-06-04T23:59:59.000Z

49

Modelling transient heat conduction in solids at multiple length and time scales: A coupled non-equilibrium molecular dynamics/continuum approach  

SciTech Connect

A method for controlling the thermal boundary conditions of non-equilibrium molecular dynamics simulations is presented. The method is simple to implement into a conventional molecular dynamics code and independent of the atomistic model employed. It works by regulating the temperature in a thermostatted boundary region by feedback control to achieve the desired temperature at the edge of an inner region where the true atomistic dynamics are retained. This is necessary to avoid intrinsic boundary effects in non-equilibrium molecular dynamics simulations. Three thermostats are investigated: the global deterministic Nose-Hoover thermostat and two local stochastic thermostats, Langevin and stadium damping. The latter thermostat is introduced to avoid the adverse reflection of phonons that occurs at an abrupt interface. The method is then extended to allow atomistic/continuum models to be thermally coupled concurrently for the analysis of large steady state and transient heat conduction problems. The effectiveness of the algorithm is demonstrated for the example of heat flow down a three-dimensional atomistic rod of uniform cross-section subjected to a variety of boundary conditions.

Jolley, Kenny [Department of Engineering, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Gill, Simon P.A. [Department of Engineering, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)], E-mail: spg3@le.ac.uk

2009-10-20T23:59:59.000Z

50

NREL: Continuum Magazine Home Page  

NLE Websites -- All DOE Office Websites (Extended Search)

NREL Spectrum of Clean Energy Innovation NREL Spectrum of Clean Energy Innovation Issue 3 Print Version Share this resource Continuum Magazine Dan Says NREL Leads Wind Farm Modeling Research NREL Leads Wind Farm Modeling Research Researchers study the atmosphere surrounding large turbines to optimize performance. Driving Solar Innovations from Laboratory to Marketplace Driving Solar Innovations from Laboratory to Marketplace Disruptive innovation is making solar cost competitive with non-renewable energy. Reaping a Harvest of Hope Reaping a Harvest of Hope Five years after a devastating tornado, Greensburg, Kansas has new energy and a new outlook. Energy Innovation Portal Bridging Information Gap Energy Innovation Portal Bridging Information Gap Database revolutionizes intellectual property transfer from DOE's national

51

Continuum Electrostatics in Cell Biology  

E-Print Network (OSTI)

Recent experiments revealing possible nanoscale electrostatic interactions in force generation at kinetochores for chromosome motions have prompted speculation regarding possible models for interactions between positively charged molecules in kinetochores and negative charge on C-termini near the plus ends of microtubules. A clear picture of how kinetochores establish and maintain a dynamic coupling to microtubules for force generation during the complex motions of mitosis remains elusive. The current paradigm of molecular cell biology requires that specific molecules, or molecular geometries, for force generation be identified. However, it is possible to account for mitotic motions within a classical electrostatics approach in terms of experimentally known cellular electric charge interacting over nanometer distances. These charges are modeled as bound surface and volume continuum charge distributions. Electrostatic consequences of intracellular pH changes during mitosis may provide a master clock for the events of mitosis.

L. John Gagliardi

2010-02-06T23:59:59.000Z

52

Continuum Partners | Open Energy Information  

Open Energy Info (EERE)

Sector Solar Product A Denver based real estate development company, also involved in Solar PV projects. References Continuum Partners1 LinkedIn Connections CrunchBase...

53

Fifth World Congress on Computational Mechanics  

E-Print Network (OSTI)

WCCM V Fifth World Congress on Computational Mechanics July 7-12, 2002, Vienna, Austria Eds.: H Material in a Computational Fluid Dynamics Framework using Micro- Mechanical Models Nicholas Christakis London, UK e-mail: I.Bridle@gre.ac.uk Key words: granular material, continuum mechanics, micro-mechanical

Christakis, Nikolaos

54

Statistical Mechanics Model for Protein Folding  

E-Print Network (OSTI)

We present a novel statistical mechanics formalism for the theoretical description of the process of protein folding$\\leftrightarrow$unfolding transition in water environment. The formalism is based on the construction of the partition function of a protein obeying two-stage-like folding kinetics. Using the statistical mechanics model of solvation of hydrophobic hydrocarbons we obtain the partition function of infinitely diluted solution of proteins in water environment. The calculated dependencies of the protein heat capacities upon temperature are compared with the corresponding results of experimental measurements for staphylococcal nuclease and metmyoglobin.

Yakubovich, A V; Greiner, W

2010-01-01T23:59:59.000Z

55

Internet Resource Pricing Models, Mechanisms, and Methods  

E-Print Network (OSTI)

With the fast development of video and voice network applications, CDN (Content Distribution Networks) and P2P (Peer-to-Peer) content distribution technologies have gradually matured. How to effectively use Internet resources thus has attracted more and more attentions. For the study of resource pricing, a whole pricing strategy containing pricing models, mechanisms and methods covers all the related topics. We first introduce three basic Internet resource pricing models through an Internet cost analysis. Then, with the evolution of service types, we introduce several corresponding mechanisms which can ensure pricing implementation and resource allocation. On network resource pricing methods, we discuss the utility optimization in economics, and emphasize two classes of pricing methods (including system optimization and entities' strategic optimizations). Finally, we conclude the paper and forecast the research direction on pricing strategy which is applicable to novel service situation in the near future.

He, Huan; Liu, Ying

2011-01-01T23:59:59.000Z

56

Quantum-Mechanical Model of Spacetime  

E-Print Network (OSTI)

We consider a possibility to construct a quantum-mechanical model of spacetime, where Planck size quantum black holes act as the fundamental constituents of space and time. Spacetime is assumed to be a graph, where black holes lie on the vertices. Our model implies that area has a discrete spectrum with equal spacing. At macroscopic length scales our model reproduces Einstein's field equation with a vanishing cosmological constant as a sort of thermodynamical equation of state of spacetime and matter fields. In the low temperature limit, where most black holes are assumed to be in the ground state, our model implies the Unruh and the Hawking effects, whereas in the high temperature limit we find, among other things, that black hole entropy depends logarithmically on the event horizon area, instead of being proportional to the area.

Makela, J

2007-01-01T23:59:59.000Z

57

Quantum-Mechanical Model of Spacetime  

E-Print Network (OSTI)

We consider a possibility to construct a quantum-mechanical model of spacetime, where Planck size quantum black holes act as the fundamental constituents of space and time. Spacetime is assumed to be a graph, where black holes lie on the vertices. Our model implies that area has a discrete spectrum with equal spacing. At macroscopic length scales our model reproduces Einstein's field equation with a vanishing cosmological constant as a sort of thermodynamical equation of state of spacetime and matter fields. In the low temperature limit, where most black holes are assumed to be in the ground state, our model implies the Unruh and the Hawking effects, whereas in the high temperature limit we find, among other things, that black hole entropy depends logarithmically on the event horizon area, instead of being proportional to the area.

Jarmo Makela

2007-01-24T23:59:59.000Z

58

Connecting the Molecular and the Continuum Scales  

NLE Websites -- All DOE Office Websites (Extended Search)

Connecting the Molecular and the Continuum Scales Connecting the Molecular and the Continuum Scales Key Challenges: A molecular-scale understanding of structure and surface...

59

NREL: Continuum Magazine Home Page  

NLE Websites -- All DOE Office Websites (Extended Search)

NREL Leads Energy Systems Integration Issue 4 Print Version Share this resource Continuum Magazine Dan Says More than a Dream-a Renewable Electricity Future More than a Dream-a...

60

NREL: Continuum Magazine - Dan Says  

NLE Websites -- All DOE Office Websites (Extended Search)

this resource Dan Says A photo of a man standing in front of a plug-in hybrid electric vehicle and a solar charging canopy Transforming Transportation This issue of Continuum...

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

A discrete model of thin shells  

Science Conference Proceedings (OSTI)

We present a discrete model for the behavior of thin flexible structures, such as hats, leaves, and aluminum cans, which are characterized by a curved undeformed configuration. Previously such models required complex continuum mechanics formulations ...

Eitan Grinspun

2005-07-01T23:59:59.000Z

62

Mechanical Models of Fault-Related Folding  

SciTech Connect

The subject of the proposed research is fault-related folding and ground deformation. The results are relevant to oil-producing structures throughout the world, to understanding of damage that has been observed along and near earthquake ruptures, and to earthquake-producing structures in California and other tectonically-active areas. The objectives of the proposed research were to provide both a unified, mechanical infrastructure for studies of fault-related foldings and to present the results in computer programs that have graphical users interfaces (GUIs) so that structural geologists and geophysicists can model a wide variety of fault-related folds (FaRFs).

Johnson, A. M.

2003-01-09T23:59:59.000Z

63

Multiscale Modeling of Defect Mechanics in Nuclear Materials  

Science Conference Proceedings (OSTI)

Abstract Scope, The key to developing advanced materials for nuclear applications is ... Physics-Based Homogenization of Random Continuum Microstructures.

64

Atom-to-continuum methods for gaining a fundamental understanding of fracture.  

SciTech Connect

This report describes an Engineering Sciences Research Foundation (ESRF) project to characterize and understand fracture processes via molecular dynamics modeling and atom-to-continuum methods. Under this aegis we developed new theory and a number of novel techniques to describe the fracture process at the atomic scale. These developments ranged from a material-frame connection between molecular dynamics and continuum mechanics to an atomic level J integral. Each of the developments build upon each other and culminated in a cohesive zone model derived from atomic information and verified at the continuum scale. This report describes an Engineering Sciences Research Foundation (ESRF) project to characterize and understand fracture processes via molecular dynamics modeling and atom-to-continuum methods. The effort is predicated on the idea that processes and information at the atomic level are missing in engineering scale simulations of fracture, and, moreover, are necessary for these simulations to be predictive. In this project we developed considerable new theory and a number of novel techniques in order to describe the fracture process at the atomic scale. Chapter 2 gives a detailed account of the material-frame connection between molecular dynamics and continuum mechanics we constructed in order to best use atomic information from solid systems. With this framework, in Chapter 3, we were able to make a direct and elegant extension of the classical J down to simulations on the scale of nanometers with a discrete atomic lattice. The technique was applied to cracks and dislocations with equal success and displayed high fidelity with expectations from continuum theory. Then, as a prelude to extension of the atomic J to finite temperatures, we explored the quasi-harmonic models as efficient and accurate surrogates of atomic lattices undergoing thermo-elastic processes (Chapter 4). With this in hand, in Chapter 5 we provide evidence that, by using the appropriate energy potential, the atomic J integral we developed is calculable and accurate at finite/room temperatures. In Chapter 6, we return in part to the fundamental efforts to connect material behavior at the atomic scale to that of the continuum. In this chapter, we devise theory that predicts the onset of instability characteristic of fracture/failure via atomic simulation. In Chapters 7 and 8, we describe the culmination of the project in connecting atomic information to continuum modeling. In these chapters we show that cohesive zone models are: (a) derivable from molecular dynamics in a robust and systematic way, and (b) when used in the more efficient continuum-level finite element technique provide results that are comparable and well-correlated with the behavior at the atomic-scale. Moreover, we show that use of these same cohesive zone elements is feasible at scales very much larger than that of the lattice. Finally, in Chapter 9 we describe our work in developing the efficient non-reflecting boundary conditions necessary to perform transient fracture and shock simulation with molecular dynamics.

McDowell, David Lynn (Georgia Institute of Technology, Atlanta, GA); Reedy, Earl David, Jr.; Templeton, Jeremy Alan; Jones, Reese E.; Moody, Neville Reid; Zimmerman, Jonathan A.; Belytschko, Ted. (Northwestern University, Evanston, IL); Zhou, Xiao Wang; Lloyd, Jeffrey T. (Georgia Institute of Technology, Atlanta, GA); Oswald, Jay (Northwestern University, Evanston, IL); Delph, Terry J. (Lehigh University, Bethlehem, PA); Kimmer, Christopher J. (Indiana University Southeast, New Albany, IN)

2011-08-01T23:59:59.000Z

65

Human walking model predicts joint mechanics, electromyography and mechanical economy  

E-Print Network (OSTI)

In this paper, we present an under-actuated model of human walking, comprising only a soleus muscle and flexion/extension monoarticular hip muscles. The remaining muscle groups of the human leg are modeled using quasi-passive, ...

Endo, Ken

66

Solving Multidimensional Continuum Mechanics Solving Multidimensional...  

National Nuclear Security Administration (NNSA)

June 2005, Crowne Crowne Plaza, Vienna Austria Plaza, Vienna Austria Russian Federal Nuclear Center - VNIIEF Institute of Theoretical Institute of Theoretical and Mathematical...

67

Sensitivity filtering from a continuum mechanics perspective  

Science Conference Proceedings (OSTI)

In topology optimization filtering is a popular approach for preventing numerical instabilities. This short note shows that the well-known sensitivity filtering technique, that prevents checkerboards and ensures mesh-independent designs in density-based ... Keywords: Filtering, Regularization, Topology optimization

Ole Sigmund; Kurt Maute

2012-10-01T23:59:59.000Z

68

Assessment of reduced mechanisms using One Dimensional Stochastic Turbulence model  

E-Print Network (OSTI)

Thermochemical information Semi-empirical methods Chemical kinetics information Detail chemical kinetics mechanism Transport model Transport parameters Computational simulation

Chien, Li-Chun

2010-01-01T23:59:59.000Z

69

Random matrix theory for modeling uncertainties in computational mechanics  

E-Print Network (OSTI)

Random matrix theory for modeling uncertainties in computational mechanics C. Soize Laboratory of Engineering Mechanics, University of Marne-la-Vall´ee, 5 boulevard Descartes, 77454 Marne-la-Vallée, France, e in computational mechanics. If data uncertainties can be modeled by parametric probabilistic methods, for a given

Paris-Sud XI, Université de

70

Modeling and Experimental Validation of Multiscale Mechanical ...  

Science Conference Proceedings (OSTI)

Jul 31, 2012 ... Jonathan Zimmerman, Sandia National Laboratories. Scope, The mechanical behavior of a material has a strong and complex connection to its ...

71

LANL: Mechanical testing and modeling in MST  

NLE Websites -- All DOE Office Websites (Extended Search)

MST For information on mechanical testing in MST Division contact: Mark Bourke, bourke@lanl.gov Materials Science and Technology Division Facility Focus Materials Science and...

72

Coupled Thermal-Hydrological-Mechanical-Chemical Model and Experiments...  

Open Energy Info (EERE)

of Applications for Research, Development and Analysis of Geothermal Technologies Project Type Topic 2 Integrated Chemical, Thermal, Mechanical and Hydrological Modeling...

73

Mechanical Characterization and Modeling of Next-Generation Solid ...  

Science Conference Proceedings (OSTI)

Symposium, Energy Conversion/Fuel Cells. Presentation Title, Mechanical Characterization and Modeling of Next-Generation Solid Oxide Fuel Cells and Stacks.

74

A Hydro-Thermo-Mechanical Numerical Model For Hdr Geothermal...  

Open Energy Info (EERE)

Hydro-Thermo-Mechanical Numerical Model For Hdr Geothermal Reservoir Evaluation Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: A...

75

Access Control: Policies, Models, and Mechanisms  

Science Conference Proceedings (OSTI)

Access control is the process of mediating every request to resources and data maintained by a system and determining whether the request should be granted or denied. The access control decision is enforced by a mechanism implementing regulations established ...

Pierangela Samarati; Sabrina De Capitani di Vimercati

2000-09-01T23:59:59.000Z

76

Continuum-based sensitivity analysis for coupled atomistic and continuum simulations for 2-D applications using bridging scale decomposition  

Science Conference Proceedings (OSTI)

The concept of linking simulations at multiple length and time scales is found useful for studying local physical phenomena such as crack propagation. Many multi-scale methods, which couple molecular dynamics models with continuum models, have been proposed ... Keywords: Bridging scale method, Design sensitivity analysis, Multi-scale simulation

Yunxiang Wang, Kuang-Hua Chang

2013-06-01T23:59:59.000Z

77

Integrated Chemical, Thermal, Mechanical and Hydrological Modeling...  

Open Energy Info (EERE)

489,476 1,602,500 Retrieved from "http:en.openei.orgwindex.php?titleIntegratedChemical,Thermal,MechanicalandHydrologicalModeling&oldid313283" Category:...

78

Non-Thermal Continuum toward SGRB2(N-LMH)  

E-Print Network (OSTI)

An analysis of continuum antenna temperatures observed in the Green Bank Telescope (GBT) spectrometer bandpasses is presented for observations toward SgrB2(N-LMH). Since 2004, we have identified four new prebiotic molecules toward this source by means of rotational transitions between low energy levels; concurrently, we have observed significant continuum in the GBT spectrometer bandpasses centered at 85 different frequencies in the range of 1 to 48 GHz. The continuum heavily influences the molecular spectral features since we have observed far more absorption lines than emission lines for each of these new molecular species. Hence, it is important to understand the nature, distribution, and intensity of the underlying continuum in the GBT bandpasses for the purposes of radiative transfer, i.e. the means by which reliable molecular abundances are estimated. We find that the GBT spectrometer bandpass continuum is consistent with optically-thin, non thermal (synchrotron) emission with a flux density spectral index of -0.7 and a Gaussian source size of ~143" at 1 GHz that decreases with increasing frequency as nu^(-0.52). Some support for this model is provided by high frequency Very Large Array (VLA) observations of SgrB2.

J. M. Hollis; P. R. Jewell; Anthony J. Remijan; F. J. Lovas

2007-03-15T23:59:59.000Z

79

NREL: Continuum Magazine Home Page  

NLE Websites -- All DOE Office Websites (Extended Search)

Deliberate Science Deliberate Science Issue 2 Print Version Share this resource Continuum Magazine Dan Says Reinventing Material Science Reinventing Material Science It's not often that scientists set out to reinvent an entire field of study, but it's happening now. Better Biofuels through Computational Analysis Better Biofuels through Computational Analysis Developing and applying a powerful arsenal of computational tools for producing biofuels. Supercomputing Drives Innovation Supercomputing Drives Innovation Researchers are finding new ways of tackling our nation's energy challenges. Carbon Nanotubes for Batteries Carbon Nanotubes for Batteries Groundbreaking battery technology holds potential to revolutionize powering vehicles. Rewiring Algae's Catalytic Circuits Rewiring Algae's Catalytic Circuits

80

MASSIVELY PARALLEL FULLY COUPLED IMPLICIT MODELING OF COUPLED THERMAL-HYDROLOGICAL-MECHANICAL PROCESSES FOR ENHANCED GEOTHERMAL SYSTEM RESERVOIRS  

SciTech Connect

Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing) to create the reservoir. The advancement of EGS greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid system and our ability to reliably predict how reservoirs behave under stimulation and production. In order to increase our understanding of how reservoirs behave under these conditions, we have developed a physics-based rock deformation and fracture propagation simulator by coupling a discrete element model (DEM) for fracturing with a continuum multiphase flow and heat transport model. In DEM simulations, solid rock is represented by a network of discrete elements (often referred as particles) connected by various types of mechanical bonds such as springs, elastic beams or bonds that have more complex properties (such as stress-dependent elastic constants). Fracturing is represented explicitly as broken bonds (microcracks), which form and coalesce into macroscopic fractures when external load is applied. DEM models have been applied to a very wide range of fracturing processes from the molecular scale (where thermal fluctuations play an important role) to scales on the order of 1 km or greater. In this approach, the continuum flow and heat transport equations are solved on an underlying fixed finite element grid with evolving porosity and permeability for each grid cell that depends on the local structure of the discrete element network (such as DEM particle density). The fluid pressure gradient exerts forces on individual elements of the DEM network, which therefore deforms and fractures. Such deformation/fracturing in turn changes the permeability, which again changes the evolution of fluid pressure, coupling the two phenomena. The intimate coupling between fracturing and fluid flow makes the meso-scale DEM simulations necessary, as these methods have substantial advantages over conventional continuum mechanical models of elastic rock deformation. The challenges that must be overcome to simulate EGS reservoir stimulation, preliminary results, progress to date and near future research directions and opportunities will be discussed.

Robert Podgorney; Hai Huang; Derek Gaston

2010-02-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Pyrolysis mechanisms of lignin model compounds  

DOE Green Energy (OSTI)

The flash vacuum pyrolysis of lignin model compounds was studied under conditions optimized for the production of liquid products to provide mechanistic insight into the reaction pathways that lead to product formation. The major reaction products can be explained by cleavage of the C-O either linkage by a free radial or concerted 1,2-elimination.

Britt, P.F.; Buchanan, A.C. III; Cooney, M.J.

1997-06-01T23:59:59.000Z

82

Thermo-Poroelastic Modeling of Reservoir Stimulation and Microseismicity Using Finite Element Method with Damage Mechanics  

E-Print Network (OSTI)

Stress and permeability variations around a wellbore and in the reservoir are of much interest in petroleum and geothermal reservoir development. Water injection causes significant changes in pore pressure, temperature, and stress in hot reservoirs, changing rock permeability. In this work, two- and three-dimensional finite element methods were developed to simulate coupled reservoirs with damage mechanics and stress-dependent permeability. The model considers the influence of fluid flow, temperature, and solute transport in rock deformation and models nonlinear behavior with continuum damage mechanics and stress-dependent permeability. Numerical modeling was applied to analyze wellbore stability in swelling shale with two- and three-dimensional damage/fracture propagation around a wellbore and injection-induced microseismic events. The finite element method (FEM) was used to solve the displacement, pore pressure, temperature, and solute concentration problems. Solute mass transport between drilling fluid and shale formation was considered to study salinity effects. Results show that shear and tensile failure can occur around a wellbore in certain drilling conditions where the mud pressure lies between the reservoir pore pressure and fracture gradient. The fully coupled thermo-poro-mechanical FEM simulation was used to model damage/fracture propagation and microseismic events caused by fluid injection. These studies considered wellbore geometry in small-scale modeling and point-source injection, assuming singularity fluid flux for large-scale simulation. Damage mechanics was applied to capture the effects of crack initiation, microvoid growth, and fracture propagation. The induced microseismic events were modeled in heterogeneous geological media, assuming the Weibull distribution functions for modulus and permeability. The results of this study indicate that fluid injection causes the effective stress to relax in the damage phase and to concentrate at the interface between the damage phase and the intact rock. Furthermore, induced-stress and far-field stress influence damage propagation. Cold water injection causes the tensile stress and affects the initial fracture and fracture propagation, but fracture initiation pressure and far-field stress are critical to create a damage/fracture plane, which is normal to the minimum far-field stress direction following well stimulation. Microseismic events propagate at both well scale and reservoir-scale simulation; the cloud shape of a microseismic event is affected by permeability anisotropy and far-field stress, and deviatoric horizontal far-field stress especially contributes to the localization of the microseismic cloud.

Lee, Sang Hoon

2011-12-01T23:59:59.000Z

83

Model Development for Atomic Force Microscope Stage Mechanisms  

E-Print Network (OSTI)

Model Development for Atomic Force Microscope Stage Mechanisms Ralph C. Smith and Andrew G. Hatch of the Philippines Virginia Commonwealth University Diliman, Quezon City 1101 Richmond VA 23284 rcdelros titanate (PZT) devices employed in atomic force microscope stage mechanisms. We focus specifically on PZT

84

A mechanical model for Fourier's law of heat conduction  

E-Print Network (OSTI)

Nonequilibrium statistical mechanics close to equilibrium is a physically satisfactory theory centered on the linear response formula of Green-Kubo. This formula results from a formal first order perturbation calculation without rigorous justification. A rigorous derivation of Fourier's law for heat conduction from the laws of mechanics remains thus a major unsolved problem. In this note we present a deterministic mechanical model of a heat-conducting chain with nontrivial interactions, where kinetic energy fluctuations at the nodes of the chain are removed. In this model the derivation of Fourier's law can proceed rigorously.

David Ruelle

2011-02-27T23:59:59.000Z

85

Microstructurally-based constitutive models of cytoskeletal networks for simulation of the biomechanical response of biological cells  

E-Print Network (OSTI)

The elastic and viscoelastic stress-strain behavior of cytoskeletal networks, important to many cellular functions, is modeled via a microstructurally-informed continuum mechanics approach. The force-extension behavior of ...

Palmer, Jeffrey Shane

2008-01-01T23:59:59.000Z

86

Effect of continuum couplings in fusion of halo $^{11}$Be on $^{208}$Pb around the Coulomb barrier  

E-Print Network (OSTI)

The effect of continuum couplings in the fusion of the halo nucleus $^{11}$Be on $^{208}$Pb around the Coulomb barrier is studied using a three-body model within a coupled discretised continuum channels (CDCC) formalism. We investigate in particular the role of continuum-continuum couplings. These are found to hinder total, complete and incomplete fusion processes. Couplings to the projectile $1p_{1/2}$ bound excited state redistribute the complete and incomplete fusion cross sections, but the total fusion cross section remains nearly constant. Results show that continuum-continuum couplings enhance the irreversibility of breakup and reduce the flux that penetrates the Coulomb barrier. Converged total fusion cross sections agree with the experimental ones for energies around the Coulomb barrier, but underestimate those for energies well above the Coulomb barrier.

A. Diaz-Torres; I. J. Thompson

2001-11-16T23:59:59.000Z

87

Coupled Thermal-Chemical-Mechanical Modeling of Validation Cookoff Experiments  

DOE Green Energy (OSTI)

The cookoff of energetic materials involves the combined effects of several physical and chemical processes. These processes include heat transfer, chemical decomposition, and mechanical response. The interaction and coupling between these processes influence both the time-to-event and the violence of reaction. The prediction of the behavior of explosives during cookoff, particularly with respect to reaction violence, is a challenging task. To this end, a joint DoD/DOE program has been initiated to develop models for cookoff, and to perform experiments to validate those models. In this paper, a series of cookoff analyses are presented and compared with data from a number of experiments for the aluminized, RDX-based, Navy explosive PBXN-109. The traditional thermal-chemical analysis is used to calculate time-to-event and characterize the heat transfer and boundary conditions. A reaction mechanism based on Tarver and McGuire's work on RDX{sup 2} was adjusted to match the spherical one-dimensional time-to-explosion data. The predicted time-to-event using this reaction mechanism compares favorably with the validation tests. Coupled thermal-chemical-mechanical analysis is used to calculate the mechanical response of the confinement and the energetic material state prior to ignition. The predicted state of the material includes the temperature, stress-field, porosity, and extent of reaction. There is little experimental data for comparison to these calculations. The hoop strain in the confining steel tube gives an estimation of the radial stress in the explosive. The inferred pressure from the measured hoop strain and calculated radial stress agree qualitatively. However, validation of the mechanical response model and the chemical reaction mechanism requires more data. A post-ignition burn dynamics model was applied to calculate the confinement dynamics. The burn dynamics calculations suffer from a lack of characterization of the confinement for the flaw-dominated failure mode experienced in the tests. High-pressure burning rates are needed for more detailed post-ignition studies. Sub-models for chemistry, mechanical response and burn dynamics need to be validated against data from less complex experiments. The sub-models can then be used in integrated analysis for comparison with experimental data taken during integrated tests.

ERIKSON,WILLIAM W.; SCHMITT,ROBERT G.; ATWOOD,A.I.; CURRAN,P.D.

2000-11-27T23:59:59.000Z

88

Notes 01. Modeling of mechanical (lumped parameter) elements  

E-Print Network (OSTI)

Fundamental elements in mechanical systems: inertias, stiffness and damping elements. Equivalent spring coefficients and associated potential energy. Equivalent mass or inertia coefficients and associated kinetic energy. Equations of motion of a rigid body in a plane. Equivalent damping coefficients and associated dissipation energy. Types of damping models (linear or viscous and nonlinear).

San Andres, Luis

2008-01-01T23:59:59.000Z

89

Performance modelling of the Orwell basic access mechanism  

Science Conference Proceedings (OSTI)

Orwell is a high speed slotted ring. Its protocol uses destination release of the slots. Because of this the carried load can be much larger than the transmission rate. A new analytical model of the Orwell basic access mechanism is presented in this ...

M. Zafirovic; I. G. Niemegeers

1987-08-01T23:59:59.000Z

90

Computational mechanical modeling of the behavior of carbon nanotubes  

Science Conference Proceedings (OSTI)

This paper presents a computational method for the mechanical simulation of carbon nanotubes, whose complexity is linear on the number of atoms. The regularity of a graphene lattice at its energy ground permits the definition of a tiling scheme that ... Keywords: carbon nanotubes, computational method, mathematical modeling, molecular dynamics, numerical simulation

Maria Morandi Cecchi; Alberto Giovanni Busetto

2007-08-01T23:59:59.000Z

91

Thesis A Numerical Model of Hydro-Thermo- Mechanical Coupling...  

NLE Websites -- All DOE Office Websites (Extended Search)

1 31 53-T Thesis A Numerical Model of Hydro-Thermo- Mechanical Coupling in a Fractured Rock Mass ECEIVED Los Alamos N A T I O N A L L A B O R A T O R Y Los Alamos National...

92

Mechanical modeling of porous oxide fuel pellet A Test Problem  

Science Conference Proceedings (OSTI)

A poro-elasto-plastic material model has been developed to capture the response of oxide fuels inside the nuclear reactors under operating conditions. Behavior of the oxide fuel and variation in void volume fraction under mechanical loading as predicted by the developed model has been reported in this article. The significant effect of void volume fraction on the overall stress distribution of the fuel pellet has also been described. An important oxide fuel issue that can have significant impact on the fuel performance is the mechanical response of oxide fuel pellet and clad system. Specifically, modeling the thermo-mechanical response of the fuel pellet in terms of its thermal expansion, mechanical deformation, swelling due to void formation and evolution, and the eventual contact of the fuel with the clad is of significant interest in understanding the fuel-clad mechanical interaction (FCMI). These phenomena are nonlinear and coupled since reduction in the fuel-clad gap affects thermal conductivity of the gap, which in turn affects temperature distribution within the fuel and the material properties of the fuel. Consequently, in order to accurately capture fuel-clad gap closure, we need to account for fuel swelling due to generation, retention, and evolution of fission gas in addition to the usual thermal expansion and mechanical deformation. Both fuel chemistry and microstructure also have a significant effect on the nucleation and growth of fission gas bubbles. Fuel-clad gap closure leading to eventual contact of the fuel with the clad introduces significant stresses in the clad, which makes thermo-mechanical response of the clad even more relevant. The overall aim of this test problem is to incorporate the above features in order to accurately capture fuel-clad mechanical interaction. Because of the complex nature of the problem, a series of test problems with increasing multi-physics coupling features, modeling accuracy, and complexity are defined with the objective of accurate simulation of fuel-clad mechanical interaction subjected to a wide-range of thermomechanical stimuli.

Nukala, Phani K [ORNL; Barai, Pallab [ORNL; Simunovic, Srdjan [ORNL; Ott, Larry J [ORNL

2009-10-01T23:59:59.000Z

93

A hybrid particle-continuum method for hydrodynamics of complex fluids  

E-Print Network (OSTI)

A previously-developed hybrid particle-continuum method [J. B. Bell, A. Garcia and S. A. Williams, SIAM Multiscale Modeling and Simulation, 6:1256-1280, 2008] is generalized to dense fluids and two and three dimensional flows. The scheme couples an explicit fluctuating compressible Navier-Stokes solver with the Isotropic Direct Simulation Monte Carlo (DSMC) particle method [A. Donev and A. L. Garcia and B. J. Alder, ArXiv preprint 0908.0510]. To achieve bidirectional dynamic coupling between the particle (microscale) and continuum (macroscale) regions, the continuum solver provides state-based boundary conditions to the particle subdomain, while the particle solver provides flux-based boundary conditions for the continuum subdomain. The equilibrium diffusive (Brownian) motion of a large spherical bead suspended in a particle fluid is examined, demonstrating that the hybrid method correctly reproduces the velocity autocorrelation function of the bead but only if thermal fluctuations are included in the continuum solver. Finally, the hybrid is applied to the well-known adiabatic piston problem and it is found that the hybrid correctly reproduces the slow non-equilibrium relaxation of the piston toward thermodynamic equilibrium but, again, only the continuum solver includes stochastic (white-noise) flux terms. These examples clearly demonstrate the need to include fluctuations in continuum solvers employed in hybrid multiscale methods.

A. Donev; J. B. Bell; A. L. Garcia; B. J. Alder

2009-10-20T23:59:59.000Z

94

Implementing and assessing computational modeling in introductory mechanics  

E-Print Network (OSTI)

Students taking introductory physics are rarely exposed to computational modeling. In a one-semester large lecture introductory calculus-based mechanics course at Georgia Tech, students learned to solve physics problems using the VPython programming environment. During the term 1357 students in this course solved a suite of fourteen computational modeling homework questions delivered using an online commercial course management system. Their proficiency with computational modeling was evaluated in a proctored environment using a novel central force problem. The majority of students (60.4%) successfully completed the evaluation. Analysis of erroneous student-submitted programs indicated that a small set of student errors explained why most programs failed. We discuss the design and implementation of the computational modeling homework and evaluation, the results from the evaluation and the implications for instruction in computational modeling in introductory STEM courses.

Caballero, Marcos D; Schatz, Michael F

2011-01-01T23:59:59.000Z

95

Mechanical properties and modeling of seal-forming lithologies  

Science Conference Proceedings (OSTI)

Specific goals and accomplishments of this research include: (1) The evaluation of models of salt diaper ascent that involve either power law, dislocation creep as determined experimentally by Horseman et al. (1993) or linear, fluid-assisted creep as reported by Spiers et al. (1988, 1990, 1992). We have compared models assuming these two, experimentally evaluated flow laws and examined the predictions they make regarding diaper incubation periods, ascent velocities, deviatoric stresses and strain rates. (2) The evaluation of the effects of differential loading on the initiation an of salt structures. (3) Examination of the role of basement faults on the initiation and morphologic evolution of salt structures. (4) Evaluation of the mechanical properties of shale as a function of pressure and determination of the nature of its brittle-ductile transition. (5) Evaluation of the mechanical anisotropies of shales with varying concentrations, distributions and preferred orientations of clay. (6) The determination of temperature and ratedependencies of strength for a shale constitutive model that can be used in numerical models that depend on viscous formulations. (7) Determination of the mechanisms of deformation for argillaceous rocks over awide range of conditions. (8) Evaluation of the effects of H[sub 2]O within clay interlayers, as adsorbed surface layers.

Kronenberg, A.K.; Russell, J.E.; Carter, N.L.; Mazariegos, R.; Ibanez, W.

1993-01-01T23:59:59.000Z

96

Curved mesh generation and mesh refinement using Lagrangian solid mechanics  

E-Print Network (OSTI)

Nonlinear continuum mechanics for ?nite element analysis,nement using Lagrangian Solid Mechanics Per-Olof Persson ?methods for computational mechanics has been emphasized in

Persson, P.-O.

2009-01-01T23:59:59.000Z

97

Far Ultraviolet Continuum Emission: Applying this Diagnostic to the Chromospheres of Solar-Mass Stars  

E-Print Network (OSTI)

The far ultraviolet (FUV) continuum flux is recognized as a very sensitive diag- nostic of the temperature structure of the Sun's lower chromosphere. Until now analysis of the available stellar FUV data has shown that solar-type stars must also have chromospheres, but quantitative analyses of stellar FUV continua require far higher quality spectra and comparison with new non-LTE chromosphere models. We present accurate far ultraviolet (FUV, 1150-1500^{\\circ}) continuum flux measurements for solar-mass stars, made feasible by the high throughput and very low detector background of the Cosmic Origins Spectrograph (COS) on the Hubbble Space Telescope. We show that the continuum flux can be measured above the detector background even for the faintest star in our sample. We find a clear trend of increasing continuum brightness temperature at all FUV wavelengths with decreasing rotational period, which provides an important measure of magnetic heating rates in stellar chromospheres. Comparison with semiempirical so...

Linsky, Jeffrey L; Ayres, Tom; Fontenla, Juan; France, Kevin

2011-01-01T23:59:59.000Z

98

A Hydro-mechanical Model and Analytical Solutions for Geomechanical Modeling of Carbon Dioxide Geological Sequestration  

SciTech Connect

We present a hydro-mechanical model for geological sequestration of carbon dioxide. The model considers the poroelastic effects by taking into account the coupling between the geomechanical response and the fluid flow in greater detail. The simplified hydro-mechanical model includes the geomechanical part that relies on the linear elasticity, while the fluid flow is based on the Darcy’s law. Two parts were coupled using the standard linear poroelasticity. Analytical solutions for pressure field were obtained for a typical geological sequestration scenario. The model predicts the temporal and spatial variation of pressure field and effects of permeability and elastic modulus of formation on the fluid pressure distribution.

Xu, Zhijie; Fang, Yilin; Scheibe, Timothy D.; Bonneville, Alain HR

2012-05-15T23:59:59.000Z

99

Mechanical properties and modeling of seal-forming lithologies  

Science Conference Proceedings (OSTI)

The goal of this research is to evaluate the roles of deformation and the occurrence of weak sedimentary lithologies subjected to gravitational loads in shaping conventional and unconventional oil and gas reservoirs. Two sedimentary lithologies that influence the geometries, physical properties, and heterogeneities of oil and gas reservoirs are shale and rocksalt. Both form effect barriers to the flow and communication of petroleum and gas and, in many cases, form the seals to major reservoirs due to their low permeabilities. Both are actively deformed in depositional environments due to their low strengths relative to gravitational loads applied. Thus, the shapes of seal-forming units, and the nature of fractures and faults that may breach them depend upon either the mechanical properties of shale or those of salt, and the loading histories to which they have been subjected. Deformed shales may, in addition, serve as unconventional reservoirs of gas if open fractures within them provide sufficient porosity. The fracture and flow properties of shales are not well constrained, and the authors are currently investigating these properties experimentally. The rheology of rocksalt, on the other hand, is well known and they believe that the time is right to apply the experimentally constrained constitutive relations for rocksalt to deformations in the Earth. Efforts are continuing on modeling fracture anisotropy and the authors have examined simple, two-mica models to evaluate the mechanical interactions they proposed for gneiss and mica-poor schists. Brief summaries of the progress and results to date for (1) the mechanical properties of schist, (2) a two-mica model of fracture anisotropy, (3) deformation of shale, and (4) modeling of salt and shale tectonics of the northern Gulf of Mexico are given in the following sections. 35 refs., 33 figs., 1 tab.

Kronenberg, A.K.; Russell, J.E.; Carter, N.L.; Mazariegos, R.; Shea, W.T.

1991-03-01T23:59:59.000Z

100

Cellular network with continuum priority set  

Science Conference Proceedings (OSTI)

We consider the following problem of spatial downlink prioritization. Mobiles arrive at a cell at locations that are determined according to some probability distribution. The farther a mobile is from the base station, the weaker is its received power ... Keywords: HSDPA, continuum, priority, scheduling

Jean-Marc Kelif; Eitan Altman

2007-10-01T23:59:59.000Z

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101

Liquid nanofilms. A mechanical model for the disjoining pressure  

E-Print Network (OSTI)

Liquids in contact with solids are submitted to intermolecular forces making liquids heterogeneous and, in a mechanical model, the stress tensor is not any more spherical as in homogeneous bulks. The aim of this article is to show that a square-gradient functional taking into account the volume liquid free energy corrected with two surface liquid density functionals is a mean field approximation allowing to study structures of very thin liquid nanofilms near plane solid walls. The model determines analytically the concept of disjoining pressure for liquid films of thicknesses of a very few number of nanometers and yields a behavior in good agreement with the shapes of experimental curves carried out by Derjaguin and his successors.

Henri Gouin

2009-04-11T23:59:59.000Z

102

Modeling the Q-cycle mechanism of transmembrane energy conversion  

E-Print Network (OSTI)

The Q-cycle mechanism plays an important role in the conversion of the redox energy into the energy of the proton electrochemical gradient across the biomembrane. The bifurcated electron transfer reaction, which is built into this mechanism, recycles one electron, thus, allowing to translocate two protons per one electron moving to the high-potential redox chain. We study a kinetic model of the Q-cycle mechanism in an artificial system which mimics the bf complex of plants and cyanobacteria in the regime of ferredoxin-dependent cyclic electron flow. Using methods of condensed matter physics, we derive a set of master equations and describe a time sequence of electron and proton transfer reactions in the complex. We find energetic conditions when the bifurcation of the electron pathways at the positive side of the membrane occurs naturally, without any additional gates. For reasonable parameter values, we show that this system is able to translocate more than 1.8 protons, on average, per one electron, with a thermodynamic efficiency of the order of 32% or higher.

Anatoly Yu. Smirnov; Franco Nori

2011-06-29T23:59:59.000Z

103

Modeling the Q-cycle mechanism of transmembrane energy conversion  

E-Print Network (OSTI)

The Q-cycle mechanism plays an important role in the conversion of the redox energy into the energy of the proton electrochemical gradient across the biomembrane. The bifurcated electron transfer reaction, which is built into this mechanism, recycles one electron, thus, allowing to translocate two protons per one electron moving to the high-potential redox chain. We study a kinetic model of the Q-cycle mechanism in an artificial system which mimics the bf complex of plants and cyanobacteria in the regime of ferredoxin-dependent cyclic electron flow. Using methods of condensed matter physics, we derive a set of master equations and describe a time sequence of electron and proton transfer reactions in the complex. We find energetic conditions when the bifurcation of the electron pathways at the positive side of the membrane occurs naturally, without any additional gates. For reasonable parameter values, we show that this system is able to translocate more than 1.8 protons, on average, per one electron, with a t...

Smirnov, Anatoly Yu

2011-01-01T23:59:59.000Z

104

CFD MODELING ANALYSIS OF MECHANICAL DRAFT COOLING TOWER  

Science Conference Proceedings (OSTI)

Industrial processes use mechanical draft cooling towers (MDCT's) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has a MDCT consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to conduct a parametric study for cooling tower performance under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model to achieve the objective. The model uses three-dimensional steady-state momentum, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of the modeling calculations was performed to investigate the impact of ambient and operating conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was benchmarked against the literature data and the SRS test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed results will be presented here.

Lee, S; Alfred Garrett, A; James02 Bollinger, J; Larry Koffman, L

2008-03-03T23:59:59.000Z

105

The Potential of MEMS for Advancing Experiments and Modeling in Cell Mechanics  

E-Print Network (OSTI)

The Potential of MEMS for Advancing Experiments and Modeling in Cell Mechanics O. Loh & A. Vaziri # Society for Experimental Mechanics 2007 Abstract Response to mechanical stimuli largely dictates cellular the hierarchical cell structure. As experimental and model-based investigations in cell mechanics advance

Vaziri, Ashkan

106

Connecting the Molecular and the Continuum Scales  

NLE Websites -- All DOE Office Websites (Extended Search)

Connecting the Connecting the Molecular and the Continuum Scales Connecting the Molecular and the Continuum Scales Key Challenges: A molecular-scale understanding of structure and surface chemistry of clay mineral surface nanoparticles. Why it Matters: With a ubiquitous presence in natural materials and strong surface reactions, nanoparticles figure importantly in a broad range of phenomena, from climate change to contaminant remediation. Accomplishments: Used molecular dynamics (MD) simulations to determine molecular-scale diffusion coefficients of water tracers and representative cations (Na+,Cs+,Sr2+) in Smectite and found a simple way to accurately relate this to bulk, pore-scale diffusion. The result is that a remarkably simple expression relates Dinterlayer to the pore-scale

107

Dyson-Schwinger Equations: Density, Temperature and Continuum Strong QCD  

E-Print Network (OSTI)

Continuum strong QCD is the application of models and continuum quantum field theory to the study of phenomena in hadronic physics, which includes; e.g., the spectrum of QCD bound states and their interactions; and the transition to, and properties of, a quark gluon plasma. We provide a contemporary perspective, couched primarily in terms of the Dyson-Schwinger equations but also making comparisons with other approaches and models. Our discourse provides a practitioners' guide to features of the Dyson-Schwinger equations [such as confinement and dynamical chiral symmetry breaking] and canvasses phenomenological applications to light meson and baryon properties in cold, sparse QCD. These provide the foundation for an extension to hot, dense QCD, which is probed via the introduction of the intensive thermodynamic variables: chemical potential and temperature. We describe order parameters whose evolution signals deconfinement and chiral symmetry restoration, and chronicle their use in demarcating the quark gluon plasma phase boundary and characterising the plasma's properties. Hadron traits change in an equilibrated plasma. We exemplify this and discuss putative signals of the effects. Finally, since plasma formation is not an equilibrium process, we discuss recent developments in kinetic theory and its application to describing the evolution from a relativistic heavy ion collision to an equilibrated quark gluon plasma.

C. D. Roberts; S. M. Schmidt

2000-05-24T23:59:59.000Z

108

SYSTEMATIC CONTINUUM ERRORS IN THE Ly{alpha} FOREST AND THE MEASURED TEMPERATURE-DENSITY RELATION  

Science Conference Proceedings (OSTI)

Continuum fitting uncertainties are a major source of error in estimates of the temperature-density relation (usually parameterized as a power-law, T {proportional_to} {Delta}{sup {gamma}-1}) of the intergalactic medium through the flux probability distribution function (PDF) of the Ly{alpha} forest. Using a simple order-of-magnitude calculation, we show that few percent-level systematic errors in the placement of the quasar continuum due to, e.g., a uniform low-absorption Gunn-Peterson component could lead to errors in {gamma} of the order of unity. This is quantified further using a simple semi-analytic model of the Ly{alpha} forest flux PDF. We find that under(over)estimates in the continuum level can lead to a lower (higher) measured value of {gamma}. By fitting models to mock data realizations generated with current observational errors, we find that continuum errors can cause a systematic bias in the estimated temperature-density relation of ({delta}({gamma})) Almost-Equal-To -0.1, while the error is increased to {sigma}{sub {gamma}} Almost-Equal-To 0.2 compared to {sigma}{sub {gamma}} Almost-Equal-To 0.1 in the absence of continuum errors.

Lee, Khee-Gan, E-mail: lee@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2012-07-10T23:59:59.000Z

109

On the band-to-continuum intensity ratio in the infrared spectra of interstellar carbonaceous dust  

E-Print Network (OSTI)

Published interpretations of the relative intensity variations of the Unidentified Infrared Bands (UIBs) and their underlying continuum are discussed. An alternative model is proposed, in which a single carrier for both emits a) mostly a continuum when it is electronically excited by photons (visible or UV), or b) exclusively the UIBs, when only chemical energy is deposited by H capture on its surface, inducing only nuclear vibrations. The bands will dominate in atomic H regions but will be overcome by thermal continuum radiation when the ambient field is strong but lacks dissociating photons (900-1100 Angstroms). The model applies to PDRs as well as to limbs of molecular clouds in the ISM and agrees quantitatively with recent satellite observations. It gives indications on atomic H density and UIB intensity provided the ambient radiation field is known. It invokes no chemical, electronic, structural or size change in order to interpret the observed intensity variations.

Renaud Papoular

2004-03-24T23:59:59.000Z

110

Fuel Modeling II  

Science Conference Proceedings (OSTI)

Mar 4, 2013 ... Integrated Computational Modeling of Materials for Nuclear Energy: ... Continuum Theory of Defects and Materials Response to Irradiation: ...

111

A CONTINUUM MECHANICS PRIMER On Constitutive Theories of Materials  

E-Print Network (OSTI)

. Since the spin tensor W is skew-symmetric, it can be represented as an axial vector w. The components and the external energy supply. #12;20 2. BALANCE LAWS Conservation of energy. Relative to an inertial frame) the energy supply density due to external sources, such as radiation. Comparison with the general balance

Liu, I-Shih

112

Determining the focal mechanisms of earthquakes by full waveform modeling  

E-Print Network (OSTI)

Determining the focal mechanism of an earthquake helps us to better characterize reservoirs, define faults, and understand the stress and strain regime. The objective of this thesis is to find the focal mechanism and depth ...

Busfar, Hussam A. (Hussam Abdullah)

2009-01-01T23:59:59.000Z

113

Radiometric Modeling of Mechanical Draft Cooling Towers to Assist in the Extraction of their Absolute Temperature  

E-Print Network (OSTI)

Radiometric Modeling of Mechanical Draft Cooling Towers to Assist in the Extraction CENTER FOR IMAGING SCIENCE Title of Dissertation: Radiometric Modeling of Mechanical Draft Cooling Towers of Mechanical Draft Cooling Towers to Assist in the Extraction of their Absolute Temperature from Remote Thermal

Salvaggio, Carl

114

Coupled-channel continuum eigenchannel basis  

E-Print Network (OSTI)

The goal of this paper is to calculate bound, resonant and scattering states in the coupled-channel formalism without relying on the boundary conditions at large distances. The coupled-channel solution is expanded in eigenchannel bases i.e. in eigenfunctions of diagonal Hamiltonians. Each eigenchannel basis may includes discrete and discretized continuum (real or complex energy) single particle states. The coupled-channel solutions are computed through diagonalization in these bases. The method is applied to a few two-channel problems. The exact bound spectrum of the Poeschl-Teller potential is well described by a basis of real energy continuum states. For the deuteron with the Reid potential the experimental energy and the $S$ and $D$ wave functions content are reproduced in the asymptotic limit of the energy cutoff. For the Noro-Taylor potential, beside the exact bound state energies the resonant state energy is also well reproduced by using the complex energy Berggren basis. It is found that the expansion of the coupled-channel wave functions in these eigenchannel bases require less computational effort than the use of any other basis. The solutions are stable and converge as the energy cutoff increases.

R. M. Id Betan

2013-11-18T23:59:59.000Z

115

Hadron resonances with a quark core embedded in the continuum  

SciTech Connect

We investigate the excited baryons and mesons which cannot be described in terms of a simple constituent quark model, such as {Lambda}(1405) and X(3872) as a resonance in a coupled channel hadron-hadron (baryon-meson or meson-meson) scattering with a 'bound state embedded in the continuum' (BSEC). For this purpose, we solve the Lippmann-Schwinger equation including a BSEC in the momentum space. This BSEC is introduced by hand, as a state not originated from a simple baryon-meson or meson-meson system. We assume it comes from the three-quark state or quark-anti quark state and show such a picture can describe the {Lambda}(1405) and X(3872) resonances.

Shimizu, Kiyotaka [Department of Physics, Sophia University, Chiyoda-ku, Tokyo 102-8554 (Japan); Takeuchi, Sachiko [Japan College of Social Work, Kiyose, Tokyo 204-8555 (Japan); Takizawa, Makoto [Showa Pharmaceutical University, Machida, Tokyo 194-8543 (Japan)

2011-05-06T23:59:59.000Z

116

Characterization and modeling of polysilicon MEMS chemical-mechanical polishing  

E-Print Network (OSTI)

Heavily used in the manufacture of integrated circuits, chemical-mechanical polishing (CMP) is becoming an enabling technology for microelectromechanical systems (MEMS). To reliably use CMP in the manufacturing process, ...

Tang, Brian D. (Brian David), 1980-

2004-01-01T23:59:59.000Z

117

Modeling of chemical mechanical polishing for shallow trench isolation  

E-Print Network (OSTI)

This thesis presents the nonlinear analysis, design, fabrication, and testing of an axial-gap magnetic induction micro machine, which is a two-phase planar motor in which the rotor is suspended above the stator via mechanical ...

Lee, Brian, 1975-

2002-01-01T23:59:59.000Z

118

Modeling the mechanical behavior of amorphous metals by shear transformation zone dynamics  

E-Print Network (OSTI)

A new mesoscale modeling technique for the thermo-mechanical behavior of amorphous metals is proposed. The modeling framework considers the shear transformation zone (STZ) as the fundamental unit of deformation, and ...

Homer, Eric Richards, 1980-

2010-01-01T23:59:59.000Z

119

An improved structural mechanics model for the FRAPCON nuclear fuel performance code  

E-Print Network (OSTI)

In order to provide improved predictions of Pellet Cladding Mechanical Interaction (PCMI) for the FRAPCON nuclear fuel performance code, a new model, the FRAPCON Radial-Axial Soft Pellet (FRASP) model, was developed. This ...

Mieloszyk, Alexander James

2012-01-01T23:59:59.000Z

120

Mechanism of Zonal Index Evolution in a Two-Layer Model  

Science Conference Proceedings (OSTI)

A mechanism that drives a zonal jet to meander in the meridional direction is investigated with a two-layer multiwave quasigeostrophic ?-plant channel model. This model isolates the zonal index characteristics of a purely eddy-driven jet. ...

Sukyoung Lee; Steven Feldstein

1996-08-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

The Neural Network Model using for Predictions Mechanical ...  

Science Conference Proceedings (OSTI)

Study of Composite Materials Application for Horizontal Axis Wind Turbine Blades ... Using the Computational Modelling to Improve Durability of Diesel Engine ...

122

Thermal-Mechanical Fatigue Life Model for Coated Superalloy ...  

Science Conference Proceedings (OSTI)

in an aggressive combustion gas environment. Coating ..... M.I. Wood and G.F. Harrison, "Modeling The Deformation Of Coated. Superalloys Under Thermal ...

123

Goal-oriented Atomistic-Continuum Adaptivity for the Quasicontinuum Approximation  

E-Print Network (OSTI)

We give a goal-oriented a posteriori error estimator for the atomistic-continuum modeling error in the quasicontinuum method, and we use this estimator to design an adaptive algorithm to compute a quantity of interest to a given tolerance by using a nearly minimal number of atomistic degrees of freedom. We present computational results that demonstrate the effectiveness of our algorithm for a periodic array of dislocations described by a Frenkel-Kontorova type model.

Marcel Arndt; Mitchell Luskin

2007-07-31T23:59:59.000Z

124

Mentorship: The Education-Research Continuum  

Science Conference Proceedings (OSTI)

Mentoring of science students stems naturally from the intertwined link between science education and science research. In fact, the mentoring relationship between a student and a scientist may be thought of analogically as a type of double helix forming the 'DNA' that defines the blueprint for the next generation of scientists. Although this analogy would not meet the rigorous tests commonly used for exploring the natural laws of the universe, the image depicted does capture how creating and sustaining the future science workforce benefits greatly from the continuum between education and research. The path science students pursue from their education careers to their research careers often involves training under an experienced and trusted advisor, i.e., a mentor. For many undergraduate science students, a summer research internship at a DOE National Laboratory is one of the many steps they will take in their Education-Research Continuum. Scientists who choose to be mentors share a commitment for both science education and science research. This commitment is especially evident within the research staff found throughout the Department of Energy's National Laboratories. Research-based internship opportunities within science, technology, engineering and mathematics (STEM) exist at most, if not all, of the Laboratories. Such opportunities for students are helping to create the next generation of highly trained professionals devoted to the task of keeping America at the forefront of scientific innovation. 'The Journal of Undergraduate Research' (JUR) provides undergraduate interns the opportunity to publish their scientific innovation and to share their passion for education and research with fellow students and scientists. The theme of this issue of the JUR (Vol. 8, 2008) is 'Science for All'. Almost 20 years have passed since the American Association for the Advancement of Science published its 1989 report, 'Science for All Americans-Project 2061'. The first recommendation for learning science stated: 'The Nature of Science includes the scientific world view, scientific methods of inquiry, and the nature of the scientific enterprise'. All three elements of the 'Nature of Science' are pivotal aspects of a research internship under the mentorship of an experienced and trusted advisor. In addition to internships for undergraduates, an important ingredient in realizing 'Science for All' is collaboration involving educators and scientists as they engage science students and the public at large to promote science literacy and to develop the next generation of STEM professionals. The DOE National Laboratories, individually and collectively, form an ideal nexus for nurturing these complementary collaborations. My 'Science for All' experiences at Lawrence Livermore National Laboratory (LLNL) over the last 30 years have spanned pre-college, college, and postdoctoral activities, including mentoring of undergraduate students. Early in my mentoring career, I became aware that undergraduates in particular needed help in answering the question 'what path (or paths) will lead to a challenging and rewarding STEM career'? For many, a successful path included a research internship that would result in expanded skills and training in addition to those received from their academic education. These internship skills were helpful whether the student's next Education-Research Continuum decision was graduate school or STEM employment. My experience at LLNL mirrors that of my colleagues at other DOE National Laboratories--internships with a dedicated mentor provide undergraduates with a unique set of skills that can underpin their future options and serve to improve the number, quality, and successful outcomes of students who enter STEM careers. 'Science for All' can also be found in the goals of 'The America COMPETES Act', which call for renewed efforts to increase investments in scientific research and development, strengthen education, and encourage entrepreneurship. Mentoring is an important ingredient in reaching these goals because the succe

Correll, D

2008-05-29T23:59:59.000Z

125

A Hydro-Thermo-Mechanical Numerical Model For Hdr Geothermal Reservoir  

Open Energy Info (EERE)

Hydro-Thermo-Mechanical Numerical Model For Hdr Geothermal Reservoir Hydro-Thermo-Mechanical Numerical Model For Hdr Geothermal Reservoir Evaluation Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: A Hydro-Thermo-Mechanical Numerical Model For Hdr Geothermal Reservoir Evaluation Details Activities (0) Areas (0) Regions (0) Abstract: A two-dimensional numerical model of coupled fluid flow, heat transfer and rock mechanics in naturally fractured rock is developed. The model is applicable to assessments of hot dry rock (HDR) geothermal reservoir characterisation experiments, and to the study of hydraulic stimulations and the heat extraction potential of HDR reservoirs. Modelling assumptions are based on the characteristics of the experimental HDR reservoir in the Carnmenellis granite in Cornwall, S. W. England. In

126

A Mechanical Fluid-Dynamical Model For Ground Movements At Campi Flegrei  

Open Energy Info (EERE)

Mechanical Fluid-Dynamical Model For Ground Movements At Campi Flegrei Mechanical Fluid-Dynamical Model For Ground Movements At Campi Flegrei Caldera Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: A Mechanical Fluid-Dynamical Model For Ground Movements At Campi Flegrei Caldera Details Activities (0) Areas (0) Regions (0) Abstract: We present here a consistent model, which explains the mechanisms of unrest phenomena at Campi Flegrei (Italy), both at short-term (years) and at secular scales. The model consists basically of two effects: the first one is related to the elastic response of the shallow crust to increasing pressure within a shallow magma chamber; the second involves the fluid-dynamics of shallow aquifers in response to increasing pressure and/or temperature at depth. The most important roles in the proposed model

127

Assessment of reduced mechanisms using One Dimensional Stochastic Turbulence model  

E-Print Network (OSTI)

turbulence model for a syngas jet flame. Proceeding of FallKerstein 2002), a turbulent syngas (CO/H2/NO) jet flame wasand DNS results of the syngas jet flame was recently done

Chien, Li-Chun

2010-01-01T23:59:59.000Z

128

Analytic Models for the Mechanical Structure of the Solar Core  

E-Print Network (OSTI)

All stars exhibit universal central behavior in terms of new homology variables (u,w). In terms of these variables, we obtain simple analytic fits to numerical standard solar models for the core and radiative zones of the ZAMS and present Suns, with a few global parameters. With these analytic fits, different theoretical models of the solar core, neutrino fluxes, and helioseismic observations can be parametrized and compared.

Dallas C. Kennedy; Sidney A. Bludman

1998-12-09T23:59:59.000Z

129

A simplified implementation of a gradient-enhanced damage model with transient length scale effects  

Science Conference Proceedings (OSTI)

Gradient-enhanced damage models with constant gradient activity suffer from spurious damage growth at high deformation levels. This issue was resolved by Geers et al. (Comput Methods Appl Mech Eng 160(1---2):133---153, 1998) by expressing the gradient ... Keywords: Continuum damage mechanics, Gradient-enhanced damage models, Regularized media, Transient internal length scale

S. Saroukhani; R. Vafadari; A. Simone

2013-06-01T23:59:59.000Z

130

Lyman Continuum Escape from Inhomogeneous ISM  

E-Print Network (OSTI)

We have studied the effects of gas density inhomogeneities on the escape of ionising Lyman continuum (Lyc) photons from Milky Way-type galaxies via 3D numerical simulations using the Monte Carlo radiative transfer code CRASH (Ciardi et al. 2001). To this aim a comparison between a smooth Gaussian distribution (GDD) and an inhomogeneous, fractal one (FDD) has been made with realistic assumptions for the ionising stellar sources based on available data in the solar neighborhood. In both cases the escape fraction f_esc increases with ionisation rate N_gamma (although for the FDD with a flatter slope) and they become equal at N_gamma = 2*10^50 s^-1 where f_esc = 0.11. FDD allows escape fractions of the same order also at lower N_gamma, when Lyc photon escape is sharply suppressed by GDD. Values of the escape fraction as high as 0.6 can be reached (GDD) for N_gamma ~ 9*10^50 s^-1, corresponding to a star formation rate (SFR) of roughly 2 M_o yr^-1; at this ionising luminosity the FDD is less transparent (f_esc ~ 0.28). If high redshift galaxies have gas column densities similar to local ones, are characterized by such high SFRs and by a predominantly smooth (i.e.turbulence free) interstellar medium, our results suggest that they should considerably contribute to - and possibly dominate - the cosmic UV background.

B. Ciardi; S. Bianchi; A. Ferrara

2001-11-28T23:59:59.000Z

131

Lyman Continuum Escape from Inhomogeneous ISM  

E-Print Network (OSTI)

We have studied the effects of gas density inhomogeneities on the escape of ionising Lyman continuum (Lyc) photons from Milky Way-type galaxies via 3D numerical simulations using the Monte Carlo radiative transfer code CRASH (Ciardi et al. 2001). To this aim a comparison between a smooth Gaussian distribution (GDD) and an inhomogeneous, fractal one (FDD) has been made with realistic assumptions for the ionising stellar sources based on available data in the solar neighborhood. In both cases the escape fraction f_esc increases with ionisation rate N_gamma (although for the FDD with a flatter slope) and they become equal at N_gamma = 2*10^50 s^-1 where f_esc = 0.11. FDD allows escape fractions of the same order also at lower N_gamma, when Lyc photon escape is sharply suppressed by GDD. Values of the escape fraction as high as 0.6 can be reached (GDD) for N_gamma ~ 9*10^50 s^-1, corresponding to a star formation rate (SFR) of roughly 2 M_o yr^-1; at this ionising luminosity the FDD is less transparent (f_esc ~ 0...

Ciardi, B; Ferrara, A

2002-01-01T23:59:59.000Z

132

Continuum Edge Gyrokinetic Theory and Simulations  

Science Conference Proceedings (OSTI)

The following results are presented from the development and application of TEMPEST, a fully nonlinear (full-f) five dimensional (3d2v) gyrokinetic continuum edge-plasma code. (1) As a test of the interaction of collisions and parallel streaming, TEMPEST is compared with published analytic and numerical results for endloss of particles confined by combined electrostatic and magnetic wells. Good agreement is found over a wide range of collisionality, confining potential, and mirror ratio; and the required velocity space resolution is modest. (2) In a large-aspect-ratio circular geometry, excellent agreement is found for a neoclassical equilibrium with parallel ion flow in the banana regime with zero temperature gradient and radial electric field. (3) The four-dimensional (2d2v) version of the code produces the first self-consistent simulation results of collisionless damping of geodesic acoustic modes and zonal flow (Rosenbluth-Hinton residual) with Boltzmann electrons using a full-f code. The electric field is also found to agree with the standard neoclassical expression for steep density and ion temperature gradients in the banana regime. In divertor geometry, it is found that the endloss of particles and energy induces parallel flow stronger than the core neoclassical predictions in the SOL. (5) Our 5D gyrokinetic formulation yields a set of nonlinear electrostatic gyrokinetic equations that are for both neoclassical and turbulence simulations.

Xu, X Q; Xiong, Z; Dorr, M R; Hittinger, J A; Bodi, K; Candy, J; Cohen, B I; Cohen, R H; Colella, P; Kerbel, G D; Krasheninnikov, S; Nevins, W M; Qin, H; Rognlien, T D; Snyder, P B; Umansky, M V

2007-01-09T23:59:59.000Z

133

Mechanisms, Models, and Simulations of Metal-Coated Fiber Consolidation  

E-Print Network (OSTI)

of existing contacts as matrix plasticity and/or PLC. When the voids are small the coated fiber bundle shrinks-shaped voids with a shape factor similar to that observed in the experiments. Creep rates were microstructure fractions were introduced into the model using micromechanics-based creep constitutive relationships

Wadley, Haydn

134

Qunatum-Mechanical Model of Spacetime II: Thermodynamics of Spacetime  

E-Print Network (OSTI)

In this second part of our series of two papers, where spacetime is modelled by a graph, where Planck size quantum black holes lie on the vertices, we consider the thermodynamics of spacetime. We formulate an equation which tells in which way an accelerating, spacelike two-surface of spacetime interacts with the thermal radiation flowing through that surface. In the low temperature limit, where most quantum black holes constituting spacetime are assumed to lie in the ground state, our equation implies, among other things, the Hawking and the Unruh effects, as well as Einstein's field equation with a vanishing cosmological constant for general matter fields. We also consider the high temperature limit, where the microscopic black holes are assumed to lie in highly excited states. In this limit our model implies, among other things, that black hole entropy depends logarithmically on its area, instead of being proportional to the area.

Makela, J

2008-01-01T23:59:59.000Z

135

Neoclassical Simulation of Tokamak Plasmas using Continuum Gyrokinetc Code TEMPEST  

Science Conference Proceedings (OSTI)

We present gyrokinetic neoclassical simulations of tokamak plasmas with self-consistent electric field for the first time using a fully nonlinear (full-f) continuum code TEMPEST in a circular geometry. A set of gyrokinetic equations are discretized on a five dimensional computational grid in phase space. The present implementation is a Method of Lines approach where the phase-space derivatives are discretized with finite differences and implicit backwards differencing formulas are used to advance the system in time. The fully nonlinear Boltzmann model is used for electrons. The neoclassical electric field is obtained by solving gyrokinetic Poisson equation with self-consistent poloidal variation. With our 4D ({psi}, {theta}, {epsilon}, {mu}) version of the TEMPEST code we compute radial particle and heat flux, the Geodesic-Acoustic Mode (GAM), and the development of neoclassical electric field, which we compare with neoclassical theory with a Lorentz collision model. The present work provides a numerical scheme and a new capability for self-consistently studying important aspects of neoclassical transport and rotations in toroidal magnetic fusion devices.

Xu, X Q

2007-11-09T23:59:59.000Z

136

A multiscale Molecular Dynamics approach to Contact Mechanics  

E-Print Network (OSTI)

The friction and adhesion between elastic bodies are strongly influenced by the roughness of the surfaces in contact. Here we develop a multiscale molecular dynamics approach to contact mechanics, which can be used also when the surfaces have roughness on many different length-scales, e.g., for self affine fractal surfaces. As an illustration we consider the contact between randomly rough surfaces, and show that the contact area varies linearly with the load for small load. We also analyze the contact morphology and the pressure distribution at different magnification, both with and without adhesion. The calculations are compared with analytical contact mechanics models based on continuum mechanics.

C. Yang; U. Tartaglino; B. N. J. Persson

2005-08-10T23:59:59.000Z

137

Hybrid atomistic-continuum formulations for gaseous flows  

E-Print Network (OSTI)

Hybrid atomistic-continuum formulations allow the simulation of complex hydrodynamic phenomena at the nano and micro scales without the prohibitive cost of a fully atomistic approach. This is achieved through a domain ...

Wijesinghe, Hettithanthrige Sanith, 1974-

2003-01-01T23:59:59.000Z

138

Four-body continuum-discretized coupled-channels calculations  

SciTech Connect

The development of a continuum-bin scheme of discretization for three-body projectiles is necessary for studies of reactions of Borromean nuclei such as {sup 6}He within the continuum-discretized coupled-channels approach. Such a procedure, for constructing bin states on selected continuum energy intervals, is formulated and applied for the first time to reactions of a three-body projectile. The continuum representation uses the eigenchannel expansion of the three-body S matrix. The method is applied to the challenging case of the {sup 6}He+{sup 208}Pb reaction at 22 MeV, where an accurate treatment of both the Coulomb and the nuclear interactions with the target is necessary.

Rodriguez-Gallardo, M. [Instituto de Estructura de la Materia, CSIC, Serrano 123, E-28006 Madrid (Spain); Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Sevilla, Apartado 1065, E-41080 Sevilla (Spain); Centro de Fisica Nuclear, Universidade de Lisboa, Avenida Prof. Gama Pinto 2, P-1649-003 Lisboa (Portugal); Arias, J. M.; Moro, A. M. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Sevilla, Apartado 1065, E-41080 Sevilla (Spain); Gomez-Camacho, J. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Sevilla, Apartado 1065, E-41080 Sevilla (Spain); Centro Nacional de Aceleradores, Avenida Thomas A. Edison, E-41092 Sevilla (Spain); Thompson, I. J. [Lawrence Livermore National Laboratory, Physical Science Directorate, P. O. Box 808, L-414, Livermore, California 94551 (United States); Tostevin, J. A. [Department of Physics, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

2009-11-15T23:59:59.000Z

139

The Continuum and Dynamics of Northern Hemisphere Teleconnection Patterns  

Science Conference Proceedings (OSTI)

This study presents an alternative interpretation for Northern Hemisphere teleconnection patterns. Rather than comprising several different recurrent regimes, this study suggests that there is a continuum of teleconnection patterns. This ...

Christian Franzke; Steven B. Feldstein

2005-09-01T23:59:59.000Z

140

Distributed Hydrologic Modeling in Northwest Mexico Reveals the Links between Runoff Mechanisms and Evapotranspiration  

Science Conference Proceedings (OSTI)

A distributed hydrologic model is used to evaluate how runoff mechanisms—including infiltration excess (RI), saturation excess (RS), and groundwater exfiltration (RG)—influence the generation of streamflow and evapotranspiration (ET) in a ...

Agustín Robles-Morua; Enrique R. Vivoni; Alex S. Mayer

2012-06-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Impact of an Updated Carbon Bond Mechanism on Predictions from the CMAQ Modeling System: Preliminary Assessment  

Science Conference Proceedings (OSTI)

An updated and expanded version of the Carbon Bond mechanism (CB05) has been incorporated into the Community Multiscale Air Quality (CMAQ) modeling system to more accurately simulate wintertime, pristine, and high-altitude situations. The CB05 ...

Golam Sarwar; Deborah Luecken; Greg Yarwood; Gary Z. Whitten; William P. L. Carter

2008-01-01T23:59:59.000Z

142

Investigating the Mechanisms of Diurnal Rainfall Variability Using a Regional Climate Model  

Science Conference Proceedings (OSTI)

This study investigates the ability of a regional climate model (RCM) to simulate the diurnal cycle of precipitation over southeast Australia, to provide a basis for understanding the mechanisms that drive diurnal variability. When compared with ...

Jason P. Evans; Seth Westra

2012-10-01T23:59:59.000Z

143

On a scale invariant model of statistical mechanics and the kinetic theory of ideal gas  

Science Conference Proceedings (OSTI)

A scale invariant model of statistical mechanics is applied to derive invariant Maxwell-Boltzmann speed and Planck energy spectrum of equilibrium statistical fields including that of isotropic stationary turbulence. The latter is shown to lead to the ... Keywords: Riemann hypothesis, TOE, kinetic theory of ideal gas, statistical mechanics, thermodynamics

Siavash H. Sohrab

2011-04-01T23:59:59.000Z

144

On-line regression algorithms for learning mechanical models of robots: A survey  

Science Conference Proceedings (OSTI)

With the emergence of more challenging contexts for robotics, the mechanical design of robots is becoming more and more complex. Moreover, their missions often involve unforeseen physical interactions with the environment. To deal with these difficulties, ... Keywords: Adaptive and learning systems, Adaptive control, Mechanical models

Olivier Sigaud; Camille Salaün; Vincent Padois

2011-12-01T23:59:59.000Z

145

Determination of Electrochemical Performance and Thermo-Mechanical-Chemical Stability of SOFCs from Defect Modeling  

DOE Green Energy (OSTI)

This research was focused on two distinct but related issues. The first issue concerned using defect modeling to understand the relationship between point defect concentration and the electrochemical, thermo-chemical and mechano-chemical properties of typical solid oxide fuel cell (SOFC) materials. The second concerned developing relationships between the microstructural features of SOFC materials and their electrochemical performance. To understand the role point defects play in ceramics, a coherent analytical framework was used to develop expressions for the dependence of thermal expansion and elastic modulus on point defect concentration in ceramics. These models, collectively termed the continuum-level electrochemical model (CLEM), were validated through fits to experimental data from electrical conductivity, I-V characteristics, elastic modulus and thermo-chemical expansion experiments for (nominally pure) ceria, gadolinia-doped ceria (GDC) and yttria-stabilized zirconia (YSZ) with consistently good fits. The same values for the material constants were used in all of the fits, further validating our approach. As predicted by the continuum-level electrochemical model, the results reveal that the concentration of defects has a significant effect on the physical properties of ceramic materials and related devices. Specifically, for pure ceria and GDC, the elastic modulus decreased while the chemical expansion increased considerably in low partial pressures of oxygen. Conversely, the physical properties of YSZ remained insensitive to changes in oxygen partial pressure within the studied range. Again, the findings concurred exactly with the predictions of our analytical model. Indeed, further analysis of the results suggests that an increase in the point defect content weakens the attractive forces between atoms in fluorite-structured oxides. The reduction treatment effects on the flexural strength and the fracture toughness of pure ceria were also evaluated at room temperature. The results reveal that the flexural strength decreases significantly after heat treatment in very low oxygen partial pressure environments; however, in contrast, fracture toughness is increased by 30-40% when the oxygen partial pressure was decreased to 10{sup -20} to 10{sup -22} atm range. Fractographic studies show that microcracks developed at 800 oC upon hydrogen reduction are responsible for the decreased strength. To understand the role of microstructure on electrochemical performance, electrical impedance spectra from symmetric LSM/YSZ/LSM cells was de-convoluted to obtain the key electrochemical components of electrode performance, namely charge transfer resistance, surface diffusion of reactive species and bulk gas diffusion through the electrode pores. These properties were then related to microstructural features, such as triple-phase boundary length and tortuosity. From these experiments we found that the impedance due to oxygen adsorption obeys a power law with pore surface area, while the impedance due to charge transfer is found to obey a power-law with respect to triple phase boundary length. A model based on kinetic theory explaining the power-law relationships observed was then developed. Finally, during our EIS work on the symmetric LSM/YSZ/LSM cells a technique was developed to improve the quality of high-frequency impedance data and their subsequent de-convolution.

Eric Wachsman; Keith L. Duncan

2006-09-30T23:59:59.000Z

146

Continuum Thermodynamics of the SU(N) Gauge Theory  

E-Print Network (OSTI)

The thermodynamics of the deconfined phase of the SU(N) gauge theory is studied. Careful study is made of the approach to the continuum limit. The latent heat of the deconfinement transition is studied, for the theories with 3, 4 and 6 colors. Continuum estimates of various thermodynamic quantities are studied, and the approach to conformality investigated. The bulk thermodynamic quantities at different N are compared, to investigate the validity of 't Hooft scaling at these values of N.

Saumen Datta; Sourendu Gupta

2010-12-30T23:59:59.000Z

147

Thermodynamic modeling of transcription: sensitivity analysis differentiates biological mechanism from mathematical model-induced effects  

E-Print Network (OSTI)

as: Dresch et al. : Thermodynamic modeling of transcription:ARTICLE Open Access Thermodynamic modeling of transcription:on the analysis of thermodynamic models, which have been

Dresch, Jacqueline M; Liu, Xiaozhou; Arnosti, David N; Ay, Ahmet

2010-01-01T23:59:59.000Z

148

What Are the Sources of Mechanical Damping in Matsuno–Gill-Type Models?  

Science Conference Proceedings (OSTI)

The Matsuno–Gill model has been widely used to study the tropical large-scale circulations and atmosphere–ocean interactions. However, a common critique of this model is that it requires a strong equivalent linear mechanical damping to get ...

Jia-Lin Lin; Brian E. Mapes; Weiqing Han

2008-01-01T23:59:59.000Z

149

Numerical modeling of electrochemical-mechanical interactions in lithium polymer batteries  

Science Conference Proceedings (OSTI)

This paper presents a multi-scale finite element approach for lithium batteries to study electrochemical-mechanical interaction phenomena at macro- and micro-scales. The battery model consists of a lithium foil anode, a separator, and a porous cathode ... Keywords: Finite element method, Homogenization, Multi-scale modeling, Porous electrode theory

Stephanie Golmon; Kurt Maute; Martin L. Dunn

2009-12-01T23:59:59.000Z

150

Development of a model to calculate mechanical specific energy for air hammer drilling systems  

E-Print Network (OSTI)

Drilling for hydrocarbons is an expensive operation; consequently operators try to save costs by reducing the number of days spent during this operation. Drilling efficiently with the highest attainable rate of penetration is one of the ways drilling time could be reduced. Real-time monitoring of Mechanical Specific Energy will enable drilling engineers to detect when the optimum drilling rate for a given set of drilling parameters is not being achieved. Numerous works have been done on air hammers and rock Mechanical Specific Energy. Previous research has shown that Mechanical Specific Energy, which is a ratio that quantifies the input energy and Rate of Penetration (ROP) of a drilling system, is directly proportional to the rock compressive strength being drilled. The Mechanical Specific Energy model utilizes drilling parameters such as ROP, Weight on bit (WOB), RPM, torque, flow-rate, bottom-hole pressure, and bottom-hole temperature to show how effectively energy being put into the drill string is being converted to ROP at the bit. This research effort proposes a new model to calculate the Mechanical Specific Energy for air hammer drilling systems. A thermodynamic model for the air hammer from which the piston impact velocity and kinetic energy is obtained is presented. To be able to estimate the effective energy delivered to the rock by the hammer, the stress wave propagation model is used and factored into the Mechanical Specific Energy model. The Mechanical Specific Energy values obtained from the application of this model provide a qualitative indicator of formation pressure changes and a means for drilling engineers to detect when optimum drilling rate is not being achieved. It can be deduced from the model that the impact energy of the hammer is greatly affected by the pressure drop across the hammer and since the hammer accounts for about sixty percent of the energy required for destroying the rock, the ROP can be varied by varying the pressure drop across the hammer.

Okuchaba, Boma Jeremiah

2008-05-01T23:59:59.000Z

151

How to Fit simply Soil Mechanics Behaviour with Incremental Modelling and to Describe Drained Cyclic Behaviours  

E-Print Network (OSTI)

It has been proposed recently a new incremental modelling to describe the mechanics of soil. It is based on two parameters called the pseudo Young modulus E=1/Co and the pseudo Poisson coefficient n, which both evolve during compression. Evolution of n is known since it shall fit the Rowe's law of dilatancy, but Co has to be evaluated from experiment. In this paper we proposed a way to evaluate the Co variation from other mechanical modelling. The way cyclic behaviour of drained sample can be modelled is also described.

P. Evesque

2005-07-04T23:59:59.000Z

152

Continuum Scale Simulation of Engineering Materials: Fundamentals  

Science Conference Proceedings (OSTI)

Feb 8, 2007 ... This book describes a wide variety of materials modeling methods at the microstructure level and above. CITATION: Raabe, D. (Editor), Roters, ...

153

Assessment of RANS-based turbulent combustion models for prediction of gas turbine emissions: turbulence model and reaction mechanism effects  

DOE Green Energy (OSTI)

The goal of this study is to assess current, commonly applied turbulence and combustion models with respect to their performance in gas-turbine combustion (GTC). Reynolds Averaged Navier-Stokes (RANS)-based turbulence and chemistry models are two primary factors influencing the uncertainty in predicting turbulent combustion characteristics, especially for GTC. RANS-based methods are the design tools of choice in the gas turbine industry due to the high computational costs of LES (Large Eddy Simulation). In this study, lean premixed combustion of methane was simulated using two different reduced mechanisms (ARM9 and ARM19) along with the Eddy Dissipation Concept (EDC) turbulent chemistry interaction model to calculate the CO and NOx emissions. The effect of turbulence models was assessed by considering two different models. Both of the models tested performed well in the prediction of temperature and major species profiles. Predicted values of NO emission profiles showed an average difference of ±5 ppm compared to experimental values. Computed intermediate species profiles showed large qualitative and quantitative errors when compared with the experimental data. These discrepancies, especially the intermediate species hydrogen, indicate the challenges these reduced mechanisms and turbulence models can present when modeling pollutant emissions from gas turbine combustors.

Nanduri, J.R.; Celik, I.B.; Strakey, P.A.; Parsons, D.R.

2007-10-01T23:59:59.000Z

154

Statistical Mechanics of Image Restoration by the Plane Rotator Model Yo^hei SAIKA and Hidetoshi NISHIMORI1  

E-Print Network (OSTI)

Statistical Mechanics of Image Restoration by the Plane Rotator Model Yo^hei SAIKA and Hidetoshi) On the basis of statistical mechanics formulation for problems of image restoration and error- correcting codes image is faster than that by the Ising model at low temperature. KEYWORDS: statistical mechanics, image

Nishimori, Hidetoshi

155

Multi-scale Modelling Applied to Non Linear Constitutive Equations  

Science Conference Proceedings (OSTI)

A Continuum General Noise Brownian Thermostat with Applications to Film Morphology · A Multiscale, Nonlinear, Modeling Framework Enabling the Design and ...

156

The Application of Bayesian Neural Network Data Modeling to Study ...  

Science Conference Proceedings (OSTI)

A Continuum General Noise Brownian Thermostat with Applications to Film Morphology · A Multiscale, Nonlinear, Modeling Framework Enabling the Design and ...

157

Multi-Scale Modeling to Predict Properties of Thermoplastic ...  

Science Conference Proceedings (OSTI)

A Continuum General Noise Brownian Thermostat with Applications to Film Morphology · A Multiscale, Nonlinear, Modeling Framework Enabling the Design and ...

158

Tools, Models, Databases and Simulation Tools Developed and ...  

Science Conference Proceedings (OSTI)

A Continuum General Noise Brownian Thermostat with Applications to Film Morphology · A Multiscale, Nonlinear, Modeling Framework Enabling the Design and ...

159

A model for DNA helicase mechanism based on a flashing ratchet  

E-Print Network (OSTI)

Helicases are molecular motors that consume energy supplied by chemical reactions to unwind double-stranded nucleic acids (like DNA and RNA) and to translocate along one of the single-strands. Motivated by the recent claims, based on experimental observations on the helicase NS3 of hepatitis C virus (HCV), that monomeric helicases are governed by a Brownian ratchet mechanism, here we develope a quantitative model. Our Brownian ratchet model, which is a somewhat new reformulation of the Betterton-J\\"ulicher theory of helicases, is generic two-state model and is applicable to all helicases which follow the Brownian ratchet mechanism. We illustrate the predictive power of the model by calculating some experimentally testable motor properties of a few monomeric helicases. Speficically, we predict the speed of unwinding of the double-stranded DNA and fluctuations around the average drift of the helicase. Our predictions are in excellent quantitative agreement with the corresponding experimental data.

Garai, Ashok; Chowdhury, Debashish

2007-01-01T23:59:59.000Z

160

Spectrum of Solar Type I Continuum Noise Storm in the 50- 80 MHz band, and Plasma characteristics in the associated source region  

E-Print Network (OSTI)

Continuum observations of a solar noise storm in the frequency range of 50-80 MHz observed with the Gauribidanur radio spectrograph during 2000 September, 26 & 27, are presented here. The radio spectral index of the noise storm continuum in the band 50- 80 MHz is found to be ? 3.65 during the above period. The Noise Storm continuum radiation is explained as a consequence of the non-thermal, plasma emission mechanism. The beam-density of suprathermal electrons is estimated for the coronal plasma near the source region of storm radiation. Supplementary evidence for the density-estimate is provided by way of analysing the imaging data from the SXT on-board the Yohkoh spacecraft, and the LASCO, MDI, and EIT on board the SoHO spacecraft. Subject headings: Sun: radio radiation — radiation mechanisms: non-thermal —

G. A. Shanmugha Sundaram; K. R. Subramanian

2004-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Analysis and Application of Sheppard’s Airflow Model to Predict Mechanical Orographic Lifting and the Occurrence of Mountain Clouds  

Science Conference Proceedings (OSTI)

Mechanically driven orographic lifting is important for air pollution dispersion and weather prediction, but the small dimensions of mountain peaks often prevent numerical weather models from producing detailed forecasts. Mechanical lifting in ...

Jan Kleissl; Richard E. Honrath; Diamantino V. Henriques

2006-10-01T23:59:59.000Z

162

A thermo-mechanically coupled theory for large deformations of amorphous polymers. Part I: Formulation  

E-Print Network (OSTI)

In this Part I, of a two-part paper, we present a detailed continuum-mechanical development of a thermomechanically

Anand, Lallit

163

Comparison of problem model change mechanisms issued from CSP and TRIZ  

E-Print Network (OSTI)

1 Comparison of problem model change mechanisms issued from CSP and TRIZ RRoollaanndd DDee GGuuiioo satisfaction problem (CSP), on the other hand. Keywords: over-constrained problems, dialectical methods issued from CSP and TRIZ 2 · a set of evaluation parameters, which represent the objective of the problem

Paris-Sud XI, Université de

164

Mechanics of complex bodies: commentary on the unified modelling of material substructures  

E-Print Network (OSTI)

Basic issues of the general model-building framework of the mechanics of complex bodies are discussed. Attention is focused on the representation of the material elements, the conditions for the existence of ground states in conservative setting and the interpretation of the nature of the various balance laws occurring.

Paolo Maria Mariano

2008-03-26T23:59:59.000Z

165

Topology design of two-dimensional continuum structures using isolines  

Science Conference Proceedings (OSTI)

This paper presents the algorithm for the topological design of two-dimensional structures using isolines called isolines topology design (ITD). The topology and the shape of the design depend on an iterative algorithm, which continually adds and removes ... Keywords: 2D continuum, Evolutionary algorithm, Fixed grid, Isolines, Topology design, Topology optimisation

Mariano Victoria; Pascual Martí; Osvaldo M. Querin

2009-01-01T23:59:59.000Z

166

CONTINUUM WAVEFUNCTION SOLVER FOR W.F. PERGER  

E-Print Network (OSTI)

vectorised? No No. of lines in distributed program, including test data, etc.: 4856 CPC Program LibraryCONTINUUM WAVEFUNCTION SOLVER FOR GRASP W.F. PERGER , Z. HALABUKA , AND D. TRAUTMANN Electrical. The spacing of the radial grid at large radial distances is automatically determined to provide at least 10

Perger, Warren F.

167

Numerical Classical and Quantum Mechanical simulations of Charge Density wave models  

E-Print Network (OSTI)

We first present how to do a computer simulation of Charge Density Waves using a driven harmonic oscillator model by a numerical scheme as initially formulated by Littlewood, and then afterwards use this to present how the dielectric model as presented by this proceedure leads to a blow up at the initialization of a threshold field ET. We find that this is highly unphysical and this initiated our inquiry as to alternative models. Afterwards, we then investigate hwo to present this transport problem of CDW quantum mechanically, threough a numerical simulation of the massive Schwinger model. We find that this single chaing quantum mechanical simulation uwed to formulate solutions to CDW transport in itself is insufficient for transport of solitons(anti-solitons) through a pinning gap model of CDW. We show that a model Hamiltonian with Peierls condensation energy used to couple adjacent chains (or transverse wave vectors) permits formation of solitons (anti- solitons) which can be used to transport CDW through a potential barrier. This addition of the Peierls condensation energy term is essential for any quantum model of Charge Density Waves to give tunneling behavior as seen via a numerical simulation.

A. W. Beckwith

2004-09-13T23:59:59.000Z

168

Fluid Dynamics and Solid Mechanics, T-3: Theoretical, T: LANL Inside  

NLE Websites -- All DOE Office Websites (Extended Search)

Leader Leader Mark Schraad Deputy Group Leader Marianne Francois Administration Crystal Martinez Beverly Corrales Office Location MS B216 TA-3, Bldg 200, Rm 215 Fluid Dynamics and Solid Mechanics, T-3 Conducts basic and applied research in theoretical continuum dynamics, modern hydrodynamic theory, materials modeling, global climate modeling, numerical algorithm development, and large-scale computational simulations. There is an emphasis on developing advanced numerical methods for continuum dynamics at all flow velocities and strain rates, and coupling these methods to constitutive models for solid material response and other physical processes such as turbulence, chemical reactions, combustion, phase change, heat and mass transfer, and plasma behavior. The Fluid Dynamics Group's portfolio of research activities represents fundamental

169

THE DETONATION MECHANISM OF THE PULSATIONALLY ASSISTED GRAVITATIONALLY CONFINED DETONATION MODEL OF Type Ia SUPERNOVAE  

Science Conference Proceedings (OSTI)

We describe the detonation mechanism composing the 'pulsationally assisted' gravitationally confined detonation (GCD) model of Type Ia supernovae. This model is analogous to the previous GCD model reported in Jordan et al.; however, the chosen initial conditions produce a substantively different detonation mechanism, resulting from a larger energy release during the deflagration phase. The resulting final kinetic energy and {sup 56}Ni yields conform better to observational values than is the case for the 'classical' GCD models. In the present class of models, the ignition of a deflagration phase leads to a rising, burning plume of ash. The ash breaks out of the surface of the white dwarf, flows laterally around the star, and converges on the collision region at the antipodal point from where it broke out. The amount of energy released during the deflagration phase is enough to cause the star to rapidly expand, so that when the ash reaches the antipodal point, the surface density is too low to initiate a detonation. Instead, as the ash flows into the collision region (while mixing with surface fuel), the star reaches its maximally expanded state and then contracts. The stellar contraction acts to increase the density of the star, including the density in the collision region. This both raises the temperature and density of the fuel-ash mixture in the collision region and ultimately leads to thermodynamic conditions that are necessary for the Zel'dovich gradient mechanism to produce a detonation. We demonstrate feasibility of this scenario with three three-dimensional (3D), full star simulations of this model using the FLASH code. We characterized the simulations by the energy released during the deflagration phase, which ranged from 38% to 78% of the white dwarf's binding energy. We show that the necessary conditions for detonation are achieved in all three of the models.

Jordan, G. C. IV; Graziani, C.; Weide, K.; Norris, J.; Hudson, R.; Lamb, D. Q. [Flash Center for Computational Science, University of Chicago, Chicago, IL 60637 (United States); Fisher, R. T. [Department of Physics, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02740 (United States); Townsley, D. M. [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States); Meakin, C. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Reid, L. B. [NTEC Environmental Technology, Subiaco WA 6008 (Australia)

2012-11-01T23:59:59.000Z

170

Statistical-mechanical lattice models for protein-DNA binding in chromatin  

E-Print Network (OSTI)

Statistical-mechanical lattice models for protein-DNA binding are well established as a method to describe complex ligand binding equilibriums measured in vitro with purified DNA and protein components. Recently, a new field of applications has opened up for this approach since it has become possible to experimentally quantify genome-wide protein occupancies in relation to the DNA sequence. In particular, the organization of the eukaryotic genome by histone proteins into a nucleoprotein complex termed chromatin has been recognized as a key parameter that controls the access of transcription factors to the DNA sequence. New approaches have to be developed to derive statistical mechanical lattice descriptions of chromatin-associated protein-DNA interactions. Here, we present the theoretical framework for lattice models of histone-DNA interactions in chromatin and investigate the (competitive) DNA binding of other chromosomal proteins and transcription factors. The results have a number of applications for quant...

Teif, Vladimir B

2010-01-01T23:59:59.000Z

171

Radiometric Modeling of Mechanical Draft Cooling Towers to Assist in the Extraction of their Absolute Temperature from  

E-Print Network (OSTI)

Radiometric Modeling of Mechanical Draft Cooling Towers to Assist in the Extraction108, Aiken, SC, USA ABSTRACT Determining the internal temperature of a mechanical draft cooling tower is to estimate the temperature of the air exiting a mechanical draft cooling tower (MDCT) through the use

Salvaggio, Carl

172

Multi-level assembly model for top-down design of mechanical products  

Science Conference Proceedings (OSTI)

To enable next generation CAD tools to effectively support top-down design of products, a top-down assembly design process is refined from the traditional product design process to better exhibit the recursive-execution and structure-evolvement characteristics ... Keywords: Inheritance mechanism, Layout skeleton, Multi-level assembly model, Shape skeleton, Skeleton feature, Skeleton interface, Top-down assembly design, Top-down component design

Xiang Chen; Shuming Gao; Youdong Yang; Shuting Zhang

2012-10-01T23:59:59.000Z

173

A numerical model of hydro-thermo-mechanical coupling in a fractured rock mass  

DOE Green Energy (OSTI)

Coupled hydro-thermo-mechanical codes with the ability to model fractured materials are used for predicting groundwater flow behavior in fractured aquifers containing thermal sources. The potential applications of such a code include the analysis of groundwater behavior within a geothermal reservoir. The capability of modeling hydro-thermo systems with a dual porosity, fracture flow model has been previously developed in the finite element code, FEHM. FEHM has been modified to include stress coupling with the dual porosity feature. FEHM has been further developed to implicitly couple the dependence of fracture hydraulic conductivity on effective stress within two dimensional, saturated aquifers containing fracture systems. The cubic law for flow between parallel plates was used to model fracture permeability. The Bartin-Bandis relationship was used to determine the fracture aperture within the cubic law. The code used a Newton Raphson iteration to implicitly solve for six unknowns at each node. Results from a model of heat flow from a reservoir to the moving fluid in a single fracture compared well with analytic results. Results of a model showing the increase in fracture flow due to a single fracture opening under fluid pressure compared well with analytic results. A hot dry rock, geothermal reservoir was modeled with realistic time steps indicating that the modified FEHM code does successfully model coupled flow problems with no convergence problems.

Bower, K.M.

1996-06-01T23:59:59.000Z

174

Exploring continuum structures with a pseudo-state basis  

SciTech Connect

The ability of a recently developed square-integrable discrete basis to represent the properties of the continuum of a two-body system is investigated. The basis is obtained performing a simple analytic local scale transformation to the harmonic oscillator basis. Scattering phase-shifts and the electric transition probabilities B(E1) and B(E2) have been evaluated for several potentials using the proposed basis. Both quantities are found to be in excellent agreement with the exact values calculated from the true scattering states. The basis has been applied to describe the projectile continuum in the {sup 6}He scattering by {sup 12}C and {sup 208}Pb targets at 240 MeV/nucleon and the {sup 11}Be scattering by {sup 12}C at 67 MeV/nucleon. The calculated breakup differential cross sections are found to be in very good agreement with the available experimental data for these reactions.

Lay, J. A.; Moro, A. M.; Arias, J. M.; Gomez-Camacho, J. [Departamento de FAMN, Facultad de Fisica, Universidad de Sevilla, Apdo. 1065, E-41080 Sevilla (Spain); Departamento de FAMN, Facultad de Fisica, Universidad de Sevilla, Apdo. 1065, E-41080 Sevilla, Spain and Centro Nacional de Aceleradores, Avda. Thomas A. Edison, E-41092, Sevilla (Spain)

2010-08-15T23:59:59.000Z

175

Electron-pair excitations and the molecular Coulomb continuum  

DOE Green Energy (OSTI)

Electron-pair excitations in the molecular hydrogen continuum are described by quantizing rotations of the momentum plane of the electron pair about by the pair's relative momentum. A helium-like description of the molecular pi.Joto double ionization is thus extended to higher angular momenta of the electron pair. A simple three-state superposition is found to account surprisingly well for recent observations of noncoplanar electron-pair, molecular-axis angular distributions.

Colgan, James [Los Alamos National Laboratory

2009-01-01T23:59:59.000Z

176

NREL Leads Energy Systems Integration, Continuum Magazine: Issue 4 (Book)  

SciTech Connect

Continuum Magazine showcases NREL's latest and most impactful clean energy innovations. This issue, 'NREL Leads Energy Systems Integration' explores the discipline of energy systems integration, in particular the role of the laboratory's new, one-of-a-kind Energy System Integration Facility. NREL scientists, engineers, and analysts deeply understand the fundamental science and technologies underpinning major energy producing and consuming systems, as well as the transmission infrastructure and communications and data networks required to integrate energy systems at all scales.

Not Available

2013-04-01T23:59:59.000Z

177

Spectrum of Solar Type I Continuum Noise Storm in the 50 - 80 MHz band, and Plasma characteristics in the associated source region  

E-Print Network (OSTI)

Continuum observations of a solar noise storm in the frequency range of 50 - 80 MHz observed with the Gauribidanur radio spectrograph during 2000 September, 26 & 27, are presented here. The radio spectral index of the noise storm continuum in the band 50 - 80 MHz is found to be ~3.65 during the above period. The Noise Storm continuum radiation is explained as a consequence of the non-thermal, plasma emission mechanism. The beam-density of suprathermal electrons is estimated for the coronal plasma near the source region of storm radiation. Supplementary evidence for the density-estimate is provided by way of analysing the imaging data from the SXT on-board the Yohkoh spacecraft, and the LASCO, MDI, and EIT on board the SoHO spacecraft.

G. A. Shanmugha Sundaram; K. R. Subramanian

2004-01-20T23:59:59.000Z

178

Spectrum of Solar Type I Continuum Noise Storm in the 50 - 80 MHz band, and Plasma characteristics in the associated source region  

E-Print Network (OSTI)

Continuum observations of a solar noise storm in the frequency range of 50 - 80 MHz observed with the Gauribidanur radio spectrograph during 2000 September, 26 & 27, are presented here. The radio spectral index of the noise storm continuum in the band 50 - 80 MHz is found to be ~3.65 during the above period. The Noise Storm continuum radiation is explained as a consequence of the non-thermal, plasma emission mechanism. The beam-density of suprathermal electrons is estimated for the coronal plasma near the source region of storm radiation. Supplementary evidence for the density-estimate is provided by way of analysing the imaging data from the SXT on-board the Yohkoh spacecraft, and the LASCO, MDI, and EIT on board the SoHO spacecraft.

Sundaram, G A S

2004-01-01T23:59:59.000Z

179

Model development and calibration for the coupled thermal, hydraulic and mechanical phenomena of the bentonite  

E-Print Network (OSTI)

FOR THE COUPLED THERMAL, HYDRAULIC AND MECHANICAL PHENOMENAby the interdependence of thermal, hydraulic and mechanical

Hernelind, J.

2009-01-01T23:59:59.000Z

180

MECHANICS OF SOLIDS [published as a section of the article on MECHANICS in the 1993 printing of the  

E-Print Network (OSTI)

MECHANICS OF SOLIDS [published as a section of the article on MECHANICS in the 1993 printing INTRODUCTION The application of the principles of mechanics to bulk matter is conventionally divided into the mechanics of fluids and the mechanics of solids. The entire subject is often called continuum mechanics

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Physics and modeling of thermal flow and soil mechanics in unconsolidated porous media  

SciTech Connect

This paper describes a new formulation of nonlinear soil mechanics and multiphase thermal flow. The nonlinearites of the soil behavior and their interactions with fluid flow causing shear failure of the soil are the dominant features of the process. The numerical formulation of the coupled flow/stress solution model includes nonlinear compressibility and flow properties as functions of pressure, stress, and temperature; nonlinear, incremental, thermal poroelastic stress analysis; and shear or tensile failure and its effects on transport properties, porosity, and stress. An efficient sequential numerical scheme was developed. It is mass conservative and applicable to external coupling of existing simulators. The 1D examples show some startling new features of reservoir mechanics in unconsolidated media.

Settari, A. (Simtech Consulting Services Ltd. (US))

1992-02-01T23:59:59.000Z

182

Contact Mechanics Modeling of Homogeneous and Layered Elastic-Plastic Media: Surface Roughness and Adhesion Effects  

E-Print Network (OSTI)

H. , 2003. Fracture mechanics analysis of thin coatingsK.L. , 1985. Contact Mechanics, Cambridge University Press,J. , Chaboche, J. L. , 1994. Mechanics of Solid Materials.

Song, Zhichao

2012-01-01T23:59:59.000Z

183

CONTINUUM HALOS IN NEARBY GALAXIES: AN EVLA SURVEY (CHANG-ES). I. INTRODUCTION TO THE SURVEY  

SciTech Connect

We introduce a new survey to map the radio continuum halos of a sample of 35 edge-on spiral galaxies at 1.5 GHz and 6 GHz in all polarization products. The survey is exploiting the new wide bandwidth capabilities of the Karl G. Jansky Very Large Array (i.e., the Expanded Very Large Array) in a variety of array configurations (B, C, and D) in order to compile the most comprehensive data set yet obtained for the study of radio halo properties. This is the first survey of radio halos to include all polarization products. In this first paper, we outline the scientific motivation of the survey, the specific science goals, and the expected improvements in noise levels and spatial coverage from the survey. Our goals include investigating the physical conditions and origin of halos, characterizing cosmic-ray transport and wind speed, measuring Faraday rotation and mapping the magnetic field, probing the in-disk and extraplanar far-infrared-radio continuum relation, and reconciling non-thermal radio emission with high-energy gamma-ray models. The sample size allows us to search for correlations between radio halos and other properties, including environment, star formation rate, and the presence of active galactic nuclei. In a companion paper (Paper II) we outline the data reduction steps and present the first results of the survey for the galaxy, NGC 4631.

Irwin, Judith; Henriksen, Richard N. [Department of Physics, Engineering Physics and Astronomy, Queen's University, Kingston, ON K7L 3N6 (Canada); Beck, Rainer; Krause, Marita; Mora, Silvia Carolina; Schmidt, Philip [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Benjamin, R. A. [Department of Physics, University of Wisconsin at Whitewater, 800 West Main Street, Whitewater, WI 53190 (United States); Dettmar, Ralf-Juergen; Miskolczi, Arpad [Astronomisches Institut, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); English, Jayanne [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Heald, George; Oosterloo, Tom [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands); Johnson, Megan [National Radio Astronomy Observatory, P.O. Box 2, Greenbank, WV 24944 (United States); Li, Jiang-Tao [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Murphy, E. J. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Porter, Troy A. [Hansen Experimental Physics Laboratory, Stanford University, 452 Lomita Mall, Stanford, CA 94305 (United States); Rand, Richard J. [Department of Physics and Astronomy, University of New Mexico, 800 Yale Boulevard, NE, Albuquerque, NM 87131 (United States); Saikia, D. J. [National Centre for Radio Astrophysics, TIFR, Pune University Campus, Post Bag 3, Pune 411 007 (India); Strong, A. W. [Max-Planck-Institut fuer extraterrestrische Physik, Garching bei Muenchen (Germany); Walterbos, Rene, E-mail: irwin@astro.queensu.ca, E-mail: henriksn@astro.queensu.ca, E-mail: twiegert@astro.queensu.ca, E-mail: rbeck@mpifr-bonn.mpg.de, E-mail: mkrause@mpifr-bonn.mpg.de, E-mail: cmora@mpifr-bonn.mpg.de [Department of Astronomy, New Mexico State University, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003 (United States); and others

2012-08-15T23:59:59.000Z

184

Hydrodynamic slip boundary condition at chemically patterned surfaces: A continuum deduction from molecular dynamics  

E-Print Network (OSTI)

We investigate the slip boundary condition for single-phase flow past a chemically patterned surface. Molecular dynamics (MD) simulations show that modulation of fluid-solid interaction along a chemically patterned surface induces a lateral structure in the fluid molecular organization near the surface. Consequently, various forces and stresses in the fluid vary along the patterned surface. Given the presence of these lateral variations, a general scheme is developed to extract hydrodynamic information from MD data. With the help of this scheme, the validity of the Navier slip boundary condition is verified for the chemically patterned surface, where a local slip length can be defined. Based on the MD results, a continuum hydrodynamic model is formulated using the Navier-Stokes equation and the Navier boundary condition, with a slip length varying along the patterned surface. Steady-state velocity fields from continuum calculations are in quantitative agreement with those from MD simulations. It is shown that, when the pattern period is sufficiently small, the solid surface appears to be homogeneous, with an effective slip length that can be controlled by surface patterning. Such a tunable slip length may have important applications in nanofluidics.

Tiezheng Qian; Xiao-Ping Wang; Ping Sheng

2005-02-26T23:59:59.000Z

185

3D Modeling of Coupled Rock Deformation and Thermo-Poro-Mechanical Processes in Fractures  

E-Print Network (OSTI)

Problems involving coupled thermo-poro-chemo-mechanical processes are of great importance in geothermal and petroleum reservoir systems. In particular, economic power production from enhanced geothermal systems, effective water-flooding of petroleum reservoirs, and stimulation of gas shale reservoirs are significantly influenced by coupled processes. During such procedures, stress state in the reservoir is changed due to variation in pore fluid pressure and temperature. This can cause deformation and failure of weak planes of the formation with creation of new fractures, which impacts reservoir response. Incorporation of geomechanical factor into engineering analyses using fully coupled geomechanics-reservoir flow modeling exhibits computational challenges and numerical difficulties. In this study, we develop and apply efficient numerical models to solve 3D injection/extraction geomechanics problems formulated within the framework of thermo-poro-mechanical theory with reactive flow. The models rely on combining Displacement Discontinuity (DD) Boundary Element Method (BEM) and Finite Element Method (FEM) to solve the governing equations of thermo-poro-mechanical processes involving fracture/reservoir matrix. The integration of BEM and FEM is accomplished through direct and iterative procedures. In each case, the numerical algorithms are tested against a series of analytical solutions. 3D study of fluid injection and extraction into the geothermal reservoir illustrates that thermo-poro-mechanical processes change fracture aperture (fracture conductivity) significantly and influence the fluid flow. Simulations that consider joint stiffness heterogeneity show development of non-uniform flow paths within the crack. Undersaturated fluid injection causes large silica mass dissolution and increases fracture aperture while supersaturated fluid causes mineral precipitation and closes fracture aperture. Results show that for common reservoir and injection conditions, the impact of fully developed thermoelastic effect on fracture aperture tend to be greater compare to that of poroelastic effect. Poroelastic study of hydraulic fracturing demonstrates that large pore pressure increase especially during multiple hydraulic fracture creation causes effective tensile stress at the fracture surface and shear failure around the main fracture. Finally, a hybrid BEFEM model is developed to analyze stress redistribution in the overburden and within the reservoir during fluid injection and production. Numerical results show that fluid injection leads to reservoir dilation and induces vertical deformation, particularly near the injection well. However, fluid withdrawal causes reservoir to compact. The Mandel-Cryer effect is also successfully captured in numerical simulations, i.e., pore pressure increase/decrease is non-monotonic with a short time values that are above/below the background pore pressure.

Rawal, Chakra

2012-05-01T23:59:59.000Z

186

Resonance--Continuum Interference in Light Higgs Boson Production at a Photon Collider  

SciTech Connect

We study the effect of interference between the Standard Model Higgs boson resonance and the continuum background in the process {gamma}{gamma} {yields} H {yields} b{bar b} at a photon collider. Taking into account virtual gluon exchange between the final-state quarks, we calculate the leading corrections to the height of the resonance for the case of a light (m{sub H} < 160 GeV) Higgs boson. We find that the interference is destructive and around 0.1-0.2% of the peak height, depending on the mass of the Higgs and the scattering angle. This suppression is smaller by an order of magnitude than the anticipated experimental accuracy at a photon collider. However, the fractional suppression can be significantly larger if the Higgs coupling to b quarks is increased by physics beyond the Standard Model.

Dixon, Lance J.; Sofianatos, Yorgos; /SLAC /Stanford U., Phys. Dept.

2009-01-06T23:59:59.000Z

187

Numerical Modeling of Hydraulic Fracture Propagation Using Thermo-hydro-mechanical Analysis with Brittle Damage Model by Finite Element Method  

E-Print Network (OSTI)

Better understanding and control of crack growth direction during hydraulic fracturing are essential for enhancing productivity of geothermal and petroleum reservoirs. Structural analysis of fracture propagation and impact on fluid flow is a challenging issue because of the complexity of rock properties and physical aspects of rock failure and fracture growth. Realistic interpretation of the complex interactions between rock deformation, fluid flow, heat transfer, and fracture propagation induced by fluid injection is important for fracture network design. In this work, numerical models are developed to simulate rock failure and hydraulic fracture propagation. The influences of rock deformation, fluid flow, and heat transfer on fracturing processes are studied using a coupled thermo-hydro-mechanical (THM) analysis. The models are used to simulate microscopic and macroscopic fracture behaviors of laboratory-scale uniaxial and triaxial experiments on rock using an elastic/brittle damage model considering a stochastic heterogeneity distribution. The constitutive modeling by the energy release rate-based damage evolution allows characterizing brittle rock failure and strength degradation. This approach is then used to simulate the sequential process of heterogeneous rock failures from the initiation of microcracks to the growth of macrocracks. The hydraulic fracturing path, especially for fractures emanating from inclined wellbores and closed natural fractures, often involves mixed mode fracture propagation. Especially, when the fracture is inclined in a 3D stress field, the propagation cannot be modeled using 2D fracture models. Hence, 2D/3D mixed-modes fracture growth from an initially embedded circular crack is studied using the damage mechanics approach implemented in a finite element method. As a practical problem, hydraulic fracturing stimulation often involves fluid pressure change caused by injected fracturing fluid, fluid leakoff, and fracture propagation with brittle rock behavior and stress heterogeneities. In this dissertation, hydraulic fracture propagation is simulated using a coupled fluid flow/diffusion and rock deformation analysis. Later THM analysis is also carried out. The hydraulic forces in extended fractures are solved using a lubrication equation. Using a new moving-boundary element partition methodology (EPM), fracture propagation through heterogeneous media is predicted simply and efficiently. The method allows coupling fluid flow and rock deformation, and fracture propagation using the lubrication equation to solve for the fluid pressure through newly propagating crack paths. Using the proposed model, the 2D/3D hydraulic fracturing simulations are performed to investigate the role of material and rock heterogeneity. Furthermore, in geothermal and petroleum reservoir design, engineers can take advantage of thermal fracturing that occurs when heat transfers between injected flow and the rock matrix to create reservoir permeability. These thermal stresses are calculated using coupled THM analysis and their influence on crack propagation during reservoir stimulation are investigated using damage mechanics and thermal loading algorithms for newly fractured surfaces.

Min, Kyoung

2013-08-01T23:59:59.000Z

188

Nano-mechanics of Tunable Adhesion using Non Covalent Forces  

SciTech Connect

The objective of this program was to examine, via experiment and atomistic and continuum analysis, coordinated noncovalent bonding over a range of length scales with a view to obtaining modulated, patterned and reversible bonding at the molecular level. The first step in this project was to develop processes for depositing self-assembled monolayers (SAMs) bearing carboxylic acid and amine moieties on Si (111) surfaces and probe tips of an interfacial force microscope (IFM). This allowed the adhesive portion of the interactions between functionalized surfaces to be fully captured in the force-displacement response (force profiles) that are measured by the IFM. The interactionswere extracted in the form of traction-separation laws using combined molecular and continuum stress analyses. In this approach, the results of molecular dynamics analyses of SAMs subjected to simple stress states are used to inform continuum models of their stress-strain behavior. Continuum analyses of the IFM experiment were then conducted, which incorporate the stress-strain behavior of the SAMs and traction-separation relations that represent the interactions between the tip and functionalized Si surface. Agreement between predicted and measured force profiles was taken to imply that the traction-separation relations have been properly extracted. Scale up to larger contact areas was considered by forming Si/SAM/Si sandwiches and then separating them via fracture experiments. The mode 1 traction-separation relations have been extracted using fracture mechanics concepts under mode 1 and mixed-mode conditions. Interesting differences were noted between the three sets of traction-separation relations.

Kenneth Liechti

2012-09-08T23:59:59.000Z

189

DNA folding: structural and mechanical properties of the two-angle model for chromatin  

E-Print Network (OSTI)

We present a theoretical analysis of the structural and mechanical properties of the 30-nm chromatin fiber. Our study is based on the two-angle model introduced by Woodcock et al. (Woodcock, C. L., S. A. Grigoryev, R. A. Horowitz, and N. Whitaker. 1993. PNAS 90:9021-9025) that describes the chromatin fiber geometry in terms of the entry-exit angle of the nucleosomal DNA and the rotational setting of the neighboring nucleosomes with respect to each other. We explore analytically the different structures that arise from this building principle, and demonstrate that the geometry with the highest density is close to the one found in native chromatin fibers under physiological conditions. On the basis of this model we calculate mechanical properties of the fiber under stretching. We obtain expressions for the stress-strain characteristics which show good agreement with the results of recent stretching experiments (Cui, Y., and C. Bustamante. 2000. PNAS 97:127-132) and computer simulations (Katritch, V., C. Bustamante, and W. K. Olson. 2000. J. Mol. Biol. 295:29-40), and which provide simple physical insights into correlations between the structural and elastic properties of chromatin.

H. Schiessel; W. M. Gelbart; R. Bruinsma

2001-02-07T23:59:59.000Z

190

Calculation of Solvation Free Energies of Charged Solutes Using Mixed Cluster/Continuum Vyacheslav S. Bryantsev, Mamadou S. Diallo,, and William A. Goddard III*,  

E-Print Network (OSTI)

Calculation of Solvation Free Energies of Charged Solutes Using Mixed Cluster/Continuum Models methodologies make systematic errors in the computed free energies because of the incorrect accounting consideration. We analyze two different thermodynamic cycles for calculating the solvation free energies

Goddard III, William A.

191

Spectral Evolution of the Continuum and Disc Line in Dipping in GRO J1655-40  

E-Print Network (OSTI)

The discovery is reported of emission features in the X-ray spectrum of GRO J1655-40 obtained using Rossi-XTE on 1997, Feb 26. The features have been fitted firstly by two Gaussian lines, which in four spectra have average energies of 5.85+/-0.08 keV and 7.32+/-0.13 keV, strongly suggestive that these are the red- and blueshifted wings of an iron disc line from material with velocity ~0.33 c. The blue wing is apparently less bright than expected for a disc line subject to Doppler boosting, however, known absorption in the spectrum of GRO J1655-40 at energies between ~7 and 8 keV can reduce the apparent brightness of the blue wing. The spectra have also been fitted well using the full relativistic disc line model of Laor, plus an absorption line. This gives a restframe energy between 6.4 and 6.8 keV indicating that the line is from highly ionized iron K_alpha. The Laor model also shows that the line originates at radii extending from ~10 Schwarzschild radii (r_S) outwards. The line is direct evidence for the black hole nature of the compact object. The continuum is well described by dominant disc blackbody emission plus Comptonized emission. During dipping, spectral evolution is well modelled by allowing progressive covering of the disc blackbody and simple absorption of the Comptonized emission showing that the thermal emission is more extended. Acceptable fits are only obtained by including the disc line in the covering term, indicating that it originates in the same inner disc region as the thermal continuum. Dip ingress times and durations are used to provide the radius of the disc blackbody emitter as 170-370 r_S, and the radius of the absorber.

M. Balucinska-Church

2001-01-22T23:59:59.000Z

192

On the Intrinsic Continuum Linear Polarization of Classical Be Stars during Disk Growth and Dissipation  

E-Print Network (OSTI)

We investigate the intrinsic continuum linear polarization from axisymmetric density distributions of gas surrounding classical Be stars during the formation and dissipation of their circumstellar disks. We implement a Monte Carlo calculation of the Stokes parameters with the use of the non-LTE radiative transfer code of Sigut & Jones (2007) to reproduce the continuous polarimetric spectra of classical Be stars. The scattering of light in the nonspherical circumstellar envelopes of classical Be stars produces a distinct polarization signature that can be used to study the physical nature of the scattering environment. In this paper, we highlight the utility of polarimetric measurements as important diagnostics in the modeling of these systems. We illustrate the effects of using self-consistent calculation of the thermal structure of the circumstellar gas on the characteristic wavelength-dependence of the polarization spectrum. In showing that the principal features of the polarization spectrum originate f...

Halonen, Robbie J

2013-01-01T23:59:59.000Z

193

ENHANCING THE ATOMIC-LEVEL UNDERSTANDING OF CO2 MINERAL SEQUESTRATION MECHANISMS VIA ADVANCED COMPUTATIONAL MODELING  

SciTech Connect

Fossil fuels currently provide 85% of the world's energy needs, with the majority coming from coal, due to its low cost, wide availability, and high energy content. The extensive use of coal-fired power assumes that the resulting CO{sub 2} emissions can be vented to the atmosphere. However, exponentially increasing atmospheric CO{sub 2} levels have brought this assumption under critical review. Over the last decade, this discussion has evolved from whether exponentially increasing anthropogenic CO{sub 2} emissions will adversely affect the global environment, to the timing and magnitude of their impact. A variety of sequestration technologies are being explored to mitigate CO{sub 2} emissions. These technologies must be both environmentally benign and economically viable. Mineral carbonation is an attractive candidate technology as it disposes of CO{sub 2} as geologically stable, environmentally benign mineral carbonates, clearly satisfying the first criteria. The primary challenge for mineral carbonation is cost-competitive process development. CO{sub 2} mineral sequestration--the conversion of stationary-source CO{sub 2} emissions into mineral carbonates (e.g., magnesium and calcium carbonate, MgCO{sub 3} and CaCO{sub 3})--has recently emerged as one of the most promising sequestration options, providing permanent CO{sub 2} disposal, rather than storage. In this approach a magnesium-bearing feedstock mineral (typically serpentine or olivine; available in vast quantities globally) is specially processed and allowed to react with CO{sub 2} under controlled conditions. This produces a mineral carbonate which (1) is environmentally benign, (2) already exists in nature in quantities far exceeding those that could result from carbonating the world's known fossil fuel reserves, and (3) is stable on a geological time scale. Minimizing the process cost via optimization of the reaction rate and degree of completion is the remaining challenge. As members of the DOE/NETL managed National Mineral Sequestration Working Group we have already significantly improved our understanding of mineral carbonation. Group members at the Albany Research Center have recently shown that carbonation of olivine and serpentine, which naturally occurs over geological time (i.e., 100,000s of years), can be accelerated to near completion in hours. Further process refinement will require a synergetic science/engineering approach that emphasizes simultaneous investigation of both thermodynamic processes and the detailed microscopic, atomic-level mechanisms that govern carbonation kinetics. Our previously funded Phase I Innovative Concepts project demonstrated the value of advanced quantum-mechanical modeling as a complementary tool in bridging important gaps in our understanding of the atomic/molecular structure and reaction mechanisms that govern CO{sub 2} mineral sequestration reaction processes for the model Mg-rich lamellar hydroxide feedstock material Mg(OH){sub 2}. In the present simulation project, improved techniques and more efficient computational schemes have allowed us to expand and augment these capabilities and explore more complex Mg-rich, lamellar hydroxide-based feedstock materials, including the serpentine-based minerals. These feedstock materials are being actively investigated due to their wide availability, and low-cost CO{sub 2} mineral sequestration potential. Cutting-edge first principles quantum chemical, computational solid-state and materials simulation methodology studies proposed herein, have been strategically integrated with our new DOE supported (ASU-Argonne National Laboratory) project to investigate the mechanisms that govern mineral feedstock heat-treatment and aqueous/fluid-phase serpentine mineral carbonation in situ. This unified, synergetic theoretical and experimental approach will provide a deeper understanding of the key reaction mechanisms than either individual approach can alone. Ab initio techniques will also significantly advance our understanding of atomic-level processes at the solid/solution interface by e

A.V.G. Chizmeshya

2003-12-19T23:59:59.000Z

194

ENHANCING THE ATOMIC-LEVEL UNDERSTANDING OF CO2 MINERAL SEQUESTRATION MECHANISMS VIA ADVANCED COMPUTATIONAL MODELING  

SciTech Connect

Fossil fuels currently provide 85% of the world's energy needs, with the majority coming from coal, due to its low cost, wide availability, and high energy content. The extensive use of coalfired power assumes that the resulting CO{sub 2} emissions can be vented to the atmosphere. However, exponentially increasing atmospheric CO{sub 2} levels have brought this assumption under critical review. Over the last decade, this discussion has evolved from whether exponentially increasing anthropogenic CO{sub 2} emissions will adversely affect the global environment, to the timing and magnitude of their impact. A variety of sequestration technologies are being explored to mitigate CO{sub 2} emissions. These technologies must be both environmentally benign and economically viable. Mineral carbonation is an attractive candidate technology as it disposes of CO{sub 2} as geologically stable, environmentally benign mineral carbonates, clearly satisfying the first criteria. The primary challenge for mineral carbonation is cost-competitive process development. CO{sub 2} mineral sequestration--the conversion of stationary-source CO{sub 2} emissions into mineral carbonates (e.g., magnesium and calcium carbonate, MgCO{sub 3} and CaCO{sub 3})--has recently emerged as one of the most promising sequestration options, providing permanent CO{sub 2} disposal, rather than storage. In this approach a magnesium-bearing feedstock mineral (typically serpentine or olivine; available in vast quantities globally) is specially processed and allowed to react with CO{sub 2} under controlled conditions. This produces a mineral carbonate which (i) is environmentally benign, (ii) already exists in nature in quantities far exceeding those that could result from carbonating the world's known fossil fuel reserves, and (iii) is stable on a geological time scale. Minimizing the process cost via optimization of the reaction rate and degree of completion is the remaining challenge. As members of the DOE/NETL managed National Mineral Sequestration Working Group we have already significantly improved our understanding of mineral carbonation. Group members at the Albany Research Center have recently shown that carbonation of olivine and serpentine, which naturally occurs over geological time (i.e., 100,000s of years), can be accelerated to near completion in hours. Further process refinement will require a synergetic science/engineering approach that emphasizes simultaneous investigation of both thermodynamic processes and the detailed microscopic, atomic-level mechanisms that govern carbonation kinetics. Our previously funded Phase I Innovative Concepts project demonstrated the value of advanced quantum-mechanical modeling as a complementary tool in bridging important gaps in our understanding of the atomic/molecular structure and reaction mechanisms that govern CO{sub 2} mineral sequestration reaction processes for the model Mg-rich lamellar hydroxide feedstock material Mg(OH){sub 2}. In the present simulation project, improved techniques and more efficient computational schemes have allowed us to expand and augment these capabilities and explore more complex Mg-rich, lamellar hydroxide-based feedstock materials, including the serpentine-based minerals. These feedstock materials are being actively investigated due to their wide availability, and low-cost CO{sub 2} mineral sequestration potential. Cutting-edge first principles quantum chemical, computational solid-state and materials simulation methodology studies proposed herein, have been strategically integrated with our new DOE supported (ASU-Argonne National Laboratory) project to investigate the mechanisms that govern mineral feedstock heat-treatment and aqueous/fluid-phase serpentine mineral carbonation in situ. This unified, synergetic theoretical and experimental approach will provide a deeper understanding of the key reaction mechanisms than either individual approach can alone. Ab initio techniques will also significantly advance our understanding of atomic-level processes at the solid/solution interface by

A.V.G. Chizmeshya

2002-12-19T23:59:59.000Z

195

ENHANCING THE ATOMIC-LEVEL UNDERSTANDING OF CO2 MINERAL SEQUESTRATION MECHANISMS VIA ADVANCED COMPUTATIONAL MODELING  

SciTech Connect

Fossil fuels currently provide 85% of the world's energy needs, with the majority coming from coal, due to its low cost, wide availability, and high energy content. The extensive use of coal-fired power assumes that the resulting CO2 emissions can be vented to the atmosphere. However, exponentially increasing atmospheric CO2 levels have brought this assumption under critical review. Over the last decade, this discussion has evolved from whether exponentially increasing anthropogenic CO2 emissions will adversely affect the global environment, to the timing and magnitude of their impact. A variety of sequestration technologies are being explored to mitigate CO2 emissions. These technologies must be both environmentally benign and economically viable. Mineral carbonation is an attractive candidate technology as it disposes of CO2 as geologically stable, environmentally benign mineral carbonates, clearly satisfying the first criteria. The primary challenge for mineral carbonation is cost-competitive process development. CO2 mineral sequestration--the conversion of stationary-source CO2 emissions into mineral carbonates (e.g., magnesium and calcium carbonate, MgCO3 and CaCO3)--has recently emerged as one of the most promising sequestration options, providing permanent CO2 disposal, rather than storage. In this approach a magnesium-bearing feedstock mineral (typically serpentine or olivine; available in vast quantities globally) is specially processed and allowed to react with CO2 under controlled conditions. This produces a mineral carbonate which (1) is environmentally benign, (2) already exists in nature in quantities far exceeding those that could result from carbonating the world's known fossil fuel reserves, and (3) is stable on a geological time scale. Minimizing the process cost via optimization of the reaction rate and degree of completion is the remaining challenge. As members of the DOE/NETL managed National Mineral Sequestration Working Group we have already significantly improved our understanding of mineral carbonation. Group members at the Albany Research Center have recently shown that carbonation of olivine and serpentine, which naturally occurs over geological time (i.e., 100,000s of years), can be accelerated to near completion in hours. Further process refinement will require a synergetic science/engineering approach that emphasizes simultaneous investigation of both thermodynamic processes and the detailed microscopic, atomic-level mechanisms that govern carbonation kinetics. Our previously funded Phase I Innovative Concepts project demonstrated the value of advanced quantum-mechanical modeling as a complementary tool in bridging important gaps in our understanding of the atomic/molecular structure and reaction mechanisms that govern CO2 mineral sequestration reaction processes for the model Mg-rich lamellar hydroxide feedstock material Mg(OH)2. In the present simulation project, improved techniques and more efficient computational schemes have allowed us to expand and augment these capabilities and explore more complex Mg-rich, lamellar hydroxide-based feedstock materials, including the serpentine-based minerals. These feedstock materials are being actively investigated due to their wide availability, and low-cost CO2 mineral sequestration potential. Cutting-edge first principles quantum chemical, computational solid-state and materials simulation methodology studies proposed herein, have been strategically integrated with our new DOE supported (ASU-Argonne National Laboratory) project to investigate the mechanisms that govern mineral feedstock heat-treatment and aqueous/fluid-phase serpentine mineral carbonation in situ. This unified, synergetic theoretical and experimental approach has provided a deeper understanding of the key reaction mechanisms than either individual approach can alone. We used ab initio techniques to significantly advance our understanding of atomic-level processes at the solid/solution interface by elucidating the origin of vibrational, electronic, x-ray and electron energy loss sp

A.V.G. Chizmeshya; M.J. McKelvy; G.H. Wolf; R.W. Carpenter; D.A. Gormley; J.R. Diefenbacher; R. Marzke

2006-03-01T23:59:59.000Z

196

NREL: Continuum Magazine - The Utility-Scale Future  

NLE Websites -- All DOE Office Websites (Extended Search)

Utility-Scale Future Utility-Scale Future Issue 1 Print Version Share this resource Continuum Magazine Dan Says New Facility to Transform U.S. Energy Infrastructure New Facility to Transform U.S. Energy Infrastructure The nation's electricity infrastructure needs an overhaul. NREL's newest research facility will lead the way. Wind Innovation Enables Utility-Scale Wind Innovation Enables Utility-Scale NREL research will enable wind energy to make major contributions to meeting the nation's electrical demand. Leading Solar Expertise-A Launch Pad to the Future Leading Solar Expertise- A Launch Pad to the Future NREL is speeding solar devices from the lab to utility-scale operation. Paint it Black: One-Step Etch Cuts Solar Cell Costs Paint It Black: One-Step Etch Cuts Solar Cell Costs NREL's technique provides the solar cell manufacturing industry with a

197

UMBRAL DYNAMICS IN THE NEAR-INFRARED CONTINUUM  

SciTech Connect

We detected peaks of oscillatory power at 3 and {approx}6.5 minutes in the umbra of the central sunspot of the active region NOAA AR 10707 in data obtained in the near-infrared (NIR) continuum at 1565.7 nm. The NIR data set captured umbral dynamics around 50 km below the {tau}{sub 500} = 1 level. The umbra does not oscillate as a whole, but rather in distinct parts that are distributed over the umbral surface. The most powerful oscillations, close to a period of {approx}6.5, do not propagate upward. We noted a plethora of large umbral dots (UDs) that persisted for {>=}30 minutes and stayed in the same locations. The peaks of oscillatory power above the detected UDs are located at 3 and 5 minute oscillations, but are very weak in comparison with the oscillations of {approx}6.5 minutes.

Andic, A.; Cao, W.; Goode, P. R. [Also at Big Bear Solar Observatory, 40398 North Shore Lane, Big Bear City, CA 92314 (United States)

2011-08-01T23:59:59.000Z

198

Sierra/solid mechanics 4.22 user's guide.  

Science Conference Proceedings (OSTI)

Sierra/SolidMechanics (Sierra/SM) is a Lagrangian, three-dimensional code for the analysis of solids and structures. It provides capabilities for explicit dynamic and implicit quasistatic and dynamic analyses. The explicit dynamics capabilities allow for the efficient and robust solution of models subjected to large, suddenly applied loads. For implicit problems, Sierra/SM uses a multi-level iterative solver, which enables it to effectively solve problems with large deformations, nonlinear material behavior, and contact. Sierra/SM has a versatile library of continuum and structural elements, and an extensive library of material models. The code is written for parallel computing environments, and it allows for scalable solutions of very large problems for both implicit and explicit analyses. It is built on the SIERRA Framework, which allows for coupling with other SIERRA mechanics codes. This document describes the functionality and input structure for Sierra/SM.

Thomas, Jesse David

2011-10-01T23:59:59.000Z

199

Modeling study of ventilation, IAQ and energy impacts of residential mechanical ventilation  

SciTech Connect

This paper reports on a simulation study of indoor air quality, ventilation and energy impacts of several mechanical ventilation approaches in a single-family residential building. The study focused on a fictitious two-story house in Spokane, Washington and employed the multizone airflow and contaminant dispersal model CONTAM. The model of the house included a number of factors related to airflow including exhaust fan and forced-air system operation, duct leakage and weather effects, as well as factors related to contaminant dispersal including adsorption/desorption of water vapor and volatile organic compounds, surface losses of particles and nitrogen dioxide, outdoor contaminant concentrations, and occupant activities. The contaminants studied include carbon monoxide, carbon dioxide, nitrogen dioxide, water vapor, fine and coarse particles, and volatile organic compounds. One-year simulations were performed for four different ventilation approaches: a base case of envelope infiltration only, passive inlet vents in combination with exhaust fan operation, an outdoor intake duct connected to the forced-air system return balanced by exhaust fan operation, and a continuously-operated exhaust fan. Results discussed include whole building air change rates, air distribution within the house, heating and cooling loads, contaminants concentrations, and occupant exposure to contaminants.

Persily, A.K.

1998-05-01T23:59:59.000Z

200

Improvement of Stent Retriever Design and Efficacy of Mechanical Thrombectomy in a Flow Model  

SciTech Connect

In vitro experiments were performed to evaluate the efficacy of mechanical intracranial thrombectomy comparing the newly developed Aperio stent retriever and standard devices for stroke treatment. The Aperio (A), with an increased working length of 4 cm and a special cell design for capturing and withholding clots, was compared to three benchmark devices: the Solitaire retrievable stent (B), the Merci X6 (C), and the Merci L5 retriever (D). In a vascular glass model with pulsatile flow, reminiscent of the M1 segment of the middle cerebral artery, we repeatedly induced occlusion by generating thrombi via a modified Chandler loop system. The numbers of recanalization attempts, peripheral embolizations, and recanalizations at the site of occlusion were recorded during 10 retrieval experiments with each device. Eleven devices were able to remove the blood clots from the occluded branch. In 34 of 40 experiments, restoration of flow was obtained in 1-3 attempts. The main differences between the study devices were observed in terms of clot withholding and fragmentation during retrieval. Although there was only one fragmentation recorded for device A, disengagement of the whole clot or peripheral embolization of fragments occurred more frequently (5-7 times) with devices B, C, and D. In a vascular model, the design of device A was best at capturing and withholding thrombi during retrieval. Further study will be necessary to see whether this holds true in clinical applications.

Wenger, Katharina, E-mail: kwenger@stud.uni-frankfurt.de [Institute of Neuroradiology, University of Frankfurt am Main (Germany)] [Institute of Neuroradiology, University of Frankfurt am Main (Germany); Nagl, Frank, E-mail: fnagl@acandis.com [Acandis GmbH and Co KG (Germany)] [Acandis GmbH and Co KG (Germany); Wagner, Marlies, E-mail: Marlies.Wagner@kgu.de; Berkefeld, Joachim, E-mail: berkefeld@em.uni-frankfurt.de [Institute of Neuroradiology, University of Frankfurt am Main (Germany)] [Institute of Neuroradiology, University of Frankfurt am Main (Germany)

2013-02-15T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
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201

The abelian confinement mechanism revisited: new aspects of the Georgi-Glashow model  

E-Print Network (OSTI)

The confinement problem remains one of the most difficult problems in theoretical physics. An important step toward the solution of this problem is the Polyakov's work on abelian confinement. The Georgi-Glashow model is a natural testing ground for this mechanism which has been surprising us by its richness and wide applicability. In this work, we shed light on two new aspects of this model in 2+1 D. First, we develop a many-body description of the effective degrees of freedom. Namely, we consider a non-relativistic gas of W-bosons in the background of monopole-instanton plasma. Many-body treatment is a standard toolkit in condensed matter physics. However, we add a new twist by supplying the monopole-instantons as external background field. Using this construction, we calculate the exact form of the potential between two electric probes as a function of their separation. This potential is expressed in terms of the Meijer-G function which interpolates between logarithmic and linear behavior at small and large distances, respectively. Second, we develop a systematic approach to integrate out the effect of the W-bosons at finite temperature in the range 0gas. We repeat our analysis using the many-body description which yields the same result and provides a check on our formalism. At temperatures close to the deconfinement temperature, the gas becomes essentially two-dimensional recovering the partition function of the dual sine-Gordon model that was considered in a previous work.

Mohamed M. Anber

2013-07-31T23:59:59.000Z

202

Hybrid atomistic-continuum method for the simulation of dense fluid flows  

Science Conference Proceedings (OSTI)

We present a hybrid atomistic-continuum method for multiscale simulations of dense fluids. In this method, the atomistic part is described using a molecular dynamics description, while the continuum flow is described by a finite volume discretization ... Keywords: Hybrid algorithms, Molecular dynamics, Multiscale simulation, Nanofluidics

Thomas Werder; Jens H. Walther; Petros Koumoutsakos

2005-05-01T23:59:59.000Z

203

Exploring the mechanisms critical to the operation of metal face seals through modeling and experiments  

E-Print Network (OSTI)

This thesis aims to explore operation mechanisms of a special type of mechanical face seals: the flexible metal-to-metal face seal (FMMFS). Unique features of the FMMFS include much more flexibility in the circumferential ...

Wang, Yong, Ph. D. Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics

2008-01-01T23:59:59.000Z

204

Assessing the Continuum of Event-Based Biosurveillance Through an Operational Lens  

SciTech Connect

This research follows the Updated Guidelines for Evaluating Public Health Surveillance Systems, Recommendations from the Guidelines Working Group, published by the Centers for Disease Control and Prevention nearly a decade ago. Since then, models have been developed and complex systems have evolved with a breadth of disparate data to detect or forecast chemical, biological, and radiological events that have significant impact in the One Health landscape. How the attributes identified in 2001 relate to the new range of event-based biosurveillance (EBB) technologies is unclear. This manuscript frames the continuum of EBB methods, models, and constructs through an operational lens (i.e., aspects and attributes associated with operational considerations in the development, testing, and validation of the EBB methods and models and their use in an operational environment). A 2-day subject matter expert workshop was held to scientifically identify, develop, and vet a set of attributes for the broad range of such operational considerations. Workshop participants identified and described comprehensive attributes for the characterization of EBB. The identified attributes are: (1) event, (2) readiness, (3) operational aspects, (4) geographic coverage, (5) population coverage, (6) input data, (7) output, and (8) cost. Ultimately, the analyses herein discuss the broad scope, complexity, and relevant issues germane to EBB useful in an operational environment.

Corley, Courtney D.; Lancaster, Mary J.; Brigantic, Robert T.; Chung, James S.; Walters, Ronald A.; Arthur, Ray; Bruckner-Lea, Cindy J.; Calapristi, Augustin J.; Dowling, Glenn; Hartley, David M.; Kennedy, Shaun; Kircher, Amy; Klucking, Sara; Lee, Eva K.; McKenzie, Taylor K.; Nelson, Noele P.; Olsen, Jennifer; Pancerella, Carmen M.; Quitugua, Teresa N.; Reed, Jeremy T.; Thomas, Carla S.

2012-03-28T23:59:59.000Z

205

Coarsening of the Sn-Pb Solder Microstructure in Constitutive Model-Based Predictions of Solder Joint Thermal Mechanical Fatigue  

SciTech Connect

Thermal mechanical fatigue (TMF) is an important damage mechanism for solder joints exposed to cyclic temperature environments. Predicting the service reliability of solder joints exposed to such conditions requires two knowledge bases: first, the extent of fatigue damage incurred by the solder microstructure leading up to fatigue crack initiation, must be quantified in both time and space domains. Secondly, fatigue crack initiation and growth must be predicted since this metric determines, explicitly, the loss of solder joint functionality as it pertains to its mechanical fastening as well as electrical continuity roles. This paper will describe recent progress in a research effort to establish a microstructurally-based, constitutive model that predicts TMF deformation to 63Sn-37Pb solder in electronic solder joints up to the crack initiation step. The model is implemented using a finite element setting; therefore, the effects of both global and local thermal expansion mismatch conditions in the joint that would arise from temperature cycling.

Vianco, P.T.; Burchett, S.N.; Neilsen, M.K.; Rejent, J.A.; Frear, D.R.

1999-04-12T23:59:59.000Z

206

A comparative model of two mechanisms from which a magnetic field arises in the heart  

Science Conference Proceedings (OSTI)

There are two different mechanisms from which a magnetic field can arise in the heart. The first mechanism has the source of the magnetic field as a current dipole oriented perpendicular to the action potential wave front with the “return” currents flowing in an adjacent volume conductor. The second mechanism is one with no adjacent volume conductor and has a magnetic field that arises due to the anisotropy of the tissue. We see that the two mechanisms produce magnetic fields of similar magnitudes and similar falloff rates as distance from the tissue increases

R. A. Murdick; B. J. Roth

2004-01-01T23:59:59.000Z

207

A statistical, physical-based, micro-mechanical model of hydrogen-induced intergranular fracture in steel  

E-Print Network (OSTI)

. Introduction It is well recognized that hydrogen represents an abundant, clean and mobile energy carrier. For the hydrogen economy to be fully realized though, efficient hydrogen storage and transportation, for exampleA statistical, physical-based, micro-mechanical model of hydrogen-induced intergranular fracture

Ritchie, Robert

208

A general kinetic model: Kinetics and atomic-scale mechanisms of feldspar dissolution.  

E-Print Network (OSTI)

??This thesis presents a general kinetic model and its application to feldspar dissolution. In the framework of Monte Carlo methods, the model simulates the stochastic… (more)

Zhang, Li

2008-01-01T23:59:59.000Z

209

Numerical Study of Rarefied Hypersonic Flow Interacting With a Continuum Jet  

Science Conference Proceedings (OSTI)

An uncoupled CFD-DSMC technique is developed and applied to provide solutions for continuum jets interacting with rarefied external flows. The technique is based on a correlation of the appropriate Bird breakdown parameter for a transitional-rarefied ...

Glass Christopher E.

2000-11-01T23:59:59.000Z

210

Randomness and determinism in the interplay between the continuum and the discrete†  

Science Conference Proceedings (OSTI)

This paper provides a conceptual analysis of the role of the mathematical continuum versus the discrete in the understanding of randomness as a notion with a physical meaning or origin. The presentation is ‘informal’ as we will not ...

Francis Bailly; Giuseppe Longo

2007-04-01T23:59:59.000Z

211

Physical understanding and modeling of chemical mechanical planarization in dielectric materials  

E-Print Network (OSTI)

Chemical mechanical planarization (CMP) has become the enabling planarization technique of choice for current and emerging silicon integrated circuit (IC) fabrication processes. This work studies CMP in dielectric materials ...

Xie, Xiaolin, Ph. D. Massachusetts Institute of Technology

2007-01-01T23:59:59.000Z

212

Subgrid-Scale Eddy Parameterization by Statistical Mechanics in a Barotropic Ocean Model  

Science Conference Proceedings (OSTI)

The feasibility of using a subgrid-scale eddy parameterization, based on statistical mechanics of potential vorticity, is investigated. A specific implementation is derived for the somewhat classic barotropic vorticity equation in the case of a ...

Evguéni Kazantsev; Joël Sommeria; Jacques Verron

1998-06-01T23:59:59.000Z

213

Physical and numerical modeling of the external fluid mechanics of OTEC pilot plants  

E-Print Network (OSTI)

This study examined the near field external fluid mechanics of symmetrical OTEC pilot plant designs (20-80 MWe) under realistic deep water conditions. The objective was to assess the environmental impact of different plant ...

Singarella, Paul N.

1982-01-01T23:59:59.000Z

214

Mechanisms of Decadal Arctic Climate Variability in the Community Climate System Model, Version 2 (CCSM2)  

Science Conference Proceedings (OSTI)

Several mechanisms have been proposed to explain natural climate variability in the Arctic. These include processes related to the influence of the North Atlantic Oscillation/Arctic Oscillation (NAO/AO), anticyclonic/cyclonic regimes, changes in ...

Hugues Goosse; Marika M. Holland

2005-09-01T23:59:59.000Z

215

Model-based dummy feature placement for oxide chemical-mechanical polishing manufacturability  

Science Conference Proceedings (OSTI)

Chemical-mechanical polishing (CMP) is an enabling technique used in deep-submicron VLSI manufacturing to achieve uniformity in long range oxide planarization [1]. Post-CMP oxide topography is highly related to local spatial pattern density in layout. ...

Ruiqi Tian; D. F. Wong; Robert Boone

2000-06-01T23:59:59.000Z

216

In vitro models of cartilage degradation following joint injury : mechanical overload, inflammatory cytokines and therapeutic approaches  

E-Print Network (OSTI)

Osteoarthritis (OA) is the most common form of joint disorder. Individuals who have sustained an acute traumatic joint injury are at greater risk for the development of OA. The mechanisms by which injury causes cartilage ...

Lu, Yihong C. S

2010-01-01T23:59:59.000Z

217

Continuum discretization methods in a composite-particle scattering off a nucleus: the benchmark calculations  

E-Print Network (OSTI)

The direct comparison of two different continuum discretization methods towards the solution of a composite particle scattering off a nucleus is presented. The first approach -- the Continumm-Discretized Coupled Channel method -- is based on the differential equation formalism, while the second one -- the Wave-Packet Continuum Discretization method -- uses the integral equation formulation for the composite-particle scattering problem. As benchmark calculations we have chosen the deuteron off \

O. A. Rubtsova; V. I. Kukulin; A. M. Moro

2008-06-13T23:59:59.000Z

218

Experimental Verification of Thermo-Mechanical Models for XLPE Cable in Pipes and Ducts  

Science Conference Proceedings (OSTI)

In 2002 EPRI began investigations of the thermo-mechanical (T-M) behavior of transmission-class cable systems with extruded insulation in duct-manhole and pipe systems and began work on a design guide. The project consisted primarily of two efforts: experimental measurement of cable parameters and development of a mathematical simulation of the thermal and mechanical behavior of transmission-class cable with extruded cross-linked polyethylene (XLPE) insulation when installed in ducts and pipes. ...

2012-12-20T23:59:59.000Z

219

Higgs Mechanism in the Standard Model and a Possibility of its Direct Physical Realization  

E-Print Network (OSTI)

The aim of this work was to answer the question: Is the direct physical realization of the Higgs mechanism possible? It is shown that this mechanism cannot have a direct physical realization since the condition for this realization is not fulfilled. It means that if in the new collider at CERN a scalar particle is detected, it does not mean that it is a Higgs particle.

Kh. M. Beshtoev

2008-12-30T23:59:59.000Z

220

Mechanical properties and modeling of seal-forming lithologies. Technical progress report No. 3, March 15, 1992--June 14, 1993  

SciTech Connect

Specific goals and accomplishments of this research include: (1) The evaluation of models of salt diaper ascent that involve either power law, dislocation creep as determined experimentally by Horseman et al. (1993) or linear, fluid-assisted creep as reported by Spiers et al. (1988, 1990, 1992). We have compared models assuming these two, experimentally evaluated flow laws and examined the predictions they make regarding diaper incubation periods, ascent velocities, deviatoric stresses and strain rates. (2) The evaluation of the effects of differential loading on the initiation an of salt structures. (3) Examination of the role of basement faults on the initiation and morphologic evolution of salt structures. (4) Evaluation of the mechanical properties of shale as a function of pressure and determination of the nature of its brittle-ductile transition. (5) Evaluation of the mechanical anisotropies of shales with varying concentrations, distributions and preferred orientations of clay. (6) The determination of temperature and ratedependencies of strength for a shale constitutive model that can be used in numerical models that depend on viscous formulations. (7) Determination of the mechanisms of deformation for argillaceous rocks over awide range of conditions. (8) Evaluation of the effects of H{sub 2}O within clay interlayers, as adsorbed surface layers.

Kronenberg, A.K.; Russell, J.E.; Carter, N.L.; Mazariegos, R.; Ibanez, W.

1993-06-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Used Fuel Degradation: Experimental and Modeling Report  

Energy.gov (U.S. Department of Energy (DOE))

The report describes the strategy for coupling process level models to produce an integrated Used Fuel Degradation Model (FDM), and addresses fractional degradation rate, instant release fractions, other continuum modeling approaches, and experimental support.

222

Model studies of the structures, reactivities, and reaction mechanisms of metalloenzymes  

Science Conference Proceedings (OSTI)

Electronic structure theory, which in recent years has been actively and effectively applied to the modeling of chemical reactions involving transition-metal complexes, is now also being applied to the modeling of biological processes involving metalloenzymes. ...

K. Morokuma; D. G. Musaev; T. Vreven; H. Basch; M. Torrent; D. V. Khoroshun

2001-05-01T23:59:59.000Z

223

Mechanisms of Low Cloud–Climate Feedback in Idealized Single-Column Simulations with the Community Atmospheric Model, Version 3 (CAM3)  

Science Conference Proceedings (OSTI)

This study investigates the physical mechanism of low cloud feedback in the Community Atmospheric Model, version 3 (CAM3) through idealized single-column model (SCM) experiments over the subtropical eastern oceans. Negative cloud feedback is ...

Minghua Zhang; Christopher Bretherton

2008-09-01T23:59:59.000Z

224

Effects of Downscattering on the Continuum and Line Spectra in Powerful Wind Environment. Monte Carlo Simulations, Analytical Results and Data Analysis  

E-Print Network (OSTI)

In Paper by Titarchuk & Shrader the general formulation and results for photon reprocessing (downscattering) that included recoil and Comptonization effects due to divergence of the flow were presented. Here we show the Monte Carlo (MC) simulated continuum and line spectra. We also provide an analytical description of the simulated continuum spectra using the diffusion approximation. We have simulated the propagation of monochromatic and continuum photons in a bulk outflow from a compact object. Electron scattering of the photons within the expanding flow leads to a decrease of their energy which is of first order in V/c (where V is the outflow velocity). The downscattering effect of first order in V/c in the diverging flow is explained by semi-analytical calculations and confirmed by MC simulations. We conclude that redshifted lines and downscattering bumps are intrinsic properties of the powerful outflows for which Thomson optical depth is greater than one. We fitted our model line profiles to the observations using four free parameters, \\beta=V/c, optical depth of the wind \\tau, the wind temperature kT_e and the original line photon energy E_0. We show how the primary spectrum emitted close to the black hole is modified by reprocessing in the warm wind. In the framework of the our wind model the fluorescent iron line K_alpha is formed in the partly ionized wind as a result of illumination by central source continuum photons. The demonstrated application of our outflow model to the XMM observations of MCG 6-30-15, and to the ASCA observations of GRO J1655-40, points out a potential powerful spectral diagnostic for probes of the outflow-central object connection in Galactic and extragalactic BH sources.

Philippe Laurent; Lev Titarchuk

2006-11-06T23:59:59.000Z

225

Determination of Basic Structure-Property Relations for Processing and Modeling in Advanced Nuclear Fuel: Microstructure Evolution and Mechanical Properties  

SciTech Connect

The project objective is to study structure-property relations in solid solutions of nitrides and oxides with surrogate elements to simulate the behavior of fuels of inert matrix fuels of interest to the Advanced Fuel Cycle Initiative (AFCI), with emphasis in zirconium-based materials. Work with actual fuels will be carried out in parallel in collaboration with Los Alamos National Laboratory (LANL). Three key aspects will be explored: microstructure characterization through measurement of global texture evolution and local crystallographic variations using Electron Backscattering Diffraction (EBSD); determination of mechanical properties, including fracture toughness, quasi-static compression strength, and hardness, as functions of load and temperature, and, finally, development of structure-property relations to describe mechanical behavior of the fuels based on experimental data. Materials tested will be characterized to identify the mechanisms of deformation and fracture and their relationship to microstructure and its evolution. New aspects of this research are the inclusion of crystallographic information into the evaluation of fuel performance and the incorporation of statistical variations of microstructural variables into simplified models of mechanical behavior of fuels that account explicitly for these variations. The work is expected to provide insight into processing conditions leading to better fuel performance and structural reliability during manufacturing and service, as well as providing a simplified testing model for future fuel production.

Kirk Wheeler; Manuel Parra; Pedro Peralta

2009-03-01T23:59:59.000Z

226

Magic numbers for superheavy nuclei in relativistic continuum Hartree-Bogoliubov theory  

E-Print Network (OSTI)

The magic proton and neutron numbers are searched in the superheavy region with proton number $Z$=100 - 140 and neutron number $N$= ($Z$+30) - (2$Z$+32) by the relativistic continuum Hartree-Bogoliubov (RCHB) theory with interactions NL1, NL3, NLSH, TM1, TW99, DD-ME1, PK1, and PK1R. Based on the two-nucleon separation energies $S_{2p}$ and $S_{2n}$, the two-nucleon gaps $\\delta_{2p}$ and $\\delta_{2n}$, the shell correction energies $E_{shell}^{p}$ and $E_{shell}^{n}$, the pairing energies $E_{pair}^{p}$ and $E_{pair}^{n}$, and the pairing gaps $\\Delta_{p}$ and $\\Delta_{n}$, $Z$=120, 132, and 138 and $N$=172, 184, 198, 228, 238, and 258 are suggested to be the magic numbers within the present approach. The $\\alpha$-decay half-lives are also discussed. In addition, the potential energy surfaces of possible doubly magic nuclei are obtained by the deformation-constrained relativistic mean field (RMF) theory, and the shell effects stabilizing the nuclei are investigated. Furthermore, the formation cross sections of $^{292}_{172}$120 and $^{304}_{184}$120 at the optimal excitation energy are estimated by a phenomenological cold fusion reactions model with the structure information extracted from the constrained RMF calculation.

W. Zhang; J. Meng; S. Q. Zhang; L. S. Geng; H. Toki

2004-03-07T23:59:59.000Z

227

Modelling Quantum Mechanics by the Quantumlike Description of the Electric Signal Propagation in Transmission Lines  

E-Print Network (OSTI)

It is shown that the transmission line technology can be suitably used for simulating quantum mechanics. Using manageable and at the same time non-expensive technology, several quantum mechanical problems can be simulated for significant tutorial purposes. The electric signal envelope propagation through the line is governed by a Schrodinger-like equation for a complex function, representing the low-frequency component of the signal, In this preliminary analysis, we consider two classical examples, i.e. the Frank-Condon principle and the Ramsauer effect.

R. Fedele; M. A. Man'ko; V. I. Man'ko; V. G. Vaccaro

2002-07-30T23:59:59.000Z

228

Quantum-Mechanical Model of Spacetime I: Microscopic Properties of Spacetime  

E-Print Network (OSTI)

This is the first part in a series of two papers, where we consider a specific microscopic model of spacetime. In our model Planck size quantum black holes are taken to be the fundamental building blocks of space and time. Spacetime is assumed to be a graph, where black holes lie on the vertices. In this first paper we construct our model in details, and show how classical spacetime emerges at the long distance limit from our model. We also consider the statistics of spacetime.

Makela, J

2008-01-01T23:59:59.000Z

229

A Simple Quantum-Mechanical Model of Spacetime I: Microscopic Properties of Spacetime  

E-Print Network (OSTI)

This is the first part in a series of two papers, where we consider a specific microscopic model of spacetime. In our model Planck size quantum black holes are taken to be the fundamental building blocks of space and time. Spacetime is assumed to be a graph, where black holes lie on the vertices. In this first paper we construct our model in details, and show how classical spacetime emerges at the long distance limit from our model. We also consider the statistics of spacetime.

J. Makela

2008-05-26T23:59:59.000Z

230

Mathematical model of IRIS replication mechanism for the simulation of tactical networks  

Science Conference Proceedings (OSTI)

The Multilateral Interoperability Programme (MIP) was established to promote more successful and better harmonized operational functions for international peace-keeping forces. The C2IEDM/JC3IEDM (Command and Control Information Exchange Data Model) ... Keywords: C2IS, Simulations, Tactical radio network, Traffic modeling

Joe Mohorko; Matja Fras

2009-05-01T23:59:59.000Z

231

A Mechanism and Simple Dynamical Model of the North Atlantic Oscillation and Annular Modes  

Science Conference Proceedings (OSTI)

A simple dynamical model is presented for the basic spatial and temporal structure of the large-scale modes of intraseasonal variability and associated variations in the zonal index. Such variability in the extratropical atmosphere is known to be ...

Geoffrey K. Vallis; Edwin P. Gerber; Paul J. Kushner; Benjamin A. Cash

2004-02-01T23:59:59.000Z

232

On Adding Thermodynamic Damping Mechanisms to Refine Two Classical Models of Katabatic Winds  

Science Conference Proceedings (OSTI)

The Prandtl and layer-averaged models of katabatic winds contain some nonphysical singularities in the analytical solutions, which give unbounded steady flow anomalies at zero slope angles or adiabatic lapse rates. This study presents some simple ...

Ruping Mo

2013-07-01T23:59:59.000Z

233

Mechanisms for Wave Packet Formation and Maintenance in a Quasigeostrophic Two-Layer Model  

Science Conference Proceedings (OSTI)

A quasigeostrophic, two-layer, ?-plane channel model is used to investigate the dynamics of baroclinic wave packets. A series of experiments are performed in which an unstable flow is maintained by lower-level Ekman friction and radiative ...

J. G. Esler; P. H. Haynes

1999-08-01T23:59:59.000Z

234

An agent-based model of the cognitive mechanisms underlying the origins of creative cultural evolution  

Science Conference Proceedings (OSTI)

Human culture is uniquely cumulative and open-ended. Using a computational model of cultural evolution in which neural network based agents evolve ideas for actions through invention and imitation, we tested the hypothesis that this is due to the capacity ... Keywords: EVOC, action, agent-based model, creativity, cultural diversity, cultural evolution, gesture, homo erectus, innovation, invention, mimetic, origin of culture, recursive recall, self-triggered recall and rehearsal loop

Liane Gabora; Maryam Saberi

2011-11-01T23:59:59.000Z

235

Modelling and simulations of the chemo-mechanical behaviour of leached cement-based materials: Interactions between damage and leaching  

Science Conference Proceedings (OSTI)

The assessment of the durability of cement-based materials, which could be employed in underground structures for nuclear waste disposal, requires accounting for deterioration factors, such as chemical attacks and damage, and for the interactions between these phenomena. The objective of the present paper consists in investigating the long-term behaviour of cementitious materials by simulating their response to chemical and mechanical solicitations. In a companion paper (Stora et al., submitted to Cem. Concr. Res. 2008), the implementation of a multi-scale homogenization model into an integration platform has allowed for evaluating the evolution of the mineral composition, diffusive and elastic properties inside a concrete material subjected to leaching. To complete this previous work, an orthotropic micromechanical damage model is presently developed and incorporated in this numerical platform to estimate the mechanical and diffusive properties of damaged cement-based materials. Simulations of the chemo-mechanical behaviour of leached cementitious materials are performed with the tool thus obtained and compared with available experiments. The numerical results are insightful about the interactions between damage and chemical deteriorations.

Stora, E., E-mail: stora@univ-mlv.f [Atomic Energy Commission, CEA Saclay DEN/DANS/DPC/SCCME/Laboratoire d'Etude du Comportement des Betons et des Argiles, 91191 Gif sur Yvette (France); Universite Paris-Est, Laboratoire de Modelisation et Simulation Multiechelle, FRE3160 CNRS, 5 boulevard Descartes, 77454 Marne-la-Vallee Cedex 2 (France); Bary, B. [Atomic Energy Commission, CEA Saclay DEN/DANS/DPC/SCCME/Laboratoire d'Etude du Comportement des Betons et des Argiles, 91191 Gif sur Yvette (France); He, Q.-C. [Universite Paris-Est, Laboratoire de Modelisation et Simulation Multiechelle, FRE3160 CNRS, 5 boulevard Descartes, 77454 Marne-la-Vallee Cedex 2 (France); Deville, E.; Montarnal, P. [CEA Saclay DEN/DANS/DM2S/SFME/MTMS, 91191 Gif sur Yvette (France)

2010-08-15T23:59:59.000Z

236

An interacting-agent model of financial markets from the viewpoint of Nonextensive statistical mechanics  

E-Print Network (OSTI)

In this paper we present an interacting-agent model of financial markets. We describe a financial market through an Ising model to formulate the tendency of agents getting influenced by the other agents' investment attitude [8]. We formulate the agents' decision making on investment as the {\\it minimum energy principle for Tsallis entropy [11]}, and demonstrate that the equilibrium probability distribution function of the investment attitude of interacting-agents is the {\\it q-exponential distribution}. We also show that the power-law distribution of volatility of price fluctuations, which is often demonstrated in the empirical studies [17], can be explained naturally by our model that have their origin in the collective crowd behavior of many interacting-agents.

Kaizoji, T

2006-01-01T23:59:59.000Z

237

A Molecular Based Model for Polymer Viscoelasticity: Intra-and Inter-Molecular  

E-Print Network (OSTI)

A Molecular Based Model for Polymer Viscoelasticity: Intra- and Inter-Molecular Variability H viscoelasticity based on a stick-slip continuum molecular-based model. The model developed is a continuum tube-system is composed of long molecular chains. The dynamics of these molecular chains are developed by modeling them

238

Sustainable Transportation, Continuum Magazine, Fall 2013 / Issue 5 (Book), NREL (National Renewable Energy Laboratory)  

NLE Websites -- All DOE Office Websites (Extended Search)

L L L 2 0 1 3 / I S S U E 5 NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. NREL.GOV/CONTINUUM S U S T A I N A B L E T R A N S P O R T A T I O N 2 Continuum DAN SAYS TRANSFORMING TRANSPORTATION This issue of Continuum focuses on our contributions toward creating a sustainable transportation system-from developing more efficient electric and hydrogen fuel-cell vehicles to inventing technologies and processes for producing biofuel alternatives to gasoline, diesel, and even jet fuel. In some ways, the challenges we face in transforming our nation's vehicle

239

Analytical transformed harmonic oscillator basis for continuum discretized coupled channels calculations  

Science Conference Proceedings (OSTI)

A new method for continuum discretization in continuum-discretized coupled-channels calculations is proposed. The method is based on an analytic local-scale transformation of the harmonic-oscillator wave functions proposed for other purposes in a recent work [Karatagladis et al., Phys. Rev. C 71, 064601 (2005)]. The new approach is compared with the standard method of continuum discretization in terms of energy bins for the reactions d+{sup 58}Ni at 80 MeV, {sup 6}Li+{sup 40}Ca at 156 MeV, and {sup 6}He+{sup 208}Pb at 22 MeV and 240 MeV/nucleon. In all cases very good agreement between both approaches is found.

Moro, A. M.; Arias, J. M. [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Fisica, Universidad de Sevilla, Apartado 1065, E-41080 Sevilla (Spain); Gomez-Camacho, J. [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Fisica, Universidad de Sevilla, Apartado 1065, E-41080 Sevilla (Spain); Centro Nacional de Aceleradores, Avda Thomas A. Edison, E-41092 Sevilla (Spain); Perez-Bernal, F. [Departamento de Fisica Aplicada, Universidad de Huelva, E-21071 Huelva (Spain)

2009-11-15T23:59:59.000Z

240

Development of an ash particle deposition model considering build-up and removal mechanisms  

SciTech Connect

Slagging and fouling on heat exchanger surfaces in power boilers fired with fossil fuels and fuel mixtures has a significant influence on boiler efficiency and availability. Mathematical modelling has long been considered a suitable method to assist boiler operators to determine optimized operating conditions for an existing furnace. The ultimate goal in ash deposition prediction is hereby the determination of the total amount of material deposited and hence the determination of the total reduction in efficiency. Depending on the fuels fired the total deposited mass is a combination of ash particle deposition and ash particle erosion due to non-sticky particles. The novel ash particle deposition model presented in this work considers deposition of sticky ash particles, cleansing of deposit by non-sticky sand particles and sticking of sand due to contact with sticky ash. The steady-state modelling results for the total amount of ash deposited on the deposition probe of an entrained flow reactor presented in this work agree well with the experimental data. Only at very high fractions of sand added as non-sticky material, a significant influence of the sand on the overall mass deposited was found. Since the model considers sticking of non-sticking sand due to contact with sticky ash, the fraction of sand deposited on the probe was especially studied. Using a correction factor to consider the influence of operating time on the steady-state simulations led to good agreement between simulations and experimental data. 12 refs., 10 figs.

Kjell Strandstroem; Christian Muellera; Mikko Hupa [Abo Akademi Process Chemistry Centre, Abo (Finland)

2007-12-15T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

A finite element model for hygro-thermo-mechanical analysis of masonry walls with FRP reinforcement  

Science Conference Proceedings (OSTI)

Modeling the effects of humidity and temperature gradients on the structural behavior of masonry walls reinforced with fiber reinforced polymer (FRP) composite is of great importance. Study of interfacial stresses, in particular, is a key factor in predicting ... Keywords: FRP reinforced masonry, Moisture and temperature, Multi-layered permeable structure, Structural analysis

Mehran Khoshbakht; Mark W. Lin

2010-10-01T23:59:59.000Z

242

Southern “Annular Modes” Simulated by a Climate Model—Patterns, Mechanisms, and Uses  

Science Conference Proceedings (OSTI)

Both high-latitude (HLM) and low-latitude modes (LLM) of variability of zonal wind in the Southern Hemisphere have been identified. Through an analysis of a simulation for 1871–2200 by the CSIRO Mark 3 climate model, the extent to which these ...

I. G. Watterson

2007-09-01T23:59:59.000Z

243

Statistical properties of agent-based models in markets with continuous double auction mechanism  

E-Print Network (OSTI)

Real world markets display power-law features in variables such as price fluctuations in stocks. To further understand market behavior, we have conducted a series of market experiments on our web-based prediction market platform which allows us to reconstruct transaction networks among traders. From these networks, we are able to record the degree of a trader, the size of a community of traders, the transaction time interval among traders and other variables that are of interest. The distributions of all these variables show power-law behavior. On the other hand, agent-based models have been proposed to study the properties of real financial markets. We here study the statistical properties of these agent-based models and compare them with the results from our web-based market experiments. In this work, three agent-based models are studied, namely, zero-intelligence (ZI), zero-intelligence-plus (ZIP) and Gjerstad-Dickhaut (GD). Computer simulations of variables based on these three agent-based models were car...

Tseng, Jie-Jun; Lin, Chih-Ting; Wang, Sun-Chong; Li, Sai-Ping; 10.1016/j.physa.2009.12.034

2010-01-01T23:59:59.000Z

244

A model study on the circuit mechanism underlying decision-making in Drosophila  

Science Conference Proceedings (OSTI)

Previous elegant experiments in a flight simulator showed that conditioned Drosophila is able to make a clear-cut decision to avoid potential danger. When confronted with conflicting visual cues, the relative saliency of two competing cues is found to ... Keywords: Attention, Decision-making, Dopamine modulation, Drosophila, Feature binding, Systems-level circuit model

Zhihua Wu; Aike Guo

2011-05-01T23:59:59.000Z

245

Infinite cloud model of electrification by the precipitation mechanism in the presence of high rates of ion generation  

SciTech Connect

We have extended a simple, infinite cloud, precipitation mechanism model of thundercloud electrification to include effects due to the presence of radioactive aerosol particles resulting from fresh debris from a nuclear explosion. These effects involve ion generation, currents due to motions of ions and charged aerosol particles, and collection of ions and aerosol particles by hydrometeors and cloud droplets. Our conclusion is that an ion pair generation rate G> or approx. =10/sup 12/m/sup -3/ s/sup -1/ will prevent significant electric field growth.

Spangler, J.D.; Rosenkilde, C.E.

1979-06-20T23:59:59.000Z

246

Infinite cloud model of electrification by the precipitation mechanism in the pressence of high rates of ion generation  

SciTech Connect

We have extended a simple, infinite-cloud, precipitation-mechanism model of thundercloud electrification to include effects due to the presence of radioactive aerosol particles. These effects involve ion generation, currents due to motions of ions and charged aerosol particles, and collection of ions and aerosol particles by hydrometeors and cloud droplets. Our conclusion is that an ion-pair generation rate G equal to or greater than 10/sup 12/m/sup -3/s/sup -1/ will prevent significant electric-field growth.

Spangler, J.D.; Rosenkilde, C.E.

1978-06-19T23:59:59.000Z

247

Training and Research on Probabilistic Hydro-Thermo-Mechanical Modeling of Carbon Dioxide Geological Sequestration in Fractured Porous Rocks  

SciTech Connect

Colorado School of Mines conducted research and training in the development and validation of an advanced CO{sub 2} GS (Geological Sequestration) probabilistic simulation and risk assessment model. CO{sub 2} GS simulation and risk assessment is used to develop advanced numerical simulation models of the subsurface to forecast CO2 behavior and transport; optimize site operational practices; ensure site safety; and refine site monitoring, verification, and accounting efforts. As simulation models are refined with new data, the uncertainty surrounding the identified risks decrease, thereby providing more accurate risk assessment. The models considered the full coupling of multiple physical processes (geomechanical and fluid flow) and describe the effects of stochastic hydro-mechanical (H-M) parameters on the modeling of CO{sub 2} flow and transport in fractured porous rocks. Graduate students were involved in the development and validation of the model that can be used to predict the fate, movement, and storage of CO{sub 2} in subsurface formations, and to evaluate the risk of potential leakage to the atmosphere and underground aquifers. The main major contributions from the project include the development of: 1) an improved procedure to rigorously couple the simulations of hydro-thermomechanical (H-M) processes involved in CO{sub 2} GS; 2) models for the hydro-mechanical behavior of fractured porous rocks with random fracture patterns; and 3) probabilistic methods to account for the effects of stochastic fluid flow and geomechanical properties on flow, transport, storage and leakage associated with CO{sub 2} GS. The research project provided the means to educate and train graduate students in the science and technology of CO{sub 2} GS, with a focus on geologic storage. Specifically, the training included the investigation of an advanced CO{sub 2} GS simulation and risk assessment model that can be used to predict the fate, movement, and storage of CO{sub 2} in underground formations, and the evaluation of the risk of potential CO{sub 2} leakage to the atmosphere and underground aquifers.

Gutierrez, Marte

2013-05-31T23:59:59.000Z

248

A quantum mechanical model for the relationship between stock price and stock ownership  

SciTech Connect

The trade of a fixed stock can be regarded as the basic process that measures its momentary price. The stock price is exactly known only at the time of sale when the stock is between traders, that is, only in the case when the owner is unknown. We show that the stock price can be better described by a function indicating at any moment of time the probabilities for the possible values of price if a transaction takes place. This more general description contains partial information on the stock price, but it also contains partial information on the stock owner. By following the analogy with quantum mechanics, we assume that the time evolution of the function describing the stock price can be described by a Schroedinger type equation.

Cotfas, Liviu-Adrian [Faculty of Economic Cybernetics, Statistics and Informatics, Academy of Economic Studies, 6 Piata Romana, 010374 Bucharest (Romania)

2012-11-01T23:59:59.000Z

249

A quantum mechanical model for the relationship between stock price and stock ownership  

E-Print Network (OSTI)

The trade of a fixed stock can be regarded as the basic process that measures its momentary price. The stock price is exactly known only at the time of sale when the stock is between traders, that is, only in the case when the owner is unknown. We show that the stock price can be better described by a function indicating at any moment of time the probabilities for the possible values of price if a transaction takes place. This more general description contains partial information on the stock price, but it also contains partial information on the stock owner. By following the analogy with quantum mechanics, we assume that the time evolution of the function describing the stock price can be described by a Schrodinger type equation.

Liviu-Adrian Cotfas

2012-07-14T23:59:59.000Z

250

Application of continuum laws in discontinuity analysis based on a regularised displacement discontinuity  

E-Print Network (OSTI)

. Comp., 10(5), 99–121, (1993). [5] G. Pijaudier-Cabot and Z. Baz?ant. Nonlocal Damage Theory. ASCE J. Eng. Mech., 113(10), 1512–1533, (1987). [6] Z. Baz?ant and G. Pijaudier-Cabot. Nonlocal Continuum Damage, Localization In- stability and Convergence... Plasticity, Fundamentals and Applications, 547–561, Swansea, (1995). Pineridge Press. [9] J. Mazars and G. Pijaudier-Cabot. Continuum damage theory - application to con- crete. ASCE J. Eng. Mech., 115(2), 345–365, (1987). [10] R. Larsson and K. Runesson...

Wells, G N; Sluys, L J

251

A Simple Quantum-Mechanical Model of Spacetime II: Thermodynamics of Spacetime  

E-Print Network (OSTI)

In this second part of our series of two papers, where spacetime is modelled by a graph, where Planck size quantum black holes lie on the vertices, we consider the thermodynamics of spacetime. We formulate an equation which tells in which way an accelerating, spacelike two-surface of spacetime interacts with the thermal radiation flowing through that surface. In the low temperature limit, where most quantum black holes constituting spacetime are assumed to lie in the ground state, our equation implies, among other things, the Hawking and the Unruh effects, as well as Einstein's field equation with a vanishing cosmological constant for general matter fields. We also consider the high temperature limit, where the microscopic black holes are assumed to lie in highly excited states. In this limit our model implies, among other things, that black hole entropy depends logarithmically on its area, instead of being proportional to the area.

J. Makela

2008-05-26T23:59:59.000Z

252

Injection-Molded Long-Fiber Thermoplastic Composites: From Process Modeling to Prediction of Mechanical Properties  

SciTech Connect

This article illustrates the predictive capabilities for long-fiber thermoplastic (LFT) composites that first simulate the injection molding of LFT structures by Autodesk® Simulation Moldflow® Insight (ASMI) to accurately predict fiber orientation and length distributions in these structures. After validating fiber orientation and length predictions against the experimental data, the predicted results are used by ASMI to compute distributions of elastic properties in the molded structures. In addition, local stress-strain responses and damage accumulation under tensile loading are predicted by an elastic-plastic damage model of EMTA-NLA, a nonlinear analysis tool implemented in ABAQUS® via user-subroutines using an incremental Eshelby-Mori-Tanaka approach. Predicted stress-strain responses up to failure and damage accumulations are compared to the experimental results to validate the model.

Nguyen, Ba Nghiep; Kunc, Vlastimil; Jin, Xiaoshi; Tucker III, Charles L.; Costa, Franco

2013-12-18T23:59:59.000Z

253

MechanicalTesting  

NLE Websites -- All DOE Office Websites (Extended Search)

structures, validation of encapsulant cure stress models, development of frac- ture mechanics tests for use in adhesion studies and understanding the failure mechanism of...

254

Class of model problems in three-body quantum mechanics that admit exact solutions  

Science Conference Proceedings (OSTI)

An approach to solving scattering problems in three-body systems for cases where the mass of one of the particles is extremely small in relation to the masses of the other two particles and where the pair potentials of interaction between the particles involved are separable is developed. Exact analytic solutions to such model problems are found for the scattering of a light particle on two fixed centers and on two interacting heavy particles. It is shown that new resonances and a dynamical resonance enhancement may appear in a three-body system.

Takibayev, N. Zh., E-mail: teta@nursat.kz [Abay Kazakh National Pedagogical University (Kazakhstan)

2008-03-15T23:59:59.000Z

255

Lipid Flip-Flop Driven Mechanical and Morphological Changes in Model Membranes  

E-Print Network (OSTI)

We study, using dissipative particle dynamics simulations, the effect of active lipid flip-flop on model fluid bilayer membranes. We consider both cases of symmetric as well as asymmetric flip-flops. Symmetric flip-flop leads to a steady state of the membrane with an effective temperature higher than that of the equilibrium membrane and an effective surface tension lower than that of the equilibrium membrane. Asymmetric flip-flop leads to transient conformational changes of the membrane in the form of bud or blister formation, depending on the flip rate.

Sanoop Ramachandran; P. B. Sunil Kumar; Mohamed Laradji

2008-07-31T23:59:59.000Z

256

Zigzagging causility model of EPR correlations and on the interpretation of quantum mechanics  

Science Conference Proceedings (OSTI)

Being formalized inside the S-matrix scheme, the zigzagging causility model of EPR correlations has full Lorentz and CPT invariance. EPR correlations, proper or reversed, and Wheeler's smoky dragon metaphor are respectively pictured in a spacetime or in the momentum-energy space, as V-shaped, anti LAMBDA-shaped, or C-shaped ABC zigzags, with a summation at B over virtual states absolute value B>=*. The reversibility = * implies that causality is CPT-invariant, or arrowless, at the microlevel. Arrowed causality is a macroscopic emergence, corollary to wave retardation and probability increase. Factlike irreversibility states repression, not suppression, of blind statistical retrodiction- that is, of final cause.

de Beauregard, O.C.

1988-09-01T23:59:59.000Z

257

First-principles calculation of mechanical properties of Si <001> nanowires and comparison to nanomechanical theory  

DOE Green Energy (OSTI)

We report the results of first-principles density functional theory calculations of the Young's modulus and other mechanical properties of hydrogen-passivated Si {l_angle}001{r_angle} nanowires. The nanowires are taken to have predominantly {l_brace}100{r_brace}surfaces, with small {l_brace}110{r_brace} facets according to the Wulff shape. The Young's modulus, the equilibrium length and the constrained residual stress of a series of prismatic beams of differing sizes are found to have size dependences that scale like the surface area to volume ratio for all but the smallest beam. The results are compared with a continuum model and the results of classical atomistic calculations based on an empirical potential. We attribute the size dependence to specific physical structures and interactions. In particular, the hydrogen interactions on the surface and the charge density variations within the beam are quantified and used both to parameterize the continuum model and to account for the discrepancies between the two models and the first-principles results.

Lee, B; Rudd, R E

2006-10-19T23:59:59.000Z

258

Modeling shear failure and permeability enhancement due to coupled Thermal-Hydrological-Mechanical processes in Enhanced Geothermal Reservoirs  

Science Conference Proceedings (OSTI)

The connectivity and accessible surface area of flowing fractures, whether natural or man-made, is possibly the single most important factor, after temperature, which determines the feasibility of an Enhanced Geothermal System (EGS). Rock deformation and in-situ stress changes induced by injected fluids can lead to shear failure on preexisting fractures which can generate microseismic events, and also enhance the permeability and accessible surface area of the geothermal formation. Hence, the ability to accurately model the coupled thermal-hydrologic-mechanical (THM) processes in fractured geological formations is critical in effective EGS reservoir development and management strategies. The locations of the microseismic events can serve as indicators of the zones of enhanced permeability, thus providing vital information for verification of the coupled THM models. We will describe a general purpose computational code, FEHM, developed for this purpose, that models coupled THM processes during multiphase fluid flow and transport in fractured porous media. The code incorporates several models of fracture aperture and stress behavior combined with permeability relationships. We provide field scale examples of applications to geothermal systems to demonstrate the utility of the method.

Kelkar, Sharad [Los Alamos National Laboratory

2011-01-01T23:59:59.000Z

259

A new modeling approach of STLF with integrated dynamics mechanism and based on the fusion of dynamic optimal neighbor phase points and ICNN  

Science Conference Proceedings (OSTI)

Based on the time evolution similarity principle of the topological neighbor phase points in the Phase Space Reconstruction (PSR), a new modeling approach of Short-Term Load Forecasting (STLF) with integrated dynamics mechanism and based on the fusion ...

Zhisheng Zhang; Yaming Sun; Shiying Zhang

2006-05-01T23:59:59.000Z

260

Adaptive Breast Radiation Therapy Using Modeling of Tissue Mechanics: A Breast Tissue Segmentation Study  

Science Conference Proceedings (OSTI)

Purpose: To validate and compare the accuracy of breast tissue segmentation methods applied to computed tomography (CT) scans used for radiation therapy planning and to study the effect of tissue distribution on the segmentation accuracy for the purpose of developing models for use in adaptive breast radiation therapy. Methods and Materials: Twenty-four patients receiving postlumpectomy radiation therapy for breast cancer underwent CT imaging in prone and supine positions. The whole-breast clinical target volume was outlined. Clinical target volumes were segmented into fibroglandular and fatty tissue using the following algorithms: physical density thresholding; interactive thresholding; fuzzy c-means with 3 classes (FCM3) and 4 classes (FCM4); and k-means. The segmentation algorithms were evaluated in 2 stages: first, an approach based on the assumption that the breast composition should be the same in both prone and supine position; and second, comparison of segmentation with tissue outlines from 3 experts using the Dice similarity coefficient (DSC). Breast datasets were grouped into nonsparse and sparse fibroglandular tissue distributions according to expert assessment and used to assess the accuracy of the segmentation methods and the agreement between experts. Results: Prone and supine breast composition analysis showed differences between the methods. Validation against expert outlines found significant differences (P<.001) between FCM3 and FCM4. Fuzzy c-means with 3 classes generated segmentation results (mean DSC = 0.70) closest to the experts' outlines. There was good agreement (mean DSC = 0.85) among experts for breast tissue outlining. Segmentation accuracy and expert agreement was significantly higher (P<.005) in the nonsparse group than in the sparse group. Conclusions: The FCM3 gave the most accurate segmentation of breast tissues on CT data and could therefore be used in adaptive radiation therapy-based on tissue modeling. Breast tissue segmentation methods should be used with caution in patients with sparse fibroglandular tissue distribution.

Juneja, Prabhjot, E-mail: Prabhjot.Juneja@icr.ac.uk [Joint Department of Physics, Institute of Cancer Research, Sutton (United Kingdom)] [Joint Department of Physics, Institute of Cancer Research, Sutton (United Kingdom); Harris, Emma J. [Joint Department of Physics, Institute of Cancer Research, Sutton (United Kingdom)] [Joint Department of Physics, Institute of Cancer Research, Sutton (United Kingdom); Kirby, Anna M. [Department of Academic Radiotherapy, Royal Marsden National Health Service Foundation Trust, Sutton (United Kingdom)] [Department of Academic Radiotherapy, Royal Marsden National Health Service Foundation Trust, Sutton (United Kingdom); Evans, Philip M. [Joint Department of Physics, Institute of Cancer Research, Sutton (United Kingdom)] [Joint Department of Physics, Institute of Cancer Research, Sutton (United Kingdom)

2012-11-01T23:59:59.000Z

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261

The n+n+{alpha} system in a continuum Faddeev formulation  

Science Conference Proceedings (OSTI)

The continuum Faddeev equations for the neutron-neutron-alpha (n+n+{alpha}) system are formulated for a general interaction as well as for finite rank forces. In addition, the capture process n+n+{alpha}{yields}{sup 6}He+{gamma} is derived.

Khaldi, K. [Institute of Nuclear and Particle Physics, Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States); Faculte des Sciences, Universite de Boumerdes, 35000 Boumerdes (Algeria); Elster, Ch. [Institute of Nuclear and Particle Physics, Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States); Gloeckle, W. [Institut fuer Theoretische Physik II, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2010-11-15T23:59:59.000Z

262

Efficient Evaluation of Binding Free Energy Using Continuum Electrostatics Danzhi Huang and Amedeo Caflisch*  

E-Print Network (OSTI)

Efficient Evaluation of Binding Free Energy Using Continuum Electrostatics Solvation Danzhi Huang of the absolute free energy of binding. A predictive accuracy of about 1.0 kcal/mol is obtained for 13 and 29 into proteins of known structure require fast and accurate methods for the evaluation of binding free energies.1

Caflisch, Amedeo

263

Deliberate Science, Continuum Magazine: Clean Energy Innovation at NREL, Winter 2012 (Book)  

Science Conference Proceedings (OSTI)

This quarterly magazine is dedicated to stepping beyond the technical journals to reveal NREL's vital work in a real-world context for our stakeholders. Continuum provides insights into the latest and most impactful clean energy innovations, while spotlighting those talented researchers and unique facilities that make it all happen. This edition focuses on deliberate science.

Not Available

2012-02-01T23:59:59.000Z

264

NREL: Continuum Magazine - Electric Vehicle Battery Development Gains  

NLE Websites -- All DOE Office Websites (Extended Search)

Electric Vehicle Battery Development Gains Momentum Electric Vehicle Battery Development Gains Momentum Issue 5 Print Version Share this resource Electric Vehicle Battery Development Gains Momentum CAEBAT collaboration targets EDV batteries with longer range and lifespan, at a lower cost. A photo of two men silhouetted in front of six back-lit display screens showing battery models, located in a dark room (22008). Enlarge image NREL's modeling, simulation, and testing activities include battery safety assessment, next-generation battery technologies, material synthesis and research, subsystem analysis, and battery second use studies. Photo by Dennis Schroeder, NREL "When people get behind the wheel of an electric car, it should be a great driving experience. Period." Dr. Taeyoung Han, GM technical fellow, said,

265

Development Status of the PEBBLES Code for Pebble Mechanics: Improved Physical Models and Speed-up  

SciTech Connect

PEBBLES is a code for simulating the motion of all the pebbles in a pebble bed reactor. Since pebble bed reactors are packed randomly and not precisely placed, the location of the fuel elements in the reactor is not deterministically known. Instead, when determining operating parameters the motion of the pebbles can be simulated and stochastic locations can be found. The PEBBLES code can output information relevant for other simulations of the pebble bed reactors such as the positions of the pebbles in the reactor, packing fraction change in an earthquake, and velocity profiles created by recirculation. The goal for this level three milestone was to speedup the PEBBLES code through implementation on massively parallel computer. Work on this goal has resulted in speeding up both the single processor version and creation of a new parallel version of PEBBLES. Both the single processor version and the parallel running capability of the PEBBLES code have improved since the fiscal year start. The hybrid MPI/OpenMP PEBBLES version was created this year to run on the increasingly common cluster hardware profile that combines nodes with multiple processors that share memory and a cluster of nodes that are networked together. The OpenMP portions use the Open Multi-Processing shared memory parallel processing model to split the task across processors in a single node that shares memory. The Message Passing Interface (MPI) portion uses messages to communicate between different nodes over a network. The following are wall clock speed up for simulating an NGNP-600 sized reactor. The single processor version runs 1.5 times faster compared to the single processor version at the beginning of the fiscal year. This speedup is primarily due to the improved static friction model described in the report. When running on 64 processors, the new MPI/OpenMP hybrid version has a wall clock speed up of 22 times compared to the current single processor version. When using 88 processors, a speed up of 23 times is achieved. This speedup and other improvements of PEBBLES combine to make PEBBLES more capable and more useful for simulation of a pebble bed reactor. This report details the implementation and effects of the speedup work done over the course of the fiscal year.

Joshua J. Cogliati; Abderrafi M. Ougouag

2009-12-01T23:59:59.000Z

266

Development Status of the PEBBLES Code for Pebble Mechanics: Improved Physical Models and Speed-up  

DOE Green Energy (OSTI)

PEBBLES is a code for simulating the motion of all the pebbles in a pebble bed reactor. Since pebble bed reactors are packed randomly and not precisely placed, the location of the fuel elements in the reactor is not deterministically known. Instead, when determining operating parameters the motion of the pebbles can be simulated and stochastic locations can be found. The PEBBLES code can output information relevant for other simulations of the pebble bed reactors such as the positions of the pebbles in the reactor, packing fraction change in an earthquake, and velocity profiles created by recirculation. The goal for this level three milestone was to speedup the PEBBLES code through implementation on massively parallel computer. Work on this goal has resulted in speeding up both the single processor version and creation of a new parallel version of PEBBLES. Both the single processor version and the parallel running capability of the PEBBLES code have improved since the fiscal year start. The hybrid MPI/OpenMP PEBBLES version was created this year to run on the increasingly common cluster hardware profile that combines nodes with multiple processors that share memory and a cluster of nodes that are networked together. The OpenMP portions use the Open Multi-Processing shared memory parallel processing model to split the task across processors in a single node that shares memory. The Message Passing Interface (MPI) portion uses messages to communicate between different nodes over a network. The following are wall clock speed up for simulating an NGNP-600 sized reactor. The single processor version runs 1.5 times faster compared to the single processor version at the beginning of the fiscal year. This speedup is primarily due to the improved static friction model described in the report. When running on 64 processors, the new MPI/OpenMP hybrid version has a wall clock speed up of 22 times compared to the current single processor version. When using 88 processors, a speed up of 23 times is achieved. This speedup and other improvements of PEBBLES combine to make PEBBLES more capable and more useful for simulation of a pebble bed reactor. This report details the implementation and effects of the speedup work done over the course of the fiscal year.

Joshua J. Cogliati; Abderrafi M. Ougouag

2009-09-01T23:59:59.000Z

267

Modified Fowler-Milne method for the spectroscopic determination of thermal plasma temperature without the measurement of continuum radiation  

Science Conference Proceedings (OSTI)

A technique based on the Fowler-Milne method for the spectroscopic determination of thermal plasma temperatures without measuring continuum radiation is presented. This technique avoids the influence of continuum radiation with the combined line and continuum emission coefficients to derive the plasma temperatures. The amount of continuum emission coefficient is estimated by using an expression related to the Biberman factors. Parameters that affect the accuracy of the proposed technique and errors in the measured plasma temperatures are analyzed. It is shown that, by using the Ar I 696.5 nm line with a bandwidth of 3.27 nm without taking into account the continuum radiation, the plasma temperature measured will be lower on the order of up to 1000-3000 K for temperatures from 20 000 to 24 000 K. The theoretically predicted temperature errors are in good agreement with the experimental results, indicating that the proposed technique is reliable for plasma temperature measurement.

Ma Shuiliang [State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China); Plasma Research Laboratory, Australian National University, Canberra ACT 0200 (Australia); Gao Hongming; Wu Lin [State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China)

2011-01-15T23:59:59.000Z

268

Performance Evaluation of K-DEMO Cable-in-conduit Conductors Using the Florida Electro-Mechanical Cable Model  

Science Conference Proceedings (OSTI)

The United States ITER Project Office (USIPO) is responsible for design of the Toroidal Field (TF) insert coil, which will allow validation of the performance of significant lengths of the conductors to be used in the full scale TF coils in relevant conditions of field, current density and mechanical strain. The Japan Atomic Energy Agency (JAEA) will build the TF insert which will be tested at the Central Solenoid Model Coil (CSMC) Test facility at JAEA, Naka, Japan. Three dimensional mathematical model of TF Insert was created based on the initial design geometry data, and included the following features: orthotropic material properties of superconductor material and insulation; external magnetic field from CSMC, temperature dependent properties of the materials; pre-compression and plastic deformation in lap joint. Major geometrical characteristics of the design were preserved including cable jacket and insulation shape, mandrel outline, and support clamps and spacers. The model is capable of performing coupled structural, thermal, and electromagnetic analysis using ANSYS. Numerical simulations were performed for room temperature conditions; cool down to 4K, and the operating regime with 68kA current at 11.8 Tesla background field. Numerical simulations led to the final design of the coil producing the required strain levels on the cable, while simultaneously satisfying the ITER magnet structural design criteria.

Zhai, Yuhu

2013-07-16T23:59:59.000Z

269

A mechanics-based virtual model of NEES-UCSD shake table : theoretical development and experimental validation  

E-Print Network (OSTI)

17th ASCE Engineering Mechanics Conference , Newark, U.S.A,Journal of Engineering Mechanics, ASCE , 129(12). Thoen, B.Journal of Engineering Mechanics , 129(12), 2003. Van Den

Ozcelik, Ozgur

2008-01-01T23:59:59.000Z

270

A molecular line and continuum study of water maser sources  

E-Print Network (OSTI)

and the submm cores 131 6.1 Maser excitation 131 6.1.1 The water molecule and maser theory 131 6.1.2 Models 134 6.2 Comparison with observations 137 7 Conclusions 143 7.1 The maser environment 144 7.2 The longevity of the maser phase 145 7.3 Maser excitation 146... wavelengths was the hydroxyl radical, OH (Weinreb et al. 1963). The simultaneous detection of four OH lines, corresponding to the rotation levels of this molecule splitting into four states, provides information on the population distribution; signi ficant de...

Jenness, Timothy

1996-12-10T23:59:59.000Z

271

THERMO-HYDRO-MECHANICAL MODELING OF WORKING FLUID INJECTION AND THERMAL ENERGY EXTRACTION IN EGS FRACTURES AND ROCK MATRIX  

DOE Green Energy (OSTI)

Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing), to create the reservoir. The advancement of EGS greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid-heat system and our ability to reliably predict how reservoirs behave under stimulation and production. Reliable performance predictions of EGS reservoirs require accurate and robust modeling for strongly coupled thermal-hydrological-mechanical (THM) processes. Conventionally, these types of problems have been solved using operator-splitting methods, usually by coupling a subsurface flow and heat transport simulators with a solid mechanics simulator via input files. An alternative approach is to solve the system of nonlinear partial differential equations that govern multiphase fluid flow, heat transport, and rock mechanics simultaneously, using a fully coupled, fully implicit solution procedure, in which all solution variables (pressure, enthalpy, and rock displacement fields) are solved simultaneously. This paper describes numerical simulations used to investigate the poro- and thermal- elastic effects of working fluid injection and thermal energy extraction on the properties of the fractures and rock matrix of a hypothetical EGS reservoir, using a novel simulation software FALCON (Podgorney et al., 2011), a finite element based simulator solving fully coupled multiphase fluid flow, heat transport, rock deformation, and fracturing using a global implicit approach. Investigations are also conducted on how these poro- and thermal-elastic effects are related to fracture permeability evolution.

Robert Podgorney; Chuan Lu; Hai Huang

2012-01-01T23:59:59.000Z

272

Microsoft Word - Evaluation of an Incremental Ventilation Energy Model for Estimating Impacts of Air Sealing and Mechanical Ventilation_Final2.docx  

NLE Websites -- All DOE Office Websites (Extended Search)

XXXXX | Logue et al., Evaluation of an Incremental Ventilation Energy Model for Estimating XXXXX | Logue et al., Evaluation of an Incremental Ventilation Energy Model for Estimating Impacts of Air Sealing and Mechanical Ventilation 1 Evaluation of an Incremental Ventilation Energy Model for Estimating Impacts of Air Sealing and Mechanical Ventilation Jennifer M. Logue, William J. N. Turner, Iain S. Walker, and Brett C. Singer Environmental Energy Technologies Division June 2012 LBNL-5796E LBNL-XXXXX | Logue et al., Evaluation of an Incremental Ventilation Energy Model for Estimating Impacts of Air Sealing and Mechanical Ventilation 2 Disclaimer This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor The Regents of the University of California, nor

273

Green's function method for strength function in three-body continuum  

E-Print Network (OSTI)

Practical methods to compute dipole strengths for a three-body system by using a discretized continuum are analyzed. New techniques involving Green's function are developed, either by correcting the tail of the approximate wave function in a direct calculation of the strength function or by using a solution of a driven Schroedinger equation in a summed expression of the strength. They are compared with the complex scaling method and the Lorentz integral transform, also making use of a discretized continuum. Numerical tests are performed with a hyperscalar three-body potential in the hyperspherical-harmonics formalism. They show that the Lorentz integral transform method is less practical than the other methods because of a difficult inverse transform. These other methods provide in general comparable accuracies.

Y. Suzuki; W. Horiuchi; D. Baye

2009-12-10T23:59:59.000Z

274

Free radicals in biological energy conversion: EPR studies of model systems. Final report. [Mechanism of chlorophyll participation in photosynthesis  

DOE Green Energy (OSTI)

Energy conversion in photosynthesis is known to proceed via light-induced one-electron transfer reactions involving chlorophyll and electron donors and acceptors. Although the chemical identities of all of the components have not as yet been elucidated, considerable evidence has been accumulated which points to quinones (Q) as primary electron acceptors in both green plants and bacterial photosynthesis. Furthermore, it has been established that the initial photoprocess leads to the formation of a chlorophyll cation radical (C./sup +/). The research described in this report has as its goal the elucidation of the molecular-electronic mechanism of chlorophyll participation in photosynthesis. The following reactions have been observed: (a) Photoproduction of C./sup +/ in solution in the absence of added electron acceptors. This is a low quantum yield reaction which proceeds via the lowest excited singlet state. Bacteriochlorophyll also undergoes this reaction, whereas pheophytin does not. (b) One-electron phototransfer between the chlorophyll lowest triplet state and quinones to yield a radical pair (C./sup +/ - Q./sup +/). This may either recombine or separate. The C./sup +/ formed upon separation is unstable and reacts with hydroxylic compounds to regenerate chlorophyll. The Q./sup -/ species partly reacts with oxidized solvent and partly disproportionates. Both bacteriochlorophyll and pheophytin are also able to react with quinones in this manner. The quenching of the chlorophyll lowest singlet state by quinones does not, however, lead to detectable radical formation. These reactions seem to provide acceptable models for certain aspects of photosynthetic energy conversion, and thus elucidation of their detailed mechanisms should lead to useful insights into the nature of the biological process.

Tollin, G.

1976-08-31T23:59:59.000Z

275

Detailed measurement of the e+e- pair continuum in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV and implications for direct photon production  

E-Print Network (OSTI)

PHENIX has measured the e^+e^- pair continuum in sqrt(s_NN)=200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. The e^+e^- yield is compared to the expectations from hadronic sources, based on PHENIX measurements. In the intermediate mass region, between the masses of the phi and the J/psi meson, the yield is consistent with expectations from correlated c^bar-c production, though other mechanisms are not ruled out. In the low mass region (below the phi) the p+p inclusive mass spectrum is well described by known contributions from light meson decays. In contrast, the Au+Au minimum bias inclusive mass spectrum in this region shows an enhancement by a factor of 4.7+/-0.4(stat)+/-1.5(syst)+/-0.9(model) At low mass (m_eedirect photons. This excess is used to infer the yield of real direct photons. In central Au+Au collisions, the excess of the direct photon yield over the p+p is exponential in p_T, with inverse slope T=221+/-19(stat)+/-19(syst) MeV. Hydrodynamical models with initial temperatures ranging from T_init ~=300--600 MeV at times of 0.6--0.15 fm/c after the collision are in qualitative agreement with the direct photon data in Au+Au. For low p_T<1 GeV/c the low mass region shows a further significant enhancement that increases with centrality and has an inverse slope of T ~=100 MeV. Theoretical models under predict the low mass, low p_T enhancement.

PHENIX Collaboration; A. Adare

2009-12-01T23:59:59.000Z

276

Very blue UV-continuum slopes of low luminosity z~7 galaxies from WFC3/IR: Evidence for extremely low metallicities?  

E-Print Network (OSTI)

We use the ultra-deep WFC3/IR data over the HUDF and the Early Release Science WFC3/IR data over the CDF-South GOODS field to quantify the broadband spectral properties of star-forming galaxies at z~7. We determine the UV-continuum slope beta in these galaxies, and compare the slopes with galaxies at later times to measure the evolution in beta. For luminous L*(z=3) galaxies, we measure a mean UV-continuum slope beta of -2.0+/-0.2, which is comparable to the beta~-2 derived at similar luminosities at z~5-6. However, for the lower luminosity 0.1L*(z=3) galaxies, we measure a mean beta of -3.0+/-0.2. This is substantially bluer than is found for similar luminosity galaxies at z~4, just 800 Myr later, and even at z~5-6. In principle, the observed beta of -3.0 can be matched by a very young, dust-free stellar population, but when nebular emission is included the expected beta becomes >~-2.7. To produce these very blue beta's (i.e., beta~-3), extremely low metallicities and mechanisms to reduce the red nebular emi...

Bouwens, R J; Oesch, P A; Trenti, M; Stiavelli, M; Carollo, M; Franx, M; Van Dokkum, P G; Labbé, I; Magee, D

2009-01-01T23:59:59.000Z

277

Hierarchical Models for Batteries: Overview with Some Case Studies  

Science Conference Proceedings (OSTI)

Batteries are complex multiscale systems and a hierarchy of models has been employed to study different aspects of batteries at different resolutions. For the electrochemistry and charge transport, the models span from electric circuits, single-particle, pseudo 2D, detailed 3D, and microstructure resolved at the continuum scales and various techniques such as molecular dynamics and density functional theory to resolve the atomistic structure. Similar analogies exist for the thermal, mechanical, and electrical aspects of the batteries. We have been recently working on the development of a unified formulation for the continuum scales across the electrode-electrolyte-electrode system - using a rigorous volume averaging approach typical of multiphase formulation. This formulation accounts for any spatio-temporal variation of the different properties such as electrode/void volume fractions and anisotropic conductivities. In this talk the following will be presented: The background and the hierarchy of models that need to be integrated into a battery modeling framework to carry out predictive simulations, Our recent work on the unified 3D formulation addressing the missing links in the multiscale description of the batteries, Our work on microstructure resolved simulations for diffusion processes, Upscaling of quantities of interest to construct closures for the 3D continuum description, Sample results for a standard Carbon/Spinel cell will be presented and compared to experimental data, Finally, the infrastructure we are building to bring together components with different physics operating at different resolution will be presented. The presentation will also include details about how this generalized approach can be applied to other electrochemical storage systems such as supercapacitors, Li-Air batteries, and Lithium batteries with 3D architectures.

Pannala, Sreekanth [ORNL; Mukherjee, Partha P [ORNL; Allu, Srikanth [ORNL; Nanda, Jagjit [ORNL; Martha, Surendra K [ORNL; Dudney, Nancy J [ORNL; Turner, John A [ORNL

2012-01-01T23:59:59.000Z

278

Pore-scale study of capillary trapping mechanism during CO2 injection in geological formations  

SciTech Connect

Geological sequestration of CO{sub 2} gas emerged as a promising solution for reducing amount of green house gases in atmosphere. A number of continuum scale models are available to describe the transport phenomena of CO{sub 2} sequestration. These models rely heavily on a phenomenological description of subsurface transport phenomena and the predictions can be highly uncertain. Pore-scale models provide a better understanding of fluid displacement processes, nonetheless such models are rare. In this work we use a Smoothed Particle Hydrodynamics (SPH) model to study pore-scale displacement and capillary trapping mechanisms of super-critical CO{sub 2} in the subsurface. Simulations are carried out to investigate the effects of gravitational, viscous, and capillary forces in terms of Gravity, Capillary, and Bond numbers. Contrary to the other published continuum scale investigations, we found that not only Gravity number but also Capillary number plays an important role on the fate of injected CO{sub 2}. For large Gravity numbers (on the order of 10), most of the injected CO{sub 2} reaches the cap-rock due to gravity segregation. A significant portion of CO{sub 2} gets trapped by capillary forces when Gravity number is small (on the order of 0.1). When Gravity number is moderately high (on the order of 1), trapping patterns are heavily dependent on Capillary number. If Capillary number is very small (less than 0.001), then capillary forces dominate the buoyancy forces and a significant fraction of injected CO{sub 2} is trapped by the capillary forces. Conversely, if Capillary number is high (higher than 0.001), capillary trapping is relatively small since buoyancy dominates the capillary forces. In addition, our simulations reveal different types of capillary trapping and flow displacement mechanisms during and after injection. In gravity dominated cases leave behind was the widespread trapping mechanism. Division was the primary trapping mechanism in viscous dominated cases. In capillary dominated cases, snap-off of the CO{sub 2} plume is the most commonly observed displacement mechanism. Large CO{sub 2} blobs are created due to coalescence mechanism.

Bandara, Uditha C.; Tartakovsky, Alexandre M.; Palmer, Bruce J.

2011-11-01T23:59:59.000Z

279

A Hybrid approach to molecular continuum processes combiningGaussian basis functions and the discrete variable representation  

SciTech Connect

Gaussian basis functions, routinely employed in molecular electronic structure calculations, can be combined with numerical grid-based functions in a discrete variable representation to provide an efficient method for computing molecular continuum wave functions. This approach, combined with exterior complex scaling, obviates the need for slowly convergent single-center expansions, and allows one to study a variety of electron-molecule collision problems. The method is illustrated by computation of various bound and continuum properties of H2+.

Rescigno, Thomas N.; Horner, Daniel A.; Yip, Frank L.; McCurdy,C. William

2005-08-29T23:59:59.000Z

280

Discrete element modeling of rock deformation, fracture network development and permeability evolution under hydraulic stimulation  

SciTech Connect

Key challenges associated with the EGS reservoir development include the ability to reliably predict hydraulic fracturing and the deformation of natural fractures as well as estimating permeability evolution of the fracture network with time. We have developed a physics-based rock deformation and fracture propagation simulator by coupling a discrete element model (DEM) for fracturing with a network flow model. In DEM model, solid rock is represented by a network of discrete elements (often referred as particles) connected by various types of mechanical bonds such as springs, elastic beams or bonds that have more complex properties (such as stress-dependent elastic constants). Fracturing is represented explicitly as broken bonds (microcracks), which form and coalesce into macroscopic fractures when external and internal load is applied. The natural fractures are represented by a series of connected line segments. Mechanical bonds that intersect with such line segments are removed from the DEM model. A network flow model using conjugate lattice to the DEM network is developed and coupled with the DEM. The fluid pressure gradient exerts forces on individual elements of the DEM network, which therefore deforms the mechanical bonds and breaks them if the deformation reaches a prescribed threshold value. Such deformation/fracturing in turn changes the permeability of the flow network, which again changes the evolution of fluid pressure, intimately coupling the two processes. The intimate coupling between fracturing/deformation of fracture networks and fluid flow makes the meso-scale DEM- network flow simulations necessary in order to accurately evaluate the permeability evolution, as these methods have substantial advantages over conventional continuum mechanical models of elastic rock deformation. The challenges that must be overcome to simulate EGS reservoir stimulation, preliminary results, progress to date and near future research directions and opportunities will be discussed. Methodology for coupling the DEM model with continuum flow and heat transport models will also be discussed.

Shouchun Deng; Robert Podgorney; Hai Huang

2011-02-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

A triple-continuum approach for modeling flow and transport processes in fractured rock  

E-Print Network (OSTI)

Multiphase Tracer Transport in Heterogeneous Fractured Porousmultiphase, nonisothermal flow and solute transport in fractured porousmultiphase fluid flow, heat transfer, and chemical migration in a fractured porous

Wu, Yu-Shu; Liu, H.H.; Bodvarsson, G.S; Zellmer, K .E.

2001-01-01T23:59:59.000Z

282

Multiscale modeling of nano/micro systems by a multiscale continuum field theory  

E-Print Network (OSTI)

a multiscale the- ory for nano/micro physics. Phil Mag 85:2006) Conservation laws at nano/micro scales. J Mech MaterStresses and strains at nano/micro scales. J Mech Mater

Zeng, Xiaowei; Wang, Xianqiao; Lee, James D.; Lei, Yajie

2011-01-01T23:59:59.000Z

283

On homogenized conductivity and fractal structure in a high contrast continuum percolation model  

E-Print Network (OSTI)

In the previous article (S. Matsutani and Y. Shimosako and Y. Wang, Physica A \\bf{391} (2012) 5802-5809) we numerically investigated an electric potential problem with high contrast local conductivities ($\\gamma_0$ and $\\gamma_1$, $0conductivity and the volume fraction $p$ over $[p_c,1]$. In this article, using the duality of the conductivities and the quasi-harmonic properties, we re-investigate these topics to improve these results. We show that at $\\gamma_0\\to0$, the quasi-harmonic potential problem in CPM is quasiconformally equivalent to a random slit problem, which leads us to an observation between the conformal property and the fractal structure at the threshold. Further we extend the domain $[p_c,1]$ of the approximated curve to $[0,1]$ based on the these results, which is partially generalized to three dimensional case. These curves represent well the numerical results of the conductivities.

Shigeki Matsutani; Yoshiyuki Shimosako

2013-11-26T23:59:59.000Z

284

An Effective Continuum Model for the Gas Evolution in Internal Steam Drives  

Science Conference Proceedings (OSTI)

This report examines the gas phase growth from a supersaturated, slightly compressible, liquid in a porous medium, driven by heat transfer and controlled by the application of a constant-rate decline of the system pressure.

Tsimpanogiannis, Ioannis N.; Yortsos, Yanis C.

2002-06-11T23:59:59.000Z

285

A triple-continuum pressure-transient model for a naturally fractured vuggy reservoir  

E-Print Network (OSTI)

reservoir. The fraction of oil reserves in a vuggy fracturedcontribute to oil and gas reserves and production [Kossackreserves estimation. Field Examples Pressure transient data from two oil-

2007-01-01T23:59:59.000Z

286

Wafer heating mechanisms in a molecular gas, inductively coupled plasma: in situ, real time wafer surface measurements and three-dimensional thermal modeling  

Science Conference Proceedings (OSTI)

The authors report measurements and modeling of wafer heating mechanisms in an Ar/O{sub 2} inductively coupled plasma (ICP). The authors employed a commercially available on-wafer sensor system (PlasmaTemp developed by KLA-Tencor) consisting of an on-board electronics module housing battery power and data storage with 30 temperature sensors embedded onto the wafer at different radial positions. This system allows for real time, in situ wafer temperature measurements. Wafer heating mechanisms were investigated by combining temperature measurements from the PlasmaTemp sensor wafer with a three-dimensional heat transfer model of the wafer and a model of the ICP. Comparisons between pure Ar and Ar/O{sub 2} discharges demonstrated that two additional wafer heating mechanisms can be important in molecular gas plasmas compared to atomic gas discharges. The two mechanisms are heating from the gas phase and O-atom surface recombination. These mechanisms were shown to contribute as much as 60% to wafer heating under conditions of low bias power. This study demonstrated how the 'on-wafer' temperature sensor not only yields a temperature profile distribution across the wafer, but can be used to help determine plasma characteristics, such as ion flux profiles or plasma processing temperatures.

Titus, M. J.; Graves, D. B. [Department of Chemical Engineering, University of California, Berkeley, California 94720 (United States)

2008-09-15T23:59:59.000Z

287

Radiometric modeling of mechanical draft cooling towers to assist in the extraction of their absolute temperature from remote thermal imagery.  

E-Print Network (OSTI)

??Determination of the internal temperature of a mechanical draft cooling tower (MDCT) from remotely-sensed thermal imagery is important for many applications that provide input to… (more)

Montanaro, Matthew

2009-01-01T23:59:59.000Z

288

Modeling and Computer Simulation of the Pulsed Powering of Mechanical D.C. Circuit Breakers for the CERN/LHC Superconducting Magnet Energy Extraction System  

E-Print Network (OSTI)

This article presents the results of modeling and computer simulation of non-linear devices such as the Electromagnetic Driver of a D.C. Circuit Breaker. The mechanical and electromagnetic parts of the Driver are represented as equivalent electrical circuits and all basic processes of the Driver's magnetic circuit are calculated.

Anushat, V; Erokhin, A; Kussul, A; Medvedko, A S

2000-01-01T23:59:59.000Z

289

Chemical differentiation in regions of high mass star formation II. Molecular multiline and dust continuum studies of selected objects  

E-Print Network (OSTI)

The aim of this study is to investigate systematic chemical differentiation of molecules in regions of high mass star formation. We observed five prominent sites of high mass star formation in HCN, HNC, HCO+, their isotopes, C18O, C34S and some other molecular lines, for some sources both at 3 and 1.3 mm and in continuum at 1.3 mm. Taking into account earlier obtained data for N2H+ we derive molecular abundances and physical parameters of the sources (mass, density, ionization fraction, etc.). The kinetic temperature is estimated from CH3C2H observations. Then we analyze correlations between molecular abundances and physical parameters and discuss chemical models applicable to these species. The typical physical parameters for the sources in our sample are the following: kinetic temperature in the range ~ 30-50 K (it is systematically higher than that obtained from ammonia observations and is rather close to dust temperature), masses from tens to hundreds solar masses, gas densities ~ 10^5 cm^{-3}, ionization...

Zinchenko, I; Pirogov, L

2009-01-01T23:59:59.000Z

290

Statistical Continuum Theory for the Effective Conductivity of Fiber Filled Polymer Composites: Effect of Orientation Distribution and Aspect Ratio  

Science Conference Proceedings (OSTI)

Effective conductivity of polymer composites, filled with conducting fibers such as carbon nanotubes, is studied using statistical continuum theory. The fiber orientation distribution in the matrix plays a very important role on their effective properties. To take into account their orientation, shape and distribution, two-point and three-point probability distribution functions are used. The effect of fibers orientation is illustrated by comparing the effective conductivity of microstructures with oriented and non-oriented fibers. The randomly oriented fibers result in an isotropic effective conductivity. The increased fiber orientation distribution can lead to higher anisotropy in conductivity. The effect of fiber’s aspect ratio on the effective conductivity is studied by comparing microstructures with varying degrees of fiber orientation distribution. Results show that the increase in anisotropy leads to higher conductivity in the maximum fiber orientation distribution direction and lower conductivity in the transverse direction. These results are in agreement with various models from the literature that show the increase of the aspect ratio of fibers improves the electrical and thermal conductivity.

Mikdam, Amed; Makradi, A.; Ahzi, Said; Garmestani, Hamid; Li, Dongsheng; Remond, Y.

2010-03-01T23:59:59.000Z

291

U.S. National Committee for Rock Mechanics; and Conceptual model of fluid infiltration in fractured media. Project summary, July 28, 1997--July 27, 1998  

SciTech Connect

The title describes the two tasks summarized in this report. The remainder of the report contains information on meetings held or to be held on the subjects. The US National Committee for Rock Mechanics (USNC/RM) provides for US participation in international activities in rock mechanics, principally through adherence to the International Society for Rock Mechanics (ISRM). It also keeps the US rock mechanics community informed about new programs directed toward major areas of national concern in which rock mechanics problems represent critical or limiting factors, such as energy resources, excavation, underground storage and waste disposal, and reactor siting. The committee also guides or produces advisory studies and reports on problem areas in rock mechanics. A new panel under the auspices of the US National Committee for Rock Mechanics has been appointed to conduct a study on Conceptual Models of Fluid Infiltration in Fractured Media. The study has health and environmental applications related to the underground flow of pollutants through fractured rock in and around mines and waste repositories. Support of the study has been received from the US Nuclear Regulatory Commission and the Department of Energy`s Yucca Mountain Project Office. The new study builds on the success of a recent USNC/RM report entitled Rock Fractures and Fluid Flow: Contemporary Understanding and Applications (National Academy Press, 1996, 551 pp.). A summary of the new study is provided.

1998-09-01T23:59:59.000Z

292

Compliant mechanisms  

E-Print Network (OSTI)

The motivation for this work has been a variety of motions like navigation of pipelines, insertion operations in assembly, and gripping actions, which require the adaptation of the mechanism to the external constraints, rather than avoid them. To this effect, efforts have been made in building mechanisms that obtain the required degrees of freedom through deformations rather than explicit joints in them. Although the use of many joints provides the required number of degrees of freedom, it does so at the cost of making the system very bulky and complex. With the advent of new polymers, the possibility of building joint-free mechanisms that fulfil the requirements of adaptation has increased. Based on this approach, a Magneto Active Polymer (MAP) material has been developed here at the Texas A\\&M University, in which the actuation is performed by the conversion of electromagnetic energy into mechanical energy. The initial experimentation has proved the vast potential of the use of such a material and a few mechanisms like a magneto active peristaltic pump, have been designed and tested for the first time using this material. In this mechanism, the pumping action is obtained when a moving magnetic field produces peristaltic waves in the magneto active material shaped as a tube. Also for the first time, experiments have been conducted to analyze the response of the MAP material to a pulsating magnetic field with the intent of using the experimental results to develop a model of the MAP. In developing the design for the peristaltic pump and other conceptual models described in this thesis, ideas have been drawn from the different modes of locomotion and actuators present in lower organisms. These have been good sources of inspiration for the work done in this thesis and they have been documented in detail.

Venkataraghavan, Janarthanan T

2001-01-01T23:59:59.000Z

293

A passive mechanism for thermal stress regulation in micro-machined beam-type structures: Modeling and experiment  

Science Conference Proceedings (OSTI)

In this article, a passive mechanism for thermal stress regulation in micro-bridge structures is proposed. The mechanism is essentially a set of precisely designed parallel chevron beams that replace one of the fixed ends of the micro-bridge. The axial ...

Pezhman A. Hassanpour; Patricia M. Nieva; Amir Khajepour

2012-05-01T23:59:59.000Z

294

Ten iterative steps for model development and evaluation applied to Computational Fluid Dynamics for Environmental Fluid Mechanics  

Science Conference Proceedings (OSTI)

Computational Fluid Dynamics (CFD) is increasingly used to study a wide variety of complex Environmental Fluid Mechanics (EFM) processes, such as water flow and turbulent mixing of contaminants in rivers and estuaries and wind flow and air pollution ... Keywords: Air and water quality, Building aerodynamics, Environmental Fluid Mechanics, River hydraulics, Transverse mixing, Wind flow

B. Blocken; C. Gualtieri

2012-07-01T23:59:59.000Z

295

Parabolic Sturmians approach to the three-body continuum Coulomb problem  

E-Print Network (OSTI)

The three-body continuum Coulomb problem is treated in terms of the generalized parabolic coordinates. Approximate solutions are expressed in the form of a Lippmann-Schwinger type equation, where the Green's function includes the leading term of the kinetic energy and the total potential energy, whereas the potential contains the non-orthogonal part of the kinetic energy operator. As a test of this approach, the integral equation for the $(e^-,\\, e^-,\\, {{He}^{++}})$ system is solved numerically by using the parabolic Sturmian basis representation of the (approximate) potential. Convergence of the expansion coefficients of the solution is obtained as the basis set used to describe the potential is enlarged.

S. A. Zaytsev; Yu. V. Popov; B. Piraux

2011-08-19T23:59:59.000Z

296

Statistics of the Air-Sea Fluxes of Momentum and Mechanical Energy in a Coupled Wave-Atmosphere Model  

Science Conference Proceedings (OSTI)

An atmospheric general circulation model (GCM) and a wind wave model are coupled through the wind stress. The wind stress which forces the wave model, depends in the coupled model on the stage of development of the wave field. As the waves depend ...

Susanne L. Weber

1994-06-01T23:59:59.000Z

297

A Mechanism for the Increase of Wind Stress (Drag) Coefficient with Wind Speed over Water Surfaces: A Parametric Model  

Science Conference Proceedings (OSTI)

A mechanism is proposed for a physical explanation of the increase in wind stress (drag) coefficient with wind speed over water surfaces. The formula explicitly incorporates the contribution of both winds and waves through the parameterizations ...

S. A. Hsu

1986-01-01T23:59:59.000Z

298

Simulating flame lift-off characteristics of diesel and biodiesel fuels using detailed chemical-kinetic mechanisms and LES turbulence model.  

DOE Green Energy (OSTI)

Combustion in direct-injection diesel engines occurs in a lifted, turbulent diffusion flame mode. Numerous studies indicate that the combustion and emissions in such engines are strongly influenced by the lifted flame characteristics, which are in turn determined by fuel and air mixing in the upstream region of the lifted flame, and consequently by the liquid breakup and spray development processes. From a numerical standpoint, these spray combustion processes depend heavily on the choice of underlying spray, combustion, and turbulence models. The present numerical study investigates the influence of different chemical kinetic mechanisms for diesel and biodiesel fuels, as well as Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) turbulence models on predicting flame lift-off lengths (LOLs) and ignition delays. Specifically, two chemical kinetic mechanisms for n-heptane (NHPT) and three for biodiesel surrogates are investigated. In addition, the RNG k-{epsilon} (RANS) model is compared to the Smagorinsky based LES turbulence model. Using adaptive grid resolution, minimum grid sizes of 250 {micro}m and 125 {micro}m were obtained for the RANS and LES cases respectively. Validations of these models were performed against experimental data from Sandia National Laboratories in a constant volume combustion chamber. Ignition delay and flame lift-off validations were performed at different ambient temperature conditions. The LES model predicts lower ignition delays and qualitatively better flame structures compared to the RNG k-{epsilon} model. The use of realistic chemistry and a ternary surrogate mixture, which consists of methyl decanoate, methyl 9-decenoate, and NHPT, results in better predicted LOLs and ignition delays. For diesel fuel though, only marginal improvements are observed by using larger size mechanisms. However, these improved predictions come at a significant increase in computational cost.

Som, S; Longman, D. E.; Luo, Z; Plomer, M; Lu, T; Senecal, P.K.; Pomraning, E (Energy Systems); (Univ. of Connecticut); (CONVERGENT Science)

2012-01-01T23:59:59.000Z

299

Modelling of thermo-mechanical and irradiation behavior of metallic and oxide fuels for sodium fast reactors  

E-Print Network (OSTI)

A robust and reliable code to model the irradiation behavior of metal and oxide fuels in sodium cooled fast reactors is developed. Modeling capability was enhanced by adopting a non-empirical mechanistic approach to the ...

Karahan, Aydin

2009-01-01T23:59:59.000Z

300

High-level open evolvable systems design by process-oriented modeling: application to DNA replication mechanism  

Science Conference Proceedings (OSTI)

Open Evolvable Systems' design requires a methodological [1] and conceptual paradigm different from the conventional software design. Evolvable Systems' research [2, 6, 16, and 17] has established itself as a new research field, but the content is more ... Keywords: abstractions, design, design patterns, evolvable systems, framework, method, methodologies, modeling, process-oriented modeling, requirements analysis, requirements and architecture modeling, software engineering, specification

Behzad Bastani; Hoda Bastani

2007-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Infinite cloud model of electrification by the precipitation mechanism in a possible rainout situation. Interim report, 14 January 1976--30 July 1977  

SciTech Connect

This report examines the extent to which the ionization associated with a radioactive aerosol will limit electric field growth in a thundercloud. Favored mechanisms for thundercloud electrification, called precipitation mechanisms, involve charge separation in collisions between falling hydrometeors and cloud droplets followed by separation of the resulting charged objects as the hydrometeors fall through the cloud and the droplets move with the updraft. We have extended a simple, infinite-cloud, precipitation-mechanism model to include effects due to the presence of radioactive aerosol particles. These effects involve ion generation, convection currents due to motions of ions and charged aerosol particles, and collection of ions and aerosol particles by hydrometeors and cloud droplets.

Spangler, J.D.

1977-01-01T23:59:59.000Z

302

Integrated Computational Modeling of Materials for Nuclear Energy  

Science Conference Proceedings (OSTI)

Nuclear fuel and primary cooling system structural components are exposed to elevated ... models for safety and performance evaluation of nuclear reactors but also for the ... Continuum Theory of Defects and Materials Response to Irradiation

303

Low Dose Studies with Focused X-rays in Cell and Tissue Models: Mechanisms of Bystander and Genomic Instability Responses  

SciTech Connect

The management of the risks of exposure of people to ionizing radiation is important in relation to its uses in industry and medicine, also to natural and man-made radiation in the environment. The vase majority of exposures are at a very low level of radiation dose. The risks are of inducing cancer in the exposed individuals and a smaller risk of inducing genetic damage that can be transmitted to children conceived after exposure. Studies of these risks in exposed population studies with any accuracy above the normal levels of cancer and genetic defects unless the dose levels are high. In practice, this means that our knowledge depends very largely on the information gained from the follow-up of the survivors of the atomic bombs dropped on Japanese cities. The risks calculated from these high-dose short-duration exposures then have to be projected down to the low-dose long-term exposures that apply generally. Recent research using cells in culture has revealed that the relations hi between high- and low-dose biological damage may be much more complex than had previously been thought. The aims of this and other projects in the DOE's Low-Dose Program are to gain an understanding of the biological actions of low-dose radiation, ultimately to provide information that will lead to more accurate quantification of low-dose risk. Our project is based on the concept that the processes by which radiation induces cancer start where the individual tracks of radiation impact on cells and tissues. At the dose levels of most low-dose exposures, these events are rare and any individual cells only ''sees'' radiation tracks at intervals averaging from weeks to years apart. This contracts with the atomic bomb exposures where, on average, each cell was hit by hundreds of tracks instantaneously. We have therefore developed microbeam techniques that enable us to target cells in culture with any number of tracks, from one upwards. This approach enables us to study the biological basis of the relationship between high- and low-dose exposures. The targeting approach also allows us to study very clearly a newly recognized effect of radiation, the ''bystander effect'', which appears to dominate some low-dose responses and therefore may have a significant role in low-dose risk mechanisms. Our project also addresses the concept that the background of naturally occurring oxidative damage that takes place continually in cells due to byproducts of metabolism may play a role in treatments that modify the levels of oxidative damage, either alone or in combination with low-dose irradiation. In this project, we have used human and rodent cell lines and each set of experiments has been carried out on a single cell type. However, low-dose research has to extend into tissues because signaling between cells of different types is likely to influence the responses. Our studies have therefore also included microbeam experiments using a model tissue system that consists of an explant of a small piece of pig ureter grown in culture. The structure of this tissue is similar to that of epithelium and there it relates to the tissues in which carcinoma arises. Our studies have been able to measure bystander-induced changes in the cells growing out from the tissue fragment after it has been targeted with a few radiation tracks to mimic a low-dose exposure.

Barry D. Michael; Kathryn Held; Kevin Prise

2002-12-19T23:59:59.000Z

304

Low Dose Studies with Focused X-Rays in cell and Tissue Models: Mechanisms of Bystander and Genomic Instability Responses  

SciTech Connect

The management of the risks of exposure of people to ionizing radiation is important in relation to its uses in industry and medicine, also to natural and man-made radiation in the environment. The vase majority of exposures are at a very low level of radiation dose. The risks are of inducing cancer in the exposed individuals and a smaller risk of inducing genetic damage that can be indicate that they are low. As a result, the risks are impossible to detect in population studies with any accuracy above the normal levels of cancer and genetic defects unless the dose levels are high. In practice, this means that our knowledge depends very largely on the information gained from the follow-up of the survivors of the atomic bombs dropped on Japanese cities. The risks calculated from these high-dose short-duration exposures then have to be projected down to the low-dose long-term exposures that apply generally. Recent research using cells in culture has revealed that the relationship between high- and low-dose biological damage may be much more complex than had previously been thought. The aims of this and other projects in the DOE's Low-Dose Program are to gain an understanding of the biological actions of low-dose radiation, ultimately to provide information that will lead to more accurate quantification of low-dose risk. Our project is based on the concept that the processes by which radiation induces cancer start where the individual tracks of radiation impact on cells and tissues. At the dose levels of most low-dose exposures, these events are rare and any individual cells only ''sees'' radiation tracks at intervals averaging from weeks to years apart. This contrasts with the atomic bomb exposures where, on average, each cell was hit by hundreds of tracks instantaneously. We have therefore developed microbeam techniques that enable us to target cells in culture with any numbers of tracks, from one upwards. This approach enables us to study the biological ha sis of the relationship between high- and low-dose exposures. The targeting approach also allows us to study very clearly a newly recognized effect of radiation, the ''bystander effect'', which appears to dominate some low-dose responses and therefore may have a significant role in low-dose risk mechanisms. Our project also addresses the concept that the background of naturally occurring oxidative damage that takes place continually in cells due to byproducts of metabolism may play a role in low-dose radiation risk. This project therefore also examines how cells are damaged by treatments that modify the levels of oxidative damage, either alone or in combination with low-dose irradiation. In this project, we have used human and rodent cell lines and each set of experiments has been carried out on a single cell type. However, low-dose research has to extend into tissues because signaling between cells of different types is likely to influence the responses. Our studies have therefore also included microbeam experiments using a model tissue system that consists of an explant of a small piece of pig ureter grown in culture. The structure of this tissue is similar to that of epithelium and therefore it relates to the tissues in which carcinoma arises. Our studies have been able to measure bystander-induced changes in the cells growing out from the tissue fragment after it has been targeted with a few radiation tracks to mimic a low-dose exposure.

Kathy Held; Kevin Prise; Barry Michael; Melvyn Folkard

2002-12-14T23:59:59.000Z

305

DENSE GAS TRACERS IN PERSEUS: RELATING THE N{sub 2}H{sup +}, NH{sub 3}, AND DUST CONTINUUM PROPERTIES OF PRE- AND PROTOSTELLAR CORES  

SciTech Connect

We investigate 35 prestellar cores and 36 protostellar cores in the Perseus molecular cloud. We find a very tight correlation between the physical parameters describing the N{sub 2}H{sup +} and NH{sub 3} gas. Both the velocity centroids and the line widths of N{sub 2}H{sup +} and NH{sub 3} correlate much better than either species correlates with CO, as expected if the nitrogen-bearing species are probing primarily the dense core gas where the CO has been depleted. We also find a tight correlation in the inferred abundance ratio between N{sub 2}H{sup +} and para-NH{sub 3} across all cores, with N(p-NH{sub 3})/N(N{sub 2}H{sup +}) = 22 +- 10. We find a mild correlation between NH{sub 3} (and N{sub 2}H{sup +}) column density and the (sub)millimeter dust continuum derived H{sub 2} column density for prestellar cores, N(p-NH{sub 3})/N(H{sub 2}) {approx}10{sup -8}, but do not find a fixed ratio for protostellar cores. The observations suggest that in the Perseus molecular cloud the formation and destruction mechanisms for the two nitrogen-bearing species are similar, regardless of the physical conditions in the dense core gas. While the equivalence of N{sub 2}H{sup +} and NH{sub 3} as powerful tracers of dense gas is validated, the lack of correspondence between these species and the (sub)millimeter dust continuum observations for protostellar cores is disconcerting and presently unexplained.

Johnstone, Doug; Kirk, Helen [National Research Council Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Rosolowsky, Erik [University of British Columbia Okanagan, Kelowna, BC V1V 1V7 (Canada); Tafalla, Mario, E-mail: doug.johnstone@nrc-cnrc.gc.c [Observatorio Astronomico Nacional (IGN), Alfonso XII 3, E-28014 Madrid (Spain)

2010-03-10T23:59:59.000Z

306

ME346A Introduction to Statistical Mechanics Wei Cai Stanford University Win 2011 Handout 12. Ising Model  

E-Print Network (OSTI)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.2 Monte Carlo simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4 is destroyed by thermal fluc- tuation. Hence the 2D Ising model has a critical temperature Tc, belo

Cai, Wei

307

Redshifted emission lines and radiative recombination continuum from the Wolf-Rayet binary theta Muscae: evidence for a triplet system?  

E-Print Network (OSTI)

We present XMM-Newton observations of the WC binary Theta Muscae (WR 48), the second brightest Wolf-Rayet binary in optical wavelengths. The system consists of a short-period (19.1375 days) WC5/WC6 + O6/O7V binary and possibly has an additional O supergiant companion (O9.5/B0Iab) which is optically identified at a separation of ~46 mas. Strong emission lines from highly ionized ions of C, O, Ne, Mg, Si, S, Ar, Ca and Fe are detected. The spectra are fitted by a multi-temperature thin-thermal plasma model with an interstellar absorption N_H = 2--3*10**21 cm**-2. Lack of nitrogen line indicates that the abundance of carbon is at least an order of magnitude larger than that of nitrogen. A Doppler shift of ~630 km/s is detected for the OVIII line, while similar shifts are obtained from the other lines. The reddening strongly suggests that the emission lines originated from the wind-wind shock zone, where the average velocity is ~600 km/s. The red-shift motion is inconsistent with a scenario in which the X-rays originate from the wind-wind collision zone in the short-period binary, and would be evidence supporting the widely separated O supergiant as a companion. This may make up the collision zone be lying behind the short-period binary. In addition to the emission lines, we also detected the RRC (radiative recombination continuum) structure from carbon around 0.49 keV. This implies the existence of additional cooler plasma.

Yasuharu Sugawara; Yohko Tsuboi; Yoshitomo Maeda

2008-10-07T23:59:59.000Z

308

Application of the multi-mechanism deformation model for three-dimensional simulations of salt : behavior for the strategic petroleum reserve.  

Science Conference Proceedings (OSTI)

The U.S. Strategic Petroleum Reserve stores crude oil in 62 solution-mined caverns in salt domes located in Texas and Louisiana. Historically, three-dimensional geomechanical simulations of the behavior of the caverns have been performed using a power law creep model. Using this method, and calibrating the creep coefficient to field data such as cavern closure and surface subsidence, has produced varying degrees of agreement with observed phenomena. However, as new salt dome locations are considered for oil storage facilities, pre-construction geomechanical analyses are required that need site-specific parameters developed from laboratory data obtained from core samples. The multi-mechanism deformation (M-D) model is a rigorous mathematical description of both transient and steady-state creep phenomena. Recent enhancements to the numerical integration algorithm within the model have created a more numerically stable implementation of the M-D model. This report presents computational analyses to compare the results of predictions of the geomechanical behavior at the West Hackberry SPR site using both models. The recently-published results using the power law creep model produced excellent agreement with an extensive set of field data. The M-D model results show similar agreement using parameters developed directly from laboratory data. It is also used to predict the behavior for the construction and operation of oil storage caverns at a new site, to identify potential problems before a final cavern layout is designed.

Ehgartner, Brian L.; Sobolik, Steven Ronald; Bean, James E.

2010-07-01T23:59:59.000Z

309

Determining Greenland Ice Sheet sensitivity to regional climate change: one-way coupling of a 3-D thermo-mechanical ice sheet model with a mesoscale climate model  

E-Print Network (OSTI)

responsible almost 40% of the ice sheet’s total dischargeCurrently, no coupled Greenland Ice Sheet model experimentaccelerated melting of Greenland ice sheet, Science, v. 313,

Schlegel, Nicole-Jeanne

2011-01-01T23:59:59.000Z

310

Posters Atmospheric Emitted Radiance Interferometer: Status and Water Vapor Continuum Results  

NLE Websites -- All DOE Office Websites (Extended Search)

9 9 Posters Atmospheric Emitted Radiance Interferometer: Status and Water Vapor Continuum Results H. E. Revercomb, R. O. Knuteson, W. L. Smith, F. A. Best, and R. G. Dedecker University of Wisconsin Madison, Wisconsin H. B. Howell National Oceanic and Atmospheric Administration Systems Design and Applications Branch Madison, Wisconsin Introduction Accurate and spectrally detailed observations of the thermal emission from radiatively important atmospheric gases, aerosols, and clouds are now being provided to the Atmospheric Radiation Measurement (ARM) data base by the Atmospheric Emitted Radiance Interferometer (AERI) prototype at the Southern Great Plains Cloud and Radiation Testbed (CART) site. Spectra over the range from 520 to 3000 cm -1 (3 to 19 microns) with a resolution of 0.5 cm

311

Quantum coherence and entanglement induced by the continuum between distant localized states  

Science Conference Proceedings (OSTI)

It is demonstrated that two distant quantum wells separated by a reservoir with a continuous spectrum can possess bound eigenstates embedded in the continuum. These represent a linear superposition of quantum states localized in the wells. We show that such a state can be isolated in the course of free evolution from any initial state by a null-result measurement in the reservoir, or it can be reached without such a measurement in the many-body case. The resulting superposition is regulated by the ratio of couplings between the wells and the reservoir. In particular, one can lock the system in one of the wells by enhancing this ratio. By tuning parameters of the quantum wells, many-body entangled states in distant wells can be produced through interactions and statistics.

Ping Jing [State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Li Xinqi [State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Department of Physics, Beijing Normal University, Beijing 100875 (China); Gurvitz, Shmuel [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel)

2011-04-15T23:59:59.000Z

312

Constant-temperature level densities in the quasi-continuum of Th and U isotopes  

E-Print Network (OSTI)

Particle-gamma coincidences have been measured to obtain gamma-ray spectra as a function of excitation energy for 231-233Th and 237-239U. The level densities, which were extracted using the Oslo method, show a constant temperature behavior. The isotopes display very similar temperatures in the quasi-continuum, however, the even-odd isotopes reveal a constant entropy increase Delta S compared to their even-even neighbors. The entropy excess depends on available orbitals for the last unpaired valence neutron of the heated nuclear system. Also, experimental microcanonical temperature and heat capacity have been extracted. Several poles in the heat capacity curve support the idea that an almost continuous melting of Cooper pairs is responsible for the constant-temperature behavior.

M. Guttormsen; B. Jurado; J. N. Wilson; M. Aiche; L. A. Bernstein; Q. Ducasse; F. Giacoppo; A. Goergen; F. Gunsing; T. W. Hagen; A. C. Larsen; M. Lebois; B. Leniau; T. Renstroem; S. J. Rose; S. Siem; T. Tornyi; G. M. Tveten; M. Wiedeking

2013-06-25T23:59:59.000Z

313

QCD THERMODYNAMICS WITH NF=2+1 NEAR THE CONTINUUM LIMIT AT REALISTIC QUARK MASSES.  

Science Conference Proceedings (OSTI)

We report on our study of QCD thermodynamics with 2 + 1 flavors of dynamical quarks. In this proceeding we present several thermodynamic quantities and our recent calculation of the critical temperature. In order to investigate the thermodynamic properties of QCD near the continuum limit we adopt improved staggered (p4) quarks coupled with tree-level Symanzik improved glue on N{sub t} = 4 and 6 lattices. The simulations are performed with a physical value of the strange quark mass and light quark masses which are in the range of m{sub q}/m{sub s} = 0.05 - 0.4. The lightest quark mass corresponds to a pion mass of about 150 MeV.

UMEDA, T.

2006-07-23T23:59:59.000Z

314

Extension of continuum time-dependent Hartree-Fock method to proton states  

E-Print Network (OSTI)

This paper deals with the solution of the spherically symmetric time-dependent Hartree-Fock approximation applied to nuclear giant monopole resonances in the small amplitude regime. The problem is spatially unbounded as the resonance state is in the continuum. The practical requirement to perform the calculation in a finite-sized spatial region yields an artificial boundary, which is not present physically. The question of how to ensure the boundary does not interfere with the internal solution, while keeping the overall calculation time low is studied. Here we propose an absorbing boundary condition scheme to handle the conflict. The derivation, via a Laplace transform method, and implementation is described. An inverse Laplace transform required by the absorbing boundaries is calculated using a method of non-linear least squares. The accuracy and efficiency of the scheme is tested and results presented to support the case that they are a effective way of handling the artificial boundary.

C. I. Pardi; P. D. Stevenson; K. Xu

2013-06-19T23:59:59.000Z

315

Radio continuum observations of the Leo Triplet at 2.64 GHz  

E-Print Network (OSTI)

Aims. The magnetic fields of the member galaxies NGC 3628 and NGC 3627 show morphological peculiarities, suggesting that interactions within the group may be caused by stripping of the magnetic field. This process could supply the intergalactic space with magnetised material, a scenario considered as a possible source of intergalactic magnetic fields (as seen eg. in the Taffy pairs of galaxies). Additionally, the plumes are likely to be the tidal dwarf galaxy candidates. Methods. We performed radio continuum mapping observations at 2.64 GHz using the 100-m Effelsberg radio telescope. We obtained total power and polarised intensity maps of the Triplet. These maps were analysed together with the archive data, and the magnetic field strength (as well as the magnetic energy density) was estimated. Results. Extended emission was not detected either in the total power or the polarised intensity maps. We obtained upper limits of the magnetic field strength and the energy density of the magnetic field in the Triplet....

Nikiel-Wroczy?ski, B; Urbanik, M; We?gowiec, M; Beck, R; Bomans, D J; Adebahr, B

2013-01-01T23:59:59.000Z

316

The Deepest Spectrum of the Universe? Constraints on the Lyman Continuum Background at High Redshift  

E-Print Network (OSTI)

We describe an ongoing experiment to search for the meta-galactic Lyman-continuum background at z~2-3. We are obtaining one of the deepest optical spectra ever, using LRIS/Keck-II to search for the fluorescent Ly-alpha emission from optically thick HI clouds. The null results of our pilot study (Bunker, Marleau & Graham 1998) placed a 3-sigma upper bound on the mean intensity of the ionizing background of J_{nu 0} radiation field. We have recently greatly extended our search, obtaining a 16-hour spectrum which is sensitive to UV background fluxes ~1E-21 erg/s/cm^2/Hz/sr (z~2.3 at 3-sigma, assuming the HI clouds are ~10arcsec in extent). We describe how the results of this study can be used to constrain the quasar luminosity function and the contribution of high-redshift star-forming galaxies to the ambient ionizing background.

Andrew J. Bunker; Francine R. Marleau; James R. Graham

1999-12-31T23:59:59.000Z

317

The Deepest Spectrum of the Universe? Constraints on the Lyman Continuum Background at High Redshift  

E-Print Network (OSTI)

We describe an ongoing experiment to search for the meta-galactic Lyman-continuum background at z~2-3. We are obtaining one of the deepest optical spectra ever, using LRIS/Keck-II to search for the fluorescent Ly-alpha emission from optically thick HI clouds. The null results of our pilot study (Bunker, Marleau & Graham 1998) placed a 3-sigma upper bound on the mean intensity of the ionizing background of J_{nu 0} radiation field. We have recently greatly extended our search, obtaining a 16-hour spectrum which is sensitive to UV background fluxes ~1E-21 erg/s/cm^2/Hz/sr (z~2.3 at 3-sigma, assuming the HI clouds are ~10arcsec in extent). We describe how the results of this study can be used to constrain the quasar luminosity function and the contribution of...

Bunker, A J; Graham, J R; Bunker, Andrew J.; Marleau, Francine R.; Graham, James R.

1999-01-01T23:59:59.000Z

318

Parabolic sturmians approach to the three-body continuum Coulomb problem  

SciTech Connect

The three-body continuum Coulomb problem is treated in terms of the generalized parabolic coordinates. Approximate solutions are expressed in the form of a Lippmann-Schwinger-type equation, where the Green's function includes the leading term of the kinetic energy and the total potential energy, whereas the potential contains the non-orthogonal part of the kinetic energy operator. As a test of this approach, the integral equation for the (e{sup -}, e{sup -}, He{sup ++}) system has been solved numerically by using the parabolic Sturmian basis representation of the (approximate) potential. Convergence of the expansion coefficients of the solution has been obtained as the basis set used to describe the potential is enlarged.

Zaytsev, S. A., E-mail: zaytsev@fizika.khstu.ru [Pacific National University (Russian Federation); Popov, Yu. V. [Moscow State University, Nuclear Physics Institute (Russian Federation)] [Moscow State University, Nuclear Physics Institute (Russian Federation); Piraux, B. [Universite catholique de Louvain, Institute of Condensed Matter and Nanosciences (Belgium)] [Universite catholique de Louvain, Institute of Condensed Matter and Nanosciences (Belgium)

2013-03-15T23:59:59.000Z

319

ALMA SUBMILLIMETER CONTINUUM IMAGING OF THE HOST GALAXIES OF GRB 021004 AND GRB 080607  

SciTech Connect

We report 345 GHz continuum observations of the host galaxies of gamma-ray bursts (GRBs) 021004 and 080607 at z > 2 using the Atacama Large Millimeter/Submillimeter Array (ALMA) in Cycle 0. Of the two bursts, GRB 021004 is one of the few GRBs that originate in a Lyman limit host, while GRB 080607 is classified as a 'dark burst' and its host galaxy is a candidate of dusty star-forming galaxy at z {approx} 3. With an order of magnitude improvement in the sensitivities of the new imaging searches, we detect the host galaxy of GRB 080607 with a flux of S{sub 345} = 0.31 {+-} 0.09 mJy and a corresponding infrared luminosity of L{sub IR} = (2.4-4.5) Multiplication-Sign 10{sup 11} L{sub Sun }. However, the host galaxy of GRB 021004 remains undetected and the ALMA observations allow us to place a 3{sigma} upper limit of L{sub IR} < 3.1 Multiplication-Sign 10{sup 11} L{sub Sun} for the host galaxy. The continuum imaging observations show that the two galaxies are not ultraluminous infrared galaxies, but are at the faintest end of the dusty galaxy population that gives rise to the submillimeter extragalactic background light. The derived star formation rates of the two GRB host galaxies are less than 100 M{sub Sun} yr{sup -1}, which are broadly consistent with optical measurements. The result suggests that the large extinction (A{sub V} {approx} 3) in the afterglow of GRB 080607 is confined along its particularly dusty sight line, and not representative of the global properties of the host galaxy.

Wang, Wei-Hao; Huang, Kui-Yun [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Chen, Hsiao-Wen [Department of Astronomy and Astrophysics and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States)

2012-12-20T23:59:59.000Z

320

Mechanisms Determining the Atlantic Thermohaline Circulation Response to Greenhouse Gas Forcing in a Non-Flux-Adjusted Coupled Climate Model  

Science Conference Proceedings (OSTI)

Models of the North Atlantic thermohaline circulation (THC) show a range of responses to the high-latitude warming and freshening characteristic of global warming scenarios. Most simulate a weakening of the THC, with some suggesting possible ...

R. B. Thorpe; J. M. Gregory; T. C. Johns; R. A. Wood; J. F. B. Mitchell

2001-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

A Model Study of Oceanic Mechanisms Affecting Equatorial Pacific Sea Surface Temperature during the 1997–98 El Niño  

Science Conference Proceedings (OSTI)

In this study, the processes affecting sea surface temperature variability over the 1992–98 period, encompassing the very strong 1997–98 El Niño event, are analyzed. A tropical Pacific Ocean general circulation model, forced by a combination of ...

Jérôme Vialard; Christophe Menkes; Jean-Philippe Boulanger; Pascale Delecluse; Eric Guilyardi; Michael J. McPhaden; Gurvan Madec

2001-07-01T23:59:59.000Z

322

Preferential mode of gas invasion in sediments : grain-scale model of coupled multiphase fluid flow and sediment mechanics  

E-Print Network (OSTI)

We present a discrete element model for simulating, at the grain scale, gas migration in brine-saturated deformable media. We rigorously account for the presence of two fluids in the pore space by incorporating forces on ...

Jain, Antone Kumar

2009-01-01T23:59:59.000Z

323

Molecular-orbital decomposition of the ionization continuum for a diatomic molecule by angle-and energy-resolved photoelectron spectroscopy.  

E-Print Network (OSTI)

Molecular-orbital decomposition of the ionization continuum for a diatomic molecule by angle and the state of the ion follow Hund's case b coupling. The formalism is based on the molecular-orbital decomposition of the ionization continuum and therefore fully incorporates the molecular nature

Zare, Richard N.

324

Utility-Scale Future, Continuum Magazine: Clean Energy Innovation at NREL, Spring 2011, Issue 1 Vol. 1  

Science Conference Proceedings (OSTI)

This quarterly magazine is dedicated to stepping beyond the technical journals to reveal NREL's vital work in a real-world context for our stakeholders. Continuum provides insights into the latest and most impactful clean energy innovations, while spotlighting those talented researchers and unique facilities that make it all happen. This edition focuses on creating a utility-scale future.

Not Available

2011-08-01T23:59:59.000Z

325

A Manifestly Gauge Invariant, Continuum Calculation of the SU(N) Yang-Mills two-loop beta function  

E-Print Network (OSTI)

The manifestly gauge invariant Exact Renormalisation Group provides a framework for performing continuum computations in SU(N) Yang-Mills theory, without fixing the gauge. We use this formalism to compute the two-loop beta function in a manifestly gauge invariant way, and without specifying the details of the regularisation scheme.

Tim R. Morris; Oliver J. Rosten

2005-08-04T23:59:59.000Z

326

Bohmian Mechanics  

E-Print Network (OSTI)

Bohmian mechanics is a theory about point particles moving along trajectories. It has the property that in a world governed by Bohmian mechanics, observers see the same statistics for experimental results as predicted by quantum mechanics. Bohmian mechanics thus provides an explanation of quantum mechanics. Moreover, the Bohmian trajectories are defined in a non-conspiratorial way by a few simple laws.

Detlef Duerr; Sheldon Goldstein; Roderich Tumulka; Nino Zanghi

2009-03-15T23:59:59.000Z

327

Mechanical down jar mechanism  

SciTech Connect

This paper describes a mechanical down jar mechanism for freeing stuck objects within a well bore and for conducting other down hole activities. It comprises: an elongate tubular housing having anvil means; mandrel means adapted for connection to an object to be moved downwardly within the well bore and being disposed in telescoping relation with the anvil means and the elongate tubular housing, the mandrel means adapted to be struck by the anvil means to impart a downwardly directed jarring force to the object; the elongate tubular housing having internal firing and recocking detent groove means located in axially spaced relation and forming a firing lug support land therebetween; a radially expandable and retractable firing lug assembly being disposed within the elongate tubular housing and in absence of force being applied axially thereto being radially restrained by the firing lug support land; load spring means being disposed within the elongate tubular housing and being in downward force transmitting relation with the firing lug assembly; recocking spring means being disposed within the elongate tubular housing and having upward axial force transmitting relation with the firing lug assembly.

Taylor, W.T.

1991-12-03T23:59:59.000Z

328

The Mechanics of Implementing a Consistent Instructional Feedback Model in the Development of a Computer-Based Engineering Course  

Science Conference Proceedings (OSTI)

A computer-based education course to teach an undergraduate engineering course in statics has been developed at Texas A&M University. In the initial design phase, the authors used a very simply constructed feedback model. However, once development was ...

Clayton C. Nelson; Billie J. Hughes; Ralph E. Virgo

1987-05-01T23:59:59.000Z

329

Geometric polyhedral models for nanotubes comprising hexagonal lattices  

Science Conference Proceedings (OSTI)

Two new models for the geometric structure of nanotubes comprising hexagonal lattices are described. The existing models for nanotubes typically involve rolled up planar sheets and ignore discrepancies due to curvature. The first of the models presented ... Keywords: Boron nitride nanotubes, Carbon nanotubes, Continuum models, Geometric models, Wall thickness

Barry J. Cox; James M. Hill

2011-05-01T23:59:59.000Z

330

Multiscale Modeling of Grain Boundary Segregation and Embrittlement in Tungsten for Mechanistic Design of Alloys for Coal Fired Plants  

SciTech Connect

Based on a recent discovery of premelting-like grain boundary segregation in refractory metals occurring at high temperatures and/or high alloying levels, this project investigated grain boundary segregation and embrittlement in tungsten (W) based alloys. Specifically, new interfacial thermodynamic models have been developed and quantified to predict high-temperature grain boundary segregation in the W-Ni binary alloy and W-Ni-Fe, W-Ni-Ti, W-Ni-Co, W-Ni-Cr, W-Ni-Zr and W-Ni-Nb ternary alloys. The thermodynamic modeling results have been experimentally validated for selected systems. Furthermore, multiscale modeling has been conducted at continuum, atomistic and quantum-mechanical levels to link grain boundary segregation with embrittlement. In summary, this 3-year project has successfully developed a theoretical framework in combination with a multiscale modeling strategy for predicting grain boundary segregation and embrittlement in W based alloys.

Luo, Jian; Tomar, Vikas; Zhou, Naixie; Lee, Hongsuk

2013-06-30T23:59:59.000Z

331

Addressing the Recalcitrance of Cellulose Degradation through Cellulase Discovery, Nano-scale Elucidation of Molecular Mechanisms, and Kinetic Modeling  

DOE Green Energy (OSTI)

This research project was designed to play a vital role in the development of low cost sugars from cellulosic biomass and contributing to the national effort to displace fossil fuel usage in the USA transportation sector. The goal was to expand the portfolio of cell wall degrading enzymes through innovative research at the nano-scale level, prospecting for novel cellulases and building a kinetic framework for the development of more effective enzymatic conversion processes. More precisely, the goal was to elucidate the molecular mechanisms for some cellulases that are very familiar to members of our research team and to investigate what we hope are novel cellulases or new enzyme combinations from the world of plant pathogenic fungi and bacteria. Hydrolytic activities of various cellulases and cellulase cocktails were monitored at the nanoscale of cellulose fibrils and the microscale of pretreated cellulose particles, and we integrated this insight into a heterogeneous reaction framework. The over-riding approach for this research program was the application of innovative and cutting edge optical and high-throughput screening and analysis techniques for observing how cellulases hydrolyze real substrates.

Walker, Larry P., Bergstrom, Gary; Corgie, Stephane; Craighead, Harold; Gibson, Donna; Wilson, David

2011-06-13T23:59:59.000Z

332

Least-squares variational principles and the finite element method: theory, formulations, and models for solid and fluid mechanics  

E-Print Network (OSTI)

We consider the application of least-squares variational principles and the finite element method to the numerical solution of boundary value problems arising in the fields of solidand fluidmechanics.For manyof these problems least-squares principles offer many theoretical and computational advantages in the implementation of the corresponding finite element model that are not present in the traditional weak form Galerkin finite element model.Most notably, the use of least-squares principles leads to a variational unconstrained minimization problem where stability conditions such as inf-sup conditions (typically arising in mixed methods using weak form Galerkin finite element formulations) never arise. In addition, the least-squares based finite elementmodelalways yields a discrete system ofequations witha symmetric positive definite coeffcientmatrix.These attributes, amongst manyothers highlightedand detailed in this work, allow the developmentofrobust andeffcient finite elementmodels for problems of practical importance. The research documented herein encompasses least-squares based formulations for incompressible and compressible viscous fluid flow, the bending of thin and thick plates, and for the analysis of shear-deformable shell structures.

Pontaza, Juan Pablo

2003-12-01T23:59:59.000Z

333

Hybrid Orbital and Numerical Grid Representationfor Electronic Continuum Processes: Double Photoionization of Atomic Beryllium  

SciTech Connect

A general approach for ab initio calculations of electronic continuum processes is described in which the many-electron wave function is expanded using a combination of orbitals at short range and the finite-element discrete variable representation(FEM-DVR) at larger distances. The orbital portion of the basis allows the efficient construction of many-electron configurations in which some of the electrons are bound, but because the orbitals are constructed from an underlying FEM-DVR grid, the calculation of two-electron integrals retains the efficiency of the primitive FEM-DVR approach. As an example, double photoionization of beryllium is treated in a calculation in which the 1s{sup 2} core is frozen. This approach extends the use of exterior complex scaling (ECS) successfully applied to helium and H{sub 2} to calculations with two active electrons on more complicated targets. Integrated, energy-differential and triply-differential cross sections are exhibited, and the results agree well with other theoretical investigations.

Yip, Frank L; McCurdy, C. William; Rescigno, Thomas N

2010-04-19T23:59:59.000Z

334

Hybrid orbital and numerical grid representation for electronic continuum processes: Double photoionization of atomic beryllium  

SciTech Connect

A general approach for ab initio calculations of electronic continuum processes is described in which the many-electron wave function is expanded using a combination of orbitals at short range and the finite-element discrete-variable representation (FEM-DVR) at larger distances. The orbital portion of the basis allows efficient construction of many-electron configurations in which some of the electrons are bound, but because the orbitals are constructed from an underlying FEM-DVR grid, the calculation of two-electron integrals retains the efficiency of the primitive FEM-DVR approach. As an example, double photoionization of beryllium is treated in a calculation in which the 1s{sup 2} core is frozen. This approach extends the use of exterior complex scaling (ECS), successfully applied to helium and H{sub 2}, to calculations with two active electrons on more complicated targets. Integrated, energy-differential and triply-differential cross sections are exhibited, and the results agree well with other theoretical investigations.

Yip, F. L.; Rescigno, T. N. [Lawrence Berkeley National Laboratory, Chemical Sciences, and Ultrafast X-ray Science Laboratory, Berkeley, California 94720 (United States); McCurdy, C. W. [Lawrence Berkeley National Laboratory, Chemical Sciences, and Ultrafast X-ray Science Laboratory, Berkeley, California 94720 (United States); Departments of Applied Science and Chemistry, University of California, Davis, California 95616 (United States)

2010-05-15T23:59:59.000Z

335

Conservation Laws for Coupled Hydro-mechanical Processes in Unsaturated Porous Media: Theory and Implementation  

Science Conference Proceedings (OSTI)

We develop conservation laws for coupled hydro-mechanical processes in unsaturated porous media using three-phase continuum mixture theory. From the first law of thermodynamics, we identify energy-conjugate variables for constitutive modeling at macroscopic scale. Energy conjugate expressions identified relate a certain measure of effective stress to the deformation of the solid matrix, the degree of saturation to the matrix suction, the pressure in each constituent phase to the corresponding intrinsic volume change of this phase, and the seepage forces to the corresponding pressure gradients. We then develop strong and weak forms of boundary-value problems relevant for 3D finite element modeling of coupled hydro-mechanical processes in unsaturated porous media. The paper highlights a 3D numerical example illustrating the advances in the solution of large-scale coupled finite element systems, as well as the challenges in developing more predictive tools satisfying the basic conservation laws and the observed constitutive responses for unsaturated porous materials.

Borja, R I; White, J A

2010-02-19T23:59:59.000Z

336

Atoms-to-Continuum (AtC): A User Package for LAMMPS  

Science Conference Proceedings (OSTI)

Atomic Scale Deformation Mechanisms of Amorphous Polyethylene under Tensile Loading · Atomistic Predictions of Age Hardening in Al-Cu Alloys.

337

The Continuous Spectrum in Baroclinic Models with Uniform Potential Vorticity Gradient and Ekman Damping  

Science Conference Proceedings (OSTI)

Analytic solutions of the continuous spectrum are obtained for quasigeostrophic models in which the basic-state meridional potential vorticity (PV) gradient is uniform but nonzero. The modes that form the continuous spectrum—continuum modes—are ...

Hylke de Vries

2009-09-01T23:59:59.000Z

338

Modeling Hot Mix Asphalt Compaction Using a Thermodynamics Based Compressible Viscoelastic Model within the Framework of Multiple Natural Configurations  

E-Print Network (OSTI)

Hot mix asphalt (HMA) is a composite material that exhibits a nonlinear response that is dependent on temperature, type of loading and strain level. The properties of HMA are highly influenced by the type and amount of the constituents used and also depend on its internal structure. In such a material the variable effects of the compaction process assume a central importance in determining material performance. It is generally accepted that the theoretical knowledge about material behavior during compaction is limited and it is therefore hard to predict and manage (the effect of) a compaction process. This work makes an attempt to address such a specific need by developing a continuum model that can be adapted for simulating the compaction of hot mix asphalt (HMA) using the notion of multiple natural configurations. A thermodynamic framework is employed to study the non-linear dissipative response associated with HMA by specifying the forms for the stored energy and the rate of dissipation function for the material; a viscoelastic compressible fluid model is developed using this framework to model the compaction of hot mix asphalt. It is further anticipated that the present work will aid in the development of better constitutive models capable of capturing the mechanics of processes like compaction both in the laboratory and in the field. The continuum model developed was implemented in the finite element method, which was employed to setup a simulation environment for hot mix asphalt compaction. The finite element method was used for simulating compaction in the laboratory and in various field compaction projects.

Koneru, Saradhi

2010-08-01T23:59:59.000Z

339

Bohmian mechanics contradicts quantum mechanics  

E-Print Network (OSTI)

Bohmian mechanics contradicts quantum mechanics Arnold Neumaier Institut fur Mathematik, Universit://solon.cma.univie.ac.at/#24;neum/ Abstract. It is shown that, for a harmonic oscillator in the ground state, Bohmian mechanics and quantum mechanics predict values of opposite sign for certain time correlations. The discrepancy can

Neumaier, Arnold

340

Mechanism and computational model for Lyman-{alpha}-radiation generation by high-intensity-laser four-wave mixing in Kr-Ar gas  

SciTech Connect

We present a theoretical model combined with a computational study of a laser four-wave mixing process under optical discharge in which the non-steady-state four-wave amplitude equations are integrated with the kinetic equations of initial optical discharge and electron avalanche ionization in Kr-Ar gas. The model is validated by earlier experimental data showing strong inhibition of the generation of pulsed, tunable Lyman-{alpha} (Ly-{alpha}) radiation when using sum-difference frequency mixing of 212.6 nm and tunable infrared radiation (820-850 nm). The rigorous computational approach to the problem reveals the possibility and mechanism of strong auto-oscillations in sum-difference resonant Ly-{alpha} generation due to the combined effect of (i) 212.6-nm (2+1)-photon ionization producing initial electrons, followed by (ii) the electron avalanche dominated by 843-nm radiation, and (iii) the final breakdown of the phase matching condition. The model shows that the final efficiency of Ly-{alpha} radiation generation can achieve a value of {approx}5x10{sup -4} which is restricted by the total combined absorption of the fundamental and generated radiation.

Louchev, Oleg A.; Saito, Norihito; Wada, Satoshi [Advanced Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198 (Japan); Bakule, Pavel [STFC, ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX (United Kingdom); Yokoyama, Koji [Advanced Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198 (Japan); Advanced Meson Science Laboratory, RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan); Ishida, Katsuhiko; Iwasaki, Masahiko [Advanced Meson Science Laboratory, RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan)

2011-09-15T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

NEW TWO-DIMENSIONAL MODELS OF SUPERNOVA EXPLOSIONS BY THE NEUTRINO-HEATING MECHANISM: EVIDENCE FOR DIFFERENT INSTABILITY REGIMES IN COLLAPSING STELLAR CORES  

Science Conference Proceedings (OSTI)

The neutrino-driven explosion mechanism for core-collapse supernovae in its modern flavor relies on the additional support of hydrodynamical instabilities in achieving shock revival. Two possible candidates, convection and the so-called standing accretion shock instability (SASI), have been proposed for this role. In this paper, we discuss new successful simulations of supernova explosions that shed light on the relative importance of these two instabilities. While convection has so far been observed to grow first in self-consistent hydrodynamical models with multi-group neutrino transport, we here present the first such simulation in which the SASI grows faster while the development of convection is initially inhibited. We illustrate the features of this SASI-dominated regime using an explosion model of a 27 M{sub Sun} progenitor, which is contrasted with a convectively dominated model of an 8.1 M{sub Sun} progenitor with subsolar metallicity, whose early post-bounce behavior is more in line with previous 11.2 M{sub Sun} and 15 M{sub Sun} explosion models. We analyze the conditions discriminating between the two different regimes, showing that a high mass-accretion rate and a short advection timescale are conducive for strong SASI activity. We also briefly discuss some important factors for capturing the SASI-driven regime, such as general relativity, the progenitor structure, a nuclear equation of state leading to a compact proto-neutron star, and the neutrino treatment. Finally, we evaluate possible implications of our findings for two-dimensional and three-dimensional supernova simulations.

Mueller, Bernhard; Janka, Hans-Thomas [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); Heger, Alexander, E-mail: bjmuellr@mpa-garching.mpg.de, E-mail: thj@mpa-garching.mpg.de, E-mail: alexander.heger@monash.edu [School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States)

2012-12-10T23:59:59.000Z

342

SOME OCEAN MODEL FUNDAMENTALS  

E-Print Network (OSTI)

The purpose of these lectures is to present elements of the equations and algorithms used in numerical models of the large-scale ocean circulation. Such models generally integrate the ocean’s primitive equations, which are based on Newton’s Laws applied to a continuum fluid under hydrostatic balance in a spherical geometry, along with linear irreversible thermodynamics and subgrid scale (SGS) parameterizations. During formulations of both the kinematics and dynamics, we highlight issues related to the use of a generalized vertical coordinate. The vertical coordinate is arguably the most critical element determining how a model is designed and applications to which a model is of use.

Stephen M. Griffies

2005-01-01T23:59:59.000Z

343

Atomistic Modeling on Deformation Mechanisms  

Science Conference Proceedings (OSTI)

Mar 12, 2012... Microstructure in Compression of Nanoscale Metallic Pillars by Molecular Dynamics Simulation: Frederic Sansoz1; 1University of Vermont

344

Mechanical Design  

SciTech Connect

The particle beam of the SXR (soft x-ray) beam line in the LCLS (Linac Coherent Light Source) has a high intensity in order to penetrate through samples at the atomic level. However, the intensity is so high that many experiments fail because of severe damage. To correct this issue, attenuators are put into the beam line to reduce this intensity to a level suitable for experimentation. Attenuation is defined as 'the gradual loss in intensity of any flux through a medium' by [1]. It is found that Beryllium and Boron Carbide can survive the intensity of the beam. At very thin films, both of these materials work very well as filters for reducing the beam intensity. Using a total of 12 filters, the first 9 being made of Beryllium and the rest made of Boron Carbide, the beam's energy range of photons can be attenuated between 800 eV and 9000 eV. The design of the filters allows attenuation for different beam intensities so that experiments can obtain different intensities from the beam if desired. The step of attenuation varies, but is relative to the thickness of the filter as a power function of 2. A relationship for this is f(n) = x{sub 0}2{sup n} where n is the step of attenuation desired and x{sub 0} is the initial thickness of the material. To allow for this desired variation, a mechanism must be designed within the test chamber. This is visualized using a 3D computer aided design modeling tool known as Solid Edge.

2010-08-25T23:59:59.000Z

345

Modeling  

National Nuclear Security Administration (NNSA)

the interconnections between a structural transformation front and a growing crack A.B. Freidin Institute of Problems in Mechanical Engineering Russian Academy of Sciences, St....

346

How realistic are solar model atmospheres?  

E-Print Network (OSTI)

Recently, new solar model atmospheres have been developed to replace classical 1D LTE hydrostatic models and used to for example derive the solar chemical composition. We aim to test various models against key observational constraints. In particular, a 3D model used to derive the solar abundances, a 3D MHD model (with an imposed 10 mT vertical magnetic field), 1D models from the PHOENIX project, the 1D MARCS model, and the 1D semi-empirical model of Holweger & M\\"uller. We confront the models with observational diagnostics of the temperature profile: continuum centre-to-limb variations (CLV), absolute continuum fluxes, and the wings of hydrogen lines. We also test the 3D models for the intensity distribution of the granulation and spectral line shapes. The predictions from the 3D model are in excellent agreement with the continuum CLV observations, performing even better than the Holweger & M\\"uller model (constructed largely to fulfil such observations). The predictions of the 1D theoretical models ...

Pereira, Tiago M D; Collet, Remo; Thaler, Irina; Trampedach, Regner; Leenaarts, Jorrit

2013-01-01T23:59:59.000Z

347

Ideas By Statistical Mechanics (ISM)  

Science Conference Proceedings (OSTI)

Ideas by Statistical Mechanics (ISM) is a generic program to model evolution and propagation of ideas/patterns throughout populations subjected to endogenous and exogenous interactions. The program is based on the author's work in Statistical Mechanics ... Keywords: neocortical interactions, risk management, simulated annealing, statistical mechanics

Lester Ingber

2007-08-01T23:59:59.000Z

348

A Viscoelastic-Viscoplastic Analysis of Fiber Reinforced Polymer Composites Undergoing Mechanical Loading and Temperature Changes  

E-Print Network (OSTI)

This study presents a combined viscoelastic (VE)-viscoplastic (VP) analysis for Fiber Reinforced Polymer (FRP) composites subject to simultaneous mechanical load and conduction of heat. The studied FRP composites consist of unidirectional fibers, which are considered as linearly elastic with regards to their mechanical response, and isotropic polymeric matrix, which shows viscoelastic-viscoplastic response under various stresses and temperatures. Due to the viscoelastic and viscoplastic behavior of the polymeric matrix, the overall FRP composites exhibit a combined time-dependent and inelastic behavior. A simplified micromechanical model, consisting of a unit-cell with four fiber and matrix subcells, is formulated to homogenize the overall heat conduction and viscoelastic-viscoplastic responses of the FRP composites. The micromechanical model is compatible with a displacement based finite element (FE) and is implemented at the Gaussian integration points within the continuum finite elements, which is useful for analyzing the overall time-dependent response of FRP composite structures under various boundary conditions. The Schapery nonlinear integral model combined with the Perzyna viscoplastic model is used to describe the viscoelastic-viscoplastic response of the polymer constituents. An integrated time integration algorithm is formulated at the micromechanics level in order to solve the nonlinear viscoelastic-viscoplastic constitutive model at the matrix subcells and obtain the overall nonlinear response of the FRP. The viscoelastic-viscoplastic micromechanical model is validated usingexperimental data on off-axis glass/epoxy FRP composites available in literature. The overall response of the FRP composites determined from the simplified micromechanical model is also compared with the ones generated from microstructures of FRP with various fiber arrangements dispersed in homogeneous polymer matrix. The microstructural models of the FRP with detailed fiber arrangements are generated using FE. The effects of thermal stresses, due to the mismatches in the coefficient of thermal expansions of the fibers and polymeric matrix, and stress concentrations/discontinuities near the fiber and matrix interfaces on the overall thermo-mechanical deformation of FRP composites are studied using the two micromechanical models discussed above. Finally, an example of structural analysis is performed on a polymeric smart sandwich composite beam, having FRP skins and polymeric foam core with piezoelectric sensors integrated to the FRP skins, undergoing three point bending at an elevated temperature. The creep displacement is compared to experimental data available in literature.

Jeon, Jaehyeuk

2013-08-01T23:59:59.000Z

349

Suzaku Discovery of the Strong Radiative Recombination Continuum of Iron from the Supernova Remnant W49B  

E-Print Network (OSTI)

We present a hard X-ray spectrum of unprecedented quality of the Galactic supernova remnant W49B obtained with the Suzaku satellite. The spectrum exhibits an unusual structure consisting of a saw-edged bump above 8 keV. This bump cannot be explained by any combination of high-temperature plasmas in ionization equilibrium. We firmly conclude that this bump is caused by the strong radiative recombination continuum (RRC) of iron, detected for the first time in a supernova remnant. The electron temperature derived from the bremsstrahlung continuum shape and the slope of the RRC is 1.5 keV. On the other hand, the ionization temperature derived from the observed intensity ratios between the RRC and K-alpha lines of iron is 2.7 keV. These results indicate that the plasma is in a highly overionized state. Volume emission measures independently determined from the fluxes of the thermal and RRC components are consistent with each other, suggesting the same origin of these components.

Ozawa, Midori; Yamaguchi, Hiroya; Masai, Kuniaki; Tamagawa, Toru

2009-01-01T23:59:59.000Z

350

Starting from Quantum Mechanics - Programmaster.org  

Science Conference Proceedings (OSTI)

Computational Modeling and Simulation of Advanced Materials for Energy Applications: Starting from Quantum Mechanics Sponsored by: TMS/ASM: ...

351

Continuum and Quantum-Chemical Modeling of Oxygen Reduction on the Cathode in a Solid Oxide Fuel Cell  

DOE Green Energy (OSTI)

Solid oxide fuel cells (SOFCs) have several advantages over other types of fuels cells such as high-energy efficiency and excellent fuel flexibility. To be economically competitive, however, new materials with extraordinary transport and catalytic properties must be developed to dramatically improve the performance while reducing the cost. This article reviews recent advancements in understanding oxygen reduction on various cathode materials using phenomenological and quantum chemical approaches in order to develop novel cathode materials with high catalytic activity toward oxygen reduction. We summarize a variety of results relevant to understanding the interactions between O2 and cathode materials at the molecular level as predicted using quantum-chemical cal-culations and probed using in situ surface vibrational spectroscopy. It is hoped that this in-depth understanding may provide useful insights into the design of novel cath-ode materials for a new generation of SOFCs.

Choi, Yongman; Mebane, David S.; Wang, Jeng-Han; Liu, Meilin

2009-10-08T23:59:59.000Z

352

Current SPE Hydrodynamic Modeling and Path Forward  

SciTech Connect

Extensive work has been conducted on SPE analysis efforts: Fault effects Non-uniform weathered layer analysis MUNROU: material library incorporation, parallelization, and development of non-locking tets Development of a unique continuum-based-visco-plastic strain-rate-dependent material model With corrected SPE data path is now set for a multipronged approach to fully understand experimental series shot effects.

Knight, Earl E. [Los Alamos National Laboratory; Rougier, Esteban [Los Alamos National Laboratory

2012-08-14T23:59:59.000Z

353

3.021J / 1.021J / 10.333J / 18.361J / 22.00J Introduction to Modeling and Simulation, Spring 2008  

E-Print Network (OSTI)

This course explores the basic concepts of computer modeling and simulation in science and engineering. We'll use techniques and software for simulation, data analysis and visualization. Continuum, mesoscale, atomistic and ...

Buehler, Markus

354

Methods for modeling impact-induced reactivity changes in small reactors.  

SciTech Connect

This paper describes techniques for determining impact deformation and the subsequent reactivity change for a space reactor impacting the ground following a potential launch accident or for large fuel bundles in a shipping container following an accident. This technique could be used to determine the margin of subcriticality for such potential accidents. Specifically, the approach couples a finite element continuum mechanics model (Pronto3D or Presto) with a neutronics code (MCNP). DAGMC, developed at the University of Wisconsin-Madison, is used to enable MCNP geometric queries to be performed using Pronto3D output. This paper summarizes what has been done historically for reactor launch analysis, describes the impact criticality analysis methodology, and presents preliminary results using representative reactor designs.

Tallman, Tyler N.; Radel, Tracy E.; Smith, Jeffrey A.; Villa, Daniel L.; Smith, Brandon M. (U. of Wisconsin, Madison, WI); Radel, Ross F.; Lipinski, Ronald J.; Wilson, Paul Philip Hood (U. of Wisconsin, Madison, WI)

2010-10-01T23:59:59.000Z

355

Positron annihilation in the Galactic Center: ''Cheshire cat'' Compton scattering and ''excess continuum''  

SciTech Connect

Two separate observations of the ..gamma..-ray spectrum originating from the Galactic Center were made by HEAO-3 in the fall of 1979 and in the spring of 1980. The 2..gamma.. 511 KeV annihilation line flux decreased by a factor of three over the corresponding six month period, whereas the excess ..gamma..-ray continuum below the 511 KeV line, often interpreted as 3..gamma.. decay of orthopositronium, barely changed. This apparent discrepancy in the temporal behavior makes it difficult to associate the bulk of the excess continuum with the 3..gamma.. decay of positronium. We will show that Compton scattering of the line and high energy radiation provides a natural explanation for the surprisingly small change seen in the excess continuum. 11 refs., 2 figs.

Bildsten, M.L.; Zurek, W.H.

1986-01-01T23:59:59.000Z

356

Subsurface Uranium Fate and Transport: Integrated Experiments and Modeling of Coupled Biogeochemical Mechanisms of Nanocrystalline Uraninite Oxidation by Fe(III)-(hydr)oxides - Project Final Report  

Science Conference Proceedings (OSTI)

Subsurface bacteria including sulfate reducing bacteria (SRB) reduce soluble U(VI) to insoluble U(IV) with subsequent precipitation of UO2. We have shown that SRB reduce U(VI) to nanometer-sized UO2 particles (1-5 nm) which are both intra- and extracellular, with UO2 inside the cell likely physically shielded from subsequent oxidation processes. We evaluated the UO2 nanoparticles produced by Desulfovibrio desulfuricans G20 under growth and non-growth conditions in the presence of lactate or pyruvate and sulfate, thiosulfate, or fumarate, using ultrafiltration and HR-TEM. Results showed that a significant mass fraction of bioreduced U (35-60%) existed as a mobile phase when the initial concentration of U(VI) was 160 µM. Further experiments with different initial U(VI) concentrations (25 - 900 ?M) in MTM with PIPES or bicarbonate buffers indicated that aggregation of uraninite depended on the initial concentrations of U(VI) and type of buffer. It is known that under some conditions SRB-mediated UO2 nanocrystals can be reoxidized (and thus remobilized) by Fe(III)-(hydr)oxides, common constituents of soils and sediments. To elucidate the mechanism of UO2 reoxidation by Fe(III) (hydr)oxides, we studied the impact of Fe and U chelating compounds (citrate, NTA, and EDTA) on reoxidation rates. Experiments were conducted in anaerobic batch systems in PIPES buffer. Results showed EDTA significantly accelerated UO2 reoxidation with an initial rate of 9.5?M day-1 for ferrihydrite. In all cases, bicarbonate increased the rate and extent of UO2 reoxidation with ferrihydrite. The highest rate of UO2 reoxidation occurred when the chelator promoted UO2 and Fe(III) (hydr)oxide dissolution as demonstrated with EDTA. When UO2 dissolution did not occur, UO2 reoxidation likely proceeded through an aqueous Fe(III) intermediate as observed for both NTA and citrate. To complement to these laboratory studies, we collected U-bearing samples from a surface seep at the Rifle field site and have measured elevated U concentrations in oxic iron-rich sediments. To translate experimental results into numerical analysis of U fate and transport, a reaction network was developed based on Sani et al. (2004) to simulate U(VI) bioreduction with concomitant UO2 reoxidation in the presence of hematite or ferrihydrite. The reduction phase considers SRB reduction (using lactate) with the reductive dissolution of Fe(III) solids, which is set to be microbially mediated as well as abiotically driven by sulfide. Model results show the oxidation of HS– by Fe(III) directly competes with UO2 reoxidation as Fe(III) oxidizes HS– preferentially over UO2. The majority of Fe reduction is predicted to be abiotic, with ferrihydrite becoming fully consumed by reaction with sulfide. Predicted total dissolved carbonate concentrations from the degradation of lactate are elevated (log(pCO2) ~ –1) and, in the hematite system, yield close to two orders-of-magnitude higher U(VI) concentrations than under initial carbonate concentrations of 3 mM. Modeling of U(VI) bioreduction with concomitant reoxidation of UO2 in the presence of ferrihydrite was also extended to a two-dimensional field-scale groundwater flow and biogeochemically reactive transport model for the South Oyster site in eastern Virginia. This model was developed to simulate the field-scale immobilization and subsequent reoxidation of U by a biologically mediated reaction network.

Peyton, Brent M. [Montana State University; Timothy, Ginn R. [University of California Davis; Sani, Rajesh K. [South Dakota School of Mines and Technology

2013-08-14T23:59:59.000Z

357

A General Systems Theory for Chaos, Quantum Mechanics and Gravity for Dynamical Systems of all Space-Time Scales  

E-Print Network (OSTI)

Non-local connections, i. e. long-range space-time correlations intrinsic to the observed subatomic dynamics of quantum systems is also exhibited by macro-scale dynamical systems as selfsimilar fractal space-time fluctuations and is identified as self-organized criticality. The author has developed a general systems theory for the observed self-organized criticality applicable to dynamical systems of all space-time scales based on the concept that spatial integration of enclosed small-scale fluctuations results in the formation of large eddy circulation. The eddy energy spectrum therefore represents the statistical normal distribution according to the Central Limit Theorem. The additive amplitudes of eddies, when squared (variance or eddy kinetic energy), represent the statistical normal (probability) distribution, a result observed in the subatomic dynamics of quantum systems. The model predicts Kepler's laws of planetary motion for eddy circulation dynamics. Inverse square law of gravitation therefore applies to the eddy continuum ranging from subatomic to macro-scale dynamical systems, e.g. weather systems. The model is similar to a superstring model for subatomic dynamics which unifies quantum mechanical and classical concepts and manifestation of matter is visualised as vibrational modes in string-like energy flow patterns. The cumulative sum of centripetal forces in a hierarchy of vortex circulations may result in the observed inverse square law form for gravitational attraction between inertial masses of the eddies.

A M Selvam

2005-03-03T23:59:59.000Z

358

Virtual cityscapes: recent advances in crowd modeling and traffic simulation  

Science Conference Proceedings (OSTI)

We survey our recent work on interactive modeling, generation, and control of large-scale crowds and traffic for simulating digital cities. These include multi-agent navigation, simulating large crowds with emerging behaviors as well as interactive simulation ... Keywords: continuum traffic, crowd modeling, digital cities, multi-agent simulation

Ming C. Lin; Dinesh Manocha

2010-09-01T23:59:59.000Z

359

The Continuum of Hydroclimate Variability in Western North America during the Last Millennium  

Science Conference Proceedings (OSTI)

The distribution of climatic variance across the frequency spectrum has substantial importance for anticipating how climate will evolve in the future. Here power spectra and power laws (?) are estimated from instrumental, proxy, and climate model ...

Toby R. Ault; Julia E. Cole; Jonathan T. Overpeck; Gregory T. Pederson; Scott St. George; Bette Otto-Bliesner; Connie A. Woodhouse; Clara Deser

2013-08-01T23:59:59.000Z

360

A non-local, ordinary-state-based viscoelasticity model for peridynamics.  

SciTech Connect

A non-local, ordinary-state-based, peridynamics viscoelasticity model is developed. In this model, viscous effects are added to deviatoric deformations and the bulk response remains elastic. The model uses internal state variables and is conceptually similar to linearized isotropic viscolelasticity in the local theory. The modulus state, which is used to form the Jacobian matrix in Newton-Raphson algorithms, is presented. The model is shown to satisfy the 2nd law of thermodynamics and is applicable to problems in solid continuum mechanics where fracture and rate effects are important; it inherits all the advantages for modeling fracture associated with peridynamics. By combining this work with the previously published ordinary-state-based plasticity model, the model may be amenable to viscoplasticity problems where plasticity and rate effects are simultaneously important. Also, the model may be extended to include viscous effects for spherical deformations as well. The later two extensions are not presented and may be the subject of further work.

Mitchell, John Anthony

2011-10-01T23:59:59.000Z

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361

Higgs Mechanism for Gravitons  

E-Print Network (OSTI)

Just like the vector gauge bosons in the gauge theories, it is now known that gravitons acquire mass in the process of spontaneous symmetry breaking of diffeomorphisms through the condensation of scalar fields. The point is that we should find the gravitational Higgs mechanism such that it results in massive gravity in a flat Minkowski space-time without non-unitary propagating modes. This is usually achieved by including higher-derivative terms in scalars and tuning the cosmological constant to be a negative value in a proper way. Recently, a similar but different gravitational Higgs mechanism has been advocated by Chamseddine and Mukhanov where one can relax the negative cosmological constant to zero or positive one. In this work, we investigate why the non-unitary ghost mode decouples from physical Hilbert space in a general space-time dimension. Moreover, we generalize the model to possess an arbitrary potential and clarify under what conditions the general model exhibits the gravitational Higgs mechanism. By searching for solutions to the conditions, we arrive at two classes of potentials exhibiting gravitational Higgs mechanism. One class includes the model by Chamseddine and Mukhanov in a specific case while the other is completely a new model.

Ichiro Oda

2010-03-07T23:59:59.000Z

362

Acceleration Mechanisms  

E-Print Network (OSTI)

Glossary I. Background and context of the subject II. Stochastic acceleration III. Resonant scattering IV. Diffusive shock acceleration V. DSA at multiple shocks VI. Applications of DSA VII. Acceleration by parallel electric fields VIII. Other acceleration mechanisms IX. Future directions X. Appendix: Quasilinear equations XI. Bibliography

Melrose, D B

2009-01-01T23:59:59.000Z

363

QCD thermodynamics with $N_f=2+1$ near the continuum limit at realistic quark masses  

E-Print Network (OSTI)

We report on our study of QCD thermodynamics with 2+1 flavors of dynamical quarks. In this proceeding we present several thermodynamic quantities and our recent calculation of the critical temperature. In order to investigate the thermodynamic properties of QCD near the continuum limit we adopt improved staggered (p4) quarks coupled with tree-level Symanzik improved glue on $N_t=4$ and 6 lattices. The simulations are performed with a physical value of the strange quark mass and light quark masses which are in the range of $m_q/m_s=0.05-0.4$. The lightest quark mass corresponds to a pion mass of about 150 MeV.

Takashi Umeda

2006-10-03T23:59:59.000Z

364

Defect microstructural evolution in ion irradiated metallic nanofoils: Kinetic Monte Carlo simulation versus cluster dynamics modeling and in situ transmission electron microscopy experiments  

SciTech Connect

Understanding materials degradation under intense irradiation is important for the development of next generation nuclear power plants. Here we demonstrate that defect microstructural evolution in molybdenum nanofoils in situ irradiated and observed on a transmission electron microscope can be reproduced with high fidelity using an object kinetic Monte Carlo (OKMC) simulation technique. Main characteristics of defect evolution predicted by OKMC, namely, defect density and size distribution as functions of foil thickness, ion fluence and flux, are in excellent agreement with those obtained from the in situ experiments and from previous continuum-based cluster dynamics modeling. The combination of advanced in situ experiments and high performance computer simulation/modeling is a unique tool to validate physical assumptions/mechanisms regarding materials response to irradiation, and to achieve the predictive power for materials stability and safety in nuclear facilities.

Xu Donghua; Wirth, Brian D. [Department of Nuclear Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States); Li Meimei [Division of Nuclear Engineering, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kirk, Marquis A. [Division of Materials Science, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2012-09-03T23:59:59.000Z

365

Models  

E-Print Network (OSTI)

• A very typical statistical/econometric model assumes something like yt ? i.i.d. f (y, x, ?) (1) where f (·) is a parametric family known up to parameters ?. • Parameter estimation: maximum likelihood ˆ?n = arg max ? ln f (Yt, Xt, ?) (2) t • What if the basic model assumptions of (1) are violated? The parametric family may not contain the true model f0(x, y) that generated the data; or the data may not be i.i.d.; etc. Misspecified

Stas Kolenikov; U Of Missouri; U Of Missouri

2007-01-01T23:59:59.000Z

366

Coupled thermal-hydrological-mechanical analyses of the Yucca Mountain Drift Scale Test - Comparison of field measurements to predictions of four different numerical models  

E-Print Network (OSTI)

mechanical analyses of the Yucca Mountain Drift Scale Test –Chemical Responses in the Yucca Mountain Drift Scale Test.Heating Phase of the Yucca Mountain Drift Scale Test. In:

2004-01-01T23:59:59.000Z

367

An autonomy-oriented computing mechanism for modeling the formation of energy distribution networks: crude oil distribution in U.S. and Canada  

Science Conference Proceedings (OSTI)

An efficient, economical, as well as reliable energy distribution system plays important roles in distributing energy resources from energy suppliers to energy consumers in different regions. In this paper, we present a decentralized self-organized mechanism ...

Benyun Shi; Jiming Liu

2010-09-01T23:59:59.000Z

368

Ionization of Stark states with half-cycle pulses: Interference effects in the continuum  

SciTech Connect

We study the ionization of extreme Stark states in sodium by THz electromagnetic half-cycle pulses. The results of our full-quantum calculations reveal the presence of an oscillatory pattern in the ionization spectra of extreme red (downhill) states that have been kicked away from the ion core (downhill with respect to the potential imposed by the Stark field). We find no oscillations in the spectra of extreme blue (uphill) states that have been kicked towards the ion core (also downhill with respect to the Stark potential). The oscillatory pattern in the red state ionization spectra is explained with a one-dimensional semiclassical model in terms of interferences between two classical paths. This model also predicts that the blue state ionization spectra should also show oscillatory behavior. The absence of the oscillations in the full calculations can be regarded as a breakdown of the one-dimensional model in representing the ionization dynamics of these states. We find that the one-dimensional model fails when the duration of the THz pulse is comparable to the classical Kepler orbit time.

Manescu, Corneliu; Krause, Jeffrey L. [Quantum Theory Project, University of Florida, Gainesville, Florida 32611-8435, USA (United States); Schafer, Kenneth J. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001, USA (United States)

2003-07-01T23:59:59.000Z

369

Experimental Verification of Thermo-Mechanical Models for Cross-Linked Polyethylene Cable in Pipes and Ducts: Interim Report on First Cable Test  

Science Conference Proceedings (OSTI)

In 2002, the Electric Power Research Institute (EPRI) began investigations of the thermo-mechanical (T-M) behavior of transmission-class cable systems with extruded insulation in duct-manhole and pipe systems and began work on a design guide. The project consisted primarily of two efforts: experimental measurement of cable parameters and development of a mathematical simulation of the thermal and mechanical behavior of transmission-class cable with extruded cross-linked polyethylene (XLPE) ...

2013-12-23T23:59:59.000Z

370

Foam process models.  

Science Conference Proceedings (OSTI)

In this report, we summarize our work on developing a production level foam processing computational model suitable for predicting the self-expansion of foam in complex geometries. The model is based on a finite element representation of the equations of motion, with the movement of the free surface represented using the level set method, and has been implemented in SIERRA/ARIA. An empirically based time- and temperature-dependent density model is used to encapsulate the complex physics of foam nucleation and growth in a numerically tractable model. The change in density with time is at the heart of the foam self-expansion as it creates the motion of the foam. This continuum-level model uses an homogenized description of foam, which does not include the gas explicitly. Results from the model are compared to temperature-instrumented flow visualization experiments giving the location of the foam front as a function of time for our EFAR model system.

Moffat, Harry K.; Noble, David R.; Baer, Thomas A. (Procter & Gamble Co., West Chester, OH); Adolf, Douglas Brian; Rao, Rekha Ranjana; Mondy, Lisa Ann

2008-09-01T23:59:59.000Z

371

22.00J / 1.021J / 2.030J / 3.021J / 10.333J / 18.361J / HST.558J Introduction to Modeling and Simulation, Spring 2006  

E-Print Network (OSTI)

Basic concepts of computer modeling in science and engineering using discrete particle systems and continuum fields. Techniques and software for statistical sampling, simulation, data analysis and visualization. Use of ...

Yip, Sidney

372

22.00J / 1.021J / 3.021J / 10.333J / 18.361J / 2.030J / HST.558 Introduction to Modeling and Simulation, Spring 2002  

E-Print Network (OSTI)

Basic concepts of computer modeling in science and engineering using discrete particle systems and continuum fields. Techniques and software for statistical sampling, simulation, data analysis and visualization. Use of ...

Yip, Sidney

373

On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars  

E-Print Network (OSTI)

The F-GAMMA program is a coordinated effort to investigate the physics of Active Galactic Nuclei (AGNs) via multi-frequency monitoring of {\\em Fermi} blazars. The current study is concerned with the broad-band radio spectra composed of measurement at ten frequencies between 2.64 and 142 GHz. It is shown that any of the 78 sources studied can be classified in terms of their variability characteristics in merely 5 types of variability. The first four types are dominated by spectral evolution and can be reproduced by a simple two-component system made of the quiescent spectrum of a large scale jet populated with a flaring event evolving according to Marscher & Gear (1985). The last type is characterized by an achromatic change of the broad-band spectrum which must be attributed to a completely different mechanism. Here are presented, the classification, the assumed physical system and the results of simulations that have been conducted.

Angelakis, E; Nestoras, I; Fromm, C M; Schmidt, R; Zensus, J A; Marchili, N; Krichbaum, T P; Perucho-Pla, M; Ungerechts, H; Sievers, A; Riquelme, D

2011-01-01T23:59:59.000Z

374

Four-body continuum-discretized coupled-channels calculations: Application to {sup 6}He+{sup 64}Zn at 13.6 MeV  

Science Conference Proceedings (OSTI)

The recently developed four-body continuum-discretized coupled-channels (CDCC) method, making use of the binning procedure, is applied to the reaction {sup 6}He+{sup 64}Zn at 13.6 MeV (around the Coulomb barrier). Excellent agreement with available elastic data is found.

Rodriguez-Gallardo, M. [IEM, CSIC, Serrano 123, 28006 Madrid (Spain); Depto. FAMN, Universidad de Sevilla, Apdo. 1065, Sevilla (Spain); Arias, J. M.; Moro, A. M. [Depto. FAMN, Universidad de Sevilla, Apdo. 1065, Sevilla (Spain); Gomez-Camacho, J. [Depto. FAMN, Universidad de Sevilla, Apdo. 1065, Sevilla (Spain); CNA, Av. Thomas A. Edison 7, 41092 Sevilla (Spain); Thompson, I. J. [LLNL, PO Box 808, Livermore, CA 94551 (United States); Tostevin, J. A. [Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

2010-04-26T23:59:59.000Z

375

The Continuum of Northern Hemisphere Teleconnection Patterns and a Description of the NAO Shift with the Use of Self-Organizing Maps  

Science Conference Proceedings (OSTI)

In this study, the method of self-organizing maps (SOMs) is used with NCEP–NCAR reanalysis data to advance the continuum perspective of Northern Hemisphere teleconnection patterns and to shed light on the secular eastward shift of the North ...

Nathaniel C. Johnson; Steven B. Feldstein; Bruno Tremblay

2008-12-01T23:59:59.000Z

376

Multiscale modeling for fluid transport in nanosystems.  

SciTech Connect

Atomistic-scale behavior drives performance in many micro- and nano-fluidic systems, such as mircrofludic mixers and electrical energy storage devices. Bringing this information into the traditionally continuum models used for engineering analysis has proved challenging. This work describes one such approach to address this issue by developing atomistic-to-continuum multi scale and multi physics methods to enable molecular dynamics (MD) representations of atoms to incorporated into continuum simulations. Coupling is achieved by imposing constraints based on fluxes of conserved quantities between the two regions described by one of these models. The impact of electric fields and surface charges are also critical, hence, methodologies to extend finite-element (FE) MD electric field solvers have been derived to account for these effects. Finally, the continuum description can have inconsistencies with the coarse-grained MD dynamics, so FE equations based on MD statistics were derived to facilitate the multi scale coupling. Examples are shown relevant to nanofluidic systems, such as pore flow, Couette flow, and electric double layer.

Lee, Jonathan W.; Jones, Reese E.; Mandadapu, Kranthi Kiran; Templeton, Jeremy Alan; Zimmerman, Jonathan A.

2013-09-01T23:59:59.000Z

377

Computational Mechanistic Studies of Acid-Catalyzed Lignin Model Dimers for Lignin Depolymerization  

Science Conference Proceedings (OSTI)

Lignin is a heterogeneous alkyl-aromatic polymer that constitutes up to 30% of plant cell walls, and is used for water transport, structure, and defense. The highly irregular and heterogeneous structure of lignin presents a major obstacle in the development of strategies for its deconstruction and upgrading. Here we present mechanistic studies of the acid-catalyzed cleavage of lignin aryl-ether linkages, combining both experimental studies and quantum chemical calculations. Quantum mechanical calculations provide a detailed interpretation of reaction mechanisms including possible intermediates and transition states. Solvent effects on the hydrolysis reactions were incorporated through the use of a conductor-like polarizable continuum model (CPCM) and with cluster models including explicit water molecules in the first solvation shell. Reaction pathways were computed for four lignin model dimers including 2-phenoxy-phenylethanol (PPE), 1-(para-hydroxyphenyl)-2-phenoxy-ethanol (HPPE), 2-phenoxy-phenyl-1,3-propanediol (PPPD), and 1-(para-hydroxyphenyl)-2-phenoxy-1,3-propanediol (HPPPD). Lignin model dimers with a para-hydroxyphenyl ether (HPPE and HPPPD) show substantial differences in reactivity relative to the phenyl ether compound (PPE and PPPD) which have been clarified theoretically and experimentally. The significance of these results for acid deconstruction of lignin in plant cell walls will be discussed.

Kim, S.; Sturgeon, M. R.; Chmely, S. C.; Paton, R. S.; Beckham, G. T.

2013-01-01T23:59:59.000Z

378

Spectral Evolution of the Continuum and Disc Line in Dipping in GRO J1655-40  

E-Print Network (OSTI)

The discovery is reported of emission features in the X-ray spectrum of GRO J1655-40 obtained using Rossi-XTE on 1997, Feb 26. The features have been fitted firstly by two Gaussian lines, which in four spectra have average energies of 5.85+/-0.08 keV and 7.32+/-0.13 keV, strongly suggestive that these are the red- and blueshifted wings of an iron disc line from material with velocity ~0.33 c. The blue wing is apparently less bright than expected for a disc line subject to Doppler boosting, however, known absorption in the spectrum of GRO J1655-40 at energies between ~7 and 8 keV can reduce the apparent brightness of the blue wing. The spectra have also been fitted well using the full relativistic disc line model of Laor, plus an absorption line. This gives a restframe energy between 6.4 and 6.8 keV indicating that the line is from highly ionized iron K_alpha. The Laor model also shows that the line originates at radii extending from ~10 Schwarzschild radii (r_S) outwards. The line is direct evidence for the b...

Balucinska-Church, M

2001-01-01T23:59:59.000Z

379

Continuum gamma-ray emission from light dark matter positrons and electrons  

E-Print Network (OSTI)

The annihilation of light dark matter was recently advocated as a possible explanation of the large positron injection rate at the Galactic center deduced from observations by the SPI spectrometer aboard INTEGRAL. The modelling of internal Bremsstrahlung and in-flight annihilation radiations associated to this process drastically reduced the mass range of this light dark matter particle. We estimate critically the various energy losses and radiations involved in the propagation of the positron before its annihilation --in- flight or at rest. Using a simple model with mono-energetic positrons injected and confined to the Galactic bulge, we compute energy losses and gamma-ray radiations caused by ionization, Bremsstrahlung interactions as well as in-flight and at rest annihilation and compare these predictions to the available observations, for various injection energies. Confronting the predictions with observations by the CGRO/EGRET, CGRO/COMPTEL, INTEGRAL/SPI and INTEGRAL/IBIS/ISGRI instruments, we deduce a mass upper bound of 3 to 7.5 MeV/c^2 for the hypothetical light dark matter particle. The most restrictive limit is in agreement with the value previously found by Beacom and Yuksel and was obtained under similar assumptions, while the 7.5 MeV/c^2 value corresponds to more conservative choices and to a partially ionized propagation medium. We stress how the limit depends on the degree of ionization of the propagation medium and how its precision could be improved by a better appraisal of data uncertainties.

P. Sizun; M. Casse; S. Schanne

2006-07-17T23:59:59.000Z

380

A multiphase constitutive modeling framework for unsaturated soil behavior  

E-Print Network (OSTI)

We develop a framework for constitutive modeling of unsaturated soils that has the embedded elements of lower scale grain to grain contacts. Continuum models developed from this framework will possess two different phases idealizing the solid grains and their interactions. As a consequence, two different constitutive relationships, corresponding to the grain to grain contact and bulk behavior, co-exist in a constitutive model and govern the response of the model. To be specific, grain to grain sliding under dry or wet condition is idealized and appears as a simple contact law embedded in a continuum framework. There is no need to define plastic strain, as this quantity naturally emerges at the continuum scale as the consequence of frictional sliding at the lower scale. In addition, the effective stress can be naturally worked out from the grain to grain contact law embedded in the model without being subjected to any interpretation. This, in our opinion, is a closer representation of unsaturated soil behavior, compared to existing continuum approaches that map everything onto a single stress-strain relationship. In this paper, the framework is presented in its simplest form that takes into account sliding on a single orientation. Grain to grain contact law with capillary effects is used for the demonstration of the concept, and the technical details behind it. Generalization of the framework for better representation of unsaturated soil behavior will also be sketched out.

Giang D. Nguyen; Yixiang Gan

2013-10-31T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Deformation Mechanisms  

Science Conference Proceedings (OSTI)

Table 2   Grain-boundary-sliding models accommodated by dislocation motion ( Eq 9 )...D IPB . Ï? 0 is ignored for region II. 41 Bardeen-Herring source 480 The creation of dislocations on a solute-free mantle

382

A quantum mechanical derivation of the Schwarzschild radius and its quantum correction using a model density distribution: Skin of a black hole  

E-Print Network (OSTI)

Using a single particle density distribution for a system of self-gravitating particles which ultimately forms a black hole, we from a condensed matter point of view derive the Schwarzschild radius and by including the quantum mechanical exchange energy we find a small correction to the Schwarzschild radius, which we designate as the skin of the black hole.

Subodha Mishra

2007-03-16T23:59:59.000Z

383

NREL: Continuum Magazine - At $2.15 a Gallon, Cellulosic Ethanol Could Be  

NLE Websites -- All DOE Office Websites (Extended Search)

At $2.15 a Gallon, Cellulosic Ethanol Could Be Cost Competitive At $2.15 a Gallon, Cellulosic Ethanol Could Be Cost Competitive Issue 5 Print Version Share this resource At $2.15 a Gallon, Cellulosic Ethanol Could Be Cost Competitive DOE challenge met-research advances cut costs to produce fuel from non-food plant sources. A photo showing a silhouette of a man wearing glass in a dark room lit only by a band of light consisting or red, blue, and white dots (26186). Enlarge image In NREL's new Energy Systems Integration Facility, the Insight Collaboration Laboratory shows a 3D model of cellulose microfibrils. Photo by Dennis Schroeder, NREL Imagine a near perfect transportation fuel-it's clean, domestic, abundant, and renewable. Now imagine that it's also affordable. Bringing this vision closer to reality was the challenge the U.S.

384

NREL: Continuum Magazine - New Facility to Transform U.S. Energy  

NLE Websites -- All DOE Office Websites (Extended Search)

Energy Systems Integration Facility to Transform U.S. Energy Infrastructure Energy Systems Integration Facility to Transform U.S. Energy Infrastructure Issue 1 Print Version Share this resource Energy Systems Integration Facility to Transform U.S. Energy Infrastructure The nation's electricity infrastructure needs a 21st century overhaul. NREL's newest research facility will lead the way. Everyone knows that Thomas Edison invented the light bulb. But not many know that one of his greatest inventions was not the invention itself, but the research laboratory from whence it came. Edison's original research and development laboratory in Menlo Park, N.J., was the first of its kind and revolutionized the process of technological research. Later, the fusion of business and technology achieved at his West Orange, N.J. facility provided a model for modern corporate and governmental

385

CONTINUUM HALOS IN NEARBY GALAXIES: AN EVLA SURVEY (CHANG-ES). II. FIRST RESULTS ON NGC 4631  

Science Conference Proceedings (OSTI)

We present the first results from the Continuum Halos in Nearby Galaxies-an EVLA Survey (CHANG-ES), a new survey of 35 edge-on galaxies to search for both in-disk and extraplanar radio continuum emission. CHANG-ES is exploiting the new wide-band, multi-channel capabilities of the Karl G. Jansky Very Large Array (i.e., the Expanded Very Large Array or EVLA) with observations in two bands centered at 1.5 and 6 GHz in a variety of array configurations with full polarization. The motivation and science case for the survey are presented in a companion paper (Paper I). These first results are based on C-array test observations in both observing bands of the well-known radio halo galaxy, NGC 4631. In this paper, we outline the observations and the data reduction steps that are required for wide-band calibration and mapping of EVLA data, including polarization. With modest on-source observing times (30 minutes at 1.5 GHz and 75 minutes at 6 GHz for the test data), we have achieved best rms noise levels of 22 and 3.5 {mu}Jy beam{sup -1} at 1.5 GHz and 6 GHz, respectively. New disk-halo features have been detected, among them two at 1.5 GHz that appear as loops in projection. We present the first 1.5 GHz spectral index map of NGC 4631 to be formed from a single wide-band observation in a single array configuration. This map represents tangent slopes to the intensities within the band centered at 1.5 GHz, rather than fits across widely separated frequencies as has been done in the past and is also the highest spatial resolution spectral index map yet presented for this galaxy. The average spectral index in the disk is {alpha}-bar{sub 1.5GHz} = -0.84 {+-} 0.05 indicating that the emission is largely non-thermal, but a small global thermal contribution is sufficient to explain a positive curvature term in the spectral index over the band. Two specific star-forming regions have spectral indices that are consistent with thermal emission. Polarization results (uncorrected for internal Faraday rotation) are consistent with previous observations and also reveal some new features. On broad scales, we find strong support for the notion that magnetic fields constrain the X-ray-emitting hot gas.

Irwin, Judith; Henriksen, Richard N. [Department of Physics, Engineering Physics and Astronomy, Queen's University, Kingston, ON K7L 3N6 (Canada); Beck, Rainer; Krause, Marita; Mora, Silvia Carolina; Schmidt, Philip [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121, Bonn (Germany); Benjamin, R. A. [Department of Physics, University of Wisconsin at Whitewater, 800 West Main St., Whitewater, WI 53190 (United States); Dettmar, Ralf-Juergen; Miskolczi, Arpad [Astronomisches Institut, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); English, Jayanne [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Heald, George; Oosterloo, Tom [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA, Dwingeloo (Netherlands); Johnson, Megan [National Radio Astronomy Observatory, P.O. Box 2, Greenbank, WV 24944 (United States); Li, Jiang-Tao [Department of Astronomy, University of Massachusetts, 710 North Pleasant St., Amherst, MA 01003 (United States); Murphy, E. J. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Porter, Troy A. [Hansen Experimental Physics Laboratory, Stanford University, 452 Lomita Mall, Stanford, CA 94305 (United States); Rand, Richard J. [Department of Physics and Astronomy, University of New Mexico, 800 Yale Boulevard, NE, Albuquerque, NM 87131 (United States); Saikia, D. J. [National Centre for Radio Astrophysics, TIFR, Pune University Campus, Post Bag 3, Pune 411 007 (India); Strong, A. W. [Max-Planck-Institut fuer extraterrestrische Physik, Garching bei Muenchen (Germany); Walterbos, Rene, E-mail: irwin@astro.queensu.ca, E-mail: henriksn@astro.queensu.ca, E-mail: twiegert@astro.queensu.ca, E-mail: rbeck@mpifr-bonn.mpg.de, E-mail: mkrause@mpifr-bonn.mpg.de, E-mail: cmora@mpifr-bonn.mpg.de [Department of Astronomy, New Mexico State University, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003 (United States); and others

2012-08-15T23:59:59.000Z

386

Modeling  

NLE Websites -- All DOE Office Websites (Extended Search)

ALE-AMR ALE-AMR code Wangyi Liu, John Bernard, Alex Friedman, Nathan Masters, Aaron Fisher, Velemir Mlaker, Alice Koniges, David Eder June 4, 2011 Abstract In this paper we describe an implementation of a single-fluid inter- face model in the ALE-AMR code to simulate surface tension effects. The model does not require explicit information on the physical state of the two phases. The only change to the existing fluid equations is an additional term in the stress tensor. We show results of applying the model to an expanding Al droplet surrounded by an Al vapor, where additional droplets are created. 1 Introduction The Neutralized Drift Compression Experiment II (NDCX II) is an induction accelerator planned for initial commissioning in 2012. The final design calls for a 3 MeV, Li+ ion beam, delivered in a bunch with characteristic pulse duration of 1 ns, and transverse dimension of order 1 mm. The

387

Green fluorescent protein as a mechanical sensor  

E-Print Network (OSTI)

Inquiry into intracellular and cytoskeletal mechanics requires an intracellular mechanical sensor to verify models of sub-cellular structure dynamics. To this end, the green fluorescent protein (GFP) is considered as a ...

Muso, Taro M. (Taro Michael)

2007-01-01T23:59:59.000Z

388

Perfect Implementation of Normal-Form Mechanisms  

E-Print Network (OSTI)

Privacy and trust affect our strategic thinking, yet they have not been precisely modeled in mechanism design. In settings of incomplete information, traditional implementations of a normal-form mechanism ---by disregarding ...

Izmalkov, Sergei

389

Hot Dry Rock Geothermal Reservoir Model Development at Los Alamos  

DOE Green Energy (OSTI)

Discrete fracture and continuum models are being developed to simulate Hot Dry Rock (HDR) geothermal reservoirs. The discrete fracture model is a two-dimensional steady state simulator of fluid flow and tracer transport in a fracture network which is generated from assumed statistical properties of the fractures. The model's strength lies in its ability to compute the steady state pressure drop and tracer response in a realistic network of interconnected fractures. The continuum approach models fracture behavior by treating permeability and porosity as functions of temperature and effective stress. With this model it is practical to model transient behavior as well as the coupled processes of fluid flow, heat transfer, and stress effects in a three-dimensional system. The model capabilities being developed will also have applications in conventional geothermal systems undergoing reinjection and in fractured geothermal reservoirs in general.

Robinson, Bruce A.; Birdsell, Stephen A.

1989-03-21T23:59:59.000Z

390

Hot Dry Rock geothermal reservoir model development at Los Alamos  

DOE Green Energy (OSTI)

Discrete fracture and continuum models are being developed to simulate Hot Dry Rock (HDR) geothermal reservoirs. The discrete fracture model is a two-dimensional steady state simulator of fluid flow and tracer transport in a fracture network which is generated from assumed statistical properties of the fractures. The model's strength lies in its ability to compute the steady state pressure drop and tracer response in a realistic network of interconnected fractures. The continuum approach models fracture behavior by treating permeability and porosity as functions of temperature and effective stress. With this model it is practical to model transient behavior as well as the coupled processes of fluid flow, heat transfer, and stress effects in a three-dimensional system. The model capabilities being developed will also have applications in conventional geothermal systems undergoing reinjection and in fractured geothermal reservoirs in general. 15 refs., 7 figs.

Robinson, B.A.; Birdsell, S.A.

1989-01-01T23:59:59.000Z

391

Gas Bubbles and Gas Pancakes at Liquid/Solid Interface: A Continuum Theory Incorporated with Molecular Interactions  

E-Print Network (OSTI)

The states of gas accumulated at the liquid-solid interface are analyzed based on the continuum theory where the Hamaker constant is used to describe the long-range interaction at the microscopic scale. The Hamaker constant is always negative, whereas the gas spreading coefficient can be either sign. Despite the complexity of gas, including that the density profile may not be uniform due to absorption on both solid and liquid surfaces, we predict three possible gas states at the liquid-solid interface, i.e. complete wetting, partial wetting and pseudopartial wetting. These possible gas states correspond respectively to a gas pancake (or film) surrounded by a wet solid, a gas bubble with a finite contact angle, and a gas bubble(s) coexisting with a gas pancake. Typical thickness of the gas pancakes is at the nanoscale within the force range of the long-range interaction, whereas the radius of the gas bubbles can be large. The state of gas bubble(s) coexisting with a gas film is predicted theoretically for the first time. Our theoretical results can contribute to the development of a unified picture of gas nucleation at the liquid-solid interface.

Zhaoxia Li; Xuehua Zhang; Lijuan Zhang; Xiaocheng Zeng; Jun Hu; Haiping Fang

2006-08-04T23:59:59.000Z

392

Fracture Modeling and Flow Behavior in Shale Gas Reservoirs Using Discrete Fracture Networks  

E-Print Network (OSTI)

Fluid flow process in fractured reservoirs is controlled primarily by the connectivity of fractures. The presence of fractures in these reservoirs significantly affects the mechanism of fluid flow. They have led to problems in the reservoir which results in early water breakthroughs, reduced tertiary recovery efficiency due to channeling of injected gas or fluids, dynamic calculations of recoverable hydrocarbons that are much less than static mass balance ones due to reservoir compartmentalization, and dramatic production changes due to changes in reservoir pressure as fractures close down as conduits. These often lead to reduced ultimate recoveries or higher production costs. Generally, modeling flow behavior and mass transport in fractured porous media is done using the dual-continuum concept in which fracture and matrix are modeled as two separate kinds of continua occupying the same control volume (element) in space. This type of numerical model cannot reproduce many commonly observed types of fractured reservoir behavior since they do not explicitly model the geometry of discrete fractures, solution features, and bedding that control flow pathway geometry. This inaccurate model of discrete feature connectivity results in inaccurate flow predictions in areas of the reservoir where there is not good well control. Discrete Fracture Networks (DFN) model has been developed to aid is solving some of these problems experienced by using the dual continuum models. The Discrete Fracture Networks (DFN) approach involves analysis and modeling which explicitly incorporates the geometry and properties of discrete features as a central component controlling flow and transport. DFN are stochastic models of fracture architecture that incorporate statistical scaling rules derived from analysis of fracture length, height, spacing, orientation, and aperture. This study is focused on developing a methodology for application of DFN to a shale gas reservoir and the practical application of DFN simulator (FracGen and NFflow) for fracture modeling of a shale gas reservoir and also studies the interaction of the different fracture properties on reservoir response. The most important results of the study are that a uniform fracture network distribution and fracture aperture produces the highest cumulative gas production for the different fracture networks and fracture/well properties considered.

Ogbechie, Joachim Nwabunwanne

2011-12-01T23:59:59.000Z

393

Modeling Time-dependent Responses of Piezoelectric Fiber Composite  

E-Print Network (OSTI)

The existence of polymer constituent in piezoelectric fiber composites (PFCs) could lead to significant viscoelastic behaviors, affecting overall performance of PFCs. High mechanical and electrical stimuli often generate significant amount of heat, increasing temperatures of the PFCs. At elevated temperatures, most materials, especially polymers show pronounced time-dependent behaviors. Predicting time-dependent responses of the PFCs becomes important to improve reliability in using PFCs. We study overall performance of PFCs having unidirectional piezoceramic fibers, such as PZT fibers, dispersed in viscoelastic polymer matrix. Two types of PFCs are studied, which are active fiber composites (AFCs) and macro fiber composites (MFCs). AFCs and MFCs consist of unidirectional PZT fibers dispersed in epoxy placed between two interdigitated electrode and kapton layers. The AFCs have a circular fiber cross-section while the MFCs have a square fiber cross-section. Finite element (FE) models of representative volume elements (RVEs) of active PFCs, having square and circular fiber cross-sections, are generated for composites with 20, 40, and 60 percent fiber contents. Two FE micromechanical models having one fiber embedded in epoxy matrix and five fibers placed in epoxy matrix are considered. A continuum 3D piezoelectric element in ABAQUS FE is used. A general time-integral function is applied for the mechanical, electrical, and piezoelectric properties in order to incorporate the time-dependent effect and histories of loadings. The effective properties of PZT-5A/epoxy and PZT-7A/LaRC-SI piezocomposites determined from the FE micromechanical models are compared to available experimental data and analytical solutions in the literature. Furthermore, the effect of viscoelastic behaviors of the LaRC-SI matrix at an elevated temperature on the overall electro-mechanical and piezoelectric constants are examined.

Li, Kuo-An

2009-12-01T23:59:59.000Z

394

Continuum representation of a continuous size distribution of particles engaged in rapid granular flow  

Science Conference Proceedings (OSTI)

Natural and industrial granular flows often consist of several particle sizes, approximately forming a continuous particle size distribution (PSD). Continuous PSDs are ubiquitous, though existing kinetic-theory-based, hydrodynamic models for rapid granular flows are limited to a discrete number of species. The objective of this work is twofold: (i) to determine the number of discrete species required to accurately approximate a continuous PSD and (ii) to validate these results via a comparison with molecular dynamics (MD) simulations of continuous PSDs. With regard to the former, several analytic (Gaussian and lognormal) and experimental (coal and lunar soil simulants) distributions are investigated. Transport coefficients (pressure, shear viscosity, etc.) of the granular mixture given by the polydisperse theory of Garz´o et al. [“Enskog theory for polydisperse granular mixtures. I. Navier-Stokes order transport,” Phys. Rev. E 76, 031303 (2007);“Enskog theory for polydisperse granular mixtures. I. Navier-Stokes order transport,” 76, 031304 (2007)] are compared using an increasing number of species s to approximate the given PSD. These discrete approximations are determined by matching the first 2s moments of the approximation and the given continuous distribution. Relatively few species are required to approximate moderately wide distributions (Gaussian, lognormal), whereas even wider distributions (coal and lunar soil simulants) require a larger number of species. Regarding the second objective, a comparison between MD simulations and kinetictheory predictions for a simple shear flow of both Gaussian and lognormal PSDs reveal essentially no loss of accuracy stemming from the polydisperse theory itself (as compared to theories for monodisperse systems) or from the discrete approximations of continuous PSDs used in the polydisperse theory. C #2; 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4744987

Murray, J.A.; Benyahia, S.; Metzger, P.; Hrenya, C.M.

2012-01-01T23:59:59.000Z

395

Asymptotic Approximations to the Distributed Activation Energy Model  

E-Print Network (OSTI)

Asymptotic Approximations to the Distributed Activation Energy Model M.J.McGuinness1 , E. Donskoi2 by a continuum distribution in activation energy of individual re- actions. An individual reaction is characterised by a pre-exponential coefficient and an activation energy. The distribution, usually Gaussian

McGuinness, Mark

396

Coupled Thermal-Hydrological-Mechanical Processes in Salt, Hot...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Coupled Thermal-Hydrological-Mechanical Processes in Salt, Hot Granular Salt Consolidation, Constitutive Model and Micromechanics Coupled Thermal-Hydrological-Mechanical Processes...

397

Introducing a Partitioning Mechanism for PAHs into the Community Multiscale Air Quality Modeling System and Its Application to Simulating the Transport of Benzo(a)pyrene over Europe  

Science Conference Proceedings (OSTI)

Into the Community Multiscale Air Quality modeling system (CMAQ) that is widely used for simulating the transport and fate of air pollutants, a new module was inserted that accounts for the partitioning of semivolatile organic compounds—in ...

Armin Aulinger; Volker Matthias; Markus Quante

2007-11-01T23:59:59.000Z

398

An Investigation of Ice Production Mechanisms in Small Cumuliform Clouds Using a 3D Model with Explicit Microphysics. Part II: Case Study of New Mexico Cumulus Clouds  

Science Conference Proceedings (OSTI)

A new 3D model with explicit liquid- and ice-phase microphysics and a detailed treatment of ice nucleation and multiplication processes is applied to study ice formation and evolution in cumulus clouds. Simulation results are compared with in ...

Mikhail Ovtchinnikov; Yefim L. Kogan; Alan M. Blyth

2000-09-01T23:59:59.000Z

399

Stommel’s Box Model of Thermohaline Circulation Revisited—The Role of Mechanical Energy Supporting Mixing and the Wind-Driven Gyration  

Science Conference Proceedings (OSTI)

The classical two-box model of Stommel is extended in two directions: replacing the buoyancy constraint with an energy constraint and including the wind-driven gyre. Stommel postulated a buoyancy constraint for the thermohaline circulation, and ...

Yu Ping Guan; Rui Xin Huang

2008-04-01T23:59:59.000Z

400

INDEXING MECHANISM  

DOE Patents (OSTI)

A device is presented for loading and unloading fuel elements containing material fissionable by neutrons of thermal energy. The device comprises a combination of mechanical features Including a base, a lever pivotally attached to the base, an Indexing plate on the base parallel to the plane of lever rotation and having a plurality of apertures, the apertures being disposed In rows, each aperture having a keyway, an Index pin movably disposed to the plane of lever rotation and having a plurality of apertures, the apertures being disposed in rows, each aperture having a keyway, an index pin movably disposed on the lever normal to the plane rotation, a key on the pin, a sleeve on the lever spaced from and parallel to the index pin, a pair of pulleys and a cable disposed between them, an open collar rotatably attached to the sleeve and linked to one of the pulleys, a pin extending from the collar, and a bearing movably mounted in the sleeve and having at least two longitudinal grooves in the outside surface.

Kock, L.J.

1959-09-22T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Materials Reliability Program: PWR Internals Age-Related Material Properties, Degradation Mechanisms, Models, and Basis Data - State of Knowledge (MRP-211)  

Science Conference Proceedings (OSTI)

The purpose of this report is to summarize the current state-of-knowledge of neutron irradiation-induced property changes in austenitic stainless steels, principally solution-annealed Type 304 and 304L materials, cold-worked and solution-annealed Type 316 and 316L materials, and Type 308 weld metal. The age-related degradation models were evaluated by an expert panel assembled by EPRI and the Reactor Internals Focus Group (RI-FG). This panel endorsed models to be used in functionality evaluations and sug...

2007-12-19T23:59:59.000Z

402

Climate Studies with a Multi-Layer Energy Balance Model. Part II: The Role of Feedback Mechanisms in the CO2 Problem  

Science Conference Proceedings (OSTI)

The sensitivity of climate to a doubling of the atmospheric CO2, content has been studied using the GLAS multi-layer energy balance model. In response to a doubled CO2 content, tropospheric temperature lapse rate decreases at low latitudes but ...

Ming-Dah Chou; Li Peng; Albert Arking

1982-12-01T23:59:59.000Z

403

Physicalism versus quantum mechanics  

E-Print Network (OSTI)

Foundations of Quantum Mechanics. (Princeton UniversityMind, Matter, and Quantum Mechanics, (Springer, Berlin & NewMindful Universe: Quantum Mechanics and the Participating

Stapp, Henry P; Theoretical Physics Group; Physics Division

2009-01-01T23:59:59.000Z

404

Using ex vivo organ culture models as surrogates to investigate morphological and functional differences of mammary glands derived from mouse strains that differ in cancer susceptibility to understand the underlying mechanisms of radiation sensitivity or resistance  

NLE Websites -- All DOE Office Websites (Extended Search)

ex vivo organ culture models as surrogates to investigate morphological and functional ex vivo organ culture models as surrogates to investigate morphological and functional differences of mammary glands derived from mouse strains that differ in cancer susceptibility to understand the underlying mechanisms of radiation sensitivity or resistance Alvin Lo, Joni D. Mott, Jian-Hua Mao, and Mina J. Bissell Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley CA 94720 Goal: Within the Lawrence Berkeley National Laboratory's Low Dose SFA, as part of Project 2, we are using a systems genetics approach to determine the contribution of non-targeted and targeted radiation effects for risk of mammary carcinogenesis. The goal of this work is to characterize the mammary gland of the parental mouse strains, and the F1 and F2 generations used in these studies with respect to tissue

405

Global existence for a hydrogen storage model with full energy balance  

E-Print Network (OSTI)

A thermo-mechanical model describing hydrogen storage by use of metal hydrides has been recently proposed in a paper by Bonetti, Fr\\'emond and Lexcellent. It describes the formation of hydrides using the phase transition approach. By virtue of the laws of continuum thermo-mechanics, the model leads to a phase transition problem in terms of three state variables: the temperature, the phase parameter representing the fraction of one solid phase, and the pressure, and is derived within a generalization of the principle of virtual powers proposed by Fr\\'emond accounting for micro-forces, responsible for the phase transition, in the whole energy balance of the system. Three coupled nonlinear partial differential equations combined with initial and boundary conditions have to be solved. The main difficulty in investigating the resulting system of partial differential equations relies on the presence of the squared time derivative of the order parameter in the energy balance equation. Here, the global existence of a...

Bonetti, Elena; Laurençot, Philippe

2011-01-01T23:59:59.000Z

406

NREL: Continuum Magazine - Archive  

NLE Websites -- All DOE Office Websites (Extended Search)

Deliberate Science The NREL Spectrum of Clean Energy Innovation NREL Leads Energy Systems Integration Sustainable Transportation Previous Next NREL is a national laboratory of...

407

Continuum Computational Plasticity  

Science Conference Proceedings (OSTI)

Mar 2, 2011 ... Microstructural Evolution and Its Effect on Plastic Flow and Strain .... Pb-free interconnects are being used extensively in Electronic Packaging.

408

Interactive Session A: Mechanisms/Models for Mechanical Behavior  

Science Conference Proceedings (OSTI)

Sep 10, 2012... Milling Tests: Ralf Webler1; Markus Krottenthaler1; Steffen Neumeier1; Karsten Durst1; Mathias Göken1; 1University Erlangen-Nuremberg

409

Constitutive Model for the Time-Dependent Mechanical Behavior of 430 Stainless Steel and FeCrAlY Foams in Sulfur-Bearing Environments  

Science Conference Proceedings (OSTI)

The mechanical behavior of 430 stainless steel and pre-oxidized FeCrAlY open-cell foam materials of various densities was evaluated in compression at temperatures between 450 C and 600 C in an environment containing hydrogen sulfide and water vapor. Both materials showed negligible corrosion due to the gaseous atmosphere for up to 168 hours. The monotonic stress-strain response of these materials was found to be dependent on both the strain rate and their density, and the 430 stainless steel foam materials exhibited less stress relaxation than FeCrAlY for similar experimental conditions. Using the results from multiple hardening-relaxation and monotonic tests, an empirical constitutive equation was derived to predict the stress-strain behavior of FeCrAlY foams as a function of temperature and strain rate. These results are discussed in the context of using these materials in a black liquor gasifier to accommodate the chemical expansion of the refractory liner resulting from its reaction with the soda in the black liquor.

Hemrick, James Gordon [ORNL; Lara-Curzio, Edgar [ORNL

2013-01-01T23:59:59.000Z

410

Mesoscopic model for filament orientation in growing actin networks: the role of obstacle geometry  

E-Print Network (OSTI)

Propulsion by growing actin networks is a universal mechanism used in many different biological systems. Although the core molecular machinery for actin network growth is well preserved in most cases, the geometry of the propelled obstacle can vary considerably. In recent years, filament orientation distribution has emerged as an important observable characterizing the structure and dynamical state of the growing network. Here we derive several continuum equations for the orientation distribution of filaments growing behind stiff obstacles of various shapes and validate the predicted steady state orientation patterns by stochastic computer simulations based on discrete filaments. We use an ordinary differential equation approach to demonstrate that for flat obstacles of finite size, two fundamentally different orientation patterns peaked at either +35/-35 or +70/0/-70 degrees exhibit mutually exclusive stability, in agreement with earlier results for flat obstacles of very large lateral extension. We calculate and validate phase diagrams as a function of model parameters and show how this approach can be extended to obstacles with piecewise straight contours. For curved obstacles, we arrive at a partial differential equation in the continuum limit, which again is in good agreement with the computer simulations. In all cases, we can identify the same two fundamentally different orientation patterns, but only within an appropriate reference frame, which is adjusted to the local orientation of the obstacle contour. Our results suggest that two fundamentally different network architectures compete with each other in growing actin networks, irrespective of obstacle geometry, and clarify how simulated and electron tomography data have to be analyzed for non-flat obstacle geometries.

Julian Weichsel; Ulrich S. Schwarz

2013-04-13T23:59:59.000Z

411

Single Cell Mechanics BIOMATERIALS  

E-Print Network (OSTI)

Single Cell Mechanics BIOMATERIALS Our goal is to develop fundamental tools to measure the response of live cells to mechanical stimulation. The mechanisms by which cells convert mechanical forces evaluate the underlying mechanisms of cell mechanics. Objective Impact and Customers · Cancer, heart

412

A new stochastic interpretation of quantum mechanics  

E-Print Network (OSTI)

The reinterpretation of quantum mechanical formalism in terms of a classical model with a continuous material "$\\Psi$-field" acting upon a point-like particle which is subjected to large friction and random forces is proposed. This model gives a mechanism for sudden "quantum jumps" and provides a simple explanation of "Schrödinger Cat" phenomena.

Alicki, R

1997-01-01T23:59:59.000Z

413

A new stochastic interpretation of quantum mechanics  

E-Print Network (OSTI)

The reinterpretation of quantum mechanical formalism in terms of a classical model with a continuous material "$\\Psi$-field" acting upon a point-like particle which is subjected to large friction and random forces is proposed. This model gives a mechanism for sudden "quantum jumps" and provides a simple explanation of "Schr\\"odinger Cat" phenomena.

Robert Alicki

1997-11-24T23:59:59.000Z

414

Travelling waves in hybrid chemotaxis models  

E-Print Network (OSTI)

Hybrid models of chemotaxis combine agent-based models of cells with partial differential equation models of extracellular chemical signals. In this paper, travelling wave properties of hybrid models of bacterial chemotaxis are investigated. Bacteria are modelled using an agent-based (individual-based) approach with internal dynamics describing signal transduction. In addition to the chemotactic behaviour of the bacteria, the individual-based model also includes cell proliferation and death. Cells consume the extracellular nutrient field (chemoattractant) which is modelled using a partial differential equation. Mesoscopic and macroscopic equations representing the behaviour of the hybrid model are derived and the existence of travelling wave solutions for these models is established. It is shown that cell proliferation is necessary for the existence of non-transient (stationary) travelling waves in hybrid models. Additionally, a numerical comparison between the wave speeds of the continuum models and the hybr...

Franz, Benjamin; Painter, Kevin J; Erban, Radek

2013-01-01T23:59:59.000Z

415

The SGB/NP Hydration Free Energy Model Based on the Surface Generalized Born Solvent Reaction Field and  

E-Print Network (OSTI)

The SGB/NP Hydration Free Energy Model Based on the Surface Generalized Born Solvent Reaction Field and Novel Nonpolar Hydration Free Energy Estimators EMILIO GALLICCHIO, LINDA YU ZHANG, RONALD M. LEVY Generalized Born continuum dielectric electrostatic model using explicit solvent free energy perturbation

416

The influence of helium on mechanical properties of model austenitic alloys, determined using sup 59 Ni isotopic tailoring and fast reactor irradiation  

Science Conference Proceedings (OSTI)

The objective of this effort is to study the separate and synergistic effects of helium and other important variables on the evolution of microstructure and macroscopic properties during irradiation of structural metals. The alloys employed in this study were nominally Fe-15Cr-25Ni, Fe-15Cr-25Ni-0.04P and Fe-15Cr-45Ni (wt %) in both the cold worked and annealed conditions. Tensile testing and microscopy continue on specimens removed from the first, second and third discharges of the {sup 59}Ni isotopic doping experiment. The results to date indicate that helium/dpa ratios typical of fusion reactors (4 to 19 appm/dpa) do not lead to significant changes in the yield strength of model Fe-Cr-Ni alloys. Measurements of helium generated in undoped specimens from the second and third discharges show that the helium/dpa ratio increases during irradiation in FFTF due to the production of {sup 59}Ni. In specimens doped with {sup 59}Ni prior to irradiation, the helium/dpa ratio can increase, decrease or remain the same during the second irradiation interval. This behavior occurs because the cross sections for the production and burnout of {sup 59}Ni are very sensitive to core location and the nature of neighboring components. 14 refs., 5 figs., 3 tabs.

Hamilton, M.L.; Garner, F.A. (Pacific Northwest Lab., Richland, WA (USA)); Oliver, B.M. (Rockwell International Corp., Canoga Park, CA (USA))

1990-11-01T23:59:59.000Z

417

A Baroclinic Model of turbulent dusty flows  

SciTech Connect

The problem considered here is the numerical simulation of the turbulent dusty flow induced by explosions over soil surfaces. Some of the unresolved issues are: (1) how much dust is scoured from such surfaces; (2) where does the dust go in the boundary layer; (3) what is the dusty boundary layer height versus time; (4) what are the dusty boundary layer profiles; (5) how much of the dust mass becomes entrained into the dust stem; and (6) where does the dust go in the buoyant cloud? The author proposes a Baroclinic Model for flows with large density variations that actually calculates the turbulent mixing and transport of dust on an adaptive grid. The model is based on the following idealizations: (1) a loose dust bed; (2) an instantaneous shock fluidization of the dust layer; (3) the dust and air are in local equilibrium (so air viscosity enforces the no-slip condition); (4) the dust-air mixture is treated as a continuum dense fluid with zero viscosity; and (5) the turbulent mixing is dominated by baroclinically-generated vorticity. These assumptions lead to an inviscid set of conservation laws for the mixture, which are solved by means of a high-order Godunov algorithm for gasdynamics. Adaptive Mesh Refinement (AMR) is used to capture the turbulent mixing processes on the grid. One of the unique characteristics of these flows is that mixing occurs because vorticity is produced by an inviscid, baroclinic mechanism. A number of examples are presented to illustrate these baroclinic effects including shock interactions with dense-gas layers and dust beds, and dusty wall jets of airblast precursors. The conclusion of these studies is that dusty boundary layers grow because of mass entrainment from the fluidized bed (and not because of viscous wall drag) as proven by the Mass Integral Equation.

Kuhl, A.L.

1992-04-01T23:59:59.000Z

418

Mechanisms of gas precipitation in plasma-exposed tungsten  

Science Conference Proceedings (OSTI)

Precipitation in subsurface bubbles is a key process that governs how hydrogen isotopes migrate through and become trapped within plasma-exposed tungsten. We describe a continuum-scale model of hydrogen diffusion in plasma-exposed materials that includes the effects of precipitation. The model can account for bubble expansion via dislocation loop punching, using an accurate equation of state to determine the internal pressure. This information is used to predict amount of hydrogen trapped by bubbles, as well as the conditions where the bubbles become saturated. In an effort to validate the underlying assumptions, we compare our results with published positron annihilation and thermal desorption spectroscopy data, as well as our own measurements using the tritium plasma experiment (TPE).

R. D. Kolasinski; D. F. Cowgill; D. C. Donovan; M. Shimada

2012-05-01T23:59:59.000Z

419

The Bolocam Galactic Plane Survey IV: 1.1 and 0.35 mm Dust Continuum Emission in the Galactic Center Region  

E-Print Network (OSTI)

The Bolocam Galactic Plane Survey (BGPS) data for a six square degree region of the Galactic plane containing the Galactic center is analyzed and compared to infrared and radio continuum data. The BGPS 1.1 mm emission consists of clumps interconnected by a network of fainter filaments surrounding cavities, a few of which are filled with diffuse near-IR emission indicating the presence of warm dust or with radio continuum characteristic of HII regions or supernova remnants. New 350 {\\mu}m images of the environments of the two brightest regions, Sgr A and B, are presented. Sgr B2 is the brightest mm-emitting clump in the Central Molecular Zone and may be forming the closest analog to a super star cluster in the Galaxy. The Central Molecular Zone (CMZ) contains the highest concentration of mm and sub-mm emitting dense clumps in the Galaxy. Most 1.1 mm features at positive longitudes are seen in silhouette against the 3.6 to 24 {\\mu}m background observed by the Spitzer Space Telescope. However, only a few clumps ...

Bally, John; Battersby, Cara; Bradley, Eric Todd; Cyganowski, Claudia; Dowell, Darren; Drosback, Meredith; Dunham, Miranda K; Evans, Neal J; Ginsburg, Adam; Glenn, Jason; Harvey, Paul; Mills, Elisabeth; Merello, Manuel; Rosolowsky, Erik; Schlingman, Wayne; Shirley, Yancy L; Stringfellow, Guy S; Walawender, Josh; Williams, Jonathan; 10.1088/0004-637X/721/1/137

2010-01-01T23:59:59.000Z

420

Multiple temperature kinetic model and gas-kinetic method for hypersonic non-equilibrium flow computations  

Science Conference Proceedings (OSTI)

It is well known that for increasingly rarefied flowfields, the predictions from continuum formulation, such as the Navier-Stokes equations lose accuracy. For the high speed diatomic molecular flow in the transitional regime, the inaccuracies are partially ... Keywords: Gas-kinetic method, Hypersonic and rarefied flows, Multiple temperature kinetic model

Kun Xu; Xin He; Chunpei Cai

2008-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Mechanics of Peridynamic Membranes  

National Nuclear Security Administration (NNSA)

JBAidun AdvMatSci090831 JBAidun AdvMatSci090831 1 Accurate Prediction of Dynamic Fracture with Peridynamics John B. Aidun & Stewart A. Silling Multiscale Dynamic Material Modeling Sandia National Laboratories Prague, Czech Republic August 30 - September 3, 2009 Joint U.S.-Russian Conference on Advances in Materials Science SAND2009-5095C Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. JBAidun AdvMatSci090831 2 Fracture Mechanics Theory and Dynamic Fracture * Onset of crack growth can be accurately predicted * Crack growth speed and direction cannot! Wanted: A successful method for simulating Dynamic Fracture * Such a method must be able to reproduce the

422

Sandia National Laboratories: Careers: Mechanical Engineering  

NLE Websites -- All DOE Office Websites (Extended Search)

Mechanical Engineering Mechanical Engineering Engineering photo Sandia mechanical engineers design and develop advanced components and systems for national-defense programs, homeland security, and other applications. Mechanical engineers at Sandia work on design, analysis, manufacturing, and test activities in many areas, including nuclear weapons and power, renewable energy, intelligent machines, robotics, pulsed power, missile defense, remote sensing, advanced manufacturing, and micro- and nanosystems. Sandia mechanical engineers are an integral part of multidisciplinary teams that employ state-of-the-art technologies, such as sophisticated software tools for design, analysis, modeling, and simulation; micro- and nanotechnologies; and advanced materials, materials processing, and fabrication.

423

Mechanical Characterization of Nodular Ductile Iron  

SciTech Connect

The objective of this study is to characterize the strength and fracture response of nodular ductile iron (NDI) and its underlying ferritic matrix phase. Quasistatic and split Hopkinson pressure bar (SHPB) compression tests were performed on NDI and a model material for the NDI matrix phase (Fe-Si alloy). Smooth and notch round bar (NRB) samples were loaded in tension until fracture to determine strain-at-failure with varying stress triaxiality. Multiple tests were performed on each small and large smooth bar samples to obtain fracture statistics with sample size. Fracture statistics are important for initializing simulations of fragmentation events. Johnson-Cook strength models were developed for the NDI and the Fe-Si alloy. NDI strength model parameters are: A = 525 MPa, B = 650 MPa, n = 0.6, and C = 0.0205. The average SHPB experimental strain-rate of 2312/s was used for the reference strain-rate in this model. Fe-Si alloy strength model parameters are: A=560 MPa, B = 625 MPa, n = 0.5, and C = 0.02. The average SHPB experimental strain-rate of 2850/s was used for the reference strain-rate in this model. A Johnson-Cook failure model was developed for NDI with model parameters: D{sub 1} = 0.029, D{sub 2} = 0.44, D{sub 3} = -1.5, and D{sub 4} = D{sub 5} = 0. An exponential relationship was developed for the elongation-at-failure statistics as a function of length-scale with model parameters: S{sub f1} = 0.108, S{sub f2} = -0.00169, and L{sub m} = 32.4 {mu}m. NDI strength and failure models, including failure statistics, will be used in continuum-scale simulations of explosively-driven ring fragmentation. The Fe-Si alloy strength model will be used in mesoscale simulations of spall fracture in NDI, where the NDI matrix phase is captured explicitly.

Springer, H K

2012-01-03T23:59:59.000Z

424

Mechanism of pressure welding  

SciTech Connect

Thesis. The mechanism in polycrystalline aluminum, copper, silver, and gold was investigated. (19 figures) (DLC)

Mohamed, H.A.E.F.

1973-12-01T23:59:59.000Z

425

CARTESIAN MECHANICS* Sophie Roux  

E-Print Network (OSTI)

1 CARTESIAN MECHANICS* Sophie Roux (Centre Alexandre Koyré, EHESS, Paris) Introduction For many the search for a mathematical treatment of phenomena, on the other hand the demand for mechanical as the typical mechanical philosopher, and contrasted as such to the founder of mechanics as a science, namely

Paris-Sud XI, Université de

426

INTRODUCTION TO THE MECHANICS  

E-Print Network (OSTI)

INTRODUCTION TO THE MECHANICS OF A CONTINUOUS MEDIUM Lawrence E. Malvern Professor of Mechanics princi- ples common to all branches of solid and fluid mechanics, designed to appeal to the intuition science. The book arose from the need to provide a general preparation in contin- uum mechanics

Kaminski, Edouard

427

Graduate quantum mechanics reform  

Science Conference Proceedings (OSTI)

We address four main areas in which graduatequantum mechanics education can be improved: course content

L. D. Carr; S. B. McKagan

2009-01-01T23:59:59.000Z

428

Mechanical Behavior and Modeling - Programmaster.org  

Science Conference Proceedings (OSTI)

Oct 29, 2013 ... Because of their low density, high temperature strength, and notch insensitivity silicon carbide fiber reinforced silicon carbide ceramic matrix ...

429

Modeling and Experimental Validation of Multiscale Mechanical ...  

Science Conference Proceedings (OSTI)

Mar 4, 2013 ... Program Organizers: Nathan Mara, Los Alamos National Laboratory; ..... of Energy's National Nuclear Security Administration under contract ...

430

Modeling the Mechanical Properties of Gum Metal  

Science Conference Proceedings (OSTI)

... significantly, a feature that may also lead to pinning of dislocations. This work is supported by the National Science Foundation, and Toyota Motor Corporation.

431

MPMD Sympoisum: Mechanics and Materials Modeling and ...  

Science Conference Proceedings (OSTI)

May 1, 2007 ... Non-member price: 156.00. TMS Student Member price: 114.00. Product In Stock . Description These papers are based on presentations ...

432

Mechanical Characterization and Modeling - Programmaster.org  

Science Conference Proceedings (OSTI)

Mar 3, 2011 ... Characterization of Nuclear Reactor Materials and Components with .... Reduction Initiative of the National Nuclear Security Administration in ...

433

Four-dimensional understanding of quantum mechanics  

E-Print Network (OSTI)

In this paper I will try to convince that quantum mechanics does not have to lead to indeterminism, but is just a natural consequence of four-dimensional nature of our world - that for example particles shouldn't be imagined as 'moving points' in space, but as their trajectories in the spacetime like in optimizing action formulation of Lagrangian mechanics. There will be analyzed simplified model - Boltzmann distribution among trajectories occurs to give quantum mechanic like behavior - for example electron moving in proton's potential would make some concrete trajectory which average exactly to the probability distribution of the quantum mechanical ground state. We will use this model to build intuition about quantum mechanics and discuss its generalizations to get some effective approximation of physics. We will see that topological excitations of the simplest model obtained this way already creates known from physics particle structure, their decay modes and electromagnetic/gravitational interactions between them.

Jarek Duda

2009-10-14T23:59:59.000Z

434

Spectral dimension in graph models of causal quantum gravity  

E-Print Network (OSTI)

The phenomenon of scale dependent spectral dimension has attracted special interest in the quantum gravity community over the last eight years. It was first observed in computer simulations of the causal dynamical triangulation (CDT) approach to quantum gravity and refers to the reduction of the spectral dimension from 4 at classical scales to 2 at short distances. Thereafter several authors confirmed a similar result from different approaches to quantum gravity. Despite the contribution from different approaches, no analytical model was proposed to explain the numerical results as the continuum limit of CDT. In this thesis we introduce graph ensembles as toy models of CDT and show that both the continuum limit and a scale dependent spectral dimension can be defined rigorously. First we focus on a simple graph ensemble, the random comb. It does not have any dynamics from the gravity point of view, but serves as an instructive toy model to introduce the characteristic scale of the graph, study the continuum limit and define the scale dependent spectral dimension. Having defined the continuum limit, we study the reduction of the spectral dimension on more realistic toy models, the multigraph ensembles, which serve as a radial approximation of CDT. We focus on the (recurrent) multigraph approximation of the two-dimensional CDT whose ensemble measure is analytically controlled. The latter comes from the critical Galton-Watson process conditioned on non-extinction. Next we turn our attention to transient multigraph ensembles, corresponding to higher-dimensional CDT. Firstly we study their fractal properties and secondly calculate the scale dependent spectral dimension and compare it to computer simulations. We comment further on the relation between Horava-Lifshitz gravity, asymptotic safety, multifractional spacetimes and CDT-like models.

Georgios Giasemidis

2013-10-30T23:59:59.000Z

435

Adaptive mechanism design: a metalearning approach  

Science Conference Proceedings (OSTI)

Auction mechanism design has traditionally been a largely analytic process, relying on assumptions such as fully rational bidders. In practice, however, bidders often exhibit unknown and variable behavior, making them difficult to model and complicating ... Keywords: auctions, machine learning, mechanism design, metalearning

David Pardoe; Peter Stone; Maytal Saar-Tsechansky; Kerem Tomak

2006-08-01T23:59:59.000Z

436

NSLS Mechanical Tech  

NLE Websites -- All DOE Office Websites (Extended Search)

Mechanical Tech Mechanical Tech The Mechanical Technician group is supervised by Robert Scheuerer and consists of Mechanical Technicians with fabrication/machining, assembly, installation, and alignment/surveying skills. This group also serves as an interface to Central Fabrication Services when more complex or larger fabrication efforts are needed. The Mechanical Tech group is responsible for fabricating, installing, aligning, and troubleshooting the mechanical hardware used on NSLS and SDL accelerators, front ends, and User beamlines, often starting solely from Mechanical Design group drawings or CAD files. The Mechanical Tech Group is responsible for the fabrication, assembly and installation of components at the NSLS. These components include all mechanical assemblies and RF cavities. Another part of their job is to

437

Reaction mechanisms of pair transfer  

E-Print Network (OSTI)

The mechanisms of nuclear transfer reactions are described for the transfer of two nucleons from one nucleus to another. Two-nucleon overlap functions are defined in various coordinate systems, and their transformation coefficients given between coordinate systems. Post and prior couplings are defined for sequential transfer mechanisms, and it is demonstrated that the combination of `prior-post' couplings avoids non-orthogonality terms, but does not avoid couplings that do not have good zero-range approximations. The simultaneous and sequential mechanisms are demonstrated for the $^{124}$Sn(p,t)$^{122}$Sn reaction at 25 MeV using shell-model overlap functions. The interference between the various simultaneous and sequential amplitudes is shown.

Ian J. Thompson

2012-04-13T23:59:59.000Z

438

Does the Higgs Mechanism Exist?  

E-Print Network (OSTI)

This paper explores the argument structure of the concept of spontaneous symmetry breaking in the electroweak gauge theory of the Standard Model: the so-called Higgs mechanism. As commonly understood, the Higgs argument is designed to introduce the masses of the gauge bosons by a spontaneous breaking of the gauge symmetry of an additional field, the Higgs field. The technical derivation of the Higgs mechanism, however, consists in a mere re-shuffling of degrees of freedom by transforming the Higgs Lagrangian in a gauge-invariant manner. This already raises serious doubts about the adequacy of the entire manoeuvre. It will be shown that no straightforward ontic interpretation of the Higgs mechanism is tenable since gauge transformations possess no real instantiations. In addition, the explanatory value of the Higgs argument will be critically examined.

Holger Lyre

2008-06-08T23:59:59.000Z

439

Internal pipe attachment mechanism  

DOE Patents (OSTI)

An attachment mechanism is described for repairing or extending fluid carrying pipes, casings, conduits, etc. utilizing one-way motion of spring tempered fingers to provide a mechanical connection between the attachment mechanism and the pipe. The spring tempered fingers flex to permit insertion into a pipe to a desired insertion depth. The mechanical connection is accomplished by reversing the insertion motion and the mechanical leverage in the fingers forces them outwardly against the inner wall of the pipe. A seal is generated by crushing a sealing assembly by the action of setting the mechanical connection. 6 figures.

Bast, R.M.; Chesnut, D.A.; Henning, C.D.; Lennon, J.P.; Pastrnak, J.W.; Smith, J.A.

1994-12-13T23:59:59.000Z

440

Formation of deformation textures in face-centered-cubic materials studied by in-situ high-energy x-ray diffraction and self-consistent model.  

Science Conference Proceedings (OSTI)

The evolution of deformation textures in copper and a brass that are representative of fcc metals with different stacking fault energies (SFEs) during cold rolling is predicted using a self-consistent (SC) model. The material parameters used for describing the micromechanical behavior of each metal are determined from the high-energy X-ray (HEXRD) diffraction data. At small reductions, a reliable prediction of the evolution of the grain orientation distribution that is represented as the continuous increase of the copper and brass components is achieved for both metals when compared with the experimental textures. With increasing deformation, the model could characterize the textures of copper, i.e., the strengthening of the copper component, when dislocation slip is still the dominant mechanism. For a brass at moderate and large reductions, a reliable prediction of its unique feature of texture evolution, i.e., the weakening of the copper component and the strengthening of the brass component, could only be achieved when proper boundary conditions together with some specified slip/twin systems are considered in the continuum micromechanics mainly containing twinning and shear banding. The present investigation suggests that for fcc metals with a low SFE, the mechanism of shear banding is the dominant contribution to the texture development at large deformations.

Jia, N.; Nie, Z. H.; Ren, Y.; Peng, R. L.; Wang, Y. D.; Zhao, X.; X-Ray Science Division; Northeastern Univ.; Linkoping Univ.; Beijing Inst. of Tech.

2010-05-01T23:59:59.000Z

Note: This page contains sample records for the topic "mechanics continuum modeling" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

The Department of Mechanical Engineering --Engineering Mechanics  

E-Print Network (OSTI)

, Missile, Research, Development and Engineering Directorate's Propulsion Iaborato'. Ills primaly areas of research are in numerical combustion, and the thermal and mechanical aging ofnitrate esterpropellants decomposition and combustion. Stabilizers are added to the propellants to neutralize the decomposition products

Endres. William J.

442

Complex Mechanical Properties of Steel  

E-Print Network (OSTI)

?i friction stress ?y stress necessary to propagate yield ? bias A number of models in the committee CONTENTS ix a crack length a1 reliability constant a2 material fatigue properties constant a3 lubricant constant C material constant ci chemical... for failure to occur. In addition to this, stress concentration, temperature, corro- sion, residual stress and basic mechanical properties influence fatigue failure [10]. 2.1 FATIGUE CRACK GROWTH 5 2.1.1 Fatigue Failure Concepts There are four concepts applied...

Dimitriu, Radu

443

Compliant mechanism learning toolkit  

E-Print Network (OSTI)

This thesis concerns a toolkit designed to assist in learning the behavior of complaint mechanisms. In the design of complaint mechanisms, increasingly complicated designs behave in ways that are harder to intuitively ...

Allard, Nicholas (Nicholas A.)

2006-01-01T23:59:59.000Z

444

Atomistic modeling of nanowires, small-scale fatigue damage in cast magnesium, and materials for MEMS.  

Science Conference Proceedings (OSTI)

Lightweight and miniaturized weapon systems are driving the use of new materials in design such as microscale materials and ultra low-density metallic materials. Reliable design of future weapon components and systems demands a thorough understanding of the deformation modes in these materials that comprise the components and a robust methodology to predict their performance during service or storage. Traditional continuum models of material deformation and failure are not easily extended to these new materials unless microstructural characteristics are included in the formulation. For example, in LIGA Ni and Al-Si thin films, the physical size is on the order of microns, a scale approaching key microstructural features. For a new potential structural material, cast Mg offers a high stiffness-to-weight ratio, but the microstructural heterogeneity at various scales requires a structure-property continuum model. Processes occurring at the nanoscale and microscale develop certain structures that drive material behavior. The objective of the work presented in this report was to understand material characteristics in relation to mechanical properties at the nanoscale and microscale in these promising new material systems. Research was conducted primarily at the University of Colorado at Boulder to employ tightly coupled experimentation and simulation to study damage at various material size scales under monotonic and cyclic loading conditions. Experimental characterization of nano/micro damage will be accomplished by novel techniques such as in-situ environmental scanning electron microscopy (ESEM), 1 MeV transmission electron microscopy (TEM), and atomic force microscopy (AFM). New simulations to support experimental efforts will include modified embedded atom method (MEAM) atomistic simulations at the nanoscale and single crystal micromechanical finite element simulations. This report summarizes the major research and development accomplishments for the LDRD project titled 'Atomistic Modeling of Nanowires, Small-scale Fatigue Damage in Cast Magnesium, and Materials for MEMS'. This project supported a strategic partnership between Sandia National Laboratories and the University of Colorado at Boulder by providing funding for the lead author, Ken Gall, and his students, while he was a member of the University of Colorado faculty.

Dunn, Martin L. (University of Colorado, Boulder, CO); Talmage, Mellisa J. (University of Colorado, Boulder, CO); McDowell, David L., 1956- (,-Georgia Institute of Technology, Atlanta, GA); West, Neil (University of Colorado, Boulder, CO); Gullett, Philip Michael (Mississippi State University , MS); Miller, David C. (University of Colorado, Boulder, CO); Spark, Kevin (University of Colorado, Boulder, CO); Diao, Jiankuai (University of Colorado, Boulder, CO); Horstemeyer, Mark F. (Mississippi State University , MS); Zimmerman, Jonathan A.; Gall, K (Georgia Institute of Technology, Atlanta, GA)

2006-10-01T23:59:59.000Z

445

QUICK QUANTUM MECHANICS ---Introduction ---  

E-Print Network (OSTI)

QUICK QUANTUM MECHANICS --- Introduction --- The following notes are intended to be a supplement to your study of Liboff's ``Introductory Quantum Mechanics.'' They are not an alternative! My purpose here of Classical Mechanics After Newton found his equations of motion, physicists knew they would have to wait

Jackson, Andrew D.

446

Renormalizable extra-dimensional models  

E-Print Network (OSTI)

Non-Abelian gauge theories may have continuum limits in more than four dimensions, supported by non-trivial ultra-violet fixed points. Moreover, such theories can be expected to be accessible to Wilson's epsilon expansion. We investigate this series for SU(N) Yang-Mills, in particular for the fixed point coupling and critical exponent nu, up to four loops. From the model-building point of view, such theories would be effectively perturbatively renormalizable in the normal way. A particularly attractive possibility is the construction of renormalizable extra-dimensional models of the weak interactions, which have the potential to address the full hierarchy problem. The simplest such gauge-Higgs unification model is however ruled out by a combination of theoretical and phenomenological constraints.

Tim R. Morris

2004-10-10T23:59:59.000Z

447

N=8 superconformal mechanics  

E-Print Network (OSTI)

We construct new models of N=8 superconformal mechanics asso