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Sample records for 1-d transport equations

  1. A New 2D-Transport, 1D-Diffusion Approximation of the Boltzmann Transport equation

    SciTech Connect

    Larsen, Edward

    2013-06-17

    The work performed in this project consisted of the derivation, implementation, and testing of a new, computationally advantageous approximation to the 3D Boltz- mann transport equation. The solution of the Boltzmann equation is the neutron flux in nuclear reactor cores and shields, but solving this equation is difficult and costly. The new “2D/1D” approximation takes advantage of a special geometric feature of typical 3D reactors to approximate the neutron transport physics in a specific (ax- ial) direction, but not in the other two (radial) directions. The resulting equation is much less expensive to solve computationally, and its solutions are expected to be sufficiently accurate for many practical problems. In this project we formulated the new equation, discretized it using standard methods, developed a stable itera- tion scheme for solving the equation, implemented the new numerical scheme in the MPACT code, and tested the method on several realistic problems. All the hoped- for features of this new approximation were seen. For large, difficult problems, the resulting 2D/1D solution is highly accurate, and is calculated about 100 times faster than a 3D discrete ordinates simulation.

  2. Transient 1D transport equation simulated by a mixed Green element formulation

    NASA Astrophysics Data System (ADS)

    Taigbenu, Akpofure Efemena; Onyejekwe, Okey Oseloka

    1997-08-01

    New discrete element equations or coefficients are derived for the transient 1D diffusion-advection or transport equation based on the Green element replication of the differential equation using linear elements. The Green element method (GEM), which solves the singular boundary integral theory (a Fredholm integral equation of the second kind) on a typical element, gives rise to a banded global coefficient matrix which is amenable to efficient matrix solvers. It is herein derived for the transient 1D transport equation with uniform and non-uniform ambient flow conditions and in which first-order decay of the containment is allowed to take place. Because the GEM implements the singular boundary integral theory within each element at a time, the integrations are carried out in exact fashion, thereby making the application of the boundary integral theory more utilitarian. This system of discrete equations, presented herein for the first time, using linear interpolating functions in the spatial dimensions shows promising stable characteristics for advection-dominant transport. Three numerical examples are used to demonstrate the capabilities of the method. The second-order-correct Crank-Nicolson scheme and the modified fully implicit scheme with a difference weighting value of two give superior solutions in all simulated examples.

  3. Discontinuous Galerkin finite element method applied to the 1-D spherical neutron transport equation

    SciTech Connect

    Machorro, Eric . E-mail: machorro@amath.washington.edu

    2007-04-10

    Discontinuous Galerkin finite element methods are used to estimate solutions to the non-scattering 1-D spherical neutron transport equation. Various trial and test spaces are compared in the context of a few sample problems whose exact solution is known. Certain trial spaces avoid unphysical behaviors that seem to plague other methods. Comparisons with diamond differencing and simple corner-balancing are presented to highlight these improvements.

  4. Exponentially-convergent Monte Carlo for the 1-D transport equation

    SciTech Connect

    Peterson, J. R.; Morel, J. E.; Ragusa, J. C.

    2013-07-01

    We define a new exponentially-convergent Monte Carlo method for solving the one-speed 1-D slab-geometry transport equation. This method is based upon the use of a linear discontinuous finite-element trial space in space and direction to represent the transport solution. A space-direction h-adaptive algorithm is employed to restore exponential convergence after stagnation occurs due to inadequate trial-space resolution. This methods uses jumps in the solution at cell interfaces as an error indicator. Computational results are presented demonstrating the efficacy of the new approach. (authors)

  5. On a 1D nonlocal transport equation with nonlocal velocity and subcritical or supercritical diffusion

    NASA Astrophysics Data System (ADS)

    Lazar, Omar

    2016-11-01

    We study a 1D transport equation with nonlocal velocity with subcritical or supercritical dissipation. For all data in the weighted Sobolev space Hk (wλ,κ) ∩L∞, where k = max ⁡ (0 , 3 / 2 - α) and wλ,κ is a given family of Muckenhoupt weights, we prove a global existence result in the subcritical case α ∈ (1 , 2). We also prove a local existence theorem for large data in H2 (wλ,κ) ∩L∞ in the supercritical case α ∈ (0 , 1). The proofs are based on the use of the weighted Littlewood-Paley theory, interpolation along with some new commutator estimates.

  6. Quadratic Finite Element Method for 1D Deterministic Transport

    SciTech Connect

    Tolar, Jr., D R; Ferguson, J M

    2004-01-06

    In the discrete ordinates, or SN, numerical solution of the transport equation, both the spatial ({und r}) and angular ({und {Omega}}) dependences on the angular flux {psi}{und r},{und {Omega}}are modeled discretely. While significant effort has been devoted toward improving the spatial discretization of the angular flux, we focus on improving the angular discretization of {psi}{und r},{und {Omega}}. Specifically, we employ a Petrov-Galerkin quadratic finite element approximation for the differencing of the angular variable ({mu}) in developing the one-dimensional (1D) spherical geometry S{sub N} equations. We develop an algorithm that shows faster convergence with angular resolution than conventional S{sub N} algorithms.

  7. DNA charge transport: Moving beyond 1D

    NASA Astrophysics Data System (ADS)

    Zhang, Yuqi; Zhang, William B.; Liu, Chaoren; Zhang, Peng; Balaeff, Alexander; Beratan, David N.

    2016-10-01

    Charge transport across novel DNA junctions has been studied for several decades. From early attempts to move charge across DNA double crossover junctions to recent studies on DNA three-way junctions and G4 motifs, it is becoming clear that efficient cross-junction charge migration requires strong base-to-base electronic coupling at the junction, facilitated by favorable pi-stacking. We review recent progress toward the goal of manipulating and controlling charge transport through DNA junctions.

  8. Mass conservation: 1-D open channel flow equations

    USGS Publications Warehouse

    DeLong, Lewis L.

    1989-01-01

    Unsteady flow simulation in natural rivers is often complicated by meandering channels of compound section. Hydraulic properties and the length of the wetted channel may vary significantly as a meandering river inundates its adjacent floodplain. The one-dimensional, unsteady, open-channel flow equations can be extended to simulate floods in channels of compound section. It will be shown that equations derived from the addition of differential equations individually describing flow in main and overbank channels do not in general conserve mass when overbank and main channels are of different lengths.

  9. Interaction of environmental contaminants with zebrafish organic anion transporting polypeptide, Oatp1d1 (Slco1d1)

    SciTech Connect

    Popovic, Marta; Zaja, Roko; Fent, Karl; Smital, Tvrtko

    2014-10-01

    Polyspecific transporters from the organic anion transporting polypeptide (OATP/Oatp) superfamily mediate the uptake of a wide range of compounds. In zebrafish, Oatp1d1 transports conjugated steroid hormones and cortisol. It is predominantly expressed in the liver, brain and testes. In this study we have characterized the transport of xenobiotics by the zebrafish Oatp1d1 transporter. We developed a novel assay for assessing Oatp1d1 interactors using the fluorescent probe Lucifer yellow and transient transfection in HEK293 cells. Our data showed that numerous environmental contaminants interact with zebrafish Oatp1d1. Oatp1d1 mediated the transport of diclofenac with very high affinity, followed by high affinity towards perfluorooctanesulfonic acid (PFOS), nonylphenol, gemfibrozil and 17α-ethinylestradiol; moderate affinity towards carbaryl, diazinon and caffeine; and low affinity towards metolachlor. Importantly, many environmental chemicals acted as strong inhibitors of Oatp1d1. A strong inhibition of Oatp1d1 transport activity was found by perfluorooctanoic acid (PFOA), chlorpyrifos-methyl, estrone (E1) and 17β-estradiol (E2), followed by moderate to low inhibition by diethyl phthalate, bisphenol A, 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4 tetrahydronapthalene and clofibrate. In this study we identified Oatp1d1 as a first Solute Carrier (SLC) transporter involved in the transport of a wide range of xenobiotics in fish. Considering that Oatps in zebrafish have not been characterized before, our work on zebrafish Oatp1d1 offers important new insights on the understanding of uptake processes of environmental contaminants, and contributes to the better characterization of zebrafish as a model species. - Highlights: • We optimized a novel assay for determination of Oatp1d1 interactors • Oatp1d1 is the first SLC characterized fish xenobiotic transporter • PFOS, nonylphenol, diclofenac, EE2, caffeine are high affinity Oatp1d1substrates • PFOA, chlorpyrifos

  10. 1D-transport properties of single superconducting lead nanowires

    NASA Astrophysics Data System (ADS)

    Michotte, S.; Mátéfi-Tempfli, S.; Piraux, L.

    2003-09-01

    We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have uniform diameter of ∼40 nm and a very large aspect ratio (∼500). The diameter of the nanowire is small enough to ensure a 1D superconducting regime in a wide temperature range below Tc. The non-zero resistance in the superconducting state and its variation caused by fluctuations of the superconducting order parameter were measured versus temperature, magnetic field, and applied DC current (or voltage). The current induced breakdowns in the V- I characteristics may be explained by the formation of phase slip centers. Moreover, DC voltage driven measurements reveal the existence of a new S-shape behavior near the formation of these phase slip centers.

  11. Benchmarks and models for 1-D radiation transport in stochastic participating media

    SciTech Connect

    Miller, D S

    2000-08-21

    Benchmark calculations for radiation transport coupled to a material temperature equation in a 1-D slab and 1-D spherical geometry binary random media are presented. The mixing statistics are taken to be homogeneous Markov statistics in the 1-D slab but only approximately Markov statistics in the 1-D sphere. The material chunk sizes are described by Poisson distribution functions. The material opacities are first taken to be constant and then allowed to vary as a strong function of material temperature. Benchmark values and variances for time evolution of the ensemble average of material temperature energy density and radiation transmission are computed via a Monte Carlo type method. These benchmarks are used as a basis for comparison with three other approximate methods of solution. One of these approximate methods is simple atomic mix. The second approximate model is an adaptation of what is commonly called the Levermore-Pomraning model and which is referred to here as the standard model. It is shown that recasting the temperature coupling as a type of effective scattering can be useful in formulating the third approximate model, an adaptation of a model due to Su and Pomraning which attempts to account for the effects of scattering in a stochastic context. This last adaptation shows consistent improvement over both the atomic mix and standard models when used in the 1-D slab geometry but shows limited improvement in the 1-D spherical geometry. Benchmark values are also computed for radiation transmission from the 1-D sphere without material heating present. This is to evaluate the performance of the standard model on this geometry--something which has never been done before. All of the various tests demonstrate the importance of stochastic structure on the solution. Also demonstrated are the range of usefulness and limitations of a simple atomic mix formulation.

  12. Molecular characterization of zebrafish Oatp1d1 (Slco1d1), a novel organic anion-transporting polypeptide.

    PubMed

    Popovic, Marta; Zaja, Roko; Fent, Karl; Smital, Tvrtko

    2013-11-22

    The organic anion-transporting polypeptide (OATP/Oatp) superfamily includes a group of polyspecific transporters that mediate transport of large amphipathic, mostly anionic molecules across cell membranes of eukaryotes. OATPs/Oatps are involved in the disposition and elimination of numerous physiological and foreign compounds. However, in non-mammalian species, the functional properties of Oatps remain unknown. We aimed to elucidate the role of Oatp1d1 in zebrafish to gain insights into the functional and structural evolution of the OATP1/Oatp1 superfamily. We show that diversification of the OATP1/Oatp1 family occurs after the emergence of jawed fish and that the OATP1A/Oatp1a and OATP1B/Oatp1b subfamilies appeared at the root of tetrapods. The Oatp1d subfamily emerged in teleosts and is absent in tetrapods. The zebrafish Oatp1d1 is similar to mammalian OATP1A/Oatp1a and OATP1B/Oatp1b members, with the main physiological role in transport and balance of steroid hormones. Oatp1d1 activity is dependent upon pH gradient, which could indicate bicarbonate exchange as a mode of transport. Our analysis of evolutionary conservation and structural properties revealed that (i) His-79 in intracellular loop 3 is conserved within OATP1/Oatp1 family and is crucial for the transport activity; (ii) N-glycosylation impacts membrane targeting and is conserved within the OATP1/Oatp1 family with Asn-122, Asn-133, Asn-499, and Asn-512 residues involved; (iii) the evolutionarily conserved cholesterol recognition interaction amino acid consensus motif is important for membrane localization; and (iv) Oatp1d1 is present in dimeric and possibly oligomeric form in the cell membrane. In conclusion, we describe the first detailed characterization of a new Oatp transporter in zebrafish, offering important insights into the functional evolution of the OATP1/Oatp1 family and the physiological role of Oatp1d1.

  13. The 1D Kardar-Parisi-Zhang equation: Height distribution and universality

    NASA Astrophysics Data System (ADS)

    Sasamoto, Tomohiro

    2016-02-01

    The Kardar-Parisi-Zhang (KPZ) equation, which was introduced in 1986 as a model equation to describe the dynamics of an interface motion, has been attracting renewed interest in recent years. In particular, the height distribution of its 1D version was determined exactly for a few special initial conditions. Its relevance in experiments was demonstrated and our understanding of the mathematical structures behind its tractability has deepened considerably. There are also new developments in the applicability of the KPZ universality in wider contexts. This paper is a short introductory review on the basics of the equation and on a few recent topics.

  14. Transport equations for oscillating neutrinos

    NASA Astrophysics Data System (ADS)

    Zhang, Yunfan; Burrows, Adam

    2013-11-01

    We derive a suite of generalized Boltzmann equations, based on the density-matrix formalism, that incorporates the physics of neutrino oscillations for two- and three-flavor oscillations, matter refraction, and self-refraction. The resulting equations are straightforward extensions of the classical transport equations that nevertheless contain the full physics of quantum oscillation phenomena. In this way, our broadened formalism provides a bridge between the familiar neutrino transport algorithms employed by supernova modelers and the more quantum-heavy approaches frequently employed to illuminate the various neutrino oscillation effects. We also provide the corresponding angular-moment versions of this generalized equation set. Our goal is to make it easier for astrophysicists to address oscillation phenomena in a language with which they are familiar. The equations we derive are simple and practical, and are intended to facilitate progress concerning oscillation phenomena in the context of core-collapse supernova theory.

  15. Transport equations in tokamak plasmas

    SciTech Connect

    Callen, J. D.; Hegna, C. C.; Cole, A. J.

    2010-05-15

    Tokamak plasma transport equations are usually obtained by flux surface averaging the collisional Braginskii equations. However, tokamak plasmas are not in collisional regimes. Also, ad hoc terms are added for neoclassical effects on the parallel Ohm's law, fluctuation-induced transport, heating, current-drive and flow sources and sinks, small magnetic field nonaxisymmetries, magnetic field transients, etc. A set of self-consistent second order in gyroradius fluid-moment-based transport equations for nearly axisymmetric tokamak plasmas has been developed using a kinetic-based approach. The derivation uses neoclassical-based parallel viscous force closures, and includes all the effects noted above. Plasma processes on successive time scales and constraints they impose are considered sequentially: compressional Alfven waves (Grad-Shafranov equilibrium, ion radial force balance), sound waves (pressure constant along field lines, incompressible flows within a flux surface), and collisions (electrons, parallel Ohm's law; ions, damping of poloidal flow). Radial particle fluxes are driven by the many second order in gyroradius toroidal angular torques on a plasma species: seven ambipolar collision-based ones (classical, neoclassical, etc.) and eight nonambipolar ones (fluctuation-induced, polarization flows from toroidal rotation transients, etc.). The plasma toroidal rotation equation results from setting to zero the net radial current induced by the nonambipolar fluxes. The radial particle flux consists of the collision-based intrinsically ambipolar fluxes plus the nonambipolar fluxes evaluated at the ambipolarity-enforcing toroidal plasma rotation (radial electric field). The energy transport equations do not involve an ambipolar constraint and hence are more directly obtained. The 'mean field' effects of microturbulence on the parallel Ohm's law, poloidal ion flow, particle fluxes, and toroidal momentum and energy transport are all included self-consistently. The

  16. Transport equations in tokamak plasmasa)

    NASA Astrophysics Data System (ADS)

    Callen, J. D.; Hegna, C. C.; Cole, A. J.

    2010-05-01

    Tokamak plasma transport equations are usually obtained by flux surface averaging the collisional Braginskii equations. However, tokamak plasmas are not in collisional regimes. Also, ad hoc terms are added for neoclassical effects on the parallel Ohm's law, fluctuation-induced transport, heating, current-drive and flow sources and sinks, small magnetic field nonaxisymmetries, magnetic field transients, etc. A set of self-consistent second order in gyroradius fluid-moment-based transport equations for nearly axisymmetric tokamak plasmas has been developed using a kinetic-based approach. The derivation uses neoclassical-based parallel viscous force closures, and includes all the effects noted above. Plasma processes on successive time scales and constraints they impose are considered sequentially: compressional Alfvén waves (Grad-Shafranov equilibrium, ion radial force balance), sound waves (pressure constant along field lines, incompressible flows within a flux surface), and collisions (electrons, parallel Ohm's law; ions, damping of poloidal flow). Radial particle fluxes are driven by the many second order in gyroradius toroidal angular torques on a plasma species: seven ambipolar collision-based ones (classical, neoclassical, etc.) and eight nonambipolar ones (fluctuation-induced, polarization flows from toroidal rotation transients, etc.). The plasma toroidal rotation equation results from setting to zero the net radial current induced by the nonambipolar fluxes. The radial particle flux consists of the collision-based intrinsically ambipolar fluxes plus the nonambipolar fluxes evaluated at the ambipolarity-enforcing toroidal plasma rotation (radial electric field). The energy transport equations do not involve an ambipolar constraint and hence are more directly obtained. The "mean field" effects of microturbulence on the parallel Ohm's law, poloidal ion flow, particle fluxes, and toroidal momentum and energy transport are all included self-consistently. The

  17. Validation of 1-D transport and sawtooth models for ITER

    SciTech Connect

    Connor, J.W.; Turner, M.F.; Attenberger, S.E.; Houlberg, W.A.

    1996-12-31

    In this paper the authors describe progress on validating a number of local transport models by comparing their predictions with relevant experimental data from a range of tokamaks in the ITER profile database. This database, the testing procedure and results are discussed. In addition a model for sawtooth oscillations is used to investigate their effect in an ITER plasma with alpha-particles.

  18. Morphodynamics and sediment tracers in 1-D (MAST-1D): 1-D sediment transport that includes exchange with an off-channel sediment reservoir

    NASA Astrophysics Data System (ADS)

    Lauer, J. Wesley; Viparelli, Enrica; Piégay, Hervé

    2016-07-01

    Bed material transported in geomorphically active gravel bed rivers often has a local source at nearby eroding banks and ends up sequestered in bars not far downstream. However, most 1-D numerical models for gravel transport assume that gravel originates from and deposits on the channel bed. In this paper, we present a 1-D framework for simulating morphodynamic evolution of bed elevation and size distribution in a gravel-bed river that actively exchanges sediment with its floodplain, which is represented as an off-channel sediment reservoir. The model is based on the idea that sediment enters the channel at eroding banks whose elevation depends on total floodplain sediment storage and on the average elevation of the floodplain relative to the channel bed. Lateral erosion of these banks occurs at a specified rate that can represent either net channel migration or channel widening. Transfer of material out of the channel depends on a typical bar thickness and a specified lateral exchange rate due either to net channel migration or narrowing. The model is implemented using an object oriented framework that allows users to explore relationships between bank supply, bed structure, and lateral change rates. It is applied to a ∼50-km reach of the Ain River, France, that experienced significant reduction in sediment supply due to dam construction during the 20th century. Results are strongly sensitive to lateral exchange rates, showing that in this reach, the supply of sand and gravel at eroding banks and the sequestration of gravel in point bars can have strong influence on overall reach-scale sediment budgets.

  19. Transport Equations In Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Callen, J. D.

    2009-11-01

    Tokamak plasma transport equations are usually obtained by flux surface averaging the collisional Braginskii equations. However, tokamak plasmas are not in collisional regimes. Also, ad hoc terms are added for: neoclassical effects on the parallel Ohm's law (trapped particle effects on resistivity, bootstrap current); fluctuation-induced transport; heating, current-drive and flow sources and sinks; small B field non-axisymmetries; magnetic field transients etc. A set of self-consistent second order in gyroradius fluid-moment-based transport equations for nearly axisymmetric tokamak plasmas has been developed recently using a kinetic-based framework. The derivation uses neoclassical-based parallel viscous force closures, and includes all the effects noted above. Plasma processes on successive time scales (and constraints they impose) are considered sequentially: compressional Alfv'en waves (Grad-Shafranov equilibrium, ion radial force balance); sound waves (pressure constant along field lines, incompressible flows within a flux surface); and ion collisions (damping of poloidal flow). Radial particle fluxes are driven by the many second order in gyroradius toroidal angular torques on the plasma fluid: 7 ambipolar collision-based ones (classical, neoclassical, etc.) and 8 non-ambipolar ones (fluctuation-induced, polarization flows from toroidal rotation transients etc.). The plasma toroidal rotation equation [1] results from setting to zero the net radial current induced by the non-ambipolar fluxes. The radial particle flux consists of the collision-based intrinsically ambipolar fluxes plus the non-ambipolar fluxes evaluated at the ambipolarity-enforcing toroidal plasma rotation (radial electric field). The energy transport equations do not involve an ambipolar constraint and hence are more directly obtained. The resultant transport equations will be presented and contrasted with the usual ones. [4pt] [1] J.D. Callen, A.J. Cole, C.C. Hegna, ``Toroidal Rotation In

  20. Stability and accuracy of 3D neutron transport simulations using the 2D/1D method in MPACT

    DOE PAGES

    Collins, Benjamin; Stimpson, Shane; Kelley, Blake W.; Young, Mitchell T. H.; Kochunas, Brendan; Graham, Aaron; Larsen, Edward W.; Downar, Thomas; Godfrey, Andrew

    2016-08-25

    We derived a consistent “2D/1D” neutron transport method from the 3D Boltzmann transport equation, to calculate fuel-pin-resolved neutron fluxes for realistic full-core Pressurized Water Reactor (PWR) problems. The 2D/1D method employs the Method of Characteristics to discretize the radial variables and a lower order transport solution to discretize the axial variable. Our paper describes the theory of the 2D/1D method and its implementation in the MPACT code, which has become the whole-core deterministic neutron transport solver for the Consortium for Advanced Simulations of Light Water Reactors (CASL) core simulator VERA-CS. We also performed several applications on both leadership-class and industry-classmore » computing clusters. Results are presented for whole-core solutions of the Watts Bar Nuclear Power Station Unit 1 and compared to both continuous-energy Monte Carlo results and plant data.« less

  1. Testing a 1-D Analytical Salt Intrusion Model and the Predictive Equation in Malaysian Estuaries

    NASA Astrophysics Data System (ADS)

    Gisen, Jacqueline Isabella; Savenije, Hubert H. G.

    2013-04-01

    Little is known about the salt intrusion behaviour in Malaysian estuaries. Study on this topic sometimes requires large amounts of data especially if a 2-D or 3-D numerical models are used for analysis. In poor data environments, 1-D analytical models are more appropriate. For this reason, a fully analytical 1-D salt intrusion model, based on the theory of Savenije in 2005, was tested in three Malaysian estuaries (Bernam, Selangor and Muar) because it is simple and requires minimal data. In order to achieve that, site surveys were conducted in these estuaries during the dry season (June-August) at spring tide by moving boat technique. Data of cross-sections, water levels and salinity were collected, and then analysed with the salt intrusion model. This paper demonstrates a good fit between the simulated and observed salinity distribution for all three estuaries. Additionally, the calibrated Van der Burgh's coefficient K, Dispersion coefficient D0, and salt intrusion length L, for the estuaries also displayed a reasonable correlations with those calculated from the predictive equations. This indicates that not only is the salt intrusion model valid for the case studies in Malaysia but also the predictive model. Furthermore, the results from this study describe the current state of the estuaries with which the Malaysian water authority in Malaysia can make decisions on limiting water abstraction or dredging. Keywords: salt intrusion, Malaysian estuaries, discharge, predictive model, dispersion

  2. Application of MSOR iteration with Newton scheme for solutions of 1D nonlinear porous medium equations

    NASA Astrophysics Data System (ADS)

    Chew, J. V. L.; Sulaiman, J.

    2016-06-01

    This paper considers Newton-MSOR iterative method for solving 1D nonlinear porous medium equation (PME). The basic concept of proposed iterative method is derived from a combination of one step nonlinear iterative method which known as Newton method with Modified Successive Over Relaxation (MSOR) method. The reliability of Newton-MSOR to obtain approximate solution for several PME problems is compared with Newton-Gauss-Seidel (Newton-GS) and Newton-Successive Over Relaxation (Newton-SOR). In this paper, the formulation and implementation of these three iterative methods have also been presented. From four examples of PME problems, numerical results showed that Newton-MSOR method requires lesser number of iterations and computational time as compared with Newton-GS and Newton-SOR methods.

  3. Roles of TBC1D1 and TBC1D4 in insulin- and exercise-stimulated glucose transport of skeletal muscle

    PubMed Central

    Cartee, Gregory D.

    2014-01-01

    This review focuses on two paralogue Rab GTPase activating proteins known as TBC1D1 Tre-2/BUB2/cdc 1 domain family (TBC1D) 1 and TBC1D4 (also called Akt Substrate of 160 kDa, AS160) and their roles in controlling skeletal muscle glucose transport in response to the independent and combined effects of insulin and exercise. Convincing evidence implicates Akt2-dependent TBC1D4 phosphorylation on T642 as a key part of the mechanism for insulin-stimulated glucose uptake by skeletal muscle. TBC1D1 phosphorylation on several insulin-responsive sites (including T596, a site corresponding to T642 in TBC1D4) does not appear to be essential for in vivo insulin-stimulated glucose uptake by skeletal muscle. In vivo exercise or ex vivo contraction of muscle result in greater TBC1D1 phosphorylation on S237 that is likely to be secondary to increased AMP-activated protein kinase activity and potentially important for contraction-stimulated glucose uptake. Several studies that evaluated both normal and insulin-resistant skeletal muscle stimulated with a physiological insulin concentration after a single exercise session found that greater post-exercise insulin-stimulated glucose uptake was accompanied by greater TBC1D4 phosphorylation on several sites. In contrast, enhanced post-exercise insulin sensitivity was not accompanied by greater insulin-stimulated TBC1D1 phosphorylation. The mechanism for greater TBC1D4 phosphorylation in insulin-stimulated muscles after acute exercise is uncertain, and a causal link between enhanced TBC1D4 phosphorylation and increased post-exercise insulin sensitivity has yet to be established. In summary, TBC1D1 and TBC1D4 have important, but distinct roles in regulating muscle glucose transport in response to insulin and exercise. PMID:25280670

  4. TCTEX1D2 mutations underlie Jeune asphyxiating thoracic dystrophy with impaired retrograde intraflagellar transport.

    PubMed

    Schmidts, Miriam; Hou, Yuqing; Cortés, Claudio R; Mans, Dorus A; Huber, Celine; Boldt, Karsten; Patel, Mitali; van Reeuwijk, Jeroen; Plaza, Jean-Marc; van Beersum, Sylvia E C; Yap, Zhi Min; Letteboer, Stef J F; Taylor, S Paige; Herridge, Warren; Johnson, Colin A; Scambler, Peter J; Ueffing, Marius; Kayserili, Hulya; Krakow, Deborah; King, Stephen M; Beales, Philip L; Al-Gazali, Lihadh; Wicking, Carol; Cormier-Daire, Valerie; Roepman, Ronald; Mitchison, Hannah M; Witman, George B

    2015-01-01

    The analysis of individuals with ciliary chondrodysplasias can shed light on sensitive mechanisms controlling ciliogenesis and cell signalling that are essential to embryonic development and survival. Here we identify TCTEX1D2 mutations causing Jeune asphyxiating thoracic dystrophy with partially penetrant inheritance. Loss of TCTEX1D2 impairs retrograde intraflagellar transport (IFT) in humans and the protist Chlamydomonas, accompanied by destabilization of the retrograde IFT dynein motor. We thus define TCTEX1D2 as an integral component of the evolutionarily conserved retrograde IFT machinery. In complex with several IFT dynein light chains, it is required for correct vertebrate skeletal formation but may be functionally redundant under certain conditions. PMID:26044572

  5. TCTEX1D2 mutations underlie Jeune asphyxiating thoracic dystrophy with impaired retrograde intraflagellar transport

    PubMed Central

    Schmidts, Miriam; Hou, Yuqing; Cortés, Claudio R.; Mans, Dorus A.; Huber, Celine; Boldt, Karsten; Patel, Mitali; van Reeuwijk, Jeroen; Plaza, Jean-Marc; van Beersum, Sylvia E. C.; Yap, Zhi Min; Letteboer, Stef J. F.; Taylor, S. Paige; Herridge, Warren; Johnson, Colin A.; Scambler, Peter J.; Ueffing, Marius; Kayserili, Hulya; Krakow, Deborah; King, Stephen M.; Beales, Philip L.; Al-Gazali, Lihadh; Wicking, Carol; Cormier-Daire, Valerie; Roepman, Ronald; Mitchison, Hannah M.; Witman, George B.; Al-Turki, Saeed; Anderson, Carl; Anney, Richard; Antony, Dinu; Asimit, Jennifer; Ayub, Mohammad; Barrett, Jeff; Barroso, Inês; Bentham, Jamie; Bhattacharya, Shoumo; Blackwood, Douglas; Bobrow, Martin; Bochukova, Elena; Bolton, Patrick; Boustred, Chris; Breen, Gerome; Brion, Marie-Jo; Brown, Andrew; Calissano, Mattia; Carss, Keren; Chatterjee, Krishna; Chen, Lu; Cirak, Sebhattin; Clapham, Peter; Clement, Gail; Coates, Guy; Collier, David; Cosgrove, Catherine; Cox, Tony; Craddock, Nick; Crooks, Lucy; Curran, Sarah; Daly, Allan; Danecek, Petr; Smith, George Davey; Day-Williams, Aaron; Day, Ian; Durbin, Richard; Edkins, Sarah; Ellis, Peter; Evans, David; Farooqi, I. Sadaf; Fatemifar, Ghazaleh; Fitzpatrick, David; Flicek, Paul; Floyd, Jamie; Foley, A. Reghan; Franklin, Chris; Futema, Marta; Gallagher, Louise; Gaunt, Tom; Geschwind, Daniel; Greenwood, Celia; Grozeva, Detelina; Guo, Xiaosen; Gurling, Hugh; Hart, Deborah; Hendricks, Audrey; Holmans, Peter; Huang, Jie; Humphries, Steve E.; Hurles, Matt; Hysi, Pirro; Jackson, David; Jamshidi, Yalda; Jewell, David; Chris, Joyce; Kaye, Jane; Keane, Thomas; Kemp, John; Kennedy, Karen; Kent, Alastair; Kolb-Kokocinski, Anja; Lachance, Genevieve; Langford, Cordelia; Lee, Irene; Li, Rui; Li, Yingrui; Ryan, Liu; Lönnqvist, Jouko; Lopes, Margarida; MacArthur, Daniel G.; Massimo, Mangino; Marchini, Jonathan; Maslen, John; McCarthy, Shane; McGuffin, Peter; McIntosh, Andrew; McKechanie, Andrew; McQuillin, Andrew; Memari, Yasin; Metrustry, Sarah; Min, Josine; Moayyeri, Alireza; Morris, James; Muddyman, Dawn; Muntoni, Francesco; Northstone, Kate; O'Donovan, Michael; O'Rahilly, Stephen; Onoufriadis, Alexandros; Oualkacha, Karim; Owen, Michael; Palotie, Aarno; Panoutsopoulou, Kalliope; Parker, Victoria; Parr, Jeremy; Paternoster, Lavinia; Paunio, Tiina; Payne, Felicity; Perry, John; Pietilainen, Olli; Plagnol, Vincent; Quail, Michael A.; Quaye, Lydia; Raymond, Lucy; Rehnström, Karola; Brent Richards, J.; Ring, Sue; Ritchie, Graham R S; Savage, David B.; Schoenmakers, Nadia; Semple, Robert K.; Serra, Eva; Shihab, Hashem; Shin, So-Youn; Skuse, David; Small, Kerrin; Smee, Carol; Soler, Artigas María; Soranzo, Nicole; Southam, Lorraine; Spector, Tim; St Pourcain, Beate; St. Clair, David; Stalker, Jim; Surdulescu, Gabriela; Suvisaari, Jaana; Tachmazidou, Ioanna; Tian, Jing; Timpson, Nic; Tobin, Martin; Valdes, Ana; van Kogelenberg, Margriet; Vijayarangakannan, Parthiban; Wain, Louise; Walter, Klaudia; Wang, Jun; Ward, Kirsten; Wheeler, Ellie; Whittall, Ros; Williams, Hywel; Williamson, Kathy; Wilson, Scott G.; Wong, Kim; Whyte, Tamieka; ChangJiang, Xu; Zeggini, Eleftheria; Zhang, Feng; Zheng, Hou-Feng

    2015-01-01

    The analysis of individuals with ciliary chondrodysplasias can shed light on sensitive mechanisms controlling ciliogenesis and cell signalling that are essential to embryonic development and survival. Here we identify TCTEX1D2 mutations causing Jeune asphyxiating thoracic dystrophy with partially penetrant inheritance. Loss of TCTEX1D2 impairs retrograde intraflagellar transport (IFT) in humans and the protist Chlamydomonas, accompanied by destabilization of the retrograde IFT dynein motor. We thus define TCTEX1D2 as an integral component of the evolutionarily conserved retrograde IFT machinery. In complex with several IFT dynein light chains, it is required for correct vertebrate skeletal formation but may be functionally redundant under certain conditions. PMID:26044572

  6. A Least-Squares Transport Equation Compatible with Voids

    SciTech Connect

    Hansen, Jon; Peterson, Jacob; Morel, Jim; Ragusa, Jean; Wang, Yaqi

    2014-12-01

    Standard second-order self-adjoint forms of the transport equation, such as the even-parity, odd-parity, and self-adjoint angular flux equation, cannot be used in voids. Perhaps more important, they experience numerical convergence difficulties in near-voids. Here we present a new form of a second-order self-adjoint transport equation that has an advantage relative to standard forms in that it can be used in voids or near-voids. Our equation is closely related to the standard least-squares form of the transport equation with both equations being applicable in a void and having a nonconservative analytic form. However, unlike the standard least-squares form of the transport equation, our least-squares equation is compatible with source iteration. It has been found that the standard least-squares form of the transport equation with a linear-continuous finite-element spatial discretization has difficulty in the thick diffusion limit. Here we extensively test the 1D slab-geometry version of our scheme with respect to void solutions, spatial convergence rate, and the intermediate and thick diffusion limits. We also define an effective diffusion synthetic acceleration scheme for our discretization. Our conclusion is that our least-squares Sn formulation represents an excellent alternative to existing second-order Sn transport formulations

  7. Significance of flow clustering and sequencing on sediment transport: 1D sediment transport modelling

    NASA Astrophysics Data System (ADS)

    Hassan, Kazi; Allen, Deonie; Haynes, Heather

    2016-04-01

    This paper considers 1D hydraulic model data on the effect of high flow clusters and sequencing on sediment transport. Using observed flow gauge data from the River Caldew, England, a novel stochastic modelling approach was developed in order to create alternative 50 year flow sequences. Whilst the observed probability density of gauge data was preserved in all sequences, the order in which those flows occurred was varied using the output from a Hidden Markov Model (HMM) with generalised Pareto distribution (GP). In total, one hundred 50 year synthetic flow series were generated and used as the inflow boundary conditions for individual flow series model runs using the 1D sediment transport model HEC-RAS. The model routed graded sediment through the case study river reach to define the long-term morphological changes. Comparison of individual simulations provided a detailed understanding of the sensitivity of channel capacity to flow sequence. Specifically, each 50 year synthetic flow sequence was analysed using a 3-month, 6-month or 12-month rolling window approach and classified for clusters in peak discharge. As a cluster is described as a temporal grouping of flow events above a specified threshold, the threshold condition used herein is considered as a morphologically active channel forming discharge event. Thus, clusters were identified for peak discharges in excess of 10%, 20%, 50%, 100% and 150% of the 1 year Return Period (RP) event. The window of above-peak flows also required cluster definition and was tested for timeframes 1, 2, 10 and 30 days. Subsequently, clusters could be described in terms of the number of events, maximum peak flow discharge, cumulative flow discharge and skewness (i.e. a description of the flow sequence). The model output for each cluster was analysed for the cumulative flow volume and cumulative sediment transport (mass). This was then compared to the total sediment transport of a single flow event of equivalent flow volume

  8. Nodal collocation approximation for the multidimensional PL equations applied to transport source problems

    SciTech Connect

    Verdu, G.; Capilla, M.; Talavera, C. F.; Ginestar, D.

    2012-07-01

    PL equations are classical high order approximations to the transport equations which are based on the expansion of the angular dependence of the angular neutron flux and the nuclear cross sections in terms of spherical harmonics. A nodal collocation method is used to discretize the PL equations associated with a neutron source transport problem. The performance of the method is tested solving two 1D problems with analytical solution for the transport equation and a classical 2D problem. (authors)

  9. Epitaxial 1D electron transport layers for high-performance perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Han, Gill Sang; Chung, Hyun Suk; Kim, Dong Hoe; Kim, Byeong Jo; Lee, Jin-Wook; Park, Nam-Gyu; Cho, In Sun; Lee, Jung-Kun; Lee, Sangwook; Jung, Hyun Suk

    2015-09-01

    We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport.We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport

  10. Assessment of an efficient numerical solution of the 1D Richards' equation on bare soil

    NASA Astrophysics Data System (ADS)

    Varado, N.; Braud, I.; Ross, P. J.; Haverkamp, R.

    2006-05-01

    A new numerical scheme has been proposed by Ross [Ross, P.J., 2003. Modeling soil water and solute transport—fast, simplified numerical solutions. Agronomy Journal 95, 1352-1361] to solve the 1D Richards' equation [Richards, L.A., 1931. Capillary conduction of liquids through porous medium. Physics 1, 318-333]. This non-iterative solution uses the description of soil properties proposed by Brooks and Corey [Brooks, R.H., Corey, A.T., 1964. Hydraulic properties of porous media. Colorado State University, Fort Collins]. It allows the derivation of an analytical expression for the Kirchhoff potential used in the calculation of water fluxes. The degree of saturation is used as the dependent variable when the soil is unsaturated and the Kirchhoff potential is used in case of saturation. A space and time discretisation scheme leads to a tridiagonal set of linear equations that is solved non-iteratively. We propose in this paper an extensive test of this numerical method, evaluated only on a single case by Ross. The tests are conducted in two steps. First, the solution is assessed against two analytical solutions. The first one [Basha, H.A., 1999. Multidimensional linearized nonsteady infiltration with prescribed boundary conditions at the soil surface. Water Resources Research 35(1), 75-93] provides the water content profile when simplified soil characteristics such as the exponential law of Gardner [Gardner, W.R., 1958. Some steady-state solutions of the unsaturated moisture flow equations with application to evaporation from a water table. Soil Science 85, 228-232] are used. The Ross solution is compared to this solution on eight different soils that were fitted to this law. Analytical solution with the Brooks and Corey models is not available at the moment for the moisture profile but some exist for cumulative infiltration. Therefore, the second analytical solution, used in this study, is the one developed by Parlange et al. [Parlange, J.-Y., Haverkamp, R., Touma, J

  11. Dimensional reduction study of piezoelectric ceramics constitutive equations from 3-D to 2-D and 1-D.

    PubMed

    Zhu, Meiling; Leighton, Glenn

    2008-11-01

    Accurate performance evaluation is crucial to the design and development of macro/micro-sized piezoelectric devices, and key to this is the proper use of the stiffness/ compliance and piezoelectric coefficients of the piezoelectric ceramics involved. Although the literature points out effective piezoelectric coefficients e(31,f) and d(33,f) for thin film materials and reduced dimensionality of equations for bulk material, the elastic and piezoelectric coefficients remain unchanged from the 3-D equations in most reported 1-D and 2-D analyses of the macro/micro-sized devices involving the e form of the constitutive equations. The use of unchanged coefficients leads to variations between numerically predicted and experimental results in most devices. To understand effects of the dimensional reduction from 3-D to 2-D and 1-D on stiffness/compliance and piezoelectric coefficients, this paper derives the 2-D and 1-D constitutive equations from the 3-D equations, focusing on the discussion of often-required device configurations for sensor and actuator design and analysis. Two modified coefficients are proposed, termed reduced and enhanced, which enable better understanding of effects of the dimensional reduction and also effects on the design and analysis of sensors and actuators.

  12. The gBL transport equations

    SciTech Connect

    Mynick, H.E.

    1989-05-01

    The transport equations arising from the ''generalized Balescu- Lenard'' (gBL) collision operator are obtained, and some of their properties examined. The equations contain neoclassical and turbulent transport as two special cases, having the same structure. The resultant theory offers potential explanation for a number of results not well understood, including the anomalous pinch, observed ratios of Q/GAMMAT on TFTR, and numerical reproduction of ASDEX profiles by a model for turbulent transport invoked without derivation, but by analogy to neoclassical theory. The general equations are specialized to consideration of a number of particular transport mechanisms of interest. 10 refs.

  13. Experimental investigations of heat transport dynamics in a 1D porous medium column

    NASA Astrophysics Data System (ADS)

    Cherubini, Claudia; Pastore, Nicola; Giasi, Concetta I.; Allegretti, Nicoletta M.

    2016-04-01

    A laboratory physical model has been set up to analyse the forced convective flow and the related heat transport dynamics through a 1d porous medium column. In particular, the experiments regard the observation of thermal breakthrough curves obtained through a continuous flow injection in correspondence of eight thermocouple positioned uniformly along a thermally isolated column of porous medium. The experiment has been conducted for different flow rates in order to investigate the critical issues regarding heat transport phenomena such as the influence of non-linear flow regime, the relationship between the thermal dispersion with the flow velocity and the validity of the local thermal equilibrium assumption between the fluid and solid phase. The results emphasize the magnitude of the errors of the commonly used assumptions in the numerical modelling of heat transport.

  14. Long distance transport of ultracold atoms using a 1D optical lattice

    NASA Astrophysics Data System (ADS)

    Schmid, Stefan; Thalhammer, Gregor; Winkler, Klaus; Lang, Florian; Hecker Denschlag, Johannes

    2006-08-01

    We study the horizontal transport of ultracold atoms over macroscopic distances of up to 20 cm with a moving 1D optical lattice. By using an optical Bessel beam to form the optical lattice, we can achieve nearly homogeneous trapping conditions over the full transport length, which is crucial in order to hold the atoms against gravity for such a wide range. Fast transport velocities of up to 6 m s-1 (corresponding to about 1100 photon recoils) and accelerations of up to 2600 m s-2 are reached. Even at high velocities the momentum of the atoms is precisely defined with an uncertainty of less than one photon recoil. This allows for construction of an atom catapult with high kinetic energy resolution, which might have applications in novel collision experiments.

  15. High-Order Central WENO Schemes for 1D Hamilton-Jacobi Equations

    NASA Technical Reports Server (NTRS)

    Bryson, Steve; Levy, Doron; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    In this paper we derive fully-discrete Central WENO (CWENO) schemes for approximating solutions of one dimensional Hamilton-Jacobi (HJ) equations, which combine our previous works. We introduce third and fifth-order accurate schemes, which are the first central schemes for the HJ equations of order higher than two. The core ingredient is the derivation of our schemes is a high-order CWENO reconstructions in space.

  16. Evaluation of the Transport of Natural Radioactive Materials in Large Lysimeters Using Hydrus-1D

    NASA Astrophysics Data System (ADS)

    Pontedeiro, E.; Cipriani, M.; van Genuchten, M.; Simunek, J.

    2007-12-01

    The mining industry in Brazil often uses raw materials that contain relatively high concentrations of naturally occurring radioactive materials (referred to as NORM). Ores of relatively low grade typically are used to produce refined metals of high purity (e.g., Nb, Ta, Sn, and Au) using pyrometallurgic processes. The final waste is a slag rich in natural radioactive contaminants (the U and Th decay series), which are then usually deposited in industrial landfills. To study the long-term fate and transport of radionuclides leached from the NORM wastes, several large (3 m deep) lysimeters were constructed at the Pocos de Caldas Laboratory of the Brazilian Nuclear Energy Commision (CNEN). The lysimeters were packed with surface soils and slags from one of the mining sites in South East Brazil. Main purpose of our lysimeter experiments was to follow the dissolution and transport of radionuclides from the slags under natural climatic conditions. Leaching rates and radionuclide concentrations of the effluent were observed during a three-year time period. A variety of physical and chemical properties of the soils and slags (including laboratory batch equilibrium sorption values) were also determined. The data were analyzed using several computer software packages, including the STANMOD code for analytical modeling of decay chain transport during steady flow, the HYDRUS-1D code for variably-saturated flow and the transport of multiple solutes, and the HP1 code for a more comprehensive analysis of the geochemistry involved. In this presentation we describe the experimental setup and provide preliminary results of the theoretical analyses, especially those using HYDRUS-1D.

  17. AKNS hierarchy, Darboux transformation and conservation laws of the 1D nonautonomous nonlinear Schroedinger equations

    SciTech Connect

    Zhao Dun; Zhang Yujuan; Lou Weiwei; Luo Honggang

    2011-04-15

    By constructing nonisospectral Ablowitz-Kaup-Newell-Segur (AKNS) hierarchy, we investigate the nonautonomous nonlinear Schroedinger (NLS) equations which have been used to describe the Feshbach resonance management in matter-wave solitons in Bose-Einstein condensate and the dispersion and nonlinearity managements for optical solitons. It is found that these equations are some special cases of a new integrable model of nonlocal nonautonomous NLS equations. Based on the Lax pairs, the Darboux transformation and conservation laws are explored. It is shown that the local external potentials would break down the classical infinite number of conservation laws. The result indicates that the integrability of the nonautonomous NLS systems may be nontrivial in comparison to the conventional concept of integrability in the canonical case.

  18. Nodally exact Ritz discretizations of 1D diffusion-absorption and Helmholtz equations by variational FIC and modified equation methods

    NASA Astrophysics Data System (ADS)

    Felippa, C. A.; Oñate, E.

    2007-01-01

    This article presents the first application of the Finite Calculus (FIC) in a Ritz-FEM variational framework. FIC provides a steplength parametrization of mesh dimensions, which is used to modify the shape functions. This approach is applied to the FEM discretization of the steady-state, one-dimensional, diffusion-absorption and Helmholtz equations. Parametrized linear shape functions are directly inserted into a FIC functional. The resulting Ritz-FIC equations are symmetric and carry a element-level free parameter coming from the function modification process. Both constant- and variable-coefficient cases are studied. It is shown that the parameter can be used to produce nodally exact solutions for the constant coefficient case. The optimal value is found by matching the finite-order modified differential equation (FOMoDE) of the Ritz-FIC equations with the original field equation. The inclusion of the Ritz-FIC models in the context of templates is examined. This inclusion shows that there is an infinite number of nodally exact models for the constant coefficient case. The ingredients of these methods (FIC, Ritz, MoDE and templates) can be extended to multiple dimensions

  19. Singular solutions to Protter's problem for (3+1)-D degenerate wave equation

    NASA Astrophysics Data System (ADS)

    Nikolov, Aleksey; Popivanov, Nedyu

    2012-11-01

    In 1952 M. H. Protter introduced some boundary value problems for weakly hyperbolic equations in a domain bounded by two characteristic surfaces and non-characteristic plane region. Such problems arise in fluid dynamics. They are multidimensional analogues of the Darboux problems on the plain. The Protter problems are not well possed since the homogeneous adjoint problems have infinitely many nontrivial classical solutions. In 1993 Popivanov and Schneider found the reason of this fact: the unique generalized solution of a Protter problem may have a strong power-type singularity at the vertex of one of the characteristic surfaces. It is interesting that this singularity is isolated at this point and does not propagate along the bicharacteristics. In the present paper we represent the asymptotic behavior of these singularities when the right-hand side of the equation is of the form of a harmonic polynomial.

  20. Stochastic Heat Equation Limit of a (2 + 1)d Growth Model

    NASA Astrophysics Data System (ADS)

    Borodin, Alexei; Corwin, Ivan; Toninelli, Fabio Lucio

    2016-07-01

    We determine a {q to 1} limit of the two-dimensional q-Whittaker driven particle system on the torus studied previously in Corwin and Toninelli (Electron. Commun. Probab. 21(44):1-12, 2016). This has an interpretation as a (2 + 1)-dimensional stochastic interface growth model, which is believed to belong to the so-called anisotropic Kardar-Parisi-Zhang (KPZ) class. This limit falls into a general class of two-dimensional systems of driven linear SDEs which have stationary measures on gradients. Taking the number of particles to infinity we demonstrate Gaussian free field type fluctuations for the stationary measure. Considering the temporal evolution of the stationary measure, we determine that along characteristics, correlations are asymptotically given by those of the (2 + 1)-dimensional additive stochastic heat equation. This confirms (for this model) the prediction that the non-linearity for the anisotropic KPZ equation in (2 + 1)-dimension is irrelevant.

  1. Shock capturing data assimilation algorithm for 1D shallow water equations

    NASA Astrophysics Data System (ADS)

    Tirupathi, Seshu; Tchrakian, Tigran T.; Zhuk, Sergiy; McKenna, Sean

    2016-02-01

    We propose a new data assimilation algorithm for shallow water equations in one dimension. The algorithm is based upon Discontinuous Galerkin spatial discretization of shallow water equations (DG-SW model) and the continuous formulation of the minimax filter. The latter allows for construction of a robust estimation of the state of the DG-SW model and computes worst-case bounds for the estimation error, provided the uncertain parameters belong to a given bounding set. Numerical studies show that, given sparse observations from numerical or physical experiments, the proposed algorithm quickly reconstructs the true solution even in the presence of shocks, rarefaction waves and unknown values of model parameters. The minimax filter is compared against the ensemble Kalman filter (EnKF) for a benchmark dam-break problem and the results show that the minimax filter converges faster to the true solution for sparse observations.

  2. A transport equation for reaction rate in turbulent flows

    NASA Astrophysics Data System (ADS)

    Sabelnikov, V. A.; Lipatnikov, A. N.; Chakraborty, N.; Nishiki, S.; Hasegawa, T.

    2016-08-01

    New transport equations for chemical reaction rate and its mean value in turbulent flows have been derived and analyzed. Local perturbations of the reaction zone by turbulent eddies are shown to play a pivotal role even for weakly turbulent flows. The mean-reaction-rate transport equation is shown to involve two unclosed dominant terms and a joint closure relation for the sum of these two terms is developed. Obtained analytical results and, in particular, the closure relation are supported by processing two widely recognized sets of data obtained from earlier direct numerical simulations of statistically planar 1D premixed flames associated with both weak large-scale and intense small-scale turbulence.

  3. A critical comparison of the numerical solution of the 1D filtered Vlasov-Poisson equation

    NASA Astrophysics Data System (ADS)

    Viñas, A. F.; Klimas, A. J.

    2003-04-01

    We present a comparison of the numerical solution of the filtered Vlasov-Poisson system of equations using the Fourier-Fourier and the Flux-Balance-MacCormack methods in the electrostatic, non-relativistic case. We show that the splitting method combined with the Flux-Balance-MacCormack scheme provides an efficient and accurate scheme for integrating the filtered Vlasov-Poisson system in their self-consistent field. Finally we present various typical problems of interest in plasma physics research which can be studied with the scheme presented here.

  4. Mechanisms of 1D crystal growth in reactive vapor transport: indium nitride nanowires.

    PubMed

    Vaddiraju, Sreeram; Mohite, Aditya; Chin, Alan; Meyyappan, M; Sumanasekera, Gamini; Alphenaar, Bruce W; Sunkara, Mahendra K

    2005-08-01

    Indium nitride (InN) nanowire synthesis using indium (In) vapor transport in a dissociated ammonia environment (reactive vapor transport) is studied in detail to understand the nucleation and growth mechanisms involved with the so-called "self-catalysis" schemes. The results show that the nucleation of InN crystal occurs first on the substrate. Later, In droplets are formed on top of the InN crystals because of selective wetting of In onto InN crystals. Further growth via liquid-phase epitaxy through In droplets leads the growth in one dimension (1D), resulting in the formation of InN nanowires. The details about the nucleation and growth aspects within these self-catalysis schemes are rationalized further by demonstrating the growth of heteroepitaxially oriented nanowire arrays on single-crystal substrates and "tree-like" morphologies on a variety of substrates. However, the direct nitridation of In droplets using dissociated ammonia results in the spontaneous nucleation and basal growth of nanowires directly from the In melt surface, which is quite different from the above-mentioned nucleation mechanism with the reactive vapor transport case. The InN nanowires exhibit a band gap of 0.8 eV, whereas the mixed phase of InN and In(2)O(3) nanowires exhibit a peak at approximately 1.9 eV in addition to that at 0.8 eV.

  5. The telegraph equation in charged particle transport

    NASA Technical Reports Server (NTRS)

    Gombosi, T. I.; Jokipii, J. R.; Kota, J.; Lorencz, K.; Williams, L. L.

    1993-01-01

    We present a new derivation of the telegraph equation which modifies its coefficients. First, an infinite order partial differential equation is obtained for the velocity space solid angle-averaged phase-space distribution of particles which underwent at least a few collisions. It is shown that, in the lowest order asymptotic expansion, this equation simplifies to the well-known diffusion equation. The second-order asymptotic expansion for isotropic small-angle scattering results in a modified telegraph equation with a signal propagation speed of v(5/11) exp 1/2 instead of the usual v/3 exp 1/2. Our derivation of a modified telegraph equation follows from an expansion of the Boltzmann equation in the relevant smallness parameters and not from a truncation of an eigenfunction expansion. This equation is consistent with causality. It is shown that, under steady state conditions in a convecting plasma, the telegraph equation may be regarded as a diffusion equation with a modified transport coefficient, which describes a combination of diffusion and cosmic-ray inertia.

  6. Bed-load transport modelling by coupling an empirical routing scheme and a hydrological-1-D-hydrodynamic model - case study application for a large alpine valley

    NASA Astrophysics Data System (ADS)

    Gems, B.; Achleitner, S.; Plörer, M.; Schöberl, F.; Huttenlau, M.; Aufleger, M.

    2012-12-01

    Sediment transport in mountain rivers and torrents is a substantial process within the assessment of flood related hazard potential and vulnerability in alpine catchments. Focusing on fluvial transport processes, river bed erosion and deposition considerably affects the extent of inundation. The present work deals with scenario-specific bed-load transport modelling in a large alpine valley in the Austrian Alps. A routing scheme founding on empirical equations for the calculation of transport capacities, incipient motion conditions and drag forces is set up and applied to the case study area for two historic flood events. The required hydraulic data result from a distributed hydrological-1-D-hydraulic model. Hydraulics and bed-load transport are simulated sequentially providing a technically well-founded and feasible methodology for the estimation of bed-load transport rates during flood events.

  7. On inter-tidal transport equation

    USGS Publications Warehouse

    Cheng, Ralph T.; Feng, Shizuo; Pangen, Xi

    1989-01-01

    The transports of solutes, sediments, nutrients, and other tracers are fundamental to the interactive physical, chemical, and biological processes in estuaries. The characteristic time scales for most estuarine biological and chemical processes are on the order of several tidal cycles or longer. To address the long-term transport mechanism meaningfully, the formulation of an inter-tidal conservation equation is the main subject of this paper. The commonly used inter-tidal conservation equation takes the form of a convection-dispersion equation in which the convection is represented by the Eulerian residual current, and the dispersion terms are due to the introduction of a Fickian hypothesis, unfortunately, the physical significance of this equation is not clear, and the introduction of a Fickian hypothesis is at best an ad hoc approximation. Some recent research results on the Lagrangian residual current suggest that the long-term transport problem is more closely related to the Lagrangian residual current than to the Eulerian residual current. With the aid of additional insight of residual current, the inter-tidal transport equation has been reformulated in this paper using a small perturbation method for a weakly nonlinear tidal system. When tidal flows can be represented by an M2 system, the new intertidal transport equation also takes the form of a convective-dispersion equation without the introduction of a Fickian hypothesis. The convective velocity turns out to be the first order Lagrangian residual current (the sum of the Eulerian residual current and the Stokes’ drift), and the correlation terms take the form of convection with the Stokes’ drift as the convective velocity. The remaining dispersion terms are perturbations of lower order solution to higher order solutions due to shear effect and turbulent mixing.

  8. Resolution of the 1D regularized Burgers equation using a spatial wavelet approximation

    NASA Technical Reports Server (NTRS)

    Liandrat, J.; Tchamitchian, PH.

    1990-01-01

    The Burgers equation with a small viscosity term, initial and periodic boundary conditions is resolved using a spatial approximation constructed from an orthonormal basis of wavelets. The algorithm is directly derived from the notions of multiresolution analysis and tree algorithms. Before the numerical algorithm is described these notions are first recalled. The method uses extensively the localization properties of the wavelets in the physical and Fourier spaces. Moreover, the authors take advantage of the fact that the involved linear operators have constant coefficients. Finally, the algorithm can be considered as a time marching version of the tree algorithm. The most important point is that an adaptive version of the algorithm exists: it allows one to reduce in a significant way the number of degrees of freedom required for a good computation of the solution. Numerical results and description of the different elements of the algorithm are provided in combination with different mathematical comments on the method and some comparison with more classical numerical algorithms.

  9. Aspheric surface testing by irradiance transport equation

    NASA Astrophysics Data System (ADS)

    Shomali, Ramin; Darudi, Ahmad; Nasiri, Sadollah; Asgharsharghi Bonab, Armir

    2010-10-01

    In this paper a method for aspheric surface testing is presented. The method is based on solving the Irradiance Transport Equation (ITE).The accuracy of ITE normally depends on the amount of the pick to valley of the phase distribution. This subject is investigated by a simulation procedure.

  10. Transport of an interacting Bose gas in 1D disordered lattices

    SciTech Connect

    D'Errico, C.; Chaudhuri, S.; Gori, L.; Kumar, A.; Lucioni, E.; Tanzi, L.; Inguscio, M.; Modugno, G.

    2014-08-20

    We use ultracold atoms in a quasiperiodic lattice to study two outstanding problems in the physics of disordered systems: a) the anomalous diffusion of a wavepacket in the presence of disorder, interactions and noise; b) the transport of a disordered superfluid. a) Our results show that the subdiffusion, observed when interaction alone is present, can be modelled with a nonlinear diffusion equation and the peculiar shape of the expanding density profiles can be connected to the microscopic nonlinear diffusion coefficients. Also when noise alone is present we can describe the observed normal diffusion dynamics by existing microscopic models. In the unexplored regime in which noise and interaction are combined, instead, we observe an anomalous diffusion, that we model with a generalized diffusion equation, where noise- and interaction-induced contributions add each other. b) We find that an instability appearing at relatively large momenta can be employed to locate the fluid-insulator crossover driven by disorder. By investigating the momentum-dependent transport, we observe a sharp crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. The set of critical disorder and interaction strengths for which such critical momentum vanishes, can be identified with the separation between a fluid regime and an insulating one and can be related to the predicted zero-temperature superfluid-Bose glass transition.

  11. Numerical solution of the electron transport equation

    NASA Astrophysics Data System (ADS)

    Woods, Mark

    The electron transport equation has been solved many times for a variety of reasons. The main difficulty in its numerical solution is that it is a very stiff boundary value problem. The most common numerical methods for solving boundary value problems are symmetric collocation methods and shooting methods. Both of these types of methods can only be applied to the electron transport equation if the boundary conditions are altered with unrealistic assumptions because they require too many points to be practical. Further, they result in oscillating and negative solutions, which are physically meaningless for the problem at hand. For these reasons, all numerical methods for this problem to date are a bit unusual because they were designed to try and avoid the problem of extreme stiffness. This dissertation shows that there is no need to introduce spurious boundary conditions or invent other numerical methods for the electron transport equation. Rather, there already exists methods for very stiff boundary value problems within the numerical analysis literature. We demonstrate one such method in which the fast and slow modes of the boundary value problem are essentially decoupled. This allows for an upwind finite difference method to be applied to each mode as is appropriate. This greatly reduces the number of points needed in the mesh, and we demonstrate how this eliminates the need to define new boundary conditions. This method is verified by showing that under certain restrictive assumptions, the electron transport equation has an exact solution that can be written as an integral. We show that the solution from the upwind method agrees with the quadrature evaluation of the exact solution. This serves to verify that the upwind method is properly solving the electron transport equation. Further, it is demonstrated that the output of the upwind method can be used to compute auroral light emissions.

  12. Pdf - Transport equations for chemically reacting flows

    NASA Technical Reports Server (NTRS)

    Kollmann, W.

    1989-01-01

    The closure problem for the transport equations for pdf and the characteristic functions of turbulent, chemically reacting flows is addressed. The properties of the linear and closed equations for the characteristic functional for Eulerian and Lagrangian variables are established, and the closure problem for the finite-dimensional case is discussed for pdf and characteristic functions. It is shown that the closure for the scalar dissipation term in the pdf equation developed by Dopazo (1979) and Kollmann et al. (1982) results in a single integral, in contrast to the pdf, where double integration is required. Some recent results using pdf methods obtained for turbulent flows with combustion, including effects of chemical nonequilibrium, are discussed.

  13. Reactive Transport Modeling of Microbially-Mediated Chromate Reduction in 1-D Soil Columns

    NASA Astrophysics Data System (ADS)

    Qiu, H.; Viamajala, S.; Alam, M. M.; Peyton, B. M.; Petersen, J. N.; Yonge, D. R.

    2002-12-01

    Cr(VI) reduction tests were performed with the well known metal reducing bacterium Shewanella oneidensis MR-1 in liquid phase batch reactors and continuous flow soil columns under anaerobic conditions. In the batch tests, the cultures were grown with fumarate as the terminal electron acceptor and lactate as the electron donor in a simulated groundwater medium to determine yield coefficients and specific growth rates. The bench-scale soil column experiments were carried out with MR-1 to test the hypothesis that the kinetic parameters obtained in batch studies, combined with microbial attachment /detachment processes, will accurately predict reactive transport of Cr(VI) during bacterial Cr(VI) reduction in a soil matrix. Cr(VI)-free simulated groundwater media containing fumarate as the limiting substrate and lactate was supplied to a 2.1cm (ID) x 15 cm soil column inoculated with MR-1 for a duration of 9 residence times to allow for biomass to build-up in the column. Thereafter the column was supplied with both Cr(VI) and substrate. The concentrations of effluent substrate, biomass and Cr(VI) were monitored on a periodic basis and attached biomass in the column was measured in the termination of each column test. A reactive transport model was developed in which 6 governing equations deal with Cr(VI) bioreaction, fumarate (as electron donor) consumption, aqueous biomass growth and transport, solid biomass detachment and attachment kinetics, aqueous and solid phase enzyme reaction and transport, respectively. The model incorporating the enzyme reaction kinetics for Cr(VI) reduction, Monod kinetic expressions for substrate depletion, nonlinear attachment and detachment kinetics for aqueous and solid phase microorganism concentration, was solved by a fully implicit, finite-difference procedure using RT3D (A Modular Computer Code for Reactive Multi-species Transport in 3-Dimensional Groundwater Systems) platform in one dimension. Cr(VI)-free column data was used to

  14. Column Testing and 1D Reactive Transport Modeling to Evaluate Uranium Plume Persistence Processes

    NASA Astrophysics Data System (ADS)

    Johnson, R. H.; Morrison, S.; Morris, S.; Tigar, A.; Dam, W. L.; Dayvault, J.

    2015-12-01

    At many U.S. Department of Energy Office of Legacy Management sites, 100 year natural flushing was selected as a remedial option for groundwater uranium plumes. However, current data indicate that natural flushing is not occurring as quickly as expected and solid-phase and aqueous uranium concentrations are persistent. At the Grand Junction, Colorado office site, column testing was completed on core collected below an area where uranium mill tailings have been removed. The total uranium concentration in this core was 13.2 mg/kg and the column was flushed with laboratory-created water with no uranium and chemistry similar to the nearby Gunnison River. The core was flushed for a total of 91 pore volumes producing a maximum effluent uranium concentration of 6,110 μg/L at 2.1 pore volumes and a minimum uranium concentration of 36.2 μg/L at the final pore volume. These results indicate complex geochemical reactions at small pore volumes and a long tailing affect at greater pore volumes. Stop flow data indicate the occurrence of non-equilibrium processes that create uranium concentration rebound. These data confirm the potential for plume persistence, which is occurring at the field scale. 1D reactive transport modeling was completed using PHREEQC (geochemical model) and calibrated to the column test data manually and using PEST (inverse modeling calibration routine). Processes of sorption, dual porosity with diffusion, mineral dissolution, dispersion, and cation exchange were evaluated separately and in combination. The calibration results indicate that sorption and dual porosity are major processes in explaining the column test data. These processes are also supported by fission track photographs that show solid-phase uranium residing in less mobile pore spaces. These procedures provide valuable information on plume persistence and secondary source processes that may be used to better inform and evaluate remedial strategies, including natural flushing.

  15. Quantum and semi-classical transport in RTDs using NEMO 1-D

    NASA Technical Reports Server (NTRS)

    Klimeck, G.; Stout, P.; Bowen, R. C.

    2003-01-01

    NEMO 1-D has been developed primarily for the simulation of resonant tunneling diodes, and quantitative and predictive agreements with experimental high performance, high current density devices have been achieved in the past.

  16. GIS-based channel flow and sediment transport simulation using CCHE1D coupled with AnnAGNPS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    CCHE1D (Center for Computational Hydroscience and Engineering 1-Dimensional model) simulates unsteady free-surface flows with nonequilibrium, nonuniform sediment transport in dendritic channel networks. Since early 1990’s, the model and its software packages have been developed and continuously main...

  17. Maximal stochastic transport in the Lorenz equations

    NASA Astrophysics Data System (ADS)

    Agarwal, Sahil; Wettlaufer, John

    2015-11-01

    We calculate the stochastic upper bounds for the Lorenz equations using an extension of the background method. In analogy with Rayleigh-Benard convection the upper bounds are for heat transport versus Rayleigh number. As might be expected the stochastic upper bounds are larger than the deterministic counterpart of Souza and Doering (2015), but their variation with noise amplitude exhibits surprising behavior. Below the transition to chaotic dynamics the upper bounds increase monotonically with noise amplitude. However, in the chaotic regime this monotonicity is lost; at a particular Rayleigh number the bound may increase or decrease with noise amplitude. The origin of this behavior is the coupling between the noise and unstable periodic orbits. This is confirmed by examining the close returns plots of the full solutions to the stochastic equations. Finally, we note that these solutions demonstrate that the effect of noise is equivalent to the effect of chaos.

  18. Maximal stochastic transport in the Lorenz equations

    NASA Astrophysics Data System (ADS)

    Agarwal, Sahil; Wettlaufer, J. S.

    2016-01-01

    We calculate the stochastic upper bounds for the Lorenz equations using an extension of the background method. In analogy with Rayleigh-Bénard convection the upper bounds are for heat transport versus Rayleigh number. As might be expected, the stochastic upper bounds are larger than the deterministic counterpart of Souza and Doering [1], but their variation with noise amplitude exhibits interesting behavior. Below the transition to chaotic dynamics the upper bounds increase monotonically with noise amplitude. However, in the chaotic regime this monotonicity depends on the number of realizations in the ensemble; at a particular Rayleigh number the bound may increase or decrease with noise amplitude. The origin of this behavior is the coupling between the noise and unstable periodic orbits, the degree of which depends on the degree to which the ensemble represents the ergodic set. This is confirmed by examining the close returns plots of the full solutions to the stochastic equations and the numerical convergence of the noise correlations. The numerical convergence of both the ensemble and time averages of the noise correlations is sufficiently slow that it is the limiting aspect of the realization of these bounds. Finally, we note that the full solutions of the stochastic equations demonstrate that the effect of noise is equivalent to the effect of chaos.

  19. Rounding errors may be beneficial for simulations of atmospheric flow: results from the forced 1D Burgers equation

    NASA Astrophysics Data System (ADS)

    Düben, Peter D.; Dolaptchiev, Stamen I.

    2015-08-01

    Inexact hardware can reduce computational cost, due to a reduced energy demand and an increase in performance, and can therefore allow higher-resolution simulations of the atmosphere within the same budget for computation. We investigate the use of emulated inexact hardware for a model of the randomly forced 1D Burgers equation with stochastic sub-grid-scale parametrisation. Results show that numerical precision can be reduced to only 12 bits in the significand of floating-point numbers—instead of 52 bits for double precision—with no serious degradation in results for all diagnostics considered. Simulations that use inexact hardware on a grid with higher spatial resolution show results that are significantly better compared to simulations in double precision on a coarser grid at similar estimated computing cost. In the second half of the paper, we compare the forcing due to rounding errors to the stochastic forcing of the stochastic parametrisation scheme that is used to represent sub-grid-scale variability in the standard model setup. We argue that stochastic forcings of stochastic parametrisation schemes can provide a first guess for the upper limit of the magnitude of rounding errors of inexact hardware that can be tolerated by model simulations and suggest that rounding errors can be hidden in the distribution of the stochastic forcing. We present an idealised model setup that replaces the expensive stochastic forcing of the stochastic parametrisation scheme with an engineered rounding error forcing and provides results of similar quality. The engineered rounding error forcing can be used to create a forecast ensemble of similar spread compared to an ensemble based on the stochastic forcing. We conclude that rounding errors are not necessarily degrading the quality of model simulations. Instead, they can be beneficial for the representation of sub-grid-scale variability.

  20. EFDC1D - A ONE DIMENSIONAL HYDRODYNAMIC AND SEDIMENT TRANSPORT MODEL FOR RIVER AND STREAM NETWORKS: MODEL THEORY AND USERS GUIDE

    EPA Science Inventory

    This technical report describes the new one-dimensional (1D) hydrodynamic and sediment transport model EFDC1D. This model that can be applied to stream networks. The model code and two sample data sets are included on the distribution CD. EFDC1D can simulate bi-directional unstea...

  1. Asymptotic Analysis of Transport Equation in Annulus

    NASA Astrophysics Data System (ADS)

    Wu, Lei; Yang, Xiongfeng; Guo, Yan

    2016-09-01

    We consider the diffusive limit of a steady neutron transport equation with one-speed velocity in a two-dimensional annulus. A classical theorem in Bensoussan et al. (Publ Res Inst Math Sci 15:53-157, 1979) states that the solution can be approximated in L^{∞} by the sum of the interior solution and Knudsen layer derived from Milne problem. However, this result was disproved in Wu and Guo (Commun Math Phys 336:1473-1553, 2015) in a plate via a different boundary layer expansion with geometric correction. In this paper, we established the diffusive limit and provide a counterexample to Bensoussan et al. (1979) in non-convex domains.

  2. Complementing Graphenes: 1D Interplanar Charge Transport in Polymeric Graphitic Carbon Nitrides.

    PubMed

    Merschjann, Christoph; Tschierlei, Stefanie; Tyborski, Tobias; Kailasam, Kamalakannan; Orthmann, Steven; Hollmann, Dirk; Schedel-Niedrig, Thomas; Thomas, Arne; Lochbrunner, Stefan

    2015-12-22

    Charge transport in polymeric graphitic carbon nitrides is shown to proceed via diffusive hopping of electron and hole polarons with reasonably high mobilities >10(-5) cm(2) V(-1) s(-1). The power-law behavior of the ultrafast luminescence decay exhibits that the predominant transport direction is perpendicular to the graphitic polymer sheets, thus complementing 2D materials like graphene. PMID:26543003

  3. Detection and characterization of uranium-humic complexes during 1D transport studies

    SciTech Connect

    Lesher, Emily K.; Honeyman, Bruce D.; Ranville, James F.

    2013-05-01

    The speciation and transport of uranium (VI) through porous media is highly dependent on solution conditions, the presence of complexing ligands, and the nature of the porous media. The dependency on many variables makes prediction of U transport in bench-scale experiments and in the field difficult. In particular, the identification of colloidal U phases poses a technical challenge. Transport of U in the presence and absence of natural organic matter (Suwannee River humic acid, SRHA) through silica sand and hematite coated silica sand was tested at pH 4 and 5 using static columns, where flow is controlled by gravity and residence time between advective pore volume exchanges can be strictly controlled. The column effluents were characterized by traditional techniques including ICPMS quantification of total [U] and [Fe], TOC analysis of [DOC], and pH analysis, and also by non-traditional techniques: flow field flow fractionation with online ICPMS detection (FlFFF-ICPMS) and specific UV absorbance (SUVA) characterization of effluent fractions. Key results include that the transport of U through the columns was enhanced by pre-equilibration with SRHA, and previously deposited U was remobilized by the addition of SRHA. The advanced techniques yielded important insights on the mechanisms of transport: FlFFF-ICPMS identified a U-SRHA complex as the mobile U species and directly quantified relative amounts of the complex, while specific UV absorbance (SUVA) measurements indicated a composition-based fractionation onto the porous media.

  4. Quantum transport through disordered 1D wires: Conductance via localized and delocalized electrons

    SciTech Connect

    Gopar, Víctor A.

    2014-01-14

    Coherent electronic transport through disordered systems, like quantum wires, is a topic of fundamental and practical interest. In particular, the exponential localization of electron wave functions-Anderson localization-due to the presence of disorder has been widely studied. In fact, Anderson localization, is not an phenomenon exclusive to electrons but it has been observed in microwave and acoustic experiments, photonic materials, cold atoms, etc. Nowadays, many properties of electronic transport of quantum wires have been successfully described within a scaling approach to Anderson localization. On the other hand, anomalous localization or delocalization is, in relation to the Anderson problem, a less studied phenomenon. Although one can find signatures of anomalous localization in very different systems in nature. In the problem of electronic transport, a source of delocalization may come from symmetries present in the system and particular disorder configurations, like the so-called Lévy-type disorder. We have developed a theoretical model to describe the statistical properties of transport when electron wave functions are delocalized. In particular, we show that only two physical parameters determine the complete conductance distribution.

  5. 1D momentum-conserving systems: the conundrum of anomalous versus normal heat transport

    NASA Astrophysics Data System (ADS)

    Li, Yunyun; Liu, Sha; Li, Nianbei; Hänggi, Peter; Li, Baowen

    2015-04-01

    Transport and the spread of heat in Hamiltonian one dimensional momentum conserving nonlinear systems is commonly thought to proceed anomalously. Notable exceptions, however, do exist of which the coupled rotator model is a prominent case. Therefore, the quest arises to identify the origin of manifest anomalous energy and momentum transport in those low dimensional systems. We develop the theory for both, the statistical densities for momentum- and energy-spread and particularly its momentum-/heat-diffusion behavior, as well as its corresponding momentum/heat transport features. We demonstrate that the second temporal derivative of the mean squared deviation of the momentum spread is proportional to the equilibrium correlation of the total momentum flux. Subtracting the part which corresponds to a ballistic momentum spread relates (via this integrated, subleading momentum flux correlation) to an effective viscosity, or equivalently, to the underlying momentum diffusivity. We next put forward the intriguing hypothesis: normal spread of this so adjusted excess momentum density causes normal energy spread and alike normal heat transport (Fourier Law). Its corollary being that an anomalous, superdiffusive broadening of this adjusted excess momentum density in turn implies an anomalous energy spread and correspondingly anomalous, superdiffusive heat transport. This hypothesis is successfully corroborated within extensive molecular dynamics simulations over large extended time scales. Our numerical validation of the hypothesis involves four distinct archetype classes of nonlinear pair-interaction potentials: (i) a globally bounded pair interaction (the noted coupled rotator model), (ii) unbounded interactions acting at large distances (the coupled rotator model amended with harmonic pair interactions), (iii) the case of a hard point gas with unbounded square-well interactions and (iv) a pair interaction potential being unbounded at short distances while displaying an

  6. Model equations for high current transport

    SciTech Connect

    Lee, E.P.

    1985-06-01

    The use of distribution functions to model transverse beam dynamics is discussed. Emphasis is placed on envelope equations, moments, the Vlasov equation, and the Kapchinski-Vladimirskij distribution. 10 refs.

  7. Impact of water table fluctuations on water flow and solute transport in 1D column systems

    NASA Astrophysics Data System (ADS)

    Rühle, F.; Stumpp, C.

    2012-04-01

    Although hydrological processes and mass fluxes in the unsaturated and saturated zone have been well studied separately, little is known about transition processes between these zones. Since the transition zone is dynamic and varies spatially and temporally with fluctuations of the water table, water flow and solute transport are believed to vary dynamically, too. This may influence the transport and fate of dissolved contaminants and consequently the quality of groundwater. In order to protect and maintain drinking water resources, improved understanding about hydrological processes at the dynamic interface between the unsaturated and saturated zone is needed. The objective of this study was to investigate the impact of water table fluctuations on one-dimensional vertical flow and solute transport in laboratory column systems. Therefore, two flow-through columns were constantly irrigated with groundwater at an infiltration rate of 4.7 cm/d. In one column the water table was kept statically fixed in the middle, in the other column the water table was continually fluctuated by regularly raising and lowering the outflow tube. Several multi-tracer experiments were conducted and compared injecting the tracers bromide, deuterium and 18-oxygen at different water levels. Data modelling was performed with a lumped parameter model to simulate the hydrological fluxes. Our results showed that at static water table and similar water fluxes in both columns, structural heterogeneities due to packing lead to differences in solute transport, e.g. different dispersivity. Tracer breakthrough curves were well simulated with the lumped parameter model indicating that the systems were at steady state. When the water table was fluctuated small differences in solute transport were observed. Even with a fluctuating water table the lumped parameter model yielded high modelling accuracy and indicated that under certain hydrological conditions water table fluctuations lead to slightly

  8. Development of a 3D to 1D Particle Transport Model to Predict Deposition in the Lungs

    NASA Astrophysics Data System (ADS)

    Oakes, Jessica M.; Grandmont, Celine; Shadden, Shawn C.; Vignon-Clementel, Irene E.

    2014-11-01

    Aerosolized particles are commonly used for therapeutic drug delivery as they can be delivered to the body systemically or be used to treat lung diseases. Recent advances in computational resources have allowed for sophisticated pulmonary simulations, however it is currently impossible to solve for airflow and particle transport for all length and time scales of the lung. Instead, multi-scale methods must be used. In our recent work, where computational methods were employed to solve for airflow and particle transport in the rat airways (Oakes et al. (2014), Annals of Biomedical Engineering 42, 899), the number of particles to exit downstream of the 3D domain was determined. In this current work, the time-dependent Lagrangian description of particles was used to numerically solve a 1D convection-diffusion model (trumpet model, Taulbee and Yu (1975), Journal of Applied Physiology, 38, 77) parameterized specifically for the lung. The expansion of the airway dimensions was determined based on data collected from our aerosol exposure experiments (Oakes et al. (2014), Journal of Applied Physiology, 116, 1561). This 3D-1D framework enables us to predict the fate of particles in the whole lung. This work was supported by the Whitaker Foundation at the IIE, a INRIA Associated Team Postdoc Grant, and a UC Presidential Fellowship.

  9. Transport equations for multicomponent anisotropic space plasmas - A review

    NASA Technical Reports Server (NTRS)

    Barakat, A. R.; Schunk, R. W.

    1982-01-01

    An attempt is made to present a unified approach to the study of transport phenomena in multicomponent anisotropic space plasmas. In particular, a system of generalized transport equations is presented that can be applied to widely different plasma flow conditions. The generalized transport equations can describe subsonic and supersonic flows, collision-dominated and collisionless flows, plasma flows in rapidly changing magnetic field configurations, multicomponent plasma flows with large temperature differences between the interacting species, and plasma flows that contain anisotropic temperature distributions. In addition, if Maxwell's equations of electricity and magnetism are added to the system of transport equations, they can be used to model electrostatic shocks, double layers, and magnetic merging processes. These transport equations also contain terms which act to regulate both the heat flow and temperature anisotropy, processes which appear to be operating in the solar wind.

  10. A rain splash transport equation assimilating field and laboratory measurements

    NASA Astrophysics Data System (ADS)

    Dunne, Thomas; Malmon, Daniel V.; Mudd, Simon M.

    2010-03-01

    Process-based models of hillslope evolution require transport equations relating sediment flux to its major controls. An equation for rain splash transport in the absence of overland flow was constructed by modifying an approach developed by Reeve (1982) and parameterizing it with measurements from single-drop laboratory experiments and simulated rainfall on a grassland in East Africa. The equation relates rain splash to hillslope gradient, the median raindrop diameter of a storm, and ground cover density; the effect of soil texture on detachability can be incorporated from other published results. The spatial and temporal applicability of such an equation for rain splash transport in the absence of overland flow on uncultivated hillslopes can be estimated from hydrological calculations. The predicted transport is lower than landscape-averaged geologic erosion rates from Kenya but is large enough to modify short, slowly eroding natural hillslopes as well as microtopographic interrill surfaces between which overland flow transports the mobilized sediment.

  11. Interpretation of MSL REMS data using 1D coupled heat and water vapor transport model of Mars subsurface

    NASA Astrophysics Data System (ADS)

    Gloesener, Elodie; Karatekin, Özgür; Dehant, Véronique

    2016-04-01

    MSL Rover Environmental Monitoring Station (REMS) performed high-resolution measurements of temperature and relative humidity during more than one Martian year. In this work, a 1D subsurface model is used to study water vapor exchange between the atmosphere and the subsurface at Gale crater using REMS data. The thermal model used includes several layers of varying thickness with depth and properties that can be changed to correspond to those of Martian rocks at locations studied. It also includes the transport of water vapor through porous Martian regolith and the different phases considered are vapor, ice and adsorbed H2O. The total mass flux is given by the sum of diffusive and advective transport. The role of an adsorbing regolith on water transfer as well as the range of parameters with significant effect on water transport in Martian conditions are investigated. In addition, kinetics of the adsorption process is considered to examine its influence on the water vapor exchange between the subsurface and the atmosphere.

  12. A 1-D Size Specific Numerical Model for Gravel Transport That Includes Sediment Exchange with a Floodplain

    NASA Astrophysics Data System (ADS)

    Lauer, Wesley; Viparelli, Enrica; Piegay, Herve

    2014-05-01

    Sedimentary deposits adjacent to rivers can represent important sources and sinks for bed material sediment, particularly on decadal and longer timescales. The Morphodynamics and Sediment Tracers in 1-D model (MAST-1D) is a size-specific sediment transport model that allows for active exchange between channel and floodplain sediment on river reaches of tens to hundreds of kilometers in length. The model is intended to provide a mechanism for performing a first-order assessment of the likely importance of off-channel sediment exchange in controlling decadal-scale geomorphic trends, thereby helping plan and/or prioritize field data collection and higher resolution modeling work. The model develops a sediment budget for short segments of an alluvial valley. Each segment encompasses several active river bends. In each segment, a sediment transport capacity computation is performed to determine the downstream flux of bed material sediment, following the approach of most other 1-D sediment transport models. However, the model differs from most other bed evolution models in that sediment can be exchanged with the floodplain in each segment, and mass conservation is applied to both the active layer and floodplain sediment storage reservoirs. The potential for net imbalances in overall exchange as well as the size specific nature of the computations allows the model to simulate reach-scale aggradation/degradation and/or changes in bed texture. The inclusion of fine sediment in the model allows it to track geochemical tracer material and also provides a mechanism to simulate, to first order, the effects of changes in the supply of silt and clay on overall channel hydraulic capacity. The model is applied to a ~40 km reach of the Ain River, a tributary of the Rhône River in eastern France that has experienced a significant sediment deficit as a result of the construction of several dams between 1920 and 1970. MAST-1D simulations result in both incision and the formation of a

  13. Transport equations for partially ionized reactive plasma in magnetic field

    NASA Astrophysics Data System (ADS)

    Zhdanov, V. M.; Stepanenko, A. A.

    2016-06-01

    Transport equations for partially ionized reactive plasma in magnetic field taking into account the internal degrees of freedom and electronic excitation of plasma particles are derived. As a starting point of analysis the kinetic equation with a binary collision operator written in the Wang-Chang and Uhlenbeck form and with a reactive collision integral allowing for arbitrary chemical reactions is used. The linearized variant of Grad's moment method is applied to deduce the systems of moment equations for plasma and also full and reduced transport equations for plasma species nonequilibrium parameters.

  14. Assessment of phenol infiltration resilience in soil media by HYDRUS-1D transport model for a waste discharge site.

    PubMed

    Adhikari, K; Pal, S; Chakraborty, B; Mukherjee, S N; Gangopadhyay, A

    2014-10-01

    The movement of contaminants through soil imparts a variety of geo-environmental problem inclusive of lithospheric pollution. Near-surface aquifers are often vulnerable to contamination from surface source if overlying soil possesses poor resilience or contaminant attenuation capacity. The prediction of contaminant transport through soil is urged to protect groundwater from sources of pollutants. Using field simulation through column experiments and mathematical modeling like HYDRUS-1D, assessment of soil resilience and movement of contaminants through the subsurface to reach aquifers can be predicted. An outfall site of effluents of a coke oven plant comprising of alarming concentration of phenol (4-12.2 mg/L) have been considered for studying groundwater condition and quality, in situ soil characterization, and effluent characterization. Hydrogeological feature suggests the presence of near-surface aquifers at the effluent discharge site. Analysis of groundwater of nearby locality reveals the phenol concentration (0.11-0.75 mg/L) exceeded the prescribed limit of WHO specification (0.002 mg/L). The in situ soil, used in column experiment, possess higher saturated hydraulic conductivity (KS  = 5.25 × 10(-4) cm/s). The soil containing 47 % silt, 11 % clay, and 1.54% organic carbon content was found to be a poor absorber of phenol (24 mg/kg). The linear phenol adsorption isotherm model showed the best fit (R(2) = 0.977, RMSE = 1.057) to the test results. Column experiments revealed that the phenol removal percent and the length of the mass transfer zone increased with increasing bed heights. The overall phenol adsorption efficiency was found to be 42-49%. Breakthrough curves (BTCs) predicted by HYDRUS-1D model appears to be close fitting with the BTCs derived from the column experiments. The phenol BTC predicted by the HYDRUS-1D model for 1.2 m depth subsurface soil, i.e., up to the depth of groundwater in the study area, showed that the exhaustion

  15. Assessment of phenol infiltration resilience in soil media by HYDRUS-1D transport model for a waste discharge site.

    PubMed

    Adhikari, K; Pal, S; Chakraborty, B; Mukherjee, S N; Gangopadhyay, A

    2014-10-01

    The movement of contaminants through soil imparts a variety of geo-environmental problem inclusive of lithospheric pollution. Near-surface aquifers are often vulnerable to contamination from surface source if overlying soil possesses poor resilience or contaminant attenuation capacity. The prediction of contaminant transport through soil is urged to protect groundwater from sources of pollutants. Using field simulation through column experiments and mathematical modeling like HYDRUS-1D, assessment of soil resilience and movement of contaminants through the subsurface to reach aquifers can be predicted. An outfall site of effluents of a coke oven plant comprising of alarming concentration of phenol (4-12.2 mg/L) have been considered for studying groundwater condition and quality, in situ soil characterization, and effluent characterization. Hydrogeological feature suggests the presence of near-surface aquifers at the effluent discharge site. Analysis of groundwater of nearby locality reveals the phenol concentration (0.11-0.75 mg/L) exceeded the prescribed limit of WHO specification (0.002 mg/L). The in situ soil, used in column experiment, possess higher saturated hydraulic conductivity (KS  = 5.25 × 10(-4) cm/s). The soil containing 47 % silt, 11 % clay, and 1.54% organic carbon content was found to be a poor absorber of phenol (24 mg/kg). The linear phenol adsorption isotherm model showed the best fit (R(2) = 0.977, RMSE = 1.057) to the test results. Column experiments revealed that the phenol removal percent and the length of the mass transfer zone increased with increasing bed heights. The overall phenol adsorption efficiency was found to be 42-49%. Breakthrough curves (BTCs) predicted by HYDRUS-1D model appears to be close fitting with the BTCs derived from the column experiments. The phenol BTC predicted by the HYDRUS-1D model for 1.2 m depth subsurface soil, i.e., up to the depth of groundwater in the study area, showed that the exhaustion

  16. Asymptotic analysis of the several competitive equations to solve the time-dependent neutron transport equation

    SciTech Connect

    Shin, U.; Miller, W.F. Jr. |; Morel, J.E.

    1994-10-01

    Using conventional diffusion limit analysis, we asymptotically compare three competitive time-dependent equations (the telegrapher`s equation, the time-dependent Simplified P{sub 2} (SP{sub 2}) equation, and the time-dependent Simplified Evcn-Parity (SEP) equation). The time-dependent SP{sub 2} equation contains higher order asymptotic approximations of the time-dependent transport equation than the other equations in a physical regime in which the time-dependent diffusion equation is the leading order approximation. In addition, we derive the multigroup modified time-dependent SP{sub 2} equation from the multigroup time-dependent transport equation by means of an asymptotic expansion in which the multigroup time-dependent diffusion equation is the leading, order approximation. Numerical comparisons of the timedependent diffusion, the telegrapher`s, the time-dependent SP{sub 2}, and S{sub 8} solutions in 2-D X-Y geometry show that, in most cases, the SP{sub 2} solutions contain most of the transport corrections for the diffusion approximation.

  17. Compressible turbulence transport equations for generalized second order closure

    SciTech Connect

    Cloutman, L D

    1999-05-01

    Progress on the theory of second order closure in turbulence models of various types requires knowledge of the transport equations for various turbulence correlations. This report documents a procedure that provides such equations for a wide variety of turbulence averages for compressible flows of a multicomponent fluid. Generalizing some work by Germano for incompressible flows, we introduce an appropriate extension of his generalized second order correlations and use a generalized mass-weighted averaging procedure to derive transport equations for the correlations. The averaging procedure includes all of the commonly used averages as special cases. The resulting equations provide an internally consistent starting point for future work in developing single-point statistical turbulence transport models for fluid flows. The form invariance of the in-compressible equations also holds for the compressible case, and we discuss some of the closure issues and frequently ignored complications of statistical turbulence models of compressible flows.

  18. A 2D/1D coupling neutron transport method based on the matrix MOC and NEM methods

    SciTech Connect

    Zhang, H.; Zheng, Y.; Wu, H.; Cao, L.

    2013-07-01

    A new 2D/1D coupling method based on the matrix MOC method (MMOC) and nodal expansion method (NEM) is proposed for solving the three-dimensional heterogeneous neutron transport problem. The MMOC method, used for radial two-dimensional calculation, constructs a response matrix between source and flux with only one sweep and then solves the linear system by using the restarted GMRES algorithm instead of the traditional trajectory sweeping process during within-group iteration for angular flux update. Long characteristics are generated by using the customization of commercial software AutoCAD. A one-dimensional diffusion calculation is carried out in the axial direction by employing the NEM method. The 2D and ID solutions are coupled through the transverse leakage items. The 3D CMFD method is used to ensure the global neutron balance and adjust the different convergence properties of the radial and axial solvers. A computational code is developed based on these theories. Two benchmarks are calculated to verify the coupling method and the code. It is observed that the corresponding numerical results agree well with references, which indicates that the new method is capable of solving the 3D heterogeneous neutron transport problem directly. (authors)

  19. A new least-squares transport equation compatible with voids

    SciTech Connect

    Hansen, J. B.; Morel, J. E.

    2013-07-01

    We define a new least-squares transport equation that is applicable in voids, can be solved using source iteration with diffusion-synthetic acceleration, and requires only the solution of an independent set of second-order self-adjoint equations for each direction during each source iteration. We derive the equation, discretize it using the S{sub n} method in conjunction with a linear-continuous finite-element method in space, and computationally demonstrate various of its properties. (authors)

  20. Relativistic transport equations for electromagnetic scalar, and pseudoscalar potentials

    SciTech Connect

    Shin, G.R.; Rafelski, J.

    1995-10-01

    The authors propose a particular form of relativistic transport equations arising from the classical limit of single-time Wigner function for Dirac particles evolving in the presence of scalar, pseudoscalar, and electromagnetic fields. These relativistic Vlasov-type equations for the particle and the antiparticle sector of the Fock space can be also obtained assuming the validity of the Liouville`s equation given a suitable classical Hamiltonian and the associated force. 11 refs.

  1. Onsager's-principle-consistent 13-moment transport equations.

    PubMed

    Singh, Narendra; Agrawal, Amit

    2016-06-01

    A new set of generalized transport equations is derived for higher-order moments which are generated in evolution equation for stress tensor and heat flux vector in 13-moment equations. The closure we employ satisfies Onsager's symmetry principle. In the derivation, we do not employ a phase density function based on Hermite polynomial series in terms of higher-order moments, unlike Grad's approach. The distribution function is rather chosen to satisfy collision invariance, and H-theorem and capture relatively strong deviations from equilibrium. The phase density function satisfies the linearized Boltzmann equation and provides the correct value of the Prandtl number for monatomic gas. The derived equations are compared with Grad's 13-moments equations for gas modeled as Maxwellian molecule. The merits of the proposed equations against Grad's and R13 equations are discussed. In particular, it is noted that the proposed equations contain higher-order terms compared to these equations but require a fewer number of boundary conditions as compared to the R13 equations. The Knudsen number envelope which can be covered to describe flows with these equations is therefore expected to be larger as compared to the earlier equations.

  2. Central role of the observable electric potential in transport equations.

    PubMed

    Garrido, J; Compañ, V; López, M L

    2001-07-01

    Nonequilibrium systems are usually studied in the framework of transport equations that involve the true electric potential (TEP), a nonobservable variable. Nevertheless another electric potential, the observable electric potential (OEP), may be defined to construct a useful set of transport equations. In this paper several basic characteristics of the OEP are deduced and emphasized: (i) the OEP distribution depends on thermodynamic state of the solution, (ii) the observable equations have a reference value for all other transport equations, (iii) the bridge that connects the OEP with a certain TEP is usually defined by the ion activity coefficient, (iv) the electric charge density is a nonobservable variable, and (v) the OEP formulation constitutes a natural model for studying the fluxes in membrane systems. PMID:11461346

  3. Central role of the observable electric potential in transport equations.

    PubMed

    Garrido, J; Compañ, V; López, M L

    2001-07-01

    Nonequilibrium systems are usually studied in the framework of transport equations that involve the true electric potential (TEP), a nonobservable variable. Nevertheless another electric potential, the observable electric potential (OEP), may be defined to construct a useful set of transport equations. In this paper several basic characteristics of the OEP are deduced and emphasized: (i) the OEP distribution depends on thermodynamic state of the solution, (ii) the observable equations have a reference value for all other transport equations, (iii) the bridge that connects the OEP with a certain TEP is usually defined by the ion activity coefficient, (iv) the electric charge density is a nonobservable variable, and (v) the OEP formulation constitutes a natural model for studying the fluxes in membrane systems.

  4. Transport equations with second-order differential collision operators

    SciTech Connect

    Cosner, C.; Lenhart, S.M.; Protopopescu, V.

    1988-07-01

    This paper discusses existence, uniqueness, and a priori estimates for time-dependent and time-independent transport equations with unbounded collision operators. These collision operators are described by second-order differential operators resulting from diffusion in the velocity space. The transport equations are degenerate parabolic-elliptic partial differential equations, that are treated by modifications of the Fichera-Oleinik-Radkevic Theory of second-order equations with nonnegative characteristic form. They consider weak solutions in spaces that are extensions of L/sup rho/ to include traces on certain parts of the boundary. This extension is necessary due to the nonclassical boundary conditions imposed by the transport problem, which requires a specific analysis of the behavior of our weak solutions.

  5. Kinetic theory of transport processes in partially ionized reactive plasma, I: General transport equations

    NASA Astrophysics Data System (ADS)

    Zhdanov, V. M.; Stepanenko, A. A.

    2016-03-01

    In this paper we derive the set of general transport equations for multicomponent partially ionized reactive plasma in the presence of electric and magnetic fields taking into account the internal degrees of freedom and electronic excitation of plasma particles. Our starting point is a generalized Boltzmann equation with the collision integral in the Wang-Chang and Uhlenbeck form and a reactive collision integral. We obtain a set of conservation equations for such plasma and employ a linearized variant of Grad's moment method to derive the system of moment (or transport) equations for the plasma species nonequilibrium parameters. Full and reduced transport equations, resulting from the linearized system of moment equations, are presented, which can be used to obtain transport relations and expressions for transport coefficients of electrons and heavy plasma particles (molecules, atoms and ions) in partially ionized reactive plasma.

  6. Volume transport and generalized hydrodynamic equations for monatomic fluids.

    PubMed

    Eu, Byung Chan

    2008-10-01

    In this paper, the effects of volume transport on the generalized hydrodynamic equations for a pure simple fluid are examined from the standpoint of statistical mechanics and, in particular, kinetic theory of fluids. First, we derive the generalized hydrodynamic equations, namely, the constitutive equations for the stress tensor and heat flux for a single-component monatomic fluid, from the generalized Boltzmann equation in the presence of volume transport. Then their linear steady-state solutions are derived and examined with regard to the effects of volume transport on them. The generalized hydrodynamic equations and linear constitutive relations obtained for nonconserved variables make it possible to assess Brenner's proposition [Physica A 349, 11 (2005); Physica A 349, 60 (2005)] for volume transport and attendant mass and volume velocities as well as the effects of volume transport on the Newtonian law of viscosity, compression/dilatation (bulk viscosity) phenomena, and Fourier's law of heat conduction. On the basis of study made, it is concluded that the notion of volume transport is sufficiently significant to retain in irreversible thermodynamics of fluids and fluid mechanics.

  7. Transport equations for the inflationary trispectrum

    SciTech Connect

    Anderson, Gemma J.; Seery, David; Mulryne, David J. E-mail: D.Mulryne@qmul.ac.uk

    2012-10-01

    We use transport techniques to calculate the trispectrum produced in multiple-field inflationary models with canonical kinetic terms. Our method allows the time evolution of the local trispectrum parameters, τ{sub NL} and g{sub NL}, to be tracked throughout the inflationary phase. We illustrate our approach using examples. We give a simplified method to calculate the superhorizon part of the relation between field fluctuations on spatially flat hypersurfaces and the curvature perturbation on uniform density slices, ζ, and obtain its third-order part for the first time. We clarify how the 'backwards' formalism of Yokoyama et al. relates to our analysis and other recent work. We supply explicit formulae which enable each inflationary observable to be computed in any canonical model of interest, using a suitable first-order ODE solver.

  8. A stable scheme for computation of coupled transport and equilibrium equations in tokamaks

    NASA Astrophysics Data System (ADS)

    Fable, E.; Angioni, C.; Ivanov, A. A.; Lackner, K.; Maj, O.; Yu, S.; Medvedev; Pautasso, G.; Pereverzev, G. V.

    2013-03-01

    The coupled system consisting of 1D radial transport equations and the quasi-static 2D magnetic equilibrium equation for axisymmetric systems (tokamaks) is known to be prone to numerical instabilities, either due to propagation of numerical errors in the iteration process, or due to the choice of the numerical scheme itself. In this paper, a possible origin of these instabilities, specifically associated with the latter condition, is discussed and an approach is chosen, which is shown to have good accuracy and stability properties. This scheme is proposed to be used within those codes for which the poloidal flux ψ is the quantity solved for in the current diffusion equation. Mathematical arguments are used to study the convergence properties of the proposed scheme.

  9. Osmotic Transport across Cell Membranes in Nondilute Solutions: A New Nondilute Solute Transport Equation

    PubMed Central

    Elmoazzen, Heidi Y.; Elliott, Janet A.W.; McGann, Locksley E.

    2009-01-01

    The fundamental physical mechanisms of water and solute transport across cell membranes have long been studied in the field of cell membrane biophysics. Cryobiology is a discipline that requires an understanding of osmotic transport across cell membranes under nondilute solution conditions, yet many of the currently-used transport formalisms make limiting dilute solution assumptions. While dilute solution assumptions are often appropriate under physiological conditions, they are rarely appropriate in cryobiology. The first objective of this article is to review commonly-used transport equations, and the explicit and implicit assumptions made when using the two-parameter and the Kedem-Katchalsky formalisms. The second objective of this article is to describe a set of transport equations that do not make the previous dilute solution or near-equilibrium assumptions. Specifically, a new nondilute solute transport equation is presented. Such nondilute equations are applicable to many fields including cryobiology where dilute solution conditions are not often met. An illustrative example is provided. Utilizing suitable transport equations that fit for two permeability coefficients, fits were as good as with the previous three-parameter model (which includes the reflection coefficient, σ). There is less unexpected concentration dependence with the nondilute transport equations, suggesting that some of the unexpected concentration dependence of permeability is due to the use of inappropriate transport equations. PMID:19348741

  10. From analytical solutions of solute transport equations to multidimensional time-domain random walk (TDRW) algorithms

    NASA Astrophysics Data System (ADS)

    Bodin, Jacques

    2015-03-01

    In this study, new multi-dimensional time-domain random walk (TDRW) algorithms are derived from approximate one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) analytical solutions of the advection-dispersion equation and from exact 1-D, 2-D, and 3-D analytical solutions of the pure-diffusion equation. These algorithms enable the calculation of both the time required for a particle to travel a specified distance in a homogeneous medium and the mass recovery at the observation point, which may be incomplete due to 2-D or 3-D transverse dispersion or diffusion. The method is extended to heterogeneous media, represented as a piecewise collection of homogeneous media. The particle motion is then decomposed along a series of intermediate checkpoints located on the medium interface boundaries. The accuracy of the multi-dimensional TDRW method is verified against (i) exact analytical solutions of solute transport in homogeneous media and (ii) finite-difference simulations in a synthetic 2-D heterogeneous medium of simple geometry. The results demonstrate that the method is ideally suited to purely diffusive transport and to advection-dispersion transport problems dominated by advection. Conversely, the method is not recommended for highly dispersive transport problems because the accuracy of the advection-dispersion TDRW algorithms degrades rapidly for a low Péclet number, consistent with the accuracy limit of the approximate analytical solutions. The proposed approach provides a unified methodology for deriving multi-dimensional time-domain particle equations and may be applicable to other mathematical transport models, provided that appropriate analytical solutions are available.

  11. Renormalized transport equations for the bistable potential model

    NASA Astrophysics Data System (ADS)

    Weidlich, Wolfgang; Grabert, Hermann

    1980-09-01

    Renormalized transport equations for general Fokker-Planck systems are derived and applied to the bistable potential model. The exact equation for the expectation value < x> t can be evaluated in both domains < D>∈ x ± and < x>∈ D 0 outside and between the potential minima, leading to drastic differences of the dynamics prevailing in D ± and D 0, respectively.

  12. Renormalization of transport equations in Fokker-Planck models

    NASA Astrophysics Data System (ADS)

    Grabert, Hermann; Weidlich, Wolfgang

    1980-06-01

    This paper is concerned with the derivation of nonlinear fluctuation-renormalized transport equations of a fluctuating thermodynamic system, on the assumption that the macroscopic variables defining a state undergo a Fokker-Planck process. It is shown that the renormalization effect may consist of two parts: a renormalization of the thermodynamic forces and a renormalization of the transport coefficients. Closed analytical expressions for the renormalized quantities in terms of the bare quantities appearing in the Fokker-Planck equation are derived. A scheme for the approximate evaluation of these expressions is given.

  13. Transport in molecular states language: Generalized quantum master equation approach

    NASA Astrophysics Data System (ADS)

    Esposito, Massimiliano; Galperin, Michael

    2009-05-01

    A simple scheme, capable of treating transport in molecular junctions in the language of many-body states, is presented. By introducing an ansatz in Liouville space, similar to the generalized Kadanoff-Baym approximation, a quantum master equation (QME)-like expression is derived starting from the exact equation of motion for Hubbard operators. Using an effective Liouville space propagation, a dressing similar to the standard diagrammatic one is proposed. The scheme is compared to the standard QME approach and its applicability to transport calculations is discussed.

  14. A rain splash transport equation assimilating field and laboratory measurements

    USGS Publications Warehouse

    Dunne, T.; Malmon, D.V.; Mudd, S.M.

    2010-01-01

    Process-based models of hillslope evolution require transport equations relating sediment flux to its major controls. An equation for rain splash transport in the absence of overland flow was constructed by modifying an approach developed by Reeve (1982) and parameterizing it with measurements from single-drop laboratory experiments and simulated rainfall on a grassland in East Africa. The equation relates rain splash to hillslope gradient, the median raindrop diameter of a storm, and ground cover density; the effect of soil texture on detachability can be incorporated from other published results. The spatial and temporal applicability of such an equation for rain splash transport in the absence of overland flow on uncultivated hillslopes can be estimated from hydrological calculations. The predicted transport is lower than landscape-averaged geologic erosion rates from Kenya but is large enough to modify short, slowly eroding natural hillslopes as well as microtopographic interrill surfaces between which overland flow transports the mobilized sediment. Copyright 2010 by the American Geophysical Union. Copyright 2010 by the American Geophysical Union.

  15. Properties of an affine transport equation and its holonomy

    NASA Astrophysics Data System (ADS)

    Vines, Justin; Nichols, David A.

    2016-10-01

    An affine transport equation was used recently to study properties of angular momentum and gravitational-wave memory effects in general relativity. In this paper, we investigate local properties of this transport equation in greater detail. Associated with this transport equation is a map between the tangent spaces at two points on a curve. This map consists of a homogeneous (linear) part given by the parallel transport map along the curve plus an inhomogeneous part, which is related to the development of a curve in a manifold into an affine tangent space. For closed curves, the affine transport equation defines a "generalized holonomy" that takes the form of an affine map on the tangent space. We explore the local properties of this generalized holonomy by using covariant bitensor methods to compute the generalized holonomy around geodesic polygon loops. We focus on triangles and "parallelogramoids" with sides formed from geodesic segments. For small loops, we recover the well-known result for the leading-order linear holonomy (˜ Riemann × area), and we derive the leading-order inhomogeneous part of the generalized holonomy (˜ Riemann × area^{3/2}). Our bitensor methods let us naturally compute higher-order corrections to these leading results. These corrections reveal the form of the finite-size effects that enter into the holonomy for larger loops; they could also provide quantitative errors on the leading-order results for finite loops.

  16. Multilevel methods for transport equations in diffusive regimes

    NASA Technical Reports Server (NTRS)

    Manteuffel, Thomas A.; Ressel, Klaus

    1993-01-01

    We consider the numerical solution of the single-group, steady state, isotropic transport equation. An analysis by means of the moment equations shows that a discrete ordinate S(sub N) discretization in direction (angle) with a least squares finite element discretization in space does not behave properly in the diffusion limit. A scaling of the S(sub N) equations is introduced so that the least squares discretization has the correct diffusion limit. For the resulting discrete system a full multigrid algorithm was developed.

  17. Dopamine D1, D2, D3 Receptors, Vesicular Monoamine Transporter Type-2 (VMAT2) and Dopamine Transporter (DAT) Densities in Aged Human Brain

    PubMed Central

    Sun, Jianjun; Xu, Jinbin; Cairns, Nigel J.; Perlmutter, Joel S.; Mach, Robert H.

    2012-01-01

    The dopamine D1, D2, D3 receptors, vesicular monoamine transporter type-2 (VMAT2), and dopamine transporter (DAT) densities were measured in 11 aged human brains (aged 77–107.8, mean: 91 years) by quantitative autoradiography. The density of D1 receptors, VMAT2, and DAT was measured using [3H]SCH23390, [3H]dihydrotetrabenazine, and [3H]WIN35428, respectively. The density of D2 and D3 receptors was calculated using the D3-preferring radioligand, [3H]WC-10 and the D2-preferring radioligand [3H]raclopride using a mathematical model developed previously by our group. Dopamine D1, D2, and D3 receptors are extensively distributed throughout striatum; the highest density of D3 receptors occurred in the nucleus accumbens (NAc). The density of the DAT is 10–20-fold lower than that of VMAT2 in striatal regions. Dopamine D3 receptor density exceeded D2 receptor densities in extrastriatal regions, and thalamus contained a high level of D3 receptors with negligible D2 receptors. The density of dopamine D1 linearly correlated with D3 receptor density in the thalamus. The density of the DAT was negligible in the extrastriatal regions whereas the VMAT2 was expressed in moderate density. D3 receptor and VMAT2 densities were in similar level between the aged human and aged rhesus brain samples, whereas aged human brain samples had lower range of densities of D1 and D2 receptors and DAT compared with the aged rhesus monkey brain. The differential density of D3 and D2 receptors in human brain will be useful in the interpretation of PET imaging studies in human subjects with existing radiotracers, and assist in the validation of newer PET radiotracers having a higher selectivity for dopamine D2 or D3 receptors. PMID:23185343

  18. Analysis of discrete reaction-diffusion equations for autocatalysis and continuum diffusion equations for transport

    SciTech Connect

    Wang, Chi-Jen

    2013-01-01

    In this thesis, we analyze both the spatiotemporal behavior of: (A) non-linear “reaction” models utilizing (discrete) reaction-diffusion equations; and (B) spatial transport problems on surfaces and in nanopores utilizing the relevant (continuum) diffusion or Fokker-Planck equations. Thus, there are some common themes in these studies, as they all involve partial differential equations or their discrete analogues which incorporate a description of diffusion-type processes. However, there are also some qualitative differences, as shall be discussed below.

  19. Transport equations for a general class of evolution equations with random perturbations

    NASA Astrophysics Data System (ADS)

    Guo, Maozheng; Wang, Xiao-Ping

    1999-10-01

    We derive transport equations from a general class of equations of form iut=H(X,D)u+V(X,D)u where H(X,D) and V(X,D) are pseudodifferential operators (Weyl operator) with symbols H(x,k) and V(x,k), where H(x,k) being polynomial in k and smooth in x,V(x,k) is a mean zero random function and is stationary in space variable. We also consider system of equations in the above form. Such equations cover many of the equations that arise in wave propagations, such as those considered in a paper by Ryzhik, Papanicolaou, and Keller [Wave Motion 24, 327-370 (1996)]. Our results generalize those by Ryzhik, Papanicolau, and Keller.

  20. Approximation of the transport equation by a weighted particle method

    SciTech Connect

    Mas-Gallic, S.; Poupaud, F.

    1988-08-01

    We study a particle method for numerically solving a model equation for the neutron transport. We present the method and develop the theoretical convergence analysis. We prove the stability and the convergence of the method in L/sup infinity/. Some computational test results are given.

  1. Correction of the wavefront using the irradiance transport equation

    NASA Astrophysics Data System (ADS)

    García, M.; Granados, F.; Cornejo, A.

    2008-07-01

    The correction of the wavefront in optical systems implies the use of wavefront sensors, software, and auxiliary optical systems. We propose evaluated the wavefront using the fact that the wavefront and its intensity are related in the mathematical expression the irradiance transport equation (ITE)

  2. Analysis of Transition-Sensitized Turbulent Transport Equations

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.; Thacker, William D.; Gatski, Thomas B.; Grosch, Chester E,

    2005-01-01

    The dynamics of an ensemble of linear disturbances in boundary-layer flows at various Reynolds numbers is studied through an analysis of the transport equations for the mean disturbance kinetic energy and energy dissipation rate. Effects of adverse and favorable pressure-gradients on the disturbance dynamics are also included in the analysis Unlike the fully turbulent regime where nonlinear phase scrambling of the fluctuations affects the flow field even in proximity to the wall, the early stage transition regime fluctuations studied here are influenced cross the boundary layer by the solid boundary. The dominating dynamics in the disturbance kinetic energy and dissipation rate equations are described. These results are then used to formulate transition-sensitized turbulent transport equations, which are solved in a two-step process and applied to zero-pressure-gradient flow over a flat plate. Computed results are in good agreement with experimental data.

  3. Monte Carlo simulation of high-field transport equations

    SciTech Connect

    Abdolsalami, F.

    1989-01-01

    The author has studied the importance of the intracollisional field effect in the quantum transport equation derived by Khan, Davies and Wilkins (Phys. Rev. B36, 2578(1987)) via Monte Carlo simulations. This transport equation is identical to the integral form of the Boltzmann transport equation except that the scattering-in rates contain the auxiliary function of energy width {radical}{vert bar}{alpha}{vert bar} instead of the sharp delta function of the semiclassical theory where {alpha} = {pi}{h bar}{sup 2} e/m* E {center dot} q. Here, E is the electric field, q is the phonon wave vector of m* is the effective mass. The transport equation studied corresponds to a single parabolic band of infinite width and is valid in the field dominated limit, i.e. {radical}{vert bar}{alpha}{vert bar} {much gt} h/{tau}{sub sc}, where {tau}{sup {minus}1} is the electron scattering-out rate. In his simulation, he takes the single parabolic band to be the central valley of GaAs with transition to higher valleys shut off. Electrons are assumed to scatter with polar optic and acoustic phonons with the scattering parameters chosen to simulate GaAs. The loss of intervalley scattering mechanism for high electric fields is compensated for by increasing each of the four scattering rates relative to the real values in GaAs by a factor {gamma}. The transport equation studied contains the auxilliary function which is not positive definite. Therefore, it can not represent a probability of scattering in a Monte Carlo simulation. The question whether or not intracollisional field effect is important can be resolved by replacing the nonpositive definite auxilliary function by a test positive definite function of width {radical}{vert bar}{alpha}{vert bar} and comparing the results of the Monte Carlo simulation of this quantum transport equation with those of the Boltzmann transport equation. If the results are identical, the intracollisional field effect is not important.

  4. A bedload transport equation for the Cerastoderma edule cockle

    NASA Astrophysics Data System (ADS)

    Anta, Jose; Peña, Enrique; Puertas, Jerónimo; Cea, Luis

    2013-02-01

    Hydrodynamics play an important role in the structure of many marine ecosystems of bivalves. After severe storm periods, large amounts of the Cerastoderma edule stocks were transported from the Lombos do Ulla shellfish bed (Spain). This paper presents the results of laboratory experiments carried out to analyze the bedload transport of this bivalve emulating the stormy shellfish bed conditions. Flow velocities were measured using particle image velocimetry and the double averaged methodology was applied to determine the main flow characteristics over different cockle patches. The flow structure exhibits properties of skimming and isolated flows depending on the density of bivalves. Bed shear stress was determined from the log-law and the cockles were geometrically characterized in order to derive specific bedload transport equations in a conventional deterministic sediment transport framework. The obtained formulas can be implemented in common numerical codes to further analyze mollusk stability, bedload transport and dispersal in their aquatic systems.

  5. 1D and 3D anthropometric data application on public transport vehicle layout and on oil and gas laboratories work environment design.

    PubMed

    Pastura, F C H; Guimarães, C P; Zamberlan, M C P; Cid, G L; Santos, V S; Streit, P; Paranhos, A G; Cobbe, R T; Cobbe, K T; Batista, D S

    2012-01-01

    The goal of this paper is to present 1D and 3D anthropometric data applied to two distinct design situations: one related to the interior layout of a public transport vehicle and another one related to oil and gas laboratories work environment design. On this study, the 1D anthropometric data were extracted from the Brazilian anthropometric database developed by INT and the 3D anthropometric data were obtained using a Cyberware 3D whole body scanner. A second purpose of this paper is to present the 3D human scanning data as a tool that can help designers on decision making.

  6. Higher-order approximation of contaminant transport equation for turbulent channel flows based on centre manifolds and its numerical solution

    NASA Astrophysics Data System (ADS)

    Ngo-Cong, D.; Mohammed, F. J.; Strunin, D. V.; Skvortsov, A. T.; Mai-Duy, N.; Tran-Cong, T.

    2015-06-01

    The contaminant transport process governed by the advection-diffusion equation plays an important role in modelling industrial and environmental flows. In this article, our aim is to accurately reduce the 2-D advection-diffusion equation governing the dispersion of a contaminant in a turbulent open channel flow to its 1-D approximation. The 1-D model helps to quickly estimate the horizontal size of contaminant clouds based on the values of the model coefficients. We derive these coefficients analytically and investigate numerically the model convergence. The derivation is based on the centre manifold theory to obtain successively more accurate approximations in a consistent manner. Two types of the average velocity profile are considered: the classical logarithmic profile and the power profile. We further develop the one-dimensional integrated radial basis function network method as a numerical approach to obtain the numerical solutions to both the original 2-D equation and the approximate 1-D equations. We compare the solutions of the original models with their centre-manifold approximations at very large Reynolds numbers. The numerical results obtained from the approximate 1-D models are in good agreement with those of the original 2-D model for both the logarithmic and power velocity profiles.

  7. Numerical Study of Fractional Ensemble Average Transport Equations

    NASA Astrophysics Data System (ADS)

    Kim, S.; Park, Y.; Gyeong, C. B.; Lee, O.

    2014-12-01

    In this presentation, a newly developed theory is applied to the case of stationary and non-stationary stochastic advective flow field, and a numerical solution method is presented for the resulting fractional Fokker-Planck equation (fFPE), which describes the evolution of the probability density function (PDF) of contaminant concentration. The derived fFPE is evaluated for three different form: 1) purely advective form, 2) second-order moment form and 3) second-order cumulant form. The Monte Carlo analysis of the fractional governing equation is then performed in a stochastic flow field, generated by a fractional Brownian motion for the stationary and non-stationary stochastic advection, in order to provide a benchmark for the results obtained from the fFPEs. When compared to the Monte Carlo simulation based PDFs and their ensemble average, the second-order cumulant form gives a good fit in terms of the shape and mode of the PDF of the contaminant concentration. Therefore, it is quite promising that the non-Fickian transport behavior can be modeled by the derived fractional ensemble average transport equations either by means of the long memory in the underlying stochastic flow, or by means of the time-space non-stationarity of the underlying stochastic flow, or by means of the time and space fractional derivatives of the transport equations. This subject is supported by Korea Ministry of Environment as "The Eco Innovation Project : Non-point source pollution control research group"

  8. Transport equations for subdiffusion with nonlinear particle interaction.

    PubMed

    Straka, P; Fedotov, S

    2015-02-01

    We show how the nonlinear interaction effects 'volume filling' and 'adhesion' can be incorporated into the fractional subdiffusive transport of cells and individual organisms. To this end, we use microscopic random walk models with anomalous trapping and systematically derive generic non-Markovian and nonlinear governing equations for the mean concentrations of the subdiffusive cells or organisms. We uncover an interesting interaction between the nonlinearities and the non-Markovian nature of the transport. In the subdiffusive case, this interaction manifests itself in a nontrivial combination of nonlinear terms with fractional derivatives. In the long time limit, however, these equations simplify to a form without fractional operators. This provides an easy method for the study of aggregation phenomena. In particular, this enables us to show that volume filling can prevent "anomalous aggregation," which occurs in subdiffusive systems with a spatially varying anomalous exponent.

  9. Modeling Large Water Infiltration Events in Small Plots Using the 1-D Finite Water-content Method and Numerical Solutions to the Richards' Equation.

    NASA Astrophysics Data System (ADS)

    Brown, A.; Dahlke, H. E.

    2015-12-01

    The ability of soil to infiltrate large volumes of water is fundamental to managed aquifer recharge (MAR) when using infiltration basins or agricultural fields. In order to investigate the feasibility of using agricultural fields for MAR we conducted a field experiment designed to not only assess the resilience of alfalfa (Medicago sativa) to large (300 mm), short duration (1.5 hour), repeated irrigation events during the winter but also how crop resilience was influenced by soil water movement. We hypothesized that large irrigation amounts designed for groundwater recharge could cause prolonged saturated conditions in the root-zone and yield loss. Tensiometers were installed at two depths (60 and 150 cm) in a loam soil to monitor the changes in soil matric potential within and below the root-zone following irrigation events in each of five experimental plots (8 x 16 m2). To simulate the individual infiltration events we employed the HYDRUS-1D computational module (Simunek et al., 2005) and compared the finite-water content vadose zone flow method (Ogden et al. 2015) with numerical solutions to the Richards' equation. For both models we assumed a homogenous and isotropic root zone that is initially unsaturated with no water flow. Here we assess the ability of these two models to account for the control volume applied to the plots and to capture sharp changes in matric potential that were observed in the early time after an irrigation pulse. The goodness-of-fit of the models was evaluated using the root mean square error (RMSE) for observed and predicted values of cumulative infiltration over time, wetting front depth over time and water content at observation nodes. For the finite-water content method, the RMSE values and output for observation nodes were similar to that from the HYDRUS-1D solution. This indicates that the finite-water content method may be useful for predicting the fate of large volumes of water applied for MAR. Moreover, both models suggest a

  10. Inverse problems for homogeneous transport equations: II. The multidimensional case

    NASA Astrophysics Data System (ADS)

    Bal, Guillaume

    2000-08-01

    A companion paper by Bal (Bal G 2000 Inverse Problems 16 997) and this paper are parts I and II of a series dealing with the reconstruction from boundary measurements of the scattering operator of homogeneous linear transport equations. This part II deals with the case of convex bounded domains in dimensions higher than one. We distinguish the analysis of smooth boundaries from that of boundaries with discontinuities such as corners. We propose a reconstruction in the case of degenerate symmetric scattering operators and show the well-posedness of the inverse problem. The proof of well-posedness is based on a decomposition of angular moments of the transport solution into unbounded and bounded components. This decomposition allows us to show the linear independence of a sufficiently large number of angular moments of the transport solution that are used to construct an invertible system for the scattering coefficients to be reconstructed.

  11. Multiple mobility edges in a 1D Aubry chain with Hubbard interaction in presence of electric field: Controlled electron transport

    NASA Astrophysics Data System (ADS)

    Saha, Srilekha; Maiti, Santanu K.; Karmakar, S. N.

    2016-09-01

    Electronic behavior of a 1D Aubry chain with Hubbard interaction is critically analyzed in presence of electric field. Multiple energy bands are generated as a result of Hubbard correlation and Aubry potential, and, within these bands localized states are developed under the application of electric field. Within a tight-binding framework we compute electronic transmission probability and average density of states using Green's function approach where the interaction parameter is treated under Hartree-Fock mean field scheme. From our analysis we find that selective transmission can be obtained by tuning injecting electron energy, and thus, the present model can be utilized as a controlled switching device.

  12. Optimal Transport, Convection, Magnetic Relaxation and Generalized Boussinesq Equations

    NASA Astrophysics Data System (ADS)

    Brenier, Yann

    2009-10-01

    We establish a connection between optimal transport theory (see Villani in Topics in optimal transportation. Graduate studies in mathematics, vol. 58, AMS, Providence, 2003, for instance) and classical convection theory for geophysical flows (Pedlosky, in Geophysical fluid dynamics, Springer, New York, 1979). Our starting point is the model designed few years ago by Angenent, Haker, and Tannenbaum (SIAM J. Math. Anal. 35:61-97, 2003) to solve some optimal transport problems. This model can be seen as a generalization of the Darcy-Boussinesq equations, which is a degenerate version of the Navier-Stokes-Boussinesq (NSB) equations. In a unified framework, we relate different variants of the NSB equations (in particular what we call the generalized hydrostatic-Boussinesq equations) to various models involving optimal transport (and the related Monge-Ampère equation, Brenier in Commun. Pure Appl. Math. 64:375-417, 1991; Caffarelli in Commun. Pure Appl. Math. 45:1141-1151, 1992). This includes the 2D semi-geostrophic equations (Hoskins in Annual review of fluid mechanics, vol. 14, pp. 131-151, Palo Alto, 1982; Cullen et al. in SIAM J. Appl. Math. 51:20-31, 1991, Arch. Ration. Mech. Anal. 185:341-363, 2007; Benamou and Brenier in SIAM J. Appl. Math. 58:1450-1461, 1998; Loeper in SIAM J. Math. Anal. 38:795-823, 2006) and some fully nonlinear versions of the so-called high-field limit of the Vlasov-Poisson system (Nieto et al. in Arch. Ration. Mech. Anal. 158:29-59, 2001) and of the Keller-Segel for Chemotaxis (Keller and Segel in J. Theor. Biol. 30:225-234, 1971; Jäger and Luckhaus in Trans. Am. Math. Soc. 329:819-824, 1992; Chalub et al. in Mon. Math. 142:123-141, 2004). Mathematically speaking, we establish some existence theorems for local smooth, global smooth or global weak solutions of the different models. We also justify that the inertia terms can be rigorously neglected under appropriate scaling assumptions in the generalized Navier-Stokes-Boussinesq equations

  13. Implicitly causality enforced solution of multidimensional transient photon transport equation.

    PubMed

    Handapangoda, Chintha C; Premaratne, Malin

    2009-12-21

    A novel method for solving the multidimensional transient photon transport equation for laser pulse propagation in biological tissue is presented. A Laguerre expansion is used to represent the time dependency of the incident short pulse. Owing to the intrinsic causal nature of Laguerre functions, our technique automatically always preserve the causality constrains of the transient signal. This expansion of the radiance using a Laguerre basis transforms the transient photon transport equation to the steady state version. The resulting equations are solved using the discrete ordinates method, using a finite volume approach. Therefore, our method enables one to handle general anisotropic, inhomogeneous media using a single formulation but with an added degree of flexibility owing to the ability to invoke higher-order approximations of discrete ordinate quadrature sets. Therefore, compared with existing strategies, this method offers the advantage of representing the intensity with a high accuracy thus minimizing numerical dispersion and false propagation errors. The application of the method to one, two and three dimensional geometries is provided. PMID:20052050

  14. Renormalization group methods for the Reynolds stress transport equations

    NASA Technical Reports Server (NTRS)

    Rubinstein, R.

    1992-01-01

    The Yakhot-Orszag renormalization group is used to analyze the pressure gradient-velocity correlation and return to isotropy terms in the Reynolds stress transport equations. The perturbation series for the relevant correlations, evaluated to lowest order in the epsilon-expansion of the Yakhot-Orszag theory, are infinite series in tensor product powers of the mean velocity gradient and its transpose. Formal lowest order Pade approximations to the sums of these series produce a rapid pressure strain model of the form proposed by Launder, Reece, and Rodi, and a return to isotropy model of the form proposed by Rotta. In both cases, the model constants are computed theoretically. The predicted Reynolds stress ratios in simple shear flows are evaluated and compared with experimental data. The possibility is discussed of deriving higher order nonlinear models by approximating the sums more accurately. The Yakhot-Orszag renormalization group provides a systematic procedure for deriving turbulence models. Typical applications have included theoretical derivation of the universal constants of isotropic turbulence theory, such as the Kolmogorov constant, and derivation of two equation models, again with theoretically computed constants and low Reynolds number forms of the equations. Recent work has applied this formalism to Reynolds stress modeling, previously in the form of a nonlinear eddy viscosity representation of the Reynolds stresses, which can be used to model the simplest normal stress effects. The present work attempts to apply the Yakhot-Orszag formalism to Reynolds stress transport modeling.

  15. Analytical model of solutions of (2+1)-D heat convection equations in a shape memory alloy device immersed in a blood vessel

    NASA Astrophysics Data System (ADS)

    Maher Abourabia, Aly; Hassan, Kawsar Mohammad; Abo-Elghar, Eman Mohammad

    2015-02-01

    We investigate a bio-system composed of a shape memory alloy (SMA) immersed and subjected to heat convection in a blood vessel, affected by heart beats that create a wave motion of long wavelength. The tackled model in (2+1)-D is based on the continuity and momentum equations for the fluid phase, besides; the state of the SMA are described via previous works in the form of statistical distributions of energy for both Martensite and Austenite phases. The solution based on the reductive perturbation technique gives a thermal diffusion-like equation as a key for expressing the temperature and velocity components of the blood. In terms of two cases concerning the difference between the wave numbers in the perpendicular directions, it is found that the system's temperature increases nonlinearly from a minimum initial temperature 293 K (20 °C) up to a maximum value about 316.68 K (43.68 °C), then tends to decrease along the blood flow (anisotropy of K and L) direction. In both cases it is observed that the SMA acquires most of this temperature raising not the blood because of its conventional biological limits (37-40 °C). The range of the heart beats wave numbers characteristic for each person plays an important role in realizing phase changes in the anisotropic case leading to the formation of the hysteresis loops Martensite-Austenite-Martensite or vice versa, according to the energy variation. The entropy generation σ is investigated for the system (Blood + SMA), it predicts that along the flow direction the system gains energy convectively up to a maximum value, then reverses his tendency to gradually loosing energy passing by the equilibrium state, then the system looses energy to the surroundings by the same amount which was gained beforehand. The loss diminishes but stops before arriving to equilibrium again. For certain differences in wave numbers the system starts to store energy again after it passes by the state of equilibrium for the second time. In the

  16. Status of the solar and infrared radiation submodels in the LLNL 1-D and 2-D chemical-transport models

    SciTech Connect

    Grant, K.E.; Taylor, K.E.; Ellis, J.S.; Wuebbles, D.J.

    1987-07-01

    The authors have implemented a series of state of the art radiation transport submodels in previously developed one dimensional and two dimensional chemical transport models of the troposphere and stratosphere. These submodels provide the capability of calculating accurate solar and infrared heating rates. They are a firm basis for further radiation submodel development as well as for studying interactions between radiation and model dynamics under varying conditions of clear sky, clouds, and aerosols. 37 refs., 3 figs.

  17. Quantum-mechanical transport equation for atomic systems.

    NASA Technical Reports Server (NTRS)

    Berman, P. R.

    1972-01-01

    A quantum-mechanical transport equation (QMTE) is derived which should be applicable to a wide range of problems involving the interaction of radiation with atoms or molecules which are also subject to collisions with perturber atoms. The equation follows the time evolution of the macroscopic atomic density matrix elements of atoms located at classical position R and moving with classical velocity v. It is quantum mechanical in the sense that all collision kernels or rates which appear have been obtained from a quantum-mechanical theory and, as such, properly take into account the energy-level variations and velocity changes of the active (emitting or absorbing) atom produced in collisions with perturber atoms. The present formulation is better suited to problems involving high-intensity external fields, such as those encountered in laser physics.

  18. Vorticity Preserving Flux Corrected Transport Scheme for the Acoustic Equations

    SciTech Connect

    Lung, Tyler B.; Roe, Phil; Morgan, Nathaniel R.

    2012-08-15

    Long term research goals are to develop an improved cell-centered Lagrangian Hydro algorithm with the following qualities: 1. Utilizes Flux Corrected Transport (FCT) to achieve second order accuracy with multidimensional physics; 2. Does not rely on the one-dimensional Riemann problem; and 3. Implements a form of vorticity control. Short term research goals are to devise and implement a 2D vorticity preserving FCT solver for the acoustic equations on an Eulerian mesh: 1. Develop a flux limiting mechanism for systems of governing equations with symmetric wave speeds; 2. Verify the vorticity preserving properties of the scheme; and 3. Compare the performance of the scheme to traditional MUSCL-Hancock and other algorithms.

  19. Glucose transporter type I deficiency (G1D) at 25 (1990–2015): Presumptions, facts and the lives of persons with this rare disease

    PubMed Central

    Pascual, Juan M.; Ronen, Gabriel M.

    2015-01-01

    As is often the case for rare diseases, the number of published reviews and case reports of Glucose transporter type I deficiency (G1D) approaches or exceeds that of original research. This can indicate medical interest, but also scientific stagnation. In assessing this state of affairs here, we focus not on what is peculiar or disparate about G1D, but on the assumptions that have reigned thus far undisputed, and critique them as a potential impediment to progress. To summarize the most common G1D phenotype, we trace the 25-year story of G1D in parallel with the natural history of one of two index patients, identified in 1990 by one of us (G.M.R.) and brought up to date by the other (J.M.P.) while later examining widely-repeated but little-scrutinized statements. Among them are those that pertain to assumptions about brain fuels; energy-failure; cerebrospinal glucose concentration; the purpose of ketogenic diet; the role of the defective blood brain barrier; genotype-phenotype correlations; a bewildering array of phenotypes; ictogenesis, seizures and the electroencephalogram; the use of mice to model the disorder; and what treatments may and may not be expected to accomplish. We reach the forgone conclusion that the proper study of mankind - and of one of its ailments (G1D) - is man itself (rather than mice, isolated cells or extrapolated inferences), and propose a framework for rigorous investigation that we hope will lead to a better understanding and to better treatments for this and for rare disorders in general. These considerations, together with experience drawn from other disorders, lead, as a logical consequence, to the nullification of the view that therapeutic development (i.e., trials) for rare diseases could or should be accelerated without the most vigorous scientific scrutiny: Trial and error constitute an inseparable couple, such that, at the present time, hastening the former is bound to precipitate the latter. PMID:26341673

  20. Advanced Nodal P3/SP3 Axial Transport Solvers for the MPACT 2D/1D Scheme

    SciTech Connect

    Stimpson, Shane G; Collins, Benjamin S

    2015-01-01

    As part of its initiative to provide multiphysics simulations of nuclear reactor cores, the Consortium for Advanced Simulation of Light Water Reactors (CASL) is developing the Virtual Environment for Reactor Applications Core Simulator (VERA-CS). The MPACT code, which is the primary neutron transport solver of VERA-CS, employs the two-dimensional/one-dimensional (2D/1D) method to solve 3-dimensional neutron transport problems and provide sub-pin-level resolution of the power distribution. While 2D method of characteristics is used to solve for the transport effects within each plane, 1D-nodal methods are used axially. There have been extensive studies of the 2D/1D method with a variety nodal methods, and the P3/SP3 solver has proved to be an effective method of providing higher-fidelity solutions while maintaining a low computational burden.The current implementation in MPACT wraps a one-node nodal expansion method (NEM) kernel for each moment, iterating between them and performing multiple sweeps to resolve flux distributions. However, it has been observed that this approach is more sensitive to convergence problems. This paper documents the theory and application two new nodal P3/SP3 approaches to be used within the 2D/1D method in MPACT. These two approaches aim to provide enhanced stability compared with the pre-existing one-node approach. Results from the HY-NEM-SP3 solver show that the accuracy is consistent with the one-node formulations and provides improved convergence for some problems; but the solver has issues with cases in thin planes. Although the 2N-SENM-SP3 solver is still under development, it is intended to resolve the issues with HY-NEM-SP3 but it will incur some additional computational burden by necessitating an additional 1D-CMFD-P3 solver to generate the second moment cell-averaged scalar flux.

  1. Coupling WEPP and 3ST1D models for improved prediction of flow and sediment transport at watershed scales

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Watershed modeling is a key component of watershed management that involves the simulation of hydrological and fluvial processes for predicting flow and sediment transport within a watershed. For practical purposes, most numerical models have been developed to simulate either runoff and soil erosion...

  2. Modeling tracer transport in randomly heterogeneous porous media by nonlocal moment equations: Anomalous transport

    NASA Astrophysics Data System (ADS)

    Morales-Casique, E.; Lezama-Campos, J. L.; Guadagnini, A.; Neuman, S. P.

    2013-05-01

    Modeling tracer transport in geologic porous media suffers from the corrupt characterization of the spatial distribution of hydrogeologic properties of the system and the incomplete knowledge of processes governing transport at multiple scales. Representations of transport dynamics based on a Fickian model of the kind considered in the advection-dispersion equation (ADE) fail to capture (a) the temporal variation associated with the rate of spreading of a tracer, and (b) the distribution of early and late arrival times which are often observed in field and/or laboratory scenarios and are considered as the signature of anomalous transport. Elsewhere we have presented exact stochastic moment equations to model tracer transport in randomly heterogeneous aquifers. We have also developed a closure scheme which enables one to provide numerical solutions of such moment equations at different orders of approximations. The resulting (ensemble) average and variance of concentration fields were found to display a good agreement against Monte Carlo - based simulation results for mildly heterogeneous (or well-conditioned strongly heterogeneous) media. Here we explore the ability of the moment equations approach to describe the distribution of early arrival times and late time tailing effects which can be observed in Monte-Carlo based breakthrough curves (BTCs) of the (ensemble) mean concentration. We show that BTCs of mean resident concentration calculated at a fixed space location through higher-order approximations of moment equations display long tailing features of the kind which is typically associated with anomalous transport behavior and are not represented by an ADE model with constant dispersive parameter, such as the zero-order approximation.

  3. A numerical spectral approach to solve the dislocation density transport equation

    NASA Astrophysics Data System (ADS)

    Djaka, K. S.; Taupin, V.; Berbenni, S.; Fressengeas, C.

    2015-09-01

    A numerical spectral approach is developed to solve in a fast, stable and accurate fashion, the quasi-linear hyperbolic transport equation governing the spatio-temporal evolution of the dislocation density tensor in the mechanics of dislocation fields. The approach relies on using the Fast Fourier Transform algorithm. Low-pass spectral filters are employed to control both the high frequency Gibbs oscillations inherent to the Fourier method and the fast-growing numerical instabilities resulting from the hyperbolic nature of the transport equation. The numerical scheme is validated by comparison with an exact solution in the 1D case corresponding to dislocation dipole annihilation. The expansion and annihilation of dislocation loops in 2D and 3D settings are also produced and compared with finite element approximations. The spectral solutions are shown to be stable, more accurate for low Courant numbers and much less computation time-consuming than the finite element technique based on an explicit Galerkin-least squares scheme.

  4. Modeling of Flow Transition Using an Intermittency Transport Equation

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.

    1999-01-01

    A new transport equation for intermittency factor is proposed to model transitional flows. The intermittent behavior of the transitional flows is incorporated into the computations by modifying the eddy viscosity, mu(sub t), obtainable from a turbulence model, with the intermittency factor, gamma: mu(sub t, sup *) = gamma.mu(sub t). In this paper, Menter's SST model (Menter, 1994) is employed to compute mu(sub t) and other turbulent quantities. The proposed intermittency transport equation can be considered as a blending of two models - Steelant and Dick (1996) and Cho and Chung (1992). The former was proposed for near-wall flows and was designed to reproduce the streamwise variation of the intermittency factor in the transition zone following Dhawan and Narasimha correlation (Dhawan and Narasimha, 1958) and the latter was proposed for free shear flows and was used to provide a realistic cross-stream variation of the intermittency profile. The new model was used to predict the T3 series experiments assembled by Savill (1993a, 1993b) including flows with different freestream turbulence intensities and two pressure-gradient cases. For all test cases good agreements between the computed results and the experimental data are observed.

  5. Transport equations of electrodiffusion processes in the laboratory reference frame.

    PubMed

    Garrido, Javier

    2006-02-23

    The transport equations of electrodiffusion processes use three reference frames for defining the fluxes: Fick's reference in diffusion, solvent-fixed reference in transference numbers, and laboratory fluxes in electric conductivity. The convenience of using only one reference frame is analyzed here from the point of view of the thermodynamics of irreversible processes. A relation between the fluxes of ions and solvent and the electric current density is deduced first from a mass and volume balance. This is then used to show that (i) the laboratory and Fick's diffusion coefficients are identical and (ii) the transference numbers of both the solvent and the ion in the laboratory reference frame are related. Finally, four experimental methods for the measurement of ion transference numbers are analyzed critically. New expressions for evaluating transference numbers for the moving boundary method and the chronopotentiometry technique are deduced. It is concluded that the ion transport equation in the laboratory reference frame plays a key role in the description of electrodiffusion processes. PMID:16494340

  6. Transport equations of electrodiffusion processes in the laboratory reference frame.

    PubMed

    Garrido, Javier

    2006-02-23

    The transport equations of electrodiffusion processes use three reference frames for defining the fluxes: Fick's reference in diffusion, solvent-fixed reference in transference numbers, and laboratory fluxes in electric conductivity. The convenience of using only one reference frame is analyzed here from the point of view of the thermodynamics of irreversible processes. A relation between the fluxes of ions and solvent and the electric current density is deduced first from a mass and volume balance. This is then used to show that (i) the laboratory and Fick's diffusion coefficients are identical and (ii) the transference numbers of both the solvent and the ion in the laboratory reference frame are related. Finally, four experimental methods for the measurement of ion transference numbers are analyzed critically. New expressions for evaluating transference numbers for the moving boundary method and the chronopotentiometry technique are deduced. It is concluded that the ion transport equation in the laboratory reference frame plays a key role in the description of electrodiffusion processes.

  7. Heptanoate as a neural fuel: energetic and neurotransmitter precursors in normal and glucose transporter I-deficient (G1D) brain

    PubMed Central

    Marin-Valencia, Isaac; Good, Levi B; Ma, Qian; Malloy, Craig R; Pascual, Juan M

    2013-01-01

    It has been postulated that triheptanoin can ameliorate seizures by supplying the tricarboxylic acid cycle with both acetyl-CoA for energy production and propionyl-CoA to replenish cycle intermediates. These potential effects may also be important in other disorders associated with impaired glucose metabolism because glucose supplies, in addition to acetyl-CoA, pyruvate, which fulfills biosynthetic demands via carboxylation. In patients with glucose transporter type I deficiency (G1D), ketogenic diet fat (a source only of acetyl-CoA) reduces seizures, but other symptoms persist, providing the motivation for studying heptanoate metabolism. In this work, metabolism of infused [5,6,7-13C3]heptanoate was examined in the normal mouse brain and in G1D by 13C-nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS). In both groups, plasma glucose was enriched in 13C, confirming gluconeogenesis from heptanoate. Acetyl-CoA and glutamine levels became significantly higher in the brain of G1D mice relative to normal mice. In addition, brain glutamine concentration and 13C enrichment were also greater when compared with glutamate in both animal groups, suggesting that heptanoate and/or C5 ketones are primarily metabolized by glia. These results enlighten the mechanism of heptanoate metabolism in the normal and glucose-deficient brain and encourage further studies to elucidate its potential antiepileptic effects in disorders of energy metabolism. PMID:23072752

  8. Neglected transport equations: extended Rankine-Hugoniot conditions and J -integrals for fracture

    NASA Astrophysics Data System (ADS)

    Davey, K.; Darvizeh, R.

    2016-03-01

    Transport equations in integral form are well established for analysis in continuum fluid dynamics but less so for solid mechanics. Four classical continuum mechanics transport equations exist, which describe the transport of mass, momentum, energy and entropy and thus describe the behaviour of density, velocity, temperature and disorder, respectively. However, one transport equation absent from the list is particularly pertinent to solid mechanics and that is a transport equation for movement, from which displacement is described. This paper introduces the fifth transport equation along with a transport equation for mechanical energy and explores some of the corollaries resulting from the existence of these equations. The general applicability of transport equations to discontinuous physics is discussed with particular focus on fracture mechanics. It is well established that bulk properties can be determined from transport equations by application of a control volume methodology. A control volume can be selected to be moving, stationary, mass tracking, part of, or enclosing the whole system domain. The flexibility of transport equations arises from their ability to tolerate discontinuities. It is insightful thus to explore the benefits derived from the displacement and mechanical energy transport equations, which are shown to be beneficial for capturing the physics of fracture arising from a displacement discontinuity. Extended forms of the Rankine-Hugoniot conditions for fracture are established along with extended forms of J -integrals.

  9. Neglected transport equations: extended Rankine-Hugoniot conditions and J -integrals for fracture

    NASA Astrophysics Data System (ADS)

    Davey, K.; Darvizeh, R.

    2016-09-01

    Transport equations in integral form are well established for analysis in continuum fluid dynamics but less so for solid mechanics. Four classical continuum mechanics transport equations exist, which describe the transport of mass, momentum, energy and entropy and thus describe the behaviour of density, velocity, temperature and disorder, respectively. However, one transport equation absent from the list is particularly pertinent to solid mechanics and that is a transport equation for movement, from which displacement is described. This paper introduces the fifth transport equation along with a transport equation for mechanical energy and explores some of the corollaries resulting from the existence of these equations. The general applicability of transport equations to discontinuous physics is discussed with particular focus on fracture mechanics. It is well established that bulk properties can be determined from transport equations by application of a control volume methodology. A control volume can be selected to be moving, stationary, mass tracking, part of, or enclosing the whole system domain. The flexibility of transport equations arises from their ability to tolerate discontinuities. It is insightful thus to explore the benefits derived from the displacement and mechanical energy transport equations, which are shown to be beneficial for capturing the physics of fracture arising from a displacement discontinuity. Extended forms of the Rankine-Hugoniot conditions for fracture are established along with extended forms of J -integrals.

  10. Focusing Quantum Many-body Dynamics: The Rigorous Derivation of the 1D Focusing Cubic Nonlinear Schrödinger Equation

    NASA Astrophysics Data System (ADS)

    Chen, Xuwen; Holmer, Justin

    2016-08-01

    We consider the dynamics of N bosons in 1D. We assume that the pair interaction is attractive and given by {N^{β-1}V(N^{β}.) where } where {int V ≤slant 0}. We develop new techniques in treating the N-body Hamiltonian so that we overcome the difficulties generated by the attractive interaction and establish new energy estimates. We also prove the optimal 1D collapsing estimate which reduces the regularity requirement in the uniqueness argument by half a derivative. We derive rigorously the 1D focusing cubic NLS with a quadratic trap as the {N → ∞} limit of the N-body dynamic and hence justify the mean-field limit and prove the propagation of chaos for the focusing quantum many-body system.

  11. Rayleigh streaming simulation using the vorticity transport equation

    NASA Astrophysics Data System (ADS)

    Sastrapradja, Debbie

    One part of understanding thermoacoustic devices involves studying a physical phenomenon called acoustic streaming, a steady fluid flow induced by oscillating acoustic waves. Current numerical calculation of acoustic streaming can involve major computing time and resources. In order to develop a quicker model, the vorticity transport equation (VTE) is used. The goal of using the VTE is to obtain a relatively fast solution with minimal computational resources, which in this case is a single PC. The intent of this method is that it is used in the early design stage of thermoacoustic devices where preliminary (although less detailed) fast results are desired. It is also preferred that the computing power be minimized as not to tie up other resources for the optimized design of thermoacoustic devices. The most well known type of acoustic streaming, Rayleigh streaming, is simulated using the VTE method. A clustered grid is utilized to capture the boundary layer effect on the acoustic streaming. The governing equations used are the VTE, Poisson's equation, and an equation that relates the stream function with the velocity. The outline of the method of calculation involves (i) generating a clustered grid and ensuring there are enough points in the boundary layer, (ii) transforming the clustered grid into the uniform computational grid, (iii) transforming the governing equations to account for the clustering, (iv) calculating the vorticity and the stream function at each grid point using a Direct Method, and (v) calculating the acoustic streaming velocity using the stream function. Steps (iv) through (v) are repeated until the solution converges. It is demonstrated that the VTE method to calculate Rayleigh streaming works well. There are two cases being simulated in the research, a parallel plate case and a cylindrical tube case. The numerical results agree with the analytical results for both cases, although there are some discrepancies in the cylindrical tube case. At

  12. Renormalization group analysis of the Reynolds stress transport equation

    NASA Technical Reports Server (NTRS)

    Rubinstein, R.; Barton, J. M.

    1992-01-01

    The pressure velocity correlation and return to isotropy term in the Reynolds stress transport equation are analyzed using the Yakhot-Orszag renormalization group. The perturbation series for the relevant correlations, evaluated to lowest order in the epsilon-expansion of the Yakhot-Orszag theory, are infinite series in tensor product powers of the mean velocity gradient and its transpose. Formal lowest order Pade approximations to the sums of these series produce a fast pressure strain model of the form proposed by Launder, Reece, and Rodi, and a return to isotropy model of the form proposed by Rotta. In both cases, the model constant are computed theoretically. The predicted Reynolds stress ratios in simple shear flows are evaluated and compared with experimental data. The possibility is discussed of driving higher order nonlinear models by approximating the sums more accurately.

  13. Riccati equation for simulation of leads in quantum transport

    NASA Astrophysics Data System (ADS)

    Bravi, M.; Farchioni, R.; Grosso, G.; Pastori Parravicini, G.

    2014-10-01

    We present a theoretical procedure with numerical demonstration of a workable and efficient method to evaluate the surface Green's function of semi-infinite leads connected to a device. Such a problem always occurs in quantum transport calculations but also in the study of surfaces and heterojunctions. We show here that these semi-infinite leads can be properly described by real-energy Green's functions obtained analytically by a smart solution of the Riccati matrix equation. The performance of our method is demonstrated in the case of a multichain two-dimensional electron-gas system, composed of a central ribbon connected to two semi-infinite leads, pierced by two opposite magnetic fields.

  14. A simple Boltzmann transport equation for ballistic to diffusive transient heat transport

    SciTech Connect

    Maassen, Jesse Lundstrom, Mark

    2015-04-07

    Developing simplified, but accurate, theoretical approaches to treat heat transport on all length and time scales is needed to further enable scientific insight and technology innovation. Using a simplified form of the Boltzmann transport equation (BTE), originally developed for electron transport, we demonstrate how ballistic phonon effects and finite-velocity propagation are easily and naturally captured. We show how this approach compares well to the phonon BTE, and readily handles a full phonon dispersion and energy-dependent mean-free-path. This study of transient heat transport shows (i) how fundamental temperature jumps at the contacts depend simply on the ballistic thermal resistance, (ii) that phonon transport at early times approach the ballistic limit in samples of any length, and (iii) perceived reductions in heat conduction, when ballistic effects are present, originate from reductions in temperature gradient. Importantly, this framework can be recast exactly as the Cattaneo and hyperbolic heat equations, and we discuss how the key to capturing ballistic heat effects is to use the correct physical boundary conditions.

  15. Transport equations for linear surface waves with random underlying flows

    NASA Astrophysics Data System (ADS)

    Bal, Guillaume; Chou, Tom

    1999-11-01

    We define the Wigner distribution and use it to develop equations for linear surface capillary-gravity wave propagation in the transport regime. The energy density a(r, k) contained in waves propagating with wavevector k at field point r is given by dota(r,k) + nabla_k[U_⊥(r,z=0) \\cdotk + Ω(k)]\\cdotnabla_ra [13pt] \\: hspace1in - (nabla_r\\cdotU_⊥)a - nabla_r(k\\cdotU_⊥)\\cdotnabla_ka = Σ(δU^2) where U_⊥(r, z=0) is a slowly varying surface current, and Ω(k) = √(k^3+k)tanh kh is the free capillary-gravity dispersion relation. Note that nabla_r\\cdotU_⊥(r,z=0) neq 0, and that the surface currents exchange energy density with the propagating waves. When an additional weak random current √\\varepsilon δU(r/\\varepsilon) varying on the scale of k-1 is included, we find an additional scattering term Σ(δU^2) as a function of correlations in δU. Our results can be applied to the study of surface wave energy transport over a turbulent ocean.

  16. Generalized parallel heat transport equations in collisional to weakly collisional plasmas

    NASA Astrophysics Data System (ADS)

    Zawaideh, Emad; Kim, N. S.; Najmabadi, Farrokh

    1988-11-01

    A new set of two-fluid heat-transport equations for heat conduction in collisional to weakly collisional plasmas was derived on the basis of gyrokinetic equations in flux coordinates. In these equations, no restrictions on the anisotropy of the ion distribution function or the collisionality are imposed. In the highly collisional limit, these equations reduce to the classical heat conduction equation of Spitzer and Haerm (1953), while in the weakly collisional limit, they describe a saturated heat flux. Numerical examples comparing these equations with conventional heat transport equations are presented.

  17. 1-D steady state analysis of a two-equation coupled system for determination of tissue temperature in liver during radio frequency ablation.

    PubMed

    Peng, Tingying; O'Neill, David P; Payne, Stephen J

    2009-01-01

    An analytical solution is provided for a two-equation coupled model for determination of liver tissue temperature during radio frequency ablation in the steady state with one-dimension in space. Both analytical analysis and model simulation were conducted to investigate the effects of two crucial system parameters: blood perfusion rate and convective heat transfer coefficient on the tissue temperature field. The quantitative criteria were also derived, under which the two-equation coupled system can be approximated to a conventional single bio-heat equation system such as the Pennes model.

  18. Quasi steady-states, spin statistics, and interaction-induced transport of ultra-cold atoms in 1D optical lattices

    NASA Astrophysics Data System (ADS)

    Chien, Chih-Chun; Zwolak, Michael; di Ventra, Massimiliano

    2012-02-01

    We consider several non-equilibrium scenarios where ultra-cold atoms are initially loaded into the ground state of a 1D optical lattice. The system is then set out of equilibrium either by inducing a density imbalance or by imposing time-dependent inhomogeneous interactions. To monitor the dynamics, we have implemented the micro-canonical approach to transport [1] which has been previously used to study electron dynamics in nanoscale systems. We have found that by removing particles on the right half of the lattice, fermions form a quasi steady-state current, which can be observed as a plateau in the current as a function of time. In contrast, the bosonic current oscillates and decays to zero in the thermodynamic limit [2]. The difference appears in uniform lattices as well as lattices with a harmonic trap. Further, when light-induced interactions are applied to half of the lattice, we have found, using a Hartree-Fock approximation, a conducting-nonconducting transition in the fermionic case as the interaction increases. Our studies are relevant to recent experiments on transport of ultra-cold atoms and address fundamental issues in nanoscale electronic transport. [4pt] [1] Di Ventra and Todorov,J. Phys. Cond. Matt. 16, 8025 (2004).[0pt] [2] Chien, Zwolak, Di Ventra, arXiv: 1110.1646.

  19. Recent Advances in the Modeling of the Transport of Two-Plasmon-Decay Electrons in the 1-D Hydrodynamic Code LILAC

    NASA Astrophysics Data System (ADS)

    Delettrez, J. A.; Myatt, J. F.; Yaakobi, B.

    2015-11-01

    The modeling of the fast-electron transport in the 1-D hydrodynamic code LILAC was modified because of the addition of cross-beam-energy-transfer (CBET) in implosion simulations. Using the old fast-electron with source model CBET results in a shift of the peak of the hard x-ray (HXR) production from the end of the laser pulse, as observed in experiments, to earlier in the pulse. This is caused by a drop in the laser intensity of the quarter-critical surface from CBET interaction at lower densities. Data from simulations with the laser plasma simulation environment (LPSE) code will be used to modify the source algorithm in LILAC. In addition, the transport model in LILAC has been modified to include deviations from the straight-line algorithm and non-specular reflection at the sheath to take into account the scattering from collisions and magnetic fields in the corona. Simulation results will be compared with HXR emissions from both room-temperature plastic and cryogenic target experiments. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  20. The effect of modafinil on the rat dopamine transporter and dopamine receptors D1-D3 paralleling cognitive enhancement in the radial arm maze.

    PubMed

    Karabacak, Yasemin; Sase, Sunetra; Aher, Yogesh D; Sase, Ajinkya; Saroja, Sivaprakasam R; Cicvaric, Ana; Höger, Harald; Berger, Michael; Bakulev, Vasiliy; Sitte, Harald H; Leban, Johann; Monje, Francisco J; Lubec, Gert

    2015-01-01

    A series of drugs have been reported to increase memory performance modulating the dopaminergic system and herein modafinil was tested for its working memory (WM) enhancing properties. Reuptake inhibition of dopamine, serotonin (SERT) and norepinephrine (NET) by modafinil was tested. Sixty male Sprague-Dawley rats were divided into six groups (modafinil-treated 1-5-10 mg/kg body weight, trained and untrained and vehicle treated trained and untrained rats; daily injected intraperitoneally for a period of 10 days) and tested in a radial arm maze (RAM), a paradigm for testing spatial WM. Hippocampi were taken 6 h following the last day of training and complexes containing the unphosphorylated or phosphorylated dopamine transporter (DAT-CC and pDAT-CC) and complexes containing the D1-3 dopamine receptor subunits (D1-D3-CC) were determined. Modafinil was binding to the DAT but insignificantly to SERT or NET and dopamine reuptake was blocked specifically (IC50 = 11.11 μM; SERT 1547 μM; NET 182 μM). From day 8 (day 9 for 1 mg/kg body weight) modafinil was decreasing WM errors (WMEs) in the RAM significantly and remarkably at all doses tested as compared to the vehicle controls. WMEs were linked to the D2R-CC and the pDAT-CC. pDAT and D1-D3-CC levels were modulated significantly and modafinil was shown to enhance spatial WM in the rat in a well-documented paradigm at all the three doses and dopamine reuptake inhibition with subsequent modulation of D1-3-CC is proposed as a possible mechanism of action. PMID:26347626

  1. Part i: Lie-Backlund Theory and Linearization of Differential Equations. Part II: Monte Carlo Simulations of 1-D Quantum Spin Models.

    NASA Astrophysics Data System (ADS)

    Cullen, John J.

    Part I begins with an account of groups of Lie -Back-lund (L-B) tangent transformations; it is then shown that L-B symmetry operators depending on integrals (nonlocal variables), such as discussed by Konopelchenko and Mokhnachev (1979), are related by change of variables to the L-B operators which involve no more than derivatives. A general method is set down for transforming a given L-B operator into a new one, by any invertible transformation depending on (. . ., D(,x)('-1) u, u, u(,x), . . .). It is shown that once a given differential equation admits a L-B operator, there is in general a very large number of related ("secondary") equations which admit the same operator. The L-B Theory involving nonlocal variables is used to characterize group theoretically the linearization both of the Burgers equation, u(,t) + uu(,x) - u(,xx) = 0, and of the o.d.e. u(,xx) + (omega)('2)(x)u + Ku('-3) = 0. Secondary equations are found to play an important role in understanding the group theoretical background to the linearization of differential equations. Part II deals with Monte Carlo simulations of the l-d quantum Heisenberg and XY-models, using an approach suggested by Suzuki (1976). The simulation is actually carried out on a 2-d, m x N, Isinglike system, equivalent to the original N-spin quantum system when m (--->) (INFIN). The results for m (LESSTHEQ) 10 and kT/(VBAR)J(VBAR) (GREATERTHEQ) .0125 are good enough to show that the method is generally applicable to quantum spin models; however some difficulties caused by singular bonding in the classical lattice (Wiesler 1982) and by the generation of unwanted states have to be taken into account in practice. The finite-size scaling method of Fisher and Ferdinard is adapted for use near T = 0 in the ferromagnetic Heisenberg model; applied to the simulation data it shows that the low temperature susceptibiltiy behaves at T('-(gamma)), where (gamma) = 1.32 (+OR-) 10%. Also, simple and potentially useful finite-size scaling

  2. On the derivation of vector radiative transfer equation for polarized radiative transport in graded index media

    NASA Astrophysics Data System (ADS)

    Zhao, J. M.; Tan, J. Y.; Liu, L. H.

    2012-02-01

    Light transport in graded index media follows a curved trajectory determined by Fermat's principle. Besides the effect of variation of the refractive index on the transport of radiative intensity, the curved ray trajectory will induce geometrical effects on the transport of polarization ellipse. This paper presents a complete derivation of vector radiative transfer equation for polarized radiation transport in absorption, emission and scattering graded index media. The derivation is based on the analysis of the conserved quantities for polarized light transport along curved trajectory and a novel approach. The obtained transfer equation can be considered as a generalization of the classic vector radiative transfer equation that is only valid for uniform refractive index media. Several variant forms of the transport equation are also presented, which include the form for Stokes parameters defined with a fixed reference and the Eulerian forms in the ray coordinate and in several common orthogonal coordinate systems.

  3. Modeling water flow and bacterial transport in undisturbed lysimeters under irrigations of dairy shed effluent and water using HYDRUS-1D.

    PubMed

    Jiang, Shuang; Pang, Liping; Buchan, Graeme D; Simůnek, Jirí; Noonan, Mike J; Close, Murray E

    2010-02-01

    HYDRUS-1D was used to simulate water flow and leaching of fecal coliforms and bromide (Br) through six undisturbed soil lysimeters (70 cm depth by 50 cm diameter) under field conditions. Dairy shed effluent (DSE) spiked with Br was applied to the lysimeters, which contained fine sandy loam layers. This application was followed by fortnightly spray or flood water irrigation. Soil water contents were measured at four soil depths over 171 days, and leachate was collected from the bottom. The post-DSE period simulations yielded a generally decreased saturated water content compared to the pre-DSE period, and an increased saturated hydraulic conductivity and air-entry index, suggesting that changes in soil hydraulic properties (e.g. via changes in structure) can be induced by irrigation and seasonal effects. The single-porosity flow model was successful in simulating water flow under natural climatic conditions and spray irrigation. However, for lysimeters under flood irrigation, when the effect of preferential flow paths becomes more significant, the good agreement between predicted and observed water contents could only be achieved by using a dual-porosity flow model. Results derived from a mobile-immobile transport model suggest that compared to Br, bacteria were transported through a narrower pore-network with less mass exchange between mobile and immobile water zones. Our study suggests that soils with higher topsoil clay content and soils under flood irrigation are at a high risk of bacteria leaching through preferential flow paths. Irrigation management strategies must minimize the effect of preferential flow to reduce bacterial leaching from land applications of effluent.

  4. Modeling water flow and bacterial transport in undisturbed lysimeters under irrigations of dairy shed effluent and water using HYDRUS-1D.

    PubMed

    Jiang, Shuang; Pang, Liping; Buchan, Graeme D; Simůnek, Jirí; Noonan, Mike J; Close, Murray E

    2010-02-01

    HYDRUS-1D was used to simulate water flow and leaching of fecal coliforms and bromide (Br) through six undisturbed soil lysimeters (70 cm depth by 50 cm diameter) under field conditions. Dairy shed effluent (DSE) spiked with Br was applied to the lysimeters, which contained fine sandy loam layers. This application was followed by fortnightly spray or flood water irrigation. Soil water contents were measured at four soil depths over 171 days, and leachate was collected from the bottom. The post-DSE period simulations yielded a generally decreased saturated water content compared to the pre-DSE period, and an increased saturated hydraulic conductivity and air-entry index, suggesting that changes in soil hydraulic properties (e.g. via changes in structure) can be induced by irrigation and seasonal effects. The single-porosity flow model was successful in simulating water flow under natural climatic conditions and spray irrigation. However, for lysimeters under flood irrigation, when the effect of preferential flow paths becomes more significant, the good agreement between predicted and observed water contents could only be achieved by using a dual-porosity flow model. Results derived from a mobile-immobile transport model suggest that compared to Br, bacteria were transported through a narrower pore-network with less mass exchange between mobile and immobile water zones. Our study suggests that soils with higher topsoil clay content and soils under flood irrigation are at a high risk of bacteria leaching through preferential flow paths. Irrigation management strategies must minimize the effect of preferential flow to reduce bacterial leaching from land applications of effluent. PMID:19775719

  5. Analytical solution for one-dimensional advection-dispersion transport equation with distance-dependent coefficients

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mathematical models describing contaminant transport in heterogeneous porous media are often formulated as an advection-dispersion transport equation with distance-dependent transport coefficients. In this work, a general analytical solution is presented for the linear, one-dimensional advection-di...

  6. Time-Dependent Ginzburg-Landau Equation and Boltzmann Transport Equation for Charge-Density-Wave Conductors

    NASA Astrophysics Data System (ADS)

    Takane, Yositake; Hayashi, Masahiko; Ebisawa, Hiromichi

    2016-08-01

    The time-dependent Ginzburg-Landau equation and the Boltzmann transport equation for charge-density-wave (CDW) conductors are derived from a microscopic one-dimensional model by applying the Keldysh Green's function approach under a quasiclassical approximation. The effects of an external electric field and impurity pinning of the CDW are fully taken into account without relying on a phenomenological argument. These equations simultaneously describe the spatiotemporal dynamics of both the CDW and quasiparticles; thus, they serve as a starting point to develop a general framework to analyze various nonequilibrium phenomena, such as current conversion between the CDW condensate and quasiparticles, in realistic CDW conductors. It is shown that, in typical situations, the equations correctly describe the nonlinear behavior of electric conductivity in a simpler manner.

  7. The kinetics of selective biological transport. II. Equations for induced uphill transport of sugars in human erythrocytes.

    PubMed

    Miller, D M

    1965-07-01

    Equations describing the movement of sugars during induced uphill transport were derived on the assumption of a simple carrier transport mechanism and subjected to experimental verification. Since there was good agreement between the experimental points and the theoretical curves, no changes in the original postulates were required.

  8. Parameterized isoprene and monoterpene emissions from the boreal forest floor: Implementation into a 1D chemistry-transport model and investigation of the influence on atmospheric chemistry

    NASA Astrophysics Data System (ADS)

    Mogensen, Ditte; Aaltonen, Hermanni; Aalto, Juho; Bäck, Jaana; Kieloaho, Antti-Jussi; Gierens, Rosa; Smolander, Sampo; Kulmala, Markku; Boy, Michael

    2015-04-01

    Volatile organic compounds (VOCs) are emitted from the biosphere and can work as precursor gases for aerosol particles that can affect the climate (e.g. Makkonen et al., ACP, 2012). VOC emissions from needles and leaves have gained the most attention, however other parts of the ecosystem also have the ability to emit a vast amount of VOCs. This, often neglected, source can be important e.g. at periods where leaves are absent. Both sources and drivers related to forest floor emission of VOCs are currently limited. It is thought that the sources are mainly due to degradation of organic matter (Isidorov and Jdanova, Chemosphere, 2002), living roots (Asensio et al., Soil Biol. Biochem., 2008) and ground vegetation. The drivers are biotic (e.g. microbes) and abiotic (e.g. temperature and moisture). However, the relative importance of the sources and the drivers individually are currently poorly understood. Further, the relative importance of these factors is highly dependent on the tree species occupying the area of interest. The emission of isoprene and monoterpenes where measured from the boreal forest floor at the SMEAR II station in Southern Finland (Hari and Kulmala, Boreal Env. Res., 2005) during the snow-free period in 2010-2012. We used a dynamic method with 3 automated chambers analyzed by Proton Transfer Reaction - Mass Spectrometer (Aaltonen et al., Plant Soil, 2013). Using this data, we have developed empirical parameterizations for the emission of isoprene and monoterpenes from the forest floor. These parameterizations depends on abiotic factors, however, since the parameterizations are based on field measurements, biotic features are captured. Further, we have used the 1D chemistry-transport model SOSAA (Boy et al., ACP, 2011) to test the seasonal relative importance of inclusion of these parameterizations of the forest floor compared to the canopy crown emissions, on the atmospheric reactivity throughout the canopy.

  9. Transport equation for plasmas in a stationary-homogeneous turbulence

    NASA Astrophysics Data System (ADS)

    Wang, Shaojie

    2016-02-01

    For a plasma in a stationary homogeneous turbulence, the Fokker-Planck equation is derived from the nonlinear Vlasov equation by introducing the entropy principle. The ensemble average in evaluating the kinetic diffusion tensor, whose symmetry has been proved, can be computed in a straightforward way when the fluctuating particle trajectories are provided. As an application, it has been shown that a mean parallel electric filed can drive a particle flux through the Stokes-Einstein relation, independent of the details of the fluctuations.

  10. Simple jumping process with memory: Transport equation and diffusion

    NASA Astrophysics Data System (ADS)

    Kamińska, A.; Srokowski, T.

    2004-06-01

    We present a stochastic jumping process, defined in terms of jump-size probability density and jumping rate, which is a generalization of the well-known kangaroo process. The definition takes into account two process values: after and before the jump. Therefore, the process is able to preserve memory about its previous values. It possesses a simple stationary limit. Its master equation is interpreted as the kinetic equation with variable collision rate. The process can be easily applied to model systems which relax to distributions other than Maxwellian. The case of a constant jumping rate corresponds to the diffusion process, either normal or ballistic.

  11. 1D Thermal-Hydraulic-Chemical (THC) Reactive transport modeling for deep geothermal systems: A case study of Groß Schönebeck reservoir, Germany

    NASA Astrophysics Data System (ADS)

    Driba, D. L.; De Lucia, M.; Peiffer, S.

    2014-12-01

    Fluid-rock interactions in geothermal reservoirs are driven by the state of disequilibrium that persists among solid and solutes due to changing temperature and pressure. During operation of enhanced geothermal systems, injection of cooled water back into the reservoir disturbs the initial thermodynamic equilibrium between the reservoir and its geothermal fluid, which may induce modifications in permeability through changes in porosity and pore space geometry, consequently bringing about several impairments to the overall system.Modeling of fluid-rock interactions induced by injection of cold brine into Groß Schönebeck geothermal reservoir system situated in the Rotliegend sandstone at 4200m depth have been done by coupling geochemical modeling Code Phreeqc with OpenGeoSys. Through batch modeling the re-evaluation of the measured hydrochemical composition of the brine has been done using Quintessa databases, the results from the calculation indicate that a mineral phases comprising of K-feldspar, hematite, Barite, Calcite and Dolomite was found to match the hypothesis of equilibrium with the formation fluid, Reducing conditions are presumed in the model (pe = -3.5) in order to match the amount of observed dissolved Fe and thus considered as initial state for the reactive transport modeling. based on a measured composition of formation fluids and the predominant mineralogical assemblage of the host rock, a preliminary 1D Reactive transport modeling (RTM) was run with total time set to 30 years; results obtained for the initial simulation revealed that during this period, no significant change is evident for K-feldspar. Furthermore, the precipitation of calcite along the flow path in the brine results in a drop of pH from 6.2 to a value of 5.2 noticed over the simulated period. The circulation of cooled fluid in the reservoir is predicted to affect the temperature of the reservoir within the first 100 -150m from the injection well. Examination of porosity change in

  12. AN EXACT PEAK CAPTURING AND OSCILLATION-FREE SCHEME TO SOLVE ADVECTION-DISPERSION TRANSPORT EQUATIONS

    EPA Science Inventory

    An exact peak capturing and essentially oscillation-free (EPCOF) algorithm, consisting of advection-dispersion decoupling, backward method of characteristics, forward node tracking, and adaptive local grid refinement, is developed to solve transport equations. This algorithm repr...

  13. Eigen decomposition solution to the one-dimensional time-dependent photon transport equation.

    PubMed

    Handapangoda, Chintha C; Pathirana, Pubudu N; Premaratne, Malin

    2011-02-14

    The time-dependent one-dimensional photon transport (radiative transfer) equation is widely used to model light propagation through turbid media with a slab geometry, in a vast number of disciplines. Several numerical and semi-analytical techniques are available to accurately solve this equation. In this work we propose a novel efficient solution technique based on eigen decomposition of the vectorized version of the photon transport equation. Using clever transformations, the four variable integro-differential equation is reduced to a set of first order ordinary differential equations using a combination of a spectral method and the discrete ordinates method. An eigen decomposition approach is then utilized to obtain the closed-form solution of this reduced set of ordinary differential equations. PMID:21369115

  14. Triheptanoin for glucose transporter type I deficiency (G1D): Modulation of human ictogenesis, cerebral metabolic rate and cognitive indices by a food supplement

    PubMed Central

    Pascual, Juan M.; Liu, Peiying; Mao, Deng; Kelly, Dorothy; Hernandez, Ana; Sheng, Min; Good, Levi B.; Ma, Qian; Marin-Valencia, Isaac; Zhang, Xuchen; Park, Jason Y.; Hynan, Linda S.; Stavinoha, Peter; Roe, Charles R.; Lu, Hanzhang

    2015-01-01

    Objective G1D is commonly associated with electrographic spike-wave and - less-noticeably – with absence seizures. The G1D syndrome has long been attributed to energy (i.e., ATP-synthetic) failure, as have experimental, toxic-rodent epilepsies to impaired brain metabolism and tricarboxylic acid (TCA) cycle intermediate depletion. Indeed, a (seldom-acknowledged) function of glucose and other substrates is the generation of brain TCAs via carbon-donor reactions collectively named anaplerosis. However, TCAs are preserved in murine G1D. This renders inferences about energy failure premature and suggests a different hypothesis, also grounded on our findings, that consumption of alternate TCA precursors is stimulated, potentially detracting from other functions. Second, common ketogenic diets can ameliorate G1D seizures, but lead to a therapeutically-counterintuitive reduction in blood glucose available to the brain, and they can prove ineffective in 1/3 of cases. While developing G1D treatments, all of this motivated us to: a) uphold (rather than attenuate) the residual brain glucose flux that all G1D patients possess; and b) stimulate the TCA cycle, including anaplerosis. Therefore, we tested the medium-chain triglyceride triheptanoin, a widely-used medical food supplement that can fulfill both of these metabolic roles. The rationale is that ketone bodies derived from ketogenic diets are not anaplerotic, in contrast with triheptanoin metabolites, as we have shown in the G1D mouse brain. Design We supplemented the regular diet of a case series of G1D patients with food-grade triheptanoin. First we confirmed that, despite their frequent electroencephalographic (EEG) presence as spike-waves, most seizures are rarely visible, such that perceptions by patients or others are inadequate for treatment evaluation. Thus, we used EEG, quantitative neuropsychological, blood analytical, and MRI cerebral metabolic rate measurements as main outcomes. Setting Academic and

  15. Numerical evaluation of the intensity transport equation for well-known wavefronts and intensity distributions

    NASA Astrophysics Data System (ADS)

    Campos-García, Manuel; Granados-Agustín, Fermín.; Cornejo-Rodríguez, Alejandro; Estrada-Molina, Amilcar; Avendaño-Alejo, Maximino; Moreno-Oliva, Víctor Iván.

    2013-11-01

    In order to obtain a clearer interpretation of the Intensity Transport Equation (ITE), in this work, we propose an algorithm to solve it for some particular wavefronts and its corresponding intensity distributions. By simulating intensity distributions in some planes, the ITE is turns into a Poisson equation with Neumann boundary conditions. The Poisson equation is solved by means of the iterative algorithm SOR (Simultaneous Over-Relaxation).

  16. PC-1D installation manual and user's guide

    SciTech Connect

    Basore, P.A.

    1991-05-01

    PC-1D is a software package for personal computers that uses finite-element analysis to solve the fully-coupled two-carrier semiconductor transport equations in one dimension. This program is particularly useful for analyzing the performance of optoelectronic devices such as solar cells, but can be applied to any bipolar device whose carrier flows are primarily one-dimensional. This User's Guide provides the information necessary to install PC-1D, define a problem for solution, solve the problem, and examine the results. Example problems are presented which illustrate these steps. The physical models and numerical methods utilized are presented in detail. This document supports version 3.1 of PC-1D, which incorporates faster numerical algorithms with better convergence properties than previous versions of the program. 51 refs., 17 figs., 5 tabs.

  17. Fractional Advective-Dispersive Equation as a Model of Solute Transport in Porous Media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding and modeling transport of solutes in porous media is a critical issue in the environmental protection. The common model is the advective-dispersive equation (ADE) describing the superposition of the advective transport and the Brownian motion in water-filled pore space. Deviations from...

  18. Conservative differencing of the electron Fokker-Planck transport equation

    SciTech Connect

    Langdon, A.B.

    1981-01-12

    We need to extend the applicability and improve the accuracy of kinetic electron transport codes. In this paper, special attention is given to modelling of e-e collisions, including the dominant contributions arising from anisotropy. The electric field and spatial gradient terms are also considered. I construct finite-difference analogues to the Fokker-Planck integral-differential collision operator, which conserve the particle number, momentum and energy integrals (sums) regardless of the coarseness of the velocity zoning. Such properties are usually desirable, but are especially useful, for example, when there are spatial regions and/or time intervals in which the plasma is cool, so that the collision operator acts rapidly and the velocity distribution is poorly resolved, yet it is crucial that gross conservation properties be respected in hydro-transport applications, such as in the LASNEX code. Some points are raised concerning spatial differencing and time integration.

  19. Analytical Theory of the Destruction Terms in Dissipation Rate Transport Equations

    NASA Technical Reports Server (NTRS)

    Rubinstein, Robert; Zhou, Ye

    1996-01-01

    Modeled dissipation rate transport equations are often derived by invoking various hypotheses to close correlations in the corresponding exact equations. D. C. Leslie suggested that these models might be derived instead from Kraichnan's wavenumber space integrals for inertial range transport power. This suggestion is applied to the destruction terms in the dissipation rate equations for incompressible turbulence, buoyant turbulence, rotating incompressible turbulence, and rotating buoyant turbulence. Model constants like C(epsilon 2) are expressed as integrals; convergence of these integrals implies the absence of Reynolds number dependence in the corresponding destruction term. The dependence of C(epsilon 2) on rotation rate emerges naturally; sensitization of the modeled dissipation rate equation to rotation is not required. A buoyancy related effect which is absent in the exact transport equation for temperature variance dissipation, but which sometimes improves computational predictions, also arises naturally. Both the presence of this effect and the appropriate time scale in the modeled transport equation depend on whether Bolgiano or Kolmogorov inertial range scaling applies. A simple application of these methods leads to a preliminary, dissipation rate equation for rotating buoyant turbulence.

  20. Radiative or neutron transport modeling using a lattice Boltzmann equation framework

    NASA Astrophysics Data System (ADS)

    Bindra, H.; Patil, D. V.

    2012-07-01

    In this paper, the lattice Boltzmann equation (LBE)-based framework is used to obtain the solution for the linear radiative or neutron transport equation. The LBE framework is devised for the integrodifferential forms of these equations which arise due to the inclusion of the scattering terms. The interparticle collisions are neglected, hence omitting the nonlinear collision term. Furthermore, typical representative examples for one-dimensional or two-dimensional geometries and inclusion or exclusion of the scattering term (isotropic and anisotropic) in the Boltzmann transport equation are illustrated to prove the validity of the method. It has been shown that the solution from the LBE methodology is equivalent to the well-known Pn and Sn methods. This suggests that the LBE can potentially provide a more convenient and easy approach to solve the physical problems of neutron and radiation transport.

  1. Radiative or neutron transport modeling using a lattice Boltzmann equation framework.

    PubMed

    Bindra, H; Patil, D V

    2012-07-01

    In this paper, the lattice Boltzmann equation (LBE)-based framework is used to obtain the solution for the linear radiative or neutron transport equation. The LBE framework is devised for the integrodifferential forms of these equations which arise due to the inclusion of the scattering terms. The interparticle collisions are neglected, hence omitting the nonlinear collision term. Furthermore, typical representative examples for one-dimensional or two-dimensional geometries and inclusion or exclusion of the scattering term (isotropic and anisotropic) in the Boltzmann transport equation are illustrated to prove the validity of the method. It has been shown that the solution from the LBE methodology is equivalent to the well-known P(n) and S(n) methods. This suggests that the LBE can potentially provide a more convenient and easy approach to solve the physical problems of neutron and radiation transport.

  2. Solutions to bi-Maxwellian transport equations for SAR-arc conditions

    NASA Technical Reports Server (NTRS)

    Demars, H. G.; Schunk, R. W.

    1986-01-01

    The first subsonic solutions of the bi-Maxwellian-based 16-moment set of transport equations for stable auroral red (SAR) arc conditions are presented. These are compared with the solutions obtained from the Maxwellian-based 13-moment transport equations for the same boundary conditions. Close agreement between the 16-moment and 13-moment solutions was obtained for the drift velocity, total electron temperature, total proton heat flow, and total electron heat flow profiles. On the other hand, significant discrepancies were found. Thus, the 16-moment density profile falls off more rapidly with increasing altitude than that computed with the 13-moment equations; the total proton temperature is less in the 16-moment case than in the 13-moment case by several thousand degrees at most altitudes; and differences exist in the ratios of the proton and electron temperature anisotropies with the altitude. A simplified set of transport equations was obtained by dropping terms which remain relatively small at all altitudes.

  3. Least-squares finite element discretizations of neutron transport equations in 3 dimensions

    SciTech Connect

    Manteuffel, T.A; Ressel, K.J.; Starkes, G.

    1996-12-31

    The least-squares finite element framework to the neutron transport equation introduced in is based on the minimization of a least-squares functional applied to the properly scaled neutron transport equation. Here we report on some practical aspects of this approach for neutron transport calculations in three space dimensions. The systems of partial differential equations resulting from a P{sub 1} and P{sub 2} approximation of the angular dependence are derived. In the diffusive limit, the system is essentially a Poisson equation for zeroth moment and has a divergence structure for the set of moments of order 1. One of the key features of the least-squares approach is that it produces a posteriori error bounds. We report on the numerical results obtained for the minimum of the least-squares functional augmented by an additional boundary term using trilinear finite elements on a uniform tesselation into cubes.

  4. Rayleigh streaming simulation in a cylindrical tube using the vorticity transport equation

    NASA Astrophysics Data System (ADS)

    Sastrapradja, Debbie; Sparrow, Victor W.

    2006-05-01

    Current numerical calculation of acoustic streaming can involve major computing time and resources. To develop a quicker model, the vorticity transport equation (VTE) is used. In this paper Rayleigh streaming in a cylindrical tube is simulated using the VTE. The goal of using the VTE is to obtain a relatively fast solution with minimal computational resources, which in this case is a single PC. A clustered grid is utilized to capture the boundary layer effect on the acoustic streaming. The governing equations used are the VTE, Poisson's equation, and an equation that relates the stream function with the velocity. It is demonstrated that the VTE method to calculate Rayleigh streaming works well.

  5. Reprint of : Connection between wave transport through disordered 1D waveguides and energy density inside the sample: A maximum-entropy approach

    NASA Astrophysics Data System (ADS)

    Mello, Pier A.; Shi, Zhou; Genack, Azriel Z.

    2016-08-01

    We study the average energy - or particle - density of waves inside disordered 1D multiply-scattering media. We extend the transfer-matrix technique that was used in the past for the calculation of the intensity beyond the sample to study the intensity in the interior of the sample by considering the transfer matrices of the two segments that form the entire waveguide. The statistical properties of the two disordered segments are found using a maximum-entropy ansatz subject to appropriate constraints. The theoretical expressions are shown to be in excellent agreement with 1D transfer-matrix simulations.

  6. Generalized parallel heat transport equations in collisional to weakly collisional plasmas

    SciTech Connect

    Zawaideh, E.; Kim, N.S.; Najmabadi, F.

    1988-11-01

    A new set of two-fluid heat transport equations that is valid from collisional to weakly collisional limits is derived. Starting from gyrokinetic equations in flux coordinates, a set of moment equations describing plasma energy transport along the field lines of a space- and time-dependent magnetic field is derived. No restrictions on the anisotropy of the ion distribution function or collisionality are imposed. In the highly collisional limit, these equations reduce to the classical heat conduction equation (e.g., Spitzer and Haerm or Braginskii), while in the weakly collisional limit, they describe a saturated heat flux (flux limited). Numerical examples comparing these equations with conventional heat transport equations show that in the limit where the ratio of the mean free path lambda to the scale length of the temperature gradient L/sub T/ approaches zero, there is no significant difference between the solutions of the new and conventional heat transport equations. As lambda/L/sub T/..-->..1, the conventional heat conduction equation contains a significantly larger error than (lambda/L/sub T/)/sup 2/. The error is found to be O(lambda/L)/sup 2/, where L is the smallest of the scale lengths of the gradient in the magnetic field, or the macroscopic plasma parameters (e.g., velocity scale length, temperature scale length, and density scale length). The accuracy of the flux-limited model depends significantly on the value of the flux limit parameter which, in general, is not known. The new set of equations shows that the flux-limited parameter is a function of the magnetic field and plasma parameter profiles.

  7. Modeling ballistic effects in frequency-dependent transient thermal transport using diffusion equations

    NASA Astrophysics Data System (ADS)

    Maassen, Jesse; Lundstrom, Mark

    2016-03-01

    Understanding ballistic phonon transport effects in transient thermoreflectance experiments and explaining the observed deviations from classical theory remains a challenge. Diffusion equations are simple and computationally efficient but are widely believed to break down when the characteristic length scale is similar or less than the phonon mean-free-path. Building on our prior work, we demonstrate how well-known diffusion equations, namely, the hyperbolic heat equation and the Cattaneo equation, can be used to model ballistic phonon effects in frequency-dependent periodic steady-state thermal transport. Our analytical solutions are found to compare excellently to rigorous numerical results of the phonon Boltzmann transport equation. The correct physical boundary conditions can be different from those traditionally used and are paramount for accurately capturing ballistic effects. To illustrate the technique, we consider a simple model problem using two different, commonly used heating conditions. We demonstrate how this framework can easily handle detailed material properties, by considering the case of bulk silicon using a full phonon dispersion and mean-free-path distribution. This physically transparent approach provides clear insights into the nonequilibrium physics of quasi-ballistic phonon transport and its impact on thermal transport properties.

  8. Solution and Study of the Two-Dimensional Nodal Neutron Transport Equation

    SciTech Connect

    Panta Pazos, Ruben; Biasotto Hauser, Eliete; Tullio de Vilhena, Marco

    2002-07-01

    In the last decade Vilhena and coworkers reported an analytical solution to the two-dimensional nodal discrete-ordinates approximations of the neutron transport equation in a convex domain. The key feature of these works was the application of the combined collocation method of the angular variable and nodal approach in the spatial variables. By nodal approach we mean the transverse integration of the SN equations. This procedure leads to a set of one-dimensional S{sub N} equations for the average angular fluxes in the variables x and y. These equations were solved by the old version of the LTS{sub N} method, which consists in the application of the Laplace transform to the set of nodal S{sub N} equations and solution of the resulting linear system by symbolic computation. It is important to recall that this procedure allow us to increase N the order of S{sub N} up to 16. To overcome this drawback we step forward performing a spectral painstaking analysis of the nodal S{sub N} equations for N up to 16 and we begin the convergence of the S{sub N} nodal equations defining an error for the angular flux and estimating the error in terms of the truncation error of the quadrature approximations of the integral term. Furthermore, we compare numerical results of this approach with those of other techniques used to solve the two-dimensional discrete approximations of the neutron transport equation. (authors)

  9. A time dependent mixing model to close PDF equations for transport in heterogeneous aquifers

    NASA Astrophysics Data System (ADS)

    Schüler, L.; Suciu, N.; Knabner, P.; Attinger, S.

    2016-10-01

    Probability density function (PDF) methods are a promising alternative to predicting the transport of solutes in groundwater under uncertainty. They make it possible to derive the evolution equations of the mean concentration and the concentration variance, used in moment methods. The mixing model, describing the transport of the PDF in concentration space, is essential for both methods. Finding a satisfactory mixing model is still an open question and due to the rather elaborate PDF methods, a difficult undertaking. Both the PDF equation and the concentration variance equation depend on the same mixing model. This connection is used to find and test an improved mixing model for the much easier to handle concentration variance. Subsequently, this mixing model is transferred to the PDF equation and tested. The newly proposed mixing model yields significantly improved results for both variance modelling and PDF modelling.

  10. Transport equations for low-energy solar particles in evolving interplanetary magnetic fields

    NASA Technical Reports Server (NTRS)

    Ng, C. K.

    1988-01-01

    Two new forms of a simplified Fokker-Planck equation are derived for the transport of low-energy solar energetic particles in an evolving interplanetary magnetic field, carried by a variable radial solar wind. An idealized solution suggests that the 'invariant' anisotropy direction reported by Allum et al. (1974) may be explained within the conventional theoretical framework. The equations may be used to relate studies of solar particle propagation to solar wind transients, and vice versa.

  11. Lorentz force correction to the Boltzmann radiation transport equation and its implications for Monte Carlo algorithms.

    PubMed

    Bouchard, Hugo; Bielajew, Alex

    2015-07-01

    To establish a theoretical framework for generalizing Monte Carlo transport algorithms by adding external electromagnetic fields to the Boltzmann radiation transport equation in a rigorous and consistent fashion. Using first principles, the Boltzmann radiation transport equation is modified by adding a term describing the variation of the particle distribution due to the Lorentz force. The implications of this new equation are evaluated by investigating the validity of Fano's theorem. Additionally, Lewis' approach to multiple scattering theory in infinite homogeneous media is redefined to account for the presence of external electromagnetic fields. The equation is modified and yields a description consistent with the deterministic laws of motion as well as probabilistic methods of solution. The time-independent Boltzmann radiation transport equation is generalized to account for the electromagnetic forces in an additional operator similar to the interaction term. Fano's and Lewis' approaches are stated in this new equation. Fano's theorem is found not to apply in the presence of electromagnetic fields. Lewis' theory for electron multiple scattering and moments, accounting for the coupling between the Lorentz force and multiple elastic scattering, is found. However, further investigation is required to develop useful algorithms for Monte Carlo and deterministic transport methods. To test the accuracy of Monte Carlo transport algorithms in the presence of electromagnetic fields, the Fano cavity test, as currently defined, cannot be applied. Therefore, new tests must be designed for this specific application. A multiple scattering theory that accurately couples the Lorentz force with elastic scattering could improve Monte Carlo efficiency. The present study proposes a new theoretical framework to develop such algorithms.

  12. Solutions to bi-Maxwellian transport equations for radial solar wind beyond 28 R(S)

    NASA Technical Reports Server (NTRS)

    Demars, H. G.; Schunk, R. W.

    1991-01-01

    This paper presents solar wind solutions for radial flow between 28 solar radii and 1 AU using the bi-Maxwellian-based 16-moment set of transport equations. In addition to the number density, drift velocity, and parallel and perpendicular temperatures, the 16-moment equations account for the transport of both longitudinal and transverse thermal energies as well as stress. Also, using the 16-moment approximation for the distribution function and assuming plasma parameter values characteristic of the solar wind, contour plots are generated for the proton velocity distribution function. It is shown how the shape of these plots depends on various macroscopic plasma parameters.

  13. Solving the transport equation with quadratic finite elements: Theory and applications

    SciTech Connect

    Ferguson, J.M.

    1997-12-31

    At the 4th Joint Conference on Computational Mathematics, the author presented a paper introducing a new quadratic finite element scheme (QFEM) for solving the transport equation. In the ensuing year the author has obtained considerable experience in the application of this method, including solution of eigenvalue problems, transmission problems, and solution of the adjoint form of the equation as well as the usual forward solution. He will present detailed results, and will also discuss other refinements of his transport codes, particularly for 3-dimensional problems on rectilinear and non-rectilinear grids.

  14. h-Refinement for simple corner balance scheme of SN transport equation on distorted meshes

    NASA Astrophysics Data System (ADS)

    Yang, Rong; Yuan, Guangwei

    2016-11-01

    The transport sweep algorithm is a common method for solving discrete ordinate transport equation, but it breaks down once a concave cell appears in spatial meshes. To deal with this issue a local h-refinement for simple corner balance (SCB) scheme of SN transport equation on arbitrary quadrilateral meshes is presented in this paper by using a new subcell partition. It follows that a hybrid mesh with both triangle and quadrilateral cells is generated, and the geometric quality of these cells improves, especially it is ensured that all cells become convex. Combining with the original SCB scheme, an adaptive transfer algorithm based on the hybrid mesh is constructed. Numerical experiments are presented to verify the utility and accuracy of the new algorithm, especially for some application problems such as radiation transport coupled with Lagrangian hydrodynamic flow. The results show that it performs well on extremely distorted meshes with concave cells, on which the original SCB scheme does not work.

  15. Variational approach to solving the spectral Boltzmann transport equation in transient thermal grating for thin films

    NASA Astrophysics Data System (ADS)

    Chiloyan, Vazrik; Zeng, Lingping; Huberman, Samuel; Maznev, Alexei A.; Nelson, Keith A.; Chen, Gang

    2016-07-01

    The phonon Boltzmann transport equation (BTE) is widely utilized to study non-diffusive thermal transport. We find a solution of the BTE in the thin film transient thermal grating (TTG) experimental geometry by using a recently developed variational approach with a trial solution supplied by the Fourier heat conduction equation. We obtain an analytical expression for the thermal decay rate that shows excellent agreement with Monte Carlo simulations. We also obtain a closed form expression for the effective thermal conductivity that demonstrates the full material property and heat transfer geometry dependence, and recovers the limits of the one-dimensional TTG expression for very thick films and the Fuchs-Sondheimer expression for very large grating spacings. The results demonstrate the utility of the variational technique for analyzing non-diffusive phonon-mediated heat transport for nanostructures in multi-dimensional transport geometries, and will assist the probing of the mean free path distribution of materials via transient grating experiments.

  16. Equations of state and transport properties of mixtures in the warm dense regime

    SciTech Connect

    Hou, Yong; Dai, Jiayu; Kang, Dongdong; Ma, Wen; Yuan, Jianmin

    2015-02-15

    We have performed average-atom molecular dynamics to simulate the CH and LiH mixtures in the warm dense regime, and obtained equations of state and the ionic transport properties. The electronic structures are calculated by using the modified average-atom model, which have included the broadening of energy levels, and the ion-ion pair potentials of mixtures are constructed based on the temperature-dependent density functional theory. The ionic transport properties, such as ionic diffusion and shear viscosity, are obtained through the ionic velocity correlation functions. The equations of state and transport properties for carbon, hydrogen and lithium, hydrogen mixtures in a wide region of density and temperature are calculated. Through our computing the average ionization degree, average ion-sphere diameter and transition properties in the mixture, it is shown that transport properties depend not only on the ionic mass but also on the average ionization degree.

  17. Un-collided-flux preconditioning for the first order transport equation

    SciTech Connect

    Rigley, M.; Koebbe, J.; Drumm, C.

    2013-07-01

    Two codes were tested for the first order neutron transport equation using finite element methods. The un-collided-flux solution is used as a preconditioner for each of these methods. These codes include a least squares finite element method and a discontinuous finite element method. The performance of each code is shown on problems in one and two dimensions. The un-collided-flux preconditioner shows good speedup on each of the given methods. The un-collided-flux preconditioner has been used on the second-order equation, and here we extend those results to the first order equation. (authors)

  18. A 1D exact treatment of shock waves within spectral methods in plane geometry

    NASA Astrophysics Data System (ADS)

    Bonazzola, Silvano; Marck, Jean-Alain

    1991-12-01

    A high-accuracy numerical technique is presented which employs two moving grids, respectively before and after the shock formation, to solve 1D Euler equations that are coupled with the transport equations for the entropy and the chemical abundances in cases with and without shock formation. Chebychev polynomial series are used to expand quantities on both sides of the matching point, and Rankine-Hugoniot conditions are used to ascertain the shock velocity after shock formation. Illustrative results are presented.

  19. New Travelling Wave Solutions of Burgers Equation with Finite Transport Memory

    NASA Astrophysics Data System (ADS)

    Sakthivel, Rathinasamy; Chun, Changbum; Lee, Jonu

    2010-09-01

    The nonlinear evolution equations with finite memory have a wide range of applications in science and engineering. The Burgers equation with finite memory transport (time-delayed) describes convection-diffusion processes. In this paper, we establish the new solitary wave solutions for the time-delayed Burgers equation. The extended tanh method and the exp-function method have been employed to reveal these new solutions. Further, we have calculated the numerical solutions of the time-delayed Burgers equation with initial conditions by using the homotopy perturbation method (HPM). Our results show that the extended tanh and exp-function methods are very effective in finding exact solutions of the considered problem and HPM is very powerful in finding numerical solutions with good accuracy for nonlinear partial differential equations without any need of transformation or perturbation

  20. Analytical Tests for Ray Effect Errors in Discrete Ordinate Methods for Solving the Neutron Transport Equation

    SciTech Connect

    Chang, B

    2004-03-22

    This paper contains three analytical solutions of transport problems which can be used to test ray-effect errors in the numerical solutions of the Boltzmann Transport Equation (BTE). We derived the first two solutions and the third was shown to us by M. Prasad. Since this paper is intended to be an internal LLNL report, no attempt was made to find the original derivations of the solutions in the literature in order to cite the authors for their work.

  1. Analytical solution for the advection-dispersion transport equation in layered media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The advection-dispersion transport equation with first-order decay was solved analytically for multi-layered media using the classic integral transform technique (CITT). The solution procedure used an associated non-self-adjoint advection-diffusion eigenvalue problem that had the same form and coef...

  2. Time-independent one-speed neutron transport equation with anisotropic scattering in absorbing media

    SciTech Connect

    Hangelbroek, R. J.

    1980-06-01

    This report treats the time-independent, one-speed neutron transport equation with anisotropic scattering in absorbing media. For nuclear gain operators existence and uniqueness of solutions to the half-space and finite-slab problems are proved in L/sub 2/-space. The formulas needed for explicit calculations are derived by the use of perturbation theory techniques.

  3. Exact analytical solutions for contaminant transport in rivers 1. The equilibrium advection-dispersion equation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Analytical solutions of the advection-dispersion equation and related models are indispensable for predicting or analyzing contaminant transport processes in streams and rivers, as well as in other surface water bodies. Many useful analytical solutions originated in disciplines other than surface-w...

  4. A variational solution to the transport equation subject to an affine constraint.

    SciTech Connect

    Pousin, Jerome G.; Najm, Habib N.; Picq, Martine; Pebay, Philippe Pierre

    2004-02-01

    We establish an existence and uniqueness theorem for the transport equation subject to an inequality affine constraint, viewed as a constrained optimization problem. Then we derive a Space-Time Integrated Least Squares (STILS) scheme for its numerical approximation. Furthermore, we discuss some L{sup 2}-projection strategies and with numerical examples we show that there are not relevant for that problem.

  5. Parallel algorithms for 2-D cylindrical transport equations of Eigenvalue problem

    SciTech Connect

    Wei, J.; Yang, S.

    2013-07-01

    In this paper, aimed at the neutron transport equations of eigenvalue problem under 2-D cylindrical geometry on unstructured grid, the discrete scheme of Sn discrete ordinate and discontinuous finite is built, and the parallel computation for the scheme is realized on MPI systems. Numerical experiments indicate that the designed parallel algorithm can reach perfect speedup, it has good practicality and scalability. (authors)

  6. Measuring the contour of a wavefront using the Irradiance Transport Equation (ITE)

    NASA Astrophysics Data System (ADS)

    Castillo-Rodríguez, Luis; Granados-Agustín, Fermín; Fernández-Guasti, Manuel; Cornejo-Rodríguez, Alejandro

    2006-01-01

    The Irradiance Transport Equation (ITE), found by Teague, had been used in optics with different applications. One of the field where had been used is in optical testing, for example, with the method developed by Takeda. In this paper following the idea of using different optical and mathematical analysis method, theorical and experimental results are presented.

  7. Development of a hybrid deterministic/stochastic method for 1D nuclear reactor kinetics

    SciTech Connect

    Terlizzi, Stefano; Dulla, Sandra; Ravetto, Piero; Rahnema, Farzad; Zhang, Dingkang

    2015-12-31

    A new method has been implemented for solving the time-dependent neutron transport equation efficiently and accurately. This is accomplished by coupling the hybrid stochastic-deterministic steady-state coarse-mesh radiation transport (COMET) method [1,2] with the new predictor-corrector quasi-static method (PCQM) developed at Politecnico di Torino [3]. In this paper, the coupled method is implemented and tested in 1D slab geometry.

  8. Development of a hybrid deterministic/stochastic method for 1D nuclear reactor kinetics

    NASA Astrophysics Data System (ADS)

    Terlizzi, Stefano; Rahnema, Farzad; Zhang, Dingkang; Dulla, Sandra; Ravetto, Piero

    2015-12-01

    A new method has been implemented for solving the time-dependent neutron transport equation efficiently and accurately. This is accomplished by coupling the hybrid stochastic-deterministic steady-state coarse-mesh radiation transport (COMET) method [1,2] with the new predictor-corrector quasi-static method (PCQM) developed at Politecnico di Torino [3]. In this paper, the coupled method is implemented and tested in 1D slab geometry.

  9. Number-resolved master equation approach to quantum measurement and quantum transport

    NASA Astrophysics Data System (ADS)

    Li, Xin-Qi

    2016-08-01

    In addition to the well-known Landauer-Büttiker scattering theory and the nonequilibrium Green's function technique for mesoscopic transports, an alternative (and very useful) scheme is quantum master equation approach. In this article, we review the particle-number ( n)-resolved master equation ( n-ME) approach and its systematic applications in quantum measurement and quantum transport problems. The n-ME contains rich dynamical information, allowing efficient study of topics such as shot noise and full counting statistics analysis. Moreover, we also review a newly developed master equation approach (and its n-resolved version) under self-consistent Born approximation. The application potential of this new approach is critically examined via its ability to recover the exact results for noninteracting systems under arbitrary voltage and in presence of strong quantum interference, and the challenging non-equilibrium Kondo effect.

  10. Coupling lattice Boltzmann and continuum equations for flow and reactive transport in porous media.

    SciTech Connect

    Coon, Ethan; Porter, Mark L.; Kang, Qinjun; Moulton, John D.; Lichtner, Peter C.

    2012-06-18

    In spatially and temporally localized instances, capturing sub-reservoir scale information is necessary. Capturing sub-reservoir scale information everywhere is neither necessary, nor computationally possible. The lattice Boltzmann Method for solving pore-scale systems. At the pore-scale, LBM provides an extremely scalable, efficient way of solving Navier-Stokes equations on complex geometries. Coupling pore-scale and continuum scale systems via domain decomposition. By leveraging the interpolations implied by pore-scale and continuum scale discretizations, overlapping Schwartz domain decomposition is used to ensure continuity of pressure and flux. This approach is demonstrated on a fractured medium, in which Navier-Stokes equations are solved within the fracture while Darcy's equation is solved away from the fracture Coupling reactive transport to pore-scale flow simulators allows hybrid approaches to be extended to solve multi-scale reactive transport.

  11. Benchmark solutions for the galactic ion transport equations: Energy and spatially dependent problems

    NASA Astrophysics Data System (ADS)

    Ganapol, Barry D.; Townsend, Lawrence W.; Wilson, John W.

    1989-03-01

    Nontrivial benchmark solutions are developed for the galactic ion transport (GIT) equations in the straight-ahead approximation. These equations are used to predict potential radiation hazards in the upper atmosphere and in space. Two levels of difficulty are considered: (1) energy independent, and (2) spatially independent. The analysis emphasizes analytical methods never before applied to the GIT equations. Most of the representations derived have been numerically implemented and compared to more approximate calculations. Accurate ion fluxes are obtained (3 to 5 digits) for nontrivial sources. For monoenergetic beams, both accurate doses and fluxes are found. The benchmarks presented are useful in assessing the accuracy of transport algorithms designed to accommodate more complex radiation protection problems. In addition, these solutions can provide fast and accurate assessments of relatively simple shield configurations.

  12. Vectorization of the time-dependent Boltzmann transport equation: Application to deep penetration problems

    NASA Astrophysics Data System (ADS)

    Cobos, Agustín C.; Poma, Ana L.; Alvarez, Guillermo D.; Sanz, Darío E.

    2016-10-01

    We introduce an alternative method to calculate the steady state solution of the angular photon flux after a numerical evolution of the time-dependent Boltzmann transport equation (BTE). After a proper discretization the transport equation was converted into an ordinary system of differential equations that can be iterated as a weighted Richardson algorithm. As a different approach, in this work the time variable regulates the iteration process and convergence criteria is based on physical parameters. Positivity and convergence was assessed from first principles and a modified Courant-Friedrichs-Lewy condition was devised to guarantee convergence. The Penelope Monte Carlo method was used to test the convergence and accuracy of our approach for different phase space discretizations. Benchmarking was performed by calculation of total fluence and photon spectra in different one-dimensional geometries irradiated with 60Co and 6 MV photon beams and radiological applications were devised.

  13. Asymptotic-preserving methods for hyperbolic and transport equations with random inputs and diffusive scalings

    SciTech Connect

    Jin, Shi; Xiu, Dongbin; Zhu, Xueyu

    2015-05-15

    In this paper we develop a set of stochastic numerical schemes for hyperbolic and transport equations with diffusive scalings and subject to random inputs. The schemes are asymptotic preserving (AP), in the sense that they preserve the diffusive limits of the equations in discrete setting, without requiring excessive refinement of the discretization. Our stochastic AP schemes are extensions of the well-developed deterministic AP schemes. To handle the random inputs, we employ generalized polynomial chaos (gPC) expansion and combine it with stochastic Galerkin procedure. We apply the gPC Galerkin scheme to a set of representative hyperbolic and transport equations and establish the AP property in the stochastic setting. We then provide several numerical examples to illustrate the accuracy and effectiveness of the stochastic AP schemes.

  14. Exact PDF equations and closure approximations for advective-reactive transport

    SciTech Connect

    Venturi, D.; Tartakovsky, Daniel M.; Tartakovsky, Alexandre M.; Karniadakis, George E.

    2013-06-01

    Mathematical models of advection–reaction phenomena rely on advective flow velocity and (bio) chemical reaction rates that are notoriously random. By using functional integral methods, we derive exact evolution equations for the probability density function (PDF) of the state variables of the advection–reaction system in the presence of random transport velocity and random reaction rates with rather arbitrary distributions. These PDF equations are solved analytically for transport with deterministic flow velocity and a linear reaction rate represented mathematically by a heterog eneous and strongly-correlated random field. Our analytical solution is then used to investigate the accuracy and robustness of the recently proposed large-eddy diffusivity (LED) closure approximation [1]. We find that the solution to the LED-based PDF equation, which is exact for uncorrelated reaction rates, is accurate even in the presence of strong correlations and it provides an upper bound of predictive uncertainty.

  15. Benchmark solutions for the galactic ion transport equations: Energy and spatially dependent problems

    NASA Technical Reports Server (NTRS)

    Ganapol, Barry D.; Townsend, Lawrence W.; Wilson, John W.

    1989-01-01

    Nontrivial benchmark solutions are developed for the galactic ion transport (GIT) equations in the straight-ahead approximation. These equations are used to predict potential radiation hazards in the upper atmosphere and in space. Two levels of difficulty are considered: (1) energy independent, and (2) spatially independent. The analysis emphasizes analytical methods never before applied to the GIT equations. Most of the representations derived have been numerically implemented and compared to more approximate calculations. Accurate ion fluxes are obtained (3 to 5 digits) for nontrivial sources. For monoenergetic beams, both accurate doses and fluxes are found. The benchmarks presented are useful in assessing the accuracy of transport algorithms designed to accommodate more complex radiation protection problems. In addition, these solutions can provide fast and accurate assessments of relatively simple shield configurations.

  16. An asymptotic-preserving Lagrangian algorithm for the time-dependent anisotropic heat transport equation

    SciTech Connect

    Chacon, Luis; del-Castillo-Negrete, Diego; Hauck, Cory D.

    2014-09-01

    We propose a Lagrangian numerical algorithm for a time-dependent, anisotropic temperature transport equation in magnetized plasmas in the large guide field regime. The approach is based on an analytical integral formal solution of the parallel (i.e., along the magnetic field) transport equation with sources, and it is able to accommodate both local and non-local parallel heat flux closures. The numerical implementation is based on an operator-split formulation, with two straightforward steps: a perpendicular transport step (including sources), and a Lagrangian (field-line integral) parallel transport step. Algorithmically, the first step is amenable to the use of modern iterative methods, while the second step has a fixed cost per degree of freedom (and is therefore scalable). Accuracy-wise, the approach is free from the numerical pollution introduced by the discrete parallel transport term when the perpendicular to parallel transport coefficient ratio X /X becomes arbitrarily small, and is shown to capture the correct limiting solution when ε = X⊥L2/X1L2 → 0 (with L∥∙ L⊥ , the parallel and perpendicular diffusion length scales, respectively). Therefore, the approach is asymptotic-preserving. We demonstrate the capabilities of the scheme with several numerical experiments with varying magnetic field complexity in two dimensions, including the case of transport across a magnetic island.

  17. Deterministic proton transport solving a one dimensional Fokker-Planck equation

    SciTech Connect

    Marr, D.; Prael, R.; Adams, K.; Alcouffe, R.

    1997-10-01

    The transport of protons through matter is characterized by many interactions which cause small deflections and slight energy losses. The few which are catastrophic or cause large angle scattering can be viewed as extinction for many applications. The transport of protons at this level of approximation can be described by a Fokker Planck Equation. This equation is solved using a deterministic multigroup differencing scheme with a highly resolved set of discrete ordinates centered around the beam direction which is adequate to properly account for deflections and energy losses due to multiple Coulomb scattering. Comparisons with LAHET for a large variety of problems ranging from 800 MeV protons on a copper step wedge to 10 GeV protons on a sandwich of material are presented. The good agreement with the Monte Carlo code shows that the solution method is robust and useful for approximate solutions of selected proton transport problems.

  18. Turbulence transport equations for variable-density turbulence and their relationship to two-field models

    SciTech Connect

    Besnard, D. CEA Centre d'Etudes de Limeil, 94 - Villeneuve-Saint-Georges ); Harlow, F.H.; Rauenzahn, R.M.; Zemach, C. )

    1992-06-01

    This study gives an updated account of our current ability to describe multimaterial compressible turbulent flows by means of a one-point transport model. Evolution equations are developed for a number of second-order correlations of turbulent data, and approximations of the gradient type are applied to additional correlations to close the system of equations. The principal fields of interest are the one- point Reynolds tensor for variable-density flow, the turbulent energy dissipation rate, and correlations for density-velocity and density- density fluctuations. This single-field description of turbulent flows is compared in some detail to two-field flow equations for nonturbulent, highly dispersed flow with separate variables for each field. This comparison suggests means for improved modeling of some correlations not subjected to evolution equations.

  19. 1-D Numerical Analysis of ABCC Engine Performance

    NASA Technical Reports Server (NTRS)

    Holden, Richard

    1999-01-01

    ABCC engine combines air breathing and rocket engine into a single engine to increase the specific impulse over an entire flight trajectory. Except for the heat source, the basic operation of the ABCC is similar to the basic operation of the RBCC engine. The ABCC is intended to have a higher specific impulse than the RBCC for single stage Earth to orbit vehicle. Computational fluid dynamics (CFD) is a useful tool for the analysis of complex transport processes in various components in ABCC propulsion system. The objective of the present research was to develop a transient 1-D numerical model using conservation of mass, linear momentum, and energy equations that could be used to predict flow behavior throughout a generic ABCC engine following a flight path. At specific points during the development of the 1-D numerical model a myriad of tests were performed to prove the program produced consistent, realistic numbers that follow compressible flow theory for various inlet conditions.

  20. Multi-term approximation to the Boltzmann transport equation for electron energy distribution functions in nitrogen

    NASA Astrophysics Data System (ADS)

    Feng, Yue

    Plasma is currently a hot topic and it has many significant applications due to its composition of both positively and negatively charged particles. The energy distribution function is important in plasma science since it characterizes the ability of the plasma to affect chemical reactions, affect physical outcomes, and drive various applications. The Boltzmann Transport Equation is an important kinetic equation that provides an accurate basis for characterizing the distribution function---both in energy and space. This dissertation research proposes a multi-term approximation to solve the Boltzmann Transport Equation by treating the relaxation process using an expansion of the electron distribution function in Legendre polynomials. The elastic and 29 inelastic cross sections for electron collisions with nitrogen molecules (N2) and singly ionized nitrogen molecules ( N+2 ) have been used in this application of the Boltzmann Transport Equation. Different numerical methods have been considered to compare the results. The numerical methods discussed in this thesis are the implicit time-independent method, the time-dependent Euler method, the time-dependent Runge-Kutta method, and finally the implicit time-dependent relaxation method by generating the 4-way grid with a matrix solver. The results show that the implicit time-dependent relaxation method is the most accurate and stable method for obtaining reliable results. The results were observed to match with the published experimental data rather well.

  1. Solutions to bi-Maxwellian transport equations for the polar wind

    NASA Technical Reports Server (NTRS)

    Demars, H. G.; Schunk, R. W.

    1989-01-01

    In this study, polar wind solutions are obtained for a broad range of O(+) density, H(+) drift velocity, electron temperature and H(+) temperature boundary conditions. The bi-Maxwellian-based 16-moment set of transport equations is used, since this set is expected to be superior to Maxwellian-based equations in describing large temperature anisotropies and heat flows. The present solutions corroborate earlier results when similar boundary conditions are used. Also, for previously unexplored combinations of boundary conditions, the present solutions are often qualitatively different from any obtained before.

  2. Petrov-galerkin finite element method for solving the neutron transport equation

    SciTech Connect

    Greenbaum, A.; Ferguson, J.M.

    1986-05-01

    A finite element using different trial and test spaces in introduced for solving the neutron transport equation in spherical geometry. It is shown that the widely used discrete ordinates method can also be thought of as such a finite element technique, in which integrals appearing in the difference equations are replaced by one-point Gauss quadrature formulas (midpoint rule). Comparison of accuracy between the new method and the discrete ordinates method is discussed, and numerical examples are given to illustrate the greater accuracy of the new technique.

  3. H-mode transitions and limit cycle oscillations from mean field transport equations

    NASA Astrophysics Data System (ADS)

    Staebler, Gary M.; Groebner, R. J.

    2015-01-01

    The mean field toroidal and parallel momentum transport equations will be shown to admit both one-step transitions to suppressed transport (L/H) and limit cycle oscillations (LCO). Both types of transitions are driven by the suppression of turbulence by the mean field ExB velocity shear. Using experimental data to evaluate the coefficients of a reduced transport model, the observed frequency of the LCO can be matched. The increase in the H-mode power threshold above and below a minimum density agrees with the trends in the model. Both leading and lagging phase relations between the turbulent density fluctuation amplitude and the ExB velocity shear can occur depending on the evolution of the linear growth rate of the turbulence. The transport solutions match the initial phase of the L/H transition where the poloidal and ExB velocities are observed to change, and the density fluctuations drop, faster than the diamagnetic velocity.

  4. Analytical solution of the advection-diffusion transport equation using a change-of-variable and integral transform technique

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This paper presents a formal exact solution of the linear advection-diffusion transport equation with constant coefficients for both transient and steady-state regimes. A classical mathematical substitution transforms the original advection-diffusion equation into an exclusively diffusive equation. ...

  5. A novel heterocyclic compound targeting the dopamine transporter improves performance in the radial arm maze and modulates dopamine receptors D1-D3.

    PubMed

    Saroja, Sivaprakasam R; Aher, Yogesh D; Kalaba, Predrag; Aher, Nilima Y; Zehl, Martin; Korz, Volker; Subramaniyan, Saraswathi; Miklosi, Andras G; Zanon, Lisa; Neuhaus, Winfried; Höger, Harald; Langer, Thierry; Urban, Ernst; Leban, Johann; Lubec, Gert

    2016-10-01

    A series of compounds targeting the dopamine transporter (DAT) haS been shown to improve memory performance most probably by re-uptake inhibition. Although specific DAT inhibitors are available, there is limited information about specificity, mechanism and in particular the effect on dopamine receptors. It was therefore the aim of the study to test the DAT inhibitor 4-(diphenyl-methanesulfinylmethyl)-2-methyl-thiazole (code: CE-111), synthetized in our laboratory for the specificity to target DAT, for the effects upon spatial memory and for induced dopamine receptor modulation. Re-uptake inhibition was tested for DAT (IC50=3.2μM), serotonin transporter, SERT (IC50=272291μM) and noradrenaline transporter, NET (IC50=174μM). Spatial memory was studied in the radial arm maze (RAM) in male Sprague-Dawley rats that were intraperitoneally injected with CE-111 (1 or 10mg/kg body weight). Performance in the RAM was improved using 1 and 10mg/kg body weight of CE-111. Training and treatment effects on presynaptic, postsynaptic and extrasynaptic D1 and D2- receptors and dopamine receptor containing complexes as well as on activated DAT were observed. CE-111 was crossing the blood-brain barrier comparable to modafinil and was identified as effective to improve memory performance in the RAM. Dopamine re-uptake inhibition along with modulations in dopamine receptors are proposed as potential underlying mechanisms. PMID:27288589

  6. Physics of a magnetic filter for negative ion sources. I. Collisional transport across the filter in an ideal, 1D filter

    SciTech Connect

    Boeuf, J. P.; Chaudhury, B.; Garrigues, L.

    2012-11-15

    Magnetic filters are used in negative ion sources for neutral beam injection in fusion devices to reduce the electron temperature in the extraction region in order to limit negative ion destruction by fast electrons. The drop in electron temperature through the filter is due to the enhanced residence time and collisional energy losses of electrons trapped in the magnetic field. The mechanisms controlling particle and energy transport through the magnetic filter in negative ion sources of the ITER type are still not clear and the aim of this paper is to clarify and quantify these mechanisms. A particle-in-cell Monte Carlo simulation is used to revisit and analyze the role and operation of the magnetic filter in an 'ideal' one-dimensional configuration and to study the stability of the one-dimensional solution in a two-dimensional configuration with periodic boundary conditions. The roles of collisions and instabilities on electron transport through the filter are discussed. The influence of a more realistic geometry on electron transport through the filter is analyzed in the companion paper [Boeuf et al., Phys. Plasmas 19, 113510 (2012)].

  7. Electron and ion transport equations in computational weakly-ionized plasmadynamics

    SciTech Connect

    Parent, Bernard; Macheret, Sergey O.; Shneider, Mikhail N.

    2014-02-15

    A new set of ion and electron transport equations is proposed to simulate steady or unsteady quasi-neutral or non-neutral multicomponent weakly-ionized plasmas through the drift–diffusion approximation. The proposed set of equations is advantaged over the conventional one by being considerably less stiff in quasi-neutral regions because it can be integrated in conjunction with a potential equation based on Ohm's law rather than Gauss's law. The present approach is advantaged over previous attempts at recasting the system by being applicable to plasmas with several types of positive ions and negative ions and by not requiring changes to the boundary conditions. Several test cases of plasmas enclosed by dielectrics and of glow discharges between electrodes show that the proposed equations yield the same solution as the standard equations but require 10 to 100 times fewer iterations to reach convergence whenever a quasi-neutral region forms. Further, several grid convergence studies indicate that the present approach exhibits a higher resolution (and hence requires fewer nodes to reach a given level of accuracy) when ambipolar diffusion is present. Because the proposed equations are not intrinsically linked to specific discretization or integration schemes and exhibit substantial advantages with no apparent disadvantage, they are generally recommended as a substitute to the fluid models in which the electric field is obtained from Gauss's law as long as the plasma remains weakly-ionized and unmagnetized.

  8. TRANSPORT EQUATION FOR MHD TURBULENCE: APPLICATION TO PARTICLE ACCELERATION AT INTERPLANETARY SHOCKS

    SciTech Connect

    Sokolov, Igor V.; Gombosi, Tamas I.; Roussev, Ilia I.; Skender, Marina; Usmanov, Arcadi V. E-mail: tamas@umich.edu E-mail: Arcadi.Usmanov.1@gsfc.nasa.gov

    2009-05-01

    The aim of the present paper is to unify the various transport equations for turbulent waves that are used in different areas of space physics. Here, we mostly focus on the magnetohydrodynamic turbulence, in particular the Alfvenic turbulence. The applied methods, however, are general and can be extended to other forms of turbulence, for example the acoustic turbulence, or Langmuir plasma waves. With minor modifications, the derivations followed here can be extended for relativistic motions, thus making it possible to apply them to the wave transport in astrophysical objects with high plasma speeds (radiojets), or strong gravity (black hole surroundings)

  9. Green function solution of the Boltzmann transport equation for semiconducting thin film with rough boundaries

    NASA Astrophysics Data System (ADS)

    Ketenoğlu, D.; Ünal, B.

    2012-08-01

    In this study the Green function solution of the Boltzmann transport equation on semiconducting thin film with irregular walls has been applied for the first time. The effects of electron scattering caused by these irregularities on the electrical conductivity have been investigated. First of all by using coordinate transformations, the irregularities on the walls have been transferred into the volume and in this way the both surfaces have been brought into flat forms. By taking two models, Gaussian and exponential, for random potential energy term contained in the transformed Hamiltonian as the perturbation, the resistivity results have been calculated and compared with the ones obtained from the methods widely known in the literature. The Boltzmann transport equation has been solved in relaxation time approximation for the irregular walled system in the case of no magnetic field.

  10. Numerical solution of the time dependent neutron transport equation by the method of the characteristics

    SciTech Connect

    Talamo, Alberto

    2013-05-01

    This study presents three numerical algorithms to solve the time dependent neutron transport equation by the method of the characteristics. The algorithms have been developed taking into account delayed neutrons and they have been implemented into the novel MCART code, which solves the neutron transport equation for two-dimensional geometry and an arbitrary number of energy groups. The MCART code uses regular mesh for the representation of the spatial domain, it models up-scattering, and takes advantage of OPENMP and OPENGL algorithms for parallel computing and plotting, respectively. The code has been benchmarked with the multiplication factor results of a Boiling Water Reactor, with the analytical results for a prompt jump transient in an infinite medium, and with PARTISN and TDTORT results for cross section and source transients. The numerical simulations have shown that only two numerical algorithms are stable for small time steps.

  11. Improved master equation approach to quantum transport: From Born to self-consistent Born approximation

    SciTech Connect

    Jin, Jinshuang; Li, Jun; Liu, Yu; Li, Xin-Qi; Yan, YiJing

    2014-06-28

    Beyond the second-order Born approximation, we propose an improved master equation approach to quantum transport under self-consistent Born approximation. The basic idea is to replace the free Green's function in the tunneling self-energy diagram by an effective reduced propagator under the Born approximation. This simple modification has remarkable consequences. It not only recovers the exact results for quantum transport through noninteracting systems under arbitrary voltages, but also predicts the challenging nonequilibrium Kondo effect. Compared to the nonequilibrium Green's function technique that formulates the calculation of specific correlation functions, the master equation approach contains richer dynamical information to allow more efficient studies for such as the shot noise and full counting statistics.

  12. A heterocyclic compound CE-103 inhibits dopamine reuptake and modulates dopamine transporter and dopamine D1-D3 containing receptor complexes.

    PubMed

    Sase, Ajinkya; Aher, Yogesh D; Saroja, Sivaprakasam R; Ganesan, Minu Karthika; Sase, Sunetra; Holy, Marion; Höger, Harald; Bakulev, Vasiliy; Ecker, Gerhard F; Langer, Thierry; Sitte, Harald H; Leban, Johann; Lubec, Gert

    2016-03-01

    A series of compounds have been reported to enhance memory via the DA system and herein a heterocyclic compound was tested for working memory (WM) enhancement. 2-((benzhydrylsulfinyl)methyl)thiazole (CE-103) was synthesized in a six-step synthesis. Binding of CE-103 to the dopamine (DAT), serotonin (SERT) and norepinephrine (NET) transporters and dopamine reuptake inhibition was tested as well as blood brain permeation and a screen for GPCR targets. 60 male Sprague Dawley rats were divided into six groups: CE-103 treated 1-10 mg/kg body weight, trained (TDI) and yoked (YDI) and vehicle treated, trained (TVI) and yoked (YVI) rats. Daily single intraperitoneal injections for a period of 10 days were administered and rats were tested in a radial arm maze (RAM). Hippocampi were taken 6 h following the last day of training and complexes containing the unphosphorylated or phosphorylated dopamine transporter (DAT) and complexes containing the D1-3 dopamine receptor subunits were determined. CE-103 was binding to the DAT but insignificantly to SERT or NET and dopamine reuptake was blocked specifically (IC50 = 14.73 μM). From day eight the compound was decreasing WM errors in the RAM significantly at both doses tested as compared to the vehicle controls. In the trained CE-103-treated group levels of the complex containing the phosphorylated dopamine transporter (pDAT) as well as D1R were decreased while levels of complexes containing D2R and D3R were significantly increased. CE-103 was shown to enhance spatial WM and DA reuptake inhibition with subsequent modulation of D1-3 receptors is proposed as a possible mechanism of action. PMID:26407764

  13. Wave-front sensing by use of a Green's function solution to the intensity transport equation.

    PubMed

    Woods, Simon C; Greenaway, Alan H

    2003-03-01

    A method for reconstructing an unknown wave front from measurements of its intensity distribution on two planes along the direction of propagation is described. The method solves the intensity transport equation by use of Neumann boundary conditions, leading to a solution that requires only matrix multiplication. The method provides real-time wave-front reconstruction with high accuracy and is easily reposed to permit reconstruction of the wave front in any orthonormal basis set. PMID:12630836

  14. Benchmark solutions for the galactic heavy-ion transport equations with energy and spatial coupling

    NASA Technical Reports Server (NTRS)

    Ganapol, Barry D.; Townsend, Lawrence W.; Lamkin, Stanley L.; Wilson, John W.

    1991-01-01

    Nontrivial benchmark solutions are developed for the galactic heavy ion transport equations in the straightahead approximation with energy and spatial coupling. Analytical representations of the ion fluxes are obtained for a variety of sources with the assumption that the nuclear interaction parameters are energy independent. The method utilizes an analytical LaPlace transform inversion to yield a closed form representation that is computationally efficient. The flux profiles are then used to predict ion dose profiles, which are important for shield design studies.

  15. Existence of weak solutions for compressible Navier-Stokes equations with entropy transport

    NASA Astrophysics Data System (ADS)

    Maltese, David; Michálek, Martin; Mucha, Piotr B.; Novotný, Antonin; Pokorný, Milan; Zatorska, Ewelina

    2016-10-01

    We consider the compressible Navier-Stokes system with variable entropy. The pressure is a nonlinear function of the density and the entropy/potential temperature which, unlike in the Navier-Stokes-Fourier system, satisfies only the transport equation. We provide existence results within three alternative weak formulations of the corresponding classical problem. Our constructions hold for the optimal range of the adiabatic coefficients from the point of view of the nowadays existence theory.

  16. Two-dimensional boltzmann transport equation approach to simulation of local ion implantation

    NASA Astrophysics Data System (ADS)

    Komarov, F. F.; Mozolevski, I. E.; Rogach, V. P.

    1995-05-01

    A new theoretical model and software tool is proposed for simulation of two-dimensional local ion implantation in a target of arbitrary geometry. The program uses an algorithm of numerical solution of the boundary value problem for Boltzmann transport equation in two dimensions and permits to calculate the angular and energy distribution function of the particles moving in a multilayered multicomponent target. The program is essentially time saving and can be implemented on an IBM PC AT standard configuration computer.

  17. Hyperfine-induced spin relaxation of a hopping carrier: implications for spin transport in 1-D vs 3-D organic semiconductors

    NASA Astrophysics Data System (ADS)

    Mkhitaryan, Vagharsh; Dobrovitski, Viatcheslav; 0 Team

    2015-03-01

    The hyperfine coupling of a carrier spin to a nuclear spin bath is a predominant channel for the carrier spin relaxation in organic semiconductors. We investigate the hyperfine-induced spin relaxation of a carrier performing a random walk on a d-dimensional regular lattice theoretically, in a transport regime typical for organic semiconductors. We show that in d = 1 and d = 2 the time dependence of spin polarization, P (t) , is dominated by a superexponential decay, crossing over to an exponential tail at long times. The faster decay is attributed to multiple self-intersections (returns) of the random walk trajectories, which occur more often in lower dimensions. We also show, analytically and numerically, that the returns lead to sensitivity of P (t) to external electric and magnetic fields, and this sensitivity strongly depends on dimensionality of the system (d = 1 vs. d = 3). Furthermore, we consider the coordinate dependence of spin polarization, σ (r) , in a hypothetic lateral or vertical organic spin-valve device. We demonstrate that, while σ (r) is essentially exponential, the effect of multiple self-intersections can be identified in transport measurements from the specific field-dependence of spin relaxation length. This work was supported by the Department of Energy-Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

  18. A 1D analysis of two high order MOC methods

    SciTech Connect

    Everson, M. S.; Forget, B.

    2012-07-01

    The work presented here provides two different methods for evaluating angular fluxes along long characteristics. One is based off a projection of the 1D transport equation onto a complete set of Legendre polynomials, while the other uses the 1D integral transport equation to evaluate the angular flux values at specific points along each track passing through a cell. The Moment Long Characteristic (M-LC) method is shown to provide 2(P+1) spatial convergence and significant gains in accuracy with the addition of only a few spatial degrees of freedom. The M-LC method, though, is shown to be ill-conditioned at very high order and for optically thin geometries. The Point Long Characteristic (P-LC) method, while less accurate, significantly improves stability to problems with optically thin cells. The P-LC method is also more flexible, allowing for extra angular flux evaluations along a given track to give a more accurate representation of the shape along each track. This is at the expense of increasing the degrees of freedom of the system, though, and requires an increase in memory storage. This work concludes that both may be used simultaneously within the same geometry to provide the best mix of accuracy and stability possible. (authors)

  19. A transport equation for the scalar dissipation in reacting flows with variable density: First results

    NASA Technical Reports Server (NTRS)

    Mantel, T.

    1993-01-01

    Although the different regimes of premixed combustion are not well defined, most of the recent developments in turbulent combustion modeling are led in the so-called flamelet regime. The goal of these models is to give a realistic expression to the mean reaction rate (w). Several methods can be used to estimate (w). Bray and coworkers (Libby & Bray 1980, Bray 1985, Bray & Libby 1986) express the instantaneous reaction rate by means of a flamelet library and a frequency which describes the local interaction between the laminar flamelets and the turbulent flowfield. In another way, the mean reaction rate can be directly connected to the flame surface density (Sigma). This quantity can be given by the transport equation of the coherent flame model initially proposed by Marble & Broadwell 1977 and developed elsewhere. The mean reaction rate, (w), can also be estimated thanks to the evolution of an arbitrary scalar field G(x, t) = G(sub O) which represents the flame sheet. G(x, t) is obtained from the G-equation proposed by Williams 1985, Kerstein et al. 1988 and Peters 1993. Another possibility proposed in a recent study by Mantel & Borghi 1991, where a transport equation for the mean dissipation rate (epsilon(sub c)) of the progress variable c is used to determine (w). In their model, Mantel & Borghi 1991 considered a medium with constant density and constant diffusivity in the determination of the transport equation for (epsilon(sub c)). A comparison of different flamelet models made by Duclos et al. 1993 shows the realistic behavior of this model even in the case of constant density. Our objective in this present report is to present preliminary results on the study of this equation in the case of variable density and variable diffusivity. Assumptions of constant pressure and a Lewis number equal to unity allow us to significantly simplify the equation. A systematic order of magnitude analysis based on adequate scale relations is performed on each term of the

  20. Analytical Solutions of a Fractional Diffusion-advection Equation for Solar Cosmic-Ray Transport

    NASA Astrophysics Data System (ADS)

    Litvinenko, Yuri E.; Effenberger, Frederic

    2014-12-01

    Motivated by recent applications of superdiffusive transport models to shock-accelerated particle distributions in the heliosphere, we analytically solve a one-dimensional fractional diffusion-advection equation for the particle density. We derive an exact Fourier transform solution, simplify it in a weak diffusion approximation, and compare the new solution with previously available analytical results and with a semi-numerical solution based on a Fourier series expansion. We apply the results to the problem of describing the transport of energetic particles, accelerated at a traveling heliospheric shock. Our analysis shows that significant errors may result from assuming an infinite initial distance between the shock and the observer. We argue that the shock travel time should be a parameter of a realistic superdiffusive transport model.

  1. Analytical solutions of a fractional diffusion-advection equation for solar cosmic-ray transport

    SciTech Connect

    Litvinenko, Yuri E.; Effenberger, Frederic

    2014-12-01

    Motivated by recent applications of superdiffusive transport models to shock-accelerated particle distributions in the heliosphere, we analytically solve a one-dimensional fractional diffusion-advection equation for the particle density. We derive an exact Fourier transform solution, simplify it in a weak diffusion approximation, and compare the new solution with previously available analytical results and with a semi-numerical solution based on a Fourier series expansion. We apply the results to the problem of describing the transport of energetic particles, accelerated at a traveling heliospheric shock. Our analysis shows that significant errors may result from assuming an infinite initial distance between the shock and the observer. We argue that the shock travel time should be a parameter of a realistic superdiffusive transport model.

  2. The derivation and moments solution of approximate transport equations for the implantation of ions into amorphous targets

    NASA Astrophysics Data System (ADS)

    Ashworth, D. G.; Bowyer, M. D. J.; Oven, R.

    1995-06-01

    Commencing with the LSS integro-differential equation, an approximate transport equation is derived from which the moments of the range distribution may be obtained. The resulting equation set is known as the Kent Range ALgorithm (KRAL). The method for numerical solution of these equations, when written as a set of coupled second order ordinary differential equations (ODEs) of the initial value type, is then outlined. Solution is achieved by recasting the equation set in the form of first order ODEs designed for iterative solution. The technique used is an iterative refinement (or residual correction) procedure and the set of first order ODEs is called the Kent Optimised Range ALgorithm (KORAL). Finally, the first three moments from KORAL, first and second order PRAL codes and the full transport equation code KUBBIC-91 are compared with Monte Carlo data obtained from a TRIM code modified to treat targets of infinite extent. Comparisons are performed using consistent nuclear and electronic energy loss models.

  3. Effects of microscopic transport coefficients on fission observables calculated by the Langevin equation

    NASA Astrophysics Data System (ADS)

    Usang, M. D.; Ivanyuk, F. A.; Ishizuka, C.; Chiba, S.

    2016-10-01

    Nuclear fission is treated by using the Langevin dynamical description with macroscopic and microscopic transport coefficients (mass and friction tensors), and it is elucidated how the microscopic (shell and pairing) effects in the transport coefficients, especially their dependence on temperature, affects various fission observables. We found that the microscopic transport coefficients, calculated by linear response theory, change drastically as a function of temperature: in general, the friction increases with growing temperature while the mass tensor decreases. This temperature dependence brings a noticeable change in the mass distribution and kinetic energies of fission fragments from nuclei around 236U at an excitation energy of 20 MeV. The prescission kinetic energy decreases from 25 MeV at low temperature to about 2.5 MeV at high temperature. In contrast, the Coulomb kinetic energy increases as the temperature increases. Interpolating the microscopic transport coefficients among the various temperatures enabled our Langevin equation to use the microscopic transport coefficients at a deformation-dependent local temperature of the dynamical evolution. This allowed us to compare directly the fission observables of both macroscopic and microscopic calculations, and we found almost identical results under the conditions considered in this work.

  4. Temperature-dependent thermal conductivity in silicon nanostructured materials studied by the Boltzmann transport equation

    NASA Astrophysics Data System (ADS)

    Romano, Giuseppe; Esfarjani, Keivan; Strubbe, David A.; Broido, David; Kolpak, Alexie M.

    2016-01-01

    Nanostructured materials exhibit low thermal conductivity because of the additional scattering due to phonon-boundary interactions. As these interactions are highly sensitive to the mean free path (MFP) of phonons, MFP distributions in nanostructures can be dramatically distorted relative to bulk. Here we calculate the MFP distribution in periodic nanoporous Si for different temperatures, using the recently developed MFP-dependent Boltzmann transport equation. After analyzing the relative contribution of each phonon branch to thermal transport in nanoporous Si, we find that at room temperature optical phonons contribute 17 % to heat transport, compared to 5 % in bulk Si. Interestingly, we observe a constant thermal conductivity over the range 200 K transport of acoustic phonons with long intrinsic MFP and the temperature dependence of the heat capacity. Our findings, which are in qualitative agreement with the temperature trend of thermal conductivities measured in nanoporous Si-based systems, shed light on the origin of the reduction of thermal conductivity in nanostructured materials and demonstrate the necessity of multiscale heat transport engineering, in which the bulk material and geometry are optimized concurrently.

  5. Analytical solution of equations describing slow axonal transport based on the stop-and-go hypothesis

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Andrey

    2011-06-01

    This paper presents an analytical solution for slow axonal transport in an axon. The governing equations for slow axonal transport are based on the stop-and-go hypothesis which assumes that organelles alternate between short periods of rapid movement on microtubules (MTs), short on-track pauses, and prolonged off-track pauses, when they temporarily disengage from MTs. The model includes six kinetic states for organelles: two for off-track organelles (anterograde and retrograde), two for running organelles, and two for pausing organelles. An analytical solution is obtained for a steady-state situation. To obtain the analytical solution, the governing equations are uncoupled by using a perturbation method. The solution is validated by comparing it with a high-accuracy numerical solution. Results are presented for neurofilaments (NFs), which are characterized by small diffusivity, and for tubulin oligomers, which are characterized by large diffusivity. The difference in transport modes between these two types of organelles in a short axon is discussed. A comparison between zero-order and first-order approximations makes it possible to obtain a physical insight into the effects of organelle reversals (when organelles change the type of a molecular motor they are attached to, an anterograde versus retrograde motor).

  6. Two-dimensional phase unwrapping using the transport of intensity equation.

    PubMed

    Pandey, Neeraj; Ghosh, Amitava; Khare, Kedar

    2016-03-20

    We report a method for two-dimensional phase unwrapping based on the transport of intensity equation (TIE). Given a wrapped phase profile, we generate an auxiliary complex field and propagate it to small distances to simulate two intensity images on closely spaced planes. Using the longitudinal intensity derivative of the auxiliary field as an input, the TIE is solved by employing the regularized Fourier-transform-based approach. The resultant phase profile is automatically in the unwrapped form, as it has been obtained as a solution of a partial differential equation rather than as an argument of a complex-valued function. Our simulations and experimental results suggest that this approach is fast and accurate and provides a simple and practical solution for routine phase unwrapping tasks in interferometry and digital holography. PMID:27140583

  7. A coupling model of the radiative transport equation for calculating photon migration in biological tissue

    NASA Astrophysics Data System (ADS)

    Fujii, Hiroyuki; Okawa, Shinpei; Yamada, Yukio; Hoshi, Yoko; Watanabe, Masao

    2015-12-01

    Development of a physically accurate and computationally efficient photon migration model for turbid media is crucial for optical computed tomography such as diffuse optical tomography. For the development, this paper constructs a space-time coupling model of the radiative transport equation with the photon diffusion equation. In the coupling model, a space-time regime of the photon migration is divided into the ballistic and diffusive regimes with the interaction between the both regimes to improve the accuracy of the results and the efficiency of computation. The coupling model provides an accurate description of the photon migration in various turbid media in a wide range of the optical properties, and reduces computational loads when compared with those of full calculation of the RTE.

  8. Modeling Heat Conduction and Radiation Transport with the Diffusion Equation in NIF ALE-AMR

    SciTech Connect

    Fisher, A C; Bailey, D S; Kaiser, T B; Gunney, B N; Masters, N D; Koniges, A E; Eder, D C; Anderson, R W

    2009-10-06

    The ALE-AMR code developed for NIF is a multi-material hydro-code that models target assembly fragmentation in the aftermath of a shot. The combination of ALE (Arbitrary Lagrangian Eulerian) hydro with AMR (Adaptive Mesh Refinement) allows the code to model a wide range of physical conditions and spatial scales. The large range of temperatures encountered in the NIF target chamber can lead to significant fluxes of energy due to thermal conduction and radiative transport. These physical effects can be modeled approximately with the aid of the diffusion equation. We present a novel method for the solution of the diffusion equation on a composite mesh in order to capture these physical effects.

  9. The use of Galerkin finite-element methods to solve mass-transport equations

    USGS Publications Warehouse

    Grove, David B.

    1977-01-01

    The partial differential equation that describes the transport and reaction of chemical solutes in porous media was solved using the Galerkin finite-element technique. These finite elements were superimposed over finite-difference cells used to solve the flow equation. Both convection and flow due to hydraulic dispersion were considered. Linear and Hermite cubic approximations (basis functions) provided satisfactory results: however, the linear functions were computationally more efficient for two-dimensional problems. Successive over relaxation (SOR) and iteration techniques using Tchebyschef polynomials were used to solve the sparce matrices generated using the linear and Hermite cubic functions, respectively. Comparisons of the finite-element methods to the finite-difference methods, and to analytical results, indicated that a high degree of accuracy may be obtained using the method outlined. The technique was applied to a field problem involving an aquifer contaminated with chloride, tritium, and strontium-90. (Woodard-USGS)

  10. Stochastic interpretation of the advection-diffusion equation and its relevance to bed load transport

    NASA Astrophysics Data System (ADS)

    Ancey, C.; Bohorquez, P.; Heyman, J.

    2015-12-01

    The advection-diffusion equation is one of the most widespread equations in physics. It arises quite often in the context of sediment transport, e.g., for describing time and space variations in the particle activity (the solid volume of particles in motion per unit streambed area). Phenomenological laws are usually sufficient to derive this equation and interpret its terms. Stochastic models can also be used to derive it, with the significant advantage that they provide information on the statistical properties of particle activity. These models are quite useful when sediment transport exhibits large fluctuations (typically at low transport rates), making the measurement of mean values difficult. Among these stochastic models, the most common approach consists of random walk models. For instance, they have been used to model the random displacement of tracers in rivers. Here we explore an alternative approach, which involves monitoring the evolution of the number of particles moving within an array of cells of finite length. Birth-death Markov processes are well suited to this objective. While the topic has been explored in detail for diffusion-reaction systems, the treatment of advection has received no attention. We therefore look into the possibility of deriving the advection-diffusion equation (with a source term) within the framework of birth-death Markov processes. We show that in the continuum limit (when the cell size becomes vanishingly small), we can derive an advection-diffusion equation for particle activity. Yet while this derivation is formally valid in the continuum limit, it runs into difficulty in practical applications involving cells or meshes of finite length. Indeed, within our stochastic framework, particle advection produces nonlocal effects, which are more or less significant depending on the cell size and particle velocity. Albeit nonlocal, these effects look like (local) diffusion and add to the intrinsic particle diffusion (dispersal due

  11. Really TVD advection schemes for the depth-integrated transport equation

    NASA Astrophysics Data System (ADS)

    Mercier, Ch.; Delhez, E. J. M.

    This paper explores the use of TVD advection schemes to solve the depth-integrated transport equation for tracers in finite volume marine models. Numerical experiments show that the blind application of the usual TVD schemes and associated flux limiters can lead to non-TVD solutions when applied in complex geometries. Spatial and/or temporal variations of the local bathymetry can indeed break the TVD property of the usual schemes. Really TVD schemes can be recovered by taking into account the local depth and its variations in the formulation of the flux limiters. Using this approach, a generalized superbee limiter is introduced and validated.

  12. Gluon transport equation with effective mass and dynamical onset of Bose–Einstein condensation

    DOE PAGES

    Blaizot, Jean-Paul; Jiang, Yin; Liao, Jinfeng

    2016-05-01

    In this paper we study the transport equation describing a dense system of gluons, in the small scattering angle approximation, taking into account medium-generated effective masses of the gluons. We focus on the case of overpopulated systems that are driven to Bose–Einstein condensation on their way to thermalization. Lastly, the presence of a mass modifies the dispersion relation of the gluon, as compared to the massless case, but it is shown that this does not change qualitatively the scaling behavior in the vicinity of the onset.

  13. Phase retrieval by using the transport-of-intensity equation with Hilbert transform.

    PubMed

    Li, Wei-Shuo; Chen, Chun-Wei; Lin, Kuo-Feng; Chen, Hou-Ren; Tsai, Chih-Ya; Chen, Chyong-Hua; Hsieh, Wen-Feng

    2016-04-01

    Phase recovery by solving the transport-of-intensity equation (TIE) is a non-iterative and non-interferometric phase retrieval technique. From solving the TIE with conventional, one partial derivative and Hilbert transform methods for both the periodic and aperiodic samples, we demonstrate that the Hilbert transform method can provide the smoother phase images with edge enhancement and fine structures. Furthermore, compared with the images measured by optical and atomic force microscopy, the Hilbert transform method has the ability to quantitatively map out the phase images for both the periodic and aperiodic structures. PMID:27192301

  14. Unified description of equation of state and transport properties of nuclear matter

    SciTech Connect

    Benhar, Omar; Farina, Nicola; Valli, Marco; Fiorilla, Salvatore

    2008-10-13

    Correlated basis function perturbation theory and the formalism of cluster expansions have been recently employed to obtain an effective interaction from a state-of-the-art nucleon nucleon potential model. The approach based on the effective interaction allows for a consistent description of the nuclear matter ground state and nucleon-nucleon scattering in the nuclear medium. This paper reports the the results of numerical calculations of different properties of nuclear and neutron matter, including the equation of state and the shear viscosity and thermal conductivity transport coefficients, carried out using the effective interaction.

  15. Transport equations of energy for ferromagnetic insulators in contact with electrodes.

    PubMed

    Wegrowe, J-E

    2013-09-11

    A phenomenological derivation of the transport equations for ferromagnetic moments and associated energy and heat is proposed. The model describes the transfer of energy through an interface composed of a ferromagnetic insulator in contact with normal electrodes. A reduction method applied to the ferromagnetic degrees of freedom allows a two-channel model to be defined for the transport of magnetic moments. It is shown that a heat current flowing into the insulating ferromagnet-produced e.g. by electromagnetic resonance, thermal gradient, magneto-mechanical or magneto-optical excitations-can generate a magneto-voltaic potential and a pure spin-current in the non-ferromagnetic electrode. PMID:23941895

  16. Theoretical analysis of integral neutron transport equation using collision probability method with quadratic flux approach

    SciTech Connect

    Shafii, Mohammad Ali Meidianti, Rahma Wildian, Fitriyani, Dian; Tongkukut, Seni H. J.; Arkundato, Artoto

    2014-09-30

    Theoretical analysis of integral neutron transport equation using collision probability (CP) method with quadratic flux approach has been carried out. In general, the solution of the neutron transport using the CP method is performed with the flat flux approach. In this research, the CP method is implemented in the cylindrical nuclear fuel cell with the spatial of mesh being conducted into non flat flux approach. It means that the neutron flux at any point in the nuclear fuel cell are considered different each other followed the distribution pattern of quadratic flux. The result is presented here in the form of quadratic flux that is better understanding of the real condition in the cell calculation and as a starting point to be applied in computational calculation.

  17. A Piecewise Bi-Linear Discontinuous Finite Element Spatial Discretization of the Sn Transport Equation

    SciTech Connect

    Bailey, T S; Chang, J H; Warsa, J S; Adams, M L

    2010-12-22

    We present a new spatial discretization of the discrete-ordinates transport equation in two-dimensional Cartesian (X-Y) geometry for arbitrary polygonal meshes. The discretization is a discontinuous finite element method (DFEM) that utilizes piecewise bi-linear (PWBL) basis functions, which are formally introduced in this paper. We also present a series of numerical results on quadrilateral and polygonal grids and compare these results to a variety of other spatial discretizations that have been shown to be successful on these grid types. Finally, we note that the properties of the PWBL basis functions are such that the leading-order piecewise bi-linear discontinuous finite element (PWBLD) solution will satisfy a reasonably accurate diffusion discretization in the thick diffusion limit, making the PWBLD method a viable candidate for many different classes of transport problems.

  18. Representative equations for the thermodynamic and transport properties of fluids near the gas-liquid critical point

    NASA Technical Reports Server (NTRS)

    Sengers, J. V.; Basu, R. S.; Sengers, J. M. H. L.

    1981-01-01

    A survey is presented of representative equations for various thermophysical properties of fluids in the critical region. Representative equations for the transport properties are included. Semi-empirical modifications of the theoretically predicted asymtotic critical behavior that yield simple and practical representations of the fluid properties in the critical region are emphasized.

  19. Application of the multigrid amplitude function method for time-dependent transport equation using MOC

    SciTech Connect

    Tsujita, K.; Endo, T.; Yamamoto, A.

    2013-07-01

    An efficient numerical method for time-dependent transport equation, the mutigrid amplitude function (MAF) method, is proposed. The method of characteristics (MOC) is being widely used for reactor analysis thanks to the advances of numerical algorithms and computer hardware. However, efficient kinetic calculation method for MOC is still desirable since it requires significant computation time. Various efficient numerical methods for solving the space-dependent kinetic equation, e.g., the improved quasi-static (IQS) and the frequency transform methods, have been developed so far mainly for diffusion calculation. These calculation methods are known as effective numerical methods and they offer a way for faster computation. However, they have not been applied to the kinetic calculation method using MOC as the authors' knowledge. Thus, the MAF method is applied to the kinetic calculation using MOC aiming to reduce computation time. The MAF method is a unified numerical framework of conventional kinetic calculation methods, e.g., the IQS, the frequency transform, and the theta methods. Although the MAF method is originally developed for the space-dependent kinetic calculation based on the diffusion theory, it is extended to transport theory in the present study. The accuracy and computational time are evaluated though the TWIGL benchmark problem. The calculation results show the effectiveness of the MAF method. (authors)

  20. Systematic derivation of reaction-diffusion equations with distributed delays and relations to fractional reaction-diffusion equations and hyperbolic transport equations: Application to the theory of Neolithic transition

    NASA Astrophysics Data System (ADS)

    Vlad, Marcel Ovidiu; Ross, John

    2002-12-01

    We introduce a general method for the systematic derivation of nonlinear reaction-diffusion equations with distributed delays. We study the interactions among different types of moving individuals (atoms, molecules, quasiparticles, biological organisms, etc). The motion of each species is described by the continuous time random walk theory, analyzed in the literature for transport problems, whereas the interactions among the species are described by a set of transformation rates, which are nonlinear functions of the local concentrations of the different types of individuals. We use the time interval between two jumps (the transition time) as an additional state variable and obtain a set of evolution equations, which are local in time. In order to make a connection with the transport models used in the literature, we make transformations which eliminate the transition time and derive a set of nonlocal equations which are nonlinear generalizations of the so-called generalized master equations. The method leads under different specified conditions to various types of nonlocal transport equations including a nonlinear generalization of fractional diffusion equations, hyperbolic reaction-diffusion equations, and delay-differential reaction-diffusion equations. Thus in the analysis of a given problem we can fit to the data the type of reaction-diffusion equation and the corresponding physical and kinetic parameters. The method is illustrated, as a test case, by the study of the neolithic transition. We introduce a set of assumptions which makes it possible to describe the transition from hunting and gathering to agriculture economics by a differential delay reaction-diffusion equation for the population density. We derive a delay evolution equation for the rate of advance of agriculture, which illustrates an application of our analysis.

  1. Equations of the surface harmonics method for solving time-dependent neutron transport problems and their verification

    NASA Astrophysics Data System (ADS)

    Boyarinov, V. F.; Kondrushin, A. E.; Fomichenko, P. A.

    2013-12-01

    Time-dependent equations of the surface harmonics method (SHM) are obtained for planar one-dimensional geometry. The equations are verified by calculations of test problems from Benchmark Problem Book ANL-7416, and the capabilities and efficiency of applying the SHM for solving the time-dependent neutron transport equation in the diffusion approximation are demonstrated. The results of the work show that the implementation of the SHG for full-scale computations will make possible substantial progress in the efficient solution of time-dependent problems of neutron transport in nuclear reactors.

  2. Analytical solutions of the one-dimensional advection-dispersion solute transport equation subject to time-dependent boundary conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Analytical solutions of the advection-dispersion solute transport equation remain useful for a large number of applications in science and engineering. In this paper we extend the Duhamel theorem, originally established for diffusion type problems, to the case of advective-dispersive transport subj...

  3. Predicting fractional bed load transport rates: Application of the Wilcock-Crowe equations to a regulated gravel bed river

    USGS Publications Warehouse

    Gaeuman, D.; Andrews, E.D.; Kraus, A.; Smith, W.

    2009-01-01

    Bed load samples from four locations in the Trinity River of northern California are analyzed to evaluate the performance of the Wilcock-Crowe bed load transport equations for predicting fractional bed load transport rates. Bed surface particles become smaller and the fraction of sand on the bed increases with distance downstream from Lewiston Dam. The dimensionless reference shear stress for the mean bed particle size (t*rm) is largest near the dam, but varies relatively little between the more downstream locations. The relation between t*rm and the reference shear stresses for other size fractions is constant across all locations. Total bed load transport rates predicted with the Wilcock-Crowe equations are within a factor of 2 of sampled transport rates for 68% of all samples. The Wilcock-Crowe equations nonetheless consistently under-predict the transport of particles larger than 128 mm, frequently by more than an order of magnitude. Accurate prediction of the transport rates of the largest particles is important for models in which the evolution of the surface grain size distribution determines subsequent bed load transport rates. Values of term estimated from bed load samples are up to 50% larger than those predicted with the Wilcock-Crowe equations, and sampled bed load transport approximates equal mobility across a wider range of grain sizes than is implied by the equations. Modifications to theWilcock-Crowe equation for determining t*rm and the hiding function used to scale term to other grain size fractions are proposed to achieve the best fit to observed bed load transport in the Trinity River. Copyright 2009 by the American eophysical Union.

  4. Nonlinear diffusion acceleration for the multigroup transport equation discretized with S{sub N} and continuous FEM with rattlesnake

    SciTech Connect

    Wang, Y.

    2013-07-01

    Nonlinear diffusion acceleration (NDA) can improve the performance of a neutron transport solver significantly especially for the multigroup eigenvalue problems. The high-order transport equation and the transport-corrected low-order diffusion equation form a nonlinear system in NDA, which can be solved via a Picard iteration. The consistency of the correction of the low-order equation is important to ensure the stabilization and effectiveness of the iteration. It also makes the low-order equation preserve the scalar flux of the high-order equation. In this paper, the consistent correction for a particular discretization scheme, self-adjoint angular flux (SAAF) formulation with discrete ordinates method (S{sub N}) and continuous finite element method (CFEM) is proposed for the multigroup neutron transport equation. Equations with the anisotropic scatterings and a void treatment are included. The Picard iteration with this scheme has been implemented and tested with RattleS{sub N}ake, a MOOSE-based application at INL. Convergence results are presented. (authors)

  5. Performance assessment of several equations of state and second virial coefficients in modified Enskog theory: Results for transport properties

    NASA Astrophysics Data System (ADS)

    Kiani, M.; Alavianmehr, M. M.; Otoofat, M.; Mohsenipour, A. A.; Ghatee, A.

    2015-11-01

    In this work, we identify a simple method for predicting transport properties of fluids over wide ranges of temperatures and pressure. In this respect, the capability of several equations of state (EOS) and second virial coefficient correlations to predict transport properties of fluids including carbon dioxide, methane and argon using modified Enskog theory (MET) is investigated. The transport properties in question are viscosity and thermal conductivity. The results indicate that the SRK EOS employed in the modified Enskog theory outperforms other equations of state. The average absolute deviation was found to be 12.2 and 18.5% for, respectively, the calculated thermal conductivity and viscosity using the MET.

  6. Nonlinear Acceleration of a Continuous Finite Element Discretization of the Self-Adjoint Angular Flux Form of the Transport Equation

    SciTech Connect

    Richard Sanchez; Cristian Rabiti; Yaqi Wang

    2013-11-01

    Nonlinear acceleration of a continuous finite element (CFE) discretization of the transport equation requires a modification of the transport solution in order to achieve local conservation, a condition used in nonlinear acceleration to define the stopping criterion. In this work we implement a coarse-mesh finite difference acceleration for a CFE discretization of the second-order self-adjoint angular flux (SAAF) form of the transport equation and use a postprocessing to enforce local conservation. Numerical results are given for one-group source calculations of one-dimensional slabs. We also give a novel formal derivation of the boundary conditions for the SAAF.

  7. Transport Equations Resolution By N-BEE Anti-Dissipative Scheme In 2D Model Of Low Pressure Glow Discharge

    SciTech Connect

    Kraloua, B.; Hennad, A.

    2008-09-23

    The aim of this paper is to determine electric and physical properties by 2D modelling of glow discharge low pressure in continuous regime maintained by term constant source. This electric discharge is confined in reactor plan-parallel geometry. This reactor is filled by Argon monatomic gas. Our continuum model the order two is composed the first three moments the Boltzmann's equations coupled with Poisson's equation by self consistent method. These transport equations are discretized by the finite volumes method. The equations system is resolved by a new technique, it is about the N-BEE explicit scheme using the time splitting method.

  8. Boltzmann equation and Monte Carlo studies of electron transport in resistive plate chambers

    NASA Astrophysics Data System (ADS)

    Bošnjaković, D.; Petrović, Z. Lj; White, R. D.; Dujko, S.

    2014-10-01

    A multi term theory for solving the Boltzmann equation and Monte Carlo simulation technique are used to investigate electron transport in Resistive Plate Chambers (RPCs) that are used for timing and triggering purposes in many high energy physics experiments at CERN and elsewhere. Using cross sections for electron scattering in C2H2F4, iso-C4H10 and SF6 as an input in our Boltzmann and Monte Carlo codes, we have calculated data for electron transport as a function of reduced electric field E/N in various C2H2F4/iso-C4H10/SF6 gas mixtures used in RPCs in the ALICE, CMS and ATLAS experiments. Emphasis is placed upon the explicit and implicit effects of non-conservative collisions (e.g. electron attachment and/or ionization) on the drift and diffusion. Among many interesting and atypical phenomena induced by the explicit effects of non-conservative collisions, we note the existence of negative differential conductivity (NDC) in the bulk drift velocity component with no indication of any NDC for the flux component in the ALICE timing RPC system. We systematically study the origin and mechanisms for such phenomena as well as the possible physical implications which arise from their explicit inclusion into models of RPCs. Spatially-resolved electron transport properties are calculated using a Monte Carlo simulation technique in order to understand these phenomena.

  9. Phase-space finite elements in a least-squares solution of the transport equation

    SciTech Connect

    Drumm, C.; Fan, W.; Pautz, S.

    2013-07-01

    The linear Boltzmann transport equation is solved using a least-squares finite element approximation in the space, angular and energy phase-space variables. The method is applied to both neutral particle transport and also to charged particle transport in the presence of an electric field, where the angular and energy derivative terms are handled with the energy/angular finite elements approximation, in a manner analogous to the way the spatial streaming term is handled. For multi-dimensional problems, a novel approach is used for the angular finite elements: mapping the surface of a unit sphere to a two-dimensional planar region and using a meshing tool to generate a mesh. In this manner, much of the spatial finite-elements machinery can be easily adapted to handle the angular variable. The energy variable and the angular variable for one-dimensional problems make use of edge/beam elements, also building upon the spatial finite elements capabilities. The methods described here can make use of either continuous or discontinuous finite elements in space, angle and/or energy, with the use of continuous finite elements resulting in a smaller problem size and the use of discontinuous finite elements resulting in more accurate solutions for certain types of problems. The work described in this paper makes use of continuous finite elements, so that the resulting linear system is symmetric positive definite and can be solved with a highly efficient parallel preconditioned conjugate gradients algorithm. The phase-space finite elements capability has been built into the Sceptre code and applied to several test problems, including a simple one-dimensional problem with an analytic solution available, a two-dimensional problem with an isolated source term, showing how the method essentially eliminates ray effects encountered with discrete ordinates, and a simple one-dimensional charged-particle transport problem in the presence of an electric field. (authors)

  10. Finite element approximation of the radiative transport equation in a medium with piece-wise constant refractive index

    SciTech Connect

    Lehtikangas, O.; Tarvainen, T.; Kim, A.D.; Arridge, S.R.

    2015-02-01

    The radiative transport equation can be used as a light transport model in a medium with scattering particles, such as biological tissues. In the radiative transport equation, the refractive index is assumed to be constant within the medium. However, in biomedical media, changes in the refractive index can occur between different tissue types. In this work, light propagation in a medium with piece-wise constant refractive index is considered. Light propagation in each sub-domain with a constant refractive index is modeled using the radiative transport equation and the equations are coupled using boundary conditions describing Fresnel reflection and refraction phenomena on the interfaces between the sub-domains. The resulting coupled system of radiative transport equations is numerically solved using a finite element method. The approach is tested with simulations. The results show that this coupled system describes light propagation accurately through comparison with the Monte Carlo method. It is also shown that neglecting the internal changes of the refractive index can lead to erroneous boundary measurements of scattered light.

  11. Optical cryptosystem based on phase-truncated Fresnel diffraction and transport of intensity equation.

    PubMed

    Zhang, Chenggong; He, Wenqi; Wu, Jiachen; Peng, Xiang

    2015-04-01

    A novel optical cryptosystem based on phase-truncated Fresnel diffraction (PTFD) and transport of intensity equation (TIE) is proposed. By using the phase truncation technique, a phase-encoded plaintext could be encrypted into a real-valued noise-like intensity distribution by employing a random amplitude mask (RAM) and a random phase mask (RPM), which are regarded as two secret keys. For decryption, a generalized amplitude-phase retrieval (GAPR) algorithm combined with the TIE method are proposed to recover the plaintext with the help of two keys. Different from the current phase-truncated-based optical cryptosystems which need record the truncated phase as decryption keys, our scheme do not need the truncated phase because of the introducing of the TIE method. Moreover, the proposed scheme is expected to against existing attacks. A set of numerical simulation results show the feasibility and security of the proposed method. PMID:25968722

  12. An asymptotic-preserving scheme for the semiconductor Boltzmann equation toward the energy-transport limit

    NASA Astrophysics Data System (ADS)

    Hu, Jingwei; Wang, Li

    2015-01-01

    We design an asymptotic-preserving scheme for the semiconductor Boltzmann equation which leads to an energy-transport system for electron mass and energy as mean free path goes to zero. As opposed to the classical drift-diffusion limit where the stiff collisions are all in one scale, new difficulties arise in the two-scale stiff collision terms because the simple BGK penalization [15] fails to drive the solution to the correct limit. We propose to set up a spatially dependent threshold on the penalization of the stiffer collision operator such that the evolution of the solution resembles a Hilbert expansion at the continuous level. Formal asymptotic analysis and numerical results confirm the efficiency and accuracy of our scheme.

  13. Silicon wafer microstructure imaging using InfraRed Transport of Intensity Equation

    NASA Astrophysics Data System (ADS)

    Li, Hongru; Feng, Guoying; Bourgade, Thomas; Zuo, Chao; Du, Yongzhao; Zhou, Shouhuan; Asundi, Anand

    2015-03-01

    A novel quantitative 3D imaging system of silicon microstructures using InfraRed Transport of Intensity Equation (IRTIE) is proposed in this paper. By recording the intensity at multiple planes and using FFT or DCT based TIE solver, fast and accurate phase retrieval for both uniform and non-uniform intensity distributions is proposed. Numerical simulation and experiments confirm the accuracy and reliability of the proposed method. The application of IR-TIE for inspection of micro-patterns in visibly opaque media using 1310 nm light source is demonstrated. For comparison, micro-patterns are also inspected by the contact scanning mode Taylor Hobson system. Quantitative agreement suggests the possibility of using IR-TIE for phase imaging of silicon wafers.

  14. A non-equilibrium equation-of-motion approach to quantum transport utilizing projection operators

    NASA Astrophysics Data System (ADS)

    Ochoa, Maicol A.; Galperin, Michael; Ratner, Mark A.

    2014-11-01

    We consider a projection operator approach to the non-equilbrium Green function equation-of-motion (PO-NEGF EOM) method. The technique resolves problems of arbitrariness in truncation of an infinite chain of EOMs and prevents violation of symmetry relations resulting from the truncation (equivalence of left- and right-sided EOMs is shown and symmetry with respect to interchange of Fermi or Bose operators before truncation is preserved). The approach, originally developed by Tserkovnikov (1999 Theor. Math. Phys. 118 85) for equilibrium systems, is reformulated to be applicable to time-dependent non-equilibrium situations. We derive a canonical form of EOMs, thus explicitly demonstrating a proper result for the non-equilibrium atomic limit in junction problems. A simple practical scheme applicable to quantum transport simulations is formulated. We perform numerical simulations within simple models and compare results of the approach to other techniques and (where available) also to exact results.

  15. An asymptotic-preserving scheme for the semiconductor Boltzmann equation toward the energy-transport limit

    SciTech Connect

    Hu, Jingwei; Wang, Li

    2015-01-15

    We design an asymptotic-preserving scheme for the semiconductor Boltzmann equation which leads to an energy-transport system for electron mass and energy as mean free path goes to zero. As opposed to the classical drift-diffusion limit where the stiff collisions are all in one scale, new difficulties arise in the two-scale stiff collision terms because the simple BGK penalization [15] fails to drive the solution to the correct limit. We propose to set up a spatially dependent threshold on the penalization of the stiffer collision operator such that the evolution of the solution resembles a Hilbert expansion at the continuous level. Formal asymptotic analysis and numerical results confirm the efficiency and accuracy of our scheme.

  16. Iterative feedback algorithm for phase retrieval based on transport of intensity equation

    NASA Astrophysics Data System (ADS)

    Liu, Kaifeng; Cheng, Hong; Zhang, Cheng; Shen, Chuan; Zhang, Fen; Wei, Sui

    2015-12-01

    In this paper, a novel phase retrieval algorithm is presented which combines the advantages of the Transport of Intensity Equation (TIE) method and the iteration method. TIE method is fast, but its precision is not high. Though the convergence rate of iteration method is slow, its result is more accurate. This algorithm consists of Iterative Angular Spectrum (IAS) method to utilize the physical constraints between the object and the spectral domain, and the relationship between the intensity and phase among the wave propagation. Firstly, the phase at the object plane is calculated from two intensity images by TIE. Then this result is treated as the initial phase of the IAS. Finally, the phase information at the object plane is acquired according the reversibility of the optical path. During the iteration process, the feedback mechanism is imposed on it that improve the convergence rate and the precision of phase retrieval and the simulation results are given.

  17. Parallel Simulation of Ion Implantation for Multi-Component Targets Using Boltzmann Transport Equation

    NASA Astrophysics Data System (ADS)

    Wang, Shyh-Wei; Guo, Shuang-Fa

    1998-07-01

    A stepwise Boltzmann transport equation (BTE) simulation using non-uniform energy grid momentum matrix and exact nuclear scattering cross-section is successfully parallelized to simulate the ion implantation of multi-component targets. Assuming that the interactions of ion with different target atoms are independent, the scattering of ions with different components can be calculated concurrently by different processors. It is developed on CONVEX SPP-1000 and the software environment of parallel virtual machine (PVM) with a master-slave paradigm. A speedup of 3.3 has been obtained for the simulation of As ions implanted into AZ1350 (C6.2H6O1N0.15S0.06) which is composed of five components. In addition, our new scheme gives better agreement with the experimental results for heavy ion implantation than the conventional method using a uniform energy grid and approximated scattering function.

  18. A discrete ordinates approximation to the neutron transport equation applied to generalized geometries

    SciTech Connect

    DeHart, M.D.

    1992-12-01

    A method for applying the discrete ordinates method for solution of the neutron transport equation in arbitary two-dimensional meshes has been developed. The finite difference approach normally used to approximate spatial derivatives in extrapolating angular fluxes across a cell is replaced by direct solution of the characteristic form of the transport equation for each discrete direction. Thus, computational cells are not restricted to the traditional shape of a mesh element within a given coordinate system. However, in terms of the treatment of energy and angular dependencies, this method resembles traditional discrete ordinates techniques. Using the method developed here, a general two-dimensional space can be approximated by an irregular mesh comprised of arbitrary polygons. The present work makes no assumptions about the orientations or the number of sides in a given cell, and computes all geometric relationships between each set of sides in each cell for each discrete direction. A set of non-reentrant polygons can therefore be used to represent any given two dimensional space. Results for a number of test problems have been compared to solutions obtained from traditional methods, with good agreement. Comparisons include benchmarks against analytical results for problems with simple geometry, as well numerical results obtained from traditional discrete ordinates methods by applying the ANISN and TWOTRAN computer programs. Numerical results were obtained for problems ranging from simple one-dimensional geometry to complicated multidimensional configurations. These results have demonstrated the ability of the developed method to closely approximate complex geometrical configurations and to obtain accurate results for problems that are extremely difficult to model using traditional methods.

  19. Master equation approach to charge injection and transport in organic insulators

    NASA Astrophysics Data System (ADS)

    Freire, José A.; Voss, Grasiela

    2005-03-01

    We develop a master equation model of a disordered organic insulator sandwiched between metallic electrodes by treating as rate processes both the injection and the internal transport. We show how the master equation model allows for the inclusion of crucial correlation effects in the charge transport, particularly of the Pauli exclusion principle and of space-charge effects, besides, being dependent on just the microscopic form of the transfer rate between the localized electronic states, it allows for the investigation of different microscopic scenarios in the organic, such as polaronic hopping, correlated energy levels, interaction with image charge, etc. The model allows for a separate analysis of the injection and the recombination currents. We find that the disorder, besides increasing the injection current, eliminates the possibility of observation of a Fowler-Nordheim injection current at zero temperature, and that it does not alter the Schottky barrier size of the zero-field thermionic injection current from the value based on the energy difference between the electrode Fermi level and the highest occupied molecular orbital/lowest unoccupied molecular orbital levels in the organic, but it makes the Arrhenius temperature dependence appear at larger temperatures. We investigate how the I(V ) characteristics of a device is affected by the presence of correlations in the site energy distribution and by the form of the internal hopping rate, specifically the Miller-Abrahams rate and the Marcus or small-polaron rate. We show that the disorder does not modify significantly the eβ√E field dependence of the net current due to the Schottky barrier lowering caused by the attraction between the charge and its image in the electrode.

  20. High Order Finite Volume Nonlinear Schemes for the Boltzmann Transport Equation

    SciTech Connect

    Bihari, B L; Brown, P N

    2005-03-29

    The authors apply the nonlinear WENO (Weighted Essentially Nonoscillatory) scheme to the spatial discretization of the Boltzmann Transport Equation modeling linear particle transport. The method is a finite volume scheme which ensures not only conservation, but also provides for a more natural handling of boundary conditions, material properties and source terms, as well as an easier parallel implementation and post processing. It is nonlinear in the sense that the stencil depends on the solution at each time step or iteration level. By biasing the gradient calculation towards the stencil with smaller derivatives, the scheme eliminates the Gibb's phenomenon with oscillations of size O(1) and reduces them to O(h{sup r}), where h is the mesh size and r is the order of accuracy. The current implementation is three-dimensional, generalized for unequally spaced meshes, fully parallelized, and up to fifth order accurate (WENO5) in space. For unsteady problems, the resulting nonlinear spatial discretization yields a set of ODE's in time, which in turn is solved via high order implicit time-stepping with error control. For the steady-state case, they need to solve the non-linear system, typically by Newton-Krylov iterations. There are several numerical examples presented to demonstrate the accuracy, non-oscillatory nature and efficiency of these high order methods, in comparison with other fixed-stencil schemes.

  1. First-principles calculation method for electron transport based on the grid Lippmann-Schwinger equation

    NASA Astrophysics Data System (ADS)

    Egami, Yoshiyuki; Iwase, Shigeru; Tsukamoto, Shigeru; Ono, Tomoya; Hirose, Kikuji

    2015-09-01

    We develop a first-principles electron-transport simulator based on the Lippmann-Schwinger (LS) equation within the framework of the real-space finite-difference scheme. In our fully real-space-based LS (grid LS) method, the ratio expression technique for the scattering wave functions and the Green's function elements of the reference system is employed to avoid numerical collapse. Furthermore, we present analytical expressions and/or prominent calculation procedures for the retarded Green's function, which are utilized in the grid LS approach. In order to demonstrate the performance of the grid LS method, we simulate the electron-transport properties of the semiconductor-oxide interfaces sandwiched between semi-infinite jellium electrodes. The results confirm that the leakage current through the (001 )Si -SiO2 model becomes much larger when the dangling-bond state is induced by a defect in the oxygen layer, while that through the (001 )Ge -GeO2 model is insensitive to the dangling bond state.

  2. In-focus quantitative intensity and phase imaging with the numerical focusing transport of intensity equation method

    NASA Astrophysics Data System (ADS)

    Tian, Xiaolin; Meng, Xin; Yu, Wei; Song, Xiaojun; Xue, Liang; Liu, Cheng; Wang, Shouyu

    2016-10-01

    Microscopy combined with the transport of intensity equation is capable of retrieving both intensity and phase distributions of samples from both in-focus and defocus intensities. However, during measurements, the focal plane is often decided artificially and the improper choice may induce errors in quantitative intensity and phase retrieval. In order to obtain accurate in-focus information, quantitative intensity and phase imaging with the numerical focusing transport of intensity equation method combined with cellular duty ratio criterion and numerical wavefront propagation is introduced in this paper. Both numerical simulations and experimental measurements are provided proving this designed method can increase both retrieved in-focus intensity and phase accuracy and reduce dependence of focal plane determination in transport of intensity equation measurements. It is believed that the proposed method can be potentially applied in various fields as in-focus compensation for quantitative phase imaging and automatic focal plane determination, etc.

  3. TH-E-BRE-02: A Forward Scattering Approximation to Dose Calculation Using the Linear Boltzmann Transport Equation

    SciTech Connect

    Catt, B; Snyder, M

    2014-06-15

    Purpose: To investigate the use of the linear Boltzmann transport equation as a dose calculation tool which can account for interface effects, while still having faster computation times than Monte Carlo methods. In particular, we introduce a forward scattering approximation, in hopes of improving calculation time without a significant hindrance to accuracy. Methods: Two coupled Boltzmann transport equations were constructed, one representing the fluence of photons within the medium, and the other, the fluence of electrons. We neglect the scattering term within the electron transport equation, resulting in an extreme forward scattering approximation to reduce computational complexity. These equations were then solved using a numerical technique for solving partial differential equations, known as a finite difference scheme, where the fluence at each discrete point in space is calculated based on the fluence at the previous point in the particle's path. Using this scheme, it is possible to develop a solution to the Boltzmann transport equations by beginning with boundary conditions and iterating across the entire medium. The fluence of electrons can then be used to find the dose at any point within the medium. Results: Comparisons with Monte Carlo simulations indicate that even simplistic techniques for solving the linear Boltzmann transport equation yield expected interface effects, which many popular dose calculation algorithms are not capable of predicting. Implementation of a forward scattering approximation does not appear to drastically reduce the accuracy of this algorithm. Conclusion: Optimized implementations of this algorithm have been shown to be very accurate when compared with Monte Carlo simulations, even in build up regions where many models fail. Use of a forward scattering approximation could potentially give a reasonably accurate dose distribution in a shorter amount of time for situations where a completely accurate dose distribution is not

  4. A Novel Algorithm for Solving the Multidimensional Neutron Transport Equation on Massively Parallel Architectures

    SciTech Connect

    Azmy, Yousry

    2014-06-10

    We employ the Integral Transport Matrix Method (ITMM) as the kernel of new parallel solution methods for the discrete ordinates approximation of the within-group neutron transport equation. The ITMM abandons the repetitive mesh sweeps of the traditional source iterations (SI) scheme in favor of constructing stored operators that account for the direct coupling factors among all the cells' fluxes and between the cells' and boundary surfaces' fluxes. The main goals of this work are to develop the algorithms that construct these operators and employ them in the solution process, determine the most suitable way to parallelize the entire procedure, and evaluate the behavior and parallel performance of the developed methods with increasing number of processes, P. The fastest observed parallel solution method, Parallel Gauss-Seidel (PGS), was used in a weak scaling comparison with the PARTISN transport code, which uses the source iteration (SI) scheme parallelized with the Koch-baker-Alcouffe (KBA) method. Compared to the state-of-the-art SI-KBA with diffusion synthetic acceleration (DSA), this new method- even without acceleration/preconditioning-is completitive for optically thick problems as P is increased to the tens of thousands range. For the most optically thick cells tested, PGS reduced execution time by an approximate factor of three for problems with more than 130 million computational cells on P = 32,768. Moreover, the SI-DSA execution times's trend rises generally more steeply with increasing P than the PGS trend. Furthermore, the PGS method outperforms SI for the periodic heterogeneous layers (PHL) configuration problems. The PGS method outperforms SI and SI-DSA on as few as P = 16 for PHL problems and reduces execution time by a factor of ten or more for all problems considered with more than 2 million computational cells on P = 4.096.

  5. On the forward-backward-in-time approach for Monte Carlo solution of Parker's transport equation: One-dimensional case

    NASA Astrophysics Data System (ADS)

    Bobik, P.; Boschini, M. J.; Della Torre, S.; Gervasi, M.; Grandi, D.; La Vacca, G.; Pensotti, S.; Putis, M.; Rancoita, P. G.; Rozza, D.; Tacconi, M.; Zannoni, M.

    2016-05-01

    The cosmic rays propagation inside the heliosphere is well described by a transport equation introduced by Parker in 1965. To solve this equation, several approaches were followed in the past. Recently, a Monte Carlo approach became widely used in force of its advantages with respect to other numerical methods. In this approach the transport equation is associated to a fully equivalent set of stochastic differential equations (SDE). This set is used to describe the stochastic path of quasi-particle from a source, e.g., the interstellar space, to a specific target, e.g., a detector at Earth. We present a comparison of forward-in-time and backward-in-time methods to solve the cosmic rays transport equation in the heliosphere. The Parker equation and the related set of SDE in the several formulations are treated in this paper. For the sake of clarity, this work is focused on the one-dimensional solutions. Results were compared with an alternative numerical solution, namely, Crank-Nicolson method, specifically developed for the case under study. The methods presented are fully consistent each others for energy greater than 400 MeV. The comparison between stochastic integrations and Crank-Nicolson allows us to estimate the systematic uncertainties of Monte Carlo methods. The forward-in-time stochastic integrations method showed a systematic uncertainty <5%, while backward-in-time stochastic integrations method showed a systematic uncertainty <1% in the studied energy range.

  6. Real time quantitative phase microscopy based on single-shot transport of intensity equation (ssTIE) method

    NASA Astrophysics Data System (ADS)

    Yu, Wei; Tian, Xiaolin; He, Xiaoliang; Song, Xiaojun; Xue, Liang; Liu, Cheng; Wang, Shouyu

    2016-08-01

    Microscopy based on transport of intensity equation provides quantitative phase distributions which opens another perspective for cellular observations. However, it requires multi-focal image capturing while mechanical and electrical scanning limits its real time capacity in sample detections. Here, in order to break through this restriction, real time quantitative phase microscopy based on single-shot transport of the intensity equation method is proposed. A programmed phase mask is designed to realize simultaneous multi-focal image recording without any scanning; thus, phase distributions can be quantitatively retrieved in real time. It is believed the proposed method can be potentially applied in various biological and medical applications, especially for live cell imaging.

  7. A fast, parallel algorithm to solve the basic fluvial erosion/transport equations

    NASA Astrophysics Data System (ADS)

    Braun, J.

    2012-04-01

    Quantitative models of landform evolution are commonly based on the solution of a set of equations representing the processes of fluvial erosion, transport and deposition, which leads to predict the geometry of a river channel network and its evolution through time. The river network is often regarded as the backbone of any surface processes model (SPM) that might include other physical processes acting at a range of spatial and temporal scales along hill slopes. The basic laws of fluvial erosion requires the computation of local (slope) and non-local (drainage area) quantities at every point of a given landscape, a computationally expensive operation which limits the resolution of most SPMs. I present here an algorithm to compute the various components required in the parameterization of fluvial erosion (and transport) and thus solve the basic fluvial geomorphic equation, that is very efficient because it is O(n) (the number of required arithmetic operations is linearly proportional to the number of nodes defining the landscape), and is fully parallelizable (the computation cost decreases in a direct inverse proportion to the number of processors used to solve the problem). The algorithm is ideally suited for use on latest multi-core processors. Using this new technique, geomorphic problems can be solved at an unprecedented resolution (typically of the order of 10,000 X 10,000 nodes) while keeping the computational cost reasonable (order 1 sec per time step). Furthermore, I will show that the algorithm is applicable to any regular or irregular representation of the landform, and is such that the temporal evolution of the landform can be discretized by a fully implicit time-marching algorithm, making it unconditionally stable. I will demonstrate that such an efficient algorithm is ideally suited to produce a fully predictive SPM that links observationally based parameterizations of small-scale processes to the evolution of large-scale features of the landscapes on

  8. A fully coupled Monte Carlo/discrete ordinates solution to the neutron transport equation. Final report

    SciTech Connect

    Filippone, W.L.; Baker, R.S.

    1990-12-31

    The neutron transport equation is solved by a hybrid method that iteratively couples regions where deterministic (S{sub N}) and stochastic (Monte Carlo) methods are applied. Unlike previous hybrid methods, the Monte Carlo and S{sub N} regions are fully coupled in the sense that no assumption is made about geometrical separation or decoupling. The hybrid method provides a new means of solving problems involving both optically thick and optically thin regions that neither Monte Carlo nor S{sub N} is well suited for by themselves. The fully coupled Monte Carlo/S{sub N} technique consists of defining spatial and/or energy regions of a problem in which either a Monte Carlo calculation or an S{sub N} calculation is to be performed. The Monte Carlo region may comprise the entire spatial region for selected energy groups, or may consist of a rectangular area that is either completely or partially embedded in an arbitrary S{sub N} region. The Monte Carlo and S{sub N} regions are then connected through the common angular boundary fluxes, which are determined iteratively using the response matrix technique, and volumetric sources. The hybrid method has been implemented in the S{sub N} code TWODANT by adding special-purpose Monte Carlo subroutines to calculate the response matrices and volumetric sources, and linkage subrountines to carry out the interface flux iterations. The common angular boundary fluxes are included in the S{sub N} code as interior boundary sources, leaving the logic for the solution of the transport flux unchanged, while, with minor modifications, the diffusion synthetic accelerator remains effective in accelerating S{sub N} calculations. The special-purpose Monte Carlo routines used are essentially analog, with few variance reduction techniques employed. However, the routines have been successfully vectorized, with approximately a factor of five increase in speed over the non-vectorized version.

  9. The piecewise linear discontinuous finite element method applied to the RZ and XYZ transport equations

    NASA Astrophysics Data System (ADS)

    Bailey, Teresa S.

    In this dissertation we discuss the development, implementation, analysis and testing of the Piecewise Linear Discontinuous Finite Element Method (PWLD) applied to the particle transport equation in two-dimensional cylindrical (RZ) and three-dimensional Cartesian (XYZ) geometries. We have designed this method to be applicable to radiative-transfer problems in radiation-hydrodynamics systems for arbitrary polygonal and polyhedral meshes. For RZ geometry, we have implemented this method in the Capsaicin radiative-transfer code being developed at Los Alamos National Laboratory. In XYZ geometry, we have implemented the method in the Parallel Deterministic Transport code being developed at Texas A&M University. We discuss the importance of the thick diffusion limit for radiative-transfer problems, and perform a thick diffusion-limit analysis on our discretized system for both geometries. This analysis predicts that the PWLD method will perform well in this limit for many problems of physical interest with arbitrary polygonal and polyhedral cells. Finally, we run a series of test problems to determine some useful properties of the method and verify the results of our thick diffusion limit analysis. Finally, we test our method on a variety of test problems and show that it compares favorably to existing methods. With these test problems, we also show that our method performs well in the thick diffusion limit as predicted by our analysis. Based on PWLD's solid finite-element foundation, the desirable properties it shows under analysis, and the excellent performance it demonstrates on test problems even with highly distorted spatial grids, we conclude that it is an excellent candidate for radiative-transfer problems that need a robust method that performs well in thick diffusive problems or on distorted grids.

  10. The advective-dispersive equation with spatial fractional derivatives as a model for tracer transport in structured soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The classical model to describe solute transport in soil is based on the advective-dispersive equation where Fick’s law is used to explain dispersion. From the microscopic point of view this is equivalent to consider that the motion of the particles of solute may be simulated by the Brownian motion....

  11. Developing Sediment Transport and Dredging Prediction Model of Ohio River at Olmsted Locks and Dams Area using HEC-RAS (1D/2D)By Ganesh Raj Ghimire1 and Bruce A. Devantier 2

    NASA Astrophysics Data System (ADS)

    Ghimire, G. R.

    2015-12-01

    Sediment deposition is a serious issue in the construction and operation of large reservoir and inland navigation projects in the United States and around the world. Olmsted Locks and Dams in the Ohio River navigation system is facing similar challenges of huge sediment deposition during the ongoing in-wet construction methodology since 1993. HEC-RAS 5.0 integrated with ArcGIS, will be used to yield unsteady 2D hydrodynamic model of Ohio River at Olmsted area. Velocity, suspended sediment, bed sediment and hydrographic survey data acquired from public archives of USGS and USACE Louisville District will be input into the model. Calibration and validation of model will be performed against the measured stage, flow and velocity data. It will be subjected to completely unsteady 1D sediment transport modeling new to HEC-RAS 5.0 which incorporates sediment load and bed gradation via a DSS file, commercial dredging and BSTEM model. Sediment model will be calibrated to replicate the historical bed volume changes. Excavated cross-sections at Olmsted area will also be used to predict the sediment volume trapped inside the ditch over the period between excavations and placement of dam shells at site. Model will attempt to replicate historical dredging volume data and compare with the deposition volume from simulation model to formulate the dredging prediction model. Hence, the results of this research will generate a model that can form a basis for scheduling the dredging event prior to the placement of off-shore cast shells replacing the current as and when required approach of dredging plan. 1 Graduate Student, Department of Civil Engineering, Southern Illinois University Carbondale Carbondale, Illinois, 62901-6603 2 Professor, Department of Civil Engineering, Southern Illinois University Carbondale Carbondale, Illinois, 62901-6603

  12. A space–angle DGFEM approach for the Boltzmann radiation transport equation with local angular refinement

    SciTech Connect

    Kópházi, József Lathouwers, Danny

    2015-09-15

    In this paper a new method for the discretization of the radiation transport equation is presented, based on a discontinuous Galerkin method in space and angle that allows for local refinement in angle where any spatial element can support its own angular discretization. To cope with the discontinuous spatial nature of the solution, a generalized Riemann procedure is required to distinguish between incoming and outgoing contributions of the numerical fluxes. A new consistent framework is introduced that is based on the solution of a generalized eigenvalue problem. The resulting numerical fluxes for the various possible cases where neighboring elements have an equal, higher or lower level of refinement in angle are derived based on tensor algebra and the resulting expressions have a very clear physical interpretation. The choice of discontinuous trial functions not only has the advantage of easing local refinement, it also facilitates the use of efficient sweep-based solvers due to decoupling of unknowns on a large scale thereby approaching the efficiency of discrete ordinates methods with local angular resolution. The approach is illustrated by a series of numerical experiments. Results show high orders of convergence for the scalar flux on angular refinement. The generalized Riemann upwinding procedure leads to stable and consistent solutions. Further the sweep-based solver performs well when used as a preconditioner for a Krylov method.

  13. Phase retrieval in arbitrarily shaped aperture with the transport-of-intensity equation

    NASA Astrophysics Data System (ADS)

    Huang, Lei; Zuo, Chao; Idir, Mourad; Qu, Weijuan; Asundi, Anand

    2015-03-01

    Phase is not easy to detect directly as intensity, but sometimes it contains the really desired information. The transport-of-intensity equation (TIE) is a powerful tool to retrieve the phase from the intensity. However, by considering the boundary energy exchange and the whole energy conversation in the field of view, the current popular Fast Fourier transform (FFT) based TIE solver can only retrieve the phase under homogeneous Neumann boundary condition. For many applications, the boundary condition could be more complex and general. A novel TIE phase retrieval method is proposed to deal with an optical field under a general boundary condition. In this method, an arbitrarily-shape hard aperture is added in the optical field. In our method, the TIE is solved by using iterative discrete cosine transforms (DCT) method, which contains a phase compensation mechanism to improve the retrieval results. The proposed method is verified in simulation with an arbitrary phase, an arbitrarily-shaped aperture, and non-uniform intensity distribution. Experiment is also carried out to check its feasibility and the method proposed in this work is very easy and straightforward to use in a practical measurement as a flexible phase retrieval tool.

  14. A Transport Equation Approach to Modeling the Influence of Surface Roughness on Boundary Layer Transition

    NASA Astrophysics Data System (ADS)

    Langel, Christopher Michael

    A computational investigation has been performed to better understand the impact of surface roughness on the flow over a contaminated surface. This thesis highlights the implementation and development of the roughness amplification model in the flow solver OVERFLOW-2. The model, originally proposed by Dassler, Kozulovic, and Fiala, introduces an additional scalar field roughness amplification quantity. This value is explicitly set at rough wall boundaries using surface roughness parameters and local flow quantities. This additional transport equation allows non-local effects of surface roughness to be accounted for downstream of rough sections. This roughness amplification variable is coupled with the Langtry-Menter model and used to modify the criteria for transition. Results from flat plate test cases show good agreement with experimental transition behavior on the flow over varying sand grain roughness heights. Additional validation studies were performed on a NACA 0012 airfoil with leading edge roughness. The computationally predicted boundary layer development demonstrates good agreement with experimental results. New tests using varying roughness configurations are being carried out at the Texas A&M Oran W. Nicks Low Speed Wind Tunnel to provide further calibration of the roughness amplification method. An overview and preliminary results are provided of this concurrent experimental investigation.

  15. Universal limiter for transient interpolation modeling of the advective transport equations: The ULTIMATE conservative difference scheme

    NASA Technical Reports Server (NTRS)

    Leonard, B. P.

    1988-01-01

    A fresh approach is taken to the embarrassingly difficult problem of adequately modeling simple pure advection. An explicit conservative control-volume formation makes use of a universal limiter for transient interpolation modeling of the advective transport equations. This ULTIMATE conservative difference scheme is applied to unsteady, one-dimensional scalar pure advection at constant velocity, using three critical test profiles: an isolated sine-squared wave, a discontinuous step, and a semi-ellipse. The goal, of course, is to devise a single robust scheme which achieves sharp monotonic resolution of the step without corrupting the other profiles. The semi-ellipse is particularly challenging because of its combination of sudden and gradual changes in gradient. The ULTIMATE strategy can be applied to explicit conservation schemes of any order of accuracy. Second-order schemes are unsatisfactory, showing steepening and clipping typical of currently popular so-called high resolution shock-capturing of TVD schemes. The ULTIMATE third-order upwind scheme is highly satisfactory for most flows of practical importance. Higher order methods give predictably better step resolution, although even-order schemes generate a (monotonic) waviness in the difficult semi-ellipse simulation. Little is to be gained above ULTIMATE fifth-order upwinding which gives results close to the ultimate for which one might hope.

  16. Multi-filter transport of intensity equation solver with equalized noise sensitivity.

    PubMed

    Martinez-Carranza, J; Falaggis, K; Kozacki, T

    2015-09-01

    Phase retrieval based on the Transport of Intensity Equation (TIE) has shown to be a powerful tool to obtain the phase of complex fields. Recently, it has been proven that the performance of TIE techniques can be improved when using unequally spaced measurement planes. In this paper, an algorithm is presented that recovers accurately the phase of a complex objects from a set of intensity measurements obtained at unequal plane separations. This technique employs multiple band-pass filters in the frequency domain of the axial derivative and uses these specific frequency bands for the calculation of the final phase. This provides highest accuracy for TIE based phase recovery giving minimal phase error for a given set of measurement planes. Moreover, because each of these band-pass filters has a distinct sensitivity to noise, a new plane selection strategy is derived that equalizes the error contribution of all frequency bands. It is shown that this new separation strategy allows controlling the final error of the retrieved phase without using a priori information of the object. This is an advantage compared to previous optimum phase retrieval techniques. In order to show the stability and robustness of this new technique, we present the numerical simulations.

  17. Optimal monotonization of a high-order accurate bicompact scheme for the nonstationary multidimensional transport equation

    NASA Astrophysics Data System (ADS)

    Aristova, E. N.; Rogov, B. V.; Chikitkin, A. V.

    2016-06-01

    A hybrid scheme is proposed for solving the nonstationary inhomogeneous transport equation. The hybridization procedure is based on two baseline schemes: (1) a bicompact one that is fourth-order accurate in all space variables and third-order accurate in time and (2) a monotone first-order accurate scheme from the family of short characteristic methods with interpolation over illuminated faces. It is shown that the first-order accurate scheme has minimal dissipation, so it is called optimal. The solution of the hybrid scheme depends locally on the solutions of the baseline schemes at each node of the space-time grid. A monotonization procedure is constructed continuously and uniformly in all mesh cells so as to keep fourth-order accuracy in space and third-order accuracy in time in domains where the solution is smooth, while maintaining a high level of accuracy in domains of discontinuous solution. Due to its logical simplicity and uniformity, the algorithm is well suited for supercomputer simulation.

  18. On the prediction of horizontal bubbly flows using the interfacial area transport equation

    SciTech Connect

    Talley, J. D.; Kim, S.

    2012-07-01

    To solve the two-fluid model utilized in current nuclear reactor system analysis codes, the interfacial area concentration (a i) is estimated through flow regime dependent correlations that rely on static regime transition criteria. This approach does not capture the continuous evolution of the interfacial structures, and thus, it can pose numerical issues near the transition boundaries. The interfacial area transport equation (IATE) can help address these shortcomings by providing a dynamic prediction of a a{sub i} through mechanistic source and sink terms that account for bubble coalescence and breakup. Most of the previous work for this approach has focused on vertical two-phase flow. However, relatively few studies have been performed for horizontal two-phase flows, where buoyancy strongly affects the phase distribution. To develop a one-dimensional, area-averaged form of the IATE for adiabatic, horizontal bubbly flows the following considerations are necessary: (1) pressure drop estimation, (2) bubble velocity/void fraction estimation, (3) determination of bubble interaction mechanisms, and (4) treatment of the asymmetric phase distribution. In the current work, treatment of the asymmetric phase distribution is presented. (authors)

  19. An inexact Newton method for fully-coupled solution of the Navier-Stokes equations with heat and mass transport

    SciTech Connect

    Shadid, J.N.; Tuminaro, R.S.; Walker, H.F.

    1997-02-01

    The solution of the governing steady transport equations for momentum, heat and mass transfer in flowing fluids can be very difficult. These difficulties arise from the nonlinear, coupled, nonsymmetric nature of the system of algebraic equations that results from spatial discretization of the PDEs. In this manuscript the authors focus on evaluating a proposed nonlinear solution method based on an inexact Newton method with backtracking. In this context they use a particular spatial discretization based on a pressure stabilized Petrov-Galerkin finite element formulation of the low Mach number Navier-Stokes equations with heat and mass transport. The discussion considers computational efficiency, robustness and some implementation issues related to the proposed nonlinear solution scheme. Computational results are presented for several challenging CFD benchmark problems as well as two large scale 3D flow simulations.

  20. Finite Element Solution of the Self-Adjoint Angular Flux Equation for Coupled Electron-Photon Transport

    SciTech Connect

    Liscum-Powell, Jennifer L.; Prinja, Anil B.; Morel, Jim E.; Lorence, Leonard J Jr.

    2002-11-15

    A novel approach is proposed for charged particle transport calculations using a recently developed second-order, self-adjoint angular flux (SAAF) form of the Boltzmann transport equation with continuous slowing-down. A finite element discretization that is linear continuous in space and linear discontinuous (LD) in energy is described and implemented in a one-dimensional, planar geometry, multigroup, discrete ordinates code for charged particle transport. The cross-section generating code CEPXS is used to generate the electron and photon transport cross sections employed in this code. The discrete ordinates SAAF transport equation is solved using source iteration in conjunction with an inner iteration acceleration scheme and an outer iteration acceleration scheme. Outer iterations are required with the LD energy discretization scheme because the two angular flux unknowns within each group are coupled, which gives rise to effective upscattering. The inner iteration convergence is accelerated using diffusion synthetic acceleration, and the outer iteration convergence is accelerated using a diamond difference approximation to the LD energy discretization. Computational results are given that demonstrate the effectiveness of our convergence acceleration schemes and the accuracy of our discretized SAAF equation.

  1. Solution of the within-group multidimensional discrete ordinates transport equations on massively parallel architectures

    NASA Astrophysics Data System (ADS)

    Zerr, Robert Joseph

    2011-12-01

    The integral transport matrix method (ITMM) has been used as the kernel of new parallel solution methods for the discrete ordinates approximation of the within-group neutron transport equation. The ITMM abandons the repetitive mesh sweeps of the traditional source iterations (SI) scheme in favor of constructing stored operators that account for the direct coupling factors among all the cells and between the cells and boundary surfaces. The main goals of this work were to develop the algorithms that construct these operators and employ them in the solution process, determine the most suitable way to parallelize the entire procedure, and evaluate the behavior and performance of the developed methods for increasing number of processes. This project compares the effectiveness of the ITMM with the SI scheme parallelized with the Koch-Baker-Alcouffe (KBA) method. The primary parallel solution method involves a decomposition of the domain into smaller spatial sub-domains, each with their own transport matrices, and coupled together via interface boundary angular fluxes. Each sub-domain has its own set of ITMM operators and represents an independent transport problem. Multiple iterative parallel solution methods have investigated, including parallel block Jacobi (PBJ), parallel red/black Gauss-Seidel (PGS), and parallel GMRES (PGMRES). The fastest observed parallel solution method, PGS, was used in a weak scaling comparison with the PARTISN code. Compared to the state-of-the-art SI-KBA with diffusion synthetic acceleration (DSA), this new method without acceleration/preconditioning is not competitive for any problem parameters considered. The best comparisons occur for problems that are difficult for SI DSA, namely highly scattering and optically thick. SI DSA execution time curves are generally steeper than the PGS ones. However, until further testing is performed it cannot be concluded that SI DSA does not outperform the ITMM with PGS even on several thousand or tens of

  2. Transport Equations for CAD Modeling of Al(x)Ga(1-x)N/GaN HEMTs

    NASA Technical Reports Server (NTRS)

    Freeman, Jon C.

    2003-01-01

    BEMTs formed from Al(x)Ga(1-x)N/GaN heterostructures are being investigated for high RF power and efficiency around the world by many groups, both academic and industrial. In these devices, the 2DEG formation is dominated by both spontaneous and piezoelectric polarization fields, with each component having nearly the same order of magnitude. The piezoelectric portion is induced by the mechanical strain in the structure, and to analyze these devices, one must incorporate the stress/strain relationships, along with the standard semiconductor transport equations. These equations for Wurtzite GaN are not easily found in the open literature, hence this paper summarizes them, along with the constitutive equations for piezoelectric materials. The equations are cast into the format for the Wurtzite crystal class, which is the most common way GaN is grown epitaxially.

  3. Evaluation of an analytic linear Boltzmann transport equation solver for high-density inhomogeneities

    SciTech Connect

    Lloyd, S. A. M.; Ansbacher, W.

    2013-01-15

    Purpose: Acuros external beam (Acuros XB) is a novel dose calculation algorithm implemented through the ECLIPSE treatment planning system. The algorithm finds a deterministic solution to the linear Boltzmann transport equation, the same equation commonly solved stochastically by Monte Carlo methods. This work is an evaluation of Acuros XB, by comparison with Monte Carlo, for dose calculation applications involving high-density materials. Existing non-Monte Carlo clinical dose calculation algorithms, such as the analytic anisotropic algorithm (AAA), do not accurately model dose perturbations due to increased electron scatter within high-density volumes. Methods: Acuros XB, AAA, and EGSnrc based Monte Carlo are used to calculate dose distributions from 18 MV and 6 MV photon beams delivered to a cubic water phantom containing a rectangular high density (4.0-8.0 g/cm{sup 3}) volume at its center. The algorithms are also used to recalculate a clinical prostate treatment plan involving a unilateral hip prosthesis, originally evaluated using AAA. These results are compared graphically and numerically using gamma-index analysis. Radio-chromic film measurements are presented to augment Monte Carlo and Acuros XB dose perturbation data. Results: Using a 2% and 1 mm gamma-analysis, between 91.3% and 96.8% of Acuros XB dose voxels containing greater than 50% the normalized dose were in agreement with Monte Carlo data for virtual phantoms involving 18 MV and 6 MV photons, stainless steel and titanium alloy implants and for on-axis and oblique field delivery. A similar gamma-analysis of AAA against Monte Carlo data showed between 80.8% and 87.3% agreement. Comparing Acuros XB and AAA evaluations of a clinical prostate patient plan involving a unilateral hip prosthesis, Acuros XB showed good overall agreement with Monte Carlo while AAA underestimated dose on the upstream medial surface of the prosthesis due to electron scatter from the high-density material. Film measurements

  4. A 1-D dusty plasma photonic crystal

    SciTech Connect

    Mitu, M. L.; Ticoş, C. M.; Toader, D.; Banu, N.; Scurtu, A.

    2013-09-21

    It is demonstrated numerically that a 1-D plasma crystal made of micron size cylindrical dust particles can, in principle, work as a photonic crystal for terahertz waves. The dust rods are parallel to each other and arranged in a linear string forming a periodic structure of dielectric-plasma regions. The dispersion equation is found by solving the waves equation with the boundary conditions at the dust-plasma interface and taking into account the dielectric permittivity of the dust material and plasma. The wavelength of the electromagnetic waves is in the range of a few hundred microns, close to the interparticle separation distance. The band gaps of the 1-D plasma crystal are numerically found for different types of dust materials, separation distances between the dust rods and rod diameters. The distance between levitated dust rods forming a string in rf plasma is shown experimentally to vary over a relatively wide range, from 650 μm to about 1350 μm, depending on the rf power fed into the discharge.

  5. Equation of state and transport property measurements of warm dense matter.

    SciTech Connect

    Knudson, Marcus D.; Desjarlais, Michael Paul

    2009-10-01

    Location of the liquid-vapor critical point (c.p.) is one of the key features of equation of state models used in simulating high energy density physics and pulsed power experiments. For example, material behavior in the location of the vapor dome is critical in determining how and when coronal plasmas form in expanding wires. Transport properties, such as conductivity and opacity, can vary an order of magnitude depending on whether the state of the material is inside or outside of the vapor dome. Due to the difficulty in experimentally producing states near the vapor dome, for all but a few materials, such as Cesium and Mercury, the uncertainty in the location of the c.p. is of order 100%. These states of interest can be produced on Z through high-velocity shock and release experiments. For example, it is estimated that release adiabats from {approx}1000 GPa in aluminum would skirt the vapor dome allowing estimates of the c.p. to be made. This is within the reach of Z experiments (flyer plate velocity of {approx}30 km/s). Recent high-fidelity EOS models and hydrocode simulations suggest that the dynamic two-phase flow behavior observed in initial scoping experiments can be reproduced, providing a link between theory and experiment. Experimental identification of the c.p. in aluminum would represent the first measurement of its kind in a dynamic experiment. Furthermore, once the c.p. has been experimentally determined it should be possible to probe the electrical conductivity, opacity, reflectivity, etc. of the material near the vapor dome, using a variety of diagnostics. We propose a combined experimental and theoretical investigation with the initial emphasis on aluminum.

  6. Application of the three-dimensional telegraph equation to cosmic-ray transport

    NASA Astrophysics Data System (ADS)

    Tautz, Robert C.; Lerche, Ian

    2016-10-01

    An analytical solution to the three-dimensional telegraph equation is presented. This equation has recently received some attention but so far the treatment has been one-dimensional. By using the structural similarity to the Klein-Gordon equation, the telegraph equation can be solved in closed form. Illustrative examples are used to discuss the qualitative differences from the diffusion solution. A comparison with a numerical test-particle simulation reveals that some features of an intensity profile can be better explained using the telegraph approach.

  7. Discontinuous isogeometric analysis methods for the first-order form of the neutron transport equation with discrete ordinate (SN) angular discretisation

    NASA Astrophysics Data System (ADS)

    Owens, A. R.; Welch, J. A.; Kópházi, J.; Eaton, M. D.

    2016-06-01

    In this paper two discontinuous Galerkin isogeometric analysis methods are developed and applied to the first-order form of the neutron transport equation with a discrete ordinate (SN) angular discretisation. The discontinuous Galerkin projection approach was taken on both an element level and the patch level for a given Non-Uniform Rational B-Spline (NURBS) patch. This paper describes the detailed dispersion analysis that has been used to analyse the numerical stability of both of these schemes. The convergence of the schemes for both smooth and non-smooth solutions was also investigated using the method of manufactured solutions (MMS) for multidimensional problems and a 1D semi-analytical benchmark whose solution contains a strongly discontinuous first derivative. This paper also investigates the challenges posed by strongly curved boundaries at both the NURBS element and patch level with several algorithms developed to deal with such cases. Finally numerical results are presented both for a simple pincell test problem as well as the C5G7 quarter core MOX/UOX small Light Water Reactor (LWR) benchmark problem. These numerical results produced by the isogeometric analysis (IGA) methods are compared and contrasted against linear and quadratic discontinuous Galerkin finite element (DGFEM) SN based methods.

  8. Charged-particle transport in gases in electric and magnetic fields crossed at arbitrary angles: Multiterm solution of Boltzmann's equation.

    PubMed

    White, R D; Ness, K F; Robson, R E; Li, B

    1999-08-01

    A multiterm solution of the Boltzmann equation has been developed and used to calculate transport coefficients of charged-particle swarms in gases under the influence of electric and magnetic fields crossed at arbitrary angles psi. The hierarchy resulting from a spherical harmonic decomposition of the Boltzmann equation in the hydrodynamic regime [Ness, Phys. Rev. A 47, 327 (1993)] is solved numerically by representing the speed dependence of the phase-space distribution function in terms of an expansion in Sonine polynomials about a weighted sum of Maxwellian distributions at different temperatures. Results are given for charged-particle swarms in certain model gases over a range of psi and field strengths. The variation of the transport coefficients with psi is addressed using physical arguments. The errors associated with the two-term approximation and inadequacies of Legendre polynomial expansions are highlighted.

  9. Quantitative TEM-based phase retrieval of MgO nano-cubes using the transport of intensity equation.

    PubMed

    Petersen, Tim C; Keast, Vicki J; Paganin, David M

    2008-08-01

    Through focus series of images are collected from MgO nano-cube crystals in the transmission electron microscope (TEM). The experimental data is used to solve the transport of intensity equation (TIE) to retrieve phase maps, which portray the morphology of the cubes and are quantified by the mean inner potential V(0). Particular attention is given to the practical difficulties associated with TIE phase retrieval of non-conducting polyhedron particles.

  10. Kershaw closures for linear transport equations in slab geometry II: High-order realizability-preserving discontinuous-Galerkin schemes

    NASA Astrophysics Data System (ADS)

    Schneider, Florian

    2016-10-01

    This paper provides a generalization of the realizability-preserving discontinuous-Galerkin scheme given in [3] to general full-moment models that can be closed analytically. It is applied to the class of Kershaw closures, which are able to provide a cheap closure of the moment problem. This results in an efficient algorithm for the underlying linear transport equation. The efficiency of high-order methods is demonstrated using numerical convergence tests and non-smooth benchmark problems.

  11. Determination of transport wind speed in the gaussian plume diffusion equation for low-lying point sources

    NASA Astrophysics Data System (ADS)

    Wang, I. T.

    A general method for determining the effective transport wind speed, overlineu, in the Gaussian plume equation is discussed. Physical arguments are given for using the generalized overlineu instead of the often adopted release-level wind speed with the plume diffusion equation. Simple analytical expressions for overlineu applicable to low-level point releases and a wide range of atmospheric conditions are developed. A non-linear plume kinematic equation is derived using these expressions. Crosswind-integrated SF 6 concentration data from the 1983 PNL tracer experiment are used to evaluate the proposed analytical procedures along with the usual approach of using the release-level wind speed. Results of the evaluation are briefly discussed.

  12. A Spatial Discretization Scheme for Solving the Transport Equation on Unstructured Grids of Polyhedra

    SciTech Connect

    Thompson, K.G.

    2000-11-01

    In this work, we develop a new spatial discretization scheme that may be used to numerically solve the neutron transport equation. This new discretization extends the family of corner balance spatial discretizations to include spatial grids of arbitrary polyhedra. This scheme enforces balance on subcell volumes called corners. It produces a lower triangular matrix for sweeping, is algebraically linear, is non-negative in a source-free absorber, and produces a robust and accurate solution in thick diffusive regions. Using an asymptotic analysis, we design the scheme so that in thick diffusive regions it will attain the same solution as an accurate polyhedral diffusion discretization. We then refine the approximations in the scheme to reduce numerical diffusion in vacuums, and we attempt to capture a second order truncation error. After we develop this Upstream Corner Balance Linear (UCBL) discretization we analyze its characteristics in several limits. We complete a full diffusion limit analysis showing that we capture the desired diffusion discretization in optically thick and highly scattering media. We review the upstream and linear properties of our discretization and then demonstrate that our scheme captures strictly non-negative solutions in source-free purely absorbing media. We then demonstrate the minimization of numerical diffusion of a beam and then demonstrate that the scheme is, in general, first order accurate. We also note that for slab-like problems our method actually behaves like a second-order method over a range of cell thicknesses that are of practical interest. We also discuss why our scheme is first order accurate for truly 3D problems and suggest changes in the algorithm that should make it a second-order accurate scheme. Finally, we demonstrate 3D UCBL's performance on several very different test problems. We show good performance in diffusive and streaming problems. We analyze truncation error in a 3D problem and demonstrate robustness in a

  13. A Reynolds-averaged turbulence modeling approach using three transport equations for the turbulent viscosity, kinetic energy, and dissipation rate

    NASA Astrophysics Data System (ADS)

    Yoshizawa, Akira; Abe, Hiroyuki; Matsuo, Yuichi; Fujiwara, Hitoshi; Mizobuchi, Yasuhiro

    2012-07-01

    A Reynolds-averaged approach to turbulent shear flows is sought with resort to a three-equation method. Its novelty is the introduction of a turbulent-viscosity transport equation through the transport equation for the Reynolds stress in addition to those for the turbulent kinetic energy and the dissipation rate. The latter two equations are used for evaluating the dimensional coefficients in the former. The aim of this model is to enhance the capability to cope with nonstationary and advection effects in various turbulent flows. The adaptability to them is confirmed through the application to homogeneous-shear and supersonic free-shear flows. In particular, the reasonable prediction is obtained in the latter where the growth rate of the shear layer is suppressed with the increase in the convective Mach number. The present model is also applied to a three-dimensional flow past a wing tip as an instance of complex aeronautical flows, and the excessive diffusion of the trailing vortices is shown to be suppressed. The turbulent-viscosity representation for the Reynolds stress is systematically supplemented with nonlinear effects of mean-velocity gradient tensors, and its adequacy is verified in a channel flow.

  14. Goal-based angular adaptivity applied to a wavelet-based discretisation of the neutral particle transport equation

    SciTech Connect

    Goffin, Mark A.; Buchan, Andrew G.; Dargaville, Steven; Pain, Christopher C.; Smith, Paul N.; Smedley-Stevenson, Richard P.

    2015-01-15

    A method for applying goal-based adaptive methods to the angular resolution of the neutral particle transport equation is presented. The methods are applied to an octahedral wavelet discretisation of the spherical angular domain which allows for anisotropic resolution. The angular resolution is adapted across both the spatial and energy dimensions. The spatial domain is discretised using an inner-element sub-grid scale finite element method. The goal-based adaptive methods optimise the angular discretisation to minimise the error in a specific functional of the solution. The goal-based error estimators require the solution of an adjoint system to determine the importance to the specified functional. The error estimators and the novel methods to calculate them are described. Several examples are presented to demonstrate the effectiveness of the methods. It is shown that the methods can significantly reduce the number of unknowns and computational time required to obtain a given error. The novelty of the work is the use of goal-based adaptive methods to obtain anisotropic resolution in the angular domain for solving the transport equation. -- Highlights: •Wavelet angular discretisation used to solve transport equation. •Adaptive method developed for the wavelet discretisation. •Anisotropic angular resolution demonstrated through the adaptive method. •Adaptive method provides improvements in computational efficiency.

  15. Thermoelectric coefficients of n -doped silicon from first principles via the solution of the Boltzmann transport equation

    NASA Astrophysics Data System (ADS)

    Fiorentini, Mattia; Bonini, Nicola

    2016-08-01

    We present a first-principles computational approach to calculate thermoelectric transport coefficients via the exact solution of the linearized Boltzmann transport equation, also including the effect of nonequilibrium phonon populations induced by a temperature gradient. We use density functional theory and density functional perturbation theory for an accurate description of the electronic and vibrational properties of a system, including electron-phonon interactions; carriers' scattering rates are computed using standard perturbation theory. We exploit Wannier interpolation (both for electronic bands and electron-phonon matrix elements) for an efficient sampling of the Brillouin zone, and the solution of the Boltzmann equation is achieved via a fast and stable conjugate gradient scheme. We discuss the application of this approach to n -doped silicon. In particular, we discuss a number of thermoelectric properties such as the thermal and electrical conductivities of electrons, the Lorenz number and the Seebeck coefficient, including the phonon drag effect, in a range of temperatures and carrier concentrations. This approach gives results in good agreement with experimental data and provides a detailed characterization of the nature and the relative importance of the individual scattering mechanisms. Moreover, the access to the exact solution of the Boltzmann equation for a realistic system provides a direct way to assess the accuracy of different flavors of relaxation time approximation, as well as of models that are popular in the thermoelectric community to estimate transport coefficients.

  16. Macroscopic transport equations in many-body systems from microscopic exclusion processes in disordered media: a review

    NASA Astrophysics Data System (ADS)

    Galanti, Marta; Fanelli, Duccio; Piazza, Francesco

    2016-08-01

    Describing particle transport at the macroscopic or mesoscopic level in non-ideal environments poses fundamental theoretical challenges in domains ranging from inter and intra-cellular transport in biology to diffusion in porous media. Yet, often the nature of the constraints coming from many-body interactions or reflecting a complex and confining environment are better understood and modeled at the microscopic level. In this paper we review the subtle link between microscopic exclusion processes and the mean-field equations that ensue from them in the continuum limit. We show that in an inhomogeneous medium, i.e. when jumps are controlled by site-dependent hopping rates, one can obtain three different nonlinear advection-diffusion equations in the continuum limit, suitable for describing transport in the presence of quenched disorder and external fields, depending on the particular rule embodying site inequivalence at the microscopic level. In a situation that might be termed point-like scenario, when particles are treated as point-like objects, the effect of crowding as imposed at the microscopic level manifests in the mean-field equations only if some degree of inhomogeneity is enforced into the model. Conversely, when interacting agents are assigned a finite size, under the more realistic extended crowding framework, exclusion constraints persist in the unbiased macroscopic representation.

  17. Investigating transport capacity equations in sediment yield modelling for the Cariri semi-arid region of Paraiba-PB/Brazil

    NASA Astrophysics Data System (ADS)

    De Figueiredo, E. E.; Souto, C. C. R. A.; Vieira, Z. C.

    2015-03-01

    In the semi arid Cariri region of the state of Paraiba, Brazil, runoff is of the Hortonian type generated by excess of rainfall over infiltration capacity, and soil erosion is governed by rainfall intensity and sediment size. However, the governing sediment transport mechanism is not well understood. Sediment transport generally depends on the load of sediment provided by soil erosion and on the transport capacity of the flow. The latter is mainly governed by mechanisms such as water shear stress, or stream power. Accordingly, the load of sediment transported by the flow may vary depending on the mechanism involved in the equation of estimation. Investigation of the sediment transport capacity of the flow via a distributed physically-based model is an important and necessary task, but quite rare in semi-arid climates, and particularly in the Cariri region of the state of Paraíba/Brazil. In this study, the equations of Yalin, Engelund & Hansen, Laursen, DuBoys and Bagnold have been coupled with the MOSEE distributed physically based model aiming at identifying the mechanisms leading to the best model simulations when compared with data observed at various basin scales and land uses in the study region. The results obtained with the investigated methods were quite similar and satisfactory suggesting the feasibility of the mechanisms involved, but the observed values were better represented with Bagnold's equation, which is physically grounded on the stream power, and we recommend it for simulations of similar climate, runoff generation mechanisms and sediment characteristics as in the study region.

  18. A one-equation turbulence transport model for high Reynolds number wall-bounded flows

    NASA Technical Reports Server (NTRS)

    Baldwin, Barrett S.; Barth, Timothy J.

    1990-01-01

    A one-equation turbulence model that avoids the need for an algebraic length scale is derived from a simplified form of the standard k-epsilon model equations. After calibration based on well established properties of the flow over a flat plate, predictions of several other flows are compared with experiment. The preliminary results presented indicate that the model has predictive and numerical properties of sufficient interest to merit further investigation and refinement. The one-equation model is also analyzed numerically and robust solution methods are presented.

  19. Quantum transport equation for systems with rough surfaces and its application to ultracold neutrons in a quantizing gravity field

    SciTech Connect

    Escobar, M.; Meyerovich, A. E.

    2014-12-15

    We discuss transport of particles along random rough surfaces in quantum size effect conditions. As an intriguing application, we analyze gravitationally quantized ultracold neutrons in rough waveguides in conjunction with GRANIT experiments (ILL, Grenoble). We present a theoretical description of these experiments in the biased diffusion approximation for neutron mirrors with both one- and two-dimensional (1D and 2D) roughness. All system parameters collapse into a single constant which determines the depletion times for the gravitational quantum states and the exit neutron count. This constant is determined by a complicated integral of the correlation function (CF) of surface roughness. The reliable identification of this CF is always hindered by the presence of long fluctuation-driven correlation tails in finite-size samples. We report numerical experiments relevant for the identification of roughness of a new GRANIT waveguide and make predictions for ongoing experiments. We also propose a radically new design for the rough waveguide.

  20. Influence of surface water/groundwater interactions on stream and wetland water quality: analytical solutions for coupled contaminant transport equations

    NASA Astrophysics Data System (ADS)

    Melek Kazezyilmaz-Alhan, Cevza

    2014-05-01

    Wetlands are located in transitional zones between uplands and downstream flooded systems and surface water/groundwater interactions are frequently observed especially in riparian wetlands where the water level fluctuates frequently during the rainy season. Moreover, surface water/groundwater interactions also influence the characteristics of contaminant transport in pools and riffles, and in meandering type of streams. Therefore, it is important to investigate and solve these processes accurately to improve the prediction of downstream water quality. Although there are many experimental and numerical studies available in the literature which discuss and model the surface water/ground water interactions in streams and wetlands, very few analytical solutions have been conducted. Analytical solutions are helpful tools for verification of numerical solutions and they provide fast and accurate results for practical problems. Furthermore, they provide an understanding to the influence of each parameter in hydrological and contaminant transport models for streams and wetlands. In order to contribute to the research in understanding the behavior of water quality in streams and wetlands, analytical solutions are developed for the coupled contaminant transport equations of several transient storage and wetland models. Among these models are the wetland model WETland Solute TrANsport Dynamics (WETSAND) developed by Kazezyilmaz-Alhan et al. (2007), the transient storage models developed by Bencala and Walters (1983), and Kazezyilmaz-Alhan and Medina (2006). WETSAND is a general comprehensive wetland model, which has both surface flow and solute transport components. In this wetland model, water quality components are solved by advection-dispersion-reaction equations which incorporate surface water/groundwater interactions by including the incoming/outgoing mass due to the groundwater recharge/discharge. The transient storage model developed by Bencala and Walters (1983

  1. Predictions of Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions Using an Intermittency Transport Equation

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Hultgren, Lennart S.; Ashpis, David E.

    2003-01-01

    A new transport equation for the intermittency factor was proposed to predict separated and transitional boundary layers under low-pressure turbine airfoil conditions. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, t , with the intermittency factor, y. Turbulent quantities are predicted by using Menter s two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model, which not only can reproduce the experimentally observed streamwise variation of the intermittency in the transition zone, but also can provide a realistic cross-stream variation of the intermittency profile. In this paper, the intermittency model is used to predict a recent separated and transitional boundary layer experiment under low pressure turbine airfoil conditions. The experiment provides detailed measurements of velocity, turbulent kinetic energy and intermittency profiles for a number of Reynolds numbers and freestream turbulent intensity conditions and is suitable for validation purposes. Detailed comparisons of computational results with experimental data are presented and good agreements between the experiments and predictions are obtained.

  2. Implementation of the LAX-Wendroff Method in Cobra-TF for Solving Two-Phase Flow Transport Equations

    SciTech Connect

    Salko, Robert K; Wang, Dean; Ren, Kangyu

    2016-01-01

    COBRA-TF (Coolant Boiling in Rod Arrays Two Fluid), or CTF, is a subchannel code used to conduct the reactor core thermal hydraulic (T/H) solution in both standalone and coupled multi-physics applications. CTF applies the first-order upwind spatial discretization scheme for solving two-phase flow conservation equations. In this work, the second-order Lax-Wendroff (L-W) scheme has been implemented in CTF to solve the two-phase flow transport equations to improve numerical accuracy in both temporal and spatial discretization. To avoid the oscillation issue, a non-linear flux limiter VA (Van Albada) is employed for the convective terms in the transport equations. Assessments have been carried out to evaluate the performance and stability of the implemented second-order L-W scheme. It has been found that the L-W scheme performs better than the upwind scheme for the single-phase and two-phase flow problems in terms of numerical accuracy and computational efficiency.

  3. Transport solutions of the Lamé equations and shock elastic waves

    NASA Astrophysics Data System (ADS)

    Alexeyeva, L. A.; Kaishybaeva, G. K.

    2016-07-01

    The Lamé system describing the dynamics of an isotropic elastic medium affected by a steady transport load moving at subsonic, transonic, or supersonic speed is considered. Its fundamental and generalized solutions in a moving frame of reference tied to the transport load are analyzed. Shock waves arising in the medium at supersonic speeds are studied. Conditions on the jump in the stress, displacement rate, and energy across the shock front are obtained using distribution theory. Numerical results concerning the dynamics of an elastic medium influenced by concentrated transport loads moving at sub-, tran- and supersonic speeds are presented.

  4. The nature and role of advection in advection-diffusion equations used for modelling bed load transport

    NASA Astrophysics Data System (ADS)

    Ancey, Christophe; Bohorquez, Patricio; Heyman, Joris

    2016-04-01

    The advection-diffusion equation arises quite often in the context of sediment transport, e.g., for describing time and space variations in the particle activity (the solid volume of particles in motion per unit streambed area). Stochastic models can also be used to derive this equation, with the significant advantage that they provide information on the statistical properties of particle activity. Stochastic models are quite useful when sediment transport exhibits large fluctuations (typically at low transport rates), making the measurement of mean values difficult. We develop an approach based on birth-death Markov processes, which involves monitoring the evolution of the number of particles moving within an array of cells of finite length. While the topic has been explored in detail for diffusion-reaction systems, the treatment of advection has received little attention. We show that particle advection produces nonlocal effects, which are more or less significant depending on the cell size and particle velocity. Albeit nonlocal, these effects look like (local) diffusion and add to the intrinsic particle diffusion (dispersal due to velocity fluctuations), with the important consequence that local measurements depend on both the intrinsic properties of particle displacement and the dimensions of the measurement system.

  5. Is Onsager symmetry relevant in the transport equations for magnetically confined plasmas

    SciTech Connect

    Balescu, R. )

    1991-03-01

    A global, algebraic view of the transport processes in a magnetically confined plasma is developed. Both the neoclassical (banana) and the anomalous transport matrices are represented in a factorized form, thus separating the roles of the dynamics and of the geometric constraints. The self-adjointness of the collision operator (the sole condition for classical Onsager symmetry) is shown to be a necessary, but not sufficient condition for this symmetry in confined plasmas. The latter results for the banana transport matrix from a delicate relationship between dynamic and geometric components. This structure is not present in the anomalous transport matrix, and the Onsager symmetry is broken in this case. It is stressed that the symmetry breaking does not violate any general principles.

  6. Bombardment induced ion transport. Part I: Numerical investigation of bombardment induced ion transport through glasses and membranes on the basis of the Nernst-Planck-Poisson equations.

    PubMed

    Schäfer, M; Weitzel, K-M

    2011-12-01

    The bombardment of condensed matter by low energy ion beams induces ion transport through the material. A general theory for bombardment induced ion transport (BIIT) based on numerical solutions of the well known Nernst-Planck-Poisson equations is presented. The theory is applicable to polymer membranes as well as ion-conducting glasses with the implementation of appropriate boundary conditions. The fundamental properties of the theory, i.e. the capability to describe the potential, the field and the concentration/charge density profile within the two classes of materials mentioned above are demonstrated. In particular, the theory is capable of describing experimental observables which will be further elaborated in part II of this miniseries.

  7. Transport Equation Based Wall Distance Computations Aimed at Flows With Time-Dependent Geometry

    NASA Technical Reports Server (NTRS)

    Tucker, Paul G.; Rumsey, Christopher L.; Bartels, Robert E.; Biedron, Robert T.

    2003-01-01

    Eikonal, Hamilton-Jacobi and Poisson equations can be used for economical nearest wall distance computation and modification. Economical computations may be especially useful for aeroelastic and adaptive grid problems for which the grid deforms, and the nearest wall distance needs to be repeatedly computed. Modifications are directed at remedying turbulence model defects. For complex grid structures, implementation of the Eikonal and Hamilton-Jacobi approaches is not straightforward. This prohibits their use in industrial CFD solvers. However, both the Eikonal and Hamilton-Jacobi equations can be written in advection and advection-diffusion forms, respectively. These, like the Poisson s Laplacian, are commonly occurring industrial CFD solver elements. Use of the NASA CFL3D code to solve the Eikonal and Hamilton-Jacobi equations in advective-based forms is explored. The advection-based distance equations are found to have robust convergence. Geometries studied include single and two element airfoils, wing body and double delta configurations along with a complex electronics system. It is shown that for Eikonal accuracy, upwind metric differences are required. The Poisson approach is found effective and, since it does not require offset metric evaluations, easiest to implement. The sensitivity of flow solutions to wall distance assumptions is explored. Generally, results are not greatly affected by wall distance traits.

  8. Transport Equation Based Wall Distance Computations Aimed at Flows With Time-Dependent Geometry

    NASA Technical Reports Server (NTRS)

    Tucker, Paul G.; Rumsey, Christopher L.; Bartels, Robert E.; Biedron, Robert T.

    2003-01-01

    Eikonal, Hamilton-Jacobi and Poisson equations can be used for economical nearest wall distance computation and modification. Economical computations may be especially useful for aeroelastic and adaptive grid problems for which the grid deforms, and the nearest wall distance needs to be repeatedly computed. Modifications are directed at remedying turbulence model defects. For complex grid structures, implementation of the Eikonal and Hamilton-Jacobi approaches is not straightforward. This prohibits their use in industrial CFD solvers. However, both the Eikonal and Hamilton-Jacobi equations can be written in advection and advection-diffusion forms, respectively. These, like the Poisson's Laplacian, are commonly occurring industrial CFD solver elements. Use of the NASA CFL3D code to solve the Eikonal and Hamilton-Jacobi equations in advective-based forms is explored. The advection-based distance equations are found to have robust convergence. Geometries studied include single and two element airfoils, wing body and double delta configurations along with a complex electronics system. It is shown that for Eikonal accuracy, upwind metric differences are required. The Poisson approach is found effective and, since it does not require offset metric evaluations, easiest to implement. The sensitivity of flow solutions to wall distance assumptions is explored. Generally, results are not greatly affected by wall distance traits.

  9. Generalized semi-analytical solutions to multispecies transport equation coupled with sequential first-order reaction network with spatially or temporally variable transport and decay coefficients

    NASA Astrophysics Data System (ADS)

    Suk, Heejun

    2016-08-01

    This paper presents a semi-analytical procedure for solving coupled the multispecies reactive solute transport equations, with a sequential first-order reaction network on spatially or temporally varying flow velocities and dispersion coefficients involving distinct retardation factors. This proposed approach was developed to overcome the limitation reported by Suk (2013) regarding the identical retardation values for all reactive species, while maintaining the extensive capability of the previous Suk method involving spatially variable or temporally variable coefficients of transport, general initial conditions, and arbitrary temporal variable inlet concentration. The proposed approach sequentially calculates the concentration distributions of each species by employing only the generalized integral transform technique (GITT). Because the proposed solutions for each species' concentration distributions have separable forms in space and time, the solution for subsequent species (daughter species) can be obtained using only the GITT without the decomposition by change-of-variables method imposing the limitation of identical retardation values for all the reactive species by directly substituting solutions for the preceding species (parent species) into the transport equation of subsequent species (daughter species). The proposed solutions were compared with previously published analytical solutions or numerical solutions of the numerical code of the Two-Dimensional Subsurface Flow, Fate and Transport of Microbes and Chemicals (2DFATMIC) in three verification examples. In these examples, the proposed solutions were well matched with previous analytical solutions and the numerical solutions obtained by 2DFATMIC model. A hypothetical single-well push-pull test example and a scale-dependent dispersion example were designed to demonstrate the practical application of the proposed solution to a real field problem.

  10. Comparison of solutions to bi-Maxwellian and Maxwellian transport equations for subsonic flows. [in terrestrial ionosphere

    NASA Technical Reports Server (NTRS)

    Demars, H. G.; Schunk, R. W.

    1987-01-01

    Conditions corresponding to the steady state subsonic flow of a fully ionized electron-proton plasma in the terrestrial ionosphere are presently characterized by systematically comparing the solutions to the bi-Maxwellian-based 16-moment and Maxwellian-based 13-moment transport equations. The former can account for large temperature anisotropies and the flow of both parallel and perpendicular thermal energy, while the latter account for small temperature anisotropies and only a total heat flow. The comparison is conducted for 2000-10,000 K lower boundary temperatures and 1-4-K/km temperature gradients, over the 1500-13,000-km altitude range.

  11. Generalized linear Boltzmann equation, describing non-classical particle transport, and related asymptotic solutions for small mean free paths

    NASA Astrophysics Data System (ADS)

    Rukolaine, Sergey A.

    2016-05-01

    In classical kinetic models a particle free path distribution is exponential, but this is more likely to be an exception than a rule. In this paper we derive a generalized linear Boltzmann equation (GLBE) for a general free path distribution in the framework of Alt's model. In the case that the free path distribution has at least first and second finite moments we construct an asymptotic solution to the initial value problem for the GLBE for small mean free paths. In the special case of the one-speed transport problem the asymptotic solution results in a diffusion approximation to the GLBE.

  12. A Piecewise Linear Discontinuous Finite Element Spatial Discretization of the Transport Equation in 2D Cylindrical Geometry

    SciTech Connect

    Bailey, T S; Adams, M L; Chang, J H

    2008-10-01

    We present a new spatial discretization of the discrete-ordinates transport equation in two-dimensional cylindrical (RZ) geometry for arbitrary polygonal meshes. This discretization is a discontinuous finite element method that utilizes the piecewise linear basis functions developed by Stone and Adams. We describe an asymptotic analysis that shows this method to be accurate for many problems in the thick diffusion limit on arbitrary polygons, allowing this method to be applied to radiative transfer problems with these types of meshes. We also present numerical results for multiple problems on quadrilateral grids and compare these results to the well-known bi-linear discontinuous finite element method.

  13. Transport properties and equation of state for HCNO mixtures in and beyond the warm dense matter regime

    SciTech Connect

    Ticknor, Christopher; Collins, Lee A.; Kress, Joel D.

    2015-08-04

    We present simulations of a four component mixture of HCNO with orbital free molecular dynamics (OFMD). These simulations were conducted for 5–200 eV with densities ranging between 0.184 and 36.8 g/cm3. We extract the equation of state from the simulations and compare to average atom models. We found that we only need to add a cold curve model to find excellent agreement. In addition, we studied mass transport properties. We present fits to the self-diffusion and shear viscosity that are able to reproduce the transport properties over the parameter range studied. We compare these OFMD results to models based on the Coulomb coupling parameter and one-component plasmas.

  14. Transport properties and equation of state for HCNO mixtures in and beyond the warm dense matter regime

    DOE PAGES

    Ticknor, Christopher; Collins, Lee A.; Kress, Joel D.

    2015-08-04

    We present simulations of a four component mixture of HCNO with orbital free molecular dynamics (OFMD). These simulations were conducted for 5–200 eV with densities ranging between 0.184 and 36.8 g/cm3. We extract the equation of state from the simulations and compare to average atom models. We found that we only need to add a cold curve model to find excellent agreement. In addition, we studied mass transport properties. We present fits to the self-diffusion and shear viscosity that are able to reproduce the transport properties over the parameter range studied. We compare these OFMD results to models based onmore » the Coulomb coupling parameter and one-component plasmas.« less

  15. Transport properties and equation of state for HCNO mixtures in and beyond the warm dense matter regime.

    PubMed

    Ticknor, Christopher; Collins, Lee A; Kress, Joel D

    2015-08-01

    We present simulations of a four-component mixture of HCNO with orbital free molecular dynamics (OFMD). These simulations were conducted for 5-200 eV with densities ranging between 0.184 and 36.8 g/cm3. We extract the equation of state from the simulations and compare to average atom models. We found that we only need to add a cold curve model to find excellent agreement. Additionally, we studied mass transport properties. We present fits to the self-diffusion and shear viscosity that are able to reproduce the transport properties over the parameter range studied. We compare these OFMD results to models based on the Coulomb coupling parameter and one-component plasmas.

  16. Discontinuous Galerkin discretization of the Reynolds-averaged Navier-Stokes equations with the shear-stress transport model

    NASA Astrophysics Data System (ADS)

    Schoenawa, Stefan; Hartmann, Ralf

    2014-04-01

    In this article we consider the development of Discontinuous Galerkin (DG) methods for the numerical approximation of the Reynolds-averaged Navier-Stokes (RANS) equations with the shear-stress transport (SST) model by Menter. This turbulence model is based on a blending of the Wilcox k-ω model used near the wall and the k-ɛ model used in the rest of the domain where the blending functions depend on the distance to the nearest wall. For the computation of the distance of each quadrature point in the domain to the nearest of the curved, piecewise polynomial wall boundaries, we propose a stabilized continuous finite element (FE) discretization of the eikonal equation. Furthermore, we propose a new wall boundary condition for the dissipation rate ω based on the projection of the analytic near-wall behavior of ω onto the discrete ansatz space of the DG discretization. Finally, we introduce an artificial viscosity to the discretization of the turbulence kinetic energy (k-)equation to suppress oscillations of k near the underresolved boundary layer edge. The wall distance computation based on the continuous FE discretization of the eikonal equation is demonstrated for an internal and three external/aerodynamic flow geometries including a three-element high-lift configuration. The DG discretization of the RANS equations with the SST model is demonstrated for turbulent flows past a flat plate and the RAE2822 airfoil (Cases 9 and 10). The results are compared to the underlying k-ω model and experimental data.

  17. Structural stability of a 1D compressible viscoelastic fluid model

    NASA Astrophysics Data System (ADS)

    Huo, Xiaokai; Yong, Wen-An

    2016-07-01

    This paper is concerned with a compressible viscoelastic fluid model proposed by Öttinger. Although the model has a convex entropy, the Hessian matrix of the entropy does not symmetrize the system of first-order partial differential equations due to the non-conservative terms in the constitutive equation. We show that the corresponding 1D model is symmetrizable hyperbolic and dissipative and satisfies the Kawashima condition. Based on these, we prove the global existence of smooth solutions near equilibrium and justify the compatibility of the model with the Navier-Stokes equations.

  18. Kershaw closures for linear transport equations in slab geometry I: Model derivation

    NASA Astrophysics Data System (ADS)

    Schneider, Florian

    2016-10-01

    This paper provides a new class of moment models for linear kinetic equations in slab geometry. These models can be evaluated cheaply while preserving the important realizability property, that is the fact that the underlying closure is non-negative. Several comparisons with the (expensive) state-of-the-art minimum-entropy models are made, showing the similarity in approximation quality of the two classes.

  19. A solution of the monoenergetic neutral particle transport equation for adjacent half-spaces with anisotropic scattering

    NASA Astrophysics Data System (ADS)

    Ganapol, B. D.; Mostacci, D.; Previti, A.

    2016-07-01

    We present highly accurate solutions to the neutral particle transport equation in a half-space. While our initial motivation was in response to a recently published solution based on Chandrasekhar's H-function, the presentation to follow has taken on a more comprehensive tone. The solution by H-functions certainly did achieved high accuracy but was limited to isotropic scattering and emission from spatially uniform and linear sources. Moreover, the overly complicated nature of the H-function approach strongly suggests that its extension to anisotropic scattering and general sources is not at all practical. For this reason, an all encompassing theory for the determination of highly precise benchmarks, including anisotropic scattering for a variety of spatial source distributions, is presented for particle transport in a half-space. We illustrate the approach via a collection of cases including tables of 7-place flux benchmarks to guide transport methods developers. The solution presented can be applied to a considerable number of one and two half-space transport problems with variable sources and represents a state-of-the-art benchmark solution.

  20. Hierarchical Equation of Motion Investigation of Decoherence and Relaxation Dynamics in Nonequilibrium Transport through Interacting Quantum Dots

    NASA Astrophysics Data System (ADS)

    Hartle, Rainer; Cohen, Guy; Reichman, David R.; Millis, Andrew J.

    2014-03-01

    A recently developed hierarchical quantum master equation approach is used to investigate nonequilibrium electron transport through an interacting double quantum dot system in the regime where the inter-dot coupling is weaker than the coupling to the electrodes. The corresponding eigenstates provide tunneling paths that may interfere constructively or destructively, depending on the energy of the tunneling electrons. Electron-electron interactions are shown to quench these interference effects in bias-voltage dependent ways, leading, in particular, to negative differential resistance, population inversion and an enhanced broadening of resonances in the respective transport characteristics. Relaxation times are found to be very long, and to be correlated with very slow dynamics of the inter-dot coherences (off diagonal density matrix elements). The ability of the hierarchical quantum master equation approach to access very long time scales is crucial for the study of this physics. This work is supported by the National Science Foundation (NSF DMR-1006282 and NSF CHE-1213247), the Yad Hanadiv-Rothschild Foundation (via a Rothschild Fellowship for GC) and the Alexander von Humboldt Foundation (via a Feodor Lynen fellowship for RH).

  1. A device adaptive inflow boundary condition for Wigner equations of quantum transport

    SciTech Connect

    Jiang, Haiyan; Lu, Tiao; Cai, Wei

    2014-02-01

    In this paper, an improved inflow boundary condition is proposed for Wigner equations in simulating a resonant tunneling diode (RTD), which takes into consideration the band structure of the device. The original Frensley inflow boundary condition prescribes the Wigner distribution function at the device boundary to be the semi-classical Fermi–Dirac distribution for free electrons in the device contacts without considering the effect of the quantum interaction inside the quantum device. The proposed device adaptive inflow boundary condition includes this effect by assigning the Wigner distribution to the value obtained from the Wigner transform of wave functions inside the device at zero external bias voltage, thus including the dominant effect on the electron distribution in the contacts due to the device internal band energy profile. Numerical results on computing the electron density inside the RTD under various incident waves and non-zero bias conditions show much improvement by the new boundary condition over the traditional Frensley inflow boundary condition.

  2. A device adaptive inflow boundary condition for Wigner equations of quantum transport

    NASA Astrophysics Data System (ADS)

    Jiang, Haiyan; Lu, Tiao; Cai, Wei

    2014-02-01

    In this paper, an improved inflow boundary condition is proposed for Wigner equations in simulating a resonant tunneling diode (RTD), which takes into consideration the band structure of the device. The original Frensley inflow boundary condition prescribes the Wigner distribution function at the device boundary to be the semi-classical Fermi-Dirac distribution for free electrons in the device contacts without considering the effect of the quantum interaction inside the quantum device. The proposed device adaptive inflow boundary condition includes this effect by assigning the Wigner distribution to the value obtained from the Wigner transform of wave functions inside the device at zero external bias voltage, thus including the dominant effect on the electron distribution in the contacts due to the device internal band energy profile. Numerical results on computing the electron density inside the RTD under various incident waves and non-zero bias conditions show much improvement by the new boundary condition over the traditional Frensley inflow boundary condition.

  3. Assessment and improvement of the 2D/1D method stability in DeCART

    SciTech Connect

    Stimpson, S.; Young, M.; Collins, B.; Kelley, B.; Downar, T.

    2013-07-01

    As part of ongoing work with Consortium for Advanced Simulation of Light Water Reactors (CASL), the 2D/1D code, DeCART, has demonstrated some of the advantages of the 2D/1D method with respect to realistic, full-core analysis, particularly over explicit 3D transport methods, which generally have higher memory and computation requirements. The 2D/1D method performs 2D-radial transport sweeps coupled with ID-axial diffusion calculations to provide a full 3D simulation. DeCART employs the 2D method of characteristics for the radial sweeps and ID one-node nodal diffusion for the axial sweeps, coupling the two methods with transverse leakages to ensure a more consistent representation of the transport equation. It has been observed that refinement of the axial plane thickness leads to instabilities in the calculation scheme. This work assesses the sources of these instabilities and the approaches to improve them, especially with respect to negative scattering cross sections and the tightness of the 2D-radial/ID-axial coupling schemes. Fourier analyses show that the existing iteration scheme is not unconditionally stable, suggesting a tighter coupling scheme is required. For this reason 3D-CMFD has been implemented, among other developments, to ensure more stable calculation. A matrix of test cases has been used to assess the convergence, with the primary parameter being the axial plane thickness, which has been refined down to 1 cm. These cases demonstrate the issues observed and how the modification improve the stability. However, it is apparent that more work is necessary to ensure unconditional stability. (authors)

  4. Analysis of the electric currents in 1D premixed flames under applied voltages

    NASA Astrophysics Data System (ADS)

    Han, Jie; Belhi, Memdouh; Bisetti, Fabrizio; Casey, Tiernan; Im, Hong G.; Chen, Jyh-Yuan

    2015-11-01

    Studying electric currents in flames has practical aspects such as the determination of the ionic structure of a flame, the analysis of the flame behavior under an electric field and the use of flame electric properties for combustion diagnostics. This study proposes a simplified model to compute the electric currents in lean-to-stoichiometric 1D premixed flames under applied voltages. The Navier-Stokes equations coupled with transport equations for neutral and charged species along with a Poisson equation for the electric potential are solved. The model reproduces qualitatively the voltage-current characteristic found experimentally. The sensitivity of the electric currents to the applied voltage, equivalence ratio, and pressure is studied and the key parameters affecting the saturation current are determined. Results show that the saturation current is controlled by the amount of charged species created by the chemi-ionization reaction. We found that the recombination rate of electrons with cations and transport coefficients of charged species are the most important parameters affecting the voltage at witch saturation occurs. Analytical formulas for the voltage-current characteristic and the potential of saturation are developed and used to explain the obtained results.

  5. Orbit-averaged drift kinetic equation for the study of alpha-particle transport in tokamaks

    SciTech Connect

    Sager, G.T.; Miley, G.H. . Fusion Studies Lab.); Burrell, K.H. )

    1990-11-01

    Neoclassical transport of minority suprathermal alpha particles is investigated. This paper departs from previous investigations in that (a) the banana-width ordering parameter {rho}{sub {theta}}/L is not formally restricted to be a small parameter and (b) a linearized collision operator that retains the effects of pitch-angle scattering, electron and ion drag, and speed diffusion is used. A step model approximation for the large-aspect-ratio, circular-cross-section tokamak magnetic field is adopted to simplify the orbit-averaging procedure. Assuming that the suprathermal alphas are in the banana regime, an asymptotic expansion in {tau}{sub B}/{tau}{sub S} {much lt} l is carried out.

  6. Fast linear solver for radiative transport equation with multiple right hand sides in diffuse optical tomography

    NASA Astrophysics Data System (ADS)

    Jia, Jingfei; Kim, Hyun K.; Hielscher, Andreas H.

    2015-12-01

    It is well known that radiative transfer equation (RTE) provides more accurate tomographic results than its diffusion approximation (DA). However, RTE-based tomographic reconstruction codes have limited applicability in practice due to their high computational cost. In this article, we propose a new efficient method for solving the RTE forward problem with multiple light sources in an all-at-once manner instead of solving it for each source separately. To this end, we introduce here a novel linear solver called block biconjugate gradient stabilized method (block BiCGStab) that makes full use of the shared information between different right hand sides to accelerate solution convergence. Two parallelized block BiCGStab methods are proposed for additional acceleration under limited threads situation. We evaluate the performance of this algorithm with numerical simulation studies involving the Delta-Eddington approximation to the scattering phase function. The results show that the single threading block RTE solver proposed here reduces computation time by a factor of 1.5-3 as compared to the traditional sequential solution method and the parallel block solver by a factor of 1.5 as compared to the traditional parallel sequential method. This block linear solver is, moreover, independent of discretization schemes and preconditioners used; thus further acceleration and higher accuracy can be expected when combined with other existing discretization schemes or preconditioners.

  7. Equation of state and transport properties of warm dense helium via quantum molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Li, Zhi-Guo; Cheng, Yan; Chen, Qi-Feng; Chen, Xiang-Rong

    2016-05-01

    The equation of state, self-diffusion, and viscosity coefficients of helium have been investigated by quantum molecular dynamics (QMD) simulations in the warm dense matter regime. Our simulations are validated through the comparison with the reliable experimental data. The calculated principal and reshock Hugoniots of liquid helium are in good agreement with the gas-gun data. On this basis, we revisit the issue for helium, i.e., the possibility of the instabilities predicted by chemical models at around 2000 GPa and 10 g/cm3 along the pressure isotherms of 6309, 15 849, and 31 623 K. Our calculations show no indications of instability in this pressure-temperature region, which reconfirm the predictions of previous QMD simulations. The self-diffusion and viscosity coefficients of warm dense helium have been systematically investigated by the QMD simulations. We carefully test the finite-size effects and convergences of statistics, and obtain numerically converged self-diffusion and viscosity coefficients by using the Kubo-Green formulas. The present results have been used to evaluate the existing one component plasma models. Finally, the validation of the Stokes-Einstein relationship for helium in the warm dense regime is discussed.

  8. Fully automated, high speed, tomographic phase object reconstruction using the transport of intensity equation in transmission and reflection configurations.

    PubMed

    Nguyen, Thanh; Nehmetallah, George; Tran, Dat; Darudi, Ahmad; Soltani, Peyman

    2015-12-10

    While traditional transport of intensity equation (TIE) based phase retrieval of a phase object is performed through axial translation of the CCD, in this work a tunable lens TIE is employed in both transmission and reflection configurations. These configurations are extended to a 360° tomographic 3D reconstruction through multiple illuminations from different angles by a custom fabricated rotating assembly of the phase object. Synchronization circuitry is developed to control the CCD camera and the Arduino board, which in its turn controls the tunable lens and the stepper motor to automate the tomographic reconstruction process. Finally, a MATLAB based user friendly graphical user interface is developed to control the whole system and perform tomographic reconstruction using both multiplicative and inverse radon based techniques. PMID:26836869

  9. Phase retrieval with the transport-of-intensity equation in an arbitrarily-shaped aperture by iterative discrete cosine transforms

    DOE PAGES

    Huang, Lei; Zuo, Chao; Idir, Mourad; Qu, Weijuan; Asundi, Anand

    2015-04-21

    A novel transport-of-intensity equation (TIE) based phase retrieval method is proposed with putting an arbitrarily-shaped aperture into the optical wavefield. In this arbitrarily-shaped aperture, the TIE can be solved under non-uniform illuminations and even non-homogeneous boundary conditions by iterative discrete cosine transforms with a phase compensation mechanism. Simulation with arbitrary phase, arbitrary aperture shape, and non-uniform intensity distribution verifies the effective compensation and high accuracy of the proposed method. Experiment is also carried out to check the feasibility of the proposed method in real measurement. Comparing to the existing methods, the proposed method is applicable for any types of phasemore » distribution under non-uniform illumination and non-homogeneous boundary conditions within an arbitrarily-shaped aperture, which enables the technique of TIE with hard aperture become a more flexible phase retrieval tool in practical measurements.« less

  10. PHASE RETRIEVAL, SYMMETRIZATION RULE AND TRANSPORT OF INTENSITY EQUATION IN APPLICATION TO INDUCTION MAPPING OF MAGNETIC MATERIALS.

    SciTech Connect

    VOLKOV,V.V.; ZHU,Y.

    2002-08-04

    Recent progress in the field of noninterferometric phase retrieval brings the ordinary Fresnel microscopy to a new quantitative level, suitable for recovering both the amplitude and phase of the object, based on image intensity measurements of the object. We show that this is sufficient for in-plane component mapping of magnetic induction for small magnetic elements with known geometry ranging from micro- to few nanometers size. In present paper we re-examine some conservation principles used for the transport-of-intensity (TIE) equation derived by Teaque for application to phase retrieval in light and X-ray optics. In particular, we prove that the intensity conservation law should be replaced in general case with the energy-flow conservation law. This law describes the amplitude-phase balance of the partially coherent beam on its propagation along the optical path, valid both for light and electron optics. This substitution has at least two important fundamental consequences.

  11. Series integration of the diaphragm cell transport equation when the diffusion coefficient is a function of concentration

    NASA Technical Reports Server (NTRS)

    Cain, Judith B.; Baird, James K.

    1992-01-01

    An integral of the form, t = B0 + BL ln(Delta-c) + B1(Delta-c) + B2(Delta-c)-squared + ..., where t is the time and Delta-c is the concentration difference across the frit, is derived in the case of the diaphragm cell transport equation where the interdiffusion coefficient is a function of concentration. The coefficient, B0, is a constant of the integration, while the coefficients, BL, B1, B2,..., depend in general upon the constant, the compartment volumes, and the interdiffusion coefficient and various of its concentration derivatives evaluated at the mean concentration for the cell. Explicit formulas for BL, B1, B2,... are given.

  12. Gradient flipping algorithm: introducing non-convex constraints in wavefront reconstructions with the transport of intensity equation.

    PubMed

    Parvizi, A; Van den Broek, W; Koch, C T

    2016-04-18

    The transport of intensity equation (TIE) is widely applied for recovering wave fronts from an intensity measurement and a measurement of its variation along the direction of propagation. In order to get around the problem of non-uniqueness and ill-conditionedness of the solution of the TIE in the very common case of unspecified boundary conditions or noisy data, additional constraints to the solution are necessary. Although from a numerical optimization point of view, convex constraint as imposed to by total variation minimization is preferable, we will show that in many cases non-convex constraints are necessary to overcome the low-frequency artifacts so typical for convex constraints. We will provide simulated and experimental examples that demonstrate the superiority of solutions to the TIE obtained by our recently introduced gradient flipping algorithm over a total variation constrained solution. PMID:27137272

  13. Phase retrieval with the transport-of-intensity equation in an arbitrarily-shaped aperture by iterative discrete cosine transforms

    SciTech Connect

    Huang, Lei; Zuo, Chao; Idir, Mourad; Qu, Weijuan; Asundi, Anand

    2015-04-21

    A novel transport-of-intensity equation (TIE) based phase retrieval method is proposed with putting an arbitrarily-shaped aperture into the optical wavefield. In this arbitrarily-shaped aperture, the TIE can be solved under non-uniform illuminations and even non-homogeneous boundary conditions by iterative discrete cosine transforms with a phase compensation mechanism. Simulation with arbitrary phase, arbitrary aperture shape, and non-uniform intensity distribution verifies the effective compensation and high accuracy of the proposed method. Experiment is also carried out to check the feasibility of the proposed method in real measurement. Comparing to the existing methods, the proposed method is applicable for any types of phase distribution under non-uniform illumination and non-homogeneous boundary conditions within an arbitrarily-shaped aperture, which enables the technique of TIE with hard aperture become a more flexible phase retrieval tool in practical measurements.

  14. Fully automated, high speed, tomographic phase object reconstruction using the transport of intensity equation in transmission and reflection configurations.

    PubMed

    Nguyen, Thanh; Nehmetallah, George; Tran, Dat; Darudi, Ahmad; Soltani, Peyman

    2015-12-10

    While traditional transport of intensity equation (TIE) based phase retrieval of a phase object is performed through axial translation of the CCD, in this work a tunable lens TIE is employed in both transmission and reflection configurations. These configurations are extended to a 360° tomographic 3D reconstruction through multiple illuminations from different angles by a custom fabricated rotating assembly of the phase object. Synchronization circuitry is developed to control the CCD camera and the Arduino board, which in its turn controls the tunable lens and the stepper motor to automate the tomographic reconstruction process. Finally, a MATLAB based user friendly graphical user interface is developed to control the whole system and perform tomographic reconstruction using both multiplicative and inverse radon based techniques.

  15. Simultaneous resolution of the micromagnetic and spin transport equations applied to current-induced domain wall dynamics

    NASA Astrophysics Data System (ADS)

    Sturma, M.; Bellegarde, C.; Toussaint, J.-C.; Gusakova, D.

    2016-09-01

    In this paper, we use simulations to study current-induced domain wall dynamics by simultaneously resolving the spin transport and micromagnetic equations for a three-dimensional ferromagnetic strip. In contrast to local approaches, which neglect mutual interaction between spins and magnetic moments, our approach recalculates the spin distribution at each time step using the generalized drift diffusion model, which takes the transverse spin absorption phenomenon into account. We quantified the differences between a local approach and treatment based on a self-consistent method by plotting the domain wall velocity as a function of the domain wall width. We also characterized the domain wall velocity and the Walker breakdown condition as a function of the transverse spin absorption length l⊥, which plays a crucial role in domain wall dynamics.

  16. Minimising the error in eigenvalue calculations involving the Boltzmann transport equation using goal-based adaptivity on unstructured meshes

    NASA Astrophysics Data System (ADS)

    Goffin, Mark A.; Baker, Christopher M. J.; Buchan, Andrew G.; Pain, Christopher C.; Eaton, Matthew D.; Smith, Paul N.

    2013-06-01

    This article presents a method for goal-based anisotropic adaptive methods for the finite element method applied to the Boltzmann transport equation. The neutron multiplication factor, k, is used as the goal of the adaptive procedure. The anisotropic adaptive algorithm requires error measures for k with directional dependence. General error estimators are derived for any given functional of the flux and applied to k to acquire the driving force for the adaptive procedure. The error estimators require the solution of an appropriately formed dual equation. Forward and dual error indicators are calculated by weighting the Hessian of each solution with the dual and forward residual respectively. The Hessian is used as an approximation of the interpolation error in the solution which gives rise to the directional dependence. The two indicators are combined to form a single error metric that is used to adapt the finite element mesh. The residual is approximated using a novel technique arising from the sub-grid scale finite element discretisation. Two adaptive routes are demonstrated: (i) a single mesh is used to solve all energy groups, and (ii) a different mesh is used to solve each energy group. The second method aims to capture the benefit from representing the flux from each energy group on a specifically optimised mesh. The k goal-based adaptive method was applied to three examples which illustrate the superior accuracy in criticality problems that can be obtained.

  17. Minimising the error in eigenvalue calculations involving the Boltzmann transport equation using goal-based adaptivity on unstructured meshes

    SciTech Connect

    Goffin, Mark A.; Baker, Christopher M.J.; Buchan, Andrew G.; Pain, Christopher C.; Eaton, Matthew D.; Smith, Paul N.

    2013-06-01

    This article presents a method for goal-based anisotropic adaptive methods for the finite element method applied to the Boltzmann transport equation. The neutron multiplication factor, k{sub eff}, is used as the goal of the adaptive procedure. The anisotropic adaptive algorithm requires error measures for k{sub eff} with directional dependence. General error estimators are derived for any given functional of the flux and applied to k{sub eff} to acquire the driving force for the adaptive procedure. The error estimators require the solution of an appropriately formed dual equation. Forward and dual error indicators are calculated by weighting the Hessian of each solution with the dual and forward residual respectively. The Hessian is used as an approximation of the interpolation error in the solution which gives rise to the directional dependence. The two indicators are combined to form a single error metric that is used to adapt the finite element mesh. The residual is approximated using a novel technique arising from the sub-grid scale finite element discretisation. Two adaptive routes are demonstrated: (i) a single mesh is used to solve all energy groups, and (ii) a different mesh is used to solve each energy group. The second method aims to capture the benefit from representing the flux from each energy group on a specifically optimised mesh. The k{sub eff} goal-based adaptive method was applied to three examples which illustrate the superior accuracy in criticality problems that can be obtained.

  18. Boundary-artifact-free phase retrieval with the transport of intensity equation: fast solution with use of discrete cosine transform.

    PubMed

    Zuo, Chao; Chen, Qian; Asundi, Anand

    2014-04-21

    The transport of intensity equation (TIE) is a two-dimensional second order elliptic partial differential equation that must be solved under appropriate boundary conditions. However, the boundary conditions are difficult to obtain in practice. The fast Fourier transform (FFT) based TIE solutions are widely adopted for its speed and simplicity. However, it implies periodic boundary conditions, which lead to significant boundary artifacts when the imposed assumption is violated. In this work, TIE phase retrieval is considered as an inhomogeneous Neumann boundary value problem with the boundary values experimentally measurable around a hard-edged aperture, without any assumption or prior knowledge about the test object and the setup. The analytic integral solution via Green's function is given, as well as a fast numerical implementation for a rectangular region using the discrete cosine transform. This approach is applicable for the case of non-uniform intensity distribution with no extra effort to extract the boundary values from the intensity derivative signals. Its efficiency and robustness have been verified by several numerical simulations even when the objects are complex and the intensity measurements are noisy. This method promises to be an effective fast TIE solver for quantitative phase imaging applications. PMID:24787811

  19. A verification regime for the spatial discretization of the SN transport equations

    SciTech Connect

    Schunert, S.; Azmy, Y.

    2012-07-01

    The order-of-accuracy test in conjunction with the method of manufactured solutions is the current state of the art in computer code verification. In this work we investigate the application of a verification procedure including the order-of-accuracy test on a generic SN transport solver that implements the AHOTN spatial discretization. Different types of semantic errors, e.g. removal of a line of code or changing a single character, are introduced randomly into the previously verified S{sub N} code and the proposed verification procedure is used to identify the coding mistakes (if possible) and classify them. Itemized by error type we record the stage of the verification procedure where the error is detected and report the frequency with which the errors are correctly identified at various stages of the verification. Errors that remain undetected by the verification procedure are further scrutinized to determine the reason why the introduced coding mistake eluded the verification procedure. The result of this work is that the verification procedure based on an order-of-accuracy test finds almost all detectable coding mistakes but rarely, 1.44% of the time, and under certain circumstances can fail. (authors)

  20. Effective theory of black holes in the 1/D expansion

    NASA Astrophysics Data System (ADS)

    Emparan, Roberto; Shiromizu, Tetsuya; Suzuki, Ryotaku; Tanabe, Kentaro; Tanaka, Takahiro

    2015-06-01

    The gravitational field of a black hole is strongly localized near its horizon when the number of dimensions D is very large. In this limit, we can effectively replace the black hole with a surface in a background geometry (e.g. Minkowski or Anti-deSitter space). The Einstein equations determine the effective equations that this `black hole surface' (or membrane) must satisfy. We obtain them up to next-to-leading order in 1/ D for static black holes of the Einstein-(A)dS theory. To leading order, and also to next order in Minkowski backgrounds, the equations of the effective theory are the same as soap-film equations, possibly up to a redshift factor. In particular, the Schwarzschild black hole is recovered as a spherical soap bubble. Less trivially, we find solutions for `black droplets', i.e. black holes localized at the boundary of AdS, and for non-uniform black strings.

  1. Multigroup discrete ordinates solution of Boltzmann-Fokker-Planck equations and cross section library development of ion transport

    SciTech Connect

    Prinja, A.K.

    1995-08-01

    We have developed and successfully implemented a two-dimensional bilinear discontinuous in space and time, used in conjunction with the S{sub N} angular approximation, to numerically solve the time dependent, one-dimensional, one-speed, slab geometry, (ion) transport equation. Numerical results and comparison with analytical solutions have shown that the bilinear-discontinuous (BLD) scheme is third-order accurate in the space ad time dimensions independently. Comparison of the BLD results with diamond-difference methods indicate that the BLD method is both quantitavely and qualitatively superior to the DD scheme. We note that the form of the transport operator is such that these conclusions carry over to energy dependent problems that include the constant-slowing-down-approximation term, and to multiple space dimensions or combinations thereof. An optimized marching or inversion scheme or a parallel algorithm should be investigated to determine if the increased accuracy can compensate for the extra overhead required for a BLD solution, and then could be compared to other discretization methods such as nodal or characteristic schemes.

  2. Plasma transport near material boundaries

    SciTech Connect

    Singer, C.E.

    1985-06-01

    The fluid theory of two-dimensional (2-d) plasma transport in axisymmetric devices is reviewed. The forces which produce flow across the magnetic field in a collisional plasma are described. These flows may lead to up-down asymmetries in the poloidal rotation and radial fluxes. Emphasis is placed on understanding the conditions under which the known 2-d plasma fluid equations provide a valid description of these processes. Attempts to extend the fluid treatment to less collisional, turbulent plasmas are discussed. A reduction to the 1-d fluid equations used in many computer simulations is possible when sources or boundary conditions provide a large enough radial scale length. The complete 1-d fluid equations are given in the text, and 2-d fluid equations are given in the Appendix.

  3. Reynolds transport theorem for a two-phase flow

    NASA Astrophysics Data System (ADS)

    Collado, Francisco J.

    2007-01-01

    Transport equations for one-dimensional (1d), steady, two-phase flow have been proposed based on the fact that if the phases have different velocities, they cannot cover the same distance (the control volume length) in the same time. Thus, working in the same control volume for the two phases, the time scales of the phases have to be different. From this approach, transport balances for 1D, steady, two-phase flow have been already derived, supplying acceptable correlations for two-phase flow. Here, based on the strict application of the Reynolds transport theorem, general transport balances for two-phase flow are suggested.

  4. Computational methods in tokamak transport

    SciTech Connect

    Houlberg, W.A.; Attenberger, S.E.; Lao, L.L.

    1982-06-01

    A variety of numerical methods for solving the time-dependent fluid transport equations for tokamak plasmas is presented. Among the problems discussed are techniques for solving the sometimes very stiff parabolic equations for particle and energy flow, treating convection-dominated energy transport that leads to large cell Reynolds numbers, optimizing the flow of a code to reduce the time spent updating the particle and energy source terms, coupling the one-dimensional (1-D) flux-surface-averaged fluid transport equations to solutions of the 2-D Grad-Shafranov equation for the plasma geometry, handling extremely fast transient problems such as internal MHD disruptions and pellet injection, and processing the output to summarize the physics parameters over the potential operating regime for reactors. Emphasis is placed on computational efficiency in both computer time and storage requirements.

  5. Kinetic energy equations for the average-passage equation system

    NASA Technical Reports Server (NTRS)

    Johnson, Richard W.; Adamczyk, John J.

    1989-01-01

    Important kinetic energy equations derived from the average-passage equation sets are documented, with a view to their interrelationships. These kinetic equations may be used for closing the average-passage equations. The turbulent kinetic energy transport equation used is formed by subtracting the mean kinetic energy equation from the averaged total instantaneous kinetic energy equation. The aperiodic kinetic energy equation, averaged steady kinetic energy equation, averaged unsteady kinetic energy equation, and periodic kinetic energy equation, are also treated.

  6. A novel 1D/2D model for simulating conjugate heat transfer applied to flow boiling in tubes with external fins

    NASA Astrophysics Data System (ADS)

    Ocłoń, Paweł; Łopata, Stanisław; Nowak, Marzena

    2014-09-01

    This study presents a novel, simplified model for the time-efficient simulation of transient conjugate heat transfer in round tubes. The flow domain and the tube wall are modeled in 1D and 2D, respectively and empirical correlations are used to model the flow domain in 1D. The model is particularly useful when dealing with complex physics, such as flow boiling, which is the main focus of this study. The tube wall is assumed to have external fins. The flow is vertical upwards. Note that straightforward computational fluid dynamics (CFD) analysis of conjugate heat transfer in a system of tubes, leads to 3D modeling of fluid and solid domains. Because correlation is used and dimensionality reduced, the model is numerically more stable and computationally more time-efficient compared to the CFD approach. The benefit of the proposed approach is that it can be applied to large systems of tubes as encountered in many practical applications. The modeled equations are discretized in space using the finite volume method, with central differencing for the heat conduction equation in the solid domain, and upwind differencing of the convective term of the enthalpy transport equation in the flow domain. An explicit time discretization with forward differencing was applied to the enthalpy transport equation in the fluid domain. The conduction equation in the solid domain was time discretized using the Crank-Nicholson scheme. The model is applied in different boundary conditions and the predicted boiling patterns and temperature fields are discussed.

  7. A novel 1D/2D model for simulating conjugate heat transfer applied to flow boiling in tubes with external fins

    NASA Astrophysics Data System (ADS)

    Ocłoń, Paweł; Łopata, Stanisław; Nowak, Marzena

    2015-04-01

    This study presents a novel, simplified model for the time-efficient simulation of transient conjugate heat transfer in round tubes. The flow domain and the tube wall are modeled in 1D and 2D, respectively and empirical correlations are used to model the flow domain in 1D. The model is particularly useful when dealing with complex physics, such as flow boiling, which is the main focus of this study. The tube wall is assumed to have external fins. The flow is vertical upwards. Note that straightforward computational fluid dynamics (CFD) analysis of conjugate heat transfer in a system of tubes, leads to 3D modeling of fluid and solid domains. Because correlation is used and dimensionality reduced, the model is numerically more stable and computationally more time-efficient compared to the CFD approach. The benefit of the proposed approach is that it can be applied to large systems of tubes as encountered in many practical applications. The modeled equations are discretized in space using the finite volume method, with central differencing for the heat conduction equation in the solid domain, and upwind differencing of the convective term of the enthalpy transport equation in the flow domain. An explicit time discretization with forward differencing was applied to the enthalpy transport equation in the fluid domain. The conduction equation in the solid domain was time discretized using the Crank-Nicholson scheme. The model is applied in different boundary conditions and the predicted boiling patterns and temperature fields are discussed.

  8. Finite difference numerical method for the superlattice Boltzmann transport equation and case comparison of CPU(C) and GPU(CUDA) implementations

    SciTech Connect

    Priimak, Dmitri

    2014-12-01

    We present a finite difference numerical algorithm for solving two dimensional spatially homogeneous Boltzmann transport equation which describes electron transport in a semiconductor superlattice subject to crossed time dependent electric and constant magnetic fields. The algorithm is implemented both in C language targeted to CPU and in CUDA C language targeted to commodity NVidia GPU. We compare performances and merits of one implementation versus another and discuss various software optimisation techniques.

  9. A deterministic solution of the first order linear Boltzmann transport equation in the presence of external magnetic fields

    SciTech Connect

    St Aubin, J. Keyvanloo, A.; Fallone, B. G.; Vassiliev, O.

    2015-02-15

    Purpose: Accurate radiotherapy dose calculation algorithms are essential to any successful radiotherapy program, considering the high level of dose conformity and modulation in many of today’s treatment plans. As technology continues to progress, such as is the case with novel MRI-guided radiotherapy systems, the necessity for dose calculation algorithms to accurately predict delivered dose in increasingly challenging scenarios is vital. To this end, a novel deterministic solution has been developed to the first order linear Boltzmann transport equation which accurately calculates x-ray based radiotherapy doses in the presence of magnetic fields. Methods: The deterministic formalism discussed here with the inclusion of magnetic fields is outlined mathematically using a discrete ordinates angular discretization in an attempt to leverage existing deterministic codes. It is compared against the EGSnrc Monte Carlo code, utilizing the emf-macros addition which calculates the effects of electromagnetic fields. This comparison is performed in an inhomogeneous phantom that was designed to present a challenging calculation for deterministic calculations in 0, 0.6, and 3 T magnetic fields oriented parallel and perpendicular to the radiation beam. The accuracy of the formalism discussed here against Monte Carlo was evaluated with a gamma comparison using a standard 2%/2 mm and a more stringent 1%/1 mm criterion for a standard reference 10 × 10 cm{sup 2} field as well as a smaller 2 × 2 cm{sup 2} field. Results: Greater than 99.8% (94.8%) of all points analyzed passed a 2%/2 mm (1%/1 mm) gamma criterion for all magnetic field strengths and orientations investigated. All dosimetric changes resulting from the inclusion of magnetic fields were accurately calculated using the deterministic formalism. However, despite the algorithm’s high degree of accuracy, it is noticed that this formalism was not unconditionally stable using a discrete ordinate angular discretization

  10. Ab initio simulations for matter deep in the interior of giant planets: equation of state data and transport coefficients

    NASA Astrophysics Data System (ADS)

    Redmer, Ronald; Becker, Andreas; Bethkenhagen, Mandy; French, Martin; Lorenzen, Winfried

    2014-05-01

    The behavior of warm dense matter (pressures of several Mbar and temperatures of several eV) is of paramount importance for interior and dynamo models of giant planets. However, the high-pressure phase diagram of even the simplest and most abundant elements hydrogen and helium as well as that of molecular systems (e.g. water, ammonia, methane and their mixtures) is not well known. The complexity of the behavior arises from metal-insulator transitions and demixing phenomena that occur at high pressures. New phases with exotic properties (e.g. superionic phases with proton conduction) have been predicted as well. These effects will have a strong impact on interior and dynamo models of solar and extrasolar giant planets. We apply ab initio molecular dynamics simulations based on finite-temperature density functional theory to calculate the equation of state data, the high-pressure phase diagram, and the transport properties (electrical and thermal conductivity, viscosity) for a wide range of densities and temperatures. We present new results for hydrogen-helium mixtures and for water, ammonia, and methane. We discuss implications for the interior and magnetic field structure of the gas giants Jupiter and Saturn and the ice giants Uranus and Neptune.

  11. Practical procedure for retrieval of quantitative phase map for two-phase interface using the transport of intensity equation.

    PubMed

    Zhang, Xiaobin; Oshima, Yoshifumi

    2015-11-01

    A practical procedure for retrieving quantitative phase distribution at the interface between a thin amorphous germanium (a-Ge) film and vacuum based on the transport of intensity equation is proposed. First, small regions were selected in transmission electron microscopy (TEM) images with three different focus settings in order to avoid phase modulation due to low frequency noise. Second, the selected TEM image and its three reflected images were combined for mirror-symmetry to meet the boundary requirements. However, in this symmetrization, extra phase modulation arose due to the discontinuous nature of Fresnel fringes at the boundaries among the four parts of the combined image. Third, a corrected phase map was obtained by subtracting a linear fit to the extra phase modulation. The phase shift for a thin a-Ge film was determined to be approximately 0.5 rad, indicating that the average inner potential was 18.3 V. The validity of the present phase retrieval is discussed using simple simulations. PMID:26177522

  12. Semi-analytical solution to the frequency-dependent Boltzmann transport equation for cross-plane heat conduction in thin films

    SciTech Connect

    Hua, Chengyun; Minnich, Austin J.

    2015-05-07

    Cross-plane heat transport in thin films with thicknesses comparable to the phonon mean free paths is of both fundamental and practical interest for applications such as light-emitting diodes and quantum well lasers. However, physical insight is difficult to obtain for the cross-plane geometry due to the challenge of solving the Boltzmann equation in a finite domain. Here, we present a semi-analytical series expansion method to solve the transient, frequency-dependent Boltzmann transport equation that is valid from the diffusive to ballistic transport regimes and rigorously includes the frequency-dependence of phonon properties. Further, our method is more than three orders of magnitude faster than prior numerical methods and provides a simple analytical expression for the thermal conductivity as a function of film thickness. Our result enables a straightforward physical understanding of cross-plane heat conduction in thin films.

  13. The diffusion approximation versus the telegraph equation for modeling solar energetic particle transport with adiabatic focusing. I. Isotropic pitch-angle scattering

    SciTech Connect

    Effenberger, Frederic; Litvinenko, Yuri E.

    2014-03-01

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

  14. STOMP Subsurface Transport Over Multiple Phases Version 1.0 Addendum: ECKEChem Equilibrium-Conservation-Kinetic Equation Chemistry and Reactive Transport

    SciTech Connect

    White, Mark D.; McGrail, B. Peter

    2005-12-01

    flow and transport simulator, STOMP (Subsurface Transport Over Multiple Phases). Prior to these code development activities, the STOMP simulator included sequential and scalable implementations for numerically simulating the injection of supercritical CO2 into deep saline aquifers. Additionally, the sequential implementations included operational modes that considered nonisothermal conditions and kinetic dissolution of CO2 into the saline aqueous phase. This addendum documents the advancement of these numerical simulation capabilities to include reactive transport in the STOMP simulator through the inclusion of the recently PNNL developed batch geochemistry solution module ECKEChem (Equilibrium-Conservation-Kinetic Equation Chemistry). Potential geologic reservoirs for sequestering CO2 include deep saline aquifers, hydrate-bearing formations, depleted or partially depleted natural gas and petroleum reservoirs, and coal beds. The mechanisms for sequestering carbon dioxide in geologic reservoirs include physical trapping, dissolution in the reservoir fluids, hydraulic trapping (hysteretic entrapment of nonwetting fluids), and chemical reaction. This document and the associated code development and verification work are concerned with the chemistry of injecting CO2 into geologic reservoirs. As geologic sequestration of CO2 via chemical reaction, namely precipitation reactions, are most dominate in deep saline aquifers, the principal focus of this document is the numerical simulation of CO2 injection, migration, and geochemical reaction in deep saline aquifers. The ECKEChem batch chemistry module was developed in a fashion that would allow its implementation into all operational modes of the STOMP simulator, making it a more versatile chemistry component. Additionally, this approach allows for verification of the ECKEChem module against more classical reactive transport problems involving aqueous systems.

  15. Numerical simulations of heavily polluted fine-grained sediment remobilization using 1D, 1D+, and 2D channel schematization.

    PubMed

    Kaiglová, Jana; Langhammer, Jakub; Jiřinec, Petr; Janský, Bohumír; Chalupová, Dagmar

    2015-03-01

    This article used various hydrodynamic and sediment transport models to analyze the potential and the limits of different channel schematizations. The main aim was to select and evaluate the most suitable simulation method for fine-grained sediment remobilization assessment. Three types of channel schematization were selected to study the flow potential for remobilizing fine-grained sediment in artificially modified channels. Schematization with a 1D cross-sectional horizontal plan, a 1D+ approach, splitting the riverbed into different functional zones, and full 2D mesh, adopted in MIKE by the DHI modeling suite, was applied to the study. For the case study, a 55-km stretch of the Bílina River, in the Czech Republic, Central Europe, which has been heavily polluted by the chemical and coal mining industry since the mid-twentieth century, was selected. Long-term exposure to direct emissions of toxic pollutants including heavy metals and persistent organic pollutants (POPs) resulted in deposits of pollutants in fine-grained sediments in the riverbed. Simulations, based on three hydrodynamic model schematizations, proved that for events not exceeding the extent of the riverbed profile, the 1D schematization can provide comparable results to a 2D model. The 1D+ schematization can improve accuracy while keeping the benefits of high-speed simulation and low requirements of input DEM data, but the method's suitability is limited by the channel properties. PMID:25687259

  16. Upstream Design and 1D-CAE

    NASA Astrophysics Data System (ADS)

    Sawada, Hiroyuki

    Recently, engineering design environment of Japan is changing variously. Manufacturing companies are being challenged to design and bring out products that meet the diverse demands of customers and are competitive against those produced by rising countries(1). In order to keep and strengthen the competitiveness of Japanese companies, it is necessary to create new added values as well as conventional ones. It is well known that design at the early stages has a great influence on the final design solution. Therefore, design support tools for the upstream design is necessary for creating new added values. We have established a research society for 1D-CAE (1 Dimensional Computer Aided Engineering)(2), which is a general term for idea, methodology and tools applicable for the upstream design support, and discuss the concept and definition of 1D-CAE. This paper reports our discussion about 1D-CAE.

  17. Numerical Solution of 3D Poisson-Nernst-Planck Equations Coupled with Classical Density Functional Theory for Modeling Ion and Electron Transport in a Confined Environment

    SciTech Connect

    Meng, Da; Zheng, Bin; Lin, Guang; Sushko, Maria L.

    2014-08-29

    We have developed efficient numerical algorithms for the solution of 3D steady-state Poisson-Nernst-Planck equations (PNP) with excess chemical potentials described by the classical density functional theory (cDFT). The coupled PNP equations are discretized by finite difference scheme and solved iteratively by Gummel method with relaxation. The Nernst-Planck equations are transformed into Laplace equations through the Slotboom transformation. Algebraic multigrid method is then applied to efficiently solve the Poisson equation and the transformed Nernst-Planck equations. A novel strategy for calculating excess chemical potentials through fast Fourier transforms is proposed which reduces computational complexity from O(N2) to O(NlogN) where N is the number of grid points. Integrals involving Dirac delta function are evaluated directly by coordinate transformation which yields more accurate result compared to applying numerical quadrature to an approximated delta function. Numerical results for ion and electron transport in solid electrolyte for Li ion batteries are shown to be in good agreement with the experimental data and the results from previous studies.

  18. TBC1D1 reduces palmitate oxidation by inhibiting β-HAD activity in skeletal muscle.

    PubMed

    Maher, A C; McFarlan, J; Lally, J; Snook, L A; Bonen, A

    2014-11-01

    In skeletal muscle the Rab-GTPase-activating protein TBC1D1 has been implicated in the regulation of fatty acid oxidation by an unknown mechanism. We determined whether TBC1D1 altered fatty acid utilization via changes in protein-mediated fatty acid transport and/or selected enzymes regulating mitochondrial fatty acid oxidation. We also determined the effects of TBC1D1 on glucose transport and oxidation. Electrotransfection of mouse soleus muscles with TBC1D1 cDNA increased TBC1D1 protein after 2 wk (P<0.05), without altering its paralog AS160. TBC1D1 overexpression decreased basal palmitate oxidation (-22%) while blunting 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR)-stimulated palmitate oxidation (-18%). There was a tendency to increase fatty acid esterification (+10 nmol·g(-1)·60 min(-1), P=0.07), which reflected the reduction in fatty acid oxidation (-12 nmol·g(-1)·60 min(-1)). Concomitantly, basal (+21%) and AICAR-stimulated glucose oxidation (+8%) were increased in TBC1D1-transfected muscles relative to their respective controls (P<0.05), independent of changes in GLUT4 and glucose transport. The reductions in TBC1D1-mediated fatty acid oxidation could not be attributed to changes in the transporter FAT/CD36, muscle mitochondrial content, CPT1 expression or the expression and phosphorylation of AS160, acetyl-CoA carboxylase, or AMPK. However, TBC1D1 overexpression reduced β-HAD enzyme activity (-18%, P<0.05). In conclusion, TBC1D1-mediated reduction of muscle fatty acid oxidation appears to occur via inhibition of β-HAD activity.

  19. DESIGN PACKAGE 1D SYSTEM SAFETY ANALYSIS

    SciTech Connect

    L.R. Eisler

    1995-02-02

    The purpose of this analysis is to systematically identify and evaluate hazards related to the Yucca Mountain Project Exploratory Studies Facility (ESF) Design Package 1D, Surface Facilities, (for a list of design items included in the package 1D system safety analysis see section 3). This process is an integral part of the systems engineering process; whereby safety is considered during planning, design, testing, and construction. A largely qualitative approach was used since a radiological System Safety analysis is not required. The risk assessment in this analysis characterizes the accident scenarios associated with the Design Package 1D structures/systems/components in terms of relative risk and includes recommendations for mitigating all identified risks. The priority for recommending and implementing mitigation control features is: (1) Incorporate measures to reduce risks and hazards into the structure/system/component (S/S/C) design, (2) add safety devices and capabilities to the designs that reduce risk, (3) provide devices that detect and warn personnel of hazardous conditions, and (4) develop procedures and conduct training to increase worker awareness of potential hazards, on methods to reduce exposure to hazards, and on the actions required to avoid accidents or correct hazardous conditions. The scope of this analysis is limited to the Design Package 1D structures/systems/components (S/S/Cs) during normal operations excluding hazards occurring during maintenance and ''off normal'' operations.

  20. Deconvolution/identification techniques for 1-D transient signals

    SciTech Connect

    Goodman, D.M.

    1990-10-01

    This paper discusses a variety of nonparametric deconvolution and identification techniques that we have developed for application to 1-D transient signal problems. These methods are time-domain techniques that use direct methods for matrix inversion. Therefore, they are not appropriate for large data'' problems. These techniques involve various regularization methods and permit the use of certain kinds of a priori information in estimating the unknown. These techniques have been implemented in a package using standard FORTRAN that should make the package readily transportable to most computers. This paper is also meant to be an instruction manual for the package. 25 refs., 17 figs., 1 tab.

  1. Enhancing Solar Cell Efficiencies through 1-D Nanostructures

    PubMed Central

    2009-01-01

    The current global energy problem can be attributed to insufficient fossil fuel supplies and excessive greenhouse gas emissions resulting from increasing fossil fuel consumption. The huge demand for clean energy potentially can be met by solar-to-electricity conversions. The large-scale use of solar energy is not occurring due to the high cost and inadequate efficiencies of existing solar cells. Nanostructured materials have offered new opportunities to design more efficient solar cells, particularly one-dimensional (1-D) nanomaterials for enhancing solar cell efficiencies. These 1-D nanostructures, including nanotubes, nanowires, and nanorods, offer significant opportunities to improve efficiencies of solar cells by facilitating photon absorption, electron transport, and electron collection; however, tremendous challenges must be conquered before the large-scale commercialization of such cells. This review specifically focuses on the use of 1-D nanostructures for enhancing solar cell efficiencies. Other nanostructured solar cells or solar cells based on bulk materials are not covered in this review. Major topics addressed include dye-sensitized solar cells, quantum-dot-sensitized solar cells, and p-n junction solar cells.

  2. Combined rate equation and Monte Carlo studies of electron transport in a GaAs/Al0.45Ga0.55As quantum-cascade laser

    NASA Astrophysics Data System (ADS)

    Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

    2012-11-01

    Comparison of the Monte Carlo and rate equation methods as applied to the study of electron transport in a mid-infrared quantum cascade laser structure initially proposed by Page et al (2001 Appl. Phys. Lett. 78 3529) is presented for a range of realistic injector doping levels. An analysis of the difference between these two methods is given. It is suggested that justified approximations of the rate equation method, originated by imposing Fermi-Dirac statistics and the same electron effective temperature for each of the energy sub-bands, can be interpreted as partial inclusion of electron-electron interactions. Results of the rate equation method may be used as good initial conditions for a more precise Monte Carlo simulation. An algorithm combining rate equation and Monte Carlo simulations is examined. A reasonable agreement between the introduced method and a fully self-consistent resolution of Monte Carlo and Schrödinger coupled with Poisson equations is demonstrated. The computation time may be reduced when the combined algorithm is used.

  3. Centrosome Positioning in 1D Cell Migration

    NASA Astrophysics Data System (ADS)

    Adlerz, Katrina; Aranda-Espinoza, Helim

    During cell migration, the positioning of the centrosome and nucleus define a cell's polarity. For a cell migrating on a two-dimensional substrate the centrosome is positioned in front of the nucleus. Under one-dimensional confinement, however, the centrosome is positioned behind the nucleus in 60% of cells. It is known that the centrosome is positioned by CDC42 and dynein for cells moving on a 2D substrate in a wound-healing assay. It is currently unknown, however, if this is also true for cells moving under 1D confinement, where the centrosome position is often reversed. Therefore, centrosome positioning was studied in cells migrating under 1D confinement, which mimics cells migrating through 3D matrices. 3 to 5 μm fibronectin lines were stamped onto a glass substrate and cells with fluorescently labeled nuclei and centrosomes migrated on the lines. Our results show that when a cell changes directions the centrosome position is maintained. That is, when the centrosome is between the nucleus and the cell's trailing edge and the cell changes direction, the centrosome will be translocated across the nucleus to the back of the cell again. A dynein inhibitor did have an influence on centrosome positioning in 1D migration and change of directions.

  4. Vapor Transport Within the Thermal Diffusion Cloud Chamber

    NASA Technical Reports Server (NTRS)

    Ferguson, Frank T.; Heist, Richard H.; Nuth, Joseph A., III

    2000-01-01

    A review of the equations used to determine the 1-D vapor transport in the thermal diffusion cloud chamber (TDCC) is presented. These equations closely follow those of the classical Stefan tube problem in which there is transport of a volatile species through a noncondensible, carrier gas. In both cases, the very plausible assumption is made that the background gas is stagnant. Unfortunately, this assumption results in a convective flux which is inconsistent with the momentum and continuity equations for both systems. The approximation permits derivation of an analytical solution for the concentration profile in the Stefan tube, but there is no computational advantage in the case of the TDCC. Furthermore, the degree of supersaturation is a sensitive function of the concentration profile in the TD CC and the stagnant background gas approximation can make a dramatic difference in the calculated supersaturation. In this work, the equations typically used with a TDCC are compared with very general transport equations describing the 1-D diffusion of the volatile species. Whereas no pressure dependence is predicted with the typical equations, a strong pressure dependence is present with the more general equations given in this work. The predicted behavior is consistent with observations in diffusion cloud experiments. It appears that the new equations may account for much of the pressure dependence noted in TDCC experiments, but a comparison between the new equations and previously obtained experimental data are needed for verification.

  5. Regimes of suprathermal electron transport

    SciTech Connect

    Glinsky, M.E.

    1995-07-01

    Regimes of the one-dimensional (1-D) transport of suprathermal electrons into a cold background plasma are delineated. A well ordered temporal progression is found through eras where {ital J}{center_dot}{ital E} heating, hot electron--cold electron collisional heating, and diffusive heat flow dominate the cold electron energy equation. Scaling relations for how important quantities such as the width and temperature of the heated layer of cold electrons evolve with time are presented. These scaling relations are extracted from a simple 1-D model of the transport which can be written in dimensionless form with one free parameter. The parameter is shown to be the suprathermal electron velocity divided by the drift velocity of cold electrons which balances the suprathermal current. Special attention is paid to the assumptions which allow the reduction from the collisional Vlasov equation, using a Fokker--Planck collision operator, to this simple model. These model equations are numerically solved and compared to both the scaling relations and a more complete multigroup electron diffusion transport. Implications of the scaling relations on fast ion generation, magnetic field generation, and electric field inhibition of electron transport are examined as they apply to laser heated plasmas. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  6. Weak second-order splitting schemes for Lagrangian Monte Carlo particle methods for the composition PDF/FDF transport equations

    SciTech Connect

    Wang Haifeng Popov, Pavel P.; Pope, Stephen B.

    2010-03-01

    We study a class of methods for the numerical solution of the system of stochastic differential equations (SDEs) that arises in the modeling of turbulent combustion, specifically in the Monte Carlo particle method for the solution of the model equations for the composition probability density function (PDF) and the filtered density function (FDF). This system consists of an SDE for particle position and a random differential equation for particle composition. The numerical methods considered advance the solution in time with (weak) second-order accuracy with respect to the time step size. The four primary contributions of the paper are: (i) establishing that the coefficients in the particle equations can be frozen at the mid-time (while preserving second-order accuracy), (ii) examining the performance of three existing schemes for integrating the SDEs, (iii) developing and evaluating different splitting schemes (which treat particle motion, reaction and mixing on different sub-steps), and (iv) developing the method of manufactured solutions (MMS) to assess the convergence of Monte Carlo particle methods. Tests using MMS confirm the second-order accuracy of the schemes. In general, the use of frozen coefficients reduces the numerical errors. Otherwise no significant differences are observed in the performance of the different SDE schemes and splitting schemes.

  7. Mesh adaptation on the sphere using optimal transport and the numerical solution of a Monge-Ampère type equation

    NASA Astrophysics Data System (ADS)

    Weller, Hilary; Browne, Philip; Budd, Chris; Cullen, Mike

    2016-03-01

    An equation of Monge-Ampère type has, for the first time, been solved numerically on the surface of the sphere in order to generate optimally transported (OT) meshes, equidistributed with respect to a monitor function. Optimal transport generates meshes that keep the same connectivity as the original mesh, making them suitable for r-adaptive simulations, in which the equations of motion can be solved in a moving frame of reference in order to avoid mapping the solution between old and new meshes and to avoid load balancing problems on parallel computers. The semi-implicit solution of the Monge-Ampère type equation involves a new linearisation of the Hessian term, and exponential maps are used to map from old to new meshes on the sphere. The determinant of the Hessian is evaluated as the change in volume between old and new mesh cells, rather than using numerical approximations to the gradients. OT meshes are generated to compare with centroidal Voronoi tessellations on the sphere and are found to have advantages and disadvantages; OT equidistribution is more accurate, the number of iterations to convergence is independent of the mesh size, face skewness is reduced and the connectivity does not change. However anisotropy is higher and the OT meshes are non-orthogonal. It is shown that optimal transport on the sphere leads to meshes that do not tangle. However, tangling can be introduced by numerical errors in calculating the gradient of the mesh potential. Methods for alleviating this problem are explored. Finally, OT meshes are generated using observed precipitation as a monitor function, in order to demonstrate the potential power of the technique.

  8. Stochastic uncertainty analysis for solute transport in randomly heterogeneous media using a Karhunen-Loève-based moment equation approach

    USGS Publications Warehouse

    Liu, Gaisheng; Lu, Zhiming; Zhang, Dongxiao

    2007-01-01

    A new approach has been developed for solving solute transport problems in randomly heterogeneous media using the Karhunen-Loève-based moment equation (KLME) technique proposed by Zhang and Lu (2004). The KLME approach combines the Karhunen-Loève decomposition of the underlying random conductivity field and the perturbative and polynomial expansions of dependent variables including the hydraulic head, flow velocity, dispersion coefficient, and solute concentration. The equations obtained in this approach are sequential, and their structure is formulated in the same form as the original governing equations such that any existing simulator, such as Modular Three-Dimensional Multispecies Transport Model for Simulation of Advection, Dispersion, and Chemical Reactions of Contaminants in Groundwater Systems (MT3DMS), can be directly applied as the solver. Through a series of two-dimensional examples, the validity of the KLME approach is evaluated against the classical Monte Carlo simulations. Results indicate that under the flow and transport conditions examined in this work, the KLME approach provides an accurate representation of the mean concentration. For the concentration variance, the accuracy of the KLME approach is good when the conductivity variance is 0.5. As the conductivity variance increases up to 1.0, the mismatch on the concentration variance becomes large, although the mean concentration can still be accurately reproduced by the KLME approach. Our results also indicate that when the conductivity variance is relatively large, neglecting the effects of the cross terms between velocity fluctuations and local dispersivities, as done in some previous studies, can produce noticeable errors, and a rigorous treatment of the dispersion terms becomes more appropriate.

  9. The FC-1D: The profitable alternative Flying Circus Commercial Aviation Group

    NASA Technical Reports Server (NTRS)

    Meza, Victor J.; Alvarez, Jaime; Harrington, Brook; Lujan, Michael A.; Mitlyng, David; Saroughian, Andy; Silva, Alex; Teale, Tim

    1994-01-01

    The FC-1D was designed as an advanced solution for a low cost commercial transport meeting or exceeding all of the 1993/1994 AIAA/Lockheed request for proposal requirements. The driving philosophy behind the design of the FC-1D was the reduction of airline direct operating costs. Every effort was made during the design process to have the customer in mind. The Flying Circus Commercial Aviation Group targeted reductions in drag, fuel consumption, manufacturing costs, and maintenance costs. Flying Circus emphasized cost reduction throughout the entire design program. Drag reduction was achieved by implementation of the aft nacelle wing configuration to reduce cruise drag and increase cruise speeds. To reduce induced drag, rather than increasing the wing span of the FC-1D, spiroids were included in the efficient wing design. Profile and friction drag are reduced by using riblets in place of paint around the fuselage and empennage of the FC-1D. Choosing a single aisle configuration enabled the Flying Circus to optimize the fuselage diameter. Thus, reducing fuselage drag while gaining high structural efficiency. To further reduce fuel consumption a weight reduction program was conducted through the use of composite materials. An additional quality of the FC-1D is its design for low cost manufacturing and assembly. As a result of this design attribute, the FC-1D will have fewer parts which reduces weight as well as maintenance and assembly costs. The FC-1D is affordable and effective, the apex of commercial transport design.

  10. Microlens Masses from 1-D Parallaxes and Heliocentric Proper Motions

    NASA Astrophysics Data System (ADS)

    Gould, Andrew

    2014-12-01

    One-dimensional (1-D) microlens parallaxes can be combined with heliocentric lens-source relative proper motion measurements to derive the lens mass and distance, as suggested by Ghosh et al. (2004). Here I present the first mathematical anlysis of this procedure, which I show can be represented as a quadratic equation. Hence, it is formally subject to a two-fold degeneracy. I show that this degeneracy can be broken in many cases using the relatively crude 2-D parallax information that is often available for microlensing events. I also develop an explicit formula for the region of parameter space where it is more difficult to break this degeneracy. Although no mass/distance measurements have yet been made using this technique, it is likely to become quite common over the next decade.

  11. Parallelization of the Red-Black Algorithm on Solving the Second-Order PN Transport Equation with the Hybrid Finite Element Method

    SciTech Connect

    Yaqi Wang; Cristian Rabiti; Giuseppe Palmiotti

    2011-06-01

    The Red-Black algorithm has been successfully applied on solving the second-order parity transport equation with the PN approximation in angle and the Hybrid Finite Element Method (HFEM) in space, i.e., the Variational Nodal Method (VNM) [1,2,3,4,5]. Any transport solving techniques, including the Red-Black algorithm, need to be parallelized in order to take the advantage of the development of supercomputers with multiple processors for the advanced modeling and simulation. To our knowledge, an attempt [6] was done to parallelize it, but it was devoted only to the z axis plans in three-dimensional calculations. General parallelization of the Red-Black algorithm with the spatial domain decomposition has not been reported in the literature. In this summary, we present our implementation of the parallelization of the Red-Black algorithm and its efficiency results.

  12. A non-linear discontinuous Petrov-Galerkin method for removing oscillations in the solution of the time-dependent transport equation

    SciTech Connect

    Merton, S. R.; Smedley-Stevenson, R. P.; Pain, C. C.

    2012-07-01

    This paper describes a Non-Linear Discontinuous Petrov-Galerkin method and its application to the one-speed Boltzmann Transport Equation (BTE) for space-time problems. The purpose of the method is to remove unwanted oscillations in the transport solution which occur in the vicinity of sharp flux gradients, while improving computational efficiency and numerical accuracy. This is achieved by applying artificial dissipation in the solution gradient direction, internal to an element using a novel finite element (FE) Riemann approach. The added dissipation is calculated at each node of the finite element mesh based on local behaviour of the transport solution on both the spatial and temporal axes of the problem. Thus a different dissipation is used in different elements. The magnitude of dissipation that is used is obtained from a gradient-informed scaling of the advection velocities in the stabilisation term. This makes the method in its most general form non-linear. The method is implemented within a very general finite element Riemann framework. This makes it completely independent of choice of angular basis function allowing one to use different descriptions of the angular variation. Results show the non-linear scheme performs consistently well in demanding time-dependent multi-dimensional neutron transport problems. (authors)

  13. Finite Element Flux-Corrected Transport (FEM-FCT) for the Euler and Navier-Stokes equations

    NASA Technical Reports Server (NTRS)

    Loehner, Rainald; Morgan, Ken; Peraire, Jaime; Vahdati, Mehdi

    1987-01-01

    A high resolution finite element method for the solution of problems involving high speed compressible flows is presented. The method uses the concepts of flux-corrected transport and is presented in a form which is suitable for implementation on completely unstructured triangular or tetrahedral meshes. Transient and steady state examples are solved to illustrate the performance of the algorithm.

  14. Interaction of Dopamine Transporter Gene and Observed Parenting Behaviors on Attention-Deficit/Hyperactivity Disorder: A Structural Equation Modeling Approach

    ERIC Educational Resources Information Center

    Li, James J.; Lee, Steve S.

    2013-01-01

    Emerging evidence suggests that some individuals may be simultaneously more responsive to the effects from environmental adversity "and" enrichment (i.e., differential susceptibility). Given that parenting behavior and a variable number tandem repeat polymorphism in the 3'untranslated region of the dopamine transporter (DAT1) gene…

  15. 1D fast coded aperture camera.

    PubMed

    Haw, Magnus; Bellan, Paul

    2015-04-01

    A fast (100 MHz) 1D coded aperture visible light camera has been developed as a prototype for imaging plasma experiments in the EUV/X-ray bands. The system uses printed patterns on transparency sheets as the masked aperture and an 80 channel photodiode array (9 V reverse bias) as the detector. In the low signal limit, the system has demonstrated 40-fold increase in throughput and a signal-to-noise gain of ≈7 over that of a pinhole camera of equivalent parameters. In its present iteration, the camera can only image visible light; however, the only modifications needed to make the system EUV/X-ray sensitive are to acquire appropriate EUV/X-ray photodiodes and to machine a metal masked aperture. PMID:25933861

  16. 1D fast coded aperture camera.

    PubMed

    Haw, Magnus; Bellan, Paul

    2015-04-01

    A fast (100 MHz) 1D coded aperture visible light camera has been developed as a prototype for imaging plasma experiments in the EUV/X-ray bands. The system uses printed patterns on transparency sheets as the masked aperture and an 80 channel photodiode array (9 V reverse bias) as the detector. In the low signal limit, the system has demonstrated 40-fold increase in throughput and a signal-to-noise gain of ≈7 over that of a pinhole camera of equivalent parameters. In its present iteration, the camera can only image visible light; however, the only modifications needed to make the system EUV/X-ray sensitive are to acquire appropriate EUV/X-ray photodiodes and to machine a metal masked aperture.

  17. 1D-VAR Retrieval Using Superchannels

    NASA Technical Reports Server (NTRS)

    Liu, Xu; Zhou, Daniel; Larar, Allen; Smith, William L.; Schluessel, Peter; Mango, Stephen; SaintGermain, Karen

    2008-01-01

    Since modern ultra-spectral remote sensors have thousands of channels, it is difficult to include all of them in a 1D-var retrieval system. We will describe a physical inversion algorithm, which includes all available channels for the atmospheric temperature, moisture, cloud, and surface parameter retrievals. Both the forward model and the inversion algorithm compress the channel radiances into super channels. These super channels are obtained by projecting the radiance spectra onto a set of pre-calculated eigenvectors. The forward model provides both super channel properties and jacobian in EOF space directly. For ultra-spectral sensors such as Infrared Atmospheric Sounding Interferometer (IASI) and the NPOESS Airborne Sounder Testbed Interferometer (NAST), a compression ratio of more than 80 can be achieved, leading to a significant reduction in computations involved in an inversion process. Results will be shown applying the algorithm to real IASI and NAST data.

  18. Pollutant transport by shallow water equations on unstructured meshes: Hyperbolization of the model and numerical solution via a novel flux splitting scheme

    NASA Astrophysics Data System (ADS)

    Vanzo, Davide; Siviglia, Annunziato; Toro, Eleuterio F.

    2016-09-01

    The purpose of this paper is twofold. First, using the Cattaneo's relaxation approach, we reformulate the system of governing equations for the pollutant transport by shallow water flows over non-flat topography and anisotropic diffusion as hyperbolic balance laws with stiff source terms. The proposed relaxation system circumvents the infinite wave speed paradox which is inherent in standard advection-diffusion models. This turns out to give a larger stability range for the choice of the time step. Second, following a flux splitting approach, we derive a novel numerical method to discretise the resulting problem. In particular, we propose a new flux splitting and study the associated two systems of differential equations, called the "hydrodynamic" and the "relaxed diffusive" system, respectively. For the presented splitting we analyse the resulting two systems of differential equations and propose two discretisation schemes of the Godunov-type. These schemes are simple to implement, robust, accurate and fast when compared with existing methods. The resulting method is implemented on unstructured meshes and is systematically assessed for accuracy, robustness and efficiency on a carefully selected suite of test problems including non-flat topography and wetting and drying problems. Formal second order accuracy is assessed through convergence rates studies.

  19. Nonlinear simulations of combustion instabilities with a quasi-1D Navier-Stokes code

    NASA Astrophysics Data System (ADS)

    Haugen, Nils Erland L.; Langørgen, Øyvind; Sannan, Sigurd

    2011-11-01

    As lean premixed combustion systems are more susceptible to combustion instabilities than non-premixed systems, there is an increasing demand for improved numerical design tools that can predict the occurrence of combustion instabilities with high accuracy. The inherent nonlinearities in combustion instabilities can be of crucial importance, and we here propose an approach in which the one-dimensional (1D) Navier-Stokes and scalar transport equations are solved for geometries of variable cross-section. The focus is on attached flames, and for this purpose a new phenomenological model for the unsteady heat release from a flame front is introduced. In the attached flame method (AFM) the heat release occurs over the full length of the flame. The nonlinear code with the use of the AFM approach is validated against analytical results and against an experimental study of thermoacoustic instabilities in oxy-fuel flames by Ditaranto and Hals [Combustion and Flame 146 (2006) 493-512]. The numerical simulations are in accordance with the experimental measurements and the analytical results and both the frequencies and the amplitudes of the resonant acoustic pressure modes are reproduced with good accuracy.

  20. D4Z - a new renumbering for iterative solution of ground-water flow and solute- transport equations

    USGS Publications Warehouse

    Kipp, K.L.; Russell, T.F.; Otto, J.S.

    1992-01-01

    D4 zig-zag (D4Z) is a new renumbering scheme for producing a reduced matrix to be solved by an incomplete LU preconditioned, restarted conjugate-gradient iterative solver. By renumbering alternate diagonals in a zig-zag fashion, a very low sensitivity of convergence rate to renumbering direction is obtained. For two demonstration problems involving groundwater flow and solute transport, iteration counts are related to condition numbers and spectra of the reduced matrices.

  1. Transportation.

    ERIC Educational Resources Information Center

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with transportation and energy use. Its objective is for the student to be able to discuss the implication of energy usage as it applies to the area of transportation. Some topics covered are efficiencies of various transportation…

  2. Implicit solution of Stokes flow equation with material transport: toward thermal convection simulation under the self-gravitating field with free surface

    NASA Astrophysics Data System (ADS)

    Furuichi, M.; Nakagawa, T.; May, D.

    2013-12-01

    Stabilizing a numerical oscillation in free surface treatment is chagrining topic for a geodynamics simulation [e.g. Kaus et al. 2010, Duretz et al., 2011]. It is especially important for the Stokes flow simulation under the self-gravitating field based on 'Spherical Cartesian' method [Gerya et al., 2007], which is useful for simulating a long time scale dynamics of sinking metal rich materials to construct planetary core. The conventional explicit time stepping algorithm, which solves Stokes flow equation for a given material distribution at a previous time step, however has a difficulty for simulating dynamics such as a thermal convection, after the construction of layered structure in the planetary interior because of numerical oscillation. One effective approach for such numerically problematic behavior is an implicit treatment of advection term. In this study, three types of implicit strategy are discussed. First is the full implicit treatment with iterative non-linear solver which uses transported density by maker-in-cell method as nonlinear update. The maker-in-cell method is commonly used as low diffusive advection method, but is computationally expensive with makers to mesh interpolation. Second approach uses semi-Lagrangian method for nonlinear update instead of the maker-in-cell method to reduce computational cost. Third approach is to solve the Stokes flow equation combined with the linearized advection term in central-difference discretization to avoid the nonlinear update by the transport. In the second and third algorithms, physical value at the next time step is still transported by low diffusive maker-in-cell method. These three types of implicit method are examined by numerical experiment.

  3. A mechanistic-stochastic formulation of bed load particle motions: From individual particle forces to the Fokker-Planck equation under low transport rates

    NASA Astrophysics Data System (ADS)

    Fan, Niannian; Zhong, Deyu; Wu, Baosheng; Foufoula-Georgiou, Efi; Guala, Michele

    2014-03-01

    Bed load transport is a highly complex process. The probability density function (PDF) of particle velocities results from the local particle momentum variability in response to fluid drag and interactions with the bed. Starting from the forces exerted on a single particle under low transport rates (i.e., rolling and sliding regimes), we derive here the nonlinear stochastic Langevin equation (LE) to describe the dynamics of a single particle, accounting for both the deterministic and the stochastic components of such forces. Then, the Fokker-Planck equation (FPE), which describes the evolution of the PDF of the ensemble particle velocities, is derived from the LE. We show that the theoretical PDFs of both streamwise and cross-stream velocities obtained by solving the FPE under equilibrium conditions have exponential form (PDFs of both positive and negative velocities decay exponentially), consistent with the experimental data by Roseberry et al. Moreover, we theoretically show how the exponential-like PDF of an ensemble of particle velocities results from the forces exerted on a single particle. We also show that the simulated particle motions using the proposed Langevin model exhibit an emergent nonlinear relationship between hop distances and travel times (power law with exponent 5/3), in agreement with the experimental data, providing a statistical description of the particles' random motion in the context of a stochastic transport process. Finally, our study emphasizes that the motion of individual particles, described by the LE, and the behavior of the ensemble, described by the FPE, are connected within a statistical mechanics framework.

  4. Schrödinger equation Monte Carlo in three dimensions for simulation of carrier transport in three-dimensional nanoscale metal oxide semiconductor field-effect transistors

    NASA Astrophysics Data System (ADS)

    Liu, Keng-Ming; Chen, Wanqiang; Register, Leonard F.; Banerjee, Sanjay K.

    2008-12-01

    A quantum transport simulator, Schrödinger equation Monte Carlo (SEMC) in three dimensions, is presented that provides a rigorous yet reasonably computationally efficient quantum mechanical treatment of real scattering processes within quantum transport simulations of nanoscale three-dimensional (3D) metal oxide semiconductor field-effect transistor (MOSFET) geometries such as quantum wire and multigate field-effect transistors. This work represents an extension of earlier versions of SEMC for simulating quantum transport and scattering in systems with relatively simpler quasi-one-dimensional and quasi-two-dimensional geometries such as quantum-cascade lasers (via SEMC in one dimension) and silicon-on-insulator or dual-gate MOSFETs (via SEMC in two dimensions), respectively. However, the limiting computational considerations can be significantly different. The SEMC approach represents a variation in nonequilibrium Green's function techniques with scattering as well as carrier injection into the simulation region treated via Monte Carlo techniques. Scattering mechanisms include intravalley and intervalley scatterings, intrasubband and intersubband scatterings via acoustic and optical phonons, and, in the former case, surface roughness scattering. SEMC-3D simulations of a silicon omega-gate nanoscale n-channel MOSFET are provided to illustrate the modeling technique as well as the complexity of scattering effects in such nanoscale devices.

  5. Calreticulin Controls the Rate of Assembly of CD1d Molecules in the Endoplasmic Reticulum*

    PubMed Central

    Zhu, Yajuan; Zhang, Wei; Veerapen, Natacha; Besra, Gurdyal; Cresswell, Peter

    2010-01-01

    CD1d is an MHC class I-like molecule comprised of a transmembrane glycoprotein (heavy chain) associated with β2-microglobulin (β2m) that presents lipid antigens to NKT cells. Initial folding of the heavy chain involves its glycan-dependent association with calreticulin (CRT), calnexin (CNX), and the thiol oxidoreductase ERp57, and is followed by assembly with β2m to form the heterodimer. Here we show that in CRT-deficient cells CD1d heavy chains convert to β2m-associated dimers at an accelerated rate, indicating faster folding of the heavy chain, while the rate of intracellular transport after assembly is unaffected. Unlike the situation with MHC class I molecules, antigen presentation by CD1d is not impaired in the absence of CRT. Instead, there are elevated levels of stable and functional CD1d on the surface of CRT-deficient cells. Association of the heavy chains with the ER chaperones Grp94 and Bip is observed in the absence of CRT, and these may replace CRT in mediating CD1d folding and assembly. ER retention of free CD1d heavy chains is impaired in CRT-deficient cells, allowing their escape and subsequent expression on the plasma membrane. However, these free heavy chains are rapidly internalized and degraded in lysosomes, indicating that β2m association is required for the exceptional resistance of CD1d to lysosomal degradation that is normally observed. PMID:20861015

  6. Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

    PubMed Central

    2014-01-01

    Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol–gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol–gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices. PMID:24521308

  7. Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Kuo, Shou-Yi; Lin, Hsin-I.

    2014-02-01

    Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol-gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol-gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices.

  8. Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays.

    PubMed

    Kuo, Shou-Yi; Lin, Hsin-I

    2014-01-01

    Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol-gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol-gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices. PMID:24521308

  9. Boundary conditions for the neutral and ionospheric transport equations at the base of the equatorial F region

    SciTech Connect

    Duhau, S.; Louro, A.A.

    1987-12-01

    In previous works, the authors used a simple model of the equatorial E and F regions to predict simultaneously zonal neutral and ion velocities and vertical currents at the base of the F region. In this work, the model is extended to include effects not considered previously: ion-neutral drag at the F region base, the E region dynamo electric field, and the F region zonal electric field. The model is used to predict the variables mentioned above as functions of time and latitude. The results of the calculations show first that the ion velocity is quite sensitive to the combination of the three effects, and a substantial improvement over previous results is found upon comparison with meaured values. The calculated zonal neutral wind also reveals the influence of ion drag through its latitudinal variations. Finally, the current density perpendicular to the geomagnetic field exhibits two pronounced peaks of the order of 10/sup -7/ A m/sup -2/ sunrise and sunset at the dip equator. copyright American Geophysical Union 1987

  10. 1D-1D Coulomb drag in a 6 Million Mobility Bi-layer Heterostructure

    NASA Astrophysics Data System (ADS)

    Bilodeau, Simon; Laroche, Dominique; Xia, Jian-Sheng; Lilly, Mike; Reno, John; Pfeiffer, Loren; West, Ken; Gervais, Guillaume

    We report Coulomb drag measurements in vertically-coupled quantum wires. The wires are fabricated in GaAs/AlGaAs bilayer heterostructures grown from two different MBE chambers: one at Sandia National Laboratories (1.2M mobility), and the other at Princeton University (6M mobility). The previously observed positive and negative drag signals are seen in both types of devices, demonstrating the robustness of the result. However, attempts to determine the temperature dependence of the drag signal in the 1D regime proved challenging in the higher mobility heterostructure (Princeton), in part because of difficulties in aligning the wires within the same transverse subband configuration. Nevertheless, this work, performed at the Microkelvin laboratory of the University of Florida, is an important proof-of-concept for future investigations of the temperature dependence of the 1D-1D drag signal down to a few mK. Such an experiment could confirm the Luttinger charge density wave interlocking predicted to occur in the wires. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL8500.

  11. Deletion of the Rab GAP Tbc1d1 modifies glucose, lipid, and energy homeostasis in mice.

    PubMed

    Hargett, Stefan R; Walker, Natalie N; Hussain, Syed S; Hoehn, Kyle L; Keller, Susanna R

    2015-08-01

    Tbc1d1 is a Rab GTPase-activating protein (GAP) implicated in regulating intracellular retention and cell surface localization of the glucose transporter GLUT4 and thus glucose uptake in a phosphorylation-dependent manner. Tbc1d1 is most abundant in skeletal muscle but is expressed at varying levels among different skeletal muscles. Previous studies with male Tbc1d1-deficient (Tbc1d1(-/-)) mice on standard and high-fat diets established a role for Tbc1d1 in glucose, lipid, and energy homeostasis. Here we describe similar, but also additional abnormalities in male and female Tbc1d1(-/-) mice. We corroborate that Tbc1d1 loss leads to skeletal muscle-specific and skeletal muscle type-dependent abnormalities in GLUT4 expression and glucose uptake in female and male mice. Using subcellular fractionation, we show that Tbc1d1 controls basal intracellular GLUT4 retention in large skeletal muscles. However, cell surface labeling of extensor digitorum longus muscle indicates that Tbc1d1 does not regulate basal GLUT4 cell surface exposure as previously suggested. Consistent with earlier observations, female and male Tbc1d1(-/-) mice demonstrate increased energy expenditure and skeletal muscle fatty acid oxidation. Interestingly, we observe sex-dependent differences in in vivo phenotypes. Female, but not male, Tbc1d1(-/-) mice have decreased body weight and impaired glucose and insulin tolerance, but only male Tbc1d1(-/-) mice show increased lipid clearance after oil gavage. We surmise that similar changes at the tissue level cause differences in whole-body metabolism between male and female Tbc1d1(-/-) mice and between male Tbc1d1(-/-) mice in different studies due to variations in body composition and nutrient handling.

  12. Deletion of the Rab GAP Tbc1d1 modifies glucose, lipid, and energy homeostasis in mice.

    PubMed

    Hargett, Stefan R; Walker, Natalie N; Hussain, Syed S; Hoehn, Kyle L; Keller, Susanna R

    2015-08-01

    Tbc1d1 is a Rab GTPase-activating protein (GAP) implicated in regulating intracellular retention and cell surface localization of the glucose transporter GLUT4 and thus glucose uptake in a phosphorylation-dependent manner. Tbc1d1 is most abundant in skeletal muscle but is expressed at varying levels among different skeletal muscles. Previous studies with male Tbc1d1-deficient (Tbc1d1(-/-)) mice on standard and high-fat diets established a role for Tbc1d1 in glucose, lipid, and energy homeostasis. Here we describe similar, but also additional abnormalities in male and female Tbc1d1(-/-) mice. We corroborate that Tbc1d1 loss leads to skeletal muscle-specific and skeletal muscle type-dependent abnormalities in GLUT4 expression and glucose uptake in female and male mice. Using subcellular fractionation, we show that Tbc1d1 controls basal intracellular GLUT4 retention in large skeletal muscles. However, cell surface labeling of extensor digitorum longus muscle indicates that Tbc1d1 does not regulate basal GLUT4 cell surface exposure as previously suggested. Consistent with earlier observations, female and male Tbc1d1(-/-) mice demonstrate increased energy expenditure and skeletal muscle fatty acid oxidation. Interestingly, we observe sex-dependent differences in in vivo phenotypes. Female, but not male, Tbc1d1(-/-) mice have decreased body weight and impaired glucose and insulin tolerance, but only male Tbc1d1(-/-) mice show increased lipid clearance after oil gavage. We surmise that similar changes at the tissue level cause differences in whole-body metabolism between male and female Tbc1d1(-/-) mice and between male Tbc1d1(-/-) mice in different studies due to variations in body composition and nutrient handling. PMID:26015432

  13. Transport coefficients and cross sections for electrons in water vapour: comparison of cross section sets using an improved Boltzmann equation solution.

    PubMed

    Ness, K F; Robson, R E; Brunger, M J; White, R D

    2012-01-14

    This paper revisits the issues surrounding computation of electron transport properties in water vapour as a function of E/n(0) (the ratio of the applied electric field to the water vapour number density) up to 1200 Td. We solve the Boltzmann equation using an improved version of the code of Ness and Robson [Phys. Rev. A 38, 1446 (1988)], facilitating the calculation of transport coefficients to a considerably higher degree of accuracy. This allows a correspondingly more discriminating test of the various electron-water vapour cross section sets proposed by a number of authors, which has become an important issue as such sets are now being applied to study electron driven processes in atmospheric phenomena [P. Thorn, L. Campbell, and M. Brunger, PMC Physics B 2, 1 (2009)] and in modeling charged particle tracks in matter [A. Munoz, F. Blanco, G. Garcia, P. A. Thorn, M. J. Brunger, J. P. Sullivan, and S. J. Buckman, Int. J. Mass Spectrom. 277, 175 (2008)]. PMID:22260590

  14. Compendium of NASA data base for the global tropospheric experiment's Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE-A)

    NASA Technical Reports Server (NTRS)

    Gregory, Gerald L.; Scott, A. Donald, Jr.

    1995-01-01

    This compendium describes aircraft data that are available from NASA's Transport and Atmospheric Chemistry near the Equator - Atlantic (TRACE-A) conducted in September/October 1992. The broad objectives of TRACE-A were to study chemical processes and long-range transport associated with South American and African continental outflow during periods of widespread vegetation burning, and to understand the ozone enhancements observed from satellite data measured over the southern tropical Atlantic Ocean during the September/October time period. Flight experiments were conducted from Brazil, South Africa, Namibia, and the Ascension Island. This document provides a representation of aircraft data that are available from NASA Langley's Distributed Active Archive Center (DAAC). The data format of time series and altitude profile plots is not intended to support original analyses, but to assist the reader in identifying data that are of interest. This compendium is for only the NASA aircraft data. The DAAC data base includes numerous supporting data-meteorological products, results from surface studies, satellite observations, and data from sonde releases.

  15. TCTEX1D4 Interactome in Human Testis: Unraveling the Function of Dynein Light Chain in Spermatozoa

    PubMed Central

    Freitas, Maria João; Korrodi-Gregório, Luís; Morais-Santos, Filipa; da Cruz e Silva, Edgar

    2014-01-01

    Abstract Studies were designed to identify the TCTEX1D4 interactome in human testis, with the purpose of unraveling putative protein complexes essential to male reproduction and thus novel TCTEX1D4 functions. TCTEX1D4 is a dynein light chain that belongs to the DYNT1/TCTEX1 family. In spermatozoa, it appears to be important to sperm motility, intraflagellar transport, and acrosome reaction. To contribute to the knowledge on TCTEX1D4 function in testis and spermatozoa, a yeast two-hybrid assay was performed in testis, which allowed the identification of 40 novel TCTEX1D4 interactors. Curiously, another dynein light chain, TCTEX1D2, was identified and its existence demonstrated for the first time in human spermatozoa. Immunofluorescence studies proved that TCTEX1D2 is an intra-acrosomal protein also present in the midpiece, suggesting a role in cargo movement in human spermatozoa. Further, an in silico profile of TCTEX1D4 revealed that most TCTEX1D4 interacting proteins were not previously characterized and the ones described present a very broad nature. This reinforces TCTEX1D4 as a dynein light chain that is capable of interacting with a variety of functionally different proteins. These observations collectively contribute to a deeper molecular understanding of the human spermatozoa function. PMID:24606217

  16. TCTEX1D4 interactome in human testis: unraveling the function of dynein light chain in spermatozoa.

    PubMed

    Freitas, Maria João; Korrodi-Gregório, Luís; Morais-Santos, Filipa; Cruz e Silva, Edgar da; Fardilha, Margarida

    2014-04-01

    Studies were designed to identify the TCTEX1D4 interactome in human testis, with the purpose of unraveling putative protein complexes essential to male reproduction and thus novel TCTEX1D4 functions. TCTEX1D4 is a dynein light chain that belongs to the DYNT1/TCTEX1 family. In spermatozoa, it appears to be important to sperm motility, intraflagellar transport, and acrosome reaction. To contribute to the knowledge on TCTEX1D4 function in testis and spermatozoa, a yeast two-hybrid assay was performed in testis, which allowed the identification of 40 novel TCTEX1D4 interactors. Curiously, another dynein light chain, TCTEX1D2, was identified and its existence demonstrated for the first time in human spermatozoa. Immunofluorescence studies proved that TCTEX1D2 is an intra-acrosomal protein also present in the midpiece, suggesting a role in cargo movement in human spermatozoa. Further, an in silico profile of TCTEX1D4 revealed that most TCTEX1D4 interacting proteins were not previously characterized and the ones described present a very broad nature. This reinforces TCTEX1D4 as a dynein light chain that is capable of interacting with a variety of functionally different proteins. These observations collectively contribute to a deeper molecular understanding of the human spermatozoa function.

  17. Radiation Transport

    SciTech Connect

    Urbatsch, Todd James

    2015-06-15

    We present an overview of radiation transport, covering terminology, blackbody raditation, opacities, Boltzmann transport theory, approximations to the transport equation. Next we introduce several transport methods. We present a section on Caseology, observing transport boundary layers. We briefly broach topics of software development, including verification and validation, and we close with a section on high energy-density experiments that highlight and support radiation transport.

  18. Vlasov-Poisson in 1D: waterbags

    NASA Astrophysics Data System (ADS)

    Colombi, Stéphane; Touma, Jihad

    2014-07-01

    We revisit in one dimension the waterbag method to solve numerically Vlasov-Poisson equations. In this approach, the phase-space distribution function f (x, v) is initially sampled by an ensemble of patches, the waterbags, where f is assumed to be constant. As a consequence of Liouville theorem, it is only needed to follow the evolution of the border of these waterbags, which can be done by employing an orientated, self-adaptive polygon tracing isocontours of f. This method, which is entropy conserving in essence, is very accurate and can trace very well non-linear instabilities as illustrated by specific examples. As an application of the method, we generate an ensemble of single-waterbag simulations with decreasing thickness to perform a convergence study to the cold case. Our measurements show that the system relaxes to a steady state where the gravitational potential profile is a power law of slowly varying index β, with β close to 3/2 as found in the literature. However, detailed analysis of the properties of the gravitational potential shows that at the centre, β > 1.54. Moreover, our measurements are consistent with the value β = 8/5 = 1.6 that can be analytically derived by assuming that the average of the phase-space density per energy level obtained at crossing times is conserved during the mixing phase. These results are incompatible with the logarithmic slope of the projected density profile β - 2 ≃ -0.47 obtained recently by Schulz et al. using an N-body technique. This sheds again strong doubts on the capability of N-body techniques to converge to the correct steady state expected in the continuous limit.

  19. Computational transport methodology based on decomposition of a problem domain into transport and diffusive subdomains

    SciTech Connect

    Anistratov, Dmitriy Y.; Stehle, Nicholas D.

    2012-10-15

    A large class of radiative transfer and particle transport problems contain highly diffusive regions. It is possible to reduce computational costs by solving a diffusion problem in diffusive subdomains instead of the transport equation. This enables one to decrease the dimensionality of the transport problem. In this paper we present a methodology for decomposition of a spatial domain of a transport problem into transport and diffusion subregions. We develop methods for solving one-group problems in 1D slab geometry. To identify and locate diffusive regions, we develop metrics for measuring transport effects that are based on the quasidiffusion (Eddington) factor. We present the results of test problems that demonstrate the accuracy of the proposed methodology.

  20. Human serotonin 1D receptor is encoded by a subfamily of two distinct genes: 5-HT1D alpha and 5-HT1D beta.

    PubMed Central

    Weinshank, R L; Zgombick, J M; Macchi, M J; Branchek, T A; Hartig, P R

    1992-01-01

    The serotonin 1D (5-HT1D) receptor is a pharmacologically defined binding site and functional receptor site. Observed variations in the properties of 5-HT1D receptors in different tissues have led to the speculation that multiple receptor proteins with slightly different properties may exist. We report here the cloning, deduced amino acid sequences, pharmacological properties, and second-messenger coupling of a pair of human 5-HT1D receptor genes, which we have designated 5-HT1D alpha and 5-HT1D beta due to their strong similarities in sequence, pharmacological properties, and second-messenger coupling. Both genes are free of introns in their coding regions, are expressed in the human cerebral cortex, and can couple to inhibition of adenylate cyclase activity. The pharmacological binding properties of these two human receptors are very similar, and match closely the pharmacological properties of human, bovine, and guinea pig 5-HT1D sites. Both receptors exhibit high-affinity binding of sumatriptan, a new anti-migraine medication, and thus are candidates for the pharmacological site of action of this drug. Images PMID:1565658

  1. Novel electronic structures of self-organized 1D surface nanostructures

    NASA Astrophysics Data System (ADS)

    Yeom, Han Woong

    2002-03-01

    Recently we have searched for the exotic physical properties of the nanostructures formed on semiconductor surfaces by STM and photoelectron spectroscopy [1]. The major objects have been the 1D chains of metal adsorbates on Si or SiC surfaces. It now seems obvious that such (sub)nanometer-scale atomic chains possess significant technological implications for the future device technology. Furthermore those systems provide very attractive and unprecedented opportunity to study exotic physical properties of 1D electronic systems in detail, such as Peierls instability, charge density wave (CDW), electron correlation, non-Fermi liquid behavior, and interplay of defects with 1D excitations (1D solitons, 1D domain walls and etc). The present talk focuses on the recent experimental and theoretical studies for the novel electronic properties of the 1D atomic chain systems on the Si(111) surface such as Si(111)4x1-In [2], Si(111)5x2-Au [3], Si(557)5x2-Au [4], and Si(111)3x2-Ba(or Ca) [5]. These systems have well defined one dimensional electronic bands, which exhibit intriguing properties challenging our present understanding. The major points of debates right now are the origin of the periodicity-doubling phase transition of Si(111)4x1-In in relation to 1D CDW [2], the nature of the band gap (or pseudo gap) of Si(111)5x2-Au (also related to 1D CDW idea) [3], the Si(111)3x2-Ba (or Ca) surface (1D Mott-Hubbard system ?) [5], and the nature of the band dispersion of the Si(557)5x2-Au surface (any Luttinger liquid behavior ?) [4]. Some new aspects of these systems are introduced such as the doping dependence of the 1D CDW system and the transport measurements across the 1D CDW transition. References [1] For a recent review, see H. W. Yeom, J. Electron Spectro. and Rel. Phenom., 114-116, 283 (2001). [2] H.W. Yeom et al., Phys. Rev. Lett. 82, 4898 (1999); C. Kumpf et al, Phys. Rev. Lett. 85, 4916 (2001); H.W. Yeom et al., submitted; G. Le Lay et al., submitted; J.-H. Cho et al

  2. Scattering coefficients and gray-body factor for 1D BEC acoustic black holes: Exact results

    NASA Astrophysics Data System (ADS)

    Fabbri, Alessandro; Balbinot, Roberto; Anderson, Paul R.

    2016-03-01

    A complete set of exact analytic solutions to the mode equation is found in the region exterior to the acoustic horizon for a class of 1D Bose-Einstein condensate acoustic black holes. From these, analytic expressions for the scattering coefficients and gray-body factor are obtained. The results are used to verify previous predictions regarding the behaviors of the scattering coefficients and gray-body factor in the low-frequency limit.

  3. EXTENSION OF THE 1D FOUR-GROUP ANALYTIC NODAL METHOD TO FULL MULTIGROUP

    SciTech Connect

    B. D. Ganapol; D. W. Nigg

    2008-09-01

    In the mid 80’s, a four-group/two-region, entirely analytical 1D nodal benchmark appeared. It was readily acknowledged that this special case was as far as one could go in terms of group number and still achieve an analytical solution. In this work, we show that by decomposing the solution to the multigroup diffusion equation into homogeneous and particular solutions, extension to any number of groups is a relatively straightforward exercise using the mathematics of linear algebra.

  4. 1-D Numerical Analysis of RBCC Engine Performance

    NASA Technical Reports Server (NTRS)

    Han, Samuel S.

    1998-01-01

    An RBCC engine combines air breathing and rocket engines into a single engine to increase the specific impulse over an entire flight trajectory. Considerable research pertaining to RBCC propulsion was performed during the 1960's and these engines were revisited recently as a candidate propulsion system for either a single-stage-to-orbit (SSTO) or two-stage-to-orbit (TSTO) launch vehicle. There are a variety of RBCC configurations that had been evaluated and new designs are currently under development. However, the basic configuration of all RBCC systems is built around the ejector scramjet engine originally developed for the hypersonic airplane. In this configuration, a rocket engine plays as an ejector in the air-augmented initial acceleration mode, as a fuel injector in scramjet mode and the rocket in all rocket mode for orbital insertion. Computational fluid dynamics (CFD) is a useful tool for the analysis of complex transport processes in various components in RBCC propulsion systems. The objective of the present research was to develop a transient 1-D numerical model that could be used to predict flow behavior throughout a generic RBCC engine following a flight path.

  5. KAM Tori for 1D Nonlinear Wave Equationswith Periodic Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Chierchia, Luigi; You, Jiangong

    In this paper, one-dimensional (1D) nonlinear wave equations with periodic boundary conditions are considered; V is a periodic smooth or analytic function and the nonlinearity f is an analytic function vanishing together with its derivative at u≡0. It is proved that for ``most'' potentials V(x), the above equation admits small-amplitude periodic or quasi-periodic solutions corresponding to finite dimensional invariant tori for an associated infinite dimensional dynamical system. The proof is based on an infinite dimensional KAM theorem which allows for multiple normal frequencies.

  6. A parameter-free dynamic alternative to hyper-viscosity for coupled transport equations: Application to the simulation of 3D squall lines using spectral elements

    NASA Astrophysics Data System (ADS)

    Marras, Simone; Giraldo, Francis X.

    2015-02-01

    The stabilization of high order spectral elements to solve the transport equations for tracers in the atmosphere remains an active topic of research among atmospheric modelers. This paper builds on our previous work on variational multiscale stabilization (VMS) and discontinuity capturing (DC) (Marras et al. (2012) [7]) and shows the applicability of VMS+DC to realistic atmospheric problems that involve physics coupling with phase change in the simulation of 3D deep convection. We show that the VMS+DC approach is a robust technique that can damp the high order modes characterizing the spectral element solution of complex coupled transport problems. The method has important properties that techniques of more common use often lack: 1) it is free of a user-defined parameter, 2) it is anisotropic in that it only acts along the flow direction, 3) it is numerically consistent, and 4) it can improve the monotonicity of high-order spectral elements. The proposed method is assessed by comparing the results against those obtained with a fourth-order hyper-viscosity programmed in the same code. The main conclusion that arises is that tuning can be fully avoided without loss of accuracy if the dissipative scheme is properly designed. Finally, the cost of parallel communication is that of a second order operator which means that fewer communications are required by VMS+DC than by a hyper-viscosity method; fewer communications translate into a faster and more scalable code, which is of vital importance as we approach the exascale range of computing.

  7. Hermite WENO limiting for multi-moment finite-volume methods using the ADER-DT time discretization for 1-D systems of conservation laws

    SciTech Connect

    Norman, Matthew R.

    2014-11-24

    New Hermite Weighted Essentially Non-Oscillatory (HWENO) interpolants are developed and investigated within the Multi-Moment Finite-Volume (MMFV) formulation using the ADER-DT time discretization. Whereas traditional WENO methods interpolate pointwise, function-based WENO methods explicitly form a non-oscillatory, high-order polynomial over the cell in question. This study chooses a function-based approach and details how fast convergence to optimal weights for smooth flow is ensured. Methods of sixth-, eighth-, and tenth-order accuracy are developed. We compare these against traditional single-moment WENO methods of fifth-, seventh-, ninth-, and eleventh-order accuracy to compare against more familiar methods from literature. The new HWENO methods improve upon existing HWENO methods (1) by giving a better resolution of unreinforced contact discontinuities and (2) by only needing a single HWENO polynomial to update both the cell mean value and cell mean derivative. Test cases to validate and assess these methods include 1-D linear transport, the 1-D inviscid Burger's equation, and the 1-D inviscid Euler equations. Smooth and non-smooth flows are used for evaluation. These HWENO methods performed better than comparable literature-standard WENO methods for all regimes of discontinuity and smoothness in all tests herein. They exhibit improved optimal accuracy due to the use of derivatives, and they collapse to solutions similar to typical WENO methods when limiting is required. The study concludes that the new HWENO methods are robust and effective when used in the ADER-DT MMFV framework. Finally, these results are intended to demonstrate capability rather than exhaust all possible implementations.

  8. Hermite WENO limiting for multi-moment finite-volume methods using the ADER-DT time discretization for 1-D systems of conservation laws

    DOE PAGES

    Norman, Matthew R.

    2014-11-24

    New Hermite Weighted Essentially Non-Oscillatory (HWENO) interpolants are developed and investigated within the Multi-Moment Finite-Volume (MMFV) formulation using the ADER-DT time discretization. Whereas traditional WENO methods interpolate pointwise, function-based WENO methods explicitly form a non-oscillatory, high-order polynomial over the cell in question. This study chooses a function-based approach and details how fast convergence to optimal weights for smooth flow is ensured. Methods of sixth-, eighth-, and tenth-order accuracy are developed. We compare these against traditional single-moment WENO methods of fifth-, seventh-, ninth-, and eleventh-order accuracy to compare against more familiar methods from literature. The new HWENO methods improve upon existingmore » HWENO methods (1) by giving a better resolution of unreinforced contact discontinuities and (2) by only needing a single HWENO polynomial to update both the cell mean value and cell mean derivative. Test cases to validate and assess these methods include 1-D linear transport, the 1-D inviscid Burger's equation, and the 1-D inviscid Euler equations. Smooth and non-smooth flows are used for evaluation. These HWENO methods performed better than comparable literature-standard WENO methods for all regimes of discontinuity and smoothness in all tests herein. They exhibit improved optimal accuracy due to the use of derivatives, and they collapse to solutions similar to typical WENO methods when limiting is required. The study concludes that the new HWENO methods are robust and effective when used in the ADER-DT MMFV framework. Finally, these results are intended to demonstrate capability rather than exhaust all possible implementations.« less

  9. A WENO-solver combined with adaptive momentum discretization for the Wigner transport equation and its application to resonant tunneling diodes

    SciTech Connect

    Dorda, Antonius Schürrer, Ferdinand

    2015-03-01

    We present a novel numerical scheme for the deterministic solution of the Wigner transport equation, especially suited to deal with situations in which strong quantum effects are present. The unique feature of the algorithm is the expansion of the Wigner function in local basis functions, similar to finite element or finite volume methods. This procedure yields a discretization of the pseudo-differential operator that conserves the particle density on arbitrarily chosen grids. The high flexibility in refining the grid spacing together with the weighted essentially non-oscillatory (WENO) scheme for the advection term allows for an accurate and well-resolved simulation of the phase space dynamics. A resonant tunneling diode is considered as test case and a detailed convergence study is given by comparing the results to a non-equilibrium Green's functions calculation. The impact of the considered domain size and of the grid spacing is analyzed. The obtained convergence of the results towards a quasi-exact agreement of the steady state Wigner and Green's functions computations demonstrates the accuracy of the scheme, as well as the high flexibility to adjust to different physical situations.

  10. A WENO-solver combined with adaptive momentum discretization for the Wigner transport equation and its application to resonant tunneling diodes

    PubMed Central

    Dorda, Antonius; Schürrer, Ferdinand

    2015-01-01

    We present a novel numerical scheme for the deterministic solution of the Wigner transport equation, especially suited to deal with situations in which strong quantum effects are present. The unique feature of the algorithm is the expansion of the Wigner function in local basis functions, similar to finite element or finite volume methods. This procedure yields a discretization of the pseudo-differential operator that conserves the particle density on arbitrarily chosen grids. The high flexibility in refining the grid spacing together with the weighted essentially non-oscillatory (WENO) scheme for the advection term allows for an accurate and well-resolved simulation of the phase space dynamics. A resonant tunneling diode is considered as test case and a detailed convergence study is given by comparing the results to a non-equilibrium Green's functions calculation. The impact of the considered domain size and of the grid spacing is analyzed. The obtained convergence of the results towards a quasi-exact agreement of the steady state Wigner and Green's functions computations demonstrates the accuracy of the scheme, as well as the high flexibility to adjust to different physical situations. PMID:25892748

  11. Kinetics of solute adsorption at solid/solution interfaces: a theoretical development of the empirical pseudo-first and pseudo-second order kinetic rate equations, based on applying the statistical rate theory of interfacial transport.

    PubMed

    Rudzinski, Wladyslaw; Plazinski, Wojciech

    2006-08-24

    For practical applications of solid/solution adsorption processes, the kinetics of these processes is at least as much essential as their features at equilibrium. Meanwhile, the general understanding of this kinetics and its corresponding theoretical description are far behind the understanding and the level of theoretical interpretation of adsorption equilibria in these systems. The Lagergren empirical equation proposed at the end of 19th century to describe the kinetics of solute sorption at the solid/solution interfaces has been the most widely used kinetic equation until now. This equation has also been called the pseudo-first order kinetic equation because it was intuitively associated with the model of one-site occupancy adsorption kinetics governed by the rate of surface reaction. More recently, its generalization for the two-sites-occupancy adsorption was proposed and called the pseudo-second-order kinetic equation. However, the general use and the wide applicability of these empirical equations during more than one century have not resulted in a corresponding fundamental search for their theoretical origin. Here the first theoretical development of these equations is proposed, based on applying the new fundamental approach to kinetics of interfacial transport called the Statistical Rate Theory. It is shown that these empirical equations are simplified forms of a more general equation developed here, for the case when the adsorption kinetics is governed by the rate of surface reactions. The features of that general equation are shown by presenting exhaustive model investigations, and the applicability of that equation is tested by presenting a quantitative analysis of some experimental data reported in the literature.

  12. Assessing 1D Atmospheric Solar Radiative Transfer Models: Interpretation and Handling of Unresolved Clouds.

    NASA Astrophysics Data System (ADS)

    Barker, H. W.; Stephens, G. L.; Partain, P. T.; Bergman, J. W.; Bonnel, B.; Campana, K.; Clothiaux, E. E.; Clough, S.; Cusack, S.; Delamere, J.; Edwards, J.; Evans, K. F.; Fouquart, Y.; Freidenreich, S.; Galin, V.; Hou, Y.; Kato, S.; Li, J.;  Mlawer, E.;  Morcrette, J.-J.;  O'Hirok, W.;  Räisänen, P.;  Ramaswamy, V.;  Ritter, B.;  Rozanov, E.;  Schlesinger, M.;  Shibata, K.;  Sporyshev, P.;  Sun, Z.;  Wendisch, M.;  Wood, N.;  Yang, F.

    2003-08-01

    The primary purpose of this study is to assess the performance of 1D solar radiative transfer codes that are used currently both for research and in weather and climate models. Emphasis is on interpretation and handling of unresolved clouds. Answers are sought to the following questions: (i) How well do 1D solar codes interpret and handle columns of information pertaining to partly cloudy atmospheres? (ii) Regardless of the adequacy of their assumptions about unresolved clouds, do 1D solar codes perform as intended?One clear-sky and two plane-parallel, homogeneous (PPH) overcast cloud cases serve to elucidate 1D model differences due to varying treatments of gaseous transmittances, cloud optical properties, and basic radiative transfer. The remaining four cases involve 3D distributions of cloud water and water vapor as simulated by cloud-resolving models. Results for 25 1D codes, which included two line-by-line (LBL) models (clear and overcast only) and four 3D Monte Carlo (MC) photon transport algorithms, were submitted by 22 groups. Benchmark, domain-averaged irradiance profiles were computed by the MC codes. For the clear and overcast cases, all MC estimates of top-of-atmosphere albedo, atmospheric absorptance, and surface absorptance agree with one of the LBL codes to within ±2%. Most 1D codes underestimate atmospheric absorptance by typically 15-25 W m-2 at overhead sun for the standard tropical atmosphere regardless of clouds.Depending on assumptions about unresolved clouds, the 1D codes were partitioned into four genres: (i) horizontal variability, (ii) exact overlap of PPH clouds, (iii) maximum/random overlap of PPH clouds, and (iv) random overlap of PPH clouds. A single MC code was used to establish conditional benchmarks applicable to each genre, and all MC codes were used to establish the full 3D benchmarks. There is a tendency for 1D codes to cluster near their respective conditional benchmarks, though intragenre variances typically exceed those for

  13. Brady 1D seismic velocity model ambient noise prelim

    DOE Data Explorer

    Mellors, Robert J.

    2013-10-25

    Preliminary 1D seismic velocity model derived from ambient noise correlation. 28 Green's functions filtered between 4-10 Hz for Vp, Vs, and Qs were calculated. 1D model estimated for each path. The final model is a median of the individual models. Resolution is best for the top 1 km. Poorly constrained with increasing depth.

  14. Endoplasmic Reticulum Glycoprotein Quality Control Regulates CD1d Assembly and CD1d-mediated Antigen Presentation*

    PubMed Central

    Kunte, Amit; Zhang, Wei; Paduraru, Crina; Veerapen, Natacha; Cox, Liam R.; Besra, Gurdyal S.; Cresswell, Peter

    2013-01-01

    The non-classical major histocompatibility complex (MHC) homologue CD1d presents lipid antigens to innate-like lymphocytes called natural-killer T (NKT) cells. These cells, by virtue of their broad cytokine repertoire, shape innate and adaptive immune responses. Here, we have assessed the role of endoplasmic reticulum glycoprotein quality control in CD1d assembly and function, specifically the role of a key component of the quality control machinery, the enzyme UDP glucose glycoprotein glucosyltransferase (UGT1). We observe that in UGT1-deficient cells, CD1d associates prematurely with β2-microglobulin (β2m) and is able to rapidly exit the endoplasmic reticulum. At least some of these CD1d-β2m heterodimers are shorter-lived and can be rescued by provision of a defined exogenous antigen, α-galactosylceramide. Importantly, we show that in UGT1-deficient cells the CD1d-β2m heterodimers have altered antigenicity despite the fact that their cell surface levels are unchanged. We propose that UGT1 serves as a quality control checkpoint during CD1d assembly and further suggest that UGT1-mediated quality control can shape the lipid repertoire of newly synthesized CD1d. The quality control process may play a role in ensuring stability of exported CD1d-β2m complexes, in facilitating presentation of low abundance high affinity antigens, or in preventing deleterious responses to self lipids. PMID:23615906

  15. Realizing 1-D conducting channel between oppositely gated regions in bilayer graphene

    NASA Astrophysics Data System (ADS)

    Lee, Janghee; Watanabe, Kenji; Taniguchi, Takashi; Lee, Hu-Jong

    The band gap of bilayer graphene (BLG) can be tuned by applying an external electric field perpendicular to the plane of a BLG sheet. If direction of the electric fields in two adjacent regions in BLG are opposite, one-dimensional (1-D) conducting channel emerges at the boundary between two regions with chiral nature. In this presentation, we introduce a method for fabricating two pairs of split-gates attached to BLG, which is sandwiched between two atomically clean hexagonal boron nitride (h-BN) single crystals and thus allows ballistic transport of carriers at least within the device size. Current-voltage characteristics show a large transport gap, which is comparable to the results obtained from optical measurements and numerical calculations. Opening the band gap in two adjacent regions of the BLG flake by oppositely gated electric fields, we observed metallic behavior in transport characteristics along the boundary between the two regions although the resistance of two gapped regions are a few hundreds of k Ω. These results indicate that a 1-D conducting channel formed between the two regions where the induced band gaps were inverted to each other. The formation of this 1-D conducting channel mimics the topological edge conducting channels emerging at the boundary of a two-dimensional topological insulator and may be utilized for applying BLG to valleytronics

  16. Analytic 1D pn junction diode photocurrent solutions following ionizing radiation and including time-dependent changes in the carrier lifetime.

    SciTech Connect

    Axness, Carl L.; Keiter, Eric Richard; Kerr, Bert

    2011-04-01

    Circuit simulation tools (e.g., SPICE) have become invaluable in the development and design of electronic circuits in radiation environments. These codes are often employed to study the effect of many thousands of devices under transient current conditions. Device-scale simulation tools (e.g., MEDICI) are commonly used in the design of individual semiconductor components, but require computing resources that make their incorporation into a circuit code impossible for large-scale circuits. Analytic solutions to the ambipolar diffusion equation, an approximation to the carrier transport equations, may be used to characterize the transient currents at nodes within a circuit simulator. We present new transient 1D excess carrier density and photocurrent density solutions to the ambipolar diffusion equation for low-level radiation pulses that take into account a finite device geometry, ohmic fields outside the depleted region, and an arbitrary change in the carrier lifetime due to neutron irradiation or other effects. The solutions are specifically evaluated for the case of an abrupt change in the carrier lifetime during or after, a step, square, or piecewise linear radiation pulse. Noting slow convergence of the raw Fourier series for certain parameter sets, we use closed-form formulas for some of the infinite sums to produce 'partial closed-form' solutions for the above three cases. These 'partial closed-form' solutions converge with only a few tens of terms, which enables efficient large-scale circuit simulations.

  17. New analytic 1D pn junction diode transient photocurrent solutions following ionizing radiation and including time-dependent carrier lifetime degradation from a non-concurrent neutron pulse.

    SciTech Connect

    Axness, Carl L.; Keiter, Eric Richard; Kerr, Bert

    2010-07-01

    Circuit simulation codes, such as SPICE, are invaluable in the development and design of electronic circuits in radiation environments. These codes are often employed to study the effect of many thousands of devices under transient current conditions. Device-scale simulation codes are commonly used in the design of individual semiconductor components, but computational requirements limit their use to small-scale circuits. Analytic solutions to the ambipolar diffusion equation, an approximation to the carrier transport equations, may be used to characterize the transient currents at nodes within a circuit simulator. We present new analytic transient excess carrier density and photocurrent solutions to the ambipolar diffusion equation for 1-D abrupt-junction pn diodes. These solutions incorporate low-level radiation pulses and take into account a finite device geometry, ohmic fields outside the depleted region, and an arbitrary change in the carrier lifetime due to neutron irradiation or other effects. The solutions are specifically evaluated for the case of an abrupt change in the carrier lifetime during or after, a step, square, or piecewise linear radiation pulse. Noting slow convergence of the Fourier series solutions for some parameters sets, we evaluate portions of the solutions using closed-form formulas, which result in a two order of magnitude increase in computational efficiency.

  18. D1/D5 dopamine receptors modulate spatial memory formation.

    PubMed

    da Silva, Weber C N; Köhler, Cristiano C; Radiske, Andressa; Cammarota, Martín

    2012-02-01

    We investigated the effect of the intra-CA1 administration of the D1/D5 receptor antagonist SCH23390 and the D1/D5 receptor agonist SKF38393 on spatial memory in the water maze. When given immediately, but not 3h after training, SCH23390 hindered long-term spatial memory formation without affecting non-spatial memory or the normal functionality of the hippocampus. On the contrary, post-training infusion of SKF38393 enhanced retention and facilitated the spontaneous recovery of the original spatial preference after reversal learning. Our findings demonstrate that hippocampal D1/D5 receptors play an essential role in spatial memory processing.

  19. A Semiconductor Device Noise Model: A Deterministic Approach to Semiconductor Device Current Noise for Semiclassical Transport

    SciTech Connect

    Noaman, B. A.; Korman, C. E.

    2009-04-23

    In this paper, we present a deterministic approach to calculate terminal current noise characteristics in semiconductor devices in the framework of semiclassical transport based on the spherical harmonics of the Boltzmann Transport Equation. The model relies on the solution of the Boltzmann equation in the frequency domain with special initial and boundary conditions. The terminal current fluctuation is directly related to scattering without the additional Langevin noise term added to the calculation. Simulation results are presented for the terminal current spectral density for a 1-D n{sup +}nn{sup +} structure due to elastic-acoustic and intervally scattering.

  20. Photochemistry of O(1D) and O(1S) lines in the coma of 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Cessateur, Gaël; De Keyser, Johan; Maggiolo, Romain; Gibbons, Andrew; Gronoff, Guillaume; Gunell, Herbert; Dhooghe, Frederik; Loreau, Jérôme; Vaeck, Nathalie; Altwegg, Kathrin; Bieler, Andre; Briois, Christelle; Calmonte, Ursina; Combi, Michael; Fuselier, Stephen; Gombosi, Tamas; Haessig, Myrtha; Le Roy, Lena; Neefs, Eddy; Rubin, Martin

    2016-04-01

    We present here a chemistry-emission coupled model to study the production and loss mechanisms of the O(1D) and O(1S) states, for comet 67P/Churyumov-Gerasimenko. The recent discovery of O2 in significant abundance relative to water (3.80% +/- 0.85%, Bieler et al. 2015) within the coma of 67P has been taken into consideration for the first time in such models. We evaluate the effect of the presence of O2 on the green to red-doublet emission intensity ratio, which is traditionally used to assess the CO2 abundance within cometary atmospheres. Model simulations, solving the continuity equation with transport, show that not taking O2 into account leads to an underestimation of the CO2 abundance within 67P. This strongly suggests that the green to red-doublet emission intensity ratio alone is not a proper tool for determining the CO2 abundance, as previously suggested. O2 might indeed be a rather common and abundant parent species, following the re-analysis of the comet 1P/Halley data (Rubin et al. 2015). Therefore, it is likely that earlier determinations of the CO2 abundance in cometary atmospheres have to be revisited.

  1. A human serotonin 1D receptor variant (5HT1D beta) encoded by an intronless gene on chromosome 6.

    PubMed Central

    Demchyshyn, L; Sunahara, R K; Miller, K; Teitler, M; Hoffman, B J; Kennedy, J L; Seeman, P; Van Tol, H H; Niznik, H B

    1992-01-01

    An intronless gene encoding a serotonin receptor (5HT1D beta) has been cloned and functionally expressed in mammalian fibroblast cultures. Based on the deduced amino acid sequence, the gene encodes a 390-amino acid protein displaying considerable homology, within putative transmembrane domains (approximately 75% identity) to the canine and human 5HT1D receptors. Membranes prepared from CHO cells stably expressing the receptor bound [3H]serotonin with high affinity (Kd 4 nM) and displayed a pharmacological profile consistent, but not identical, with that of the characterized serotonin 5HT1D receptor. Most notably, metergoline and serotonergic piperazine derivatives, as a group, display 3- to 8-fold lower affinity for the 5HT1D beta receptor than for the 5HT1D receptor, whereas both receptors display similar affinities for tryptamine derivatives, including the antimigraine drug sumatriptan. Northern blot analysis revealed an mRNA of approximately 5.5 kilobases expressed in human and monkey frontal cortex, medulla, striatum, hippocampus and amygdala but not in cerebellum, olfactory tubercle, and pituitary. The 5HT1D beta gene maps to human chromosome 6. The existence of multiple neuronal 5HT1D-like receptors may help account for some of the complexities associated with [3H]serotonin binding patterns in native membranes. Images PMID:1351684

  2. 60. BOILER CHAMBER No. 1, D LOOP STEAM GENERATOR AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    60. BOILER CHAMBER No. 1, D LOOP STEAM GENERATOR AND MAIN COOLANT PUMP LOOKING NORTHEAST (LOCATION OOO) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  3. Severe Hypertriglyceridemia in Glut1D on Ketogenic Diet.

    PubMed

    Klepper, Joerg; Leiendecker, Baerbel; Heussinger, Nicole; Lausch, Ekkehart; Bosch, Friedrich

    2016-04-01

    High-fat ketogenic diets are the only treatment available for Glut1 deficiency (Glut1D). Here, we describe an 8-year-old girl with classical Glut1D responsive to a 3:1 ketogenic diet and ethosuximide. After 3 years on the diet a gradual increase of blood lipids was followed by rapid, severe asymptomatic hypertriglyceridemia (1,910 mg/dL). Serum lipid apheresis was required to determine liver, renal, and pancreatic function. A combination of medium chain triglyceride-oil and a reduction of the ketogenic diet to 1:1 ratio normalized triglyceride levels within days but triggered severe myoclonic seizures requiring comedication with sultiam. Severe hypertriglyceridemia in children with Glut1D on ketogenic diets may be underdiagnosed and harmful. In contrast to congenital hypertriglyceridemias, children with Glut1D may be treated effectively by dietary adjustments alone. PMID:26902182

  4. 1D Nanostructures: Controlled Fabrication and Energy Applications

    SciTech Connect

    Hu, Michael Z.

    2013-01-01

    Jian Wei, Xuchun Song, Chunli Yang, and Michael Z. Hu, 1D Nanostructures: Controlled Fabrication and Energy Applications, Journal of Nanomaterials, published special issue (http://www.hindawi.com/journals/jnm/si/197254/) (2013).

  5. TBC1D24 genotype–phenotype correlation

    PubMed Central

    Balestrini, Simona; Milh, Mathieu; Castiglioni, Claudia; Lüthy, Kevin; Finelli, Mattea J.; Verstreken, Patrik; Cardon, Aaron; Stražišar, Barbara Gnidovec; Holder, J. Lloyd; Lesca, Gaetan; Mancardi, Maria M.; Poulat, Anne L.; Repetto, Gabriela M.; Banka, Siddharth; Bilo, Leonilda; Birkeland, Laura E.; Bosch, Friedrich; Brockmann, Knut; Cross, J. Helen; Doummar, Diane; Félix, Temis M.; Giuliano, Fabienne; Hori, Mutsuki; Hüning, Irina; Kayserili, Hulia; Kini, Usha; Lees, Melissa M.; Meenakshi, Girish; Mewasingh, Leena; Pagnamenta, Alistair T.; Peluso, Silvio; Mey, Antje; Rice, Gregory M.; Rosenfeld, Jill A.; Taylor, Jenny C.; Troester, Matthew M.; Stanley, Christine M.; Ville, Dorothee; Walkiewicz, Magdalena; Falace, Antonio; Fassio, Anna; Lemke, Johannes R.; Biskup, Saskia; Tardif, Jessica; Ajeawung, Norbert F.; Tolun, Aslihan; Corbett, Mark; Gecz, Jozef; Afawi, Zaid; Howell, Katherine B.; Oliver, Karen L.; Berkovic, Samuel F.; Scheffer, Ingrid E.; de Falco, Fabrizio A.; Oliver, Peter L.; Striano, Pasquale; Zara, Federico

    2016-01-01

    Objective: To evaluate the phenotypic spectrum associated with mutations in TBC1D24. Methods: We acquired new clinical, EEG, and neuroimaging data of 11 previously unreported and 37 published patients. TBC1D24 mutations, identified through various sequencing methods, can be found online (http://lovd.nl/TBC1D24). Results: Forty-eight patients were included (28 men, 20 women, average age 21 years) from 30 independent families. Eighteen patients (38%) had myoclonic epilepsies. The other patients carried diagnoses of focal (25%), multifocal (2%), generalized (4%), and unclassified epilepsy (6%), and early-onset epileptic encephalopathy (25%). Most patients had drug-resistant epilepsy. We detail EEG, neuroimaging, developmental, and cognitive features, treatment responsiveness, and physical examination. In silico evaluation revealed 7 different highly conserved motifs, with the most common pathogenic mutation located in the first. Neuronal outgrowth assays showed that some TBC1D24 mutations, associated with the most severe TBC1D24-associated disorders, are not necessarily the most disruptive to this gene function. Conclusions: TBC1D24-related epilepsy syndromes show marked phenotypic pleiotropy, with multisystem involvement and severity spectrum ranging from isolated deafness (not studied here), benign myoclonic epilepsy restricted to childhood with complete seizure control and normal intellect, to early-onset epileptic encephalopathy with severe developmental delay and early death. There is no distinct correlation with mutation type or location yet, but patterns are emerging. Given the phenotypic breadth observed, TBC1D24 mutation screening is indicated in a wide variety of epilepsies. A TBC1D24 consortium was formed to develop further research on this gene and its associated phenotypes. PMID:27281533

  6. A 1D (radial) Plasma Jet Propagation Study for the Plasma Liner Experiment (PLX)

    NASA Astrophysics Data System (ADS)

    Thompson, J. R.; Bogatu, I. N.; Galkin, S. A.; Kim, J. S.; Welch, D. R.; Thoma, C.; Golovkin, I.; Macfarlane, J. J.; Case, A.; Messer, S. J.; Witherspoon, F. D.; Cassibry, J. T.; Awe, T. J.; Hsu, S. C.

    2011-10-01

    The Plasma Liner Experiment will explore the formation of imploding spherical ``plasma liners'' that reach peak pressures of 0.1 Mbar upon stagnation. The liners will be formed through the merging of dense, high velocity plasma jets (n ~1017 cm-3, T ~3 eV, v ~50 km/s) in a spherically convergent geometry. The focus of this 1D (radial) study is argon plasma jet evolution during propagation from the rail gun source to the jet merging radius. The study utilizes the Large Scale Plasma (LSP) PIC code with atomic physics included through the use of a non-Local Thermal Equilibrium (NLTE) Equation of State (EOS) table. We will present scenarios for expected 1D (radial) plasma jet evolution, from upon exiting the PLX rail gun to reaching the jet merging radius. The importance of radiation cooling early in the simulation is highlighted. Work supported by US DOE grant DE-FG02-05ER54835.

  7. Zero finite-temperature charge stiffness within the half-filled 1D Hubbard model

    SciTech Connect

    Carmelo, J.M.P.; Gu, Shi-Jian; Sacramento, P.D.

    2013-12-15

    Even though the one-dimensional (1D) Hubbard model is solvable by the Bethe ansatz, at half-filling its finite-temperature T>0 transport properties remain poorly understood. In this paper we combine that solution with symmetry to show that within that prominent T=0 1D insulator the charge stiffness D(T) vanishes for T>0 and finite values of the on-site repulsion U in the thermodynamic limit. This result is exact and clarifies a long-standing open problem. It rules out that at half-filling the model is an ideal conductor in the thermodynamic limit. Whether at finite T and U>0 it is an ideal insulator or a normal resistor remains an open question. That at half-filling the charge stiffness is finite at U=0 and vanishes for U>0 is found to result from a general transition from a conductor to an insulator or resistor occurring at U=U{sub c}=0 for all finite temperatures T>0. (At T=0 such a transition is the quantum metal to Mott–Hubbard-insulator transition.) The interplay of the η-spin SU(2) symmetry with the hidden U(1) symmetry beyond SO(4) is found to play a central role in the unusual finite-temperature charge transport properties of the 1D half-filled Hubbard model. -- Highlights: •The charge stiffness of the half-filled 1D Hubbard model is evaluated. •Its value is controlled by the model symmetry operator algebras. •We find that there is no charge ballistic transport at finite temperatures T>0. •The hidden U(1) symmetry controls the U=0 phase transition for T>0.

  8. NOKIN1D: one-dimensional neutron kinetics based on a nodal collocation method

    NASA Astrophysics Data System (ADS)

    Verdú, G.; Ginestar, D.; Miró, R.; Jambrina, A.; Barrachina, T.; Soler, Amparo; Concejal, Alberto

    2014-06-01

    The TRAC-BF1 one-dimensional kinetic model is a formulation of the neutron diffusion equation in the two energy groups' approximation, based on the analytical nodal method (ANM). The advantage compared with a zero-dimensional kinetic model is that the axial power profile may vary with time due to thermal-hydraulic parameter changes and/or actions of the control systems but at has the disadvantages that in unusual situations it fails to converge. The nodal collocation method developed for the neutron diffusion equation and applied to the kinetics resolution of TRAC-BF1 thermal-hydraulics, is an adaptation of the traditional collocation methods for the discretization of partial differential equations, based on the development of the solution as a linear combination of analytical functions. It has chosen to use a nodal collocation method based on a development of Legendre polynomials of neutron fluxes in each cell. The qualification is carried out by the analysis of the turbine trip transient from the NEA benchmark in Peach Bottom NPP using both the original 1D kinetics implemented in TRAC-BF1 and the 1D nodal collocation method.

  9. Rab GAPs AS160 and Tbc1d1 play nonredundant roles in the regulation of glucose and energy homeostasis in mice.

    PubMed

    Hargett, Stefan R; Walker, Natalie N; Keller, Susanna R

    2016-02-15

    The related Rab GTPase-activating proteins (Rab GAPs) AS160 and Tbc1d1 regulate the trafficking of the glucose transporter GLUT4 that controls glucose uptake in muscle and fat cells and glucose homeostasis. AS160- and Tbc1d1-deficient mice exhibit different adipocyte- and skeletal muscle-specific defects in glucose uptake, GLUT4 expression and trafficking, and glucose homeostasis. A recent study analyzed male mice with simultaneous deletion of AS160 and Tbc1d1 (AS160(-/-)/Tbc1d1(-/-) mice). Herein, we describe abnormalities in male and female AS160(-/-)/Tbc1d1(-/-) mice on another strain background. We confirm the earlier observation that GLUT4 expression and glucose uptake defects of single-knockout mice join in AS160(-/-)/Tbc1d1(-/-) mice to affect all skeletal muscle and adipose tissues. In large mixed fiber-type skeletal muscles, changes in relative basal GLUT4 plasma membrane association in AS160(-/-) and Tbc1d1(-/-) mice also combine in AS160(-/-)/Tbc1d1(-/-) mice. However, we found different glucose uptake abnormalities in isolated skeletal muscles and adipocytes than reported previously, resulting in different interpretations of how AS160 and Tbc1d1 regulate GLUT4 translocation to the cell surface. In support of a larger role for AS160 in glucose homeostasis, in contrast with the previous study, we find similarly impaired glucose and insulin tolerance in AS160(-/-)/Tbc1d1(-/-) and AS160(-/-) mice. However, in vivo glucose uptake abnormalities in AS160(-/-)/Tbc1d1(-/-) skeletal muscles differ from those observed previously in AS160(-/-) mice, indicating additional defects due to Tbc1d1 deletion. Similar to AS160- and Tbc1d1-deficient mice, AS160(-/-)/Tbc1d1(-/-) mice show sex-specific abnormalities in glucose and energy homeostasis. In conclusion, our study supports nonredundant functions for AS160 and Tbc1d1. PMID:26625902

  10. Rab GAPs AS160 and Tbc1d1 play nonredundant roles in the regulation of glucose and energy homeostasis in mice.

    PubMed

    Hargett, Stefan R; Walker, Natalie N; Keller, Susanna R

    2016-02-15

    The related Rab GTPase-activating proteins (Rab GAPs) AS160 and Tbc1d1 regulate the trafficking of the glucose transporter GLUT4 that controls glucose uptake in muscle and fat cells and glucose homeostasis. AS160- and Tbc1d1-deficient mice exhibit different adipocyte- and skeletal muscle-specific defects in glucose uptake, GLUT4 expression and trafficking, and glucose homeostasis. A recent study analyzed male mice with simultaneous deletion of AS160 and Tbc1d1 (AS160(-/-)/Tbc1d1(-/-) mice). Herein, we describe abnormalities in male and female AS160(-/-)/Tbc1d1(-/-) mice on another strain background. We confirm the earlier observation that GLUT4 expression and glucose uptake defects of single-knockout mice join in AS160(-/-)/Tbc1d1(-/-) mice to affect all skeletal muscle and adipose tissues. In large mixed fiber-type skeletal muscles, changes in relative basal GLUT4 plasma membrane association in AS160(-/-) and Tbc1d1(-/-) mice also combine in AS160(-/-)/Tbc1d1(-/-) mice. However, we found different glucose uptake abnormalities in isolated skeletal muscles and adipocytes than reported previously, resulting in different interpretations of how AS160 and Tbc1d1 regulate GLUT4 translocation to the cell surface. In support of a larger role for AS160 in glucose homeostasis, in contrast with the previous study, we find similarly impaired glucose and insulin tolerance in AS160(-/-)/Tbc1d1(-/-) and AS160(-/-) mice. However, in vivo glucose uptake abnormalities in AS160(-/-)/Tbc1d1(-/-) skeletal muscles differ from those observed previously in AS160(-/-) mice, indicating additional defects due to Tbc1d1 deletion. Similar to AS160- and Tbc1d1-deficient mice, AS160(-/-)/Tbc1d1(-/-) mice show sex-specific abnormalities in glucose and energy homeostasis. In conclusion, our study supports nonredundant functions for AS160 and Tbc1d1.

  11. A simplified spherical harmonic method for coupled electron-photon transport calculations

    SciTech Connect

    Josef, J.A.

    1997-12-01

    In this thesis the author has developed a simplified spherical harmonic method (SP{sub N} method) and associated efficient solution techniques for 2-D multigroup electron-photon transport calculations. The SP{sub N} method has never before been applied to charged-particle transport. He has performed a first time Fourier analysis of the source iteration scheme and the P{sub 1} diffusion synthetic acceleration (DSA) scheme applied to the 2-D SP{sub N} equations. The theoretical analyses indicate that the source iteration and P{sub 1} DSA schemes are as effective for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. In addition, he has applied an angular multigrid acceleration scheme, and computationally demonstrated that it performs as well as for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. It has previously been shown for 1-D S{sub N} calculations that this scheme is much more effective than the DSA scheme when scattering is highly forward-peaked. The author has investigated the applicability of the SP{sub N} approximation to two different physical classes of problems: satellite electronics shielding from geomagnetically trapped electrons, and electron beam problems.

  12. Significant enhancement of power conversion efficiency for dye sensitized solar cell using 1D/3D network nanostructures as photoanodes.

    PubMed

    Wang, Hao; Wang, Baoyuan; Yu, Jichao; Hu, Yunxia; Xia, Chen; Zhang, Jun; Liu, Rong

    2015-03-23

    The single-crystalline TiO2 nanorod arrays with rutile phase have attracted much attention in the dye sensitized solar cells (DSSCs) applications because of their superior chemical stability, better electron transport properties, higher refractive index and low production cost. However, it suffers from a low surface area as compared with TiO2 nanoparticle films. In order to enlarge the surface area of TiO2 nanorod arrays, the 1D nanorods/3D nanotubes sample was synthesized using a facile two-step hydrothermal process involving hydrothermal growth 1D/3D nanorods and followed by post-etching treatment. In such bi-layer structure, the oriented TiO2 nanorods layer could provide direct pathway for fast electron transportation, and the 3D nanotubes layer offers a higher surface area for dye loading, therefore, the 1D nanorods/3D nanotubes photoanode exhibited faster electron transport and higher surface area than either 1D or 3D nanostructures alone, and an highest efficiency of 7.68% was achieved for the DSSCs based on 1D nanorods/3D nanotubes photoanode with further TiCl4 treatment.

  13. Neutronic analysis of the 1D and 1E banks reflux detection system

    SciTech Connect

    Blanchard, A.

    1999-12-21

    Two H Canyon neutron monitoring systems for early detection of postulated abnormal reflux conditions in the Second Uranium Cycle 1E and 1D Mixer-Settle Banks have been designed and built. Monte Carlo neutron transport simulations using the general purpose, general geometry, n-particle MCNP code have been performed to model expected response of the monitoring systems to varying conditions.The confirmatory studies documented herein conclude that the 1E and 1D neutron monitoring systems are able to achieve adequate neutron count rates for various neutron source and detector configurations, thereby eliminating excessive integration count time. Neutron count rate sensitivity studies are also performed. Conversely, the transport studies concluded that the neutron count rates are statistically insensitive to nitric acid content in the aqueous region and to the transition region length. These studies conclude that the 1E and 1D neutron monitoring systems are able to predict the postulated reflux conditions for all examined perturbations in the neutron source and detector configurations. In the cases examined, the relative change in the neutron count rates due to postulated transitions from normal {sup 235}U concentration levels to reflux levels remain satisfactory detectable.

  14. COMPARISON OF MONTE CARLO METHODS FOR NONLINEAR RADIATION TRANSPORT

    SciTech Connect

    W. R. MARTIN; F. B. BROWN

    2001-03-01

    Five Monte Carlo methods for solving the nonlinear thermal radiation transport equations are compared. The methods include the well-known Implicit Monte Carlo method (IMC) developed by Fleck and Cummings, an alternative to IMC developed by Carter and Forest, an ''exact'' method recently developed by Ahrens and Larsen, and two methods recently proposed by Martin and Brown. The five Monte Carlo methods are developed and applied to the radiation transport equation in a medium assuming local thermodynamic equilibrium. Conservation of energy is derived and used to define appropriate material energy update equations for each of the methods. Details of the Monte Carlo implementation are presented, both for the random walk simulation and the material energy update. Simulation results for all five methods are obtained for two infinite medium test problems and a 1-D test problem, all of which have analytical solutions. Conclusions regarding the relative merits of the various schemes are presented.

  15. Synthesis, characterization, and physical properties of 1D nanostructures

    NASA Astrophysics Data System (ADS)

    Marley, Peter Mchael

    The roster of materials exhibiting metal---insulator transitions with sharply discontinuous switching of electrical conductivity close to room temperature remains rather sparse despite the fundamental interest in the electronic instabilities manifested in such materials and the plethora of potential technological applications, ranging from frequency-agile metamaterials to electrochromic coatings and Mott field-effect transistors. Vanadium oxide bronzes with the general formula MxV2O 5, provide a wealth of compositions and frameworks where strong electron correlation can be systematically (albeit thus far only empirically) tuned. Charge fluctuations along the quasi-1D frameworks of MxV 2O5 bronzes have evinced much recent interest owing to the manifestation of colossal metal---insulator transitions and superconductivity. We start with a general review on the phase transitions, both electronic and structural, of vanadium oxide bronzes in Chapter 1. In Chapter 2, we demonstrate an unprecedented reversible transformation between double-layered (delta) and tunnel (beta) quasi-1D geometries for nanowires of a divalent vanadium bronze CaxV2O5 (x ˜0.23) upon annealing-induced dehydration and hydrothermally-induced hydration. Such a facile hydration/dehydration-induced interconversion between two prominent quasi-1D structures (accompanied by a change in charge ordering motifs) has not been observed in the bulk and is posited to result from the ease of propagation of crystallographic slip processes across the confined nanowire widths for the delta→beta conversion and the facile diffusion of water molecules within the tunnel geometries for the beta→delta reversion. We demonstrate in Chapter 3 unprecedented pronounced metal-insulator transitions induced by application of a voltage for nanowires of a vanadium oxide bronze with intercalated divalent cations, beta-PbxV 2O5 (x ˜0.33). The induction of the phase transition through application of an electric field at room

  16. Synthesis, characterization, and physical properties of 1D nanostructures

    NASA Astrophysics Data System (ADS)

    Marley, Peter Mchael

    The roster of materials exhibiting metal---insulator transitions with sharply discontinuous switching of electrical conductivity close to room temperature remains rather sparse despite the fundamental interest in the electronic instabilities manifested in such materials and the plethora of potential technological applications, ranging from frequency-agile metamaterials to electrochromic coatings and Mott field-effect transistors. Vanadium oxide bronzes with the general formula MxV2O 5, provide a wealth of compositions and frameworks where strong electron correlation can be systematically (albeit thus far only empirically) tuned. Charge fluctuations along the quasi-1D frameworks of MxV 2O5 bronzes have evinced much recent interest owing to the manifestation of colossal metal---insulator transitions and superconductivity. We start with a general review on the phase transitions, both electronic and structural, of vanadium oxide bronzes in Chapter 1. In Chapter 2, we demonstrate an unprecedented reversible transformation between double-layered (delta) and tunnel (beta) quasi-1D geometries for nanowires of a divalent vanadium bronze CaxV2O5 (x ˜0.23) upon annealing-induced dehydration and hydrothermally-induced hydration. Such a facile hydration/dehydration-induced interconversion between two prominent quasi-1D structures (accompanied by a change in charge ordering motifs) has not been observed in the bulk and is posited to result from the ease of propagation of crystallographic slip processes across the confined nanowire widths for the delta→beta conversion and the facile diffusion of water molecules within the tunnel geometries for the beta→delta reversion. We demonstrate in Chapter 3 unprecedented pronounced metal-insulator transitions induced by application of a voltage for nanowires of a vanadium oxide bronze with intercalated divalent cations, beta-PbxV 2O5 (x ˜0.33). The induction of the phase transition through application of an electric field at room

  17. Hair on non-extremal D1-D5 bound states

    NASA Astrophysics Data System (ADS)

    Roy, Pratik; Srivastava, Yogesh K.; Virmani, Amitabh

    2016-09-01

    We consider a truncation of type IIB supergravity on four-torus where in addition to the Ramond-Ramond 2-form field, the Ramond-Ramond axion ( w) and the NS-NS 2-form field ( B) are also retained. In the ( w, B) sector we construct a linearised perturbation carrying only left moving momentum on two-charge non-extremal D1-D5 geometries of Jejjala, Madden, Ross and Titchener. The perturbation is found to be smooth everywhere and normalisable. It is constructed by matching to leading order solutions of the perturbation equations in the inner and outer regions of the geometry.

  18. Analytic solutions for the approximated 1-D Monge-Kantorovich mass transfer problems

    NASA Astrophysics Data System (ADS)

    Lu, Xiaojun; Lv, Xiaofen

    2016-10-01

    This paper mainly investigates the approximation of a global maximizer of the 1-D Monge-Kantorovich mass transfer problem through the approach of nonlinear differential equations with Dirichlet boundary. Using an approximation mechanism, the primal maximization problem can be transformed into a sequence of minimization problems. By applying the canonical duality theory, one is able to derive a sequence of analytic solutions for the minimization problems. In the final analysis, the convergence of the sequence to a global maximizer of the primal Monge-Kantorovich problem will be demonstrated.

  19. SEAWAT-based simulation of axisymmetric heat transport.

    PubMed

    Vandenbohede, Alexander; Louwyck, Andy; Vlamynck, Nele

    2014-01-01

    Simulation of heat transport has its applications in geothermal exploitation of aquifers and the analysis of temperature dependent chemical reactions. Under homogeneous conditions and in the absence of a regional hydraulic gradient, groundwater flow and heat transport from or to a well exhibit radial symmetry, and governing equations are reduced by one dimension (1D) which increases computational efficiency importantly. Solute transport codes can simulate heat transport and input parameters may be modified such that the Cartesian geometry can handle radial flow. In this article, SEAWAT is evaluated as simulator for heat transport under radial flow conditions. The 1971, 1D analytical solution of Gelhar and Collins is used to compare axisymmetric transport with retardation (i.e., as a result of thermal equilibrium between fluid and solid) and a large diffusion (conduction). It is shown that an axisymmetric simulation compares well with a fully three dimensional (3D) simulation of an aquifer thermal energy storage systems. The influence of grid discretization, solver parameters, and advection solution is illustrated. Because of the high diffusion to simulate conduction, convergence criterion for heat transport must be set much smaller (10(-10) ) than for solute transport (10(-6) ). Grid discretization should be considered carefully, in particular the subdivision of the screen interval. On the other hand, different methods to calculate the pumping or injection rate distribution over different nodes of a multilayer well lead to small differences only.

  20. SEAWAT-based simulation of axisymmetric heat transport.

    PubMed

    Vandenbohede, Alexander; Louwyck, Andy; Vlamynck, Nele

    2014-01-01

    Simulation of heat transport has its applications in geothermal exploitation of aquifers and the analysis of temperature dependent chemical reactions. Under homogeneous conditions and in the absence of a regional hydraulic gradient, groundwater flow and heat transport from or to a well exhibit radial symmetry, and governing equations are reduced by one dimension (1D) which increases computational efficiency importantly. Solute transport codes can simulate heat transport and input parameters may be modified such that the Cartesian geometry can handle radial flow. In this article, SEAWAT is evaluated as simulator for heat transport under radial flow conditions. The 1971, 1D analytical solution of Gelhar and Collins is used to compare axisymmetric transport with retardation (i.e., as a result of thermal equilibrium between fluid and solid) and a large diffusion (conduction). It is shown that an axisymmetric simulation compares well with a fully three dimensional (3D) simulation of an aquifer thermal energy storage systems. The influence of grid discretization, solver parameters, and advection solution is illustrated. Because of the high diffusion to simulate conduction, convergence criterion for heat transport must be set much smaller (10(-10) ) than for solute transport (10(-6) ). Grid discretization should be considered carefully, in particular the subdivision of the screen interval. On the other hand, different methods to calculate the pumping or injection rate distribution over different nodes of a multilayer well lead to small differences only. PMID:24571415

  1. 1D Scaling with Ablation for K-Shell Radiation from Stainless Steel Wire Arrays

    SciTech Connect

    Giuliani, J. L.; Thornhill, J. W.; Dasgupta, A.; Davis, J.; Clark, R. W.; Jones, B.; Cuneo, M.; Coverdale, C. A.; Deeney, C.

    2009-01-21

    A 1D Lagrangian magnetohydrodynamic z-pinch simulation code is extended to include wire ablation. The plasma transport coefficients are calibrated to reproduce the K-shell yields measured on the Z generator for three stainless steel arrays of diameter 55 mm and masses ranging from 1.8 to 2.7 mg. The resulting 1D scaling model is applied to a larger SS array (65 mm and 2.5 mg) on the refurbished Z machine. Simulation results predict a maximum K-shell yield of 77 kJ for an 82 kV charging voltage. This maximum drops to 42 kJ at 75 kV charging. Neglecting the ablation precursor leads to a {approx}10% change in the calculated yield.

  2. Membranes having aligned 1-D nanoparticles in a matrix layer for improved fluid separation

    DOEpatents

    Revanur, Ravindra; Lulevich, Valentin; Roh, Il Juhn; Klare, Jennifer E.; Kim, Sangil; Noy, Aleksandr; Bakajin, Olgica

    2015-12-22

    Membranes for fluid separation are disclosed. These membranes have a matrix layer sandwiched between an active layer and a porous support layer. The matrix layer includes 1-D nanoparticles that are vertically aligned in a porous polymer matrix, and which substantially extend through the matrix layer. The active layer provides species-specific transport, while the support layer provides mechanical support. A matrix layer of this type has favorable surface morphology for forming the active layer. Furthermore, the pores that form in the matrix layer tend to be smaller and more evenly distributed as a result of the presence of aligned 1-D nanoparticles. Improved performance of separation membranes of this type is attributed to these effects.

  3. 1D nanocrystals with precisely controlled dimensions, compositions, and architectures

    NASA Astrophysics Data System (ADS)

    Pang, Xinchang; He, Yanjie; Jung, Jaehan; Lin, Zhiqun

    2016-09-01

    The ability to synthesize a diverse spectrum of one-dimensional (1D) nanocrystals presents an enticing prospect for exploring nanoscale size- and shape-dependent properties. Here we report a general strategy to craft a variety of plain nanorods, core-shell nanorods, and nanotubes with precisely controlled dimensions and compositions by capitalizing on functional bottlebrush-like block copolymers with well-defined structures and narrow molecular weight distributions as nanoreactors. These cylindrical unimolecular nanoreactors enable a high degree of control over the size, shape, architecture, surface chemistry, and properties of 1D nanocrystals. We demonstrate the synthesis of metallic, ferroelectric, upconversion, semiconducting, and thermoelectric 1D nanocrystals, among others, as well as combinations thereof.

  4. The GIRAFFE Archive: 1D and 3D Spectra

    NASA Astrophysics Data System (ADS)

    Royer, F.; Jégouzo, I.; Tajahmady, F.; Normand, J.; Chilingarian, I.

    2013-10-01

    The GIRAFFE Archive (http://giraffe-archive.obspm.fr) contains the reduced spectra observed with the intermediate and high resolution multi-fiber spectrograph installed at VLT/UT2 (ESO). In its multi-object configuration and the different integral field unit configurations, GIRAFFE produces 1D spectra and 3D spectra. We present here the status of the archive and the different functionalities to select and download both 1D and 3D data products, as well as the present content. The two collections are available in the VO: the 1D spectra (summed in the case of integral field observations) and the 3D field observations. These latter products can be explored using the VO Paris Euro3D Client (http://voplus.obspm.fr/ chil/Euro3D).

  5. Pitch-based pattern splitting for 1D layout

    NASA Astrophysics Data System (ADS)

    Nakayama, Ryo; Ishii, Hiroyuki; Mikami, Koji; Tsujita, Koichiro; Yaegashi, Hidetami; Oyama, Kenichi; Smayling, Michael C.; Axelrad, Valery

    2015-07-01

    The pattern splitting algorithm for 1D Gridded-Design-Rules layout (1D layout) for sub-10 nm node logic devices is shown. It is performed with integer linear programming (ILP) based on the conflict graph created from a grid map for each designated pitch. The relation between the number of times for patterning and the minimum pitch is shown systematically with a sample pattern of contact layer for each node. From the result, the number of times for patterning for 1D layout is fewer than that for conventional 2D layout. Moreover, an experimental result including SMO and total integrated process with hole repair technique is presented with the sample pattern of contact layer whose pattern density is relatively high among critical layers (fin, gate, local interconnect, contact, and metal).

  6. 1D nanocrystals with precisely controlled dimensions, compositions, and architectures.

    PubMed

    Pang, Xinchang; He, Yanjie; Jung, Jaehan; Lin, Zhiqun

    2016-09-16

    The ability to synthesize a diverse spectrum of one-dimensional (1D) nanocrystals presents an enticing prospect for exploring nanoscale size- and shape-dependent properties. Here we report a general strategy to craft a variety of plain nanorods, core-shell nanorods, and nanotubes with precisely controlled dimensions and compositions by capitalizing on functional bottlebrush-like block copolymers with well-defined structures and narrow molecular weight distributions as nanoreactors. These cylindrical unimolecular nanoreactors enable a high degree of control over the size, shape, architecture, surface chemistry, and properties of 1D nanocrystals. We demonstrate the synthesis of metallic, ferroelectric, upconversion, semiconducting, and thermoelectric 1D nanocrystals, among others, as well as combinations thereof. PMID:27634531

  7. Flexible Photodetectors Based on 1D Inorganic Nanostructures

    PubMed Central

    Lou, Zheng

    2015-01-01

    Flexible photodetectors with excellent flexibility, high mechanical stability and good detectivity, have attracted great research interest in recent years. 1D inorganic nanostructures provide a number of opportunities and capabilities for use in flexible photodetectors as they have unique geometry, good transparency, outstanding mechanical flexibility, and excellent electronic/optoelectronic properties. This article offers a comprehensive review of several types of flexible photodetectors based on 1D nanostructures from the past ten years, including flexible ultraviolet, visible, and infrared photodetectors. High‐performance organic‐inorganic hybrid photodetectors, as well as devices with 1D nanowire (NW) arrays, are also reviewed. Finally, new concepts of flexible photodetectors including piezophototronic, stretchable and self‐powered photodetectors are examined to showcase the future research in this exciting field. PMID:27774404

  8. GIS-BASED 1-D DIFFUSIVE WAVE OVERLAND FLOW MODEL

    SciTech Connect

    KALYANAPU, ALFRED; MCPHERSON, TIMOTHY N.; BURIAN, STEVEN J.

    2007-01-17

    This paper presents a GIS-based 1-d distributed overland flow model and summarizes an application to simulate a flood event. The model estimates infiltration using the Green-Ampt approach and routes excess rainfall using the 1-d diffusive wave approximation. The model was designed to use readily available topographic, soils, and land use/land cover data and rainfall predictions from a meteorological model. An assessment of model performance was performed for a small catchment and a large watershed, both in urban environments. Simulated runoff hydrographs were compared to observations for a selected set of validation events. Results confirmed the model provides reasonable predictions in a short period of time.

  9. Observation of Dynamical Fermionization in 1D Bose Gases

    NASA Astrophysics Data System (ADS)

    Malvania, Neel; Xia, Lin; Xu, Wei; Wilson, Joshua M.; Zundel, Laura A.; Rigol, Marcos; Weiss, David S.

    2016-05-01

    The momentum distribution of a harmonically trapped 1D Bose gases in the Tonks-Girardeau limit is expected to undergo dynamical fermionization. That is, after the harmonic trap is suddenly turned off, the momentum distribution steadily transforms into that of an ideal Fermi gas in the same initial trap. We measure 1D momentum distributions at variable times after such a quench, and observe the predicted dynamical fermionization. In addition to working in the strong coupling limit, we also perform the experiment with intermediate coupling, where theoretical calculations are more challenging.

  10. 1D GAS-DYNAMIC SIMULATION OF SHOCK-WAVE PROCESSES VIA INTERNET

    SciTech Connect

    Khishchenko, K. V.; Levashov, P. R.; Povarnitsyn, M. E.; Zakharenkov, A. S.

    2009-12-28

    We present a Web-interface for 1D simulation of different shock-wave experiments. The choosing of initial parameters, the modeling itself and output data treatment can be made directly via the Internet. The interface is based upon the expert system on shock-wave data and equations of state and contains both the Eulerian and Lagrangian Godunov hydrocodes. The availability of equations of state for a broad set of substances makes this system a useful tool for planning and interpretation of shock-wave experiments. As an example of simulation with the system, results of modeling of multistep shock loading of potassium between polytetrafluoroethylene and stainless steel plates are presented in comparison with experimental data from Shakhray et al.(2005).

  11. Numerical Modeling of Imploding Plasma liners Using the 1D Radiation-Hydrodynamics Code HELIOS

    NASA Astrophysics Data System (ADS)

    Davis, J. S.; Hanna, D. S.; Awe, T. J.; Hsu, S. C.; Stanic, M.; Cassibry, J. T.; Macfarlane, J. J.

    2010-11-01

    The Plasma Liner Experiment (PLX) is attempting to form imploding plasma liners to reach 0.1 Mbar upon stagnation, via 30--60 spherically convergent plasma jets. PLX is partly motivated by the desire to develop a standoff driver for magneto-inertial fusion. The liner density, atomic makeup, and implosion velocity will help determine the maximum pressure that can be achieved. This work focuses on exploring the effects of atomic physics and radiation on the 1D liner implosion and stagnation dynamics. For this reason, we are using Prism Computational Science's 1D Lagrangian rad-hydro code HELIOS, which has both equation of state (EOS) table-lookup and detailed configuration accounting (DCA) atomic physics modeling. By comparing a series of PLX-relevant cases proceeding from ideal gas, to EOS tables, to DCA treatments, we aim to identify how and when atomic physics effects are important for determining the peak achievable stagnation pressures. In addition, we present verification test results as well as brief comparisons to results obtained with RAVEN (1D radiation-MHD) and SPHC (smoothed particle hydrodynamics).

  12. Simulation of Field-Scale Non-Fickian Plumes With Spatiotemporal Fractional Advection- Dispersion Equations

    NASA Astrophysics Data System (ADS)

    Benson, D. A.; Zhang, Y.

    2006-12-01

    Conservative solute transport through natural media is typically "anomalous" or non-Fickian. The anomalous transport may be characterized by faster than linear growth of the centered second moment, or non-Gaussian leading or trailing edges of a plume emanating from a point source. These characteristics develop because of non-local dependence on either past (time) or far upstream (space) concentrations. Non-local equations developed to describe anomalous dispersion usually focus on constant transport parameters and/or independence of the transport on space dimension. These simplifications have been useful for fitting simple transport processes, such as laboratory column tests or 1-D projections of field data. However, they may be insufficient for real field settings, where direction-dependent depositional processes and nonstationary heterogeneity can occur. We develop a generalized, multi-dimensional, spatiotemporal fractional advection- dispersion equation (fADE) with variable parameters to characterize regional-scale anomalous dispersion processes including trapping in immobile zones and/or super-Fickian rapid transport. A Lagrangian numerical model of the space-time fractional transport equation is developed in which solute particles can disperse in both space and time, depending on the medium heterogeneity properties, such as the connectivity and statistical distributions of high versus low-permeability deposits. In the generalized fADE, the range of the order of fractional time derivative is (0 2], representing a wide range of possible trapping behavior. The extension of the order to the range (1 2] is novel to transport theory. We apply the numerical model in 1-D and 2-D to the MADE site tritium plumes, and results indicate that this method can capture the main behaviors of realistic plumes, including local variations of spreading, direction-dependent scaling rates, and arbitrary rapid transport along preferential flow paths. Since the governing equation

  13. Non-cooperative Brownian donkeys: A solvable 1D model

    NASA Astrophysics Data System (ADS)

    Jiménez de Cisneros, B.; Reimann, P.; Parrondo, J. M. R.

    2003-12-01

    A paradigmatic 1D model for Brownian motion in a spatially symmetric, periodic system is tackled analytically. Upon application of an external static force F the system's response is an average current which is positive for F < 0 and negative for F > 0 (absolute negative mobility). Under suitable conditions, the system approaches 100% efficiency when working against the external force F.

  14. 1D design style implications for mask making and CEBL

    NASA Astrophysics Data System (ADS)

    Smayling, Michael C.

    2013-09-01

    At advanced nodes, CMOS logic is being designed in a highly regular design style because of the resolution limitations of optical lithography equipment. Logic and memory layouts using 1D Gridded Design Rules (GDR) have been demonstrated to nodes beyond 12nm.[1-4] Smaller nodes will require the same regular layout style but with multiple patterning for critical layers. One of the significant advantages of 1D GDR is the ease of splitting layouts into lines and cuts. A lines and cuts approach has been used to achieve good pattern fidelity and process margin to below 12nm.[4] Line scaling with excellent line-edge roughness (LER) has been demonstrated with self-aligned spacer processing.[5] This change in design style has important implications for mask making: • The complexity of the masks will be greatly reduced from what would be required for 2D designs with very complex OPC or inverse lithography corrections. • The number of masks will initially increase, as for conventional multiple patterning. But in the case of 1D design, there are future options for mask count reduction. • The line masks will remain simple, with little or no OPC, at pitches (1x) above 80nm. This provides an excellent opportunity for continual improvement of line CD and LER. The line pattern will be processed through a self-aligned pitch division sequence to divide pitch by 2 or by 4. • The cut masks can be done with "simple OPC" as demonstrated to beyond 12nm.[6] Multiple simple cut masks may be required at advanced nodes. "Coloring" has been demonstrated to below 12nm for two colors and to 8nm for three colors. • Cut/hole masks will eventually be replaced by e-beam direct write using complementary e-beam lithography (CEBL).[7-11] This transition is gated by the availability of multiple column e-beam systems with throughput adequate for high- volume manufacturing. A brief description of 1D and 2D design styles will be presented, followed by examples of 1D layouts. Mask complexity for 1

  15. Effect of low transverse magnetic field on the confinement strength in a quasi-1D wire

    SciTech Connect

    Kumar, Sanjeev; Thomas, K. J.; Smith, L. W.; Farrer, I.; Ritchie, D. A.; Jones, G. A. C.; Griffiths, J.; Pepper, M.

    2013-12-04

    Transport measurements in a quasi-one dimensional (1D) quantum wire are reported in the presence of low transverse magnetic field. Differential conductance shows weak quantised plateaus when the 2D electrons are squeezed electrostatically. Application of a small transverse magnetic field (0.2T) enhances the overall degree of quantisation due to the formation of magneto-electric subbands. The results show the role of magnetic field to fine tune the confinement strength in low density wires when interaction gives rise to double row formation.

  16. Conservational PDF Equations of Turbulence

    NASA Technical Reports Server (NTRS)

    Shih, Tsan-Hsing; Liu, Nan-Suey

    2010-01-01

    Recently we have revisited the traditional probability density function (PDF) equations for the velocity and species in turbulent incompressible flows. They are all unclosed due to the appearance of various conditional means which are modeled empirically. However, we have observed that it is possible to establish a closed velocity PDF equation and a closed joint velocity and species PDF equation through conditions derived from the integral form of the Navier-Stokes equations. Although, in theory, the resulted PDF equations are neither general nor unique, they nevertheless lead to the exact transport equations for the first moment as well as all higher order moments. We refer these PDF equations as the conservational PDF equations. This observation is worth further exploration for its validity and CFD application

  17. Penetration equations

    SciTech Connect

    Young, C.W.

    1997-10-01

    In 1967, Sandia National Laboratories published empirical equations to predict penetration into natural earth materials and concrete. Since that time there have been several small changes to the basic equations, and several more additions to the overall technique for predicting penetration into soil, rock, concrete, ice, and frozen soil. The most recent update to the equations was published in 1988, and since that time there have been changes in the equations to better match the expanding data base, especially in concrete penetration. This is a standalone report documenting the latest version of the Young/Sandia penetration equations and related analytical techniques to predict penetration into natural earth materials and concrete. 11 refs., 6 tabs.

  18. The Effective Equation Method

    NASA Astrophysics Data System (ADS)

    Kuksin, Sergei; Maiocchi, Alberto

    In this chapter we present a general method of constructing the effective equation which describes the behavior of small-amplitude solutions for a nonlinear PDE in finite volume, provided that the linear part of the equation is a hamiltonian system with a pure imaginary discrete spectrum. The effective equation is obtained by retaining only the resonant terms of the nonlinearity (which may be hamiltonian, or may be not); the assertion that it describes the limiting behavior of small-amplitude solutions is a rigorous mathematical theorem. In particular, the method applies to the three- and four-wave systems. We demonstrate that different possible types of energy transport are covered by this method, depending on whether the set of resonances splits into finite clusters (this happens, e.g. in case of the Charney-Hasegawa-Mima equation), or is connected (this happens, e.g. in the case of the NLS equation if the space-dimension is at least two). For equations of the first type the energy transition to high frequencies does not hold, while for equations of the second type it may take place. Our method applies to various weakly nonlinear wave systems, appearing in plasma, meteorology and oceanography.

  19. Modeling of impurity spectroscopy in the divertor and SOL of DIII-D using the 1D multifluid model NEWT1D

    SciTech Connect

    West, W.P.; Evans, T.E.; Brooks, N.H.

    1996-10-01

    NEWT1D, a one dimensional multifluid model of the scrape-off layer and divertor plasma, has been used to model the plasma including the distribution of carbon ionization states in the SOL and divertor of ELMing H-mode at two injected power levels in DIII-D. Comparison of the code predictions to the measured divertor and scrape-off layer (SOL) plasma density and temperature shows good agreement. Comparison of the predicted line emissions to the spectroscopic data suggests that physically sputtered carbon from the strike point is not transported up the flux tube; a distributed source of carbon a few centimeters up the flux tube is required to achieve reasonable agreement.

  20. Phase diagram of a bulk 1d lattice Coulomb gas

    NASA Astrophysics Data System (ADS)

    Démery, V.; Monsarrat, R.; Dean, D. S.; Podgornik, R.

    2016-01-01

    The exact solution, via transfer matrix, of the simple one-dimensional lattice Coulomb gas (1d LCG) model can reproduce peculiar features of ionic liquid capacitors, such as overscreening, layering, and camel- and bell-shaped capacitance curves. Using the same transfer matrix method, we now compute the bulk properties of the 1d LCG in the constant voltage ensemble. We unveil a phase diagram with rich structure exhibiting low-density disordered and high-density ordered phases, separated by a first-order phase transition at low temperature; the solid state at full packing can be ordered or not, depending on the temperature. This phase diagram, which is strikingly similar to its three-dimensional counterpart, also sheds light on the behaviour of the confined system.

  1. 1D Josephson quantum interference grids: diffraction patterns and dynamics

    NASA Astrophysics Data System (ADS)

    Lucci, M.; Badoni, D.; Corato, V.; Merlo, V.; Ottaviani, I.; Salina, G.; Cirillo, M.; Ustinov, A. V.; Winkler, D.

    2016-02-01

    We investigate the magnetic response of transmission lines with embedded Josephson junctions and thus generating a 1D underdamped array. The measured multi-junction interference patterns are compared with the theoretical predictions for Josephson supercurrent modulations when an external magnetic field couples both to the inter-junction loops and to the junctions themselves. The results provide a striking example of the analogy between Josephson phase modulation and 1D optical diffraction grid. The Fiske resonances in the current-voltage characteristics with voltage spacing {Φ0}≤ft(\\frac{{\\bar{c}}}{2L}\\right) , where L is the total physical length of the array, {Φ0} the magnetic flux quantum and \\bar{c} the speed of light in the transmission line, demonstrate that the discrete line supports stable dynamic patterns generated by the ac Josephson effect interacting with the cavity modes of the line.

  2. Constructing 3D interaction maps from 1D epigenomes

    PubMed Central

    Zhu, Yun; Chen, Zhao; Zhang, Kai; Wang, Mengchi; Medovoy, David; Whitaker, John W.; Ding, Bo; Li, Nan; Zheng, Lina; Wang, Wei

    2016-01-01

    The human genome is tightly packaged into chromatin whose functional output depends on both one-dimensional (1D) local chromatin states and three-dimensional (3D) genome organization. Currently, chromatin modifications and 3D genome organization are measured by distinct assays. An emerging question is whether it is possible to deduce 3D interactions by integrative analysis of 1D epigenomic data and associate 3D contacts to functionality of the interacting loci. Here we present EpiTensor, an algorithm to identify 3D spatial associations within topologically associating domains (TADs) from 1D maps of histone modifications, chromatin accessibility and RNA-seq. We demonstrate that active promoter–promoter, promoter–enhancer and enhancer–enhancer associations identified by EpiTensor are highly concordant with those detected by Hi-C, ChIA-PET and eQTL analyses at 200 bp resolution. Moreover, EpiTensor has identified a set of interaction hotspots, characterized by higher chromatin and transcriptional activity as well as enriched TF and ncRNA binding across diverse cell types, which may be critical for stabilizing the local 3D interactions. PMID:26960733

  3. Constructing 3D interaction maps from 1D epigenomes.

    PubMed

    Zhu, Yun; Chen, Zhao; Zhang, Kai; Wang, Mengchi; Medovoy, David; Whitaker, John W; Ding, Bo; Li, Nan; Zheng, Lina; Wang, Wei

    2016-01-01

    The human genome is tightly packaged into chromatin whose functional output depends on both one-dimensional (1D) local chromatin states and three-dimensional (3D) genome organization. Currently, chromatin modifications and 3D genome organization are measured by distinct assays. An emerging question is whether it is possible to deduce 3D interactions by integrative analysis of 1D epigenomic data and associate 3D contacts to functionality of the interacting loci. Here we present EpiTensor, an algorithm to identify 3D spatial associations within topologically associating domains (TADs) from 1D maps of histone modifications, chromatin accessibility and RNA-seq. We demonstrate that active promoter-promoter, promoter-enhancer and enhancer-enhancer associations identified by EpiTensor are highly concordant with those detected by Hi-C, ChIA-PET and eQTL analyses at 200 bp resolution. Moreover, EpiTensor has identified a set of interaction hotspots, characterized by higher chromatin and transcriptional activity as well as enriched TF and ncRNA binding across diverse cell types, which may be critical for stabilizing the local 3D interactions. PMID:26960733

  4. Development of 1D Liner Compression Code for IDL

    NASA Astrophysics Data System (ADS)

    Shimazu, Akihisa; Slough, John; Pancotti, Anthony

    2015-11-01

    A 1D liner compression code is developed to model liner implosion dynamics in the Inductively Driven Liner Experiment (IDL) where FRC plasmoid is compressed via inductively-driven metal liners. The driver circuit, magnetic field, joule heating, and liner dynamics calculations are performed at each time step in sequence to couple these effects in the code. To obtain more realistic magnetic field results for a given drive coil geometry, 2D and 3D effects are incorporated into the 1D field calculation through use of correction factor table lookup approach. Commercial low-frequency electromagnetic fields solver, ANSYS Maxwell 3D, is used to solve the magnetic field profile for static liner condition at various liner radius in order to derive correction factors for the 1D field calculation in the code. The liner dynamics results from the code is verified to be in good agreement with the results from commercial explicit dynamics solver, ANSYS Explicit Dynamics, and previous liner experiment. The developed code is used to optimize the capacitor bank and driver coil design for better energy transfer and coupling. FRC gain calculations are also performed using the liner compression data from the code for the conceptual design of the reactor sized system for fusion energy gains.

  5. Quantum Diffusion on Molecular Tubes: Universal Scaling of the 1D to 2D Transition

    NASA Astrophysics Data System (ADS)

    Chuang, Chern; Lee, Chee Kong; Moix, Jeremy M.; Knoester, Jasper; Cao, Jianshu

    2016-05-01

    The transport properties of disordered systems are known to depend critically on dimensionality. We study the diffusion coefficient of a quantum particle confined to a lattice on the surface of a tube, where it scales between the 1D and 2D limits. It is found that the scaling relation is universal and independent of the temperature, disorder, and noise parameters, and the essential order parameter is the ratio between the localization length in 2D and the circumference of the tube. Phenomenological and quantitative expressions for transport properties as functions of disorder and noise are obtained and applied to real systems: In the natural chlorosomes found in light-harvesting bacteria the exciton transfer dynamics is predicted to be in the 2D limit, whereas a family of synthetic molecular aggregates is found to be in the homogeneous limit and is independent of dimensionality.

  6. Quantum Diffusion on Molecular Tubes: Universal Scaling of the 1D to 2D Transition.

    PubMed

    Chuang, Chern; Lee, Chee Kong; Moix, Jeremy M; Knoester, Jasper; Cao, Jianshu

    2016-05-13

    The transport properties of disordered systems are known to depend critically on dimensionality. We study the diffusion coefficient of a quantum particle confined to a lattice on the surface of a tube, where it scales between the 1D and 2D limits. It is found that the scaling relation is universal and independent of the temperature, disorder, and noise parameters, and the essential order parameter is the ratio between the localization length in 2D and the circumference of the tube. Phenomenological and quantitative expressions for transport properties as functions of disorder and noise are obtained and applied to real systems: In the natural chlorosomes found in light-harvesting bacteria the exciton transfer dynamics is predicted to be in the 2D limit, whereas a family of synthetic molecular aggregates is found to be in the homogeneous limit and is independent of dimensionality. PMID:27232033

  7. Adjoint Method and Predictive Control for 1-D Flow in NASA Ames 11-Foot Transonic Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan; Ardema, Mark

    2006-01-01

    This paper describes a modeling method and a new optimal control approach to investigate a Mach number control problem for the NASA Ames 11-Foot Transonic Wind Tunnel. The flow in the wind tunnel is modeled by the 1-D unsteady Euler equations whose boundary conditions prescribe a controlling action by a compressor. The boundary control inputs to the compressor are in turn controlled by a drive motor system and an inlet guide vane system whose dynamics are modeled by ordinary differential equations. The resulting Euler equations are thus coupled to the ordinary differential equations via the boundary conditions. Optimality conditions are established by an adjoint method and are used to develop a model predictive linear-quadratic optimal control for regulating the Mach number due to a test model disturbance during a continuous pitch

  8. Tctex1d2 associates with short-rib polydactyly syndrome proteins and is required for ciliogenesis

    PubMed Central

    Gholkar, Ankur A.; Senese, Silvia; Lo, Yu-Chen; Capri, Joseph; Deardorff, William J; Dharmarajan, Harish; Contreras, Ely; Hodara, Emmanuelle; Whitelegge, Julian P; Jackson, Peter K; Torres, Jorge Z

    2015-01-01

    Short-rib polydactyly syndromes (SRPS) arise from mutations in genes involved in retrograde intraflagellar transport (IFT) and basal body homeostasis, which are critical for cilia assembly and function. Recently, mutations in WDR34 or WDR60 (candidate dynein intermediate chains) were identified in SRPS. We have identified and characterized Tctex1d2, which associates with Wdr34, Wdr60 and other dynein complex 1 and 2 subunits. Tctex1d2 and Wdr60 localize to the base of the cilium and their depletion causes defects in ciliogenesis. We propose that Tctex1d2 is a novel dynein light chain important for trafficking to the cilium and potentially retrograde IFT and is a new molecular link to understanding SRPS pathology. PMID:25830415

  9. Tctex1d2 associates with short-rib polydactyly syndrome proteins and is required for ciliogenesis.

    PubMed

    Gholkar, Ankur A; Senese, Silvia; Lo, Yu-Chen; Capri, Joseph; Deardorff, William J; Dharmarajan, Harish; Contreras, Ely; Hodara, Emmanuelle; Whitelegge, Julian P; Jackson, Peter K; Torres, Jorge Z

    2015-01-01

    Short-rib polydactyly syndromes (SRPS) arise from mutations in genes involved in retrograde intraflagellar transport (IFT) and basal body homeostasis, which are critical for cilia assembly and function. Recently, mutations in WDR34 or WDR60 (candidate dynein intermediate chains) were identified in SRPS. We have identified and characterized Tctex1d2, which associates with Wdr34, Wdr60 and other dynein complex 1 and 2 subunits. Tctex1d2 and Wdr60 localize to the base of the cilium and their depletion causes defects in ciliogenesis. We propose that Tctex1d2 is a novel dynein light chain important for trafficking to the cilium and potentially retrograde IFT and is a new molecular link to understanding SRPS pathology.

  10. Derivation and Solution of Multifrequency Radiation Diffusion Equations for Homogeneous Refractive Lossy Media

    SciTech Connect

    Shestakov, A I; Vignes, R M; Stolken, J S

    2010-01-05

    Starting from the radiation transport equation for homogeneous, refractive lossy media, we derive the corresponding time-dependent multifrequency diffusion equations. Zeroth and first moments of the transport equation couple the energy density, flux and pressure tensor. The system is closed by neglecting the temporal derivative of the flux and replacing the pressure tensor by its diagonal analogue. The system is coupled to a diffusion equation for the matter temperature. We are interested in modeling annealing of silica (SiO{sub 2}). We derive boundary conditions at a planar air-silica interface taking account of reflectivities. The spectral dimension is discretized into a finite number of intervals leading to a system of multigroup diffusion equations. Three simulations are presented. One models cooling of a silica slab, initially at 2500 K, for 10 s. The other two are 1D and 2D simulations of irradiating silica with a CO{sub 2} laser, {lambda} = 10.59 {micro}m. In 2D, we anneal a disk (radius = 0.4, thickness = 0.4 cm) with a laser, Gaussian profile (r{sub 0} = 0.5 mm for 1/e decay).

  11. A Course in Transport Phenomena in Multicomponent, Multiphase, Reacting Systems.

    ERIC Educational Resources Information Center

    Carbonell, R. G.; Whitaker, S.

    1978-01-01

    This course concentrates on a rigorous development of the multicomponent transport equations, boundary conditions at phase interfaces, and volume-averaged transport equations for multiphase reacting systems. (BB)

  12. Extended-Range Ultrarefractive 1D Photonic Crystal Prisms

    NASA Technical Reports Server (NTRS)

    Ting, David Z.

    2007-01-01

    A proposal has been made to exploit the special wavelength-dispersive characteristics of devices of the type described in One-Dimensional Photonic Crystal Superprisms (NPO-30232) NASA Tech Briefs, Vol. 29, No. 4 (April 2005), page 10a. A photonic crystal is an optical component that has a periodic structure comprising two dielectric materials with high dielectric contrast (e.g., a semiconductor and air), with geometrical feature sizes comparable to or smaller than light wavelengths of interest. Experimental superprisms have been realized as photonic crystals having three-dimensional (3D) structures comprising regions of amorphous Si alternating with regions of SiO2, fabricated in a complex process that included sputtering. A photonic crystal of the type to be exploited according to the present proposal is said to be one-dimensional (1D) because its contrasting dielectric materials would be stacked in parallel planar layers; in other words, there would be spatial periodicity in one dimension only. The processes of designing and fabricating 1D photonic crystal superprisms would be simpler and, hence, would cost less than do those for 3D photonic crystal superprisms. As in 3D structures, 1D photonic crystals may be used in applications such as wavelength-division multiplexing. In the extended-range configuration, it is also suitable for spectrometry applications. As an engineered structure or artificially engineered material, a photonic crystal can exhibit optical properties not commonly found in natural substances. Prior research had revealed several classes of photonic crystal structures for which the propagation of electromagnetic radiation is forbidden in certain frequency ranges, denoted photonic bandgaps. It had also been found that in narrow frequency bands just outside the photonic bandgaps, the angular wavelength dispersion of electromagnetic waves propagating in photonic crystal superprisms is much stronger than is the angular wavelength dispersion obtained

  13. Non-linearity in Bayesian 1-D magnetotelluric inversion

    NASA Astrophysics Data System (ADS)

    Guo, Rongwen; Dosso, Stan E.; Liu, Jianxin; Dettmer, Jan; Tong, Xiaozhong

    2011-05-01

    This paper applies a Bayesian approach to examine non-linearity for the 1-D magnetotelluric (MT) inverse problem. In a Bayesian formulation the posterior probability density (PPD), which combines data and prior information, is interpreted in terms of parameter estimates and uncertainties, which requires optimizing and integrating the PPD. Much work on 1-D MT inversion has been based on (approximate) linearized solutions, but more recently fully non-linear (numerical) approaches have been applied. This paper directly compares results of linearized and non-linear uncertainty estimation for 1-D MT inversion; to do so, advanced methods for both approaches are applied. In the non-linear formulation used here, numerical optimization is carried out using an adaptive-hybrid algorithm. Numerical integration applies Metropolis-Hastings sampling, rotated to a principal-component parameter space for efficient sampling of correlated parameters, and employing non-unity sampling temperatures to ensure global sampling. Since appropriate model parametrizations are generally not known a priori, both under- and overparametrized approaches are considered. For underparametrization, the Bayesian information criterion is applied to determine the number of layers consistent with the resolving power of the data. For overparametrization, prior information is included which favours simple structure in a manner similar to regularized inversion. The data variance and/or trade-off parameter regulating data and prior information are treated in several ways, including applying fixed optimal estimates (an empirical Bayesian approach) or including them as hyperparameters in the sampling (hierarchical Bayesian). The latter approach has the benefit of accounting for the uncertainty in the hyperparameters in estimating model parameter uncertainties. Non-linear and linearized inversion results are compared for synthetic test cases and for the measured COPROD1 MT data by considering marginal probability

  14. Viscous behavior in a quasi-1D fractal cluster glass.

    PubMed

    Etzkorn, S J; Hibbs, Wendy; Miller, Joel S; Epstein, A J

    2002-11-11

    The spin glass transition of a quasi-1D organic-based magnet ([MnTPP][TCNE]) is explored using both ac and dc measurements. A scaling analysis of the ac susceptibility shows a spin glass transition near 4 K, with a viscous decay of the thermoremanent magnetization recorded above 4 K. We propose an extension to a fractal cluster model of spin glasses that determines the dimension of the spin clusters (D) ranging from approximately 0.8 to over 1.5 as the glass transition is approached. Long-range dipolar interactions are suggested as the origin of this low value for the apparent lower critical dimension.

  15. Practical variational tomography for critical 1D systems

    NASA Astrophysics Data System (ADS)

    Lee, Jong Yeon; Landon-Cardinal, Olivier

    2015-03-01

    We further investigate a recently introduced efficient quantum state reconstruction procedure targeted to states well-approximated by the multi-scale entanglement renormalization ansatz (MERA). First, we introduce an improved optimization scheme that can be easily generalized for MERA states with larger bond dimension. Second, we provide a detailed analysis of the error propagation and quantify how it affects the distance between the experimental state and the reconstructed state. Third, we explain how to bound this distance using local data, providing an efficient scalable certification method. Fourth, we examine the performance of MERA tomography on the ground states of several 1D critical models.

  16. Nonlocal Order Parameters for the 1D Hubbard Model

    NASA Astrophysics Data System (ADS)

    Montorsi, Arianna; Roncaglia, Marco

    2012-12-01

    We characterize the Mott-insulator and Luther-Emery phases of the 1D Hubbard model through correlators that measure the parity of spin and charge strings along the chain. These nonlocal quantities order in the corresponding gapped phases and vanish at the critical point Uc=0, thus configuring as hidden order parameters. The Mott insulator consists of bound doublon-holon pairs, which in the Luther-Emery phase turn into electron pairs with opposite spins, both unbinding at Uc. The behavior of the parity correlators is captured by an effective free spinless fermion model.

  17. Coherent thermal conductance of 1-D photonic crystals

    NASA Astrophysics Data System (ADS)

    Tschikin, Maria; Ben-Abdallah, Philippe; Biehs, Svend-Age

    2012-10-01

    We present an exact calculation of coherent thermal conductance in 1-D multilayer photonic crystals using the S-matrix method. In particular, we study the thermal conductance in a bilayer structure of Si/vacuum or Al2O3/vacuum slabs by means of the exact radiative heat flux expression. Based on the results obtained for the Al2O3/vacuum structure we show by comparison with previous works that the material losses and (localized) surface modes supported by the inner layers play a fundamental role and cannot be omitted in the definition of thermal conductance. Our results could have significant implications in the conception of efficient thermal barriers.

  18. Universal low-energy physics in 1D strongly repulsive multi-component Fermi gases

    NASA Astrophysics Data System (ADS)

    Jiang, Yuzhu; He, Peng; Guan, Xi-Wen

    2016-04-01

    It has been shown (Yang and You 2011 Chin. Phys. Lett. 28 020503) that at zero temperature the ground state of the one-dimensional (1D) w-component Fermi gas coincides with that of the spinless Bose gas in the limit ω \\to ∞ . This behavior was experimentally evidenced through quasi-1D tightly trapping ultracold 173Yb atoms in a recent paper (Pagano et al 2014 Nat. Phys. 10 198). However, understanding of low-temperature behavior of Fermi gases with a repulsive interaction requires spin-charge separated conformal field theories of an effective Tomonaga-Luttinger liquid and an antiferromagnetic SU(w) Heisenberg spin chain. Here we analytically derive universal thermodynamics of 1D strongly repulsive fermionic gases with SU(w) symmetry via the Yang-Yang thermodynamic Bethe ansatz method. The analytical free energy and magnetic properties of the systems at low temperature in a weak magnetic field are obtained through the Wiener-Hopf method. In particular, the free energy essentially manifests the spin-charge separated conformal field theories for high-symmetry systems with arbitrary repulsive interaction strength. We also find that the sound velocity of the Fermi gases in the large w limit coincides with that for the spinless Bose gas, whereas the spin velocity vanishes quickly as w becomes large. This indicates strong suppression of the Fermi exclusion statistics by the commutativity feature among the w-component fermions with different spin states in the Tomonaga-Luttinger liquid phase. Moreover, the equations of state and critical behavior of physical quantities at finite temperature are analytically derived in terms of the polylogarithm functions in the quantum critical region.

  19. Co-crystal engineering: a novel method to obtain one-dimensional (1D) carbon nanocrystals of corannulene-fullerene by a solution process.

    PubMed

    Wang, Yu; Li, Yang; Zhu, Weigang; Liu, Jinyu; Zhang, Xiaotao; Li, Rongjin; Zhen, Yonggang; Dong, Huanli; Hu, Wenping

    2016-08-11

    In this study, 1D nanocrystals composed of C60 and corannulene were synthesized efficiently through cocrystallization by a solution process. These 1D nanocrystals display high electron transport characteristics of up to 0.11 cm(2) V(-1) s(-1) and good photoresponse of 0.09 A W(-1), indicating their potential applications in optoelectronics. The results suggest that co-crystal engineering provides a novel strategy for the rational design of new carbon-based crystalline nanomaterials. PMID:27480136

  20. Leptin Reduces the Expression and Increases the Phosphorylation of the Negative Regulators of GLUT4 Traffic TBC1D1 and TBC1D4 in Muscle of ob/ob Mice

    PubMed Central

    Sáinz, Neira; Rodríguez, Amaia; Catalán, Victoria; Becerril, Sara; Ramírez, Beatriz; Lancha, Andoni; Burgos-Ramos, Emma; Gómez-Ambrosi, Javier; Frühbeck, Gema

    2012-01-01

    Leptin improves insulin sensitivity in skeletal muscle. Our goal was to determine whether proteins controlling GLUT4 traffic are altered by leptin deficiency and in vivo leptin administration in skeletal muscle of wild type and ob/ob mice. Leptin-deficient ob/ob mice were divided in three groups: control, leptin-treated (1 mg/kg/d) and leptin pair-fed ob/ob mice. Microarray analysis revealed that 1,546 and 1,127 genes were regulated by leptin deficiency and leptin treatment, respectively. Among these, we identified 24 genes involved in intracellular vesicle-mediated transport in ob/ob mice. TBC1 domain family, member 1 (Tbc1d1), a negative regulator of GLUT4 translocation, was up-regulated (P = 0.001) in ob/ob mice as compared to wild types. Importantly, leptin treatment reduced the transcript levels of Tbc1d1 (P<0.001) and Tbc1d4 (P = 0.004) in the leptin-treated ob/ob as compared to pair-fed ob/ob animals. In addition, phosphorylation levels of TBC1D1 and TBC1D4 were enhanced in leptin-treated ob/ob as compared to control ob/ob (P = 0.015 and P = 0.023, respectively) and pair-fed ob/ob (P = 0.036 and P = 0.034, respectively) mice. Despite similar GLUT4 protein expression in wild type and ob/ob groups a different immunolocalization of this protein was evidenced in muscle sections. Leptin treatment increased GLUT4 immunoreactivity in gastrocnemius and extensor digitorum longus sections of leptin-treated ob/ob mice. Moreover, GLUT4 protein detected in immunoprecipitates from TBC1D4 was reduced by leptin replacement compared to control ob/ob (P = 0.013) and pair-fed ob/ob (P = 0.037) mice. Our findings suggest that leptin enhances the intracellular GLUT4 transport in skeletal muscle of ob/ob animals by reducing the expression and activity of the negative regulators of GLUT4 traffic TBC1D1 and TBC1D4. PMID:22253718

  1. Quasi 1-D Analysis of a Circular, Compressible, Turbulent Jet Laden with Water Droplets. Appendix C

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Recent experimental studies indicate that presence of small amount of liquid droplets reduces the Overall Sound Pressure Level (OASPL) of a jet. Present study is aimed at numerically investigating the effect of liquid particles on the overall flow quantities of a heated, compressible round jet. The jet is assumed perfectly expanded. A quasi-1D model was developed for this purpose which uses area-averaged quantities that satisfy integral conservation equations. Special attention is given to represent the early development region since it is acoustically important. Approximate velocity and temperature profiles were assumed in this region to evaluate entrainment rate. Experimental correlations were used to obtain spreading rate of shear layer. The base flow thus obtained is then laden with water droplets at the exit of the nozzle. Mass, momentum and energy coupling between the two phases is represented using empirical relations. Droplet size and mass loading are varied to observe their effect on flow variables.

  2. Survey of Multi-Material Closure Models in 1D Lagrangian Hydrodynamics

    SciTech Connect

    Maeng, Jungyeoul Brad; Hyde, David Andrew Bulloch

    2015-07-28

    Accurately treating the coupled sub-cell thermodynamics of computational cells containing multiple materials is an inevitable problem in hydrodynamics simulations, whether due to initial configurations or evolutions of the materials and computational mesh. When solving the hydrodynamics equations within a multi-material cell, we make the assumption of a single velocity field for the entire computational domain, which necessitates the addition of a closure model to attempt to resolve the behavior of the multi-material cells’ constituents. In conjunction with a 1D Lagrangian hydrodynamics code, we present a variety of both the popular as well as more recently proposed multi-material closure models and survey their performances across a spectrum of examples. We consider standard verification tests as well as practical examples using combinations of fluid, solid, and composite constituents within multi-material mixtures. Our survey provides insights into the advantages and disadvantages of various multi-material closure models in different problem configurations.

  3. Statistical investigation and thermal properties for a 1-D impact system with dissipation

    NASA Astrophysics Data System (ADS)

    Díaz I., Gabriel; Livorati, André L. P.; Leonel, Edson D.

    2016-05-01

    The behavior of the average velocity, its deviation and average squared velocity are characterized using three techniques for a 1-D dissipative impact system. The system - a particle, or an ensemble of non-interacting particles, moving in a constant gravitation field and colliding with a varying platform - is described by a nonlinear mapping. The average squared velocity allows to describe the temperature for an ensemble of particles as a function of the parameters using: (i) straightforward numerical simulations; (ii) analytically from the dynamical equations; (iii) using the probability distribution function. Comparing analytical and numerical results for the three techniques, one can check the robustness of the developed formalism, where we are able to estimate numerical values for the statistical variables, without doing extensive numerical simulations. Also, extension to other dynamical systems is immediate, including time dependent billiards.

  4. A simple quasi-1D model of Fibonacci anyons

    NASA Astrophysics Data System (ADS)

    Aasen, David; Mong, Roger; Clarke, David; Alicea, Jason; Fendley, Paul

    2015-03-01

    There exists various ways of understanding the topological properties of Ising anyons--from simple free-fermion toy models to formal topological quantum field theory. For other types of anyons simple toy models rarely exist; their properties have to be obtained using formal self-consistency relations. We explore a family of gapped 1D local bosonic models that in a certain limit become trivial to solve and provide an intuitive picture for Fibonacci anyons. One can interpret this model as a quasi-1D wire that forms the building block of a 2D topological phase with Fibonacci anyons. With this interpretation all topological properties of the Fibonacci anyons become manifest including ground state degeneracy and braid relations. We conjecture that the structure of the model is protected by an emergent symmetry analogous to fermion parity. 1) NSF Grant DMR-1341822 2) Institute for Quantum Information and Matter, an NSF physics frontier center with support from the Moore Foundation. 3) NSERC-PGSD.

  5. Engineered atom-light interactions in 1D photonic crystals

    NASA Astrophysics Data System (ADS)

    Martin, Michael J.; Hung, Chen-Lung; Yu, Su-Peng; Goban, Akihisa; Muniz, Juan A.; Hood, Jonathan D.; Norte, Richard; McClung, Andrew C.; Meenehan, Sean M.; Cohen, Justin D.; Lee, Jae Hoon; Peng, Lucas; Painter, Oskar; Kimble, H. Jeff

    2014-05-01

    Nano- and microscale optical systems offer efficient and scalable quantum interfaces through enhanced atom-field coupling in both resonators and continuous waveguides. Beyond these conventional topologies, new opportunities emerge from the integration of ultracold atomic systems with nanoscale photonic crystals. One-dimensional photonic crystal waveguides can be engineered for both stable trapping configurations and strong atom-photon interactions, enabling novel cavity QED and quantum many-body systems, as well as distributed quantum networks. We present the experimental realization of such a nanophotonic quantum interface based on a nanoscale photonic crystal waveguide, demonstrating a fractional waveguide coupling of Γ1 D /Γ' of 0 . 32 +/- 0 . 08 , where Γ1 D (Γ') is the atomic emission rate into the guided (all other) mode(s). We also discuss progress towards intra-waveguide trapping of ultracold Cs. This work was supported by the IQIM, an NSF Physics Frontiers Center with support from the Moore Foundation, the DARPA ORCHID program, the AFOSR QuMPASS MURI, the DoD NSSEFF program, NSF, and the Kavli Nanoscience Institute (KNI) at Caltech.

  6. 1D and 2D urban dam-break flood modelling in Istanbul, Turkey

    NASA Astrophysics Data System (ADS)

    Ozdemir, Hasan; Neal, Jeffrey; Bates, Paul; Döker, Fatih

    2014-05-01

    Urban flood events are increasing in frequency and severity as a consequence of several factors such as reduced infiltration capacities due to continued watershed development, increased construction in flood prone areas due to population growth, the possible amplification of rainfall intensity due to climate change, sea level rise which threatens coastal development, and poorly engineered flood control infrastructure (Gallegos et al., 2009). These factors will contribute to increased urban flood risk in the future, and as a result improved modelling of urban flooding according to different causative factor has been identified as a research priority (Gallegos et al., 2009; Ozdemir et al. 2013). The flooding disaster caused by dam failures is always a threat against lives and properties especially in urban environments. Therefore, the prediction of dynamics of dam-break flows plays a vital role in the forecast and evaluation of flooding disasters, and is of long-standing interest for researchers. Flooding occurred on the Ayamama River (Istanbul-Turkey) due to high intensity rainfall and dam-breaching of Ata Pond in 9th September 2009. The settlements, industrial areas and transportation system on the floodplain of the Ayamama River were inundated. Therefore, 32 people were dead and millions of Euros economic loses were occurred. The aim of this study is 1 and 2-Dimensional flood modelling of the Ata Pond breaching using HEC-RAS and LISFLOOD-Roe models and comparison of the model results using the real flood extent. The HEC-RAS model solves the full 1-D Saint Venant equations for unsteady open channel flow whereas LISFLOOD-Roe is the 2-D shallow water model which calculates the flow according to the complete Saint Venant formulation (Villanueva and Wright, 2006; Neal et al., 2011). The model consists a shock capturing Godunov-type scheme based on the Roe Riemann solver (Roe, 1981). 3 m high resolution Digital Surface Model (DSM), natural characteristics of the pond

  7. Theory of contributon transport

    SciTech Connect

    Painter, J.W.; Gerstl, S.A.W.; Pomraning, G.C.

    1980-10-01

    A general discussion of the physics of contributon transport is presented. To facilitate this discussion, a Boltzmann-like transport equation for contributons is obtained, and special contributon cross sections are defined. However, the main goal of this study is to identify contributon transport equations and investigate possible deterministic solution techniques. Four approaches to the deterministic solution of the contributon transport problem are investigated. These approaches are an attempt to exploit certain attractive properties of the contributon flux, psi = phi phi/sup +/, where phi and phi/sup +/ are the solutions to the forward and adjoint Boltzmann transport equations.

  8. Comparison of 1D and 2D modelling with soil erosion model SMODERP

    NASA Astrophysics Data System (ADS)

    Kavka, Petr; Weyskrabova, Lenka; Zajicek, Jan

    2013-04-01

    The contribution presents a comparison of a runoff simulated by profile method (1D) and spatially distributed method (2D). Simulation model SMODERP is used for calculation and prediction of soil erosion and surface runoff from agricultural land. SMODERP is physically based model that includes the processes of infiltration (Phillips equation), surface runoff (kinematic wave based equation), surface retention, surface roughness and vegetation impact on runoff. 1D model was developed in past, new 2D model was developed in last two years. The model is being developed at the Department of Irrigation, Drainage and Landscape Engineering, Civil Engineering Faculty, CTU in Prague. 2D model was developed as a tool for widespread GIS software ArcGIS. The physical relations were implemented through Python script. This script uses ArcGIS system tools for raster and vectors treatment of the inputs. Flow direction is calculated by Steepest Descent algorithm in the preliminary version of 2D model. More advanced multiple flow algorithm is planned in the next version. Spatially distributed models enable to estimate not only surface runoff but also flow in the rills. Surface runoff is described in the model by kinematic wave equation. Equation uses Manning roughness coefficient for surface runoff. Parameters for five different soil textures were calibrated on the set of forty measurements performed on the laboratory rainfall simulator. For modelling of the rills a specific sub model was created. This sub model uses Manning formula for flow estimation. Numerical stability of the model is solved by Courant criterion. Spatial scale is fixed. Time step is dynamically changed depending on how flow is generated and developed. SMODERP is meant to be used not only for the research purposes, but mainly for the engineering practice. We also present how the input data can be obtained based on available resources (soil maps and data, land use, terrain models, field research, etc.) and how can

  9. Glut1 deficiency (G1D): Epilepsy and metabolic dysfunction in a mouse model of the most common human phenotype

    PubMed Central

    Marin-Valencia, Isaac; Good, Levi B.; Ma, Qian; Duarte, Joao; Bottiglieri, Teodoro; Sinton, Christopher M.; Heilig, Charles W.; Pascual, Juan M.

    2012-01-01

    Brain glucose supplies most of the carbon required for acetyl-coenzyme A (acetyl-CoA) generation (an important step for myelin synthesis) and for neurotransmitter production via further metabolism of acetyl-CoA in the tricarboxylic acid (TCA) cycle. However, it is not known whether reduced brain glucose transporter type I (GLUT-1) activity, the hallmark of the GLUT-1 deficiency (G1D) syndrome, leads to acetyl-CoA, TCA or neurotransmitter depletion. This question is relevant because, in its most common form in man, G1D is associated with cerebral hypomyelination (manifested as microcephaly) and epilepsy, suggestive of acetyl-CoA depletion and neurotransmitter dysfunction, respectively. Yet, brain metabolism in G1D remains underexplored both theoretically and experimentally, partly because computational models of limited brain glucose transport are subordinate to metabolic assumptions and partly because current hemizygous G1D mouse models manifest a mild phenotype not easily amenable to investigation. In contrast, adult antisense G1D mice replicate the human phenotype of spontaneous epilepsy associated with robust thalamocortical electrical oscillations. Additionally, and in consonance with human metabolic imaging observations, thalamus and cerebral cortex display the lowest GLUT-1 expression and glucose uptake in the mutant mouse. This depletion of brain glucose is associated with diminished plasma fatty acids and elevated ketone body levels, and with decreased brain acetyl-CoA and fatty acid contents, consistent with brain ketone body consumption and with stimulation of brain beta-oxidation and/or diminished cerebral lipid synthesis. In contrast with other epilepsies, astrocyte glutamine synthetase expression, cerebral TCA cycle intermediates, amino acid and amine neurotransmitter contents are also intact in G1D. The data suggest that the TCA cycle is preserved in G1D because reduced glycolysis and acetyl-CoA formation can be balanced by enhanced ketone body

  10. Final LDRD report : the physics of 1D and 2D electron gases in III-nitride heterostructure NWs.

    SciTech Connect

    Armstrong, Andrew M.; Arslan, Ilke; Upadhya, Prashanth C.; Morales, Eugenia T.; Leonard, Francois Leonard; Li, Qiming; Wang, George T.; Talin, Albert Alec; Prasankumar, Rohit P.; Lin, Yong

    2009-09-01

    The proposed work seeks to demonstrate and understand new phenomena in novel, freestanding III-nitride core-shell nanowires, including 1D and 2D electron gas formation and properties, and to investigate the role of surfaces and heterointerfaces on the transport and optical properties of nanowires, using a combined experimental and theoretical approach. Obtaining an understanding of these phenomena will be a critical step that will allow development of novel, ultrafast and ultraefficient nanowire-based electronic and photonic devices.

  11. Beautiful equations

    NASA Astrophysics Data System (ADS)

    Viljamaa, Panu; Jacobs, J. Richard; Chris; JamesHyman; Halma, Matthew; EricNolan; Coxon, Paul

    2014-07-01

    In reply to a Physics World infographic (part of which is given above) about a study showing that Euler's equation was deemed most beautiful by a group of mathematicians who had been hooked up to a functional magnetic-resonance image (fMRI) machine while viewing mathematical expressions (14 May, http://ow.ly/xHUFi).

  12. Review of Zero-D and 1-D Models of Blood Flow in the Cardiovascular System

    PubMed Central

    2011-01-01

    Background Zero-dimensional (lumped parameter) and one dimensional models, based on simplified representations of the components of the cardiovascular system, can contribute strongly to our understanding of circulatory physiology. Zero-D models provide a concise way to evaluate the haemodynamic interactions among the cardiovascular organs, whilst one-D (distributed parameter) models add the facility to represent efficiently the effects of pulse wave transmission in the arterial network at greatly reduced computational expense compared to higher dimensional computational fluid dynamics studies. There is extensive literature on both types of models. Method and Results The purpose of this review article is to summarise published 0D and 1D models of the cardiovascular system, to explore their limitations and range of application, and to provide an indication of the physiological phenomena that can be included in these representations. The review on 0D models collects together in one place a description of the range of models that have been used to describe the various characteristics of cardiovascular response, together with the factors that influence it. Such models generally feature the major components of the system, such as the heart, the heart valves and the vasculature. The models are categorised in terms of the features of the system that they are able to represent, their complexity and range of application: representations of effects including pressure-dependent vessel properties, interaction between the heart chambers, neuro-regulation and auto-regulation are explored. The examination on 1D models covers various methods for the assembly, discretisation and solution of the governing equations, in conjunction with a report of the definition and treatment of boundary conditions. Increasingly, 0D and 1D models are used in multi-scale models, in which their primary role is to provide boundary conditions for sophisticate, and often patient-specific, 2D and 3D models

  13. Classical non-Markovian Boltzmann equation

    SciTech Connect

    Alexanian, Moorad

    2014-08-01

    The modeling of particle transport involves anomalous diffusion, (x²(t) ) ∝ t{sup α} with α ≠ 1, with subdiffusive transport corresponding to 0 < α < 1 and superdiffusive transport to α > 1. These anomalies give rise to fractional advection-dispersion equations with memory in space and time. The usual Boltzmann equation, with only isolated binary collisions, is Markovian and, in particular, the contributions of the three-particle distribution function are neglected. We show that the inclusion of higher-order distribution functions give rise to an exact, non-Markovian Boltzmann equation with resulting transport equations for mass, momentum, and kinetic energy with memory in both time and space. The two- and the three-particle distribution functions are considered under the assumption that the two- and the three-particle correlation functions are translationally invariant that allows us to obtain advection-dispersion equations for modeling transport in terms of spatial and temporal fractional derivatives.

  14. Decay-ratio calculation in the frequency domain with the LAPUR code using 1D-kinetics

    SciTech Connect

    Munoz-Cobo, J. L.; Escriva, A.; Garcia, C.; Berna, C.

    2012-07-01

    This paper deals with the problem of computing the Decay Ratio in the frequency domain codes as the LAPUR code. First, it is explained how to calculate the feedback reactivity in the frequency domain using slab-geometry i.e. 1D kinetics, also we show how to perform the coupling of the 1D kinetics with the thermal-hydraulic part of the LAPUR code in order to obtain the reactivity feedback coefficients for the different channels. In addition, we show how to obtain the reactivity variation in the complex domain by solving the eigenvalue equation in the frequency domain and we compare this result with the reactivity variation obtained in first order perturbation theory using the 1D neutron fluxes of the base case. Because LAPUR works in the linear regime, it is assumed that in general the perturbations are small. There is also a section devoted to the reactivity weighting factors used to couple the reactivity contribution from the different channels to the reactivity of the entire reactor core in point kinetics and 1D kinetics. Finally we analyze the effects of the different approaches on the DR value. (authors)

  15. Axion string dynamics I: 2+1D

    NASA Astrophysics Data System (ADS)

    Fleury, Leesa M.; Moore, Guy D.

    2016-05-01

    If the axion exists and if the initial axion field value is uncorrelated at causally disconnected points, then it should be possible to predict the efficiency of cosmological axion production, relating the axionic dark matter density to the axion mass. The main obstacle to making this prediction is correctly treating the axion string cores. We develop a new algorithm for treating the axionic string cores correctly in 2+1 dimensions. When the axionic string cores are given their full physical string tension, axion production is about twice as efficient as in previous simulations. We argue that the string network in 2+1 dimensions should behave very differently than in 3+1 dimensions, so this result cannot be simply carried over to the physical case. We outline how to extend our method to 3+1D axion string dynamics.

  16. Connected components of irreducible maps and 1D quantum phases

    NASA Astrophysics Data System (ADS)

    Szehr, Oleg; Wolf, Michael M.

    2016-08-01

    We investigate elementary topological properties of sets of completely positive (CP) maps that arise in quantum Perron-Frobenius theory. We prove that the set of primitive CP maps of fixed Kraus rank is path-connected and we provide a complete classification of the connected components of irreducible CP maps at given Kraus rank and fixed peripheral spectrum in terms of a multiplicity index. These findings are then applied to analyse 1D quantum phases by studying equivalence classes of translational invariant matrix product states that correspond to the connected components of the respective CP maps. Our results extend the previously obtained picture in that they do not require blocking of physical sites, they lead to analytic paths, and they allow us to decompose into ergodic components and to study the breaking of translational symmetry.

  17. Glycolipid antigen processing for presentation by CD1d molecules.

    PubMed

    Prigozy, T I; Naidenko, O; Qasba, P; Elewaut, D; Brossay, L; Khurana, A; Natori, T; Koezuka, Y; Kulkarni, A; Kronenberg, M

    2001-01-26

    The requirement for processing glycolipid antigens in T cell recognition was examined with mouse CD1d-mediated responses to glycosphingolipids (GSLs). Although some disaccharide GSL antigens can be recognized without processing, the responses to three other antigens, including the disaccharide GSL Gal(alpha1-->2)GalCer (Gal, galactose; GalCer, galactosylceramide), required removal of the terminal sugars to permit interaction with the T cell receptor. A lysosomal enzyme, alpha-galactosidase A, was responsible for the processing of Gal(alpha1-->2)GalCer to generate the antigenic monosaccharide epitope. These data demonstrate a carbohydrate antigen processing system analogous to that used for peptides and an ability of T cells to recognize processed fragments of complex glycolipids.

  18. Solves the Multigroup Neutron Diffusion Equation

    1995-06-23

    GNOMER is a program which solves the multigroup neutron diffusion equation in 1D, 2D and 3D cartesian geometry. The program is designed to calculate the global core power distributions (with thermohydraulic feedbacks), as well as power distribution and homogenized cross sections over a fuel assembly.

  19. Transport of Solid Material in Dynamically Evolving 1d Disk Models with Pressure Maxima

    NASA Astrophysics Data System (ADS)

    Tarczay-Nehéz, Dóra; Regály, Zsolt; Sándor, Zsolt

    2013-07-01

    Planet formation theory based on the core-accretion scenario suffers from the very fast loss of dust particles, the building blocks of planetesimals. Thus, the available material to build planets is consumed before a significant mass of dust are able to stick together. An effective solution to this problem might be a pressure trap. The radial drift of the dust particles are caused by the difference in the orbital velocity of the gas and the dust particles. At the edges of the accretionally dead zone in a protoplanetary disk (Gammie, 1996), the gradient of the gas pressure vanishes serving a trap for dust particles under inward drift. The increased density of dust particles there may accelerate the formation of planetesimals, and by subsequent collisions even the formation of planets and planetary cores. In the present work we investigate the mass growth due to the dust particle accumulation in pressure maxima. Our results support the idea of rapid planet formation via core-accretion, but we find that the efficiency of dust accumulation depends on the disk physical parameters.

  20. Pfaffian statistics through adiabatic transport in the 1D coherent state representation.

    PubMed

    Seidel, Alexander

    2008-11-01

    Recent work has shown that the low energy sector of certain quantum Hall states is adiabatically connected to simple charge-density-wave patterns that appear, e.g., when the system is deformed into a thin torus. Here it is shown that the patterns emerging in this limit already determine the non-Abelian statistics of the nu=1 Moore-Read state. Aside from the knowledge of these patterns, the method only relies on the principle of adiabatic continuity, the effectively noncommutative geometry in a strong magnetic field, and topological as well as locality arguments.