Mechanical reaction-diffusion model for bacterial population dynamics
Ngamsaad, Waipot
2015-01-01T23:59:59.000Z
The effect of mechanical interaction between cells on the spreading of bacterial population was investigated in one-dimensional space. A nonlinear reaction-diffusion equation has been formulated as a model for this dynamics. In this model, the bacterial cells are treated as the rod-like particles that interact, when contacting each other, through the hard-core repulsion. The repulsion introduces the exclusion process that causes the fast diffusion in bacterial population at high density. The propagation of the bacterial density as the traveling wave front in long time behavior has been analyzed. The analytical result reveals that the front speed is enhanced by the exclusion process---and its value depends on the packing fraction of cell. The numerical solutions of the model have been solved to confirm this prediction.
Diffusive Shock Acceleration: the Fermi Mechanism
Matthew G. Baring
1997-11-16T23:59:59.000Z
The mechanism of diffusive Fermi acceleration at collisionless plasma shock waves is widely invoked in astrophysics to explain the appearance of non-thermal particle populations in a variety of environments, including sites of cosmic ray production, and is observed to operate at several sites in the heliosphere. This review outlines the principal results from the theory of diffusive shock acceleration, focusing first on how it produces power-law distributions in test-particle regimes, where the shock dynamics are dominated by the thermal populations that provide the seed particles for the acceleration process. Then the importance of non-linear modifications to the shock hydrodynamics by the accelerated particles is addressed, emphasizing how these subsequently influence non-thermal spectral formation.
Diffusion-based DNA target colocalization by thermodynamic mechanisms
Antonio Scialdone; Mario Nicodemi
2011-05-04T23:59:59.000Z
In eukaryotic cell nuclei, a variety of DNA interactions with nuclear elements occur, which, in combination with intra- and inter- chromosomal cross-talks, shape a functional 3D architecture. In some cases they are organized by active, i.e. actin/myosin, motors. More often, however, they have been related to passive diffusion mechanisms. Yet, the crucial questions on how DNA loci recognize their target and are reliably shuttled to their destination by Brownian diffusion are still open. Here, we complement the current experimental scenario by considering a physics model, in which the interaction between distant loci is mediated by diffusing bridging molecules. We show that, in such a system, the mechanism underlying target recognition and colocalization is a thermodynamic switch-like process (a phase transition) that only occurs if the concentration and affinity of binding molecules is above a threshold, or else stable contacts are not possible. We also briefly discuss the kinetics of this "passive-shuttling" process, as produced by random diffusion of DNA loci and their binders, and derive predictions based on the effects of genomic modifications and deletions.
MULTISCALE MODELING OF DIFFUSION-INDUCED DEFORMATION PROCESSES
Ponce, V. Miguel
MULTISCALE MODELING OF DIFFUSION- INDUCED DEFORMATION PROCESSES Dr. Eugene Olevsky Friday, February 19, 2010 Engineering Bldg. Room E 300 Sintering is a high temperature process of bonding together of matter transport by different diffusion mechanisms driven by the high surface energy of aggregates
Adsorption, Desorption, and Diffusion of Nitrogen in a Model...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
II. Diffusion Limited Kinetics in Amorphous Adsorption, Desorption, and Diffusion of Nitrogen in a Model Nanoporous Material: II. Diffusion Limited Kinetics in Amorphous Abstract:...
CONVERTIBLE BONDS IN A DEFAULTABLE DIFFUSION MODEL
Jeanblanc, Monique
CONVERTIBLE BONDS IN A DEFAULTABLE DIFFUSION MODEL Tomasz R. Bielecki Department of Applied Research Grant PS12918. #12;2 Convertible Bonds in a Defaultable Diffusion Model 1 Introduction In [4), such as Convertible Bonds (CB), and we provided a rigorous decomposition of a CB into a bond component and a (game
Forecasting Turbulent Modes with Nonparametric Diffusion Models
Tyrus Berry; John Harlim
2015-01-27T23:59:59.000Z
This paper presents a nonparametric diffusion modeling approach for forecasting partially observed noisy turbulent modes. The proposed forecast model uses a basis of smooth functions (constructed with the diffusion maps algorithm) to represent probability densities, so that the forecast model becomes a linear map in this basis. We estimate this linear map by exploiting a previously established rigorous connection between the discrete time shift map and the semi-group solution associated to the backward Kolmogorov equation. In order to smooth the noisy data, we apply diffusion maps to a delay embedding of the noisy data, which also helps to account for the interactions between the observed and unobserved modes. We show that this delay embedding biases the geometry of the data in a way which extracts the most predictable component of the dynamics. The resulting model approximates the semigroup solutions of the generator of the underlying dynamics in the limit of large data and in the observation noise limit. We will show numerical examples on a wide-range of well-studied turbulent modes, including the Fourier modes of the energy conserving Truncated Burgers-Hopf (TBH) model, the Lorenz-96 model in weakly chaotic to fully turbulent regimes, and the barotropic modes of a quasi-geostrophic model with baroclinic instabilities. In these examples, forecasting skills of the nonparametric diffusion model are compared to a wide-range of stochastic parametric modeling approaches, which account for the nonlinear interactions between the observed and unobserved modes with white and colored noises.
Modelling international wind energy diffusion: Are the patterns of induced diffusion `S'
Feigon, Brooke
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
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...
Lithium diffusion mechanisms in layered intercalation compounds A. Van der Ven*
Ceder, Gerbrand
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
A Diffusion Model in Population Genetics with Mutation and Dynamic
O'Leary, Michael
A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness Mike O'Leary Department of Mathematics Towson University May 24, 2008 Mike O'Leary (Towson University) A Diffusion Model in Genetics May Miller, Georgetown University Mike O'Leary (Towson University) A Diffusion Model in Genetics May 24, 2008
Distributed Energy Resources Market Diffusion Model
Maribu, Karl Magnus; Firestone, Ryan; Marnay, Chris; Siddiqui,Afzal S.
2006-06-16T23:59:59.000Z
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.
Modelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity,
Cambridge, University of
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 the diffusion of both niobium and carbon. These elements diffuse at very different rates. A model is presented
Distributed Wind Diffusion Model Overview (Presentation)
Preus, R.; Drury, E.; Sigrin, B.; Gleason, M.
2014-07-01T23:59:59.000Z
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.
Adsorption, Desorption, and Diffusion of Nitrogen in a Model...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
I. Surface Limited Desorption Kinetics in Adsorption, Desorption, and Diffusion of Nitrogen in a Model Nanoporous Material: I. Surface Limited Desorption Kinetics in Abstract: The...
Beta Advection-Diffusion Model Columbia Basin Research
Washington at Seattle, University of
Beta Advection-Diffusion Model Jim Norris Columbia Basin Research University of Washington Box Model (SSM) is loosely called a Beta Advection-Diffusion model. The SSM estimates a single parameter this single parameter characterized fish migration. The purpose of this note is to define the Beta Advection
Diffusion model of the non-stoichiometric uranium dioxide
Moore, Emily, E-mail: emily.moore@cea.fr [CEA Saclay, DEN-DPC-SCCME, 91191 Gif-sur-Yvette Cedex (France); Guéneau, Christine, E-mail: christine.gueneau@cea.fr [CEA Saclay, DEN-DPC-SCCME, 91191 Gif-sur-Yvette Cedex (France); Crocombette, Jean-Paul, E-mail: jean-paul.crocombette@cea.fr [CEA Saclay, DEN DEN, Service de Recherches de Métallurgie Physique, 91191 Gif-sur-Yvette Cedex (France)
2013-07-15T23:59:59.000Z
Uranium dioxide (UO{sub 2}), which is used in light water reactors, exhibits a large range of non-stoichiometry over a wide temperature scale up to 2000 K. Understanding diffusion behavior of uranium oxides under such conditions is essential to ensure safe reactor operation. The current understanding of diffusion properties is largely limited by the stoichiometric deviations inherent to the fuel. The present DICTRA-based model considers diffusion across non-stoichiometric ranges described by experimentally available data. A vacancy and interstitial model of diffusion is applied to the U–O system as a function of its defect structure derived from CALPHAD-type thermodynamic descriptions. Oxygen and uranium self and tracer diffusion coefficients are assessed for the construction of a mobility database. Chemical diffusion coefficients of oxygen are derived with respect to the Darken relation and migration energies of defects are evaluated as a function of stoichiometric deviation. - Graphical abstract: Complete description of Oxygen–Uranium diffusion as a function of composition at various temperatures according to the developed Dictra model. - Highlights: • Assessment of a uranium–oxygen diffusion model with Dictra. • Complete description of U–O diffusion over wide temperature and composition range. • Oxygen model includes terms for interstitial and vacancy migration. • Interaction terms between defects help describe non-stoichiometric domain of UO{sub 2±x}. • Uranium model is separated into mobility terms for the cationic species.
Lin, Yiheng; Xia, Guangrui [Department of Materials Engineering, The University of British Columbia, 309-6350 Stores Rd, Vancouver, British Columbia V6T 1Z4 (Canada); Yasuda, Hiroshi; Wise, Rick [Texas Instruments, 13121 TI Blvd., Dallas, Texas 75243 (United States); Schiekofer, Manfred; Benna, Bernhard [Texas Instruments Deutschland GmbH, Haggertystrasse 1, 85356 Freising (Germany)
2014-10-14T23:59:59.000Z
The use of carbon (C) in SiGe base layers is an important approach to control the base layer dopant phosphorus (P) diffusion and thus enhance PNP heterojunction bipolar transistor (HBT) performance. This work quantitatively investigated the carbon impacts on P diffusion in Si{sub 0.82}Ge{sub 0.18}:C and Si:C under rapid thermal anneal conditions. The carbon molar fraction is up to 0.32%. The results showed that the carbon retardation effect on P diffusion is less effective for Si{sub 0.82}Ge{sub 0.18}:C than for Si:C. In Si{sub 0.82}Ge{sub 0.18}:C, there is an optimum carbon content at around 0.05% to 0.1%, beyond which more carbon incorporation does not retard P diffusion any more. This behavior is different from the P diffusion behavior in Si:C and the B in Si:C and low Ge SiGe:C, which can be explained by the decreased interstitial-mediated diffusion fraction f{sub I}{sup P,?SiGe} to 95% as Ge content increases to 18%. Empirical models were established to calculate the time-averaged point defect concentrations and effective diffusivities as a function of carbon and was shown to agree with previous studies on boron, phosphorus, arsenic and antimony diffusion with carbon.
A Mesoscale Diffusion Model in Population Genetics with
O'Leary, Michael
' & $ % A Mesoscale Diffusion Model in Population Genetics with Dynamic Fitness Mike O'Leary Towson University Judith R. Miller Georgetown University 1 #12;A mesoscale diffusion model in population genetics that dominance and epistasis are absent. April 28, 2005 Mike O'Leary and Judith Miller Slide 2 #12;A mesoscale
Maeta, Takahiro [Graduate School of System Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan); GlobalWafers Japan Co., Ltd., Higashikou, Seirou-machi, Kitakanbara-gun, Niigata 957-0197 (Japan); Sueoka, Koji [Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan)
2014-08-21T23:59:59.000Z
Ge-based substrates are being developed for applications in advanced nano-electronic devices because of their higher intrinsic carrier mobility than Si. The stability and diffusion mechanism of impurity atoms in Ge are not well known in contrast to those of Si. Systematic studies of the stable sites of 2nd to 6th row element impurity atoms in Ge crystal were undertaken with density functional theory (DFT) and compared with those in Si crystal. It was found that most of the impurity atoms in Ge were stable at substitutional sites, while transition metals in Si were stable at interstitial sites and the other impurity atoms in Si were stable at substitutional sites. Furthermore, DFT calculations were carried out to clarify the mechanism responsible for the diffusion of impurity atoms in Ge crystals. The diffusion mechanism for 3d transition metals in Ge was found to be an interstitial-substitutional diffusion mechanism, while in Si this was an interstitial diffusion mechanism. The diffusion barriers in the proposed diffusion mechanisms in Ge and Si were quantitatively verified by comparing them to the experimental values in the literature.
Zhang, Qi, S.M. Massachusetts Institute of Technology
2008-01-01T23:59:59.000Z
While large scale diffusion of alternative fuel vehicles (AFVs) is widely anticipated, the mechanisms that determine their success or failure are ill understood. Analysis of an AFV transition model developed at MIT has ...
Compaction Effects on Uniformity, Moisture Diffusion, and Mechanical Properties of Asphalt Pavements
Kassem, Emad Abdel-Rahman Ahmed
2011-08-08T23:59:59.000Z
in gyratory specimens were related to the mixture mechanical properties measured using the Overlay and Hamburg tests. The second part of this study focused on studying the relationship between air void distribution and moisture diffusion. A laboratory test...
Diffusion Bonding Aluminium Alloys and Composites: New Approaches and Modelling
Cambridge, University of
Diffusion Bonding Aluminium Alloys and Composites: New Approaches and Modelling Amir A. Shirzadi for advanced aluminium alloys and composites will enable them to be more widely used. The aim of this Ph of the research, two new methods for TLP diffusion bonding of aluminium-based composites (aluminium alloys
Modeling biofilms with dual extracellular electron transfer mechanisms
Renslow, Ryan S.; Babauta, Jerome T.; Kuprat, Andrew P.; Schenk, Jim; Ivory, Cornelius; Fredrickson, Jim K.; Beyenal, Haluk
2013-11-28T23:59:59.000Z
Electrochemically active biofilms have a unique form of respiration in which they utilize solid external materials as their terminal electron acceptor for metabolism. Currently, two primary mechanisms have been identified for long-range extracellular electron transfer (EET): a diffusion- and a conduction-based mechanism. Evidence in the literature suggests that some biofilms, particularly Shewanella oneidensis, produce components requisite for both mechanisms. In this study, a generic model is presented that incorporates both diffusion- and conduction-based mechanisms and allows electrochemically active biofilms to utilize both simultaneously. The model was applied to Shewanella oneidensis and Geobacter sulfurreducens biofilms using experimentally generated data found the literature. Our simulation results showed that 1) biofilms having both mechanisms available, especially if they can interact, may have metabolic advantage over biofilms that can use only a single mechanism; 2) the thickness of Geobacter sulfurreducens biofilms is likely not limited by conductivity; 3) accurate intrabiofilm diffusion coefficient values are critical for current generation predictions; and 4) the local biofilm potential and redox potential are two distinct measurements and cannot be assumed to have identical values. Finally, we determined that cyclic and squarewave voltammetry are currently not good tools to determine the specific percentage of extracellular electron transfer mechanisms used by biofilms. The developed model will be a critical tool in designing experiments to explain EET mechanisms.
Developing the Galactic Diffuse Emission Model for the GLAST Large Area Telescope
Moskalenko, Igor V.; Strong, Andrew W.; Digel, Seth W.; Porter, Troy A.
2007-04-30T23:59:59.000Z
Diffuse emission is produced in energetic cosmic ray (CR) interactions, mainly protons and electrons, with the interstellar gas and radiation field and contains the information about particle spectra in distant regions of the Galaxy. It may also contain information about exotic processes such as dark matter annihilation, black hole evaporation etc. A model of the diffuse emission is important for determination of the source positions and spectra. Calculation of the Galactic diffuse continuum g-ray emission requires a model for CR propagation as the first step. Such a model is based on theory of particle transport in the interstellar medium as well as on many kinds of data provided by different experiments in Astrophysics and Particle and Nuclear Physics. Such data include: secondary particle and isotopic production cross sections, total interaction nuclear cross sections and lifetimes of radioactive species, gas mass calibrations and gas distribution in the Galaxy (H{sub 2}, H I, H II), interstellar radiation field, CR source distribution and particle spectra at the sources, magnetic field, energy losses, g-ray and synchrotron production mechanisms, and many other issues. We are continuously improving the GALPROP model and the code to keep up with a flow of new data. Improvement in any field may affect the Galactic diffuse continuum g-ray emission model used as a background model by the GLAST LAT instrument. Here we report about the latest improvements of the GALPROP and the diffuse emission model.
Extending ballistic graphene FET lumped element models to diffusive devices
Paris-Sud XI, Université de
Extending ballistic graphene FET lumped element models to diffusive devices G Vincenzi1,2 , G graphene field effect device model is presented. The model is based on the "Top-of-the-barrier" approach which is usually valid only for ballistic graphene nanotransistors. Proper modifications are introduced
The ramifications of diffusive volume transport in classical fluid mechanics
Bielenberg, James R. (James Ronald), 1976-
2004-01-01T23:59:59.000Z
The thesis that follows consists of a collection of work supporting and extending a novel reformulation of fluid mechanics, wherein the linear momentum per unit mass in a fluid continuum, m, is supposed equal to the volume ...
Nonlocal models in continuum mechanics
Johnson, N.L. [Los Alamos National Lab., NM (United States); Phan-Thien, N. [Sydney Univ., NSW (Australia). Dept. of Mechanical Engineering
1993-09-01T23:59:59.000Z
The recent appearance of nonlocal methods is examined in the light of traditional continuum mechanics. A comparison of nonlocal approaches in the fields of solid and fluid mechanics reveals that no consistent definition of a nonlocal theory has been used. We suggest a definition based on the violation of the principle of local action in continuum mechanics. From the consideration of the implications of a nonlocal theory based on this definition, we conclude that constitutive relations with nonlocal terms can confuse the traditional separation of the roles between conservation laws and constitutive relations. The diversity of motivations for the nonlocal approaches are presented, resulting primarily from deficiencies in numerical solutions to practical problems. To illustrate these concepts, the history of nonlocal terms in the field of viscoelastic fluids is reviewed. A specific example of a viscoelastic constitutive relation that contains a stress diffusion term is applied to a simple shear flow and found not to be a physical description of any known fluid. We conclude by listing questions that should be asked of nonlocal approaches.
A mechanical model of early salt dome growth
Irwin, Frank Albert
1988-01-01T23:59:59.000Z
of Department) December 1988 A Mechanical Analysis of Early Salt Dome Growth. (December 1988) Frank Albert Irwin, B. S. , Texas A&M University Chair of Advisory Committee: Dr. Raymond C. Fletcher A two-layer superposition model, the lower layer representing... of the sediments results in growth rates much higher than those observed. Analysis of the case with a diffusivity of 104m2/Ka agrees with all observa- tions. A range of diffusivities which will produce a realistic salt dome model is then determined. The lower...
Modelling of monovacancy diffusion in W over wide temperature range
Bukonte, L., E-mail: laura.bukonte@helsinki.fi; Ahlgren, T.; Heinola, K. [Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki (Finland)
2014-03-28T23:59:59.000Z
The diffusion of monovacancies in tungsten is studied computationally over a wide temperature range from 1300?K until the melting point of the material. Our modelling is based on Molecular Dynamics technique and Density Functional Theory. The monovacancy migration barriers are calculated using nudged elastic band method for nearest and next-nearest neighbour monovacancy jumps. The diffusion pre-exponential factor for monovacancy diffusion is found to be two to three orders of magnitude higher than commonly used in computational studies, resulting in attempt frequency of the order 10{sup 15} Hz. Multiple nearest neighbour jumps of monovacancy are found to play an important role in the contribution to the total diffusion coefficient, especially at temperatures above 2/3 of T{sub m}, resulting in an upward curvature of the Arrhenius diagram. The probabilities for different nearest neighbour jumps for monovacancy in W are calculated at different temperatures.
Kwong, S. [National Nuclear Laboratory (United Kingdom)] [National Nuclear Laboratory (United Kingdom); Jivkov, A.P. [Research Centre for Radwaste and Decommissioning and Modelling and Simulation Centre, University of Manchester (United Kingdom)] [Research Centre for Radwaste and Decommissioning and Modelling and Simulation Centre, University of Manchester (United Kingdom)
2013-07-01T23:59:59.000Z
Deep geologic disposal of high activity and long-lived radioactive waste is being actively considered and pursued in many countries, where low permeability geological formations are used to provide long term waste contaminant with minimum impact to the environment and risk to the biosphere. A multi-barrier approach that makes use of both engineered and natural barriers (i.e. geological formations) is often used to further enhance the containment performance of the repository. As the deep repository system subjects to a variety of thermo-hydro-chemo-mechanical (THCM) effects over its long 'operational' lifespan (e.g. 0.1 to 1.0 million years, the integrity of the barrier system will decrease over time (e.g. fracturing in rock or clay)). This is broadly referred as media degradation in the present study. This modelling study examines the effects of media degradation on diffusion dominant solute transport in fractured media that are typical of deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes, while the effects of degradation is studied using a pore network model that considers the media diffusivity and network changes. Model results are presented to demonstrate the use of a 3D pore-network model, using a novel architecture, to calculate macroscopic properties of the medium such as diffusivity, subject to pore space changes as the media degrade. Results from a reactive transport model of a representative geological waste disposal package are also presented to demonstrate the effect of media property change on the solute migration behaviour, illustrating the complex interplay between kinetic biogeochemical processes and diffusion dominant transport. The initial modelling results demonstrate the feasibility of a coupled modelling approach (using pore-network model and reactive transport model) to examine the long term behaviour of deep geological repositories with media property change under complex geochemical conditions. (authors)
Modelling Electrical Car Diffusion Based on Agent Tao Zhang, 3
Aickelin, Uwe
the UK government's 2020 target of cutting emission. Figure 1. city energy consumption in UK, 2009 government announced a project that anyone who buys an electric plug-in car from 2011 will get a 25% discountModelling Electrical Car Diffusion Based on Agent 1 Lei Yu, ,2 Tao Zhang, 3 Siebers Peer-Ola, 4
Flux-Limited Diffusion Approximation Models of Giant Planet Formation by Disk Instability
Boss, Alan P
2008-01-01T23:59:59.000Z
Both core accretion and disk instability appear to be required as formation mechanisms in order to explain the entire range of giant planets found in extrasolar planetary systems. Disk instability is based on the formation of clumps in a marginally-gravitationally unstable protoplanetary disk. These clumps can only be expected to contract and survive to become protoplanets if they are able to lose thermal energy through a combination of convection and radiative cooling. Here we present several new three dimensional, radiative hydrodynamics models of self-gravitating protoplanetary disks, where radiative transfer is handled in the flux-limited diffusion approximation. We show that while the flux-limited models lead to higher midplane temperatures than in a diffusion approximation model without the flux-limiter, the difference in temperatures does not appear to be sufficiently high to have any significant effect on the formation of self-gravitating clumps. Self-gravitating clumps form rapidly in the models both...
Transport Corrections in Nodal Diffusion Codes for HTR Modeling
Abderrafi M. Ougouag; Frederick N. Gleicher
2010-08-01T23:59:59.000Z
The cores and reflectors of High Temperature Reactors (HTRs) of the Next Generation Nuclear Plant (NGNP) type are dominantly diffusive media from the point of view of behavior of the neutrons and their migration between the various structures of the reactor. This means that neutron diffusion theory is sufficient for modeling most features of such reactors and transport theory may not be needed for most applications. Of course, the above statement assumes the availability of homogenized diffusion theory data. The statement is true for most situations but not all. Two features of NGNP-type HTRs require that the diffusion theory-based solution be corrected for local transport effects. These two cases are the treatment of burnable poisons (BP) in the case of the prismatic block reactors and, for both pebble bed reactor (PBR) and prismatic block reactor (PMR) designs, that of control rods (CR) embedded in non-multiplying regions near the interface between fueled zones and said non-multiplying zones. The need for transport correction arises because diffusion theory-based solutions appear not to provide sufficient fidelity in these situations.
Assessment of a Molecular Diffusion Model in MELCOR
Chang OH; Richard Moore
2005-06-01T23:59:59.000Z
The MELCOR (version 1.8.5) [1] computer code with INEEL revisions is being improved for the analysis of very high temperature gas-cooled reactors [2]. Following a loss-of-coolant accident, flow through the reactor vessel may initially stagnate due to a non-uniform concentration of helium and air. However, molecular diffusion will eventually result in a uniform concentration of air and helium. The differences in fluid temperatures within the reactor vessel will then result in the establishment of a natural circulation flow that can supply significant amounts of air to the reactor core. The heat released by the resulting oxidation of graphite in the reactor core has the potential to increase the peak fuel temperature. In order to analyze the effects of oxidation on the response of the reactor during accidents, a molecular diffusion model was added to MELCOR. The model is based on Fick's Second Law for spatially uniform pressure and temperature. This paper describes equimolal counter diffusion experiments in a two bulb diffusion cell and the results of the assessment calculations.
Characterization and modeling of thermal diffusion and aggregation in nanofluids.
Gharagozloo, Patricia E.; Goodson, Kenneth E. (Stanford University, Stanford, CA)
2010-05-01T23:59:59.000Z
Fluids with higher thermal conductivities are sought for fluidic cooling systems in applications including microprocessors and high-power lasers. By adding high thermal conductivity nanoscale metal and metal oxide particles to a fluid the thermal conductivity of the fluid is enhanced. While particle aggregates play a central role in recent models for the thermal conductivity of nanofluids, the effect of particle diffusion in a temperature field on the aggregation and transport has yet to be studied in depth. The present work separates the effects of particle aggregation and diffusion using parallel plate experiments, infrared microscopy, light scattering, Monte Carlo simulations, and rate equations for particle and heat transport in a well dispersed nanofluid. Experimental data show non-uniform temporal increases in thermal conductivity above effective medium theory and can be well described through simulation of the combination of particle aggregation and diffusion. The simulation shows large concentration distributions due to thermal diffusion causing variations in aggregation, thermal conductivity and viscosity. Static light scattering shows aggregates form more quickly at higher concentrations and temperatures, which explains the increased enhancement with temperature reported by other research groups. The permanent aggregates in the nanofluid are found to have a fractal dimension of 2.4 and the aggregate formations that grow over time are found to have a fractal dimension of 1.8, which is consistent with diffusion limited aggregation. Calculations show as aggregates grow the viscosity increases at a faster rate than thermal conductivity making the highly aggregated nanofluids unfavorable, especially at the low fractal dimension of 1.8. An optimum nanoparticle diameter for these particular fluid properties is calculated to be 130 nm to optimize the fluid stability by reducing settling, thermal diffusion and aggregation.
Modeling Infinite Dilution and Fickian Diffusion Coefficients of Carbon Dioxide in Water
Firoozabadi, Abbas
Modeling Infinite Dilution and Fickian Diffusion Coefficients of Carbon Dioxide in Water J. Wambui infinite dilution diffusion coefficients for carbon dioxide and water mixtures. The model takes, carbon dioxide, classical thermodynamics Introduction The increase in atmospheric concentrations of CO2
Tracer diffusion at low temperature in kinetically constrained models
Oriane Blondel
2015-05-15T23:59:59.000Z
We describe the motion of a tracer in an environment given by a kinetically constrained spin model (KCSM) at equilibrium. We check convergence of its trajectory properly rescaled to a Brownian motion and positivity of the diffusion coefficient $D$ as soon as the spectral gap of the environment is positive (which coincides with the ergodicity region under general conditions). Then we study the asymptotic behavior of $D$ when the density $1-q$ of the environment goes to $1$ in two classes of KCSM. For noncooperative models, the diffusion coefficient $D$ scales like a power of $q$, with an exponent that we compute explicitly. In the case of the Fredrickson-Andersen one-spin facilitated model, this proves a prediction made in Jung, Garrahan and Chandler [Phys. Rev. E 69 (2004) 061205]. For the East model, instead we prove that the diffusion coefficient is comparable to the spectral gap, which goes to zero faster than any power of $q$. This result contradicts the prediction of physicists (Jung, Garrahan and Chandler [Phys. Rev. E 69 (2004) 061205; J. Chem. Phys. 123 (2005) 084509]), based on numerical simulations, that suggested $D\\sim \\operatorname {gap}^{\\xi}$ with $\\xi<1$.
Numerical Modeling of Diffusion in Fractured Media for Gas-Injection
Firoozabadi, Abbas
; Arana 2001; Darvish et al. 2006). Coats (1989) has modeled the effect of diffusion in dual- porosity
Flux-Limited Diffusion Approximation Models of Giant Planet Formation by Disk Instability
Alan P. Boss
2008-01-28T23:59:59.000Z
Both core accretion and disk instability appear to be required as formation mechanisms in order to explain the entire range of giant planets found in extrasolar planetary systems. Disk instability is based on the formation of clumps in a marginally-gravitationally unstable protoplanetary disk. These clumps can only be expected to contract and survive to become protoplanets if they are able to lose thermal energy through a combination of convection and radiative cooling. Here we present several new three dimensional, radiative hydrodynamics models of self-gravitating protoplanetary disks, where radiative transfer is handled in the flux-limited diffusion approximation. We show that while the flux-limited models lead to higher midplane temperatures than in a diffusion approximation model without the flux-limiter, the difference in temperatures does not appear to be sufficiently high to have any significant effect on the formation of self-gravitating clumps. Self-gravitating clumps form rapidly in the models both with and without the flux-limiter. These models suggest that the reason for the different outcomes of numerical models of disk instability by different groups cannot be attributed solely to the handling of radiative transfer, but rather appears to be caused by a range of numerical effects and assumptions. Given the observational imperative to have disk instability form at least some extrasolar planets, these models imply that disk instability remains as a viable giant planet formation mechanism.
Kostic, Milivoje M.
Electromagnetic Nature of Thermo-Mechanical Mass-Energy Transfer Due to Photon Diffusive Re and the Physics law of forced interactions will be violated, since these thermo-mechanical phenomena are neither force interactions, namely all electro-chemical and thermo-mechanical phenomena, the latter as reasoned
An Ion Diffusion Model in Semi-Permeable Clay Materials. | EMSL
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Here we proposed a model by coupling electrodynamics and nonequilibrium thermodynamics to describe ion diffusion in the clay materials. The developed model was validated...
Superdiffusion in a Model for Diffusion in a Molecularly Crowded Environment
Dietrich Stauffer; Christian Schulze; Dieter W. Heermann
2007-06-05T23:59:59.000Z
We present a model for diffusion in a molecularly crowded environment. The model consists of random barriers in percolation network. Random walks in the presence of slowly moving barriers show normal diffusion for long times, but anomalous diffusion at intermediate times. The effective exponents for square distance versus time usually are below one at these intermediate times, but can be also larger than one for high barrier concentrations. Thus we observe sub- as well as super-diffusion in a crowded environment.
Doctoral Defense "Thermal-hydro-mechanical model
Kamat, Vineet R.
Doctoral Defense "Thermal-hydro-mechanical model for freezing and thawing soils" Yao Zhang Date been implemented in a finite element system, with a thermal-hydro- mechanical framework being used
Martin, R.C.
1990-01-01T23:59:59.000Z
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.
Goudon, Thierry
A Coupled Model for Radiative Transfer: Doppler Effects, Equilibrium and Non-Equilibrium Diffusion. The interaction terms take into account both scattering and absorption/emission phenomena, as well as Doppler-diffusion equations. Key words. Hydrodynamic limits. Diffusion approximation. Radiative transfer. Doppler correction
Modelling of unidirectional thermal diffusers in shallow water
Lee, Joseph Hun-Wei
1977-01-01T23:59:59.000Z
This study is an experimental and theoretical investigation of the temperature field and velocity field induced by a unidirectional thermal diffuser in shallow water. A multiport thermal diffuser is essentially a pipe laid ...
Magnetic field diffusion modeling of a small enclosed firing system
Warne, L.K.; Merewether, K.O.
1996-01-01T23:59:59.000Z
Intense magnetic fields exist in the immediate vicinity of a lightning strike (and near power lines). Conducting barriers increase the rise time (and thus decrease the rise rate) interior to the barrier, but typically do not prevent penetration of the magnetic field, since the lightning current fall time may be larger than the barrier diffusion time. Thus, substantial energy is present in the interior field, although the degradation of rise rate makes it more difficult to couple into electrical circuits. This report assesses the threat posed by the diffusive magnetic field to interior components and wire loops (where voltages are induced). Analytical and numerical bounding analyses are carried out on a pill box shaped conducting barrier to develop estimates for the worst case magnetic field threats inside the system. Worst case induced voltages and energies are estimated and compared with threshold charge voltages and energies on the output capacitor of the system. Variability of these quantities with respect to design parameters are indicated. The interior magnetic field and induced voltage estimates given in this report can be used as excitations for more detailed interior and component models.
Numerical study of energy diffusion in King models
Tom Theuns
1995-11-07T23:59:59.000Z
The energy diffusion coefficients D_n(E) (n=1,2) for a system of equal mass particles moving self-consistently in an N-body realisation of a King model are computed from the probability per unit time, P(E, Delta E), that a star with initial energy E will undergo an energy change Delta E. In turn, P is computed from the number of times during the simulation that a particle in a state of given energy undergoes a transition to another state. These particle states are defined directly from the time evolution of E by identifying them with the event occuring between two local maxima in the E(t) curve. If one assumes next that energy changes are uncorrelated between different states, one can use diffusion theory to compute D_n(E). The simulations employ N=512, 2048,... , 32768 particles and are performed using an implementation of Aarseth's direct integrator N-body1 on a massively parallel computer. The more than seven million transitions measured in the largest N simulation provide excellent statistics. The numerically determined D(E)'s are compared against their theoretical counterparts which are computed from phase-space averaged rates of energy change due to independent binary encounters. The overall agreement between them is impressive over most of the energy range, notwithstanding the very different type of approximations involved, giving considerable support to the valid usage of these theoretical expressions to simulate dynamical evolution in Fokker-Planck type calculations.
Regulation mechanisms in spatial stochastic development models
Dmitri Finkelshtein; Yuri Kondratiev
2008-09-04T23:59:59.000Z
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.
ASSISTANT PROFESSOR OF MECHANICAL ENGINEERING COMPUTATIONAL MODELING
ASSISTANT PROFESSOR OF MECHANICAL ENGINEERING COMPUTATIONAL MODELING COLLEGE OF ENGINEERING The Department of Mechanical Engineering at Colorado State University invites applications for a tenure processes with emphasis on applying the models to engineering systems of interest in the energy or materials
A Multiphase Solute Diffusion Model for Dendritic Alloy Solidification
Beckermann, Christoph
phenomena, Ni and Beckermann[4] proposed a two-phase model for mass, momentum, energy, and species transport averaging process, phase interaction terms appear in the resulting macro- scopic balance equations, are with the Department of Mechanical Engineering, The University of Iowa, Iowa City, IA 52242. Manuscript submitted
Probing the brain’s white matter with diffusion MRI and a tissue dependent diffusion model
Piatkowski, Jakub Przemyslaw
2014-06-27T23:59:59.000Z
While diffusion MRI promises an insight into white matter microstructure in vivo, the axonal pathways that connect different brain regions together can only partially be segmented using current methods. Here we present ...
Reaction-Diffusion systems for the microscopic cellular model of the cardiac electric field
Veneroni, Marco
Reaction-Diffusion systems for the microscopic cellular model of the cardiac electric field Marco-diffusion systems arising from the math- ematical models of the electric activity of cardiac ventricular cells Veneroni Abstract. The paper deals with a mathematical model for the electric activity of the heart
Reaction-Diffusion systems for the macroscopic Bidomain model of the cardiac electric field
Veneroni, Marco
Reaction-Diffusion systems for the macroscopic Bidomain model of the cardiac electric field Marco Veneroni Abstract. The paper deals with a mathematical model for the electric activity of the heart the mathematical viewpoint the model is made up of a degenerate parabolic reaction diffusion system coupled
Efficient Reformulation of Solid-Phase Diffusion in Physics-Based Lithium-Ion Battery Models
Subramanian, Venkat
Efficient Reformulation of Solid-Phase Diffusion in Physics-Based Lithium-Ion Battery Models materials of porous electrodes for a rigorous pseudo-2D model for lithium-ion batteries. Concentration-ion battery models is the inclusion of solid phase diffusion in a second dimension r. It increases
A Process Model of Quantum Mechanics
William Sulis
2014-04-21T23:59:59.000Z
A process model of quantum mechanics utilizes a combinatorial game to generate a discrete and finite causal space upon which can be defined a self-consistent quantum mechanics. An emergent space-time M and continuous wave function arise through a non-uniform interpolation process. Standard non-relativistic quantum mechanics emerges under the limit of infinite information (the causal space grows to infinity) and infinitesimal scale (the separation between points goes to zero). The model has the potential to address several paradoxes in quantum mechanics while remaining computationally powerful.
Lateral Water Diffusion in an Artificial Macroporous System: Modeling and Experimental Evidence
Mohanty, Binayak P.
Lateral Water Diffusion in an Artificial Macroporous System: Modeling and Experimental Evidence P systems, lateral mass exchange between macropores and the soil matrix is generally modeled as an apparent diffusion, the system is thus characterized by a single can be determined from moment analysis of the concen
Ponce, V. Miguel
holding storm water in parking lots is examined by using a diffusion wave model of catchment dynamics in urban storm water management. INTRODUCTION Urban development decreases surface roughness and infil, we use the diffusion wave model to quantify runoff detention in parking lots. Four extreme storms
On the existence of solutions for a drift-diffusion system arising in corrosion modelling
Paris-Sud XI, UniversitÃ© de
On the existence of solutions for a drift-diffusion system arising in corrosion modelling I-diffusion system describing the corrosion of an iron based alloy in a nuclear waste repository. In comparison of the corrosion model lies in the boundary conditions which are of Robin type and induce an additional coupling
A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness
O'Leary, Michael
A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness Mike O'Leary Department of Mathematics Towson University PDE Seminar Vanderbilt University November 2008 Mike O'Leary (Towson University are joint with Judith Miller, Georgetown University. Mike O'Leary (Towson University) A Diffusion Model
Subgrid models for mass and thermal diffusion in turbulent mixing
Sharp, David H [Los Alamos National Laboratory; Lim, Hyunkyung [STONY BROOK UNIV; Li, Xiao - Lin [STONY BROOK UNIV; Gilmm, James G [STONY BROOK UNIV
2008-01-01T23:59:59.000Z
We are concerned with the chaotic flow fields of turbulent mixing. Chaotic flow is found in an extreme form in multiply shocked Richtmyer-Meshkov unstable flows. The goal of a converged simulation for this problem is twofold: to obtain converged solutions for macro solution features, such as the trajectories of the principal shock waves, mixing zone edges, and mean densities and velocities within each phase, and also for such micro solution features as the joint probability distributions of the temperature and species concentration. We introduce parameterized subgrid models of mass and thermal diffusion, to define large eddy simulations (LES) that replicate the micro features observed in the direct numerical simulation (DNS). The Schmidt numbers and Prandtl numbers are chosen to represent typical liquid, gas and plasma parameter values. Our main result is to explore the variation of the Schmidt, Prandtl and Reynolds numbers by three orders of magnitude, and the mesh by a factor of 8 per linear dimension (up to 3200 cells per dimension), to allow exploration of both DNS and LES regimes and verification of the simulations for both macro and micro observables. We find mesh convergence for key properties describing the molecular level of mixing, including chemical reaction rates between the distinct fluid species. We find results nearly independent of Reynolds number for Re 300, 6000, 600K . Methodologically, the results are also new. In common with the shock capturing community, we allow and maintain sharp solution gradients, and we enhance these gradients through use of front tracking. In common with the turbulence modeling community, we include subgrid scale models with no adjustable parameters for LES. To the authors' knowledge, these two methodologies have not been previously combined. In contrast to both of these methodologies, our use of Front Tracking, with DNS or LES resolution of the momentum equation at or near the Kolmogorov scale, but without resolving the Batchelor scale, allows a feasible approach to the modeling of high Schmidt number flows.
Mechanical modeling of the growth of salt structures
Alfaro, R.A.M.
1993-05-01T23:59:59.000Z
A 2D numerical model for studying the morphology and history of salt structures by way of computer simulations is presented. The model is based on conservation laws for physical systems, a fluid marker equation to keep track of the salt/sediments interface, and two constitutive laws for rocksalt. When buoyancy alone is considered, the fluid-assisted diffusion model predicts evolution of salt structures 2.5 times faster than the power-law creep model. Both rheological laws predict strain rates of the order of 4.0 {times} 10{sup {minus}15}s{sup {minus}1} for similar structural maturity level of salt structures. Equivalent stresses and viscosities predicted by the fluid-assisted diffusion law are 10{sup 2} times smaller than those predicted by the power-law creep rheology. Use of East Texas Basin sedimentation rates and power-law creep rheology indicate that differential loading is an effective mechanism to induce perturbations that amplify and evolve to mature salt structures, similar to those observed under natural geological conditions.
A model of riots dynamics: shocks, diffusion and thresholds
Berestycki, Henri; Rodriguez, Nancy
2015-01-01T23:59:59.000Z
We introduce and analyze several variants of a system of differential equations which model the dynamics of social outbursts, such as riots. The systems involve the coupling of an explicit variable representing the intensity of rioting activity and an underlying (implicit) field of social tension. Our models include the effects of exogenous and endogenous factors as well as various propagation mechanisms. From numerical and mathematical analysis of these models we show that the assumptions made on how different locations influence one another and how the tension in the system disperses play a major role on the qualitative behavior of bursts of social unrest. Furthermore, we analyze here various properties of these systems, such as the existence of traveling wave solutions, and formulate some new open mathematical problems which arise from our work.
Comprehensive mechanisms for combustion chemistry: Experiment, modeling, and sensitivity analysis
Dryer, F.L.; Yetter, R.A. [Princeton Univ., NJ (United States)
1993-12-01T23:59:59.000Z
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.
Developing A Laser Shockwave Model For Characterizing Diffusion Bonded Interfaces
James A. Smith; Jeffrey M. Lacy; Barry H. Rabin
2014-07-01T23:59:59.000Z
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.
Zhao, Xuanhe
2008-01-01T23:59:59.000Z
in elastic solids date at least back to Gibbs (1878), who formulated a thermodynamic theory of largeJournal of the Mechanics and Physics of Solids 56 (2008) 17791793 A theory of coupled diffusion and mixing the network with the small molecules. Both the small molecules and the long polymers are taken
Lee, Shiu-Hang; Kamae, Tuneyoshi; Ellison, Donald C.
2008-07-02T23:59:59.000Z
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.
NUMERICAL MODELING FOR THE FORMATION MECHANISM OF 3D TOPOGRAPHY ON MICROBIAL MAT SURFACES
Patel, Harsh Jay
2013-09-27T23:59:59.000Z
determined. A deterministic model includes both a dynamic model, and a static model. Compared to a deterministic solute diffusion model, a stochastic diffusion model has one or more stochastic elements. Concentration diffusion system formulated... solute diffusion equation, which merely appears in the form of a number line, the quasi-2D solute diffusion equation forms a Cartesian grid system. Also, for the explicit quasi-2D solute diffusion equation (Eq. 4), concentration variation is measured...
MODELING THE DIFFUSION OF MICRO-CHP IN A RESIDENTIAL AREA
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
Modelling CO2 diffusion and assimilation in a leaf with axisymmetric finite volumes
Herbin, RaphaÃ¨le
Modelling CO2 diffusion and assimilation in a leaf with axisymmetric finite volumes Emily GallouÃ«t. This paper deals with the numerical simulation of the diffusion and assimilation by photosynthesis of CO2 medium, from experimental measurements of the pointwise value of internal CO2 concentration, giving some
Wax diffusivity under given thermal gradient: a mathematical model , A. Fasano
Primicerio, Mario
Wax diffusivity under given thermal gradient: a mathematical model S. Correra , A. Fasano , L. Fusi , M. Primicerio , F. Rosso Abstract In this paper we describe how to obtain wax diffusivity and solubility in a saturated crude oil using the measurements of solid wax deposit in the experimental apparatus
A Combined Molecular Dynamics and Diffusion Model of Single Proton Conduction through Gramicidin
Schumaker, Mark
A Combined Molecular Dynamics and Diffusion Model of Single Proton Conduction through Gramicidin through the gramicidin pore is described by a potential of mean force and diffusion coefficient obtained in the hydrogen bonding structure of pore waters without an excess proton. Proton entrance and exit were
A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness
O'Leary, Michael
A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness Mike O'Leary Department of Mathematics Towson University World Conference on Nonlinear Analysis Orlando, FL July 2008 Mike O'Leary of this work are joint with Judith Miller, Georgetown University. Mike O'Leary (Towson University) A Diffusion
Modeling-Thermo-electrochemistry, Capacity Degradation and Mechanics...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
Modeling-Thermo-electrochemistry, Capacity Degradation and Mechanics with SEI Layer Modeling-Thermo-electrochemistry, Capacity Degradation and Mechanics with SEI Layer 2011 DOE...
Modeling of diffusive mass transport in micropores in cement based materials
Yamaguchi, Tetsuji, E-mail: yamaguchi.tetsuji@jaea.go.j [Japan Atomic Energy Agency, Shirakata, Tokai, Ibaraki 319-1195 (Japan); Negishi, Kumi [Japan Atomic Energy Agency, Shirakata, Tokai, Ibaraki 319-1195 (Japan); Taiheiyo Consultant Company Limited, 2-4-2, Osaku, Sakura, Chiba 285-8655 (Japan); Hoshino, Seiichi; Tanaka, Tadao [Japan Atomic Energy Agency, Shirakata, Tokai, Ibaraki 319-1195 (Japan)
2009-12-15T23:59:59.000Z
In order to predict long-term leaching behavior of cement constituents for safety assessments of radioactive waste disposal, we modeled diffusive mass transport in micropores in cement based materials. Based on available knowledge on the pore structure, we developed a transport porosity model that enables us to estimate effective porosity available for diffusion (transport porosity) in cement based materials. We microscopically examined the pore structure of hardened cement pastes to partially verify the model. Effective diffusivities of tritiated water in hardened cement pastes were also obtained experimentally, and were shown to be proportional to the estimated transport porosity.
A Signal Processing Model of Quantum Mechanics
Chris Thron; Johnny Watts
2012-05-08T23:59:59.000Z
This paper develops a deterministic model of quantum mechanics as an accumulation-and-threshold process. The model arises from an analogy with signal processing in wireless communications. Complex wavefunctions are interpreted as expressing the amplitude and phase information of a modulated carrier wave. Particle transmission events are modeled as the outcome of a process of signal accumulation that occurs in an extra (non-spacetime) dimension. Besides giving a natural interpretation of the wavefunction and the Born rule, the model accommodates the collapse of the wave packet and other quantum paradoxes such as EPR and the Ahanorov-Bohm effect. The model also gives a new perspective on the 'relational' nature of quantum mechanics: that is, whether the wave function of a physical system is "real" or simply reflects the observer's partial knowledge of the system. We simulate the model for a 2-slit experiment, and indicate possible deviations of the model's predictions from conventional quantum mechanics. We also indicate how the theory may be extended to a field theory.
Diffusion in silicon isotope heterostructures
Silvestri, Hughes Howland
2004-05-14T23:59:59.000Z
The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and {sup 28}Si enriched layers, enables the observation of {sup 30}Si self-diffusion from the natural layers into the {sup 28}Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly positively charged P species. Additionally, the temperature dependence of the diffusion coefficient of Si in Ge was measured over the temperature range of 550 C to 900 C using a buried Si layer in an epitaxially grown Ge layer.
Lilien, Gary Louis
1978-01-01T23:59:59.000Z
This paper deals with the background, development and calibration of a model of innovation-diffusion, designed to help allocate government field test and demonstration resources in support of a photovoltaic technology ...
Non-Linear Drying Diffusion and Viscoelastic Drying Shrinkage Modeling in Hardened Cement Pastes
Leung, Chin K.
2010-07-14T23:59:59.000Z
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...
MECHANICAL BEHAVIOUR OF PVC: MODEL EVALUATION
Miroshnychenko, Dmitri
MECHANICAL BEHAVIOUR OF PVC: MODEL EVALUATION BY DMYTRO MIROSHNYCHENKO A MASTER'S THESIS SUBMITTED in the prediction of the Treloar data . . . 60 3 The yield stress of oriented PVC and its prediction 66 3 of oriented PVC . . . . . . 69 3.4 Prediction of the yield stress of oriented PVC . . . . . . . . . . . . . 73
Mental Models of Physical Mechanisms and Their
de Kleer, Johan
is that of mechanistic devices, including physical machines, electronic and hydraulic systems, and even hybrids such as electro--mechanical systems. Our top-level goals are: (1) to investigate what it means for a person to understand a complex system, in particular, the mental models that experts form of how a system functions
A Finite Element Algorithm of a Nonlinear Diffusive Climate Energy Balance Model
DÃaz, JesÃºs Ildefonso
A Finite Element Algorithm of a Nonlinear Diffusive Climate Energy Balance Model R. BERMEJO,1 J. This model belongs to the category of energy balance models introduced independently by the climatologists M climate. The energy balance model we are dealing with consists of a two-dimensional nonlinear parabolic
Faith, Duane Willbern
1977-01-01T23:59:59.000Z
ANALYTICAL MODELING OF THE INTERACTION OF ENZYME CATALYSIS AND DIFFUSION PROCESSES AT THE INTRACELLULAR LEVEL A Thesis by Duane Nillbern Faith Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirement... for the degree of MASTER OF SCIENCE May 1977 Major Subject: Bioengineering ANALYTICAL MODELING OF THE INTERACTION OF ENZYME CATALYSIS AND DIFFUSION PROCESSES AT THE INTRACELLULAR LEVEL A Thesis by Duane Willbern Faith Approved as to style and content by...
Paris-Sud XI, Université de
Bond Graph Modeling of Current Diffusion in Magnetic Cores Hervé Morel, Bruno Allard, Sabrine M, F-69621 Villeurbanne Cedex, France KEYBOARD: Bond Graphs, Variational approximation, Diffusive with the diffusion representation. Both approaches yield a same bond graph representation. 2. MODELING CURRENT
Modeling cation diffusion in compacted water-saturatedNa-bentonite at low ionic strength
Bourg, Ian C.; Sposito, Garrison; Bourg, Alain C.M.
2007-08-28T23:59:59.000Z
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}.
Mode stabilization mechanism of buried waveguide lasers with lateral diffused junctions
Yu, K.L.; Chen, T.R.; Koren, U.; Lau, K.Y.; Margalit, S.; Yariv, A.
1983-03-01T23:59:59.000Z
The mode stabilization behavior of the buried active waveguide with lateral diffused junction is theoretically investigated. The study shows that for an active waveguide of width around 5 ..mu..m with a lateral diffused junction in the middle, the single fundamental transverse mode is preferred as the injection level is raised. The theoretical results are found to be in good agreement with experimental results observed in the groove transverse junction InGaAsP/InP laser.
Efficient Reformulation of Solid-Phase Diffusion in Physics-Based Lithium-Ion Battery Models
Subramanian, Venkat
Efficient Reformulation of Solid-Phase Diffusion in Physics-Based Lithium-Ion Battery Models, Berkeley, California 94720-8168, USA Lithium-ion batteries are typically modeled using porous electrode the active materials of porous electrodes for a pseudo-two- dimensional model for lithium-ion batteries
Dynamic modeling of three-phase upflow fixed-bed reactor including pore diffusion C. Julcoura
Paris-Sud XI, Université de
Dynamic modeling of three-phase upflow fixed-bed reactor including pore diffusion C. Julcoura , R-phase upflow fixed-bed reactor are investigated using a non-isothermal heterogeneous model including gas not limiting, so that the simplest model predicts accurately the transient reactor behavior. Keywords: fixed-bed
Using a Quasipotential Transformation for Modeling Diffusion Media inPolymer-Electrolyte Fuel Cells
Weber, Adam Z.; Newman, John
2008-08-29T23:59:59.000Z
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.
Are Aftershocks of Large Californian Earthquakes Diffusing?
Helmstetter, A; Sornette, D; Helmstetter, Agnes; Ouillon, Guy; Sornette, Didier
2003-01-01T23:59:59.000Z
We analyze 21 aftershock sequences of California to test for evidence of space-time diffusion. Aftershock diffusion may result from stress diffusion and is also predicted by any mechanism of stress weakening. Here, we test an alternative mechanism to explain aftershock diffusion, based on multiple cascades of triggering. In order to characterize aftershock diffusion, we develop two methods, one based on a suitable time and space windowing that has been calibrated on the ETAS model of triggered seismicity, the other using a wavelet transform adapted to the removal of background seismicity. Both methods confirm that diffusion of seismic activity is very weak, much weaker than reported in previous studies. A possible mechanism explaining the weakness of observed diffusion is the effect of geometry, including the localization of aftershocks on a fractal fault network and the impact of extended rupture lengths which control the typical distances of interaction between earthquakes.
Bourg, I.C.; Sposito, G.; Bourg, A.C.M.
2008-08-15T23:59:59.000Z
Assessments of bentonite barrier performance in waste management scenarios require an accurate description of the diffusion of water and solutes through the barrier. A two-compartment macropore/nanopore model (on which smectite interlayer nanopores are treated as a distinct compartment of the overall pore space) was applied to describe the diffusion of {sup 22}Na{sup +} in compacted, water-saturated Na-bentonites and then compared with the well-known surface diffusion model. The two-compartment model successfully predicted the observed weak ionic strength dependence of the apparent diffusion coefficient (D{sub a}) of Na{sup +}, whereas the surface diffusion model did not, thus confirming previous research indicating the strong influence of interlayer nanopores on the properties of smectite clay barriers. Since bentonite mechanical properties and pore water chemistry have been described successfully with two-compartment models, the results in the present study represent an important contribution toward the construction of a comprehensive two-compartment model of compacted bentonite barriers.
Statistical Mechanical Models and Topological Color Codes
H. Bombin; M. A. Martin-Delgado
2007-11-03T23:59:59.000Z
We find that the overlapping of a topological quantum color code state, representing a quantum memory, with a factorized state of qubits can be written as the partition function of a 3-body classical Ising model on triangular or Union Jack lattices. This mapping allows us to test that different computational capabilities of color codes correspond to qualitatively different universality classes of their associated classical spin models. By generalizing these statistical mechanical models for arbitrary inhomogeneous and complex couplings, it is possible to study a measurement-based quantum computation with a color code state and we find that their classical simulatability remains an open problem. We complement the meaurement-based computation with the construction of a cluster state that yields the topological color code and this also gives the possibility to represent statistical models with external magnetic fields.
Coupled Thermal-Hydrological-Mechanical-Chemical Model and Experiments...
Broader source: Energy.gov (indexed) [DOE]
Coupled Thermal-Hydrological-Mechanical-Chemical Model and Experiments for Optimization of Enhanced Geothermal System Development and Production Coupled Thermal-Hydrological-Mechan...
A simplified model for thermal-wave cavity self-consistent measurement of thermal diffusivity
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
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.
Modeling the Effect of Finite-Rate Hydrogen Diffusion on Porosity Formation in Aluminum Alloys
Beckermann, Christoph
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
Physical causes and modeling challenges of anomalous diffusion of sediment tracers
Physical causes and modeling challenges of anomalous diffusion of sediment tracers Douglas] #12;Velocity autocorrelation: Controlled by inertia 0.1 1 Dispersion: inertial at short time particles spend much more time at rest than in motion. Stochastic modeling approach: Direct solution of f
A comparison between the fission matrix method, the diffusion model and the transport model
Dehaye, B.; Hugot, F. X.; Diop, C. M. [Commissariat a l'Energie Atomique et aux Energies Alternatives, Direction de l'Energie Nucleaire, Departement de Modelisation des Systemes et Structures, CEA DEN/DM2S, PC 57, F-91191 Gif-sur-Yvette cedex (France)
2013-07-01T23:59:59.000Z
The fission matrix method may be used to solve the critical eigenvalue problem in a Monte Carlo simulation. This method gives us access to the different eigenvalues and eigenvectors of the transport or fission operator. We propose to compare the results obtained via the fission matrix method with those of the diffusion model, and an approximated transport model. To do so, we choose to analyse the mono-kinetic and continuous energy cases for a Godiva-inspired critical sphere. The first five eigenvalues are computed with TRIPOLI-4{sup R} and compared to the theoretical ones. An extension of the notion of the extrapolation distance is proposed for the modes other than the fundamental one. (authors)
Mechanical Models of Fault-Related Folding
Johnson, A. M.
2003-01-09T23:59:59.000Z
The subject of the proposed research is fault-related folding and ground deformation. The results are relevant to oil-producing structures throughout the world, to understanding of damage that has been observed along and near earthquake ruptures, and to earthquake-producing structures in California and other tectonically-active areas. The objectives of the proposed research were to provide both a unified, mechanical infrastructure for studies of fault-related foldings and to present the results in computer programs that have graphical users interfaces (GUIs) so that structural geologists and geophysicists can model a wide variety of fault-related folds (FaRFs).
Random Motion with Interfacial Contact: Driven Diffusion vis-a-vis Mechanical Activation
Goohpattader, P S
2012-01-01T23:59:59.000Z
Rolling of a small sphere on a solid support is governed by a non-linear friction that is akin to the Coulombic dry fiction. No motion occurs when the external field is weaker than the frictional resistance. However, with the intervention of an external noise, a viscous friction like property emerges; thus the sphere rolls with an uniform drift velocity that is proportional to the applied field. As the sphere rolls, it rocks forward and backward resulting in substantial fluctuation of displacement opposite to the net drift. The ratio of the integrated probabilities of the negative to positive work fluctuations decreases monotonically with the time of observation, from which a temperature like intensive parameter can be estimated. This parameter conforms to the Einstein's ratio of diffusivity and mobility that increases almost linearly, even though the diffusivity increases super-linearly, with the strength of the noise. A new barrier crossing experiment is introduced that can be performed either with a hard (...
advanced diffusion model: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
. . . . 18 3.4.1 Heat Exchanger - Code description . . . . . . . . . . . . . . . 18 3.4.2 Simulation ResultsADVANCED POWER PLANT MODELING WITH APPLICATIONS TO THE ADVANCED BOILING...
Diffusion and Dispersion Characterization of a Numerical Tsunami Model
Tolkova, Elena
and numerical model. This plan is currently under devel- opment at the NCTR and a proof of concept has been-computed database of unit source solutions to determine the offshore tsunami waves. It then uses the MOST model (in nested grid mode) to propagate the offshore waves onshore for select regions. The critical factor
User's guide to the MESOI diffusion model and to the utility programs UPDATE and LOGRVU
Athey, G.F.; Allwine, K.J.; Ramsdell, J.V.
1981-11-01T23:59:59.000Z
MESOI is an interactive, Lagrangian puff trajectory diffusion model. The model is documented separately (Ramsdell and Athey, 1981); this report is intended to provide MESOI users with the information needed to successfully conduct model simulations. The user is also provided with guidance in the use of the data file maintenance and review programs; UPDATE and LOGRVU. Complete examples are given for the operaton of all three programs and an appendix documents UPDATE and LOGRVU.
Human walking model predicts joint mechanics, electromyography and mechanical economy
Endo, Ken
In this paper, we present an under-actuated model of human walking, comprising only a soleus muscle and flexion/extension monoarticular hip muscles. The remaining muscle groups of the human leg are modeled using quasi-passive, ...
Stochastic Modeling and Direct Simulation of the Diffusion Media for Polymer Electrolyte Fuel Cells
Schmidt, Volker
Cells Yun Wang* and Xuhui Feng Renewable Energy Resources Lab (RERL) and National Fuel Cell Research the stochastic-model-based reconstruction of the gas diffusion layer (GDL) of polymer electrolyte fuel cells on pore-level transport and scrutinize the macroscopic approach vastly adopted in current fuel cell
Analysis of model equations for stress-enhanced diffusion in coal
Segatti, Antonio
Analysis of model equations for stress-enhanced diffusion in coal layers Andro Mikeli´c Andro coal seams. A typical procedure is the injection of carbon dioxide via deviated wells drilled inside the coal seams. Carbon dioxide displaces the methane adsorbed on the internal surface of the coal
Weber, Adam
2010-03-05T23:59:59.000Z
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.
Atomistic Models of Long-Term Hydrogen Diffusion in Metals M. P. Ariza1,a
Ortiz, Michael
and efficient storage of hydrogen is one of the key challenges in developing a hydrogen economy. RecentlyAtomistic Models of Long-Term Hydrogen Diffusion in Metals M. P. Ariza1,a , K. G. Wang,2,b , and M-speed, high-capacity, reversible hydrogen storage applications. Notably, the absorption and desorption
Numerical Solution of Two Asset Jump Diffusion Models for Option Valuation
Forsyth, Peter A.
Numerical Solution of Two Asset Jump Diffusion Models for Option Valuation Simon S. Clift and Peter parabolic partial integro-differential equation (PIDE). An implicit, finite difference method is derived with an FFT. The method prices both American and European style contracts indepen- dent (under some simple
A continuous surface tension force formulation for diffuse-interface models
Frey, Pascal
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
Mathematical Model for Mixing Reactants in a Capillary Microreactor by Transverse Diffusion of
Krylov, Sergey
. The theory uses a single simplifying assumption that the longitudinal diffusion is negligible; this assumption is readily satisfied. We then develop a numerical model of TDLFP and use it to simulate. These requirements can be met by confining the nanoliter-volume reaction mixture in a microfabricated well,5 oil drop
Random Motion with Interfacial Contact: Driven Diffusion vis-a-vis Mechanical Activation
P. S. Goohpattader; M. K. Chaudhury
2012-03-21T23:59:59.000Z
Rolling of a small sphere on a solid support is governed by a non-linear friction that is akin to the Coulombic dry fiction. No motion occurs when the external field is weaker than the frictional resistance. However, with the intervention of an external noise, a viscous friction like property emerges; thus the sphere rolls with an uniform drift velocity that is proportional to the applied field. As the sphere rolls, it rocks forward and backward resulting in substantial fluctuation of displacement opposite to the net drift. The ratio of the integrated probabilities of the negative to positive work fluctuations decreases monotonically with the time of observation, from which a temperature like intensive parameter can be estimated. This parameter conforms to the Einstein's ratio of diffusivity and mobility that increases almost linearly, even though the diffusivity increases super-linearly, with the strength of the noise. A new barrier crossing experiment is introduced that can be performed either with a hard (e.g. a steel ball) or with a soft (e.g. a water drop) sphere in contact with a periodically undulated substrate. The frequency of barrier crossing follows the classical transition state equation allowing a direct estimation of the effective temperature. These experiments as well as certain numerical simulations suggest that the effective temperature of a system controlled by a non-linear friction may not have a unique value.
Diffusive limit for the random Lorentz gas
Alessia Nota
2014-10-14T23:59:59.000Z
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.
Transient model of an intermediate surge system for the Paducah Gaseous Diffusion Plant
Beard, B.; Blankenship, J.G.; McGrady, P.W.
1989-09-01T23:59:59.000Z
Engineering design work (Reference 1) is underway for intermediate surge systems to be added to the Paducah Gaseous Diffusion Plant (PGDP) cascade as part of the Process Inventory Control System (PICS) project. These systems would be located between 000 buildings and lower half 00 buildings and would remove or add inventory during cascade transients in order to protect cascade compressors from overload and surge. Similar systems were operated in the Oak Ridge Gaseous Diffusion Plant cascade and are operated in the Portsmouth Gaseous Diffusion Plant cascade. A steady state flow analysis of the system to be installed at the PGDP has been made. The flow analysis did not address response of the surge system to the cascade transients, nor did it address automatic control of the system. The need to address these issues prompted development of the transient model described in this report. 2 refs., 8 figs., 2 tabs.
Asymptotics for the maximum likelihood estimators of diffusion models
Jeong, Minsoo
2009-05-15T23:59:59.000Z
: : : : : : 24 3 First Order Distribution and the Histogram of t(^fi2) { CEV : : : : : 25 4 First Order Distributions of t(^fi1) and t(^fi2) : : : : : : : : : : : : : : 33 1 CHAPTER I INTRODUCTION The difiusion model was originally designed and has long been used... of the estimator. Wooldridge (1994) shows that AD3 together with AD1 and AD2 implies1 AD4: S(^ ) = 0 with probability approaching to one as T !1 and ? ! 0. AD5: w?1?H(~ )?H( 0)?w?10= op(1) and w0(^ ? 0) = Op(1). Thus, with these conditions, we have w?1S(^ ) = w?1S...
Modeling diffusion of electrical appliances in the residential sector
McNeil, Michael A.; Letschert, Virginie E.
2009-11-22T23:59:59.000Z
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.
Shell-shocked diffusion model for the light curve of SN2006gy
Nathan Smith; Richard McCray
2007-10-18T23:59:59.000Z
We explore a simple model for the high luminosity of SN 2006gy involving photon diffusion of shock-deposited thermal energy. The distinguishing property of the model is that the large ``stellar'' radius of 160 AU required to prevent adiabatic losses is not the true stellar radius, but rather, the radius of an opaque, unbound circumstellar envelope, created when 10 Msun was ejected in the decade before the supernova in an eruption analogous to that of eta Carinae. The supernova light is produced primarily by diffusion of thermal energy following the passage of the blast wave through this shell. This model differs from traditional models of supernova debris interacting with external CSM in that here the shell is optically thick and the escape of radiation is delayed. We show that any model attempting to account for SN2006gy's huge luminosity with radiation emitted by ongoing CSM interaction fails for the following basic reason: the CSM density required to achieve the observed luminosity makes the same circumstellar envelope opaque, forcing a thermal diffusion solution. In our model, the weaker CSM interaction giving rise to SN2006gy's characteristic Type IIn spectrum and soft X-rays is not linked to the power source of the visual continuum; instead, it arises after the blast wave breaks free of the opaque shell into the surrounding wind. While a simple diffusion model can explain the gross properties of the early light curve of SN2006gy, it predicts that the light curve must plummet rapidly at late-times, unless an additional power source is present.
A Conceptual Approach to Two-Scale Constitutive Modelling For Hydro-Mechanical Coupling
Giang D. Nguyen; Abbas El-Zein; Terry Bennett
2014-06-05T23:59:59.000Z
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.
Coupled Thermal-Hydrological-Mechanical-Chemical Model And Experiments...
Broader source: Energy.gov (indexed) [DOE]
Coupled Thermal-Hydrological-Mechanical-Chemical Model And Experiments For Optimization Of Enhanced Geothermal System Development And Production: Evaluation of Stimulation at the...
Coupled Thermal-Hydrological-Mechanical-Chemical Model and Experiments...
Broader source: Energy.gov (indexed) [DOE]
Coupled Thermal-Hydrological-Mechanical-Chemical Model and Experiments for Optimization of Enhanced Geothermal System Development and Production Eric Sonnenthal (PI) Jonny...
Shell Model for Atomistic Simulation of Lithium Diffusion in Mixed Mn/Ti Oxides
Kerisit, Sebastien N.; Chaka, Anne M.; Droubay, Timothy C.; Ilton, Eugene S.
2014-10-23T23:59:59.000Z
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.
Anand, Lallit
In this paper we develop a thermodynamically-consistent coupled-theory which accounts for diffusion of hydrogen, diffusion of heat, and large elastic–viscoplastic deformations of metals. The theory should be of utility in ...
Koumetz, Serge D., E-mail: Serge.Koumetz@univ-rouen.fr; Martin, Patrick; Murray, Hugues [Normandie Université-Université de Rouen-ENSICAEN-UMR 6508 LaMIPS, Laboratoire commun CNRS-NXP-PRESTO-ENSICAEN-UCBN 2, rue de la Girafe BP 5120, F-14079 Caen (France)
2014-09-14T23:59:59.000Z
Experimental results on the diffusion of grown-in beryllium (Be) in indium gallium arsenide (In{sub 0.53}Ga{sub 0.47}As) and indium gallium arsenide phosphide (In{sub 0.73}Ga{sub 0.27}As{sub 0.58}P{sub 0.42}) gas source molecular beam epitaxy alloys lattice-matched to indium phosphide (InP) can be successfully explained in terms of a combined kick-out and dissociative diffusion mechanism, involving neutral Be interstitials (Be{sub i}{sup 0}), singly positively charged gallium (Ga), indium (In) self-interstitials (I{sub III}{sup +}) and singly positively charged Ga, In vacancies (V{sub III}{sup +}). A new numerical method of solution to the system of diffusion equations, based on the finite difference approximations and Bairstow's method, is proposed.
Zhu, Qingyu; Moggridge, Geoff D.; D’Agostino, Carmine
2015-04-29T23:59:59.000Z
conventional techniques (e.g. Van Geet and Adamson, 1964). However, none of these efforts is able to give a full description of the temperature and composition dependence of mutual diffusion coefficients for a range of non-ideal liquid mixture. In particular... . Farad. Soc., 45, 801-818. Hwang, S.C., Robinson, R.L., 1977. Vapor–Liquid equilibriums at 25 oC for nine alcohol- hydrocarbon binary systems. J. Chem. Eng. Data 22,319–325. 24 Johnson, P.A., Babb, A.L., 1956. Self-diffusion in liquids. I...
Siala, F.M.F. (Center for Solar Energy Studies, Tripoli (Libya)); Hooper, F.C. (Univ. of Toronto, Ontario (Canada))
1990-01-01T23:59:59.000Z
The development of a new, semi-empirical model for the directional distribution of the diffuse radiance is reported. The proposed regression-type model, with the form of its base functions obtained from physical principles, is based on a combination of the purely physical reasoning approach and the purely empirical approach. Direct multiple-scattering calculations are circumvented through the use of the method of successive orders of scattering. The model is calibrated for the mean diffuse radiance estimated under all sky conditions reported in a large and comprehensive diffuse radiance data set. It is found that only a small increase in accuracy is gained by including higher orders of scattering, and this increase does not justify the complexity of the resulting model. Therefore, the single scattering approximation is recommended. The use of the model is illustrated in a typical application, in which the fraction of diffuse radiation intercepted by the receive of a compound parabolic concentrator is computed.
Modeling Solute Diffusion in the Presence of Pore-Scale Heterogeneity
FLEMING,SEAN W.; HAGGERTY,ROY
1999-10-21T23:59:59.000Z
A range of pore diffusivities, D{sub p}, is implied by the high degree of pore-scale heterogeneity observed in core samples of the Culebra (dolomite) Member of the Rustler formation, NM. Earlier tracer tests in the culebra at the field-scale have confirmed significant heterogeneity in diffusion rate coefficients (the combination of D{sub p} and matrix block size). In this study, expressions for solute diffusion in the presence of multiple simultaneous matrix diffusivities are presented and used to model data from eight laboratory-scale diffusion experiments performed on five Culebra samples. A lognormal distribution of D{sub p} is assumed within each of the lab samples. The estimated standard deviation ({sigma}{sub d}) of In(D{sub p}) within each sample ranges from 0 to 1, with most values lying between 0.5 and 1. The variability over all samples leads to a combined {sigma}{sub d} in the range of 1.0 to 1.2, which appears to be consistent with a best-fit statistical distribution of formation factor measurements for similar Culebra samples. A comparison of the estimation results to other rock properties suggests that, at the lab-scale, the geometric mean of D{sub p} increases with bulk porosity and the quantity of macroscopic features such as vugs and fractures. However, {sigma}{sub d} appears to be determined by variability within such macroscopic features and/or by micropore-scale heterogeneity. In addition, comparison of these experiments to those at larger spatial scales suggests that increasing sample volume results in an increase in {sigma}{sub d}.
Multiclass Diffuse Interface Models for Semi-Supervised Learning on Graphs
Garcia-Cardona, Cristina; Percus, Allon G
2012-01-01T23:59:59.000Z
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.
Modeling torque versus speed, shot noise, and rotational diffusion of the bacterial flagellar motor
Thierry Mora; Howard Yu; Ned S. Wingreen
2009-10-05T23:59:59.000Z
We present a minimal physical model for the flagellar motor that enables bacteria to swim. Our model explains the experimentally measured torque-speed relationship of the proton-driven E. coli motor at various pH and temperature conditions. In particular, the dramatic drop of torque at high rotation speeds (the "knee") is shown to arise from saturation of the proton flux. Moreover, we show that shot noise in the proton current dominates the diffusion of motor rotation at low loads. This suggests a new way to probe the discreteness of the energy source, analogous to measurements of charge quantization in superconducting tunnel junctions.
Consistency of Ambipolar Diffusion Models with Infall in the L1544 Protostellar Core
Glenn E. Ciolek; Shantanu Basu
1999-09-25T23:59:59.000Z
Recent high-resolution studies of the L1544 protostellar core by Tafalla et al. and Williams et al. reveal the structure and kinematics of the gas. The observations of this prestellar core provide a natural test for theoretical models of core formation and evolution. Based on their results, the above authors claim a discrepancy with the implied infall motions from ambipolar diffusion models. In this paper, we reexamine the earlier ambipolar diffusion models, and conclude that the L1544 core can be understood to be a magnetically supercritical core undergoing magnetically diluted collapse. We also present a new model specifically designed to simulate the formation and evolution of the L1544 core. This model, which uses reasonable input parameters, yields mass and radial density distributions, as well as neutral and ion infall speed profiles, that are in very good agreement with physical values deduced by observations. The lifetime of the core is also in good agreement with prestellar core lifetimes estimated from statistics of an ensemble of cores. The observational input can act to constrain other currently unobserved quantities such as the degree of ionization, and the background magnetic field strength and orientation near the L1544 core.
Modelling of stable isotope fractionation by methane oxidation and diffusion in landfill cover soils
Mahieu, Koenraad [Laboratory of Applied Physical Chemistry (ISOFYS), Ghent University, Coupure links 653, B-9000 Ghent (Belgium); Department of Applied Mathematics, Biometrics and Process Control (BIOMATH), Ghent University, Coupure links 653, B-9000 Ghent (Belgium)], E-mail: Koenraad.mahieu@lid.kviv.be; De Visscher, Alex [Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive N.W., Calgary, Alberta, T2N 1N4 (Canada); Vanrolleghem, Peter A. [Department of Applied Mathematics, Biometrics and Process Control (BIOMATH), Ghent University, Coupure links 653, B-9000 Ghent (Belgium); Department of Civil Engineering (modelEAU), Universite Laval, Pavillon Pouliot, Quebec, G1K 7P4 (Canada); Van Cleemput, Oswald [Laboratory of Applied Physical Chemistry (ISOFYS), Ghent University, Coupure links 653, B-9000 Ghent (Belgium)
2008-07-01T23:59:59.000Z
A technique to measure biological methane oxidation in landfill cover soils that is gaining increased interest is the measurement of stable isotope fractionation in the methane. Usually to quantify methane oxidation, only fractionation by oxidation is taken into account. Recently it was shown that neglecting the isotope fractionation by diffusion results in underestimation of the methane oxidation. In this study a simulation model was developed that describes gas transport and methane oxidation in landfill cover soils. The model distinguishes between {sup 12}CH{sub 4}, {sup 13}CH{sub 4}, and {sup 12}CH{sub 3}D explicitly, and includes isotope fractionation by diffusion and oxidation. To evaluate the model, the simulations were compared with column experiments from previous studies. The predicted concentration profiles and isotopic profiles match the measured ones very well, with a root mean square deviation (RMSD) of 1.7 vol% in the concentration and a RMSD of 0.8 per mille in the {delta}{sup 13}C value, with {delta}{sup 13}C the relative {sup 13}C abundance as compared to an international standard. Overall, the comparison shows that a model-based isotope approach for the determination of methane oxidation efficiencies is feasible and superior to existing isotope methods.
Mesoscopic modeling of stochastic reaction-diffusion kinetics in the subdiffusive regime
Emilie Blanc; Stefan Engblom; Andreas Hellander; Per Lötstedt
2015-03-24T23:59:59.000Z
Subdiffusion has been proposed as an explanation of various kinetic phenomena inside living cells. In order to fascilitate large-scale computational studies of subdiffusive chemical processes, we extend a recently suggested mesoscopic model of subdiffusion into an accurate and consistent reaction-subdiffusion computational framework. Two different possible models of chemical reaction are revealed and some basic dynamic properties are derived. In certain cases those mesoscopic models have a direct interpretation at the macroscopic level as fractional partial differential equations in a bounded time interval. Through analysis and numerical experiments we estimate the macroscopic effects of reactions under subdiffusive mixing. The models display properties observed also in experiments: for a short time interval the behavior of the diffusion and the reaction is ordinary, in an intermediate interval the behavior is anomalous, and at long times the behavior is ordinary again.
Modeling thermal/chemical/mechanical response of energetic materials
Baer, M.R.; Hobbs, M.L.; Gross, R.J. [and others
1995-07-01T23:59:59.000Z
An overview of modeling at Sandia National Laboratories is presented which describes coupled thermal, chemical and mechanical response of energetic materials. This modeling addresses cookoff scenarios for safety assessment studies in systems containing energetic materials. Foundation work is discussed which establishes a method for incorporating chemistry and mechanics into multidimensional analysis. Finite element analysis offers the capabilities to simultaneously resolve reactive heat transfer and structural mechanics in complex geometries. Nonlinear conduction heat transfer, with multiple step finite-rate chemistry, is resolved using a thermal finite element code. Rate equations are solved element-by-element using a modified matrix-free stiff solver This finite element software was developed for the simulation of systems requiring large numbers of finite elements. An iterative implicit scheme, based on the conjugate gradient method, is used and a hemi-cube algorithm is employed for the determination of view factors in surface-to-surface radiation transfer The critical link between the reactive heat transfer and mechanics is the introduction of an appropriate constitutive material model providing a stress-strain relationship for quasi-static mechanics analysis. This model is formally derived from bubble nucleation theory, and parameter variations of critical model parameters indicate that a small degree of decomposition leads to significant mechanical response. Coupled thermal/chemical/mechanical analysis is presented which simulates experiments designed to probe cookoff thermal-mechanical response of energetic materials.
Rock mechanics models evaluation report. [Contains glossary
Not Available
1987-08-01T23:59:59.000Z
This report documents the evaluation of the thermal and thermomechanical models and codes for repository subsurface design and for design constraint analysis. The evaluation was based on a survey of the thermal and thermomechanical codes and models that are applicable to subsurface design, followed by a Kepner-Tregoe (KT) structured decision analysis of the codes and models. The primary recommendations of the analysis are that the DOT code be used for two-dimensional thermal analysis and that the STEALTH and HEATING 5/6 codes be used for three-dimensional and complicated two-dimensional thermal analysis. STEALTH and SPECTROM 32 are recommended for thermomechanical analyses. The other evaluated codes should be considered for use in certain applications. A separate review of salt creep models indicate that the commonly used exponential time law model is appropriate for use in repository design studies. 38 refs., 1 fig., 7 tabs.
Nucleus-nucleus cold fusion reactions analyzed with the l-dependent 'fusion by diffusion' model
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
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.
Quantum mechanical Hamiltonian models of the computation process
Benioff, P.
1983-01-01T23:59:59.000Z
As noted in the proceedings of this conference it is of importance to determine if quantum mechanics imposes fundamental limits on the computation process. Some aspects of this problem have been examined by the development of different types of quantum mechanical Hamiltonian models of Turing machines. (Benioff 1980, 1982a, 1982b, 1982c). Turing machines were considered because they provide a standard representation of all digital computers. Thus, showing the existence of quantum mechanical models of all Turing machines is equivalent to showing the existence of quantum mechanical models of all digital computers. The types of models considered all had different properties. Some were constructed on two-dimensional lattices of quantum spin systems of spin 1/2 (Benioff 1982b, 1982c) or higher spins (Benioff 1980). All the models considered Turing machine computations which were made reversible by addition of a history tape. Quantum mechanical models of Bennett's reversible machines (Bennett 1973) in which the model makes a copy of the computation result and then erases the history and undoes the computation in lockstep to recover the input were also developed (Benioff 1982a). To avoid technical complications all the types of models were restricted to modelling an arbitrary but finite number of computation steps.
Model to predict the mechanical behaviour of oriented rigid PVC
Miroshnychenko, Dmitri
Model to predict the mechanical behaviour of oriented rigid PVC D. J. Hitt*1 and D. Miroshnychenko2 The mechanical properties of PVC sheets can be modified substantially by both uniaxial and biaxial stretching pattern in the relationship between tensile properties of oriented PVC products and imposed strains
Schick, W.C. Jr.; Milani, S.; Duncombe, E.
1980-03-01T23:59:59.000Z
A model has been devised for incorporating into the thermal feedback procedure of the PDQ few-group diffusion theory computer program the explicit calculation of depletion and temperature dependent fuel-rod shrinkage and swelling at each mesh point. The model determines the effect on reactivity of the change in hydrogen concentration caused by the variation in coolant channel area as the rods contract and expand. The calculation of fuel temperature, and hence of Doppler-broadened cross sections, is improved by correcting the heat transfer coefficient of the fuel-clad gap for the effects of clad creep, fuel densification and swelling, and release of fission-product gases into the gap. An approximate calculation of clad stress is also included in the model.
Modeling Control Mechanisms with Normative Multiagent Systems
van der Torre, Leon
of renewable energy. We apply a conceptual model based on normative multiagent systems (NMAS). We propose to stimulate the production of #12;energy from renewable sources [20]. The ruling involves an obligation for energy sup- pliers to produce evidence of having distributed a certain minimal amount of renewable energy
General coarse-grained red blood cell models: I. Mechanics
Fedosov, Dmitry A; Karniadakis, George E
2009-01-01T23:59:59.000Z
We present a rigorous procedure to derive coarse-grained red blood cell (RBC) models, which lead to accurate mechanical properties of realistic RBCs. Based on a semi-analytic theory linear and non-linear elastic properties of the RBC membrane can be matched with those obtained in optical tweezers stretching experiments. In addition, we develop a nearly stress-free model which avoids a number of pitfalls of existing RBC models, such as non-biconcave equilibrium shape and dependence of RBC mechanical properties on the triangulation quality. The proposed RBC model is suitable for use in many existing numerical methods, such as Lattice Boltzmann, Multiparticle Collision Dynamics, Immersed Boundary, etc.
General coarse-grained red blood cell models: I. Mechanics
Dmitry A. Fedosov; Bruce Caswell; George E. Karniadakis
2009-05-01T23:59:59.000Z
We present a rigorous procedure to derive coarse-grained red blood cell (RBC) models, which lead to accurate mechanical properties of realistic RBCs. Based on a semi-analytic theory linear and non-linear elastic properties of the RBC membrane can be matched with those obtained in optical tweezers stretching experiments. In addition, we develop a nearly stress-free model which avoids a number of pitfalls of existing RBC models, such as non-biconcave equilibrium shape and dependence of RBC mechanical properties on the triangulation quality. The proposed RBC model is suitable for use in many existing numerical methods, such as Lattice Boltzmann, Multiparticle Collision Dynamics, Immersed Boundary, etc.
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
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.
Mechanisms and models of effective thermal conductivities of nanofluids.
Yu, W.; France, D. M.; Singh, D.; Timofeeva, E. V.; Smith, D. S.; Routbort, J. L.; Univ. of Illinois
2010-08-01T23:59:59.000Z
The physical mechanisms and mathematical models of the effective thermal conductivities of nanofluids have long been of interest to the nanofluid research community because the effective thermal conductivities of nanofluids cannot generally be fully explained and predicted by classical effective medium theories. This review article summarizes considerable progress made on this topic. Specifically, the physical mechanisms and mathematical models of the effective thermal conductivities of nanofluids are reviewed, the potential contributions of those physical mechanisms are evaluated, and the comparisons of the theoretical predictions and experimental data are presented along with opportunities for future research.
Modeling precursor diffusion and reaction of atomic layer deposition in porous structures
Keuter, Thomas, E-mail: t.keuter@fz-juelich.de; Menzler, Norbert Heribert; Mauer, Georg; Vondahlen, Frank; Vaßen, Robert; Buchkremer, Hans Peter [Forschungszentrum Jülich, Institute of Energy and Climate Research (IEK-1), 52425 Jülich (Germany)
2015-01-01T23:59:59.000Z
Atomic layer deposition (ALD) is a technique for depositing thin films of materials with a precise thickness control and uniformity using the self-limitation of the underlying reactions. Usually, it is difficult to predict the result of the ALD process for given external parameters, e.g., the precursor exposure time or the size of the precursor molecules. Therefore, a deeper insight into ALD by modeling the process is needed to improve process control and to achieve more economical coatings. In this paper, a detailed, microscopic approach based on the model developed by Yanguas-Gil and Elam is presented and additionally compared with the experiment. Precursor diffusion and second-order reaction kinetics are combined to identify the influence of the porous substrate's microstructural parameters and the influence of precursor properties on the coating. The thickness of the deposited film is calculated for different depths inside the porous structure in relation to the precursor exposure time, the precursor vapor pressure, and other parameters. Good agreement with experimental results was obtained for ALD zirconiumdioxide (ZrO{sub 2}) films using the precursors tetrakis(ethylmethylamido)zirconium and O{sub 2}. The derivation can be adjusted to describe other features of ALD processes, e.g., precursor and reactive site losses, different growth modes, pore size reduction, and surface diffusion.
Modeling Different Failure Mechanisms in Metals
Zhang, Liang
2012-02-14T23:59:59.000Z
. Keeler [1] and Goodwin [2] first introduced the concept of the forming limit diagram (FLD). The FLD plots the limiting major and minor strains that can be achieved along different stress or strain paths. It characterizes the sheet metal formability..., the quadratic yield criterions are still often employed to examine the validity of new models. 6 Keeler and Brazier [7] observed that, for steel sheets, the limiting major strain under plane strain conditions increases with increasing sheet thickness...
Lee, Shiu-Hang; Nagataki, Shigehiro
2012-01-01T23:59:59.000Z
To better model the efficient production of cosmic rays (CRs) in supernova remnants (SNRs) with the associated coupling between CR production and SNR dynamics, we have generalized an existing cr-hydro-NEI code (i.e., Ellison et al. 2012) to include the following processes: (1) an explicit calculation of the upstream precursor structure including the position dependent flow speed, density, temperature, and magnetic field strength; (2) a momentum and space dependent CR diffusion coefficient; (3) an explicit calculation of magnetic field amplification (MFA); (4) calculation of the maximum CR momentum using the amplified magnetic field; (5) a finite Alfven speed for the particle scattering centers; and (6) the ability to accelerate a superthermal seed population of CRs as well as the ambient thermal plasma. While a great deal of work has been done modeling SNRs, most work has concentrated on either the continuum emission from relativistic electrons or ions, or the thermal emission from the shock heated plasma. Ou...
Time integration for diffuse interface models for two-phase flow
Aland, Sebastian, E-mail: sebastian.aland@tu-dresden.de
2014-04-01T23:59:59.000Z
We propose a variant of the ?-scheme for diffuse interface models for two-phase flow, together with three new linearization techniques for the surface tension. These involve either additional stabilizing force terms, or a fully implicit coupling of the Navier–Stokes and Cahn–Hilliard equation. In the common case that the equations for interface and flow are coupled explicitly, we find a time step restriction which is very different to other two-phase flow models and in particular is independent of the grid size. We also show that the proposed stabilization techniques can lift this time step restriction. Even more pronounced is the performance of the proposed fully implicit scheme which is stable for arbitrarily large time steps. We demonstrate in a Taylor-flow application that this superior coupling between flow and interface equation can decrease the computation time by several orders of magnitude.
Density functional theory study of the mechanism of Li diffusion in rutile RuO{sub 2}
Jung, Jongboo; Cho, Maenghyo [WCU Program on Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)] [WCU Program on Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Zhou, Min, E-mail: min.zhou@gatech.edu [WCU Program on Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of) [WCU Program on Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); George W. Woodruff School of Mechanical Engineering, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States)
2014-01-15T23:59:59.000Z
First-principle calculations are carried out to study the diffusion of Li ions in rutile structure RuO{sub 2}, a material for positive electrodes in rechargeable Li ion batteries. The calculations focus on migration pathways and energy barriers for diffusion in Li-poor and Li-rich phases using the Nudged Elastic Band Method. Diffusion coefficients estimated based on calculated energy barriers are in good agreement with experimental values reported in the literature. The results confirm the anisotropic nature of diffusion of Li ions in one-dimensional c channels along the [001] crystalline direction of rutile RuO{sub 2} and show that Li diffusion in the Li-poor phase is faster than in the Li-rich phase. The findings of fast Li diffusion and feasible Li insertion at low temperatures in the host rutile RuO{sub 2} suggest this material is a good ionic conductor for Li transport. The finding also suggests possible means for enhancing the performance of RuO{sub 2}-based electrode materials.
Thermo-mechanical structural modelling of FRP composite sandwich panels exposed to fire
Ramroth, William T.
2006-01-01T23:59:59.000Z
CALIFORNIA, SAN DIEGO Thermo-mechanical Structural ModellingABSTRACT OF THE DISSERTATION Thermo-mechanical Structuralpolymer matrix), and thermo-mechanical (structural)
Theoretical Modeling of Mechanical-Electrical Coupling of Carbon Nanotubes
Lu, Jun-Qiang [ORNL; Jiang, Hanqiang [Arizona State University
2008-01-01T23:59:59.000Z
Carbon nanotubes have been studied extensively due to their unique properties, ranging from electrical, mechanical, optical, to thermal properties. The coupling between the electrical and mechanical properties of carbon nanotubes has emerged as a new field, which raises both interesting fundamental problems and huge application potentials. In this article, we will review our recently work on the theoretical modeling on mechanical-electrical coupling of carbon nanotubes subject to various loading conditions, including tension/compression, torsion, and squashing. Some related work by other groups will be also mentioned.
Dynamics of Enzyme Digestion of a Single Elastic Fiber Under Tension: An Anisotropic Diffusion Model
Ascânio D. Araújo; Arnab Majumdar; Harikrishnan Parame swaran; Béla Suki
2009-10-07T23:59:59.000Z
We study the enzymatic degradation of an elastic fiber under tension using an an isotropic random-walk model, coupled with binding-unbinding reactions that weaken the fiber. The fiber is represented by a chain of elastic springs in series, surrounded by two layers of sites along which enzyme molecules can diffuse. Through numerical simulations we show that the fiber stiffness decreases exponentially with two distinct regimes. The time constant associated with the first regime decreases with increasing applied force, which is in agreement with published experimental data. In addition, a simple mean field calculation allows us to partition the time constant into geometrical, chemical and externally controllable factors, which is corroborated by the simulations.
Phase transitions in a reaction-diffusion model on a line with boundaries
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
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.
Experimental Verification of a Cracked Fuel Mechanical Model
Williford, R. E.
1982-12-01T23:59:59.000Z
This report describes the results of a series of laboratory experiments conducted to independently verify a model that describes the nonlinear mechanical behavior of cracked fuel in pelletized UO{sub 2}/Zircaloy nuclear fuel rods under normal operating conditions. After a brief description of the analytical model, each experiment is discussed in detail. Experiments were conducted to verify the general behavior and numerical values for the three primary independent modelling parameters (effective crack roughness, effective gap roughness, and total crack length), and to verify the model predictions that the effective Young's moduli for cracked fuel systems were substantially less than those for solid UO{sub 2} pellets. In general, the model parameters and predictions were confirmed, and new insight was gained concerning the complexities of cracked fuel mechanics.
Donovan, Amy R.; Oppenheimer, Clive
2014-11-27T23:59:59.000Z
(Stirling, 151 2008). For Massey, space is dynamic: it must be thought of in relation to time. It resists 152 enclosure in a model. In considering geographical models in light of this, O’Sullivan (2004) 153 suggests that “it is vital that modelling... , 215 noting the presence of social, psychological and geographical uncertainties (see also Stirling, 216 2007, 2008; Wynne, 1992; Jasanoff, 2004, 2005). Understanding the complex ways in which 217 uncertainty is generated is critical in appreciating...
Measurements and modeling of soot formation and radiation in microgravity jet diffusion flames
Ku, J.C.; Tong, L. [Wayne State Univ., Detroit, MI (United States). Mechanical Engineering Dept.; Greenberg, P.S. [NASA Lewis Research Center, Cleveland, OH (United States). Microgravity Combustion Branch
1996-12-31T23:59:59.000Z
This is a computational and experimental study for soot formation and radiative heat transfer in jet diffusion flames under normal gravity (1-g) and microgravity (0-g) conditions. Instantaneous soot volume fraction maps are measured using a full-field imaging absorption technique developed by the authors. On modeling, the authors have coupled flame structure and soot formation models with detailed radiation transfer calculations. Favre-averaged boundary layer equations with a k-e-g turbulence model are used to predict the flow field, and a conserved scalar approach with an assumed {beta}-pdf are used to predict gaseous species mole fraction. Scalar transport equations are used to describe soot volume fraction and number density distributions, with formation and oxidation terms modeled by one-step rate equations and thermophoretic effects included. An energy equation is included to couple flame structure and radiation analyses through iterations, neglecting turbulence-radiation interactions. The YIX solution for a finite cylindrical enclosure is used for radiative heat transfer calculations. The spectral absorption coefficient for soot aggregates is calculated from the Rayleigh solution using complex refractive index data from a Drude-Lorentz model. The exponential-wide-band model is used to calculate the spectral absorption coefficient for H{sub 2}O and CO{sub 2}. Predicted soot volume fraction and temperature results agree well with published data for a normal gravity co-flow laminar flames and turbulent jet flames. Predicted soot volume fraction results also agree with the data for 1-g and 0-g laminar jet flames as well as 1-g turbulent jet flames.
Giovanni Pastore; Michael R. Tonks; Derek R. Gaston; Richard L. Williamson; David Andrs; Richard Martineau
2014-03-01T23:59:59.000Z
Based on density functional theory (DFT) and empirical potential calculations, the diffusivity of fission gas atoms (Xe) in UO2 nuclear fuel has been calculated for a range of non-stoichiometry (i.e. UO2x), under both out-of-pile (no irradiation) and in-pile (irradiation) conditions. This was achieved by first deriving expressions for the activation energy that account for the type of trap site that the fission gas atoms occupy, which includes the corresponding type of mobile cluster, the charge state of these defects and the chemistry acting as boundary condition. In the next step DFT calculations were used to estimate migration barriers and internal energy contributions to the thermodynamic properties and calculations based on empirical potentials were used to estimate defect formation and migration entropies (i.e. pre-exponentials). The diffusivities calculated for out-of-pile conditions as function of the UO2x nonstoichiometrywere used to validate the accuracy of the diffusion models and the DFT calculations against available experimental data. The Xe diffusivity is predicted to depend strongly on the UO2x non-stoichiometry due to a combination of changes in the preferred Xe trap site and in the concentration of uranium vacancies enabling Xe diffusion, which is consistent with experiments. After establishing the validity of the modeling approach, it was used for studying Xe diffusion under in-pile conditions, for which experimental data is very scarce. The radiation-enhanced Xe diffusivity is compared to existing empirical models. Finally, the predicted fission gas diffusion rates were implemented in the BISON fuel performance code and fission gas release from a Risø fuel rod irradiation experiment was simulated. 2014 Elsevier B.V. All rights
Plimpton, Steve
2005-01-01T23:59:59.000Z
Cell Modeling via Reacting Diffusive Particles Steven J. Plimpton and Alex Slepoy Sandia National-based simulator called ChemCell that we are developing with the goal of modeling the protein chemistry are represented by triangulated surfaces. Diffusing particles represent proteins, complexes, or other biomolecules
Implementation of two-equation soot flamelet models for laminar diffusion flames
Carbonell, D.; Oliva, A.; Perez-Segarra, C.D. [Centre Tecnologic de Transferencia de Calor (CTTC), Universitat Politecnica de Catalunya (UPC), ETSEIAT, Colom 11, E-08222, Terrassa (Barcelona) (Spain)
2009-03-15T23:59:59.000Z
The two-equation soot model proposed by Leung et al. [K.M. Leung, R.P. Lindstedt, W.P. Jones, Combust. Flame 87 (1991) 289-305] has been derived in the mixture fraction space. The model has been implemented using both Interactive and Non-Interactive flamelet strategies. An Extended Enthalpy Defect Flamelet Model (E-EDFM) which uses a flamelet library obtained neglecting the soot formation is proposed as a Non-Interactive method. The Lagrangian Flamelet Model (LFM) is used to represent the Interactive models. This model uses direct values of soot mass fraction from flamelet calculations. An Extended version (E-LFM) of this model is also suggested in which soot mass fraction reaction rates are used from flamelet calculations. Results presented in this work show that the E-EDFM predict acceptable results. However, it overpredicts the soot volume fraction due to the inability of this model to couple the soot and gas-phase mechanisms. It has been demonstrated that the LFM is not able to predict accurately the soot volume fraction. On the other hand, the extended version proposed here has been shown to be very accurate. The different flamelet mathematical formulations have been tested and compared using well verified reference calculations obtained solving the set of the Full Transport Equations (FTE) in the physical space. (author)
Modeling and analyses of postulated UF{sub 6} release accidents in gaseous diffusion plant
Kim, S.H.; Taleyarkhan, R.P.; Keith, K.D.; Schmidt, R.W. [Oak Ridge National Lab., TN (United States); Carter, J.C. [J.C. Carter Associates, Inc., Oak Ridge, TN (United States); Dyer, R.H. [Dyer Enterprises, Oak Ridge, TN (United States)
1995-10-01T23:59:59.000Z
Computer models have been developed to simulate the transient behavior of aerosols and vapors as a result of a postulated accident involving the release of uranium hexafluoride (UF{sub 6}) into the process building of a gaseous diffusion plant. UF{sub 6} undergoes an exothermic chemical reaction with moisture (H{sub 2}O) in the air to form hydrogen fluoride (HF) and radioactive uranyl fluoride (UO{sub 2}F{sub 2}). As part of a facility-wide safety evaluation, this study evaluated source terms consisting of UO{sub 2}F{sub 2} as well as HF during a postulated UF{sub 6} release accident in a process building. In the postulated accident scenario, {approximately}7900 kg (17,500 lb) of hot UF{sub 6} vapor is released over a 5 min period from the process piping into the atmosphere of a large process building. UO{sub 2}F{sub 2} mainly remains as airborne-solid particles (aerosols), and HF is in a vapor form. Some UO{sub 2}F{sub 2} aerosols are removed from the air flow due to gravitational settling. The HF and the remaining UO{sub 2}F{sub 2} are mixed with air and exhausted through the building ventilation system. The MELCOR computer code was selected for simulating aerosols and vapor transport in the process building. MELCOR model was first used to develop a single volume representation of a process building and its results were compared with those from past lumped parameter models specifically developed for studying UF{sub 6} release accidents. Preliminary results indicate that MELCOR predicted results (using a lumped formulation) are comparable with those from previously developed models.
Proton diffusion pathways and rates in Y-doped BaZrO3 solid oxide electrolyte from quantum mechanics
Goddard III, William A.
Proton diffusion pathways and rates in Y-doped BaZrO3 solid oxide electrolyte from quantum barriers for intraoctahedral and interoctahedral proton transfers. We find activation energy Ea values of 0.48 and 0.49 eV for the intraoctahedral proton transfers on OO edges 2.58 and 2.59 Å of ZrO6 and YO6
DIFFUSION IN SOLIDSDIFFUSION IN SOLIDS FICK'S LAWS
Subramaniam, Anandh
Diffusion bonding To comprehend many materials related phenomenon one must understand Diffusion. The focusDIFFUSION IN SOLIDSDIFFUSION IN SOLIDS FICK'S LAWS KIRKENDALL EFFECT ATOMIC MECHANISMS Diffusion in Solids P.G. Shewmon McGraw-Hill, New York (1963) #12;Oxidation Roles of Diffusion Creep Aging
Effective Diffusion-Medium Thickness for Simplified Polymer-Electrolyte-Fuel-Cell Modeling
Weber, Adam; Weber, Adam Z.
2008-07-30T23:59:59.000Z
In this manuscript, conformal mapping is applied to a rib/channel domain of a polymer-electrolyte-fuel-cell diffusion medium. The analysis leads to the calculation of an effective diffusion-medium thickness, which can subsequently be used in 1-D simulations to account for the average rib/channel 2-D geometric effect. Extensions of the analysis to anisotropic and multilayer diffusion media are also given. Both equations and figures show the impact on a given variable at the catalyst layer of having a combined conducting/nonconducting boundary across from it.
Surveying Diffusion in Complex Geometries. An Essay
Denis Grebenkov
2009-09-08T23:59:59.000Z
The surrounding world surprises us by the beauty and variety of complex shapes that emerge from nanometric to macroscopic scales. Natural or manufactured materials (sandstones, sedimentary rocks and cement), colloidal solutions (proteins and DNA), biological cells, tissues and organs (lungs, kidneys and placenta), they all present irregularly shaped "scenes" for a fundamental transport "performance", that is, diffusion. Here, the geometrical complexity, entangled with the stochastic character of diffusive motion, results in numerous fascinating and sometimes unexpected effects like diffusion screening or localization. These effects control many diffusion-mediated processes that play an important role in heterogeneous catalysis, biochemical mechanisms, electrochemistry, growth phenomena, oil recovery, or building industry. In spite of a long and rich history of academic and industrial research in this field, it is striking to see how little we know about diffusion in complex geometries, especially the one which occurs in three dimensions. We present our recent results on restricted diffusion. We look into the role of geometrical complexity at different levels, from boundary microroughness to hierarchical structure and connectivity of the whole diffusion-confining domain. We develop a new approach which consists in combining fast random walk algorithms with spectral tools. The main focus is on studying diffusion in model complex geometries (von Koch boundaries, Kitaoka acinus, etc.), as well as on developing and testing spectral methods. We aim at extending this knowledge and at applying the accomplished arsenal of theoretical and numerical tools to structures found in nature and industry.
Non-Linear Drying Diffusion and Viscoelastic Drying Shrinkage Modeling in Hardened Cement Pastes
Leung, Chin K.
2010-07-14T23:59:59.000Z
of diffusion rate over short drops of ambient relative humidity. Techniques to determine drying isotherms prior to full equilibration of mass loss, as well as converting mass loss into concentration of water vapor were developed. Using the measured water vapor...
Wu, Ona
2002-01-01T23:59:59.000Z
Diffusion (DWI) and perfusion weighted (PWI) magnetic resonance imaging (MRI) provide significant insight into acute stroke and can potentially be useful for clinical decision-making. In particular, current therapeutic ...
Hydro-mechanical modelling of geological CO2 storage and the study of possible caprock fracture element modelling of a hypothetical underground carbon dioxide (CO2) storage operation. The hydro
Kostic, Milivoje M.
, the mass-energy equivalence and the Physics law of forced interactions will be violated, since these thermo-mechanical phenomena are neither gravitational nor nuclear interactions. It is widely believed that thermal heat
An Improved Probabilistic Fracture Mechanics Model for Pressurized Thermal Shock
Dickson, T.L.
2001-10-29T23:59:59.000Z
This paper provides an overview of an improved probabilistic fracture mechanics (PFM) model used for calculating the conditional probabilities of fracture and failure of a reactor pressure vessel (RPV) subjected to pressurized-thermal-shock (PTS) transients. The updated PFM model incorporates several new features: expanded databases for the fracture toughness properties of RPV steels; statistical representations of the fracture toughness databases developed through application of rigorous mathematical procedures; and capability of generating probability distributions for RPV fracture and failure. The updated PFM model was implemented into the FAVOR fracture mechanics program, developed at Oak Ridge National Laboratory as an applications tool for RPV integrity assessment; an example application of that implementation is discussed herein. Applications of the new PFM model are providing essential input to a probabilistic risk assessment (PRA) process that will establish an improved technical basis for re-assessment of current PTS regulations by the US Nuclear Regulatory Commission (NRC). The methodology described herein should be considered preliminary and subject to revision in the PTS re-evaluation process.
Xu, Zhijie; Fang, Yilin; Scheibe, Timothy D.; Bonneville, Alain
2012-05-15T23:59:59.000Z
We present a hydro-mechanical model for geological sequestration of carbon dioxide. The model considers the poroelastic effects by taking into account the coupling between the geomechanical response and the fluid flow in greater detail. The simplified hydro-mechanical model includes the geomechanical part that relies on the linear elasticity, while the fluid flow is based on the Darcy’s law. Two parts were coupled using the standard linear poroelasticity. Analytical solutions for pressure field were obtained for a typical geological sequestration scenario. The model predicts the temporal and spatial variation of pressure field and effects of permeability and elastic modulus of formation on the fluid pressure distribution.
Ziebarth, Benedikt, E-mail: Benedikt.Ziebarth@iwm.fraunhofer.de; Gumbsch, Peter [Fraunhofer Institut für Werkstoffmechanik IWM, Wöhlerstr. 11, 79108 Freiburg (Germany); Karlsruher Institut für Technologie, Institut für Ausgewandte Materialien (IAM-ZBS), Engelbert-Arnold-Str. 4, 76131 Karlsruhe (Germany); Mrovec, Matous; Elsässer, Christian [Fraunhofer Institut für Werkstoffmechanik IWM, Wöhlerstr. 11, 79108 Freiburg (Germany)
2014-09-07T23:59:59.000Z
Sodium decorated stacking faults (SFs) were recently identified as the primary cause of potential-induced degradation in silicon (Si) solar-cells due to local electrical short-circuiting of the p-n junctions. In the present study, we investigate these defects by first principles calculations based on density functional theory in order to elucidate their structural, thermodynamic, and electronic properties. Our calculations show that the presence of sodium (Na) atoms leads to a substantial elongation of the Si-Si bonds across the SF, and the coverage and continuity of the Na layer strongly affect the diffusion behavior of Na within the SF. An analysis of the electronic structure reveals that the presence of Na in the SF gives rise to partially occupied defect levels within the Si band gap that participate in electrical conduction along the SF.
Luettmer-Strathmann, Jutta
Study of the Thermal Diffusion Behavior of Alkane/Benzene Mixtures by Thermal Diffusion Forced mixtures of linear alkanes (heptane, nonane, undecane, tridecane, pentadecane, heptadecane) in benzene has and temperatures. The Soret coefficient ST of the alkane was found to be negative for these n-alkane/benzene
Bloemen, S; Aerts, C; Dupret, M A; Østensen, R H; Degroote, P; Müller-Ringat, E; Rauch, T
2014-01-01T23:59:59.000Z
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...
MECHANICAL PROPERTY CHARACTERIZATIONS AND PERFORMANCE MODELING OF SOFC SEALS
Koeppel, Brian J.; Vetrano, John S.; Nguyen, Ba Nghiep; Sun, Xin; Khaleel, Mohammad A.
2008-03-26T23:59:59.000Z
This study provides modeling tools for the design of reliable seals for SOFC stacks. The work consists of 1) experimental testing to determine fundamental properties of SOFC sealing materials, and 2) numerical modeling of stacks and sealing systems. The material tests capture relevant temperature-dependent physical and mechanical data needed by the analytical models such as thermal expansion, strength, fracture toughness, and relaxation behavior for glass-ceramic seals and other materials. Testing has been performed on both homogenous specimens and multiple material assemblies to investigate the effect of interfacial reactions. A viscoelastic continuum damage model for a glass-ceramic seal was developed to capture the nonlinear behavior of this material at high temperatures. This model was implemented in the MSC MARC finite element code and was used for a detailed analysis of a planar SOFC stack under thermal cycling conditions. Realistic thermal loads for the stack were obtained using PNNL’s in-house multiphysics solver. The accumulated seal damage and component stresses were evaluated for multiple thermal loading cycles, and regions of high seal damage susceptible to cracking were identified. Selected test results, numerical model development, and analysis results will be presented.
On a Model of Quantum Mechanics and the Mind
J. Acacio de Barros
2014-04-16T23:59:59.000Z
In this paper I discuss Stapp's (2014) interesting proposal of using the Quantum Zeno Effect to account for the mind/matter interaction. In particular, I discuss some of the motivations for it, and then argue that, in his current version, his model is circular (a solution to this, proposed by Kathryn Laskey, is presented), insofar as the mind/matter problem is concerned. I also present an alternative approach to some of the appealing aspects of using quantum mechanics to think about consciousness.
A mechanical model of early salt dome growth
Irwin, Frank Albert
1988-01-01T23:59:59.000Z
salt and the upper layer representing the overlying sediment, is used to study the mechanics of growth in the early stages of salt dome formation. Three cases of this model, each representing a particular rate of removal of the surface topography..., are examined to determine which case best fits observations of salt domes in East Texas, Northwest Germany, and the North Sea. These observations include the spacing and growth rate of the dome and the amount of deformation of the sediments above the dome...
Ortiz, Michael
across several disciplines such as surface chemistry and catalysis, applied physics, metallurgy and on-the-fly kinetic Monte Carlo simulations A. Ramasubramaniam Program in Applied and Computational) Department of Mechanical and Aerospace Engineering and Program in Applied and Computational Mathematics
Modeling the Q-cycle mechanism of transmembrane energy conversion
Anatoly Yu. Smirnov; Franco Nori
2011-06-29T23:59:59.000Z
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.
Modeling of diffusion of injected electron spins in spin-orbit coupled microchannels
Zarbo, Liviu P.; Sinova, Jairo; Knezevic, I.; Wunderlich, J.; Jungwirth, T.
2010-01-01T23:59:59.000Z
We report on a theoretical study of spin dynamics of an ensemble of spin-polarized electrons injected in a diffusive microchannel with linear Rashba and Dresselhaus spin-orbit coupling. We explore the dependence of the spin-precession and spin...
N + 1 dimensional quantum mechanical model for a closed universe
T. R. Mongan
1999-02-10T23:59:59.000Z
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.
The mechanisms underlying convergent evolution in the plumage patterns of birds
Gluckman, Thanh-Lan
2015-03-03T23:59:59.000Z
receptors (Yoshihara et al. 2012). Models of within-feather pattern formation The proposed organizing mechanism for within-feather pattern formation in birds is reaction-diffusion, based on Alan Turing’s (1952) original proposition The mechanisms...
A Mechanical Model for CCK-Induced Acalculous Gallbladder Pain
unknown authors
2010-01-01T23:59:59.000Z
Associate Editor Peter E. McHugh oversaw the review of this article. Abstract—This study investigates the potential correlation between acalculous biliary pain and mechanical stress during the bile-emptying phase. This study is built on the previously developed mathematical model used to estimate stress in the gallbladder wall during emptying [Li, W. G., X. Y. Luo, et al. Comput. Math. Methods Med. 9(1):27–45, 2008]. Although the total stress was correctly predicted using the previous model, the contribution from patient-specific active stress induced by the cholecystokinin (CCK) test was overlooked. In this article, we evaluate both the active and passive components of pressure in a gallbladder, which undergoes isotonic refilling, isometric contraction and emptying during the infusion of CCK. The pressure is estimated from in vivo ultrasonographical scan measurements of gallbladder emp-tying during CCK tests, assuming that the gallbladder is a thin ellipsoidal membrane. The passive stress is caused by the volume and shape changes during refilling at the gallbladder basal pressure, whereas the active stress arises from the pressure rise during the isometric gallbladder contraction after the CCK infusion. The effect on the stress estimates of the gallbladder to the liver is evaluated to be small by comparing numerical simulations of a gallbladder model with and without a rigid ‘flat top ’ boundary. The model was applied to 51 subjects, and the peak total stress was found to have a strong correlation with the pain stimulated by CCK, as measured by the patient pain score questionnaires. Consistent with our previous study for a smaller sample, it is found that the success rate in predicting of CCK-induced pain is over 75%.
Free Body Analysis, Beam Mechanics, and Finite Element Modeling of the Mandible of Alligator
Free Body Analysis, Beam Mechanics, and Finite Element Modeling of the Mandible of Alligator arm mechanics, 2D and 3D beam mod- els, and three high-resolution finite element models- pared with the beam models, the Alligator finite element models exhibited less spatial variability
Title: Hydraulic modeling of a mixed water level control hydro-mechanical gate
Paris-Sud XI, UniversitÃ© de
Title: Hydraulic modeling of a mixed water level control hydro-mechanical gate Ludovic Cassan1 Abstract: The article describes the hydraulic functioning of a mixed water level control hydro- mechanical of the model to reproduce the functioning of this complex hydro-mechanical system. CE database Subject headings
Deployment Mechanism Design with Behavioral Modeling Based on Pro/Engineer Motion Skeleton
kind of motion mechanisms, is often used to stretch out solar panels or antennas in spacecraftDeployment Mechanism Design with Behavioral Modeling Based on Pro/Engineer Motion Skeleton Chao.com.cn Keywords: Deployment mechanism, Motion skeleton, Behavioral modeling, Feasibility analysis Abstract
Bachas, C.P.
1988-02-01T23:59:59.000Z
We review the solution and properties of the diffusion equation in a hierarchical or ultrametric space. 11 refs.
Unitary dilation models of Turing machines in quantum mechanics
Benioff, P. [Environmental Assessment Division, Building 900, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Environmental Assessment Division, Building 900, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
1995-05-01T23:59:59.000Z
A goal of quantum-mechanical models of the computation process is the description of operators that model changes in the information-bearing degrees of freedom. Iteration of the operators should correspond to steps in the computation, and the final state of halting computations should be stable under iteration. The problem is that operators constructed directly from the process description do not have these properties. In general these operators annihilate the halted state. If information-erasing steps are present, there are additional problems. These problems are illustrated in this paper by consideration of operators for two simple one-step processes and two simple Turing machines. In general the operators are not unitary and, if erasing steps are present, they are not even contraction operators. Various methods of extension or dilation to unitary operators are discussed. Here unitary power dilations are considered as a solution to these problems. It is seen that these dilations automatically provide a good solution to the initial- and final-state problems. For processes with erasing steps, recording steps must be included prior to the dilation, but only for the steps that erase information. Hamiltonians for these processes are also discussed. It is noted that {ital H}, described by exp({minus}{ital iH}{Delta})={ital U}{sup {ital T}}, where {ital U}{sup {ital T}} is a unitary step operator for the process and {Delta} a time interval, has complexity problems. These problems and those noted above are avoided here by the use of the Feynman approach to constructing Hamiltonians directly from the unitary power dilations of the model operators. It is seen that the Hamiltonians so constructed have some interesting properties.
element modelling of a hypothetical underground carbon dioxide (CO2) storage operation. The hydro-mechanical properties of the materials modelled are chosen to be representative of a potential injection site. For high on the injection process, and on site and rock properties. Rutqvist et al. (2008) showed through a coupled
Design and modeling of carbon nanotube-based compliant mechanisms
DiBiasio, Christopher M. (Christopher Michael)
2007-01-01T23:59:59.000Z
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 ...
Belucz, Bernadett; Forgacs-Dajka, Emese
2015-01-01T23:59:59.000Z
Babcock-Leighton type solar dynamo models with single-celled meridional circulation are successful in reproducing many solar cycle features. Recent observations and theoretical models of meridional circulation do not indicate a single-celled flow pattern. We examine the role of complex multi-cellular circulation patterns in a Babcock-Leighton solar dynamo in advection- and diffusion-dominated regimes. We show from simulations that presence of a weak, second, high-latitude reverse cell speeds up the cycle and slightly enhances the poleward branch in butterfly diagram, whereas the presence of a second cell in depth reverses the tilt of butterfly wing to an anti-solar type. A butterfly diagram constructed from middle of convection zone yields a solar-like pattern, but this may be difficult to realize in the Sun because of magnetic buoyancy effects. Each of the above cases behaves similarly in higher and lower magnetic diffusivity regimes. However, our dynamo with a meridional circulation containing four cells in...
Shingledecker, Christopher N
2014-01-01T23:59:59.000Z
Research over the past four decades has shown a rich variety of complex organic molecular content in some meteorites. This current study is an attempt to gain a better insight into the thermal conditions experienced by these molecules inside meteorites during atmospheric entry. In particular, we wish to understand possible chemical processes that can occur during entry and that might have had an effect on complex organic or prebiotic species that were delivered in this way to the early Earth. A simulation was written in Fortran to model heating by the shock generated during entry and the subsequent thermal diffusion inside the body of a meteorite. Experimental data was used for the thermal parameters of several types of meteorites, including iron-nickel and several classes of chondrites. A Sutton-Graves model of stagnation-point heating was used to calculate peak surface temperatures and an explicit difference formula was used to generate thermal diffusion profiles for both chondrites and iron-nickel type met...
Modeling genome-wide replication kinetics reveals a mechanism for regulation of replication timing
Bechhoefer, John
Modeling genome-wide replication kinetics reveals a mechanism for regulation of replication timing, University of Massachusetts Medical School, Worcester, MA, USA * Corresponding author. Department of Physics, testable, biochemically plausible mechanism for the regulation of replication timing in eukaryotes
Song, Jing, 1972-
2004-01-01T23:59:59.000Z
Building proper reaction mechanisms is crucial to model the system dynamic properties for many industrial processes with complex chemical reaction phenomena. Because of the complexity of a reaction mechanism, computer-aided ...
Current-based 4D shape analysis for the mechanical personalization of heart models
Paris-Sud XI, Université de
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
A Mechanism-based Model for Deformation Twinning in Polycrystalline...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
in Polycrystalline FCC Steel. Abstract: Deformation twinning, a common and important plastic deformation mechanism, is the key contributor to the excellent combination of...
Modeling biofilms with dual extracellular electron transfer mechanisms...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
a unique form of respiration in which they utilize solid external materials as their terminal electron acceptor for metabolism. Currently, two primary mechanisms have been...
De Luca, A.; Texier, M.; Burle, N.; Oison, V.; Pichaud, B. [Aix-Marseille Université, IM2NP UMR 7334, Faculté des Sciences et Techniques, Campus de Saint-Jérôme, Avenue Escadrille Normandie Niemen - Case 142, F-13397 Marseille Cedex (France); Portavoce, A., E-mail: alain.portavoce@im2np.fr [CNRS, IM2NP UMR 7334, Faculté des Sciences et Techniques, Campus de Saint-Jérôme, Avenue Escadrille Normandie Niemen - Case 142, F-13397 Marseille Cedex (France); Grosjean, C. [STMicroelectronics, Rousset (France)
2014-01-07T23:59:59.000Z
Two doses (10{sup 13} and 10{sup 15}?cm{sup ?2}) of tungsten (W) atoms were implanted in different Si(001) wafers in order to study W diffusion in Si. The samples were annealed or oxidized at temperatures between 776 and 960?°C. The diffusion profiles were measured by secondary ion mass spectrometry, and defect formation was studied by transmission electron microscopy and atom probe tomography. W is shown to reduce Si recrystallization after implantation and to exhibit, in the temperature range investigated, a solubility limit close to 0.15%–0.2%, which is higher than the solubility limit of usual metallic impurities in Si. W diffusion exhibits unusual linear diffusion profiles with a maximum concentration always located at the Si surface, slower kinetics than other metals in Si, and promotes vacancy accumulation close to the Si surface, with the formation of hollow cavities in the case of the higher W dose. In addition, Si self-interstitial injection during oxidation is shown to promote W-Si clustering. Taking into account these observations, a diffusion model based on the simultaneous diffusion of interstitial W atoms and W-Si atomic pairs is proposed since usual models used to model diffusion of metallic impurities and dopants in Si cannot reproduce experimental observations.
N = 4 supersymmetric mechanics: Harmonic superspace as a universal tool of model-building
Ivanov, E. A., E-mail: eivanov@theor.jinr.ru [Joint Institute for Nuclear Research, Bogoliubov Laboratory of Theoretical Physics (Russian Federation)
2013-08-15T23:59:59.000Z
We overview applications of the harmonic superspace approach in models of N = 4supersymmetric mechanics, with emphasis on some recent results.
Guin, J.A.
1998-12-31T23:59:59.000Z
The overall objective of this project was to investigate the diffusion of coal and petroleum asphaltenes in the pores of a supported catalyst. Experimental measurements together with mathematical modeling was conducted to determine how the diffusion rate of asphaltenes, as well as some model compounds, depended on molecule sizes and shapes. The process of diffusion in the pores of a porous medium may occur by several mechanisms. Hindered diffusion occurs when the sizes of the diffusion molecules are comparable to those of the porous pores through which they are diffusing. Hindered diffusion phenomena have been widely observed in catalytic hydrotreatment of asphaltenes, heavy oils, coal derived liquids, etc. Pore diffusion limitations can be greater in spent catalysts due to the deposition of coke and metals in the pores. In this work, a general mathematical model was developed for the hindered diffusion-adsorption of solute in a solvent onto porous materials, e. g. catalysts, from a surrounding bath. This diffusion model incorporated the nonuniformities of pore structures in the porous media. A numerical method called the Method of Lines was used to solve the nonlinear partial differential equations resulting from the mathematical model. The accuracy of the numerical solution was verified by both a mass balance in the diffusion system and satisfactory agreement with known solutions in several special cases.
Min, Kyoung
2013-07-16T23:59:59.000Z
are studied using a coupled thermo-hydro-mechanical (THM) analysis. The models are used to simulate microscopic and macroscopic fracture behaviors of laboratory-scale uniaxial and triaxial experiments on rock using an elastic/brittle damage model considering...
Substrate Hydroxylation in Methane Monooxygenase: Quantitative Modeling via Mixed Quantum Mechanics/
Gherman, Benjamin F.
at an atomic level of detail.4-7 In particular, the use of ab initio quantum chemical methods based on densitySubstrate Hydroxylation in Methane Monooxygenase: Quantitative Modeling via Mixed Quantum Mechanics with mixed quantum mechanics/molecular mechanics (QM/MM) methods, the hydroxylation of methane
Salvaggio, Carl
of Mechanical Draft Cooling Towers to Assist in the Extraction of their Absolute Temperature from Remote Thermal Abstract Determination of the internal temperature of a mechanical draft cooling tower (MDCT) from remotelyRadiometric Modeling of Mechanical Draft Cooling Towers to Assist in the Extraction
Brindley, T. L.; Tarantino, J. J.; Locke, A. L. [CDM, 325 Kentucky Ave., Kevil, Kentucky 42053 (United States); Dollins, D. W. [Department of Energy, Paducah Gaseous Diffusion Plant, Paducah Kentucky 42001 (United States)
2006-07-01T23:59:59.000Z
This paper describes how 4-Dimensional (4D) Data Visualization Modeling was used to evaluate historical data and to help guide the decisions for the sampling necessary to complete a Remedial Investigation/Feasibility Study (RI/FS) for the burial ground sites at the Department of Energy (DOE) Paducah Gaseous Diffusion Plant (PGDP). DOE at the Paducah Site is primarily involved in environmental cleanup and landlord activities. The scope of this project was to prepare a work plan for identifying the data available and the data required to conduct an RI/FS for the Burial Ground Operable Unit (BGOU) located within and near PGDP. The work plan focuses on collecting existing information about contamination in and around the burial grounds and determining what additional data are required to support an assessment of risks to human health and the environment and to support future decisions regarding actions to reduce these risks. (authors)
Lee, Sang Hoon
2012-02-14T23:59:59.000Z
coupled thermo-poro-mechanical FEM simulation was used to model damage/fracture propagation and microseismic events caused by fluid injection. These studies considered wellbore geometry in small-scale modeling and point-source injection, assuming...
An improved structural mechanics model for the FRAPCON nuclear fuel performance code
Mieloszyk, Alexander James
2012-01-01T23:59:59.000Z
In order to provide improved predictions of Pellet Cladding Mechanical Interaction (PCMI) for the FRAPCON nuclear fuel performance code, a new model, the FRAPCON Radial-Axial Soft Pellet (FRASP) model, was developed. This ...
A Hydro-Thermo-Mechanical Numerical Model For Hdr Geothermal...
Published Journal International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1996 DOI 10.10160148-9062(96)00002-2 Citation T. W. Hicks,R. J. Pine,J....
Characterization and modeling of polysilicon MEMS chemical-mechanical polishing
Tang, Brian D. (Brian David), 1980-
2004-01-01T23:59:59.000Z
Heavily used in the manufacture of integrated circuits, chemical-mechanical polishing (CMP) is becoming an enabling technology for microelectromechanical systems (MEMS). To reliably use CMP in the manufacturing process, ...
Notes 01. Modeling of mechanical (lumped parameter) elements
San Andres, Luis
2008-01-01T23:59:59.000Z
Fundamental elements in mechanical systems: inertias, stiffness and damping elements. Equivalent spring coefficients and associated potential energy. Equivalent mass or inertia coefficients and associated kinetic energy. Equations of motion of a...
Modeling of chemical mechanical polishing for shallow trench isolation
Lee, Brian, 1975-
2002-01-01T23:59:59.000Z
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 ...
Continuum models of deformation mechanisms in nanocrystalline metals
Jérusalem, Antoine, 1979-
2007-01-01T23:59:59.000Z
Nanocrystalline metals are polycrystalline metals with grain sizes in the nanometer range. They have attracted significant interest in recent years due to their unique mechanical and electrical properties. The main objective ...
Cambridge, University of
Experimental testing and modelling of a passive mechanical steering compensator for high of the method to the control of motorcycles steer- ing instabilities. Simulation studies have shown-- This paper presents experimental results and a modelling study of a prototype mechanical device that repre
Thermo-mechanical modelling of Black Sea Basin (de)formation S. Cloetingh*, G. Spadini1
Beekman, Fred
Thermo-mechanical modelling of Black Sea Basin (de)formation S. Cloetingh*, G. Spadini1 , J.D. Van; received in revised form 7 January 2002; accepted 19 July 2002 Abstract We present the results of a thermo by rifting and subsequent sediment loading. Thermo-mechanical modelling of integrated lithospheric strength
ThreadedComposite: A Mechanism for Building Concurrent and Parallel Ptolemy II Models
ThreadedComposite: A Mechanism for Building Concurrent and Parallel Ptolemy II Models Edward A. Lee Electrical Engineering and Computer Sciences University of California at Berkeley Technical Report No. UCBComposite: A Mechanism for Building Concurrent and Parallel Ptolemy II Models Edward A. Lee UC Berkeley eal
WELL-POSEDNESS OF A THERMO-MECHANICAL MODEL FOR SHAPE MEMORY ALLOYS UNDER TENSION
Stefanelli, Ulisse
WELL-POSEDNESS OF A THERMO-MECHANICAL MODEL FOR SHAPE MEMORY ALLOYS UNDER TENSION PAVEL KREJC´I AND ULISSE STEFANELLI Abstract. We present a model of the full thermo-mechanical evolution of a shape memory on a time-discretization of the problem are provided. 1. Introduction Shape memory alloys (SMAs) belong
Modeling benzene plume elongation mechanisms exerted by ethanol using RT3D with a general
Alvarez, Pedro J.
Modeling benzene plume elongation mechanisms exerted by ethanol using RT3D with a general substrate ethanol on benzene fate and transport in fuel-contaminated groundwater and to discern the most influential benzene plume elongation mechanisms. The model, developed as a module for the Reactive Transport in 3
Long-range dispersion and spatial diffusion of fault waves in the Burridge-Knopoff earthquake model
Alain M. Dikandé
2004-02-13T23:59:59.000Z
The Burridge-Knopoff model of earthquakes has recently gained increased interest for the consistency of the predicted energy released by sismic faults, with the Gutenberg-Richter scaling law. The present work suggests an improvement of this model to account for long-range dispersions and large spatial diffusion of sismic faults. An enhancement of the threshold speed of shock waves driven by translated fault fronts is pointed out and shown to result from the interactions between components of the system situated far aways them and others. Due to the enhanced threshold speed, size of the sismic fault gets increased but a control effect can still be gained from tunable dispersion extent irrespective of the total length of the system. To the viewpoint of the Burridge-Knopoff block-lattice model, this last consideration introduces the possibility of sizable but finite interactions among infinitely aligned massive blocks. Implications on the fault wave propagation are examined by numerical simulations of the improved nonlinear partial differential equation.
Shattow, Genevieve M; Bibiano, Antonio
2015-01-01T23:59:59.000Z
With the installation of the Cosmic Origins Spectrograph on the Hubble Space Telescope, measurements of the metal content of the low redshift intergalactic medium (IGM) are now available. Using a new grid-based model for diffuse gas coupled to the SAGE semi-analytic model of galaxy formation, we examine the impact of supernova feedback on the pollution of the IGM. We consider different assumptions for the reheating and ejection of gas by supernovae and their dependence on galaxy circular velocity and gas surface density. Where metals are present, we find the most likely metallicity to be $-1.5 < $log$_{10}$(Z/Z$_{\\odot}$)$< -1.0$ at $z = 0$, consistent with both observations and more sophisticated hydrodynamic simulations. Our model predicts that the regions of the IGM with the highest metallicities will be near galaxies with M$_{\\star} \\sim 10^{10.5}h^{-1}$M$_{\\odot}$ and in environments of densities $\\sim 10 \\times$ the mean. We also find that 90% of IGM metals at $z = 0$ are ejected by galaxies with ...
Diffusive Acceleration of Ions at Interplanetary Shocks
Matthew G. Baring; Errol J. Summerlin
2005-06-08T23:59:59.000Z
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.
Ignatyev, Yu G
2011-01-01T23:59:59.000Z
The evolution of a superthermal relic component of matter is studied on the basis of non-equilibrium model of Universe and the Fokker-Planck type kinetic equation offered by one of the authors.
Zeng, Yi
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 ...
Internship Parallel Computer Evaluation Parallelization of a Lagrangian Particle Diffusion Model
use case is a nuclear accident like a core meltdown at a atomic power plant, where atomic radiation emits in the air. The Lagrangian model can predict how the nuclear cloud spreads under different that will be computed. Particle: One single molecule floating in the wind field. Compute unit: One unit that runs
RIS-M-2361 DESCRIPTION OF THE RIS PUFF DIFFUSION MODEL
for industrial operations and construction planning. The dispersion of such atmospheric pollutants is commonly-dimensional model simulates the release of Gaussian pollutant puffs and predicts their concentration mixing depth have been considered. INIS descriptors; ADVECTION; AIR POLLUTION; BOUNDARY LAYERS; CLUSTER
Multi-factor jump-diffusion models of electricity Thilo MEYER-BRANDIS
features of electricity prices with a particular attention to the European energy ex- changes and develop a statistical procedure for estimat- ing the sum-OU model from data. Key Words: electricity prices is therefore necessary for energy risk management, pricing of electricity-related options and evaluation
van der Zwaan, Bob; Rosler, Hilke; Kober, Tom; Aboumahboub, Tino; Calvin, Katherine V.; Gernaat, David; Marangoni, Giacomo; McCollum, David
2013-11-01T23:59:59.000Z
We investigate the long-term global energy technology diffusion patterns required to reach a stringent climate change target with a maximum average atmospheric temperature increase of 2°C. If the anthropogenic temperature increase is to be limited to 2°C, total CO2 emissions have to be reduced massively, so as to reach substantial negative values during the second half of the century. Particularly power sector CO2 emissions should become negative from around 2050 onwards according to most models used for this analysis in order to compensate for GHG emissions in other sectors where abatement is more costly. The annual additional capacity deployment intensity (expressed in GW/yr) for solar and wind energy until 2030 needs to be around that recently observed for coal-based power plants, and will have to be several times higher in the period 2030–2050. Relatively high agreement exists across models in terms of the aggregated low-carbon energy system cost requirements on the supply side until 2050, which amount to about 50 trillion US$.
Coupled Thermal-Hydrological-Mechanical-Chemical Model And Experiments...
Model And Experiments For Optimization Of Enhanced Geothermal System Development And Production: Evaluation of Stimulation at the Newberry Volcano EGS Demonstration Site Coupled...
Mechanical models of the 1975 Kalapana, Hawaii earthquake and tsunami
Kirby, James T.
interpretation of geological data from Kilauea, along with modeling of the tsunami using recent seismic analyses) a structural interpretation of geological data with (ii) modeling of the tsunami using recent seismic analy, because of its limited onshore expression near Kalapana. We argue that several different interpretations
Eaglesham, D.J.; Stolk, P.A.; Cheng, J.Y.; Gossmann, H.J.; Poate, J.M. [AT and T Bell Labs., Murray Hill, NJ (United States); Haynes, T.E. [Oak Ridge National Lab., TN (United States). Solid State Div.
1995-04-01T23:59:59.000Z
Ion implantation is used at several critical stages of Si integrated circuit manufacturing. The authors show how {l_brace}311{r_brace} defects arising after implantation are responsible for both enhanced dopant diffusion during annealing, and stable dislocations post-anneal. They observe {l_brace}311{r_brace} defects in the earliest stages of an anneal. They subsequently undergo rapid Ostwald ripening and evaporation. At low implant doses evaporation dominates, and they can quantitatively relate the interstitials emitted from these defects to the transient enhancement in diffusivity of dopants such as B and P. At higher doses Ostwald ripening is significant, and they observe the defects to undergo a series of unfaulting reactions to form both Frank loops and perfect dislocations. They demonstrate the ability to control both diffusion and dislocations by the addition of small amounts of carbon impurities.
Modeling heat conduction and radiation transport with the diffusion equation in
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOEThe Bonneville PowerCherries 82981-1cnHighandSWPA / SPRA /Ml'. William Hirst HirstModelingAssessing theheat
Assessment of reduced mechanisms using One Dimensional Stochastic Turbulence model
Chien, Li-Chun
2010-01-01T23:59:59.000Z
turbulence model for a syngas jet flame. Proceeding of FallKerstein 2002), a turbulent syngas (CO/H2/NO) jet flame wasand DNS results of the syngas jet flame was recently done
Grün, G., E-mail: gruen@am.uni-erlangen.de; Klingbeil, F.
2014-01-15T23:59:59.000Z
In this paper, we present a numerical scheme for the diffuse-interface model in [3] for two-phase flow of immiscible, incompressible fluids. As that model is in particular consistent with thermodynamics, energy estimates are expected to carry over to the discrete setting. By a subtle discretization of the convective coupling with the flux of the phase-field in the momentum equation, we prove discrete consistency with thermodynamics. Numerical experiments in two spatial dimensions – ranging from Rayleigh–Taylor instability to a comparison with previous modeling approaches – indicate the full practicality of our scheme and enable a first validation of the new modeling approach in [3].
A numerical modeling study on desert oasis self-supporting mechanisms
Chu, Peter C.
A numerical modeling study on desert oasis self-supporting mechanisms Peter C. Chua, *, Shihua Lub February 2005 Abstract Oasis self-supporting mechanisms due to oasis breeze circulation (OBC) are proposed from the oasis makes the oasis surface colder than the surrounding desert surface. The sensible heat
Muscle and prosthesis contributions to amputee walking mechanics: A modeling study
Ben-Yakar, Adela
Muscle and prosthesis contributions to amputee walking mechanics: A modeling study Anne K or the prosthesis must provide the functional tasks normally provided by the ankle muscles. Three-dimensional (3D and prosthesis contributions to amputee walking mechanics, including the subtasks of body support, forward
MODELISATION DU TAUX DE DEFAILLANCE EN MECANIQUE MECHANICAL FAILURE RATE MODEL
Paris-Sud XI, Université de
. Summary Electromechanical and mechanical equipment reliability databases do not seem as widespread of the reliability of (electro-)mechanical equipment and the dispersion of failure rates for apparently similar. This statement explains itself by the nature of its which do not propose prediction reliability model but present
NUMERICAL MODELLING OF AUTOGENOUS HEALING AND RECOVERY OF MECHANICAL PROPERTIES IN ULTRA-HIGH
Boyer, Edmond
in the cementitious matrix can react with carbon dioxide dissolved in the water filling the crack. Autogenous healingNUMERICAL MODELLING OF AUTOGENOUS HEALING AND RECOVERY OF MECHANICAL PROPERTIES IN ULTRA into the crack and leads to a partial recovery of mechanical properties (Young's modulus, tensile strength
Identifying Mathematical Models of the Mechanically Ventilated Lung Using Equation Discovery
Kersting, Kristian
1 Identifying Mathematical Models of the Mechanically Ventilated Lung Using Equation Discovery in intensive care medicine by all means. Nevertheless, it can induce severe mechanical stress to the lung, which generally impairs the outcome of the therapy. To reduce the risk of a ventilator induced lung
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
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.
Fluorine Plasma Treatments of Poly(propylene) Films, 2 Modeling Reaction Mechanisms and
Kushner, Mark
Fluorine Plasma Treatments of Poly(propylene) Films, 2 Modeling Reaction Mechanisms and Scalinga of commodity hydrocarbon polymers such as poly(propylene) (PP) can be modified by functionalization with plasma
Application of the 3-D Hydro-Mechanical Model GEOFRAC in enhanced geothermal systems
Vecchiarelli, Alessandra
2013-01-01T23:59:59.000Z
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 ...
Haldar, Krishnendu 1978-
2012-12-06T23:59:59.000Z
Magnetic shape memory alloys (MSMAs) are a class of active materials that de- form under magnetic and mechanical loading conditions. This work is concerned with the modeling of MSMAs constitutive responses. The hysteretic magneto...
Coal thermolysis modeling: The effects of restricted diffusion on thermal reaction pathways
Buchanan, A.C. III; Britt, P.F.; Biggs, C.A.
1989-01-01T23:59:59.000Z
The technique of model compound immobilization by covalent surface attachment is being employed to investigate the potential impact of restricted diffusional mobility on the thermal reactivity of coal. This restricted mobility may be imposed in coal as a consequence of its cross-linked, macromolecular structure. A detailed study of the thermolysis of surface-immobilized bibenzyl showed that the rate of unimolecular C-C homolysis is similar to that in fluid phases. Recent studies have foucused on the thermally induced, free radical chain decomposition reactions for surface-immobilized 1,3-diphenylpropane and 1,4-diphenylbutane. For 1,4-diphenylbutane both the reaction rate and product composition are strongly dependent on surface coverage and, hence, the proximity of 1.4-diphenylbutane molecules and hydrogen abstracting radicals on the surface. The rates and selectivities of these key bimolecular reaction steps on the surface might also be affected by the structure of neighboring molecules. In the current study, we are beginning to probe this feature by examining the influence of the structure of co-attached aromatic molecules such as biphenyl and diphenylmethane on the reaction rate and regioselectivity in the thermolysis of 1,4-diphenylbutane. 7 refs. , 1 fig., 2 tabs.
A First-Order Mechanical Device to Model Traumatized Craniovascular
. This secondary response, in turn, causes cell death and potentially permanent impairment, all of which is further exacerbated by au- toregulatory dysfunction. Recovery is unpredictable and most cognitive improvement comes, but the endpoint for partial or full recovery is unknown. Modeling of injury causation and the resulting
Model construction: elements of a computational mechanism Jan M. _Zytkow
Ras, Zbigniew W.
Academy of Sciences, Warsaw, Poland zytkow@uncc.edu Abstract Model construction is one of the key scienti of the mainsteps. As a body of mass m rolls down its kinetic energy grows from zero to mv2=2, where v is the nal velocity. At the same time, its potential energy decreases from gmh to zero, where g is Earth acceleration
Turing instability in reaction-diffusion systems with nonlinear diffusion
Zemskov, E. P., E-mail: zemskov@ccas.ru [Russian Academy of Sciences, Dorodnicyn Computing Center (Russian Federation)
2013-10-15T23:59:59.000Z
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.
Paris-Sud XI, UniversitÃ© de
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) In this paper we present the macroscopic model describing the hydro-mechanical behaviour of such class
The Harrison Diffusion Kinetics Regimes in Solute Grain Boundary Diffusion
Belova, Irina [University of Newcastle, NSW, Australia; Fiedler, T [University of Newcastle, NSW, Australia; Kulkarni, Nagraj S [ORNL; Murch, Prof. Graeme [University of Newcastle, NSW, Australia
2012-01-01T23:59:59.000Z
Knowledge of the limits of the principal Harrison kinetics regimes (Type-A, B and C) for grain boundary diffusion is very important for the correct analysis of the depth profiles in a tracer diffusion experiment. These regimes for self-diffusion have been extensively studied in the past by making use of the phenomenological Lattice Monte Carlo (LMC) method with the result that the limits are now well established. The relationship of those self-diffusion limits to the corresponding ones for solute diffusion in the presence of solute segregation to the grain boundaries remains unclear. In the present study, the influence of solute segregation on the limits is investigated with the LMC method for the well-known parallel grain boundary slab model by showing the equivalence of two diffusion models. It is shown which diffusion parameters are useful for identifying the limits of the Harrison kinetics regimes for solute grain boundary diffusion. It is also shown how the measured segregation factor from the diffusion experiment in the Harrison Type-B kinetics regime may differ from the global segregation factor.
Prinja, A.K.
1998-09-01T23:59:59.000Z
In this work, it has been shown that, for the given sets of parameters (transport coefficients), the Tangent-Predictor (TP) continuation method, which was used in the coarsest grid, works remarkably well. The problems in finding an initial guess that resides well within Newton`s method radius of convergence are alleviated by correcting the initial guess by the predictor step of the TP method. The TP method works well also in neutral gas puffing and impurity simulations. The neutral gas puffing simulation is performed by systematically increasing the fraction of puffing rate according to the TP method until it reaches a desired condition. Similarly, the impurity simulation characterized by using the fraction of impurity density as the continuation parameter, is carried out in line with the TP method. Both methods show, as expected, a better performance than the classical embedding (CE) method. The convergence criteria {epsilon} is set to be 10{sup {minus}9} based on the fact that lower value of {epsilon} does not alter the solution significantly. Correspondingly, the number of Newton`s iterations in the corrector step of the TP method decrease substantially, an extra point in terms of code speed. The success of the TP method enlarges the possibility of including other sets of parameters (operations and physics). With the availability of the converged coarsest grid solution, the next forward step to the multigrid cycle becomes possible. The multigrid method shows that the memory storage problems that plagued the application of Newton`s method on fine grids, are of no concern. An important result that needs to be noted here is the performance of the FFCD model. The FFCD model is relatively simple and is based on the overall results the model has shown to predict different divertor plasma parameters. The FFCD model treats exactly the implementation of the deep penetration of energetic neutrals emerging from the divertor plate. The resulting ionization profiles are relatively smooth as a consequence of the less localized recycling, leading to an improved convergence rate of the numerical algorithm. Peak plasma density is lower and the temperature correspondingly higher than those predicted by the standard diffusion model. It is believed that the FFCD model is more accurate. With both the TP continuation and multigrid methods, the author has demonstrated the robustness of these two methods. A mutually beneficial hybridization between the TP method and multigrid methods is clearly an alternative for edge plasma simulation. While the fundamental transport model considered in this work has ignored important physics such as drifts and currents, he has nevertheless demonstrated the versatility and robustness of the numerical scheme to handle such new physics. The application of gaseous-radiative divertor model in this work is just a beginning and up to this point numerically, the future is exciting.
Yang, L.H.; Ding, Y.M. [China University of Mining & Technology, Xuzhou (China). College of Resources and Geoscience
2009-07-01T23:59:59.000Z
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.
A non-isothermal PEM fuel cell model including two water transport mechanisms in the
Münster, Westfälische Wilhelms-Universität
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
Ponder, Jay
Polarizable Atomic Multipole Water Model for Molecular Mechanics Simulation Pengyu Ren and Jay W empirical potential is proposed for water. The model uses a polarizable atomic multipole description of electrostatic interactions. Multipoles through the quadrupole are assigned to each atomic center based
Ice sheets and their dynamics Continuum thermo-mechanical model of a glacier
Cerveny, Vlastislav
Ice sheets and their dynamics Continuum thermo-mechanical model of a glacier Shallow Ice Approximation (SIA) SIA-I Iterative Improvement Technique Benchmarks Numerical modeling of ice-sheet dynamics and Cartography, Zdiby 1.6.2010 Ondej Soucek Ph.D. defense #12;Ice sheets and their dynamics Continuum thermo
Samarati, Pierangela
: it defines the (high-level) rules according to which access control must be regulated.1 Security modelAccess Control: Policies, Models, and Mechanisms Pierangela Samarati1 and Sabrina De Capitani di. In this chapter we investigate the basic concepts behind access control design and enforcement, and point out
A flow resistance model for assessing the impact of vegetation on flood routing mechanics
Katul, Gabriel
control in urban storm water runoff [Kirby et al., 2005], and linking tidal hydrodynamic forcing to flow and field studies. The proposed model asymptotically recovers the flow resistance formulation when the waterA flow resistance model for assessing the impact of vegetation on flood routing mechanics Gabriel G
Vajda, Sandor
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
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
Understanding Creep Mechanisms in Graphite with Experiments, Multiscale Simulations, and Modeling
Eapen, Jacob; Murty, Korukonda; Burchell, Timothy
2014-06-02T23:59:59.000Z
Disordering mechanisms in graphite have a long history with conflicting viewpoints. Using Raman and x-ray photon spectroscopy, 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.
Som, S; Longman, D. E.; Luo, Z; Plomer, M; Lu, T; Senecal, P.K.; Pomraning, E (Energy Systems); (Univ. of Connecticut); (CONVERGENT Science)
2012-01-01T23:59:59.000Z
Combustion in direct-injection diesel engines occurs in a lifted, turbulent diffusion flame mode. Numerous studies indicate that the combustion and emissions in such engines are strongly influenced by the lifted flame characteristics, which are in turn determined by fuel and air mixing in the upstream region of the lifted flame, and consequently by the liquid breakup and spray development processes. From a numerical standpoint, these spray combustion processes depend heavily on the choice of underlying spray, combustion, and turbulence models. The present numerical study investigates the influence of different chemical kinetic mechanisms for diesel and biodiesel fuels, as well as Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) turbulence models on predicting flame lift-off lengths (LOLs) and ignition delays. Specifically, two chemical kinetic mechanisms for n-heptane (NHPT) and three for biodiesel surrogates are investigated. In addition, the RNG k-{epsilon} (RANS) model is compared to the Smagorinsky based LES turbulence model. Using adaptive grid resolution, minimum grid sizes of 250 {micro}m and 125 {micro}m were obtained for the RANS and LES cases respectively. Validations of these models were performed against experimental data from Sandia National Laboratories in a constant volume combustion chamber. Ignition delay and flame lift-off validations were performed at different ambient temperature conditions. The LES model predicts lower ignition delays and qualitatively better flame structures compared to the RNG k-{epsilon} model. The use of realistic chemistry and a ternary surrogate mixture, which consists of methyl decanoate, methyl 9-decenoate, and NHPT, results in better predicted LOLs and ignition delays. For diesel fuel though, only marginal improvements are observed by using larger size mechanisms. However, these improved predictions come at a significant increase in computational cost.
Fully coupled thermal-mechanical-fluid flow model for nonliner geologic systems
Hart, R.D.
1981-01-01T23:59:59.000Z
A single model is presented which describes fully coupled thermal-mechanical-fluid flow behavior of highly nonlinear, dynamic or quasistatic, porous geologic systems. The mathematical formulation for the model utilizes the continuum theory of mixtures to describe the multiphase nature of the system, and incremental linear constitutive theory to describe the path dependency of nonlinear material behavior. The model, incorporated in an explicit finite difference numerical procedure, was implemented in two different computer codes. A special-purpose one-dimensional code, SNEAKY, was written for initial validation of the coupling mechanisms and testing of the coupled model logic. A general purpose commercially available code, STEALTH, developed for modeling dynamic nonlinear thermomechanical processes, was modified to include fluid flow behavior and the coupling constitutive model. The fully explicit approach in the coupled calculation facilitated the inclusion of the coupling mechanisms and complex constitutive behavior. Analytical solutions pertaining to consolidation theory for soils, thermoelasticity for solids, and hydrothermal convection theory provided verification of stress and fluid flow, stress and conductive heat transfer, and heat transfer and fluid flow couplings, respectively, in the coupled model. A limited validation of the adequacy of the coupling constitutive assumptions was also performed by comparison with the physical response from two laboratory tests. Finally, the full potential of the coupled model is illustrated for geotechnical applications in energy-resource related areas. Examples in the areas of nuclear waste isolation and cut-and-fill mining are cited.
Moisture Diffusion in Asphalt Binders and Fine Aggregate Mixtures
Vasconcelos, Kamilla L.
2011-08-08T23:59:59.000Z
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...
Review of enhanced vapor diffusion in porous media
Webb, S.W.; Ho, C.K.
1998-08-01T23:59:59.000Z
Vapor diffusion in porous media in the presence of its own liquid has often been treated similar to gas diffusion. The gas diffusion rate in porous media is much lower than in free space due to the presence of the porous medium and any liquid present. However, enhanced vapor diffusion has also been postulated such that the diffusion rate may approach free-space values. Existing data and models for enhanced vapor diffusion, including those in TOUGH2, are reviewed in this paper.
Failure Predictions for VHTR Core Components using a Probabilistic Contiuum Damage Mechanics Model
Fok, Alex
2013-10-30T23:59:59.000Z
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.
Paris-Sud XI, Université de
regulation. The main contribution of this paper is to design a new control scheme based on model-free controlA Dual Model-Free Control of Underactuated Mechanical Systems, Application to The Inertia Wheel method allowing recent model-free control technique to deal with underactuated mechanical systems
Shell model nuclear matrix elements for competing mechanisms contributing to double beta decay
Horoi, Mihai [Department of Physics, Central Michigan University, Mount Pleasant, Michigan, 48859 (United States)
2013-12-30T23:59:59.000Z
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.
Chalupecký, Vladimír; Kruschwitz, Jens; Muntean, Adrian
2012-01-01T23:59:59.000Z
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.
Modelling the thermo-mechanical volume change behaviour of compacted expansive clays
Paris-Sud XI, Université de
Modelling the thermo-mechanical volume change behaviour of compacted expansive clays Anh-Minh Tang expansive clays are often considered as a possible buffer material in high-level deep radioactive waste disposals. After the installation of waste canisters, the engineered clay barriers are subjected to thermo
Guidoni, Leonardo
Hybrid Car-Parrinello/Molecular Mechanics Modelling of Transition Metal Complexes: Structure). We have recently developed a QM/MM extension of a Car-Parrinello scheme [5]. These hybrid Car functional theory embedded in a classical force field description. The power of such a combined Car
A Recurrent Neural Multi-Model for Mechanical Systems Dynamics Compensation
Borissova, Daniela
Mexico D.F., Mexico ** Institute of Information Technologies, 1113 Sofia Abstract: The paper proposed nonlinear mechanical plants with backlash. The parameters and states of the local recurrent neural network of the plant model. For example, N a r e n d r a and P a r t h a s a r a t h y [5], applied FFNN for system
Angular approach combined to mechanical model for tool breakage detection by eddy current sensors
Paris-Sud XI, Université de
1 Angular approach combined to mechanical model for tool breakage detection by eddy current sensors solution is proposed for the estimate of cutting force using eddy current sensors implemented close eccentricity obtained during the machining from the eddy current sensors signals. Efficiency and reliability
Neural mechanisms of saccade target selection: gated accumulator model of the visualmotor cascade
Schall, Jeffrey D.
Neural mechanisms of saccade target selection: gated accumulator model of the visualmotor cascade, Vanderbilt University, PMB 407817, 2301 Vanderbilt Place, Nashville, TN 37240-7817, USA Keywords: accumulator neurons in the frontal eye field as evidence for stimulus salience that is accumulated in a network
Virtual Electrodes Mechanisms Predictions with a Current-Lifted Monodomain Model
Boyer, Edmond
Virtual Electrodes Mechanisms Predictions with a Current-Lifted Monodomain Model Yves Coudi`ere1 cost. The source term is derived from a lifting principle ap- plied to the resolution, and an excitation part, that remains unchanged. Equivalently, we make a lifting of the stimula- tion functions
MECHANICAL MODELING OF GLASS AND CARBON EPOXY COMPOSITES Barzin Mobasher 1
Mobasher, Barzin
MECHANICAL MODELING OF GLASS AND CARBON EPOXY COMPOSITES Barzin Mobasher 1 , Associate Member ASCE and flexural loading. INTRODUCTION In order to commercially utilize new composite materials in civil of composite laminates. The proposed methodology can be used as a new composite material or used
Thermo-mechanical modeling of plasterboard lined partition submitted to fire load.
Paris-Sud XI, Université de
of full scale tests under the ISO 834 thermal loading curve [2]. This last requirement can not be met whenThermo-mechanical modeling of plasterboard lined partition submitted to fire load. Authors: S partition submitted to fire load. A fundamental key to solve such a problem is the development
MODEL OF MECHANISM BEHAVIOR FOR VERIFICATION OF PLC Jos M. Machado
Paris-Sud XI, UniversitÃ© de
MODEL OF MECHANISM BEHAVIOR FOR VERIFICATION OF PLC PROGRAMS JosÃ© 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
Lin, Liwei
Introduction to Finite Element Modeling Engineering analysis of mechanical systems have been of the FEM (don't misuse the FEM - a numerical tool) Finite Element Analysis A typical finite element quantities (e.g., strains and stresses) at selected elements Basic Theory The way finite element analysis
REVIEW AND IMPROVEMENT OF SIMPLE MECHANICAL MODELS FOR PREDICTING THE FORCE-DISPLACEMENT RESPONSE OF
Thévenaz, Jacques
engineering demand parameters and mechanical models that link local and global deformation quantities. Although unreinforced masonry (URM) is one of the most used construction materials for residential quantities, e.g. curvature profiles and shear strain profiles, we show that this is due to the formation
Comparison of problem model change mechanisms issued from CSP and TRIZ
Paris-Sud XI, Université de
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
Fluid Mechanics and Tt.ansDOrtPhenomena A Mathematical Model for a Dissolving Polymer
Edwards, David A.
Fluid Mechanics and Tt.ansDOrtPhenomena A Mathematical Model for a Dissolving Polymer David A boundary-value problem. The boundary separates the polymer into two distinct states: glassy and rub- bery- ablefront speed and a self-regulatingmass uptake. Introduction In the last few years, new uses for polymers
Nicola Zamponi
2014-02-25T23:59:59.000Z
A system of drift-diffusion equations with electric field under Dirichlet boundary conditions is analyzed. The system of strongly coupled parabolic equations for particle density and spin density vector describes the spin-polarized semi-classical electron transport in ferromagnetic semiconductors. The presence of a nonconstant and nonsmooth magnetization vector, solution of the Landau-Lifshitz equation, causes the diffusion matrix to be dependent from space and time and to have in general poor regularity properties, thus making the analysis challenging. To partially overcome the analytical difficulties the velocity saturation hypothesis is made, which results in a bounded drift velocity. The global-in-time existence and uniqueness of weak solutions is shown by means of a semi-discretization in time, which yields an elliptic semilinear problem, and a quadratic entropy inequality, which allow for the limit of vanishing time step size. The convergence of the weak solutions to the steady state, under some restrictions on the parameters and data, is shown. Finally the higher regularity of solutions for a smooth magnetization in two space dimensions is shown through a diagonalization argument, which allows to get rid of the cross diffusion terms in the fluid equations, and the iterative application of Gagliardo-Nirenberg inequalities and a generalized version of Aubin lemma.
Thermal Particle Injection in Nonlinear Diffusive Shock Acceleration
Donald C. Ellison; Pasquale Blasi; Stefano Gabici
2005-07-05T23:59:59.000Z
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.
* corresponding Auithor. Email: cxw31@psu.edu Modeling Discharge and Charge Characteristics
Wang, Chao-Yang
of Mechanical Engineering & Pennsylvania Transportation Institute The Pennsylvania State University University Park, PA 16802, USA S.M. Li Department of Mechanical Engineering University of Hawaii at Manoa Honolulu model which includes both the proton diffusion in the nickel active material and the hydrogen diffusion
Mavko, B.; Cizelj, L. (Jozef Stefan Inst., Reactor Engineering Div., P.O. Box 100, 61111 Ljubljana, Slovenia (YU))
1992-05-01T23:59:59.000Z
In this paper a model for estimating the failure probability of axially cracked steam generator tubes is proposed. The model compares observed crack length distribution with critical crack length distribution by means of probabilistic fracture mechanics. The observed crack length is influenced by measured data, measurement reliability, sizing accuracy, and predicted crack growth rate. The critical crack length is defined by a deterministic mechanical model. All cracks are conservatively assumed to extend through the tube wall. The effect of the plugging limit is studied along with the number of cracked tubes to perform risk-based lifetime optimization of steam generators. A numerical example presented considers hypothetical accidental operating conditions during a feedwater line break.
Coleman-Weinberg mechanism in a three-dimensional supersymmetric Chern-Simons-matter model
Ferrari, A. F. [Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adelia, 166, 09210-170, Santo Andre, SP (Brazil); Gallegos, E. A.; Gomes, M.; Silva, A. J. da [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, 05315-970, Sao Paulo, SP (Brazil); Lehum, A. C. [Escola de Ciencias e Tecnologia, Universidade Federal do Rio Grande do Norte, Caixa Postal 1524, 59072-970, Natal, RN (Brazil); Nascimento, J. R.; Petrov, A. Yu. [Departamento de Fisica, Universidade Federal da Paraiba, Caixa Postal 5008, 58051-970, Joao Pessoa, Paraiba (Brazil)
2010-07-15T23:59:59.000Z
Using the superfield formalism, we study the dynamical breaking of gauge symmetry and superconformal invariance in the N=1 three-dimensional supersymmetric Chern-Simons model, coupled to a complex scalar superfield with a quartic self-coupling. This is an analogue of the conformally invariant Coleman-Weinberg model in four spacetime dimensions. We show that a mass for the gauge and matter superfields are dynamically generated after two-loop corrections to the effective superpotential. We also discuss the N=2 extension of our work, showing that the Coleman-Weinberg mechanism in such model is not feasible, because it is incompatible with perturbation theory.
Advani, S.H.
1983-01-01T23:59:59.000Z
Model formulations and governing equations for the investigation of the thermo-mechanical, consolidation and failure responses associated with UCG are given. Typical results from sample finite element model representations are presented. The examples quoted include the simulation of the transient temperature profiles, thermo-elastic stresses incorporating temperature dependent material properties and fracture responses. The application of the developed models to the evaluation of field experiments is demonstrated by the simulation of the Hoe Creek II experiments. The numerical experiments for different overburden failure thresholds demonstrated the pronounced sensitivity of the predicted cavity shapes with respect to the assumed properties.
Development of a reduced n-heptane oxidation mechanism for HCCI combustion modeling
Maroteaux, F.; Noel, L. [University Pierre et Marie Curie, INRIA Rocquencourt, B.P. 105, 78153 Le Chesnay Cedex (France)
2006-07-15T23:59:59.000Z
Homogeneous charge compression ignition (HCCI) is one of the alternatives to reduce significantly engine emissions for future regulations. This new alternative combustion process is mainly controlled by chemical kinetics in comparison with the conventional combustion in internal combustion engines. The optimization of the engine over the complete engine operation range requires an accurate analysis of the combustion process under all operating conditions; detailed modeling of the HCCI process is an opportunity to realize the engine optimization at lower cost. The combination of CFD computations with detailed chemistry leads to excessive computation times, and is not achievable with current computer capabilities. In this paper, a reduced chemical model for n-heptane is described, in view of its implementation into a CFD simulation code. In the first part, the reduction process to get to the 61-step mechanism is detailed and then the 26-step mechanism is described; this further reduction is carried out under various conditions that include a range of interest in engine applications. The third part is dedicated to extensive validation work in reference to the original detailed mechanism and two reduced mechanisms published in the literature, focusing on the prediction of ignition delay times under constant as well as variable volume conditions. A good and accurate reproduction of both ignition delay times and heat release can be reached with the 26-step model. (author)
Turbulence Modelling and Stirring Mechanisms in the Cosmological Large-scale Structure
Iapichino, L; Niemeyer, J C; Merklein, J
2011-01-01T23:59:59.000Z
FEARLESS (Fluid mEchanics with Adaptively Refined Large Eddy SimulationS) is a numerical scheme for modelling subgrid-scale turbulence in cosmological adaptive mesh refinement simulations. In this contribution, the main features of this tool will be outlined. We discuss the application of this method to cosmological simulations of the large-scale structure. The simulations show that the production of turbulence has a different redshift dependence in the intra-cluster medium and the warm-hot intergalactic medium, caused by the distinct stirring mechanisms (mergers and shock interactions) acting in them. Some properties of the non-thermal pressure support in the two baryon phases are also described.
Is Arnold diffusion relevant to global diffusion?
Seiichiro Honjo; Kunihiko Kaneko
2003-07-27T23:59:59.000Z
Global diffusion of Hamiltonian dynamical systems is investigated by using a coupled standard maps. Arnold web is visualized in the frequency space, using local rotation numbers, while Arnold diffusion and resonance overlaps are distinguished by the residence time distributions at resonance layers. Global diffusion in the phase space is shown to be accelerated by diffusion across overlapped resonances generated by the coupling term, rather than Arnold diffusion along the lower-order resonances. The former plays roles of hubs for transport in the phase space, and accelerate the diffusion.
Diffusion processes in general relativistic radiating spheres
Barreto, W.; Herrera, L.; Santos, N.O. (Oriente Universidad, Cumana (Venezuela); Universidad Central de Venezuela, Caracas; Observatorio Nacional do Brasil, Rio de Janeiro (Brazil))
1989-09-01T23:59:59.000Z
The influence of diffusion processes on the dynamics of general relativistic radiating spheres is systematically studied by means of two examples. Differences between the streaming-out limit and the diffusion limit are exhibited, for both models, through the evolution curves of dynamical variables. In particular it is shown the Bondi mass decreases, for both models, in the diffusion limit as compared with its value at the streaming-out regime. 15 refs.
Matti Maricq, M. [Research and Advanced Engineering, Ford Motor Company, Dearborn, MI (United States)
2011-01-15T23:59:59.000Z
Data are presented to compare soot formation in both surrogate and practical fatty acid methyl ester biodiesel and petroleum fuel diffusion flames. The approach here uses differential mobility analysis to follow the size distributions and electrical charge of soot particles as they evolve in the flame, and laser ablation particle mass spectrometry to elucidate their composition. Qualitatively, these soot properties exhibit a remarkably similar development along the flames. The size distributions begin as a single mode of precursor nanoparticles, evolve through a bimodal phase marking the onset of aggregate formation, and end in a self preserving mode of fractal-like particles. Both biodiesel and hydrocarbon fuels yield a common soot composition dominated by C{sub x}H{sub y}{sup +} ions, stabilomer PAHs, and fullerenes in the positive ion mass spectrum, and C{sub x}{sup -} and C{sub 2x}H{sup -} in the negative ion spectrum. These ion intensities initially grow with height in the diffusion flames, but then decline during later stages, consistent with soot carbonization. There are important quantitative differences between fuels. The surrogate biodiesel fuel methyl butanoate substantially reduces soot levels, but soot formation and evolution in this flame are delayed relative to both soy and petroleum fuels. In contrast, soots from soy and hexadecane flames exhibit nearly quantitative agreement in their size distribution and composition profiles with height, suggesting similar soot precursor chemistry. (author)
Enabling HCCI modeling: The RIOT/CMCS Web Service for Automatic Reaction Mechanism Reduction
Oluwole, O; Pitz, W J; Schuchardt, K; Rahn, L A; Green, Jr., W H; Leahy, D; Pancerella, C; Sj?berg, M; Dec, J
2005-12-12T23:59:59.000Z
New approaches are being developed to facilitate multidisciplinary collaborative research of Homogeneous Charge Compression Ignition (HCCI) combustion processes. In this paper, collaborative sharing of the Range Identification and Optimization Toolkit (RIOT) and related data and models is discussed. RIOT is a developmental approach to reduce the computational complexity of detailed chemical kinetic mechanisms, enabling their use in modeling kinetically-controlled combustion applications such as HCCI. These approaches are being developed and piloted as a part of the Collaboratory for Multiscale Chemical Sciences (CMCS) project. The capabilities of the RIOT code are shared through a portlet in the CMCS portal that allows easy specification and processing of RIOT inputs, remote execution of RIOT, tracking of data pedigree and translation of RIOT outputs (such as the reduced model) to a table view and to the commonly-used CHEMKIN mechanism format. The reduced model is thus immediately ready to be used for more efficient simulation of the chemically reacting system of interest. This effort is motivated by the need to improve computational efficiency in modeling HCCI systems. Preliminary use of the web service to obtain reduced models for this application has yielded computational speedup factors of up to 20 as presented in this paper.
Parallel flow diffusion battery
Yeh, H.C.; Cheng, Y.S.
1984-01-01T23:59:59.000Z
A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.
Advances in constitutive modelling of jointed rock hydro mechanical interactions at laboratory scale
Paris-Sud XI, UniversitÃ© de
) INPL-LAEGO-ENSMN, Parc de Saurupt, Ecole des mines, 54000 Nancy, France) (2) INERIS, Parc de Saurupt. The hydro mechanical modelling performed using 3DEC code can be improved from the previous analysis through dÃ©bit hydraulique dans la fracture. La modÃ©lisation hydromÃ©canique rÃ©alisÃ©e Ã l'aide du code 3DEC peut
Effects of turbulent diffusion on the chemistry of diffuse clouds
P. Lesaffre; M. Gerin; P. Hennebelle
2007-04-24T23:59:59.000Z
Aims. We probe the effect of turbulent diffusion on the chemistry at the interface between a cold neutral medium (CNM) cloudlet and the warm neutral medium (WNM). Methods. We perform moving grid, multifluid, 1D, hydrodynamical simulations with chemistry including thermal and chemical diffusion. The diffusion coefficients are enhanced to account for turbulent diffusion. We post-process the steady-states of our simulations with a crude model of radiative transfer to compute line profiles. Results. Turbulent diffusion spreads out the transition region between the CNM and the WNM. We find that the CNM slightly expands and heats up: its CH and H$_2$ content decreases due to the lower density. The change of physical conditions and diffusive transport increase the H$^+$ content in the CNM which results in increased OH and H$_2$O. Diffusion transports some CO out of the CNM. It also brings H$_2$ into contact with the warm gas with enhanced production of CH$^+$, H$_3^+$, OH and H$_2$O at the interface. O lines are sensitive to the spread of the thermal profile in the intermediate region between the CNM and the WNM. Enhanced molecular content at the interface of the cloud broadens the molecular line profiles and helps exciting transitions of intermediate energy. The relative molecular yield are found higher for bigger clouds. Conclusions. Turbulent diffusion can be the source of additional molecular production and should be included in chemical models of the interstellar medium (ISM). It also is a good candidate for the interpretation of observational problems such as warm H$_2$, CH$^+$ formation and presence of H$_3^+$.
Discrete modelling of capillary mechanisms in multi-phase granular media
L. Scholtès; B. Chareyre F. Nicot; F. Darve
2012-03-06T23:59:59.000Z
A numerical study of multi-phase granular materials based upon micro-mechanical modelling is proposed. Discrete element simulations are used to investigate capillary induced effects on the friction properties of a granular assembly in the pendular regime. Capillary forces are described at the local scale through the Young-Laplace equation and are superimposed to the standard dry particle interaction usually well simulated through an elastic-plastic relationship. Both effects of the pressure difference between liquid and gas phases and of the surface tension at the interface are integrated into the interaction model. Hydraulic hysteresis is accounted for based on the possible mechanism of formation and breakage of capillary menisci at contacts. In order to upscale the interparticular model, triaxial loading paths are simulated on a granular assembly and the results interpreted through the Mohr-Coulomb criterion. The micro-mechanical approach is validated with a capillary cohesion induced at the macroscopic scale. It is shown that interparticular menisci contribute to the soil resistance by increasing normal forces at contacts. In addition, more than the capillary pressure level or the degree of saturation, our findings highlight the importance of the density number of liquid bonds on the overall behaviour of the material.
Fang, Yilin; Nguyen, Ba Nghiep; Carroll, Kenneth C.; Xu, Zhijie; Yabusaki, Steven B.; Scheibe, Timothy D.; Bonneville, Alain
2013-09-12T23:59:59.000Z
Geomechanical alteration of porous media is generally ignored for most shallow subsurface applications, whereas CO2 injection, migration, and trapping in deep saline aquifers will be controlled by coupled multifluid flow, energy transfer, and geomechanical processes. The accurate assessment of the risks associated with potential leakage of injected CO2 and the design of effective injection systems requires that we represent these coupled processes within numerical simulators. The objectives of this study were to develop a coupled thermal-hydro-mechanical model into a single software, and to examine the coupling of thermal, hydrological, and geomechanical processes for simulation of CO2 injection into the subsurface for carbon sequestration. A numerical model is developed to couple nonisothermal multiphase hydrological and geomechanical processes for prediction of multiple interconnected processes for carbon sequestration in deep saline aquifers. The geomechanics model was based on Rigid Body-Spring Model (RBSM), one of the discrete methods to model discontinuous rock system. Poisson’s effect that was often ignored by RBSM was considered in the model. The simulation of large-scale and long-term coupled processes in carbon capture and storage projects requires large memory and computational performance. Global Array Toolkit was used to build the model to permit the high performance simulations of the coupled processes. The model was used to simulate a case study with several scenarios to demonstrate the impacts of considering coupled processes and Poisson’s effect for the prediction of CO2 sequestration.
Control of transversal instabilities in reaction-diffusion systems
Molnos, Sonja; Totz, Jan Frederik; Engel, Harald
2015-01-01T23:59:59.000Z
In two-dimensional reaction-diffusion systems, local curvature perturbations in the shape of traveling waves are typically damped out and disappear in the course of time. If, however, the inhibitor diffuses much faster than the activator, transversal instabilities can arise, leading from flat to folded, spatio-temporally modulated wave shapes and to spreading spiral turbulence. For experimentally relevant parameter values, the photosensitive Belousov-Zhabotinsky reaction (PBZR) does not exhibit transversal wave instabilities. Here, we propose a mechanism to artificially induce these instabilities via a wave shape dependent spatio-temporal feedback loop, and study the emerging wave patterns. In numerical simulations with the modified Oregonator model for the PBZR using experimentally realistic parameter values we demonstrate the feasibility of this control scheme. Conversely, in a piecewise-linear version of the FitzHugh-Nagumo model transversal instabilities and spiral turbulence in the uncontrolled system ar...
Progress Report for Diffusion Welding of the NGNP Process Application Heat Exchangers
R.E. Mizia; D.E. Clark; M.V. Glazoff; T.E. Lister; T.L. Trowbridge
2011-12-01T23:59:59.000Z
The U.S. Department of Energy selected the high temperature gas-cooled reactor as the basis for the Next Generation Nuclear Plant (NGNP). The NGNP will demonstrate the use of nuclear power for electricity, hydrogen production, and process heat applications. The NGNP Project is currently investigating the use of metallic, diffusion welded, compact heat exchangers to transfer heat from the primary (reactor side) heat transport system to the secondary heat transport system. An intermediate heat exchanger will transfer this heat to downstream applications such as hydrogen production, process heat, and electricity generation. The channeled plates that make up the heat transfer surfaces of the intermediate heat exchanger will have to be assembled into an array by diffusion welding. This report describes the preliminary results of a scoping study that evaluated the diffusion welding process parameters and the resultant mechanical properties of diffusion welded joints using Alloy 800H. The long-term goal of the program is to progress towards demonstration of small heat exchanger unit cells fabricated with diffusion welds. Demonstration through mechanical testing of the unit cells will support American Society of Mechanical Engineers rules and standards development, reduce technical risk, and provide proof of concept for heat exchanger fabrication methods needed to deploy heat exchangers in several potential NGNP configurations.1 Researchers also evaluated the usefulness of modern thermodynamic and diffusion computational tools (Thermo-Calc and Dictra) in optimizing the parameters for diffusion welding of Alloy 800H. The modeling efforts suggested a temperature of 1150 C for 1 hour with an applied pressure of 5 MPa using 15 {micro}m nickel foil as joint filler to reduce chromium oxidation on the welded surfaces. Good agreement between modeled and experimentally determined concentration gradients was achieved
Modeling, simulation, and testing of the mechanical dynamics of and RF MEMS switch.
Sumali, Hartono; Epp, David S.; Massad, Jordan Elias; Dyck, Christopher William; Starr, Michael James
2005-07-01T23:59:59.000Z
Mechanical dynamics can be a determining factor for the switching speed of radio-frequency microelectromechanical systems (RF MEMS) switches. This paper presents the simulation of the mechanical motion of a microswitch under actuation. The switch has a plate suspended by springs. When an electrostatic actuation is applied, the plate moves toward the substrate and closes the switch. Simulations are calculated via a high-fidelity finite element model that couples solid dynamics with electrostatic actuation. It incorporates non-linear coupled dynamics and accommodates fabrication variations. Experimental modal analysis gives results in the frequency domain that verifies the natural frequencies and mode shapes predicted by the model. An effective 1D model is created and used to calculate an actuation voltage waveform that minimizes switch velocity at closure. In the experiment, the switch is actuated with this actuation voltage, and the displacements of the switch at various points are measured using a laser Doppler velocimeter through a microscope. The experiments are repeated on several switches from different batches. The experimental results verify the model.
Mechanical Behaviour of the Short Models of LHC Main Dipole Magnets
Andreyev, N I; Casarejos, E; Kurtyka, T; Rathjen, C; Perini, D; Siegel, N; Tommasini, D; Vanenkov, I
1998-01-01T23:59:59.000Z
A series of single and twin aperture 1 metre magnet models has been built and tested in the framework of the R&D program of main superconducting dipole magnets for the Large Hadron Collider project. The se models, designed for a nominal field of 8.3 T at 1.8 K, have been constructed to test the performance of SC coils and to optimise various design options for the full length 15 metre long dipoles. T he models have been extensively equipped with a specially developed mechanical instrumentation, enabling both the control of main assembly parameters - like coil azimuthal and axial pre-load, stress i n the outer shrinking cylinder - and also the monitoring of magnet behaviour during cooling and energising, under the action of electromagnetic forces. The instrumentation used, mainly based on strain gauge transducers, is described and the results of mechanical measurements obtained during power tests of the models are discussed and compared with the design predictions based on Finite Element calc ulations.
Mappings From Models Presenting Topological Mass Mechanisms to Purely Topological Models
Amaral, R.L.P.G.; Costa, J.V. [Instituto de Fisica, Universidade Federal Fluminense, Niteroi (Brazil); Ventura, O.S. [Centro Federal de Educacao Tecnologica do Espirito Santo, Vitoria (Brazil); Centro Universitario de Vila Velha, Vila Velha - ES (Brazil); Uniest, Cariacica-ES (Brazil); Bouffon, L.O. [Centro Federal de Educacao Tecnologica do Espirito Santo, Vitoria (Brazil); Escola Superior de Ciencias da Santa Casa de Misericordia de Vitoria, Vitoria-ES (Brazil); Lemes, V.E.R. [Instituto de Fisica, Universidade do Estado do Rio de Janeiro, Rio de Janeiro - RJ (Brazil)
2004-12-02T23:59:59.000Z
We discuss a class of mappings between the fields of the Cremmer-Sherk and pure BF model in 4D. These mappings are established both with an iterative procedure as well as with an exact mapping procedure. Related equivalences in 5D and 3D are discussed.
A minimal model for the inelastic mechanics of biopolymer networks and cells
Lars Wolff; Klaus Kroy
2012-05-27T23:59:59.000Z
Live cells have ambiguous mechanical properties. They were often described as either elastic solids or viscoelastic fluids and have recently been classified as soft glassy materials characterized by weak power-law rheology. Nonlinear rheological measurements have moreover revealed a pronounced inelastic response indicative of a competition between stiffening and softening. It is an intriguing question whether these observations can be explained from the material properties of much simpler in-vitro reconstituted networks of biopolymers that serve as reduced model systems for the cytoskeleton. Here, we explore the mechanism behind the inelastic response of cells and biopolymer networks, theoretically. Our analysis is based on the model of the inelastic glassy wormlike chain that accounts for the nonlinear polymer dynamics and transient crosslinking in biopolymer networks. It explains how inelastic and kinematic-hardening type behavior naturally emerges from the antagonistic mechanisms of viscoelastic stress-stiffening due to the polymers and inelastic fluidization due to bond breaking. It also suggests a simple set of schematic constitutive equations which faithfully reproduce the rich inelastic phenomenology of biopolymer networks and cells.
Eric Wachsman; Keith L. Duncan
2006-09-30T23:59:59.000Z
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.
Pruess, Karsten; Zhang, Keni
2008-11-17T23:59:59.000Z
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.
Benioff, P.A.
1981-01-01T23:59:59.000Z
Work done before on the construction of quantum mechanical Hamiltonian models of Turing machines and general descrete processes is extended here to include processes which erase their own histories. The models consist of three phases, the forward process phase in which a map T is iterated and a history of iterations is generated, a copy phase which is activated if and only if T reaches a fix point, and an erase phase which erases the iteration history, undoes the iterations of T and recovers the initial state except for the copy system. A ballast system is used to stop the evolution at the desired state. The general model so constructed is applied to Turing machines. The main changes are that the system undergoing the evolution corresponding to T iterations becomes three systems corresponding to the internal machine, the computation tape, and computation head. Also the copy phase becomes more complex since it is desired that this correspond also to a copying Turing machine.
Supporting Kibble-Zurek Mechanism in Quantum Ising Model through a Trapped Ion
Jin-Ming Cui; Yun-Feng Huang; Zhao Wang; Dong-Yang Cao; Jian Wang; Wei-Min Lv; Yong Lu; Le Luo; Adolfo del Campo; Yong-Jian Han; Chuan-Feng Li; Guang-Can Guo
2015-05-21T23:59:59.000Z
Progress in quantum simulation has fostered the research on far-from-equilibrium dynamics. The Kibble-Zurek mechanism is the paradigmatic framework to account for the non adiabatic critical dynamics of a system driven across a phase transition in a finite time. Its study in the quantum regime is hindered by the requisite of ground state cooling. We report the experimental quantum simulation of critical dynamics in the transverse-field Ising model by a set of non-equilibrium processes in the pseudo-momentum space, that can be probed with high accuracy using a single trapped ion. Our results support the validity of the Kibble-Zurek mechanism in the quantum regime and advance the quantum simulation of critical systems far-away from equilibrium.
Statistical mechanics model for the transit free energy of monatomic liquids
Duane C. Wallace; Eric D. Chisolm; N. Bock; G. De Lorenzi-Venneri
2010-04-19T23:59:59.000Z
In applying Vibration-Transit (V-T) theory of liquid dynamics to the thermodynamic properties of monatomic liquids, the point has been reached where an improved model is needed for the small (approx. 10%) transit contribution. Toward this goal, an analysis of the available high-temperature experimental entropy data for elemental liquids was recently completed [D. C. Wallace, E. D. Chisolm, and N. Bock, Phys. Rev. B 79, 051201 (2009)]. This analysis yields a common curve of transit entropy vs. T/\\theta_{tr}, where T is temperature and \\theta_{tr} is a scaling temperature for each element. In the present paper, a statistical mechanics model is constructed for the transit partition function, and is calibrated to the experimental transit entropy curve. The model has two scalar parameters, and captures the temperature scaling of experiment. The calibrated model fits the experimental liquid entropy to high accuracy at all temperatures. With no additional parameters, the model also agrees with both experiment and molecular dynamics for the internal energy vs. T for Na. With the calibrated transit model, V-T theory provides equations subject to ab initio evaluation for thermodynamic properties of monatomic liquids. This will allow the range of applicability of the theory, and its overall accuracy, to be determined. More generally, the hypothesis of V-T theory, which divides the many-atom potential energy valleys into random and symmetric classes, can also be tested for its application beyond monatomic systems.
M. Lin; D. Kicker; B. Damjanac; M. Board; M. Karakouzian
2006-07-05T23:59:59.000Z
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.
Convergence Speed of GARCH Option Price to Diffusion Option Price
Wang, Yazhen
Convergence Speed of GARCH Option Price to Diffusion Option Price Jin-Chuan Duan National constructed GARCH model will weakly converge to a bi- variate diffusion. Naturally the European option price under the GARCH model will also converge to its bivariate diffusion counterpart. This paper investigates
Ressel, G.; Primig, S. [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben (Austria); Christian Doppler Laboratory for Early Stages of Precipitation, Montanuniversität Leoben, A-8700 Leoben (Austria); Parz, P.; Puff, W. [Institute of Materials Physics, Graz University of Technology, A-8010 Graz (Austria); Leitner, H.; Clemens, H. [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben (Austria)
2014-03-28T23:59:59.000Z
In order to improve the mechanical properties at elevated temperatures, several types of steels are mechanically alloyed with yttria. The processes that are active during milling differ dependent on the individual powder constituents. Nevertheless, some theories exist which try to describe the mechanism of producing a metastable phase during milling. However, even in the system iron–yttria, the mechanisms taking place during milling are still not well understood. By using the example of a simple iron–yttria model alloy, this paper attempts to elucidate the structure of mechanically milled powder particles and, consequently, to clarify the functionality of mechanical alloying in the last stage of milling. Positron annihilation experiments on milled materials revealed “open” volumes which are enriched in yttria. Electron backscatter diffraction and atom probe tomography as complimentary techniques allowed an identification of these “open” volumes as mainly vacancies, where enrichments of Y and O occur. From these results, it can be concluded that especially vacancies are responsible for producing a metastable phase, whereby yttria is dissolved in pure iron.
Thermal and mechanical denaturation properties of a DNA model with three sites per nucleotide
Florescu, Ana-Maria; 10.1063/1.3626870
2011-01-01T23:59:59.000Z
In this paper, we show that the coarse grain model for DNA, which has been proposed recently by Knotts, Rathore, Schwartz and de Pablo (J. Chem. Phys. 126, 084901 (2007)), can be adapted to describe the thermal and mechanical denaturation of long DNA sequences by adjusting slightly the base pairing contribution. The adjusted model leads to (i) critical temperatures for long homogeneous sequences that are in good agreement with both experimental ones and those obtained from statistical models, (ii) a realistic step-like denaturation behaviour for long inhomogeneous sequences, and (iii) critical forces at ambient temperature of the order of 10 pN, close to measured values. The adjusted model furthermore supports the conclusion that the thermal denaturation of long homogeneous sequences corresponds to a first-order phase transition and yields a critical exponent for the critical force equal to sigma=0.70. This model is both geometrically and energetically realistic, in the sense that the helical structure and th...
Comparison of QM-Only and QM/MM Models for the Mechanism of Tungsten-Dependent Acetylene Hydratase
Liao, Rongzhen
Comparison of QM-Only and QM/MM Models for the Mechanism of Tungsten-Dependent Acetylene Hydratase study on the formation of vinyl alcohol in the catalytic cycle of tungsten-dependent acetylene hydratase
Computational tool for comparison of kinematic mechanisms and commonly used kinematic models
Hollerbach, K.; Hollister, A.M.; Van Vorhis, R.L.
1997-03-01T23:59:59.000Z
Accurate, reliable, and reproducible methods to measure the movements of human joints have been elusive. Currently, three-dimensional recording methods are used to track the motion of one segment relative to another as the joint moves. Six parameters describe the moving segment`s location and orientation relative to the reference segment: three translations (x, y, and z) and three rotations (yaw, pitch and roll) in the reference frame. The raw data can be difficult to interpret. For this reason, several methods have been developed to measure the motion of human joints and to describe the resulting data. For example, instant helical axes or screw deviation axes (Kinzell et al., 1972), the Joint Coordinate System of Grood and Suntay (1983), and the Euler angle method have been used to describe the movements of bones relative to each other. None of these methods takes into account the physical kinematic mechanism producing the joint motion. More recently, Lupichuk (1995) has developed an algorithm to find, for an arbitrary revolute, the axis` position and orientation in three- dimensional space. Each of these methods has advantages and disadvantages in analyzing joint kinematics. The authors have developed software to provide a means of comparing these methods for arbitrary, single degree of freedom, kinematic mechanisms. Our objective is to demonstrate the software and to show how it can be used to compare the results from the different kinematic models as they are applied to specific kinematic mechanisms.
On a 2D hydro-mechanical lattice approach for modelling hydraulic fracture
Grassl, Peter; Gallipoli, Domenico; Wheeler, Simon J
2014-01-01T23:59:59.000Z
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.
A mathematical model for investigating the mechanical behaviour of salt cavities
Lambert, G.M.S.; Creed, M.R.; Dean, F.; Leigh, M.J.
1988-01-01T23:59:59.000Z
Cavities in salt are widely used for the storage of natural gas and other substances. When used for the storage of gas, the pressure in the cavity may be reduced to well below the geostatic pressure in the surrounding salt. In these conditions the salt will creep and the shape and size of the cavity will change. The ability to predict these changes, and the effect they may have on the subsurface system is necessary for the efficient operation of the storage. British Gas has developed a mathematical model for investigating this mechanical behaviour of salt cavities. It is based on an extensive programme of experimental work to determine the rheological behaviour of the salt. This paper describes this model and shows how it has been used to solve a number of typical problems encountered in the planning and operation of salt cavities.
Equilibrium statistical mechanics and energy partition for the shallow water model
Renaud, Antoine; Bouchet, Freddy
2015-01-01T23:59:59.000Z
The aim of this paper is to use large deviation theory in order to compute the entropy of macrostates for the microcanonical measure of the shallow water system. The main prediction of this full statistical mechanics computation is the energy partition between a large scale vortical flow and small scale fluctuations related to inertia-gravity waves. We introduce for that purpose a discretized model of the continuous shallow water system, and compute the corresponding statistical equilibria. We argue that microcanonical equilibrium states of the discretized model in the continuous limit are equilibrium states of the actual shallow water system. We show that the presence of small scale fluctuations selects a subclass of equilibria among the states that were previously computed by phenomenological approaches that were neglecting such fluctuations. In the limit of weak height fluctuations, the equilibrium state can be interpreted as two subsystems in thermal contact: one subsystem corresponds to the large scale v...
Magnetic and Mechanical Analysis of the HQ Model Quadrupole Designs for LARP
Felice, Helene; Caspi, Shlomo; Ferracin, Paolo; Kashikhin, Vadim; Novitski, Igor; Sabbi, GianLuca; Zlobin, Alexander
2008-06-01T23:59:59.000Z
Insertion quadrupoles with large bore and high gradient are required to upgrade the luminosity of the Large Hadron Collider (LHC). The US LHC Accelerator Research Program is developing Nb{sub 3}Sn technology for the upgrade. This effort includes a series of 1 m long Technology Quadrupoles (TQ), to demonstrate the reproducibility at moderate field, and High-gradient Quadrupoles (HQ) to explore the magnet performance limits in terms of peak fields, forces and stresses. The HQ models are expected to achieve peak fields of 15 T or higher. A coil aperture of 90 mm, corresponding to gradients above 300 T/m, was chosen as the baseline. Peak stresses above 150 MPa are expected. Progress on the magnetic and mechanical design of the HQ models will be reported.
Thermal-mechanical modeling of deep borehole disposal of high-level radioactive waste.
Arnold, Bill Walter; Hadgu, Teklu
2010-12-01T23:59:59.000Z
Disposal of high-level radioactive waste, including spent nuclear fuel, in deep (3 to 5 km) boreholes is a potential option for safely isolating these wastes from the surface and near-surface environment. Existing drilling technology permits reliable and cost-effective construction of such deep boreholes. Conditions favorable for deep borehole disposal in crystalline basement rocks, including low permeability, high salinity, and geochemically reducing conditions, exist at depth in many locations, particularly in geologically stable continental regions. Isolation of waste depends, in part, on the effectiveness of borehole seals and potential alteration of permeability in the disturbed host rock surrounding the borehole. Coupled thermal-mechanical-hydrologic processes induced by heat from the radioactive waste may impact the disturbed zone near the borehole and borehole wall stability. Numerical simulations of the coupled thermal-mechanical response in the host rock surrounding the borehole were conducted with three software codes or combinations of software codes. Software codes used in the simulations were FEHM, JAS3D, Aria, and Adagio. Simulations were conducted for disposal of spent nuclear fuel assemblies and for the higher heat output of vitrified waste from the reprocessing of fuel. Simulations were also conducted for both isotropic and anisotropic ambient horizontal stress in the host rock. Physical, thermal, and mechanical properties representative of granite host rock at a depth of 4 km were used in the models. Simulation results indicate peak temperature increases at the borehole wall of about 30 C and 180 C for disposal of fuel assemblies and vitrified waste, respectively. Peak temperatures near the borehole occur within about 10 years and decline rapidly within a few hundred years and with distance. The host rock near the borehole is placed under additional compression. Peak mechanical stress is increased by about 15 MPa (above the assumed ambient isotropic stress of 100 MPa) at the borehole wall for the disposal of fuel assemblies and by about 90 MPa for vitrified waste. Simulated peak volumetric strain at the borehole wall is about 420 and 2600 microstrain for the disposal of fuel assemblies and vitrified waste, respectively. Stress and volumetric strain decline rapidly with distance from the borehole and with time. Simulated peak stress at and parallel to the borehole wall for the disposal of vitrified waste with anisotropic ambient horizontal stress is about 440 MPa, which likely exceeds the compressive strength of granite if unconfined by fluid pressure within the borehole. The relatively small simulated displacements and volumetric strain near the borehole suggest that software codes using a nondeforming grid provide an adequate approximation of mechanical deformation in the coupled thermal-mechanical model. Additional modeling is planned to incorporate the effects of hydrologic processes coupled to thermal transport and mechanical deformation in the host rock near the heated borehole.
Microfabricated diffusion source
Oborny, Michael C. (Albuquerque, NM); Frye-Mason, Gregory C. (Cedar Crest, NM); Manginell, Ronald P. (Albuquerque, NM)
2008-07-15T23:59:59.000Z
A microfabricated diffusion source to provide for a controlled diffusion rate of a vapor comprises a porous reservoir formed in a substrate that can be filled with a liquid, a headspace cavity for evaporation of the vapor therein, a diffusion channel to provide a controlled diffusion of the vapor, and an outlet to release the vapor into a gas stream. The microfabricated diffusion source can provide a calibration standard for a microanalytical system. The microanalytical system with an integral diffusion source can be fabricated with microelectromechanical systems technologies.
Surveying Diffusion in Complex Geometries. An Essay
Grebenkov, Denis
2009-01-01T23:59:59.000Z
The surrounding world surprises us by the beauty and variety of complex shapes that emerge from nanometric to macroscopic scales. Natural or manufactured materials (sandstones, sedimentary rocks and cement), colloidal solutions (proteins and DNA), biological cells, tissues and organs (lungs, kidneys and placenta), they all present irregularly shaped "scenes" for a fundamental transport "performance", that is, diffusion. Here, the geometrical complexity, entangled with the stochastic character of diffusive motion, results in numerous fascinating and sometimes unexpected effects like diffusion screening or localization. These effects control many diffusion-mediated processes that play an important role in heterogeneous catalysis, biochemical mechanisms, electrochemistry, growth phenomena, oil recovery, or building industry. In spite of a long and rich history of academic and industrial research in this field, it is striking to see how little we know about diffusion in complex geometries, especially the one whic...
Rood, Richard B; Jablonowski, Christiane
2012-10-31T23:59:59.000Z
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.
Creep effects in diffusion bonding of oxygen-free copper
Moilanen, Antti
Diffusion is the transport of atoms or particles through the surrounding material. Various microstructural changes in metals are based on the diffusion phenomena. In solid metals the diffusion is closely related to crystallographic defects. In single-component metals the dominant mechanism of diffusion is the vacancy mechanism. Diffusion bonding is a direct technological application of diffusion. It is an advanced solidstate joining process in which the surfaces of two components are brought to contact with each other and heated under a pressing load in a controlled environment. During the process, the contact surfaces are bonded by atomic diffusion across the interface and as a result, one solid piece is formed. The condition of high temperature and low applied stress combined with relatively long process duration enables the creep effects to take place in bonded metals. Furthermore, creep causes unwanted permanent deformations in the bonded components. Some authors suggest that there could be a threshold fo...
Sollich, Peter
(foams, emulsions etc.) as well as to conventional glassÂforming liquids is discussed. I. INTRODUCTION is Bouchaud's model of glasses [J.ÂP. Bouchaud, J. Physique I 2 1705 (1992)], as extended to describe)].) We investigate the breakdown, near the glass transition, of the (generalized) StokesÂ Einstein
Commercial Building Partnerships Replication and Diffusion
Antonopoulos, Chrissi A.; Dillon, Heather E.; Baechler, Michael C.
2013-09-16T23:59:59.000Z
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.
Thermo-mechanical Behavior of Lithium-ion Battery Electrodes
An, Kai
2013-11-25T23:59:59.000Z
THERMO-MECHANICAL BEHAVIOR OF LITHIUM-ION BATTERY ELECTRODES A Thesis by KAI AN Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree... on the thermo-mechanical behavior of lithium ion battery electrodes. It presents a single particle model of random lattice spring elements coupled with solid phase Li-ion diffusion under active temperature effects. The thermal features are realized by solving...
Lin, Che-Jen [ORNL; Pongprueksa, Pruek [Lamar University; Lindberg, Steven Eric [ORNL; Jang, Carey [U.S. Environmental Protection Agency, Raleigh, North Carolina; Braverman, Thomas [U.S. Environmental Protection Agency, Raleigh, North Carolina; Bullock, Russell O [NOAA; Ho, Thomas [ORNL; Chu, Hsing-Wei [Lamar University
2008-03-01T23:59:59.000Z
In this study, the model response in terms of simulated mercury concentration and deposition to boundary condition (BC), initial condition (IC), model grid resolution (12 km versus 36 km), and two alternative Hg(II) reduction mechanisms, was investigated. The model response to the change of gaseous elemental mercury (GEM) concentration from 0 to 2 ngm3 in IC/BC is found to be very linear (r240.99) based on the results of sensitivity simulations in July 2001. An increase of 1 ngm3 of GEM in BC resulted in an increase of 0.81 ngm3 in the monthly average of total mercury concentration, and 1270 ngm2 in the monthly total deposition. IC has similar but weaker effects compared to those of BC. An increase of 1 ngm3 of GEM in IC resulted in an increase of 0.14 ngm3 in the monthly average of total mercury concentration, and 250 ngm2 in the monthly total deposition. Varying reactive gaseous mercury (RGM) or particulate mercury (PHg) in BC/IC has much less significant impact. Simulation results at different grid resolutions show good agreement (slope 0.950 1.026, r 0.816 0.973) in mercury concentration, dry deposition, and total deposition. The agreement in wet deposition is somewhat weaker (slope 0.770 0.794, r 0.685 0.892) due to the difference in emission dilution and simulated precipitation that subsequently change reaction rates in the aqueous phase. Replacing the aqueous Hg(II)-HO2 reduction by either RGM reduction by CO (51018cm3 molecule1 s1) or photoreduction of RGM (1105 s1) gives significantly better model agreement with the wet deposition measured by Mercury Deposition Network (MDN). Possible ranges of the reduction rates are estimated based on model sensitivity results. The kinetic estimate requires further verification by laboratory studies.
Roumen Tsekov
2011-04-15T23:59:59.000Z
A new approach to thermo-quantum diffusion is proposed and a nonlinear quantum Smoluchowski equation is derived, which describes classical diffusion in the field of the Bohm quantum potential. A nonlinear thermo-quantum expression for the diffusion front is obtained, being a quantum generalization of the classical Einstein law. The quantum diffusion at zero temperature is also described and a new dependence of the position dispersion on time is derived. A stochastic Bohm-Langevin equation is also proposed.
Bower, Allan F; Sethuraman, Vijay A; 10.1016/j.jmps.2011.01.003
2011-01-01T23:59:59.000Z
We formulate the continuum field equations and constitutive equations that govern deformation, stress, and electric current flow in a Li-ion half-cell. The model considers mass transport through the system, deformation and stress in the anode and cathode, electrostatic fields, as well as the electrochemical reactions at the electrode/electrolyte interfaces. It extends existing analyses by accounting for the effects of finite strains and plastic flow in the electrodes, and by exploring in detail the role of stress in the electrochemical reactions at the electrode-electrolyte interfaces. In particular, we find that that stress directly influences the rest potential at the interface, so that a term involving stress must be added to the Nernst equation if the stress in the solid is significant. The model is used to predict the variation of stress and electric potential in a model 1-D half-cell, consisting of a thin film of Si on a rigid substrate, a fluid electrolyte layer, and a solid Li cathode. The predicted c...
Testing eccentricity pumping mechanisms to model eccentric long period sdB binaries with MESA
Vos, Joris; Marchant, Pablo; Van Winckel, Hans
2015-01-01T23:59:59.000Z
Hot subdwarf-B stars in long-period binaries are found to be on eccentric orbits, even though current binary-evolution theory predicts those objects to be circularised before the onset of Roche-lobe overflow (RLOF). We aim to find binary-evolution mechanisms that can explain these eccentric long-period orbits, and reproduce the currently observed period-eccentricity diagram. Three different processes are considered; tidally-enhanced wind mass-loss, phase-dependent RLOF on eccentric orbits and the interaction between a circumbinary disk and the binary. The binary module of the stellar-evolution code MESA (Modules for Experiments in Stellar Astrophysics) is extended to include the eccentricity-pumping processes. The effects of different input parameters on the final period and eccentricity of a binary-evolution model are tested with MESA. The end products of models with only tidally-enhanced wind mass-loss can indeed be eccentric, but these models need to lose too much mass, and invariably end up with a helium ...
Mass-Spring Model for Simulation of Heart Valve Tissue Mechanical Behavior Peter E. Hammer1,2,4,*
1 Mass-Spring Model for Simulation of Heart Valve Tissue Mechanical Behavior Peter E. Hammer1, Cambridge, MA Abbreviated title: Mass-Spring Model for Simulation of Heart Valve Tissue * Address, MA, USA. E-mail address: peter.hammer@childrens.harvard.edu. #12;2 Abstract Heart valves
Sciortino, Francesco
, their energy of the local minima referred to as inherent struc- tures , eIS IS' stands for inherent structures10 . For the case of the Kob-Andersen Lennard-Jones model 11,12 , the number eIS deIS of dis- tinct basins of energy depth between eIS and eIS+deIS follows a Gaussian distribution 5,6 eIS deIS = e Ne- eIS - Eo 2/2 2 2 2
Spin Matrix Theory: A quantum mechanical model of the AdS/CFT correspondence
Troels Harmark; Marta Orselli
2014-10-31T23:59:59.000Z
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 (super)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 transition occurs due to finite-N effects. For sufficiently high temperatures the partially deconfined phase has a classical regime. We find a matrix model description of this regime at any coupling g. Setting g=0 it is a theory of N^2+1 harmonic oscillators while for large g it becomes 2N harmonic oscillators.
HO,PAULINE; JOHANNES,JUSTINE E.; BUSS,RICHARD J.; MEEKS,ELLEN
2001-05-01T23:59:59.000Z
As part of a project with SEMATECH, detailed chemical reaction mechanisms have been developed that describe the gas-phase and surface chemistry occurring during the fluorocarbon plasma etching of silicon dioxide and related materials. The fluorocarbons examined are C{sub 2}F{sub 6}, CHF{sub 3} and C{sub 4}F{sub 8}, while the materials studied are silicon dioxide, silicon, photoresist, and silica-based low-k dielectrics. These systems were examined at different levels, ranging from in-depth treatment of C{sub 2}F{sub 6} plasma etch of oxide, to a fairly cursory examination of C{sub 4}F{sub 8} etch of the low-k dielectric. Simulations using these reaction mechanisms and AURORA, a zero-dimensional model, compare favorably with etch rates measured in three different experimental reactors, plus extensive diagnostic absolute density measurements of electron and negative ions, relative density measurements of CF, CF{sub 2}, SiF and SiF{sub 2} radicals, ion current densities, and mass spectrometric measurements of relative ion densities.
Three-body Interactions Improve the Prediction of Rate and Mechanism in Protein Folding Models
M. R. Ejtehadi; S. P. Avall; S. S. Plotkin
2004-07-14T23:59:59.000Z
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.
Rutqvist, Jonny; Majer, Ernie; Oldenburg, Curt; Peterson, John; Vasco, Don
2006-06-07T23:59:59.000Z
In this paper, we present progress made in a study aimed atincreasing the understanding of the relative contributions of differentmechanisms that may be causing the seismicity occurring at The Geysersgeothermal field, California. The approach we take is to integrate: (1)coupled reservoir geomechanical numerical modeling, (2) data fromrecently upgraded and expanded NCPA/Calpine/LBNL seismic arrays, and (3)tens of years of archival InSAR data from monthly satellite passes. Wehave conducted a coupled reservoir geomechanical analysis to studypotential mechanisms induced by steam production. Our simulation resultscorroborate co-locations of hypocenter field observations of inducedseismicity and their correlation with steam production as reported in theliterature. Seismic and InSAR data are being collected and processed foruse in constraining the coupled reservoir geomechanicalmodel.
Characterizing unsaturated diffusion in porous tuff gravel
Hu, Qinhong; Kneafsey, Timothy J.; Roberts, Jeffery J.; Tomutsa, Liviu; Wang, Joseph, S.Y.
2003-11-12T23:59:59.000Z
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.
A Sequential Fluid-mechanic Chemical-kinetic Model of Propane HCCI Combustion
Aceves, S M; Flowers, D L; Martinez-Frias, J; Smith, J R; Westbrook, C; Pitz, W; Dibble, R; Wright, J F; Akinyemi, W C; Hessel, R P
2000-11-29T23:59:59.000Z
We have developed a methodology for predicting combustion and emissions in a Homogeneous Charge Compression Ignition (HCCI) Engine. This methodology combines a detailed fluid mechanics code with a detailed chemical kinetics code. Instead of directly linking the two codes, which would require an extremely long computational time, the methodology consists of first running the fluid mechanics code to obtain temperature profiles as a function of time. These temperature profiles are then used as input to a multi-zone chemical kinetics code. The advantage of this procedure is that a small number of zones (10) is enough to obtain accurate results. This procedure achieves the benefits of linking the fluid mechanics and the chemical kinetics codes with a great reduction in the computational effort, to a level that can be handled with current computers. The success of this procedure is in large part a consequence of the fact that for much of the compression stroke the chemistry is inactive and thus has little influence on fluid mechanics and heat transfer. Then, when chemistry is active, combustion is rather sudden, leaving little time for interaction between chemistry and fluid mixing and heat transfer. This sequential methodology has been capable of explaining the main characteristics of HCCI combustion that have been observed in experiments. In this paper, we use our model to explore an HCCI engine running on propane. The paper compares experimental and numerical pressure traces, heat release rates, and hydrocarbon and carbon monoxide emissions. The results show an excellent agreement, even in parameters that are difficult to predict, such as chemical heat release rates. Carbon monoxide emissions are reasonably well predicted, even though it is intrinsically difficult to make good predictions of CO emissions in HCCI engines. The paper includes a sensitivity study on the effect of the heat transfer correlation on the results of the analysis. Importantly, the paper also shows a numerical study on how parameters such as swirl rate, crevices and ceramic walls could help in reducing HC and CO emissions from HCCI engines.
A.V.G. Chizmeshya; M.J. McKelvy; G.H. Wolf; R.W. Carpenter; D.A. Gormley; J.R. Diefenbacher; R. Marzke
2006-03-01T23:59:59.000Z
Fossil fuels currently provide 85% of the world's energy needs, with the majority coming from coal, due to its low cost, wide availability, and high energy content. The extensive use of coal-fired power assumes that the resulting CO2 emissions can be vented to the atmosphere. However, exponentially increasing atmospheric CO2 levels have brought this assumption under critical review. Over the last decade, this discussion has evolved from whether exponentially increasing anthropogenic CO2 emissions will adversely affect the global environment, to the timing and magnitude of their impact. A variety of sequestration technologies are being explored to mitigate CO2 emissions. These technologies must be both environmentally benign and economically viable. Mineral carbonation is an attractive candidate technology as it disposes of CO2 as geologically stable, environmentally benign mineral carbonates, clearly satisfying the first criteria. The primary challenge for mineral carbonation is cost-competitive process development. CO2 mineral sequestration--the conversion of stationary-source CO2 emissions into mineral carbonates (e.g., magnesium and calcium carbonate, MgCO3 and CaCO3)--has recently emerged as one of the most promising sequestration options, providing permanent CO2 disposal, rather than storage. In this approach a magnesium-bearing feedstock mineral (typically serpentine or olivine; available in vast quantities globally) is specially processed and allowed to react with CO2 under controlled conditions. This produces a mineral carbonate which (1) is environmentally benign, (2) already exists in nature in quantities far exceeding those that could result from carbonating the world's known fossil fuel reserves, and (3) is stable on a geological time scale. Minimizing the process cost via optimization of the reaction rate and degree of completion is the remaining challenge. As members of the DOE/NETL managed National Mineral Sequestration Working Group we have already significantly improved our understanding of mineral carbonation. Group members at the Albany Research Center have recently shown that carbonation of olivine and serpentine, which naturally occurs over geological time (i.e., 100,000s of years), can be accelerated to near completion in hours. Further process refinement will require a synergetic science/engineering approach that emphasizes simultaneous investigation of both thermodynamic processes and the detailed microscopic, atomic-level mechanisms that govern carbonation kinetics. Our previously funded Phase I Innovative Concepts project demonstrated the value of advanced quantum-mechanical modeling as a complementary tool in bridging important gaps in our understanding of the atomic/molecular structure and reaction mechanisms that govern CO2 mineral sequestration reaction processes for the model Mg-rich lamellar hydroxide feedstock material Mg(OH)2. In the present simulation project, improved techniques and more efficient computational schemes have allowed us to expand and augment these capabilities and explore more complex Mg-rich, lamellar hydroxide-based feedstock materials, including the serpentine-based minerals. These feedstock materials are being actively investigated due to their wide availability, and low-cost CO2 mineral sequestration potential. Cutting-edge first principles quantum chemical, computational solid-state and materials simulation methodology studies proposed herein, have been strategically integrated with our new DOE supported (ASU-Argonne National Laboratory) project to investigate the mechanisms that govern mineral feedstock heat-treatment and aqueous/fluid-phase serpentine mineral carbonation in situ. This unified, synergetic theoretical and experimental approach has provided a deeper understanding of the key reaction mechanisms than either individual approach can alone. We used ab initio techniques to significantly advance our understanding of atomic-level processes at the solid/solution interface by elucidating the origin of vibrational, electronic, x-ray and electron energy loss sp
Analytical solutions to matrix diffusion problems
Kekäläinen, Pekka, E-mail: pekka.kekalainen@helsinki.fi [Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland)
2014-10-06T23:59:59.000Z
We report an analytical method to solve in a few cases of practical interest the equations which have traditionally been proposed for the matrix diffusion problem. In matrix diffusion, elements dissolved in ground water can penetrate the porous rock surronuding the advective flow paths. In the context of radioactive waste repositories this phenomenon provides a mechanism by which the area of rock surface in contact with advecting elements is greatly enhanced, and can thus be an important delay mechanism. The cases solved are relevant for laboratory as well for in situ experiments. Solutions are given as integral representations well suited for easy numerical solution.
The Standard model as a low-energy effective theory: what is triggering the Higgs mechanism?
Fred Jegerlehner
2014-07-02T23:59:59.000Z
The discovery of the Higgs by ATLAS and CMS at the LHC not only provided the last missing building block of the electroweak Standard Model, the mass of the Higgs has been found to have a very peculiar value about 126 GeV, which is such that vacuum stability is extending up to the Planck scale. This may have much deeper drawback than anticipated so far. The impact on the running of the SM gauge, Yukawa and Higgs couplings up to the Planck scale has been discussed in several articles recently. Here we consider the impact on the running masses and we discuss the role of quadratic divergences within the Standard Model. The change of sign of the coefficient of the quadratically divergent terms showing up at about mu_0 ~ 1.4 x 10^16 GeV may be understood as a first order phase transition restoring the symmetric phase, while its large negative values at lower scales triggers the Higgs mechanism, running parameters evolve in such a way that the symmetry is restored two orders of magnitude before the Planck scale. Thus, the electroweak phase transition takes place at the scale mu_0 and not at the electroweak scale v ~ 250 GeV. The SM Higgs system and its phase transition could play a key role for the inflation of the early universe. Also baryogenesis has to be reconsidered under the aspect that perturbative arguments surprisingly work up to the Planck scale.
Fractal Location and Anomalous Diffusion Dynamics for Oil Wells from the KY Geological Survey
Andrew, Keith; Andrew, Kevin A
2009-01-01T23:59:59.000Z
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.
Oxygen diffusion in titanite: Lattice diffusion and fast-path diffusion in single crystals
Watson, E. Bruce
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 be recognized as responsible for oxygen diffusion. The diffusion profiles showed two segments: a steep one close
Telleria, Maria J
2010-01-01T23:59:59.000Z
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 ...
A Continuum Coupled Moisture-mechanical Constitutive Model for Asphalt Concrete
Shakiba, Maryam
2013-12-09T23:59:59.000Z
procedure and give insight into the various damage inducing mechanisms in asphalt concrete. In this dissertation, thermo-hygro-mechanical constitutive relationships are developed based on the principle of virtual power and laws of thermodynamics in order...
Wang, Yong, Ph. D. Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics
2008-01-01T23:59:59.000Z
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 ...
Minko, P., E-mail: peterminko@yahoo.com; Bücker, A. [University Hospital Homburg/Saar, Department of Diagnostic and Interventional Radiology (Germany); Laschke, M.; Menger, M. [University Hospital Homburg/Saar, Institute of Clinical and Experimental Surgery (Germany); Bohle, R. [University Hospital Homburg/Saar, Department of Pathology (Germany); Katoh, M. [University Hospital Homburg/Saar, Department of Diagnostic and Interventional Radiology (Germany)
2013-06-08T23:59:59.000Z
PurposeTo investigate the efficacy and safety of mechanical thrombectomy for iliac vein thrombosis using Rotarex and Aspirex catheters in a pig model.Materials and MethodsIliac vein thrombosis was induced in six pigs by means of an occlusion-balloon catheter and thrombin injection. The presence of thrombi was verified by digital subtraction angiography (DSA) and computed tomography (CT). Thrombectomy was performed using 6F and 8F Rotarex and 6F, 8F, and 10F Aspirex catheters (Straub Medical AG, Wangs, Switzerland). After intervention, DSA and CT were repeated to evaluate the efficacy of mechanical thrombectomy and to exclude local complications. In addition, pulmonary CT was performed to rule out pulmonary embolism. Finally, all pigs were killed, and iliac veins were dissected to perform macroscopic and histological examination.ResultsThrombus induction was successfully achieved in all animals as verified by DSA and CT. Subsequent thrombectomy lead to incomplete recanalization of the iliac veins with residual thrombi in all cases. However, the use of the 6F and 8F Rotarex catheters caused vessel perforation and retroperitoneal hemorrhage in all cases. Application of the Aspirex device caused one small transmural perforation in a vessel treated with a 10F Aspirex catheter, and this was only seen microscopically. Pulmonary embolism was detected in one animal treated with the Rotarex catheters, whereas no pulmonary emboli were seen in animals treated with the Aspirex catheters.ConclusionThe Aspirex catheter allowed subtotal and safe recanalization of iliac vein thrombosis. In contrast, the use of the Rotarex catheter caused macroscopically obvious vessel perforations in all cases.
Song, Zhichao
2012-01-01T23:59:59.000Z
adhesion in microelectromechanical systems. ASME J. Tribol.microtribology for microelectromechanical systems. Wear 200,forces in microelectromechanical systems: mechanisms,
18.366 Random Walks and Diffusion, Spring 2005
Bazant, Martin Z.
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, ...
DIFFUSE RADIO EMISSION IN ABELL 754
Kale, Ruta; Dwarakanath, K. S. [Raman Research Institute, Bangalore 560080 (India)], E-mail: ruta@rri.res.in, E-mail: dwaraka@rri.res.in
2009-07-10T23:59:59.000Z
We present a low-frequency study of the diffuse radio emission in the galaxy cluster A754. We present a new 150 MHz image of the galaxy cluster A754 made with the Giant Metrewave Radio Telescope and discuss the detection of four diffuse features. We compare the 150 MHz image with the images at 74, 330, and 1363 MHz; one new diffuse feature is detected. The flux density upper limits at 330 and 1363 MHz imply a synchrotron spectral index, {alpha}>2 (S {proportional_to} {nu}{sup -{alpha}}), for the new feature. The 'west relic' detected at 74 MHz is not detected at 150 MHz and is thus consistent with its nondetection at 1363 MHz and 330 MHz. Integrated spectra of all the diffuse features are presented. The fourth diffuse feature is located along the proposed merger axis in A754 and 0.7 Mpc away from the peak of X-ray emission; we refer to it as a relic. We have made use of the framework of the adiabatic compression model to obtain spectra. We show that the spectrum of the fourth diffuse feature is consistent with that of a cocoon of a radio galaxy lurking for about 9 x 10{sup 7} yr; no shock compression is required. The other three diffuse emission have spectra steeper than 1.5 and could be cocoons lurking for longer time. We discuss other possibilities such as shocks and turbulent reacceleration being responsible for the diffuse emission in A754.
Non-Fickian ionic diffusion across high-concentration gradients
Carey, A.E.; Wheatcraft, S.W. [Univ. of Nevada, Reno, NV (United States)] [Univ. of Nevada, Reno, NV (United States); Glass, R.J. [Sandia National Laboratory, Albuquerque, NM (United States)] [and others] [Sandia National Laboratory, Albuquerque, NM (United States); and others
1995-09-01T23:59:59.000Z
A non-Fickian physico-chemical model for electrolyte transport in high-ionic strength systems is developed and tested with laboratory experiments with copper sulfate as an example electrolyte. The new model is based on irreversible thermodynamics and uses measured mutual diffusion coefficients, varying with concentration. Compared to a traditional Fickian model, the new model predicts less diffusion and asymmetric diffusion profiles. Laboratory experiments show diffusion rates even smaller than those predicted by our non-Fickian model, suggesting that there are additional, unaccounted for processes retarding diffusion. Ionic diffusion rates maybe a limiting factor in transporting salts whose effect on fluid density will in turn significantly affect the flow regime. These findings have important implications for understanding and predicting solute transport in geologic settings where dense, saline solutions occur. 30 refs., 5 figs.
Particle-in-Cell Modeling of Magnetized Argon Plasma Flow Through Small Mechanical Apertures
Adam B. Sefkow and Samuel A. Cohen
2009-04-09T23:59:59.000Z
Motivated by observations of supersonic argon-ion flow generated by linear helicon-heated plasma devices, a three-dimensional particle-in-cell (PIC) code is used to study whether stationary electrostatic layers form near mechanical apertures intersecting the flow of magnetized plasma. By self-consistently evaluating the temporal evolution of the plasma in the vicinity of the aperture, the PIC simulations characterize the roles of the imposed aperture and applied magnetic field on ion acceleration. The PIC model includes ionization of a background neutral-argon population by thermal and superthermal electrons, the latter found upstream of the aperture. Near the aperture, a transition from a collisional to a collisionless regime occurs. Perturbations of density and potential, with mm wavelengths and consistent with ion acoustic waves, propagate axially. An ion acceleration region of length ~ 200?300 ?D,e forms at the location of the aperture and is found to be an electrostatic double layer, with axially-separated regions of net positive and negative charge. Reducing the aperture diameter or increasing its length increases the double layer strength.
Zhang, Minghua; Bretherton, Christopher S.; Blossey, Peter; Austin, Phillip A.; Bacmeister, J.; Bony, Sandrine; Brient, Florent; Cheedela, Suvarchal K.; Cheng, Anning; Del Genio, Anthony D.; De Roode, Stephan R.; Endo , Satoshi; Franklin, Charmaine N.; Golaz, Jean-Christophe; Hannay, Cecile; Heus, Thijs; Isotta, Francesco A.; Jean-Louis, Dufresne; Kang, In-Sik; Kawai, Hideaki; Koehler, M.; Larson, Vincent E.; Liu, Yangang; Lock, Adrian; Lohmann, U.; Khairoutdinov, Marat; Molod, Andrea M.; Neggers, Roel; Rasch, Philip J.; Sandu, Irina; Senkbeil, Ryan; Siebesma, A. P.; Siegenthaler-Le Drian, Colombe; Stevens, Bjorn; Suarez, Max; Xu, Kuan-Man; Von Salzen, Knut; Webb, Mark; Wolf, Audrey; Zhao, M.
2013-12-26T23:59:59.000Z
Large Eddy Models (LES) and Single Column Models (SCM) are used in a surrogate climate change 101 to investigate the physical mechanism of low cloud feedbacks in climate models. Enhanced surface-102 driven boundary layer turbulence and shallow convection in a warmer climate are found to be 103 dominant mechanisms in SCMs.
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
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.
Ritchie, Robert
and compressors, despite the fact that they can be extremely susceptible to such hydrogen embrittlement, is well documented. Hydrogen, either as an external gas, resulting from electrochemical reactionsA statistical, physical-based, micro-mechanical model of hydrogen-induced intergranular fracture
Hammes-Schiffer, Sharon
Model Proton-Coupled Electron Transfer Reactions in Solution: Predictions of Rates, Mechanisms isotope effects for proton-coupled electron transfer (PCET) reactions. These studies are based, the solvent is represented as a dielectric continuum, and the active electrons and transferring protons
A thermo-hydro-mechanical coupled model in local thermal non-equilibrium for fractured HDR reservoir
Boyer, Edmond
artificially fractured hot dry rock (HDR) reservoirs requires three main ingredients: (1) a proper thermoA thermo-hydro-mechanical coupled model in local thermal non-equilibrium for fractured HDR reservoir Rachel Geleta,b , Benjamin Loreta, , Nasser Khalilib aLaboratoire Sols, Solides, Structures, B
Lattice Boltzmann computations for reaction-diffusion equations
Ponce Dawson, S.; Chen, S.; Doolen, G.D. (Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))
1993-01-15T23:59:59.000Z
A lattice Boltzmann model for reaction-diffusion systems is developed. The method provides an efficient computational scheme for simulating a variety of problems described by the reaction-diffusion equations. Diffusion phenomena, the decay to a limit cycle, and the formation of Turing patterns are studied. The results of lattice Boltzmann calculations are compared with the lattice gas method and with theoretical predictions, showing quantitative agreement. The model is extended to include velocity convection in chemically reacting fluid flows.
Modulation of Drug Transport Properties by Multicomponent Diffusion in Surfactant Aqueous Solutions
Annunziata, Onofrio
Modulation of Drug Transport Properties by Multicomponent Diffusion in Surfactant Aqueous Solutions ReceiVed July 1, 2008 Diffusion coefficients of drug compounds are crucial parameters used for modeling diffusion. A multicomponent diffusion study on drug-surfactant-water ternary mixtures is reported here
Pina-Jordan, Jose Gregorio
1985-01-01T23:59:59.000Z
Neutron Counting. The maximun uptake of uranium was 134 ppm in 30 days. A kinetic model to analyze the ur anium uptake was developed, and it was deter mined that intr apar ticle diffusion was the controlling mechanism of the uptake process... with Super? cial Velocity of Seawater in a Fluidized Bed of Spherical Particles. Correlation By Gunn 26 Uranium Uptake Data Using Kinetic Model for Film Diffusion Control (POG503) . 66 27 Uranium Uptake Data Using Kinetic Model for Intraparticle...
Microstructure and Mechanical Property Studies on Neutron-Irradiated Ferritic Fe-Cr Model Alloys
Jian Gan; Maria Okuniewski; Wei-Ying Chen; Yinbin Miao; Carolyn A. Tomchik; James F. Stubbins; Y. Q. Wu; Stu A. Maloy
2014-06-01T23:59:59.000Z
Model Fe, Fe-10Cr and Fe-14Cr alloys were irradiated in Advanced Test Reactor at 300°C and 450°C to target doses of 0.01, 0.1 and 1 dpa. The microstructure and the mechanical property of irradiated specimens were investigated using TEM, APT and hardness measurements. The irradiation-induced hardening was consistent with the observed microstructures. For lower doses of 0.01 and 0.1 dpa, the formation of dislocation loops was the primarily contributor to the hardening; no a’ precipitates of resolvable sizes were observed. By 1 dpa, additional increase in hardening were attributed to the formation of a high density of 1-2 nm a' precipitates. In Fe, the hardness increased less as a function of irradiation dose compared to Fe-Cr alloys because of the lack of a' precipitation and differences in loop structures. Three single-parameter effects have been studied: the Cr content, the irradiation temperature and the grain size. The addition of Cr reduced the mobility of both ½<111> and <100> dislocation loops, leading to a smaller loop size and higher loop density. Also, the Cr contents were positively correlated to the density of a' precipitates, but were less relevant to the precipitate size. Higher irradiation temperature of 450°C resulted in a preferential production of the immobile <100> loops over the mobile ½<111> loops (ex. a ratio of 8:1 in Fe-10Cr irradiated 450°C to 0.01 dpa). At lower temperature of 300°C, heterogeneous formation of dislocation loops at the vicinity of line dislocations frequently. In Fe, the development of dislocation loops was suppressed (compared to Fe-Cr alloys) due to a combination of smaller grain size, high initial dislocation density and high defect mobility.
FLAMMABLE GAS DIFFUSION THROUGH SINGLE SHELL TANK (SST) DOMES
MEACHAM, J.E.
2003-11-10T23:59:59.000Z
This report quantified potential hydrogen diffusion through Hanford Site Single-Shell tank (SST) domes if the SSTs were hypothetically sealed airtight. Results showed that diffusion would keep headspace flammable gas concentrations below the lower flammability limit in the 241-AX and 241-SX SST. The purpose of this document is to quantify the amount of hydrogen that could diffuse through the domes of the SSTs if they were hypothetically sealed airtight. Diffusion is assumed to be the only mechanism available to reduce flammable gas concentrations. The scope of this report is limited to the 149 SSTs.
Nonlinear friction in quantum mechanics
Roumen Tsekov
2013-03-10T23:59:59.000Z
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.
Einstein relation for reversible diffusions in random environment
Gantert, Nina
Einstein relation for reversible diffusions in random environment N. Gantert P. Mathieu A the Einstein re- lation for this model. It says that the derivative at 0 of the effective velocity under an additional local drift equals the diffusivity of the model without drift. The Einstein rela- tion
Convergence Speed of GARCH Option Price to Diffusion Option Price
Chaudhuri, Sanjay
Convergence Speed of GARCH Option Price to Diffusion Option Price Jin-Chuan Duan, Yazhen Wang that as the time interval between two consecutive observations shrinks to zero, a properly constructed GARCH model will weakly converge to a bivariate diffusion. Naturally the European option price under the GARCH model
Heydarkhan Tehrani, Ardeshir
2013-08-26T23:59:59.000Z
This dissertation is devoted to the virtual investigation of the mechanical behavior of micro/nano polymer composites (MNPCs). Advanced composite materials are favored by the automotive industry and army departments for their customizable tailored...
Physical understanding and modeling of chemical mechanical planarization in dielectric materials
Xie, Xiaolin, Ph. D. Massachusetts Institute of Technology
2007-01-01T23:59:59.000Z
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 ...
Wee, Brian (Brian J.)
2013-01-01T23:59:59.000Z
This thesis seeks to assess the viability of a space qualified shape memory polymer (SMP) mechanical counter pressure (MCP) suit. A key development objective identified by the International Space Exploration Coordination ...
Heydarkhan Tehrani, Ardeshir
2013-08-26T23:59:59.000Z
This dissertation is devoted to the virtual investigation of the mechanical behavior of micro/nano polymer composites (MNPCs). Advanced composite materials are favored by the automotive industry and army departments for their customizable tailored...
Eichenfield, Matt; Safavi-Naeini, Amir H; Vahala, Kerry J; Painter, Oskar
2009-01-01T23:59:59.000Z
Periodically structured materials can sustain both optical and mechanical excitations which are tailored by the geometry. Here we analyze the properties of dispersively coupled planar photonic and phononic crystals: optomechanical crystals. In particular, the properties of co-resonant optical and mechanical cavities in quasi-1D (patterned nanobeam) and quasi-2D (patterned membrane) geometries are studied. It is shown that the mechanical Q and optomechanical coupling in these structures can vary by many orders of magnitude with modest changes in geometry. An intuitive picture is developed based upon a perturbation theory for shifting material boundaries that allows the optomechanical properties to be designed and optimized. Several designs are presented with mechanical frequency ~ 1-10 GHz, optical Q-factor Qo > 10^7, motional masses meff 100 femtograms, optomechanical coupling length LOM 10^7.
Physical and numerical modeling of the external fluid mechanics of OTEC pilot plants
Singarella, Paul N.
1982-01-01T23:59:59.000Z
This study examined the near field external fluid mechanics of symmetrical OTEC pilot plant designs (20-80 MWe) under realistic deep water conditions. The objective was to assess the environmental impact of different plant ...
Enhanced Vapor-Phase Diffusion in Porous Media - LDRD Final Report
Ho, C.K.; Webb, S.W.
1999-01-01T23:59:59.000Z
As part of the Laboratory-Directed Research and Development (LDRD) Program at Sandia National Laboratories, an investigation into the existence of enhanced vapor-phase diffusion (EVD) in porous media has been conducted. A thorough literature review was initially performed across multiple disciplines (soil science and engineering), and based on this review, the existence of EVD was found to be questionable. As a result, modeling and experiments were initiated to investigate the existence of EVD. In this LDRD, the first mechanistic model of EVD was developed which demonstrated the mechanisms responsible for EVD. The first direct measurements of EVD have also been conducted at multiple scales. Measurements have been made at the pore scale, in a two- dimensional network as represented by a fracture aperture, and in a porous medium. Significant enhancement of vapor-phase transport relative to Fickian diffusion was measured in all cases. The modeling and experimental results provide additional mechanisms for EVD beyond those presented by the generally accepted model of Philip and deVries (1957), which required a thermal gradient for EVD to exist. Modeling and experimental results show significant enhancement under isothermal conditions. Application of EVD to vapor transport in the near-surface vadose zone show a significant variation between no enhancement, the model of Philip and deVries, and the present results. Based on this information, the model of Philip and deVries may need to be modified, and additional studies are recommended.
Mechanical characterization and modelling of the heavy tungsten allow IT180
Scapin, M
2015-01-01T23:59:59.000Z
Pure tungsten or its alloys(WHA) find applications in several fields, especially due to the fact that these materials show a good combination of mechanical and thermal properties and they are commonly used in aerospace, automotive, metal working processes, military and nuclear technologies. Looking at the scientific literature, a lack in the mechanical characterization over wide ranges in temperature and strain-rates was found, especially forW–Ni–Cu alloys.
Paris-Sud XI, Université de
A chemo-poro-mechanical model of oilwell cement carbonation under CO2 geological storage conditions may impact the mechanical behaviour of wellbore cement in the context of CO2 storage. The model process. The major chemical reactions occurring within cement and their consequences on the volumes
Analytical modelling of hydrogen transport in reactor containments
Manno, V.
1983-01-01T23:59:59.000Z
There are two diffusion processes, molecular and turbulent, which should be modelled in different ways. Molecular diffusion is modelled by Wilke's formula for the multi-component gas diffusion, where the diffusion constants ...
Adaptive multigroup radiation diffusion
Williams, Richard B., Sc. D. Massachusetts Institute of Technology
2005-01-01T23:59:59.000Z
This thesis describes the development and implementation of an algorithm for dramatically increasing the accuracy and reliability of multigroup radiation diffusion simulations at low group counts. This is achieved by ...
Mechanisms of light harvesting by photosystem II in plants
Amarnath, Kapil; Schneider, Anna R; Fleming, Graham R
2015-01-01T23:59:59.000Z
Light harvesting by photosystem II (PSII) in plants is highly efficient and acclimates to rapid changes in the intensity of sunlight. However, the mechanisms of PSII light harvesting have remained experimentally inaccessible. Using a structure-based model of excitation energy flow in 200 nanometer (nm) x 200 nm patches of the grana membrane, where PSII is located, we accurately simulated chlorophyll fluorescence decay data with no free parameters. Excitation movement through the light harvesting antenna is diffusive, but becomes subdiffusive in the presence of charge separation at reaction centers. The influence of membrane morphology on light harvesting efficiency is determined by the excitation diffusion length of 50 nm in the antenna. Our model provides the basis for understanding how nonphotochemical quenching mechanisms affect PSII light harvesting in grana membranes.
Journal Diffusion Factors a measure of diffusion? Tove Faber Frandsen
Paris-Sud XI, Université de
1 Journal Diffusion Factors a measure of diffusion? Tove Faber Frandsen Royal School of Library In this paper we show that the measure of diffusion introduced by Ian Rowlands called the Journal Diffusion Factor (JDF) is highly negatively correlated with the number of citations, leading highly cited journals
Physical process Mechanical mechanisms
Berlin,Technische Universität
1 Physical process Generation · Mechanical mechanisms F = m·a · Electric/Magnetic mechanisms F = B·i·l · Fluid dynamic/Hydraulic mechanisms q, p, ij · Thermal/Optical #12;2 Source unit
Diffusion of tungsten clusters on tungsten (110) surface
Chen, Dong; Hu, Wangyu; Yang, Jianyu; Deng, Huiqiu; Sun, Lixian; Gao, Fei
2009-04-01T23:59:59.000Z
Using molecular dynamics simulation and modified analytic embedded-atom method, we have investigated the self-diffusion of clusters on a tungsten (110) surface. As compared to the linear-chain configuration, the close-packed islands for tungsten clusters containing more than nine adatoms have been predicted to be more stable with the relatively lower binding energies. The migration energies show an interesting and oscillating behavior with increasing cluster size. The tetramer, hexamer and octamer have obviously higher migration energies than the others. The different atomic configurations and diffusion mechanisms have been determined during the diffusion processes. It is clear that the dimer-shearing mechanism occurs inside the hexamer, while it occurs at the periphery of heptamer. The successive hopping mechanism of individual atom is of critical importance in the migration of the clusters containing five or fewer adatoms. In addition, the diffusion of a cluster with nine adatoms is achieved through the changes of the cluster shape.
Mitchell, John Anthony; Epp, David S.; Wittwer, Jonathan W.
2005-10-01T23:59:59.000Z
Damping vibrations is important in the design of some types of inertial sensing devices. One method for adding damping to a device is to use magnetic forces generated by a static magnetic field interacting with eddy currents. In this report, we develop a 2-dimensional finite element model for the analysis of quasistatic eddy currents in a thin sheet of conducting material. The model was used for design and sensitivity analyses of a novel mechanical oscillator that consists of a shuttle mass (thin sheet of conducting material) and a set of folded spring elements. The oscillator is damped through the interaction of a static magnetic field and eddy currents in the shuttle mass. Using a prototype device and Laser Dopler Velocimetry (LDV), measurements were compared to the model in a validation study using simulation based uncertainty analyses. Measurements were found to follow the trends predicted by the model.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Anand, M.; Rajagopal, K.; Rajagopal, K. R.
2003-01-01T23:59:59.000Z
Multiple interacting mechanisms control the formation and dissolution of clots to maintain blood in a state of delicate balance. In addition to a myriad of biochemical reactions, rheological factors also play a crucial role in modulating the response of blood to external stimuli. To date, a comprehensive model for clot formation and dissolution, that takes into account the biochemical, medical and rheological factors, has not been put into place, the existing models emphasizing either one or the other of the factors. In this paper, after discussing the various biochemical, physiologic and rheological factors at some length, we develop a modelmore »for clot formation and dissolution that incorporates many of the relevant crucial factors that have a bearing on the problem. The model, though just a first step towards understanding a complex phenomenon, goes further than previous models in integrating the biochemical, physiologic and rheological factors that come into play.« less
Mechanisms of aerosol-forced AMOC variability in a state of the art climate model
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
R. Fedele; M. A. Man'ko; V. I. Man'ko; V. G. Vaccaro
2002-07-30T23:59:59.000Z
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.
Evidence of Multi-Process Matrix Diffusion in a Single Fracturefrom a Field Tracer Test
Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur; Molz, Fred J.
2005-06-11T23:59:59.000Z
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.
Thomas, Brian G.
the flow-rate and solidification time histories. An efficient one-dimensional (1-D) heat transfer model
Oxygen diffusion and reactivity at low temperature on bare amorphous olivine-type silicate
Minissale, M., E-mail: marco.minissale@obspm.fr; Congiu, E.; Dulieu, F. [LERMA-LAMAp, Université de Cergy-Pontoise, Observatoire de Paris, ENS, UPMC, UMR 8112 du CNRS, 5 Mail Gay Lussac, 95000 Cergy Pontoise Cedex (France)] [LERMA-LAMAp, Université de Cergy-Pontoise, Observatoire de Paris, ENS, UPMC, UMR 8112 du CNRS, 5 Mail Gay Lussac, 95000 Cergy Pontoise Cedex (France)
2014-02-21T23:59:59.000Z
The mobility of O atoms at very low temperatures is not generally taken into account, despite O diffusion would add to a series of processes leading to the observed rich molecular diversity in space. We present a study of the mobility and reactivity of O atoms on an amorphous silicate surface. Our results are in the form of reflection absorption infrared spectroscopy and temperature-programmed desorption spectra of O{sub 2} and O{sub 3} produced via two pathways: O + O and O{sub 2} + O, investigated in a submonolayer regime and in the range of temperature between 6.5 and 30 K. All the experiments show that ozone is formed efficiently on silicate at any surface temperature between 6.5 and 30 K. The derived upper limit for the activation barriers of O + O and O{sub 2} + O reactions is ?150 K/k{sub b}. Ozone formation at low temperatures indicates that fast diffusion of O atoms is at play even at 6.5 K. Through a series of rate equations included in our model, we also address the reaction mechanisms and show that neither the Eley–Rideal nor the hot atom mechanisms alone can explain the experimental values. The rate of diffusion of O atoms, based on modeling results, is much higher than the one generally expected, and the diffusive process proceeds via the Langmuir-Hinshelwood mechanism enhanced by tunnelling. In fact, quantum effects turn out to be a key factor that cannot be neglected in our simulations. Astrophysically, efficient O{sub 3} formation on interstellar dust grains would imply the presence of huge reservoirs of oxygen atoms. Since O{sub 3} is a reservoir of elementary oxygen, and also of OH via its hydrogenation, it could explain the observed concomitance of CO{sub 2} and H{sub 2}O in the ices.
Determination of Matrix Diffusion Properties of Granite
Holtta, Pirkko; Siitari-Kauppi, Marja; Huittinen, Nina [Laboratory of Radiochemistry, P.O. Box 55, University of Helsinki, FI-00014 (Finland); Poteri, Antti [VTT Processes, P.O. Box 1608, VTT, FI-02044 (Finland)
2007-07-01T23:59:59.000Z
Rock-core column experiments were introduced to estimate the diffusion and sorption properties of Kuru Grey granite used in block-scale experiments. The objective was to examine the processes causing retention in solute transport through rock fractures, especially matrix diffusion. The objective was also to estimate the importance of retention processes during transport in different scales and flow conditions. Rock-core columns were constructed from cores drilled into the fracture and were placed inside tubes to form flow channels in the 0.5 mm gap between the cores and the tube walls. Tracer experiments were performed using uranin, HTO, {sup 36}Cl, {sup 131}I, {sup 22}Na and {sup 85}Sr at flow rates of 1-50 {mu}L.min{sup -1}. Rock matrix was characterized using {sup 14}C-PMMA method, scanning electron microscopy (SEM), energy dispersive X-ray micro analysis (EDX) and the B.E.T. method. Solute mass flux through a column was modelled by applying the assumption of a linear velocity profile and molecular diffusion. Coupling of the advection and diffusion processes was based on the model of generalised Taylor dispersion in the linear velocity profile. Experiments could be modelled applying a consistent parameterization and transport processes. The results provide evidence that it is possible to investigate matrix diffusion at the laboratory scale. The effects of matrix diffusion were demonstrated on the slightly-sorbing tracer breakthrough curves. Based on scoping calculations matrix diffusion begins to be clearly observable for non-sorbing tracer when the flow rate is 0.1 {mu}L.min{sup -1}. The experimental results presented here cannot be transferred directly to the spatial and temporal scales that prevail in an underground repository. However, the knowledge and understanding of transport and retention processes gained from this study is transferable to different scales from laboratory to in-situ conditions. (authors)
Control of transversal instabilities in reaction-diffusion systems
Sonja Molnos; Jakob Löber; Jan Frederik Totz; Harald Engel
2015-01-15T23:59:59.000Z
In two-dimensional reaction-diffusion systems, local curvature perturbations in the shape of traveling waves are typically damped out and disappear in the course of time. If, however, the inhibitor diffuses much faster than the activator, transversal instabilities can arise, leading from flat to folded, spatio-temporally modulated wave shapes and to spreading spiral turbulence. For experimentally relevant parameter values, the photosensitive Belousov-Zhabotinsky reaction (PBZR) does not exhibit transversal wave instabilities. Here, we propose a mechanism to artificially induce these instabilities via a wave shape dependent spatio-temporal feedback loop, and study the emerging wave patterns. In numerical simulations with the modified Oregonator model for the PBZR using experimentally realistic parameter values we demonstrate the feasibility of this control scheme. Conversely, in a piecewise-linear version of the FitzHugh-Nagumo model transversal instabilities and spiral turbulence in the uncontrolled system are shown to be suppressed in the presence of control, thereby stabilising flat wave propagation.
HINDERED DIFFUSION OF ASPHALTENES AT ELEVATED TEMPERATURE AND PRESSURE
James A. Guin; Ganesh Ramakrishnan
1999-10-07T23:59:59.000Z
During this time period, experiments were performed to study the diffusion controlled uptake of quinoline and a coal asphaltene into porous carbon catalyst pellets. Cyclohexane and toluene were used as solvents for quinoline and the coal asphaltene respectively. The experiments were performed at 27 C and 75 C, at a pressure of 250 psi (inert gas) for the quinoline/cyclohexane system. For the coal asphaltene/toluene system, experiments were performed at 27 C, also at a pressure of 250 psi. These experiments were performed in a 20 cm{sup 3} microautoclave, the use of which is advantageous since it is economical from both a chemical procurement and waste disposal standpoint due to the small quantities of solvents and catalysts used. A C++ program was written to simulate data using a mathematical model which incorporated both diffusional and adsorption mechanisms. The simulation results showed that the mathematical model satisfactorily fitted the adsorptive diffusion of quinoline and the coal asphaltene onto a porous activated carbon. For the quinoline/cyclohexane system, the adsorption constant decreased with an increase in temperature. The adsorption constant for the coal asphaltene/toluene system at 27 C was found to be much higher than that of the quinoline/cyclohexane system at the same temperature. Apparently the coal asphaltenes have a much greater affinity for the surface of the carbon catalyst than is evidenced by the quinoline molecule.
Multiscale Modeling of TiO2 Nanoparticle Production in Flame Reactors: Effect of Chemical Mechanism
Raman, Venkat
, catalysis, energy, and semiconductors. Titanium dioxide (TiO2) nanoparticles are traditionally used and Engineering Mechanics, The UniVersity of Texas, Austin, Texas 78712 For titanium dioxide (TiO2) nanoparticles in the flame with detailed titanium oxidation chemistry, compared to one-step chemistry. Finally, a large
3D imaging and mechanical modeling of helical buckling in Medicago truncatula plant roots
Cohen, Itai
such as drought impedes root growth and conse- quently has severe negative effects on yield (1). As world popu they grow. Soil compaction resulting from agricultural activities or from environ- mental changes while facing a decline in agricultural soil quality including increased mechanical impe- dance of soil
Tang, Xianzhu [College of William and Mary, Williamsburg, VA (United States); Boozer, A.H. [Columbia Univ., New York, NY (United States)
1996-12-31T23:59:59.000Z
A wide range of transport problems are of advection-diffusion type. Typical fluid problems of this type are the relaxation of temperature differences in a room or the spread of a contaminant in a river. Important examples in plasma include the relaxation of electrons in a region of stochastic magnetic field lines and the evolution of the magnetic field embedded in a conducting fluid. The archetypal model equation is the advection-diffusion equation. The quantity being transported is {phi}. The flow velocity of the medium, v(x, t), is assumed given and independent of {phi}. The diffusive flux is {Tau}{sub d} = -D{del}{phi}. If the flow is chaotic, the properties of the transport are determined by the spatial and time dependence of the finite time Lyapunov exponent {lambda}({xi}, t). The rapid diffusive transport occurs only along the field line (s line) of the vector s, which defines the stable direction in which neighboring points asymptotically converge. The topology of the s lines affects the diffusive transport through the finite time Lyapunov exponent. We discover that the spatial variation of the finite time Lyapunov exponent along the s lines is smooth and determined by the topology of the s lines. For example, the finite time Lyapunov exponent reaches local minima if the s line makes a sharp bend. These topological bends hinder the diffusive transport and act as a barrier for diffusive relaxation. Such barriers for diffusion reside inside the chaotic region and they persist even the flow is highly chaotic. In the case of the electron relaxation in a region of stochastic field lines, there is a rapid diffusive relaxation of the spatial inhomogeneity in the electron distribution function which is typical of the chaotic transport of a passive scalar. But the diffusive relaxation of the pitch angle distribution is much slower.
Development and validation of a transition model based on a mechanical approximation
Vizinho, R; Silvestre, M
2015-01-01T23:59:59.000Z
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...
PHYSICAL REVIEW E 85, 061128 (2012) Universal anomalous diffusion of weakly damped particles
Wilkinson, Michael
2012-01-01T23:59:59.000Z
Gothenburg, Sweden (Received 6 March 2012; published 26 June 2012) We show that anomalous diffusion arises. In this paper we describe two physically natural models for the diffusion of a particle that is accelerated- Rosenbluth model for diffusion [7,8], in which a test particle interacts with a gas of point masses via
Logue, J. M.; Turner, W. J.N.; Walker, I. S.; Singer, B. C.
2015-01-01T23:59:59.000Z
Changing the air exchange rate of a home (the sum of the infiltration and mechanical ventilation airflow rates) affects the annual thermal conditioning energy. Large-scale changes to air exchange rates of the housing stock can significantly alter the residential sector's energy consumption. However, the complexity of existing residential energy models is a barrier to the accurate quantification of the impact of policy changes on a state or national level. The Incremental Ventilation Energy (IVE) model developed in this study combines the output of simple air exchange models with a limited set of housing characteristics to estimate the associated change in energy demand of homes. The IVE model was designed specifically to enable modellers to use existing databases of housing characteristics to determine the impact of ventilation policy change on a population scale. The IVE model estimates of energy change when applied to US homes with limited parameterisation are shown to be comparable to the estimates of a well-validated, complex residential energy model.
Reverse-selective diffusion in nanocomposite membranes
Reghan J. Hill
2005-10-27T23:59:59.000Z
The permeability of certain polymer membranes with impenetrable nanoinclusions increases with the particle volume fraction (Merkel et al., Science, 296, 2002). This intriguing observation contradicts even qualitative expectations based on Maxwell's classical theory of conduction/diffusion in composites with homogeneous phases. This letter presents a simple theoretical interpretation based on classical models of diffusion and polymer physics. An essential feature of the theory is a polymer-segment depletion layer at the inclusion-polymer interface. The accompanying increase in free volume leads to a significant increase in the local penetrant diffusivity, which, in turn, increases the bulk permeability while exhibiting reverse selectivity. This model captures the observed dependence of the bulk permeability on the inclusion size and volume fraction, providing a straightforward connection between membrane microstructure and performance.
Logue, Jennifer M.
2014-01-01T23:59:59.000Z
weather files for representative cities within each climatewas modeled in the representative city for each of the sevenclimate zones and representative cities were used: 2A hot/
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...
Dalan, Fabio.
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 ...
A density functional theory model of mechanically activated silyl ester hydrolysis
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
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.
ES2A7 -Fluid Mechanics Example Classes Model Answers to Example Questions (Set II)
Thomas, Peter J.
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
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.
MECHANICAL TEST RESULTS ON DIPOLE MODEL C-l 25 mm ALUMINUM COLLARS
Peters, C.
2010-01-01T23:59:59.000Z
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
Bottom Drag, eddy diffusivity, wind work and the power integrals
Young, William R.
Bottom Drag, eddy diffusivity, wind work and the power integrals Bill Young, Andrew Thompson field i.e., the meridional heat flux is pro Moreover, the mechanical energy balance in a statistical Moreover, the mechanical energy balance in a statistically st Appendix A) is U-2 x = | - 2 |2 + hyp
Collective motion in quantum diffusive environment
V. M. Kolomietz; S. Å berg; S. V. Radionov
2007-06-16T23:59:59.000Z
The general problem of dissipation in macroscopic large-amplitude collective motion and its relation to energy diffusion of intrinsic degrees of freedom of a nucleus is studied. By applying the cranking approach to the nuclear many-body system, a set of coupled dynamical equations for the collective classical variable and the quantum mechanical occupancies of the intrinsic nuclear states is derived. Different dynamical regimes of the intrinsic nuclear motion and its consequences on time properties of collective dissipation are discussed.
Tiwary, C. S., E-mail: cst.iisc@gmail.com; Chattopadhyay, K. [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Chakraborty, S.; Mahapatra, D. R. [Department of Aerospace Engineering, Indian Institute of Science, Bangalore 560012 (India)
2014-05-28T23:59:59.000Z
This paper attempts to gain an understanding of the effect of lamellar length scale on the mechanical properties of two-phase metal-intermetallic eutectic structure. We first develop a molecular dynamics model for the in-situ grown eutectic interface followed by a model of deformation of Al-Al{sub 2}Cu lamellar eutectic. Leveraging the insights obtained from the simulation on the behaviour of dislocations at different length scales of the eutectic, we present and explain the experimental results on Al-Al{sub 2}Cu eutectic with various different lamellar spacing. The physics behind the mechanism is further quantified with help of atomic level energy model for different length scale as well as different strain. An atomic level energy partitioning of the lamellae and the interface regions reveals that the energy of the lamellae core are accumulated more due to dislocations irrespective of the length-scale. Whereas the energy of the interface is accumulated more due to dislocations when the length-scale is smaller, but the trend is reversed when the length-scale is large beyond a critical size of about 80?nm.
Competing mechanisms of chiral symmetry breaking in a generalized Gross-Neveu model
Boehmer, Christian; Thies, Michael [Institut fuer Theoretische Physik III, Universitaet Erlangen-Nuernberg, D-91058 Erlangen (Germany)
2010-05-15T23:59:59.000Z
Chiral symmetry of the 2-dimensional chiral Gross-Neveu model is broken explicitly by a bare mass term as well as a splitting of scalar and pseudoscalar coupling constants. The vacuum and light hadrons--mesons and baryons which become massless in the chiral limit--are explored analytically in leading order of the derivative expansion by means of a double sine-Gordon equation. Depending on the parameters, this model features new phenomena as compared to previously investigated 4-fermion models: spontaneous breaking of parity, a nontrivial chiral vacuum angle, twisted kinklike baryons whose baryon number reflects the vacuum angle, crystals with alternating baryons, and appearance of a false vacuum.
THE DIFFUSION APPROXIMATION FOR THE LINEAR BOLTZMANN EQUATION
THE DIFFUSION APPROXIMATION FOR THE LINEAR BOLTZMANN EQUATION WITH VANISHING SCATTERING COEFFICIENT equation, Diffusion approximation, Neutron transport equation, Radiative transfer equation subject, 23], neutron transport theory [27]. A typical model linear Boltzmann equation is (t +· x)f(t,x,)= 1
Hernelind, J.
2009-01-01T23:59:59.000Z
Time ( day) Measured SKI STUK SKB JAEA (b) Relative humidityROCMAS SKB (Sweden) ABAQUS STUK (Finland) ELMER 2. OUTLINEunit volume. 3.5 The STUK model The numerical calculations
3D Modeling of Coupled Rock Deformation and Thermo-Poro-Mechanical Processes in Fractures
Rawal, Chakra
2012-07-16T23:59:59.000Z
and failure of weak planes of the formation with creation of new fractures, which impacts reservoir response. Incorporation of geomechanical factor into engineering analyses using fully coupled geomechanics-reservoir flow modeling exhibits computational...
NUMERICAL MODELING FOR THE FORMATION MECHANISM OF 3D TOPOGRAPHY ON MICROBIAL MAT SURFACES
Patel, Harsh Jay
2013-09-27T23:59:59.000Z
, an innovative modeling approach was employed that focuses on the interface growth of the microbial mat surfaces using a combined stochastic and deterministic approach. A range of different initial conditions were simulated to evaluate the 3D topography evolution...
Andersohn, Alexander
2013-08-27T23:59:59.000Z
Many mechanicstic models aimed at predicting tissue behavior attempt to connect constitutive factors (such as effects due to collagen or fibrin concentrations) with the overall tissue behavior. Such a link between constitutive and material behaviors...
Derivation of Newton's Law of Gravitation Based on a Fluid Mechanical Singularity Model of Particles
Xiao-Song Wang
2006-10-25T23:59:59.000Z
We speculate that the universe may be filled with a kind of fluid which may be called aether or tao. Thus, Newton's law of gravitation is derived by methods of hydrodynamics based on a sink flow model of particles.
University of California, Berkeley; Lawrence Berkeley National Laboratory; Raymond, Kenneth; Pluth, Michael D.; Tiedemann, Bryan E.F.; van Halbeek, Herman; Nunlist, Rudi; Raymond, Kenneth N.
2007-10-22T23:59:59.000Z
Understanding the solution behavior of supramolecular assemblies is essential for a full understanding of the formation and chemistry of synthetic host-guest systems. While the interaction between host and guest molecules is generally the focus of mechanistic studies of host-guest complexes, the interaction of the host-guest complex with other species in solution remains largely unknown, although in principle accessible by diffusion studies. Several NMR techniques are available to monitor diffusion and have recently been reviewed. Pulsed gradient spin-echo (PGSE) NMR methods have attracted increasing interest, since they allow diffusion coefficients to be measured with high accuracy; they have been successfully used with observation of {sup 7}Li and {sup 31}P nuclei as well as with {sup 1}H NMR. We report here the direct measurement of diffusion coefficients to observe ion-association interactions by counter cations with a highly-charged supramolecular assembly. Raymond and coworkers have described the design and chemistry of a class of metal-ligand supramolecular assemblies over the past decade. The [Ga{sub 4}L{sub 6}]{sup 12-} (L = 1,5-bis(2,3-dihydroxybenzamido)naphthalene) (1) (Figure 1) assembly has garnered the most attention, with the exploration of the dynamics and mechanism of guest exchange as well as the ability of 1 to achieve either stoichiometric or catalytic reactions inside its interior cavity. Recent studies have revealed the importance of counter cations in solution on the chemistry of 1. During the mechanistic study of the C-H bond activation of aldehydes by [Cp*Ir(PMe{sub 3})(olefin){sup +} {contained_in} 1]{sup 11-} a stepwise guest dissociation mechanism with an ion-paired intermediate was proposed. Similarly, in the mechanism for the hydrolysis of iminium cations generated from the 3-aza Cope rearrangement of enammonium cations in 1, the presence of an exterior ion association was part of the kinetic model. To further substantiate the indirect kinetic evidence for such ion-paired species, we sought to explore the solution behavior of 1 by studying the diffusion of 1 with varying alkali and tetraalkyl ammonium cations. For large molecules in solution, such as synthetic supramolecular assemblies, the diffusion behavior of host and guest molecules can provide valuable information on host-guest interaction. One characteristic feature of a stable host-guest complex is that the host and guest molecules diffuse at the same rate in solution; this has been observed in a number of supramolecular systems. In order to confirm that this system was suitable for study by diffusion NMR spectroscopy, a PGSE-DOSY spectrum was acquired of [NEt{sub 4} {contained_in} 1]{sup 11-} (Figure 2), which shows that the host and guest molecules diffuse at the same rate. Quantitative analysis of the data, from monitoring the integral of host and guest resonances as a function of applied gradient strength, gave identical diffusion coefficients, confirming that the host and guest molecules diffuse together.
Mathematical analysis for fractional diffusion equations: forward
Boyer, Franck
or dumping WasteGroundwater flow Base rock Underground storage Soil gapsmicro scale about 100m Field: macro-Diffusion equation Result of Field Test (Adams& Gelhar, 1992) t0 t1 t2 t3 t0 Pollution source Model Prediction Univ. #12;· Determination of contamination source t u = u + F We need detailed mathematical researches
Particle-scale CO2 adsorption kinetics modeling considering three reaction mechanisms
Suh, Dong-Myung; Sun, Xin
2013-09-01T23:59:59.000Z
In the presence of water (H2O), dry and wet adsorptions of carbon dioxide (CO2) and physical adsorption of H2O happen concurrently in a sorbent particle. The three reactions depend on each other and have a complicated, but important, effect on CO2 capturing via a solid sorbent. In this study, transport phenomena in the sorbent were modeled, including the tree reactions, and a numerical solving procedure for the model also was explained. The reaction variable distribution in the sorbent and their average values were calculated, and simulation results were compared with experimental data to validate the proposed model. Some differences, caused by thermodynamic parameters, were observed between them. However, the developed model reasonably simulated the adsorption behaviors of a sorbent. The weight gained by each adsorbed species, CO2 and H2O, is difficult to determine experimentally. It is known that more CO2 can be captured in the presence of water. Still, it is not yet known quantitatively how much more CO2 the sorbent can capture, nor is it known how much dry and wet adsorptions separately account for CO2 capture. This study addresses those questions by modeling CO2 adsorption in a particle and simulating the adsorption process using the model. As adsorption temperature changed into several values, the adsorbed amount of each species was calculated. The captured CO2 in the sorbent particle was compared quantitatively between dry and wet conditions. As the adsorption temperature decreased, wet adsorption increased. However, dry adsorption was reduced.
COSMIC-RAY DIFFUSION IN A SECTORED MAGNETIC FIELD IN THE DISTANT HELIOSHEATH
Florinski, V. [Department of Physics, University of Alabama, Huntsville, AL 35899 (United States); Alouani-Bibi, F.; Guo, X. [Center for Space Plasma and Aeronomic Research, University of Alabama, Huntsville, AL 35899 (United States); Kota, J. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States)
2012-07-20T23:59:59.000Z
Very high intensities of galactic cosmic rays measured by Voyager 1 in the heliosheath appear to be incompatible with the presence of a modulation 'wall' near the heliopause produced by a pile up of the heliospheric magnetic field. We propose that the modulation wall is a structure permeable to cosmic rays as a result of a sectored magnetic field topology compressed by plasma slowdown on approach to the heliopause and stretched to high latitudes by latitudinal flows in the heliosheath. The tightly folded warped current sheet permits efficient cosmic-ray transport in the radial direction via a drift-like mechanism. We show that when stochastic variations in the sector widths are taken into account, particle transport becomes predominantly diffusive both along and across the magnetic sectors. Using a test-particle model for cosmic rays in the heliosheath we investigate the dependence of the diffusion coefficients on the properties of the sector structure and on particle energy.
L\\'evy Fluctuations and Tracer Diffusion in Dilute Suspensions of Algae and Bacteria
Zaid, Irwin M; Yeomans, Julia M
2010-01-01T23:59:59.000Z
Swimming microorganisms rely on effective mixing strategies to achieve efficient nutrient influx. Recent experiments, probing the mixing capability of unicellular biflagellates, revealed that passive tracer particles exhibit anomalous non-Gaussian diffusion when immersed in a dilute suspension of self-motile Chlamydomonas reinhardtii algae. Qualitatively, this observation can be explained by the fact that the algae induce a fluid flow that may occasionally accelerate the colloidal tracers to relatively large velocities. A satisfactory quantitative theory of enhanced mixing in dilute active suspensions, however, is lacking at present. In particular, it is unclear how non-Gaussian signatures in the tracers' position distribution are linked to the self-propulsion mechanism of a microorganism. Here, we develop a systematic theoretical description of anomalous tracer diffusion in active suspensions, based on a simplified tracer-swimmer interaction model that captures the typical distance scaling of a microswimmer'...
Central engines of Gamma Ray Bursts. Magnetic mechanism in the collapsar model
Maxim V. Barkov; Serguei S. Komissarov
2008-09-08T23:59:59.000Z
In this study we explore the magnetic mechanism of hypernovae and relativistic jets of long duration gamma ray bursts within the collapsar scenario. This is an extension of our earlier work [1]. We track the collapse of massive rotating stars onto a rotating central black hole using axisymmetric general relativistic magnetohydrodynamic code that utilizes a realistic equation of state and takes into account the cooling associated with emission of neutrinos and the energy losses due to dissociation of nuclei. The neutrino heating is not included. We describe solutions with different black hole rotation, mass accretion rate, and strength of progenitor's magnetic field. Some of them exhibits strong explosions driven by Poynting-dominated jets with power up to $12\\times10^{51} {erg s}^{-1}$. These jets originate from the black hole and powered via the Blandford-Znajek mechanism. A provisional criterion for explosion is derived. A number of simulation movies can be downloaded from http://www.maths.leeds.ac.uk/~serguei/research/movies/anim.html
Harris, D.O.; Lim, E.Y.; Dedhia, D.D.; Woo, H.H.; Chou, C.K.
1982-06-01T23:59:59.000Z
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.
Skinner, F. K. [Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto Western Hospital, 60 Leonard Street, 7th floor, 7KD411, Toronto, Ontario M5T 2S8 (Canada) [Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto Western Hospital, 60 Leonard Street, 7th floor, 7KD411, Toronto, Ontario M5T 2S8 (Canada); Department of Medicine (Neurology), University of Toronto, 200 Elizabeth Street, Toronto, Ontario M5G 2C4 (Canada); Department of Physiology, University of Toronto Medical Sciences Building, 3rd Floor, 1 King's College Circle, Toronto, Ontario M5S 1A8 (Canada); Ferguson, K. A. [Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto Western Hospital, 60 Leonard Street, 7th floor, 7KD411, Toronto, Ontario M5T 2S8 (Canada) [Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto Western Hospital, 60 Leonard Street, 7th floor, 7KD411, Toronto, Ontario M5T 2S8 (Canada); Department of Physiology, University of Toronto Medical Sciences Building, 3rd Floor, 1 King's College Circle, Toronto, Ontario M5S 1A8 (Canada)
2013-12-15T23:59:59.000Z
There is an undisputed need and requirement for theoretical and computational studies in Neuroscience today. Furthermore, it is clear that oscillatory dynamical output from brain networks is representative of various behavioural states, and it is becoming clear that one could consider these outputs as measures of normal and pathological brain states. Although mathematical modeling of oscillatory dynamics in the context of neurological disease exists, it is a highly challenging endeavour because of the many levels of organization in the nervous system. This challenge is coupled with the increasing knowledge of cellular specificity and network dysfunction that is associated with disease. Recently, whole hippocampus in vitro preparations from control animals have been shown to spontaneously express oscillatory activities. In addition, when using preparations derived from animal models of disease, these activities show particular alterations. These preparations present an opportunity to address challenges involved with using models to gain insight because of easier access to simultaneous cellular and network measurements, and pharmacological modulations. We propose that by developing and using models with direct links to experiment at multiple levels, which at least include cellular and microcircuit, a cycling can be set up and used to help us determine critical mechanisms underlying neurological disease. We illustrate our proposal using our previously developed inhibitory network models in the context of these whole hippocampus preparations and show the importance of having direct links at multiple levels.
Welch, Stephen; Miles, Steward; Kumar, Suresh; Lemaire, Tony; Chan, Alan
A hierarchy of coupling strategies for integrating advanced three-dimensional modelling methodologies for prediction of the thermo-mechanical response of structures in fire has been developed and systematically assessed. ...
Knott, Michael [Department of Chemistry, Cambridge University, Lensfield Road, Cambridge CB2 1EW (United Kingdom)] [Department of Chemistry, Cambridge University, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Best, Robert B., E-mail: robertbe@helix.nih.gov [Department of Chemistry, Cambridge University, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)
2014-05-07T23:59:59.000Z
Many proteins undergo a conformational transition upon binding to their cognate binding partner, with intrinsically disordered proteins (IDPs) providing an extreme example in which a folding transition occurs. However, it is often not clear whether this occurs via an “induced fit” or “conformational selection” mechanism, or via some intermediate scenario. In the first case, transient encounters with the binding partner favour transitions to the bound structure before the two proteins dissociate, while in the second the bound structure must be selected from a subset of unbound structures which are in the correct state for binding, because transient encounters of the incorrect conformation with the binding partner are most likely to result in dissociation. A particularly interesting situation involves those intrinsically disordered proteins which can bind to different binding partners in different conformations. We have devised a multi-state coarse-grained simulation model which is able to capture the binding of IDPs in alternate conformations, and by applying it to the binding of nuclear coactivator binding domain (NCBD) to either ACTR or IRF-3 we are able to determine the binding mechanism. By all measures, the binding of NCBD to either binding partner appears to occur via an induced fit mechanism. Nonetheless, we also show how a scenario closer to conformational selection could arise by choosing an alternative non-binding structure for NCBD.
OXYGEN DIFFUSION IN HYPOSTOICHIOMETRIC URANIUM DIOXIDE
Kim, Kee Chul
2010-01-01T23:59:59.000Z
Research Division OXYGEN DIFFUSION IN HYPOSTOICHIOMETRIC11905 -DISCLAIMER - OXYGEN DIFFUSION IN HYPOSTOICHIOMETRICc o n e e n i g woroxygen self-diffusion coefficient
Mass fluctuations and diffusion in time-dependent random environments
Giorgio Krstulovic; Rehab Bitane; Jeremie Bec
2012-03-27T23:59:59.000Z
A mass ejection model in a time-dependent random environment with both temporal and spatial correlations is introduced. When the environment has a finite correlation length, individual particle trajectories are found to diffuse at large times with a displacement distribution that approaches a Gaussian. The collective dynamics of diffusing particles reaches a statistically stationary state, which is characterized in terms of a fluctuating mass density field. The probability distribution of density is studied numerically for both smooth and non-smooth scale-invariant random environments. A competition between trapping in the regions where the ejection rate of the environment vanishes and mixing due to its temporal dependence leads to large fluctuations of mass. These mechanisms are found to result in the presence of intermediate power-law tails in the probability distribution of the mass density. For spatially differentiable environments, the exponent of the right tail is shown to be universal and equal to -3/2. However, at small values, it is found to depend on the environment. Finally, spatial scaling properties of the mass distribution are investigated. The distribution of the coarse-grained density is shown to posses some rescaling properties that depend on the scale, the amplitude of the ejection rate, and the H\\"older exponent of the environment.
Persistent energy flow for a stochastic wave equation model in nonequilibrium statistical mechanics
Lawrence E. Thomas
2012-04-29T23:59:59.000Z
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.
Barker, Erin I.; Choi, Kyoo Sil; Sun, Xin; Deda, Erin; Allison, John; Li, Mei; Forsmark, Joy; Zindel, Jacob; Godlewski, Larry
2014-09-30T23:59:59.000Z
Magnesium alloys have become popular alternatives to aluminums and steels for the purpose of vehicle light-weighting. However, Mg alloys are hindered from wider application due to limited ductility as well as poor creep and corrosion performance. Understanding the impact of microstructural features on bulk response is key to improving Mg alloys for more widespread use and for moving towards truly predicting modeling capabilities. This study focuses on modeling the intrinsic features, particularly volume fraction and morphology of beta phase present, of cast Mg alloy microstructure and quantifying their impact on bulk performance. Computational results are compared to experimental measurements of cast plates of Mg alloy with varying aluminum content.
A quantum mechanical model for the relationship between stock price and stock ownership
Liviu-Adrian Cotfas
2012-09-05T23:59:59.000Z
The trade of a fixed stock can be regarded as the basic process that measures its momentary price. The stock price is exactly known only at the time of sale when the stock is between traders, that is, only in the case when the owner is unknown. We show that the stock price can be better described by a function indicating at any moment of time the probabilities for the possible values of price if a transaction takes place. This more general description contains partial information on the stock price, but it also contains partial information on the stock owner. By following the analogy with quantum mechanics, we assume that the time evolution of the function describing the stock price can be described by a Schrodinger type equation.
Melanin, a promising radioprotector: Mechanisms of actions in a mice model
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
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.
Chen, Reuven
, Denmark c Nordic Laboratory for Luminescence Dating, Department of Earth Science, Aarhus University, RisÃ¸ luminescence Pulsed OSL Thermoluminescence Quartz Luminescence lifetimes Kinetic rate equations Kinetic model temperature is raised, and has been observed in both thermo- luminescence (TL) and optically stimulated
Physiologically realistic modelling of a mechanism for neural representation of intervals of time
Fukai, Tomoki
-8610, Japan c CREST, Japan Science and Technology (JST), Saitama 332-0012, Japan Abstract A model, Fuji Xerox Co. Ltd., 430 Sakai, Nakai-machi, Ashigarakami-gun, Kanagawa 259-0157, Japan b Department as well as the difference stated above, will lead us to the idea that an interval of time, T
Multi-Configuration Model Tuning for Precision Opto-Mechanical Systems
on a testbed at the MIT Space Systems Lab (SSL) in order to gauge its usefulness. The traditional model tuning will be performed by a colleague in the SSL who will use such methods as trial-and- error parameter updating comments. Thanks to the DOCS team at MIT's SSL, esp
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.
Electro-diffusion in a plasma with two ion species
Kagan, Grigory; Tang Xianzhu [Theoretical Division Los Alamos National Laboratory Los Alamos, New Mexico 87545 (United States)
2012-08-15T23:59:59.000Z
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.
Kelkar, Sharad [Los Alamos National Laboratory
2011-01-01T23:59:59.000Z
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.
Nguyen, Ba Nghiep; Kunc, Vlastimil; Jin, Xiaoshi; Tucker III, Charles L.; Costa, Franco
2013-12-18T23:59:59.000Z
This article illustrates the predictive capabilities for long-fiber thermoplastic (LFT) composites that first simulate the injection molding of LFT structures by Autodesk® Simulation Moldflow® Insight (ASMI) to accurately predict fiber orientation and length distributions in these structures. After validating fiber orientation and length predictions against the experimental data, the predicted results are used by ASMI to compute distributions of elastic properties in the molded structures. In addition, local stress-strain responses and damage accumulation under tensile loading are predicted by an elastic-plastic damage model of EMTA-NLA, a nonlinear analysis tool implemented in ABAQUS® via user-subroutines using an incremental Eshelby-Mori-Tanaka approach. Predicted stress-strain responses up to failure and damage accumulations are compared to the experimental results to validate the model.
Nd3+ ion diffusion during sintering of Nd:YAG transparent ceramics
Hollingsworth, J P; Kuntz, J D; Soules, T F
2008-10-24T23:59:59.000Z
Using an electron microprobe, we measured and characterized the Nd{sup 3+} ion diffusion across a boundary between Nd doped and undoped ceramic yttrium aluminum garnet (YAG) for different temperature ramps and hold times and temperatures. The results show significant Nd ion diffusion on the order of micrometers to tens of micrometers depending on the time and temperature of sintering. The data fit well a model including bulk diffusion, grain boundary diffusion and grain growth. Grain boundary diffusion dominates and grain growth limits grain boundary diffusion by reducing the total cross sectional area of grain boundaries.
Diffusion-controlled generation of a proton-motive force across a biomembrane
Anatoly Yu. Smirnov; Sergey E. Savel'ev; Franco Nori
2009-12-04T23:59:59.000Z
Respiration in bacteria involves a sequence of energetically-coupled electron and proton transfers creating an electrochemical gradient of protons (a proton-motive force) across the inner bacterial membrane. With a simple kinetic model we analyze a redox loop mechanism of proton-motive force generation mediated by a molecular shuttle diffusing inside the membrane. This model, which includes six electron-binding and two proton-binding sites, reflects the main features of nitrate respiration in E. coli bacteria. We describe the time evolution of the proton translocation process. We find that the electron-proton electrostatic coupling on the shuttle plays a significant role in the process of energy conversion between electron and proton components. We determine the conditions where the redox loop mechanism is able to translocate protons against the transmembrane voltage gradient above 200 mV with a thermodynamic efficiency of about 37%, in the physiologically important range of temperatures from 250 to 350 K.
Oterkus, Selda [Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ 85721 (United States); Madenci, Erdogan, E-mail: madenci@email.arizona.edu [Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ 85721 (United States); Agwai, Abigail [Intel Corporation, Chandler, AZ 85226 (United States)
2014-05-15T23:59:59.000Z
This study presents the derivation of ordinary state-based peridynamic heat conduction equation based on the Lagrangian formalism. The peridynamic heat conduction parameters are related to those of the classical theory. An explicit time stepping scheme is adopted for numerical solution of various benchmark problems with known solutions. It paves the way for applying the peridynamic theory to other physical fields such as neutronic diffusion and electrical potential distribution.
International diffusion practice : lessons from South Korea's New Village Movement
Kim, Jung Hwa, M.C.P. Massachusetts Institute of Technology
2013-01-01T23:59:59.000Z
This research focuses on how South Korea's development model-namely, the Saemaul Undong, or the New Village Movement-is diffused internationally, in particular, to the developing country of Vietnam. South Korea's successful ...
Diffusion driven object propulsion in density stratified fluids
Lenahan, Conor (Conor P.)
2009-01-01T23:59:59.000Z
An experimental study was conducted in order to verify the appropriateness of a two dimensional model of the flow creating diffusion driven object propulsion in density stratified fluids. Initial flow field experiments ...
Salloum, Maher N.; Shugard, Andrew D.; Kanouff, Michael P.; Gharagozloo, Patricia E.
2013-03-01T23:59:59.000Z
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.
Modeling Regional Air Quality Using the Near-Explicit Master Chemical Mechanism
Li, Jingyi
2014-08-01T23:59:59.000Z
C. ................................................................................................................. 32 Figure 2-6 Pollutant rose for isopentane at C35C. Panels (a)-(c) are based on the data where the predicted wind direction and wind speed agree well with observations. Panels (d)-(f) are based on the remaining data. Units are ppb... during the entire episode. Model performance criteria and goals for particulate matter are based on the recommendations of Boylan and Russell (2006). MFB=2/N×?(Cp-Co)/(Cp+Co). Cp=predictions; Co=observations; N=number of data points. (b) Predicted...
Class of model problems in three-body quantum mechanics that admit exact solutions
Takibayev, N. Zh., E-mail: teta@nursat.kz [Abay Kazakh National Pedagogical University (Kazakhstan)
2008-03-15T23:59:59.000Z
An approach to solving scattering problems in three-body systems for cases where the mass of one of the particles is extremely small in relation to the masses of the other two particles and where the pair potentials of interaction between the particles involved are separable is developed. Exact analytic solutions to such model problems are found for the scattering of a light particle on two fixed centers and on two interacting heavy particles. It is shown that new resonances and a dynamical resonance enhancement may appear in a three-body system.
Causal Baryon Diffusion and Colored Noise
J. I. Kapusta; C. Young
2014-04-18T23:59:59.000Z
We construct a model of baryon diffusion which has the desired properties of causality and analyticity. The model also has the desired property of colored noise, meaning that the noise correlation function is not a Dirac delta function in space and time; rather, it depends on multiple time and length constants. The model can readily be incorporated in 3+1 dimensional second order viscous hydro-dynamical models of heavy ion collisions, which is particularly important at beam energies where the baryon density is large.
Diffusion limited reactions in confined environments
Jeremy D. Schmit; Ercan Kamber; Jané Kondev
2007-11-19T23:59:59.000Z
We study the effect of confinement on diffusion limited bimolecular reactions within a lattice model where a small number of reactants diffuse amongst a much larger number of inert particles. When the number of inert particles is held constant the rate of the reaction is slow for small reaction volumes due to limited mobility from crowding, and for large reaction volumes due to the reduced concentration of the reactants. The reaction rate proceeds fastest at an intermediate confinement corresponding to volume fraction near 1/2 and 1/3 in two and three dimensions, respectively. We generalize the model to off-lattice systems with hydrodynamic coupling and predict that the optimal reaction rate for monodisperse colloidal systems occurs when the volume fraction is ~0.18. Finally, we discuss the application of our model to bimolecular reactions inside cells as well as the dynamics of confined polymers.
Bounds on charge and heat diffusivities in momentum dissipating holography
Andrea Amoretti; Alessandro Braggio; Nicodemo Magnoli; Daniele Musso
2015-06-17T23:59:59.000Z
Inspired by a recently conjectured universal bound for thermo-electric diffusion constants in quantum critical, strongly coupled systems and relying on holographic analytical computations, we investigate the possibility of formulating Planckian bounds in different holographic models featuring momentum dissipation. For a simple massive gravity dilaton model at zero charge density we find robust linear in temperature resistivity and entropy density alongside a constant electric susceptibility. In addition we explicitly find that the sum of the thermo-electric diffusion constants is bounded.
Zhai, Yuhu
2013-07-16T23:59:59.000Z
The United States ITER Project Office (USIPO) is responsible for design of the Toroidal Field (TF) insert coil, which will allow validation of the performance of significant lengths of the conductors to be used in the full scale TF coils in relevant conditions of field, current density and mechanical strain. The Japan Atomic Energy Agency (JAEA) will build the TF insert which will be tested at the Central Solenoid Model Coil (CSMC) Test facility at JAEA, Naka, Japan. Three dimensional mathematical model of TF Insert was created based on the initial design geometry data, and included the following features: orthotropic material properties of superconductor material and insulation; external magnetic field from CSMC, temperature dependent properties of the materials; pre-compression and plastic deformation in lap joint. Major geometrical characteristics of the design were preserved including cable jacket and insulation shape, mandrel outline, and support clamps and spacers. The model is capable of performing coupled structural, thermal, and electromagnetic analysis using ANSYS. Numerical simulations were performed for room temperature conditions; cool down to 4K, and the operating regime with 68kA current at 11.8 Tesla background field. Numerical simulations led to the final design of the coil producing the required strain levels on the cable, while simultaneously satisfying the ITER magnet structural design criteria.
Benioff, P.
1980-01-01T23:59:59.000Z
A microscopic quantum mechanical model of computers as represented by Turing machines is constructed. It is shown that for each number N and Turing machine Q there exists a Hamiltonian H/sub N//sup Q/ and a class of appropriate initial states such that, if PSI/sub Q//sup N/(0) is such an initial state, then PSI/sub Q//sup N/(t) = exp(-iH/sub N//sup Q/t) PSI/sub Q//sup N/(0) correctly describes at times t/sub 3/, t/sub 6/,..., t/sub 3N/ model states that correspond to the completion of the first, second,..., Nth computation step of Q. The model parameters can be adjusted so that for an arbitrary time interval ..delta.. around t/sub 3/, t/sub 6/,..., t/sub 3N/, the machine part of PSI/sub Q//sup N/(t) is stationary. 1 figure.
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
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.
Robert Podgorney; Chuan Lu; Hai Huang
2012-01-01T23:59:59.000Z
Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing), to create the reservoir. The advancement of EGS greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid-heat system and our ability to reliably predict how reservoirs behave under stimulation and production. Reliable performance predictions of EGS reservoirs require accurate and robust modeling for strongly coupled thermal-hydrological-mechanical (THM) processes. Conventionally, these types of problems have been solved using operator-splitting methods, usually by coupling a subsurface flow and heat transport simulators with a solid mechanics simulator via input files. An alternative approach is to solve the system of nonlinear partial differential equations that govern multiphase fluid flow, heat transport, and rock mechanics simultaneously, using a fully coupled, fully implicit solution procedure, in which all solution variables (pressure, enthalpy, and rock displacement fields) are solved simultaneously. This paper describes numerical simulations used to investigate the poro- and thermal- elastic effects of working fluid injection and thermal energy extraction on the properties of the fractures and rock matrix of a hypothetical EGS reservoir, using a novel simulation software FALCON (Podgorney et al., 2011), a finite element based simulator solving fully coupled multiphase fluid flow, heat transport, rock deformation, and fracturing using a global implicit approach. Investigations are also conducted on how these poro- and thermal-elastic effects are related to fracture permeability evolution.
California at Riverside, University of
A novel mechanism and kinetic model to explain enhanced xylose yields from dilute sulfuric acid stover Dilute sulfuric acid Hydrothermal pretreatment Kinetic model Xylose a b s t r a c t Pretreatment of corn stover in 0.5% sulfuric acid at 160 Â°C for 40 min realized a maximum monomeric plus oligomeric
Paris-Sud XI, Université de
Impact of drainage on soil-forming mechanisms in a French Albeluvisol: Input of mineralogical data. This was considered as a model case to study the velocity of mineralogical changes in soil as a result of eluviation modelling based on mineralogical data in order to identify and characterise the mineralogical
Rodriguez, David
2011-01-01T23:59:59.000Z
Experimental tests of Bell inequalities often require supplementary assumptions, one of the usual ones being the "no-enhancement" assumption. Here we show how an already well known Local Hidden Variables (LHV) model for the Clauser-Horne-Shimony-Holt inequality, when extended to account for the probabilities of detection when the polarizers are removed (such as how it would need to be done in a test of the Clauser-Horne inequality), gives rise, as the most natural feature, to the so-called "enhancement" (breaking of the no-enhancement assumption formulated by Clauser and Horne themselves for the operational expression of their inequality). Aside from exposing that key role of enhancement, our work is useful (at least in our case it has been) to gain understanding on some other known results. We also add some comments that we think may be thought-provoking.
Buyukdagli, Sahin; 10.1016/j.cplett.2009.11.061
2010-01-01T23:59:59.000Z
In this Letter, we investigate the link between thermal denaturation and mechanical unzipping for two models of DNA, namely the Dauxois-Peyrard-Bishop model and a variant thereof we proposed recently. We show that the critical line that separates zipped from unzipped DNA sequences in mechanical unzipping experiments is a power-law in the temperature-force plane. We also prove that for the investigated models the corresponding critical exponent is proportional to the critical exponent alpha, which characterizes the behaviour of the specific heat in the neighbourhood of the critical temperature for thermal denaturation.
State protection under collective damping and diffusion
Ponte, M. A. de [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 369, 13560-590 Sao Carlos, SP (Brazil); Departamento de Fisica, Universidade Regional do Cariri, 63010-970 Juazeiro do Norte, CE (Brazil); Mizrahi, S. S. [Departamento de Fisica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil); Moussa, M. H. Y. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 369, 13560-590 Sao Carlos, SP (Brazil)
2011-07-15T23:59:59.000Z
In this paper we provide a recipe for state protection in a network of oscillators under collective damping and diffusion. Our strategy is to manipulate the network topology, i.e., the way the oscillators are coupled together, the strength of their couplings, and their natural frequencies, in order to create a relaxation-diffusion-free channel. This protected channel defines a decoherence-free subspace (DFS) for nonzero-temperature reservoirs. Our development also furnishes an alternative approach to build up DFSs that offers two advantages over the conventional method: it enables the derivation of all the network-protected states at once, and also reveals, through the network normal modes, the mechanism behind the emergence of these protected domains.
Goudreau, G.L.
1993-03-01T23:59:59.000Z
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.
Karl Svozil
2001-06-29T23:59:59.000Z
Three extensions and reinterpretations of nonclassical probabilities are reviewed. (i) We propose to generalize the probability axiom of quantum mechanics to self-adjoint positive operators of trace one. Furthermore, we discuss the Cartesian and polar decomposition of arbitrary normal operators and the possibility to operationalize the corresponding observables. Thereby we review and emphasize the use of observables which maximally represent the context. (ii) In the second part, we discuss Pitowsky polytopes for automaton logic as well as for generalized urn models and evaluate methods to find the resulting Boole-Bell type (in)equalities. (iii) Finally, so-called ``parameter cheats'' are introduced, whereby parameters are transformed bijectively and nonlinearly in such a way that classical systems mimic quantum correlations and vice versa. It is even possible to introduce parameter cheats which violate the Boole-Bell type inequalities stronger than quantum ones, thereby trespassing the Tsirelson limit. The price to be paid is nonuniformity.
Development Status of the PEBBLES Code for Pebble Mechanics: Improved Physical Models and Speed-up
Joshua J. Cogliati; Abderrafi M. Ougouag
2009-12-01T23:59:59.000Z
PEBBLES is a code for simulating the motion of all the pebbles in a pebble bed reactor. Since pebble bed reactors are packed randomly and not precisely placed, the location of the fuel elements in the reactor is not deterministically known. Instead, when determining operating parameters the motion of the pebbles can be simulated and stochastic locations can be found. The PEBBLES code can output information relevant for other simulations of the pebble bed reactors such as the positions of the pebbles in the reactor, packing fraction change in an earthquake, and velocity profiles created by recirculation. The goal for this level three milestone was to speedup the PEBBLES code through implementation on massively parallel computer. Work on this goal has resulted in speeding up both the single processor version and creation of a new parallel version of PEBBLES. Both the single processor version and the parallel running capability of the PEBBLES code have improved since the fiscal year start. The hybrid MPI/OpenMP PEBBLES version was created this year to run on the increasingly common cluster hardware profile that combines nodes with multiple processors that share memory and a cluster of nodes that are networked together. The OpenMP portions use the Open Multi-Processing shared memory parallel processing model to split the task across processors in a single node that shares memory. The Message Passing Interface (MPI) portion uses messages to communicate between different nodes over a network. The following are wall clock speed up for simulating an NGNP-600 sized reactor. The single processor version runs 1.5 times faster compared to the single processor version at the beginning of the fiscal year. This speedup is primarily due to the improved static friction model described in the report. When running on 64 processors, the new MPI/OpenMP hybrid version has a wall clock speed up of 22 times compared to the current single processor version. When using 88 processors, a speed up of 23 times is achieved. This speedup and other improvements of PEBBLES combine to make PEBBLES more capable and more useful for simulation of a pebble bed reactor. This report details the implementation and effects of the speedup work done over the course of the fiscal year.
Falsification of dark energy by fluid mechanics
Gibson, Carl H
2012-01-01T23:59:59.000Z
The 2011 Nobel Prize in Physics was awarded for the discovery of accelerating supernovae dimness, suggesting a remarkable change in the expansion rate of the Universe from a decrease since the big bang to an increase, driven by anti-gravity forces of a mysterious dark energy material comprising 70% of the Universe mass-energy. Fluid mechanical considerations falsify both the accelerating expansion and dark energy concepts. Kinematic viscosity is neglected in current standard models of self-gravitational structure formation, which rely on cold dark matter CDM condensations and clusterings that are also falsified by fluid mechanics. Weakly collisional CDM particles do not condense but diffuse away. Photon viscosity predicts superclustervoid fragmentation early in the plasma epoch and protogalaxies at the end. At the plasma-gas transition, the plasma fragments into Earth-mass gas planets in trillion planet clumps (proto-globular-star-cluster PGCs). The hydrogen planets freeze to form the dark matter of galaxies ...
Modeling mechanical properties of core-shell rubber-modified epoxies
Wang, X.; Xiao, K.; Ye, L.; Mai, Y.W.; Wang, C.H.; Rose, L.R.F.
2000-01-24T23:59:59.000Z
Experiments have been carried out to quantify the effects of rubber content and strain rate on the elastic and plastic deformation behavior of core-shell rubber-modified epoxies. Both the Young's modulus and the yield stress were found to be slightly dependent on strain rate, but very sensitive to the volume fraction of rubber particles. Finite element analyses have also been performed to determine the influences of rubber content on the bulk elasticity modulus and the yield stress. By comparing with experimental results, it is found that the Young's modulus of rubber-toughened epoxies can be accurately estimated using the Mori-Tanaka method, provided that the volume fraction of rubber particles is appropriately evaluated. A yield function is provided that the volume fraction of rubber particles is appropriately evaluated. A yield function is proposed to quantify the effects of hydrostatic stress on the plastic yielding behaviors of rubber-modified epoxies. Agreement with experimental results is good. Also, a visco-plastic model is developed to simulate the strain-rate-dependent stress-strain relations.
Reduction of phosphorus diffusion in germanium by fluorine implantation
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
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.
Bo Jakobsen; Kristine Niss; Claudio Maggi; Niels Boye Olsen; Tage Christensen; Jeppe C. Dyre
2010-05-26T23:59:59.000Z
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.
E-Print Network 3.0 - advective-diffusive heat transfer Sample...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
The Likelihood of Rapid Climate PI Peter Challenor (SOC) Summary: Balance Model - 2-D sea ice: thermodynamics, advection, diffusion 12; Realistic world geometry on a 36x... ,...
Predictive modelling of boiler fouling
Not Available
1992-01-01T23:59:59.000Z
In this reporting period, efforts were initiated to supplement the comprehensive flow field description obtained from the RNG-Spectral Element Simulations by incorporating, in a general framework, appropriate modules to model particle and condensable species transport to the surface. Specifically, a brief survey of the literature revealed the following possible mechanisms for transporting different ash constituents from the host gas to boiler tubes as deserving prominence in building the overall comprehensive model: (1) Flame-volatilized species, chiefly sulfates, are deposited on cooled boiler tubes via the mechanism of classical vapor diffusion. This mechanism is more efficient than the particulate ash deposition, and as a result there is usually an enrichment of condensable salts, chiefly sulfates, in boiler deposits; (2) Particle diffusion (Brownian motion) may account for deposition of some fine particles below 0. 1 mm in diameter in comparison with the mechanism of vapor diffusion and particle depositions, however, the amount of material transported to the tubes via this route is probably small. (3) Eddy diffusion, thermophoretic and electrophoretic deposition mechanisms are likely to have a marked influence in transporting 0.1 to 5[mu]m particles from the host gas to cooled boiler tubes; (4) Inertial impaction is the dominant mechanism in transporting particles above 5[mu]m in diameter to water and steam tubes in pulverized coal fired boiler, where the typical flue gas velocity is between 10 to 25 m/s. Particles above 10[mu]m usually have kinetic energies in excess of what can be dissipated at impact (in the absence of molten sulfate or viscous slag deposit), resulting in their entrainment in the host gas.
Microviscometric studies on thermal diffusion
Reyna, Eddie
1959-01-01T23:59:59.000Z
for its improvement. This in~estigation was supported in part by the Convsir Division of General Dynamics Corporation. TABLE OF CONTENTS Chapter III INTRODUCTION EXPERINENTAL NETHODS AND PROCEDUPJIS Thermal Diffusion Column Viscosity Measurements.... The main interest of 6 tais work was the molecular weight dependence of the thermal diffusion coefficient and the suitability of thermal diffusion as a method of frac- tionation of polymers. Since the work of Debye and Bueche, applications of thermal...
Sahay, Sundeep
SME-Entrepreneurship Global Conference 2006 - Refereed Paper Bakke et al.: ICT diffusion and usage factors, infrastructures and post-adoption behaviour Paper for the conference: "SME Entrepreneurship. Keywords: Diffusion models, infrastructure, domestication, small and medium sized enterprises, SME, ICT
Ian Robertson
2007-04-28T23:59:59.000Z
Development and validation of constitutive models for polycrystalline materials subjected to high strain-rate loading over a range of temperatures are needed to predict the response of engineering materials to in-service type conditions. To account accurately for the complex effects that can occur during extreme and variable loading conditions, requires significant and detailed computational and modeling efforts. These efforts must be integrated fully with precise and targeted experimental measurements that not only verify the predictions of the models, but also provide input about the fundamental processes responsible for the macroscopic response. Achieving this coupling between modeling and experiment is the guiding principle of this program. Specifically, this program seeks to bridge the length scale between discrete dislocation interactions with grain boundaries and continuum models for polycrystalline plasticity. Achieving this goal requires incorporating these complex dislocation-interface interactions into the well-defined behavior of single crystals. Despite the widespread study of metal plasticity, this aspect is not well understood for simple loading conditions, let alone extreme ones. Our experimental approach includes determining the high-strain rate response as a function of strain and temperature with post-mortem characterization of the microstructure, quasi-static testing of pre-deformed material, and direct observation of the dislocation behavior during reloading by using the in situ transmission electron microscope deformation technique. These experiments will provide the basis for development and validation of physically-based constitutive models. One aspect of the program involves the direct observation of specific mechanisms of micro-plasticity, as these indicate the boundary value problem that should be addressed. This focus on the pre-yield region in the quasi-static effort (the elasto-plastic transition) is also a tractable one from an experimental and modeling viewpoint. In addition, our approach will minimize the need to fit model parameters to experimental data to obtain convergence. These are critical steps to reach the primary objective of simulating and modeling material performance under extreme loading conditions. During this project, the following achievements have been obtained: 1. Twins have been observed to act as barriers to dislocation propagation and as sources of and sinks to dislocations. 2. Nucleation of deformation twins in nitrogen strengthened steel is observed to be closely associated with planar slip bands. The appearance of long twins through heavily dislocated microstructures occurs by short twins nucleating at one slip band, propagating through the dislocation-free region, and terminating at the next slip band. This process is repeated throughout the entire grain. 3. A tamped-laser ablation loading technique has been developed to introduce high strain rate, high stress and low strains. 4. Both dislocation slip and twinning are present in high strain-rate deformed zirconium, with the relative contribution of each mode to the deformation depending on the initial texture. 5. In situ IR thermal measurements have been used to show that the majority of plastic work is dissipated as heat even under conditions in which twinning is the dominant deformation mode.
A. I. Asvarov
2000-01-21T23:59:59.000Z
In present study I examine the capability of diffusive shock acceleration mechanism to explain existing data on radio emission from evolved large diameter shell-type adiabatic supernova remnants (SNRs). Time-dependent ''onion-shell'' model for the radio emission of SNRs is developed, which is based on the assumptions: a) acceleration takes place from thermal energies and test-particle approximation is valid; b) the problem of injection is avoided by introducing, like Bell (1978), two injection parameters; c) to take into consideration very late stages of SNR evolution the analytic approximation of Cox and Andersen (1982) for the shell structure is used; c)no radiative cooling. Constructed Surface Brightness - Diameter $(\\Sigma -D)$ tracks are compared with the empirical $\\Sigma -D$ diagram. The main conclusion of the study is that the DSA mechanism is capable of explaining all the statistics of radio SNRs including very large diameter remnants and giant galactic loops.
Effect of elasticity of wall on diffusion in nano channel
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
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.
Non-Brownian molecular self-diffusion in bulk water
Janez Stepišnik; Aleš Mohori?; Igor Serša
2010-10-06T23:59:59.000Z
The paper presents the velocity autocorrelation spectrum of bulk water measured by a new technique of NMR modulated gradient spin echo method. This technique is unprecedented for the spectrum measurement in the frequency interval between a few Hz to about 100 kHz with respect to directness and clarity of results and shows that a simple model of Brownian self-diffusion is not applicable to describe the diffusion dynamics of water molecules. The observed temperature dependant spectra of water show the existence of a slow chain-like dynamics in water, which we explain by coupling of diffusing molecule to broken bonds in the hydrogen bond network.
Schlegel, Nicole-Jeanne
2011-01-01T23:59:59.000Z
ice sheet model with a mesoscale climate model By Nicole-ice sheet model with a mesoscale climate model Copyrightice sheet model with a mesoscale climate model by Nicole-
Diffuse emission of high-energy neutrinos from gamma-ray burst fireballs
Irene Tamborra; Shin'ichiro Ando
2015-04-01T23:59:59.000Z
Gamma-ray bursts (GRBs) have been suggested as possible sources of the high-energy neutrino flux recently detected by the IceCube telescope. We revisit the fireball emission model and elaborate an analytical prescription to estimate the high-energy neutrino prompt emission from pion and kaon decays, assuming that the leading mechanism for the neutrino production is lepto-hadronic. To this purpose, we include hadronic, radiative and adiabatic cooling effects and discuss their relevance for long- (including high- and low-luminosity) and short-duration GRBs. The expected diffuse neutrino background is derived, by requiring that the GRB high-energy neutrino counterparts follow up-to-date gamma-ray luminosity functions and redshift evolutions of the long and short GRBs. Although dedicated stacking searches have been unsuccessful up to now, we find that the GRBs could contribute up to a few percents to the observed IceCube high-energy neutrino flux for sub-PeV energies, assuming that the latter has a diffuse origin. The high-luminosity component gives the dominant contribution to the diffuse neutrino emission, while the fluxes from both the low-luminosity and the short-duration GRBs are significantly smaller. Our findings confirm the most-recent IceCube results on the GRB searches and suggest that larger exposure is mandatory to detect high-energy neutrinos from GRBs in the near future.
Cage diffusion in liquid mercury Yaspal S. Badyal
Montfrooij, Wouter
University, Massachusetts 02138, USA Ignatz M. de Schepper Interfaculty Reactor Institute, TU Delft, 2629 JB(q,E). It is believed that cage diffusion plays an important part in the dynamics of real fluids, such as noble gas on the fast short-time decay mechanism of liquid mercury pertinent to cage diffu- sion. Recent neutron
Titus, M. J.; Graves, D. B. [Department of Chemical Engineering, University of California, Berkeley, California 94720 (United States)
2008-09-15T23:59:59.000Z
The authors report measurements and modeling of wafer heating mechanisms in an Ar/O{sub 2} inductively coupled plasma (ICP). The authors employed a commercially available on-wafer sensor system (PlasmaTemp developed by KLA-Tencor) consisting of an on-board electronics module housing battery power and data storage with 30 temperature sensors embedded onto the wafer at different radial positions. This system allows for real time, in situ wafer temperature measurements. Wafer heating mechanisms were investigated by combining temperature measurements from the PlasmaTemp sensor wafer with a three-dimensional heat transfer model of the wafer and a model of the ICP. Comparisons between pure Ar and Ar/O{sub 2} discharges demonstrated that two additional wafer heating mechanisms can be important in molecular gas plasmas compared to atomic gas discharges. The two mechanisms are heating from the gas phase and O-atom surface recombination. These mechanisms were shown to contribute as much as 60% to wafer heating under conditions of low bias power. This study demonstrated how the 'on-wafer' temperature sensor not only yields a temperature profile distribution across the wafer, but can be used to help determine plasma characteristics, such as ion flux profiles or plasma processing temperatures.
Lerebours, C; Scheiner, S; Pivonka, P
2015-01-01T23:59:59.000Z
We propose a multiscale mechanobiological model of bone remodelling to investigate the site-specific evolution of bone volume fraction across the midshaft of a femur. The model includes hormonal regulation and biochemical coupling of bone cell populations, the influence of the microstructure on bone turnover rate, and mechanical adaptation of the tissue. Both microscopic and tissue-scale stress/strain states of the tissue are calculated from macroscopic loads by a combination of beam theory and micromechanical homogenisation. This model is applied to simulate the spatio-temporal evolution of a human midshaft femur scan subjected to two deregulating circumstances: (i) osteoporosis and (ii) mechanical disuse. Both simulated deregulations led to endocortical bone loss, cortical wall thinning and expansion of the medullary cavity, in accordance with experimental findings. Our model suggests that these observations are attributable to a large extent to the influence of the microstructure on bone turnover rate. Mec...
Portable vapor diffusion coefficient meter
Ho, Clifford K. (Albuquerque, NM)
2007-06-12T23:59:59.000Z
An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.
Lithium diffusion at Si-C interfaces in silicon-graphene composites
Odbadrakh, Khorgolkhuu [Joint Institute for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States); McNutt, N. W. [Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States); Nicholson, D. M. [Computational Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States); Department of Physics, University of North Carolina, Asheville, North Carolina 28804 (United States); Rios, O. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States); Keffer, D. J. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)
2014-08-04T23:59:59.000Z
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.
Lithium diffusion at Si-C interfaces in Silicon-Graphene composites
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
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.
Raboin, P J
1998-01-01T23:59:59.000Z
The Computational Mechanics thrust area is a vital and growing facet of the Mechanical Engineering Department at Lawrence Livermore National Laboratory (LLNL). This work supports the development of computational analysis tools in the areas of structural mechanics and heat transfer. Over 75 analysts depend on thrust area-supported software running on a variety of computing platforms to meet the demands of LLNL programs. Interactions with the Department of Defense (DOD) High Performance Computing and Modernization Program and the Defense Special Weapons Agency are of special importance as they support our ParaDyn project in its development of new parallel capabilities for DYNA3D. Working with DOD customers has been invaluable to driving this technology in directions mutually beneficial to the Department of Energy. Other projects associated with the Computational Mechanics thrust area include work with the Partnership for a New Generation Vehicle (PNGV) for ''Springback Predictability'' and with the Federal Aviation Administration (FAA) for the ''Development of Methodologies for Evaluating Containment and Mitigation of Uncontained Engine Debris.'' In this report for FY-97, there are five articles detailing three code development activities and two projects that synthesized new code capabilities with new analytic research in damage/failure and biomechanics. The article this year are: (1) Energy- and Momentum-Conserving Rigid-Body Contact for NIKE3D and DYNA3D; (2) Computational Modeling of Prosthetics: A New Approach to Implant Design; (3) Characterization of Laser-Induced Mechanical Failure Damage of Optical Components; (4) Parallel Algorithm Research for Solid Mechanics Applications Using Finite Element Analysis; and (5) An Accurate One-Step Elasto-Plasticity Algorithm for Shell Elements in DYNA3D.
Murawski, Matthew Thomas
2001-01-01T23:59:59.000Z
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
2001-01-01T23:59:59.000Z
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...
Reaction and diffusion in turbulent combustion
Pope, S.B. [Mechanical and Aerospace Engineering, Ithaca, NY (United States)
1993-12-01T23:59:59.000Z
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.
NONE
1998-09-01T23:59:59.000Z
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.
Solar mechanics thermal response capabilities.
Dobranich, Dean D.
2009-07-01T23:59:59.000Z
In many applications, the thermal response of structures exposed to solar heat loads is of interest. Solar mechanics governing equations were developed and integrated with the Calore thermal response code via user subroutines to provide this computational simulation capability. Solar heat loads are estimated based on the latitude and day of the year. Vector algebra is used to determine the solar loading on each face of a finite element model based on its orientation relative to the sun as the earth rotates. Atmospheric attenuation is accounted for as the optical path length varies from sunrise to sunset. Both direct and diffuse components of solar flux are calculated. In addition, shadowing of structures by other structures can be accounted for. User subroutines were also developed to provide convective and radiative boundary conditions for the diurnal variations in air temperature and effective sky temperature. These temperature boundary conditions are based on available local weather data and depend on latitude and day of the year, consistent with the solar mechanics formulation. These user subroutines, coupled with the Calore three-dimensional thermal response code, provide a complete package for addressing complex thermal problems involving solar heating. The governing equations are documented in sufficient detail to facilitate implementation into other heat transfer codes. Suggestions for improvements to the approach are offered.
Li, Teng
oxide thin films on polyimide substrates Cheng Peng,1 Zheng Jia,2 Dan Bianculli,1 Teng Li,2,a) and Jun thicknesses (200 and 80 nm) deposited on polyimide substrates inside a scanning electron microscope. The crack model, the cohesive toughness and fracture strength of ITO thin films and the ITO/polyimide interfacial
Boerner, A. J. [IEAVP, ORISE, Oak Ridge, TN (United States); Maldonado, D. G. [IEAVP, ORISE, Oak Ridge, TN (United States; Hansen, Tom [Ameriphysics, LLC (United States)
2012-06-01T23:59:59.000Z
This report contains the technical basis in support of the DOE?s derivation of Authorized Limits (ALs) for the DOE Paducah C-746-U Landfill. 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. The ORISE-derived soil guidelines are specifically applicable to the Landfill at the end of its operational life. A suggested 'upper bound' multiple of the derived soil guidelines for individual shipments is provided.
Paris-Sud XI, Université de
modelling of the magneto-mechanical behaviour of dual- phase steels F MBALLA-MBALLA 1,2 , O HUBERT 1. The dual-phase is a steel composed of ferrite and martensite phases. Each phase can be considered of high performance steels as dual phase (DP) steels has been observed. Steel production involves several
Dunn, James Elliott
1959-01-01T23:59:59.000Z
AN EXPERIMENTAL MEASUREMENT QF THE THERMAL CONDUCTIVITY AND DIFFUSIVITY OF A POROUS SOLID LIQUID SYSTEM By James Elliott Dunn A Thesis Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in partial... fulfillment of the reQuirements for the degree of MASTER OF SCIENCE August 1959 Major Sub)ect: Mechanical Engineering AN EXPERIMENTAL MEASURFJ1ENT OF THE THERMAL CONDUCTIVITY AND DIFFUSIVITY OF A POROUS SOLID LIQUID SYSTEM A Thesis James Elliott Dunn...
Diffuser for augmenting a wind turbine
Foreman, Kenneth M. (North Bellmore, NY); Gilbert, Barry L. (Westbury, NY)
1984-01-01T23:59:59.000Z
A diffuser for augmenting a wind turbine having means for energizing the boundary layer at several locations along the diffuser walls is improved by the addition of a short collar extending radially outward from the outlet of the diffuser.
Komornicka, Dorota [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, ul. Okolna 2, 50-420 Wroclaw (Poland); Wolcyrz, Marek, E-mail: m.wolcyrz@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, ul. Okolna 2, 50-420 Wroclaw (Poland); Pietraszko, Adam [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, ul. Okolna 2, 50-420 Wroclaw (Poland)
2012-08-15T23:59:59.000Z
Local structure of dirubidium tetralithium tris(selenate(VI)) dihydrate - Rb{sub 2}Li{sub 4}(SeO{sub 4}){sub 3}{center_dot} 2H{sub 2}O has been determined basing on the modeling of X-ray diffuse scattering. The origin of observed structured diffuse streaks is SeO{sub 4} tetrahedra switching between two alternative positions in two quasi-planar layers existing in each unit cell and formation of domains with specific SeO{sub 4} tetrahedra configuration locally fulfilling condition for C-centering in the 2a Multiplication-Sign 2b Multiplication-Sign c superstructure cell. The local structure solution is characterized by a uniform distribution of rather large domains (ca. thousand of unit cells) in two layers, but also monodomains can be taken into account. Inside a single domain SeO{sub 4} tetrahedra are ordered along ab-diagonal forming two-string ribbons. Inside the ribbons SeO{sub 4} and LiO{sub 4} tetrahedra share the oxygen corners, whereas ribbons are bound to each other by a net of hydrogen bonds and fastened by corner sharing SeO{sub 4} tetrahedra of the neighboring layers. - Graphical abstract: Experimental sections of the reciprocal space showing diffraction effects observed for RLSO. Bragg spots are visible on sections with integer indices (1 kl section - on the left), streaks - on sections with fractional ones (1.5 kl section - on the right). At the center: resulting local structure of the A package modeled as a microdomain: two-string ribbons of ordered oxygen-corners-sharing SeO{sub 4} and LiO{sub 4} terahedra extended along ab-diagonal are seen; ribbons are bound by hydrogen bonds (shown in pink); the multiplied 2a Multiplication-Sign 2b unit cell is shown. Highlights: Black-Right-Pointing-Pointer X-ray diffuse scattering in RLSO was registered and modeled. Black-Right-Pointing-Pointer The origin of diffuse streaks is SeO{sub 4} tetrahedra switching in two structure layers. Black-Right-Pointing-Pointer The local structure is characterized by a uniform distribution of microdomains. Black-Right-Pointing-Pointer Inside a single domain SeO{sub 4} tetrahedra are ordered along ab-diagonal forming ribbons. Black-Right-Pointing-Pointer The ribbons are bound to each other by a net of hydrogen bonds.
Independent Oversight Review, Portsmouth Gaseous Diffusion Plant...
Office of Environmental Management (EM)
January 2013 Independent Oversight Review, Portsmouth Gaseous Diffusion Plant - January 2013 January 2013 Review of the Portsmouth Gaseous Diffusion Plant Work Planning and Control...
Independent Activity Report, Portsmouth Gaseous Diffusion Plant...
Office of Environmental Management (EM)
Portsmouth Gaseous Diffusion Plant - August 2011 Independent Activity Report, Portsmouth Gaseous Diffusion Plant - August 2011 August 2011 Orientation Visit to the Portsmouth...
Cain, Jeremy P.; Laskin, Alexander; Kholghy, Mohammad Reza; Thomson, Murray; Wang, Hai
2014-10-29T23:59:59.000Z
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.
Cation self-diffusion in Fe/sub 2/O/sub 3/
Hoshino, K.; Peterson, N.L.
1984-01-01T23:59:59.000Z
Self-diffusion of /sup 59/Fe in single crystals of Fe/sub 2/O/sub 3/ parallel to the c-axis has been measured as a function of temperature (1150 to 1340/sup 0/C) and oxygen partial pressure (2 x 10/sup -3/) less than or equal to Po/sub 2/ less than or equal to 1 atm). The oxygen partial pressure dependence of the diffusivity indicates that cation self-diffusion occurs by an interstitial-type mechanism. The simultaneous diffusion of /sup 52/Fe and /sup 59/Fe has been measured in Fe/sub 2/O/sub 3/ at 1251/sup 0/C and Po/sub 2/ = 1.91 x 10/sup -2/ atm. The small value of the isotope effect (f..delta..K = 0.067 +- 0.016) is consistent with diffusion of Fe ions by an interstitially mechanism.
Microstructural Evolution and interfacial motion in systems with diffusion barriers
Perry H. Leo
2009-03-05T23:59:59.000Z
This research program was designed to model and simulate phase transformations in systems containing diffusion barriers. The modeling work included mass flow, phase formation, and microstructural evolution in interdiffusing systems. Simulation work was done by developing Cahn-Hilliard and phase field equations governing both the temporal and spatial evolution of the composition and deformation fields and other important phase variables.
A reaction-subdiffusion model of fluorescence recovery after photobleaching (FRAP)
S. B. Yuste; E. Abad; K. Lindenberg
2014-07-30T23:59:59.000Z
Anomalous diffusion, in particular subdiffusion, is frequently invoked as a mechanism of motion in dense biological media, and may have a significant impact on the kinetics of binding/unbinding events at the cellular level. In this work we incorporate anomalous diffusion in a previously developed model for FRAP experiments. Our particular implementation of subdiffusive transport is based on a continuous time random walk (CTRW) description of the motion of fluorescent particles, as CTRWs lend themselves particularly well to the inclusion of binding/unbinding events. In order to model switching between bound and unbound states of fluorescent subdiffusive particles, we derive a fractional reaction-subdiffusion equation of rather general applicability. Using suitable initial and boundary conditions, this equation is then incorporated in the model describing two-dimensional kinetics of FRAP experiments. We find that this model can be used to obtain excellent fits to experimental data. Moreover, recovery curves corresponding to different radii of the circular bleach spot can be fitted by a single set of parameters. While not enough evidence has been collected to claim with certainty that CTRW is the underlying transport mechanism in FRAP experiments, the compatibility of our results with experimental data fuels the discussion as to whether normal diffusion or anomalous diffusion is the appropriate model, and as to whether anomalous diffusion effects are important to fully understand the outcomes of FRAP experiments. On a more technical side, we derive explicit analytic solutions of our model in certain limits.
Cages and anomalous diffusion in vibrated dense granular media
Camille Scalliet; Andrea Gnoli; Andrea Puglisi; Angelo Vulpiani
2015-04-28T23:59:59.000Z
A vertically shaken granular medium hosts a blade rotating around a fixed vertical axis, which acts as a mesorheological probe. At high densities, independently from the shaking intensity, the blade's dynamics show strong caging effects, marked by transient sub-diffusion and a maximum in the velocity power density spectrum (vpds), at a resonant frequency $\\sim 10$ Hz. Interpreting the data through a diffusing harmonic cage model allows us to retrieve the elastic constant of the granular medium and its collective diffusion coefficient. For high frequencies $f$, a tail $\\sim 1/f$ in the vpds reveals non-trivial correlations in the intra-cage micro-dynamics. At very long times (larger than $10$ s), a super-diffusive behavior emerges, ballistic in the most extreme cases. Consistently, the distribution of slow velocity inversion times $\\tau$ displays a power-law decay, likely due to persistent collective fluctuations of the host medium.
Hot carrier diffusion in graphene
Ruzicka, Brian Andrew; Wang, Shuai; Werake, Lalani Kumari; Weintrub, Ben; Loh, Kian Ping; Zhao, Hui
2010-11-01T23:59:59.000Z
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...
Microviscometric studies on thermal diffusion
Reyna, Eddie
1959-01-01T23:59:59.000Z
proportions until Clusiui and Dickel introduced a type of therrail diffusion column 4 which caused a thermal circul~tion in addition to thermal diffusion. With tni' equipment they were able to separate chlorine isotopes. Applying this same method..., it was decided to . onstruct equipment which could measure the viscosity and concentration of 0. 1 ml. samples. It was desired to have the reproduceability of the viscosimeter better than I'X since the dilute solutions to be studied had maximum viscosities...
Boron diffusion in silicon devices
Rohatgi, Ajeet (Atlanta, GA); Kim, Dong Seop (Atlanta, GA); Nakayashiki, Kenta (Smyrna, GA); Rounsaville, Brian (Stockbridge, GA)
2010-09-07T23:59:59.000Z
Disclosed are various embodiments that include a process, an arrangement, and an apparatus for boron diffusion in a wafer. In one representative embodiment, a process is provided in which a boric oxide solution is applied to a surface of the wafer. Thereafter, the wafer is subjected to a fast heat ramp-up associated with a first heating cycle that results in a release of an amount of boron for diffusion into the wafer.
Rutqvist, Jonny; Majer, Ernie; Oldenburg, Curt; Peterson, John; Vasco, Don
2006-01-01T23:59:59.000Z
coupled reservoir geomechanical numerical modeling, (2) datacoupled reservoir geomechanical numerical modeling, (2) datareservoir geomechanical analysis will be corroborated with, and constrained by, data
Mechanical Engineering Department Seminar Series
Papalambros, Panos
Challenges through Modeling, Control and Design Micheal Zinn Associate Professor, Mechanical & Biomedical overcome them, we have undertaken a coordinated effort to develop improved modeling, controls, and device manipulation approaches. The modeling investigation has focused on developing improved models by which
Diffuse Source Transmissibility Upscaling
Nunna, Krishna Chaitanya
2014-10-03T23:59:59.000Z
of the geologic models for flow simulation remains part of the subsurface workflows. The industry also faces new reservoir engineering challenges. Unconventional reservoirs (tight gas / shale oil / shale gas) have low permeabilities ranging from micro to nano...
Li, Jingyi
2012-02-14T23:59:59.000Z
aldehydes generated from parent VOCs are tracked separately using tagged reactive species approach (Ying and Krishnan, 2010). As an example, the freshly emitted formaldehyde in the mechanisms is tracked using species HCHO, while the secondary formaldehyde...