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1

Mechanism model for shale gas transport considering diffusion, adsorption/desorption and Darcy flow  

Science Journals Connector (OSTI)

To improve the understanding of the transport mechanism in shale gas reservoirs and build a theoretical basic for ... on productivity evaluation and efficient exploitation, various gas transport mechanisms within...

Ming-qiang Wei ???; Yong-gang Duan ???…

2013-07-01T23:59:59.000Z

2

Shale-Gas Permeability and Diffusivity Inferred by Improved Formulation of Relevant Retention and Transport Mechanisms  

Science Journals Connector (OSTI)

A theoretically improved model incorporating the relevant mechanisms of gas retention and transport in gas-bearing shale formations is presented for determination of intrinsic gas permeability and diffusivity. Th...

Faruk Civan; Chandra S. Rai; Carl H. Sondergeld

2011-02-01T23:59:59.000Z

3

DIFFUSION MECHANISMS FOR MULTIMEDIA BROADCASTING IN MOBILE AD HOC NETWORKS  

E-Print Network [OSTI]

DIFFUSION MECHANISMS FOR MULTIMEDIA BROADCASTING IN MOBILE AD HOC NETWORKS E. Baccelli Hitachi HSAL: Philippe.Jacquet@inria.fr ABSTRACT Scarce bandwidth and interferences in mobile ad-hoc networks yield in view to gain enough performance and allow applications such as multimedia diffusion in an ad hoc

Paris-Sud XI, Université de

4

Efficient diffusive mechanisms of O atoms at very low temperatures on surfaces of astrophysical interest  

E-Print Network [OSTI]

At the low temperatures of interstellar dust grains, it is well established that surface chemistry proceeds via diffusive mechanisms of H atoms weakly bound (physisorbed) to the surface. Until recently, however, it was unknown whether atoms heavier than hydrogen could diffuse rapidly enough on interstellar grains to react with other accreted species. In addition, models still require simple reduction as well as oxidation reactions to occur on grains to explain the abundances of various molecules. In this paper we investigate O-atom diffusion and reactivity on a variety of astrophysically relevant surfaces (water ice of three different morphologies, silicate, and graphite) in the 6.5 - 25 K temperature range. Experimental values were used to derive a diffusion law that emphasizes that O atoms diffuse by quantum mechanical tunnelling at temperatures as low as 6.5 K. The rate of diffusion on each surface, based on modelling results, were calculated and an empirical law is given as a function of the surface tempe...

Congiu, E; Baouche, S; Chaabouni, H; Moudens, A; Cazaux, S; Manicò, G; Pirronello, V; Dulieu, F

2014-01-01T23:59:59.000Z

5

Modelling international wind energy diffusion: Are the patterns of induced diffusion `S'  

E-Print Network [OSTI]

Modelling international wind energy diffusion: Are the patterns of induced diffusion `S' shaped datasets, the paper explores the patterns of international wind energy diffusion in OECD countries. The model employed in the paper predicted that wind energy, as a complex and expensive innovation, would

Feigon, Brooke

6

Shell Model for Atomistic Simulation of Lithium Diffusion in...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Shell Model for Atomistic Simulation of Lithium Diffusion in Mixed MnTi Oxides. Shell Model for Atomistic Simulation of Lithium Diffusion in Mixed MnTi Oxides. Abstract: Mixed...

7

Modeling Intragranular Diffusion in Low-Connectivity Granular...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

can produce diffusive behavior that appears as if the solute had undergone slow sorption, even in the absence of any sorption process. This mechanism may help explain some...

8

A diffuse interface model with immiscibility preservation  

SciTech Connect (OSTI)

A new, simple, and computationally efficient interface capturing scheme based on a diffuse interface approach is presented for simulation of compressible multiphase flows. Multi-fluid interfaces are represented using field variables (interface functions) with associated transport equations that are augmented, with respect to an established formulation, to enforce a selected interface thickness. The resulting interface region can be set just thick enough to be resolved by the underlying mesh and numerical method, yet thin enough to provide an efficient model for dynamics of well-resolved scales. A key advance in the present method is that the interface regularization is asymptotically compatible with the thermodynamic mixture laws of the mixture model upon which it is constructed. It incorporates first-order pressure and velocity non-equilibrium effects while preserving interface conditions for equilibrium flows, even within the thin diffused mixture region. We first quantify the improved convergence of this formulation in some widely used one-dimensional configurations, then show that it enables fundamentally better simulations of bubble dynamics. Demonstrations include both a spherical-bubble collapse, which is shown to maintain excellent symmetry despite the Cartesian mesh, and a jetting bubble collapse adjacent a wall. Comparisons show that without the new formulation the jet is suppressed by numerical diffusion leading to qualitatively incorrect results.

Tiwari, Arpit, E-mail: atiwari2@illinois.edu [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)] [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Freund, Jonathan B., E-mail: jbfreund@illinois.edu [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Pantano, Carlos [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)] [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)

2013-11-01T23:59:59.000Z

9

Lithium diffusion mechanisms in layered intercalation compounds A. Van der Ven*  

E-Print Network [OSTI]

Lithium diffusion mechanisms in layered intercalation compounds A. Van der Ven* , G. Ceder; accepted 28 December 2000 Abstract We investigate the mechanisms of lithium diffusion in layered intercalation compounds from ®rst-principles. We focus on LixCoO2 and ®nd that lithium diffusion

Ceder, Gerbrand

10

Antiproton Flux in Cosmic Ray Propagation Models with Anisotropic Diffusion  

E-Print Network [OSTI]

Recently a cosmic ray propagation model has been introduced, where anisotropic diffusion is used as a mechanism to allow for $\\mathcal{O}(100)$ km/s galactic winds. This model predicts a reduced antiproton background flux, suggesting an excess is being observed. We implement this model in GALPROP v50.1 and perform a $\\chi^2$ analysis for B/C, $^{10}$Be/$^{9}$Be, and the recent PAMELA $\\bar{p}/p$ datasets. By introducing a power-index parameter $\\alpha$ that dictates the dependence of the diffusion coefficient $D_{xx}$ on height $|z|$ away from the galactic plane, we confirm that isotropic diffusion models with $\\alpha=0$ cannot accommodate high velocity convective winds suggested by ROSAT, while models with $\\alpha=1$ ($D_{xx}\\propto |z|$) can give a very good fit. A fit to B/C and $^{10}$Be/$^{9}$Be data predicts a lower $\\bar{p}/p$ flux ratio than the PAMELA measurement at energies between approximately 2 GeV to 20 GeV. A combined fit including in addition the $\\bar{p}/p$ data is marginal, suggesting only a partial contribution to the measured antiproton flux.

Phillip Grajek; Kaoru Hagiwara

2010-12-02T23:59:59.000Z

11

Distributed Energy Resources Market Diffusion Model  

SciTech Connect (OSTI)

Distributed generation (DG) technologies, such as gas-fired reciprocating engines and microturbines, have been found to be economically beneficial in meeting commercial-sector electrical, heating, and cooling loads. Even though the electric-only efficiency of DG is lower than that offered by traditional central stations, combined heat and power (CHP) applications using recovered heat can make the overall system energy efficiency of distributed energy resources (DER) greater. From a policy perspective, however, it would be useful to have good estimates of penetration rates of DER under various economic and regulatory scenarios. In order to examine the extent to which DER systems may be adopted at a national level, we model the diffusion of DER in the US commercial building sector under different technical research and technology outreach scenarios. In this context, technology market diffusion is assumed to depend on the system's economic attractiveness and the developer's knowledge about the technology. The latter can be spread both by word-of-mouth and by public outreach programs. To account for regional differences in energy markets and climates, as well as the economic potential for different building types, optimal DER systems are found for several building types and regions. Technology diffusion is then predicted via two scenarios: a baseline scenario and a program scenario, in which more research improves DER performance and stronger technology outreach programs increase DER knowledge. The results depict a large and diverse market where both optimal installed capacity and profitability vary significantly across regions and building types. According to the technology diffusion model, the West region will take the lead in DER installations mainly due to high electricity prices, followed by a later adoption in the Northeast and Midwest regions. Since the DER market is in an early stage, both technology research and outreach programs have the potential to increase DER adoption, and thus, shift building energy consumption to a more efficient alternative.

Maribu, Karl Magnus; Firestone, Ryan; Marnay, Chris; Siddiqui,Afzal S.

2006-06-16T23:59:59.000Z

12

Distributed Wind Diffusion Model Overview (Presentation)  

SciTech Connect (OSTI)

Distributed wind market demand is driven by current and future wind price and performance, along with several non-price market factors like financing terms, retail electricity rates and rate structures, future wind incentives, and others. We developed a new distributed wind technology diffusion model for the contiguous United States that combines hourly wind speed data at 200m resolution with high resolution electricity load data for various consumer segments (e.g., residential, commercial, industrial), electricity rates and rate structures for utility service territories, incentive data, and high resolution tree cover. The model first calculates the economics of distributed wind at high spatial resolution for each market segment, and then uses a Bass diffusion framework to estimate the evolution of market demand over time. The model provides a fundamental new tool for characterizing how distributed wind market potential could be impacted by a range of future conditions, such as electricity price escalations, improvements in wind generator performance and installed cost, and new financing structures. This paper describes model methodology and presents sample results for distributed wind market potential in the contiguous U.S. through 2050.

Preus, R.; Drury, E.; Sigrin, B.; Gleason, M.

2014-07-01T23:59:59.000Z

13

Modeling gas displacement kinetics in coal with Maxwell-Stefan diffusion theory  

SciTech Connect (OSTI)

The kinetics of binary gas counter-diffusion and Darcy flow in a large coal sample were modeled, and the results compared with data from experimental laboratory investigations. The study aimed for a better understanding of the CO{sub 2}-sequestration enhanced coalbed methane (ECBM) recovery process. The transport model used was based on the bidisperse diffusion mechanism and Maxwell-Stefan (MS) diffusion theory. This provides an alternative approach to simulate multicomponent gas diffusion and flow in bulk coals. A series of high-stress core flush tests were performed on a large coal sample sourced from a Bowen Basin coal mine in Queensland, Australia to investigate the kinetics of one gas displacing another. These experimental results were used to derive gas diffusivities, and to examine the predictive capability of the diffusion model. The simulations show good agreements with the displacement experiments revealing that MS diffusion theory is superior for describing diffusion of mixed gases in coals compared with the constant Fick diffusivity model. The optimized effective micropore and macropore diffusivities are comparable with experimental measurements achieved by other researchers.

Wei, X.R.; Wang, G.X.; Massarotto, P.; Rudolph, V.; Golding, S.D. [University of Queensland, Brisbane, Qld. (Australia). Division of Chemical Engineering

2007-12-15T23:59:59.000Z

14

Lattice Boltzmann modeling of multicomponent diffusion in narrow channels  

Science Journals Connector (OSTI)

We investigate lattice Boltzmann (LB) modeling of multicomponent diffusion for finite Knudsen numbers. Analytic solutions for binary diffusion in narrow channels, where both molecular and Knudsen diffusion are of importance, are obtained for the standard and higher-order LB methods and validated against the results from the direct simulation Monte Carlo (DSMC) method. The LB methods are shown to reproduce the diffusion slip phenomena. In the DSMC method, while fluid particles are diffusely reflected on a wall, significant component slip and a kinetic boundary layer are observed. It is shown that a higher-order LB method accurately captures the characteristics observed in the DSMC method.

Seung Hyun Kim; Heinz Pitsch; Iain D. Boyd

2009-01-08T23:59:59.000Z

15

Numerical Early Warning Model Research of Landfill Gas Permeation and Diffusion Considering Flow-Temperature Coupling  

Science Journals Connector (OSTI)

Based on seepage mechanics in porous medium gas and heat transfer theory, numerical early warning model is established, which is on quantitative description of migration and release of landfill gas and penetration and diffusion of energy, and dynamic ... Keywords: component, landfill gas, flow-temperature coupling, gas pressure and temperature distribution, numerical early warning model

Xue Qiang; Feng Xia-ting; Ma Shi-jin; Zhou Xiao-jun

2009-10-01T23:59:59.000Z

16

Mutual diffusion in binary Ar-Kr mixtures and empirical diffusion models  

Science Journals Connector (OSTI)

Molecular dynamics simulations of four binary Ar-Kr mixtures are used to compute self- and mutual-diffusion coefficients. Results using mean squared displacements and using velocity correlation functions are presented. The diffusivity coefficients are also presented in the time and frequency domains where a comparatively low frequency structure is evident in some simulations. The computed diffusivities are dependent on the maximum time over which the velocity correlation functions are integrated and the time at which the Einstein relationships are evaluated. This dependence explains in part the small systematic differences between our results (20–80 ps) and earlier molecular dynamics results (<4 ps) in the system Ar-Kr. We compare the computed mutual diffusion coefficients to two empirical models, Darken’s model and the common force model. Darken’s model is consistent with our results over the entire frequency range we resolve. At frequencies lower than about 5 ps-1 Darken’s model and the common force model converge and we cannot discriminate between them. At higher frequencies the common force model prediction is significantly different from the computed mutual diffusion coefficient. Assumptions regarding the contribution of cross correlations that are implicit in the empirical models are discussed and tested against our simulation results. The net contribution of velocity cross correlations is found to be negligible, as is often assumed in deriving Darken’s model, but the individual cross-correlation terms are substantial and negative—a finding contrary to common assumptions. © 1996 The American Physical Society.

Yanhua Zhou and Gregory H. Miller

1996-02-01T23:59:59.000Z

17

Ising Model of Diffusion in Molecular Sieves  

Science Journals Connector (OSTI)

We have developed a new analytical theory for activated diffusion in zeolites at finite loadings, including the effect of adsorbate-adsorbate interactions. Excellent qualitative agreement is obtained comparing our new theory to kinetic Monte Carlo simulations. We have applied this theory to benzene diffusion in faujasite, to help resolve discrepancies among different experiments. Our results are in qualitative agreement with pulsed field gradient NMR, and in qualitative disagreement with tracer zero-length column data.

Chandra Saravanan; Fabien Jousse; Scott M. Auerbach

1998-06-29T23:59:59.000Z

18

Dynamic physiological modeling for functional diffuse optical tomography  

E-Print Network [OSTI]

,c and David A. Boasa a Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging and brain that reflect competing metabolic demands and cardiovascular dynamics. The diffuse nature of near- namic response. In this paper, we present a linear state-space model for DOT analysis that models

19

Discrepancies in Shortwave Diffuse Measured and Modeled Irradiances in Antarctica  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Discrepancies in Shortwave Diffuse Measured and Discrepancies in Shortwave Diffuse Measured and Modeled Irradiances in Antarctica A. Payton, P. Ricchiazzi, and C. Gautier University of California Santa Barbara, California D. Lubin Scripps Scripps Institution of Oceanography La Jolla, California Introduction Measurements of clear-sky shortwave (SW) radiation at the surface show discrepancies between measurements and model simulations, but only for certain measurements across time and space. Most of the observations entail broadband measurements. A spectral and spatial analysis of the occurrence of this discrepancy may lend insight into the responsible processes. Langley calibrated multi-filter rotating shadowband radiometer (MFRSR) measurements collected at the Antarctic coastline reveal significant

20

NUMERICAL MODELLING OF AUTOGENOUS HEALING AND RECOVERY OF MECHANICAL PROPERTIES IN ULTRA-HIGH  

E-Print Network [OSTI]

, hydro-chemo- mechanical coupling ABSTRACT Cracks, caused by shrinkage or external loading, reduce. In this study, a hydro-chemo-mechanical model was developed to simulate autogenous healing by further hydration into water was modelled based on micro-mechanical observations. The diffusion process has been simulated

Boyer, Edmond

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Lattice Boltzmann Models for Nonlinear Diffusion Filtering  

Science Journals Connector (OSTI)

The lattice Boltzmann method has attracted more and more attention ... modeling physical systems. The idea of the lattice Boltzmann method is to construct a simplified discrete ... equations. In this paper, we pr...

Björn Jawerth; Peng Lin; Eric Sinzinger

1999-01-01T23:59:59.000Z

22

Well testing model for multi-fractured horizontal well for shale gas reservoirs with consideration of dual diffusion in matrix  

Science Journals Connector (OSTI)

Abstract Shale gas reservoir is typical unconventional reservoir, it's necessary to take advantage of multi-stage fractured horizontal well so as to develop those kinds of reservoirs, which can form high conductivity hydraulic fractures and activate natural fractures. Due to the existence of concentration gap between matrix and fractures, desorption gas can simultaneously diffuse into the natural fractures and hydraulic fractures. This process can be called dual diffusion. Based on the triple-porosity cubic model, this paper establishes a new well testing model of multi-stage fractured horizontal well in shale gas reservoir with consideration of the unique mechanisms of desorption and dual diffusion in matrix. Laplace transformation is employed to solve this new model. The pseudo pressure transient responses are inverted into real time space with stehfest numerical inversion algorithm. Type curves are plotted, and different flow regimes in shale gas reservoirs are identified and the effects of relevant parameters are analyzed as well. Considering the mechanism of dual diffusion in matrix, the flow can be divided into five regimes: early linear flow; pseudo-steady state inter-porosity flow; the diffusion from matrix into micro-fractures; the diffusion from matrix into hydraulic fractures and boundary-dominated flow. There are large distinctions of pressure response between pseudo steady state diffusion and unsteady state diffusion under different value of pore volume ratio. It's similar to the feature of pseudo-steady state inter-porosity flow, diffusion coefficient and Langmuir parameters reflect the characters of pseudo-steady state diffusion. The numbers of stage of hydraulic fractures have certain impact on the shape factor of matrix and the inter-porosity coefficient. This new model is validated compared with some existing models. Finally, coupled with an application, this mew model can be approximately reliable and make some more precise productivity prediction.

Leng Tian; Cong Xiao; Mingjin Liu; Daihong Gu; Guangyu Song; Helong Cao; Xianglong Li

2014-01-01T23:59:59.000Z

23

Modelling Electrical Car Diffusion Based on Agent Tao Zhang, 3  

E-Print Network [OSTI]

Modelling Electrical Car Diffusion Based on Agent 1 Lei Yu, ,2 Tao Zhang, 3 Siebers Peer-Ola, 4 to include things like car parking charges, price of electrical car, energy awareness and word of mouth parking rates and other incentives on the uptake of electrical cars. The goal of this case study

Aickelin, Uwe

24

Modelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity,  

E-Print Network [OSTI]

Modelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity, and coarsening N. Fujita and H. K. D. H. Bhadeshia The growth of niobium carbide in austenite involves for the overall transformation kinetics of niobium carbide precipitation in austenite that takes into account

Cambridge, University of

25

Unfolding rates for the diffusion-collision model  

Science Journals Connector (OSTI)

In the diffusion-collision model, the unfolding rates are given by the likelihood of secondary structural cluster dissociation. In this work, we introduce an unfolding rate calculation for proteins whose secondary structural elements are ? helices, modeled from thermal escape over a barrier that arises from the free energy in buried hydrophobic residues. Our results are in good agreement with currently accepted values for the attempt rate.

Chris Beck and Xavier Siemens

2001-10-24T23:59:59.000Z

26

Effect of atomic scale plasticity on hydrogen diffusion in iron: Quantum mechanically informed and on-the-fly kinetic  

E-Print Network [OSTI]

viewpoints, is futile. Among several mechanisms proposed for hydrogen embrittlement (HE) of metals, hydrogenEffect of atomic scale plasticity on hydrogen diffusion in iron: Quantum mechanically informed-assisted diffusion and trapping of hydrogen by crystalline defects in iron. Given an embedded atom (EAM) potential

Ortiz, Michael

27

Relativistic Diffusion Model and Analysis of Large Transverse Momentum Distributions  

SciTech Connect (OSTI)

In order to describe large transverse momentum (pT) distributions observed in high energy nucleus-nucleus collisions, a stochastic model in the three dimensional rapidity space is introduced. The fundamental solution of the radial symmetric diffusion equation is Gaussian-like in radial rapidity. We can also derive a pT or radial rapidity distribution function, where a distribution of emission center is taken into account. The solution is applied to the analysis of observed large p T distributions of charged particles. It is shown that our model approaches to a power function of p T in the high transverse momentum limit.

Suzuki, Naomichi [Department of Comprehensive Management, Matsumoto University, Matsumoto 390-1295 (Japan); Biyajima, Minoru [Department of Physics, Shinshu University, Matsumoto, 390-8621 (Japan)

2006-04-11T23:59:59.000Z

28

Relativistic diffusion model and analysis of large transverse momentum distributions  

E-Print Network [OSTI]

In order to describe large transverse momentum ($p_T$) distributions observed in high energy nucleus-nucleus collisions, a stochastic model in the three dimensional rapidity space is introduced. The fundamental solution of the radial symmetric diffusion equation is Gaussian-like in radial rapidity. We can also derive a $p_T$ or radial rapidity distribution function, where a distribution of emission center is taken into account. It is applied to the analysis of observed large $p_T$ distributions of charged particles. It is shown that our model approaches to a power function of $p_T$ in the high transverse momentum limit.

Naomichi Suzuki; Minoru Biyajima

2005-10-01T23:59:59.000Z

29

Nonlinear diffusion theory model for xenon-induced flux oscillations  

SciTech Connect (OSTI)

A nonlinear model is developed for the xenon induced flux oscillation problem that occurs in nuclear power plants. The model is based on Galerkins's method of weighted residuals applied to multigroup diffusion theory. A similar linear model is developed by the same methods in order to consider the effects of the nonlinearities of the system. The effects of multi- and single-energy group considerations are also examined. Finally the effects of various number of basis functions used to approximate the flux, iodine, and xenon concentrations is determined. A partial listing of the computer program XORA, developed from the nonlinear and linear models, is given along with representative input and output from this program.

Teachman, J.D.

1981-01-01T23:59:59.000Z

30

Modeling diffusion of innovations in a social network X. Guardiola,1  

E-Print Network [OSTI]

Modeling diffusion of innovations in a social network X. Guardiola,1 A. Di´az-Guilera,1 C. J. Pe model of diffusion of innovations in a social network with upgrading costs is introduced. Agents of diffusion of innovations in a social network. In order to un- derstand the complex behavior of technology

Diaz-Guilera, Albert

31

Atomic-scale diffusion mechanisms via intermediate species Ant Ural,* P. B. Griffin, and J. D. Plummer  

E-Print Network [OSTI]

available isotopically enriched Si structures yielded the values of the transport capacities of I and V.4 evidence for the intermediate diffusion mechanism of boron in silicon has been obtained at short diffusion an intermediate species determines the overall migration of an impurity. First, we present a general formu- lation

Ural, Ant

32

The impact of diffusion type on multiscale discrete fracture model numerical simulation for shale gas  

Science Journals Connector (OSTI)

Abstract The development of unconventional gas reservoirs represents totally distinctive characteristics as compared with the conventional reservoirs. The complex pore structure in shale reservoir determines its special flow mechanism, which can be divided into several categories according to the size and type of pores- non Darcy flow, gas slippage, adsorption-desorption and gas diffusion effect. Based on the gas molecules diffusion form in porous media and combining with the multi-scale distribution structural characteristics of shale gas reservoirs, the shale gas diffusion mechanisms in the shale reservoir space including the diffusion of dissolved gases in the organic kerogen and the diffusion of free gas in the nanopores are analyzed in this paper. Meanwhile, the diffusion in the nanopores consists of Knudsen diffusion (KN ? 10), Fick diffusion (KN ? 0.1) and transition diffusion (0.1 shale gas flow in matrix and fracture networks, and also for their mass transfer in between without neglecting its varying-scale nature following the concept of discrete fracture network (DFN). In addition, we also investigate the different diffusion mechanisms' influences on the production and pressure in the tight shale gas reservoir. Ultimately, concluding that the gas diffusion mechanisms in micro-and nano-scale matrix block have a greater impact on the distribution of shale gas production (especially the production at early time) and reservoir pressure.

Lidong Mi; Hanqiao Jiang; Junjian Li

2014-01-01T23:59:59.000Z

33

Diffusion modeling of fission product release during depressurized core conduction cooldown conditions  

SciTech Connect (OSTI)

A simple model for diffusion through the silicon carbide layer of TRISO particles is applied to the data for accident condition testing of fuel spheres for the High-Temperature Reactor program of the Federal Republic of Germany (FRG). Categorization of sphere release of {sup 137}Cs based on fast neutron fluence permits predictions of release with an accuracy comparable to that of the US/FRG accident condition fuel performance model. Calculations are also performed for {sup 85}Kr, {sup 90}Sr, and {sup 110m}Ag. Diffusion of cesium through SiC suggests that models of fuel failure should consider fuel performance during repeated accident condition thermal cycling. Microstructural considerations in models in fission product release are discussed. The neutron-induced segregation of silicon within the SiC structure is postulated as a mechanism for enhanced fission product release during accident conditions. An oxygen-enhanced SiC decomposition mechanism is also discussed. 12 refs., 11 figs., 2 tabs.

Martin, R.C.

1990-01-01T23:59:59.000Z

34

Pattern formation in reaction diffusion systems: a Galerkin model  

Science Journals Connector (OSTI)

Reaction diffusion systems are extremely useful for studying pattern formation in biological systems. We carry out a Lorenz like few mode truncation of a reaction diffusion system and show that it not only giv...

A. Bhattacharyay; J.K. Bhattacharjee

2001-06-01T23:59:59.000Z

35

Regulation mechanisms in spatial stochastic development models  

E-Print Network [OSTI]

The aim of this paper is to analyze different regulation mechanisms in spatial continuous stochastic development models. We describe the density behavior for models with global mortality and local establishment rates. We prove that the local self-regulation via a competition mechanism (density dependent mortality) may suppress a unbounded growth of the averaged density if the competition kernel is superstable.

Dmitri Finkelshtein; Yuri Kondratiev

2008-09-04T23:59:59.000Z

36

Modeling Control Mechanisms with Normative Multiagent Systems  

E-Print Network [OSTI]

. This paper is about control mechanisms for virtual organizations. As a case study, we discuss the Renewables of renewable energy. We apply a conceptual model based on normative multiagent systems (NMAS). We proposeModeling Control Mechanisms with Normative Multiagent Systems: the Case of the Renewables

van der Torre, Leon

37

Social network inference of smartphone users based on information diffusion models  

Science Journals Connector (OSTI)

In this paper we propose models for inferring a social network of smartphone users. By applying the concept of information diffusion models to the log of application executions in smartphones, strength of relationships among users will be estimated as ... Keywords: information diffusion model, log analysis, smartphone, social network inference

Tomonobu Ozaki; Minoru Etoh

2011-12-01T23:59:59.000Z

38

Gas-Phase Diffusion in Porous Media: Comparison of Models Stephen W. Webb  

Office of Scientific and Technical Information (OSTI)

Gas-Phase Diffusion in Porous Media: Comparison of Models Gas-Phase Diffusion in Porous Media: Comparison of Models Stephen W. Webb Sandia National Laboratories Albuquerque, New Mexico 87 185 ABSTRACT Two models are commonly used to analyze gas- phase diffusion in porous media in the presence of advection, the Advective-Dispersive Model (ADM) and the Dusty-gas Model (DGM). The ADM, which is used in TOUGH2, is based on a simple linear addition of advection calculated by Darcy's law and ordinary diffusion using Fick's law with a porosity- tortuosity-gas saturation multiplier to account for the porous medium. Another approach for gas-phase transport in porous media is the Dusty-Gas Model. This model applies the kinetic theory of gases to the gaseous components and the porous media (or "dust") to combine transport due to diffusion and

39

Quantitative Model of Price Diffusion and Market Friction Based on Trading as a Mechanistic Random Process  

E-Print Network [OSTI]

Quantitative Model of Price Diffusion and Market Friction Based on Trading as a Mechanistic Random 2002; published 13 March 2003) We model trading and price formation in a market under the assumption for the most basic properties of markets, such as the diffusion rate of prices (which is the standard measure

40

Developing A Laser Shockwave Model For Characterizing Diffusion Bonded Interfaces  

SciTech Connect (OSTI)

12. Other advances in QNDE and related topics: Preferred Session Laser-ultrasonics Developing A Laser Shockwave Model For Characterizing Diffusion Bonded Interfaces 41st Annual Review of Progress in Quantitative Nondestructive Evaluation Conference QNDE Conference July 20-25, 2014 Boise Centre 850 West Front Street Boise, Idaho 83702 James A. Smith, Jeffrey M. Lacy, Barry H. Rabin, Idaho National Laboratory, Idaho Falls, ID ABSTRACT: The US National Nuclear Security Agency has a Global Threat Reduction Initiative (GTRI) which is assigned with reducing the worldwide use of high-enriched uranium (HEU). A salient component of that initiative is the conversion of research reactors from HEU to low enriched uranium (LEU) fuels. An innovative fuel is being developed to replace HEU. The new LEU fuel is based on a monolithic fuel made from a U-Mo alloy foil encapsulated in Al-6061 cladding. In order to complete the fuel qualification process, the laser shock technique is being developed to characterize the clad-clad and fuel-clad interface strengths in fresh and irradiated fuel plates. The Laser Shockwave Technique (LST) is being investigated to characterize interface strength in fuel plates. LST is a non-contact method that uses lasers for the generation and detection of large amplitude acoustic waves to characterize interfaces in nuclear fuel plates. However the deposition of laser energy into the containment layer on specimen’s surface is intractably complex. The shock wave energy is inferred from the velocity on the backside and the depth of the impression left on the surface from the high pressure plasma pulse created by the shock laser. To help quantify the stresses and strengths at the interface, a finite element model is being developed and validated by comparing numerical and experimental results for back face velocities and front face depressions with experimental results. This paper will report on initial efforts to develop a finite element model for laser shock.

James A. Smith; Jeffrey M. Lacy; Barry H. Rabin

2014-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Social Network Inference of Smartphone Users Based on Information Diffusion Models  

Science Journals Connector (OSTI)

In this paper we propose models for inferring a social network of smartphone users. By applying the concept of information diffusion models to the log of application executions in smartphones, strength of rela...

Tomonobu Ozaki; Minoru Etoh

2011-01-01T23:59:59.000Z

42

Comprehensive mechanisms for combustion chemistry: Experiment, modeling, and sensitivity analysis  

SciTech Connect (OSTI)

This research program is an integrated experimental/numerical effort to study pyrolysis and oxidation reactions and mechanisms for small-molecule hydrocarbon structures under conditions representative of combustion environments. The experimental aspects of the work are conducted in large diameter flow reactors, at pressures from one to twenty atmospheres, temperatures from 550 K to 1200 K, and with observed reaction times from 10{sup {minus}2} to 5 seconds. Gas sampling of stable reactant, intermediate, and product species concentrations provides not only substantial definition of the phenomenology of reaction mechanisms, but a significantly constrained set of kinetic information with negligible diffusive coupling. Analytical techniques used for detecting hydrocarbons and carbon oxides include gas chromatography (GC), and gas infrared (NDIR) and FTIR methods are utilized for continuous on-line sample detection of light absorption measurements of OH have also been performed in an atmospheric pressure flow reactor (APFR), and a variable pressure flow (VPFR) reactor is presently being instrumented to perform optical measurements of radicals and highly reactive molecular intermediates. The numerical aspects of the work utilize zero and one-dimensional pre-mixed, detailed kinetic studies, including path, elemental gradient sensitivity, and feature sensitivity analyses. The program emphasizes the use of hierarchical mechanistic construction to understand and develop detailed kinetic mechanisms. Numerical studies are utilized for guiding experimental parameter selections, for interpreting observations, for extending the predictive range of mechanism constructs, and to study the effects of diffusive transport coupling on reaction behavior in flames. Modeling using well defined and validated mechanisms for the CO/H{sub 2}/oxidant systems.

Dryer, F.L.; Yetter, R.A. [Princeton Univ., NJ (United States)

1993-12-01T23:59:59.000Z

43

Atomistic modeling of diffusion coefficient in fusion reactor first wall material tungsten  

Science Journals Connector (OSTI)

Abstract Tungsten is remarkable for its robustness, especially it has the highest melting point of all the non–alloyed metals. Metallic material tungsten and tungsten alloys have been widely used in aerospace, weapon, nuclear industries and fusion reactor. Tungsten is expected to be the fusion reactor first wall material for this reason. In this paper, self-diffusion coefficients of metallic material tungsten have been investigated via molecular dynamics simulation method using the modified embedded atom potential model. Diffusion activation energy of tungsten can be gotten according to Arrhenius relation between the self-diffusion coefficients simulation results and temperatures. The dipole interaction model is introduced to analyze metallic material tungsten self-diffusion process in a uniform magnetic field. The strong magnetic field increases diffusion activation energy by 34.52% and limits self-diffusion coefficient by 1.15% in 2 T uniform magnetic field.

Zenghui Wang; Kaixuan Zhao; Weiming Chen; Xiaodi Chen; Longyan Zhang

2014-01-01T23:59:59.000Z

44

Modeling the mechanical response of PBX 9501  

SciTech Connect (OSTI)

An engineering overview of the mechanical response of Plastic-Bonded eXplosives (PBXs), specifically PBX 9501, will be provided with emphasis on observed mechanisms associated with different types of mechanical testing. Mechanical tests in the form of uniaxial tension, compression, cyclic loading, creep (compression and tension), and Hopkinson bar show strain rate and temperature dependence. A range of mechanical behavior is observed which includes small strain recoverable response in the form of viscoelasticity; change in stiffness and softening beyond peak strength due to damage in the form microcracks, debonding, void formation and the growth of existing voids; inelastic response in the form of irrecoverable strain as shown in cyclic tests, and viscoelastic creep combined with plastic response as demonstrated in creep and recovery tests. The main focus of this paper is to elucidate the challenges and issues involved in modeling the mechanical behavior of PBXs for simulating thermo-mechanical responses in engineering components. Examples of validation of a constitutive material model based on a few of the observed mechanisms will be demonstrated against three point bending, split Hopkinson pressure bar and Brazilian disk geometry.

Ragaswamy, Partha [Los Alamos National Laboratory; Lewis, Matthew W [Los Alamos National Laboratory; Liu, Cheng [Los Alamos National Laboratory; Thompson, Darla G [Los Alamos National Laboratory

2010-01-01T23:59:59.000Z

45

3-D Model of Broadband Emission from Supernova Remnants Undergoing Non-linear Diffusive Shock Acceleration  

SciTech Connect (OSTI)

We present a 3-dimensional model of supernova remnants (SNRs) where the hydrodynamical evolution of the remnant is modeled consistently with nonlinear diffusive shock acceleration occurring at the outer blast wave. The model includes particle escape and diffusion outside of the forward shock, and particle interactions with arbitrary distributions of external ambient material, such as molecular clouds. We include synchrotron emission and cooling, bremsstrahlung radiation, neutral pion production, inverse-Compton (IC), and Coulomb energy-loss. Boardband spectra have been calculated for typical parameters including dense regions of gas external to a 1000 year old SNR. In this paper, we describe the details of our model but do not attempt a detailed fit to any specific remnant. We also do not include magnetic field amplification (MFA), even though this effect may be important in some young remnants. In this first presentation of the model we don't attempt a detailed fit to any specific remnant. Our aim is to develop a flexible platform, which can be generalized to include effects such as MFA, and which can be easily adapted to various SNR environments, including Type Ia SNRs, which explode in a constant density medium, and Type II SNRs, which explode in a pre-supernova wind. When applied to a specific SNR, our model will predict cosmic-ray spectra and multi-wavelength morphology in projected images for instruments with varying spatial and spectral resolutions. We show examples of these spectra and images and emphasize the importance of measurements in the hard X-ray, GeV, and TeV gamma-ray bands for investigating key ingredients in the acceleration mechanism, and for deducing whether or not TeV emission is produced by IC from electrons or pion-decay from protons.

Lee, Shiu-Hang; Kamae, Tuneyoshi; Ellison, Donald C.

2008-07-02T23:59:59.000Z

46

Proton diffusion pathways and rates in Y-doped BaZrO3 solid oxide electrolyte from quantum mechanics  

E-Print Network [OSTI]

solid oxide fuel cells based on yttria-stabilized zirconia. In addition, doped perovskite oxides oftenProton diffusion pathways and rates in Y-doped BaZrO3 solid oxide electrolyte from quantum solid oxide proton conductors the principal fea- tures of the proton transport mechanism are generally

Goddard III, William A.

47

Atomistic Models of Long-Term Hydrogen Diffusion in Metals M. P. Ariza1,a  

E-Print Network [OSTI]

-storage-related applications including, but not limited to, hydrogen embrittlement, grain boundary diffusion, and various and the kinetics of hydrogen atoms. One example is hydrogen embrittlement, that is, the material becomes brittleAtomistic Models of Long-Term Hydrogen Diffusion in Metals M. P. Ariza1,a , K. G. Wang,2,b , and M

Ortiz, Michael

48

MODELING THE DIFFUSION OF MICRO-CHP IN A RESIDENTIAL AREA  

E-Print Network [OSTI]

i MODELING THE DIFFUSION OF MICRO-CHP IN A RESIDENTIAL AREA by Christian Chemaly A thesis submitted OF MICRO-CHP IN A RESIDENTIAL AREA by Christian Chemaly A thesis presented on the diffusion of micro-CHP shows that micro-CHP will not reach 50% of the market in less than 20 years. Furthermore it analyses

49

An assessment of advanced mobile services acceptance: Contributions from TAM and diffusion theory models  

Science Journals Connector (OSTI)

Today, in addition to traditional mobile services, there are new ones already being used, thanks to the advances in 3G-related technologies. Our work contributed to the emerging body of research by integrating TAM and Diffusion Theory. Based on a sample ... Keywords: Advanced mobile services, Diffusion of innovation theory, Perceived benefits, Social influences, TAM model, The Netherlands

Carolina López-Nicolás; Francisco J. Molina-Castillo; Harry Bouwman

2008-09-01T23:59:59.000Z

50

Modeling the diffuse reflectance due to a narrow beam incident on a turbid medium  

E-Print Network [OSTI]

of an asymptotic analysis of the radiative transport equation for strong scattering, weak absorption, and a narrow of the radiative transport equation, we show that this diffuse reflectance model gives results that are accurate for the diffuse reflectance from the solution of the radiative transport equation. However, using the solution

Kim, Arnold D.

51

Multiclass Diffuse Interface Models for Semi-supervised Learning on Graphs  

E-Print Network [OSTI]

Multiclass Diffuse Interface Models for Semi-supervised Learning on Graphs Cristina Garcia-Cardona1: Graph Segmentation, Diffuse Interfaces, Learning on Graphs. Abstract: We present a graph-based variational algorithm for multiclass classification of high-dimensional data, moti- vated by total variation

Percus, Allon

52

Coupled Kinetic, Thermal, and Mechanical Modeling of FIB Micro...  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Coupled Kinetic, Thermal, and Mechanical Modeling of FIB Micro-machined Electrodes Coupled Kinetic, Thermal, and Mechanical Modeling of FIB Micro-machined Electrodes 2010 DOE...

53

Modelling diffusion of energy innovations on a heterogeneous social net work and approaches to integration of realworld data  

E-Print Network [OSTI]

Modelling diffusion of energy innovations on a heterogeneous social net work and approaches A model has been developed to simulate the diffusion of energy innovations on a heteroge neous social applying these ideas to model ling the diffusion of domestic energy innovations on a social network

Rucklidge, Alastair

54

STATISTICAL MECHANICS: FROM ISING MODELS TO UNITARY MINIMAL MODELS  

E-Print Network [OSTI]

STATISTICAL MECHANICS: FROM ISING MODELS TO UNITARY MINIMAL MODELS Paul A. PEARCE Mathematics universality classes of critical behaviour including the critical and tricritical Ising model, the critical of a ferromagnet with his Ph.D. student Ising2 . This period gave birth to the subject of exactly solvable lattice

Pearce, Paul A.

55

Generalized diffusion model in optical tomography with clear layers  

E-Print Network [OSTI]

transport equation that describes the den- sity of photons in the phase space, i.e., as a function of po increasingly often.9 For computational savings an approximation to radiative transport is often preferred solve phase-space transport equa- tions instead of the inaccurate diffusion equations.12,16 A large

Ren, Kui

56

High phosphorous doped germanium: Dopant diffusion and modeling  

E-Print Network [OSTI]

The in situ n-type doping of Ge thin films epitaxial grown on Si substrates is limited to 1?×?10[superscript 19]?cm[superscript ?3] by the phosphorous out-diffusion during growth at 600?°C. By studying the phosphorous ...

Cai, Yan

57

A reaction-diffusion model of the human brain development  

Science Journals Connector (OSTI)

The anatomical variability of the human brain folds remains an unclear and challenging issue. Several hypotheses coexist for explaining the rapid development of cortical sulci and it is clear that understanding their variability would improve the comparison ... Keywords: brain development, folding, reaction-diffusion equations

Julien Lefèvre; Jean-François Mangin

2010-04-01T23:59:59.000Z

58

Lattice Boltzmann model for the bimolecular autocatalytic reaction–diffusion equation  

Science Journals Connector (OSTI)

Abstract A lattice Boltzmann model for the bimolecular autocatalytic reaction–diffusion equation is proposed. By using multi-scale technique and the Chapman–Enskog expansion on complex lattice Boltzmann equation, we obtain a series of complex partial differential equations, complex equilibrium distribution function and its complex moments. Then, the complex reaction–diffusion equation is recovered with higher-order accuracy of the truncation error. This equation can be used to describe the bimolecular autocatalytic reaction–diffusion systems, in which a rich variety of behaviors have been observed. Based on this model, the Fitzhugh–Nagumo model and the Gray–Scott model are simulated. The comparisons between the LBM results and the Alternative Direction Implicit results are given in detail. The numerical examples show that assumptions of source term can be used to raise the accuracy of the truncation error of the lattice Boltzmann scheme for the complex reaction–diffusion equation.

Jianying Zhang; Guangwu Yan

2014-01-01T23:59:59.000Z

59

Implementation of a Stochastic Eddy-Diffusivity/Mass-Flux Parameterization into the Navy Global Environmental Model  

Science Journals Connector (OSTI)

A unified boundary layer and shallow convection parameterization based on a stochastic eddy-diffusivity/mass-flux (EDMF) approach is implemented and tested in the Navy Global Environmental Model (NAVGEM). The primary goals of this work are to ...

Kay Sušelj; Timothy F. Hogan; João Teixeira

2014-12-01T23:59:59.000Z

60

Non-Linear Drying Diffusion and Viscoelastic Drying Shrinkage Modeling in Hardened Cement Pastes  

E-Print Network [OSTI]

modeling with an average diffusion coefficient and with determined viscoelastic parameters from creep tests agreed well compared to the shrinkage data from experiments, indicating that drying shrinkage of cement paste may be considered as a poroviscoelastic...

Leung, Chin K.

2010-07-14T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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 Stochastic Advection-Diffusion Model for the Rocky Flats Soil Plutonium Data  

Science Journals Connector (OSTI)

An advection-diffusion equation with time and space dependent random coefficients is derived as a model for the plutonium concentration changes in the surface soil around the Rocky Flats Plant northwest of Denver...

Jaroslav Mohapl

2000-03-01T23:59:59.000Z

62

Two-bath model for activated surface diffusion of interacting adsorbates  

E-Print Network [OSTI]

The diffusion and low vibrational motions of adsorbates on surfaces can be well described by a purely stochastic model, the so-called interacting single adsorbate model, for low-moderate coverages (\\theta \\lesssim 0.12). Within this model, the effects of thermal surface phonons and adsorbate-adsorbate collisions are accounted for by two uncorrelated noise functions which arise in a natural way from a two-bath model based on a generalization of the one-bath Caldeira-Leggett Hamiltonian. As an illustration, the model is applied to the diffusion of Na atoms on a Cu(001) surface with different coverages.

R. Martinez-Casado; A. S. Sanz; G. Rojas-Lorenzo; S. Miret-Artes

2008-10-10T23:59:59.000Z

63

A modified multiple-relaxation-time lattice Boltzmann model for convection-diffusion equation  

E-Print Network [OSTI]

A modified lattice Boltzmann model with multiple relaxation times (MRT) for the convection-diffusion equation (CDE) is proposed. By modifying the relaxation matrix, as well as choosing the corresponding equilibrium distribution functions properly, the present model can recover the CDE with anisotropic diffusion coefficient without any deviation terms even when the velocity vector varies with space or time through the Chapman-Enskog analysis. This model is firstly validated by simulating the diffusion of a Gaussian hill, which demonstrates it can handle the anisotropic diffusion problem correctly. Then it is adopted to calculate the longitudinal dispersion coefficient of the Taylor-Aris dispersion. Numerical results show that elimination of the deviation terms can help to reduce the numerical errors under the condition of non-zero velocity vector, especially when the dimensionless relaxation time is relatively large.

Huang, Rongzong

2014-01-01T23:59:59.000Z

64

Self-Diffusion in a Nonuniform Model System  

Science Journals Connector (OSTI)

We prove that the motion of a tagged particle in a one-dimensional fluid of hard point particles in an external potential U may be asymptotically described by a diffusion process. The process is spatially homogeneous or inhomogeneous according to whether U varies on a microscopic or macroscopic scale. The latter process can still be described by a simple Langevin equation, provided that one interprets it in the sense of Stratonovich.

Detlef Dürr; Sheldon Goldstein; Joel L. Lebowitz

1986-11-17T23:59:59.000Z

65

Modeling cation diffusion in compacted water-saturatedNa-bentonite at low ionic strength  

SciTech Connect (OSTI)

Sodium bentonites are used as barrier materials for the isolation of landfills and are under consideration for a similar use in the subsurface storage of high-level radioactive waste. The performance of these barriers is determined in large part by molecular diffusion in the bentonite pore space. We tested two current models of cation diffusion in bentonite against experimental data on the relative apparent diffusion coefficients of two representative cations, sodium and strontium. On the 'macropore/nanopore' model, solute molecules are divided into two categories, with unequal pore-scale diffusion coefficients, based on location: in macropores or in interlayer nanopores. On the 'surface diffusion' model, solute molecules are divided into categories based on chemical speciation: dissolved or adsorbed. The macropore/nanopore model agrees with all experimental data at partial montmorillonite dry densities ranging from 0.2 (a dilute bentonite gel) to 1.7 kg dm{sup -3} (a highly compacted bentonite with most of its pore space located in interlayer nanopores), whereas the surface diffusion model fails at partial montmorillonite dry densities greater than about 1.2 kg dm{sup -3}.

Bourg, Ian C.; Sposito, Garrison; Bourg, Alain C.M.

2007-08-28T23:59:59.000Z

66

Modeling and measurement of Al interlayer diffusion in Pd(100): A low-energy ion scattering study  

Science Journals Connector (OSTI)

The Pd(001)-(2×2)p4g-Al surface consists of 0.5 monolayer of Al diffusing into the second layer during annealing and causing a p4g clock reconstruction. This is an interesting bimetallic alloy due to the ability to shift the Al cyclically and reproducibly from the second layer to the first and then back again. This is achieved by lifting the Al from the second layer by the absorption of O2 at room temperature and then removing the oxygen with hydrogen at 200 °C. If the surface is again heated, the Al diffuses back into the second layer and again produces the clock reconstruction. This cyclic process has been found to be repeatable continuously, and scanning tunneling microscope studies have revealed that the diffusion takes place midterrace rather than at a terrace edge. A model has been derived to calculate the activation energy for this process using Fick’s second law with a special boundary condition on the second atomic layer. Furthermore, using low-energy ion scattering, the activation energy for the diffusion of Al from the first to the second atomic layer has been measured to be 0.41±0.02 eV. This value suggests that Pd atoms are segregating through the Al to the surface via the exchange process. Measurements at higher temperatures have revealed that the activation barrier for diffusion between the second and third layers is 2.0±0.4 eV, which suggests that the diffusion of the Al into the bulk is via the vacancy mechanism.

M. J. Gladys; F. Samavat; B. V. King; D. J. O’Connor

2004-04-28T23:59:59.000Z

67

Modeling Multi-state Diffusion Process in Complex Networks: Theory and Applications  

E-Print Network [OSTI]

Modeling Multi-state Diffusion Process in Complex Networks: Theory and Applications Yishi Lin John networks (e.g., the Internet or online social networks). Conventional approach is to use SIS model (or its derivatives). However, these models usually are over-simplified and may not be applicable in realistic

Lui, John C.S.

68

Using a Quasipotential Transformation for Modeling Diffusion Media inPolymer-Electrolyte Fuel Cells  

SciTech Connect (OSTI)

In this paper, a quasipotential approach along with conformal mapping is used to model the diffusion media of a polymer-electrolyte fuel cell. This method provides a series solution that is grid independent and only requires integration along a single boundary to solve the problem. The approach accounts for nonisothermal phenomena, two-phase flow, correct placement of the electronic potential boundary condition, and multilayer media. The method is applied to a cathode diffusion medium to explore the interplay between water and thermal management and performance, the impact of the rib-to-channel ratio, and the existence of diffusion under the rib and flooding phenomena.

Weber, Adam Z.; Newman, John

2008-08-29T23:59:59.000Z

69

A simplified model for thermal-wave cavity self-consistent measurement of thermal diffusivity  

SciTech Connect (OSTI)

A simplified theoretical model was developed for the thermal-wave cavity (TWC) technique in this study. This model takes thermal radiation into account and can be employed for absolute measurements of the thermal diffusivity of gas and liquid samples without any knowledge of geometrical and thermal parameters of the components of the TWC. Using this model and cavity-length scans, thermal diffusivities of air and distilled water were accurately and precisely measured as (2.191 ± 0.004) × 10{sup ?5} and (1.427 ± 0.009) × 10{sup ?7} m{sup 2}?s{sup ?1}, respectively, in very good agreement with accepted literature values.

Shen, Jun, E-mail: jun.shen@nrc-cnrc.gc.ca; Zhou, Jianqin; Gu, Caikang [Energy, Mining and Environment Portfolio, National Research Council Canada, 4250 East Mall, Vancouver, British Columbia V6T 1W5 (Canada)] [Energy, Mining and Environment Portfolio, National Research Council Canada, 4250 East Mall, Vancouver, British Columbia V6T 1W5 (Canada); Neill, Stuart [Energy, Mining and Environment Portfolio, National Research Council Canada, 1200 Montreal Road, Building M-9, Ottawa, Ontario K1A 0R6 (Canada)] [Energy, Mining and Environment Portfolio, National Research Council Canada, 1200 Montreal Road, Building M-9, Ottawa, Ontario K1A 0R6 (Canada); Michaelian, Kirk H.; Fairbridge, Craig [CanmetENERGY, Natural Resources Canada, One Oil Drive Patch, Devon, Alberta T9G 1A8 (Canada)] [CanmetENERGY, Natural Resources Canada, One Oil Drive Patch, Devon, Alberta T9G 1A8 (Canada); Astrath, Nelson G. C.; Baesso, Mauro L. [Departamento de Física, Universidade Estadual de Maringá, Av. Colombo 5790, Maringá, Paraná 87020-900 (Brazil)] [Departamento de Física, Universidade Estadual de Maringá, Av. Colombo 5790, Maringá, Paraná 87020-900 (Brazil)

2013-12-15T23:59:59.000Z

70

Efficient Reformulation of Solid-Phase Diffusion in Physics-Based Lithium-Ion Battery Models  

E-Print Network [OSTI]

Efficient Reformulation of Solid-Phase Diffusion in Physics-Based Lithium-Ion Battery Models or approximation for the solid phase. One of the major difficulties in simulating Li-ion battery models is the need typically solve electrolyte con- centration, electrolyte potential, solid-state potential, and solid-state

Subramanian, Venkat

71

Modeling the Effect of Finite-Rate Hydrogen Diffusion on Porosity Formation in Aluminum Alloys  

E-Print Network [OSTI]

Modeling the Effect of Finite-Rate Hydrogen Diffusion on Porosity Formation in Aluminum Alloys KENT of hydrogen in the melt is developed to predict pore formation during the solidification of aluminum alloys by Lee et al.[3] Recent examples of porosity models for aluminum alloy castings, including the effect

Beckermann, Christoph

72

Study of the nitrogen diffusion mechanism in R2Fe17 Y. D. Zhang, J. I. Budnick, and W. A. Hines  

E-Print Network [OSTI]

Study of the nitrogen diffusion mechanism in R2Fe17 Y. D. Zhang, J. I. Budnick, and W. A. Hines 06269 D. P. Yang Department of Physics, College of the Holy Cross, Worcester, Massachusetts 01610

Yang, De-Ping

73

Two-dimensional model of a reaction-diffusion system as a typewriter  

Science Journals Connector (OSTI)

Pattern formation is a common phenomenon, which appears in biological systems, especially in cell differentiation processes. The proper level for understanding the creation of patterns seems to be a physicochemical description. The most fundamental models should be based on systems, in which only chemical reactions and diffusion transport occur (reaction-diffusion systems). In order to present a richness of patterns, we show here the asymptotic patterns in the form of capital letters obtained in two-dimensional reaction-diffusion systems with zero-flux boundary conditions. All capital letters are obtained in the same model, but initial conditions and sizes of the systems are different for each letter. The chemical model consists of elementary reactions and is realistic. It can be realized experimentally in continuous-flow unstirred reactor with an enzymatic reaction allosterically inhibited by an excess of its reactant and product.

Andrzej L. Kawczy?ski and Bart?omiej Legawiec

2001-10-09T23:59:59.000Z

74

Modeling-Thermo-electrochemistry, Capacity Degradation and Mechanics...  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

& Publications Microscale Electrode Design Using Coupled Kinetic, Thermal and Mechanical Modeling Modeling - Scale-Bridging Simulations Active Materials in Li-ion Batteries,...

75

Lattice Boltzmann Models for Anisotropic Diffusion of Images  

Science Journals Connector (OSTI)

The lattice Boltzmann method has attracted more and more attention ... modeling physical systems. The idea of the lattice Boltzmann method is to construct a simplified discrete ... partial differential equations....

Björn Jawerth; Peng Lin; Eric Sinzinger

1999-12-01T23:59:59.000Z

76

A Lattice Boltzmann model for diffusion of binary gas mixtures  

E-Print Network [OSTI]

used. This is fundamentally unsuitable for extension to multi-component systems containing gases of differing molecular masses that are modelled with the ideal gas equation of state. Also, existing methods for implementing boundary conditions...

Bennett, Sam

2010-10-12T23:59:59.000Z

77

Parareal in time 3D numerical solver for the LWR Benchmark neutron diffusion transient model  

E-Print Network [OSTI]

We present a parareal in time algorithm for the simulation of neutron diffusion transient model. The method is made efficient by means of a coarse solver defined with large time steps and steady control rods model. Using finite element for the space discretization, our implementation provides a good scalability of the algorithm. Numerical results show the efficiency of the parareal method on large light water reactor transient model corresponding to the Langenbuch-Maurer-Werner (LMW) benchmark [1].

Baudron, Anne-Marie A -M; Maday, Yvon; Riahi, Mohamed Kamel; Salomon, Julien

2014-01-01T23:59:59.000Z

78

Microstructure and mechanical properties of diffusion bonded W/steel joint using V/Ni composite interlayer  

SciTech Connect (OSTI)

Diffusion bonding between W and steel using V/Ni composite interlayer was carried out in vacuum at 1050 °C and 10 MPa for 1 h. The microstructural examination and mechanical property evaluation of the joints show that the bonding of W to steel was successful. No intermetallic compound was observed at the steel/Ni and V/W interfaces for the joints bonded. The electron probe microanalysis and X-ray diffraction analysis revealed that Ni{sub 3}V, Ni{sub 2}V, Ni{sub 2}V{sub 3} and NiV{sub 3} were formed at the Ni/V interface. The tensile strength of about 362 MPa was obtained for as-bonded W/steel joint and the failure occurred at W near the V/W interface. The nano-indentation test across the joining interfaces demonstrated the effect of solid solution strengthening and intermetallic compound formation in the diffusion zone. - Highlights: • Diffusion bonding of W to steel was realized using V/Ni composite interlayer. • The interfacial microstructure of the joint was clarified. • Several V–Ni intermetallic compounds were formed in the interface region. • The application of V/Ni composite interlayer improved the joining quality.

Liu, W.S.; Cai, Q.S., E-mail: cai2009pm@163.com; Ma, Y.Z.; Wang, Y.Y.; Liu, H.Y.; Li, D.X.

2013-12-15T23:59:59.000Z

79

A radially resolved kinetic model for nonlocal electron ripple diffusion losses in tokamaks  

SciTech Connect (OSTI)

A relatively simple radially resolved kinetic model is applied to the ripple diffusion problem for electrons in tokamaks. The distribution function f(r,v) is defined on a two-dimensional grid, where r is the radial coordinate and v is the velocity coordinate. Particle transport in the radial direction is from ripple and banana diffusion and transport in the velocity direction is described by the Fokker-Planck equation. Particles and energy are replaced by source functions that are adjusted to maintain a constant central density and temperature. The relaxed profiles of f(r,v) show that the electron distribution function at the wall contains suprathermal electrons that have diffused from the interior that enhance ripple transport. The transport at the periphery is therefore nonlocal. The energy replacement times from the computational model are near to the experimental replacement times for tokamak discharges in the compilation by Pfeiffer and Waltz [Nucl. Fusion 19, 51 (1979)].

Robertson, Scott [Department of Physics and Center for Integrated Plasma Studies, University of Colorado, Boulder, Colorado 80309-0390 (United States)

2006-09-15T23:59:59.000Z

80

Comparison of light scattering models for diffuse optical tomography  

E-Print Network [OSTI]

different models for light propagation in tissues: (1) the radiative transport equation, (2) the delta of the radiative transport equation that take into account forward-peaked scattering analytically. Using simulated data from the numerical solution of radiative transport equation, we solve the inverse problem

Kim, Arnold D.

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

A Reaction-Diffusion Model of Cancer Invasion  

Science Journals Connector (OSTI)

...A. G.J and Department of Physics IE. T. G.J. Temple University...behavior of the model but it does facilitate the derivation of...Lide, D. R., (ed.) CRC Handbook of Chemistry and Physics. Boca Raton, FL: CRC Press...

Robert A. Gatenby and Edward T. Gawlinski

1996-12-15T23:59:59.000Z

82

Improved Modeling and Understanding of Diffusion-Media Wettability on Polymer-Electrolyte-Fuel-Cell Performance  

SciTech Connect (OSTI)

A macroscopic-modeling methodology to account for the chemical and structural properties of fuel-cell diffusion media is developed. A previous model is updated to include for the first time the use of experimentally measured capillary pressure -- saturation relationships through the introduction of a Gaussian contact-angle distribution into the property equations. The updated model is used to simulate various limiting-case scenarios of water and gas transport in fuel-cell diffusion media. Analysis of these results demonstrate that interfacial conditions are more important than bulk transport in these layers, where the associated mass-transfer resistance is the result of higher capillary pressures at the boundaries and the steepness of the capillary pressure -- saturation relationship. The model is also used to examine the impact of a microporous layer, showing that it dominates the response of the overall diffusion medium. In addition, its primary mass-transfer-related effect is suggested to be limiting the water-injection sites into the more porous gas-diffusion layer.

Weber, Adam

2010-03-05T23:59:59.000Z

83

Reaction-Diffusion Model for Combustion with Fuel Consumption: I. Dirichlet Boundary Conditions  

Science Journals Connector (OSTI)

......9JT, UK Department of Chemistry, University of Leeds...Reaction-Diffusion Model for Combustion with Fuel Consumption...SCOTT Department of Chemistry, University of Leeds...runaway in stockpiles of coal, wool, cellulose...smouldering or fully fledged combustion and their attendant......

G. ZHANG; J. H. MERKIN; S. K. SCOTT

1991-01-01T23:59:59.000Z

84

Sufficient Stochastic Maximum Principle in a Regime-Switching Diffusion Model  

SciTech Connect (OSTI)

We prove a sufficient stochastic maximum principle for the optimal control of a regime-switching diffusion model. We show the connection to dynamic programming and we apply the result to a quadratic loss minimization problem, which can be used to solve a mean-variance portfolio selection problem.

Donnelly, Catherine, E-mail: C.Donnelly@hw.ac.uk [Heriot-Watt University, Department of Actuarial Mathematics and Statistics (United Kingdom)

2011-10-15T23:59:59.000Z

85

MRI based diffusion and perfusion predictive model to estimate stroke Stephen E. Rosea,  

E-Print Network [OSTI]

MRI based diffusion and perfusion predictive model to estimate stroke evolution Stephen E. Rosea and perfusion images acquired in the acute stage of stroke. The validity of this methodology was tested on novel patient data including data acquired from an independent stroke clinic. Regions-of-interest (ROIs

McLachlan, Geoff

86

A continuous surface tension force formulation for diffuse-interface models  

E-Print Network [OSTI]

A continuous surface tension force formulation for diffuse-interface models Junseok Kim October 2004 Available online 30 November 2004 Abstract We present a new surface tension force formulation field because pressure includes the gradient terms resulting from the modified surface tension term

Frey, Pascal

87

Physical causes and modeling challenges of anomalous diffusion of sediment tracers  

E-Print Network [OSTI]

Physical causes and modeling challenges of anomalous diffusion of sediment tracers Douglas Jerolmack Earth & Environmental Science, UPenn [sediment@sas.upenn.edu] "Bridging the Gap", Princeton U., 2" describable by: 1. Particle volume, v [L3 ]. 2.Average velocity, us , of bed load sediment [L/T]. 3. Surface

88

An advanced diffusion model to identify emergent research issues: the case of optoelectronic devices  

E-Print Network [OSTI]

1 An advanced diffusion model to identify emergent research issues: the case of optoelectronic of keywords in published articles. In this paper we show how emerging topics in the field of optoelectronic the identified keywords were used to technological topics in the field of optoelectronic devices

Boyer, Edmond

89

Unified moving-boundary model with fluctuations for unstable diffusive growth Matteo Nicoli  

E-Print Network [OSTI]

examples are found in thin-film production by chemical vapor deposition and electrochemical deposition. The model also incorporates noise terms that account for fluctuations in the diffusive and attachment that are sometimes solv- able. For instance, electrochemical deposition ECD of met- als 4,5 has been and still is 6

Cuerno, Rodolfo

90

Quantum-corrected drift-diffusion models: Solution fixed point map and finite element approximation  

SciTech Connect (OSTI)

This article deals with the analysis of the functional iteration, denoted Generalized Gummel Map (GGM), proposed in [C. de Falco, A.L. Lacaita, E. Gatti, R. Sacco, Quantum-Corrected Drift-Diffusion Models for Transport in Semiconductor Devices, J. Comp. Phys. 204 (2) (2005) 533-561] for the decoupled solution of the Quantum Drift-Diffusion (QDD) model. The solution of the problem is characterized as being a fixed point of the GGM, which permits the establishment of a close link between the theoretical existence analysis and the implementation of a numerical tool, which was lacking in previous non-constructive proofs [N.B. Abdallah, A. Unterreiter, On the stationary quantum drift-diffusion model, Z. Angew. Math. Phys. 49 (1998) 251-275, R. Pinnau, A. Unterreiter, The stationary current-voltage characteristics of the quantum drift-diffusion model, SIAM J. Numer. Anal. 37 (1) (1999) 211-245]. The finite element approximation of the GGM is illustrated, and the main properties of the numerical fixed point map (discrete maximum principle and order of convergence) are discussed. Numerical results on realistic nanoscale devices are included to support the theoretical conclusions.

Falco, Carlo de [School of Mathematical Sciences, Dublin City University, Glasnevin, Dublin 9 (Ireland); Jerome, Joseph W. [Department of Mathematics, Northwestern University, 2033 Sheridan Road, Evanston, IL 60208-2730 (United States); Sacco, Riccardo [Dipartimento di Matematica 'F.Brioschi', Politecnico di Milano, via Bonardi 9, 20133 Milano (Italy)], E-mail: riccardo.sacco@polimi.it

2009-03-20T23:59:59.000Z

91

On Similarities between Biological and Social Evolutionary Mechanisms: Mathematical Modeling  

E-Print Network [OSTI]

of widely diffused social innovation that enhances theof widely diffused social innovation that enhances the

Grinin, Leonid; Markov, Alexander; Korotayev, Andrey

2013-01-01T23:59:59.000Z

92

Standing Waves in a Two-Dimensional Reaction-Diffusion Model with the Short-Wave Instability  

E-Print Network [OSTI]

Standing Waves in a Two-Dimensional Reaction-Diffusion Model with the Short-Wave Instability Milos 25, 1998; In Final Form: October 19, 1998 Various patterns of standing waves are found beyond the onset of the short-wave instability in a model reaction- diffusion system. These include plain

Epstein, Irving R.

93

Modeling diffusion of electrical appliances in the residential sector  

SciTech Connect (OSTI)

This paper presents a methodology for modeling residential appliance uptake as a function of root macroeconomic drivers. The analysis concentrates on four major energy end uses in the residential sector: refrigerators, washing machines, televisions and air conditioners. The model employs linear regression analysis to parameterize appliance ownership in terms of household income, urbanization and electrification rates according to a standard binary choice (logistic) function. The underlying household appliance ownership data are gathered from a variety of sources including energy consumption and more general standard of living surveys. These data span a wide range of countries, including many developing countries for which appliance ownership is currently low, but likely to grow significantly over the next decades as a result of economic development. The result is a 'global' parameterization of appliance ownership rates as a function of widely available macroeconomic variables for the four appliances studied, which provides a reliable basis for interpolation where data are not available, and forecasting of ownership rates on a global scale. The main value of this method is to form the foundation of bottom-up energy demand forecasts, project energy-related greenhouse gas emissions, and allow for the construction of detailed emissions mitigation scenarios.

McNeil, Michael A.; Letschert, Virginie E.

2009-11-22T23:59:59.000Z

94

Direct constraints on diffusion models from cosmic-ray positron data: Excluding the minimal model for dark matter searches  

Science Journals Connector (OSTI)

Galactic cosmic-ray (CR) transport parameters are usually constrained by the boron-to-carbon ratio. This procedure is generically plagued with degeneracies between the diffusion coefficient and the vertical extent of the Galactic magnetic halo. The latter is of paramount importance for indirect dark matter (DM) searches because it fixes the amount of DM annihilation or decay that contributes to the local antimatter CR flux. These degeneracies could be broken by using secondary radioactive species, but the current data still have large error bars, and this method is extremely sensitive to the very local interstellar medium properties. Here, we propose to use the low-energy CR positrons in the GeV range as another direct constraint on diffusion models. We show that the PAMELA data disfavor small diffusion halo (L?3??kpc) and large diffusion slope models and exclude the minimal configuration [Maurin et al. Astrophys. J. 555, 585 (2001); Donato et al. Phys. Rev. D 69, 063501 (2004)] widely used in the literature to bracket the uncertainties in the DM signal predictions. This is complementary to indirect constraints (diffuse radio and gamma-ray emissions) and has a strong impact on DM searches. Indeed, this makes the antiproton constraints more robust while enhancing the discovery/exclusion potential of current and future experiments, like AMS-02 and GAPS, especially in the antiproton and antideuteron channels.

Julien Lavalle; David Maurin; Antje Putze

2014-10-15T23:59:59.000Z

95

Direct constraints on diffusion models from cosmic-ray positron data: Excluding the Minimal model for dark matter searches  

E-Print Network [OSTI]

Galactic Cosmic-ray (CR) transport parameters are usually constrained by the boron-to-carbon ratio. This procedure is generically plagued with degeneracies between the diffusion coefficient and the vertical extent of the Galactic magnetic halo. The latter is of paramount importance for indirect dark matter (DM) searches, because it fixes the amount of DM annihilation or decay that contributes to the local antimatter CR flux. These degeneracies could be broken by using secondary radioactive species, but the current data still have large error bars, and this method is extremely sensitive to the very local interstellar medium (ISM) properties. Here, we propose to use the low-energy CR positrons in the GeV range as another direct constraint on diffusion models. We show that the PAMELA data disfavor small diffusion halo ($L\\lesssim 3$ kpc) and large diffusion slope models, and exclude the minimal ({\\em min}) configuration (Maurin et al. 2001, Donato et al. 2004) widely used in the literature to bracket the uncertainties in the DM signal predictions. This is complementary to indirect constraints (diffuse radio and gamma-ray emissions) and has strong impact on DM searches. Indeed this makes the antiproton constraints more robust while enhancing the discovery/exclusion potential of current and future experiments, like AMS-02 and GAPS, especially in the antiproton and antideuteron channels.

Julien Lavalle; David Maurin; Antje Putze

2015-01-22T23:59:59.000Z

96

Modelling market diffusion of electric vehicles with real world driving data — Part I: Model structure and validation  

Science Journals Connector (OSTI)

Abstract The future market diffusion of electric vehicles (EVs) is of great importance for transport related green house gas emissions and energy demand. But most studies on the market diffusion of \\{EVs\\} focus on average driving patters and neglect the great variations in daily driving of individuals present in real-world driving data. Yet these variations are important for \\{EVs\\} since range limitations and the electric driving share of plug-in hybrids strongly impact the economic evaluation and consumer acceptance of EVs. Additionally, studies often focus on private cars only and neglect that commercial buyers account for relevant market shares in vehicle sales. Here, we propose a detailed, user specific model for the market diffusion of \\{EVs\\} and evaluation of EV market diffusion policies based on real-world driving data. The data and model proposed include both private and commercial users in Germany and allow the calculation of realistic electric driving shares for all usage patterns. The proposed model explicitly includes user heterogeneity in driving behaviour, different user groups, psychological aspects and the effect of charge-at-home options. Our results show that the proposed model reproduces group specific market shares, gives confidence bands of market shares and simulates individual electric driving shares.

Patrick Plötz; Till Gnann; Martin Wietschel

2014-01-01T23:59:59.000Z

97

Dynamic Analysis and Modeling of Jansen Mechanism  

Science Journals Connector (OSTI)

Abstract Theo Jansen mechanism is gaining wide spread popularity among legged robotics researchers due to its scalable design, energy efficiency, low payload to machine load ratio, bio-inspired locomotion, deterministic foot trajectory among others. In this paper, we present dynamic analysis of a four legged Theo Jansen link mechanism using projection method that results in constraint force and equivalent Lagrange's equation of motion necessary for any meaningful extension and/or optimization of this niche mechanism. Numerical simulations using MaTX is presented in conjunction with the dynamic analysis. This research sets a theoretical basis for future investigation into Theo Jansen mechanism.

Shunsuke Nansai; Mohan Rajesh Elara; Masami Iwase

2013-01-01T23:59:59.000Z

98

LANL: Mechanical testing and modeling in MST  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

etc.). As the effects of processing are to critical to accurate prediction of its mechanical behavior, MST hosts a range of metallographic and characterization tools. Specific...

99

Diffusive limit for the random Lorentz gas  

E-Print Network [OSTI]

We review some recent results concerning the derivation of the diffusion equation and the validation of Fick's law for the microscopic model given by the random Lorentz Gas. These results are achieved by using a linear kinetic equation as an intermediate level of description between our original mechanical system and the diffusion equation.

Alessia Nota

2014-10-14T23:59:59.000Z

100

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

Open Energy Info (EERE)

to the most hydraulically conductive fractures in two orthogonal and vertical fracture sets. The mathematical model representing the hydro-mechanical interactions that are...

Note: This page contains sample records for the topic "diffusion mechanisms models" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
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We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

A Conceptual Approach to Two-Scale Constitutive Modelling For Hydro-Mechanical Coupling  

E-Print Network [OSTI]

Large scale modelling of fluid flow coupled with solid failure in geothermal reservoirs or hydrocarbon extraction from reservoir rocks usually involves behaviours at two scales: lower scale of the inelastic localization zone, and larger scale of the bulk continuum where elastic behaviour can be reasonably assumed. The hydraulic conductivities corresponding to the mechanical properties at these two scales are different. In the bulk elastic host rock, the hydraulic conductivity does not vary much with the deformation, while it significantly changes in the lower scale of the localization zone due to inelastic deformation. Increase of permeability due to fracture and/or dilation, or reduction of permeability due to material compaction can take place inside this zone. The challenge is to predict the evolution of hydraulic conductivities coupled with the mechanical behaviour of the material in all stages of the deformation process. In the early stage of diffuse deformation, the permeability of the material can be reasonably assumed to be homogenous over the whole Representative Volume Element (RVE) However, localized failure results in distinctly different conductivities in different parts of the RVE. This paper establishes a general framework and corresponding field equations to describe the hydro-mechanical coupling in both diffuse and localized stages of deformation in rocks. In particular, embedding the lower scale hydro-mechanical behaviour of the localization zone inside an elastic bulk, together with their corresponding effective sizes, helps effectively deal with scaling issues in large-scale modelling. Preliminary results are presented which demonstrate the promising features of this new approach.

Giang D. Nguyen; Abbas El-Zein; Terry Bennett

2014-06-05T23:59:59.000Z

102

A simulation model for the diffusion of a new technology in an environment populated by heterogeneous agents. The case of business to business (B2B) ecommerce.  

E-Print Network [OSTI]

1 A simulation model for the diffusion of a new technology in an environment populated. + , Vistori F. § Abstract In this paper we propose an agent­based simulation model for the diffusion

Gallo, Giorgio

103

Shell Model for Atomistic Simulation of Lithium Diffusion in Mixed Mn/Ti Oxides  

SciTech Connect (OSTI)

Mixed Mn/Ti oxides present attractive physicochemical properties such as their ability to accommodate Li for application in Li-ion batteries. In this work, atomic parameters for Mn were developed to extend an existing shell model of the Li-Ti-O system and allow simulations of pure and lithiated Mn and mixed Mn/Ti oxide polymorphs. The shell model yielded good agreement with experimentally-derived structures (i.e. lattice parameters and inter-atomic distances) and represented an improvement over existing potential models. The shell model was employed in molecular dynamics (MD) simulations of Li diffusion in the 1×1 c direction channels of LixMn1 yTiyO2 with the rutile structure, where 0 ? x ? 0.25 and 0 ? y ? 1. In the infinite dilution limit, the arrangement of Mn and Ti ions in the lattice was found to have a significant effect on the activation energy for Li diffusion in the c channels due to the destabilization of half of the interstitial octahedral sites. Anomalous diffusion was demonstrated for Li concentrations as low as x = 0.125, with a single Li ion positioned in every other c channel. Further increase in Li concentration showed not only the substantial effect of Li-Li repulsive interactions on Li mobility but also their influence on the time dependence of Li diffusion. The results of the MD simulations can inform intrinsic structure-property relationships for the rational design of improved electrode materials for Li-ion batteries.

Kerisit, Sebastien N.; Chaka, Anne M.; Droubay, Timothy C.; Ilton, Eugene S.

2014-10-23T23:59:59.000Z

104

Theory of Grain Boundary Diffusion  

Science Journals Connector (OSTI)

The previously proposed dependence of the structure of grain boundaries upon the angle of disorientation of the two grains is used as a basis of a quantitative consideration of diffusion along grain boundaries and in particular of the apparent activation energies. At small angles in the dislocation range the diffusion is controlled by volume diffusion mechanism. At high angles near 45° the model of a uniform grain boundary is applicable. In the intermediate range an array of rod-like areas of distorted lattice leads to low or even negative apparent activation energies. The theory is in good agreement with experiment.

R. Smoluchowski

1952-08-01T23:59:59.000Z

105

Multiclass Diffuse Interface Models for Semi-Supervised Learning on Graphs  

E-Print Network [OSTI]

We present a graph-based variational algorithm for multiclass classification of high-dimensional data, motivated by total variation techniques. The energy functional is based on a diffuse interface model with a periodic potential. We augment the model by introducing an alternative measure of smoothness that preserves symmetry among the class labels. Through this modification of the standard Laplacian, we construct an efficient multiclass method that allows for sharp transitions between classes. The experimental results demonstrate that our approach is competitive with the state of the art among other graph-based algorithms.

Garcia-Cardona, Cristina; Percus, Allon G

2012-01-01T23:59:59.000Z

106

Diffusion of PAH in Potato and Carrot Slices and Application for a Potato Model  

Science Journals Connector (OSTI)

Diffusion of PAH in Potato and Carrot Slices and Application for a Potato Model ... The average daily consump tion of potatoes and potato products in Denmark is 126 g, which is 58% of fruit and vegetable consumption (2). ... It can be estimated from the concentration in bulk soil, CS (mg kg-1), using the partition coefficient KSW (L kg-1): Where fOC is the fraction of organic carbon (kg kg-1); ? is the density of the soil (wet or dry, kg L-1); WS is the volume fraction of water in the soil (L L-1); KOC (L kg-1) is the partition coefficient between organic carbon and water and can be estimated from ref 19 The equilibrium BCF of potatoes (kg kg-1) in soil can then be calculated from the ratio of eqs 20 and 21: From the radial diffusion model, an estimate for k2 can be deduced (20) where D2 is the diffusion coefficient of the chemical in compartment 2, here DP (eq 10); R is the radius of the potato (m). ...

Stefan Trapp; Anita Cammarano; Ettore Capri; Fredrik Reichenberg; Philipp Mayer

2007-03-24T23:59:59.000Z

107

Controlling reactivity of nanoporous catalyst materials by tuning reaction product-pore interior interactions: Statistical mechanical modeling  

SciTech Connect (OSTI)

Statistical mechanical modeling is performed of a catalytic conversion reaction within a functionalized nanoporous material to assess the effect of varying the reaction product-pore interior interaction from attractive to repulsive. A strong enhancement in reactivity is observed not just due to the shift in reaction equilibrium towards completion but also due to enhanced transport within the pore resulting from reduced loading. The latter effect is strongest for highly restricted transport (single-file diffusion), and applies even for irreversible reactions. The analysis is performed utilizing a generalized hydrodynamic formulation of the reaction-diffusion equations which can reliably capture the complex interplay between reaction and restricted transport.

Wang, Jing [Ames Laboratory; Ackerman, David M. [Ames Laboratory; Lin, Victor S.-Y. [Ames Laboratory; Pruski, Marek [Ames Laboratory; Evans, James W. [Ames Laboratory

2013-04-02T23:59:59.000Z

108

A diffusion-kinetic model for pulverized-coal combustion and heat-and-mass transfer in a gas stream  

Science Journals Connector (OSTI)

A diffusion-kinetic model for pulverized-coal combustion and heat-and-mass transfer in a gas stream is proposed, and the results of numerical simulation of the burnout dynamics of Kansk-Achinsk coals in the pu...

E. A. Boiko; S. V. Pachkovskii

2008-12-01T23:59:59.000Z

109

Evolving an Information Diffusion Model Using a Genetic Algorithm for Monthly River Discharge Time Series Interpolation and Forecasting  

Science Journals Connector (OSTI)

The identification of the rainfall–runoff relationship is a significant precondition for surface–atmosphere process research and operational flood forecasting, especially in inadequately monitored basins. Based on an information diffusion model (...

Chengzu Bai; Mei Hong; Dong Wang; Ren Zhang; Longxia Qian

2014-12-01T23:59:59.000Z

110

E-Print Network 3.0 - advanced diffusion model Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

of Michigan Collection: Geosciences 2 Oxygen self-diffusion fast-paths'' in titanite single crystals and a general method for deconvolving self-diffusion Summary:...

111

Modeling heat conduction and radiation transport with the diffusion equation in  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

heat conduction and radiation transport with the diffusion equation in NIF ALE-AMR heat conduction and radiation transport with the diffusion equation in NIF ALE-AMR This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2010 J. Phys.: Conf. Ser. 244 022075 (http://iopscience.iop.org/1742-6596/244/2/022075) Download details: IP Address: 50.136.219.251 The article was downloaded on 18/04/2013 at 01:36 Please note that terms and conditions apply. View the table of contents for this issue, or go to the journal homepage for more Home Search Collections Journals About Contact us My IOPscience Modeling Heat Conduction and Radiation Transport with the Diffusion Equation in NIF ALE-AMR A.C. Fisher 1 , D.S. Bailey 1 , T.B. Kaiser 1 , B.T.N. Gunney 1 , N.D. Masters 1 , A.E. Koniges 2 , D.C. Eder 1 , R.W. Anderson 1 1: Lawrence Livermore National Laboratory,

112

Nucleus-nucleus cold fusion reactions analyzed with the l-dependent 'fusion by diffusion' model  

SciTech Connect (OSTI)

We present a modified version of the Fusion by Diffusion (FBD) model aimed at describing the synthesis of superheavy nuclei in cold fusion reactions, in which a low excited compound nucleus emits only one neutron. The modified FBD model accounts for the angular momentum dependence of three basic factors determining the evaporation residue cross section: the capture cross section {sigma}{sub cap}(l), the fusion probability P{sub fus}(l), and the survival probability P{sub surv}(l). The fusion hindrance factor, the inverse of P{sub fus}(l), is treated in terms of thermal fluctuations in the shape degrees of freedom and is expressed as a solution of the Smoluchowski diffusion equation. The l dependence of P{sub fus}(l) results from the l-dependent potential energy surface of the colliding system. A new parametrization of the distance of starting point of the diffusion process is introduced. An analysis of a complete set of 27 excitation functions for production of superheavy nuclei in cold fusion reactions, studied in experiments at GSI Darmstadt, RIKEN Tokyo, and LBNL Berkeley, is presented. The FBD model satisfactorily reproduces shapes and absolute cross sections of all the cold fusion excitation functions. It is shown that the peak position of the excitation function for a given 1n reaction is determined by the Q value of the reaction and the height of the fission barrier of the final nucleus. This fact could possibly be used in future experiments (with well-defined beam energy) for experimental determination of the fission barrier heights.

Cap, T.; Siwek-Wilczynska, K.; Wilczynski, J. [Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Hoza 69, PL-00-681 Warsaw (Poland); Andrzej Soltan Institute for Nuclear Studies, PL-05-400 Otwock-Swierk (Poland)

2011-05-15T23:59:59.000Z

113

Numerical modeling of two-phase behavior in the PEFC gas diffusion layer  

SciTech Connect (OSTI)

A critical performance limitation in the polymer electrolye fuel cell (PEFC) is attributed to the mass transport loss originating from suboptimal liquid water transport and flooding phenomena. Liquid water can block the porous pathways in the fibrous gas diffusion layer (GDL) and the catalyst layer (CL), thus hindering oxygen transport from the flow field to the electrochemically actives sites in the catalyst layer. In this paper, the study of the two phase behavior and the durability implications due to the wetting characteristics in the carbon paper GDL are presented using a pore-scale modeling framework.

Mukherjee, Partha Pa223876 [Los Alamos National Laboratory; Kang, Qinjun [Los Alamos National Laboratory; Mukundan, Rangachary [Los Alamos National Laboratory; Borup, Rod L [Los Alamos National Laboratory

2009-01-01T23:59:59.000Z

114

Diffusion and magnetic relaxation in model porous media Aniket Bhattacharya and S. D. Mahanti  

E-Print Network [OSTI]

-dimensional analogs resemble commercially prepared Vycors and aerogels. When diffusion rates are compared for two

Bhattacharya, Aniket

115

MODELING THE THERMAL DIFFUSE SOFT AND HARD X-RAY EMISSION IN M17  

SciTech Connect (OSTI)

We present numerical models of very young wind driven superbubbles. The parameters chosen for the simulations correspond to the particular case of the M17 nebula, but are appropriate for any young superbubble in which the wind sources have not completely dispersed their parental cloud. From the simulations, we computed the diffuse emission in the soft ([0.5-1.5] keV) and hard ([1.5-5] keV) X-ray bands. The total luminosity in our simulations agrees with the observations of Hyodo et al., about two orders of magnitude below the prediction of the standard model of Weaver et al.. The difference with respect to the standard (adiabatic) model is the inclusion of radiative cooling, which is still important in such young bubbles. We show that for this type of object the diffuse hard X-ray luminosity is significant compared to that of soft X-rays, contributing as much as 10% of the total luminosity, in contrast with more evolved bubbles where the hard X-ray emission is indeed negligible, being at least four orders of magnitude lower than the soft X-ray emission.

Velazquez, P. F.; Rodriguez-Gonzalez, A.; Esquivel, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Ap. 70-543, 04510 D.F. (Mexico)] [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Ap. 70-543, 04510 D.F. (Mexico); Rosado, M. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ap. 70-248, 04510 D.F. (Mexico)] [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ap. 70-248, 04510 D.F. (Mexico); Reyes-Iturbide, J., E-mail: pablo@nucleares.unam.mx, E-mail: ary@nucleares.unam.mx, E-mail: esquivel@nucleares.unam.mx, E-mail: margarit@astro.unam.mx [LATO-DCET/Universidade Estadual de Santa Cruz, Rodovia Jorge Amado, km 16, 45662-000 Ilheus, BA (Brazil)

2013-04-10T23:59:59.000Z

116

On Similarities between Biological and Social Evolutionary Mechanisms: Mathematical Modeling  

E-Print Network [OSTI]

of widely diffused social innovation that enhances theof widely diffused social innovation that enhances theinnovations and new elements from other societies. Social

Grinin, Leonid; Markov, Alexander; Korotayev, Andrey

2013-01-01T23:59:59.000Z

117

Model-based image reconstruction from time-resolved diffusion data  

SciTech Connect (OSTI)

This paper addresses the issue of reconstructing the unknown field of absorption and scattering coefficients from time-resolved measurements of diffused light in a computationally efficient manner. The intended application is optical tomography, which has generated considerable interest in recent times. The inverse problem is posed in the Bayesian framework. The maximum {ital a posteriori} (MAP) estimate is used to compute the reconstruction. We use an edge- preserving generalized Gaussian Markov random field to model the unknown image. The diffusion model used for the measurements is solved forward in time using a finite-difference approach known as the alternating-directions implicit method. This method requires the inversion of a tridiagonal matrix at each time step and is therefore of O(N) complexity, where N is the dimensionality of the image. Adjoint differentiation is used to compute the sensitivity of the measurements with respect to the unknown image. The novelty of our method lies in the computation of the sensitivity since we can achieve it in O(N) time as opposed to O(N{sup 2}) time required by the perturbation approach. We present results using simulated data to show that the proposed method yields superior quality reconstructions with substantial savings in computation.

Saquib, S.S. [Purdue Univ., Lafayette, IN (United States); Hanson, K.M.; Cunningham, G.S. [Los Alamos National Lab., NM (United States)

1997-02-01T23:59:59.000Z

118

Analytical modeling of the interaction of enzyme catalysis and diffusion processes at the intracellular level  

E-Print Network [OSTI]

of VD', diffusion fluxes of Model III to Model The effect of VD' (V L /(0 S )) on the S and P concentration profiles, 2 m 0 presented in F1gure 6, was obtained by letting D equal 0. 01 and 0. 02 respectively wh1le holding V , L, and S constant...) ? &( S(K' /K i~. l) ? Y S(K /K -"'e0lj ? z INN I BI 7 I QN P IK/KSI=I. Q) ? 3I P(K. /k -=el) ? K P(K /k =?01 j Z m si m si I . =1 00 ~ I . =100. I . ~10. o o ?3 I c:o ~o LIJ ?0 m tel Cf) W c&R ?o o Z, W X O . 00 1. 00 2. 00 3. 00 %00 6...

Faith, Duane Willbern

2012-06-07T23:59:59.000Z

119

Material-modeling and structural-mechanics aspects  

E-Print Network [OSTI]

Material-modeling and structural-mechanics aspects of the traumatic brain injury problem M for causing traumatic brain injury. Design/methodology/approach ­ Two levels of blast peak overpressure were computational investigation of impact on a human skull/brain assembly. Keywords Brain, Injuries, Modeling

Grujicic, Mica

120

A mechanical approach to mean field spin models  

E-Print Network [OSTI]

Inspired by the bridge pioneered by Guerra among statistical mechanics on lattice and analytical mechanics on 1+1 continuous Euclidean space-time, we built a self-consistent method to solve for the thermodynamics of mean-field models defined on lattice, whose order parameters self average. We show the whole procedure by analyzing in full details the simplest test case, namely the Curie-Weiss model. Further we report some applications also to models whose order parameters do not self-average, by using the Sherrington-Kirkpatrick spin glass as a guide.

Giuseppe Genovese; Adriano Barra

2009-05-07T23:59:59.000Z

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While these samples are representative of the content of NLEBeta,
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to obtain the most current and comprehensive results.


121

Understanding of interface structures and reaction mechanisms induced by Ge or GeO diffusion in Al{sub 2}O{sub 3}/Ge structure  

SciTech Connect (OSTI)

The reaction mechanisms at Al{sub 2}O{sub 3}/Ge interfaces with thermal oxidation through the Al{sub 2}O{sub 3} layer have been investigated. X-ray photoelectron spectroscopy reveals that an Al{sub 6}Ge{sub 2}O{sub 13} layer is formed near the interface, and a GeO{sub 2} layer is formed on the Al{sub 2}O{sub 3} surface, suggesting Ge or GeO diffusion from the Ge surface. It is also clarified that the Al{sub 6}Ge{sub 2}O{sub 13} layer is formed by the different mechanism with a small activation energy of 0.2 eV, compared with the GeO{sub 2} formation limited by oxygen diffusion. Formation of Al-O-Ge bonds due to the AlGeO formation could lead appropriate interface structures with high interface qualities.

Shibayama, Shigehisa [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan) [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); JSPS, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan); Kato, Kimihiko; Sakashita, Mitsuo; Takeuchi, Wakana; Taoka, Noriyuki; Nakatsuka, Osamu; Zaima, Shigeaki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)] [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

2013-08-19T23:59:59.000Z

122

Phase transitions in a reaction-diffusion model on a line with boundaries  

SciTech Connect (OSTI)

A one-dimensional model on a line of length L is investigated, which involves particle diffusion as well as single particle annihilation. There are also creation and annihilation at the boundaries. The static and dynamical behaviors of the system are studied. It is seen that the system could exhibit a dynamical phase transition. For small drift velocities, the relaxation time does not depend on the absorption rates at the boundaries. This is the fast phase. For large velocities, the smaller of the absorption rates at boundaries enter the relaxation rate and makes it longer. This is the slow phase. Finally, the effect of a random particle creation in the bulk is also investigated.

Khorrami, Mohammad, E-mail: mamwad@mailaps.org; Aghamohammadi, Amir, E-mail: mohamadi@alzahra.ac.ir [Department of Physics, Alzahra University, Tehran 19938-93973 (Iran, Islamic Republic of)] [Department of Physics, Alzahra University, Tehran 19938-93973 (Iran, Islamic Republic of)

2014-03-15T23:59:59.000Z

123

A mechanical model of early salt dome growth  

E-Print Network [OSTI]

A MECHANICAL MODEL OF EARLY SALT DOME GROWTH A Thesis by FRANK ALBERT IRWIN Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1988... Major Subject: Geology A MECHANICAL MODEL OF EARLY SALT DOME GROWTH A Thesis by FRANK ALBERT IRWIN Approved as to style and content by: aymond C. Fletcher (Chair of Committee) John H. Spang (Member) Wi tamR. B ant (Mem ) John H. Sp g (Head...

Irwin, Frank Albert

2012-06-07T23:59:59.000Z

124

Simulations of Xe and U diffusion in UO2  

SciTech Connect (OSTI)

Diffusion of xenon (Xe) and uranium (U) in UO{sub 2} is controlled by vacancy mechanisms and under irradiation the formation of mobile vacancy clusters is important. Based on the vacancy and cluster diffusion mechanisms established from density functional theory (DFT) calculations, we derive continuum thermodynamic and diffusion models for Xe and U in UO{sub 2}. In order to capture the effects of irradiation, vacancies (Va) are explicitly coupled to the Xe and U dynamics. Segregation of defects to grain boundaries in UO{sub 2} is described by combining the bulk diffusion model with models of the interaction between Xe atoms and vacancies with grain boundaries, which were derived from atomistic calculations. The diffusion and segregation models were implemented in the MOOSE-Bison-Marmot (MBM) finite element (FEM) framework and the Xe/U redistribution was simulated for a few simple microstructures.

Andersson, Anders D. [Los Alamos National Laboratory; Vyas, Shyam [Los Alamos National Laboratory; Tonks, Michael R. [Idaho National Laboratory; Casillas, Luis [Los Alamos National Laboratory; Uberuaga, Blas P. [Los Alamos National Laboratory; Millett, Paul [Idaho National Laboratory

2012-09-10T23:59:59.000Z

125

Thermal And Thermo-Mechanical Modelling of Polymer Overmoulded Electronics  

E-Print Network [OSTI]

electronics for use in the demanding automotive environment. A two shot moulding technology will protect of electronics within polymer materials is of great interest to the automotive industry as a means to protectThermal And Thermo-Mechanical Modelling of Polymer Overmoulded Electronics F. Sarvar1 , D. C

Paris-Sud XI, Université de

126

Modelling the mechanical behaviour of pharmaceutical powders during compaction  

E-Print Network [OSTI]

are made of dry powder through a powder compaction process. In the pharmaceutical industry, billionsModelling the mechanical behaviour of pharmaceutical powders during compaction C.-Y. Wua,T, O.M. Ruddyb , A.C. Benthamb , B.C. Hancockc , S.M. Besta , J.A. Elliotta a Pfizer Institute for Pharmaceutical

Elliott, James

127

Mechanical modeling of porous oxide fuel pellet A Test Problem  

SciTech Connect (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

128

Galactic outflow and diffuse gas properties at z>=1 using different baryonic feedback models  

E-Print Network [OSTI]

We measure and quantify properties of galactic outflows and diffuse gas at $z \\geq 1$ in cosmological hydrodynamical simulations. Our novel sub-resolution model, MUPPI, implements supernova feedback using fully local gas properties, where the wind velocity and mass loading are not given as input. We find the following trends at $z = 2$ by analysing central galaxies having a stellar mass higher than $10^{9} M_{\\odot}$. The outflow velocity and mass outflow rate ($\\dot{M}_{\\rm out}$) exhibit positive correlations with galaxy mass and with the star formation rate (SFR). However, most of the relations present a large scatter. The outflow mass loading factor ($\\eta$) is between $0.2 - 10$. The comparison Effective model generates a constant outflow velocity, and a negative correlation of $\\eta$ with halo mass. The number fraction of galaxies where outflow is detected decreases at lower redshifts, but remains more than $80 \\%$ over $z = 1 - 5$. High SF activity at $z \\sim 2 - 4$ drives strong outflows, causing the ...

Barai, Paramita; Murante, Giuseppe; Ragagnin, Antonio; Viel, Matteo

2014-01-01T23:59:59.000Z

129

Numerical Modeling of Diffusion in Fractured Media for Gas-Injection  

E-Print Network [OSTI]

Hoteit,* SPE, and Abbas Firoozabadi, SPE, Reservoir Engineering Research Institute Summary Diffusion in fractured reservoirs, unlike in unfractured reservoirs, can affect significantly the efficiency of gas injection in oil reser- voirs and recycling in gas/condensate reservoirs. The physical diffusion, similar

Firoozabadi, Abbas

130

Handbook on atmospheric diffusion  

SciTech Connect (OSTI)

Basic meteorological concepts are covered as well as plume rise, source effects, and diffusion models. Chapters are included on cooling tower plumes and urban diffusion. Suggestions are given for calculating diffusion in special situations, such as for instantaneous releases over complex terrain, over long distances, and during times when chemical reactions or dry or wet deposition are important. (PSB)

Hanna, S.R.; Briggs, G.A.; Hosker, R.P. Jr.

1982-01-01T23:59:59.000Z

131

Mechanical properties and modeling of seal-forming lithologies  

SciTech Connect (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

132

Bioinspired, mechanical, deterministic fractal model for hierarchical suture joints  

Science Journals Connector (OSTI)

Many biological systems possess hierarchical and fractal-like interfaces and joint structures that bear and transmit loads, absorb energy, and accommodate growth, respiration, and/or locomotion. In this paper, an elastic deterministic fractal composite mechanical model was formulated to quantitatively investigate the role of structural hierarchy on the stiffness, strength, and failure of suture joints. From this model, it was revealed that the number of hierarchies (N) can be used to tailor and to amplify mechanical properties nonlinearly and with high sensitivity over a wide range of values (orders of magnitude) for a given volume and weight. Additionally, increasing hierarchy was found to result in mechanical interlocking of higher-order teeth, which creates additional load resistance capability, thereby preventing catastrophic failure in major teeth and providing flaw tolerance. Hence, this paper shows that the diversity of hierarchical and fractal-like interfaces and joints found in nature have definitive functional consequences and is an effective geometric-structural strategy to achieve different properties with limited material options in nature when other structural geometries and parameters are biologically challenging or inaccessible. This paper also indicates the use of hierarchy as a design strategy to increase design space and provides predictive capabilities to guide the mechanical design of synthetic flaw-tolerant bioinspired interfaces and joints.

Yaning Li; Christine Ortiz; Mary C. Boyce

2012-03-01T23:59:59.000Z

133

Mechanical properties and modeling of seal-forming lithologies  

SciTech Connect (OSTI)

Both rocksalt and shale lithologies are actively deformed in response to gravitational loads associated with deposition, and both form effective seals to petroleum and natural gas. 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 salt or those of shale, and the loading histories to which they have been subjected. The objectives of this research include the determination of the mechanical properties under controlled conditions of well-characterized shales, and the numerical modeling of rocksalt (and eventually shale) formations using laboratory-based rheologies. Progress has been made towards these goals over this project period, both in our experimental program on shale deformation and model development for the growth of salt diapirs. The mechanical anisotropy of an illite-bearing shale from Louisiana has been determined and related to the preferred orientation and distribution of clays. Its strength in the absence of pore fluids has been determined at confining pressures of up to 250 MPa and at high pressure we have investigated the effects of deformation rate and temperature. A numerical finite difference code has been developed to solve the incompressible Navier-Stokes equations and validated using a two- layer linear viscous model for which analytic solutions are available. Although the code has only been validated for the linear viscous case, it is capable of solving for highly nonlinear constitutive laws as well as solving for arbitrary interfaces between the salt and overburden.

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

1992-04-01T23:59:59.000Z

134

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

SciTech Connect (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

135

Stochastic Integration for the Heterogeneous Correlation Modeling Using a Diffusion Equation  

Science Journals Connector (OSTI)

In this note, a stochastic integration scheme is proposed as an alternative to a deterministic integration scheme, usually employed for the diffusion operator in data assimilation. The stochastic integration scheme is no more than a simple ...

Olivier Pannekoucke; Laurent Vezard

2010-08-01T23:59:59.000Z

136

Modeling Infinite Dilution and Fickian Diffusion Coefficients of Carbon Dioxide in Water  

E-Print Network [OSTI]

in enhanced oil recovery (EOR), and recovery of coal-bed methane from unmineable coal seams.3 For CO2 these temperature and pressure conditions. A general formalism for Fickian diffusion coefficients is already well

Firoozabadi, Abbas

137

Estimation variationnelle robuste de mod`eles complexes de diffusion en IRM `a  

E-Print Network [OSTI]

internes c:Signal = diffusion macroscopique locale [LeBihan86] Fibres nerveuses [LeBihan95, Beaulieu98'ODF dans la direction u est d´efinie comme la projection radiale de la PDF de diffusion (u) = o P(u)d = P, 2007 9 / 26 #12;la Transform´e de Funk-Radon (FRT) La FRT (2) est une approximation de la vraie ODF (1

Brun, Chez Luc

138

Vacancy diffusion in colloidal crystals as determined by dynamical density-functional theory and the phase-field-crystal model  

E-Print Network [OSTI]

A two-dimensional crystal of repulsive dipolar particles is studied in the vicinity of its melting transition by using Brownian dynamics computer simulation, dynamical density functional theory and phase-field crystal modelling. A vacancy is created by taking out a particle from an equilibrated crystal and the relaxation dynamics of the vacancy is followed by monitoring the time-dependent one-particle density. We find that the vacancy is quickly filled up by diffusive hopping of neighbouring particles towards the vacancy center. We examine the temperature dependence of the diffusion constant and find that it decreases with decreasing temperature in the simulations. This trend is reproduced by the dynamical density functional theory. Conversely, the phase field crystal calculations predict the opposite trend. Therefore, the phase-field model needs a temperature-dependent expression for the mobility to predict trends correctly.

Sven van Teeffelen; Cristian Vasile Achim; Hartmut Löwen

2013-02-05T23:59:59.000Z

139

The blue-edge problem of the V1093 Her instability strip revisited using evolutionary models with atomic diffusion  

E-Print Network [OSTI]

We have computed a new grid of evolutionary subdwarf B star (sdB) models from the start of central He burning, taking into account atomic diffusion due to radiative levitation, gravitational settling, concentration diffusion, and thermal diffusion. We have computed the non-adiabatic pulsation properties of the models and present the predicted p-mode and g-mode instability strips. In previous studies of the sdB instability strips, artificial abundance enhancements of Fe and Ni were introduced in the pulsation driving layers. In our models, the abundance enhancements of Fe and Ni occur naturally, eradicating the need to use artificial enhancements. We find that the abundance increases of Fe and Ni were previously underestimated and show that the instability strip predicted by our simulations solves the so-called blue edge problem of the subdwarf B star g-mode instability strip. The hottest known g-mode pulsator, KIC 10139564, now resides well within the instability strip {even when only modes with low spherical...

Bloemen, S; Aerts, C; Dupret, M A; Østensen, R H; Degroote, P; Müller-Ringat, E; Rauch, T

2014-01-01T23:59:59.000Z

140

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

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141

N + 1 dimensional quantum mechanical model for a closed universe  

E-Print Network [OSTI]

A quantum mechanical model for an N + 1 dimensional universe arising from a quantum fluctuation is outlined. (3 + 1) dimensions are a closed infinitely-expanding universe and the remaining N - 3 dimensions are compact. The (3 + 1) non-compact dimensions are modeled by quantizing a canonical Hamiltonian description of a homogeneous isotropic universe. It is assumed gravity and the strong-electro-weak (SEW) forces had equal strength in the initial state. Inflation occurred when the compact N -3 dimensional space collapsed after a quantum transition from the initial state of the univers, during its evolution to the present state where gravity is much weaker than the SEW force. The model suggests the universe has no singularities and the large size of our present universe is determined by the relative strength of gravity and the SEW force today. A small cosmological constant, resulting from the zero point energy of the scalar field corresponding to the compact dimensions, makes the model universe expand forever.

T. R. Mongan

1999-02-10T23:59:59.000Z

142

Memory-induced anomalous dynamics: emergence of diffusion, subdiffusion, and superdiffusion from a single random walk model  

E-Print Network [OSTI]

We present a random walk model that exhibits asymptotic subdiffusive, diffusive, and superdiffusive behavior in different parameter regimes. This appears to be the first instance of a single random walk model leading to all three forms of behavior by simply changing parameter values. Furthermore, the model offers the great advantage of analytic tractability. Our model is non-Markovian in that the next jump of the walker is (probabilistically) determined by the history of past jumps. It also has elements of intermittency in that one possibility at each step is that the walker does not move at all. This rich encompassing scenario arising from a single model provides useful insights into the source of different types of asymptotic behavior.

Niraj Kumar; Upendra Harbola; Katja Lindenberg

2010-05-16T23:59:59.000Z

143

Effective scattering coefficient of the cerebral spinal fluid in adult head models for diffuse optical imaging  

E-Print Network [OSTI]

correct radiative transport equation (RTE); however, it is commonly assumed that scattering lengths must. Boas An efficient computation of the time-dependent forward solution for photon transport in a head of the brain. The diffusion approximation to photon transport is much faster to simulate than the physically

144

JOINT ESTIMATION OF CARDIAC KINEMATICS AND MATERIAL PARAMETERS FROM NOISY IMAGING DATA AND UNCERTAIN MECHANICAL MODEL  

E-Print Network [OSTI]

AND UNCERTAIN MECHANICAL MODEL Huafeng Liu, Edward W.B. Lo, and Pengcheng Shi Biomedical Research Laboratory

Shi, Pengcheng

145

Thermo-mechanical modeling of plasterboard lined partition submitted to fire load.  

E-Print Network [OSTI]

Thermo-mechanical modeling of plasterboard lined partition submitted to fire load. Authors: S.heck@cstb.fr Abstract: An important problem is the development of a thermo-mechanical model of plasterboard lined and the experimental validation of a deterministic and a probabilistic thermo-mechanical model of cardboard

Paris-Sud XI, Université de

146

Mechanical tests for validation of seismic isolation elastomer constitutive models  

SciTech Connect (OSTI)

High damping laminated elastomeric bearings are becoming the preferred device for seismic isolation of large buildings and structures, such as nuclear power plants. The key component of these bearings is a filled natural rubber elastomer. This material exhibits nonlinear behavior within the normal design range. The material damping cannot be classified as either viscous or hysteritic, but it seems to fall somewhere in between. This paper describes a series of tests that can be used to characterize the mechanical response of these elastomers. The tests are designed to determine the behavior of the elastomer in the time scale of the earthquake, which is typically from 30 to 60 seconds. The test results provide data for use in determining the material parameters associated with nonlinear constitutive models. 4 refs.

Kulak, R.F.; Hughes, T.H.

1992-01-01T23:59:59.000Z

147

Mechanical tests for validation of seismic isolation elastomer constitutive models  

SciTech Connect (OSTI)

High damping laminated elastomeric bearings are becoming the preferred device for seismic isolation of large buildings and structures, such as nuclear power plants. The key component of these bearings is a filled natural rubber elastomer. This material exhibits nonlinear behavior within the normal design range. The material damping cannot be classified as either viscous or hysteritic, but it seems to fall somewhere in between. This paper describes a series of tests that can be used to characterize the mechanical response of these elastomers. The tests are designed to determine the behavior of the elastomer in the time scale of the earthquake, which is typically from 30 to 60 seconds. The test results provide data for use in determining the material parameters associated with nonlinear constitutive models. 4 refs.

Kulak, R.F.; Hughes, T.H.

1992-05-01T23:59:59.000Z

148

Modeling and experiments on diffusion and activation of phosphorus in germanium  

SciTech Connect (OSTI)

We report on phosphorus diffusion and activation related phenomena in germanium. We have used both conventional thermal processing and laser annealing by pulsed nanosecond Nd:YAG laser. Chemical profiles were obtained by secondary-ion-mass spectroscopy, sheet resistance was estimated by the van der Pauw method, and structural defects were monitored by transmission electron microscopy. Our study covers the temperature range from 440 to 750 deg. C, and we were able to efficiently simulate the dopant profiles within that temperature range, taking into account a quadratic dependence of the P diffusion coefficient on the free electron concentration. To achieve that we have taken into account dopant activation dependence on temperature as well as dopant pile-up near the surface and dopant loss owing to outdiffusion during the annealing. A combined laser thermal treatment above the melting threshold prior to conventional annealing allowed the elimination of the implantation damage, so we could perceive the influence of defects on both transient dopant diffusion and outdiffusion.

Tsouroutas, P.; Tsoukalas, D.; Zergioti, I. [Department of Applied Physics, School of Applied Sciences, National Technical University of Athens, 15780 Zographou (Greece); Cherkashin, N.; Claverie, A. [CEMES/CNRS, 29 rue J. Marvig, 31055 Toulouse Cedex 4 (France)

2009-05-01T23:59:59.000Z

149

Portsmouth Gaseous Diffusion Plant | Department of Energy  

Energy Savers [EERE]

Gaseous Diffusion Plant. March 26, 2010 Enforcement Letter, Geiger Brothers Mechanical Contractors, INC - March 26, 2010 Issued to Geiger Brothers Mechanical Contractors,...

150

Enforcement Documents - Portsmouth Gaseous Diffusion Plant |...  

Broader source: Energy.gov (indexed) [DOE]

Gaseous Diffusion Plant March 26, 2010 Enforcement Letter, Geiger Brothers Mechanical Contractors, INC - March 26, 2010 Issued to Geiger Brothers Mechanical Contractors,...

151

Dependence of thermal diffusivity on organic content for Green River oil shales—Extension of the modified Cheng?Vachon model to the parallel heat?flow case  

Science Journals Connector (OSTI)

In an earlier paper [J. Appl. Phys. 50 2776 (1979)] the modified Cheng?Vachon model was found to give good agreement with experimental data on the variation of thermal diffusivity with organic content for Green River oil shales. Calculations using the model were carried out for the case where heat flows in directions perpendicular to the shale stratigraphic planes. In the present paper the above model is modified to account for experimental trends in the parallel heat?flow case. The modified model provides a self?consistent explanation for the lower degree of anisotropy (relative to theory) that has been experimentally observed for the thermal diffusivity of Green River oil shales.

Y. Wang; K. Rajeshwar; J. DuBow

1980-01-01T23:59:59.000Z

152

Port-based modeling and simulation of mechanical systems with rigid and flexible links  

Science Journals Connector (OSTI)

In this paper, a systematic procedure for the definition of the dynamical model in port-Hamiltonian form of mechanical systems is presented as the result of the power-conserving interconnection of a set of basic components (rigid bodies, flexible links, ... Keywords: flexible mechanisms, mechanisms dynamics, modeling, port-Hamiltonian systems, simulation

Alessandro Macchelli; Claudio Melchiorri; Stefano Stramigioli

2009-10-01T23:59:59.000Z

153

Design and modeling of carbon nanotube-based compliant mechanisms  

E-Print Network [OSTI]

The objective of this research is to generate the knowledge required to adapt macro- and microscale compliant mechanism theory to design carbon nanotube-based nano-scale compliant mechanisms. Molecular simulations of a ...

DiBiasio, Christopher M. (Christopher Michael)

2007-01-01T23:59:59.000Z

154

BDP: BrainSuite Diffusion Pipeline  

E-Print Network [OSTI]

BDP: BrainSuite Diffusion Pipeline Chitresh Bhushan #12; Quantify microstructural tissue ROI Connectivity ROI Statistics MPRAGE Diffusion #12;Diffusion Pipeline Dicom to NIfTI Co ROIs Custom ROIs #12;Diffusion Pipeline Dicom to NIfTI Co-registration Diffusion Modeling Tractography

Leahy, Richard M.

155

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

Open Energy Info (EERE)

Mechanical Fluid-Dynamical Model For Ground Movements At Campi Flegrei Caldera Jump to: navigation, search OpenEI Reference LibraryAdd to library Journal Article: A Mechanical...

156

Mechanisms of thiophene hydrodesulfurization on model molybdenum catalysts  

SciTech Connect (OSTI)

Hydrodesulfurization (HDS) activities and selectivities were measured for thiophene, tetrahydrothiophene (THT), and 1-butanethiol on silica-supported molybdenum catalysts at a pressure of 1 atm and temperatures ranging from 530 to 795 K. The model catalysts, which were previously characterized, feature isolated molybdenum atoms in the +2, +4, and +6 oxidation states and molybdenum dimers with each molybdenum atom in the +4 oxidation state. Silica-supported MoS{sub 2} was used for reference. Activities for thiophene and THT HDS correlate with oxidation state. Mo(II) is most active among dispersed catalysts. 1-Butanethiol activities were much larger than thiophene or THT activities and were roughly equal on all dispersed catalysts. Apparent activation energies of 43.4 and 48.5 kJ/mol were determined for thiophene HDS on Mo(II) and MoS{sub 2}/SiO{sub 2}, respectively. Dihydrothiophene, THT and 1-butanethiol were formed in thiophene HDS over Mo(II) and MoS{sub 2}/SiO{sub 2}. The major products of thiophene and THT HDS were 1-butene, 2-butene, and n-butene. Butadiene, i-butane, i-butene, methane, ethane, ethene, propane, and propene were formed in small amounts. Butadiene is thought to be the initial product of thiophene and THT desulfurization and undergoes subsequent hydrogenation and isomerization to yield the observed products. A common mechanism for HDS of thiophene and THT with 2,5-DHT as an intermediate is discussed.

Sullivan, D.L.; Ekerdt, J.G. [Univ. of Texas, Austin, TX (United States). Dept. of Chemical Engineering] [Univ. of Texas, Austin, TX (United States). Dept. of Chemical Engineering

1998-08-15T23:59:59.000Z

157

Measurements and modeling of moisture diffusion processes in transformer insulation using interdigital dielectrometry sensors  

E-Print Network [OSTI]

The presence of moisture in a transformer deteriorates the transformer insulation by decreasing its electrical, mechanical, and thermal strength. Therefore, it is important to monitor the moisture condition in both liquid ...

Du, Yanqing, 1971-

1999-01-01T23:59:59.000Z

158

Current-based 4D shape analysis for the mechanical personalization of heart models  

E-Print Network [OSTI]

Current-based 4D shape analysis for the mechanical personalization of heart models Lo¨ic Le Folgoc1. Abstract. Patient-specific models of the heart may lead to better understanding of cardiovascular diseases-mechanical model of the heart, from the kinematics of the endo- and epicardium, is presented in this paper. We use

Paris-Sud XI, Université de

159

Quantum Markovian activated surface diffusion of interacting adsorbates  

E-Print Network [OSTI]

A quantum Markovian activated atom-surface diffusion model with interacting adsorbates is proposed for the intermediate scattering function, which is shown to be complex-valued and factorizable into a classical-like and a quantum-mechanical factor. Applications to the diffusion of Na atoms on flat (weakly corrugated) and corrugated-Cu(001) surfaces at different coverages and surface temperatures are analyzed. Quantum effects are relevant to diffusion at low surface temperatures and coverages even for relatively heavy particles, such as Na atoms, where transport by tunneling is absent.

R. Martinez-Casado; A. S. Sanz; S. Miret-Artes

2008-03-04T23:59:59.000Z

160

Computer Modelling and Simulations of Enzymes and their Mechanisms .  

E-Print Network [OSTI]

??Although the tremendous catalytic power of enzymes is widely recognized, their exact mechanisms of action are still a source of debate. In order to elucidate… (more)

Alonso, Hernan

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

INTEGRATED MODELING AND FIELD STUDY OF POTENTIAL MECHANISMS FOR...  

Office of Scientific and Technical Information (OSTI)

system and contributes to the EGS, both mechanically (e.g., cooling shrinkage and fracture shear reactivation) and chemically (e.g., dissolution). * To demonstrate the...

162

Modelling multi-state diffusion process in complex networks: theory and applications  

Science Journals Connector (OSTI)

......a generalized SIS model by allowing the existence...the generalized SIS model on large graphs...to or prevents the outbreak of information or...the generalized SIS model. Experimental results...methodology can accurately predict the behaviour of...contagions such as flu or ideas in a large......

Yishi Lin; John C. S. Lui; Kyomin Jung; Sungsu Lim

2014-08-01T23:59:59.000Z

163

Efficient Reformulation of Solid-Phase Diffusion in Physics-Based Lithium-Ion Battery Models  

E-Print Network [OSTI]

in the solid phase. Introduction Physics based Li-ion battery models use porous electrode theory. One and their drawbacks Porous electrode models of Li-ion batteries often use approximations to eliminate the time and disadvantages when used in Li-ion battery models. For instance, the Duhamel's superposition method is the robust

Subramanian, Venkat

164

Establishing the Clear-Sky Diffuse Reference for BORCAL Using EPLAB Model 8-48 Pyranometers at the National Renewable Energ...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Establishing the Clear-Sky Diffuse Reference for BORCAL Establishing the Clear-Sky Diffuse Reference for BORCAL Using EPLAB Model 8-48 Pyranometers at the National Renewable Energy Laboratory I. Reda, T. L. Stoffel, and D. Myers National Renewable Energy Laboratory Golden, Colorado Abstract Precision pyranometer calibrations are important to the quality of Atmospheric Radiation Measurement's (ARM's) shortwave solar irradiance measurements. Calibrations at the National Renewable Energy Laboratory (NREL) and Southern Great Plains (SGP) are under clear-sky conditions. G = I * COS(2) + D, is used to establish the reference global during the calibration. The references for the beam irradiance, I, and the solar zenith angle, 2, are internationally recognized. There is no recognized reference for the diffuse irradiance, D. Our research goal is to establish a consistent diffuse

165

The Diffusion Approximation vs. the Telegraph Equation for Modeling Solar Energetic Particle Transport with Adiabatic Focusing. I. Isotropic Pitch-angle Scattering  

E-Print Network [OSTI]

The diffusion approximation to the Fokker-Planck equation is commonly used to model the transport of solar energetic particles in interplanetary space. In this study, we present exact analytical predictions of a higher order telegraph approximation for particle transport and compare them with the corresponding predictions of the diffusion approximation and numerical solutions of the full Fokker-Planck equation. We specifically investigate the role of the adiabatic focusing effect of a spatially varying magnetic field on an evolving particle distribution. Comparison of the analytical and numerical results shows that the telegraph approximation reproduces the particle intensity profiles much more accurately than does the diffusion approximation, especially when the focusing is strong. However, the telegraph approximation appears to offer no significant advantage over the diffusion approximation for calculating the particle anisotropy. The telegraph approximation can be a useful tool for describing both diffusiv...

Effenberger, Frederic

2014-01-01T23:59:59.000Z

166

Development of Advanced Thermal-Hydrological-Mechanical-Chemical (THMC) Modeling Capabilities for Enhanced Geothermal Systems  

Broader source: Energy.gov [DOE]

Development of Advanced Thermal-Hydrological-Mechanical-Chemical (THMC) Modeling Capabilities for Enhanced Geothermal Systems presentation at the April 2013 peer review meeting held in Denver, Colorado.

167

Mechanisms and modeling of single-event upset  

SciTech Connect (OSTI)

The basic mechanisms of single-event upset are reviewed, including charge collection in silicon junctions and transistors, and properties of single-event upset in CMOS static random access memory (SRAM) cells. The mechanisms are illustrated through the use of three-dimensional device and circuit simulations. Technology trends and implications for commercial devices are discussed.

Dodd, Paul E.

1998-10-12T23:59:59.000Z

168

Thermo-mechanical model of a cardboard-plaster-cardboard composite  

E-Print Network [OSTI]

Thermo-mechanical model of a cardboard-plaster-cardboard composite plate submitted to fire load Mechanics laboratory, Marne-la-Vall´ee University, France Abstract Generally, the standard rules require with experiments in order to predict thermo- mechanical overall partition behaviour. This research is organized

Paris-Sud XI, Université de

169

Neutrino mass mechanisms in 3-3-1 models: A short review  

E-Print Network [OSTI]

In this paper we review some mechanisms that provide light neutrinos in the framework of 3-3-1 gauge models without exotic leptons. In regard to the minimal 3-3-1 model, we call the attention to the fact that the perturbative regime of the model goes until 5 TeV. This requires alternative mechanisms in order to generate light neutrinos. In this review we discuss two mechanisms capable of generating light neutrinos in the framework of the minimal 3-3-1 model. In regard to the 3-3-1 model with right-handed neutrinos, we call the attention to the fact that in it mechanisms that generate light left-handed neutrinos also generate light right-handed neutrinos. Finally, we call the attention to the fact that the 3-3-1 model with right-handed neutrinos accommodate naturally the inverse seesaw mechanism.

Pires, C A de S

2014-01-01T23:59:59.000Z

170

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

171

Interstellar Simulations Using A Unified Microscopic-Macroscopic Monte Carlo Model with a full Gas-Grain Network including Bulk Diffusion in Ice Mantles  

E-Print Network [OSTI]

We have designed an improved algorithm that enables us to simulate the chemistry of cold dense interstellar clouds with a full gas-grain reaction network. The chemistry is treated by a unified microscopic-macroscopic Monte Carlo approach that includes photon penetration and bulk diffusion. To determine the significance of these two processes, we simulate the chemistry with three different models. In Model 1, we use an exponential treatment to follow how photons penetrate and photodissociate ice species throughout the grain mantle. Moreover, the products of photodissociation are allowed to diffuse via bulk diffusion and react within the ice mantle. Model 2 is similar to Model 1 but with a slower bulk diffusion rate. A reference Model 0, which only allows photodissociation reactions to occur on the top two layers, is also simulated. Photodesorption is assumed to occur from the top two layers in all three models. We found that the abundances of major stable species in grain mantles do not differ much among these...

Chang, Qiang

2014-01-01T23:59:59.000Z

172

The Impact of Thermal Conductivity and Diffusion Rates on Water Vapor Transport through Gas Diffusion Layers  

E-Print Network [OSTI]

Water management in a hydrogen polymer electrolyte membrane (PEM) fuel cell is critical for performance. The impact of thermal conductivity and water vapor diffusion coefficients in a gas diffusion layer (GDL) has been studied by a mathematical model. The fraction of product water that is removed in the vapour phase through the GDL as a function of GDL properties and operating conditions has been calculated and discussed. Furthermore, the current model enables identification of conditions when condensation occurs in each GDL component and calculation of temperature gradient across the interface between different layers, providing insight into the overall mechanism of water transport in a given cell design. Water transport mode and condensation conditions in the GDL components depend on the combination of water vapor diffusion coefficients and thermal conductivities of the GDL components. Different types of GDL and water removal scenarios have been identified and related to experimentally-determined GDL proper...

Burlatsky, S F; Gummallaa, M; Condita, D; Liua, F

2013-01-01T23:59:59.000Z

173

Efficient Conservative Numerical Schemes for 1D Nonlinear Spherical Diffusion Equations with Applications in Battery Modeling  

E-Print Network [OSTI]

Mathematical models of batteries which make use of the intercalation of a species into a solid phase need to solve the corresponding mass transfer problem. Because solving this equation can significantly add to the ...

Zeng, Yi

174

CoEvolutionary Incremental Modelling of Robotic Cognitive Mechanisms  

E-Print Network [OSTI]

, trahania}@ics.forth.gr Abstract. Recently, brain models attempt to support cognitive abili- ties work introduces a novel com- putational framework for incremental brain modelling, which aims properly formulated neural agents to represent brain areas. A collaborative coevolutionary method

Trahanias, Panos

175

Thermo-mechanical-metallurgical modeling for hot-press forming in consideration of the prior austenite deformation effect  

Science Journals Connector (OSTI)

Abstract In this study, a prior austenite grain refinement model was incorporated into semi-empirical diffusive transformation kinetics for application to hot-press forming. In particular, the kinetics equations were modified to include the effects of boron addition and austenite deformation on transformation behaviors during forming. To simulate the hot-press forming process, a thermo-mechanical-metallurgical model was formulated implicitly and implemented into the finite element program ABAQUS using the user subroutines UMAT and UMATHT. This nonconventional finite element modeling is appropriate to consider thermal- and transformation-associated strains. The proposed model was validated through simple finite element simulation examples, i.e., dilatometry simulation with and without external loading, and hot torsion and quenching of a rod. Finally, the hot-press forming of a U-channel-type part was simulated to study the effect of austenite deformation on the phase kinetics, hardness and residual stress. The simulation results showed that the austenite deformation had considerable influence on the final strength and residual stress distribution in the hot-press formed sheet, which resulted from an increase in ferritic phases due to the modified kinetics. In particular, the austenite deformation effect was more noticeable in the side-wall region of the U-channel where plastic deformation was the most severe.

Hyun-Ho Bok; JongWon Choi; Frédéric Barlat; Dong Woo Suh; Myoung-Gyu Lee

2014-01-01T23:59:59.000Z

176

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

177

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

178

A small-angle neutron scattering model for polydisperse spherical particles with diffusion zones and application to soft magnetic metallic glass  

Science Journals Connector (OSTI)

An enhanced polydisperse model for small-angle scattering intensity for a diluted system of spherical precipitates with diffusion zones is presented. A nonlinear regression based on the analytic result supplies parameter values and confidence intervals to verify the inhibitor concept of nanocrystallization in amorphous alloys.

Heinemann, A.

2000-12-01T23:59:59.000Z

179

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

Broader source: Energy.gov (indexed) [DOE]

of mechanistic crack growth and grain contact models for chemically induced subcritical crack growth and pressure solution, with porosity-permeability changes * Conduct...

180

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

Broader source: Energy.gov (indexed) [DOE]

of mechanistic crack growth and grain contact models for chemically induced subcritical crack growth and pressure solution, with porosity-permeability changes * Conduct...

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Diffusive Acceleration of Ions at Interplanetary Shocks  

Science Journals Connector (OSTI)

Heliospheric shocks are excellent systems for testing theories of particle acceleration in their environs. These generally fall into two classes: (1) interplanetary shocks that are linear in their ion acceleration characteristics with the non?thermal ions serving as test particles and (2) non?linear systems such as the Earth’s bow shock and the solar wind termination shock where the accelerated ions strongly influence the magnetohydrodynamic structure of the shock. This paper explores the modelling of diffusive acceleration at a particular interplanetary shock with an emphasis on explaining in situ measurements of ion distribution functions. The observational data for this event was acquired on day 292 of 1991 by the Ulysses mission. The modeling is performed using a well?known kinetic Monte Carlo simulation which has yielded good agreement with observations at several heliospheric shocks as have other theoretical techniques namely hybrid plasma simulations and numerical solution of the diffusion?convection equation. In this theory/data comparison it is demonstrated that diffusive acceleration theory can to first order successfully account for both the proton distribution data near the shock and the observation of energetic protons farther upstream of this interplanetary shock than lower energy pick?up protons using a single turbulence parameter. The principal conclusion is that diffusive acceleration of inflowing upstream ions can model this pick?up ion?rich event without the invoking any seed pre?acceleration mechanism though this investigation does not rule out the action of such pre?acceleration.

Matthew G. Baring; Errol J. Summerlin

2005-01-01T23:59:59.000Z

182

Diffusive Acceleration of Ions at Interplanetary Shocks  

E-Print Network [OSTI]

Heliospheric shocks are excellent systems for testing theories of particle acceleration in their environs. These generally fall into two classes: (1) interplanetary shocks that are linear in their ion acceleration characteristics, with the non-thermal ions serving as test particles, and (2) non-linear systems such as the Earth's bow shock and the solar wind termination shock, where the accelerated ions strongly influence the magnetohydrodynamic structure of the shock. This paper explores the modelling of diffusive acceleration at a particular interplanetary shock, with an emphasis on explaining in situ measurements of ion distribution functions. The observational data for this event was acquired on day 292 of 1991 by the Ulysses mission. The modeling is performed using a well-known kinetic Monte Carlo simulation, which has yielded good agreement with observations at several heliospheric shocks, as have other theoretical techniques, namely hybrid plasma simulations, and numerical solution of the diffusion-convection equation. In this theory/data comparison, it is demonstrated that diffusive acceleration theory can, to first order, successfully account for both the proton distribution data near the shock, and the observation of energetic protons farther upstream of this interplanetary shock than lower energy pick-up protons, using a single turbulence parameter. The principal conclusion is that diffusive acceleration of inflowing upstream ions can model this pick-up ion-rich event without the invoking any seed pre-acceleration mechanism, though this investigation does not rule out the action of such pre-acceleration.

Matthew G. Baring; Errol J. Summerlin

2005-06-08T23:59:59.000Z

183

Mathematical equations as executable models of mechanical systems  

Science Journals Connector (OSTI)

Cyber-physical systems comprise digital components that directly interact with a physical environment. Specifying the behavior desired of such systems requires analytical modeling of physical phenomena. Similarly, testing them requires simulation ...

Yun Zhu; Edwin Westbrook; Jun Inoue; Alexandre Chapoutot; Cherif Salama; Marisa Peralta; Travis Martin; Walid Taha; Marcia O'Malley; Robert Cartwright; Aaron Ames; Raktim Bhattacharya

2010-04-01T23:59:59.000Z

184

Notes 01. Modeling of mechanical (lumped parameter) elements  

E-Print Network [OSTI]

are given by the equations [][ ][] dtPE,xDxP t 0 vv T v ? == #0;#5;#0;#5; (3) where n,1j,ij,i }d{]D[ = = is a matrix of constant damping coefficients. The work performed by external forces is given by, [][ ] FxdW T ? = (4) MEEN 617..., Appendix C: Derivation of EOMs for MDOF system. L San Andr?s (2008) C-2 The principle of conservation of mechanical energy establishes that for any instant of time, 00v TV E W T V++ = + + (5) where [ ] [ ][ ] [ ] [ ][ ] 11 00 000 022 , TT Tx...

San Andres, Luis

2008-01-01T23:59:59.000Z

185

BYU PHYS 731 Statistical Mechanics Chapters 8 and 9: Sethna Professor Manuel Berrondo Ising Model  

E-Print Network [OSTI]

BYU PHYS 731 Statistical Mechanics Chapters 8 and 9: Sethna Professor Manuel Berrondo Ising Model interaction) -External eld H H = -J ij sisj - H i si Ising Hamiltonian Binary alloy type A, type B (Cu-Zn) NA - EABNAB Equivalent to Ising model J = 1 4 (EAA + EBB - 2EAB) and H = EAA - EBB Lattice gas model good

Hart, Gus

186

Vibration Stabilization of a Mechanical Model of a X-Band Linear Collider Final Focus Magnet  

SciTech Connect (OSTI)

The small beam sizes at the interaction point of a X-band linear collider require mechanical stabilization of the final focus magnets at the nanometer level. While passive systems provide adequate performance at many potential sites, active mechanical stabilization is useful if the natural or cultural ground vibration is higher than expected. A mechanical model of a room temperature linear collider final focus magnet has been constructed and actively stabilized with an accelerometer based system.

Frisch, Josef; Chang, Allison; Decker, Valentin; Doyle, Eric; Eriksson, Leif; Hendrickson, Linda; Himel, Thomas; Markiewicz, Thomas; Partridge, Richard; Seryi, Andrei; /SLAC

2006-09-28T23:59:59.000Z

187

A Producer-Consumer Model with Stoichiometric Elimination Mechanisms  

E-Print Network [OSTI]

, and the efficiency of the consumer's conversion of producer biomass to its own biomass. The elimination model we, or equivalently, the stoichiometric ratio of nutrient to biomass, as well as the biomass, is of interest on the flow of a single currency, such as energy stored in carbon compounds or biomass. This point of view

Peckham, Bruce B.

188

Carbon Nanotube Mats and Fibers with Irradiation-Improved Mechanical Characteristics: ATheoretical Model  

E-Print Network [OSTI]

Carbon Nanotube Mats and Fibers with Irradiation-Improved Mechanical Characteristics: ATheoretical model to calculate mechanical characteristics of macroscopic mats and fibers of single-walled carbon-flow technique [4]. The SWNT fibers, which in contrast to most ordinary carbon fibers could be strongly bent with

Krasheninnikov, Arkady V.

189

Prediction of Room Air Diffusion for Reduced Diffuser Flow Rates  

E-Print Network [OSTI]

modeling at the air supply device (ASHRAE Research Project RP -1009, ?Simplified Diffuser Boundary Conditions for Numerical Room Airflow Models, 2001) 2.2.4 Box model Nielsen (1989, 1992) proposed the box method with an imaginary box near.... Nielsen (1989, 13 1992). Results obtained from the box method are in good agreement with the measured data. Figure 5 Methods for momentum modeling in front of an air supply device (ASHRAE RP -1009, ?Simplified Diffuser Boundary Conditions...

Gangisetti, Kavita

2011-02-22T23:59:59.000Z

190

Application of the 3-D Hydro-Mechanical Model GEOFRAC in enhanced geothermal systems  

E-Print Network [OSTI]

GEOFRAC is a three-dimensional, geology-based, geometric-mechanical, hierarchical, stochastic model of natural rock fracture systems. The main characteristic of GEOFRAC is that it is based on statistical input representing ...

Vecchiarelli, Alessandra

2013-01-01T23:59:59.000Z

191

A Digital Model of a Dwell Mechanism for Alpha-Stirling Engine  

Science Journals Connector (OSTI)

The paper shows a digital model of a dwell mechanism dedicated to an ?-Stirling Engine. The low efficiency of an ?-Stirling Engine drives us to improve on its work...2]. The main way to achieve this is to improve...

N. M. Dehelean; V. Ciupe; E. C. Lovasz

2009-01-01T23:59:59.000Z

192

Multiscale micromechanical modeling of the thermal/mechanical properties of polymer/clay nanocomposites  

E-Print Network [OSTI]

Polymer/clay nanocomposites have been observed to exhibit enhanced thermal/mechanical properties at low weight fractions (We) of clay. Continuum-based composite modeling reveals that the enhanced properties are strongly ...

Sheng, Nuo, 1977-

2006-01-01T23:59:59.000Z

193

Mechanical Systems on an almost Kähler model of a Finsler Manifold  

E-Print Network [OSTI]

In this study, we present a new analogue of Euler-Lagrange and Hamilton equations on an almost K\\"ahler model of a Finsler manifold. Also, we give some corollories about the related mechanical systems and equations.

Mehmet Tekkoyun; O?uzhan Çelik

2012-11-06T23:59:59.000Z

194

A Continuum Coupled Moisture-mechanical Constitutive Model for Asphalt Concrete  

E-Print Network [OSTI]

constitutive relationships are implemented in the Pavement Analysis using Nonlinear Damage Approach (PANDA) finite element (FE) package to model the moisture damage effect on the complex environmental-mechanical response of asphalt concrete. The developed...

Shakiba, Maryam

2013-12-09T23:59:59.000Z

195

Dose Modeling Evaluations and Technical Support Document For the Authorized Limits Request for the DOE-Owned Property Outside the Limited Area, Paducah Gaseous Diffusion Plant Paducah, Kentucky  

SciTech Connect (OSTI)

Environmental assessments and remediation activities are being conducted by the U.S. Department of Energy (DOE) at the Paducah Gaseous Diffusion Plant (PGDP), Paducah, Kentucky. The Oak Ridge Institute for Science and Education (ORISE), a DOE prime contractor, was contracted by the DOE Portsmouth/Paducah Project Office (DOE-PPPO) to conduct radiation dose modeling analyses and derive single radionuclide soil guidelines (soil guidelines) in support of the derivation of Authorized Limits (ALs) for 'DOE-Owned Property Outside the Limited Area' ('Property') at the PGDP. The ORISE evaluation specifically included the area identified by DOE restricted area postings (public use access restrictions) and areas licensed by DOE to the West Kentucky Wildlife Management Area (WKWMA). The licensed areas are available without restriction to the general public for a variety of (primarily) recreational uses. Relevant receptors impacting current and reasonably anticipated future use activities were evaluated. In support of soil guideline derivation, a Conceptual Site Model (CSM) was developed. The CSM listed radiation and contamination sources, release mechanisms, transport media, representative exposure pathways from residual radioactivity, and a total of three receptors (under present and future use scenarios). Plausible receptors included a Resident Farmer, Recreational User, and Wildlife Worker. single radionuclide soil guidelines (outputs specified by the software modeling code) were generated for three receptors and thirteen targeted radionuclides. These soil guidelines were based on satisfying the project dose constraints. For comparison, soil guidelines applicable to the basic radiation public dose limit of 100 mrem/yr were generated. Single radionuclide soil guidelines from the most limiting (restrictive) receptor based on a target dose constraint of 25 mrem/yr were then rounded and identified as the derived soil guidelines. An additional evaluation using the derived soil guidelines as inputs into the code was also performed to determine the maximum (peak) dose for all receptors. This report contains the technical basis in support of the DOE?s derivation of ALs for the 'Property.' A complete description of the methodology, including an assessment of the input parameters, model inputs, and results is provided in this report. This report also provides initial recommendations on applying the derived soil guidelines.

Boerner, A. J. [Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN (United States). Independent Environmental Assessment and Verification Program; Maldonado, D. G. [Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN (United States). Independent Environmental Assessment and Verification Program; Hansen, Tom [Ameriphysics, LLC (United States)

2012-09-01T23:59:59.000Z

196

11136 J. Phys. Chem. 1994, 98, 11136-11142 A New Mechanism for Surface Diffusion: Motion of a Substrate-Adsorbate Complex  

E-Print Network [OSTI]

of a Substrate-Adsorbate Complex S. J. Stranick,?A. N. Parikh,*D. L. AllaraJ7$ and P. S. Weiss*J Departments for diffusion of surface adsorbates in which motion of the substrate atoms to which the adsorbates are attached results in the motion of the substrate-adsorbate complex. We show an experimental example-the motion

Parikh, Atul N.

197

Predictions from an Ising-like Statistical Mechanical Model on the Dynamic and Thermodynamic Effects of Protein Surface Electrostatics  

Science Journals Connector (OSTI)

Predictions from an Ising-like Statistical Mechanical Model on the Dynamic and Thermodynamic Effects of Protein Surface Electrostatics ...

Athi N. Naganathan

2012-10-05T23:59:59.000Z

198

Polymer, Vol. 46, no. 2, pp. 553-562 (2005) Modeling of the Mechanical Properties of Nanoparticle/Polymer Composites  

E-Print Network [OSTI]

and particles in the polymer. Several efforts have focused on the modeling of mechanical properties of nanoclay

Odegard, Gregory M.

199

Anisotropic diffusion of hydrogen atoms on the Si(100)-2×1 surface  

Science Journals Connector (OSTI)

This paper presents first-principles total-energy calculations of hydrogen-adatom diffusion on a Si(100)-2×1 reconstructed surface. The transition states for hydrogen-atom-diffusion pathways were established by mapping out the potential energy of a hydrogen atom jumping between the dangling bonds of a Si(100)-2×1 surface modeled by embedded finite silicon clusters. The diffusion barriers are high (2–3 eV) and wide (?3–4 Å), suggesting that H-atom diffusion on Si(100) proceeds via mostly a classical hopping mechanism instead of tunneling. Furthermore, diffusion of hydrogen atoms is predicted to be anisotropic, being preferentially directed parallel to the silicon-dimer rows, with an activation energy of 2.0 eV. Higher activation energies of 2.5 and 2.7 eV are predicted for diffusion perpendicular to dimer rows, for the cases of hydrogen atoms hopping from one dangling bond to a neighboring dangling bond on the same dimer and on an adjacent dimer, respectively. The mechanism for H-atom diffusion along dimer rows is markedly different from that previously proposed for Si-adatom diffusion on Si(100): H atoms are predicted to diffuse along edges of the dimer rows rather than down the middle.

Christine J. Wu and Emily A. Carter

1992-08-15T23:59:59.000Z

200

Diffuse Scattering  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Diffuse Scattering Diffuse Scattering * Anticipatory (trick) question: If you have an x-ray or neutron detector looking at a small sample volume, which will scatter more x- rays or neutrons into the detector 1 atom 100 atoms or 1000 atoms? X-ray or neutron beam Answer: Depends! Diffuse Scattering Gene E. Ice Materials Science and Technology Division Oak Ridge National Laboratory, USA National School on Neutron and X-ray Scattering ORNL/SNS June 2011 Presentation concentrates year graduate-level course into 1 hour * Skip mathematical complexities * Expose to range of applications * Develop intuition for length scales * Talk like x-ray/neutron scattering guru - Reciprocal space - Debye Temperature - Laue monotonic - Krivoglaz defects of 1st/2nd kinds! Great for cocktail parties or impressing attractive strangers-

Note: This page contains sample records for the topic "diffusion mechanisms models" 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.


201

Turing instability in reaction-diffusion systems with nonlinear diffusion  

SciTech Connect (OSTI)

The Turing instability is studied in two-component reaction-diffusion systems with nonlinear diffusion terms, and the regions in parametric space where Turing patterns can form are determined. The boundaries between super- and subcritical bifurcations are found. Calculations are performed for one-dimensional brusselator and oregonator models.

Zemskov, E. P., E-mail: zemskov@ccas.ru [Russian Academy of Sciences, Dorodnicyn Computing Center (Russian Federation)

2013-10-15T23:59:59.000Z

202

Nitrogen self-diffusion in magnetron sputtered Si-C-N films  

SciTech Connect (OSTI)

Self-diffusion was studied in magnetron sputtered nitrogen-rich amorphous compounds of the system Si-C-N by using nitrogen as a model tracer. As shown by infra-red spectroscopy a transient metastable region exists, where the structure of the material can be visualized as silicon nitride tetrahedra which are connected by carbo-diimide (-N=C=N-) bonds to a three dimensional amorphous network. In this region diffusion studies are carried out by neutron reflectometry and isotope multilayers as a function of annealing time, temperature and chemical composition. Low diffusivities between 10{sup -20} and 10{sup -24} m{sup 2}/s were found. In the metastable region, diffusion is faster than diffusion in amorphous silicon nitride by 1 to 2 orders of magnitude, while the activation enthalpies of diffusion between 3.1 and 3.4 eV are the same within error limits. This can be explained by the fact that the diffusion mechanism along SiN{sub 4} tetrahedra is identical to that in amorphous silicon nitride, however, the carbo-diimide bonds seem to widen the structure, allowing faster diffusion. A correlation between diffusivities and the number of carbo-diimid bonds present in the material is found, where the highest diffusivities are observed for materials with the highest number of carbo-diimid bonds, close to the composition Si{sub 2}CN{sub 4}.

Hueger, E.; Schmidt, H. [Institute of Metallurgy, Materials Physics Group, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Geue, T.; Stahn, J. [Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Tietze, U.; Lott, D. [Helmholtz-Zentrum Geesthacht, Max Planck Str. 1, D-21502 Geesthacht (Germany); Markwitz, A. [National Isotope Centre, GNS Science, 30 Gracefield Road, PO Box 31-312 Lower Hutt (New Zealand); Geckle, U.; Bruns, M. [Institute for Materials Research III, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)

2011-05-01T23:59:59.000Z

203

Mechanical Degradation Onset of Polyethylene Oxide Used as a Hydrosoluble Model Polymer  

E-Print Network [OSTI]

Mechanical Degradation Onset of Polyethylene Oxide Used as a Hydrosoluble Model Polymer Degradation Onset of Polyethylene Oxide Used as a Hydrosoluble Model Polymer for Enhanced Oil Recovery and for both dilute and semi dilute polyethylene oxide aqueous solutions. It reveals that the exponent k

Boyer, Edmond

204

Probabilistic uncertainty modeling for thermo-mechanical analysis of plasterboard submitted to re load  

E-Print Network [OSTI]

with a probabilistic modeling of the thermo-mechanical behavior of cardboard-plaster-cardboard (CPC) multilayer plates resistance, cardboard-plaster-cardboard multilayer, un- certainties, probabilistic model, experiments presented in the last section. A plasterboard (cardboard-plaster-cardboard (CPC) multiplayer) gives

Paris-Sud XI, Université de

205

Nonintrusive 3D reconstruction of human bone models to simulate their bio-mechanical response  

Science Journals Connector (OSTI)

3D finite element models representing functional parts of the human skeletal system, have been repeatedly introduced over the last years, to simulate biomechanical response of anatomical characteristics or investigate surgical treatment. The reconstruction ... Keywords: 3D imaging, Bio-mechanical response, Computed tomography, FEM modeling

Tsouknidas Alexander; Lontos Antonis; Savvakis Savvas; Michailidis Nikolaos

2012-06-01T23:59:59.000Z

206

A non-isothermal PEM fuel cell model including two water transport mechanisms in the  

E-Print Network [OSTI]

A non-isothermal PEM fuel cell model including two water transport mechanisms in the membrane K Freiburg Germany A dynamic two-phase flow model for proton exchange mem- brane (PEM) fuel cells and the species concentrations. In order to describe the charge transport in the fuel cell the Poisson equations

Münster, Westfälische Wilhelms-Universität

207

Phenomenological modelling of viscoplasticity Mechanics of Materials Laboratory, Rensselaer Polytechnic Institute, Troy, NY 12180-3590,  

E-Print Network [OSTI]

331 Phenomenological modelling of viscoplasticity E. Krempl Mechanics of Materials Laboratory. - The essentials of phenomenological modeling of metal deformation behavior at small strain are introduced together interpreted from a materials science viewpoint are re-analyzed from a phenomenological point of view

Paris-Sud XI, Université de

208

Numerical study on convection diffusion for gasification agent in underground coal gasification. Part I: establishment of mathematical models and solving method  

SciTech Connect (OSTI)

The aim of this article is to discuss the distribution law of the gasification agent concentration in a deep-going way during underground coal gasification and the new method of solving the problem for the convection diffusion of the gas. In this paper, the basic features of convection diffusion for the gas produced in underground coal gasification are studied. On the basis of the model experiment, through the analysis of the distribution and patterns of variation for the fluid concentration field in the process of the combustion and gasification of the coal seams within the gasifier, the 3-D non-linear unstable mathematical models on the convection diffusion for oxygen are established. In order to curb such pseudo-physical effects as numerical oscillation and surfeit which frequently occurred in the solution of the complex mathematical models, the novel finite unit algorithm, the upstream weighted multi-cell balance method is advanced in this article, and its main derivation process is introduced.

Yang, L.H.; Ding, Y.M. [China University of Mining & Technology, Xuzhou (China). College of Resources and Geoscience

2009-07-01T23:59:59.000Z

209

Enthalpy Diffusion in Multicomponent Flows  

SciTech Connect (OSTI)

The conclusions of this paper are: (1) Enthalpy diffusion preserves the second law. (2) Euler solvers will not produce correct temperatures in mixing regions. (3) Navier-Stokes solvers will only produce correct temperatures if q{sub d} is included. (4) Errors from neglecting enthalpy diffusion are most severe when differences in molecular weights are large. (5) In addition to temperature, enthalpy diffusion affects density, dilatation and other fields in subtle ways. (6) Reacting flow simulations that neglect the term are a dubious proposition. (7) Turbulence models for RANS and LES closures should preserve consistency between energy and species diffusion.

Cook, A W

2009-01-20T23:59:59.000Z

210

A Design, Simulation and Visualization Environment for Object-Oriented Mechanical and Multi-Domain Models in Modelica  

Science Journals Connector (OSTI)

The complexity of mechanical and multi-domain simulation models is rapidly increasing. Therefore new methods and standards are needed for model design. A new language, Modelica, has been proposed by an international design committee as a standard, object-oriented, ... Keywords: CAD, SolidWorks, Mechanical modeling, Simulation, Animation, Visualization, Modeling languages, Modelica, OpenGL

Hakan Larsson

1999-07-01T23:59:59.000Z

211

Understanding Creep Mechanisms in Graphite with Experiments, Multiscale Simulations, and Modeling  

SciTech Connect (OSTI)

Disordering mechanisms in graphite have a long history with conflicting viewpoints. Using Raman and x-ray photon spectroscoy, electron microscopy, x-ray diffraction experiments and atomistic modeling and simulations, the current project has developed a fundamental understanding of early-to-late state radiation damage mechanisms in nuclear reactor grade graphite (NBG-18 and PCEA). We show that the topological defects in graphite play an important role under neutron and ion irradiation.

Eapen, Jacob; Murty, Korukonda; Burchell, Timothy

2014-06-02T23:59:59.000Z

212

Drift-Diffusion Model of the Fragmentation of the External Ring Structure in the Photoluminescence Pattern Emitted by Indirect Excitons in Coupled Quantum Wells  

Science Journals Connector (OSTI)

Under optical excitation, coupled quantum wells are known to reveal fascinating features in the photoluminescence pattern originating from dipole orientated indirect excitons. The appearance of an external ring has been attributed to macroscopic charge separation in the quantum well plane. We present a classical model of nonlinear diffusion to account for the observed fragmentation of the external ring into a periodic array of islands. The model incorporates the Coulomb interactions between electrons, holes, and indirect excitons. At low temperatures, these interactions lead to pattern formation similar to the experimentally observed ring fragmentation. The fragmentation is found to persist to temperatures above the quantum degeneracy temperature of indirect excitons.

J. Wilkes, E. A. Muljarov, and A. L. Ivanov

2012-10-31T23:59:59.000Z

213

hal-00878684,version1-30Oct2013 ings, deep reservoirs, confined pillars, etc. An accurate mechanical model is especially  

E-Print Network [OSTI]

mechanical model is especially needed in the analysis of damage, aging and degradation phenomena. Following identified by Ortiz (1985), whose model, based on mixture the- ory and damage mechanics, met most Mechanics, introducing phenomenological damage variables. Although damage is inherently a non isotropic

Boyer, Edmond

214

EK424 THERMODYNAMICS AND STATISTICAL MECHANICS (Spring 2013) Thermodynamics is the study of processes (e.g., expansion of a gas, boiling of water, or diffusion  

E-Print Network [OSTI]

EK424 THERMODYNAMICS AND STATISTICAL MECHANICS (Spring 2013) Thermodynamics is the study in order to take place? We will study the thermodynamics of two types of processes: mechanical, or the chemical conversion of glucose into useful work), and a good understanding of thermodynamics is essential

Vajda, Sandor

215

EK424 THERMODYNAMICS AND STATISTICAL MECHANICS (Fall 2013) Thermodynamics is the study of processes (e.g., expansion of a gas, boiling of water, or diffusion  

E-Print Network [OSTI]

EK424 THERMODYNAMICS AND STATISTICAL MECHANICS (Fall 2013) Thermodynamics is the study in order to take place? We will study the thermodynamics of two types of processes: mechanical, or the chemical conversion of glucose into useful work), and a good understanding of thermodynamics is essential

Vajda, Sandor

216

A finite-difference computer model of solute diffusion in bacterial films with simultaneous metabolism and chemical reaction  

Science Journals Connector (OSTI)

......following Reece (1986), half the mean resistance computed at nodes,/ andy -- 1 to give...activity corrections. This fitted with the elementary analytical solution for the equilibrium...Jensen.K.F. (1975) Formation of electric triple layer by intcr- diffusion of......

George H. Dibdin

1992-10-01T23:59:59.000Z

217

Failure Predictions for VHTR Core Components using a Probabilistic Contiuum Damage Mechanics Model  

SciTech Connect (OSTI)

The proposed work addresses the key research need for the development of constitutive models and overall failure models for graphite and high temperature structural materials, with the long-term goal being to maximize the design life of the Next Generation Nuclear Plant (NGNP). To this end, the capability of a Continuum Damage Mechanics (CDM) model, which has been used successfully for modeling fracture of virgin graphite, will be extended as a predictive and design tool for the core components of the very high- temperature reactor (VHTR). Specifically, irradiation and environmental effects pertinent to the VHTR will be incorporated into the model to allow fracture of graphite and ceramic components under in-reactor conditions to be modeled explicitly using the finite element method. The model uses a combined stress-based and fracture mechanics-based failure criterion, so it can simulate both the initiation and propagation of cracks. Modern imaging techniques, such as x-ray computed tomography and digital image correlation, will be used during material testing to help define the baseline material damage parameters. Monte Carlo analysis will be performed to address inherent variations in material properties, the aim being to reduce the arbitrariness and uncertainties associated with the current statistical approach. The results can potentially contribute to the current development of American Society of Mechanical Engineers (ASME) codes for the design and construction of VHTR core components.

Fok, Alex

2013-10-30T23:59:59.000Z

218

Nitrogen Diffusion in Amorphous Silicon Nitride Isotope Multilayers Probed by Neutron Reflectometry  

Science Journals Connector (OSTI)

Amorphous silicon nitride is a model system for a covalently bound amorphous solid with a low atomic mobility where reasonable values of self-diffusivities are still lacking. We used neutron reflectometry on isotope enriched Si3?N414/Si3?N415 multilayers to determine nitrogen self-diffusivities ranging from 10-24 to 10-21??m2/s between 950 and 1250?°C. Time dependent diffusivities observed at 1150?°C indicate the presence of structural relaxation. For long annealing times (relaxed state) the diffusivities follow an Arrhenius law with an activation enthalpy of (3.6±0.4)??eV. The results are indicative of a direct diffusion mechanism without the involvement of thermal point defects.

H. Schmidt; M. Gupta; M. Bruns

2006-02-07T23:59:59.000Z

219

Nitrogen Diffusion in Amorphous Silicon Nitride Isotope Multilayers Probed by Neutron Reflectometry  

SciTech Connect (OSTI)

Amorphous silicon nitride is a model system for a covalently bound amorphous solid with a low atomic mobility where reasonable values of self-diffusivities are still lacking. We used neutron reflectometry on isotope enriched Si{sub 3} {sup 14}N{sub 4}/Si{sub 3} {sup 15}N{sub 4} multilayers to determine nitrogen self-diffusivities ranging from 10{sup -24} to 10{sup -21} m{sup 2}/s between 950 and 1250 deg. C. Time dependent diffusivities observed at 1150 deg. C indicate the presence of structural relaxation. For long annealing times (relaxed state) the diffusivities follow an Arrhenius law with an activation enthalpy of (3.6{+-}0.4) eV. The results are indicative of a direct diffusion mechanism without the involvement of thermal point defects.

Schmidt, H.; Gupta, M.; Bruns, M. [AG Thermochemie und Mikrokinetik, Fakultaet fuer Natur-und Materialwissenschaften, TU Clausthal, D-38678 Clausthal-Zellerfeld (Germany); Laboratory for Neutron Scattering, ETH Zuerich and PSI, Paul Scherrer Institute, Villigen, CH-5232 (Switzerland); Institut fuer Instrumentelle Analytik, Forschungszentrum Karlsruhe GmbH, D-76021 Karlsruhe (Germany)

2006-02-10T23:59:59.000Z

220

Diffusion of Ca and Mg in Calcite  

SciTech Connect (OSTI)

The self-diffusion of Ca and the tracer diffusion of Mg in calcite have been experimentally measured using isotopic tracers of {sup 25}Mg and {sup 44}Ca. Natural single crystals of calcite were coated with a thermally-sputtered oxide thin film and then annealed in a CO{sub 2} gas at one atmosphere total pressure and temperatures from 550 to 800 C. Diffusion coefficient values were derived from the depth profiles obtained by ion microprobe analysis. The resultant activation energies for Mg tracer diffusion and Ca self-diffusion are respectively: E{sub a}(Mg) = 284 {+-} 74 kJ/mol and E{sub a}(Ca) = 271 {+-} 80 kJ/mol. For the temperature ranges in these experiments, the diffusion of Mg is faster than Ca. The results are generally consistent in magnitude with divalent cation diffusion rates obtained in previous studies and provide a means of interpreting the thermal histories of carbonate minerals, the mechanism of dolomitization, and other diffusion-controlled processes. The results indicate that cation diffusion in calcite is relatively slow and cations are the rate-limiting diffusing species for the deformation of calcite and carbonate rocks. Application of the calcite-dolomite geothermometer to metamorphic assemblages will be constrained by cation diffusion and cooling rates. The direct measurement of Mg tracer diffusion in calcite indicates that dolomitization is unlikely to be accomplished by Mg diffusion in the solid state but by a recrystallization process.

Cygan, R.T.; Fisler, D.K.

1999-02-10T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" from the National Library of EnergyBeta (NLEBeta).
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221

Simple solar spectral model for direct and diffuse irradiance on horizontal and tilted planes at the earth's surface for cloudless atmospheres  

SciTech Connect (OSTI)

A new, simple model for calculating clear-sky direct and diffuse spectral irradiance on horizontal and tilted surfaces is presented. The model is based on previously reported simple algorithms and on comparisons with rigorous radiative transfer calculations and limited outdoor measurements. Equations for direct normal irradiance are outlined; and include: Raleigh scattering; aerosol scattering and absorption; water vapor absorption; and ozone and uniformly mixed gas absorption. Inputs to the model include solar zenith angle, collector tilt angle, atmospheric turbidity, amount of ozone and precipitable water vapor, surface pressure, and ground albedo. The model calculates terrestrial spectra from 0.3 to 4.0 ..mu..m with approximately 10 nm resolution. A major goal of this work is to provide researchers with the capability to calculate spectral irradiance for different atmospheric conditions and different collector geometries using microcomputers. A listing of the computer program is provided.

Bird, R.; Riordan, C.

1984-12-01T23:59:59.000Z

222

Shell model nuclear matrix elements for competing mechanisms contributing to double beta decay  

SciTech Connect (OSTI)

Recent progress in the shell model approach to the nuclear matrix elements for the double beta decay process are presented. This includes nuclear matrix elements for competing mechanisms to neutrionless double beta decay, a comparison between closure and non-closure approximation for {sup 48}Ca, and an updated shell model analysis of nuclear matrix elements for the double beta decay of {sup 136}Xe.

Horoi, Mihai [Department of Physics, Central Michigan University, Mount Pleasant, Michigan, 48859 (United States)

2013-12-30T23:59:59.000Z

223

Highly Unstable Double-Diffusive Finger Convection in a Hele-Shaw Cell: Baseline Experimental Data for Evaluation of Numerical Models  

SciTech Connect (OSTI)

An experimental investigation was conducted to study double-diffusive finger convection in a Hele-Shaw cell by layering a sucrose solution over a more-dense sodium chloride (NaCl) solution. The solutal Rayleigh numbers were on the order of 60,000, based upon the height of the cell (25 cm), and the buoyancy ratio was 1.2. A full-field light transmission technique was used to measure a dye tracer dissolved in the NaCl solution. They analyze the concentration fields to yield the temporal evolution of length scales associated with the vertical and horizontal finger structure as well as the mass flux. These measures show a rapid progression through two early stages to a mature stage and finally a rundown period where mass flux decays rapidly. The data are useful for the development and evaluation of numerical simulators designed to model diffusion and convection of multiple components in porous media. The results are useful for correct formulation at both the process scale (the scale of the experiment) and effective scale (where the lab-scale processes are averaged-up to produce averaged parameters). A fundamental understanding of the fine-scale dynamics of double-diffusive finger convection is necessary in order to successfully parameterize large-scale systems.

PRINGLE,SCOTT E.; COOPER,CLAY A.; GLASS JR.,ROBERT J.

2000-12-21T23:59:59.000Z

224

Hydro-Mechanical Coupling in Damaged Porous Media Containing Isolated Cracks or/and Vugs: Model and Computations  

E-Print Network [OSTI]

Hydro-Mechanical Coupling in Damaged Porous Media Containing Isolated Cracks or/and Vugs: Model In this paper we present the development of the macroscopic model describing the hydro-mechanical coupling model in the micro-porous domain saturated by a fluid. In the crack/vug domain the Stokes equation

Paris-Sud XI, Université de

225

Macroscopic corrosion front computations of sulfate attack in sewer pipes based on a micro-macro reaction-diffusion model  

E-Print Network [OSTI]

We consider a two-scale reaction diffusion system able to capture the corrosion of concrete with sulfates. Our aim here is to define and compute two macroscopic corrosion indicators: typical pH drop and gypsum profiles. Mathematically, the system is coupled, endowed with micro-macro transmission conditions, and posed on two different spatially-separated scales: one microscopic (pore scale) and one macroscopic (sewer pipe scale). We use a logarithmic expression to compute values of pH from the volume averaged concentration of sulfuric acid which is obtained by resolving numerically the two-scale system (microscopic equations with direct feedback with the macroscopic diffusion of one of the reactants). Furthermore, we also evaluate the content of the main sulfatation reaction (corrosion) product---the gypsum---and point out numerically a persistent kink in gypsum's concentration profile. Finally, we illustrate numerically the position of the free boundary separating corroded from not-yet-corroded regions.

Chalupecký, Vladimír; Kruschwitz, Jens; Muntean, Adrian

2012-01-01T23:59:59.000Z

226

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

227

MODEL OF MECHANISM BEHAVIOR FOR VERIFICATION OF PLC Jos M. Machado  

E-Print Network [OSTI]

MODEL OF MECHANISM BEHAVIOR FOR VERIFICATION OF PLC PROGRAMS José M. Machado University of Minho on formal methods is now available for checking PLC (Programmable Logic Controller) programs. To verify a PLC program, it is necessary to consider a set of properties to prove and one of the most interesting

Paris-Sud XI, Université de

228

Rotary Electrodynamics of a DC Motor: Motor as Mechanical Capacitor Lab 2: Modeling and System Identification  

E-Print Network [OSTI]

). · im is the current through the motor. Because the motor is in series with all other electrical). Because power is conserved, m = Kmim (motor efficiency is actually closer to 69%). Here, Km 0.00767 VRotary Electrodynamics of a DC Motor: Motor as Mechanical Capacitor Lab 2: Modeling and System

229

Towards Model-Based Estimation of the Cardiac Electro-Mechanical Activity from ECG Signals  

E-Print Network [OSTI]

Towards Model-Based Estimation of the Cardiac Electro-Mechanical Activity from ECG Signals by comparing the actual patient's ECG with computational results and the deformation of the biomechani- cal-to-access measurements on a patient: the ECG (Electrocardiogram), and a time sequence of volumetric ultrasound images

Coudière, Yves

230

IMPROVING THE PREDICTIVE POWER OF MODELING THE EMITTER DIFFUSION BY FULLY INCLUDING THE PHOSPHSILICATE GLASS (PSG) LAYER  

E-Print Network [OSTI]

of the phosphosilicate glass, and how the glass feeds the phosphorus into the silicon for diffusion. Due to this lack, we, phosphosilicate glass (PSG) is formed. The glass is a mixture of phosphorus pentoxide (P2O5) and silicon dioxide THE PHOSPHSILICATE GLASS (PSG) LAYER H. Wagner 1 , A. Dastgheib-Shirazi 2 , R. Chen 3 , S.T. Dunham 3 , M. Kessler 4

231

Lumped thermal model for switched reluctance motor applied to mechanical design optimization  

Science Journals Connector (OSTI)

Switched reluctance motors (SRM) are attracting much attention because of their special advantages. Generated heat, due to losses, can reduce the life time of SRMs. Therefore, taking into account thermal modeling helps to improve their performance and increase their life time. In this paper, a lumped thermal model of SRM based on the analogue circuit of conductive and convective thermal resistances is proposed. First the heat transfer equations were applied for modeling of each motor part as a thermal equivalent circuit. Then, the thermal modeling of whole SRM was done via assembling all these sub-circuits. For validity of the obtained model on a wide range of geometrical and structural properties of motor, apt heat transfer relations have been used. This comprehensive model is used to investigate the influence of dimensions on heat transfer in SRM. Finally, an optimal design of the stator yoke dimensions has been reached concerning the mechanical aspects without degrading electromagnetic characteristics of SRM.

Hossein Rouhani; Jawad Faiz; Caro Lucas

2007-01-01T23:59:59.000Z

232

Comments on Diffusion of Kr Isotopes in Solid Ar  

Science Journals Connector (OSTI)

Recently, the isotope effect for Kr diffusion in Ar was found to be f?K?0. 48. The results are consistent with a divacancy diffusion mechanism with ?K?1.

J. J. Burton

1970-10-15T23:59:59.000Z

233

Moisture Diffusion in Asphalt Binders and Fine Aggregate Mixtures  

E-Print Network [OSTI]

cost in highway maintenance and vehicle operations. One key mechanism of how moisture reaches the asphalt-aggregate interface is by its permeation or diffusion through the asphalt binder or mastic. Different techniques are available for diffusion...

Vasconcelos, Kamilla L.

2011-08-08T23:59:59.000Z

234

THE FERMI BUBBLES. II. THE POTENTIAL ROLES OF VISCOSITY AND COSMIC-RAY DIFFUSION IN JET MODELS  

SciTech Connect (OSTI)

The origin of the Fermi bubbles recently detected by the Fermi Gamma-ray Space Telescope in the inner Galaxy is mysterious. In the companion paper Guo and Mathews (Paper I), we use hydrodynamic simulations to show that they could be produced by a recent powerful active galactic nucleus (AGN) jet event. Here, we further explore this scenario to study the potential roles of shear viscosity and cosmic-ray (CR) diffusion on the morphology and CR distribution of the bubbles. We show that even a relatively low level of viscosity ({mu}{sub visc} {approx}> 3 g cm{sup -1} s{sup -1}, or {approx}0.1%-1% of Braginskii viscosity in this context) could effectively suppress the development of Kelvin-Helmholtz instabilities at the bubble surface, resulting in smooth bubble edges as observed. Furthermore, viscosity reduces circulating motions within the bubbles, which would otherwise mix the CR-carrying jet backflow near bubble edges with the bubble interior. Thus viscosity naturally produces an edge-favored CR distribution, an important ingredient to produce the observed flat gamma-ray surface brightness distribution. Generically, such a CR distribution often produces a limb-brightened gamma-ray intensity distribution. However, we show that by incorporating CR diffusion that is strongly suppressed across the bubble surface (as inferred from sharp bubble edges) but is close to canonical values in the bubble interior, we obtain a reasonably flat gamma-ray intensity profile. The similarity of the resulting CR bubble with the observed Fermi bubbles strengthens our previous result in Paper I that the Fermi bubbles were produced by a recent AGN jet event. Studies of the nearby Fermi bubbles may provide a unique opportunity to study the potential roles of plasma viscosity and CR diffusion on the evolution of AGN jets and bubbles.

Guo Fulai; Mathews, William G. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Dobler, Gregory [Kavli Institute for Theoretical Physics, University of California, Santa Barbara Kohn Hall, Santa Barbara, CA 93106 (United States); Oh, S. Peng, E-mail: fulai@ucolick.org [Department of Physics, University of California, Santa Barbara Kohn Hall, Santa Barbara, CA 93106 (United States)

2012-09-10T23:59:59.000Z

235

Copper diffusion in single-crystal ?-Zr  

Science Journals Connector (OSTI)

Tracer diffusion of Cu64 in ?-Zr single crystals has been measured in the temperature range (615-860)°C. The temperature dependences of the Cu64 diffusion coefficients in directions parallel to and perpendicular to the c axis are given by D?=0.40e-1.54 eVkT and D?=0.25e-1.60 eVkT cm2/sec, respectively. The results are discussed in terms of an interstitial diffusion mechanism.

G. M. Hood and R. J. Schultz

1975-05-15T23:59:59.000Z

236

Implementation and Application of SAPRC07 and MCM Mechanisms in the Multi-scale Community Air Quality Model  

E-Print Network [OSTI]

mechanism. In this study, two state-of-the-science photochemical mechanisms, SAPRC07 and Master Chemical Mechanism (MCM) v3.1, were implemented in the Community Multi-scale Air Quality Model (CMAQ) version 4.6 developed by the US EPA to study a high ozone (O...

Li, Jingyi

2012-02-14T23:59:59.000Z

237

Modeling the coupled mechanics, transport, and growth processes in collagen tissues.  

SciTech Connect (OSTI)

The purpose of this project is to develop tools to model and simulate the processes of self-assembly and growth in biological systems from the molecular to the continuum length scales. The model biological system chosen for the study is the tendon fiber which is composed mainly of Type I collagen fibrils. The macroscopic processes of self-assembly and growth at the fiber scale arise from microscopic processes at the fibrillar and molecular length scales. At these nano-scopic length scales, we employed molecular modeling and simulation method to characterize the mechanical behavior and stability of the collagen triple helix and the collagen fibril. To obtain the physical parameters governing mass transport in the tendon fiber we performed direct numerical simulations of fluid flow and solute transport through an idealized fibrillar microstructure. At the continuum scale, we developed a mixture theory approach for modeling the coupled processes of mechanical deformation, transport, and species inter-conversion involved in growth. In the mixture theory approach, the microstructure of the tissue is represented by the species concentration and transport and material parameters, obtained from fibril and molecular scale calculations, while the mechanical deformation, transport, and growth processes are governed by balance laws and constitutive relations developed within a thermodynamically consistent framework.

Holdych, David J.; Nguyen, Thao D.; Klein, Patrick A.; in't Veld, Pieter J.; Stevens, Mark Jackson

2006-11-01T23:59:59.000Z

238

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

SciTech Connect (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

239

Thermal Particle Injection in Nonlinear Diffusive Shock Acceleration  

E-Print Network [OSTI]

Particle acceleration in collisionless astrophysical shocks, i.e., diffusive shock acceleration (DSA), is the most likely mechanism for producing cosmic rays, at least below 10^{15} eV. Despite the success of this theory, several key elements, including the injection of thermal particles, remains poorly understood. We investigate injection in strongly nonlinear shocks by comparing a semi-analytic model of DSA with a Monte Carlo model. These two models treat injection quite differently and we show, for a particular set of parameters, how these differences influence the overall acceleration efficiency and the shape of the broad-band distribution function.

Donald C. Ellison; Pasquale Blasi; Stefano Gabici

2005-07-05T23:59:59.000Z

240

Models of stochastic, spatially varying stress in the crust compatible with focal mechanism data Smith and Heaton 1  

E-Print Network [OSTI]

Models of stochastic, spatially varying stress in the crust compatible with focal mechanism data, spatially varying stress in the crust compatible with focal mechanism data ­ Smith and Heaton 3 Introduction ­ Smith and Heaton 1 Models of stochastic, spatially varying stress in the crust compatible with focal

Greer, Julia R.

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Thermo-Hydrological-Mechanical Analysis of a Clay Barrier for Radioactive Waste Isolation: Probabilistic Calibration and Advanced Modeling  

E-Print Network [OSTI]

............................................................................. 129 5.2 Micro Structural Model .............................................................................. 136 5.3 Interaction Between Micro and Macro Structures ..................................... 138 6. MODELING OF FULL SCALE FEBEX INSITU... Conditions .................................................... 154 6.2.4 Results of Thermo-Hydro-Mechanical Analysis ............................ 156 6.2.5 Analysis of Mechanical Behavior .................................................. 161 6...

Dontha, Lakshman

2012-07-16T23:59:59.000Z

242

Accelerating and Retarding Anomalous Diffusion  

E-Print Network [OSTI]

In this paper Gaussian models of retarded and accelerated anomalous diffusion are considered. Stochastic differential equations of fractional order driven by single or multiple fractional Gaussian noise terms are introduced to describe retarding and accelerating subdiffusion and superdiffusion. Short and long time asymptotic limits of the mean squared displacement of the stochastic processes associated with the solutions of these equations are studied. Specific cases of these equations are shown to provide possible descriptions of retarding or accelerating anomalous diffusion.

Chai Hok Eab; S. C. Lim

2012-01-14T23:59:59.000Z

243

The diffusion of mobile telephones: An empirical analysis for Peru  

Science Journals Connector (OSTI)

This paper models the diffusion of mobile telephone subscriptions in Peru. Peru's mobile telephone diffusion has occurred in a concentrated market with relatively high prices and as such it features consumer behaviors such as call management, multiple ... Keywords: Diffusion forecasting, Gompertz curve, Mobile telephones, Peru, Technology diffusion

Peter Yamakawa; Gareth H. Rees; José Manuel Salas; Nikolai Alva

2013-07-01T23:59:59.000Z

244

Modeling  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

a single-fluid diffuse interface model in the ALE-AMR hydrodynamics code to simulate surface tension effects. We show simula- tions and compare them to other surface tension...

245

Shortwave, Clear-sky Diffuse Irradiance in the 350 to 1050 nm Range: Comparison of Models with RSS Measurements at the Southern Great Plains ARM Site in September/October 2001  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Shortwave, Clear-Sky Diffuse Irradiance in the Shortwave, Clear-Sky Diffuse Irradiance in the 350 to 1050 nm Range: Comparison of Models with RSS Measurements at the Southern Great Plains ARM Site in September/October 2001 J. J. Michalsky, P. W. Kiedron, Q.-L. Min, and L. C. Harrison Atmospheric Sciences Research Center State University of New York Albany, New York J. J. Michalsky Surface Radiation Research Branch Air Resources Laboratory National Oceanic and Atmospheric Administration Boulder, Colorado Abstract A rotating shadowband spectroradiometer (RSS) operating in the spectral range between 350 to 1050 nm obtained measurements of direct and diffuse components of spectral irradiance during the first diffuse irradiance IOP in the autumn of 2001. Independent measurements of the primary inputs to spectral

246

Modelling the Thermo-Mechanical Behavior of Magnesium Alloys during Indirect Extrusion  

SciTech Connect (OSTI)

One of the basic metal forming process for semi-finished products is extrusion. Since extrusion involves complex thermo-mechanical and multiaxial loading conditions resulting in large strains, high strain rates and an increase in temperature due to deformation, a proper yield criterion and hardening law should be used in the numerical modelling of the process. A phenomenological model based on a plastic potential has been proposed that takes strain, strain rate and temperature dependency on flow behaviour into consideration. A hybrid methodology of experiment and finite element simulation has been adopted in order to obtain necessary model parameters. The anisotropy/asymmetry in yielding was quantified by tensile and compression tests of specimens prepared from different directions. The identification of the corresponding model parameters was performed by a genetic algorithm. A fully coupled thermo-mechanical analysis has been used in extrusion simulations for calculation of the temperature field by considering heat fluxes and heat generated due to plastic deformation. The results of the approach adopted in this study appeared to be successful showing promising predictions of the experiments and thus may be extended to be applicable to other magnesium alloys or even other hcp metals.

Steglich, D. [GKSS Research Centre, Geesthacht (Germany); G.I.F.T., POSTECH, Pohang, Gyeongbuk (Korea, Republic of); Ertuerk, S.; Bohlen, J.; Letzig, D. [GKSS Research Centre, Geesthacht (Germany); Brocks, W. [Faculty of Engineering, Christian-Albrechts-University of Kiel (Germany)

2010-06-15T23:59:59.000Z

247

Evaluation of solar energy resources by establishing empirical models for diffuse solar radiation on tilted surface and analysis for optimum tilt angle for a prospective location in southern region of Sindh, Pakistan  

Science Journals Connector (OSTI)

Abstract Diffuse solar radiation data is very important and is required for solar energy system implementations. The main purpose of the present study is to evaluate solar energy resources by establishing diffuse solar radiation models and obtaining optimum tilt angle fora prospective location is southern region of Sindh, Pakistan. Due to the unavailability of measured diffuse solar radiation data, nine new models, based on available data from local agency and values obtain from existing models, to predict diffuse solar radiation on tilted surface has been established. The best model was chosen based on test results from statistical indicators. The optimum tilt angle for monthly, seasonally, half-yearly and yearly adjustment was determined. The optimum tilt angle varies from 0° in May, June and July to 49° in December. The yearly optimum tilt angle was found as 23°, which is close to latitude of investigated location (25°07?N). The monthly average total, beam and diffuse solar radiations were calculated for optimum and vertical tilted surfaces and were compared with those obtain for horizontal surfaces. The half-yearly adjustment of optimum tilt angle is recommended for the investigated location because very small difference in annual solar energy gains in comparison with monthly or seasonal adjustment. The total annual energy for completer year and for four seasons of the year was calculated and found that maximum total annual energy is obtained at optimum tilt angle.

Shahnawaz Farhan Khahro; Kavita Tabbassum; Shahnawaz Talpur; Mohammad Bux Alvi; Xiaozhong Liao; Lei Dong

2015-01-01T23:59:59.000Z

248

The importance of nuclear spin diffusion as an angularly independent relaxation mechanism controlling the matrix ENDOR response of radicals in molecular crystals  

Science Journals Connector (OSTI)

In the generalized matrix ENDOR line shape model [P.A. Narayana e t a l. J. Chem. Phys. 67 1990 (1977)] the ENDOR intensity is controlled by the nuclear spin lattice relaxation rate formulated as an angularly dependent electron?nuclear dipolar contribution and an angularly independent intrinsic bulk nuclear relaxation contribution. Comparison of this model with single crystal data [L. Kevan e t a l. J. Chem. Phys. 70 5006 (1979)] showed that the angularly independent relaxation rate must be more rapid than the intrinsic bulk nuclear relaxation rate. Here we identify the angularly independent relaxation rate with nuclear spindiffusion and apply this interpretation quantitatively to data on methyl radicals in lithium acetate dihydrate crystals and to the radiation generated CH3CH(NH3)?OOH? radical in alanine at 77 K.

Shulamith Schlick; Larry Kevan; K. Toriyama; M. Iwasaki

1981-01-01T23:59:59.000Z

249

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

SciTech Connect (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

250

A fully resolved active musculo-mechanical model for esophageal transport  

E-Print Network [OSTI]

Esophageal transport is a physiological process that mechanically transports an ingested food bolus from the pharynx to the stomach via the esophagus, a multi-layered muscular tube. This process involves interactions between the bolus, the esophagus, and the neurally coordinated activation of the esophageal muscles. In this work, we use an immersed boundary (IB) approach to simulate peristaltic transport in the esophagus. The bolus is treated as a viscous fluid that is actively transported by the muscular esophagus, which is modeled as an actively contracting, fiber-reinforced tube. A simplified version of our model is verified by comparison to an analytic solution to the tube dilation problem. Three different complex models of the multi-layered esophagus, which differ in their activation patterns and the layouts of the mucosal layers, are then extensively tested. To our knowledge, these simulations are the first of their kind to incorporate the bolus, the multi-layered esophagus tube, and muscle activation i...

Kou, Wenjun; Griffith, Boyce E; Pandolfino, John E; Kahrilas, Peter J; Patankar, Neelesh A

2015-01-01T23:59:59.000Z

251

Numerical Modeling Studies of The Dissolution-Diffusion-Convection ProcessDuring CO2 Storage in Saline Aquifers  

SciTech Connect (OSTI)

For purposes of geologic storage, CO2 would be injected into saline formations at supercritical temperature and pressure conditions, and would form a separate phase that is immiscible with the aqueous phase (brine). At typical subsurface temperature and pressure conditions, supercritical CO2 (scCO2) has lower density than the aqueous phase and would experience an upward buoyancy force. Accordingly, the CO2 is expected to accumulate beneath the caprock at the top of the permeable interval, and could escape from the storage formation wherever (sub-)vertical pathways are available, such as fractures or faults through the caprock, or improperly abandoned wells. Over time, an increasing fraction of CO2 may dissolve in the aqueous phase, and eventually some of the aqueous CO2 may react with rock minerals to form poorly soluble carbonates. Dissolution into the aqueous phase and eventual sequestration as carbonates are highly desirable processes as they would increase permanence and security of storage. Dissolution of CO2 will establish phase equilibrium locally between the overlying CO2 plume and the aqueous phase beneath. If the aqueous phase were immobile, CO2 dissolution would be limited by the rate at which molecular diffusion can remove dissolved CO2 from the interface between CO2-rich and aqueous phases. This is a slow process. However, dissolution of CO2 is accompanied by a small increase in the density of the aqueous phase, creating a negative buoyancy force that can give rise to downward convection of CO2-rich brine, which in turn can greatly accelerate CO2 dissolution. This study explores the process of dissolution-diffusion-convection (DDC), using high-resolution numerical simulation. We find that geometric features of convection patterns are very sensitive to small changes in problem specifications, reflecting self-enhancing feedbacks and the chaotic nature of the process. Total CO2 dissolution rates on the other hand are found to be quite robust against modest changes in problem parameters, and are essentially constant as long as no dissolved CO2 reaches the lower boundary of the system.

Pruess, Karsten; Zhang, Keni

2008-11-17T23:59:59.000Z

252

Compensatory mechanisms in fish populations: Literature reviews: Volume 3, A critical review of mathematical models for fish compensation mechanisms: Final report  

SciTech Connect (OSTI)

A critical review of population dynamics models was performed to describe previous models and to recommend approaches for future research on compensation in fish population. The models were first classified into five categories, i.e., theoretical, stock-recruitment, biomass (bioenergetic), population (number), and life cycle functions. Models in each category were then reviewed for their formulations, assumptions, limitations, and performances. A majority of the models were found to have been formulated to calculate parameters that could not be directly measured. Models developed to evaluate entrainment and impingement impacts were often applied without validation against observed data. To advance the scientific understanding of fish compensation mechanisms, future research should include complimentary studies in both model development and empirical observation. Modeling will provide a theoretical framework to integrate individual compensation mechanisms and to relate them to population level responses. Empirical observation, on the other hand, will furnish data to verify the theory. The fish compensation model should use a cohort representation that allows the incorporation of the relationships between life cycle processes and environmental conditions. Growth and mortality of fish in early life stages should be related to weather, hydrology, temperature and food in addition to competition and predation. Environmental data with an inherent stochasticity should be used as input to produce verifiable real time variations in year class strength.

Chen, C.W.

1987-05-01T23:59:59.000Z

253

Mechanical defradation of Emplacement Drifts at Yucca Mountain- A Modeling Case Study. Part I: Nonlithophysal Rock  

SciTech Connect (OSTI)

This paper outlines rock mechanics investigations associated with mechanical degradation of planned emplacement drifts at Yucca Mountain, which is the designated site for the proposed U.S. high-level nuclear waste repository. The factors leading to drift degradation include stresses from the overburden, stresses induced by the heat released from the emplaced waste, stresses due to seismically related ground motions, and time-dependent strength degradation. The welded tuff emplacement horizon consists of two groups of rock with distinct engineering properties: nonlithophysal units and lithophysal units, based on the relative proportion of lithophysal cavities. The term 'lithophysal' refers to hollow, bubble like cavities in volcanic rock that are surrounded by a porous rim formed by fine-grained alkali feldspar, quartz, and other minerals. Lithophysae are typically a few centimeters to a few decimeters in diameter. Part I of the paper concentrates on the generally hard, strong, and fractured nonlithophysal rock. The degradation behavior of the tunnels in the nonlithophysal rock is controlled by the occurrence of keyblocks. A statistically equivalent fracture model was generated based on extensive underground fracture mapping data from the Exploratory Studies Facility at Yucca Mountain. Three-dimensional distinct block analyses, generated with the fracture patterns randomly selected from the fracture model, were developed with the consideration of in situ, thermal, and seismic loads. In this study, field data, laboratory data, and numerical analyses are well integrated to provide a solution for the unique problem of modeling drift degradation.

M. Lin; D. Kicker; B. Damjanac; M. Board; M. Karakouzian

2006-07-05T23:59:59.000Z

254

Two-dimensional nonlinear advection?diffusion in a model of surfactant spreading on a thin liquid film  

Science Journals Connector (OSTI)

......Grotberg, 1994; Halpern et al., 1998), notably as a vehicle for drug delivery. + Present address: Department of Biomedical...mathematical model for the transport and spreading of oil slicks. Ecological Model. 22, 325 - 339. O ' B RIEN, S. B. G. M 1993 On......

H. A. R. Williams; O. E. Jensen

2001-01-01T23:59:59.000Z

255

Hydro-mechanical modelling of geological CO2 storage and the study of possible caprock fracture mechanisms  

E-Print Network [OSTI]

to tensile stresses is treated. The stress intensity factor is used as the driving parameter describing mechanisms N. Guy,1-2 D.M. Seyedi,1 F. Hild2 BRGM, Natural Risks & CO2 Storage Safety Division, 3 av. Claude studies have shown that gas injection into deep permeable formations induce changes of the total

256

Microstructure and Mechanical Properties of n-irradiated Fe-Cr Model Alloys  

SciTech Connect (OSTI)

High chromium ( 9-12 wt %) ferritic/martensitic steels are candidate structural materials for future fusion reactors and other advanced systems such as accelerator driven systems (ADS). Their use for these applications requires a careful assessment of their mechanical stability under high energy neutron irradiation and in aggressive environments. In particular, the Cr concentration has been shown to be a key parameter to be optimized in order to guarantee the best corrosion and swelling resistance, together with the least embrittlement. In this work, the characterization of the neutron irradiated Fe-Cr model alloys with different Cr % with respect to microstructure and mechanical tests will be presented. The behavior of Fe-Cr alloys have been studied using tensile tests at different temperature range ( from -160 deg. C to 300 deg. C). Irradiation-induced microstructure changes have been studied by TEM for two different irradiation doses at 300 deg. C. The density and the size distribution of the defects induced have been determined. The tensile test results indicate that Cr content affects the hardening behavior of Fe-Cr binary alloys. Hardening mechanisms are discussed in terms of Orowan type of approach by correlating TEM data to the measured irradiation hardening. (authors)

Matijasevic, Milena; Al Mazouzi, Abderrahim [Reactor materials research, SCK-CEN, Mol (Belgium)

2008-07-01T23:59:59.000Z

257

On a 2D hydro-mechanical lattice approach for modelling hydraulic fracture  

E-Print Network [OSTI]

A 2D lattice approach to describe hydraulic fracturing is presented. The interaction of fluid pressure and mechanical response is described by Biot's theory. The lattice model is applied to the analysis of a thick-walled cylinder, for which an analytical solution for the elastic response is derived. The numerical results obtained with the lattice model agree well with the analytical solution. Furthermore, the coupled lattice approach is applied to the fracture analysis of the thick-walled cylinder. It is shown that the proposed lattice approach provides results that are independent of the mesh size. Moreover, a strong geometrical size effect on nominal strength is observed which lies between analytically derived lower and upper bounds. This size effect decreases with increasing Biot's coefficient.

Grassl, Peter; Gallipoli, Domenico; Wheeler, Simon J

2014-01-01T23:59:59.000Z

258

A Dual Model-Free Control of Underactuated Mechanical Systems, Application to The Inertia Wheel Inverted Pendulum  

E-Print Network [OSTI]

A Dual Model-Free Control of Underactuated Mechanical Systems, Application to The Inertia Wheel underac- tuated mechanical system: the inertia wheel inverted pendulum. Numerical simulations as well: the ball and beam [9] (where the dynamics of the beam has not been taken into account) and the Planar

Paris-Sud XI, Université de

259

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

E-Print Network [OSTI]

with hydrogen embrittlement represents a particu- larly severe degradation mechanism in metallic structures and compressors, despite the fact that they can be extremely susceptible to such hydrogen embrittlementA statistical, physical-based, micro-mechanical model of hydrogen-induced intergranular fracture

Ritchie, Robert

260

Subgrid-Scale Mixing in Climate Models: A Novel Look at Diffusion, Accuracy, Stability and Climate Sensitivity  

SciTech Connect (OSTI)

This project focuses on evaluating the role of subgrid-scale dissipation in the dynamical core of atmospheric models. All dynamical cores of atmospheric general circulation models (GCMs) employ some form of subgrid-scale dissipation, either explicitly specified or inherent in the chosen numerical schemes. The dissipation processes are needed to keep the simulation stable or to satisfy important physical properties, and the hope is that they capture and mimic in some poorly understood way the true processes at the unresolved subgrid scale. There is no physical basis that such dissipation can accomplish this. We originally posed a set of numerical test cases chosen or designed to isolate the role of the filters and fixers on both the dynamical variables (pressure, temperature, velocity, vorticity) and trace constituents. From these test case results, we synthesize the information to determine the impact of the subgrid-scale assumptions on weather and climate models.

Rood, Richard B; Jablonowski, Christiane

2012-10-31T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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.


261

Sensitivity of climate change to diapycnal diffusivity in the ocean  

E-Print Network [OSTI]

The diapycnal diffusivity of the ocean is one of the least known parameters in cur- rent climate models. Measurements of this diffusivity are sparse and insufficient for compiling a global map. Inferences from inverse ...

Dalan, Fabio, 1975-

2003-01-01T23:59:59.000Z

262

Mechanical Response and Decomposition of Thermally Degraded Energetic Materials: Experiments and Model Simulations  

SciTech Connect (OSTI)

We report progress of a continuing effort to characterize and simulate the response of energetic materials (EMs), primarily HMX-based, under conditions leading to cookoff. Our experiments include mechanical-effects testing of HMX and FIMX with binder at temperatures nearing decomposition thresholds. Additional experiments have focused on decomposition of these EMs under confinement, measuring evolution of gas products and observing the effect of pressurization on the solid. Real-time measurements on HMX show abrupt changes that maybe due to sudden void collapse under increasing load. Postmortem examination shows significant internal damage to the pellets, including voids and cracks. These experiments have been used to help develop a constitutive model for pure HMX. Unconfined uniaxial compression tests were performed on HMX and LX-14 to examine the effect of binders on the deviatoric strength of EM pellets, and to assess the need of including deviatoric terms in the model. A scale-up experiment will be described that is being developed to validate the model and provide additional diagnostics.

KANESHIGE,MICHAEL J.; RENLUND,ANITA M.; SCHMITT,ROBERT G.; WELLMAN,GERALD W.

1999-10-14T23:59:59.000Z

263

Laser-enhanced diffusion of nitrogen and aluminum dopants in silicon carbide  

Science Journals Connector (OSTI)

The diffusivities of different types of dopant atoms in silicon carbide wafers are generally very low. Nd:YAG and excimer lasers have been used to dope silicon carbide with nitrogen and aluminum, respectively. Mathematical models have been presented for the temperature distributions in the wafers to understand the diffusion mechanisms in the laser doping process. Since the silicon carbide substrate reaches its peritectic temperature (3100 K) at irradiances of 80.6 and 61 MW/cm2 for Nd:YAG and excimer lasers, respectively, lower irradiances were used to achieve solid-state diffusion. The Nd:YAG laser doping process doped nitrogen to a depth of 800 nm; the KrF excimer laser doping process produced aluminum dopant depths of 200 and 450 nm for different numbers of laser pulses. Two distinct diffusion regions, near-surface and far-surface regions, were identified in the dopant concentration profiles, indicating different diffusion mechanisms in these two regions. The effective diffusion coefficients of nitrogen and aluminum were determined for both regions and found to be 2.4 × 10?5 and 9.2 × 10?6 cm2/s in the near- and far-surface regions for nitrogen, respectively, and 1.2 × 10?5 and 1.3 × 10?6 cm2/s in the near- and far-surface regions for aluminum, respectively. The calculated diffusivities are at least six orders of magnitude higher than the typical values for nitrogen and aluminum, which indicate that the laser doping process enhances significantly the diffusion of dopants in silicon carbide.

Z. Tian; N.R. Quick; A. Kar

2006-01-01T23:59:59.000Z

264

Three-body Interactions Improve the Prediction of Rate and Mechanism in Protein Folding Models  

E-Print Network [OSTI]

Here we study the effects of many-body interactions on rate and mechanism in protein folding, using the results of molecular dynamics simulations on numerous coarse-grained C-alpha-model single-domain proteins. After adding three-body interactions explicitly as a perturbation to a Go-like Hamiltonian with native pair-wise interactions only, we have found 1) a significantly increased correlation with experimental phi-values and folding rates, 2) a stronger correlation of folding rate with contact order, matching the experimental range in rates when the fraction of three-body energy in the native state is ~ 20%, and 3) a considerably larger amount of 3-body energy present in Chymotripsin inhibitor than other proteins studied.

M. R. Ejtehadi; S. P. Avall; S. S. Plotkin

2004-07-14T23:59:59.000Z

265

Commercial Building Partnerships Replication and Diffusion  

SciTech Connect (OSTI)

This study presents findings from survey and interview data investigating replication efforts of Commercial Building Partnership (CBP) partners that worked directly with the Pacific Northwest National Laboratory (PNNL). PNNL partnered directly with 12 organizations on new and retrofit construction projects, which represented approximately 28 percent of the entire U.S. Department of Energy (DOE) CBP program. Through a feedback survey mechanism, along with personal interviews, PNNL gathered quantitative and qualitative data relating to replication efforts by each organization. These data were analyzed to provide insight into two primary research areas: 1) CBP partners’ replication efforts of technologies and approaches used in the CBP project to the rest of the organization’s building portfolio (including replication verification), and, 2) the market potential for technology diffusion into the total U.S. commercial building stock, as a direct result of the CBP program. The first area of this research focused specifically on replication efforts underway or planned by each CBP program participant. Factors that impact replication include motivation, organizational structure and objectives firms have for implementation of energy efficient technologies. Comparing these factors between different CBP partners revealed patterns in motivation for constructing energy efficient buildings, along with better insight into market trends for green building practices. The second area of this research develops a diffusion of innovations model to analyze potential broad market impacts of the CBP program on the commercial building industry in the United States.

Antonopoulos, Chrissi A.; Dillon, Heather E.; Baechler, Michael C.

2013-09-16T23:59:59.000Z

266

Diffusive Accumulation of Methane Bubbles in Seabed  

E-Print Network [OSTI]

We consider seabed bearing methane bubbles. In the absence of fractures the bubbles are immovably trapped in a porous matrix by surface tension forces; therefore the dominant mechanism of transfer of gas mass becomes the diffusion of gas molecules through the liquid. The adequate description of this process requires accounting "other-than-normal" (non-Fickian) diffusion effects, thermodiffusion and gravity action. We evaluate the diffusive flux of aqueous methane and predict the possibility of existence of bubble mass accumulation zones (which can appear independently from the presence/absence of hydrate stability zone) and effect of non-Fickian drift on the capacity of shallow and deep methane-hydrate deposits.

Goldobin, D S; Levesley, J; Lovell, M A; Rochelle, C A; Jackson, P; Haywood, A; Hunter, S; Rees, J

2010-01-01T23:59:59.000Z

267

A model for a G-protein-mediated mechanism for synaptic channel modulation  

E-Print Network [OSTI]

of a feedback loop involving cytoplasmic calcium, neurotransmitters and G-protein-coupled receptors. We study from vesicles in a calcium-depen- dent manner, and the neurotransmitter diffuses across the synaptic potential. Calcium is a critical component of the release process, and its spatio-temporal dynamics can

Othmer, Hans

268

Characterizing unsaturated diffusion in porous tuff gravel  

SciTech Connect (OSTI)

Evaluation of solute diffusion in unsaturated porous gravel is very important for investigations of contaminant transport and remediation, risk assessment, and waste disposal (for example, the potential high-level nuclear waste repository at Yucca Mountain, Nevada). For a porous aggregate medium such as granular tuff, the total water content is comprised of surface water and interior water. The surface water component (water film around grains and pendular water between the grain contacts) could serve as a predominant diffusion pathway. To investigate the extent to which surface water films and contact points affect solute diffusion in unsaturated gravel, we examined the configuration of water using x-ray computed tomography in partially saturated gravel, and made quantitative measurements of diffusion at multiple water contents using two different techniques. In the first, diffusion coefficients of potassium chloride in 2-4 mm granular tuff at multiple water contents were calculated from electrical conductivity measurements using the Nernst-Einstein equation. In the second, we used laser ablation with inductively coupled plasma-mass spectrometry to perform micro-scale mapping, allowing the measurement of diffusion coefficients for a mixture of chemical tracers for tuff cubes and tetrahedrons having two contact geometries (cube-cube and cube-tetrahedron). The x-ray computed tomography images show limited contact between grains, and this could hinder the pathways for diffusive transport. Experimental results show the critical role of surface water in controlling transport pathways and hence the magnitude of diffusion. Even with a bulk volumetric water content of 1.5%, the measured solute diffusion coefficient is as low as 1.5 x 10{sup -14} m{sup 2}/s for tuff gravel. Currently used diffusion models relating diffusion coefficients to total volumetric water content inadequately describe unsaturated diffusion behavior in porous gravel at very low water contents.

Hu, Qinhong; Kneafsey, Timothy J.; Roberts, Jeffery J.; Tomutsa, Liviu; Wang, Joseph, S.Y.

2003-11-12T23:59:59.000Z

269

Modeling of short-term mechanism of arterial pressure control in the cardiovascular system: Object-oriented and acausal approach  

Science Journals Connector (OSTI)

Abstract This letter introduces an alternative approach to modeling the cardiovascular system with a short-term control mechanism published in Computers in Biology and Medicine, Vol. 47 (2014), pp. 104–112. We recommend using abstract components on a distinct physical level, separating the model into hydraulic components, subsystems of the cardiovascular system and individual subsystems of the control mechanism and scenario. We recommend utilizing an acausal modeling feature of Modelica language, which allows model variables to be expressed declaratively. Furthermore, the Modelica tool identifies which are the dependent and independent variables upon compilation. An example of our approach is introduced on several elementary components representing the hydraulic resistance to fluid flow and the elastic response of the vessel, among others. The introduced model implementation can be more reusable and understandable for the general scientific community.

Tomáš Kulhánek; Ji?í Kofránek; Marek Mateják

2014-01-01T23:59:59.000Z

270

Modeling and implementation of solder-activated joints for single actuator, centimeter-scale robotic mechanisms  

E-Print Network [OSTI]

This thesis explains when, and why, solder-based phase change materials (PCMs) are best-suited as a means to modify a robotic mechanism's kinematic and elastomechanic behavior. The preceding refers to mechanisms that possess ...

Telleria, Maria J

2010-01-01T23:59:59.000Z

271

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

272

Some approaches for modeling and analysis of a parallel mechanism with stewart platform architecture  

SciTech Connect (OSTI)

Parallel mechanisms represent a family of devices based on a closed kinematic architecture. This is in contrast to serial mechanisms, which are comprised of a chain-like series of joints and links in an open kinematic architecture. The closed architecture of parallel mechanisms offers certain benefits and disadvantages.

V. De Sapio

1998-05-01T23:59:59.000Z

273

Gravitational waves, diffusion and decoherence  

E-Print Network [OSTI]

The quite different behaviors exhibited by microscopic and macroscopic systems with respect to quantum interferences suggest that there may exist a naturally frontier between quantum and classical worlds. The value of the Planck mass (22$\\mu$g) may lead to the idea of a connection between this borderline and intrinsic fluctuations of spacetime. We show that it is possible to obtain quantitative answers to these questions by studying the diffusion and decoherence mechanisms induced on quantum systems by gravitational waves generated at the galactic or cosmic scales. We prove that this universal fluctuating environment strongly affects quantum interferences on macroscopic systems, while leaving essentially untouched those on microscopic systems. We obtain the relevant parameters which, besides the ratio of the system's mass to Planck mass, characterize the diffusion constant and decoherence time. We discuss the feasibility of experiments aiming at observing these effects in the context of ongoing progress towar...

Reynaud, Serge; Jaekel, Marc-Thierry

2008-01-01T23:59:59.000Z

274

Diffusion of Innovations over Multiplex Social Networks  

E-Print Network [OSTI]

The ways in which an innovation (e.g., new behaviour, idea, technology, product) diffuses among people can determine its success or failure. In this paper, we address the problem of diffusion of innovations over multiplex social networks where the neighbours of a person belong to one or multiple networks (or layers) such as friends, families, or colleagues. To this end, we generalise one of the basic game-theoretic diffusion models, called networked coordination game, for multiplex networks. We present analytical results for this extended model and validate them through a simulation study, finding among other properties a lower bound for the success of an innovation.While simple and leading to intuitively understandable results, to the best of our knowledge this is the first extension of a game-theoretic innovation diffusion model for multiplex networks and as such it provides a basic framework to study more sophisticated innovation dynamics.

Ramezanian, Rasoul; Magnani, Matteo; Montesi, Danilo

2014-01-01T23:59:59.000Z

275

Nuclear diffuseness as a degree of freedom  

Science Journals Connector (OSTI)

The response of the nuclear energy to changes in neutron and proton surface diffusenesses is investigated using the Thomas-Fermi model. Algebraic expressions are provided for the energy cost of changing the two diffusenesses away from their equilibrium values. This will make it possible to generalize the macroscopic-microscopic calculations of nuclear masses and deformation energies by the inclusion of the neutron and proton diffusenesses as degrees of freedom (to be varied along with the shape degrees of freedom). One result, which is suggested by the relatively low cost in macroscopic energy of increasing the diffuseness of a heavy nucleus by 10% (about 4 MeV), is that superheavy nuclei near Z=126,?N=184 may have a fair chance of becoming stabilized by shell effects. An appendix introduces an improved measure of surface diffuseness, with certain advantages over the conventional Süssmann width b.

W. D. Myers and W. J. ?wia?tecki

1998-12-01T23:59:59.000Z

276

Fractal Location and Anomalous Diffusion Dynamics for Oil Wells from the KY Geological Survey  

E-Print Network [OSTI]

Utilizing data available from the Kentucky Geonet (KYGeonet.ky.gov) the fossil fuel mining locations created by the Kentucky Geological Survey geo-locating oil and gas wells are mapped using ESRI ArcGIS in Kentucky single plain 1602 ft projection. This data was then exported into a spreadsheet showing latitude and longitude for each point to be used for modeling at different scales to determine the fractal dimension of the set. Following the porosity and diffusivity studies of Tarafdar and Roy1 we extract fractal dimensions of the fossil fuel mining locations and search for evidence of scaling laws for the set of deposits. The Levy index is used to determine a match to a statistical mechanically motivated generalized probability function for the wells. This probability distribution corresponds to a solution of a dynamical anomalous diffusion equation of fractional order that describes the Levy paths which can be solved in the diffusion limit by the Fox H function ansatz.

Andrew, Keith; Andrew, Kevin A

2009-01-01T23:59:59.000Z

277

Critical review: Radionuclide transport, sediment transport, and water quality mathematical modeling; and radionuclide adsorption/desorption mechanisms  

SciTech Connect (OSTI)

This report describes the results of a detailed literature review of radionuclide transport models applicable to rivers, estuaries, coastal waters, the Great Lakes, and impoundments. Some representatives sediment transport and water quality models were also reviewed to evaluate if they can be readily adapted to radionuclide transport modeling. The review showed that most available transport models were developed for dissolved radionuclide in rivers. These models include the mechanisms of advection, dispersion, and radionuclide decay. Since the models do not include sediment and radionuclide interactions, they are best suited for simulating short-term radionuclide migration where: (1) radionuclides have small distribution coefficients; (2) sediment concentrations in receiving water bodies are very low. Only 5 of the reviewed models include full sediment and radionuclide interactions: CHMSED developed by Fields; FETRA SERATRA, and TODAM developed by Onishi et al, and a model developed by Shull and Gloyna. The 5 models are applicable to cases where: (1) the distribution coefficient is large; (2) sediment concentrations are high; or (3) long-term migration and accumulation are under consideration. The report also discusses radionuclide absorption/desorption distribution ratios and addresses adsorption/desorption mechanisms and their controlling processes for 25 elements under surface water conditions. These elements are: Am, Sb, C, Ce, Cm, Co, Cr, Cs, Eu, I, Fe, Mn, Np, P, Pu, Pm, Ra, Ru, Sr, Tc, Th, {sup 3}H, U, Zn and Zr.

Onishi, Y.; Serne, R.J.; Arnold, E.M.; Cowan, C.E.; Thompson, F.L. [Pacific Northwest Lab., Richland, WA (United States)

1981-01-01T23:59:59.000Z

278

Models of Stochastic, Spatially Varying Stress in the Crust Compatible with Focal-Mechanism Data, and How Stress Inversions  

E-Print Network [OSTI]

Models of Stochastic, Spatially Varying Stress in the Crust Compatible with Focal-Mechanism Data. Heaton Abstract Evidence suggests that slip in earthquakes and the resultant stress changes are spatially heterogeneous. If crustal stress from past earthquakes is spatially hetero- geneous, then earthquake focal

Greer, Julia R.

279

The mechanics of unrest at Long Valley caldera, California: 1. Modeling the geometry of the source using GPS,  

E-Print Network [OSTI]

The mechanics of unrest at Long Valley caldera, California: 1. Modeling the geometry of the source 44 existing leveling monuments in Long Valley caldera in July 1999, using dual frequency global in the Long Valley area and computed the vertical deformation by differencing GPS-based and leveled

Segall, Paul

280

Mechanical models of fracture reactivation and slip on bedding surfaces during folding of the asymmetric anticline at Sheep Mountain, Wyoming  

E-Print Network [OSTI]

Mechanical models of fracture reactivation and slip on bedding surfaces during folding June 2008 Accepted 5 June 2008 Available online 13 June 2008 Keywords: Fold Fracture reactivation Bed methods to investigate the reactivation of fractures (opening and shearing) and the development of bedding

Borja, Ronaldo I.

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Fracture Modeling of Crack Propagation in Wood and Wood Composites Including Crack Tip Processes and Fiber Bridging Mechanics  

E-Print Network [OSTI]

1 Fracture Modeling of Crack Propagation in Wood and Wood Composites Including Crack Tip Processes and Fiber Bridging Mechanics J. A. Nairn, N. Matsumoto Wood Science & Engineering, Oregon State University wood and wood composites develop process zones often consisting of fibers bridging the crack surfaces

Nairn, John A.

282

18.366 Random Walks and Diffusion, Spring 2005  

E-Print Network [OSTI]

Discrete and continuum modeling of diffusion processes in physics, chemistry, and economics. Topics include central limit theorems, continuous-time random walks, Levy flights, correlations, extreme events, mixing, ...

Bazant, Martin Z.

283

Energy Transport by Classical Waves through Multilayers of Diffusing Slabs  

Science Journals Connector (OSTI)

We describe the effect of interfaces on classical wave propagation through diffusing layered media. A series resistor model for wave energy transport is introduced and we derive a...

Gerritsen, Sijmen; Bauer, Gerrit E

284

A model of multimedia components interconnection with support to communication mechanisms dynamic selection and reconfiguration  

Science Journals Connector (OSTI)

Distributed multimedia systems must provide support for interaction between its components, and this can be done by using different strategies and mechanisms of communication. A possible way to define efficient communication mechanisms is to consider ... Keywords: adaptation, communication, components, distributed multimedia systems, protocol of communication

Felipe A. P. Pinto; Adilson Barboza Lopes; André G. P. Silva; Daniel Cunha da Silva

2009-10-01T23:59:59.000Z

285

A two-path model on the effects of positivity and empathy reflected by online reviews: a choice mechanism perspective  

Science Journals Connector (OSTI)

This research uses the three choice mechanisms, i.e., cognitive, normative, and affective processes, to examine the impacts of two interrelated aspects regarding online reviews, i.e., positivity of online reviews and empathy reflected by online reviews, on online purchase intentions through two studies. Results reveal that positivity of online reviews is more strongly related to both cognitive and normative processing, whereas empathy reflected in response to searchers' problems is found to influence consumers' affective decision making, thus leading to the development of a two-path model regarding the psychological mechanisms about online reviews. Theoretical and managerial implications are discussed.

Xuehua Wang; Cheris W.C. Chow; Zhilin Yang

2012-01-01T23:59:59.000Z

286

LBNL-XXXXX | Logue et al., Evaluation of an Incremental Ventilation Energy Model for Estimating Impacts of Air Sealing and Mechanical Ventilation  

E-Print Network [OSTI]

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 for Estimating Impacts of Air Sealing and Mechanical Ventilation 2 Disclaimer This document was prepared

287

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

SciTech Connect (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.

1993-06-01T23:59:59.000Z

288

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...

Rawal, Chakra

2012-07-16T23:59:59.000Z

289

Magneto-Thermo-Mechanical Coupling, Stability Analysis and Phenomenological Constitutive Modeling of Magnetic Shape Memory Alloys  

E-Print Network [OSTI]

equations are then reduced to capture variant reorientation. A coupled magneto-mechanical boundary value problem (BVP) is solved that accounts for variant reorientation to investigate the influence of the demagnetization effect on the magnetic field...

Haldar, Krishnendu 1978-

2012-12-06T23:59:59.000Z

290

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

291

Mechanism-based constitutive modeling of L1? single-crystal plasticity  

E-Print Network [OSTI]

Ni3Al, an L12 structure intermetallic crystal, is the basic composition of the [gamma]' precipitates in nickel-based superalloys and is a major strengthening mechanism contributing to the superalloys' outstanding ...

Yin, Yuan, 1977-

2006-01-01T23:59:59.000Z

292

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

Science Journals Connector (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

293

A study on aerodynamics and mechanisms of elementary morphing models for flapping wing in bat forward flight  

E-Print Network [OSTI]

The large active wing deformation is a significant way to generate high aerodynamic forces required in bat flapping flight. Besides the twisting, the elementary morphing models of a bat wing are proposed, such as wing-bending in the spanwise direction, wing-cambering in the chordwise direction, and wing area-changing. A plate of aspect ratio 3 is used to model a bat wing and a three dimensional unsteady panel method is applied to predict the aerodynamic forces. It is found that the cambering model has a great positive influence on the lift, followed by area-changing model and then the bending model. The further study indicates that the vortex control is a main mechanism to produce high aerodynamic forces, and the mechanisms for the aerodynamic force enhancement are the asymmetry of the cambered wing and the amplifier effects of wing area-changing and wing bending. The lift and thrust are mainly generated during the downstroke and almost negligible forces during the upstroke by the integrated morphing model-wi...

Zi-Wu, Guan

2014-01-01T23:59:59.000Z

294

A continuous reading fluorescence meter for eddy diffusion studies  

E-Print Network [OSTI]

LIBRARY A AIS COLLEGE OF TEXAS A CONTINUOUS READINO FLUORESCENCE METER FOR EDDY DIFFUSION STUDIES BY Frank Wooten Moon, Jr. A Thesis Submitted to ths Qraduate Scbool of the Agricultural and Mechanical College oi' Texas in partial...

Moon, Frank Wooten

1956-01-01T23:59:59.000Z

295

ELEMENTARY DIFFUSION PROCESSES IN ALCUZN ALLOYS: AN AB INITIO STUDY  

E-Print Network [OSTI]

ELEMENTARY DIFFUSION PROCESSES IN AL­CU­ZN ALLOYS: AN AB INITIO STUDY S. GRABOWSKI AND P. ENTEL of alloys such as mechanical strength and toughness, creep and corrosion resistance are essentially

Entel, P.

296

Modeling of damage generation mechanisms in silicon at energies below the displacement threshold  

Science Journals Connector (OSTI)

We have used molecular dynamics simulation techniques to study the generation of damage in Si within the low-energy deposition regime. We have demonstrated that energy transfers below the displacement threshold can produce a significant amount of damage, usually neglected in traditional radiation damage calculations. The formation of amorphous pockets agrees with the thermal spike concept of local melting. However, we have found that the order-disorder transition is not instantaneous, but it requires some time to reach the appropriate kinetic-potential energy redistribution for melting. The competition between the rate of this energy redistribution and the energy diffusion to the surrounding atoms determines the amount of damage generated by a given deposited energy. Our findings explain the diverse damage morphology produced by ions of different masses.

Iván Santos; Luis A. Marqués; Lourdes Pelaz

2006-11-21T23:59:59.000Z

297

Mechanisms of aerosol-forced AMOC variability in a state of the art climate model  

E-Print Network [OSTI]

with a new state-of-the-art Earth system model. Anthropogenic aerosols have previously been highlighted anthropogenic aerosols force a strengthening of the AMOC by up to 20% in our state-of-the-art Earth system model

298

Nonlinear friction in quantum mechanics  

E-Print Network [OSTI]

The effect of nonlinear friction forces in quantum mechanics is studied via dissipative Madelung hydrodynamics. A new thermo-quantum diffusion equation is derived, which is solved for the particular case of quantum Brownian motion with a cubic friction. It is extended also by a chemical reaction term to describe quantum reaction-diffusion systems with nonlinear friction as well.

Roumen Tsekov

2010-03-01T23:59:59.000Z

299

Open Source Software: Management, Diffusion and Competition  

E-Print Network [OSTI]

and competitive environment such as the ICT market. 1 Introduction OSS is an alternative model of software has introduced an innovative model of software development, based on self-organized communitiesOpen Source Software: Management, Diffusion and Competition Spyridoula Lakkaé National

Kouroupetroglou, Georgios

300

Mechanical properties and modeling of seal-forming lithologies. Technical progress report No. 2, March 15, 1991--March 14, 1992  

SciTech Connect (OSTI)

Both rocksalt and shale lithologies are actively deformed in response to gravitational loads associated with deposition, and both form effective seals to petroleum and natural gas. 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 salt or those of shale, and the loading histories to which they have been subjected. The objectives of this research include the determination of the mechanical properties under controlled conditions of well-characterized shales, and the numerical modeling of rocksalt (and eventually shale) formations using laboratory-based rheologies. Progress has been made towards these goals over this project period, both in our experimental program on shale deformation and model development for the growth of salt diapirs. The mechanical anisotropy of an illite-bearing shale from Louisiana has been determined and related to the preferred orientation and distribution of clays. Its strength in the absence of pore fluids has been determined at confining pressures of up to 250 MPa and at high pressure we have investigated the effects of deformation rate and temperature. A numerical finite difference code has been developed to solve the incompressible Navier-Stokes equations and validated using a two- layer linear viscous model for which analytic solutions are available. Although the code has only been validated for the linear viscous case, it is capable of solving for highly nonlinear constitutive laws as well as solving for arbitrary interfaces between the salt and overburden.

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

1992-04-01T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Thermo-Mechanical Model Development and Validation of DirectedEnergy Deposition Additive Manufacturing of Ti-6Al-4V  

Science Journals Connector (OSTI)

Abstract A thermo-mechanical model of directed energy deposition additive manufacturing of Ti-6Al-4V is developed using measurements of the surface convection generated by gasses flowing during the deposition. In directed energy deposition, material is injected into a melt pool that is traversed to fill in a cross-section of a part, building it layer-by-layer. This creates large thermal gradients that generate plastic deformation and residual stresses. Finite element analysis (FEA) is often used to study these phenomena using simple assumptions of the surface convection. This work proposes that a detailed knowledge of the surface heat transfer is required to produce more accurate FEA results. The surface convection generated by the deposition process is measured and implemented in the thermo-mechanical model. Three depositions with different geometries and dwell times are used to validate the model using in situ measurements of the temperature and deflection as well as post-process measurements of the residual stress. An additional model is developed using the assumption of free convection on all surfaces. The results show that a measurement-based convection model is required to produce accurate simulation results.

J.C. Heigel; P. Michaleris; E.W. Reutzel

2014-01-01T23:59:59.000Z

302

Towards a taxonomy of syntactic and semantic matching mechanisms for aspect-oriented modeling  

Science Journals Connector (OSTI)

Aspect-oriented modeling (AOM) techniques have become increasingly popular over the last decade, as they enable improved modularity, separation of concerns, and reusability over conventional requirements and design modeling techniques. However, AOM notations ... Keywords: AoURN, aspect composition, aspect-oriented modeling, aspect-oriented user requirements notation, schema matching

Gunter Mussbacher; Daniele Barone; Daniel Amyot

2010-10-01T23:59:59.000Z

303

Experimental and numerical investigation of microscale hydrogen diffusion flames  

E-Print Network [OSTI]

are properly modeled. However, the code does not properly predict the air entrainment and pre-heating enhanced thermal-diffusive effects. Therefore, thermal diffusion for light species and different combustion models of time of operation. Generally, the energy density of typical hydrocarbon fuels is about 100 times higher

Leu, Tzong-Shyng "Jeremy"

304

1st workshop on diffusion networks and cascade analytics  

Science Journals Connector (OSTI)

Diffusion and cascades have been studied for many years in sociology, and different theoretical models have been developed. However, experimental validation has been always carried out in relatively small datasets. In recent years, with the availability ... Keywords: cascade modeling, diffusion networks

Peng Cui; Fei Wang; Hanghang Tong; Manuel Gomez Rodriguez

2014-02-01T23:59:59.000Z

305

Peer Effects in the Diffusion of Solar Photovoltaic Panels  

Science Journals Connector (OSTI)

Social interaction (peer) effects are recognized as a potentially important factor in the diffusion of new products. In the case of environmentally friendly goods or technologies, both marketers and policy makers are interested in the presence of causal ... Keywords: diffusion models, empirical IO methods, endogeneity, probability models, social contagion, word of mouth

Bryan Bollinger; Kenneth Gillingham

2012-11-01T23:59:59.000Z

306

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

307

Ambipolar Diffusion in a Magnetic Field  

Science Journals Connector (OSTI)

Diffusion of ions in a plasma across a magnetic field is shown to be not ambipolar in character in most arc experiments. Owing to the highly anisotropic conductivity of the medium, the ions diffuse across the field at their own intrinsic rate. Space-charge neutralization is maintained by slight adjustments of the currents in the direction of the magnetic field lines. The discrepancy between theory and experiment noted by Bohm is thus resolved and no additional mechanisms, such as plasma oscillations, need be postulated.

Albert Simon

1955-04-15T23:59:59.000Z

308

Time-space fabric underlying anomalous diffusion  

E-Print Network [OSTI]

This study unveils the time-space transforms underlying anomalous diffusion process. Based on this finding, we present the two hypotheses concerning the effect of fractal time-space fabric on physical behaviors and accordingly derive fractional quantum relationships between energy and frequency, momentum and wavenumber which further give rise to fractional Schrodinger equation. As an alternative modeling approach to the standard fractional derivatives, we introduce the concept of the Hausdorff derivative underlying the Hausdorff dimensions of metric spacetime. And in terms of the proposed hypotheses, the Hausdorff derivative is used to derive a linear anomalous transport-diffusion equation underlying anomalous diffusion process. Its Green's function solution turns out to be a new type of stretched Gaussian distribution and is compared with that from the Richardson's diffusion equation.

W Chen

2005-05-08T23:59:59.000Z

309

Technology Diffusion and Development  

Science Journals Connector (OSTI)

This chapter discusses the technology diffusion and development that play a key role in climate change mitigation. Most of the authors are engineers with long business experience in this field. In Sect. 9.1, t...

Teruo Okazaki; Mitsutsune Yamaguchi; Hiroyuki Watanabe…

2012-01-01T23:59:59.000Z

310

The role of multiple chemotactic mechanisms in a model of chemotaxis in C. elegans: different mechanisms are specialised for different environments  

Science Journals Connector (OSTI)

Unlike simpler organisms, C. elegans possesses several distinct chemosensory pathways and chemotactic mechanisms. These mechanisms and pathways are individually capable of driving chemotaxis in a chemical concentration gradient. However, it ... Keywords: ASE, C. elegans, Chemotaxis, Sodium chloride

Peter A. Appleby

2014-06-01T23:59:59.000Z

311

Enforcement Documents - Portsmouth Gaseous Diffusion Plant | Department of  

Broader source: Energy.gov (indexed) [DOE]

Portsmouth Gaseous Diffusion Plant Portsmouth Gaseous Diffusion Plant Enforcement Documents - Portsmouth Gaseous Diffusion Plant March 26, 2010 Enforcement Letter, Intennech, Inc. - March 26, 2010 Enforcement Letter issued to Intermech, Inc. related to Installation and Inspection of Anchor Bolts and Pipe Supports at the DUF6 Conversion Buildings at the Portsmouth and Paducah Gaseous Diffusion Plants March 26, 2010 Enforcement Letter, Geiger Brothers Mechanical Contractors, INC - March 26, 2010 Enforcement Letter issued to Geiger Brothers Mechanical Contractors, Inc. related to Installation and Inspection of Penetration Fire Seals at the DUF6 Conversion Building at the Portsmouth Gaseous Diffusion Plant March 26, 2010 Consent Order, Uranium Disposition Services, LLC - NCO-2010-01 Consent Order issued to Uranium Disposition Services, LLC related to

312

Quantum Entanglement and Decoherence: Beyond Particle Models. A Farewell to Quantum Mechanics's Weirdness  

E-Print Network [OSTI]

Combining abstract to laboratory projected quantum states a general analysis of headline quantum phenomena is presented. Standard representation mode is replaced; instead quantum states sustained by elementary material constituents occupy its place. Renouncing to assign leading roles to language originated in classical physics when describing genuine quantum processes, together with sustainment concept most, if not all weirdness associated to Quantum Mechanics vanishes.

O. Tapia

2014-04-02T23:59:59.000Z

313

Carbon nanotube mats and fibers with irradiationimproved mechanical characteristics: a theoretical model  

E-Print Network [OSTI]

1 Carbon nanotube mats and fibers with irradiation­improved mechanical characteristics characteristics of macroscopic mats and fibers of single­walled carbon nanotubes. We further investigate, which in contrast to most ordinary carbon fibers could be strongly bent without breaking, had much

Nordlund, Kai

314

Carbon nanotube mats and fibers with irradiation-improved mechanical characteristics: a theoretical model  

E-Print Network [OSTI]

1 Carbon nanotube mats and fibers with irradiation-improved mechanical characteristics characteristics of macroscopic mats and fibers of single-walled carbon nanotubes. We further investigate]. The SWNT fibers, which in contrast to most ordinary carbon fibers could be strongly bent without breaking

Nordlund, Kai

315

A semi-analytical model for heat and mass transfer in geothermal reservoirs to estimate fracture surface-are-to-volume ratios and thermal breakthrough using thermally-decaying and diffusing tracers  

SciTech Connect (OSTI)

A semi-analytical model was developed to conduct rapid scoping calculations of responses of thermally degrading and diffusing tracers in multi-well tracer tests in enhanced geothermal systems (EGS). The model is based on an existing Laplace transform inversion model for solute transport in dual-porosity media. The heat- and mass-transfer calculations are decoupled and conducted sequentially, taking advantage of the fact that heat transfer between fractures and the rock matrix is much more rapid than mass transfer and therefore mass transfer will effectively occur in a locally isothermal system (although the system will be nonisothermal along fracture flow pathways, which is accounted for by discretizing the flow pathways into multiple segments that have different temperature histories). The model takes advantage of the analogies between heat and mass transfer, solving the same governing equations with k{sub m}/({rho}C{sub p}){sub w} being substituted for {phi}D{sub m} in the equation for fracture transport and k{sub m}/({rho}C{sub p}){sub m} being subsituted for D{sub m} in the equation for matrix transport; where k = thermal conductivity (cal/cm-s-K), {rho} = density (g/cm{sup 3}), C{sub p} = heat capacity (at constant pressure) (cal/g-K), {phi} = matrix porosity, and D = tracer diffusion coefficient (cm{sup 2}/s), with the subscripts w and m referring to water and matrix, respectively. A significant advantage of the model is that it executes in a fraction of second on a single-CPU personal computer, making it very amenable for parameter estimation algorithms that involve repeated runs to find global minima. The combined thermal-mass transport model was used to evaluate the ability to estimate when thermal breakthrough would occur in a multi-well EGS configuration using thermally degrading tracers. Calculations were conducted to evaluate the range of values of Arrhenius parameters, A and E{sub {alpha}} (pre-exponential factor, 1/s, and activation energy, cal/mol) required to obtain interpretable responses of thermally-degrading tracers that decay according to the rate constant k{sub d} = Ae{sup -E{sub {alpha}}/RT}, where k{sub d} = decay rate constant (1/s), R = ideal gas constant (1.987 cal/mol-K), and T = absolute temperature (K). It is shown that there are relatively narrow ranges of A and E{sub {alpha}} that will result in readily interpretable tracer responses for any given combination of ambient reservoir temperature and working fluid residence time in a reservoir. The combined model was also used to simulate the responses of conservative tracers with different diffusion coefficients as a way of estimating fracture surface-area-to-volume ratios (SA/V) in multi-well EGS systems. This method takes advantage of the fact that the differences in breakthrough curves of tracers with different matrix diffusion coefficients are a function of SA/V. The model accounts for differences in diffusion coefficients as a function of temperature so that tracer responses obtained at different times can be used to obtain consistent estimates of SA/V as the reservoir cools down. Some single-well applications of this approach are simulated with a numerical model to demonstrate the potential to evaluate the effectiveness of EGS stimulations before a second well is drilled.

Reimus, Paul W [Los Alamos National Laboratory

2010-12-08T23:59:59.000Z

316

Diffusion Maps for Changing Data Diffusion Maps for Changing Data  

E-Print Network [OSTI]

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department;Diffusion Maps for Changing Data Collaborators Ronald Coifman (Yale University) Roy Lederman (Yale University) #12;Diffusion Maps for Changing Data How to compare images across sensors? Figure: Sokolov Mine

Hirn, Matthew

317

Diffusion Maps for Changing Data Diffusion Maps for Changing Data  

E-Print Network [OSTI]

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department of Mathematics Yale University July 26, 2012 Bell Labs #12;Diffusion Maps for Changing Data Collaborators Joint work with Ronald Coifman and Roy Lederman. #12;Diffusion Maps for Changing Data Overview 1 High

Hirn, Matthew

318

Diffusion Maps for Changing Data Diffusion Maps for Changing Data  

E-Print Network [OSTI]

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department of Mathematics Yale University November 29, 2012 Kansas State University Colloquium #12;Diffusion Maps;Diffusion Maps for Changing Data How to compare images across sensors? Figure: Sokolov Mine in 2009 and 2010

Hirn, Matthew

319

Diffusion Maps for Changing Data Diffusion Maps for Changing Data  

E-Print Network [OSTI]

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department in Honor of the 70th Birthday of David R. Larson #12;Diffusion Maps for Changing Data Collaborators Joint work with Ronald Coifman and Roy Lederman. #12;Diffusion Maps for Changing Data High Dimensional Data

Hirn, Matthew

320

Diffusion Maps for Changing Data Diffusion Maps for Changing Data  

E-Print Network [OSTI]

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn September 3, 2013 #12;Diffusion Maps for Changing Data Collaborators Simon Adar, Tel Aviv University Eyal Ben Dor, Tel, Clarkson University Yoel Shkolnisky, Tel Aviv University #12;Diffusion Maps for Changing Data Heat equation

Hirn, Matthew

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Development and validation of a transition model based on a mechanical approximation  

E-Print Network [OSTI]

A new 3D transition turbulence model, more accurate and faster than an empirical transition model, is proposed. The model is based on the calculation of the pre-transitional u'v' due to mean flow shear. The present transition model is fully described and verified against eight benchmark test cases. Computations are performed for the ERCOFTAC flat-plate T3A, T3C and T3L test cases. Further, the model is validated for bypass, cross-flow and separation induced transition and compared with empirical transition models. The model presents very good results for bypass transition under zero-pressure gradient and with pressure gradient flow conditions. Also the model is able to correctly predict separation induced transition. However, for very low speed and low free-stream turbulence intensity the model delays separation induced transition onset. The model also shows very good results for transition under complex cross-flow conditions in three-dimensional geometries. The 3D tested case was the 6:1 prolate-spheroid und...

Vizinho, R; Silvestre, M

2015-01-01T23:59:59.000Z

322

Electrophoretic Migration and Axial Diffusion of Individual Nanoparticles in Cylindrical Nanopores  

SciTech Connect (OSTI)

Membranes with straight, vertical nanopores have found widespread applications in chemical and biological sciences, including separation, detection, catalysis, and drug delivery. They can also serve as a model system to understand molecular behavior and fundamental mechanisms of separation, bridging the gap between conventional model systems such as flat surfaces and real chromatographic stationary phases such as micrometer-sized porous particles. We recently found that the axial motion of individual biomolecules inside nanopores can be significantly slower than in bulk solution. This suggests that either chromatographic adsorption was present and/or the viscosity inside the nanopores was unusually high. In this study, we measured the electrophoretic motion as well as the axial diffusion of individual nanoparticles in cylindrical alumina nanopores. We found that the electrophoretic mobilities and the diffusion coefficients of polystyrene nanoparticles were both substantially smaller compared to bulk solution independent of particle size or pore diameter. The results imply that the apparent solution viscosity in nanodomains is anomalous.

Han, Rui; Wang, Gufeng; Qi, Shengda; Ma, Changbei; Yeung, Edward S.

2012-08-01T23:59:59.000Z

323

Vehicle Technologies Office Merit Review 2014: Coupled Hierarchical Models for Thermal, Mechanical, Electrical and Electrochemical Processes  

Broader source: Energy.gov [DOE]

Presentation given by [company name] at 2014 DOE Hydrogen and Fuel Cells Program and Vehicle Technologies Office Annual Merit Review and Peer Evaluation Meeting about coupled hierarchical models...

324

Vacancy Jumps in PdIn: Reconciling Nuclear Relaxation and Diffusion Measurements  

E-Print Network [OSTI]

Vacancy Jumps in PdIn: Reconciling Nuclear Relaxation and Diffusion Measurements Gary S. Collins Keywords: point defect, vacancy, diffusion, defect interaction, intermetallic compound, perturbed angular correlation, PAC, nuclear relaxation, diffusion mechanisms Abstract. Vacancy jump frequencies in PdIn were

Collins, Gary S.

325

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

Science Journals Connector (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

326

Project Profile: Predictive Physico-Chemical Modeling of Intrinsic Degradation Mechanisms for Advanced Reflector Materials  

Broader source: Energy.gov [DOE]

NREL, under the Physics of Reliability: Evaluating Design Insights for Component Technologies in Solar (PREDICTS) Program will be developing a physics-based computational degradation model to assess the kinetic oxidation rates; realistic model light attenuation and transport; and multi-layer treatment with variable properties Simulation based experimental design.

327

MECHANICAL TEST RESULTS ON DIPOLE MODEL C-l 25 mm ALUMINUM COLLARS  

E-Print Network [OSTI]

P~. FI'9 . ~ C.C rv'IW\\ 707~-Th ALUMINUM ' ~LAI2.. o Pl.ATTDIPOLE MODEL C-1 25 mm ALUMINUM COLLARS C. Peters FebruaryON DIPOLE MODEL C-I 25 mm ALUMINUM COLLARS· Craig Peters

Peters, C.

2010-01-01T23:59:59.000Z

328

ES2A7 -Fluid Mechanics Example Classes Model Answers to Example Questions (Set II)  

E-Print Network [OSTI]

of msvp = 2 -1 . Calculate the mean model wind tunnel speed if the model is made to 1/10 scale. Assume in a wind tunnel. The airspeed range to be investigated is at the docking end of its range, a maximum -=-=-= --- Question 4: Sliding Board #12;A board with an area slides down an inclined ramp as is schematically

Thomas, Peter J.

329

Nonnegative Diffusion Orientation Distribution Function  

Science Journals Connector (OSTI)

Because of the well-known limitations of diffusion tensor imaging (DTI) in regions of low anisotropy and multiple fiber crossing, high angular resolution diffusion imaging (HARDI) and Q-Ball Imaging (QBI) are used to estimate the probability density ... Keywords: High angular resolution diffusion imaging (HARDI), Higher order diffusion tensor, Nonnegativity, Orientation distribution function (ODF), Principal direction

Liqun Qi; Gaohang Yu; Yi Xu

2013-02-01T23:59:59.000Z

330

Anomalous diffusion modifies solar neutrino fluxes  

E-Print Network [OSTI]

Density and temperature conditions in the solar core suggest that the microscopic diffusion of electrons and ions could be nonstandard: diffusion and friction coefficients are energy dependent, collisions are not two-body processes and retain memory beyond the single scattering event. A direct consequence of nonstandard diffusion is that the equilibrium energy distribution of particles departs from the Maxwellian one (tails goes to zero more slowly or faster than exponentially) modifying the reaction rates. This effect is qualitatively different from temperature and/or composition modification: small changes in the number of particles in the distribution tails can strongly modify the rates without affecting bulk properties, such as the sound speed or hydrostatic equilibrium, which depend on the mean values from the distribution. This mechanism can considerably increase the range of predictions for the neutrino fluxes allowed by the current experimental values (cross sections and solar properties) and can be u...

Kaniadakis, G; Lissia, M; Quarati, P

1998-01-01T23:59:59.000Z

331

A density functional theory model of mechanically activated silyl ester hydrolysis  

SciTech Connect (OSTI)

To elucidate the mechanism of the mechanically activated dissociation of chemical bonds between carboxymethylated amylose (CMA) and silane functionalized silicon dioxide, we have investigated the dissociation kinetics of the bonds connecting CMA to silicon oxide surfaces with density functional calculations including the effects of force, solvent polarizability, and pH. We have determined the activation energies, the pre-exponential factors, and the reaction rate constants of candidate reactions. The weakest bond was found to be the silyl ester bond between the silicon and the alkoxy oxygen atom. Under acidic conditions, spontaneous proton addition occurs close to the silyl ester such that neutral reactions become insignificant. Upon proton addition at the most favored position, the activation energy for bond hydrolysis becomes 31 kJ?mol{sup ?1}, which agrees very well with experimental observation. Heterolytic bond scission in the protonated molecule has a much higher activation energy. The experimentally observed bi-exponential rupture kinetics can be explained by different side groups attached to the silicon atom of the silyl ester. The fact that different side groups lead to different dissociation kinetics provides an opportunity to deliberately modify and tune the kinetic parameters of mechanically activated bond dissociation of silyl esters.

Pill, Michael F.; Schmidt, Sebastian W. [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany) [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany); Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel (Germany); Center for Nanoscience (CeNS), Geschwister-Scholl-Platz 1, 80539 Munich (Germany); Beyer, Martin K. [Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel (Germany) [Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel (Germany); Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens-Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck (Austria); Clausen-Schaumann, Hauke [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany) [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany); Center for Nanoscience (CeNS), Geschwister-Scholl-Platz 1, 80539 Munich (Germany); Kersch, Alfred, E-mail: akersch@hm.edu [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany)] [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany)

2014-01-28T23:59:59.000Z

332

Growth strains and creep in thermally grown alumina : oxide growth mechanisms.  

SciTech Connect (OSTI)

In situ measurements of growth strains and creep relaxation in {alpha}-Al{sub 2}O{sub 3} films, isothermally grown on {beta}-NiAl alloys at 1100 C, are reported and analyzed. Samples containing the reactive element Zr, and Zr-free samples, are examined. For Zr-free samples, steady state growth strains are compressive, whereas the growth strains are tensile when the reactive element (RE) is added to the alloy. This behavior is attributed to the counterflow of oxygen and aluminum interstitials, and to simultaneous counterflow of oxygen and aluminum vacancies, all moving through the grain boundaries. Cross diffusing oxygen and aluminum interstitials may merge and combine within the film, forming new oxide along grain boundary walls, a mechanism that leads to an in-plane compressive stress. Cross diffusing oxygen and aluminum vacancies will also merge and combine within the film; in this case material is removed from grain boundary walls, a mechanism that leads to an in-plane tensile stress. When no RE is present, the interstitial mechanism dominates and the resultant stress is compressive. Consistent with the 'dynamic segregation model', the RE slows the outdiffusion of Al interstitials permitting the tensile mechanism to dominate. This interpretation invokes the unconventional view that oxygen and aluminum interstitials and vacancies, created in and driven by the strong chemical gradient, all participate meaningfully in the scale growth process. Grain boundary diffusion measurements were obtained from low stress creep data, interpreted using the Coble model of grain boundary diffusion. Reported diffusion measurements of oxygen through grain boundaries of {alpha}-Al{sub 2}O{sub 3}, which are known to be inconsistent with oxide scale growth, are critically examined. A simple picture, a 'balanced defect model', emerges that is consistent with the dynamic segregation model, observed growth stresses and their dependence on the presence of a reactive element, sequential oxidation experiments, and our best knowledge about grain boundary diffusion coefficients.

Veal, B. W.; Paulikas, A. P.; Materials Science Division

2008-01-01T23:59:59.000Z

333

Evidence of Multi-Process Matrix Diffusion in a Single Fracturefrom a Field Tracer Test  

SciTech Connect (OSTI)

Compared to values inferred from laboratory tests on matrix cores, many field tracer tests in fractured rock have shown enhanced matrix diffusion coefficient values (obtained using a single-process matrix-diffusion model with a homogeneous matrix diffusion coefficient). To investigate this phenomenon, a conceptual model of multi-process matrix diffusion in a single-fracture system was developed. In this model, three matrix diffusion processes of different diffusion rates were assumed to coexist: (1) diffusion into stagnant water and infilling materials within fractures, (2) diffusion into a degraded matrix zone, and (3) further diffusion into an intact matrix zone. The validity of the conceptual model was then demonstrated by analyzing a unique tracer test conducted using a long-time constant-concentration injection. The tracer-test analysis was conducted using a numerical model capable of tracking the multiple matrix-diffusion processes. The analysis showed that in the degraded zone, a diffusion process with an enhanced diffusion rate controlled the steep rising limb and decay-like falling limb in the observed breakthrough curve, whereas in the intact matrix zone, a process involving a lower diffusion rate affected the long-term middle platform of slowly increasing tracer concentration. The different matrix-diffusion-coefficient values revealed from the field tracer test are consistent with the variability of matrix diffusion coefficient measured for rock cores with different degrees of fracture coating at the same site. By comparing to the matrix diffusion coefficient calibrated using single-process matrix diffusion, we demonstrated that this multi-process matrix diffusion may contribute to the enhanced matrix-diffusion-coefficient values for single-fracture systems at the field scale.

Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur; Molz, Fred J.

2005-06-11T23:59:59.000Z

334

Results of tritium experiments on ceramic electrolysis cells and palladium diffusers for application to fusion reactor fuel cleanup systems  

SciTech Connect (OSTI)

Tritium tests at the Tritium Systems Test Assembly have demonstrated that ceramic electrolysis cells and palladium alloy diffuser developed in Japan are possible components for a fusion reactor fuel cleanup system. Both components have been successfully operated with tritium for over a year. A failure of the first electrolysis cell was most likely the result of an over voltage on the ceramic. A simple circuit was developed to eliminate this mode of failure. The palladium diffusers tubes exhibited some degradation of mechanical properties as a result of the build up of helium from the tritium decay, after 450 days of operation with tritium, however the effects were not significant enough to affect the performance. New models of the diffuser and electrolysis cell, providing higher flow rates and more tritium compatible designs are currently being tested with tritium. 8 refs., 5 figs.

Carlson, R.V.; Binning, K.E.; Konishi, S.; Yoshida, H.; Naruse, Y.

1987-01-01T23:59:59.000Z

335

NUMERICAL MODELING FOR THE FORMATION MECHANISM OF 3D TOPOGRAPHY ON MICROBIAL MAT SURFACES  

E-Print Network [OSTI]

though, that nutrient limitation coupled with fluid motion may play a key role as a physical control. Under this model, competitions of nutrients were setup among growing microbial communities, which later evolve into specially arranged, 3D mats. However...

Patel, Harsh Jay

2013-09-27T23:59:59.000Z

336

Oxygen diffusion in titanite: Lattice diffusion and fast-path diffusion in single crystals  

E-Print Network [OSTI]

Oxygen diffusion in titanite: Lattice diffusion and fast-path diffusion in single crystals X June 2006 Editor: P. Deines Abstract Oxygen diffusion in natural and synthetic single-crystal titanite was characterized under both dry and water-present conditions. For the dry experiments, pre-polished titanite

Watson, E. Bruce

337

Mechanism of the Water Gas Shift Reaction on Pt: First Principles, Experiments, and Microkinetic Modeling  

SciTech Connect (OSTI)

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We present a microkinetic model as well as experimental data for the low-temperature water gas shift (WGS) reaction catalyzed by Pt at temperatures from 523 to 573 K and for various gas compositions at a pressure of 1 atm. Thermodynamic and kinetic parameters for the model are derived from periodic, self-consistent density functional theory (DFT-GGA) calculations on Pt(111). The destabilizing effect of high CO surface coverage on the binding energies of surface species is quantified through DFT calculations and accounted for in the microkinetic model. Deviations of specific fitted model parameters from DFT calculated parameters on Pt(111) point to the possible role of steps/defects in this reaction. Our model predicts reaction rates and reaction orders in good agreement with our experiments. The calculated and experimental apparent activation energies are 67.8 kJ/mol and 71.4 kJ/mol, respectively. The model shows that the most significant reaction channel proceeds via a carboxyl (COOH) intermediate. Formate (HCOO), which has been experimentally observed and thought to be the key WGS intermediate in the literature, is shown to act only as a spectator species.

Grabow, Lars C.; Gokhale, Amit A.; Evans, Steven T.; Dumesic, James A.; Mavrikakis, Manos

2008-03-27T23:59:59.000Z

338

Fundamentals of mechanical behavior in structural intermetallics: A synthesis of atomistic and continuum modeling  

SciTech Connect (OSTI)

After a brief account of the recent advances in computational research on mechanical behavior of structural intermetallics, currently unresolved problems and critical issues are addressed and the knowledge base for potential answers to these problems is discussed. As large-scale problems (e.g., dislocation core structures, grain boundaries, and crack tips) are treated by atomistic simulations, future development of relevant interatomic potentials should be made consistent with the results of first-principles calculations. The bulk and defect properties calculated for intermetallic compounds, both known and as yet untested, can furnish insights to alloy designers in search of new high-temperature structural intermetallics.

Yoo, M.H.; Fu, C.L.

1993-08-01T23:59:59.000Z

339

Single molecule tracking of heterogeneous diffusion  

Science Journals Connector (OSTI)

The mean square displacement of heterogeneous diffusion obeys the Einstein relation, thereby showing no sign of heterogeneities in the ensemble measurement of the diffusion constant. The signature of spatial heterogeneities appears in the time evolution of the non-Gaussian distribution and in the cross correlation between the square displacements at different times, both available from single molecule diffusional trajectories. As a quantitative measure, the non-Gaussian indicator g(t) decays asymptotically to zero according to 1/t for finite time correlation, but saturates at a plateau value for power-law correlation. In addition, the joint moment correlation function f(t,?) provides a direct probe of the memory effect of the fluctuating rate constant. A two-state diffusion model and a stochastic Gaussian model are constructed to evaluate these quantities and are shown to yield the same result within the second cumulant expansion.

Jianshu Cao

2001-03-16T23:59:59.000Z

340

THE FUTURE DEMAND FOR ALTERNATIVE FUEL PASSENGER VEHICLES: A DIFFUSION OF INNOVATION APPROACH  

E-Print Network [OSTI]

.......................................................................................................... 5 2.1 AUTOMOBILE DEMAND MODELS.....................................................................................................................20 2.2.4 The Application of Diffusion Models to Automobile Demand.......................................................................................................................................36 3.1.5 Electric Vehicles

Levinson, David M.

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Fracture mechanics models developed for piping reliability assessment in light water reactors: piping reliability project  

SciTech Connect (OSTI)

The efforts concentrated on modifications of the stratified Monte Carlo code called PRAISE (Piping Reliability Analysis Including Seismic Events) to make it more widely applicable to probabilistic fracture mechanics analysis of nuclear reactor piping. Pipe failures are considered to occur as the result of crack-like defects introduced during fabrication, that escape detection during inspections. The code modifications allow the following factors in addition to those considered in earlier work to be treated: other materials, failure criteria and subcritical crack growth characteristic; welding residual and vibratory stresses; and longitudinal welds (the original version considered only circumferential welds). The fracture mechanics background for the code modifications is included, and details of the modifications themselves provided. Additionally, an updated version of the PRAISE user's manual is included. The revised code, known as PRAISE-B was then applied to a variety of piping problems, including various size lines subject to stress corrosion cracking and vibratory stresses. Analyses including residual stresses and longitudinal welds were also performed.

Harris, D.O.; Lim, E.Y.; Dedhia, D.D.; Woo, H.H.; Chou, C.K.

1982-06-01T23:59:59.000Z

342

Spin Matrix Theory: A quantum mechanical model of the AdS/CFT correspondence  

E-Print Network [OSTI]

We introduce a new quantum mechanical theory called Spin Matrix theory (SMT). The theory is interacting with a single coupling constant g and is based on a Hilbert space of harmonic oscillators with a spin index taking values in a Lie algebra representation as well as matrix indices for the adjoint representation of U(N). We show that SMT describes N=4 super-Yang-Mills theory (SYM) near zero-temperature critical points in the grand canonical phase diagram. Equivalently, SMT arises from non-relativistic limits of N=4 SYM. Even though SMT is a non-relativistic quantum mechanical theory it contains a variety of phases mimicking the AdS/CFT correspondence. Moreover, the infinite g limit of SMT can be mapped to the supersymmetric sector of string theory on AdS_5 x S^5. We study SU(2) SMT in detail. At large N and low temperatures it is a theory of spin chains that for small g resembles planar gauge theory and for large g a non-relativistic string theory. When raising the temperature a partial deconfinement transit...

Harmark, Troels

2014-01-01T23:59:59.000Z

343

Persistent energy flow for a stochastic wave equation model in nonequilibrium statistical mechanics  

E-Print Network [OSTI]

We consider a one-dimensional partial differential equation system modeling heat flow around a ring. The system includes a Klein-Gordon wave equation for a field satisfying spatial periodic boundary conditions, as well as Ornstein-Uhlenbeck stochastic differential equations with finite rank dissipation and stochastic driving terms modeling heat baths. There is an energy flow around the ring. In the case of a linear field with different (fixed) bath temperatures, the energy flow can persist even when the interaction with the baths is turned off. A simple example is given.

Lawrence E. Thomas

2012-04-29T23:59:59.000Z

344

Modelling PV Deployment: A Tool Developed at CEEP to  

E-Print Network [OSTI]

..............................................................................................................................2 3. CEEP's Solar PV Diffusion Model Overview ..............................................................................................................12 4. Comparison of the CEEP's Solar PV Diffusion Model with Other Models ..................................................................................................................................................18 i #12;List of Figures Figure 1: Overview of CEEP's Bottom-Up Solar PV Diffusion Model

Delaware, University of

345

Physical process Mechanical mechanisms  

E-Print Network [OSTI]

1 Physical process Generation · Mechanical mechanisms F = m·a · Electric/Magnetic mechanisms F ­ Quadrupoles......shear stress fluctuations ­ High order poles...... phys. interpretation difficult Governing

Berlin,Technische Universität

346

Transition to hexagonal pattern under the variation of intrinsic length scales of a reaction diffusion system  

Science Journals Connector (OSTI)

The intrinsic length scales of a reaction diffusion system (Gierer-Meinhardt model) is varied by quasi-statically changing the diffusion constant of the activator and a transition from rolls to hexagon is dete...

J. Sienkiewicz; A. Bhattacharyay

2004-07-01T23:59:59.000Z

347

Sensitivity of Climate to Diapycnal Diffusivity: Part I. Equilibrium State; Part II. Global Warming Scenario  

E-Print Network [OSTI]

Part I: The diapycnal diffusivity in the ocean is one of the least known parameters in current climate models. Measurements of this diffusivity are sparse and insufficient for compiling a global map. Inferences from inverse ...

Dalan, Fabio.

348

Application of polymeric quenchant in heat treatment of crack-sensitive steel mechanical parts: Modeling and experiments  

Science Journals Connector (OSTI)

Success or failure of a quenching process is determined by selecting an appropriate quenchant. In this work, the quenching process of the automobile tie rods in different media including water, oil, and a polymeric solution was investigated. The microstructures and mechanical properties of the rods were predicted by a finite element simulation model. Several specimens were cut from the tie rods and heat treated by quenching in five different quenching media including water, oil, and PAG aqueous solutions with polymer concentrations of 10, 20, and 30%. The hardness tests and metallographic analyses were performed on the specimens. Considering the results of the simulations and the experiments, the optimum quenchant was selected and the tie rods were heat treated using this quenchant. The results showed that the use of Poly Alkylene Glycol (PAG) solution quenchants, with respect to its unique cooling mechanism, outperformed water and oil quenchants. The distortion and cracking was reduced compared to water quenching and, on the other hand, the mechanical properties which were not achievable by oil quenching were resulted using polymer-based quenching medium.

M. Eshraghi-Kakhki; M.A. Golozar; A. Kermanpur

2011-01-01T23:59:59.000Z

349

Small-energy series for one-dimensional quantum-mechanical models with non-symmetric potentials  

E-Print Network [OSTI]

We generalize a recently proposed small-energy expansion for one-dimensional quantum-mechanical models. The original approach was devised to treat symmetric potentials and here we show how to extend it to non-symmetric ones. Present approach is based on matching the logarithmic derivatives for the left and right solutions to the Schr\\"odinger equation at the origin (or any other point chosen conveniently) . As in the original method, each logarithmic derivative can be expanded in a small-energy series by straightforward perturbation theory. We test the new approach on four simple models, one of which is not exactly solvable. The perturbation expansion converges in all the illustrative examples so that one obtains the ground-state energy with an accuracy determined by the number of available perturbation corrections.

Paolo Amore; Francisco M. Fernández

2014-10-21T23:59:59.000Z

350

Lumped thermal model for switched reluctance motor applied to mechanical design optimization  

Science Journals Connector (OSTI)

Switched reluctance motors (SRM) are attracting much attention because of their special advantages. Generated heat, due to losses, can reduce the life time of SRMs. Therefore, taking into account thermal modeling helps to improve their performance and ... Keywords: Conduction, Convection, Motor losses, Optimal design, Switched reluctance motor, Thermal equivalent circuit

Hossein Rouhani; Jawad Faiz; Caro Lucas

2007-03-01T23:59:59.000Z

351

Development of Advanced Thermal-Hydrological-Mechanical-Chemical (THMC) Modeling Capabilities for Enhanced Geothermal Systems  

Broader source: Energy.gov [DOE]

Project objectives: Develop a general framework for effective flow of water, steam and heat in in porous and fractured geothermal formations. Develop a computational module for handling coupled effects of pressure, temperature, and induced rock deformations. Develop a reliable model of heat transfer and fluid flow in fractured rocks.

352

Melanin, a promising radioprotector: Mechanisms of actions in a mice model  

SciTech Connect (OSTI)

The radioprotective effect of extracellular melanin, a naturally occurring pigment, isolated from the fungus Gliocephalotrichum simplex was examined in BALB/C mice, and the probable mechanism of action was established. At an effective dose of 50 mg/kg body weight, melanin exhibited both prophylactic and mitigative activities, increasing the 30-day survival of mice by 100% and 60%, respectively, after exposure to radiation (7 Gy, whole body irradiation (WBI)). The protective activity of melanin was primarily due to inhibition of radiation-induced hematopoietic damages as evidenced by improvement in spleen parameters such as index, total cellularity, endogenous colony forming units, and maintenance of circulatory white blood cells and platelet counts. Melanin also reversed the radiation-induced decrease in ERK phosphorylation in splenic tissue, which may be the key feature in its radioprotective action. Additionally, our results indicated that the sustained activation of AKT, JNK and P38 proteins in splenic tissue of melanin pre-treated group may also play a secondary role. This was also supported by the fact that melanin could prevent apoptosis in splenic tissue by decreasing BAX/Bcl-XL ratio, and increasing the expressions of the proliferation markers (PCNA and Cyclin D1), compared to the radiation control group. Melanin also reduced the oxidative stress in hepatic tissue and abrogated immune imbalance by reducing the production of pro-inflammatory cytokines (IL6 and TNF?). In conclusion, our results confirmed that fungal melanin is a very effective radioprotector against WBI and the probable mechanisms of radioprotection are due to modulation in pro-survival (ERK) signaling, prevention of oxidative stress and immunomodulation. -- Highlights: ? Melanin showed promising radioprotection under pre and post irradiation condition. ? Melanin protects the hematopoietic system from radiation induced damage. ? Melanin modulates pro-survival pathways, immune system and prevents oxidative stress.

Kunwar, A., E-mail: amitbio@rediffmail.com [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Adhikary, B. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Jayakumar, S. [Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Barik, A. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Chattopadhyay, S. [Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Raghukumar, S. [Myko Tech Private Limited, Dona Paula, Goa?403004 (India)] [Myko Tech Private Limited, Dona Paula, Goa?403004 (India); Priyadarsini, K.I., E-mail: kindira@barc.gov.in [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2012-10-15T23:59:59.000Z

353

Thermo-mechanical Characterization of Metal/Polymer Composite Filaments and Printing Parameter Study for Fused Deposition Modeling in the 3D Printing Process  

Science Journals Connector (OSTI)

New metal/polymer composite filaments for fused deposition modeling (FDM) processes were developed in order to observe the thermo-mechanical properties of the new filaments. The acrylonitrile butadiene styrene (A...

Seyeon Hwang; Edgar I. Reyes; Kyoung-sik Moon…

2014-10-01T23:59:59.000Z

354

Fast diffusion of a graphene flake on a graphene layer  

Science Journals Connector (OSTI)

Diffusion of a graphene flake on a graphene layer is analyzed and a diffusion mechanism is proposed for the system under consideration. According to this mechanism, rotational transition of the flake from commensurate to incommensurate states takes place with subsequent simultaneous rotation and translational motion until the commensurate state is reached again, and so on. The molecular dynamics simulations and analytic estimates based on ab initio and semiempirical calculations demonstrate that the proposed diffusion mechanism is dominant at temperatures T?(1–3)Tcom, where Tcom corresponds to the barrier for transitions of the flake between adjacent energy minima in the commensurate states. For example, for the flake consisting of ?40, 200, and 700 atoms the contribution of the proposed diffusion mechanism through rotation of the flake to the incommensurate states exceeds that for diffusion of the flake in the commensurate states by one to two orders of magnitude at temperatures 50–150 K, 200–600 K, and 800–2400 K, respectively. The possibility to experimentally measure the barriers to relative motion of graphene layers based on the study of diffusion of a graphene flake is considered. The results obtained are also relevant for understanding of dynamic behavior of polycyclic aromatic molecules on graphene and should be qualitatively valid for a set of commensurate adsorbate-adsorbent systems.

Irina V. Lebedeva; Andrey A. Knizhnik; Andrey M. Popov; Olga V. Ershova; Yurii E. Lozovik; Boris V. Potapkin

2010-10-29T23:59:59.000Z

355

Two-dimensional thermo-mechanical finite element model for laser cladding  

SciTech Connect (OSTI)

Temperature and stress fields during Laser Cladding determine, respectively, the microstructure and residual stress induced deformation and crack formation. As laser cladding processes find application in manufacturing, understanding of the temperature and stress fields becomes crucial for development of the relationship between process parameters and service behavior. A two-dimensional model of laser cladding is developed, using the finite element software package ABAQUS. It enables an investigation of the temperature field that develops at the center plane of the material. This temperature field provides the input for a thermal stress analysis, for which generalized plane strain was assumed. The goal of the present paper is to perform a quantitative evaluation of the residual stresses that develop at the two-layered material, as a function of process parameters such as scanning speed, laser power and powder feed rate. Results of the model are presented, as applied to cladding of C95600 on AA333.

Deus, A.M. de; Mazumder, J. [Univ. of Illinois, Urbana-Champaign, IL (United States)

1996-12-31T23:59:59.000Z

356

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

SciTech Connect (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

358

First-principles simulations of exciton diffusion in organic semiconductors  

Science Journals Connector (OSTI)

Exciton diffusion is crucial for the performance of organic semiconductors in photovoltaic and solid state lighting applications. We propose a first-principles approach that can predict exciton dynamics in organic semiconductors. The method is based on time-dependent density functional theory to describe the energy and many-body wave functions of excitons. Nonadiabatic ab initio molecular dynamics is used to calculate phonon-assisted transition rates between localized exciton states. Using Monte Carlo simulations, we determine the exciton diffusion length, lifetime, diffusivity, and harvesting efficiency in poly(3-hexylthiophene) polymers at different temperatures, which agree very well with the experiments. We find that exciton diffusion is primarily determined by the density of states of low-energy excitons. A widely speculated diffusion mechanism, namely an initial downhill migration followed by thermally activated migration, is confirmed and elucidated by the simulations. Some general guidelines for designing more efficient organic solar cells are obtained from the simulations.

Xu Zhang; Zi Li; Gang Lu

2011-12-22T23:59:59.000Z

359

COUPLED MECHANICAL AND HYDRAULIC MODELING OF GEOSYNTHETIC-REINFORCED COLUMN-SUPPORTED EMBANKMENTS  

E-Print Network [OSTI]

.2.5 Excess Pore Water Pressure 310 CHAPTER SIX COMPARISON OF TWO-DIMENSIONAL AND THREE DIMENSIONAL STUDIES 323 6.1 Verification of Simplified Model 324 6.2 2D and 3D Comparisons 329 6.2.1 Maximum Settlement and Distortion... 330 6.2.2 Maximum Tension Developed in Geosynthetics 342 6.2.3 Maximum Stress Concentration ratio 349 6.2.4 Excess Pore Water Pressure 356 6.2.5 Summary 363 CHAPTER SEVEN CONCLUSIONS AND RECOMMENDATIONS 367 7.1 Conclusions...

Huang, Jie

2007-12-14T23:59:59.000Z

360

OXYGEN DIFFUSION IN HYPOSTOICHIOMETRIC URANIUM DIOXIDE  

E-Print Network [OSTI]

Research Division OXYGEN DIFFUSION IN HYPOSTOICHIOMETRIC11905 -DISCLAIMER - OXYGEN DIFFUSION IN HYPOSTOICHIOMETRICc o n e e n i g woroxygen self-diffusion coefficient

Kim, Kee Chul

2010-01-01T23:59:59.000Z

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361

Study of the performance of three micromixing models in transported scalar PDF simulations of a piloted jet diffusion flame ('Delft Flame III')  

SciTech Connect (OSTI)

Numerical simulation results are presented for a turbulent nonpremixed flame with local extinction and reignition. The transported scalar PDF approach is applied to the turbulence-chemistry interaction. The turbulent flow field is obtained with a nonlinear two-equation turbulence model. A C{sub 1} skeletal scheme is used as the chemistry model. The performance of three micromixing models is compared: the interaction by exchange with the mean model (IEM), the modified Curl's coalescence/dispersion model (CD) and the Euclidean minimum spanning tree model (EMST). With the IEM model, global extinction occurs. With the standard value of model constant C{sub f}=2, the CD model yields a lifted flame, unlike the experiments, while with the EMST model the correct flame shape is obtained. However, the conditional variances of the thermochemical quantities are underestimated with the EMST model, due to a lack of local extinction in the simulations. With the CD model, the flame becomes attached when either the value of C{sub f} is increased to 3 or the pilot flame thermal power is increased by a factor of 1.5. With increased value of C{sub f} better results for mixture fraction variance are obtained with both the CD and the EMST model. Lowering the value of C{sub f} leads to better predictions for mean temperature with EMST, but at the cost of stronger overprediction of mixture fraction variance. These trends are explained as a consequence of variance production by macroscopic inhomogeneity and the specific properties of the micromixing models. Local time stepping is applied so that convergence is obtained more quickly. Iteration averaging reduces statistical error so that the limited number of 50 particles per cell is sufficient to obtain accurate results. (author)

Merci, Bart [Department of Flow, Heat and Combustion Mechanics, Ghent University-UGent, B-9000 Ghent (Belgium); Roekaerts, Dirk [Department of Multi-Scale Physics, Delft University of Technology, Delft (Netherlands); Naud, Bertrand [CIEMAT, Madrid (Spain)

2006-02-01T23:59:59.000Z

362

HINDERED DIFFUSION OF COAL LIQUIDS  

SciTech Connect (OSTI)

It was the purpose of the project described here to carry out careful and detailed investigations of petroleum and coal asphaltene transport through model porous systems under a broad range of temperature conditions. The experimental studies were to be coupled with detailed, in-depth statistical and molecular dynamics models intended to provide a fundamental understanding of the overall transport mechanisms and a more accurate concept of the asphaltene structure. The following discussion describes some of our accomplishments.

Theodore T. Tsotsis; Muhammad Sahimi; Ian A. Webster

1996-01-01T23:59:59.000Z

363

A coupled transport and solid mechanics formulation with improved reaction kinetics parameters for modeling oxidation and decomposition in a uranium hydride bed.  

SciTech Connect (OSTI)

Modeling of reacting flows in porous media has become particularly important with the increased interest in hydrogen solid-storage beds. An advanced type of storage bed has been proposed that utilizes oxidation of uranium hydride to heat and decompose the hydride, releasing the hydrogen. To reduce the cost and time required to develop these systems experimentally, a valid computational model is required that simulates the reaction of uranium hydride and oxygen gas in a hydrogen storage bed using multiphysics finite element modeling. This SAND report discusses the advancements made in FY12 (since our last SAND report SAND2011-6939) to the model developed as a part of an ASC-P&EM project to address the shortcomings of the previous model. The model considers chemical reactions, heat transport, and mass transport within a hydride bed. Previously, the time-varying permeability and porosity were considered uniform. This led to discrepancies between the simulated results and experimental measurements. In this work, the effects of non-uniform changes in permeability and porosity due to phase and thermal expansion are accounted for. These expansions result in mechanical stresses that lead to bed deformation. To describe this, a simplified solid mechanics model for the local variation of permeability and porosity as a function of the local bed deformation is developed. By using this solid mechanics model, the agreement between our reacting bed model and the experimental data is improved. Additionally, more accurate uranium hydride oxidation kinetics parameters are obtained by fitting the experimental results from a pure uranium hydride oxidation measurement to the ones obtained from the coupled transport-solid mechanics model. Finally, the coupled transport-solid mechanics model governing equations and boundary conditions are summarized and recommendations are made for further development of ARIA and other Sandia codes in order for them to sufficiently implement the model.

Salloum, Maher N.; Shugard, Andrew D.; Kanouff, Michael P.; Gharagozloo, Patricia E.

2013-03-01T23:59:59.000Z

364

Gaseous Chemistry and Aerosol Mechanism Developments for Version 3.5.1 of the Online Regional Model, WRF-Chem  

SciTech Connect (OSTI)

We have made a number of developments in the regional coupled model WRF-Chem, with the aim of making the model more suitable for prediction of atmospheric composition and of interactions between air quality and weather. We have worked on the European domain, with a particular focus on making the model suitable for the study of night time chemistry and oxidation by the nitrate radical in the UK atmosphere. A reduced form of the Common Reactive Intermediates gas-phase chemical mechanism (CRIv2-R5) has been implemented to enable more explicit simulation of VOC degradation. N2O5 heterogeneous chemistry has been added to the existing sectional MOSAIC aerosol module, and coupled to both the CRIv2-R5 and existing CBM-Z gas phase scheme. Modifications have also been made to the sea-spray aerosol emission representation, allowing the inclusion of primary organic material in sea-spray aerosol. Driven by appropriate emissions, wind fields and chemical boundary conditions, implementation of the different developments is illustrated in order to demonstrate the impact that these changes have in the North-West European domain. These developments are now part of the freely available WRF-Chem distribution.

Archer-Nicholls, Scott; Lowe, Douglas; Utembe, Steve; Allan, James D.; Zaveri, Rahul A.; Fast, Jerome D.; Hodnebrog, Oivind; Denier van der Gon, Hugo; McFiggans, Gordon

2014-11-08T23:59:59.000Z

365

Modelling of long-term and short-term mechanisms of arterial pressure control in the cardiovascular system: An object-oriented approach  

Science Journals Connector (OSTI)

A mathematical model that provides an overall description of both the short- and long-term mechanisms of arterial pressure regulation is presented. Short-term control is exerted through the baroreceptor reflex while renal elimination plays a role in ... Keywords: Cardiovascular system, DYMOLA simulation environment, MODELICA programming language, Object-oriented modelling, Pressure control

J. Fernandez De Canete, J. Luque, J. Barbancho, V. Munoz

2014-04-01T23:59:59.000Z

366

Electro-diffusion in a plasma with two ion species  

SciTech Connect (OSTI)

Electric field is a thermodynamic force that can drive collisional inter-ion-species transport in a multicomponent plasma. In an inertial confinement fusion capsule, such transport causes fuel ion separation even with a target initially prepared to have equal number densities for the two fuel ion species. Unlike the baro-diffusion driven by ion pressure gradient and the thermo-diffusion driven by ion and electron temperature gradients, electro-diffusion has a critical dependence on the charge-to-mass ratio of the ion species. Specifically, it is shown here that electro-diffusion vanishes if the ion species have the same charge-to-mass ratio. An explicit expression for the electro-diffusion ratio is obtained and used to investigate the relative importance of electro- and baro-diffusion mechanisms. In particular, it is found that electro-diffusion reinforces baro-diffusion in the deuterium and tritium mix, but tends to cancel it in the deuterium and helium-3 mix.

Kagan, Grigory; Tang Xianzhu [Theoretical Division Los Alamos National Laboratory Los Alamos, New Mexico 87545 (United States)

2012-08-15T23:59:59.000Z

367

Particle diffusion in a spheromak  

Science Journals Connector (OSTI)

The local carbon particle diffusion coefficient was measured in the Proto S-1/C spheromak with use of a test-particle injection scheme. When the plasma was not in a force-free Taylor state, and when there were pressure gradients in the plasma, the particle diffusion was 5 times that predicted by Bohm and was consistent with collisional drift-wave diffusion. The diffusion appears to be driven by correlations of the fluctuating electric field and density. During the decay of the discharge when the plasma was in the Taylor state, the diffusion coefficient of the carbon was classical.

D. D. Meyerhofer; F. M. Levinton; M. Yamada

1988-03-07T23:59:59.000Z

368

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

Broader source: All U.S. Department of Energy (DOE) Office Webpages (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

369

Modelling of long-term and short-term mechanisms of arterial pressure control in the cardiovascular system: An object-oriented approach  

Science Journals Connector (OSTI)

Abstract A mathematical model that provides an overall description of both the short- and long-term mechanisms of arterial pressure regulation is presented. Short-term control is exerted through the baroreceptor reflex while renal elimination plays a role in long-term control. Both mechanisms operate in an integrated way over the compartmental model of the cardiovascular system. The whole system was modelled in MODELICA, which uses a hierarchical object-oriented modelling strategy, under the DYMOLA simulation environment. The performance of the controlled system was analysed by simulation in light of the existing hypothesis and validation tests previously performed with physiological data, demonstrating the effectiveness of both regulation mechanisms under physiological and pathological conditions.

J. Fernandez de Canete; J. Luque; J. Barbancho; V. Munoz

2014-01-01T23:59:59.000Z

370

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

SciTech Connect (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 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

371

Effects of interface bonding and defects on boron diffusion at Si/SiO{sub 2} interface  

SciTech Connect (OSTI)

We perform first-principles density functional calculations to find the migration pathway and barrier for B diffusion at the Si/SiO{sub 2} interface. For various interface models, in which crystalline ?-quartz or amorphous silica (a-SiO{sub 2}) is placed on Si, we examine stable and metastable configurations of B-related defects which play a role in B diffusion. While a substitutional B alone is immobile in Si, it tends to diffuse to the interface via an interstitialcy mechanism in the presence of a self-interstitial and then changes into an interstitial B in oxide via a kick-out mechanism, leaving the self-interstitial at the interface. At the defect-free interface, where bridging O atoms are inserted to remove interface dangling bonds, an interstitial B prefers to intervene between the interface Si and bridging O atoms and subsequently diffuses through the hollow space or along the network of the Si-O-Si bonds in oxide. The overall migration barriers are calculated to be 2.02–2.12?eV at the Si/?-quartz interface, while they lie in the range of 2.04?±?0.44?eV at the Si/a-SiO{sub 2} interface, similar to that in ?-quartz. The migration pathway and barrier are not significantly affected by interface defects such as suboxide bond and O protrusion, while dangling bonds in the suboxide region can increase the migration barrier by about 1.5?eV. The result that the interface generally does not hinder the B diffusion from Si to SiO{sub 2} assists in understanding the underlying mechanism for B segregation which commonly occurs at the Si/SiO{sub 2} interface.

Kim, Geun-Myeong; Oh, Young Jun; Chang, K. J., E-mail: kchang@kaist.ac.kr [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)

2013-12-14T23:59:59.000Z

372

Enforcement Letter, Geiger Brothers Mechanical Contractors, INC- March 26, 2010  

Broader source: Energy.gov [DOE]

Issued to Geiger Brothers Mechanical Contractors, Inc. related to Installation and Inspection of Penetration Fire Seals at the DUF6 Conversion Building at the Portsmouth Gaseous Diffusion Plant

373

From mechanical modeling to seismic imaging of faults: A synthetic workflow to study the impact of faults on seismic  

Science Journals Connector (OSTI)

Abstract Although typically interpreted as 2D surfaces, faults are 3D narrow zones of highly and heterogeneously strained rocks, with petrophysical properties differing from the host rock. Here we present a synthetic workflow to evaluate the potential of seismic data for imaging fault structure and properties. The workflow consists of discrete element modeling (DEM) of faulting, empirical relations to modify initial acoustic properties based on volumetric strain, and a ray-based algorithm simulating prestack depth migration (PSDM). We illustrate the application of the workflow in 2D to a 100 m displacement normal fault in a kilometer size sandstone-shale sequence at 1.5 km depth. To explore the effect of particle size on fault evolution, we ran two DEM simulations with particle assemblages of similar bulk mechanical behavior but different particle size, one with coarse (1–3 m particle radii) and the other with fine (0.5–1.5 m particle radii) particles. Both simulations produce realistic but different fault geometries and strain fields, with the finer particle size model displaying narrower fault zones and fault linkage at later stages. Seismic images of these models are highly influenced by illumination direction and wave frequency. Specular illumination highlights flat reflectors outside the fault zone, but fault related diffractions are still observable. Footwall directed illumination produces low amplitude images. Hanging wall directed illumination images the shale layers within the main fault segment and the lateral extent of fault related deformation. Resolution and the accuracy of the reflectors are proportional to wave frequency. Wave frequencies of 20 Hz or more are necessary to image the different fault structure of the coarse and fine models. At 30–40 Hz, there is a direct correlation between seismic amplitude variations and the input acoustic properties after faulting. At these high frequencies, seismic amplitude variations predict both the extent of faulting and the changes in rock properties in the fault zone.

Charlotte Botter; Nestor Cardozo; Stuart Hardy; Isabelle Lecomte; Alejandro Escalona

2014-01-01T23:59:59.000Z

374

Vacancy diffusion in the Cu(001) surface II: Random walk theory  

E-Print Network [OSTI]

Vacancy diffusion in the Cu(001) surface II: Random walk theory E. Somfai a,*,1 , R. van Gastel b Abstract We develop a version of the vacancy mediated tracer diffusion model, which follows the properties for the vacancy, and (iii) the diffusion rate of the vacancy is different, in our case strongly enhanced

van Saarloos, Wim

375

Computational mechanics  

SciTech Connect (OSTI)

The Computational Mechanics thrust area sponsors research into the underlying solid, structural and fluid mechanics and heat transfer necessary for the development of state-of-the-art general purpose computational software. The scale of computational capability spans office workstations, departmental computer servers, and Cray-class supercomputers. The DYNA, NIKE, and TOPAZ codes have achieved world fame through our broad collaborators program, in addition to their strong support of on-going Lawrence Livermore National Laboratory (LLNL) programs. Several technology transfer initiatives have been based on these established codes, teaming LLNL analysts and researchers with counterparts in industry, extending code capability to specific industrial interests of casting, metalforming, and automobile crash dynamics. The next-generation solid/structural mechanics code, ParaDyn, is targeted toward massively parallel computers, which will extend performance from gigaflop to teraflop power. Our work for FY-92 is described in the following eight articles: (1) Solution Strategies: New Approaches for Strongly Nonlinear Quasistatic Problems Using DYNA3D; (2) Enhanced Enforcement of Mechanical Contact: The Method of Augmented Lagrangians; (3) ParaDyn: New Generation Solid/Structural Mechanics Codes for Massively Parallel Processors; (4) Composite Damage Modeling; (5) HYDRA: A Parallel/Vector Flow Solver for Three-Dimensional, Transient, Incompressible Viscous How; (6) Development and Testing of the TRIM3D Radiation Heat Transfer Code; (7) A Methodology for Calculating the Seismic Response of Critical Structures; and (8) Reinforced Concrete Damage Modeling.

Goudreau, G.L.

1993-03-01T23:59:59.000Z

376

Evaluation of Cesium, Strontium, and Lead Sorption, Desorption, and Diffusion in Volcanic Tuffs from Frenchman Flat, Nevada Test Site: Macroscopic and Spectroscopic Investigations  

SciTech Connect (OSTI)

The interaction of radionuclides and other contaminants with minerals and other aquifer materials controls the rate of migration of these contaminants in groundwater. The stronger these interactions, the more a radionuclide will be retarded. Processes such as sorption and diffusion often control the migration of inorganic compounds in aquifers. In addition, these processes are often controlled by the nature of ions of interest, the nature of the aquifer materials, and the specific geochemical conditions. Parameters describing sorption and diffusion of radionuclides and other inorganic ions on aquifer materials are used in transport codes to predict the potential for migration of these contaminants into the accessible environment. Sorption and diffusion studies can help reduce the uncertainty of radionuclide transport modeling on the Nevada Test Site (NTS) and other nuclear testing areas. For example, reliable sorption equilibrium constants, obtained under a variety of conditions, can be used to suggest a plausible sorption mechanism and to provide retardation parameters that can be used in transport models. In addition, these experiments, performed under a variety of conditions, can lead to models that can accommodate changing geochemical conditions. Desorption studies can probe the reversibility of reactions and test whether the reversibility assumed by equilibrium models is justified. Kinetic studies can be used to probe the time-dependent limitations of reactions and suggest whether an equilibrium or kinetic model may be more appropriate. Finally, spectroscopic studies can be used to distinguish between different sorption mechanisms, and provide further guidance with respect to model selection.

Charalambos Papelis; Wooyong Um

2003-03-01T23:59:59.000Z

377

Cluster-continuum quantum mechanical models to guide the choice of anions for Li{sup +}-conducting ionomers  

SciTech Connect (OSTI)

A quantum-mechanical investigation on Li poly(ethylene oxide)-based ionomers was performed in the cluster-continuum solvation model (CCM) that includes specific solvation in the first shell surrounding the cation, all surrounded by a polarizable continuum. A four-state model, including a free Li cation, Li{sup +}-anion pair, triple ion, and quadrupole was used to represent the states of Li{sup +} within the ionomer in the CCM. The relative energy of each state was calculated for Li{sup +} with various anions, with dimethyl ether representing the ether oxygen solvation. The population distribution of Li{sup +} ions among states was estimated by applying Boltzmann statistics to the CCM energies. Entropy difference estimates are needed for populations to better match the true ionomer system. The total entropy change is considered to consist of four contributions: translational, rotational, electrostatic, and solvent immobilization entropies. The population of ion states is reported as a function of Bjerrum length divided by ion-pair separation with/without entropy considered to investigate the transition between states. Predicted concentrations of Li{sup +}-conducting states (free Li{sup +} and positive triple ions) are compared among a series of anions to indicate favorable features for design of an optimal Li{sup +}-conducting ionomer; the perfluorotetraphenylborate anion maximizes the conducting positive triple ion population among the series of anions considered.

Shiau, Huai-Suen; Janik, Michael J. [Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Liu, Wenjuan; Colby, Ralph H. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2013-11-28T23:59:59.000Z

378

Beta relaxation in the shear mechanics of equilibrium viscous liquids: Phenomenology and network modeling of the alpha-beta merging region  

E-Print Network [OSTI]

The phenomenology of the beta relaxation process in the shear-mechanical response of glass-forming liquids is summarized and compared to that of the dielectric beta process. Furthermore, we discuss how to model the observations by means of standard viscoelastic modeling elements. Necessary physical requirements to such a model are outlined, and it is argued that physically relevant models must be additive in the shear compliance of the alpha and beta parts. A model based on these considerations is proposed and fitted to data for Polyisobutylene 680.

Bo Jakobsen; Kristine Niss; Claudio Maggi; Niels Boye Olsen; Tage Christensen; Jeppe C. Dyre

2010-05-26T23:59:59.000Z

379

The cost efficiency of Kyoto flexible mechanisms: a top-down study with the GEM-E3 world model  

Science Journals Connector (OSTI)

Among Kyoto flexible mechanisms, emission trading (ET) shows more promise in cost efficiency but less flexibility in practice than Joint Implementation (JI) and the Clean Development Mechanism (CDM). The problem draws our attention to whether JI and ... Keywords: C68, Clean Development Mechanisms, Cost efficiency, Emission trading, Joint Implementation, Q43, Q48

Haoran Pan

2005-11-01T23:59:59.000Z

380

Diffusive Acceleration of Ions at Interplanetary Shocks  

E-Print Network [OSTI]

Heliospheric shocks are excellent systems for testing theories of particle acceleration in their environs. These generally fall into two classes: (1) interplanetary shocks that are linear in their ion acceleration characteristics, with the non-thermal ions serving as test particles, and (2) non-linear systems such as the Earth's bow shock and the solar wind termination shock, where the accelerated ions strongly influence the magnetohydrodynamic structure of the shock. This paper explores the modelling of diffusive acceleration at a particular interplanetary shock, with an emphasis on explaining in situ measurements of ion distribution functions. The observational data for this event was acquired on day 292 of 1991 by the Ulysses mission. The modeling is performed using a well-known kinetic Monte Carlo simulation, which has yielded good agreement with observations at several heliospheric shocks, as have other theoretical techniques, namely hybrid plasma simulations, and numerical solution of the diffusion-conv...

Baring, M G; Baring, Matthew G.; Summerlin, Errol J.

2005-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Light diffusing fiber optic chamber  

DOE Patents [OSTI]

A light diffusion system for transmitting light to a target area. The light is transmitted in a direction from a proximal end to a distal end by an optical fiber. A diffusing chamber is operatively connected to the optical fiber for transmitting the light from the proximal end to the distal end and transmitting said light to said target area. A plug is operatively connected to the diffusing chamber for increasing the light that is transmitted to the target area.

Maitland, Duncan J. (Lafayette, CA)

2002-01-01T23:59:59.000Z

382

Reduction of phosphorus diffusion in germanium by fluorine implantation  

SciTech Connect (OSTI)

The control of phosphorus (P) diffusion in germanium (Ge) is essential for the realisation of ultrashallow n-type junctions in Ge. This work reports a detailed study of the effect of fluorine (F) co-implantation on P diffusion in Ge. P and F profiles were characterized by secondary ion mass spectroscopy. The ion implantation damage was investigated using cross sectional transmission electron microscopy. It is shown that F co-implantation reduces the implanted P profile width and reduces both intrinsic and extrinsic P diffusion in Ge. A defect mediated mechanism for the strong influence of F co-implantation on P diffusion in Ge is proposed and invokes the formation of F{sub n}V{sub m} clusters in the F-amorphized Ge layer. A fraction of these F{sub n}V{sub m} clusters decorate the interstitial type end-of-range defects in the re-grown Ge layer and the rest react during re-growth with interstitial germanium atoms diffusing back from the amorphous crystalline interface. The Ge vacancies are then annihilated and mobile interstitial F is released and out diffuses from the surface. This results in a re-grown Ge layer which has a low vacancy concentration and in which the P diffusion rate is reduced. These results open the way to the realization of enhanced Ge n-type devices.

El Mubarek, H. A. W. [School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL (United Kingdom)

2013-12-14T23:59:59.000Z

383

Mapping higher-order brain function and resting-state networks with diffuse optical tomography  

Science Journals Connector (OSTI)

We present integrative advances in high-density diffuse optical tomography imaging arrays, large field-of-view instrumentation, and anatomical head modeling. The system was tested by...

Eggebrecht, Adam T; Ferradal, Silvina L; Robichaux-Viehoever, Amy; Hassanpour, Mahlega S; Dehghani, Hamid; Snyder, Abraham; Hershey, Tamara; Culver, Joseph P

384

Development of Reduced Combustion Mechanisms for Premixed Flame Modeling in Steam Cracking Furnaces with Emphasis on NO Emission  

Science Journals Connector (OSTI)

A systematic reduction of the detailed combustion chemistry based on the application of quasi steady state (QSS) approximation for some species leads to several reduced mechanisms (7- to 12-step) for a hydrocarbon?hydrogen fuel with a composition representative for industrial steam cracking furnaces. ... The basis for the construction of all reduced mechanisms is a skeletal mechanism obtained from the detailed GRI-Mech 3.0 and consisting of 223 elementary reaction steps. ... for the near-ignition state based on both mechanisms identified the deficiencies of the 1998-mechanism, in particular, the specifics of the low-temp. ...

G. D. Stefanidis; G. J. Heynderickx; G. B. Marin

2005-10-29T23:59:59.000Z

385

Thermal diffusion in Au?WTi?Pd metallization on silicon  

Science Journals Connector (OSTI)

This paper presents the results of investigation of thermal diffusion in Au?Wti?Pd metallization on (111) n-Si. Thin films were deposited by dc sputtering to the thickness of 50 (Pd), 100–200 (WTi) and 70–200 nm (Au). After deposition the samples were subjected to thermal treatments vacuum 1 × 10?5 mbar, at temperatures up to 600°C. Characterization included RBS, AES, XRD and SEM structural analysis and sheet resistivity measurements. During annealing up to 450°C diffusion occurs only at the Pd?Si interface, at 500°C other components interdiffuse at isolated areas of the samples and at 600°C there is total interdiffusion on components. Thermal degradation oftthe \\{WTi\\} diffusion barrier is enhanced by the growth of Pd2Si phase, during which silicon is released from the substrate and mechanical stress is introduced. Better diffusion barrier properties were obtained when \\{WTi\\} films were deposited in nitrogen or oxygen atmosphere.

M Milosavljevi?; N Bibi?; M Stojanovi?; J Turkovi?; I.H Wilson

1990-01-01T23:59:59.000Z

386

Multicomponent Gas Diffusion in Porous Electrodes  

E-Print Network [OSTI]

Multicomponent gas transport is investigated with unprecedented precision by AC impedance analysis of porous YSZ anode-supported solid oxide fuel cells. A fuel gas mixture of H2-H2O-N2 is fed to the anode, and impedance data are measured across the range of hydrogen partial pressure (10-100%) for open circuit conditions at three temperatures (800C, 850C and 900C) and for 300mA applied current at 800C. For the first time, analytical formulae for the diffusion resistance (Rb) of three standard models of multicomponent gas transport (Fick, Stefan-Maxwell, and Dusty Gas) are derived and tested against the impedance data. The tortuosity is the only fitting parameter since all the diffusion coefficients are known. Only the Dusty Gas model leads to a remarkable data collapse for over twenty experimental conditions, using a constant tortuosity consistent with permeability measurements and the Bruggeman relation. These results establish the accuracy of the Dusty Gas model for multicomponent gas diffusion in porous med...

Fu, Yeqing; Dutta, Abhijit; Mohanram, Aravind; Pietras, John D; Bazant, Martin Z

2014-01-01T23:59:59.000Z

387

A general mechanism for producing scale-invariant perturbations and small non-Gaussianity in ekpyrotic models  

E-Print Network [OSTI]

We explore a new type of entropic mechanism for generating density perturbations in a contracting phase in which there are two scalar fields, but only one has a steep negative potential. This first field dominates the energy density and is the source of the ekpyrotic equation of state. The second field has a negligible potential, but its kinetic energy density is coupled to the first field with a non-linear sigma-model type interaction. We show that for any ekpyrotic equation of state it is possible to choose the potential and the kinetic coupling such that exactly scale-invariant (or nearly scale-invariant) entropy perturbations are produced. The corresponding background solutions are stable, and the bispectrum of the entropy perturbations vanishes as no non-Gaussianity is produced during the ekpyrotic phase. Hence, the only contribution to non-Gaussianity comes from the non-linearity of the conversion process during which entropic perturbations are turned into adiabatic ones, resulting in a local non-Gaussianity parameter $f_{NL} \\sim 5$.

Anna Ijjas; Jean-Luc Lehners; Paul J. Steinhardt

2014-06-06T23:59:59.000Z

388

Mechanism of methanol synthesis on Cu(100) and Zn/Cu(100) surfaces: Comparative dipped adcluster model study  

SciTech Connect (OSTI)

The mechanism of methanol synthesis from CO{sub 2} and H{sub 2} on Cu(100) and Zn/Cu(100) surfaces was studied using the dipped adcluster model (DAM) combined with ab initio Hartree-Fock (HF) and second-order Moeller-Plesset (MP2) calculations. On clean Cu(100) surface, calculations show that five successive hydrogenations are involved in the hydrogenation of adsorbed CO{sub 2} to methanol, and the intermediates are formate, dioxomethylene, formaldehyde, and methoxy. The rate-limiting step is the hydrogenation of formate to formaldehyde, and the Cu-Cu site is responsible for the reaction on Cu(100). The roles of Zn on Zn/Cu(100) catalyst are to modify the rate-limiting step of the reaction: to lower the activation energies of this step and to stabilize the dioxomethylene intermediate at the Cu-Zn site. The present comparative results indicate that the Cu-Zn site is the active site, which cooperates with the Cu-Cu site to catalyze methanol synthesis on a Cu-based catalyst. Electron transfer from surface to adsorbates is the most important factor in affecting the reactivity of these surface catalysts.

Nakatsuji, Hiroshi; Hu, Zhenming

2000-03-05T23:59:59.000Z

389

Effect of elasticity of wall on diffusion in nano channel  

SciTech Connect (OSTI)

Confining walls of nano channel are taken to be elastic to study their effect on the diffusion coefficient of fluid flowing through the channel. The wall is elastic to the extent that it responses to molecular pressure exerted by fluid. The model to study diffusion is based on microscopic considerations. Results obtained for fluid confining to 20 atomic diameter width contrasted with results obtained by considering rigid and smooth wall. The effect of roughness of wall on diffusion can be compensated by the elastic property of wall.

Tankeshwar, K., E-mail: tankesh@pu.ac.in [Computer Centre, Panjab University Chandigarh,- 160014 (India); Srivastava, Sunita [Department of Physics, Panjab University, Chandigarh 160014 (India)

2014-04-24T23:59:59.000Z

390

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 (OSTI)

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.

NONE

1998-09-01T23:59:59.000Z

391

Anomalous diffusion modifies solar neutrino fluxes  

E-Print Network [OSTI]

Density and temperature conditions in the solar core suggest that the microscopic diffusion of electrons and ions could be nonstandard: Diffusion and friction coefficients are energy dependent, collisions are not two-body processes and retain memory beyond the single scattering event. A direct consequence of nonstandard diffusion is that the equilibrium energy distribution of particles departs from the Maxwellian one (tails goes to zero more slowly or faster than exponentially) modifying the reaction rates. This effect is qualitatively different from temperature and/or composition modification: Small changes in the number of particles in the distribution tails can strongly modify the rates without affecting bulk properties, such as the sound speed or hydrostatic equilibrium, which depend on the mean values from the distribution. This mechanism can considerably increase the range of predictions for the neutrino fluxes allowed by the current experimental values (cross sections and solar properties) and can be used to reduce the discrepancy between these predictions and the solar neutrino experiments.

G. Kaniadakis; A. Lavagno; M. Lissia; P. Quarati

1997-10-16T23:59:59.000Z

392

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

E-Print Network [OSTI]

. Ising Model February 25, 2011 Contents 1 Definition of Ising model 2 2 Solving the 1D Ising model 4 2.1 Non-interacting model (J = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Ising model = 0) . . . . . . . . . . . . . . . . . . . . . . . . . 7 3 Generalized 1D Ising model 11 3.1 Spins

Cai, Wei

393

Coupled Thermal-Hydrological-Mechanical-Chemical Model And Experiments For Optimization Of Enhanced Geothermal System Development And Production: Evaluation of Stimulation at the Newberry Volcano EGS Demonstration Site  

Broader source: Energy.gov [DOE]

Coupled Thermal-Hydrological-Mechanical-Chemical Model And Experiments For Optimization Of Enhanced Geothermal System Development And Production: Evaluation of Stimulation at the Newberry Volcano EGS Demonstration Site through Natural Isotopic Reactive Tracers and Geochemical Investigation presentation at the April 2013 peer review meeting held in Denver, Colorado.

394

Understanding open source software peer review: Review processes, parameters and statistical models, and underlying behaviours and mechanisms.  

E-Print Network [OSTI]

??Peer review is seen as an important quality assurance mechanism in both industrial development and the open source software (OSS) community. The techniques for performing… (more)

Rigby, Peter C

2011-01-01T23:59:59.000Z

395

On the effect of gas diffusion layers hydrophobicity on direct methanol fuel cell performance and degradation  

Science Journals Connector (OSTI)

Abstract Degradation and mass transport phenomena management are two of the main issues hindering direct methanol fuel cell commercialization. Water and methanol crossover through the membrane, regulated by both anode and cathode gas diffusion layers hydrophobic properties, is widely studied in the literature, while the effect of mass transport phenomena evolution on the direct methanol fuel cell degradation has not been investigated yet. This work aims to present a combined experimental and modeling analysis on the effect of the gas diffusion layers hydrophobicity on DMFC degradation, through the comparison of performance characterization and degradation tests of two different fuel cells. In one of them, the lower diffusion layer hydrophobicity and the absence of anode microporous layer determines the onset of cathode flooding, negatively affecting performance and degradation. However, the cathode surface area loss is similar between the two fuel cells, meaning that flooding does not involve modifications in cathode permanent degradation mechanisms, but it mainly determines the amplification of the cathode surface area loss effects.

F. Bresciani; C. Rabissi; M. Zago; R. Marchesi; A. Casalegno

2015-01-01T23:59:59.000Z

396

Strain effect on the adsorption, diffusion, and molecular dissociation of hydrogen on Mg (0001) surface  

SciTech Connect (OSTI)

The adsorption, diffusion, and molecular dissociation of hydrogen on the biaxially strained Mg (0001) surface have been systematically investigated by the first principle calculations based on density functional theory. When the strain changes from the compressive to tensile state, the adsorption energy of H atom linearly increases while its diffusion barrier linearly decreases oppositely. The dissociation barrier of H{sub 2} molecule linearly reduces in the tensile strain region. Through the chemical bonding analysis including the charge density difference, the projected density of states and the Mulliken population, the mechanism of the strain effect on the adsorption of H atom and the dissociation of H{sub 2} molecule has been elucidated by an s-p charge transfer model. With the reduction of the orbital overlap between the surface Mg atoms upon the lattice expansion, the charge transfers from p to s states of Mg atoms, which enhances the hybridization of H s and Mg s orbitals. Therefore, the bonding interaction of H with Mg surface is strengthened and then the atomic diffusion and molecular dissociation barriers of hydrogen decrease accordingly. Our works will be helpful to understand and to estimate the influence of the lattice deformation on the performance of Mg-containing hydrogen storage materials.

Lei, Huaping; Wang, Caizhuang; Yao, Yongxin; Hupalo, Myron [Ames Laboratory, USDOE, Ames, Iowa 50011 (United States)] [Ames Laboratory, USDOE, Ames, Iowa 50011 (United States); Wang, Yangang [Ames Laboratory, USDOE, Ames, Iowa 50011 (United States) [Ames Laboratory, USDOE, Ames, Iowa 50011 (United States); Supercomputing Center of Computer Network Information Center, CAS, Beijing 100190 (China); McDougall, Dan; Tringides, Michael; Ho, Kaiming [Ames Laboratory, USDOE, Ames, Iowa 50011 (United States) [Ames Laboratory, USDOE, Ames, Iowa 50011 (United States); Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

2013-12-14T23:59:59.000Z

397

Reaction and diffusion in turbulent combustion  

SciTech Connect (OSTI)

The motivation for this project is the need to obtain a better quantitative understanding of the technologically-important phenomenon of turbulent combustion. In nearly all applications in which fuel is burned-for example, fossil-fuel power plants, furnaces, gas-turbines and internal-combustion engines-the combustion takes place in a turbulent flow. Designers continually demand more quantitative information about this phenomenon-in the form of turbulent combustion models-so that they can design equipment with increased efficiency and decreased environmental impact. For some time the PI has been developing a class of turbulent combustion models known as PDF methods. These methods have the important virtue that both convection and reaction can be treated without turbulence-modelling assumptions. However, a mixing model is required to account for the effects of molecular diffusion. Currently, the available mixing models are known to have some significant defects. The major motivation of the project is to seek a better understanding of molecular diffusion in turbulent reactive flows, and hence to develop a better mixing model.

Pope, S.B. [Mechanical and Aerospace Engineering, Ithaca, NY (United States)

1993-12-01T23:59:59.000Z

398

MEMBRANE FUNCTION, Part 2. Passive Movement: Diffusion, Osmosis, and Gibbs-Donnan Equilibrium 1  

E-Print Network [OSTI]

such as ion gradients or sunlight. I. Passive transport Passive transport is diffusion through a membrane of the membrane. This movement is entirely by the process of diffusion (to be covered below) · ions and polar. Mechanisms of Membrane Transport There are two general modes of transport across membranes: passive transport

Prestwich, Ken

399

Classical phase diffusion in small hysteretic Josephson junctions  

SciTech Connect (OSTI)

The existence of classical phase diffusion in hysteretic junctions is demonstrated by quantitative agreement between experimental and simulated {ital I}-{ital V} curves. The simulations are based on a circuit that accurately models both the junction and its external shunting impedance at microwave frequencies. We show that the bias current at which the junction switches from the phase diffusion state to the voltage state is sensitive to dissipation at microwave frequencies.

Martinis, J.M.; Kautz, R.L. (National Institute of Standards and Technology, Boulder, Colorado 80303 (US))

1989-10-02T23:59:59.000Z

400

Diffuse-Charge Dynamics in Electrochemical Systems  

E-Print Network [OSTI]

The response of a model micro-electrochemical system to a time-dependent applied voltage is analyzed. The article begins with a fresh historical review including electrochemistry, colloidal science, and microfluidics. The model problem consists of a symmetric binary electrolyte between parallel-plate, blocking electrodes which suddenly apply a voltage. Compact Stern layers on the electrodes are also taken into account. The Nernst-Planck-Poisson equations are first linearized and solved by Laplace transforms for small voltages, and numerical solutions are obtained for large voltages. The ``weakly nonlinear'' limit of thin double layers is then analyzed by matched asymptotic expansions in the small parameter $\\epsilon = \\lambda_D/L$, where $\\lambda_D$ is the screening length and $L$ the electrode separation. At leading order, the system initially behaves like an RC circuit with a response time of $\\lambda_D L / D$ (not $\\lambda_D^2/D$), where $D$ is the ionic diffusivity, but nonlinearity violates this common picture and introduce multiple time scales. The charging process slows down, and neutral-salt adsorption by the diffuse part of the double layer couples to bulk diffusion at the time scale, $L^2/D$. In the ``strongly nonlinear'' regime (controlled by a dimensionless parameter resembling the Dukhin number), this effect produces bulk concentration gradients, and, at very large voltages, transient space charge. The article concludes with an overview of more general situations involving surface conduction, multi-component electrolytes, and Faradaic processes.

Martin Z. Bazant; Katsuyo Thornton; Armand Ajdari

2004-01-08T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Lithium diffusion at Si-C interfaces in Silicon-Graphene composites  

SciTech Connect (OSTI)

Models of intercalated Li and its diffusion in Si-Graphene interfaces are investigated using Density Functional Theory. Results suggest that the presence of interfaces alters the energetics of Li binding and diffusion significantly compared to bare Si or Graphene surfaces. Our results show that cavities along reconstructed Si surface provide diffusion paths for Li. Diffusion barriers calculated along these cavities are significantly lower than penetration barriers to bulk Si. Interaction with Si surface results in graphene defects, creating Li diffusion paths that are confined along the cavities but have still lower barrier than in bulk Si.

Odbadrakh, Khorgolkhuu [ORNL; McNutt, Nichiolas William [University of Tennessee, Knoxville (UTK); Nicholson, Donald M. [Oak Ridge National Laboratory (ORNL); Rios, Orlando [ORNL; Keffer, David J. [University of Tennessee, Knoxville (UTK)

2014-01-01T23:59:59.000Z

402

SIMPLE ANALYTICAL FORMS OF THE PERPENDICULAR DIFFUSION COEFFICIENT FOR TWO-COMPONENT TURBULENCE. I. MAGNETOSTATIC TURBULENCE  

SciTech Connect (OSTI)

We explore perpendicular diffusion based on the unified nonlinear transport theory. We derive simple analytical forms for the perpendicular mean free path and investigate the influence of different model spectra. We show that for cases where the field line random walk is normal diffusive, the perpendicular diffusion coefficient consists of only two transport regimes. Details of the spectral shape are less important, especially those of the inertial range. Only the macroscopic properties of the turbulence spectrum control the perpendicular diffusion coefficient. Simple formulae for the perpendicular diffusion coefficient are derived which can easily be implemented in solar modulation or shock acceleration codes.

Shalchi, A., E-mail: andreasm4@yahoo.com [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)

2013-09-01T23:59:59.000Z

403

Diffusion of Kr Isotopes in Solid Ar  

Science Journals Connector (OSTI)

The diffusion coefficient D=D0e-Q0RT and isotope effect for Kr78 and Kr86 in solid Ar have been measured using a tracer technique. The activation energy QKr0 depends on the interchange parameter w, but is estimated to lie in the range 3500-3900 cal mole-1, with the most reliable w giving the lower value. Thus, the two calculated QKr0 (3853 and 4050 cal mole-1) for the vacancy mechanism using a two-body (12, 6) potential appear somewhat high, but in reasonable agreement with experiment. The isotope effect gives f?K?(D78D86-1)[(8678)12-1]=0.48±0.25 which, since QKr0?QAr0, suggests that ?K?0.6 for a single-vacancy mechanism. {Here f is the correlation factor and ?K?(?278?286-1)[(8678)12-1], where ?2 is the tracer jump rate.}

E. H. C. PARKER; B. L. SMITH; H. R. GLYDE

1969-12-15T23:59:59.000Z

404

Molecular imaging of water binding state and diffusion in breast cancer using diffuse optical spectroscopy and diffusion weighted MRI  

E-Print Network [OSTI]

Molecular imaging of water binding state and diffusion inChung et al. , “In vivo water state measurements in breastby measuring tis- sue water state using diffuse optical

Chung, So Hyun; Yu, Hon; Su, Min-Ying; Cerussi, Albert E.; Tromberg, Bruce J.

2012-01-01T23:59:59.000Z

405

Rapid, automated imaging of mouse articular cartilage by microCT for early detection of osteoarthritis and finite element modelling of joint mechanics  

Science Journals Connector (OSTI)

SummaryObjective Mouse articular cartilage (AC) is mostly assessed by histopathology and its mechanics is poorly characterised. In this study: (1) we developed non-destructive imaging for quantitative assessment of AC morphology and (2) evaluated the mechanical implications of AC structural changes. Methods Knee joints obtained from naïve mice and from mice with osteoarthritis (OA) induced by destabilization of medial meniscus (DMM) for 4 and 12 weeks, were imaged by phosphotungstic acid (PTA) contrast enhanced micro-computed tomography (PTA-CT) and scored by conventional histopathology. Our software (Matlab) automatically segmented tibial AC, drew two regions centred on each tibial condyle and evaluated the volumes included. A finite element (FE) model of the whole mouse joint was implemented to evaluate AC mechanics. Results Our method achieved rapid, automated analysis of mouse AC (structural parameters in simulations estimated that AC thinning at early-stages in the DMM model (4 weeks) increases contact pressures (+39%) and Tresca stresses (+43%) in AC. Conclusion PTA-CT imaging is a fast and simple method to assess OA in murine models. Once applied more extensively to confirm its robustness, our approach will be useful for rapidly phenotyping genetically modified mice used for OA research and to improve the current understanding of mouse cartilage mechanics.

P. Das Neves Borges; A.E. Forte; T.L. Vincent; D. Dini; M. Marenzana

2014-01-01T23:59:59.000Z

406

Evaluations of nutrient diffusing substrates and the primary importance of light in controlling periphyton  

E-Print Network [OSTI]

eutrophication. In the first study, artificial channels were used to investigate the response of periphyton to different nutrient delivery mechanisms. In two channels, nutrients were delivered via diffusion to periphyton growth surfaces using modified Matlock...

Murawski, Matthew Thomas

2012-06-07T23:59:59.000Z

407

ELEMENTARY DIFFUSION PROCESSES IN AL-CU-ZN ALLOYS: AN AB INITIO STUDY  

E-Print Network [OSTI]

ELEMENTARY DIFFUSION PROCESSES IN AL-CU-ZN ALLOYS: AN AB INITIO STUDY S. GRABOWSKI AND P. ENTEL of alloys such as mechanical strength and toughness, creep and corrosion resistance are essentially

Entel, P.

408

Role of the lipid bilayer in hair-bundle mechanics  

Science Journals Connector (OSTI)

Deflection of auditory hair cell hair bundle results in a nonlinear force-displacement relationships whose molecular mechanism remains unknown. A gating spring model posits that mechano-sensitive channels are in series with a spring such that channel opening puts the activation gate in series with the spring thus reducing spring extension until further stimulation is provided. Here we present a theoretical analysis of whether the lipid membrane might be the source of nonlinearity. A hair bundle kinematic model is coupled with a lipid membrane model that includes a diffusible compartment into which the tip-link embeds and a minimally diffusive reservoir pool. Using physiological parameters this model was capable of reproducing nonlinear force-displacement plots including a negative stiffness component but required a standing tip-link tension. [Work supported in part by grants R01-DC07910 and R01-DC03896 from the NIDCD of NIH and by The Timoshenko fund from Mechanical Engineering Department at Stanford University].

Sunil Puria

2013-01-01T23:59:59.000Z

409

Diffusion current in a system of coupled Josephson junctions  

SciTech Connect (OSTI)

The role of a diffusion current in the phase dynamics of a system of coupled Josephson junctions (JJs) has been analyzed. It is shown that, by studying the temporal dependences of the superconducting, quasi-particle, diffusion, and displacement currents and the dependences of average values of these currents on the total current, it is possible to explain the main features of the current-voltage characteristic (CVC) of the system. The effect of a diffusion current on the character of CVC branching in the vicinity of a critical current and in the region of hysteresis, as well as on the part of CVC branch corresponding to a parametric resonance in the system is demonstrated. A clear interpretation of the differences in the character of CVC branching in a model of capacitively coupled JJs (CCJJ model) and a model of capacitive coupling with diffusion current (CCJJ+DC model) is proposed. It is shown that a decrease in the diffusion current in a JJ leads to the switching of this junction to an oscillating state. The results of model calculations are qualitatively consistent with the experimental data.

Shukrinov, Yu. M., E-mail: shukrinv@theor.jinr.ru; Rahmonov, I. R. [Joint Institute for Nuclear Research (Russian Federation)

2012-08-15T23:59:59.000Z

410

Time Scales and Mechanisms of Relaxation in the Energy Landscape of Polymer Glass under Deformation: Direct Atomistic Modeling  

Science Journals Connector (OSTI)

Molecular-dynamics simulation is used to explore the influence of thermal and mechanical history of typical glassy polymers on their deformation. Polymer stress-strain and energy-strain developments have been followed for different deformation velocities, also in closed extension-recompression loops. The latter simulate for the first time the experimentally observed mechanical rejuvenation and overaging of polymers, and energy partitioning reveals essential differences between mechanical and thermal rejuvenation. All results can be qualitatively interpreted by considering the ratios of the relevant time scales: for cooling down, for deformation, and for segmental relaxation.

Alexey V. Lyulin and M. A. J. Michels

2007-08-24T23:59:59.000Z

411

Active Diffusion of Motor Particles  

Science Journals Connector (OSTI)

The movement of motor particles consisting of one or several molecular motors bound to a cargo particle is studied theoretically. The particles move on patterns of immobilized filaments. Several patterns are described for which the motor particles undergo nondirected but enhanced diffusion. Depending on the walking distance of the particles and the mesh size of the patterns, the active diffusion coefficient exhibits three different regimes. For micrometer-sized motor particles in water, e.g., this diffusion coefficient can be enhanced by 2 orders of magnitude.

Stefan Klumpp and Reinhard Lipowsky

2005-12-23T23:59:59.000Z

412

AMEAerospace & Mechanical  

E-Print Network [OSTI]

AMEAerospace & Mechanical Engineering #12;Aerospace and Mechanical Engineers design complex mechanical, thermal, fluidic, acousti- cal, optical, and electronic systems, with char- acteristic sizes space. Aerospace and Mechanical Engineering (AME) students conduct basic and applied research within

Wang, Hai

413

The Magnetic Noise of a DC Electric Motor — Modeling of Three-Times-Coupled Electromagnetic, Mechanical and Acoustic Phenomena  

Science Journals Connector (OSTI)

The sound power level of the magnetic noise radiated from a DC electric motor was numerically estimated for different loading conditions and two motor designs. Since the mechanism of the magnetic noise generation...

M. Furlan; M. Boltežar

2005-01-01T23:59:59.000Z

414

A Model for the Nonlinear Mechanical Behavior of Asphalt Binders and its Application in Prediction of Rutting Susceptibility  

E-Print Network [OSTI]

The mechanical behavior of asphalt binders is nonlinear. The binders exhibit shear thinning/thickening behavior in steady shear tests and non-proportational behavior in other standard viscoelastic tests such as creep-recovery or stress relaxation...

Srinivasa Parthasarathy, Atul

2013-04-30T23:59:59.000Z

415

Transport-and diffusion-based optical tomography in small domains: a comparative study  

E-Print Network [OSTI]

reconstructions based on the radiative transport and diffusion equations in optical tomography for media of small that the propaga- tion of near-infrared light in tissues is best modeled by the radiative transport equation (RTE the transport equation by its diffusion approximation, which models the spa- tial density of photons

Bal, Guillaume

416

Ultrasonic NDT of titanium diffusion bonding with guided waves  

SciTech Connect (OSTI)

An ultrasonic guided wave technique is developed for the NDT of diffusion bonded titanium-to-titanium structures. A three-layer model based on the normal beam experimental results has been proposed. Dispersion curves and wave structure are analyzed to direct the experimental study. Two features related to Lamb waves propagating in diffusion bonded titanium plates, the spectral peak to peak ratios and the wave mode frequency shift, are extracted from the guided wave experimental results for both 2 mm (0.08 in.) and 4 mm (0.16 in.) diffusion bond panels. It is found for some specific modes and frequencies that these two features are sensitive to the diffusion bonding states and, therefore, could be used to distinguish good bond panels from poor bond ones.

Rose, J.L.; Zhu, W. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Engineering Science and Mechanics; Zaidi, M. [Boeing Co., Long Beach, CA (United States)

1998-04-01T23:59:59.000Z

417

CORELLI: the Elastic Diffuse Scattering Spectrometer at SNS | ORNL Neutron  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

The Elastic Diffuse Scattering Spectrometer The Elastic Diffuse Scattering Spectrometer CORELLI The CORELLI instrument. CORELLI is a statistical chopper spectrometer with energy discrimination. It's designed and optimized to probe complex disorder in crystalline materials through diffuse scattering of single-crystal samples. The momentum transfer ranges from 0.5 to 12 Ã…-1, and the energy of incident neutrons ranges from 10 to 200 meV. This instrument combines the high efficiency of white-beam Laue diffraction with energy discrimination by modulating the beam with a statistical chopper. A cross-correlation method is used to reconstruct the elastic signal from the modulated data. Accurate modeling of the short-range order associated with the diffuse scattering requires measurements over large volumes of three-dimensional reciprocal space, with sufficient momentum

418

Molecular Characterization of Organic Content of Soot along the Centerline of a Coflow Diffusion Flame  

SciTech Connect (OSTI)

High-resolution mass spectrometry coupled with nanospray desorption electrospray ionization was used to probe chemical constituents of young soot particles sampled along the centerline of a coflow diffusion flame of a three-component Jet-A1 surrogate. In lower positions where particles are transparent to light extinction (n= 632.8 nm), peri-condensed polycyclic aromatic hydrocarbons (PAHs) are found to be the major components of the particle material. These particles become enriched with aliphatic components as they grow in mass and size. Before carbonization occurs, the constituent species in young soot particles are aliphatic and aromatic compounds 200-600 amu in mass, some of which are oxygenated. Particles dominated by PAHs or mixtures of PAHs and aliphatics can both exhibit liquid-like appearance observed by electron microscopy and be transparent to visible light. The variations in chemical composition observed here indicate that the molecular processes of soot formation in coflow diffusion flames may be more complex than previously thought. For example, the mass growth and enrichment of aliphatic components in an initially, mostly aromatic structure region of the flame that is absent of H atoms or other free radicals indicates that there must exist at least another mechanism of soot mass growth in addition to the hydrogen-abstraction-carbon addition mechanism currently considered in fundamental models of soot formation.

Cain, Jeremy P.; Laskin, Alexander; Kholghy, Mohammad Reza; Thomson, Murray; Wang, Hai

2014-10-29T23:59:59.000Z

419

Diffusion of irreversible energy technologies under uncertainty  

SciTech Connect (OSTI)

This paper presents a model of technology diffusion is consistent with characteristics of participants in most energy markets. Whereas the models used most widely for empirical research are based on the assumption that the extended delays in adoption of cost-saving innovations are the result of either lack of knowledge about the new processes or heterogeneity across potential adopters, the model presented in this paper is based on the strategic behavior by firms. The strategic interdependence of the firms` decisions is rooted in spillover effects associated with an inability to exclude others from the learning-by-doing acquired when a firm implements a new technology. The model makes extensive use of recent developments in investment theory as it relates irreversible investments under uncertainty.

Cacallo, J.D.; Sutherland, R.J.

1993-09-01T23:59:59.000Z

420

Hot carrier diffusion in graphene  

E-Print Network [OSTI]

We report an optical study of charge transport in graphene. Diffusion of hot carriers in epitaxial graphene and reduced graphene oxide samples are studied using an ultrafast pump-probe technique with a high spatial resolution. Spatiotemporal...

Ruzicka, Brian Andrew; Wang, Shuai; Werake, Lalani Kumari; Weintrub, Ben; Loh, Kian Ping; Zhao, Hui

2010-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

Programmable Mechanical Metamaterials  

E-Print Network [OSTI]

We create mechanical metamaterials whose response to uniaxial compression can be programmed by lateral confinement, allowing monotonic, non-monotonic and hysteretic behavior. These functionalities arise from a broken rotational symmetry which causes highly nonlinear coupling of deformations along the two primary axes of these metamaterials. We introduce a soft mechanism model which captures the programmable mechanics, and outline a general design strategy for confined mechanical metamaterials. Finally, we show how inhomogeneous confinement can be explored to create multi stability and giant hysteresis.

Bastiaan Florijn; Corentin Coulais; Martin van Hecke

2014-07-17T23:59:59.000Z

422

Investigations of Near-Field Thermal-Hydrologic-Mechanical-Chemical Models for Radioactive Waste Disposal in Clay/Shale Rock  

SciTech Connect (OSTI)

Clay/shale has been considered as potential host rock for geological disposal of high-level radioactive waste throughout the world, because of its low permeability, low diffusion coefficient, high retention capacity for radionuclides, and capability to self-seal fractures. For example, Callovo-Oxfordian argillites at the Bure site, France (Fouche et al., 2004), Toarcian argillites at the Tournemire site, France (Patriarche et al., 2004), Opalinus Clay at the Mont Terri site, Switzerland (Meier et al., 2000), and Boom clay at the Mol site, Belgium (Barnichon and Volckaert, 2003) have all been under intensive scientific investigation (at both field and laboratory scales) for understanding a variety of rock properties and their relationships to flow and transport processes associated with geological disposal of radioactive waste. Figure 1-1 presents the distribution of clay/shale formations within the USA.

Liu, H.H.; Li, L.; Zheng, L.; Houseworth, J.E.; Rutqvist, J.

2011-06-20T23:59:59.000Z

423

Diffusion mechanisms in metallic supercooled liquids and glasses  

Science Journals Connector (OSTI)

... K for 9Be). It was shown recently that the 9Be spin alignment echo technique (SAE) is very effective in detecting Be hopping in glassy Vit1 and Vit4 with atomic ... Vit1 and Vit4 with atomic jump rates as low as 0.1 s-1. The SAE technique is based on the Jeener–Broekaert sequence 90°x–?1–45°y–?–45 ...

X.-P. Tang; Ulrich Geyer; Ralf Busch; William L. Johnson; Yue Wu

1999-11-11T23:59:59.000Z

424

Diffusion in confinement as a microscopic relaxation mechanism...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

form 27 January 2012 Available online 4 February 2012 a b s t r a c t Using quasielastic neutron scattering, we compare dynamics in single-element liquids, glass-forming selenium...

425

Distributed Energy Resources Market Diffusion Model  

E-Print Network [OSTI]

Ernest Orlando Lawrence Berkeley National Laboratory is anErnest Orlando Lawrence Berkeley National Laboratory,Ernest Orlando Lawrence Berkeley National Laboratory,

Maribu, Karl Magnus; Firestone, Ryan; Marnay, Chris; Siddiqui, Afzal S.

2006-01-01T23:59:59.000Z

426

Distributed Energy Resources Market Diffusion Model  

E-Print Network [OSTI]

Electrical efficiency Heat-to- power ratio Micro- turbinescosts Efficiency Heat-to-power ratio Micro- turbines Recip.Turbine 2012 Baseline Case Capital costs Maintenance costs Efficiency

Maribu, Karl Magnus; Firestone, Ryan; Marnay, Chris; Siddiqui, Afzal S.

2006-01-01T23:59:59.000Z

427

Distributed Energy Resources Market Diffusion Model  

E-Print Network [OSTI]

power generation with combined heat and power applications."central stations, combined heat and power (CHP) applicationsgeneration and combined heat and power (CHP) technologies,

Maribu, Karl Magnus; Firestone, Ryan; Marnay, Chris; Siddiqui, Afzal S.

2006-01-01T23:59:59.000Z

428

Connecting fractional anisotropy from medical images with mechanical anisotropy of a hyperviscoelastic fibre-reinforced constitutive model for brain tissue  

Science Journals Connector (OSTI)

...fibre-reinforced constitutive model for brain tissue Chiara Giordano Svein Kleiven e-mail...Technology-KTH, , Huddinge 141 52, Sweden Brain tissue modelling has been an active area of research for years. Brain matter does not follow the constitutive...

2014-01-01T23:59:59.000Z

429

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

430

Fully Lagrangian and Lattice Boltzmann Methods for the Advection-Diffusion Equation  

Science Journals Connector (OSTI)

In the last decade or so, the Lattice–Boltzmann method (LBM) has achieved great success...D-dimensional advection-diffusion equation. The LB model can be viewed as an improved version of the FL model. Numerical r...

Z. L. Guo; B. C. Shi; N. C. Wang

1999-09-01T23:59:59.000Z

431

Uptake of Reactive Black 5 by pumice and walnut activated carbon: Chemistry and adsorption mechanisms  

Science Journals Connector (OSTI)

Abstract The potential of using pumice and walnut wood activated carbon as low-cost adsorbents for the removal of the diazo dye Reactive Black 5 (RB5) from aqueous solutions was investigated. The Langmuir isotherm fit to the data specified the presence of two different natures of adsorption sites with different binding energies on the AC-W surface. Kinetic modelling showed that the adsorption behaviour and mechanism of RB5 for both adsorbents is believed to happen via surface adsorption followed by diffusion into the pores of the AC-W and pumice. The main adsorption mechanisms are hydrogen bonding, electrostatic bonding and n–? interactions.

Behzad Heibati; Susana Rodriguez-Couto; Abdeltif Amrane; Mohd. Rafatullah; Alaa Hawari; Mohammad A. Al-Ghouti

2014-01-01T23:59:59.000Z

432

Theory of correlated hops in surface diffusion  

Science Journals Connector (OSTI)

Scanning tunneling microscopy observations of long hops in the diffusion of Pb atoms on Ge surfaces are explained by the model of a Brownian particle in a periodic potential. The classical turnover theory for barrier crossing predicts a large correlated hopping probability in the underdamped limit, consistent with experiment and in agreement with simulations. The corresponding quantum theory predicts that in the underdamped limit the rate is dominated by tunneling. This causes the quantum correlated hopping probability to vanish in this limit and may be thought of as a new form of quantum localization.

Eli Pollak, Joel Bader, B. J. Berne, and Peter Talkner

1993-05-24T23:59:59.000Z

433

Diffusion or bounce back in relativistic heavy-ion collisions?  

E-Print Network [OSTI]

The time evolution of pseudorapidity distributions of produced charged hadrons in d+Au collisions at sqrt(s_NN) = 200 GeV is investigated. Results of a nonequilibrium-statistical Relativistic Diffusion Model with three sources are compared with a macroscopic "bounce back" model that does not allow for statistical equilibration at large times, but instead leads to motion reversal. When compared to the data, the results of the diffusion approach are more precise, thus emphasizing that the system is observed to be on its way to thermal equilibrium.

Georg Wolschin; Minoru Biyajima; Takuya Mizoguchi

2008-03-12T23:59:59.000Z

434

Source mechanisms and focal depths of East African earthquakes using Rayleigh-wave inversion and body-wave modelling  

Science Journals Connector (OSTI)

......the possible origin of such a thermal feature. Acknowledgments I...their implications for the thermal and mechanical properties of...Vlaar, N. J., 1983. Thermal anomalies and magmatism due...RWENZORI ZAMBIA RWENZORI RUWENZORI SUDAN L. TANCAN. N. S . ZAIRE......

Gordon N. Shudofsky

1985-12-01T23:59:59.000Z

435

Geophys. J. Int. (2000) 142, 151161 A damage mechanics model for power-law creep and earthquake  

E-Print Network [OSTI]

applied to constitutive rules for time-dependent subcritical crack growth. In both phases, the individual that transient creep dominates, with 0Crack growth in this stage is stable and decelerating. For a local softening mechanism (positive feedback), mcrack growth is unstable and accelerating. In this case

436

modeling in physiology Stabilized bubbles in the body: pressure-radius  

E-Print Network [OSTI]

modeling in physiology Stabilized bubbles in the body: pressure-radius relationships and the limits bubbles in the body: pressure-radius relationships and the limits to stabilization. J. Appl. Physiol. 82 for comparison of bubbles stabilized by different mechanisms. Gases diffuse in or out of stabilized bubbles

Raychaudhuri, Soumya

437

Chapter 1 - Introduction to Diffusion MR  

Science Journals Connector (OSTI)

Abstracts Developments in the last century have led to a better understanding of diffusion—the perpetual mixing of molecules caused by thermal motion. In this chapter, the basic principles governing the diffusion phenomenon and its measurement using magnetic resonance (MR) are reviewed. The concepts of the apparent diffusion coefficient and of the diffusion propagator as well as their MR measurements are introduced from basic principles. Finally, the influence of neural tissue microstructure on the diffusion-weighted MR signal is briefly discussed.

Peter J. Basser; Evren Özarslan

2014-01-01T23:59:59.000Z

438

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

SciTech Connect (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

439

Homotypic clusters of transcription factor binding sites: a model system for understanding the physical mechanics of gene expression  

E-Print Network [OSTI]

architectures influence the physical mechanisms that ultimately lead to transcription. A first step towards developing a more mechanistic view of CRE organization is to dissect common and simple organizational patterns [1]. One of themost common CRE build- ing... ,25,26].With this new technology, it is possible to experimentally test how different TF binding site organizations influ- ence gene expression. Even with the development of techniques to synthesize DNA more efficiently, it is still very difficult to study how...

Ezer, Daphne; Zabet, Nicolae Radu; Adryan, Boris

2014-08-01T23:59:59.000Z

440

Hot carrier diffusion in graphene  

Science Journals Connector (OSTI)

We report an optical study of charge transport in graphene. Diffusion of hot carriers in epitaxial graphene and reduced graphene-oxide samples are studied using an ultrafast pump-probe technique with a high spatial resolution. Spatiotemporal dynamics of hot carriers after a pointlike excitation are monitored. Carrier-diffusion coefficients of 11?000 and 5500?cm2?s?1 are measured in epitaxial graphene and reduced graphene-oxide samples, respectively, with a carrier temperature on the order of 3600 K. The demonstrated optical techniques can be used for noncontact and noninvasive in situ detection of transport properties of graphene.

Brian A. Ruzicka; Shuai Wang; Lalani K. Werake; Ben Weintrub; Kian Ping Loh; Hui Zhao

2010-11-08T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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

A thermo-mechanical large deformation constitutive model for polymers based on material network description: Application to a semi-crystalline polyamide 66  

Science Journals Connector (OSTI)

Abstract A visco-hyperelastic constitutive model, based on an original approach initially developed by (Billon, 2012) and applied to amorphous rubbery polymers for a one-dimensional formalism, was extended in this study to three-dimensional constitutive equations based on a thermodynamic framework. The model was applied to a semi-crystalline polyamide polymer, PA66. The experiments included tension and shear testing coupled with synchronized digital image correlation and infrared measurements device for capturing the time, temperature, and stress state dependence, as well as the complex thermomechanical coupling exhibited by the material under large deformation. A notion of equivalent strain rate (based on the time–temperature principle superposition) was also introduced to show its capability to build master curves and therefore decrease the number of testing needed to build a material database. The model is based on the Edward Vilgis theory (1986) and accounts for chains network reorganization under external loading through the introduction of an evolution equation for the internal state variable, ? ¯ , representing the degree of mobility of entanglement points. The model accounting for the equivalent strain rate notion was calibrated using master curves. The thermomechanical model agreed well with the experimental mechanical and temperature measurements under tension and shear conditions. The approach developed in this study may open a different way to model the polymer behavior.

A. Maurel-Pantel; E. Baquet; J. Bikard; J.L. Bouvard; N. Billon

2015-01-01T23:59:59.000Z

442

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

443

Hydrolytic ageing of syntactic foams for thermal insulation in deep water: degradation mechanisms and water uptake model  

Science Journals Connector (OSTI)

This paper focuses on a novel syntactic foam formulation based on a model diepoxy-diamine matrix with a controlled architecture, discusses the factors governing the long-term performance of these materials and...

V. Sauvant-Moynot; N. Gimenez; H. Sautereau

2006-07-01T23:59:59.000Z

444

A Non-linear Reaction-Diffusion System in Propagating Diffusive Wave in Nitroguanidine (NQ) Lens Using Ising-Bloch Bifurcation  

E-Print Network [OSTI]

A wave front propagating through a medium is described using the Ising--Bloch method The reaction-diffusion behaviour of an autocatalysis model of incoming waves from energetic material in a nitroguanidine lens and its interactions with Dirichlet boundaries system are examined. Wave splitting is found to occur for some relative diffusivities through introducing defects into the lens. The system is introduced using a nonlinear method with a Boltzmann--Gibbs distribution of diffusion parameters and forced into a right-hand-side divergence for final analysis. Considering the nonlinearity, the model is expanded by introducing the decomposition kinetics into the set of equations developed.

Mirfayzi, S R

2014-01-01T23:59:59.000Z

445

Diffuse scattering and partial disorder in complex structures  

Science Journals Connector (OSTI)

This review discusses the state of the field of single-crystal diffuse scattering (SCDS), including detectors, data collection and the modelling techniques. High quality, three-dimensional volumes of SCDS data can now be collected at synchrotron light sources, allowing increasingly detailed and quantitative analyses to be undertaken.

Welberry, T.R.

2014-10-28T23:59:59.000Z

446

Numerical study on the validity of the diffusion approximation  

E-Print Network [OSTI]

of photons can be accurately modeled by the radiative transport equation (RTE).9,10 Because and the radiative transport as implemented by Monte Carlo simulation in the cases of point and ball sources. Our of the difficulties in handling the RTE directly, the diffusion approximation to the transport equation has been

Virginia Tech

447

Self-similar and charged spheres in the diffusion approximation  

E-Print Network [OSTI]

We study spherical, charged and self--similar distributions of matter in the diffusion approximation. We propose a simple, dynamic but physically meaningful solution. For such a solution we obtain a model in which the distribution becomes static and changes to dust. The collapse is halted with damped mass oscillations about the absolute value of the total charge.

Barreto, W

1999-01-01T23:59:59.000Z

448

MaximumA Posteriori Estimation of Transient Enhanced Diffusion Energetics  

E-Print Network [OSTI]

into the wafer. However, ion implantation causes lattice damage, producing junctions with high sheet resistance. 2000 . Here, a comprehensive TED model is developed combin- Zing elementary physicochemical processes continuity equations describing Fickian diffusion and electric drift motion, and formation and Zannihilation

Braatz, Richard D.

449

Water diffusion and fracture in organosilicate glass film stacks Youbo Lin a  

E-Print Network [OSTI]

with an analytical model that combines water diffusion with subcritical crack growth. Fracture experi- ments showWater diffusion and fracture in organosilicate glass film stacks Youbo Lin a , Ting Y. Tsui b. OSG is very brittle and it is susceptible to stress-corrosion cracking in water

450

A Framework for Coupled Deformation-Diffusion Analysis with Application to Degradation/Healing  

E-Print Network [OSTI]

deformation-dependent diffusivity tensor we did not use k3 just to be consistent with the theory of linearized elasticity. However, in the case of finite elas- ticity, one should also use the third invariant in modeling the deformation-dependent diffusivity...

Mudunuru, Maruti Kumar

2012-07-16T23:59:59.000Z

451

HYDRODYNAMIC LIMITS FOR KINETIC EQUATIONS AND THE DIFFUSIVE APPROXIMATION OF RADIATIVE  

E-Print Network [OSTI]

HYDRODYNAMIC LIMITS FOR KINETIC EQUATIONS AND THE DIFFUSIVE APPROXIMATION OF RADIATIVE TRANSPORT of the radiative transport equation. 1. Introduction We consider a class of kinetic models equipped with a single. A general compactness frame- work is obtained for the diffusive scaling in L1 . The radiative transport

Tzavaras, Athanasios E.

452

ON THE KARLIN-KIMURA APPROACHES TO THE WRIGHT-FISHER DIFFUSION WITH FLUCTUATING  

E-Print Network [OSTI]

ON THE KARLIN-KIMURA APPROACHES TO THE WRIGHT-FISHER DIFFUSION WITH FLUCTUATING SELECTION THIERRY HUILLET Abstract. The goal of this manuscript is a comparative study of two Wright- Fisher-like diffusion in random environment. In other words, we study the effect of disorder on the usual Wright-Fisher model

Boyer, Edmond

453

hal-00181730,version1-24Oct2007 ON WRIGHT-FISHER DIFFUSION AND ITS RELATIVES  

E-Print Network [OSTI]

hal-00181730,version1-24Oct2007 ON WRIGHT-FISHER DIFFUSION AND ITS RELATIVES THIERRY HUILLET. Focus is on the Wright-Fisher diffusion model and its variations, describing the forward evolution backward and forward equations. Most of the manuscript's content focuses on the specific Wright-Fisher (WF

Paris-Sud XI, Université de

454

Filtering the Wright-Fisher diffusion. MIREILLE CHALEYAT-MAUREL1  

E-Print Network [OSTI]

Filtering the Wright-Fisher diffusion. MIREILLE CHALEYAT-MAUREL1 , VALENTINE GENON-CATALOT2 1-P`eres, 75270 Paris Cedex 06, France. e-mail: genon@math-info.univ-paris5.fr Abstract We consider a Wright, hidden Markov models, prior and posterior distributions. Running title: Wright-Fisher diffusion. #12

Boyer, Edmond

455

Phase Diffusion in Graphene-Based Josephson Junctions I. V. Borzenets, U. C. Coskun, S. J. Jones, and G. Finkelstein  

E-Print Network [OSTI]

Phase Diffusion in Graphene-Based Josephson Junctions I. V. Borzenets, U. C. Coskun, S. J. Jones July 2011; published 21 September 2011) We report on graphene-based Josephson junctions with contacts. We attribute this resistance to the phase diffusion mechanism, which has not been yet identified

Finkelstein, Gleb

456

Diffusion in a potential landscape with stochastic resetting  

E-Print Network [OSTI]

The steady state of a Brownian particle diffusing in an arbitrary potential under the stochastic resetting mechanism has been studied. We show that there are different classes of nonequilibrium steady states depending on the nature of the potential. In the stable potential landscape, the system attains a well defined steady state however existence of the steady state for the unstable landscape is constrained. We have also investigated the transient properties of the propagator towards the steady state under the stochastic resetting mechanism. Finally, we have done numerical simulations to verify our analytical results.

Arnab Pal

2014-08-09T23:59:59.000Z

457

Acetone-Assisted Oxygen Vacancy Diffusion on TiO2(110)  

SciTech Connect (OSTI)

We have studied the dynamic relationship between acetone and bridge-bonded oxygen (Ob) vacancy (VO) defect sites on the TiO2(110)-1 × 1 surface using scanning tunneling microscopy (STM) and density function theory (DFT) calculations. We report an adsorbate-assisted VO diffusion mechanism. The STM images taken at 300 K show that acetone preferably adsorbs on the VO site and is mobile. The sequential isothermal STM images directly show that the mobile acetone effectively migrates the position of VO by a combination of two acetone diffusion channels: one is the diffusion along the Ob row and moving as an alkyl group, which heals the initial VO; another is the diffusion from the Ob row to the fivecoordinated Ti4+ row and then moving along the Ti4+ row as an acetone, which leaves a VO behind. The calculated acetone diffusion barriers for the two channels are comparable and agree with experimental results.

Xia, Yaobiao; Zhang, Bo; Ye, Jingyun; Ge, Qingfeng; Zhang, Zhenrong

2012-10-18T23:59:59.000Z

458

Crossover from diffusive to ballistic transport properties in magnetic multilayers  

Science Journals Connector (OSTI)

We develop a theoretical model for computing the spin-dependent transport properties of magnetic multilayers in the presence of ballistic scattering at the interfaces and diffusive scattering within the layers for currents perpendicular to the plane of the layers. The local chemical potentials are found to be momentum and spin dependent in the vicinity of regions with ballistic scattering. We have derived the approximate macroscopic equations from the Boltzmann equation by taking into account both ballistic and diffusive scattering. With these equations, realistic data of the reflection coefficients from ab initio calculations can be explicitly included in computing magnetotransport properties. We apply our formulation to a number of interesting magnetic multilayer structures.

Y. -N. Qi and S. Zhang

2002-05-17T23:59:59.000Z

459

Characterization of U(VI) Sorption-Desorption Processes and Model Upscaling  

SciTech Connect (OSTI)

The objectives of the overall collaborative EMSP effort (with which this project is associated) were to characterize sorption and desorption processes of U(VI) on pristine and contaminated Hanford sediments over a range of sediment facies and materials properties and to relate such characterization both to fundamental molecular-scale understanding and field-scale models of geochemistry and mass transfer. The research was intended to provide new insights on the mechanisms of U(VI) retardation at Hanford, and to allow the development of approaches by which laboratory-developed geochemical models could be upscaled for defensible field-scale predictions of uranium transport in the environment. Within this broader context, objectives of the JHU-based project were to test hypotheses regarding the coupled roles of adsorption and impermeable-zone diffusion in controlling the fate and transport of U(VI) species under conditions of comparatively short-term exposure. In particular, this work tested the following hypotheses: (1) the primary adsorption processes in the Hanford sediment over the pH range of 7 to 10 are surface complexation reactions of aqueous U(VI) hydroxycarbonate and carbonate complexes with amphoteric edge sites on detrital phyllosilicates in the silt/clay size fraction; (2) macroscopic adsorption intensity (at given aqueous conditions) is a function of mineral composition and aquatic chemistry; and (3) equilibrium sorption and desorption to apply in short-term, laboratory-spiked pristine sediments; and (4) interparticle diffusion can be fully understood in terms of a model that couples molecular diffusion of uranium species in the porewater with equilibrium sorption under the relevant aqueous conditions. The primary focus of the work was on developing and applying both models and experiments to test the applicability of "local equilibrium" assumptions in the modeling interpretation of sorption retarded interparticle diffusion, as relevant to processes of U(VI) diffusion in silt/clay layers. Batch isotherm experiments were first used to confirm sorption isotherms under the intended test conditions and diffusion cell experiments were then conducted to explore the diffusion hypotheses. Important new information was obtained about the role of aqueous calcium and solid calcium carbonate in controlling sorption equilibrium with Hanford sediments. The retarded interparticle diffusion model with local sorption equilibrium was shown to very successfully simulate diffusion at high aqueous concentration of U(VI). By contrast, however, diffusion data obtained at low concentration suggested nonequilibrium of sorption even at diffusion time scales. Such nonequilibrium effects at low concentration are likely to be the result of sorption retarded intraparticle diffusion, and strong U(VI) sorption in the low concentration range.

Bai, Jing; Dong, Wenming; Ball, William P.

2006-10-12T23:59:59.000Z

460

The holographic mapping of the Standard Model onto the black hole horizon, Part I: Abelian vector field, scalar field and BEH Mechanism  

E-Print Network [OSTI]

Interactions between outgoing Hawking particles and ingoing matter are determined by gravitational forces and Standard Model interactions. In particular the gravitational interactions are responsible for the unitarity of the scattering against the horizon, as dictated by the holographic principle, but the Standard Model interactions also contribute, and understanding their effects is an important first step towards a complete understanding of the horizon's dynamics. The relation between in- and outgoing states is described in terms of an operator algebra. In this paper, the first of a series, we describe the algebra induced on the horizon by U(1) vector fields and scalar fields, including the case of an Englert-Brout-Higgs mechanism, and a more careful consideration of the transverse vector field components.

G. 't Hooft

2005-04-25T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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.


461

The effect of football helmet energy absorption mechanisms on the mitigation of cervical spinal injuries: a mathematical model  

E-Print Network [OSTI]

. The variables which are used for the mathematical model are as follows: head Head acceleration [ft/sec ] 2 x totso Torso acceleration [ft/sec ] 2 head Head velocity [ft/sec] x torso Torso velocity [ft/sec] Xl?, d Head displacement [ft] mh?d Head mass [ibm...

Yung, Adelino

1995-01-01T23:59:59.000Z

462

Verification of the integrity of barriers using gas diffusion  

SciTech Connect (OSTI)

In-situ barrier materials and designs are being developed for containment of high risk contamination as an alternative to immediate removal or remediation. The intent of these designs is to prevent the movement of contaminants in either the liquid or vapor phase by long-term containment, essentially buying time until the contaminant depletes naturally or a remediation can be implemented. The integrity of the resultant soil-binder mixture is typically assessed by a number of destructive laboratory tests (leaching, compressive strength, mechanical stability with respect to wetting and freeze-thaw cycles) which as a group are used to infer the likelihood of favorable long-term performance of the barrier. The need exists for a minimally intrusive yet quantifiable methods for assessment of a barrier`s integrity after emplacement, and monitoring of the barrier`s performance over its lifetime. Here, the authors evaluate non-destructive measurements of inert-gas diffusion (specifically, SF{sub 6}) as an indicator of waste-form integrity. The goals of this project are to show that diffusivity can be measured in core samples of soil jet-grouted with Portland cement, validate the experimental method through measurements on samples, and to calculate aqueous diffusivities from a series of diffusion measurements. This study shows that it is practical to measure SF{sub 6} diffusion rates in the laboratory on samples of grout (Portland cement and soil) typical of what might be used in a barrier. Diffusion of SF{sub 6} through grout (Portland cement and soil) is at least an order of magnitude slower than through air. The use of this tracer should be sensitive to the presence of fractures, voids, or other discontinuities in the grout/soil structure. Field-scale measurements should be practical on time-scales of a few days.

Ward, D.B. [SPECTRA Research Inst., Albuquerque, NM (United States); Williams, C.V. [Sandia National Labs., Albuquerque, NM (United States). Environmental Restoration Technologies Dept.

1997-06-01T23:59:59.000Z

463

Hierarchical 3D diffusion wavelet shape priors  

E-Print Network [OSTI]

In this paper, we propose a novel representation of prior knowledge for image segmentation, using diffusion wavelets that can reflect arbitrary continuous interdependencies in shape data. The application of diffusion ...

Langs, Georg

464

Efficient Stochastic Galerkin Methods For Random Diffusion ...  

E-Print Network [OSTI]

We discuss in this paper simulations of diffusion problems ... With PC/gPC serving as a complete basis to represent random processes, a stochastic Galerkin ... coupled diffusion equations, which can be readily written in a vector/

2008-09-16T23:59:59.000Z

465

MICROFLUIDIC CONTROL OF STEM CELL DIFFUSIBLE SIGNALING  

E-Print Network [OSTI]

MICROFLUIDIC CONTROL OF STEM CELL DIFFUSIBLE SIGNALING Katarina Blagovi, Lily Y. Kim, Alison M cell differentiation. KEYWORDS: Embryonic stem cells, microfluidic perfusion, diffusible signaling; they secrete molecules to which they respond. Microfluidics offers a potential solution to this challenge

Voldman, Joel

466

Diffusion stability of bubbles in a cluster  

Science Journals Connector (OSTI)

The diffusion stability of gas bubbles in one-fraction and two-fraction clusters ... gas concentrations in the liquid at which the bubble tends to one of two equilibrium states because of diffusion processes betw...

É. Sh. Nasibullaeva; I. Sh. Akhatov

2007-07-01T23:59:59.000Z

467

OXYGEN DIFFUSION IN UO2-x  

E-Print Network [OSTI]

~ K.C. K:i.m, "Oxygen Diffusion in Hypostoichiometricsystem for enriching uo 2 in oxygen-18 or for stoichiometry+nal of Nuclear Materials OXYGEN DIFFUSION IN U0 2 _:x K.C.

Kim, K.C.

2013-01-01T23:59:59.000Z

468

Diffusion Enhancement in Core-softened fluid confined in nanotubes  

E-Print Network [OSTI]

We study the effect of confinement in the dynamical behavior of a core-softened fluid. The fluid is modeled as a two length scales potential. This potential in the bulk reproduces the anomalous behavior observed in the density and in the diffusion of liquid water. A series of $NpT$ Molecular Dynamics simulations for this two length scales fluid confined in a nanotube were performed. We obtain that the diffusion coefficient increases with the increase of the nanotube radius for wide channels as expected for normal fluids. However, for narrow channels, the confinement shows an enhancement in the diffusion coefficient when the nanotube radius decreases. This behavior, observed for water, is explained in the framework of the two length scales potential.

José R. Bordin; Alan B. de Oliveira; Alexandre Diehl; Marcia C. Barbosa

2012-08-05T23:59:59.000Z

469

Particle production and nonlinear diffusion in relativistic systems  

E-Print Network [OSTI]

The short parton production phase in high-energy heavy-ion collisions is treated analytically as a nonlinear diffusion process. The initial buildup of the rapidity density distributions of produced charged hadrons within tau_p = 0.25 fm/c occurs in three sources during the colored partonic phase. In a two-step approach, the subsequent diffusion in pseudorapidity space during the interaction time of tau_int = 7-10 fm/c (mean duration of the collision) is essentially linear as expressed in the Relativistic Diffusion Model (RDM) which yields excellent agreement with the data at RHIC energies, and allows for predictions at LHC energies. Results for d+Au are discussed in detail.

Georg Wolschin

2008-09-06T23:59:59.000Z

470

Cysteamine-induced inhibition of acid neutralization and the increase in hydrogen ion back-diffusion in duodenal mucosa  

Science Journals Connector (OSTI)

To investigate the possible impairment of defensive mechanisms in cysteamine-induced duodenal ulceration, the effect of cysteamine on the neutralization of acid by the duodenum and the back-diffusion of hydrog...

Dr. Keiji Ohe MD; DMSc; Yoshiomi Okada MD…

1982-03-01T23:59:59.000Z

471

Studies of the mechanism of thiophene hydrodesulfurization: Conversion of 2,3- and 2,5-dihydrothiophene and model organometallic compounds  

SciTech Connect (OSTI)

Catalytic hydrodesulfurization (HDS), the process by which organically bound sulfur is removed from crude oils, is one of the largest-scale chemical processes practiced in the world. Thiophene is typical of the organosulfur compounds found in petroleum, and considerable effort has been directed toward investigating the mechanism for thiophene hydrodesulfurization. Recently, the authors have reported new kinetic information involving the HDS of thiophene, 2,3- and 2,5- dihydrothiophenes, and tetrahydrothiophene. These studies were performed with both Re/{gamma}-Al{sub 2}O{sub 3} and Mo/{gamma}-Al{sub 2}O{sub 3} catalysts using a flow microreactor system; in particular, rhenium studies provided new information data concerning reaction intermediates. They have also been able to prepare and characterize thiophene-related organometallic compounds which serve as plausible models for bonding and conversion on catalytic surfaces. The combination of these studies has led to new insights concerning alternate mechanistic pathways for thiophene HDS. This comprehensive mechanism, which is based on kinetic studies using model HDS catalysts and on the synthesis and characterization of relevant transition metal complexes, is offered as a plausible route for thiophene HDS.

Sauer, N.N.; Markel, E.J.; Schrader, G.L.; Angelici, R.J. (Iowa State Univ., Ames (USA))

1989-05-01T23:59:59.000Z

472

Diffusion in biofilms respiring on electrodes  

SciTech Connect (OSTI)

The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (De) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed for noninvasive, nondestructive, high spatial resolution in situ De measurements in living biofilms respiring on electrodes. The electrodes were polarized so that they would act as the sole terminal electron acceptor for microbial metabolism. We present our results as both two-dimensional De heat maps and surface-averaged relative effective diffusion coefficient (Drs) depth profiles. We found that (1) Drs decreases with depth in G. sulfurreducens biofilms, following a sigmoid shape; (2) Drs at a given location decreases with G. sulfurreducens biofilm age; (3) average De and Drs profiles in G. sulfurreducens biofilms are lower than those in S. oneidensis biofilms—the G. sulfurreducens biofilms studied here were on average 10 times denser than the S. oneidensis biofilms; and (4) halting the respiration of a G. sulfurreducens biofilm decreases the De values. Density, reflected by De, plays a major role in the extracellular electron transfer strategies of electrochemically active biofilms.

Renslow, Ryan S.; Babauta, Jerome T.; Majors, Paul D.; Beyenal, Haluk

2013-02-15T23:59:59.000Z

473

Traumatic brain injury and recovery mechanisms: peptide modulation of periventricular neurogenic regions by the choroid plexus–CSF nexus  

E-Print Network [OSTI]

model Baboon Lateral head movement acceleration (diffuse injury) Rat (male Wistar) Single blast,blast waves or other TBI-induc- tion procedures (Table 1). The diffuse injury model,

Johanson, Conrad; Stopa, Edward; Baird, Andrew; Sharma, Hari

2011-01-01T23:59:59.000Z

474

Heat Hyperbolic Diffusion in Planck Gas  

E-Print Network [OSTI]

In this paper we investigate the diffusion of the thermal pulse in Planck Gas. We show that the Fourier diffusion equation gives the speed of diffusion, v > c and breaks the causality of the thermal processes in Planck gas .For hyperbolic heat transport v

Miroslaw Kozlowski; Janina Marciak-Kozlowska

2006-07-06T23:59:59.000Z

475

Mechanics, mechanisms, and modeling of the chemical mechanical polishing process  

E-Print Network [OSTI]

The ever-increasing demand for high-performance microelectronic devices has motivated the semiconductor industry to design and manufacture Ultra-Large-Scale Integrated (ULSI) circuits with smaller feature size, higher ...

Lai, Jiun-Yu

2001-01-01T23:59:59.000Z

476

Modeling Slag Penetration and Refractory Degradation Using the Finite Element Method  

SciTech Connect (OSTI)

Refractory degradation due to slag penetration can significantly reduce the service life of gasifier refractory linings. This paper describes a modeling approach that was developed to predict refractory spalling as a function of operating temperature, coal feedstock and refractory type. The model simulates the coupled thermal, diffusion, and mechanical interactions of coal slag with refractory ceramics. The heat transfer and slag diffusion solutions are directly coupled through a temperature-dependent effective diffusivity for slag penetration. The effective diffusivity is defined from slag penetration tests conducted in our laboratories on specific coal slag and refractory combinations. Chemically-induced swelling of the refractory and the build-up of mechanical stresses are functions of the slag penetration. The model results are compared with analytical spalling models and validated by experimental data in order to develop an efficient refractory degradation model for implementation in a systems level gasifier model. The ultimate goal of our research is to provide a tool that will help optimize gasifier performance by balancing conversion efficiency with refractory life.

Johnson, Kenneth I.; Williford, Ralph E.; Matyas, Josef; Pilli, Siva Prasad; Sundaram, S. K.; Korolev, Vladimir N.

2008-09-01T23:59:59.000Z

477

Diffusivity of hydrogen in dilute alloys of copper and niobium in palladium  

Science Journals Connector (OSTI)

An electrochemical technique has been used to measure the diffusion coefficient of hydrogen in palladium-copper and palladium-niobium alloys between 0 and 50°C. The range of concentration for the copper and niobium additions was 0–10 at.%. For all experiments the hydrogen content was kept below 0.1 at.% and it was found that the diffusivity of hydrogen is remarkably decreased by additions of niobium. This behavior is discussed within the framework of different trapping models. In agreement with these models no dependence of the diffusivity on hydrogen concentration was observed. Copper additions also decrease the hydrogen diffusivity in palladium, but the effect is less pronounced than niobium. A measurable change of the activation energy of diffusion was observed only for the niobium alloy with the highest niobium content of 6.5 at.%. The activation energy increased by abour 7 kJ/mol compared to pure palladium.

Reiner Kirchheim; Rex B. McLellan

1980-01-01T23:59:59.000Z

478

Nanoparticle Diffusion in Polymer Nanocomposites  

Science Journals Connector (OSTI)

Large-scale molecular dynamics simulations show that nanoparticle (NP) diffusivity in weakly interacting mixtures of NPs and polymer melts has two very different classes of behavior depending on their size. NP relaxation times and their diffusivities are completely described by the local, Rouse dynamics of the polymer chains for NPs smaller than the polymer entanglement mesh size. The motion of larger NPs, which are comparable to the entanglement mesh size, is significantly slowed by chain entanglements, and is not describable by the Stokes-Einstein relationship. Our results are in essentially quantitative agreement with a force-level generalized Langevin equation theory for all the NP sizes and chain lengths explored, and imply that for these lightly entangled systems, activated NP hopping is not important.

Jagannathan T. Kalathi; Umi Yamamoto; Kenneth S. Schweizer; Gary S. Grest; Sanat K. Kumar

2014-03-12T23:59:59.000Z

479

Determination of effective water vapor diffusion coefficient in pemfc gas diffusion layers  

E-Print Network [OSTI]

route from the cathode catalyst layer to the cathode flow channels. Water can be removed from the cellDetermination of effective water vapor diffusion coefficient in pemfc gas diffusion layers Jacob M: Water vapor diffusion PEMFC Water management GDL Diffusivity MPL a b s t r a c t The primary removal

Kandlikar, Satish

480

Non-standard Fickian self-diffusion of isotopically pure boron observed by neutron reflectometry and depth profiling  

SciTech Connect (OSTI)

Neutron reflectometry (NR) studies of thin films of amorphous {sup 11}B/{sup 10}B on silicon indicate that a non-standard form of Fickian diffusion occurs across the boron interface upon annealing. In order to verify this observation, the samples were examined by neutron depth profiling (NDP). Comparison of the results from models of a step function, standard Fickian diffusion and Fickian diffusion with a fixed composition at the interface were made and compared to the previous NR results. The diffusion constant resulting from the non-standard Fickian model for the NDP data differs slightly from that obtained from the commonly used Fickian diffusion model and is not inconsistent with the NR results. This finding suggests that more information regarding diffusion at interfaces can be gained from these higher resolution neutron scattering techniques.

Baker, S.M.; Wu, K. [Harvey Mudd Coll., Claremont, CA (United States). Dept. of Chemistry; Smith, G.S.; Hubbard, K.M.; Nastasi, M. [Los Alamos National Lab., NM (United States); Downing, R.G.; Lamaze, G.P. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1995-12-31T23:59:59.000Z

Note: This page contains sample records for the topic "diffusion mechanisms models" 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.


481

Comparison of \\{WTi\\} and WTi(N) as diffusion barriers for Al and Cu metallization on Si with respect to thermal stability and diffusion behavior of Ti  

Science Journals Connector (OSTI)

Abstract The thermal stability of \\{WTi\\} and WTi(N) as diffusion barriers for Al and Cu metallization on Si (1 0 0) was investigated by time of flight secondary ion mass spectrometry (ToF-SIMS) depth profiling, X-ray diffraction (XRD), electron microscopy (SEM and TEM) and X-ray photoelectron spectroscopy (XPS). For both, Al and Cu, Ti diffusion out of \\{WTi\\} into the metal was proved to occur at elevated temperatures (400 °C for Al and 600 °C for Cu) which further results in barrier film failure. Nitrogen incorporation into \\{WTi\\} leads to an elimination of the Ti diffusion and consequently to a better thermal stability of the barrier film. It is shown that besides crystal structure, Ti diffusion into the metallization is an essential factor of the barrier failure mechanism. The failure temperature for Al is lower than for Cu.

M. Fugger; M. Plappert; C. Schäffer; O. Humbel; H. Hutter; H. Danninger; M. Nowottnick

2014-01-01T23:59:59.000Z

482

Heat transfer and pollutant formation mechanisms in insulated combustion chambers  

SciTech Connect (OSTI)

The authors have studied the quenching situation as it can be found in constant volume combustion chambers for a methane flame over a range of wall temperatures between 300 K and 600 K using Direct Numerical Simulation. To do this, the authors solved the fully compressible, one-dimensional Navier-Stokes equations with detailed mechanisms for kinetics and diffusion. This approach allows to compare various reaction schemes, to identify the most important species and reaction paths, and to investigate the influence of different modeling assumptions. The computational results show that the dimensional wall heat flux increases with wall temperature over the whole range of wall temperatures studied; this agrees well with the most recent measurements in a strongly improved experimental setup. It is found that the wall can be modeled as chemically inert and thermal diffusion processes are negligible for low wall temperatures between 300 K and 400 K. However, at higher temperatures, due to a dramatically increasing radical concentration (H, Oh, OH) at the wall, both become increasingly important leading to large heat release rates directly at the metallic wall surface of the combustion chamber, and can thus not be neglected in the modeling of the quenching process. Furthermore, these high radical concentrations adjacent to the wall indicate that the uncertainties in wall heat flux measurements at high wall temperatures could be underestimated by the experimentalists. The UHC concentration at a wall temperature of 600 K is about 20 times smaller than for 300 K after quenching. 37 refs., 12 figs., 1 tab.

Popp, P.; Baum, M.

1995-12-31T23:59:59.000Z

483

Independent Oversight Inspection, Portsmouth Gaseous Diffusion Plant -  

Broader source: Energy.gov (indexed) [DOE]

Portsmouth Gaseous Diffusion Portsmouth Gaseous Diffusion Plant - November 2006 Independent Oversight Inspection, Portsmouth Gaseous Diffusion Plant - November 2006 November 2006 Inspection of Emergency Management at the Portsmouth Gaseous Diffusion Plant The Secretary of Energy's Office of Independent Oversight, within the Office of Security and Safety Performance Assurance, conducted an inspection of the emergency management program at the Portsmouth Gaseous Diffusion Plant (PORTS) in August and September 2006. The coordination of emergency plans and procedures among USEC and DOE contractor organizations has successfully integrated the emergency management programs into a single cohesive program for the PORTS site. Other strengths include accurate hazards surveys that identify applicable

484

Assessment of BTX Concentrations Near a Petrol Station Using Diffusive Samplers  

E-Print Network [OSTI]

polluted area. Keywords: Air quality, population exposure, benzene, service Station, petrol, vapour Author manuscript, published in "International Conference Measuring Air Pollutants by Diffusive Sampling monitoring and dispersion modelling methodology was applied for assessing air quality related

Boyer, Edmond

485

Roughening due to edge diffusion for irreversible aggregation C. Ratsch,1,2,  

E-Print Network [OSTI]

Roughening due to edge diffusion for irreversible aggregation C. Ratsch,1,2, * M. C. Wheeler,2 for epitaxial growth enhances surface roughening for a model of irreversible aggregation. The reason

Ratsch, Christian

486

Diffusion of cations in chromia layers grown on iron-base alloys  

SciTech Connect (OSTI)

Diffusion of the cations Cr, Fe, Mn, and Ni in Cr{sub 2}O{sub 3} has been investigated at 1,173 K. The diffusion measurements were performed on chromia layers grown on the