Exact Turbulence Law in Collisionless Plasmas: Hybrid Simulations

Science.gov (United States)

Hellinger, P.; Verdini, A.; Landi, S.; Franci, L.; Matteini, L.

2017-12-01

An exact vectorial law for turbulence in homogeneous incompressible Hall-MHD is derived and tested in two-dimensional hybrid simulations of plasma turbulence. The simulations confirm the validity of the MHD exact law in the kinetic regime, the simulated turbulence exhibits a clear inertial range on large scales where the MHD cascade flux dominates. The simulation results also indicate that in the sub-ion range the cascade continues via the Hall term and that the total cascade rate tends to decrease at around the ion scales, especially in high-beta plasmas. This decrease is like owing to formation of non-thermal features, such as collisionless ion energization, that can not be retained in the Hall MHD approximation.

Global gyrokinetic and fluid hybrid simulations of tokamaks and stellarators

Energy Technology Data Exchange (ETDEWEB)

Cole, Michael David John

2016-07-15

Achieving commercial production of electricity by magnetic confinement fusion requires improvements in energy and particle confinement. In order to better understand and optimise confinement, numerical simulations of plasma phenomena are useful. One particularly challenging regime is that in which long wavelength MHD phenomena interact with kinetic phenomena. In such a regime, global electromagnetic gyrokinetic simulations are necessary. In this regime, computational requirements have been excessive for Eulerian methods, while Particle-in-Cell (PIC) methods have been particularly badly affected by the 'cancellation problem', a numerical problem resulting from the structure of the electromagnetic gyrokinetic equations. A number of researchers have been working on mitigating this problem with some significant successes. Another alternative to mitigating the problem is to move to a hybrid system of fluid and gyrokinetic equations. At the expense of reducing the physical content of the numerical model, particularly electron kinetic physics, it is possible in this way to perform global electromagnetic PIC simulations retaining ion gyrokinetic effects but eliminating the cancellation problem. The focus of this work has been the implementation of two such hybrid models into the gyrokinetic code EUTERPE. The two models treat electrons and the entire bulk plasma respectively as a fluid. Both models are additionally capable of considering the self-consistent interaction of an energetic ion species, described gyrokinetically, with the perturbed fields. These two models have been successfully benchmarked in linear growth rate and frequency against other codes for a Toroidal Alfven Eigenmode (TAE) case in both the linear and non-linear regimes. The m=1 internal kink mode, which is particularly challenging in terms of the fully gyrokinetic cancellation problem, has also been successfully benchmarked using the hybrid models with the MHD eigenvalue code CKA. Non

Global gyrokinetic and fluid hybrid simulations of tokamaks and stellarators

International Nuclear Information System (INIS)

Cole, Michael David John

2016-01-01

Achieving commercial production of electricity by magnetic confinement fusion requires improvements in energy and particle confinement. In order to better understand and optimise confinement, numerical simulations of plasma phenomena are useful. One particularly challenging regime is that in which long wavelength MHD phenomena interact with kinetic phenomena. In such a regime, global electromagnetic gyrokinetic simulations are necessary. In this regime, computational requirements have been excessive for Eulerian methods, while Particle-in-Cell (PIC) methods have been particularly badly affected by the 'cancellation problem', a numerical problem resulting from the structure of the electromagnetic gyrokinetic equations. A number of researchers have been working on mitigating this problem with some significant successes. Another alternative to mitigating the problem is to move to a hybrid system of fluid and gyrokinetic equations. At the expense of reducing the physical content of the numerical model, particularly electron kinetic physics, it is possible in this way to perform global electromagnetic PIC simulations retaining ion gyrokinetic effects but eliminating the cancellation problem. The focus of this work has been the implementation of two such hybrid models into the gyrokinetic code EUTERPE. The two models treat electrons and the entire bulk plasma respectively as a fluid. Both models are additionally capable of considering the self-consistent interaction of an energetic ion species, described gyrokinetically, with the perturbed fields. These two models have been successfully benchmarked in linear growth rate and frequency against other codes for a Toroidal Alfven Eigenmode (TAE) case in both the linear and non-linear regimes. The m=1 internal kink mode, which is particularly challenging in terms of the fully gyrokinetic cancellation problem, has also been successfully benchmarked using the hybrid models with the MHD eigenvalue code CKA. Non-linear simulations

Hybrid simulation of electrode plasmas in high-power diodes

International Nuclear Information System (INIS)

Welch, Dale R.; Rose, David V.; Bruner, Nichelle; Clark, Robert E.; Oliver, Bryan V.; Hahn, Kelly D.; Johnston, Mark D.

2009-01-01

New numerical techniques for simulating the formation and evolution of cathode and anode plasmas have been successfully implemented in a hybrid code. The dynamics of expanding electrode plasmas has long been recognized as a limiting factor in the impedance lifetimes of high-power vacuum diodes and magnetically insulated transmission lines. Realistic modeling of such plasmas is being pursued to aid in understanding the operating characteristics of these devices as well as establishing scaling relations for reliable extrapolation to higher voltages. Here, in addition to kinetic and fluid modeling, a hybrid particle-in-cell technique is described that models high density, thermal plasmas as an inertial fluid which transitions to kinetic electron or ion macroparticles above a prescribed energy. The hybrid technique is computationally efficient and does not require resolution of the Debye length. These techniques are first tested on a simple planar diode then applied to the evolution of both cathode and anode plasmas in a high-power self-magnetic pinch diode. The impact of an intense electron flux on the anode surface leads to rapid heating of contaminant material and diode impedance loss.

Hybrid Simulations of Plasma-Neutral-Dust Interactions at Enceladus

International Nuclear Information System (INIS)

Omidi, N.; Russell, C. T.; Jia, Y. D.; Tokar, R. L.; Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Leisner, J. S.

2010-01-01

Through ejection from its southern hemisphere, Enceladus is a dominant source of neutral gas and dust in Saturn's inner magnetosphere. The interaction of the corotating plasma with the gas and dust modifies the plasma environment around Enceladus. We use 3-D hybrid (kinetic ions, fluid electrons) simulations to examine the effects of gas and dust on the nature of the interaction region and use Cassini observations to constrain their properties.

Hybrid Fluid/Kinetic Modeling Of Magnetized High Energy Density Plasmas

Science.gov (United States)

Hansen, David; Held, Eric; King, Jacob; Stoltz, Peter; Masti, Robert; Srinivasan, Bhuvana

2017-10-01

MHD modeling with an equation of state (EOS) of the Rayleigh-Taylor (RT) instabily in Z indicates that it is seeded by the electro-thermal instability. Large thermodynamic drives associated with gradients at the interface between the liner and the coronal regions distort distribution functions and likely lead to non-local transport effects in a plasma which varies from weakly to strongly coupled. In this work, we discuss using effective potential theory along with a Chapman-Ensksog-like (CEL) formalism to develop hybrid fluid/kinetic modeling capabilities for these plasmas. Effective potential theory addresses the role of Coulomb collisions on transport across coupling regimes and the CEL approach bridges the gap between full-blow kinetic simulations and the EOS tables, which only depend locally on density and temperature. Quantitative results on the Spitzer problem across coupling coupling regimes will be presented as a first step. DOE Grant No. DE-SC0016525.

Multiscale Hy3S: Hybrid stochastic simulation for supercomputers

Directory of Open Access Journals (Sweden)

Kaznessis Yiannis N

2006-02-01

Full Text Available Abstract Background Stochastic simulation has become a useful tool to both study natural biological systems and design new synthetic ones. By capturing the intrinsic molecular fluctuations of "small" systems, these simulations produce a more accurate picture of single cell dynamics, including interesting phenomena missed by deterministic methods, such as noise-induced oscillations and transitions between stable states. However, the computational cost of the original stochastic simulation algorithm can be high, motivating the use of hybrid stochastic methods. Hybrid stochastic methods partition the system into multiple subsets and describe each subset as a different representation, such as a jump Markov, Poisson, continuous Markov, or deterministic process. By applying valid approximations and self-consistently merging disparate descriptions, a method can be considerably faster, while retaining accuracy. In this paper, we describe Hy3S, a collection of multiscale simulation programs. Results Building on our previous work on developing novel hybrid stochastic algorithms, we have created the Hy3S software package to enable scientists and engineers to both study and design extremely large well-mixed biological systems with many thousands of reactions and chemical species. We have added adaptive stochastic numerical integrators to permit the robust simulation of dynamically stiff biological systems. In addition, Hy3S has many useful features, including embarrassingly parallelized simulations with MPI; special discrete events, such as transcriptional and translation elongation and cell division; mid-simulation perturbations in both the number of molecules of species and reaction kinetic parameters; combinatorial variation of both initial conditions and kinetic parameters to enable sensitivity analysis; use of NetCDF optimized binary format to quickly read and write large datasets; and a simple graphical user interface, written in Matlab, to help users

UV-cured methacrylic-silica hybrids: Effect of oxygen inhibition on photo-curing kinetics

International Nuclear Information System (INIS)

Corcione, C. Esposito; Striani, R.; Frigione, M.

2014-01-01

Highlights: • The kinetic behavior of novel photopolymerizable organic–inorganic hybrid system was studied as a function of the composition and of the atmosphere for reactions. • The UV-curing reaction of the hybrid mixture was found fast and complete. • The combined presence of thiol monomer and nanostructured silica allows to reduce the effect of inhibition of oxygen towards the radical photopolymerization. - Abstract: The kinetic behavior of innovative photopolymerizable UV-cured methacrylic–silica hybrid formulations, previously developed, was studied and compared to that of a reference control system. The organic–inorganic (O–I) hybrids proposed in this study are obtained from organic precursors with a high siloxane content mixed with tetraethoxysilane (TEOS) in such a way to produce co-continuous silica nano-domains dispersed within a cross-linked organic phase, as a result of the hydrolysis and condensation reactions. The kinetics of the radical photopolymerization mechanism induced by UV-radiations, in presence of a suitable photoinitiator, was studied by calorimetric, FTIR and Raman spectroscopic analyses, by varying the composition of the mixtures and the atmosphere for reactions. The well known effect of oxygen on the kinetic mechanism of the free radical photopolymerization of the methacrylic–siloxane based monomers was found to be strongly reduced in the hybrid system, especially when a proper thiol was used. The experimental calorimetric data were fitted using a simple kinetic model for radical photopolymerization reactions, obtaining a good agreement between the experimental data and the theoretical model. From the comparison of the kinetic constants calculated for control and hybrid systems, it was possible to assess the effect of the composition, as well as of the atmosphere used during the photo-polymerization process, on the kinetic of photopolymerization reaction

Electric/Hybrid Vehicle Simulation

Science.gov (United States)

Slusser, R. A.; Chapman, C. P.; Brennand, J. P.

1985-01-01

ELVEC computer program provides vehicle designer with simulation tool for detailed studies of electric and hybrid vehicle performance and cost. ELVEC simulates performance of user-specified electric or hybrid vehicle under user specified driving schedule profile or operating schedule. ELVEC performs vehicle design and life cycle cost analysis.

Simulation of Mercury's magnetosheath with a combined hybrid-paraboloid model

Science.gov (United States)

Parunakian, David; Dyadechkin, Sergey; Alexeev, Igor; Belenkaya, Elena; Khodachenko, Maxim; Kallio, Esa; Alho, Markku

2017-08-01

In this paper we introduce a novel approach for modeling planetary magnetospheres that involves a combination of the hybrid model and the paraboloid magnetosphere model (PMM); we further refer to it as the combined hybrid model. While both of these individual models have been successfully applied in the past, their combination enables us both to overcome the traditional difficulties of hybrid models to develop a self-consistent magnetic field and to compensate the lack of plasma simulation in the PMM. We then use this combined model to simulate Mercury's magnetosphere and investigate the geometry and configuration of Mercury's magnetosheath controlled by various conditions in the interplanetary medium. The developed approach provides a unique comprehensive view of Mercury's magnetospheric environment for the first time. Using this setup, we compare the locations of the bow shock and the magnetopause as determined by simulations with the locations predicted by stand-alone PMM runs and also verify the magnetic and dynamic pressure balance at the magnetopause. We also compare the results produced by these simulations with observational data obtained by the magnetometer on board the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft along a dusk-dawn orbit and discuss the signatures of the magnetospheric features that appear in these simulations. Overall, our analysis suggests that combining the semiempirical PMM with a self-consistent global kinetic model creates new modeling possibilities which individual models cannot provide on their own.

Computer simulation of kinetic properties of plasmas. Progress report, October 1, 1977--September 30, 1978

International Nuclear Information System (INIS)

Denavit, J.

1978-01-01

The research is directed toward the development and testing of new numerical methods for particle and hybrid simulation of plasmas and their application to physical problems of current significance to Magnetic Fusion Energy. During the past year, research on the project has been concerned with the following specific problems: (1) analysis and computer simulations of the dissipative trapped-electron instability in tokamaks; (2) long-time-scale algorithms for numerical solutions of the drift-kinetic equation; and (3) computer simulation of field-reversed ion ring stability

Deriving simulators for hybrid Chi models

NARCIS (Netherlands)

Beek, van D.A.; Man, K.L.; Reniers, M.A.; Rooda, J.E.; Schiffelers, R.R.H.

2006-01-01

The hybrid Chi language is formalism for modeling, simulation and verification of hybrid systems. The formal semantics of hybrid Chi allows the definition of provably correct implementations for simulation, verification and realtime control. This paper discusses the principles of deriving an

Simulation of wing-body junction flows with hybrid RANS/LES methods

International Nuclear Information System (INIS)

Fu Song; Xiao Zhixiang; Chen Haixin; Zhang Yufei; Huang Jingbo

2007-01-01

In this paper, flows past two wing-body junctions, the Rood at zero angle of attack and NASA TN D-712 at 12.5 o angle of attack, are investigated with two Reynolds-Averaged Navier-Stokes (RANS) and large eddy simulation (LES) hybrid methods. One is detached eddy simulation (DES) and the other is delayed-DES, both are based on a weakly nonlinear two-equation k-ω model. While the RANS method can predict the mean flow behaviours reasonably accurately, its performance for the turbulent kinetic energy and shear stress, as compared with available experimental data, is not satisfactory. DES, through introducing a length scale in the dissipation terms of the turbulent kinetic energy equation, delivers flow separation, a vortex or the onset of vortex breakdown too early. DDES, with its delayed effect, shows a great improvement in flow structures and turbulence characteristics, and agrees well with measurements

A new hybrid scheme for simulations of highly collisional RF-driven plasmas

International Nuclear Information System (INIS)

Eremin, Denis; Hemke, Torben; Mussenbrock, Thomas

2016-01-01

This work describes a new 1D hybrid approach for modeling atmospheric pressure discharges featuring complex chemistry. In this approach electrons are described fully kinetically using particle-in-cell/Monte-Carlo (PIC/MCC) scheme, whereas the heavy species are modeled within a fluid description. Validity of the popular drift-diffusion approximation is verified against a ‘full’ fluid model accounting for the ion inertia and a fully kinetic PIC/MCC code for ions as well as electrons. The fluid models require knowledge of the momentum exchange frequency and dependence of the ion mobilities on the electric field when the ions are in equilibrium with the latter. To this end an auxiliary Monte-Carlo scheme is constructed. It is demonstrated that the drift-diffusion approximation can overestimate ion transport in simulations of RF-driven discharges with heavy ion species operated in the γ mode at the atmospheric pressure or in all discharge simulations for lower pressures. This can lead to exaggerated plasma densities and incorrect profiles provided by the drift-diffusion models. Therefore, the hybrid code version featuring the full ion fluid model should be favored against the more popular drift-diffusion model, noting that the suggested numerical scheme for the former model implies only a small additional computational cost. (paper)

Nonlinear hybrid simulation of internal kink with beam ion effects in DIII-D

Energy Technology Data Exchange (ETDEWEB)

Shen, Wei; Sheng, Zheng-Mao [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Fu, G. Y.; Tobias, Benjamin [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Zeeland, Michael Van [General Atomics, San Diego, California 92186-5608 (United States); Wang, Feng [School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China)

2015-04-15

In DIII-D sawteething plasmas, long-lived (1,1) kink modes are often observed between sawtooth crashes. The saturated kink modes have two distinct frequencies. The mode with higher frequency transits to a fishbone-like mode with sufficient on-axis neutral beam power. In this work, hybrid simulations with the global kinetic-magnetohydrodynamic (MHD) hybrid code M3D-K have been carried out to investigate the linear stability and nonlinear dynamics of the n = 1 mode with effects of energetic beam ions for a typical DIII-D discharge where both saturated kink mode and fishbone were observed. Linear simulation results show that the n = 1 internal kink mode is unstable in MHD limit. However, with kinetic effects of beam ions, a fishbone-like mode is excited with mode frequency about a few kHz depending on beam pressure profile. The mode frequency is higher at higher beam power and/or narrower radial profile consistent with the experimental observation. Nonlinear simulations have been performed to investigate mode saturation as well as energetic particle transport. The nonlinear MHD simulations show that the unstable kink mode becomes a saturated kink mode after a sawtooth crash. With beam ion effects, the fishbone-like mode can also transit to a saturated kink mode with a small but finite mode frequency. These results are consistent with the experimental observation of saturated kink mode between sawtooth crashes.

Simulating movement of tRNA through the ribosome during hybrid-state formation.

Science.gov (United States)

Whitford, Paul C; Sanbonmatsu, Karissa Y

2013-09-28

Biomolecular simulations provide a means for exploring the relationship between flexibility, energetics, structure, and function. With the availability of atomic models from X-ray crystallography and cryoelectron microscopy (cryo-EM), and rapid increases in computing capacity, it is now possible to apply molecular dynamics (MD) simulations to large biomolecular machines, and systematically partition the factors that contribute to function. A large biomolecular complex for which atomic models are available is the ribosome. In the cell, the ribosome reads messenger RNA (mRNA) in order to synthesize proteins. During this essential process, the ribosome undergoes a wide range of conformational rearrangements. One of the most poorly understood transitions is translocation: the process by which transfer RNA (tRNA) molecules move between binding sites inside of the ribosome. The first step of translocation is the adoption of a "hybrid" configuration by the tRNAs, which is accompanied by large-scale rotations in the ribosomal subunits. To illuminate the relationship between these rearrangements, we apply MD simulations using a multi-basin structure-based (SMOG) model, together with targeted molecular dynamics protocols. From 120 simulated transitions, we demonstrate the viability of a particular route during P/E hybrid-state formation, where there is asynchronous movement along rotation and tRNA coordinates. These simulations not only suggest an ordering of events, but they highlight atomic interactions that may influence the kinetics of hybrid-state formation. From these simulations, we also identify steric features (H74 and surrounding residues) encountered during the hybrid transition, and observe that flexibility of the single-stranded 3'-CCA tail is essential for it to reach the endpoint. Together, these simulations provide a set of structural and energetic signatures that suggest strategies for modulating the physical-chemical properties of protein synthesis by the

Local hybrid functionals: An assessment for thermochemical kinetics

International Nuclear Information System (INIS)

Kaupp, Martin; Bahmann, Hilke; Arbuznikov, Alexei V.

2007-01-01

Local hybrid functionals with position-dependent exact-exchange admixture are a new class of exchange-correlation functionals in density functional theory that promise to advance the available accuracy in many areas of application. Local hybrids with different local mixing functions (LMFs) governing the position dependence are validated for the heats of formation of the extended G3/99 set, and for two sets of barriers of hydrogen-transfer and heavy-atom transfer reactions (HTBH38 and NHTBH38 databases). A simple local hybrid Lh-SVWN with only Slater and exact exchange plus local correlation and a one-parameter LMF, g(r)=b(τ W (r)/τ(r)), performs best and provides overall mean absolute errors for thermochemistry and kinetics that are a significant improvement over standard state-of-the-art global hybrid functionals. In particular, this local hybrid functional does not suffer from the systematic deterioration that standard functionals exhibit for larger molecules. In contrast, local hybrids based on generalized gradient approximation exchange tend to give rise to nonintuitive LMFs, and no improved functionals have been obtained along this route. The LMF is a real-space function and thus can be analyzed in detail. We use, in particular, graphical analyses to rationalize the performance of different local hybrids for thermochemistry and reaction barriers

Computer simulation of kinetic properties of plasmas. Progress report, October 1, 1978-June 30, 1979

International Nuclear Information System (INIS)

Denavit, J.

1979-01-01

The research is directed toward the development and testing of new numerical methods for particle and hybrid simulation of plasmas, and their application to physical problems of current significance to Magnetic Fusion Energy. During the present period, research on the project has been concerned with the following specific problems: (1) Computer simulations of drift and dissipative trapped-electron instabilities in tokamaks, including radial dependence and shear stabilization. (2) Long-time-scale algorithms for numerical solutions of the drift-kinetic equation. (3) Computer simulation of field-reversed ion ring stability. (4) Nonlinear, single-mode saturation of the bump-on-tail instability

Characterization and Curing Kinetics of Epoxy/Silica Nano-Hybrids

Science.gov (United States)

Yang, Cheng-Fu; Wang, Li-Fen; Wu, Song-Mao; Su, Chean-Cheng

2015-01-01

The sol-gel technique was used to prepare epoxy/silica nano-hybrids. The thermal characteristics, curing kinetics and structure of epoxy/silica nano-hybrids were studied using differential scanning calorimetry (DSC), 29Si nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). To improve the compatibility between the organic and inorganic phases, a coupling agent was used to modify the diglycidyl ether of bisphenol A (DGEBA) epoxy. The sol-gel technique enables the silica to be successfully incorporated into the network of the hybrids, increasing the thermal stability and improving the mechanical properties of the prepared epoxy/silica nano-hybrids. An autocatalytic mechanism of the epoxy/SiO2 nanocomposites was observed. The low reaction rate of epoxy in the nanocomposites is caused by the steric hindrance in the network of hybrids that arises from the consuming of epoxide group in the network of hybrids by the silica. In the nanocomposites, the nano-scale silica particles had an average size of approximately 35 nm, and the particles were well dispersed in the epoxy matrix, according to the TEM images. PMID:28793616

An efficient algorithm for the stochastic simulation of the hybridization of DNA to microarrays

Directory of Open Access Journals (Sweden)

Laurenzi Ian J

2009-12-01

Full Text Available Abstract Background Although oligonucleotide microarray technology is ubiquitous in genomic research, reproducibility and standardization of expression measurements still concern many researchers. Cross-hybridization between microarray probes and non-target ssDNA has been implicated as a primary factor in sensitivity and selectivity loss. Since hybridization is a chemical process, it may be modeled at a population-level using a combination of material balance equations and thermodynamics. However, the hybridization reaction network may be exceptionally large for commercial arrays, which often possess at least one reporter per transcript. Quantification of the kinetics and equilibrium of exceptionally large chemical systems of this type is numerically infeasible with customary approaches. Results In this paper, we present a robust and computationally efficient algorithm for the simulation of hybridization processes underlying microarray assays. Our method may be utilized to identify the extent to which nucleic acid targets (e.g. cDNA will cross-hybridize with probes, and by extension, characterize probe robustnessusing the information specified by MAGE-TAB. Using this algorithm, we characterize cross-hybridization in a modified commercial microarray assay. Conclusions By integrating stochastic simulation with thermodynamic prediction tools for DNA hybridization, one may robustly and rapidly characterize of the selectivity of a proposed microarray design at the probe and "system" levels. Our code is available at http://www.laurenzi.net.

DNA hybridization kinetics: zippering, internal displacement and sequence dependence.

Science.gov (United States)

Ouldridge, Thomas E; Sulc, Petr; Romano, Flavio; Doye, Jonathan P K; Louis, Ard A

2013-10-01

Although the thermodynamics of DNA hybridization is generally well established, the kinetics of this classic transition is less well understood. Providing such understanding has new urgency because DNA nanotechnology often depends critically on binding rates. Here, we explore DNA oligomer hybridization kinetics using a coarse-grained model. Strand association proceeds through a complex set of intermediate states, with successful binding events initiated by a few metastable base-pairing interactions, followed by zippering of the remaining bonds. But despite reasonably strong interstrand interactions, initial contacts frequently dissociate because typical configurations in which they form differ from typical states of similar enthalpy in the double-stranded equilibrium ensemble. Initial contacts must be stabilized by two or three base pairs before full zippering is likely, resulting in negative effective activation enthalpies. Non-Arrhenius behavior arises because the number of base pairs required for nucleation increases with temperature. In addition, we observe two alternative pathways-pseudoknot and inchworm internal displacement-through which misaligned duplexes can rearrange to form duplexes. These pathways accelerate hybridization. Our results explain why experimentally observed association rates of GC-rich oligomers are higher than rates of AT- rich equivalents, and more generally demonstrate how association rates can be modulated by sequence choice.

Electric-hybrid-vehicle simulation

Science.gov (United States)

Pasma, D. C.

The simulation of electric hybrid vehicles is to be performed using experimental data to model propulsion system components. The performance of an existing ac propulsion system will be used as the baseline for comparative purposes. Hybrid components to be evaluated include electrically and mechanically driven flywheels, and an elastomeric regenerative braking system.

HTTR plant dynamic simulation using a hybrid computer

International Nuclear Information System (INIS)

Shimazaki, Junya; Suzuki, Katsuo; Nabeshima, Kunihiko; Watanabe, Koichi; Shinohara, Yoshikuni; Nakagawa, Shigeaki.

1990-01-01

A plant dynamic simulation of High-Temperature Engineering Test Reactor has been made using a new-type hybrid computer. This report describes a dynamic simulation model of HTTR, a hybrid simulation method for SIMSTAR and some results obtained from dynamics analysis of HTTR simulation. It concludes that the hybrid plant simulation is useful for on-line simulation on account of its capability of computation at high speed, compared with that of all digital computer simulation. With sufficient accuracy, 40 times faster computation than real time was reached only by changing an analog time scale for HTTR simulation. (author)

TRNSYS HYBRID wind diesel PV simulator

Energy Technology Data Exchange (ETDEWEB)

Quinlan, P.J.A.; Mitchell, J.W.; Klein, S.A.; Beckman, W.A.; Blair, N.J. [Univ. of Wisconsin, Madison, WI (United States)

1996-12-31

The Solar Energy Laboratory (SEL) has developed a wind diesel PV hybrid systems simulator, UW-HYBRID 1.0, an application of the TRNSYS 14.2 time-series simulation environment. An AC/DC bus links up to five diesels and wind turbine models, along with PV modules, a battery bank, and an AC/DC converter. Multiple units can be selected. PV system simulations include solar angle and peak power tracking options. Weather data are Typical Meteorological Year data, parametrically generated synthesized data, or external data files. PV performance simulations rely on long-standing SEL-developed algorithms. Loads data are read as scalable time series. Diesel simulations include estimated fuel-use and waste heat output, and are dispatched using a least-cost of fuel strategy. Wind system simulations include varying air density, wind shear and wake effects. Time step duration is user-selectable. UW-HYBRID 1.0 runs in Windows{reg_sign}, with TRNSED providing a customizable user interface. 12 refs., 6 figs.

Hybrid2 - The hybrid power system simulation model

Energy Technology Data Exchange (ETDEWEB)

Baring-Gould, E.I.; Green, H.J.; Dijk, V.A.P. van [National Renewable Energy Lab., Golden, CO (United States); Manwell, J.F. [Univ. of Massachusetts, Amherst, MA (United States)

1996-12-31

There is a large-scale need and desire for energy in remote communities, especially in the developing world; however the lack of a user friendly, flexible performance prediction model for hybrid power systems incorporating renewables hindered the analysis of hybrids as options to conventional solutions. A user friendly model was needed with the versatility to simulate the many system locations, widely varying hardware configurations, and differing control options for potential hybrid power systems. To meet these ends, researchers from the National Renewable Energy Laboratory (NREL) and the University of Massachusetts (UMass) developed the Hybrid2 software. This paper provides an overview of the capabilities, features, and functionality of the Hybrid2 code, discusses its validation and future plans. Model availability and technical support provided to Hybrid2 users are also discussed. 12 refs., 3 figs., 4 tabs.

Hybrid simulation models of production networks

CERN Document Server

Kouikoglou, Vassilis S

2001-01-01

This book is concerned with a most important area of industrial production, that of analysis and optimization of production lines and networks using discrete-event models and simulation. The book introduces a novel approach that combines analytic models and discrete-event simulation. Unlike conventional piece-by-piece simulation, this method observes a reduced number of events between which the evolution of the system is tracked analytically. Using this hybrid approach, several models are developed for the analysis of production lines and networks. The hybrid approach combines speed and accuracy for exceptional analysis of most practical situations. A number of optimization problems, involving buffer design, workforce planning, and production control, are solved through the use of hybrid models.

Hybrid simulation techniques applied to the earth's bow shock

Science.gov (United States)

Winske, D.; Leroy, M. M.

1985-01-01

The application of a hybrid simulation model, in which the ions are treated as discrete particles and the electrons as a massless charge-neutralizing fluid, to the study of the earth's bow shock is discussed. The essentials of the numerical methods are described in detail; movement of the ions, solution of the electromagnetic fields and electron fluid equations, and imposition of appropriate boundary and initial conditions. Examples of results of calculations for perpendicular shocks are presented which demonstrate the need for a kinetic treatment of the ions to reproduce the correct ion dynamics and the corresponding shock structure. Results for oblique shocks are also presented to show how the magnetic field and ion motion differ from the perpendicular case.

Odd-flavor Simulations by the Hybrid Monte Carlo

CERN Document Server

Takaishi, Tetsuya; Takaishi, Tetsuya; De Forcrand, Philippe

2001-01-01

The standard hybrid Monte Carlo algorithm is known to simulate even flavors QCD only. Simulations of odd flavors QCD, however, can be also performed in the framework of the hybrid Monte Carlo algorithm where the inverse of the fermion matrix is approximated by a polynomial. In this exploratory study we perform three flavors QCD simulations. We make a comparison of the hybrid Monte Carlo algorithm and the R-algorithm which also simulates odd flavors systems but has step-size errors. We find that results from our hybrid Monte Carlo algorithm are in agreement with those from the R-algorithm obtained at very small step-size.

Global Particle-in-Cell Simulations of Mercury's Magnetosphere

Science.gov (United States)

Schriver, D.; Travnicek, P. M.; Lapenta, G.; Amaya, J.; Gonzalez, D.; Richard, R. L.; Berchem, J.; Hellinger, P.

2017-12-01

Spacecraft observations of Mercury's magnetosphere have shown that kinetic ion and electron particle effects play a major role in the transport, acceleration, and loss of plasma within the magnetospheric system. Kinetic processes include reconnection, the breakdown of particle adiabaticity and wave-particle interactions. Because of the vast range in spatial scales involved in magnetospheric dynamics, from local electron Debye length scales ( meters) to solar wind/planetary magnetic scale lengths (tens to hundreds of planetary radii), fully self-consistent kinetic simulations of a global planetary magnetosphere remain challenging. Most global simulations of Earth's and other planet's magnetosphere are carried out using MHD, enhanced MHD (e.g., Hall MHD), hybrid, or a combination of MHD and particle in cell (PIC) simulations. Here, 3D kinetic self-consistent hybrid (ion particle, electron fluid) and full PIC (ion and electron particle) simulations of the solar wind interaction with Mercury's magnetosphere are carried out. Using the implicit PIC and hybrid simulations, Mercury's relatively small, but highly kinetic magnetosphere will be examined to determine how the self-consistent inclusion of electrons affects magnetic reconnection, particle transport and acceleration of plasma at Mercury. Also the spatial and energy profiles of precipitating magnetospheric ions and electrons onto Mercury's surface, which can strongly affect the regolith in terms of space weathering and particle outflow, will be examined with the PIC and hybrid codes. MESSENGER spacecraft observations are used both to initiate and validate the global kinetic simulations to achieve a deeper understanding of the role kinetic physics play in magnetospheric dynamics.

Use of a hybrid code for global-scale plasma simulation

International Nuclear Information System (INIS)

Swift, D.W.

1996-01-01

This paper presents a demonstration of the use of a hybrid code to model the Earth's magnetosphere on a global scale. The typical hybrid code calculates the interaction of fully kinetic ions and a massless electron fluid with the magnetic field. This code also includes a fluid ion component to approximate the cold ionospheric plasma that spatially overlaps with the discrete particle component. Other innovative features of the code include a numerically generated curvilinear coordinate system and subcycling of the magnetic field update to the particle push. These innovations allow the code to accommodate disparate time and distance scales. The demonstration is a simulation of the noon meridian plane of the magnetosphere. The code exhibits the formation of fast and slow-mode shocks and tearing reconnection at the magnetopause. New results include particle acceleration in the cusp and nearly field aligned currents linking the cusp and polar ionosphere. The paper also describes a density depletion instability and measures to avoid it. 27 refs., 4 figs

Wave-Kinetic Simulations of the Nonlinear Generation of Electromagnetic VLF Waves through Velocity Ring Instabilities

Science.gov (United States)

Ganguli, G.; Crabtree, C. E.; Rudakov, L.; Mithaiwala, M.

2014-12-01

Velocity ring instabilities are a common naturally occuring magnetospheric phenomenon that can also be generated by man made ionospheric experiments. These instabilities are known to generate lower-hybrid waves, which generally cannot propagte out of the source region. However, nonlinear wave physics can convert these linearly driven electrostatic lower-hybrid waves into electromagnetic waves that can escape the source region. These nonlinearly generated waves can be an important source of VLF turbulence that controls the trapped electron lifetime in the radiation belts. We develop numerical solutions to the wave-kinetic equation in a periodic box including the effects of nonlinear (NL) scattering (nonlinear Landau damping) of Lower-hybrid waves giving the evolution of the wave-spectra in wavenumber space. Simultaneously we solve the particle diffusion equation of both the background plasma particles and the ring ions, due to both linear and nonlinear Landau resonances. At initial times for cold ring ions, an electrostatic beam mode is excited, while the kinetic mode is stable. As the instability progresses the ring ions heat, the beam mode is stabilized, and the kinetic mode destabilizes. When the amplitude of the waves becomes sufficient the lower-hybrid waves are scattered (by either nearly unmagnetized ions or magnetized electrons) into electromagnetic magnetosonic waves [Ganguli et al 2010]. The effect of NL scattering is to limit the amplitude of the waves, slowing down the quasilinear relaxation time and ultimately allowing more energy from the ring to be liberated into waves [Mithaiwala et al. 2011]. The effects of convection out of the instability region are modeled, additionally limiting the amplitude of the waves, allowing further energy to be liberated from the ring [Scales et al., 2012]. Results are compared to recent 3D PIC simulations [Winske and Duaghton 2012].

Hybrid Simulation of Composite Structures

DEFF Research Database (Denmark)

Høgh, Jacob Herold

experiment. The technique has primarily been used within earthquake engineering but many other fields of engineering have utilized the method with benefit. However, these previous efforts have focused on structures with a simple boundary between the numerical and physical substructure i.e. few degrees...... the transfer system and the control and monitoring techniques in the shared boundary is therefore a key issue in this type of hybrid simulation. During the research, hybrid simulation platforms have been programmed capable of running on different time scales with advanced control and monitoring techniques...

Dynamic simulation of urban hybrid electric vehicles; Dynamische Simulation von Stadthybridfahrzeugen

Energy Technology Data Exchange (ETDEWEB)

Winke, Florian; Bargende, Michael [Stuttgart Univ. (Germany). Inst. fuer Verbrennungsmotoren und Kraftfahrwesen (IVK)

2013-09-15

As a result of the rising requirements on the development process of modern vehicles, simulation models for the prediction of fuel efficiency have become an irreplaceable tool in the automotive industry. Especially for the design of hybrid electric drivetrains, the increasingly short development cycles can only be met by the use of efficient simulation models. At the IVK of the University of Stuttgart, different approaches to simulating the longitudinal dynamics of hybrid electric vehicles were analysed and compared within the presented project. The focus of the investigations was on urban operation. The objective was to develop a hybrid vehicle concept that allows an equitable comparison with pure battery electric vehicles. (orig.)

Real-time hybrid simulation using the convolution integral method

International Nuclear Information System (INIS)

Kim, Sung Jig; Christenson, Richard E; Wojtkiewicz, Steven F; Johnson, Erik A

2011-01-01

This paper proposes a real-time hybrid simulation method that will allow complex systems to be tested within the hybrid test framework by employing the convolution integral (CI) method. The proposed CI method is potentially transformative for real-time hybrid simulation. The CI method can allow real-time hybrid simulation to be conducted regardless of the size and complexity of the numerical model and for numerical stability to be ensured in the presence of high frequency responses in the simulation. This paper presents the general theory behind the proposed CI method and provides experimental verification of the proposed method by comparing the CI method to the current integration time-stepping (ITS) method. Real-time hybrid simulation is conducted in the Advanced Hazard Mitigation Laboratory at the University of Connecticut. A seismically excited two-story shear frame building with a magneto-rheological (MR) fluid damper is selected as the test structure to experimentally validate the proposed method. The building structure is numerically modeled and simulated, while the MR damper is physically tested. Real-time hybrid simulation using the proposed CI method is shown to provide accurate results

Effect of secondary structure on the thermodynamics and kinetics of PNA hybridization to DNA hairpins

DEFF Research Database (Denmark)

Kushon, S A; Jordan, J P; Seifert, J L

2001-01-01

The binding of a series of PNA and DNA probes to a group of unusually stable DNA hairpins of the tetraloop motif has been observed using absorbance hypochromicity (ABS), circular dichroism (CD), and a colorimetric assay for PNA/DNA duplex detection. These results indicate that both stable PNA...... structures in both target and probe molecules are shown to depress the melting temperatures and free energies of the probe-target duplexes. Kinetic analysis of hybridization yields reaction rates that are up to 160-fold slower than hybridization between two unstructured strands. The thermodynamic and kinetic...

Kinetics from Replica Exchange Molecular Dynamics Simulations.

Science.gov (United States)

Stelzl, Lukas S; Hummer, Gerhard

2017-08-08

Transitions between metastable states govern many fundamental processes in physics, chemistry and biology, from nucleation events in phase transitions to the folding of proteins. The free energy surfaces underlying these processes can be obtained from simulations using enhanced sampling methods. However, their altered dynamics makes kinetic and mechanistic information difficult or impossible to extract. Here, we show that, with replica exchange molecular dynamics (REMD), one can not only sample equilibrium properties but also extract kinetic information. For systems that strictly obey first-order kinetics, the procedure to extract rates is rigorous. For actual molecular systems whose long-time dynamics are captured by kinetic rate models, accurate rate coefficients can be determined from the statistics of the transitions between the metastable states at each replica temperature. We demonstrate the practical applicability of the procedure by constructing master equation (Markov state) models of peptide and RNA folding from REMD simulations.

Dynamic Hybrid Simulation of the Lunar Wake During ARTEMIS Crossing

Science.gov (United States)

Wiehle, S.; Plaschke, F.; Angelopoulos, V.; Auster, H.; Glassmeier, K.; Kriegel, H.; Motschmann, U. M.; Mueller, J.

2010-12-01

The interaction of the highly dynamic solar wind with the Moon is simulated with the A.I.K.E.F. (Adaptive Ion Kinetic Electron Fluid) code for the ARTEMIS P1 flyby on February 13, 2010. The A.I.K.E.F. hybrid plasma simulation code is the improved version of the Braunschweig code. It is able to automatically increase simulation grid resolution in areas of interest during runtime, which greatly increases resolution as well as performance. As the Moon has no intrinsic magnetic field and no ionosphere, the solar wind particles are absorbed at its surface, resulting in the formation of the lunar wake at the nightside. The solar wind magnetic field is basically convected through the Moon and the wake is slowly filled up with solar wind particles. However, this interaction is strongly influenced by the highly dynamic solar wind during the flyby. This is considered by a dynamic variation of the upstream conditions in the simulation using OMNI solar wind measurement data. By this method, a very good agreement between simulation and observations is achieved. The simulations show that the stationary structure of the lunar wake constitutes a tableau vivant in space representing the well-known Friedrichs diagram for MHD waves.

Kinetic simulations in plasmas: a general view and some applications

Energy Technology Data Exchange (ETDEWEB)

Alves, Maria Virginia [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma]. E-mail: alves@plasma.inpe.br

1999-07-01

In these lecture notes we talk about kinetic simulations plasma physics. We present a general view of the different approach that can be given to kinetic plasmas depending on the physical problem to be investigated. Some applications of kinetic simulations to space plasma phenomena and Pierce electrodes are introduced. (author)

Kinetic simulations in plasmas: a general view and some applications

International Nuclear Information System (INIS)

Alves, Maria Virginia

1999-01-01

In these lecture notes we talk about kinetic simulations plasma physics. We present a general view of the different approach that can be given to kinetic plasmas depending on the physical problem to be investigated. Some applications of kinetic simulations to space plasma phenomena and Pierce electrodes are introduced. (author)

Fully kinetic simulations of megajoule-scale dense plasma focus

Energy Technology Data Exchange (ETDEWEB)

Schmidt, A.; Link, A.; Tang, V.; Halvorson, C.; May, M. [Lawrence Livermore National Laboratory, Livermore California 94550 (United States); Welch, D. [Voss Scientific, LLC, Albuquerque, New Mexico 87108 (United States); Meehan, B. T.; Hagen, E. C. [National Security Technologies, LLC, Las Vegas, Nevada 89030 (United States)

2014-10-15

Dense plasma focus (DPF) Z-pinch devices are sources of copious high energy electrons and ions, x-rays, and neutrons. Megajoule-scale DPFs can generate 10{sup 12} neutrons per pulse in deuterium gas through a combination of thermonuclear and beam-target fusion. However, the details of the neutron production are not fully understood and past optimization efforts of these devices have been largely empirical. Previously, we reported on the first fully kinetic simulations of a kilojoule-scale DPF and demonstrated that both kinetic ions and kinetic electrons are needed to reproduce experimentally observed features, such as charged-particle beam formation and anomalous resistivity. Here, we present the first fully kinetic simulation of a MegaJoule DPF, with predicted ion and neutron spectra, neutron anisotropy, neutron spot size, and time history of neutron production. The total yield predicted by the simulation is in agreement with measured values, validating the kinetic model in a second energy regime.

CSP-based chemical kinetics mechanisms simplification strategy for non-premixed combustion: An application to hybrid rocket propulsion

KAUST Repository

Ciottoli, Pietro P.; Malpica Galassi, Riccardo; Lapenna, Pasquale E.; Leccese, G.; Bianchi, D.; Nasuti, F.; Creta, F.; Valorani, M.

2017-01-01

A set of simplified chemical kinetics mechanisms for hybrid rocket applications using gaseous oxygen (GOX) and hydroxyl-terminated polybutadiene (HTPB) is proposed. The starting point is a 561-species, 2538-reactions, detailed chemical kinetics

A nondissipative simulation method for the drift kinetic equation

International Nuclear Information System (INIS)

Watanabe, Tomo-Hiko; Sugama, Hideo; Sato, Tetsuya

2001-07-01

With the aim to study the ion temperature gradient (ITG) driven turbulence, a nondissipative kinetic simulation scheme is developed and comprehensively benchmarked. The new simulation method preserving the time-reversibility of basic kinetic equations can successfully reproduce the analytical solutions of asymmetric three-mode ITG equations which are extended to provide a more general reference for benchmarking than the previous work [T.-H. Watanabe, H. Sugama, and T. Sato: Phys. Plasmas 7 (2000) 984]. It is also applied to a dissipative three-mode system, and shows a good agreement with the analytical solution. The nondissipative simulation result of the ITG turbulence accurately satisfies the entropy balance equation. Usefulness of the nondissipative method for the drift kinetic simulations is confirmed in comparisons with other dissipative schemes. (author)

Numerical simulation and validation of SI-CAI hybrid combustion in a CAI/HCCI gasoline engine

Science.gov (United States)

Wang, Xinyan; Xie, Hui; Xie, Liyan; Zhang, Lianfang; Li, Le; Chen, Tao; Zhao, Hua

2013-02-01

SI-CAI hybrid combustion, also known as spark-assisted compression ignition (SACI), is a promising concept to extend the operating range of CAI (Controlled Auto-Ignition) and achieve the smooth transition between spark ignition (SI) and CAI in the gasoline engine. In this study, a SI-CAI hybrid combustion model (HCM) has been constructed on the basis of the 3-Zones Extended Coherent Flame Model (ECFM3Z). An ignition model is included to initiate the ECFM3Z calculation and induce the flame propagation. In order to precisely depict the subsequent auto-ignition process of the unburned fuel and air mixture independently after the initiation of flame propagation, the tabulated chemistry concept is adopted to describe the auto-ignition chemistry. The methodology for extracting tabulated parameters from the chemical kinetics calculations is developed so that both cool flame reactions and main auto-ignition combustion can be well captured under a wider range of thermodynamic conditions. The SI-CAI hybrid combustion model (HCM) is then applied in the three-dimensional computational fluid dynamics (3-D CFD) engine simulation. The simulation results are compared with the experimental data obtained from a single cylinder VVA engine. The detailed analysis of the simulations demonstrates that the SI-CAI hybrid combustion process is characterised with the early flame propagation and subsequent multi-site auto-ignition around the main flame front, which is consistent with the optical results reported by other researchers. Besides, the systematic study of the in-cylinder condition reveals the influence mechanism of the early flame propagation on the subsequent auto-ignition.

Thermal simulation of a cooling system of hybrid commercial vehicles; Thermalsimulation eine Hybrid-LKW-Kuehlsystems

Energy Technology Data Exchange (ETDEWEB)

Stroh, Christoph; Schnoerch, Stefan; Rathberger, Christian [Magna Powertrain Engineering Center Steyr GmbH und Co. KG, St. Valentin (Austria)

2012-11-01

In the past few years hybrid vehicles have been in the center of automotive engineering efforts, in particular in the field of passenger cars. But hybrid powertrains will also be important for commercial trucks. This focus on hybrid vehicles leads to high demands on thermal management since the additional components in a hybrid vehicle need appropriate cooling or even heating. In the given paper the simulation of a complete cooling system of a hybrid commercial vehicle will be explained. For this virtual examination the commercial 1D thermal management software KULI will be used, a co-simulation with several programs will not be done deliberately. Yet all aspects which are relevant for a global assessment of the thermal management are considered. The main focus is put on the investigation of appropriate concepts for the fluid circuits, including low and high temperature circuits, electric water pumps, etc. Moreover, also a refrigerant circuit with a chiller for active battery cooling will be used, the appropriate control strategy is implemented as well. For simulating transient profiles a simple driving simulation model is included, using road profile, ambient conditions, and various vehicle parameters as input. In addition an engine model is included which enables the investigation of fuel consumption potentials. This simulation model shows how the thermal management of a hybrid vehicle can be investigated with a single program and with reasonable effort. (orig.)

Magnetoresistive sensors for measurements of DNA hybridization kinetics - effect of TINA modifications

DEFF Research Database (Denmark)

Rizzi, Giovanni; Dufva, Martin; Hansen, Mikkel Fougt

2017-01-01

We present the use of magnetoresistive sensors integrated in a microfluidic system for real-time studies of the hybridization kinetics of DNA labeled with magnetic nanoparticles to an array of surface-tethered probes. The nanoparticles were magnetized by the magnetic field from the sensor current....... A local negative reference ensured that only the specific binding signal was measured. Analysis of the real-time hybridization using a two-compartment model yielded both the association and dissociation constants kon, and koff. The effect of probe modifications with ortho-Twisted Intercalating Nucleic...

HSimulator: Hybrid Stochastic/Deterministic Simulation of Biochemical Reaction Networks

Directory of Open Access Journals (Sweden)

Luca Marchetti

2017-01-01

Full Text Available HSimulator is a multithread simulator for mass-action biochemical reaction systems placed in a well-mixed environment. HSimulator provides optimized implementation of a set of widespread state-of-the-art stochastic, deterministic, and hybrid simulation strategies including the first publicly available implementation of the Hybrid Rejection-based Stochastic Simulation Algorithm (HRSSA. HRSSA, the fastest hybrid algorithm to date, allows for an efficient simulation of the models while ensuring the exact simulation of a subset of the reaction network modeling slow reactions. Benchmarks show that HSimulator is often considerably faster than the other considered simulators. The software, running on Java v6.0 or higher, offers a simulation GUI for modeling and visually exploring biological processes and a Javadoc-documented Java library to support the development of custom applications. HSimulator is released under the COSBI Shared Source license agreement (COSBI-SSLA.

Center for Gyrokinetic/MHD Hybrid Simulation of Energetic Particle Physics in Toroidal Plasmas (CSEPP). Final report

International Nuclear Information System (INIS)

Chen, Yang

2012-01-01

At Colorado University-Boulder the primary task is to extend our gyrokinetic Particle-in-Cell simulation of tokamak micro-turbulence and transport to the area of energetic particle physics. We have implemented a gyrokinetic ion/massless fluid electron hybrid model in the global δf-PIC code GEM, and benchmarked the code with analytic results on the thermal ion radiative damping rate of Toroidal Alfven Eigenmodes (TAE) and with mode frequency and spatial structure from eigenmode analysis. We also performed nonlinear simulations of both a single-n mode (n is the toroidal mode number) and multiple-n modes, and in the case of single-n, benchmarked the code on the saturation amplitude vs. particle collision rate with analytical theory. Most simulations use the f method for both ions species, but we have explored the full-f method for energetic particles in cases where the burst amplitude of the excited instabilities is large as to cause significant re-distribution or loss of the energetic particles. We used the hybrid model to study the stability of high-n TAEs in ITER. Our simulations show that the most unstable modes in ITER lie in the rage of 10 α (0) = 0.7% for the fully shaped ITER equilibrium. We also carried nonlinear simulations of the most unstable n = 15 mode and found that the saturation amplitude for the nominal ITER discharge is too low to cause large redistribution or loss of alpha particles. To include kinetic electron effects in the hybrid model we have studied a kinetic electron closure scheme for the fluid electron model. The most important element of the closure scheme is a complete Ohm's law for the parallel electric field E || , derived by combining the quasi-neutrality condition, the Ampere's equation and the v || moment of the gyrokinetic equations. A discretization method for the closure scheme is studied in detail for a three-dimensional shear-less slab plasma. It is found that for long-wavelength shear Alfven waves the kinetic closure scheme

Lightning talk slide for "SLACKHA: Software Library for Accelerating Chemical Kinetics on Hybrid Architectures"

OpenAIRE

Niemeyer, Kyle; Sung, Chih-Jen

2018-01-01

Lightning talk slide describing the "SLACKHA: Software Library for Accelerating Chemical Kinetics on Hybrid Architectures" project at the 2018 NSF SI2 PI meeting: https://si2-pi-community.github.io/2018-meeting/

Particle simulation on the propagation and plasma heating of the lower hybrid wave in the nonuniform system

International Nuclear Information System (INIS)

Abe, Hirotada; Kajitani, Hiroyuki; Itatani, Ryohei.

1977-07-01

A particle simulation model which treats the wave excitation and propagation in the nonuniform density by the external source is developed and applied for study of the lower hybrid heating in a fusion device. As the linear theory predicts, the cold lower hybrid wave is observed to increase its perpendicular wave number as it propagates to the higher density region and to damp away near the turning point. When the wave amplitude is large or the wave energy is about a half of the initial kinetic energy at a surface of plasma, the following features are observed for the increase of the ion and electron kinetic energies. Ion perpendicular energy distributions are observed to be approximated by the two Maxwell distributions or to have the components of the high energy tail, whose parallel velocities satisfy the resonance condition: νparallel = (ω-IOTAΩ sub(iota))/kappa parallel, where ω and kappa parallel the frequency and the parallel wave number of the external source, IOTA is an integer, and Ω sub(iota) is the ion cyclotron frequency. An strong increase of the parallel kinetic energy of the electron is observed near the plasma surface. These are mainly due to the trapped electrons and the collisional heating. (auth.)

Solar-simulator-pumped atomic iodine laser kinetics

Science.gov (United States)

Wilson, H. W.; Raju, S.; Shiu, Y. J.

1983-01-01

The literature contains broad ranges of disagreement in kinetic data for the atomic iodine laser. A kinetic model of a solar-simulator-pumped iodine laser is used to select those kinetic data consistent with recent laser experiments at the Langley Research Center. Analysis of the solar-simulator-pumped laser experiments resulted in the following estimates of rate coefficients: for alkyl radical (n-C3F7) and atomic iodine (I) recombination, 4.3 x 10 to the 11th power (1.9) + or - cu cm/s; for n-C3F7I stabilized atomic iodine recombination (I + I) 3.7 x 10 to the -32nd power (2.3) + or -1 cm to the 6th power/s; and for molecular iodine (I2) quenching, 3.1 x 10 to the -11th power (1.6) + or - 1 cu cm/s. These rates are consistent with the recent measurements.

Kinetic energy recovery and power management for hybrid electric vehicles

OpenAIRE

Suntharalingam, P

2011-01-01

The major contribution of the work presented in this thesis is a thorough investigation of the constraints on regenerative braking and kinetic energy recovery enhancement for electric/hybrid electric vehicles during braking. Regenerative braking systems provide an opportunity to recycle the braking energy, which is otherwise dissipated as heat in the brake pads. However, braking energy harnessing is a relatively new concept in the automotive sector which still requires further research and de...

Simulation of storage performance on hydropneumatic driveline in dual hybrid hydraulic passenger car

Directory of Open Access Journals (Sweden)

Wasbari Faizil

2017-01-01

Full Text Available The charging process is one of the critical processes in the hydro-pneumatic driveline storage system. It converts the kinetic energy of the vehicle braking and coasting to the compression energy. This energy is stored in the storage device called the accumulator. The system is planned to be used on the dual hydro-pneumatic hybrid driveline and applied to a hydraulic hybrid passenger car. The aim of this paper is to find the effect of charging parameters on the storage performance through simulation. Through the storage behaviour, the desirable and optimal sizing of the accumulator can be selected. The paper emphasized on the effect of pressure elevation, pre-charge pressure, effective volume, thermal reaction and required time of the accumulator’s charging process. The circuit of charging process has been designed and simulated by using the hydraulic tool in the Automation Studio software. The simulation results were corroborated through the component specification for data rationality. Through the simulation, it was found that pre-charge pressure had a significant effect on the charging process. It determined the efficiency of the effective volume. The higher the pressure elevation, the higher the effective volume. Nevertheless, the more energy required to compress the nitrogen gas in the bladder. Besides, in term of volume displacement, higher volume displacement reduced charging time and lower the fluid temperature. The simulation had been positively highlighted the critical point in charging process which later on, benefited the sizing process in the component selection specification.

Hybrid neural network model for simulating sorbitol synthesis by glucose-fructose oxidoreductase in Zymomonas mobilis CP4

Directory of Open Access Journals (Sweden)

Bravo S.

2004-01-01

Full Text Available A hybrid neural network model for simulating the process of enzymatic reduction of fructose to sorbitol process catalyzed by glucose-fructose oxidoreductase in Zymomonas mobilis CP4 is presented. Data used to derive and validate the model was obtained from experiments carried out under different conditions of pH, temperature and concentrations of both substrates (glucose and fructose involved in the reaction. Sonicated and lyophilized cells were used as source of the enzyme. The optimal pH for sorbitol synthesis at 30º C is 6.5. For a value of pH of 6, the optimal temperature is 35º C. The neural network in the model computes the value of the kinetic relationship. The hybrid neural network model is able to simulate changes in the substrates and product concentrations during sorbitol synthesis under pH and temperature conditions ranging between 5 and 7.5 and 25 and 40º C, respectively. Under these conditions the rate of sorbitol synthesis shows important differences. Values computed using the hybrid neural network model have an average error of 1.7·10-3 mole.

Recent progress of hybrid simulation for energetic particles and MHD

International Nuclear Information System (INIS)

Todo, Y.

2013-01-01

Several hybrid simulation models have been constructed to study the evolution of Alfven eigenmodes destabilized by energetic particles. Recent hybrid simulation results of energetic particle driven instabilities are presented in this paper. (J.P.N.)

A hybrid flight control for a simulated raptor-30 v2 helicopter

International Nuclear Information System (INIS)

Khizer, A.N.

2015-01-01

This paper presents a hybrid flight control system for a single rotor simulated Raptor-30 V2 helicopter. Hybrid intelligent control system, combination of the conventional and intelligent control methodologies, is applied to small model helicopter. The proposed hybrid control used PID as a traditional control and fuzzy as an intelligent control so as to take the maximum advantage of advanced control theory. The helicopter model used; comes from X-Plane flight simulator and their hybrid flight control system was simulated using MATLAB/SIMULINK in a simulation platform. X-Plane is also used to visualize the performance of this proposed autopilot design. Through a series of numerous experiments, the operation of hybrid control system was investigated. Results verified that the proposed hybrid control has an excellent performance at hovering flight mode. (author)

Removal of Cadmium and Lead from Aqueous Solution by Hydroxyapatite/Chitosan Hybrid Fibrous Sorbent: Kinetics and Equilibrium Studies

Directory of Open Access Journals (Sweden)

Soyeon Park

2015-01-01

Full Text Available Hydroxyapatite (HAp/chitosan composites were prepared by a coprecipitation method, dropping a mixture of chitosan solution and phosphoric acid solution into a calcium hydroxide solution. Using the HAp/chitosan composites prepared, HAp/chitosan hybrid fibers with various HAp contents were prepared by a wet spinning method. X-ray diffraction and scanning electron microscopy analyses revealed that HAp particles were coated onto the surface of the fiber, and the surface roughness increased with increasing the HAp contents in the fiber. In order to evaluate the heavy metal removal characteristics of the HAp/chitosan hybrid fiber, adsorption tests were conducted and the results were compared with those of bare chitosan fibers. The results showed better performance in heavy metal ion removal for the HAp/chitosan hybrid fiber than the chitosan fiber. As the HAp content in the hybrid fiber increased, the removal efficiency of heavy metal ions also increased due to the increase of the specific surface area of the HAp/chitosan hybrid fiber. Adsorption kinetic and isotherm tests revealed that Pb2+ and Cd2+ adsorption to the hybrid fiber follows pseudo-second-order kinetic and Langmuir-type adsorption, respectively.

CHEMSIMUL: A simulator for chemical kinetics

DEFF Research Database (Denmark)

Kirkegaard, P.; Bjergbakke, E.

1999-01-01

CHEMSIMUL is a computer program system for numerical simulation of chemical reaction systems. It can be used for modeling complex kinetics in many contexts, in particular radiolytic processes. It contains a translator module and a module for solving theresulting coupled nonlinear ordinary...

Molecular Dynamics Simulations of Kinetic Models for Chiral Dominance in Soft Condensed Matter

DEFF Research Database (Denmark)

Toxvaerd, Søren

2001-01-01

Molecular dynamics simulation, models for isomerization kinetics, origin of biomolecular chirality......Molecular dynamics simulation, models for isomerization kinetics, origin of biomolecular chirality...

A new hybrid-Lagrangian numerical scheme for gyrokinetic simulation of tokamak edge plasma

Energy Technology Data Exchange (ETDEWEB)

Ku, S., E-mail: sku@pppl.gov [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Hager, R.; Chang, C.S. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Kwon, J.M. [National Fusion Research Institute (Korea, Republic of); Parker, S.E. [University of Colorado Boulder (United States)

2016-06-15

In order to enable kinetic simulation of non-thermal edge plasmas at a reduced computational cost, a new hybrid-Lagrangian δf scheme has been developed that utilizes the phase space grid in addition to the usual marker particles, taking advantage of the computational strengths from both sides. The new scheme splits the particle distribution function of a kinetic equation into two parts. Marker particles contain the fast space-time varying, δf, part of the distribution function and the coarse-grained phase-space grid contains the slow space-time varying part. The coarse-grained phase-space grid reduces the memory-requirement and the computing cost, while the marker particles provide scalable computing ability for the fine-grained physics. Weights of the marker particles are determined by a direct weight evolution equation instead of the differential form weight evolution equations that the conventional delta-f schemes use. The particle weight can be slowly transferred to the phase space grid, thereby reducing the growth of the particle weights. The non-Lagrangian part of the kinetic equation – e.g., collision operation, ionization, charge exchange, heat-source, radiative cooling, and others – can be operated directly on the phase space grid. Deviation of the particle distribution function on the velocity grid from a Maxwellian distribution function – driven by ionization, charge exchange and wall loss – is allowed to be arbitrarily large. The numerical scheme is implemented in the gyrokinetic particle code XGC1, which specializes in simulating the tokamak edge plasma that crosses the magnetic separatrix and is in contact with the material wall.

Kinetic Alfven waves and electron physics. II. Oblique slow shocks

International Nuclear Information System (INIS)

Yin, L.; Winske, D.; Daughton, W.

2007-01-01

One-dimensional (1D) particle-in-cell (PIC; kinetic ions and electrons) and hybrid (kinetic ions; adiabatic and massless fluid electrons) simulations of highly oblique slow shocks (θ Bn =84 deg. and β=0.1) [Yin et al., J. Geophys. Res., 110, A09217 (2005)] have shown that the dissipation from the ions is too weak to form a shock and that kinetic electron physics is required. The PIC simulations also showed that the downstream electron temperature becomes anisotropic (T e parallel )>T e perpendicular ), as observed in slow shocks in space. The electron anisotropy results, in part, from the electron acceleration/heating by parallel electric fields of obliquely propagating kinetic Alfven waves (KAWs) excited by ion-ion streaming, which cannot be modeled accurately in hybrid simulations. In the shock ramp, spiky structures occur in density and electron parallel temperature, where the ion parallel temperature decreases due to the reduction of the ion backstreaming speed. In this paper, KAW and electron physics in oblique slow shocks are further examined under lower electron beta conditions. It is found that as the electron beta is reduced, the resonant interaction between electrons and the wave parallel electric fields shifts to the tail of the electron velocity distribution, providing more efficient parallel heating. As a consequence, for β e =0.02, the electron physics is shown to influence the formation of a θ Bn =75 deg. shock. Electron effects are further enhanced at a more oblique shock angle (θ Bn =84 deg.) when both the growth rate and the range of unstable modes on the KAW branch increase. Small-scale electron and ion phase-space vortices in the shock ramp formed by electron-KAW interactions and the reduction of the ion backstreaming speed, respectively, are observed in the simulations and confirmed in homogeneous geometries in one and two spatial dimensions in the accompanying paper [Yin et al., Phys. Plasmas 14, 062104 (2007)]. Results from this study

Kinetic Energy from Supernova Feedback in High-resolution Galaxy Simulations

Science.gov (United States)

Simpson, Christine M.; Bryan, Greg L.; Hummels, Cameron; Ostriker, Jeremiah P.

2015-08-01

We describe a new method for adding a prescribed amount of kinetic energy to simulated gas modeled on a cartesian grid by directly altering grid cells’ mass and velocity in a distributed fashion. The method is explored in the context of supernova (SN) feedback in high-resolution (˜10 pc) hydrodynamic simulations of galaxy formation. Resolution dependence is a primary consideration in our application of the method, and simulations of isolated explosions (performed at different resolutions) motivate a resolution-dependent scaling for the injected fraction of kinetic energy that we apply in cosmological simulations of a 109 M⊙ dwarf halo. We find that in high-density media (≳50 cm-3) with coarse resolution (≳4 pc per cell), results are sensitive to the initial kinetic energy fraction due to early and rapid cooling. In our galaxy simulations, the deposition of small amounts of SN energy in kinetic form (as little as 1%) has a dramatic impact on the evolution of the system, resulting in an order-of-magnitude suppression of stellar mass. The overall behavior of the galaxy in the two highest resolution simulations we perform appears to converge. We discuss the resulting distribution of stellar metallicities, an observable sensitive to galactic wind properties, and find that while the new method demonstrates increased agreement with observed systems, significant discrepancies remain, likely due to simplistic assumptions that neglect contributions from SNe Ia and stellar winds.

Hybrid Simulation in Teaching Clinical Breast Examination to Medical Students.

Science.gov (United States)

Nassif, Joseph; Sleiman, Abdul-Karim; Nassar, Anwar H; Naamani, Sima; Sharara-Chami, Rana

2017-10-10

Clinical breast examination (CBE) is traditionally taught to third-year medical students using a lecture and a tabletop breast model. The opportunity to clinically practice CBE depends on patient availability and willingness to be examined by students, especially in culturally sensitive environments. We propose the use of a hybrid simulation model consisting of a standardized patient (SP) wearing a silicone breast simulator jacket and hypothesize that this, compared to traditional teaching methods, would result in improved learning. Consenting third-year medical students (N = 82) at a university-affiliated tertiary care center were cluster-randomized into two groups: hybrid simulation (breast jacket + SP) and control (tabletop breast model). Students received the standard lecture by instructors blinded to the randomization, followed by randomization group-based learning and practice sessions. Two weeks later, participants were assessed in an Objective Structured Clinical Examination (OSCE), which included three stations with SPs blinded to the intervention. The SPs graded the students on CBE completeness, and students completed a self-assessment of their performance and confidence during the examination. CBE completeness scores did not differ between the two groups (p = 0.889). Hybrid simulation improved lesion identification grades (p simulation relieved the fear of missing a lesion on CBE (p = 0.043) and increased satisfaction with the teaching method among students (p = 0.002). As a novel educational tool, hybrid simulation improves the sensitivity of CBE performed by medical students without affecting its specificity. Hybrid simulation may play a role in increasing the confidence of medical students during CBE.

Full Tokamak discharge simulation and kinetic plasma profile control for ITER

International Nuclear Information System (INIS)

Hee Kim, S.

2009-10-01

technique that simplifies the active real-time control of several kinetic plasma profiles in ITER. The response of the plasma profiles to power changes of auxiliary H and CD systems is modelled. To allow real-time update of the plasma profile response model, the related physics is simplified with several assumptions. The electron temperature profile response is modelled by simplifying the electron heat transport equation. The q profile response is modelled by directly relating it to the changes of source current density profiles. The required actuator power changes are calculated using the singular value decomposition (SVD) technique, taking the saturation of the actuator powers into account. The potential of this control technique has been shown by applying it to simulations of the ITER hybrid mode operation. (author)

Nonlinear evolution of the lower-hybrid drift instability

International Nuclear Information System (INIS)

Brackbill, J.U.; Forslund, D.W.; Quest, K.B.; Winske, D.

1984-01-01

The results of simulations of the lower-hybrid drift instability in a neutral sheet configuration are described. The simulations use an implicit formulation to relax the usual time step limitations and thus extend previous explicit calculations to weaker gradients, larger mass ratios, and long times compared with the linear growth time. The numerical results give the scaling of the saturation level, heating rates, resistivity, and cross-field diffusion and a demonstration by comparison with a fluid electron model that dissipation in the lower-hybrid drift instability is caused by electron kinetic effects

Self-consistent kinetic simulations of lower hybrid drift instability resulting in electron current driven by fusion products in tokamak plasmas

International Nuclear Information System (INIS)

Cook, J W S; Chapman, S C; Dendy, R O; Brady, C S

2011-01-01

We present particle-in-cell (PIC) simulations of minority energetic protons in deuterium plasmas, which demonstrate a collective instability responsible for emission near the lower hybrid frequency and its harmonics. The simulations capture the lower hybrid drift instability in a parameter regime motivated by tokamak fusion plasma conditions, and show further that the excited electromagnetic fields collectively and collisionlessly couple free energy from the protons to directed electron motion. This results in an asymmetric tail antiparallel to the magnetic field. We focus on obliquely propagating modes excited by energetic ions, whose ring-beam distribution is motivated by population inversions related to ion cyclotron emission, in a background plasma with a temperature similar to that of the core of a large tokamak plasma. A fully self-consistent electromagnetic relativistic PIC code representing all vector field quantities and particle velocities in three dimensions as functions of a single spatial dimension is used to model this situation, by evolving the initial antiparallel travelling ring-beam distribution of 3 MeV protons in a background 10 keV Maxwellian deuterium plasma with realistic ion-electron mass ratio. These simulations provide a proof-of-principle for a key plasma physics process that may be exploited in future alpha channelling scenarios for magnetically confined burning plasmas.

A hybrid parallel framework for the cellular Potts model simulations

Energy Technology Data Exchange (ETDEWEB)

Jiang, Yi [Los Alamos National Laboratory; He, Kejing [SOUTH CHINA UNIV; Dong, Shoubin [SOUTH CHINA UNIV

2009-01-01

The Cellular Potts Model (CPM) has been widely used for biological simulations. However, most current implementations are either sequential or approximated, which can't be used for large scale complex 3D simulation. In this paper we present a hybrid parallel framework for CPM simulations. The time-consuming POE solving, cell division, and cell reaction operation are distributed to clusters using the Message Passing Interface (MPI). The Monte Carlo lattice update is parallelized on shared-memory SMP system using OpenMP. Because the Monte Carlo lattice update is much faster than the POE solving and SMP systems are more and more common, this hybrid approach achieves good performance and high accuracy at the same time. Based on the parallel Cellular Potts Model, we studied the avascular tumor growth using a multiscale model. The application and performance analysis show that the hybrid parallel framework is quite efficient. The hybrid parallel CPM can be used for the large scale simulation ({approx}10{sup 8} sites) of complex collective behavior of numerous cells ({approx}10{sup 6}).

Key parameters analysis of hybrid HEMP simulator

International Nuclear Information System (INIS)

Mao Congguang; Zhou Hui

2009-01-01

According to the new standards on the high-altitude electromagnetic pulse (HEMP) developed by International Electrotechnical Commission (IEC), the target parameter requirements of the key structure of the hybrid HEMP simulator are decomposed. Firstly, the influences of the different excitation sources and biconical structures to the key parameters of the radiated electric field wave shape are investigated and analyzed. Then based on the influence curves the target parameter requirements of the pulse generator are proposed. Finally the appropriate parameters of the biconical structure and the excitation sources are chosen, and the computational result of the electric field in free space is presented. The results are of great value for the design of the hybrid HEMP simulator. (authors)

HRSSA – Efficient hybrid stochastic simulation for spatially homogeneous biochemical reaction networks

International Nuclear Information System (INIS)

Marchetti, Luca; Priami, Corrado; Thanh, Vo Hong

2016-01-01

This paper introduces HRSSA (Hybrid Rejection-based Stochastic Simulation Algorithm), a new efficient hybrid stochastic simulation algorithm for spatially homogeneous biochemical reaction networks. HRSSA is built on top of RSSA, an exact stochastic simulation algorithm which relies on propensity bounds to select next reaction firings and to reduce the average number of reaction propensity updates needed during the simulation. HRSSA exploits the computational advantage of propensity bounds to manage time-varying transition propensities and to apply dynamic partitioning of reactions, which constitute the two most significant bottlenecks of hybrid simulation. A comprehensive set of simulation benchmarks is provided for evaluating performance and accuracy of HRSSA against other state of the art algorithms.

HRSSA – Efficient hybrid stochastic simulation for spatially homogeneous biochemical reaction networks

Energy Technology Data Exchange (ETDEWEB)

Marchetti, Luca, E-mail: marchetti@cosbi.eu [The Microsoft Research – University of Trento Centre for Computational and Systems Biology (COSBI), Piazza Manifattura, 1, 38068 Rovereto (Italy); Priami, Corrado, E-mail: priami@cosbi.eu [The Microsoft Research – University of Trento Centre for Computational and Systems Biology (COSBI), Piazza Manifattura, 1, 38068 Rovereto (Italy); University of Trento, Department of Mathematics (Italy); Thanh, Vo Hong, E-mail: vo@cosbi.eu [The Microsoft Research – University of Trento Centre for Computational and Systems Biology (COSBI), Piazza Manifattura, 1, 38068 Rovereto (Italy)

2016-07-15

This paper introduces HRSSA (Hybrid Rejection-based Stochastic Simulation Algorithm), a new efficient hybrid stochastic simulation algorithm for spatially homogeneous biochemical reaction networks. HRSSA is built on top of RSSA, an exact stochastic simulation algorithm which relies on propensity bounds to select next reaction firings and to reduce the average number of reaction propensity updates needed during the simulation. HRSSA exploits the computational advantage of propensity bounds to manage time-varying transition propensities and to apply dynamic partitioning of reactions, which constitute the two most significant bottlenecks of hybrid simulation. A comprehensive set of simulation benchmarks is provided for evaluating performance and accuracy of HRSSA against other state of the art algorithms.

Kinetic Simulations of Type II Radio Burst Emission Processes

Science.gov (United States)

Ganse, U.; Spanier, F. A.; Vainio, R. O.

2011-12-01

The fundamental emission process of Type II Radio Bursts has been under discussion for many decades. While analytic deliberations point to three wave interaction as the source for fundamental and harmonic radio emissions, sparse in-situ observational data and high computational demands for kinetic simulations have not allowed for a definite conclusion to be reached. A popular model puts the radio emission into the foreshock region of a coronal mass ejection's shock front, where shock drift acceleration can create eletrcon beam populations in the otherwise quiescent foreshock plasma. Beam-driven instabilities are then assumed to create waves, forming the starting point of three wave interaction processes. Using our kinetic particle-in-cell code, we have studied a number of emission scenarios based on electron beam populations in a CME foreshock, with focus on wave-interaction microphysics on kinetic scales. The self-consistent, fully kinetic simulations with completely physical mass-ratio show fundamental and harmonic emission of transverse electromagnetic waves and allow for detailled statistical analysis of all contributing wavemodes and their couplings.

Operational High Resolution Chemical Kinetics Simulation, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Numerical simulations of chemical kinetics are critical to addressing urgent issues in both the developed and developing world. Ongoing demand for higher resolution...

Strategy and gaps for modeling, simulation, and control of hybrid systems

Energy Technology Data Exchange (ETDEWEB)

Rabiti, Cristian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Garcia, Humberto E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hovsapian, Rob [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kinoshita, Robert [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mesina, George L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bragg-Sitton, Shannon M. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Boardman, Richard D. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2015-04-01

The purpose of this report is to establish a strategy for modeling and simulation of candidate hybrid energy systems. Modeling and simulation is necessary to design, evaluate, and optimize the system technical and economic performance. Accordingly, this report first establishes the simulation requirements to analysis candidate hybrid systems. Simulation fidelity levels are established based on the temporal scale, real and synthetic data availability or needs, solution accuracy, and output parameters needed to evaluate case-specific figures of merit. Accordingly, the associated computational and co-simulation resources needed are established; including physical models when needed, code assembly and integrated solutions platforms, mathematical solvers, and data processing. This report first attempts to describe the figures of merit, systems requirements, and constraints that are necessary and sufficient to characterize the grid and hybrid systems behavior and market interactions. Loss of Load Probability (LOLP) and effective cost of Effective Cost of Energy (ECE), as opposed to the standard Levelized Cost of Electricty (LCOE), are introduced as technical and economical indices for integrated energy system evaluations. Financial assessment methods are subsequently introduced for evaluation of non-traditional, hybrid energy systems. Algorithms for coupled and iterative evaluation of the technical and economic performance are subsequently discussed. This report further defines modeling objectives, computational tools, solution approaches, and real-time data collection and processing (in some cases using real test units) that will be required to model, co-simulate, and optimize; (a) an energy system components (e.g., power generation unit, chemical process, electricity management unit), (b) system domains (e.g., thermal, electrical or chemical energy generation, conversion, and transport), and (c) systems control modules. Co-simulation of complex, tightly coupled

A dynamic simulation tool for the battery-hybrid hydrogen fuel cell vehicle

Energy Technology Data Exchange (ETDEWEB)

Moore, R.M. [Hawaii Natural Energy Institute, University of Hawaii, Manoa (United States); Ramaswamy, S.; Cunningham, J.M. [California Univ., Berkeley, CA (United States); Hauer, K.H. [xcellvision, Major-Hirst-Strasse 11, 38422 Wolfsburg (Germany)

2006-10-15

This paper describes a dynamic fuel cell vehicle simulation tool for the battery-hybrid direct-hydrogen fuel cell vehicle. The emphasis is on simulation of the hybridized hydrogen fuel cell system within an existing fuel cell vehicle simulation tool. The discussion is focused on the simulation of the sub-systems that are unique to the hybridized direct-hydrogen vehicle, and builds on a previous paper that described a simulation tool for the load-following direct-hydrogen vehicle. The configuration of the general fuel cell vehicle simulation tool has been previously presented in detail, and is only briefly reviewed in the introduction to this paper. Strictly speaking, the results provided in this paper only serve as an example that is valid for the specific fuel cell vehicle design configuration analyzed. Different design choices may lead to different results, depending strongly on the parameters used and choices taken during the detailed design process required for this highly non-linear and n-dimensional system. The primary purpose of this paper is not to provide a dynamic simulation tool that is the ''final word'' for the ''optimal'' hybrid fuel cell vehicle design. The primary purpose is to provide an explanation of a simulation method for analyzing the energetic aspects of a hybrid fuel cell vehicle. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Control-relevant modeling and simulation of a SOFC-GT hybrid system

OpenAIRE

Rambabu Kandepu; Lars Imsland; Christoph Stiller; Bjarne A. Foss; Vinay Kariwala

2006-01-01

In this paper, control-relevant models of the most important components in a SOFC-GT hybrid system are described. Dynamic simulations are performed on the overall hybrid system. The model is used to develop a simple control structure, but the simulations show that more elaborate control is needed.

Modular modeling and simulation of hybrid power trains; Modulare Modellbildung und Simulation von hybriden Antriebstraengen

Energy Technology Data Exchange (ETDEWEB)

Kelz, Gerald; Hirschberg, Wolfgang [Inst. fuer Fahrzeugtechnik, Technische Univ. Graz (Austria)

2009-07-01

The power train of a hybrid vehicle is considerably more complex than that of conventional vehicles. Whilst the topology of a conventional vehicle is normally fixed, the arrangement of the power train components for innovative propulsion systems is a flexible one. The aim is to find those topologies and configurations which are optimal for the intended use. Fuel consumption potentials can be derived with the aid of vehicle longitudinal dynamics simulation. Mostly these simulations are carried out using commercial software which is optimized for the standard topology and do not offer the flexibility to calculate arbitrary topologies. This article covers the modular modeling and the fuel consumption simulation of complex hybrid power trains for topology analysis. A component library for the development of arbitrary hybrid propulsion systems is introduced. The focus lies on an efficient and fast modeling which provides exact simulation results. Several models of power train components are introduced. (orig.)

Control-relevant modeling and simulation of a SOFC-GT hybrid system

Directory of Open Access Journals (Sweden)

Rambabu Kandepu

2006-07-01

Full Text Available In this paper, control-relevant models of the most important components in a SOFC-GT hybrid system are described. Dynamic simulations are performed on the overall hybrid system. The model is used to develop a simple control structure, but the simulations show that more elaborate control is needed.

Isothermal crystallization kinetics in simulated high-level nuclear waste glass

International Nuclear Information System (INIS)

Vienna, J.D.; Hrma, P.; Smith, D.E.

1997-01-01

Crystallization kinetics of a simulated high-level waste (HLW) glass were measured and modelled. Kinetics of acmite growth in the standard HW39-4 glass were measured using the isothermal method. A time-temperature-transformation (TTT) diagram was generated from these data. Classical glass-crystal transformation kinetic models were empirically applied to the crystallization data. These models adequately describe the kinetics of crystallization in complex HLW glasses (i.e., RSquared = 0.908). An approach to measurement, fitting, and use of TTT diagrams for prediction of crystallinity in a HLW glass canister is proposed

A study on optimization of hybrid drive train using Advanced Vehicle Simulator (ADVISOR)

Energy Technology Data Exchange (ETDEWEB)

Same, Adam; Stipe, Alex; Grossman, David; Park, Jae Wan [Department of Mechanical and Aeronautical Engineering, University of California, Davis, One Shields Ave, Davis, CA 95616 (United States)

2010-10-01

This study investigates the advantages and disadvantages of three hybrid drive train configurations: series, parallel, and ''through-the-ground'' parallel. Power flow simulations are conducted with the MATLAB/Simulink-based software ADVISOR. These simulations are then applied in an application for the UC Davis SAE Formula Hybrid vehicle. ADVISOR performs simulation calculations for vehicle position using a combined backward/forward method. These simulations are used to study how efficiency and agility are affected by the motor, fuel converter, and hybrid configuration. Three different vehicle models are developed to optimize the drive train of a vehicle for three stages of the SAE Formula Hybrid competition: autocross, endurance, and acceleration. Input cycles are created based on rough estimates of track geometry. The output from these ADVISOR simulations is a series of plots of velocity profile and energy storage State of Charge that provide a good estimate of how the Formula Hybrid vehicle will perform on the given course. The most noticeable discrepancy between the input cycle and the actual velocity profile of the vehicle occurs during deceleration. A weighted ranking system is developed to organize the simulation results and to determine the best drive train configuration for the Formula Hybrid vehicle. Results show that the through-the-ground parallel configuration with front-mounted motors achieves an optimal balance of efficiency, simplicity, and cost. ADVISOR is proven to be a useful tool for vehicle power train design for the SAE Formula Hybrid competition. This vehicle model based on ADVISOR simulation is applicable to various studies concerning performance and efficiency of hybrid drive trains. (author)

Kinetic Scale Structure of Low-frequency Waves and Fluctuations

Energy Technology Data Exchange (ETDEWEB)

López, Rodrigo A.; Yoon, Peter H. [Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, MD 20771 (United States); Araneda, Jaime A., E-mail: rlopezh@umd.edu, E-mail: yoonp@umd.edu [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile)

2017-08-10

The dissipation of solar wind turbulence at kinetic scales is believed to be important for the heating of the corona and for accelerating the wind. The linear Vlasov kinetic theory is a useful tool for identifying various wave modes, including kinetic Alfvén, fast magnetosonic/whistler, and ion-acoustic (or kinetic slow), and their possible roles in the dissipation. However, the kinetic mode structure in the vicinity of ion-cyclotron modes is not clearly understood. The present paper aims to further elucidate the structure of these low-frequency waves by introducing discrete particle effects through hybrid simulations and Klimontovich formalism of spontaneous emission theory. The theory and simulation of spontaneously emitted low-frequency fluctuations are employed to identify and distinguish the detailed mode structures associated with ion-Bernstein modes versus quasi-modes. The spontaneous emission theory and simulation also confirm the findings of the Vlasov theory in that the kinetic Alfvén waves can be defined over a wide range of frequencies, including the proton cyclotron frequency and its harmonics, especially for high-beta plasmas. This implies that these low-frequency modes may play predominant roles even in the fully kinetic description of kinetic scale turbulence and dissipation despite the fact that cyclotron harmonic and Bernstein modes may also play important roles in wave–particle interactions.

STEM image simulation with hybrid CPU/GPU programming

International Nuclear Information System (INIS)

Yao, Y.; Ge, B.H.; Shen, X.; Wang, Y.G.; Yu, R.C.

2016-01-01

STEM image simulation is achieved via hybrid CPU/GPU programming under parallel algorithm architecture to speed up calculation on a personal computer (PC). To utilize the calculation power of a PC fully, the simulation is performed using the GPU core and multi-CPU cores at the same time to significantly improve efficiency. GaSb and an artificial GaSb/InAs interface with atom diffusion have been used to verify the computation. - Highlights: • STEM image simulation is achieved by hybrid CPU/GPU programming under parallel algorithm architecture to speed up the calculation in the personal computer (PC). • In order to fully utilize the calculation power of the PC, the simulation is performed by GPU core and multi-CPU cores at the same time so efficiency is improved significantly. • GaSb and artificial GaSb/InAs interface with atom diffusion have been used to verify the computation. The results reveal some unintuitive phenomena about the contrast variation with the atom numbers.

STEM image simulation with hybrid CPU/GPU programming

Energy Technology Data Exchange (ETDEWEB)

Yao, Y., E-mail: yaoyuan@iphy.ac.cn; Ge, B.H.; Shen, X.; Wang, Y.G.; Yu, R.C.

2016-07-15

STEM image simulation is achieved via hybrid CPU/GPU programming under parallel algorithm architecture to speed up calculation on a personal computer (PC). To utilize the calculation power of a PC fully, the simulation is performed using the GPU core and multi-CPU cores at the same time to significantly improve efficiency. GaSb and an artificial GaSb/InAs interface with atom diffusion have been used to verify the computation. - Highlights: • STEM image simulation is achieved by hybrid CPU/GPU programming under parallel algorithm architecture to speed up the calculation in the personal computer (PC). • In order to fully utilize the calculation power of the PC, the simulation is performed by GPU core and multi-CPU cores at the same time so efficiency is improved significantly. • GaSb and artificial GaSb/InAs interface with atom diffusion have been used to verify the computation. The results reveal some unintuitive phenomena about the contrast variation with the atom numbers.

CFD simulation on condensation inside a Hybrid SIT

Energy Technology Data Exchange (ETDEWEB)

Jeon, Byong Guk; Ryu, Sung Uk; Kim, Seok; Euh, Dong Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

The concept of Hybrid Safety Injection Tank system (Hybrid SIT) was proposed by Korea Atomic Energy Research Institute (KAERI) aiming at Advanced Power Reactor Plus. The main advantage of the system is the ready injection of coolant into the reactor coolant system at high pressure. In this paper, a CFD simulation is conducted as a preliminary study. In Hybrid SITs, condensation inside the tank affects its pressure rise and injection time. In an attempt to explore the condensation in detail, we manufactured a dedicated experimental facility for visualization of condensation-induced thermal mixing and conducted a preliminary CFD simulation. Its condensation models were validated first and then computational domain was constructed. The water region was modeled as a solid for stable calculation. The CFD results gave less condensation and excessive pressurization because of lack of steam penetration into the water. In the future, the water region will be modeled as liquid using a VOF model.

A hybrid society model for simulating residential electricity consumption

International Nuclear Information System (INIS)

Xu, Minjie; Hu, Zhaoguang; Wu, Junyong; Zhou, Yuhui

2008-01-01

In this paper, a hybrid social model of econometric model and social influence model is proposed for evaluating the influence of pricing policy and public education policy on residential habit of electricity using in power resources management. And, a hybrid society simulation platform based on the proposed model, called residential electricity consumption multi-agent systems (RECMAS), is designed for simulating residential electricity consumption by multi-agent system. RECMAS is composed of consumer agent, power supplier agent, and policy maker agent. It provides the policy makers with a useful tool to evaluate power price policies and public education campaigns in different scenarios. According to an influenced diffusion mechanism, RECMAS can simulate the residential electricity demand-supply chain and analyze impacts of the factors on residential electricity consumption. Finally, the proposed method is used to simulate urban residential electricity consumption in China. (author)

A hybrid society model for simulating residential electricity consumption

Energy Technology Data Exchange (ETDEWEB)

Xu, Minjie [School of Electrical Engineering, Beijing Jiaotong University, Beijing (China); State Power Economic Research Institute, Beijing (China); Hu, Zhaoguang [State Power Economic Research Institute, Beijing (China); Wu, Junyong; Zhou, Yuhui [School of Electrical Engineering, Beijing Jiaotong University, Beijing (China)

2008-12-15

In this paper, a hybrid social model of econometric model and social influence model is proposed for evaluating the influence of pricing policy and public education policy on residential habit of electricity using in power resources management. And, a hybrid society simulation platform based on the proposed model, called residential electricity consumption multi-agent systems (RECMAS), is designed for simulating residential electricity consumption by multi-agent system. RECMAS is composed of consumer agent, power supplier agent, and policy maker agent. It provides the policy makers with a useful tool to evaluate power price policies and public education campaigns in different scenarios. According to an influenced diffusion mechanism, RECMAS can simulate the residential electricity demand-supply chain and analyze impacts of the factors on residential electricity consumption. Finally, the proposed method is used to simulate urban residential electricity consumption in China. (author)

Dynamic Performance Comparison for MPPT-PV Systems using Hybrid Pspice/Matlab Simulation

Science.gov (United States)

Aouchiche, N.; Becherif, M.; HadjArab, A.; Aitcheikh, M. S.; Ramadan, H. S.; Cheknane, A.

2016-10-01

The power generated by solar photovoltaic (PV) module depends on the surrounding irradiance and temperature. This paper presents a hybrid Matlab™/Pspice™ simulation model of PV system, combined with Cadence software SLPS. The hybridization is performed in order to gain the advantages of both simulation tools such as accuracy and efficiency in both Pspice electronic circuit and Matlab™ mathematical modelling respectively. For this purpose, the PV panel and the boost converter are developed using Pspice™ and hybridized with the mathematical Matlab™ model of maximum power point method controller (MPPT) through SLPS. The main objective is verify the significance of using the proposed hybrid simulation techniques in comparing the different MPPT algorithms such as the perturbation and observation (P&O), incremental of conductance (Inc-Cond) and counter reaction voltage using pilot cell (Pilot-Cell). Various simulations are performed under different atmospheric conditions in order to evaluate the dynamic behaviour for the system under study in terms of stability, efficiency and rapidity.

Hybrid Method Simulation of Slender Marine Structures

DEFF Research Database (Denmark)

Christiansen, Niels Hørbye

This present thesis consists of an extended summary and five appended papers concerning various aspects of the implementation of a hybrid method which combines classical simulation methods and artificial neural networks. The thesis covers three main topics. Common for all these topics...... only recognize patterns similar to those comprised in the data used to train the network. Fatigue life evaluation of marine structures often considers simulations of more than a hundred different sea states. Hence, in order for this method to be useful, the training data must be arranged so...... that a single neural network can cover all relevant sea states. The applicability and performance of the present hybrid method is demonstrated on a numerical model of a mooring line attached to a floating offshore platform. The second part of the thesis demonstrates how sequential neural networks can be used...

Kinetic simulation on collisional bounded plasma

International Nuclear Information System (INIS)

Zhu, S.P.; Sato, Tetsuya; Tomita, Yukihiro; Hatori, Tadatsugu

1998-01-01

A self-consistent kinetic simulation model on collisional bounded plasma is presented. The electric field is given by solving Poisson equation and collisions among particles (including charged particles and neutral particles) are included. The excitation and ionization of neutral particle, and recombination are also contained in the present model. The formation of potential structure near a boundary for a discharge system was used as an application of this model. (author)

Determination of the crystal-melt interface kinetic coefficient from molecular dynamics simulations

International Nuclear Information System (INIS)

Monk, J; Mendelev, M I; Yang, Y; Asta, M; Hoyt, J J; Sun, D Y

2010-01-01

The generation and dissipation of latent heat at the moving solid–liquid boundary during non-equilibrium molecular dynamics (MD) simulations of crystallization can lead to significant underestimations of the interface mobility. In this work we examine the heat flow problem in detail for an embedded atom description of pure Ni and offer strategies to obtain an accurate value of the kinetic coefficient, μ. For free-solidification simulations in which the entire system is thermostated using a Nose–Hoover or velocity rescaling algorithm a non-uniform temperature profile is observed and a peak in the temperature is found at the interface position. It is shown that if the actual interface temperature, rather than the thermostat set point temperature, is used to compute the kinetic coefficient then μ is approximately a factor of 2 larger than previous estimates. In addition, we introduce a layered thermostat method in which several sub-regions, aligned normal to the crystallization direction, are indepently thermostated to a desired undercooling. We show that as the number of thermostats increases (i.e., as the width of each independently thermostated layer decreases) the kinetic coefficient converges to a value consistent with that obtained using a single thermostat and the calculated interface temperature. Also, the kinetic coefficient was determined from an analysis of the equilibrium fluctuations of the solid–liquid interface position. We demonstrate that the kinetic coefficient obtained from the relaxation times of the fluctuation spectrum is equivalent to the two values obtained from free-solidification simulations provided a simple correction is made for the contribution of heat flow controlled interface motion. Finally, a one-dimensional phase field model that captures the effect of thermostats has been developed. The mesoscale model reproduces qualitatively the results from MD simulations and thus allows for an a priori estimate of the accuracy of a

Hydrodenitrogenation mechanism of aromatic amines. Kinetic study and simulation

International Nuclear Information System (INIS)

D'Araujo, P.A.P.

1994-06-01

The decomposition of model molecules reacting alone or in competition was studied in a fixed bed reactor at 623 K and 7 MPa over a sulfided NiMo/Al 2 O 3 catalyst. The inhibiting effect of H 2 S and some nitrogen molecules, namely quinoline type compounds plays a major role in the transformation of anilines intermediates. On the other hand H 2 S acts as a cocatalyst and promote carbon-nitrogen bond cleavage, specially at low H 2 S partial pressure. When the H 2 S partial pressure is greater than the nitrogen compound partial pressure an inhibiting effect of H 2 S occurs and its promoting effect on carbon-nitrogen bond cleavage is cancelled. Hydrogen has a positive but moderate effect in hydrogenation steps. The mechanism of carbon-nitrogen bond scission depends on the structure of the nitrogen molecule namely on the hybridization of the carbon atom bearing the nitrogen atom. If the carbon a with respect to the nitrogen is monosubstituted the mechanism is essentially a nucleophilic substitution. When the degree of substitution increases the elimination mechanism becomes more important and the two mechanisms are in competition. With a sulfided catalyst, H 2 S from the gas phase doesn't change the importance of each mechanism, it just increases the rate of the reaction. In the presence of an oxide catalyst the contribution of the two mechanisms change. This result shows the importance of the sulphur species from the surface. Using isotopic exchange we could demonstrate that the sites able to dissociate H 2 S and H 2 are the same, and that the dissociation is of heterolytic nature. The kinetic modeling of hydrotreatment reactions using the CHEMKIN/SURFACE CHEMKIN package seems to be a convenient method in order to understand the kinetic and mechanistic phenomena in hydrodenitrogenation. The preliminary simulations in the case of 2.6 diethylaniline showed that only one type of site is not sufficient in order to account for the experimental results. Further simulations

Hybrid simulations of current-carrying instabilities in Z-pinch plasmas with sheared axial flow

International Nuclear Information System (INIS)

Sotnikov, Vladimir I.; Makhin, Volodymyr; Bauer, Bruno S.; Hellinger, Petr; Travnicek, Pavel; Fiala, Vladimir; Leboeuf, Jean-Noel

2002-01-01

The development of instabilities in z-pinch plasmas has been studied with three-dimensional (3D) hybrid simulations. Plasma equilibria without and with sheared axial flow have been considered. Results from the linear phase of the hybrid simulations compare well with linear Hall magnetohydrodynamics (MHD) calculations for sausage modes. The hybrid simulations show that sheared axial flow has a stabilizing effect on the development of both sausage and kink modes

CSP-based chemical kinetics mechanisms simplification strategy for non-premixed combustion: An application to hybrid rocket propulsion

KAUST Repository

Ciottoli, Pietro P.

2017-08-14

A set of simplified chemical kinetics mechanisms for hybrid rocket applications using gaseous oxygen (GOX) and hydroxyl-terminated polybutadiene (HTPB) is proposed. The starting point is a 561-species, 2538-reactions, detailed chemical kinetics mechanism for hydrocarbon combustion. This mechanism is used for predictions of the oxidation of butadiene, the primary HTPB pyrolysis product. A Computational Singular Perturbation (CSP) based simplification strategy for non-premixed combustion is proposed. The simplification algorithm is fed with the steady-solutions of classical flamelet equations, these being representative of the non-premixed nature of the combustion processes characterizing a hybrid rocket combustion chamber. The adopted flamelet steady-state solutions are obtained employing pure butadiene and gaseous oxygen as fuel and oxidizer boundary conditions, respectively, for a range of imposed values of strain rate and background pressure. Three simplified chemical mechanisms, each comprising less than 20 species, are obtained for three different pressure values, 3, 17, and 36 bar, selected in accordance with an experimental test campaign of lab-scale hybrid rocket static firings. Finally, a comprehensive strategy is shown to provide simplified mechanisms capable of reproducing the main flame features in the whole pressure range considered.

Introducing ab initio based neural networks for transition-rate prediction in kinetic Monte Carlo simulations

Science.gov (United States)

Messina, Luca; Castin, Nicolas; Domain, Christophe; Olsson, Pär

2017-02-01

The quality of kinetic Monte Carlo (KMC) simulations of microstructure evolution in alloys relies on the parametrization of point-defect migration rates, which are complex functions of the local chemical composition and can be calculated accurately with ab initio methods. However, constructing reliable models that ensure the best possible transfer of physical information from ab initio to KMC is a challenging task. This work presents an innovative approach, where the transition rates are predicted by artificial neural networks trained on a database of 2000 migration barriers, obtained with density functional theory (DFT) in place of interatomic potentials. The method is tested on copper precipitation in thermally aged iron alloys, by means of a hybrid atomistic-object KMC model. For the object part of the model, the stability and mobility properties of copper-vacancy clusters are analyzed by means of independent atomistic KMC simulations, driven by the same neural networks. The cluster diffusion coefficients and mean free paths are found to increase with size, confirming the dominant role of coarsening of medium- and large-sized clusters in the precipitation kinetics. The evolution under thermal aging is in better agreement with experiments with respect to a previous interatomic-potential model, especially concerning the experiment time scales. However, the model underestimates the solubility of copper in iron due to the excessively high solution energy predicted by the chosen DFT method. Nevertheless, this work proves the capability of neural networks to transfer complex ab initio physical properties to higher-scale models, and facilitates the extension to systems with increasing chemical complexity, setting the ground for reliable microstructure evolution simulations in a wide range of alloys and applications.

Dynamic Modeling and Simulation on a Hybrid Power System for Electric Vehicle Applications

Directory of Open Access Journals (Sweden)

Hong-Wen He

2010-11-01

Full Text Available Hybrid power systems, formed by combining high-energy-density batteries and high-power-density ultracapacitors in appropriate ways, provide high-performance and high-efficiency power systems for electric vehicle applications. This paper first establishes dynamic models for the ultracapacitor, the battery and a passive hybrid power system, and then based on the dynamic models a comparative simulation between a battery only power system and the proposed hybrid power system was done under the UDDS (Urban Dynamometer Driving Schedule. The simulation results showed that the hybrid power system could greatly optimize and improve the efficiency of the batteries and their dynamic current was also decreased due to the participation of the ultracapacitors, which would have a good influence on batteries’ cycle life. Finally, the parameter matching for the passive hybrid power system was studied by simulation and comparisons.

Software-in-the-loop simulation of a quadcopter portion for hybrid aircraft control

Science.gov (United States)

Mansoor, Shoaib; Saedan, Mana

2018-01-01

In this paper, we present the design of the software-in-the-loop simulation framework for a quadcopter that is incorporated in our hybrid aircraft. The hybrid aircraft comprises a quad-copter and a fixed wing with one forward thrust rotor. We need to develop a split control system that utilizes a typical quadcopter controller to control four motors/propellers and a supervisor controller to control a forward thrust rotor. The supervisor controller shall take feedback signals from the quadcopter and will command the fifth rotor for stabilizing the hybrid aircraft and resolves problems like thrust saturation. The simulation simulates the control algorithm and verifies the quadcopter’s behavior using MATLAB and Simulink together. Achieving these results, we come to know how our hybrid controller will be implemented, what results to expect once the forward thrust rotor is attached to the quadcopter. The software-in-the-loop simulation of a quadcopter is one of the most effective methods for verifying overall control performance and safety of the hybrid aircraft before actual hardware implementation and flight test.

A survey of electric and hybrid vehicle simulation programs

Science.gov (United States)

Bevan, J.; Heimburger, D. A.; Metcalfe, M. A.

1978-01-01

Results of a survey conducted within the United States to determine the extent of development and capabilities of automotive performance simulation programs suitable for electric and hybrid vehicle studies are summarized. Altogether, 111 programs were identified as being in a usable state. The complexity of the existing programs spans a range from a page of simple desktop calculator instructions to 300,000 lines of a high-level programming language. The capability to simulate electric vehicles was most common, heat-engines second, and hybrid vehicles least common. Batch-operated programs are slightly more common than interactive ones, and one-third can be operated in either mode. The most commonly used language was FORTRAN, the language typically used by engineers. The higher-level simulation languages (e.g. SIMSCRIPT, GPSS, SIMULA) used by "model builders" were conspicuously lacking.

Kinetic Monte Carlo simulations of the effect of the exchange control layer thickness in CoPtCrB/CoPtCrSiO granular media

Science.gov (United States)

Almudallal, Ahmad M.; Mercer, J. I.; Whitehead, J. P.; Plumer, M. L.; van Ek, J.

2018-05-01

A hybrid Landau Lifshitz Gilbert/kinetic Monte Carlo algorithm is used to simulate experimental magnetic hysteresis loops for dual layer exchange coupled composite media. The calculation of the rate coefficients and difficulties arising from low energy barriers, a fundamental problem of the kinetic Monte Carlo method, are discussed and the methodology used to treat them in the present work is described. The results from simulations are compared with experimental vibrating sample magnetometer measurements on dual layer CoPtCrB/CoPtCrSiO media and a quantitative relationship between the thickness of the exchange control layer separating the layers and the effective exchange constant between the layers is obtained. Estimates of the energy barriers separating magnetically reversed states of the individual grains in zero applied field as well as the saturation field at sweep rates relevant to the bit write speeds in magnetic recording are also presented. The significance of this comparison between simulations and experiment and the estimates of the material parameters obtained from it are discussed in relation to optimizing the performance of magnetic storage media.

Simulation and Analysis of the Hybrid Operating Mode in ITER

International Nuclear Information System (INIS)

Kessel, C.E.; Budny, R.V.; Indireshkumar, K.

2005-01-01

The hybrid operating mode in ITER is examined with 0D systems analysis, 1.5D discharge scenario simulations using TSC and TRANSP, and the ideal MHD stability is discussed. The hybrid mode has the potential to provide very long pulses and significant neutron fluence if the physics regime can be produced in ITER. This paper reports progress in establishing the physics basis and engineering limitation for the hybrid mode in ITER

The Impact of Three-Dimensional Effects on the Simulation of Turbulence Kinetic Energy in a Major Alpine Valley

Science.gov (United States)

Goger, Brigitta; Rotach, Mathias W.; Gohm, Alexander; Fuhrer, Oliver; Stiperski, Ivana; Holtslag, Albert A. M.

2018-07-01

The correct simulation of the atmospheric boundary layer (ABL) is crucial for reliable weather forecasts in truly complex terrain. However, common assumptions for model parametrizations are only valid for horizontally homogeneous and flat terrain. Here, we evaluate the turbulence parametrization of the numerical weather prediction model COSMO with a horizontal grid spacing of Δ x = 1.1 km for the Inn Valley, Austria. The long-term, high-resolution turbulence measurements of the i-Box measurement sites provide a useful data pool of the ABL structure in the valley and on slopes. We focus on days and nights when ABL processes dominate and a thermally-driven circulation is present. Simulations are performed for case studies with both a one-dimensional turbulence parametrization, which only considers the vertical turbulent exchange, and a hybrid turbulence parametrization, also including horizontal shear production and advection in the budget of turbulence kinetic energy (TKE). We find a general underestimation of TKE by the model with the one-dimensional turbulence parametrization. In the simulations with the hybrid turbulence parametrization, the modelled TKE has a more realistic structure, especially in situations when the TKE production is dominated by shear related to the afternoon up-valley flow, and during nights, when a stable ABL is present. The model performance also improves for stations on the slopes. An estimation of the horizontal shear production from the observation network suggests that three-dimensional effects are a relevant part of TKE production in the valley.

Monte Carlo simulation of hybrid systems: An example

International Nuclear Information System (INIS)

Bacha, F.; D'Alencon, H.; Grivelet, J.; Jullien, E.; Jejcic, A.; Maillard, J.; Silva, J.; Zukanovich, R.; Vergnes, J.

1997-01-01

Simulation of hybrid systems needs tracking of particles from the GeV (incident proton beam) range down to a fraction of eV (thermic neutrons). We show how a GEANT based Monte-Carlo program can achieve this, with a realistic computer time and accompanying tools. An example of a dedicated original actinide burner is simulated with this chain. 8 refs., 5 figs

Comparison between kinetic and fluid simulations of slab ion temperature gradient driven turbulence

Energy Technology Data Exchange (ETDEWEB)

Sugama, H.; Watanabe, T.-H. [National Inst. for Fusion Science, Toki, Gifu (Japan); Horton, W. [University of Texas at Austin, Institute for Fusion Studies, Austin, Texas (United States)

2002-10-01

A detailed comparison between kinetic and fluid simulations of collisionless slab ion temperature gradient (ITG) driven turbulence is made. The nondissipative closure model (NCM) for linearly unstable modes, which is presented by Sugama, Watanabe, and Horton [Phys. Plasmas 8, 2617 (2001)], and the dissipative closure model by Hammett and Perkins (HP) [Phys. Rev. Lett. 64, 3019 (1990)] are used in separate fluid simulations. The validity of these closure models for quantitative prediction of the turbulent thermal transport is examined by comparing nonlinear results of the fluid simulations with those of the collisionless kinetic simulation of high accuracy. Simulation results show that, in the saturated turbulent state, the turbulent thermal diffusivity {chi} obtained from the HP model is significantly larger than the {chi} given by the NCM which is closer to {chi} measured in the kinetic simulation. Contrary to the dissipative form of the parallel heat flux closure relation assumed in the HP model, the NCM describes well the exact kinetic simulation, in which for some unstable wave numbers k, the imaginary part of the ratio of the parallel heat flux q{sub k} to the temperature fluctuation T{sub k} is a oscillatory function of time and sometimes takes positive values. The positive values of Im(q{sub k}/T{sub k}), imply the negative parallel heat diffusivity, correlate with the occasional inward heat flux occurring for the wave numbers k, and reduce the total {chi}. (author)

Comparison between kinetic and fluid simulations of slab ion temperature gradient driven turbulence

International Nuclear Information System (INIS)

Sugama, H.; Watanabe, T.-H.; Horton, W.

2002-10-01

A detailed comparison between kinetic and fluid simulations of collisionless slab ion temperature gradient (ITG) driven turbulence is made. The nondissipative closure model (NCM) for linearly unstable modes, which is presented by Sugama, Watanabe, and Horton [Phys. Plasmas 8, 2617 (2001)], and the dissipative closure model by Hammett and Perkins (HP) [Phys. Rev. Lett. 64, 3019 (1990)] are used in separate fluid simulations. The validity of these closure models for quantitative prediction of the turbulent thermal transport is examined by comparing nonlinear results of the fluid simulations with those of the collisionless kinetic simulation of high accuracy. Simulation results show that, in the saturated turbulent state, the turbulent thermal diffusivity χ obtained from the HP model is significantly larger than the χ given by the NCM which is closer to χ measured in the kinetic simulation. Contrary to the dissipative form of the parallel heat flux closure relation assumed in the HP model, the NCM describes well the exact kinetic simulation, in which for some unstable wave numbers k, the imaginary part of the ratio of the parallel heat flux q k to the temperature fluctuation T k is a oscillatory function of time and sometimes takes positive values. The positive values of Im(q k /T k ), imply the negative parallel heat diffusivity, correlate with the occasional inward heat flux occurring for the wave numbers k, and reduce the total χ. (author)

Hybrid statistics-simulations based method for atom-counting from ADF STEM images.

Science.gov (United States)

De Wael, Annelies; De Backer, Annick; Jones, Lewys; Nellist, Peter D; Van Aert, Sandra

2017-06-01

A hybrid statistics-simulations based method for atom-counting from annular dark field scanning transmission electron microscopy (ADF STEM) images of monotype crystalline nanostructures is presented. Different atom-counting methods already exist for model-like systems. However, the increasing relevance of radiation damage in the study of nanostructures demands a method that allows atom-counting from low dose images with a low signal-to-noise ratio. Therefore, the hybrid method directly includes prior knowledge from image simulations into the existing statistics-based method for atom-counting, and accounts in this manner for possible discrepancies between actual and simulated experimental conditions. It is shown by means of simulations and experiments that this hybrid method outperforms the statistics-based method, especially for low electron doses and small nanoparticles. The analysis of a simulated low dose image of a small nanoparticle suggests that this method allows for far more reliable quantitative analysis of beam-sensitive materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Understanding Yield Anomalies in ICF Implosions via Fully Kinetic Simulations

Science.gov (United States)

Taitano, William

2017-10-01

In the quest towards ICF ignition, plasma kinetic effects are among prime candidates for explaining some significant discrepancies between experimental observations and rad-hydro simulations. To assess their importance, high-fidelity fully kinetic simulations of ICF capsule implosions are needed. Owing to the extremely multi-scale nature of the problem, kinetic codes have to overcome nontrivial numerical and algorithmic challenges, and very few options are currently available. Here, we present resolutions of some long-standing yield discrepancy conundrums using a novel, LANL-developed, 1D-2V Vlasov-Fokker-Planck code iFP. iFP possesses an unprecedented fidelity and features fully implicit time-stepping, exact mass, momentum, and energy conservation, and optimal grid adaptation in phase space, all of which are critically important for ensuring long-time numerical accuracy of the implosion simulations. Specifically, we concentrate on several anomalous yield degradation instances observed in Omega campaigns, with the so-called ``Rygg effect'', or an anomalous yield scaling with the fuel composition, being a prime example. Understanding the physical mechanisms responsible for such degradations in non-ignition-grade Omega experiments is of great interest, as such experiments are often used for platform and diagnostic development, which are then used in ignition-grade experiments on NIF. In the case of Rygg's experiments, effects of a kinetic stratification of fuel ions on the yield have been previously proposed as the anomaly explanation, studied with a kinetic code FPION, and found unimportant. We have revisited this issue with iFP and obtained excellent yield-over-clean agreement with the original Rygg results, and several subsequent experiments. This validates iFP and confirms that the kinetic fuel stratification is indeed at the root of the observed yield degradation. This work was sponsored by the Metropolis Postdoctoral Fellowship, LDRD office, Thermonuclear Burn

Co-Simulation of Hybrid Systems with SpaceEx and Uppaal

DEFF Research Database (Denmark)

Bogomolov, Sergiy; Greitschus, Marius; Jensen, Peter Gjøl

2015-01-01

The Functional Mock-up Interface (FMI) is an industry standard which enables co-simulation of complex heterogeneous systems using multiple simulation engines. In this paper, we show how to use FMI in order to co-simulate hybrid systems modeled in the model checkers SPACEEX and UPPAAL. We show how...

Hybrid simulation of a 900 Mwe nuclear plant

International Nuclear Information System (INIS)

Constantieux, Thierry; Deat, Max.

1979-01-01

To analyse the effects on PWRs of transients originating from the network, specific means of calculation must be elaborated. One of them which was conceived and set up on a hybrid computer by FRAMATOME and the FRENCH ATOMIC ENERGY COMMISSION, is described in this paper. The method chosen to validate this code is fairly original, since it consisted in carrying out a long duration test on a plan and in simulating this on the hybrid computer; then in carefully comparing the recorded data of the test with the results of the simulation. The quality of the results, thus obtained shows that a relatively unsophisticated model is able to give a good idea of actual process behavior, but only if the types of transients to be studied with the code are well identified before its elaboration

Hybrid statistics-simulations based method for atom-counting from ADF STEM images

Energy Technology Data Exchange (ETDEWEB)

De wael, Annelies, E-mail: annelies.dewael@uantwerpen.be [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); De Backer, Annick [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Jones, Lewys; Nellist, Peter D. [Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford (United Kingdom); Van Aert, Sandra, E-mail: sandra.vanaert@uantwerpen.be [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium)

2017-06-15

A hybrid statistics-simulations based method for atom-counting from annular dark field scanning transmission electron microscopy (ADF STEM) images of monotype crystalline nanostructures is presented. Different atom-counting methods already exist for model-like systems. However, the increasing relevance of radiation damage in the study of nanostructures demands a method that allows atom-counting from low dose images with a low signal-to-noise ratio. Therefore, the hybrid method directly includes prior knowledge from image simulations into the existing statistics-based method for atom-counting, and accounts in this manner for possible discrepancies between actual and simulated experimental conditions. It is shown by means of simulations and experiments that this hybrid method outperforms the statistics-based method, especially for low electron doses and small nanoparticles. The analysis of a simulated low dose image of a small nanoparticle suggests that this method allows for far more reliable quantitative analysis of beam-sensitive materials. - Highlights: • A hybrid method for atom-counting from ADF STEM images is introduced. • Image simulations are incorporated into a statistical framework in a reliable manner. • Limits of the existing methods for atom-counting are far exceeded. • Reliable counting results from an experimental low dose image are obtained. • Progress towards reliable quantitative analysis of beam-sensitive materials is made.

Conformational Selection and Induced Fit for RNA Polymerase and RNA/DNA Hybrid Backtracked Recognition

Directory of Open Access Journals (Sweden)

Haifeng eChen

2015-11-01

Full Text Available RNA polymerase catalyzes transcription with a high fidelity. If DNA/RNA mismatch or DNA damage occurs downstream, a backtracked RNA polymerase can proofread this situation. However, the backtracked mechanism is still poorly understood. Here we have performed multiple explicit-solvent molecular dynamics (MD simulations on bound and apo DNA/RNA hybrid to study backtracked recognition. MD simulations at room temperature suggest that specific electrostatic interactions play key roles in the backtracked recognition between the polymerase and DNA/RNA hybrid. Kinetics analysis at high temperature shows that bound and apo DNA/RNA hybrid unfold via a two-state process. Both kinetics and free energy landscape analyses indicate that bound DNA/RNA hybrid folds in the order of DNA/RNA contracting, the tertiary folding and polymerase binding. The predicted Φ-values suggest that C7, G9, dC12, dC15 and dT16 are key bases for the backtracked recognition of DNA/RNA hybrid. The average RMSD values between the bound structures and the corresponding apo ones and Kolmogorov-Smirnov (KS P test analyses indicate that the recognition between DNA/RNA hybrid and polymerase might follow an induced fit mechanism for DNA/RNA hybrid and conformation selection for polymerase. Furthermore, this method could be used to relative studies of specific recognition between nucleic acid and protein.

Hybrid Large-Eddy/Reynolds-Averaged Simulation of a Supersonic Cavity Using VULCAN

Science.gov (United States)

Quinlan, Jesse; McDaniel, James; Baurle, Robert A.

2013-01-01

Simulations of a supersonic recessed-cavity flow are performed using a hybrid large-eddy/Reynolds-averaged simulation approach utilizing an inflow turbulence recycling procedure and hybridized inviscid flux scheme. Calorically perfect air enters a three-dimensional domain at a free stream Mach number of 2.92. Simulations are performed to assess grid sensitivity of the solution, efficacy of the turbulence recycling, and the effect of the shock sensor used with the hybridized inviscid flux scheme. Analysis of the turbulent boundary layer upstream of the rearward-facing step for each case indicates excellent agreement with theoretical predictions. Mean velocity and pressure results are compared to Reynolds-averaged simulations and experimental data for each case and indicate good agreement on the finest grid. Simulations are repeated on a coarsened grid, and results indicate strong grid density sensitivity. Simulations are performed with and without inflow turbulence recycling on the coarse grid to isolate the effect of the recycling procedure, which is demonstrably critical to capturing the relevant shear layer dynamics. Shock sensor formulations of Ducros and Larsson are found to predict mean flow statistics equally well.

Small-scale multi-axial hybrid simulation of a shear-critical reinforced concrete frame

Science.gov (United States)

Sadeghian, Vahid; Kwon, Oh-Sung; Vecchio, Frank

2017-10-01

This study presents a numerical multi-scale simulation framework which is extended to accommodate hybrid simulation (numerical-experimental integration). The framework is enhanced with a standardized data exchange format and connected to a generalized controller interface program which facilitates communication with various types of laboratory equipment and testing configurations. A small-scale experimental program was conducted using a six degree-of-freedom hydraulic testing equipment to verify the proposed framework and provide additional data for small-scale testing of shearcritical reinforced concrete structures. The specimens were tested in a multi-axial hybrid simulation manner under a reversed cyclic loading condition simulating earthquake forces. The physical models were 1/3.23-scale representations of a beam and two columns. A mixed-type modelling technique was employed to analyze the remainder of the structures. The hybrid simulation results were compared against those obtained from a large-scale test and finite element analyses. The study found that if precautions are taken in preparing model materials and if the shear-related mechanisms are accurately considered in the numerical model, small-scale hybrid simulations can adequately simulate the behaviour of shear-critical structures. Although the findings of the study are promising, to draw general conclusions additional test data are required.

Simulating groundwater flow in karst aquifers with distributed parameter models—Comparison of porous-equivalent media and hybrid flow approaches

Science.gov (United States)

Kuniansky, Eve L.

2016-09-22

Understanding karst aquifers, for purposes of their management and protection, poses unique challenges. Karst aquifers are characterized by groundwater flow through conduits (tertiary porosity), and (or) layers with interconnected pores (secondary porosity) and through intergranular porosity (primary or matrix porosity). Since the late 1960s, advances have been made in the development of numerical computer codes and the use of mathematical model applications towards the understanding of dual (primary [matrix] and secondary [fractures and conduits]) porosity groundwater flow processes, as well as characterization and management of karst aquifers. The Floridan aquifer system (FAS) in Florida and parts of Alabama, Georgia, and South Carolina is composed of a thick sequence of predominantly carbonate rocks. Karst features are present over much of its area, especially in Florida where more than 30 first-magnitude springs occur, numerous sinkholes and submerged conduits have been mapped, and numerous circular lakes within sinkhole depressions are present. Different types of mathematical models have been applied for simulation of the FAS. Most of these models are distributed parameter models based on the assumption that, like a sponge, water flows through connected pores within the aquifer system and can be simulated with the same mathematical methods applied to flow through sand and gravel aquifers; these models are usually referred to as porous-equivalent media models. The partial differential equation solved for groundwater flow is the potential flow equation of fluid mechanics, which is used when flow is dominated by potential energy and has been applied for many fluid problems in which kinetic energy terms are dropped from the differential equation solved. In many groundwater model codes (basic MODFLOW), it is assumed that the water has a constant temperature and density and that flow is laminar, such that kinetic energy has minimal impact on flow. Some models have

Scalable Simulation of Electromagnetic Hybrid Codes

International Nuclear Information System (INIS)

Perumalla, Kalyan S.; Fujimoto, Richard; Karimabadi, Dr. Homa

2006-01-01

New discrete-event formulations of physics simulation models are emerging that can outperform models based on traditional time-stepped techniques. Detailed simulation of the Earth's magnetosphere, for example, requires execution of sub-models that are at widely differing timescales. In contrast to time-stepped simulation which requires tightly coupled updates to entire system state at regular time intervals, the new discrete event simulation (DES) approaches help evolve the states of sub-models on relatively independent timescales. However, parallel execution of DES-based models raises challenges with respect to their scalability and performance. One of the key challenges is to improve the computation granularity to offset synchronization and communication overheads within and across processors. Our previous work was limited in scalability and runtime performance due to the parallelization challenges. Here we report on optimizations we performed on DES-based plasma simulation models to improve parallel performance. The net result is the capability to simulate hybrid particle-in-cell (PIC) models with over 2 billion ion particles using 512 processors on supercomputing platforms

Plasma environment of Titan: a 3-D hybrid simulation study

Directory of Open Access Journals (Sweden)

S. Simon

2006-05-01

Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

Plasma environment of Titan: a 3-D hybrid simulation study

Directory of Open Access Journals (Sweden)

S. Simon

2006-05-01

Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

Monte Carlo simulation on kinetics of batch and semi-batch free radical polymerization

KAUST Repository

Shao, Jing; Tang, Wei; Xia, Ru; Feng, Xiaoshuang; Chen, Peng; Qian, Jiasheng; Song, Changjiang

2015-01-01

experimental and simulation studies, we showed the capability of our Monte Carlo scheme on representing polymerization kinetics in batch and semi-batch processes. Various kinetics information, such as instant monomer conversion, molecular weight

Theory and simulation of discrete kinetic beta induced Alfven eigenmode in tokamak plasmas

International Nuclear Information System (INIS)

Wang, X; Zonca, F; Chen, L

2010-01-01

It is shown, both analytically and by numerical simulations, that, in the presence of thermal ion kinetic effects, the beta induced Alfven eigenmode (BAE)-shear Alfven wave continuous spectrum can be discretized into radially trapped eigenstates known as kinetic BAE (KBAE). While thermal ion compressibility gives rise to finite BAE accumulation point frequency, the discretization occurs via the finite Larmor radius and finite orbit width effects. Simulations and analytical theories agree both qualitatively and quantitatively. Simulations also demonstrate that KBAE can be readily excited by the finite radial gradients of energetic particles.

A hybrid gyrokinetic ion and isothermal electron fluid code for astrophysical plasma

Science.gov (United States)

Kawazura, Y.; Barnes, M.

2018-05-01

This paper describes a new code for simulating astrophysical plasmas that solves a hybrid model composed of gyrokinetic ions (GKI) and an isothermal electron fluid (ITEF) Schekochihin et al. (2009) [9]. This model captures ion kinetic effects that are important near the ion gyro-radius scale while electron kinetic effects are ordered out by an electron-ion mass ratio expansion. The code is developed by incorporating the ITEF approximation into AstroGK, an Eulerian δf gyrokinetics code specialized to a slab geometry Numata et al. (2010) [41]. The new code treats the linear terms in the ITEF equations implicitly while the nonlinear terms are treated explicitly. We show linear and nonlinear benchmark tests to prove the validity and applicability of the simulation code. Since the fast electron timescale is eliminated by the mass ratio expansion, the Courant-Friedrichs-Lewy condition is much less restrictive than in full gyrokinetic codes; the present hybrid code runs ∼ 2√{mi /me } ∼ 100 times faster than AstroGK with a single ion species and kinetic electrons where mi /me is the ion-electron mass ratio. The improvement of the computational time makes it feasible to execute ion scale gyrokinetic simulations with a high velocity space resolution and to run multiple simulations to determine the dependence of turbulent dynamics on parameters such as electron-ion temperature ratio and plasma beta.

Hybrid Multilevel Monte Carlo Simulation of Stochastic Reaction Networks

KAUST Repository

Moraes, Alvaro

2015-01-07

Stochastic reaction networks (SRNs) is a class of continuous-time Markov chains intended to describe, from the kinetic point of view, the time-evolution of chemical systems in which molecules of different chemical species undergo a finite set of reaction channels. This talk is based on articles [4, 5, 6], where we are interested in the following problem: given a SRN, X, defined though its set of reaction channels, and its initial state, x0, estimate E (g(X(T))); that is, the expected value of a scalar observable, g, of the process, X, at a fixed time, T. This problem lead us to define a series of Monte Carlo estimators, M, such that, with high probability can produce values close to the quantity of interest, E (g(X(T))). More specifically, given a user-selected tolerance, TOL, and a small confidence level, η, find an estimator, M, based on approximate sampled paths of X, such that, P (|E (g(X(T))) − M| ≤ TOL) ≥ 1 − η; even more, we want to achieve this objective with near optimal computational work. We first introduce a hybrid path-simulation scheme based on the well-known stochastic simulation algorithm (SSA)[3] and the tau-leap method [2]. Then, we introduce a Multilevel Monte Carlo strategy that allows us to achieve a computational complexity of order O(T OL−2), this is the same computational complexity as in an exact method but with a smaller constant. We provide numerical examples to show our results.

The Particle-in-Cell and Kinetic Simulation Software Center

Science.gov (United States)

Mori, W. B.; Decyk, V. K.; Tableman, A.; Fonseca, R. A.; Tsung, F. S.; Hu, Q.; Winjum, B. J.; An, W.; Dalichaouch, T. N.; Davidson, A.; Hildebrand, L.; Joglekar, A.; May, J.; Miller, K.; Touati, M.; Xu, X. L.

2017-10-01

The UCLA Particle-in-Cell and Kinetic Simulation Software Center (PICKSC) aims to support an international community of PIC and plasma kinetic software developers, users, and educators; to increase the use of this software for accelerating the rate of scientific discovery; and to be a repository of knowledge and history for PIC. We discuss progress towards making available and documenting illustrative open-source software programs and distinct production programs; developing and comparing different PIC algorithms; coordinating the development of resources for the educational use of kinetic software; and the outcomes of our first sponsored OSIRIS users workshop. We also welcome input and discussion from anyone interested in using or developing kinetic software, in obtaining access to our codes, in collaborating, in sharing their own software, or in commenting on how PICKSC can better serve the DPP community. Supported by NSF under Grant ACI-1339893 and by the UCLA Institute for Digital Research and Education.

Hybrid simulation of toroidal Alfvén eigenmode on the National Spherical Torus Experiment

Energy Technology Data Exchange (ETDEWEB)

Liu, D., E-mail: deyongl@uci.edu [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Fu, G. Y.; Podestà, M.; Breslau, J. A.; Fredrickson, E. D. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Crocker, N. A.; Kubota, S. [Department of Physics and Astronomy, University of California, Los Angles, California 90095 (United States)

2015-04-15

Energetic particle modes and Alfvén eigenmodes driven by super-Alfvénic fast ions are routinely observed in neutral beam heated plasmas on the National Spherical Torus eXperiment (NSTX). These modes can significantly impact fast ion transport and thus cause fast ion redistribution or loss. Self-consistent linear simulations of Toroidal Alfvén Eigenmodes (TAEs) in NSTX plasmas have been carried out with the kinetic/magnetohydrodynamic hybrid code M3D-K using experimental plasma parameters and profiles including plasma toroidal rotation. The simulations show that unstable TAEs with n=3,4, or 5 can be excited by the fast ions from neutral beam injection. The simulated mode frequency, mode radial structure, and phase shift are consistent with measurements from a multi-channel microwave reflectometer diagnostic. A sensitivity study on plasma toroidal rotation, safety factor q profile, and initial fast ion distribution is performed. The simulations show that rotation can have a significant destabilizing effect when the rotation is comparable or larger than the experimental level. The mode growth rate is sensitive to q profile and fast ion distribution. Although mode structure and peak position depend somewhat on q profile and plasma rotation, the variation of synthetic reflectometer response is within experimental uncertainty and it is not sensitive enough to see the difference clearly.

Numerical Simulation of Transitional, Hypersonic Flows using a Hybrid Particle-Continuum Method

Science.gov (United States)

Verhoff, Ashley Marie

Analysis of hypersonic flows requires consideration of multiscale phenomena due to the range of flight regimes encountered, from rarefied conditions in the upper atmosphere to fully continuum flow at low altitudes. At transitional Knudsen numbers there are likely to be localized regions of strong thermodynamic nonequilibrium effects that invalidate the continuum assumptions of the Navier-Stokes equations. Accurate simulation of these regions, which include shock waves, boundary and shear layers, and low-density wakes, requires a kinetic theory-based approach where no prior assumptions are made regarding the molecular distribution function. Because of the nature of these types of flows, there is much to be gained in terms of both numerical efficiency and physical accuracy by developing hybrid particle-continuum simulation approaches. The focus of the present research effort is the continued development of the Modular Particle-Continuum (MPC) method, where the Navier-Stokes equations are solved numerically using computational fluid dynamics (CFD) techniques in regions of the flow field where continuum assumptions are valid, and the direct simulation Monte Carlo (DSMC) method is used where strong thermodynamic nonequilibrium effects are present. Numerical solutions of transitional, hypersonic flows are thus obtained with increased physical accuracy relative to CFD alone, and improved numerical efficiency is achieved in comparison to DSMC alone because this more computationally expensive method is restricted to those regions of the flow field where it is necessary to maintain physical accuracy. In this dissertation, a comprehensive assessment of the physical accuracy of the MPC method is performed, leading to the implementation of a non-vacuum supersonic outflow boundary condition in particle domains, and more consistent initialization of DSMC simulator particles along hybrid interfaces. The relative errors between MPC and full DSMC results are greatly reduced as a

A conservative scheme of drift kinetic electrons for gyrokinetic simulation of kinetic-MHD processes in toroidal plasmas

Science.gov (United States)

Bao, J.; Liu, D.; Lin, Z.

2017-10-01

A conservative scheme of drift kinetic electrons for gyrokinetic simulations of kinetic-magnetohydrodynamic processes in toroidal plasmas has been formulated and verified. Both vector potential and electron perturbed distribution function are decomposed into adiabatic part with analytic solution and non-adiabatic part solved numerically. The adiabatic parallel electric field is solved directly from the electron adiabatic response, resulting in a high degree of accuracy. The consistency between electrostatic potential and parallel vector potential is enforced by using the electron continuity equation. Since particles are only used to calculate the non-adiabatic response, which is used to calculate the non-adiabatic vector potential through Ohm's law, the conservative scheme minimizes the electron particle noise and mitigates the cancellation problem. Linear dispersion relations of the kinetic Alfvén wave and the collisionless tearing mode in cylindrical geometry have been verified in gyrokinetic toroidal code simulations, which show that the perpendicular grid size can be larger than the electron collisionless skin depth when the mode wavelength is longer than the electron skin depth.

Hybrid Simulation of the Interaction of Europa's Atmosphere with the Jovian Plasma: Multiprocessor Simulations

Science.gov (United States)

Dols, V. J.; Delamere, P. A.; Bagenal, F.; Cassidy, T. A.; Crary, F. J.

2014-12-01

We model the interaction of Europa's tenuous atmosphere with the plasma of Jupiter's torus with an improved version of our hybrid plasma code. In a hybrid plasma code, the ions are treated as kinetic Macro-particles moving under the Lorentz force and the electrons as a fluid leading to a generalized formulation of Ohm's law. In this version, the spatial simulation domain is decomposed in 2 directions and is non-uniform in the plasma convection direction. The code is run on a multi-processor supercomputer that offers 16416 cores and 2GB Ram per core. This new version allows us to tap into the large memory of the supercomputer and simulate the full interaction volume (Reuropa=1561km) with a high spatial resolution (50km). Compared to Io, Europa's atmosphere is about 100 times more tenuous, the ambient magnetic field is weaker and the density of incident plasma is lower. Consequently, the electrodynamic interaction is also weaker and substantial fluxes of thermal torus ions might reach and sputter the icy surface. Molecular O2 is the dominant atmospheric product of this surface sputtering. Observations of oxygen UV emissions (specifically the ratio of OI 1356A / 1304A emissions) are roughly consistent with an atmosphere that is composed predominantely of O2 with a small amount of atomic O. Galileo observations along flybys close to Europa have revealed the existence of induced currents in a conducting ocean under the icy crust. They also showed that, from flyby to flyby, the plasma interaction is very variable. Asymmetries of the plasma density and temperature in the wake of Europa were also observed and still elude a clear explanation. Galileo mag data also detected ion cyclotron waves, which is an indication of heavy ion pickup close to the moon. We prescribe an O2 atmosphere with a vertical density column consistent with UV observations and model the plasma properties along several Galileo flybys of the moon. We compare our results with the magnetometer

Benchmark test of drift-kinetic and gyrokinetic codes through neoclassical transport simulations

International Nuclear Information System (INIS)

Satake, S.; Sugama, H.; Watanabe, T.-H.; Idomura, Yasuhiro

2009-09-01

Two simulation codes that solve the drift-kinetic or gyrokinetic equation in toroidal plasmas are benchmarked by comparing the simulation results of neoclassical transport. The two codes are the drift-kinetic δf Monte Carlo code (FORTEC-3D) and the gyrokinetic full- f Vlasov code (GT5D), both of which solve radially-global, five-dimensional kinetic equation with including the linear Fokker-Planck collision operator. In a tokamak configuration, neoclassical radial heat flux and the force balance relation, which relates the parallel mean flow with radial electric field and temperature gradient, are compared between these two codes, and their results are also compared with the local neoclassical transport theory. It is found that the simulation results of the two codes coincide very well in a wide rage of plasma collisionality parameter ν * = 0.01 - 10 and also agree with the theoretical estimations. The time evolution of radial electric field and particle flux, and the radial profile of the geodesic acoustic mode frequency also coincide very well. These facts guarantee the capability of GT5D to simulate plasma turbulence transport with including proper neoclassical effects of collisional diffusion and equilibrium radial electric field. (author)

Hybrid High-Fidelity Modeling of Radar Scenarios Using Atemporal, Discrete-Event, and Time-Step Simulation

Science.gov (United States)

2016-12-01

10 Figure 1.8 High-efficiency and high-fidelity radar system simulation flowchart . 15 Figure 1.9...Methodology roadmaps: experimental-design flowchart showing hybrid sensor models integrated from three simulation categories, followed by overall...simulation display and output produced by Java Simkit program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Figure 4.5 Hybrid

Discrete kinetic models from funneled energy landscape simulations.

Directory of Open Access Journals (Sweden)

Nicholas P Schafer

Full Text Available A general method for facilitating the interpretation of computer simulations of protein folding with minimally frustrated energy landscapes is detailed and applied to a designed ankyrin repeat protein (4ANK. In the method, groups of residues are assigned to foldons and these foldons are used to map the conformational space of the protein onto a set of discrete macrobasins. The free energies of the individual macrobasins are then calculated, informing practical kinetic analysis. Two simple assumptions about the universality of the rate for downhill transitions between macrobasins and the natural local connectivity between macrobasins lead to a scheme for predicting overall folding and unfolding rates, generating chevron plots under varying thermodynamic conditions, and inferring dominant kinetic folding pathways. To illustrate the approach, free energies of macrobasins were calculated from biased simulations of a non-additive structure-based model using two structurally motivated foldon definitions at the full and half ankyrin repeat resolutions. The calculated chevrons have features consistent with those measured in stopped flow chemical denaturation experiments. The dominant inferred folding pathway has an "inside-out", nucleation-propagation like character.

Modeling of subtle kinetic processes in plasma simulation

International Nuclear Information System (INIS)

Sydora, R.D.; Decyk, V.K.; Dawson, J.M.

1988-01-01

A new diagnostic method for plasma simulation models is presented which enables one to probe the subtle dielectric properties of the plasma medium. The procedure involves the removal of the background plasma response in order to isolate the effects of small perturbing influences which are externally added. We have found the technique accurately describes fundamental kinetic plasma behavior such as the shielding of individual test charges and currents. Wave emission studies and drag of test particles has been carried out in explicit particle algorithms as well as large time step implicit and gyrokinetic models. Accurate plasma behavior is produced and it is possible to investigate in detail, processes which can be compared with plasma kinetic theory. The technique of subtraction is not only limited to particle simulation models but also can be used in MHD or fluid models where resolution is difficult due to the intensity of the background response relative to the phenomena one is interested in measuring, such as a weakly grouwing instability or nonlinear mode coupling effect. (author)

Quasi-Static Single-Component Hybrid Simulation of a Composite Structure with Multi-Axis Control

DEFF Research Database (Denmark)

Høgh, J.; Waldbjørn, J.; Wittrup-Schmidt, J.

2015-01-01

This paper presents a quasi-static hybrid simulation performed on a single component structure. Hybrid simulation is a substructural technique, where a structure is divided into two sections: a numerical section of the main structure and a physical experiment of the remainder. In previous cases...

Simulation of ITG instabilities with fully kinetic ions and drift-kinetic electrons in tokamaks

Science.gov (United States)

Hu, Youjun; Chen, Yang; Parker, Scott

2017-10-01

A turbulence simulation model with fully kinetic ions and drift-kinetic electrons is being developed in the toroidal electromagnetic turbulence code GEM. This is motivated by the observation that gyrokinetic ions are not well justified in simulating turbulence in tokamak edges with steep density profile, where ρi / L is not small enough to be used a small parameter needed by the gyrokinetic ordering (here ρi is the gyro-radius of ions and L is the scale length of density profile). In this case, the fully kinetic ion model may be useful. Our model uses an implicit scheme to suppress high-frequency compressional Alfven waves and waves associated with the gyro-motion of ions. The ion orbits are advanced by using the well-known Boris scheme, which reproduces correct drift-motion even with large time-step comparable to the ion gyro-period. The field equation in this model is Ampere's law with the magnetic field eliminated by using an implicit scheme of Faraday's law. The current contributed by ions are computed by using an implicit δf method. A flux tube approximation is adopted, which makes the field equation much easier to solve. Numerical results of electromagnetic ITG obtained from this model will be presented and compared with the gyrokinetic results. This work is supported by U.S. Department of Energy, Office of Fusion Energy Sciences under Award No. DE-SC0008801.

Numerical simulation of collision-free plasma using Vlasov hybrid simulation

International Nuclear Information System (INIS)

Nunn, D.

1990-01-01

A novel scheme for the numerical simulation of wave particle interactions in space plasmas has been developed. The method, termed VHS or Vlasov Hybrid Simulation, is applicable to hot collision free plasmas in which the unperturbed distribution functions is smooth and free of delta function singularities. The particle population is described as a continuous Vlasov fluid in phase space-granularity and collisional effects being ignored. In traditional PIC/CIC codes the charge/current due to each simulation particle is assigned to a fixed spatial grid. In the VHS method the simulation particles sample the Vlasov fluid and provide information about the value of distribution function (F(r,v) at random points in phase space. Values of F are interpolated from the simulation particles onto a fixed grid in velocity/position or phase space. With distribution function defined on a phase space grid the plasma charge/current field is quickly calculated. The simulation particles serve only to provide information, and thus the particle population may be dynamic. Particles no longer resonant with the wavefield may be discarded from the simulation, and new particles may be inserted into the Vlasov fluid where required

Generation of lower hybrid and whistler waves by an ion velocity ring distribution

International Nuclear Information System (INIS)

Winske, D.; Daughton, W.

2012-01-01

Using fully kinetic simulations in two and three spatial dimensions, we consider the generation and nonlinear evolution of lower hybrid waves produced by a cold ion ring velocity distribution in a low beta plasma. We show that the initial development of the instability is very similar in two and three dimensions and not significantly modified by electromagnetic effects, consistent with linear theory. At saturation, the level of electric field fluctuations is a small fraction of the background thermal energy; the electric field and corresponding density fluctuations consist of long, field-aligned striations. Energy extracted from the ring goes primarily into heating the background ions and the electrons at comparable rates. The initial growth and saturation of the magnetic components of the lower hybrid waves are related to the electric field components, consistent with linear theory. As the growing electric field fluctuations saturate, parallel propagating whistler waves develop by the interaction of two lower hybrid waves. At later times, these whistlers are replaced by longer wavelength, parallel propagating whistlers that grow through the decay of the lower hybrid fluctuations. Wave matching conditions demonstrate these conversion processes of lower hybrid waves to whistler waves. The conversion efficiency (=ratio of the whistler wave energy to the energy in the saturated lower hybrid waves) is computed and found to be significant (∼15%) for the parameters of the three-dimensional simulation (and even larger in the two-dimensional simulation), although when normalized in terms of the initial kinetic energy in the ring ions the overall efficiency is very small ( −4 ). The results are compared with relevant linear and nonlinear theory.

Hybrid simulation using mixed reality for interventional ultrasound imaging training.

Science.gov (United States)

Freschi, C; Parrini, S; Dinelli, N; Ferrari, M; Ferrari, V

2015-07-01

Ultrasound (US) imaging offers advantages over other imaging modalities and has become the most widespread modality for many diagnostic and interventional procedures. However, traditional 2D US requires a long training period, especially to learn how to manipulate the probe. A hybrid interactive system based on mixed reality was designed, implemented and tested for hand-eye coordination training in diagnostic and interventional US. A hybrid simulator was developed integrating a physical US phantom and a software application with a 3D virtual scene. In this scene, a 3D model of the probe with its relative scan plane is coherently displayed with a 3D representation of the phantom internal structures. An evaluation study of the diagnostic module was performed by recruiting thirty-six novices and four experts. The performances of the hybrid (HG) versus physical (PG) simulator were compared. After the training session, each novice was required to visualize a particular target structure. The four experts completed a 5-point Likert scale questionnaire. Seventy-eight percentage of the HG novices successfully visualized the target structure, whereas only 45% of the PG reached this goal. The mean scores from the questionnaires were 5.00 for usefulness, 4.25 for ease of use, 4.75 for 3D perception, and 3.25 for phantom realism. The hybrid US training simulator provides ease of use and is effective as a hand-eye coordination teaching tool. Mixed reality can improve US probe manipulation training.

Hybrid models for the simulation of microstructural evolution influenced by coupled, multiple physical processes

Energy Technology Data Exchange (ETDEWEB)

Tikare, Veena [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hernandez-Rivera, Efrain [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Madison, Jonathan D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Holm, Elizabeth Ann [Carnegie Mellon Univ., Pittsburgh, PA (United States); Patterson, Burton R. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Homer, Eric R. [Brigham Young Univ., Provo, UT (United States). Dept. of Mechanical Engineering

2013-09-01

Most materials microstructural evolution processes progress with multiple processes occurring simultaneously. In this work, we have concentrated on the processes that are active in nuclear materials, in particular, nuclear fuels. These processes are coarsening, nucleation, differential diffusion, phase transformation, radiation-induced defect formation and swelling, often with temperature gradients present. All these couple and contribute to evolution that is unique to nuclear fuels and materials. Hybrid model that combines elements from the Potts Monte Carlo, phase-field models and others have been developed to address these multiple physical processes. These models are described and applied to several processes in this report. An important feature of the models developed are that they are coded as applications within SPPARKS, a Sandiadeveloped framework for simulation at the mesoscale of microstructural evolution processes by kinetic Monte Carlo methods. This makes these codes readily accessible and adaptable for future applications.

Hybrid classical/quantum simulation for infrared spectroscopy of water

Science.gov (United States)

Maekawa, Yuki; Sasaoka, Kenji; Ube, Takuji; Ishiguro, Takashi; Yamamoto, Takahiro

2018-05-01

We have developed a hybrid classical/quantum simulation method to calculate the infrared (IR) spectrum of water. The proposed method achieves much higher accuracy than conventional classical molecular dynamics (MD) simulations at a much lower computational cost than ab initio MD simulations. The IR spectrum of water is obtained as an ensemble average of the eigenvalues of the dynamical matrix constructed by ab initio calculations, using the positions of oxygen atoms that constitute water molecules obtained from the classical MD simulation. The calculated IR spectrum is in excellent agreement with the experimental IR spectrum.

3D hybrid simulation of the Titan's plasma environment

Science.gov (United States)

Lipatov, Alexander; Sittler, Edward, Jr.; Hartle, Richard

2007-11-01

Titan plays an important role as a simulation laboratory for multiscale kinetic plasma processes which are key processes in space and laboratory plasmas. A development of multiscale combined numerical methods allows us to use more realistic plasma models at Titan. In this report, we describe a Particle-Ion--Fluid-Ion--Fluid--Electron method of kinetic ion-neutral simulation code. This method takes into account charge-exchange and photoionization processes. The model of atmosphere of Titan was based on a paper by Sittler, Hartle, Vinas et al., [2005]. The background ions H^+, O^+ and pickup ions H2^+, CH4^+ and N2^+ are described in a kinetic approximation, where the electrons are approximated as a fluid. In this report we study the coupling between background ions and pickup ions on the multiple space scales determined by the ion gyroradiis. The first results of such a simulation of the dynamics of ions near Titan are discussed in this report and compared with recent measurements made by the Cassini Plasma Spectrometer (CAPS, [Hartle, Sittler et al., 2006]). E C Sittler Jr., R E Hartle, A F Vinas, R E Johnson, H T Smith and I Mueller-Wodarg, J. Geophys. Res., 110, A09302, 2005.R E Hartle, E C Sittler, F M Neubauer, R E Johnson, et al., Planet. Space Sci., 54, 1211, 2006.

A hybrid approach to simulate multiple photon scattering in X-ray imaging

International Nuclear Information System (INIS)

Freud, N.; Letang, J.-M.; Babot, D.

2005-01-01

A hybrid simulation approach is proposed to compute the contribution of scattered radiation in X- or γ-ray imaging. This approach takes advantage of the complementarity between the deterministic and probabilistic simulation methods. The proposed hybrid method consists of two stages. Firstly, a set of scattering events occurring in the inspected object is determined by means of classical Monte Carlo simulation. Secondly, this set of scattering events is used as a starting point to compute the energy imparted to the detector, with a deterministic algorithm based on a 'forced detection' scheme. For each scattering event, the probability for the scattered photon to reach each pixel of the detector is calculated using well-known physical models (form factor and incoherent scattering function approximations, in the case of Rayleigh and Compton scattering respectively). The results of the proposed hybrid approach are compared to those obtained with the Monte Carlo method alone (Geant4 code) and found to be in excellent agreement. The convergence of the results when the number of scattering events increases is studied. The proposed hybrid approach makes it possible to simulate the contribution of each type (Compton or Rayleigh) and order of scattering, separately or together, with a single PC, within reasonable computation times (from minutes to hours, depending on the number of pixels of the detector). This constitutes a substantial benefit, compared to classical simulation methods (Monte Carlo or deterministic approaches), which usually requires a parallel computing architecture to obtain comparable results

A hybrid approach to simulate multiple photon scattering in X-ray imaging

Energy Technology Data Exchange (ETDEWEB)

Freud, N. [CNDRI, Laboratory of Nondestructive Testing using Ionizing Radiations, INSA-Lyon Scientific and Technical University, Bat. Antoine de Saint-Exupery, 20, avenue Albert Einstein, 69621 Villeurbanne Cedex (France)]. E-mail: nicolas.freud@insa-lyon.fr; Letang, J.-M. [CNDRI, Laboratory of Nondestructive Testing using Ionizing Radiations, INSA-Lyon Scientific and Technical University, Bat. Antoine de Saint-Exupery, 20, avenue Albert Einstein, 69621 Villeurbanne Cedex (France); Babot, D. [CNDRI, Laboratory of Nondestructive Testing using Ionizing Radiations, INSA-Lyon Scientific and Technical University, Bat. Antoine de Saint-Exupery, 20, avenue Albert Einstein, 69621 Villeurbanne Cedex (France)

2005-01-01

A hybrid simulation approach is proposed to compute the contribution of scattered radiation in X- or {gamma}-ray imaging. This approach takes advantage of the complementarity between the deterministic and probabilistic simulation methods. The proposed hybrid method consists of two stages. Firstly, a set of scattering events occurring in the inspected object is determined by means of classical Monte Carlo simulation. Secondly, this set of scattering events is used as a starting point to compute the energy imparted to the detector, with a deterministic algorithm based on a 'forced detection' scheme. For each scattering event, the probability for the scattered photon to reach each pixel of the detector is calculated using well-known physical models (form factor and incoherent scattering function approximations, in the case of Rayleigh and Compton scattering respectively). The results of the proposed hybrid approach are compared to those obtained with the Monte Carlo method alone (Geant4 code) and found to be in excellent agreement. The convergence of the results when the number of scattering events increases is studied. The proposed hybrid approach makes it possible to simulate the contribution of each type (Compton or Rayleigh) and order of scattering, separately or together, with a single PC, within reasonable computation times (from minutes to hours, depending on the number of pixels of the detector). This constitutes a substantial benefit, compared to classical simulation methods (Monte Carlo or deterministic approaches), which usually requires a parallel computing architecture to obtain comparable results.

Application of a hybrid Electrocoagulation-Fenton process in yarn dye wastewater: Kinetic study

Science.gov (United States)

Riadi, L.; Sapei, L.; Lidiawati, T.; Agustin, Y. E.

2016-11-01

Reactive dyes contain a significant portion of colorants used in yarn dying process and also in textile industry. Since the COD content is usually high in such wastewater,we conducted a hybrid electrocoagulation-fenton method to treat the wastewater. This work describes the application of the hybrid system to the removal of chemical oxygen demand and color from the wastewater in a batch reactor. Having worked with initial pH of 3,0; temperature at 30°C, molar ratio of Fe2+/H2O2 =1/10 and the mol ratio H2O2/COD = 4, we got 88.3% COD conversion and 88.5% color removal. The COD degradation process can be explained in two phases, the first phase is instantaneous reaction and the second phase is first order reaction. The kinetic constant was 0.0053 minute-1 and the rate of COD degradation was 0.0053[COD] mg/L minute.

Simulation of a Wall-Bounded Flow using a Hybrid LES/RAS Approach with Turbulence Recycling

Science.gov (United States)

Quinlan, Jesse R.; Mcdaniel, James; Baurle, Robert A.

2012-01-01

Simulations of a supersonic recessed-cavity flow are performed using a hybrid large-eddy/ Reynolds-averaged simulation approach utilizing an inflow turbulence recycling procedure and hybridized inviscid flux scheme. Calorically perfect air enters the three-dimensional domain at a free stream Mach number of 2.92. Simulations are performed to assess grid sensitivity of the solution, efficacy of the turbulence recycling, and effect of the shock sensor used with the hybridized inviscid flux scheme. Analysis of the turbulent boundary layer upstream of the rearward-facing step for each case indicates excellent agreement with theoretical predictions. Mean velocity and pressure results are compared to Reynolds-averaged simulations and experimental data for each case, and these comparisons indicate good agreement on the finest grid. Simulations are repeated on a coarsened grid, and results indicate strong grid density sensitivity. The effect of turbulence recycling on the solution is illustrated by performing coarse grid simulations with and without inflow turbulence recycling. Two shock sensors, one of Ducros and one of Larsson, are assessed for use with the hybridized inviscid flux reconstruction scheme.

Dynamic Garment Simulation based on Hybrid Bounding Volume Hierarchy

Directory of Open Access Journals (Sweden)

Zhu Dongyong

2016-12-01

Full Text Available In order to solve the computing speed and efficiency problem of existing dynamic clothing simulation, this paper presents a dynamic garment simulation based on a hybrid bounding volume hierarchy. It firstly uses MCASG graph theory to do the primary segmentation for a given three-dimensional human body model. And then it applies K-means cluster to do the secondary segmentation to collect the human body’s upper arms, lower arms, upper legs, lower legs, trunk, hip and woman’s chest as the elementary units of dynamic clothing simulation. According to different shapes of these elementary units, it chooses the closest and most efficient hybrid bounding box to specify these units, such as cylinder bounding box and elliptic cylinder bounding box. During the process of constructing these bounding boxes, it uses the least squares method and slices of the human body to get the related parameters. This approach makes it possible to use the least amount of bounding boxes to create close collision detection regions for the appearance of the human body. A spring-mass model based on a triangular mesh of the clothing model is finally constructed for dynamic simulation. The simulation result shows the feasibility and superiority of the method described.

A Lookahead Behavior Model for Multi-Agent Hybrid Simulation

Directory of Open Access Journals (Sweden)

Mei Yang

2017-10-01

Full Text Available In the military field, multi-agent simulation (MAS plays an important role in studying wars statistically. For a military simulation system, which involves large-scale entities and generates a very large number of interactions during the runtime, the issue of how to improve the running efficiency is of great concern for researchers. Current solutions mainly use hybrid simulation to gain fewer updates and synchronizations, where some important continuous models are maintained implicitly to keep the system dynamics, and partial resynchronization (PR is chosen as the preferable state update mechanism. However, problems, such as resynchronization interval selection and cyclic dependency, remain unsolved in PR, which easily lead to low update efficiency and infinite looping of the state update process. To address these problems, this paper proposes a lookahead behavior model (LBM to implement a PR-based hybrid simulation. In LBM, a minimal safe time window is used to predict the interactions between implicit models, upon which the resynchronization interval can be efficiently determined. Moreover, the LBM gives an estimated state value in the lookahead process so as to break the state-dependent cycle. The simulation results show that, compared with traditional mechanisms, LBM requires fewer updates and synchronizations.

Modeling and Simulation of Renewable Hybrid Power System using Matlab Simulink Environment

Directory of Open Access Journals (Sweden)

Cristian Dragoş Dumitru

2010-12-01

Full Text Available The paper presents the modeling of a solar-wind-hydroelectric hybrid system in Matlab/Simulink environment. The application is useful for analysis and simulation of a real hybrid solar-wind-hydroelectric system connected to a public grid. Application is built on modular architecture to facilitate easy study of each component module influence. Blocks like wind model, solar model, hydroelectric model, energy conversion and load are implemented and the results of simulation are also presented. As an example, one of the most important studies is the behavior of hybrid system which allows employing renewable and variable in time energy sources while providing a continuous supply. Application represents a useful tool in research activity and also in teaching

Kinetic energy spectra, vertical resolution and dissipation in high-resolution atmospheric simulations.

Science.gov (United States)

Skamarock, W. C.

2017-12-01

We have performed week-long full-physics simulations with the MPAS global model at 15 km cell spacing using vertical mesh spacings of 800, 400, 200 and 100 meters in the mid-troposphere through the mid-stratosphere. We find that the horizontal kinetic energy spectra in the upper troposphere and stratosphere does not converge with increasing vertical resolution until we reach 200 meter level spacing. Examination of the solutions indicates that significant inertia-gravity waves are not vertically resolved at the lower vertical resolutions. Diagnostics from the simulations indicate that the primary kinetic energy dissipation results from the vertical mixing within the PBL parameterization and from the gravity-wave drag parameterization, with smaller but significant contributions from damping in the vertical transport scheme and from the horizontal filters in the dynamical core. Most of the kinetic energy dissipation in the free atmosphere occurs within breaking mid-latitude baroclinic waves. We will briefly review these results and their implications for atmospheric model configuration and for atmospheric dynamics, specifically that related to the dynamics associated with the mesoscale kinetic energy spectrum.

Advanced particle-in-cell simulation techniques for modeling the Lockheed Martin Compact Fusion Reactor

Science.gov (United States)

Welch, Dale; Font, Gabriel; Mitchell, Robert; Rose, David

2017-10-01

We report on particle-in-cell developments of the study of the Compact Fusion Reactor. Millisecond, two and three-dimensional simulations (cubic meter volume) of confinement and neutral beam heating of the magnetic confinement device requires accurate representation of the complex orbits, near perfect energy conservation, and significant computational power. In order to determine initial plasma fill and neutral beam heating, these simulations include ionization, elastic and charge exchange hydrogen reactions. To this end, we are pursuing fast electromagnetic kinetic modeling algorithms including a two implicit techniques and a hybrid quasi-neutral algorithm with kinetic ions. The kinetic modeling includes use of the Poisson-corrected direct implicit, magnetic implicit, as well as second-order cloud-in-cell techniques. The hybrid algorithm, ignoring electron inertial effects, is two orders of magnitude faster than kinetic but not as accurate with respect to confinement. The advantages and disadvantages of these techniques will be presented. Funded by Lockheed Martin.

Sampling Enrichment toward Target Structures Using Hybrid Molecular Dynamics-Monte Carlo Simulations.

Directory of Open Access Journals (Sweden)

Kecheng Yang

Full Text Available Sampling enrichment toward a target state, an analogue of the improvement of sampling efficiency (SE, is critical in both the refinement of protein structures and the generation of near-native structure ensembles for the exploration of structure-function relationships. We developed a hybrid molecular dynamics (MD-Monte Carlo (MC approach to enrich the sampling toward the target structures. In this approach, the higher SE is achieved by perturbing the conventional MD simulations with a MC structure-acceptance judgment, which is based on the coincidence degree of small angle x-ray scattering (SAXS intensity profiles between the simulation structures and the target structure. We found that the hybrid simulations could significantly improve SE by making the top-ranked models much closer to the target structures both in the secondary and tertiary structures. Specifically, for the 20 mono-residue peptides, when the initial structures had the root-mean-squared deviation (RMSD from the target structure smaller than 7 Å, the hybrid MD-MC simulations afforded, on average, 0.83 Å and 1.73 Å in RMSD closer to the target than the parallel MD simulations at 310K and 370K, respectively. Meanwhile, the average SE values are also increased by 13.2% and 15.7%. The enrichment of sampling becomes more significant when the target states are gradually detectable in the MD-MC simulations in comparison with the parallel MD simulations, and provide >200% improvement in SE. We also performed a test of the hybrid MD-MC approach in the real protein system, the results showed that the SE for 3 out of 5 real proteins are improved. Overall, this work presents an efficient way of utilizing solution SAXS to improve protein structure prediction and refinement, as well as the generation of near native structures for function annotation.

Mountain bicycle frame testing as an example of practical implementation of hybrid simulation using RTFEM

Science.gov (United States)

Mucha, Waldemar; Kuś, Wacław

2018-01-01

The paper presents a practical implementation of hybrid simulation using Real Time Finite Element Method (RTFEM). Hybrid simulation is a technique for investigating dynamic material and structural properties of mechanical systems by performing numerical analysis and experiment at the same time. It applies to mechanical systems with elements too difficult or impossible to model numerically. These elements are tested experimentally, while the rest of the system is simulated numerically. Data between the experiment and numerical simulation are exchanged in real time. Authors use Finite Element Method to perform the numerical simulation. The following paper presents the general algorithm for hybrid simulation using RTFEM and possible improvements of the algorithm for computation time reduction developed by the authors. The paper focuses on practical implementation of presented methods, which involves testing of a mountain bicycle frame, where the shock absorber is tested experimentally while the rest of the frame is simulated numerically.

CHEMSIMUL: A simulator for chemical kinetics

International Nuclear Information System (INIS)

Kirkegaard, P.; Bjergbakke, E.

1999-01-01

CHEMSIMUL is a computer program system for numerical simulation of chemical reaction systems. It can be used for modeling complex kinetics in many contexts, in particular radiolytic processes. It contains a translator module and a module for solving the resulting coupled nonlinear ordinary differential equations. An overview of the program system is given, and its use is illustrated by examples. A number of special features are described, in particular a method for verifying the mass balance. Moreover, the document contains a complete User's Guide for running CHEMSIMUL on a PC or another computer. Finally, the mathematical implementation is discussed. (au)

Numerical Simulations of Kinetic Alfvén Waves to Study Spectral ...

Indian Academy of Sciences (India)

Numerical Simulations of Kinetic Alfvén Waves to Study Spectral. Index in Solar Wind Turbulence and Particle Heating. R. P. Sharma. ∗. & H. D. Singh. Center for Energy Studies, Indian Institute of Technology, Delhi 110 016, India. ∗ e-mail: rpsharma@ces.iitd.ernet.in. Abstract. We present numerical simulations of the ...

Hybrid Network Simulation for the ATLAS Trigger and Data Acquisition (TDAQ) System

CERN Document Server

Bonaventura, Matias Alejandro; The ATLAS collaboration; Castro, Rodrigo Daniel; Foguelman, Daniel Jacob

2015-01-01

The poster shows the ongoing research in the ATLAS TDAQ group in collaboration with the University of Buenos Aires in the area of hybrid data network simulations. he Data Network and Processing Cluster filters data in real-time, achieving a rejection factor in the order of 40000x and has real-time latency constrains. The dataflow between the processing units (TPUs) and Readout System (ROS) presents a “TCP Incast”-type network pathology which TCP cannot handle it efficiently. A credits system is in place which limits rate of queries and reduces latency. This large computer network, and the complex dataflow has been modelled and simulated using a PowerDEVS, a DEVS-based simulator. The simulation has been validated and used to produce what-if scenarios in the real network. Network Simulation with Hybrid Flows: Speedups and accuracy, combined • For intensive network traffic, Discrete Event simulation models (packet-level granularity) soon becomes prohibitive: Too high computing demands. • Fluid Flow simul...

Kinetic Simulations of Dense Plasma Focus Breakdown

Science.gov (United States)

Schmidt, A.; Higginson, D. P.; Jiang, S.; Link, A.; Povilus, A.; Sears, J.; Bennett, N.; Rose, D. V.; Welch, D. R.

2015-11-01

A dense plasma focus (DPF) device is a type of plasma gun that drives current through a set of coaxial electrodes to assemble gas inside the device and then implode that gas on axis to form a Z-pinch. This implosion drives hydrodynamic and kinetic instabilities that generate strong electric fields, which produces a short intense pulse of x-rays, high-energy (>100 keV) electrons and ions, and (in deuterium gas) neutrons. A strong factor in pinch performance is the initial breakdown and ionization of the gas along the insulator surface separating the two electrodes. The smoothness and isotropy of this ionized sheath are imprinted on the current sheath that travels along the electrodes, thus making it an important portion of the DPF to both understand and optimize. Here we use kinetic simulations in the Particle-in-cell code LSP to model the breakdown. Simulations are initiated with neutral gas and the breakdown modeled self-consistently as driven by a charged capacitor system. We also investigate novel geometries for the insulator and electrodes to attempt to control the electric field profile. The initial ionization fraction of gas is explored computationally to gauge possible advantages of pre-ionization which could be created experimentally via lasers or a glow-discharge. Prepared by LLNL under Contract DE-AC52-07NA27344.

Hybrid Reynolds-Averaged/Large Eddy Simulation of a Cavity Flameholder; Assessment of Modeling Sensitivities

Science.gov (United States)

Baurle, R. A.

2015-01-01

Steady-state and scale-resolving simulations have been performed for flow in and around a model scramjet combustor flameholder. The cases simulated corresponded to those used to examine this flowfield experimentally using particle image velocimetry. A variety of turbulence models were used for the steady-state Reynolds-averaged simulations which included both linear and non-linear eddy viscosity models. The scale-resolving simulations used a hybrid Reynolds-averaged / large eddy simulation strategy that is designed to be a large eddy simulation everywhere except in the inner portion (log layer and below) of the boundary layer. Hence, this formulation can be regarded as a wall-modeled large eddy simulation. This effort was undertaken to formally assess the performance of the hybrid Reynolds-averaged / large eddy simulation modeling approach in a flowfield of interest to the scramjet research community. The numerical errors were quantified for both the steady-state and scale-resolving simulations prior to making any claims of predictive accuracy relative to the measurements. The steady-state Reynolds-averaged results showed a high degree of variability when comparing the predictions obtained from each turbulence model, with the non-linear eddy viscosity model (an explicit algebraic stress model) providing the most accurate prediction of the measured values. The hybrid Reynolds-averaged/large eddy simulation results were carefully scrutinized to ensure that even the coarsest grid had an acceptable level of resolution for large eddy simulation, and that the time-averaged statistics were acceptably accurate. The autocorrelation and its Fourier transform were the primary tools used for this assessment. The statistics extracted from the hybrid simulation strategy proved to be more accurate than the Reynolds-averaged results obtained using the linear eddy viscosity models. However, there was no predictive improvement noted over the results obtained from the explicit

Hybrid simulations of plasma transport by Kelvin-Helmholtz instability at the magnetopause: magnetic shear

Energy Technology Data Exchange (ETDEWEB)

Cowee, Misa M [Los Alamos National Laboratory; Winske, Dan [Los Alamos National Laboratory; Gary, S Peter [Los Alamos National Laboratory

2009-01-01

Two-dimensional hybrid (kinetic ions, massless fluid electrons) simulations of the Kelvin Helmholtz Instability (KHI) for a magnetopause configuration with a magnetic shear across the boundary are carried out to examine how the transport of magnetosheath plasma into the magnetosphere is affected by the shear field. Low magnetic shear conditions where the magnetosheath magnetic field is within 30{sup o} of northward is included in the simulations because KHI is thought to be important for plasma transport only for northward or near-northward interplanetary magnetic field orientations. The simulations show that coherent vortices can grow for these near-northward angles, and that they are sometimes more coherent than for pure northward conditions because the turbulence which breaks-down these vortices is reduced when there are magnetic tension forces. With increasing magnetic shear angle, the growth rate is reduced, and the vortices do not grow to as large of size which reduces the plasma transport. By tracking the individual particle motions diffusion coefficients can be obtained for the system, where the diffusion is not classical in nature but instead has a time dependence resulting from both the increasingly large-scale vortex motion and the small-scale turbulence generated in the break-down of the instabilities. Results indicate that diffusion on the order of 10{sup 9} m{sup 2}/s could possibly be generated by KHI on the flanks of the magnetosphere.

3D nozzle flow simulations including state-to-state kinetics calculation

Science.gov (United States)

Cutrone, L.; Tuttafesta, M.; Capitelli, M.; Schettino, A.; Pascazio, G.; Colonna, G.

2014-12-01

In supersonic and hypersonic flows, thermal and chemical non-equilibrium is one of the fundamental aspects that must be taken into account for the accurate characterization of the plasma. In this paper, we present an optimized methodology to approach plasma numerical simulation by state-to-state kinetics calculations in a fully 3D Navier-Stokes CFD solver. Numerical simulations of an expanding flow are presented aimed at comparing the behavior of state-to-state chemical kinetics models with respect to the macroscopic thermochemical non-equilibrium models that are usually used in the numerical computation of high temperature hypersonic flows. The comparison is focused both on the differences in the numerical results and on the computational effort associated with each approach.

MAGNETIC NULL POINTS IN KINETIC SIMULATIONS OF SPACE PLASMAS

International Nuclear Information System (INIS)

Olshevsky, Vyacheslav; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni; Deca, Jan; Divin, Andrey; Peng, Ivy Bo; Markidis, Stefano

2016-01-01

We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic particle-in-cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind, and a relaxing turbulent configuration with multiple null points. Spiral nulls are more likely created in space plasmas: in all our simulations except lunar magnetic anomaly (LMA) and quadrupolar mini-magnetosphere the number of spiral nulls prevails over the number of radial nulls by a factor of 3–9. We show that often magnetic nulls do not indicate the regions of intensive energy dissipation. Energy dissipation events caused by topological bifurcations at radial nulls are rather rare and short-lived. The so-called X-lines formed by the radial nulls in the Harris current sheet and LMA simulations are rather stable and do not exhibit any energy dissipation. Energy dissipation is more powerful in the vicinity of spiral nulls enclosed by magnetic flux ropes with strong currents at their axes (their cross sections resemble 2D magnetic islands). These null lines reminiscent of Z-pinches efficiently dissipate magnetic energy due to secondary instabilities such as the two-stream or kinking instability, accompanied by changes in magnetic topology. Current enhancements accompanied by spiral nulls may signal magnetic energy conversion sites in the observational data

Simulation of Hybrid Photovoltaic Solar Assisted Loop Heat Pipe/Heat Pump System

Directory of Open Access Journals (Sweden)

Nannan Dai

2017-02-01

Full Text Available A hybrid photovoltaic solar assisted loop heat pipe/heat pump (PV-SALHP/HP water heater system has been developed and numerically studied. The system is the combination of loop heat pipe (LHP mode and heat pump (HP mode, and the two modes can be run separately or compositely according to the weather conditions. The performances of independent heat pump (HP mode and hybrid loop heat pipe/heat pump (LHP/HP mode were simulated and compared. Simulation results showed that on typical sunny days in spring or autumn, using LHP/HP mode could save 40.6% power consumption than HP mode. In addition, the optimal switchover from LHP mode to HP mode was analyzed in different weather conditions for energy saving and the all-year round operating performances of the system were also simulated. The simulation results showed that hybrid LHP/HP mode should be utilized to save electricity on sunny days from March to November and the system can rely on LHP mode alone without any power consumption in July and August. When solar radiation and ambient temperature are low in winter, HP mode should be used

Simulation based design strategy for EMC compliance of components in hybrid vehicles

Energy Technology Data Exchange (ETDEWEB)

Maass, Uwe; Ndip, Ivan; Hoene, Eckard; Guttowski, Stephan [Fraunhofer-Institut fuer Zuverlaessigkeit und Mikrointegration (IZM), Berlin (Germany); Tschoban, Christian; Lang, Klaus-Dieter [Technische Univ. Berlin (Germany)

2012-11-01

The design of components for the power train of hybrid vehicles needs to take into account EMC compliance standards related to hazardous electromagnetic fields. Using a simulation based design strategy allows for virtual EMC tests in parallel to the mechanical / electrical power design and thus reduces (re-)design time and costs. Taking as an example a high-voltage battery for a hybrid vehicle the emitted magnetic fields outside the battery are examined. The simulation stategy is based on 3D EM simulations using a full-wave and an eddy current solver. The simulation models are based on the actual CAD data from the mechanical construction resulting in and a high geometrical aspect ratio. The impact of simulation specific aspects such as boundary conditions and excitation is given. It was found that using field simulations it is possible to identify noise sources and coupling paths as well as aid the construction of the battery. (orig.)

Hybrid RANS-LES using high order numerical methods

Science.gov (United States)

Henry de Frahan, Marc; Yellapantula, Shashank; Vijayakumar, Ganesh; Knaus, Robert; Sprague, Michael

2017-11-01

Understanding the impact of wind turbine wake dynamics on downstream turbines is particularly important for the design of efficient wind farms. Due to their tractable computational cost, hybrid RANS/LES models are an attractive framework for simulating separation flows such as the wake dynamics behind a wind turbine. High-order numerical methods can be computationally efficient and provide increased accuracy in simulating complex flows. In the context of LES, high-order numerical methods have shown some success in predictions of turbulent flows. However, the specifics of hybrid RANS-LES models, including the transition region between both modeling frameworks, pose unique challenges for high-order numerical methods. In this work, we study the effect of increasing the order of accuracy of the numerical scheme in simulations of canonical turbulent flows using RANS, LES, and hybrid RANS-LES models. We describe the interactions between filtering, model transition, and order of accuracy and their effect on turbulence quantities such as kinetic energy spectra, boundary layer evolution, and dissipation rate. This work was funded by the U.S. Department of Energy, Exascale Computing Project, under Contract No. DE-AC36-08-GO28308 with the National Renewable Energy Laboratory.

Species Entropies in the Kinetic Range of Collisionless Plasma Turbulence: Particle-in-cell Simulations

Science.gov (United States)

Gary, S. Peter; Zhao, Yinjian; Hughes, R. Scott; Wang, Joseph; Parashar, Tulasi N.

2018-06-01

Three-dimensional particle-in-cell simulations of the forward cascade of decaying turbulence in the relatively short-wavelength kinetic range have been carried out as initial-value problems on collisionless, homogeneous, magnetized electron-ion plasma models. The simulations have addressed both whistler turbulence at β i = β e = 0.25 and kinetic Alfvén turbulence at β i = β e = 0.50, computing the species energy dissipation rates as well as the increase of the Boltzmann entropies for both ions and electrons as functions of the initial dimensionless fluctuating magnetic field energy density ε o in the range 0 ≤ ε o ≤ 0.50. This study shows that electron and ion entropies display similar rates of increase and that all four entropy rates increase approximately as ε o , consistent with the assumption that the quasilinear premise is valid for the initial conditions assumed for these simulations. The simulations further predict that the time rates of ion entropy increase should be substantially greater for kinetic Alfvén turbulence than for whistler turbulence.

Global Hybrid Simulations of Energetic Particle-driven Modes in Toroidal Plasmas

International Nuclear Information System (INIS)

Fu, G.Y.; Breslau, J.; Fredrickson, E.; Park, W.; Strauss, H.R.

2004-01-01

Global hybrid simulations of energetic particle-driven MHD modes have been carried out for tokamaks and spherical tokamaks using the hybrid code M3D. The numerical results for the National Spherical Tokamak Experiments (NSTX) show that Toroidal Alfven Eigenmodes are excited by beam ions with their frequencies consistent with the experimental observations. Nonlinear simulations indicate that the n=2 mode frequency chirps down as the mode moves out radially. For ITER, it is shown that the alpha-particle effects are strongly stabilizing for internal kink mode when central safety factor q(0) is sufficiently close to unity. However, the elongation of ITER plasma shape reduces the stabilization significantly

Hybrid and electric advanced vehicle systems (heavy) simulation

Science.gov (United States)

Hammond, R. A.; Mcgehee, R. K.

1981-01-01

A computer program to simulate hybrid and electric advanced vehicle systems (HEAVY) is described. It is intended for use early in the design process: concept evaluation, alternative comparison, preliminary design, control and management strategy development, component sizing, and sensitivity studies. It allows the designer to quickly, conveniently, and economically predict the performance of a proposed drive train. The user defines the system to be simulated using a library of predefined component models that may be connected to represent a wide variety of propulsion systems. The development of three models are discussed as examples.

Coupling Chemical Kinetics and Flashes in Reactive, Thermal and Compositional Reservoir Simulation

DEFF Research Database (Denmark)

Kristensen, Morten Rode; Gerritsen, Margot G.; Thomsen, Per Grove

2007-01-01

of convergence and error test failures by more than 50% compared to direct integration without the new algorithm. To facilitate the algorithmic development we construct a virtual kinetic cell model. We use implicit one-step ESDIRK (Explicit Singly Diagonal Implicit Runge-Kutta) methods for integration...... of the kinetics. The kinetic cell model serves both as a tool for the development and testing of tailored solvers as well as a testbed for studying the interactions between chemical kinetics and phase behavior. A comparison between a Kvalue correlation based approach and a more rigorous equation of state based......Phase changes are known to cause convergence problems for integration of stiff kinetics in thermal and compositional reservoir simulations. We propose an algorithm for detection and location of phase changes based on discrete event system theory. The algorithm provides a robust way for handling...

Using Equation-Free Computation to Accelerate Network-Free Stochastic Simulation of Chemical Kinetics.

Science.gov (United States)

Lin, Yen Ting; Chylek, Lily A; Lemons, Nathan W; Hlavacek, William S

2018-06-21

The chemical kinetics of many complex systems can be concisely represented by reaction rules, which can be used to generate reaction events via a kinetic Monte Carlo method that has been termed network-free simulation. Here, we demonstrate accelerated network-free simulation through a novel approach to equation-free computation. In this process, variables are introduced that approximately capture system state. Derivatives of these variables are estimated using short bursts of exact stochastic simulation and finite differencing. The variables are then projected forward in time via a numerical integration scheme, after which a new exact stochastic simulation is initialized and the whole process repeats. The projection step increases efficiency by bypassing the firing of numerous individual reaction events. As we show, the projected variables may be defined as populations of building blocks of chemical species. The maximal number of connected molecules included in these building blocks determines the degree of approximation. Equation-free acceleration of network-free simulation is found to be both accurate and efficient.

Thermodynamic and kinetic simulation of transient liquid-phase bonding

Science.gov (United States)

Lindner, Brad

The use of numeric computational methods for the simulation of materials systems is becoming more prevalent and an understanding of these tools may soon be a necessity for Materials Engineers and Scientists. The applicability of numerical simulation methods to transient liquid-phase (TLP) bonding is evaluated using a type 316L/MBF-51 material system. The comparisons involve the calculation of bulk diffusivities, tracking of interface positions during dissolution, widening, and isothermal solidification stages, as well as comparison of elemental composition profiles. The simulations were performed with Thermo-Calc and DICTRA software packages and the experiments with differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and optical microscopic methods. Analytical methods are also discussed to enhance understanding. The results of the investigation show that while general agreement between simulations and experiments can be obtained, assumptions made with the simulation programs may cause difficulty in interpretation of the results unless the user has sufficient, mathematical, thermodynamic, kinetic, and simulation background.

A hybrid algorithm for parallel molecular dynamics simulations

Science.gov (United States)

Mangiardi, Chris M.; Meyer, R.

2017-10-01

This article describes algorithms for the hybrid parallelization and SIMD vectorization of molecular dynamics simulations with short-range forces. The parallelization method combines domain decomposition with a thread-based parallelization approach. The goal of the work is to enable efficient simulations of very large (tens of millions of atoms) and inhomogeneous systems on many-core processors with hundreds or thousands of cores and SIMD units with large vector sizes. In order to test the efficiency of the method, simulations of a variety of configurations with up to 74 million atoms have been performed. Results are shown that were obtained on multi-core systems with Sandy Bridge and Haswell processors as well as systems with Xeon Phi many-core processors.

Integration of Extended MHD and Kinetic Effects in Global Magnetosphere Models

Science.gov (United States)

Germaschewski, K.; Wang, L.; Maynard, K. R. M.; Raeder, J.; Bhattacharjee, A.

2015-12-01

Computational models of Earth's geospace environment are an important tool to investigate the science of the coupled solar-wind -- magnetosphere -- ionosphere system, complementing satellite and ground observations with a global perspective. They are also crucial in understanding and predicting space weather, in particular under extreme conditions. Traditionally, global models have employed the one-fluid MHD approximation, which captures large-scale dynamics quite well. However, in Earth's nearly collisionless plasma environment it breaks down on small scales, where ion and electron dynamics and kinetic effects become important, and greatly change the reconnection dynamics. A number of approaches have recently been taken to advance global modeling, e.g., including multiple ion species, adding Hall physics in a Generalized Ohm's Law, embedding local PIC simulations into a larger fluid domain and also some work on simulating the entire system with hybrid or fully kinetic models, the latter however being to computationally expensive to be run at realistic parameters. We will present an alternate approach, ie., a multi-fluid moment model that is derived rigorously from the Vlasov-Maxwell system. The advantage is that the computational cost remains managable, as we are still solving fluid equations. While the evolution equation for each moment is exact, it depends on the next higher-order moment, so that truncating the hiearchy and closing the system to capture the essential kinetic physics is crucial. We implement 5-moment (density, momentum, scalar pressure) and 10-moment (includes pressure tensor) versions of the model, and use local approximations for the heat flux to close the system. We test these closures by local simulations where we can compare directly to PIC / hybrid codes, and employ them in global simulations using the next-generation OpenGGCM to contrast them to MHD / Hall-MHD results and compare with observations.

Energy Management and Simulation of Photovoltaic/Hydrogen /Battery Hybrid Power System

Directory of Open Access Journals (Sweden)

Tariq Kamal

2016-06-01

Full Text Available This manuscript focuses on a hybrid power system combining a solar photovoltaic array and energy storage system based on hydrogen technology (fuel cell, hydrogen tank and electrolyzer and battery. The complete architecture is connected to the national grid through power converters to increase the continuity of power. The proposed a hybrid power system is designed to work under classical-based energy management algorithm. According to the proposed algorithm, the PV has the priority in meeting the load demands. The hydrogen technology is utilized to ensure long-term energy balance. The battery is used as a backup and/or high power device to take care of the load following problems of hydrogen technology during transient. The dynamic performance of a hybrid power system is tested under different solar radiation, temperature and load conditions for the simulation of 24 Hrs. The effectiveness of the proposed system in terms of power sharing, grid stability, power quality and voltage regulation is verified by Matlab simulation results.

Plasma and wave properties downstream of Martian bow shock: Hybrid simulations and MAVEN observations

Science.gov (United States)

Dong, Chuanfei; Winske, Dan; Cowee, Misa; Bougher, Stephen W.; Andersson, Laila; Connerney, Jack; Epley, Jared; Ergun, Robert; McFadden, James P.; Ma, Yingjuan; Toth, Gabor; Curry, Shannon; Nagy, Andrew; Jakosky, Bruce

2015-04-01

Two-dimensional hybrid simulation codes are employed to investigate the kinetic properties of plasmas and waves downstream of the Martian bow shock. The simulations are two-dimensional in space but three dimensional in field and velocity components. Simulations show that ion cyclotron waves are generated by temperature anisotropy resulting from the reflected protons around the Martian bow shock. These proton cyclotron waves could propagate downward into the Martian ionosphere and are expected to heat the O+ layer peaked from 250 to 300 km due to the wave-particle interaction. The proton cyclotron wave heating is anticipated to be a significant source of energy into the thermosphere, which impacts atmospheric escape rates. The simulation results show that the specific dayside heating altitude depends on the Martian crustal field orientations, solar cycles and seasonal variations since both the cyclotron resonance condition and the non/sub-resonant stochastic heating threshold depend on the ambient magnetic field strength. The dayside magnetic field profiles for different crustal field orientation, solar cycle and seasonal variations are adopted from the BATS-R-US Mars multi-fluid MHD model. The simulation results, however, show that the heating of O+ via proton cyclotron wave resonant interaction is not likely in the relatively weak crustal field region, based on our simplified model. This indicates that either the drift motion resulted from the transport of ionospheric O+, or the non/sub-resonant stochastic heating mechanism are important to explain the heating of Martian O+ layer. We will investigate this further by comparing the simulation results with the available MAVEN data. These simulated ion cyclotron waves are important to explain the heating of Martian O+ layer and have significant implications for future observations.

Kinetic Monte Carlo Simulation of Cation Diffusion in Low-K Ceramics

Science.gov (United States)

Good, Brian

2013-01-01

Low thermal conductivity (low-K) ceramic materials are of interest to the aerospace community for use as the thermal barrier component of coating systems for turbine engine components. In particular, zirconia-based materials exhibit both low thermal conductivity and structural stability at high temperature, making them suitable for such applications. Because creep is one of the potential failure modes, and because diffusion is a mechanism by which creep takes place, we have performed computer simulations of cation diffusion in a variety of zirconia-based low-K materials. The kinetic Monte Carlo simulation method is an alternative to the more widely known molecular dynamics (MD) method. It is designed to study "infrequent-event" processes, such as diffusion, for which MD simulation can be highly inefficient. We describe the results of kinetic Monte Carlo computer simulations of cation diffusion in several zirconia-based materials, specifically, zirconia doped with Y, Gd, Nb and Yb. Diffusion paths are identified, and migration energy barriers are obtained from density functional calculations and from the literature. We present results on the temperature dependence of the diffusivity, and on the effects of the presence of oxygen vacancies in cation diffusion barrier complexes as well.

An Engineered Kinetic Amplification Mechanism for Single Nucleotide Variant Discrimination by DNA Hybridization Probes.

Science.gov (United States)

Chen, Sherry Xi; Seelig, Georg

2016-04-20

Even a single-nucleotide difference between the sequences of two otherwise identical biological nucleic acids can have dramatic functional consequences. Here, we use model-guided reaction pathway engineering to quantitatively improve the performance of selective hybridization probes in recognizing single nucleotide variants (SNVs). Specifically, we build a detection system that combines discrimination by competition with DNA strand displacement-based catalytic amplification. We show, both mathematically and experimentally, that the single nucleotide selectivity of such a system in binding to single-stranded DNA and RNA is quadratically better than discrimination due to competitive hybridization alone. As an additional benefit the integrated circuit inherits the property of amplification and provides at least 10-fold better sensitivity than standard hybridization probes. Moreover, we demonstrate how the detection mechanism can be tuned such that the detection reaction is agnostic to the position of the SNV within the target sequence. in contrast, prior strand displacement-based probes designed for kinetic discrimination are highly sensitive to position effects. We apply our system to reliably discriminate between different members of the let-7 microRNA family that differ in only a single base position. Our results demonstrate the power of systematic reaction network design to quantitatively improve biotechnology.

Simulated Fuel Economy and Emissions Performance during City and Interstate Driving for a Heavy-Duty Hybrid Truck

Energy Technology Data Exchange (ETDEWEB)

Daw, C. Stuart; Gao, Zhiming; Smith, David E.; Laclair, Tim J.; Pihl, Josh A.; Edwards, K. Dean

2013-04-08

We compare simulated fuel economy and emissions for both conventional and hybrid class 8 heavy-duty diesel trucks operating over multiple urban and highway driving cycles. Both light and heavy freight loads were considered, and all simulations included full aftertreatment for NOx and particulate emissions controls. The aftertreatment components included a diesel oxidation catalyst (DOC), urea-selective catalytic NOx reduction (SCR), and a catalyzed diesel particulate filter (DPF). Our simulated hybrid powertrain was configured with a pre-transmission parallel drive, with a single electric motor between the clutch and gearbox. A conventional HD truck with equivalent diesel engine and aftertreatment was also simulated for comparison. Our results indicate that hybridization can significantly increase HD fuel economy and improve emissions control in city driving. However, there is less potential hybridization benefit for HD highway driving. A major factor behind the reduced hybridization benefit for highway driving is that there are fewer opportunities to utilize regenerative breaking. Our aftertreatment simulations indicate that opportunities for passive DPF regeneration are much greater for both hybrid and conventional trucks during highway driving due to higher sustained exhaust temperatures. When passive DPF regeneration is extensively utilized, the fuel penalty for particulate control is virtually eliminated, except for the 0.4%-0.9% fuel penalty associated with the slightly higher exhaust backpressure.

A hybrid method for flood simulation in small catchments combining hydrodynamic and hydrological techniques

Science.gov (United States)

Bellos, Vasilis; Tsakiris, George

2016-09-01

The study presents a new hybrid method for the simulation of flood events in small catchments. It combines a physically-based two-dimensional hydrodynamic model and the hydrological unit hydrograph theory. Unit hydrographs are derived using the FLOW-R2D model which is based on the full form of two-dimensional Shallow Water Equations, solved by a modified McCormack numerical scheme. The method is tested at a small catchment in a suburb of Athens-Greece for a storm event which occurred in February 2013. The catchment is divided into three friction zones and unit hydrographs of 15 and 30 min are produced. The infiltration process is simulated by the empirical Kostiakov equation and the Green-Ampt model. The results from the implementation of the proposed hybrid method are compared with recorded data at the hydrometric station at the outlet of the catchment and the results derived from the fully hydrodynamic model FLOW-R2D. It is concluded that for the case studied, the proposed hybrid method produces results close to those of the fully hydrodynamic simulation at substantially shorter computational time. This finding, if further verified in a variety of case studies, can be useful in devising effective hybrid tools for the two-dimensional flood simulations, which are lead to accurate and considerably faster results than those achieved by the fully hydrodynamic simulations.

Numerical simulation of plasmas

International Nuclear Information System (INIS)

Dnestrovskii, Y.N.; Kostomarov, D.P.

1986-01-01

This book contains a modern consistent and systematic presentation of numerical computer simulation of plasmas in controlled thermonuclear fusion. The authors focus on the Soviet research in mathematical modelling of Tokamak plasmas, and present kinetic hydrodynamic and transport models with special emphasis on the more recent hybrid models. Compared with the first edition (in Russian) this book has been greatly revised and updated. (orig./WL)

Temporal acceleration of spatially distributed kinetic Monte Carlo simulations

International Nuclear Information System (INIS)

Chatterjee, Abhijit; Vlachos, Dionisios G.

2006-01-01

The computational intensity of kinetic Monte Carlo (KMC) simulation is a major impediment in simulating large length and time scales. In recent work, an approximate method for KMC simulation of spatially uniform systems, termed the binomial τ-leap method, was introduced [A. Chatterjee, D.G. Vlachos, M.A. Katsoulakis, Binomial distribution based τ-leap accelerated stochastic simulation, J. Chem. Phys. 122 (2005) 024112], where molecular bundles instead of individual processes are executed over coarse-grained time increments. This temporal coarse-graining can lead to significant computational savings but its generalization to spatially lattice KMC simulation has not been realized yet. Here we extend the binomial τ-leap method to lattice KMC simulations by combining it with spatially adaptive coarse-graining. Absolute stability and computational speed-up analyses for spatial systems along with simulations provide insights into the conditions where accuracy and substantial acceleration of the new spatio-temporal coarse-graining method are ensured. Model systems demonstrate that the r-time increment criterion of Chatterjee et al. obeys the absolute stability limit for values of r up to near 1

Recovery act. Development of design and simulation tool for hybrid geothermal heat pump system

Energy Technology Data Exchange (ETDEWEB)

Wang, Shaojie [ClimateMaster, Inc., Oklahoma City, OK (United States); Ellis, Dan [ClimateMaster, Inc., Oklahoma City, OK (United States)

2014-05-29

The ground source heat pump (GSHP) system is one of the most energy efficient HVAC technologies in the current market. However, the heat imbalance may degrade the ability of the ground loop heat exchanger (GLHX) to absorb or reject heat. The hybrid GSHP system, which combines a geothermal well field with a supplemental boiler or cooling tower, can balance the loads imposed on the ground loop heat exchangers to minimize its size while retaining superior energy efficiency. This paper presents a recent simulation-based study with an intention to compare multiple common control strategies used in hybrid GSHP systems, including fixed setpoint, outside air reset, load reset, and wetbulb reset. A small office in Oklahoma City conditioned by a hybrid GSHP system was simulated with the latest version of eQUEST 3.7[1]. The simulation results reveal that the hybrid GSHP system has the excellent capability to meet the cooling and heating setpoints during the occupied hours, balance thermal loads on the ground loop, as well as improve the thermal comfort of the occupants with the undersized well field.

Hybrid Multilevel Monte Carlo Simulation of Stochastic Reaction Networks

KAUST Repository

Moraes, Alvaro

2015-01-01

even more, we want to achieve this objective with near optimal computational work. We first introduce a hybrid path-simulation scheme based on the well-known stochastic simulation algorithm (SSA)[3] and the tau-leap method [2]. Then, we introduce a Multilevel Monte Carlo strategy that allows us to achieve a computational complexity of order O(T OL−2), this is the same computational complexity as in an exact method but with a smaller constant. We provide numerical examples to show our results.

Hybrid Reynolds-Averaged/Large-Eddy Simulations of a Co-Axial Supersonic Free-Jet Experiment

Science.gov (United States)

Baurle, R. A.; Edwards, J. R.

2009-01-01

Reynolds-averaged and hybrid Reynolds-averaged/large-eddy simulations have been applied to a supersonic coaxial jet flow experiment. The experiment utilized either helium or argon as the inner jet nozzle fluid, and the outer jet nozzle fluid consisted of laboratory air. The inner and outer nozzles were designed and operated to produce nearly pressure-matched Mach 1.8 flow conditions at the jet exit. The purpose of the computational effort was to assess the state-of-the-art for each modeling approach, and to use the hybrid Reynolds-averaged/large-eddy simulations to gather insight into the deficiencies of the Reynolds-averaged closure models. The Reynolds-averaged simulations displayed a strong sensitivity to choice of turbulent Schmidt number. The baseline value chosen for this parameter resulted in an over-prediction of the mixing layer spreading rate for the helium case, but the opposite trend was noted when argon was used as the injectant. A larger turbulent Schmidt number greatly improved the comparison of the results with measurements for the helium simulations, but variations in the Schmidt number did not improve the argon comparisons. The hybrid simulation results showed the same trends as the baseline Reynolds-averaged predictions. The primary reason conjectured for the discrepancy between the hybrid simulation results and the measurements centered around issues related to the transition from a Reynolds-averaged state to one with resolved turbulent content. Improvements to the inflow conditions are suggested as a remedy to this dilemma. Comparisons between resolved second-order turbulence statistics and their modeled Reynolds-averaged counterparts were also performed.

Hybrid Reynolds-Averaged/Large-Eddy Simulations of a Coaxial Supersonic Free-Jet Experiment

Science.gov (United States)

Baurle, Robert A.; Edwards, Jack R.

2010-01-01

Reynolds-averaged and hybrid Reynolds-averaged/large-eddy simulations have been applied to a supersonic coaxial jet flow experiment. The experiment was designed to study compressible mixing flow phenomenon under conditions that are representative of those encountered in scramjet combustors. The experiment utilized either helium or argon as the inner jet nozzle fluid, and the outer jet nozzle fluid consisted of laboratory air. The inner and outer nozzles were designed and operated to produce nearly pressure-matched Mach 1.8 flow conditions at the jet exit. The purpose of the computational effort was to assess the state-of-the-art for each modeling approach, and to use the hybrid Reynolds-averaged/large-eddy simulations to gather insight into the deficiencies of the Reynolds-averaged closure models. The Reynolds-averaged simulations displayed a strong sensitivity to choice of turbulent Schmidt number. The initial value chosen for this parameter resulted in an over-prediction of the mixing layer spreading rate for the helium case, but the opposite trend was observed when argon was used as the injectant. A larger turbulent Schmidt number greatly improved the comparison of the results with measurements for the helium simulations, but variations in the Schmidt number did not improve the argon comparisons. The hybrid Reynolds-averaged/large-eddy simulations also over-predicted the mixing layer spreading rate for the helium case, while under-predicting the rate of mixing when argon was used as the injectant. The primary reason conjectured for the discrepancy between the hybrid simulation results and the measurements centered around issues related to the transition from a Reynolds-averaged state to one with resolved turbulent content. Improvements to the inflow conditions were suggested as a remedy to this dilemma. Second-order turbulence statistics were also compared to their modeled Reynolds-averaged counterparts to evaluate the effectiveness of common turbulence closure

Evaluation of integration methods for hybrid simulation of complex structural systems through collapse

Science.gov (United States)

Del Carpio R., Maikol; Hashemi, M. Javad; Mosqueda, Gilberto

2017-10-01

This study examines the performance of integration methods for hybrid simulation of large and complex structural systems in the context of structural collapse due to seismic excitations. The target application is not necessarily for real-time testing, but rather for models that involve large-scale physical sub-structures and highly nonlinear numerical models. Four case studies are presented and discussed. In the first case study, the accuracy of integration schemes including two widely used methods, namely, modified version of the implicit Newmark with fixed-number of iteration (iterative) and the operator-splitting (non-iterative) is examined through pure numerical simulations. The second case study presents the results of 10 hybrid simulations repeated with the two aforementioned integration methods considering various time steps and fixed-number of iterations for the iterative integration method. The physical sub-structure in these tests consists of a single-degree-of-freedom (SDOF) cantilever column with replaceable steel coupons that provides repeatable highlynonlinear behavior including fracture-type strength and stiffness degradations. In case study three, the implicit Newmark with fixed-number of iterations is applied for hybrid simulations of a 1:2 scale steel moment frame that includes a relatively complex nonlinear numerical substructure. Lastly, a more complex numerical substructure is considered by constructing a nonlinear computational model of a moment frame coupled to a hybrid model of a 1:2 scale steel gravity frame. The last two case studies are conducted on the same porotype structure and the selection of time steps and fixed number of iterations are closely examined in pre-test simulations. The generated unbalance forces is used as an index to track the equilibrium error and predict the accuracy and stability of the simulations.

Process Simulation for the Design and Scale Up of Heterogeneous Catalytic Process: Kinetic Modelling Issues

Directory of Open Access Journals (Sweden)

Antonio Tripodi

2017-05-01

Full Text Available Process simulation represents an important tool for plant design and optimization, either applied to well established or to newly developed processes. Suitable thermodynamic packages should be selected in order to properly describe the behavior of reactors and unit operations and to precisely define phase equilibria. Moreover, a detailed and representative kinetic scheme should be available to predict correctly the dependence of the process on its main variables. This review points out some models and methods for kinetic analysis specifically applied to the simulation of catalytic processes, as a basis for process design and optimization. Attention is paid also to microkinetic modelling and to the methods based on first principles, to elucidate mechanisms and independently calculate thermodynamic and kinetic parameters. Different case studies support the discussion. At first, we have selected two basic examples from the industrial chemistry practice, e.g., ammonia and methanol synthesis, which may be described through a relatively simple reaction pathway and the relative available kinetic scheme. Then, a more complex reaction network is deeply discussed to define the conversion of bioethanol into syngas/hydrogen or into building blocks, such as ethylene. In this case, lumped kinetic schemes completely fail the description of process behavior. Thus, in this case, more detailed—e.g., microkinetic—schemes should be available to implement into the simulator. However, the correct definition of all the kinetic data when complex microkinetic mechanisms are used, often leads to unreliable, highly correlated parameters. In such cases, greater effort to independently estimate some relevant kinetic/thermodynamic data through Density Functional Theory (DFT/ab initio methods may be helpful to improve process description.

Study on driver model for hybrid truck based on driving simulator experimental results

Directory of Open Access Journals (Sweden)

Dam Hoang Phuc

2018-04-01

Full Text Available In this paper, a proposed car-following driver model taking into account some features of both the compensatory and anticipatory model representing the human pedal operation has been verified by driving simulator experiments with several real drivers. The comparison between computer simulations performed by determined model parameters with the experimental results confirm the correctness of this mathematical driver model and identified model parameters. Then the driver model is joined to a hybrid vehicle dynamics model and the moderate car following maneuver simulations with various driver parameters are conducted to investigate influences of driver parameters on vehicle dynamics response and fuel economy. Finally, major driver parameters involved in the longitudinal control of drivers are clarified. Keywords: Driver model, Driver-vehicle closed-loop system, Car Following, Driving simulator/hybrid electric vehicle (B1

Hybrid-Lambda: simulation of multiple merger and Kingman gene genealogies in species networks and species trees.

Science.gov (United States)

Zhu, Sha; Degnan, James H; Goldstien, Sharyn J; Eldon, Bjarki

2015-09-15

There has been increasing interest in coalescent models which admit multiple mergers of ancestral lineages; and to model hybridization and coalescence simultaneously. Hybrid-Lambda is a software package that simulates gene genealogies under multiple merger and Kingman's coalescent processes within species networks or species trees. Hybrid-Lambda allows different coalescent processes to be specified for different populations, and allows for time to be converted between generations and coalescent units, by specifying a population size for each population. In addition, Hybrid-Lambda can generate simulated datasets, assuming the infinitely many sites mutation model, and compute the F ST statistic. As an illustration, we apply Hybrid-Lambda to infer the time of subdivision of certain marine invertebrates under different coalescent processes. Hybrid-Lambda makes it possible to investigate biogeographic concordance among high fecundity species exhibiting skewed offspring distribution.

Effect of hydraulic retention time on the biodegradation of complex phenolic mixture from simulated coal wastewater in hybrid UASB reactors

Energy Technology Data Exchange (ETDEWEB)

Ramakrishnan, Anushuya [Centre for Environmental Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Gupta, Sudhir Kumar [Centre for Environmental Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)], E-mail: skgupta@iitb.ac.in

2008-05-01

This study describes the feasibility of anaerobic treatment of complex phenolics mixture from a simulated synthetic coal wastewater using four identical 13.5 L (effective volume) bench scale hybrid up-flow anaerobic sludge blanket (HUASB) (combining UASB + anaerobic filter) reactors at four different hydraulic retention times (HRT) under mesophilic (27 {+-} 5 {sup o}C) conditions. Synthetic coal wastewater with an average chemical oxygen demand (COD) of 2240 mg/L and phenolics concentration of 752 mg/L was used as substrate. The phenolics contained phenol (490 mg/L); m-, o-, p-cresols (123.0, 58.6, 42 mg/L); 2,4-, 2,5-, 3,4- and 3,5-dimethyl phenols (6.3, 6.3, 4.4 and 21.3 mg/L) as major phenolic compounds. The study demonstrated that at optimum HRT, 24 h, and phenolic loading rate of 0.75 g COD/(m{sup 3}-d), the phenolics and COD removal efficiency of the reactors were 96% and 86%, respectively. Bio-kinetic models were applied to data obtained from experimental studies in hybrid UASB reactor. Grau second-order multi-component substrate removal model was best fitted to the hybrid UASB reactor. The second-order substrate removal rate constant (k{sub 2(s)}) was found as 1.72 h{sup -1} for the hybrid reactor treating complex phenolic mixture. Morphological examination of the sludge revealed rod-type Methanothrix-like, cells to be dominant on the surface.

Effect of hydraulic retention time on the biodegradation of complex phenolic mixture from simulated coal wastewater in hybrid UASB reactors

International Nuclear Information System (INIS)

Ramakrishnan, Anushuya; Gupta, Sudhir Kumar

2008-01-01

This study describes the feasibility of anaerobic treatment of complex phenolics mixture from a simulated synthetic coal wastewater using four identical 13.5 L (effective volume) bench scale hybrid up-flow anaerobic sludge blanket (HUASB) (combining UASB + anaerobic filter) reactors at four different hydraulic retention times (HRT) under mesophilic (27 ± 5 o C) conditions. Synthetic coal wastewater with an average chemical oxygen demand (COD) of 2240 mg/L and phenolics concentration of 752 mg/L was used as substrate. The phenolics contained phenol (490 mg/L); m-, o-, p-cresols (123.0, 58.6, 42 mg/L); 2,4-, 2,5-, 3,4- and 3,5-dimethyl phenols (6.3, 6.3, 4.4 and 21.3 mg/L) as major phenolic compounds. The study demonstrated that at optimum HRT, 24 h, and phenolic loading rate of 0.75 g COD/(m 3 -d), the phenolics and COD removal efficiency of the reactors were 96% and 86%, respectively. Bio-kinetic models were applied to data obtained from experimental studies in hybrid UASB reactor. Grau second-order multi-component substrate removal model was best fitted to the hybrid UASB reactor. The second-order substrate removal rate constant (k 2(s) ) was found as 1.72 h -1 for the hybrid reactor treating complex phenolic mixture. Morphological examination of the sludge revealed rod-type Methanothrix-like, cells to be dominant on the surface

Reduction Methods for Real-time Simulations in Hybrid Testing

DEFF Research Database (Denmark)

Andersen, Sebastian

2016-01-01

Hybrid testing constitutes a cost-effective experimental full scale testing method. The method was introduced in the 1960's by Japanese researchers, as an alternative to conventional full scale testing and small scale material testing, such as shake table tests. The principle of the method...... is performed on a glass fibre reinforced polymer composite box girder. The test serves as a pilot test for prospective real-time tests on a wind turbine blade. The Taylor basis is implemented in the test, used to perform the numerical simulations. Despite of a number of introduced errors in the real...... is to divide a structure into a physical substructure and a numerical substructure, and couple these in a test. If the test is conducted in real-time it is referred to as real time hybrid testing. The hybrid testing concept has developed significantly since its introduction in the 1960', both with respect...

Modeling and Simulation of Multi-scale Environmental Systems with Generalized Hybrid Petri Nets

Directory of Open Access Journals (Sweden)

Mostafa eHerajy

2015-07-01

Full Text Available Predicting and studying the dynamics and properties of environmental systems necessitates the construction and simulation of mathematical models entailing different levels of complexities. Such type of computational experiments often require the combination of discrete and continuous variables as well as processes operating at different time scales. Furthermore, the iterative steps of constructing and analyzing environmental models might involve researchers with different background. Hybrid Petri nets may contribute in overcoming such challenges as they facilitate the implementation of systems integrating discrete and continuous dynamics. Additionally, the visual depiction of model components will inevitably help to bridge the gap between scientists with distinct expertise working on the same problem. Thus, modeling environmental systems with hybrid Petri nets enables the construction of complex processes while keeping the models comprehensible for researchers working on the same project with significantly divergent education path. In this paper we propose the utilization of a special class of hybrid Petri nets, Generalized Hybrid Petri Nets (GHPN, to model and simulate environmental systems exposing processes interacting at different time-scales. GHPN integrate stochastic and deterministic semantics as well as other types of special basic events. Moreover, a case study is presented to illustrate the use of GHPN in constructing and simulating multi-timescale environmental scenarios.

A new hybrid code (CHIEF) implementing the inertial electron fluid equation without approximation

Science.gov (United States)

Muñoz, P. A.; Jain, N.; Kilian, P.; Büchner, J.

2018-03-01

We present a new hybrid algorithm implemented in the code CHIEF (Code Hybrid with Inertial Electron Fluid) for simulations of electron-ion plasmas. The algorithm treats the ions kinetically, modeled by the Particle-in-Cell (PiC) method, and electrons as an inertial fluid, modeled by electron fluid equations without any of the approximations used in most of the other hybrid codes with an inertial electron fluid. This kind of code is appropriate to model a large variety of quasineutral plasma phenomena where the electron inertia and/or ion kinetic effects are relevant. We present here the governing equations of the model, how these are discretized and implemented numerically, as well as six test problems to validate our numerical approach. Our chosen test problems, where the electron inertia and ion kinetic effects play the essential role, are: 0) Excitation of parallel eigenmodes to check numerical convergence and stability, 1) parallel (to a background magnetic field) propagating electromagnetic waves, 2) perpendicular propagating electrostatic waves (ion Bernstein modes), 3) ion beam right-hand instability (resonant and non-resonant), 4) ion Landau damping, 5) ion firehose instability, and 6) 2D oblique ion firehose instability. Our results reproduce successfully the predictions of linear and non-linear theory for all these problems, validating our code. All properties of this hybrid code make it ideal to study multi-scale phenomena between electron and ion scales such as collisionless shocks, magnetic reconnection and kinetic plasma turbulence in the dissipation range above the electron scales.

Investigation of kinetics and thermodynamics of DNA hybridization by means of 2-D fluorescence spectroscopy and soft/hard modeling techniques

Energy Technology Data Exchange (ETDEWEB)

Ebrahimi, Sara; Kompany-Zareh, Mohsen, E-mail: kmpz@dr.com

2016-02-04

Reversible hybridization reaction plays a key role in fundamental biological processes, in many laboratory techniques, and also in DNA based sensing devices. Comprehensive investigation of this process is, therefore, essential for the development of more sophisticated applications. Kinetics and thermodynamics of the hybridization reaction, as a second order process, are systematically investigated with the aid of the soft and hard chemometric methods. Labeling two complementary 21 mer DNA single strands with FAM and Texas red fluorophores, enabled recording of the florescence excitation−emission matrices during the experiments which led to three-way data sets. The presence of fluorescence resonance energy transfer in excitation and emission modes and the closure in concentration mode, made the three-way data arrays rank deficient. To acquire primary chemical information, restricted Tucker3 as a soft method was employed. Herein a model-based method, hard restricted trilinear decomposition, is introduced for in depth analysis of rank deficient three-way data sets. By employing proposed hard method, the nonlinear model parameters as well as the correct profiles could be estimated. In addition, a simple constraint is presented to extract chemically reasonable output profiles regarding the core elements of restricted Tucker3 model. - Highlights: • Hard restricted trilinear decomposition (HrTD) was introduced for model-based analysis of three-way rank deficient data. • DNA hybridization was investigated by two-dimensional fluorescence spectroscopy and soft/hard multi-way techniques. • Restricted Tucker3 analysis enabled accurate estimation of pure FRET profiles in the hybridized form. • HrTD was successfully employed to estimate kinetic and equilibrium parameters of DNA hybridization system. • The performance of the proposed methods in response to different physical stimuli was successfully evaluated.

Simulations for the transmutation of nuclear wastes with hybrid reactors

International Nuclear Information System (INIS)

Vuillier, St.

1998-06-01

A Monte Carlo simulation, devoted to the spallation, has been built in the framework of the hybrid systems proposed for the nuclear wastes incineration. This system GSPARTE, described the reactions evolution. It takes into account and improves the nuclear codes and the low and high energy particles transport in the GEANT code environment, adapted to the geometry of the hybrid reactors. Many applications and abacus useful for the wastes transmutation, have been realized with this system: production of thick target neutrons, source definition, material damages. (A.L.B.)

A hybrid hydrostatic and non-hydrostatic numerical model for shallow flow simulations

Science.gov (United States)

Zhang, Jingxin; Liang, Dongfang; Liu, Hua

2018-05-01

Hydrodynamics of geophysical flows in oceanic shelves, estuaries, and rivers, are often studied by solving shallow water model equations. Although hydrostatic models are accurate and cost efficient for many natural flows, there are situations where the hydrostatic assumption is invalid, whereby a fully hydrodynamic model is necessary to increase simulation accuracy. There is a growing concern about the decrease of the computational cost of non-hydrostatic pressure models to improve the range of their applications in large-scale flows with complex geometries. This study describes a hybrid hydrostatic and non-hydrostatic model to increase the efficiency of simulating shallow water flows. The basic numerical model is a three-dimensional hydrostatic model solved by the finite volume method (FVM) applied to unstructured grids. Herein, a second-order total variation diminishing (TVD) scheme is adopted. Using a predictor-corrector method to calculate the non-hydrostatic pressure, we extended the hydrostatic model to a fully hydrodynamic model. By localising the computational domain in the corrector step for non-hydrostatic pressure calculations, a hybrid model was developed. There was no prior special treatment on mode switching, and the developed numerical codes were highly efficient and robust. The hybrid model is applicable to the simulation of shallow flows when non-hydrostatic pressure is predominant only in the local domain. Beyond the non-hydrostatic domain, the hydrostatic model is still accurate. The applicability of the hybrid method was validated using several study cases.

Kinetics of transformations nucleated on random parallel planes: analytical modelling and computer simulation

International Nuclear Information System (INIS)

Rios, Paulo R; Assis, Weslley L S; Ribeiro, Tatiana C S; Villa, Elena

2012-01-01

In a classical paper, Cahn derived expressions for the kinetics of transformations nucleated on random planes and lines. He used those as a model for nucleation on the boundaries, edges and vertices of a polycrystal consisting of equiaxed grains. In this paper it is demonstrated that Cahn's expression for random planes may be used in situations beyond the scope envisaged in Cahn's original paper. For instance, we derived an expression for the kinetics of transformations nucleated on random parallel planes that is identical to that formerly obtained by Cahn considering random planes. Computer simulation of transformations nucleated on random parallel planes is carried out. It is shown that there is excellent agreement between simulated results and analytical solutions. Such an agreement is to be expected if both the simulation and the analytical solution are correct. (paper)

Simulations of enhanced reversed shear TFTR discharges with lower hybrid current drive

International Nuclear Information System (INIS)

Kesner, J.; Bateman, G.

1996-01-01

The BALDUR based BBK code permits predictive simulations of time-dependent tokamak discharges and has the capability to include neutral beam heating, pellet injection, bootstrap currents and lower hybrid current drive. BALDUR contains a theory based multi-regime transport model and previous work has shown excellent agreement with both L-mode and supershot TFTR discharges. These simulations reveal that core transport is dominated by η i and trapped electron modes and the outer region by resistive ballooning. We simulate enhanced reverse shear discharges by beginning with a supershot simulation with a reversed shear profile. Similarly to the TFTR experiments the reversed shear profile is obtained through the programming of the current during startup and the freezing in of these profiles by subsequent heating. At the time of transition into the enhanced confinement regime we turn off the η i and trapped-electron mode transport. We examine the further modification of the plasma current profile that can be obtained with the application of lower hybrid current drive. The results of these simulations will be discussed

Kinetic slow mode-type solitons

Directory of Open Access Journals (Sweden)

K. Baumgärtel

2005-01-01

Full Text Available One-dimensional hybrid code simulations are presented, carried out in order both to study solitary waves of the slow mode branch in an isotropic, collisionless, medium-β plasma (βi=0.25 and to test the fluid based soliton interpretation of Cluster observed strong magnetic depressions (Stasiewicz et al., 2003; Stasiewicz, 2004 against kinetic theory. In the simulations, a variety of strongly oblique, large amplitude, solitons are seen, including solitons with Alfvenic polarization, similar to those predicted by the Hall-MHD theory, and robust, almost non-propagating, solitary structures of slow magnetosonic type with strong magnetic field depressions and perpendicular ion heating, which have no counterpart in fluid theory. The results support the soliton-based interpretation of the Cluster observations, but reveal substantial deficiencies of Hall-MHD theory in describing slow mode-type solitons in a plasma of moderate beta.

Numerical Simulations of Flow and Fuel Regression Rate Coupling in Hybrid Rocket Motors

Directory of Open Access Journals (Sweden)

Marius STOIA-DJESKA

2017-03-01

Full Text Available The hybrid propulsion offers some remarkable advantages like high safety and high specific impulse and thus it is considered a promising technology for the next generation launchers and space systems. The purpose of this work is to validate a design tool for hybrid rocket motors (HRM through numerical simulations.

Cell-Free Protein Synthesis Enhancement from Real-Time NMR Metabolite Kinetics: Redirecting Energy Fluxes in Hybrid RRL Systems.

Science.gov (United States)

Panthu, Baptiste; Ohlmann, Théophile; Perrier, Johan; Schlattner, Uwe; Jalinot, Pierre; Elena-Herrmann, Bénédicte; Rautureau, Gilles J P

2018-01-19

A counterintuitive cell-free protein synthesis (CFPS) strategy, based on reducing the ribosomal fraction in rabbit reticulocyte lysate (RRL), triggers the development of hybrid systems composed of RRL ribosome-free supernatant complemented with ribosomes from different mammalian cell-types. Hybrid RRL systems maintain translational properties of the original ribosome cell types, and deliver protein expression levels similar to RRL. Here, we show that persistent ribosome-associated metabolic activity consuming ATP is a major obstacle for maximal protein yield. We provide a detailed picture of hybrid CFPS systems energetic metabolism based on real-time nuclear magnetic resonance (NMR) investigation of metabolites kinetics. We demonstrate that protein synthesis capacity has an upper limit at native ribosome concentration and that lower amounts of the ribosomal fraction optimize energy fluxes toward protein translation, consequently increasing CFPS yield. These results provide a rationalized strategy for further mammalian CFPS developments and reveal the potential of real-time NMR metabolism phenotyping for optimization of cell-free protein expression systems.

ASPEN: A fully kinetic, reduced-description particle-in-cell model for simulating parametric instabilities

International Nuclear Information System (INIS)

Vu, H.X.; Bezzerides, B.; DuBois, D.F.

1999-01-01

A fully kinetic, reduced-description particle-in-cell (RPIC) model is presented in which deviations from quasineutrality, electron and ion kinetic effects, and nonlinear interactions between low-frequency and high-frequency parametric instabilities are modeled correctly. The model is based on a reduced description where the electromagnetic field is represented by three separate temporal envelopes in order to model parametric instabilities with low-frequency and high-frequency daughter waves. Because temporal envelope approximations are invoked, the simulation can be performed on the electron time scale instead of the time scale of the light waves. The electrons and ions are represented by discrete finite-size particles, permitting electron and ion kinetic effects to be modeled properly. The Poisson equation is utilized to ensure that space-charge effects are included. The RPIC model is fully three dimensional and has been implemented in two dimensions on the Accelerated Strategic Computing Initiative (ASCI) parallel computer at Los Alamos National Laboratory, and the resulting simulation code has been named ASPEN. The authors believe this code is the first particle-in-cell code capable of simulating the interaction between low-frequency and high-frequency parametric instabilities in multiple dimensions. Test simulations of stimulated Raman scattering, stimulated Brillouin scattering, and Langmuir decay instability are presented

Multi-scale modelling and numerical simulation of electronic kinetic transport

International Nuclear Information System (INIS)

Duclous, R.

2009-11-01

This research thesis which is at the interface between numerical analysis, plasma physics and applied mathematics, deals with the kinetic modelling and numerical simulations of the electron energy transport and deposition in laser-produced plasmas, having in view the processes of fuel assembly to temperature and density conditions necessary to ignite fusion reactions. After a brief review of the processes at play in the collisional kinetic theory of plasmas, with a focus on basic models and methods to implement, couple and validate them, the author focuses on the collective aspect related to the free-streaming electron transport equation in the non-relativistic limit as well as in the relativistic regime. He discusses the numerical development and analysis of the scheme for the Vlasov-Maxwell system, and the selection of a validation procedure and numerical tests. Then, he investigates more specific aspects of the collective transport: the multi-specie transport, submitted to phase-space discontinuities. Dealing with the multi-scale physics of electron transport with collision source terms, he validates the accuracy of a fast Monte Carlo multi-grid solver for the Fokker-Planck-Landau electron-electron collision operator. He reports realistic simulations for the kinetic electron transport in the frame of the shock ignition scheme, the development and validation of a reduced electron transport angular model. He finally explores the relative importance of the processes involving electron-electron collisions at high energy by means a multi-scale reduced model with relativistic Boltzmann terms

Real-Time ECG Simulation for Hybrid Mock Circulatory Loops.

Science.gov (United States)

Korn, Leonie; Rüschen, Daniel; Zander, Niklas; Leonhardt, Steffen; Walter, Marian

2018-02-01

Classically, mock circulatory loops only simulate mechanical properties of the circulation. To connect the hydraulic world with electrophysiology, we present a real-time electrical activity model of the heart and show how to integrate this model into a real-time mock loop simulation. The model incorporates a predefined conduction pathway and a simplified volume conductor to solve the bidomain equations and the forward problem of electrocardiography, resulting in a physiological simulation of the electrocardiogram (ECG) at arbitrary electrode positions. A complete physiological simulation of the heart's excitation would be too CPU intensive. Thus, in our model, complexity was reduced to allow real-time simulation of ECG-triggered medical systems in vitro; this decreases time and cost in the development process. Conversely, the presented model can still be adapted to various pathologies by locally changing the properties of the heart's conduction pathway. To simulate the ECG, the heart is divided into suitable areas, which are innervated by the hierarchically structured conduction system. To distinguish different cardiac regions, a segmentation of the heart was performed. In these regions, Prim's algorithm was applied to identify the directed minimal spanning trees for conduction orientation. Each node of the tree was assigned to a cardiac action potential generated by its hybrid automaton to represent the heart's conduction system by the spatial distribution of action potentials. To generate the ECG output, the bidomain equations were implemented and a simple model of the volume conductor of the body was used to solve the forward problem of electrocardiography. As a result, the model simulates potentials at arbitrary electrode positions in real-time. To verify the developed real-time ECG model, measurements were made within a hybrid mock circulatory loop, including a simple ECG-triggered ventricular assist device control. The model's potential value is to simulate

Effect of sp3-hybridized defects on the oscillatory behavior of carbon nanotube oscillators

International Nuclear Information System (INIS)

Guo, Taiyu; Ding, Tony Weixi; Pei, Qing-Xiang; Zhang, Yong-Wei

2011-01-01

Using molecular dynamics simulations, we investigate the oscillatory behaviors of carbon nanotube oscillators containing sp 3 -hybridized defects formed by hydrogen chemisorption. It is found that the presence of these defects significantly affects the kinetic and potential energies of the nanotube systems, which in turn affects their oscillation periods and frequencies. We have also studied the oscillatory characteristics of the oscillators containing sp 3 -hybridized Stone-Wales defects. Our results show that it is possible to control the motion of the inner nanotube by introducing sp 3 -hybridized defects on the outer nanotube, which provides a potential way to tune the oscillatory behavior of nanotube oscillators. -- Highlights: → sp 3 -hybridized defects increase energy dissipation. → sp 3 -hybridized defects arranged in a row have stronger effect than that in a ring. → sp 3 -hybridized defects reduces the effect of SW defects.

Software development infrastructure for the HYBRID modeling and simulation project

International Nuclear Information System (INIS)

Epiney, Aaron S.; Kinoshita, Robert A.; Kim, Jong Suk; Rabiti, Cristian; Greenwood, M. Scott

2016-01-01

One of the goals of the HYBRID modeling and simulation project is to assess the economic viability of hybrid systems in a market that contains renewable energy sources like wind. The idea is that it is possible for the nuclear plant to sell non-electric energy cushions, which absorb (at least partially) the volatility introduced by the renewable energy sources. This system is currently modeled in the Modelica programming language. To assess the economics of the system, an optimization procedure is trying to find the minimal cost of electricity production. The RAVEN code is used as a driver for the whole problem. It is assumed that at this stage, the HYBRID modeling and simulation framework can be classified as non-safety “research and development” software. The associated quality level is Quality Level 3 software. This imposes low requirements on quality control, testing and documentation. The quality level could change as the application development continues.Despite the low quality requirement level, a workflow for the HYBRID developers has been defined that include a coding standard and some documentation and testing requirements. The repository performs automated unit testing of contributed models. The automated testing is achieved via an open-source python script called BuildingsP from Lawrence Berkeley National Lab. BuildingsPy runs Modelica simulation tests using Dymola in an automated manner and generates and runs unit tests from Modelica scripts written by developers. In order to assure effective communication between the different national laboratories a biweekly videoconference has been set-up, where developers can report their progress and issues. In addition, periodic face-face meetings are organized intended to discuss high-level strategy decisions with management. A second means of communication is the developer email list. This is a list to which everybody can send emails that will be received by the collective of the developers and managers

Software development infrastructure for the HYBRID modeling and simulation project

Energy Technology Data Exchange (ETDEWEB)

Epiney, Aaron S. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kinoshita, Robert A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kim, Jong Suk [Idaho National Lab. (INL), Idaho Falls, ID (United States); Rabiti, Cristian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Greenwood, M. Scott [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-09-01

One of the goals of the HYBRID modeling and simulation project is to assess the economic viability of hybrid systems in a market that contains renewable energy sources like wind. The idea is that it is possible for the nuclear plant to sell non-electric energy cushions, which absorb (at least partially) the volatility introduced by the renewable energy sources. This system is currently modeled in the Modelica programming language. To assess the economics of the system, an optimization procedure is trying to find the minimal cost of electricity production. The RAVEN code is used as a driver for the whole problem. It is assumed that at this stage, the HYBRID modeling and simulation framework can be classified as non-safety “research and development” software. The associated quality level is Quality Level 3 software. This imposes low requirements on quality control, testing and documentation. The quality level could change as the application development continues.Despite the low quality requirement level, a workflow for the HYBRID developers has been defined that include a coding standard and some documentation and testing requirements. The repository performs automated unit testing of contributed models. The automated testing is achieved via an open-source python script called BuildingsP from Lawrence Berkeley National Lab. BuildingsPy runs Modelica simulation tests using Dymola in an automated manner and generates and runs unit tests from Modelica scripts written by developers. In order to assure effective communication between the different national laboratories a biweekly videoconference has been set-up, where developers can report their progress and issues. In addition, periodic face-face meetings are organized intended to discuss high-level strategy decisions with management. A second means of communication is the developer email list. This is a list to which everybody can send emails that will be received by the collective of the developers and managers

Computer simulation of kinetic properties of plasmas. Final report

International Nuclear Information System (INIS)

Denavit, J.

1982-08-01

The research was directed toward the development and testing of new numerical methods for particle and hybrid simulation of plasmas, and their application to physical problems of current significance to Magnetic Fusion Energy. This project will terminate on August 31, 1982 and this Final Report describes: (1) the research accomplished since the last renewal on October 1, 1981; and (2) a perspective of the work done since the beginning of the project in February 1972

Hybrid (Vlasov-Fluid) simulation of ion-acoustic soliton chain formation and validity of Korteweg de-Vries model

Energy Technology Data Exchange (ETDEWEB)

Aminmansoor, F.; Abbasi, H., E-mail: abbasi@aut.ac.ir [Faculty of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of)

2015-08-15

The present paper is devoted to simulation of nonlinear disintegration of a localized perturbation into ion-acoustic solitons train in a plasma with hot electrons and cold ions. A Gaussian initial perturbation is used to model the localized perturbation. For this purpose, first, we reduce fluid system of equations to a Korteweg de-Vries equation by the following well-known assumptions. (i) On the ion-acoustic evolution time-scale, the electron velocity distribution function (EVDF) is assumed to be stationary. (ii) The calculation is restricted to small amplitude cases. Next, in order to generalize the model to finite amplitudes cases, the evolution of EVDF is included. To this end, a hybrid code is designed to simulate the case, in which electrons dynamics is governed by Vlasov equation, while cold ions dynamics is, like before, studied by the fluid equations. A comparison between the two models shows that although the fluid model is capable of demonstrating the general features of the process, to have a better insight into the relevant physics resulting from the evolution of EVDF, the use of kinetic treatment is of great importance.

Experimental and simulation analysis of the W-band SC-FDMA hybrid optical-wireless transmission

DEFF Research Database (Denmark)

Dogadaev, Anton Konstantinovich; Pang, Xiaodan; Deng, Lei

2014-01-01

We report on the experimental demonstration of the W-band hybrid optical-wireless SC-FDMA with 1.49 Gbit/s transmission over up to 2.3 m of air propagation. Provided simulation performance analysis proves a potential to reach 12.1 Gbit/s.......We report on the experimental demonstration of the W-band hybrid optical-wireless SC-FDMA with 1.49 Gbit/s transmission over up to 2.3 m of air propagation. Provided simulation performance analysis proves a potential to reach 12.1 Gbit/s....

Non-linear punctual kinetics applied to PWR reactors simulation

International Nuclear Information System (INIS)

Cysne, F.S.

1978-11-01

In order to study some kinds of nuclear reactor accidents, a simulation is made using the punctual kinetics model for the reactor core. The following integration methods are used: Hansen's method in which a linearization is made and CSMP using a variable interval fourth-order Runge Kutta method. The results were good and were compared with those obtained by the code Dinamica I which uses a finite difference integration method of backward kind. (Author) [pt

Kinetic Theory and Simulation of Single-Channel Water Transport

Science.gov (United States)

Tajkhorshid, Emad; Zhu, Fangqiang; Schulten, Klaus

Water translocation between various compartments of a system is a fundamental process in biology of all living cells and in a wide variety of technological problems. The process is of interest in different fields of physiology, physical chemistry, and physics, and many scientists have tried to describe the process through physical models. Owing to advances in computer simulation of molecular processes at an atomic level, water transport has been studied in a variety of molecular systems ranging from biological water channels to artificial nanotubes. While simulations have successfully described various kinetic aspects of water transport, offering a simple, unified model to describe trans-channel translocation of water turned out to be a nontrivial task.

Simulation-optimization framework for multi-site multi-season hybrid stochastic streamflow modeling

Science.gov (United States)

Srivastav, Roshan; Srinivasan, K.; Sudheer, K. P.

2016-11-01

A simulation-optimization (S-O) framework is developed for the hybrid stochastic modeling of multi-site multi-season streamflows. The multi-objective optimization model formulated is the driver and the multi-site, multi-season hybrid matched block bootstrap model (MHMABB) is the simulation engine within this framework. The multi-site multi-season simulation model is the extension of the existing single-site multi-season simulation model. A robust and efficient evolutionary search based technique, namely, non-dominated sorting based genetic algorithm (NSGA - II) is employed as the solution technique for the multi-objective optimization within the S-O framework. The objective functions employed are related to the preservation of the multi-site critical deficit run sum and the constraints introduced are concerned with the hybrid model parameter space, and the preservation of certain statistics (such as inter-annual dependence and/or skewness of aggregated annual flows). The efficacy of the proposed S-O framework is brought out through a case example from the Colorado River basin. The proposed multi-site multi-season model AMHMABB (whose parameters are obtained from the proposed S-O framework) preserves the temporal as well as the spatial statistics of the historical flows. Also, the other multi-site deficit run characteristics namely, the number of runs, the maximum run length, the mean run sum and the mean run length are well preserved by the AMHMABB model. Overall, the proposed AMHMABB model is able to show better streamflow modeling performance when compared with the simulation based SMHMABB model, plausibly due to the significant role played by: (i) the objective functions related to the preservation of multi-site critical deficit run sum; (ii) the huge hybrid model parameter space available for the evolutionary search and (iii) the constraint on the preservation of the inter-annual dependence. Split-sample validation results indicate that the AMHMABB model is

Diffusion and dispersion characteristics of hybridized discontinuous Galerkin methods for under-resolved turbulence simulations

Science.gov (United States)

Moura, Rodrigo; Fernandez, Pablo; Mengaldo, Gianmarco

2017-11-01

We investigate the dispersion and diffusion characteristics of hybridized discontinuous Galerkin (DG) methods. This provides us with insights to develop robust and accurate high-order DG discretizations for under-resolved flow simulations. Using the eigenanalysis technique introduced in (Moura et al., JCP, 2015 and Mengaldo et al., Computers & Fluids, 2017), we present a dispersion-diffusion analysis for the linear advection-diffusion equation. The effect of the accuracy order, the Riemann flux and the viscous stabilization are investigated. Next, we examine the diffusion characteristics of hybridized DG methods for under-resolved turbulent flows. The implicit large-eddy simulation (iLES) of the inviscid and viscous Taylor-Green vortex (TGV) problems are considered to this end. The inviscid case is relevant in the limit of high Reynolds numbers Re , i.e. negligible molecular viscosity, while the viscous case explores the effect of Re on the accuracy and robustness of the simulations. The TGV cases considered here are particularly crucial to under-resolved turbulent free flows away from walls. We conclude the talk with a discussion on the connections between hybridized and standard DG methods for under-resolved flow simulations.

Simulation of hybrid renewable microgeneration systems for variable electricity prices

International Nuclear Information System (INIS)

Brandoni, C.; Renzi, M.; Caresana, F.; Polonara, F.

2014-01-01

This paper addresses a hybrid renewable system that consists of a micro-Combined Cooling Heat and Power (CCHP) unit and a solar energy conversion device. In addition to a traditional PV system, a High Concentrator Photovoltaic (HCPV) device, the design of which is suitable for building integration application, was also modelled and embedded in the hybrid system. The work identifies the optimal management strategies for the hybrid renewable system in an effort to minimise the primary energy usage, the carbon dioxide emissions and the operational costs for variable electricity prices that result from the day-ahead electricity market. An “ad hoc” model describes the performance of the HCPV module, PV and Internal Combustion Engine, whilst the other units were simulated based on their main characteristic parameters. The developed algorithm was applied to three different building typologies. The results indicate that the best configuration is the hybrid renewable system with PV, which can provide a yearly primary energy reduction of between 20% and 30% compared to separate production. The hybrid renewable system with HCPV becomes competitive with the PV technology when the level of solar radiation is high. - Highlights: • The paper addresses a hybrid renewable system that consists of a micro-CCHP unit and a solar energy conversion device. • Both PV and High Concentrator Photovoltaic (HCPV) systems have been modelled and embedded in the hybrid system. • The work identifies the optimal management strategies for variable electricity prices. • Hybrid renewable systems provide a yearly primary energy reduction of between 20% and 30% compared to separate production. • When the level of solar radiation is high, HCPV becomes competitive with the PV technology

HIDENEK: an implicit particle simulation of kinetic-MHD phenomena in three-dimensional plasmas

International Nuclear Information System (INIS)

Tanaka, Motohiko.

1993-05-01

An advanced 'kinetic-MHD' simulation method and its applications to plasma physics are given in this lecture. This method is quite suitable for studying strong nonlinear, kinetic processes associated with large space-scale, low-frequency electromagnetic phenomena of plasmas. A full set of the Maxwell equations, and the Newton-Lorentz equations of motion for particle ions and guiding-center electrons are adopted. In order to retain only the low-frequency waves and instabilities, implicit particle-field equations are derived. The present implicit-particle method is proved to reproduce the MHD eigenmodes such as Alfven, magnetosonic and kinetic Alfven waves in a thermally near-equilibrium plasma. In the second part of the lecture, several physics applications are shown. These include not only the growth of the instabilities of beam ions against the background plasmas and helical kink of the current, but they also demonstrate nonlinear results such as pitch-angle scattering of the ions. Recent progress in the simulation of the Kelvin-Helmholtz instability is also presented with a special emphasis on the mixing of plasma particles. (author)

Hybrid simulation of scatter intensity in industrial cone-beam computed tomography

International Nuclear Information System (INIS)

Thierry, R.; Miceli, A.; Hofmann, J.; Flisch, A.; Sennhauser, U.

2009-01-01

A cone-beam computed tomography (CT) system using a 450 kV X-ray tube has been developed to challenge the three-dimensional imaging of parts of the automotive industry in short acquisition time. Because the probability of detecting scattered photons is high regarding the energy range and the area of detection, a scattering correction becomes mandatory for generating reliable images with enhanced contrast detectability. In this paper, we present a hybrid simulator for the fast and accurate calculation of the scattering intensity distribution. The full acquisition chain, from the generation of a polyenergetic photon beam, its interaction with the scanned object and the energy deposit in the detector is simulated. Object phantoms can be spatially described in form of voxels, mathematical primitives or CAD models. Uncollided radiation is treated with a ray-tracing method and scattered radiation is split into single and multiple scattering. The single scattering is calculated with a deterministic approach accelerated with a forced detection method. The residual noisy signal is subsequently deconvoluted with the iterative Richardson-Lucy method. Finally the multiple scattering is addressed with a coarse Monte Carlo (MC) simulation. The proposed hybrid method has been validated on aluminium phantoms with varying size and object-to-detector distance, and found in good agreement with the MC code Geant4. The acceleration achieved by the hybrid method over the standard MC on a single projection is approximately of three orders of magnitude.

Selection of a Planning Horizon for a Hybrid Microgrid Using Simulated Wind Forecasts

Science.gov (United States)

2014-12-01

microgrid robustness and efficiency and may provide operators with real-time guidance and control policies for microgrid operation. ACKNOWLEDGMENTS The...A PLANNING HORIZON FOR A HYBRID MICROGRID USING SIMULATED WIND FORECASTS Mumtaz Karatas Turkish Naval Academy Tuzla, Istanbul, 34942, TURKEY Emily M...Craparo Dashi I. Singham Naval Postgraduate School 1411 Cunningham Road Monterey, CA, 93943 USA ABSTRACT Hybrid microgrids containing renewable energy

Modelling the WWER-type reactor dynamics using a hybrid computer. Part 1

International Nuclear Information System (INIS)

Karpeta, C.

Results of simulation studies into reactor and steam generator dynamics of a WWER type power plant are presented. Spatial kinetics of the reactor core is described by a nodal approximation to diffusion equations, xenon poisoning equations and heat transfer equations. The simulation of the reactor model dynamics was performed on a hybrid computer. Models of both a horizontal and a vertical steam generator were developed. The dynamics was investigated over a large range of power by computing the transients on a digital computer. (author)

Hybrid vortex simulations of wind turbines using a three-dimensional viscous-inviscid panel method

DEFF Research Database (Denmark)

Ramos García, Néstor; Hejlesen, Mads Mølholm; Sørensen, Jens Nørkær

2017-01-01

adirect calculation, whereas the contribution from the large downstream wake is calculated using a mesh-based method. Thehybrid method is first validated in detail against the well-known MEXICO experiment, using the direct filament method asa comparison. The second part of the validation includes a study......A hybrid filament-mesh vortex method is proposed and validated to predict the aerodynamic performance of wind turbinerotors and to simulate the resulting wake. Its novelty consists of using a hybrid method to accurately simulate the wakedownstream of the wind turbine while reducing...

Two dimensional hybrid simulation of a curved bow shock

International Nuclear Information System (INIS)

Thomas, V.A.; Winske, D.

1990-01-01

Results are presented from two dimensional hybrid simulations of curved collisionless supercritical shocks, retaining both quasi-perpendicular and quasi-parallel sections of the shock in order to study the character and origin of the foreshock ion population. The simulations demonstrate that the foreshock ion population is dominated by ions impinging upon the quasi-parallel side of the shock, while nonlocal transport from the quasi-perpendicular side of the shock into the foreshock region is minimal. Further, it is shown that the ions gain energy by drifting significantly in the direction of the convection electric field through multiple shock encounters

Kinetics of toluene alkylation with methanol catalyzed by pure and hybridized HZSM-5 catalysts

KAUST Repository

Alabi, Wahab

2012-07-01

A kinetic study of toluene alkylation with methanol was performed over pure HZSM-5, mordenite/ZSM-5 (hybrid of mordenite and HZSM-5), and ZM13 (composite mixture of HZSM-5 and MCM-41 at pH 13). Experimental runs were conducted using a batch fluidized bed reactor at temperatures of 300, 350 and 400 °C and reaction times of 3, 5, 7, 10, 13, 15 and 20. s. The rate of toluene methylation and toluene disproportionation were studied on the three catalysts (toluene alkylation is usually accompanied by toluene disproportionation on acid catalyst). Based on the results obtained, a simplified power law kinetic model consisting of three reactions was developed to estimate the activation energies of toluene methylation and disproportionation simultaneously. Coke formation on catalysts was accounted for using both reaction time and reactant conversion decay functions. All parameters were estimated based on quasi-steady state approximation. Estimated kinetic parameters were in good agreement with experimental results. The order of alkylation ability of the catalysts was found to be ZM13 > HZSM-5 > mordenite/ZSM-5, while the reverse is for toluene disproportionation (mordenite/ZSM-5 > HZSM-5 > ZM13). Thus, alkylation of toluene is most favorable on ZM13 due to combined effect of mesoporosity induced through its synthetic route and acid content. Toluene/MeOH molar ratio of 1:1 was most suitable for toluene alkylation reaction. © 2012 Elsevier B.V.

Hybrid simulation: bringing motivation to the art of teamwork training in the operating room.

Science.gov (United States)

Kjellin, A; Hedman, L; Escher, C; Felländer-Tsai, L

2014-12-01

Crew resource management-based operating room team training will be an evident part of future surgical training. Hybrid simulation in the operating room enables the opportunity for trainees to perform higher fidelity training of technical and non-technical skills in a realistic context. We focus on situational motivation and self-efficacy, two important factors for optimal learning in light of a prototype course for teams of residents in surgery and anesthesiology and nurses. Authentic operating room teams consisting of residents in anesthesia (n = 2), anesthesia nurses (n = 3), residents in surgery (n = 2), and scrub nurses (n = 6) were, during a one-day course, exposed to four different scenarios. Their situational motivation was self-assessed (ranging from 1 = does not correspond at all to 7 = corresponds exactly) immediately after training, and their self-efficacy (graded from 1 to 7) before and after training. Training was performed in a mock-up operating theater equipped with a hybrid patient simulator (SimMan 3G; Laerdal) and a laparoscopic simulator (Lap Mentor Express; Simbionix). The functionality of the systematic hybrid procedure simulation scenario was evaluated by an exit questionnaire (graded from 1 = disagree entirely to 5 = agree completely). The trainees were mostly intrinsically motivated, engaged for their own sake, and had a rather great degree of self-determination toward the training situation. Self-efficacy among the team members improved significantly from 4 to 6 (median). Overall evaluation showed very good result with a median grading of 5. We conclude that hybrid simulation is feasible and has the possibility to train an authentic operating team in order to improve individual motivation and confidence. © The Finnish Surgical Society 2014.

Development of a Procedure to Apply Detailed Chemical Kinetic Mechanisms to CFD Simulations as Post Processing

DEFF Research Database (Denmark)

Skjøth-Rasmussen, Martin Skov; Glarborg, Peter; Jensen, Anker

2003-01-01

mechanism. It involves post-processing of data extracted from computational fluid dynamics simulations. Application of this approach successfully describes combustion chemistry in a standard swirl burner, the so-called Harwell furnace. Nevertheless, it needs validation against more complex combustion models......It is desired to make detailed chemical kinetic mechanisms applicable to the complex geometries of practical combustion devices simulated with computational fluid dynamics tools. This work presents a novel general approach to combining computational fluid dynamics and a detailed chemical kinetic...

Efficient hybrid non-equilibrium molecular dynamics--Monte Carlo simulations with symmetric momentum reversal.

Science.gov (United States)

Chen, Yunjie; Roux, Benoît

2014-09-21

Hybrid schemes combining the strength of molecular dynamics (MD) and Metropolis Monte Carlo (MC) offer a promising avenue to improve the sampling efficiency of computer simulations of complex systems. A number of recently proposed hybrid methods consider new configurations generated by driving the system via a non-equilibrium MD (neMD) trajectory, which are subsequently treated as putative candidates for Metropolis MC acceptance or rejection. To obey microscopic detailed balance, it is necessary to alter the momentum of the system at the beginning and/or the end of the neMD trajectory. This strict rule then guarantees that the random walk in configurational space generated by such hybrid neMD-MC algorithm will yield the proper equilibrium Boltzmann distribution. While a number of different constructs are possible, the most commonly used prescription has been to simply reverse the momenta of all the particles at the end of the neMD trajectory ("one-end momentum reversal"). Surprisingly, it is shown here that the choice of momentum reversal prescription can have a considerable effect on the rate of convergence of the hybrid neMD-MC algorithm, with the simple one-end momentum reversal encountering particularly acute problems. In these neMD-MC simulations, different regions of configurational space end up being essentially isolated from one another due to a very small transition rate between regions. In the worst-case scenario, it is almost as if the configurational space does not constitute a single communicating class that can be sampled efficiently by the algorithm, and extremely long neMD-MC simulations are needed to obtain proper equilibrium probability distributions. To address this issue, a novel momentum reversal prescription, symmetrized with respect to both the beginning and the end of the neMD trajectory ("symmetric two-ends momentum reversal"), is introduced. Illustrative simulations demonstrate that the hybrid neMD-MC algorithm robustly yields a correct

Efficient hybrid non-equilibrium molecular dynamics - Monte Carlo simulations with symmetric momentum reversal

Science.gov (United States)

Chen, Yunjie; Roux, Benoît

2014-09-01

Hybrid schemes combining the strength of molecular dynamics (MD) and Metropolis Monte Carlo (MC) offer a promising avenue to improve the sampling efficiency of computer simulations of complex systems. A number of recently proposed hybrid methods consider new configurations generated by driving the system via a non-equilibrium MD (neMD) trajectory, which are subsequently treated as putative candidates for Metropolis MC acceptance or rejection. To obey microscopic detailed balance, it is necessary to alter the momentum of the system at the beginning and/or the end of the neMD trajectory. This strict rule then guarantees that the random walk in configurational space generated by such hybrid neMD-MC algorithm will yield the proper equilibrium Boltzmann distribution. While a number of different constructs are possible, the most commonly used prescription has been to simply reverse the momenta of all the particles at the end of the neMD trajectory ("one-end momentum reversal"). Surprisingly, it is shown here that the choice of momentum reversal prescription can have a considerable effect on the rate of convergence of the hybrid neMD-MC algorithm, with the simple one-end momentum reversal encountering particularly acute problems. In these neMD-MC simulations, different regions of configurational space end up being essentially isolated from one another due to a very small transition rate between regions. In the worst-case scenario, it is almost as if the configurational space does not constitute a single communicating class that can be sampled efficiently by the algorithm, and extremely long neMD-MC simulations are needed to obtain proper equilibrium probability distributions. To address this issue, a novel momentum reversal prescription, symmetrized with respect to both the beginning and the end of the neMD trajectory ("symmetric two-ends momentum reversal"), is introduced. Illustrative simulations demonstrate that the hybrid neMD-MC algorithm robustly yields a correct

Advanced hybrid transient stability and EMT simulation for VSC-HVDC systems

NARCIS (Netherlands)

Van Der Meer, A.A.; Gibescu, M.; Van Der Meijden, M.A.M.M.; Kling, W.L.; Ferreira, J.A.

2015-01-01

This paper deals with advanced hybrid transient stability and electromagnetic-transient (EMT) simulation of combined ac/dc power systems containing large amounts of renewable energy sources interfaced through voltage-source converter-high-voltage direct current (VSC-HVDC). The concerning transient

On mathematical modeling and numerical simulation of chemical kinetics in turbulent lean premixed combustion

Energy Technology Data Exchange (ETDEWEB)

Lilleberg, Bjorn

2011-07-01

This thesis investigates turbulent reacting lean premixed flows with detailed treatment of the chemistry. First, the fundamental equations which govern laminar and turbulent reacting flows are presented. A perfectly stirred reactor numerical code is developed to investigate the role of unmixedness and chemical kinetics in driving combustion instabilities. This includes both global single-step and detailed chemical kinetic mechanisms. The single-step mechanisms predict to some degree a similar behavior as the detailed mechanisms. However, it is shown that simple mechanisms can by themselves introduce instabilities. Magnussens Eddy Dissipation Concept (EDC) for turbulent combustion is implemented in the open source CFD toolbox OpenFOAM R for treatment of both fast and detailed chemistry. RANS turbulence models account for the turbulent compressible flow. A database of pre-calculated chemical time scales, which contains the influence of chemical kinetics, is coupled to EDC with fast chemistry to account for local extinction in both diffusion and premixed flames. Results are compared to fast and detailed chemistry calculations. The inclusion of the database shows significantly better results than the fast chemistry calculations while having a comparably small computational cost. Numerical simulations of four piloted lean premixed jet flames falling into the 'well stirred reactor/broken reaction zones' regime, with strong finite-rate chemistry effects, are performed. Measured and predicted scalars compare well for the two jets with the lowest velocities. The two jets with the highest velocities experience extinction and reignition, and the simulations are able to capture the decrease and increase of the OH mass fractions, but the peak values are higher than in the experiments. Also numerical simulations of a lean premixed lifted jet flame with high sensitivity to turbulence modeling and chemical kinetics are performed. Limitations of the applied turbulence and

Domain-growth kinetics and aspects of pinning: A Monte Carlo simulation study

DEFF Research Database (Denmark)

Castán, T.; Lindgård, Per-Anker

1991-01-01

By means of Monte Carlo computer simulations we study the domain-growth kinetics after a quench across a first-order line to very low and moderate temperatures in a multidegenerate system with nonconserved order parameter. The model is a continuous spin model relevant for martensitic transformati......By means of Monte Carlo computer simulations we study the domain-growth kinetics after a quench across a first-order line to very low and moderate temperatures in a multidegenerate system with nonconserved order parameter. The model is a continuous spin model relevant for martensitic...... to cross over from n = 1/4 at T approximately 0 to n = 1/2 with temperature for models with pinnings of types (a) and (b). For topological pinnings at T approximately 0, n is consistent with n = 1/8, a value conceivable for several levels of hierarchically interrelated domain-wall movement. When...

Modelling and simulation of a hybrid solar heating system for greenhouse applications using Matlab/Simulink

International Nuclear Information System (INIS)

Kıyan, Metin; Bingöl, Ekin; Melikoğlu, Mehmet; Albostan, Ayhan

2013-01-01

Highlights: • Matlab/Simulink modelling of a solar hybrid greenhouse. • Estimation of greenhouse gas emission reductions. • Feasibility and cost analysis of the system. - Abstract: Solar energy is a major renewable energy source and hybrid solar systems are gaining increased academic and industrial attention due to the unique advantages they offer. In this paper, a mathematical model has been developed to investigate the thermal behavior of a greenhouse heated by a hybrid solar collector system. This hybrid system contains an evacuated tube solar heat collector unit, an auxiliary fossil fuel heating unit, a hot water storage unit, control and piping units. A Matlab/Simulink based model and software has been developed to predict the storage water temperature, greenhouse indoor temperature and the amount of auxiliary fuel, as a function of various design parameters of the greenhouse such as location, dimensions, and meteorological data of the region. As a case study, a greenhouse located in Şanlıurfa/Turkey has been simulated based on recent meteorological data and aforementioned hybrid system. The results of simulations performed on an annual basis indicate that revising the existing fossil fuel system with the proposed hybrid system, is economically feasible for most cases, however it requires a slightly longer payback period than expected. On the other hand, by reducing the greenhouse gas emissions significantly, it has a considerable positive environmental impact. The developed dynamic simulation method can be further used for designing heating systems for various solar greenhouses and optimizing the solar collector and thermal storage sizes

Kinetics of Waterborne Alkyd/Acrylic Hybrid Resin Free Radical Polymerization by Two Systems of Redox and Thermal Initiators

OpenAIRE

shirin Madadi; ali akbar Yousefi; elham Keshmirizadeh

2012-01-01

Kinetics of radical polymerizations of waterborne alkyd/acrylic hybrid resin via batch mini-emulsion technique was studied using redox initiators (TBHP/Fe2+/EDTA/AsAc  and  TBHP/Fe2+/EDTA/SFS) at relatively low temperatures and thermal initiators (BPO, KPS and AIBN) at higher temperatures to seek the most suitable initiator system. At the end of all reactions the unreacted monomer content was reduced using post-polymerization technique; consequently, leading to increased monomer conversion an...

Simulation of the fuel consumption benefits of various transmission arrangements and control strategies within a flywheel based mechanical hybrid system

Energy Technology Data Exchange (ETDEWEB)

Body, William; Brockbank, Chris [Torotrak (Development) Ltd. (United Kingdom)

2009-07-01

Flywheel based mechanical hybrid technology is being developed for both motorsport and mainstream automotive applications. One particular road car application project, part funded by the UK Government Technology Strategy Board, is being led by Jaguar Land Rover, managed by Prodrive and using advanced technology from Flybrid Systems, Ford, Ricardo. Torotrak and Xtrac. During the two year programme, the group will develop the new technology and build a demonstrator vehicle equipped with the system. The mechanical system recovers kinetic energy from the vehicle during braking to a high speed rotating flywheel via a variable drive system. When compared to an electric motor / battery arrangement, the mechanical hybrid system offers benefits in cost, weight, package, efficiency and ultimately vehicle fuel consumption. As part of the development and optimisation process in order to specify the road car system, all aspects of the mechanical hybrid system are under investigation by the group. Alongside the required quantity of energy storage and the rates of energy recovery and reapplication, a number of different physical architectures for the system are being analysed. The Torotrak full-toroidal traction drive has been assigned as the variable drive element of the mechanical hybrid system. Multiple configuration options are available including direct drive, epicyclic shunted, range extended CVT and epicyclic shunted IVT arrangements. In addition, the flywheel and variable drive system can be connected to the powertrain in a variety of different locations, from the engine through the powertrain to the wheels. This paper describes the simulation of the mechanical hybrid system with particular focus on the impact on the fuel consumption benefit, over multiple drive cycles, of the variable drive configuration, the location of the variable drive and flywheel system and the control strategy options. (orig.)

Analysis and simulation of phase transformation kinetics of zeolite A from amorphous phases

CERN Document Server

Marui, Y; Uchida, H; Takiyama, H

2003-01-01

Experiments on transformation rates of zeolite A from amorphous phases at different feed rates to alter the particle size of the amorphous phases were carried out to analyze the kinetics of the transformation, and were analyzed by performing simulation of the transformation. A clear dependence of the induction time for nucleation of zeolite A crystals on the surface area of the amorphous phase was recognized, indicating that the nucleation of zeolite A was heterogeneous and the nucleation rate was almost proportional to the size of the amorphous particles. From the simulation, the mechanism of the transformation was found to be heterogeneous nucleation of zeolite A crystals on the surface of amorphous particles followed by solution mediated phase transformation, and the transformation kinetics were well reproduced at different feed rates. (author)

Kinetic modeling and exploratory numerical simulation of chloroplastic starch degradation

Directory of Open Access Journals (Sweden)

Nag Ambarish

2011-06-01

Full Text Available Abstract Background Higher plants and algae are able to fix atmospheric carbon dioxide through photosynthesis and store this fixed carbon in large quantities as starch, which can be hydrolyzed into sugars serving as feedstock for fermentation to biofuels and precursors. Rational engineering of carbon flow in plant cells requires a greater understanding of how starch breakdown fluxes respond to variations in enzyme concentrations, kinetic parameters, and metabolite concentrations. We have therefore developed and simulated a detailed kinetic ordinary differential equation model of the degradation pathways for starch synthesized in plants and green algae, which to our knowledge is the most complete such model reported to date. Results Simulation with 9 internal metabolites and 8 external metabolites, the concentrations of the latter fixed at reasonable biochemical values, leads to a single reference solution showing β-amylase activity to be the rate-limiting step in carbon flow from starch degradation. Additionally, the response coefficients for stromal glucose to the glucose transporter kcat and KM are substantial, whereas those for cytosolic glucose are not, consistent with a kinetic bottleneck due to transport. Response coefficient norms show stromal maltopentaose and cytosolic glucosylated arabinogalactan to be the most and least globally sensitive metabolites, respectively, and β-amylase kcat and KM for starch to be the kinetic parameters with the largest aggregate effect on metabolite concentrations as a whole. The latter kinetic parameters, together with those for glucose transport, have the greatest effect on stromal glucose, which is a precursor for biofuel synthetic pathways. Exploration of the steady-state solution space with respect to concentrations of 6 external metabolites and 8 dynamic metabolite concentrations show that stromal metabolism is strongly coupled to starch levels, and that transport between compartments serves to

A Hands-On Classroom Simulation to Demonstrate Concepts in Enzyme Kinetics

Science.gov (United States)

Junker, Matthew

2010-01-01

A classroom exercise is described to introduce enzyme kinetics in an undergraduate biochemistry or chemistry course. The exercise is a simulation in which a student acts as an enzyme that "catalyzes" the unscrewing of a nut from a bolt. With other students assisting, the student enzyme carries out reactions with bolt-nut substrates under different…

Dynamic Modeling and Simulation of a Switched Reluctance Motor in a Series Hybrid Electric Vehicle

OpenAIRE

Siavash Sadeghi; Mojtaba Mirsalim; Arash Hassanpour Isfahani

2010-01-01

Dynamic behavior analysis of electric motors is required in order to accuratelyevaluate the performance, energy consumption and pollution level of hybrid electricvehicles. Simulation tools for hybrid electric vehicles are divided into steady state anddynamic models. Tools with steady-state models are useful for system-level analysiswhereas tools that utilize dynamic models give in-depth information about the behavior ofsublevel components. For the accurate prediction of hybrid electric vehicl...

Reduced Gasoline Surrogate (Toluene/n-Heptane/iso-Octane) Chemical Kinetic Model for Compression Ignition Simulations

KAUST Repository

Sarathy, Mani; Atef, Nour; Alfazazi, Adamu; Badra, Jihad; Zhang, Yu; Tzanetakis, Tom; Pei, Yuanjiang

2018-01-01

Toluene primary reference fuel (TPRF) (mixture of toluene, iso-octane and heptane) is a suitable surrogate to represent a wide spectrum of real fuels with varying octane sensitivity. Investigating different surrogates in engine simulations is a prerequisite to identify the best matching mixture. However, running 3D engine simulations using detailed models is currently impossible and reduction of detailed models is essential. This work presents an AramcoMech reduced kinetic model developed at King Abdullah University of Science and Technology (KAUST) for simulating complex TPRF surrogate blends. A semi-decoupling approach was used together with species and reaction lumping to obtain a reduced kinetic model. The model was widely validated against experimental data including shock tube ignition delay times and premixed laminar flame speeds. Finally, the model was utilized to simulate the combustion of a low reactivity gasoline fuel under partially premixed combustion conditions.

Reduced Gasoline Surrogate (Toluene/n-Heptane/iso-Octane) Chemical Kinetic Model for Compression Ignition Simulations

KAUST Repository

Sarathy, Mani

2018-04-03

Toluene primary reference fuel (TPRF) (mixture of toluene, iso-octane and heptane) is a suitable surrogate to represent a wide spectrum of real fuels with varying octane sensitivity. Investigating different surrogates in engine simulations is a prerequisite to identify the best matching mixture. However, running 3D engine simulations using detailed models is currently impossible and reduction of detailed models is essential. This work presents an AramcoMech reduced kinetic model developed at King Abdullah University of Science and Technology (KAUST) for simulating complex TPRF surrogate blends. A semi-decoupling approach was used together with species and reaction lumping to obtain a reduced kinetic model. The model was widely validated against experimental data including shock tube ignition delay times and premixed laminar flame speeds. Finally, the model was utilized to simulate the combustion of a low reactivity gasoline fuel under partially premixed combustion conditions.

Kinetics of spontaneous displacement of RNA from heteroduplexes by DNA.

OpenAIRE

Landgraf, R; Ramamurthi, K S; Sigman, D S

1996-01-01

We have used R-loop formation and direct hybridization techniques to analyze the kinetics by which RNA is displaced from a heteroduplex by DNA of identical sequence. Using random walk simulations we were able to calculate the step times for a single displacement reaction. For RNA with a GC content of 57-60% the data indicate an RNA exchange probability of 50.06%, which is indicative of a modest destabilization of the heteroduplex compared with a DNA duplex in the presence of magnesium. The av...

Kinetic equilibrium for an asymmetric tangential layer with rotation of the magnetic field

Science.gov (United States)

Belmont, Gérard; Dorville, Nicolas; Aunai, Nicolas; Rezeau, Laurence

2015-04-01

Finding kinetic equilibria for tangential current layers is a key issue for modeling plasma phenomena such as magnetic reconnection instabilities, for which theoretical and numerical studies have to start from steady-state current layers. Until 2012, all theoretical models -starting with the most famous "Harris" one- relied on distribution functions built as mono-valued functions of the trajectories invariants. For a coplanar anti-symmetric magnetic field and in absence of electric field, these models were only able to model symmetric variations of the plasma, so precluding any modeling of "magnetopause-like'' layers, which separate two plasmas of different densities and temperatures. Recently, the "BAS" model was presented (Belmont et al., 2012), where multi-valued functions were taken into account. This new tool is made necessary each time the magnetic field reversal occurs on scales larger than the particle Larmor radii, and therefore guaranties a logical transition with the MHD modeling of large scales. The BAS model so provides a new asymmetric equilibrium. It has been validated in a hybrid simulation by Aunai et al (2013), and more recently in a fully kinetic simulation as well. For this original equilibrium to be computed, the magnetic field had to stay coplanar inside the layer. We present here an important generalization, where the magnetic field rotates inside the layer (although restricted to a 180° rotation hitherto). The tangential layers so obtained are thus closer to those encountered at the real magnetopause. This will be necessary, in the future, for comparing directly the theoretical profiles with the experimental ones for the various physical parameters. As it was done previously, the equilibrium is presently tested with a hybrid simulation. Belmont, G.; Aunai, N.; Smets, R., Kinetic equilibrium for an asymmetric tangential layer, Physics of Plasmas, Volume 19, Issue 2, pp. 022108-022118-10, 2012 Aunai, N.; Belmont, G.; Smets, R., First

Energization and Transport in 3D Kinetic Simulations of MMS Magnetopause Reconnection Site Encounters with Varying Guide Fields

Science.gov (United States)

Le, A.; Daughton, W. S.; Ohia, O.; Chen, L. J.; Liu, Y. H.

2017-12-01

We present 3D fully kinetic simulations of asymmetric reconnection with plasma parameters matching MMS magnetopause diffusion region crossings with varying guide fields of 0.1 [Burch et al., Science (2016)], 0.4 [Chen et al. JGR (2017)], and 1 [Burch and Phan, GRL (2016] of the reconnecting sheath field. Strong diamagnetic drifts across the magnetopause current sheet drive lower-hybrid drift instabilities (LHDI) over a range of wavelengths [Daughton, PoP (2003); Roytershteyn et al., PRL (2012)] that develop into a turbulent state. Magnetic field tracing diagnostics are employed to characterize the turbulent magnetic geometry and to evaluate the global reconnection rate. The contributions to Ohm's law are evaluated field line by field line, including time-averaged diagnostics that allow the quantification of anomalous resistivity and viscosity. We examine how fluctuating electric fields and chaotic magnetic field lines contribute to particle mixing across the separatrix, and we characterize the accelerated electron distributions that form under varying magnetic shear or guide field. The LHDI turbulence is found to strongly enhance transport and parallel electron heating in 3D compared to 2D, particularly along the magnetospheric separatrix [Le et al., GRL (2017)]. The PIC simulation results are compared to MMS observations.

A hybrid simulation approach for integrating safety behavior into construction planning: An earthmoving case study.

Science.gov (United States)

Goh, Yang Miang; Askar Ali, Mohamed Jawad

2016-08-01

One of the key challenges in improving construction safety and health is the management of safety behavior. From a system point of view, workers work unsafely due to system level issues such as poor safety culture, excessive production pressure, inadequate allocation of resources and time and lack of training. These systemic issues should be eradicated or minimized during planning. However, there is a lack of detailed planning tools to help managers assess the impact of their upstream decisions on worker safety behavior. Even though simulation had been used in construction planning, the review conducted in this study showed that construction safety management research had not been exploiting the potential of simulation techniques. Thus, a hybrid simulation framework is proposed to facilitate integration of safety management considerations into construction activity simulation. The hybrid framework consists of discrete event simulation (DES) as the core, but heterogeneous, interactive and intelligent (able to make decisions) agents replace traditional entities and resources. In addition, some of the cognitive processes and physiological aspects of agents are captured using system dynamics (SD) approach. The combination of DES, agent-based simulation (ABS) and SD allows a more "natural" representation of the complex dynamics in construction activities. The proposed hybrid framework was demonstrated using a hypothetical case study. In addition, due to the lack of application of factorial experiment approach in safety management simulation, the case study demonstrated sensitivity analysis and factorial experiment to guide future research. Copyright © 2015 Elsevier Ltd. All rights reserved.

In Vitro Study of Adsorption Kinetics of Dextromethorphan Syrup onto Activated Charcoal in Simulated Gastric and Intestinal Fluids

Directory of Open Access Journals (Sweden)

Shobha Regmi

2017-01-01

Full Text Available Adsorption kinetics of dextromethorphan (DXM syrup in simulated gastric and intestinal fluids onto activated charcoal (AC were investigated in an in vitro model. The adsorption studies were performed as a function of time, initial concentration, and temperature. The quantification of DXM adsorbed onto AC was obtained from the Langmuir adsorption isotherms using HPLC. The maximum adsorption capacities (at 95% confidence limits of AC for DXM were 111.615 [106.38; 126.85] mg in simulated intestinal environment (pH 6.8 and 78.314 [86.206; 70.422] mg in simulated gastric environment (pH 1.2. The adsorption capacity of AC for DXM in simulated gastric fluid (pH 1.2 was not significantly different from the adoption capacity of AC for DXM in simulated intestinal fluid (pH 6.8. Moreover, the adsorption kinetics behavior of dextromethorphan onto AC followed pseudo-second-order kinetics. Our results show that AC in therapeutically acceptable doses can be beneficial in the majority of oral overdose of DXM.

Hydraulic Hybrid Fleet Vehicle Testing | Transportation Research | NREL

Science.gov (United States)

Hydraulic Hybrid Fleet Vehicle Evaluations Hydraulic Hybrid Fleet Vehicle Evaluations How Hydraulic Hybrid Vehicles Work Hydraulic hybrid systems can capture up to 70% of the kinetic energy that would -pressure reservoir to a high-pressure accumulator. When the vehicle accelerates, fluid in the high-pressure

A hybrid local/non-local framework for the simulation of damage and fracture

KAUST Repository

Azdoud, Yan

2014-01-01

Recent advances in non-local continuum models, notably peridynamics, have spurred a paradigm shift in solid mechanics simulation by allowing accurate mathematical representation of singularities and discontinuities. This doctoral work attempts to extend the use of this theory to a community more familiar with local continuum models. In this communication, a coupling strategy - the morphing method -, which bridges local and non-local models, is presented. This thesis employs the morphing method to ease use of the non-local model to represent problems with failure-induced discontinuities. First, we give a quick review of strategies for the simulation of discrete degradation, and suggest a hybrid local/non-local alternative. Second, we present the technical concepts involved in the morphing method and evaluate the quality of the coupling. Third, we develop a numerical tool for the simulation of the hybrid model for fracture and damage and demonstrate its capabilities on numerical model examples

Multiple time-scale methods in particle simulations of plasmas

International Nuclear Information System (INIS)

Cohen, B.I.

1985-01-01

This paper surveys recent advances in the application of multiple time-scale methods to particle simulation of collective phenomena in plasmas. These methods dramatically improve the efficiency of simulating low-frequency kinetic behavior by allowing the use of a large timestep, while retaining accuracy. The numerical schemes surveyed provide selective damping of unwanted high-frequency waves and preserve numerical stability in a variety of physics models: electrostatic, magneto-inductive, Darwin and fully electromagnetic. The paper reviews hybrid simulation models, the implicitmoment-equation method, the direct implicit method, orbit averaging, and subcycling

Simulation and Test of a Fuel Cell Hybrid Golf Cart

Directory of Open Access Journals (Sweden)

Jingming Liang

2014-01-01

Full Text Available This paper establishes the simulation model of fuel cell hybrid golf cart (FCHGC, which applies the non-GUI mode of the Advanced Vehicle Simulator (ADVISOR and the genetic algorithm (GA to optimize it. Simulation of the objective function is composed of fuel consumption and vehicle dynamic performance; the variables are the fuel cell stack power sizes and the battery numbers. By means of simulation, the optimal parameters of vehicle power unit, fuel cell stack, and battery pack are worked out. On this basis, GUI mode of ADVISOR is used to select the rated power of vehicle motor. In line with simulation parameters, an electrical golf cart is refitted by adding a 2 kW hydrogen air proton exchange membrane fuel cell (PEMFC stack system and test the FCHGC. The result shows that the simulation data is effective but it needs improving compared with that of the real cart test.

Computer simulations of disordering and amorphization kinetics in intermetallic compounds

International Nuclear Information System (INIS)

Spaczer, M.; Victoria, M.

1995-01-01

Molecular dynamics computer simulations on three intermetallic compounds, Cu 3 Au, Ni 3 Al and NiAl, have been performed to investigate the kinetics of the disordering and amorphization processes. These systems were chosen because reliable embedded atom potentials were developed for the constituent species and their alloys, and also because extended experimental results are available for them. Previous simulations of collision cascades with 5 keV Cu and Ni primary knock-out atom (PKA) showed a significant difference between the evolution of the short range order (SRO) and the crystalline order (CO) parameters in all of the intermetallics: a complete loss of the crystalline structure and only partial chemical disorder in the core of the cascade [T. Diaz de la Rubia et al., Phys. Rev. B 47 (1993) 11483; M. Spaczer et al., Phys. Rev. B 50 (1994) 13204]. The present paper deals with the simulation of the amorphization process in NiAl by 5 and 15 keV Ni PKAs. The kinetic energy of the atoms in the simulated systems was removed on different time scales to mimic strong or weak coupling between electrons and phonons. No evidence of amorphization was found at the end of the cascades created by the 5 keV recoils. However, the 15 keV PKA events showed that (i) in the no-coupling case the system evolved to a highly disordered state, (ii) an amorphous region with about 100 non-lattice atoms was found in the case of weak coupling, (iii) the locally melted and recrystallized region collapsed to a small dislocation loop when medium coupling was used and (iv) a highly ordered state resulted in the case of strong coupling. (orig.)

Fully kinetic simulations of magnetic reconnection in partially ionised gases

Science.gov (United States)

Innocenti, M. E.; Jiang, W.; Lapenta, G.; Markidis, S.

2016-12-01

Magnetic reconnection has been explored for decades as a way to convert magnetic energy into kinetic energy and heat and to accelerate particles in environments as different as the solar surface, planetary magnetospheres, the solar wind, accretion disks, laboratory plasmas. When studying reconnection via simulations, it is usually assumed that the plasma is fully ionised, as it is indeed the case in many of the above-mentioned cases. There are, however, exceptions, the most notable being the lower solar atmosphere. Small ionisation fractions are registered also in the warm neutral interstellar medium, in dense interstellar clouds, in protostellar and protoplanetary accreditation disks, in tokamak edge plasmas and in ad-hoc laboratory experiments [1]. We study here how magnetic reconnection is modified by the presence of a neutral background, i.e. when the majority of the gas is not ionised. The ionised plasma is simulated with the fully kinetic Particle-In-Cell (PIC) code iPic3D [2]. Collisions with the neutral background are introduced via a Monte Carlo plug-in. The standard Monte Carlo procedure [3] is employed to account for elastic, excitation and ionization electron-neutral collisions, as well as for elastic scattering and charge exchange ion-neutral collisions. Collisions with the background introduce resistivity in an otherwise collisionless plasma and modifications of the particle distribution functions: particles (and ions at a faster rate) tend to thermalise to the background. To pinpoint the consequences of this, we compare reconnection simulations with and without background. References [1] E E Lawrence et al. Physical review letters, 110(1):015001, 2013. [2] S Markidis et al. Mathematics and Computers in Simulation, 80(7):1509-1519, 2010. [3] K Nanbu. IEEE Transactions on plasma science, 28(3):971-990, 2000.

Hybrid formulation of radiation transport in optically thick divertor plasmas

Energy Technology Data Exchange (ETDEWEB)

Rosato, J.; Marandet, Y.; Bufferand, H.; Stamm, R. [PIIM, UMR 7345 Aix-Marseille Universite / CNRS, Centre de St-Jerome, Marseille (France); Reiter, D. [IEK-4 Plasmaphysik, Forschungszentrum Juelich GmbH, Juelich (Germany)

2016-08-15

Kinetic Monte Carlo simulations of coupled atom-radiation transport in optically thick divertor plasmas can be computationally very demanding, in particular in ITER relevant conditions or even larger devices, e.g. for power plant divertor studies. At high (∝ 10{sup 15} cm{sup -3}) atomic densities, it can be shown that sufficiently large divertors behave in certain areas like a black body near the first resonance line of hydrogen (Lyman α). This suggests that, at least in part, the use of continuum model (radiation hydrodynamics) can be sufficiently accurate, while being less time consuming. In this work, we report on the development of a hybrid model devoted to switch automatically between a kinetic and a continuum description according to the plasma conditions. Calculations of the photo-excitation rate in a homogeneous slab are performed as an illustration. The outlined hybrid concept might be also applicable to neutral atom transport, due to mathematical analogy of transport equations for neutrals and radiation. (copyright 2016 The Authors. Contributions to Plasma Physics published by Wiley-VCH Verlag GmbH and Co. KGaA Weinheim. This)

A kinetics database and scripts for PHREEQC

Science.gov (United States)

Hu, B.; Zhang, Y.; Teng, Y.; Zhu, C.

2017-12-01

Kinetics of geochemical reactions has been increasingly used in numerical models to simulate coupled flow, mass transport, and chemical reactions. However, the kinetic data are scattered in the literature. To assemble a kinetic dataset for a modeling project is an intimidating task for most. In order to facilitate the application of kinetics in geochemical modeling, we assembled kinetics parameters into a database for the geochemical simulation program, PHREEQC (version 3.0). Kinetics data were collected from the literature. Our database includes kinetic data for over 70 minerals. The rate equations are also programmed into scripts with the Basic language. Using the new kinetic database, we simulated reaction path during the albite dissolution process using various rate equations in the literature. The simulation results with three different rate equations gave difference reaction paths at different time scale. Another application involves a coupled reactive transport model simulating the advancement of an acid plume in an acid mine drainage site associated with Bear Creek Uranium tailings pond. Geochemical reactions including calcite, gypsum, and illite were simulated with PHREEQC using the new kinetic database. The simulation results successfully demonstrated the utility of new kinetic database.

Monte Carlo simulation for fragment mass and kinetic energy distributions from the neutron-induced fission of 235U

International Nuclear Information System (INIS)

Montoya, M.; Rojas, J.; Saettone, E.

2007-01-01

The mass and kinetic energy distribution of nuclear fragments from the thermal neutron-induced fission of 235 U have been studied using a Monte Carlo simulation. Besides reproducing the pronounced broadening on the standard deviation of the final fragment kinetic energy distribution (σ e (m)) around the mass number m = 109, our simulation also produces a second broadening around m = 125 that is in agreement with the experimental data obtained by Belhafaf et al. These results are a consequence of the characteristics of the neutron emission, the variation in the primary fragment mean kinetic energy, and the yield as a function of the mass. (Author)

Advances in continuum kinetic and gyrokinetic simulations of turbulence on open-field line geometries

Science.gov (United States)

Hakim, Ammar; Shi, Eric; Juno, James; Bernard, Tess; Hammett, Greg

2017-10-01

For weakly collisional (or collisionless) plasmas, kinetic effects are required to capture the physics of micro-turbulence. We have implemented solvers for kinetic and gyrokinetic equations in the computational plasma physics framework, Gkeyll. We use a version of discontinuous Galerkin scheme that conserves energy exactly. Plasma sheaths are modeled with novel boundary conditions. Positivity of distribution functions is maintained via a reconstruction method, allowing robust simulations that continue to conserve energy even with positivity limiters. We have performed a large number of benchmarks, verifying the accuracy and robustness of our code. We demonstrate the application of our algorithm to two classes of problems (a) Vlasov-Maxwell simulations of turbulence in a magnetized plasma, applicable to space plasmas; (b) Gyrokinetic simulations of turbulence in open-field-line geometries, applicable to laboratory plasmas. Supported by the Max-Planck/Princeton Center for Plasma Physics, the SciDAC Center for the Study of Plasma Microturbulence, and DOE Contract DE-AC02-09CH11466.

Simulation of kinetic processes in the nuclear-excited helium non-ideal dusty plasma

International Nuclear Information System (INIS)

Budnik, A.P.; Kosarev, V.A.; Rykov, V.A.; Fortov, V.E.; Vladimirov, V.I.; Deputatova, L.V.

2009-01-01

The paper is devoted to the studying of kinetic processes in the nuclear-excited plasma of the helium gas with the fine uranium (or its chemical compounds) particles admixture. A new theoretical model for the mathematical simulation of the kinetic processes in dusty plasma of helium gas was developed. The main goal of this investigation is to determine possibilities of a creation of non-ideal dusty plasma, containing nano- and micro-particles, and excited by fission fragments (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Predictive simulation of bidirectional Glenn shunt using a hybrid blood vessel model.

Science.gov (United States)

Li, Hao; Leow, Wee Kheng; Chiu, Ing-Sh

2009-01-01

This paper proposes a method for performing predictive simulation of cardiac surgery. It applies a hybrid approach to model the deformation of blood vessels. The hybrid blood vessel model consists of a reference Cosserat rod and a surface mesh. The reference Cosserat rod models the blood vessel's global bending, stretching, twisting and shearing in a physically correct manner, and the surface mesh models the surface details of the blood vessel. In this way, the deformation of blood vessels can be computed efficiently and accurately. Our predictive simulation system can produce complex surgical results given a small amount of user inputs. It allows the surgeon to easily explore various surgical options and evaluate them. Tests of the system using bidirectional Glenn shunt (BDG) as an application example show that the results produc by the system are similar to real surgical results.

Microcanonical and hybrid simulations of lattice quantum chromodynamics with dynamical fermions

International Nuclear Information System (INIS)

Sinclair, D.K.

1986-10-01

Lattice QCD is simulated using Microcanonical and Hybrid (Micro-canonical/Langevin) methods to facilitate the inclusion of dynamical fermions (quarks). We report on simulations with 4 flavors of light dynamical quarks on a 10 3 x 6 lattice to study the finite temperature deconfinement/chiral transition which should be observable in relativistic heavy ion collisions, as a function of quark mass. A first order transition is observed at large mass, weakens at intermediate mass and strengthens for very small quark mass

Simulation of a 3D MOT-Optical Molasses Hybrid for Potassium-41 Atoms

Science.gov (United States)

Peterson, W. A.; Wrubel, Jonathan

2017-04-01

We report a design and numerical model for a 3D magneto-optical trap (MOT)-optical molasses hybrid for potassium-41 atoms. In this arrangement, the usual quadrupole magnetic field is replaced by an octupole field. The octupole field has a central region of very low magnetic field where our simulations show that the atoms experience an optical molasses, resulting in sub-doppler cooling not possible in a quadrupole MOT. The simulations also show that the presence of the magneto-optical trapping force at the edge of the cooling beams provides a restoring force which cycles atoms through the molasses region. We plan to use this hybrid trap to directly load a far off-resonance optical dipole trap. Because the atoms are recycled for multiple passes through the molasses, we expect a higher phase-space density of atoms loaded into the dipole trap. Similar hybrid cooling schemes should be relevant for lithium-6 and lithium-7, which also have poorly resolved D2 hyperfine structure. Research Corporation for Science Advancement, Cottrell College Science Award.

Simulation and Parametric Analysis of a Hybrid SOFC-Gas Turbine Power Generation System

International Nuclear Information System (INIS)

Hassan, A.M.; Fahmy

2004-01-01

Combined SOFC-Gas Turbine Power Generation Systems are aimed to increase the power and efficiency obtained from the technology of using high temperature fuel cells by integrating them with gas turbines. Hybrid systems are considered in the last few years as one of the most promising technologies to obtain electric energy from the natural gas at very high efficiency with a serious potential for commercial use. The use of high temperature allows internal reforming for natural gas and thus disparity of fuel composition is allowed. Also air preheating is performed thanks to the high operating cell temperature as a task of energy integration. In this paper a modeling approach is presented for the fuel cell-gas turbine hybrid power generation systems, to obtain the sofc output voltage, power, and the overall hybrid system efficiency. The system has been simulated using HYSYS, the process simulation software to help improving the process understanding and provide a quick system solution. Parametric analysis is also presented in this paper to discuss the effect of some important SOFC operating parameters on the system performance and efficiency

Lattice Boltzmann method and gas-kinetic BGK scheme in the low-Mach number viscous flow simulations

International Nuclear Information System (INIS)

Xu Kun; He Xiaoyi

2003-01-01

Both lattice Boltzmann method (LBM) and the gas-kinetic BGK scheme are based on the numerical discretization of the Boltzmann equation with collisional models, such as, the Bhatnagar-Gross-Krook (BGK) model. LBM tracks limited number of particles and the viscous flow behavior emerges automatically from the intrinsic particle stream and collisions process. On the other hand, the gas-kinetic BGK scheme is a finite volume scheme, where the time-dependent gas distribution function with continuous particle velocity space is constructed and used in the evaluation of the numerical fluxes across cell interfaces. Currently, LBM is mainly used for low Mach number, nearly incompressible flow simulation. For the gas-kinetic scheme, the application is focusing on the high speed compressible flows. In this paper, we are going to compare both schemes in the isothermal low-Mach number flow simulations. The methodology for developing both schemes will be clarified through the introduction of operator splitting Boltzmann model and operator averaging Boltzmann model. From the operator splitting Boltzmann model, the error rooted in many kinetic schemes, which are based on the decoupling of particle transport and collision, can be easily understood. As to the test case, we choose to use the 2D cavity flow since it is one of the most extensively studied cases. Detailed simulation results with different Reynolds numbers, as well as the benchmark solutions, are presented

Simulation studies of plasma waves in the electron foreshock - The transition from reactive to kinetic instability

Science.gov (United States)

Dum, C. T.

1990-01-01

Particle simulation experiments were used to analyze the electron beam-plasma instability. It is shown that there is a transition from the reactive state of the electron beam-plasma instability to the kinetic instability of Langmuir waves. Quantitative tests, which include an evaluation of the dispersion relation for the evolving non-Maxwellian beam distribution, show that a quasi-linear theory describes the onset of this transition and applies again fully to the kinetic stage. This stage is practically identical to the late stage seen in simulations of plasma waves in the electron foreshock described by Dum (1990).

Simulation of lower hybrid current drive in enhanced reversed shear plasmas in the tokamak fusion test reactor using the lower hybrid simulation code

International Nuclear Information System (INIS)

Kaita, R.; Bernabei, S.; Budny, R.

1996-01-01

The Enhanced Reversed Shear (ERS) mode has already shown great potential for improving the performance of the Tokamak Fusion Test Reactor (TFTR) and other devices. Sustaining the ERS, however, remains an outstanding problem. Lower hybrid (LH) current drive is a possible method for modifying the current profile and controlling its time evolution. To predict its effectiveness in TFTR, the Lower Hybrid Simulation Code (LSC) model is used in the TRANSP code and the Tokamak Simulation Code (TSC). Among the results from the simulations are the following. (1) Single-pass absorption is expected in TFTR ERS plasmas. The simulations show that the LH current follows isotherms of the electron temperature. The ability to control the location of the minimum in the q profile (q min ) has been demonstrated by varying the phase velocity of the launched LH waves and observing the change in the damping location. (2) LH current drive can been used to sustain the q min location. The tendency of qmin to drift inward, as the inductive current diffuses during the formation phase of the reversed shear discharge, is prevented by the LH current driven at a fixed radial location. If this results in an expanded plasma volume with improved confinement as high power neutral beam injection is applied, the high bootstrap currents induced during this phase can then maintain the larger qmin radius. (3) There should be no LH wave damping on energetic beam particles. The values of perpendicular index of refraction in the calculations never exceed about 20, while ions at TFR injection energies are resonant with waves having values closer to 100. Other issues being addressed in the study include the LH current drive efficiency in the presence of high bootstrap currents, and the effect of fast electron diffusion on LH current localization

Nonlinear hybrid simulation of toroidicity-induced alfven eigenmode

International Nuclear Information System (INIS)

Fu, G.Y.; Park, W.

1994-11-01

Gyrokinetic/Magnetohydrodynamics hybrid simulations have been carried out using MH3D-K code to study the nonlinear saturation of the toroidicity-induced Alfven eigenmode driven by energetic particles in a tokamak plasma. It is shown that the wave particle trapping is the nonlinear saturation mechanism for the parameters considered. The corresponding density profile flattening of hot particles is observed. The saturation amplitude is proportional to the square of linear growth rate. In addition to TAE modes, a new n = 1, m = 0 global Alfven eigenmode is shown to be excited by the energetic particles

Hybrid simulation research on formation mechanism of tungsten nanostructure induced by helium plasma irradiation

Energy Technology Data Exchange (ETDEWEB)

Ito, Atsushi M., E-mail: ito.atsushi@nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Takayama, Arimichi; Oda, Yasuhiro [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Tamura, Tomoyuki; Kobayashi, Ryo; Hattori, Tatsunori; Ogata, Shuji [Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Ohno, Noriyasu; Kajita, Shin [Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Yajima, Miyuki [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Noiri, Yasuyuki [Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Yoshimoto, Yoshihide [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Saito, Seiki [Kushiro National College of Technology, Kushiro, Hokkaido 084-0916 (Japan); Takamura, Shuichi [Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota 470-0392 (Japan); Murashima, Takahiro [Tohoku University, 6-3, Aramaki-Aza-Aoba, Aoba-Ward, Sendai 980-8578 (Japan); Miyamoto, Mitsutaka [Shimane University, Matsue, Shimane 690-8504 (Japan); Nakamura, Hiroaki [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

2015-08-15

The generation of tungsten fuzzy nanostructure by exposure to helium plasma is one of the important problems for the use of tungsten material as divertor plates in nuclear fusion reactors. In the present paper, the formation mechanisms of the helium bubble and the tungsten fuzzy nanostructure were investigated by using several simulation methods. We proposed the four-step process which is composed of penetration step, diffusion and agglomeration step, helium bubble growth step, and fuzzy nanostructure formation step. As the fourth step, the formation of the tungsten fuzzy nanostructure was successfully reproduced by newly developed hybrid simulation combining between molecular dynamics and Monte-Carlo method. The formation mechanism of tungsten fuzzy nanostructure observed by the hybrid simulation is that concavity and convexity of the surface are enhanced by the bursting of helium bubbles in the region around the concavity.

Supporting interpretation of dynamic simulation. Application to chemical kinetic models; Aides a l`interpretation de simulations dynamiques. Application aux modeles de cinetique chimique

Energy Technology Data Exchange (ETDEWEB)

Braunschweig, B

1998-04-22

Numerous scientific and technical domains make constant use of dynamical simulations. Such simulators are put in the hands of a growing number of users. This phenomenon is due both to the extraordinary increase in computing performance, and to better graphical user interfaces which make simulation models easy to operate. But simulators are still computer programs which produce series of numbers from other series of numbers, even if they are displayed graphically. This thesis presents new interaction paradigms between a dynamical simulator and its user. The simulator produces a self-made interpretation of its results, thanks to a dedicated representation of its domain with objects. It shows dominant cyclic mechanisms identified by their instantaneous loop gain estimates, it uses a notion of episodes for splitting the simulation into homogeneous time intervals, and completes this by animations which rely on the graphical structure of the system. These new approaches are demonstrated with examples from chemical kinetics, because of the energic and exemplary characteristics of the encountered behaviors. They are implemented in the Spike software, Software Platform for Interactive Chemical Kinetics Experiments. Similar concepts are also shown in two other domains: interpretation of seismic wave propagation, and simulation of large projects. (author) 95 refs.

A Hybrid Wind-Farm Parametrization for Mesoscale and Climate Models

Science.gov (United States)

Pan, Yang; Archer, Cristina L.

2018-04-01

To better understand the potential impact of wind farms on weather and climate at the regional to global scales, a new hybrid wind-farm parametrization is proposed for mesoscale and climate models. The proposed parametrization is a hybrid model because it is not based on physical processes or conservation laws, but on the multiple linear regression of the results of large-eddy simulations (LES) with the geometric properties of the wind-farm layout (e.g., the blockage ratio and blockage distance). The innovative aspect is that each wind turbine is treated individually based on its position in the farm and on the wind direction by predicting the velocity upstream of each turbine. The turbine-induced forces and added turbulence kinetic energy (TKE) are first derived analytically and then implemented in the Weather Research and Forecasting model. Idealized simulations of the offshore Lillgrund wind farm are conducted. The wind-speed deficit and TKE predicted with the hybrid model are in excellent agreement with those from the LES results, while the wind-power production estimated with the hybrid model is within 10% of that observed. Three additional wind farms with larger inter-turbine spacing than at Lillgrund are also considered, and a similar agreement with LES results is found, proving that the hybrid parametrization works well with any wind farm regardless of the spacing between turbines. These results indicate the wind-turbine position, wind direction, and added TKE are essential in accounting for the wind-farm effects on the surroundings, for which the hybrid wind-farm parametrization is a promising tool.

ε-Caprolactam migration from irradiated PA-6 food packaging: kinetic simulation and measurement

International Nuclear Information System (INIS)

Rosa, Faena Machado Leite; Felix, Juliana; Araujo, Henrique Peres; Monteiro, Magali

2007-01-01

Migration of low molecular mass compounds (LMMC), such as monomers and additives, from plastic packaging into food simulants is a very important issue, concerning public health and chemical contamination of foods. Sterilization of food packaging materials with ionizing radiation is considered an alternative to other sterilization methods, but when polymers are irradiated, LMMC may be formed, as radiolysis products. According to the Brazilian legislation, specific migration tests, such as those of LMMC from packaging into simulants, should be carried out at certain temperature and time, depending on the real conditions of contact. In this work, multilayer flexible films with polyamide 6 (PA-6), used for meat foodstuffs, were studied. The ε-caprolactam (PA-6 monomer) specific migration into acetic acid 3% simulant at 40 deg C during 10 days and at 100 deg C during 30 minutes was performed. The initial monomer level in the irradiated and non irradiated PA-6 films was quantified by high resolution gas chromatography (HRGC). Radiation doses were 3 and 7 kGy. ε-caprolactam specific migration was carried out only with non irradiated films. The results showed that radiation causes a significant change in the monomer level, up or down, depending on the multilayer film type. The kinetic of the ε-caprolactam migration at both temperatures, 40 and 100 deg C was clearly explained by the numerical simulation, combining an Arrhenius equation with the Fick's second law, although this kinetic was not experimentally studied. This simulation allowed to predict diffusion parameters estimates, like diffusion coefficients and activation energies of ε-caprolactam in the films or simulant. (author)

Kinetic structures of quasi-perpendicular shocks in global particle-in-cell simulations

International Nuclear Information System (INIS)

Peng, Ivy Bo; Markidis, Stefano; Laure, Erwin; Johlander, Andreas; Vaivads, Andris; Khotyaintsev, Yuri; Henri, Pierre; Lapenta, Giovanni

2015-01-01

We carried out global Particle-in-Cell simulations of the interaction between the solar wind and a magnetosphere to study the kinetic collisionless physics in super-critical quasi-perpendicular shocks. After an initial simulation transient, a collisionless bow shock forms as a result of the interaction of the solar wind and a planet magnetic dipole. The shock ramp has a thickness of approximately one ion skin depth and is followed by a trailing wave train in the shock downstream. At the downstream edge of the bow shock, whistler waves propagate along the magnetic field lines and the presence of electron cyclotron waves has been identified. A small part of the solar wind ion population is specularly reflected by the shock while a larger part is deflected and heated by the shock. Solar wind ions and electrons are heated in the perpendicular directions. Ions are accelerated in the perpendicular direction in the trailing wave train region. This work is an initial effort to study the electron and ion kinetic effects developed near the bow shock in a realistic magnetic field configuration

Structure of the lunar wake: Two-dimensional global hybrid simulations

Czech Academy of Sciences Publication Activity Database

Trávníček, Pavel; Hellinger, Petr; Schriver, D.; Bale, S. D.

2005-01-01

Roč. 32, - (2005), L06102/1-L06102/4 ISSN 0094-8276 R&D Projects: GA ČR(CZ) GA205/05/1011 Grant - others:ESA(XE) PRODEX 14529; NSF(US) INT- 0010111; NASA (US) NAG5-11804 Institutional research plan: CEZ:AV0Z30420517 Keywords : hybrid simulations * lunar wake Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.491, year: 2005

Kinetic Monte Carlo simulation of formation of microstructures in liquid droplets

International Nuclear Information System (INIS)

Block, M; Kunert, R; Schoell, E; Boeck, T; Teubner, Th

2004-01-01

We study the deposition of indium droplets on a glass surface and the subsequent formation of silicon microcrystals inside these droplets. Kinetic Monte Carlo methods are used to analyse the influence of growth temperature, flux of incoming particles, surface coverage, and in particular an energy parameter simulating the surface tension, upon the morphology of growth. According to the experimental conditions of crystallization, a temperature gradient and diffusion in spherical droplets are included. The simulations explain the formation of silicon crystal structures in good agreement with the experiment. The dependence of their shape and the conditions of formation on the growth parameters are investigated in detail

Investigation of Coal-biomass Catalytic Gasification using Experiments, Reaction Kinetics and Computational Fluid Dynamics

Energy Technology Data Exchange (ETDEWEB)

Battaglia, Francine [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Agblevor, Foster [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Klein, Michael [Univ. of Delaware, Newark, DE (United States); Sheikhi, Reza [Northeastern Univ., Boston, MA (United States)

2015-12-31

A collaborative effort involving experiments, kinetic modeling, and computational fluid dynamics (CFD) was used to understand co-gasification of coal-biomass mixtures. The overall goal of the work was to determine the key reactive properties for coal-biomass mixed fuels. Sub-bituminous coal was mixed with biomass feedstocks to determine the fluidization and gasification characteristics of hybrid poplar wood, switchgrass and corn stover. It was found that corn stover and poplar wood were the best feedstocks to use with coal. The novel approach of this project was the use of a red mud catalyst to improve gasification and lower gasification temperatures. An important results was the reduction of agglomeration of the biomass using the catalyst. An outcome of this work was the characterization of the chemical kinetics and reaction mechanisms of the co-gasification fuels, and the development of a set of models that can be integrated into other modeling environments. The multiphase flow code, MFIX, was used to simulate and predict the hydrodynamics and co-gasification, and results were validated with the experiments. The reaction kinetics modeling was used to develop a smaller set of reactions for tractable CFD calculations that represented the experiments. Finally, an efficient tool was developed, MCHARS, and coupled with MFIX to efficiently simulate the complex reaction kinetics.

Monte Carlo simulation for fragment mass and kinetic energy distributions from the neutron-induced fission of {sup 235}U

Energy Technology Data Exchange (ETDEWEB)

Montoya, M.; Rojas, J. [Instituto Peruano de Energia Nuclear, Av. Canada 1470, Lima 41 (Peru); Saettone, E. [Facultad de Ciencias, Universidad Nacional de lngenieria, Av. Tupac Amaru 210, Apartado 31-139, Lima (Peru)

2007-07-01

The mass and kinetic energy distribution of nuclear fragments from the thermal neutron-induced fission of {sup 235}U have been studied using a Monte Carlo simulation. Besides reproducing the pronounced broadening on the standard deviation of the final fragment kinetic energy distribution ({sigma}{sub e}(m)) around the mass number m = 109, our simulation also produces a second broadening around m = 125 that is in agreement with the experimental data obtained by Belhafaf et al. These results are a consequence of the characteristics of the neutron emission, the variation in the primary fragment mean kinetic energy, and the yield as a function of the mass. (Author)

Increasing the sampling efficiency of protein conformational transition using velocity-scaling optimized hybrid explicit/implicit solvent REMD simulation

Energy Technology Data Exchange (ETDEWEB)

Yu, Yuqi; Wang, Jinan; Shao, Qiang, E-mail: qshao@mail.shcnc.ac.cn, E-mail: Jiye.Shi@ucb.com, E-mail: wlzhu@mail.shcnc.ac.cn; Zhu, Weiliang, E-mail: qshao@mail.shcnc.ac.cn, E-mail: Jiye.Shi@ucb.com, E-mail: wlzhu@mail.shcnc.ac.cn [ACS Key Laboratory of Receptor Research, Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203 (China); Shi, Jiye, E-mail: qshao@mail.shcnc.ac.cn, E-mail: Jiye.Shi@ucb.com, E-mail: wlzhu@mail.shcnc.ac.cn [UCB Pharma, 216 Bath Road, Slough SL1 4EN (United Kingdom)

2015-03-28

The application of temperature replica exchange molecular dynamics (REMD) simulation on protein motion is limited by its huge requirement of computational resource, particularly when explicit solvent model is implemented. In the previous study, we developed a velocity-scaling optimized hybrid explicit/implicit solvent REMD method with the hope to reduce the temperature (replica) number on the premise of maintaining high sampling efficiency. In this study, we utilized this method to characterize and energetically identify the conformational transition pathway of a protein model, the N-terminal domain of calmodulin. In comparison to the standard explicit solvent REMD simulation, the hybrid REMD is much less computationally expensive but, meanwhile, gives accurate evaluation of the structural and thermodynamic properties of the conformational transition which are in well agreement with the standard REMD simulation. Therefore, the hybrid REMD could highly increase the computational efficiency and thus expand the application of REMD simulation to larger-size protein systems.

Kinetic Simulation and Energetic Neutral Atom Imaging of the Magnetosphere

Science.gov (United States)

Fok, Mei-Ching H.

2011-01-01

Advanced simulation tools and measurement techniques have been developed to study the dynamic magnetosphere and its response to drivers in the solar wind. The Comprehensive Ring Current Model (CRCM) is a kinetic code that solves the 3D distribution in space, energy and pitch-angle information of energetic ions and electrons. Energetic Neutral Atom (ENA) imagers have been carried in past and current satellite missions. Global morphology of energetic ions were revealed by the observed ENA images. We have combined simulation and ENA analysis techniques to study the development of ring current ions during magnetic storms and substorms. We identify the timing and location of particle injection and loss. We examine the evolution of ion energy and pitch-angle distribution during different phases of a storm. In this talk we will discuss the findings from our ring current studies and how our simulation and ENA analysis tools can be applied to the upcoming TRIO-CINAMA mission.

Kinetic turbulence simulations at extreme scale on leadership-class systems

Energy Technology Data Exchange (ETDEWEB)

Wang, Bei [Princeton Univ., Princeton, NJ (United States); Ethier, Stephane [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Tang, William [Princeton Univ., Princeton, NJ (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Williams, Timothy [Argonne National Lab. (ANL), Argonne, IL (United States); Ibrahim, Khaled Z. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Madduri, Kamesh [The Pennsylvania State Univ., University Park, PA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Williams, Samuel [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Oliker, Leonid [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2013-01-01

Reliable predictive simulation capability addressing confinement properties in magnetically confined fusion plasmas is critically-important for ITER, a 20 billion dollar international burning plasma device under construction in France. The complex study of kinetic turbulence, which can severely limit the energy confinement and impact the economic viability of fusion systems, requires simulations at extreme scale for such an unprecedented device size. Our newly optimized, global, ab initio particle-in-cell code solving the nonlinear equations underlying gyrokinetic theory achieves excellent performance with respect to "time to solution" at the full capacity of the IBM Blue Gene/Q on 786,432 cores of Mira at ALCF and recently of the 1,572,864 cores of Sequoia at LLNL. Recent multithreading and domain decomposition optimizations in the new GTC-P code represent critically important software advances for modern, low memory per core systems by enabling routine simulations at unprecedented size (130 million grid points ITER-scale) and resolution (65 billion particles).

A hybrid-Vlasov model based on the current advance method for the simulation of collisionless magnetized plasma

Czech Academy of Sciences Publication Activity Database

Valentini, F.; Trávníček, Pavel; Califano, F.; Hellinger, Petr; Mangeney, A.

2007-01-01

Roč. 225, č. 1 (2007), s. 753-770 ISSN 0021-9991 Institutional research plan: CEZ:AV0Z30420517 Keywords : numerical simulations * hybrid simulations * Vlasov simulations Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.372, year: 2007

Treatment and kinetic modelling of a simulated dye house effluent by enzymatic catalysis.

Science.gov (United States)

Cristóvão, Raquel O; Tavares, Ana P M; Loureiro, José M; Boaventura, Rui A R; Macedo, Eugénia A

2009-12-01

Biocatalytic treatment of a synthetic dye house effluent, simulating a textile wastewater containing various reactive dyestuffs (Reactive Yellow 15, Reactive Red 239 and Reactive Black 5) and auxiliary chemicals, was investigated in a batch reactor using a commercial laccase. A high decolourisation (above 86%) was achieved at the maximum wavelength of Reactive Black 5. The decolourisation at the other dyes wavelengths (above 63% for RY15 and around 41% for RR239) and the total decolourisation based on all the visible spectrum (around 55%) were not so good, being somewhat lower than in the case of a mixture of the dyes (above 89% for RB5, 77% for RY15, 68% for RR239 and above 84% for total decolourisation). Even so, these results suggest the applicability of this method to treat textile dyeing wastewaters. Kinetic models were developed to simulate the synthetic effluent decolourisation by commercial laccase. The kinetic constants of the models were estimated by minimizing the difference between the predicted and the experimental time courses. The close correlation between the experimental data and the simulated values seems to demonstrate that the models are able to describe with remarkable accuracy the simulated effluent degradation. Water quality parameters such as TOC, COD, BOD(5) and toxicity were found to be under the maximum permissible discharge limits for textile industries wastewaters.

Simulated human patients and patient-centredness: The uncanny hybridity of nursing education, technology, and learning to care.

Science.gov (United States)

Ireland, Aileen V

2017-01-01

Positioned within a hybrid of the human and technology, professional nursing practice has always occupied a space that is more than human. In nursing education, technology is central in providing tools with which practice knowledge is mobilized so that students can safely engage with simulated human patients without causing harm to real people. However, while there is an increased emphasis on deploying these simulated humans as emissaries from person-centred care to demonstrate what it is like to care for real humans, the nature of what is really going on in simulation-what is real and what is simulated-is very rarely discussed and poorly understood. This paper explores how elements of postcolonial critical thought can aid in understanding the challenges of educating nurses to provide person-centred care within a healthcare culture that is increasingly reliant on technology. Because nursing education is itself a hybrid of real and simulated practice, it provides an appropriate case study to explore the philosophical question of technology in healthcare discourse, particularly as it relates to the relationship between the human patient and its uncanny simulated double. Drawing on postcolonial elements such as the uncanny, diaspora, hybridity, and créolité, the hybrid conditions of nursing education are examined in order to open up new possibilities of thinking about how learning to care is entangled with this technological space to assist in shaping professional knowledge of person-centred care. Considering these issues through a postcolonial lens opens up questions about the nature of the difficulty in using simulated human technologies in clinical education, particularly with the paradoxical aim of providing person-centred care within a climate that increasingly characterized as posthuman. © 2016 John Wiley & Sons Ltd.

Kinetics of Waterborne Alkyd/Acrylic Hybrid Resin Free Radical Polymerization by Two Systems of Redox and Thermal Initiators

Directory of Open Access Journals (Sweden)

shirin Madadi

2012-12-01

Full Text Available Kinetics of radical polymerizations of waterborne alkyd/acrylic hybrid resin via batch mini-emulsion technique was studied using redox initiators (TBHP/Fe2+/EDTA/AsAc  and  TBHP/Fe2+/EDTA/SFS at relatively low temperatures and thermal initiators (BPO, KPS and AIBN at higher temperatures to seek the most suitable initiator system. At the end of all reactions the unreacted monomer content was reduced using post-polymerization technique; consequently, leading to increased monomer conversion and flm formation with improved properties. The kinetics of mini-emulsion polymerization showed that in all redox initiator systems (Fe2+ catalyst + EDTA chelating agent, the radials are produced at relatively low temperature with more effcient control of the reactor temperature. It was found that at 45°C TBHP/Fe2+/EDTA/SFS redox initiator system leads to 98% monomer conversion, a much higher rate than that of systems involved thermal initiators.

Anomalous electron transport in Hall-effect thrusters: Comparison between quasi-linear kinetic theory and particle-in-cell simulations

Science.gov (United States)

Lafleur, T.; Martorelli, R.; Chabert, P.; Bourdon, A.

2018-06-01

Kinetic drift instabilities have been implicated as a possible mechanism leading to anomalous electron cross-field transport in E × B discharges, such as Hall-effect thrusters. Such instabilities, which are driven by the large disparity in electron and ion drift velocities, present a significant challenge to modelling efforts without resorting to time-consuming particle-in-cell (PIC) simulations. Here, we test aspects of quasi-linear kinetic theory with 2D PIC simulations with the aim of developing a self-consistent treatment of these instabilities. The specific quantities of interest are the instability growth rate (which determines the spatial and temporal evolution of the instability amplitude), and the instability-enhanced electron-ion friction force (which leads to "anomalous" electron transport). By using the self-consistently obtained electron distribution functions from the PIC simulations (which are in general non-Maxwellian), we find that the predictions of the quasi-linear kinetic theory are in good agreement with the simulation results. By contrast, the use of Maxwellian distributions leads to a growth rate and electron-ion friction force that is around 2-4 times higher, and consequently significantly overestimates the electron transport. A possible method for self-consistently modelling the distribution functions without requiring PIC simulations is discussed.

A hybrid simulation model for a stable auroral arc

Directory of Open Access Journals (Sweden)

P. Janhunen

Full Text Available We present a new type of hybrid simulation model, intended to simulate a single stable auroral arc in the latitude/altitude plane. The ionospheric ions are treated as particles, the electrons are assumed to follow a Boltzmann response and the magnetospheric ions are assumed to be so hot that they form a background population unaffected by the electric fields that arise. The system is driven by assumed parallel electron energisation causing a primary negative charge cloud and an associated potential structure to build up. The results show how a closed potential structure and density depletion of an auroral arc build up and how they decay after the driver is turned off. The model also produces upgoing energetic ion beams and predicts strong static perpendicular electric fields to be found in a relatively narrow altitude range (~ 5000–11 000 km.

Key words. Magnetospheric physics (magnetosphere-ionosphere interactions; auroral phenomena – Space plasma physics (numerical simulation studies

A control-oriented simulation model of a power-split hybrid electric vehicle

International Nuclear Information System (INIS)

Cipek, Mihael; Pavković, Danijel; Petrić, Joško

2013-01-01

Highlights: ► A simulation model of a two mode power-split hybrid electric vehicle (HEV) is proposed. ► Modeling the energy losses in the HEV transmission components are presented. ► The control optimization model implementation aspects are discussed. -- Abstract: A simulation model of a two mode power-split hybrid electric vehicle (HEV) is proposed in this paper for the purpose of HEV dynamics analysis and control system design. The bond graph methodology is used to model dominant dynamic effects of the mechanical part of the HEV transmission. Simple quasi-static battery model, the environment model, the tire and the power losses model of a vehicle are included, as well. A low-level electric generator speed control loop is designed, which includes a PI controller tuned according to the symmetrical optimum tuning procedure. Finally, off-line optimization by conjugate gradient-based BPTT-like optimal control algorithm, which is based on the presented mathematical model, is also given in the paper.

Portable implementation model for CFD simulations. Application to hybrid CPU/GPU supercomputers

Science.gov (United States)

Oyarzun, Guillermo; Borrell, Ricard; Gorobets, Andrey; Oliva, Assensi

2017-10-01

Nowadays, high performance computing (HPC) systems experience a disruptive moment with a variety of novel architectures and frameworks, without any clarity of which one is going to prevail. In this context, the portability of codes across different architectures is of major importance. This paper presents a portable implementation model based on an algebraic operational approach for direct numerical simulation (DNS) and large eddy simulation (LES) of incompressible turbulent flows using unstructured hybrid meshes. The strategy proposed consists in representing the whole time-integration algorithm using only three basic algebraic operations: sparse matrix-vector product, a linear combination of vectors and dot product. The main idea is based on decomposing the nonlinear operators into a concatenation of two SpMV operations. This provides high modularity and portability. An exhaustive analysis of the proposed implementation for hybrid CPU/GPU supercomputers has been conducted with tests using up to 128 GPUs. The main objective consists in understanding the challenges of implementing CFD codes on new architectures.

Test particle method for incorporation of the kinetic effects into the envelope simulations of Raman backscattering

International Nuclear Information System (INIS)

Hur, Min Sup; Suk, Hyyong

2007-01-01

A new test particle method is presented for self-consistent incorporation of the kinetic effects into the fluid three-wave model. One of the most important kinetic effects is the electron trapping and it has been found that the trapping affects significantly the behavior of Raman backscatter and Raman backward laser amplification. The conventional fluid three-wave model cannot reproduce the kinetic simulations in the trapping regime. The test particle scheme utilizes the same equations for the laser evolution as in the three-wave model. However, the plasma wave is treated by the envelope-kinetic equation, which consists of envelope evolution and the kinetic term. The core of the new scheme is employing test particles to compute the kinetic term self-consistently. The benchmarking results against the averaged particle-in-cell (aPIC) code show excellent agreements, and the computation speed gain over the aPIC is from 2 to 20 depending on parameters

Analysis and simulation of the SLD WIC [Warm Iron Calorimeter] PADS hybrid preamplifier circuitry

International Nuclear Information System (INIS)

Fox, J.D.; Horelick, D.

1990-10-01

The SLD PADS electronics consist of over 9000 channels of charge-sensitive preamplifiers followed by integrated sample/hold data storage, digitizing, and readout circuitry. This paper uses computer simulation techniques to analyze critical performance parameters of the preamplifier hybrid including its interactions with the detector system. Simulation results are presented and verified with measured performance. 6 refs., 9 figs

Evaluation of the interindividual human variation in bioactivation of methyleugenol using physiologically based kinetic modeling and Monte Carlo simulations

International Nuclear Information System (INIS)

Al-Subeihi, Ala' A.A.; Alhusainy, Wasma; Kiwamoto, Reiko; Spenkelink, Bert; Bladeren, Peter J. van; Rietjens, Ivonne M.C.M.; Punt, Ans

2015-01-01

The present study aims at predicting the level of formation of the ultimate carcinogenic metabolite of methyleugenol, 1′-sulfooxymethyleugenol, in the human population by taking variability in key bioactivation and detoxification reactions into account using Monte Carlo simulations. Depending on the metabolic route, variation was simulated based on kinetic constants obtained from incubations with a range of individual human liver fractions or by combining kinetic constants obtained for specific isoenzymes with literature reported human variation in the activity of these enzymes. The results of the study indicate that formation of 1′-sulfooxymethyleugenol is predominantly affected by variation in i) P450 1A2-catalyzed bioactivation of methyleugenol to 1′-hydroxymethyleugenol, ii) P450 2B6-catalyzed epoxidation of methyleugenol, iii) the apparent kinetic constants for oxidation of 1′-hydroxymethyleugenol, and iv) the apparent kinetic constants for sulfation of 1′-hydroxymethyleugenol. Based on the Monte Carlo simulations a so-called chemical-specific adjustment factor (CSAF) for intraspecies variation could be derived by dividing different percentiles by the 50th percentile of the predicted population distribution for 1′-sulfooxymethyleugenol formation. The obtained CSAF value at the 90th percentile was 3.2, indicating that the default uncertainty factor of 3.16 for human variability in kinetics may adequately cover the variation within 90% of the population. Covering 99% of the population requires a larger uncertainty factor of 6.4. In conclusion, the results showed that adequate predictions on interindividual human variation can be made with Monte Carlo-based PBK modeling. For methyleugenol this variation was observed to be in line with the default variation generally assumed in risk assessment. - Highlights: • Interindividual human differences in methyleugenol bioactivation were simulated. • This was done using in vitro incubations, PBK modeling

Evaluation of the interindividual human variation in bioactivation of methyleugenol using physiologically based kinetic modeling and Monte Carlo simulations

Energy Technology Data Exchange (ETDEWEB)

Al-Subeihi, Ala' A.A., E-mail: subeihi@yahoo.com [Division of Toxicology, Wageningen University, Tuinlaan 5, 6703 HE Wageningen (Netherlands); BEN-HAYYAN-Aqaba International Laboratories, Aqaba Special Economic Zone Authority (ASEZA), P. O. Box 2565, Aqaba 77110 (Jordan); Alhusainy, Wasma; Kiwamoto, Reiko; Spenkelink, Bert [Division of Toxicology, Wageningen University, Tuinlaan 5, 6703 HE Wageningen (Netherlands); Bladeren, Peter J. van [Division of Toxicology, Wageningen University, Tuinlaan 5, 6703 HE Wageningen (Netherlands); Nestec S.A., Avenue Nestlé 55, 1800 Vevey (Switzerland); Rietjens, Ivonne M.C.M.; Punt, Ans [Division of Toxicology, Wageningen University, Tuinlaan 5, 6703 HE Wageningen (Netherlands)

2015-03-01

The present study aims at predicting the level of formation of the ultimate carcinogenic metabolite of methyleugenol, 1′-sulfooxymethyleugenol, in the human population by taking variability in key bioactivation and detoxification reactions into account using Monte Carlo simulations. Depending on the metabolic route, variation was simulated based on kinetic constants obtained from incubations with a range of individual human liver fractions or by combining kinetic constants obtained for specific isoenzymes with literature reported human variation in the activity of these enzymes. The results of the study indicate that formation of 1′-sulfooxymethyleugenol is predominantly affected by variation in i) P450 1A2-catalyzed bioactivation of methyleugenol to 1′-hydroxymethyleugenol, ii) P450 2B6-catalyzed epoxidation of methyleugenol, iii) the apparent kinetic constants for oxidation of 1′-hydroxymethyleugenol, and iv) the apparent kinetic constants for sulfation of 1′-hydroxymethyleugenol. Based on the Monte Carlo simulations a so-called chemical-specific adjustment factor (CSAF) for intraspecies variation could be derived by dividing different percentiles by the 50th percentile of the predicted population distribution for 1′-sulfooxymethyleugenol formation. The obtained CSAF value at the 90th percentile was 3.2, indicating that the default uncertainty factor of 3.16 for human variability in kinetics may adequately cover the variation within 90% of the population. Covering 99% of the population requires a larger uncertainty factor of 6.4. In conclusion, the results showed that adequate predictions on interindividual human variation can be made with Monte Carlo-based PBK modeling. For methyleugenol this variation was observed to be in line with the default variation generally assumed in risk assessment. - Highlights: • Interindividual human differences in methyleugenol bioactivation were simulated. • This was done using in vitro incubations, PBK modeling

Fully kinetic simulation of ion acoustic and dust-ion acoustic waves

International Nuclear Information System (INIS)

Hosseini Jenab, S. M.; Kourakis, I.; Abbasi, H.

2011-01-01

A series of numerical simulations is presented, based on a recurrence-free Vlasov kinetic model using kinetic phase point trajectories. All plasma components are modeled kinetically via a Vlasov evolution equation, then coupled through Poisson's equation. The dynamics of ion acoustic waves in an electron-ion and in a dusty (electron-ion-dust) plasma configuration are investigated, focusing on wave decay due to Landau damping and, in particular, on the parametric dependence of the damping rate on the dust concentration and on the electron-to-ion temperature ratio. In the absence of dust, the occurrence of damping was observed, as expected, and its dependence to the relative magnitude of the electron vs ion temperature(s) was investigated. When present, the dust component influences the charge balance, enabling dust-ion acoustic waves to survive Landau damping even in the extreme regime where T e ≅ T i . The Landau damping rate is shown to be minimized for a strong dust concentration or/and for a high value of the electron-to-ion temperature ratio. Our results confirm earlier theoretical considerations and contribute to the interpretation of experimental observations of dust-ion acoustic wave characteristics.

{epsilon}-Caprolactam migration from irradiated PA-6 food packaging: kinetic simulation and measurement

Energy Technology Data Exchange (ETDEWEB)

Rosa, Faena Machado Leite [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Felix, Juliana; Araujo, Henrique Peres; Monteiro, Magali [UNESP, Araraquara, SP (Brazil). Faculdade de Ciencias Farmaceuticas. Dept. de Alimentos e Nutricao; Padula, Marisa [Instituto de Tecnologia de Alimentos (ITAL), Campinas, SP (Brazil). Centro de Tecnologia de Embalagem; Manzoli, Jose Eduardo [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Universidade Sao Judas Tadeu (USJT), Sao Paulo, SP (Brazil)], E-mail: jmanzoli@ipen.br

2007-07-01

Migration of low molecular mass compounds (LMMC), such as monomers and additives, from plastic packaging into food simulants is a very important issue, concerning public health and chemical contamination of foods. Sterilization of food packaging materials with ionizing radiation is considered an alternative to other sterilization methods, but when polymers are irradiated, LMMC may be formed, as radiolysis products. According to the Brazilian legislation, specific migration tests, such as those of LMMC from packaging into simulants, should be carried out at certain temperature and time, depending on the real conditions of contact. In this work, multilayer flexible films with polyamide 6 (PA-6), used for meat foodstuffs, were studied. The {epsilon}-caprolactam (PA-6 monomer) specific migration into acetic acid 3% simulant at 40 deg C during 10 days and at 100 deg C during 30 minutes was performed. The initial monomer level in the irradiated and non irradiated PA-6 films was quantified by high resolution gas chromatography (HRGC). Radiation doses were 3 and 7 kGy. {epsilon}-caprolactam specific migration was carried out only with non irradiated films. The results showed that radiation causes a significant change in the monomer level, up or down, depending on the multilayer film type. The kinetic of the {epsilon}-caprolactam migration at both temperatures, 40 and 100 deg C was clearly explained by the numerical simulation, combining an Arrhenius equation with the Fick's second law, although this kinetic was not experimentally studied. This simulation allowed to predict diffusion parameters estimates, like diffusion coefficients and activation energies of {epsilon}-caprolactam in the films or simulant. (author)

An Integrated Modeling Suite for Simulating the Core Induction and Kinetic Effects in Mercury's Magnetosphere

Science.gov (United States)

Jia, X.; Slavin, J.; Chen, Y.; Poh, G.; Toth, G.; Gombosi, T.

2018-05-01

We present results from state-of-the-art global models of Mercury's space environment capable of self-consistently simulating the induction effect at the core and resolving kinetic physics important for magnetic reconnection.

Sex-Based Differences in Knee Kinetics With Anterior Cruciate Ligament Strain on Cadaveric Impact Simulations

Science.gov (United States)

Schilaty, Nathan D.; Bates, Nathaniel A.; Nagelli, Christopher; Krych, Aaron J.; Hewett, Timothy E.

2018-01-01

Background: Females are at an increased risk of sustaining noncontact knee ligament injuries as compared with their male counterparts. The kinetics that load the anterior cruciate ligament (ACL) are still under dispute in the literature. Purpose/Hypothesis: The purpose of this study was to determine whether there are differences in knee kinetics between the sexes that lead to greater ACL strain in females when similar external loads are applied during a simulated drop vertical jump landing task. It was hypothesized that female limbs would demonstrate significant differences in knee abduction moment that predispose females to ACL injury when compared with males. Study Design: Controlled laboratory study. Methods: Motion analysis data of 67 athletes who performed a drop vertical jump were collected. The kinematic and kinetic data were used to categorize tertiles of relative risk, and these values were input into a cadaveric impact simulator to assess ligamentous loads during the simulated landing task. Uni- and multiaxial load cells and differential variable reluctance transducer strain sensors were utilized to collect kinetic data and maximum ACL strain for analysis. Conditions of external loads applied to the cadaveric limbs were systematically varied and randomized. Data were analyzed with 2-way repeated-measures analysis of variance and the Fisher exact test. Results: Five kinetic parameters were evaluated. Of the 5 kinetic variables, only knee abduction moment (KAM) demonstrated significant differences in females as compared with males (F 1,136 = 4.398, P = .038). When normalized to height and weight, this difference between males and females increased in significance (F 1,136 = 7.155, P = .008). Compared with males, females exhibited a 10.3-N·m increased knee abduction torque at 66 milliseconds postimpact and a 22.3-N·m increased abduction torque at 100 milliseconds postimpact. For loading condition, the condition of “maximum ACL strain” demonstrated a

The responses of crop - wild Brassica hybrids to simulated herbivory and interspecific competition: implications for transgene introgression.

Science.gov (United States)

Sutherland, Jamie P; Justinova, Lenka; Poppy, Guy M

2006-01-01

Brassica rapa grows as a wild and weedy species throughout the world and is the most likely recipient of transgenes from GM oilseed rape. For transgene introgression to occur, the critical step which must be realized, is the formation of an F1 hybrid. Concerns exist that hybrid populations could be more vigorous and competitive compared to the parental species. This study examines the effect of simulated herbivory and interspecific competition on the vegetative and reproductive performance of non-transgenic F1 hybrids and their parental lines. Several vegetative and reproductive performance measures were used to determine the effect of simulated herbivory and competition on the Brassica lines, including leaf length and biomass for herbivory and seedling height and biomass for competition. For defoliation experiments, B. rapa showed little response in terms of leaf length but B. napus and the F1 hybrid responded negatively. Brassica rapa showed elevated biomass responses, but B. napus and the hybrid demonstrated negative responses to defoliation. Defoliation at the cotyledon stage had a slight effect upon final biomass with the F1 hybrid performing significantly worse than B. napus, although seed counts were not significantly different. For the series of competition experiments, hybrids seemed to be more similar to B. rapa in terms of early seedling growth and reproductive measures. The underperformance of hybrid plants when challenged by herbivory and competition, could potentially decrease survivorship and explain the rarity of hybrids in field surveys. However, should transgene introgression occur, the dynamics of hybrids could change radically thus increasing the risk of gene flow from a transgenic oilseed rape crop to the wild recipient.

Simulating Chemical Kinetics Without Differential Equations: A Quantitative Theory Based on Chemical Pathways.

Science.gov (United States)

Bai, Shirong; Skodje, Rex T

2017-08-17

A new approach is presented for simulating the time-evolution of chemically reactive systems. This method provides an alternative to conventional modeling of mass-action kinetics that involves solving differential equations for the species concentrations. The method presented here avoids the need to solve the rate equations by switching to a representation based on chemical pathways. In the Sum Over Histories Representation (or SOHR) method, any time-dependent kinetic observable, such as concentration, is written as a linear combination of probabilities for chemical pathways leading to a desired outcome. In this work, an iterative method is introduced that allows the time-dependent pathway probabilities to be generated from a knowledge of the elementary rate coefficients, thus avoiding the pitfalls involved in solving the differential equations of kinetics. The method is successfully applied to the model Lotka-Volterra system and to a realistic H 2 combustion model.

Functional simulations of power electronics components in series-hybrid machinery for the needs of OEM

Energy Technology Data Exchange (ETDEWEB)

Liukkonen, M.; Hentunen, A.; Kyyrae, J. (Department of Electrical Engineering, Helsinki University of Technology, Espoo (Finland)); Suomela, J. (Department of Automation and Systems, Helsinki University of Technology, Espoo (Finland))

2008-07-01

A method for rapid control prototyping of the series-hybrid transmission system is proposed in this paper. The rapid control prototyping needs simulation submodels from all system components in order to develop supervisory control software. The same simulation models can also be used to optimize the drive train. The target framework for the rapid control prototyping method is the original equipment manufacturer (OEM), where the objective is to build devices from subcontractor's components. The machinery industry, as a target group, uses high power ratings for the creation of motion, which leads to high voltage and current values used in the system. Therefore, prototyping is started with careful simulations. This paper also seeks to create a general idea about the structure of the series-hybrid power transmission and assists the start of the process for designing the supervisory control. (orig.)

On the biophysics and kinetics of toehold-mediated DNA strand displacement.

Science.gov (United States)

Srinivas, Niranjan; Ouldridge, Thomas E; Sulc, Petr; Schaeffer, Joseph M; Yurke, Bernard; Louis, Ard A; Doye, Jonathan P K; Winfree, Erik

2013-12-01

Dynamic DNA nanotechnology often uses toehold-mediated strand displacement for controlling reaction kinetics. Although the dependence of strand displacement kinetics on toehold length has been experimentally characterized and phenomenologically modeled, detailed biophysical understanding has remained elusive. Here, we study strand displacement at multiple levels of detail, using an intuitive model of a random walk on a 1D energy landscape, a secondary structure kinetics model with single base-pair steps and a coarse-grained molecular model that incorporates 3D geometric and steric effects. Further, we experimentally investigate the thermodynamics of three-way branch migration. Two factors explain the dependence of strand displacement kinetics on toehold length: (i) the physical process by which a single step of branch migration occurs is significantly slower than the fraying of a single base pair and (ii) initiating branch migration incurs a thermodynamic penalty, not captured by state-of-the-art nearest neighbor models of DNA, due to the additional overhang it engenders at the junction. Our findings are consistent with previously measured or inferred rates for hybridization, fraying and branch migration, and they provide a biophysical explanation of strand displacement kinetics. Our work paves the way for accurate modeling of strand displacement cascades, which would facilitate the simulation and construction of more complex molecular systems.

Hardware-in-the-loop-simulation using the example of a compressed-natural-gas hybrid; Hardware-in-the-Loop-Simulation am Beispiel eines Erdgas-Hybridfahrzeugs

Energy Technology Data Exchange (ETDEWEB)

Boehm, M.; Mauk, T.; Reuss, H.C. [Univ. Stuttgart (Germany)

2008-07-01

This paper deals with the development of hybrid specific software for a compressed natural gas hybrid. After the presentation of the project the software development process is being illustrated. A two phase hardware-in-the-loop simulation is an important part of it. The vehicle model and the modelling process will be described. (orig.)

Supercritical kinetic analysis in simplified system of fuel debris using integral kinetic model

International Nuclear Information System (INIS)

Tuya, Delgersaikhan; Obara, Toru

2016-01-01

Highlights: • Kinetic analysis in simplified weakly coupled fuel debris system was performed. • The integral kinetic model was used to simulate criticality accidents. • The fission power and released energy during simulated accident were obtained. • Coupling between debris regions and its effect on the fission power was obtained. - Abstract: Preliminary prompt supercritical kinetic analyses in a simplified coupled system of fuel debris designed to roughly resemble a melted core of a nuclear reactor were performed using an integral kinetic model. The integral kinetic model, which can describe region- and time-dependent fission rate in a coupled system of arbitrary geometry, was used because the fuel debris system is weakly coupled in terms of neutronics. The results revealed some important characteristics of coupled systems, such as the coupling between debris regions and the effect of the coupling on the fission rate and released energy in each debris region during the simulated criticality accident. In brief, this study showed that the integral kinetic model can be applied to supercritical kinetic analysis in fuel debris systems and also that it can be a useful tool for investigating the effect of the coupling on consequences of a supercritical accident.

Reaction kinetics of oxygen on single-phase alloys, oxidation of nickel and niobium alloys

International Nuclear Information System (INIS)

Lalauze, Rene

1973-01-01

This research thesis first addresses the reaction kinetics of oxygen on alloys. It presents some generalities on heterogeneous reactions (conventional theory, theory of jumps), discusses the core reaction (with the influence of pressure), discusses the influence of metal self-diffusion on metal oxidation kinetics (equilibrium conditions at the interface, hybrid diffusion regime), reports the application of the hybrid diffusion model to the study of selective oxidation of alloys (Wagner model, hybrid diffusion model) and the study of the oxidation kinetics of an alloy forming a solid solution of two oxides. The second part reports the investigation of the oxidation of single phase nickel and niobium alloys (phase α, β and γ)

Sizing and Simulation of PV-Wind Hybrid Power System

Directory of Open Access Journals (Sweden)

Mustafa Engin

2013-01-01

Full Text Available A sizing procedure is developed for hybrid system with the aid of mathematical models for photovoltaic cell, wind turbine, and battery that are readily present in the literature. This sizing procedure can simulate the annual performance of different kinds of photovoltaic-wind hybrid power system structures for an identified set of renewable resources, which fulfills technical limitations with the lowest energy cost. The output of the program will display the performance of the system during the year, the total cost of the system, and the best size for the PV-generator, wind generator, and battery capacity. Security lightning application is selected, whereas system performance data and environmental operating conditions are measured and stored. This hybrid system, which includes a PV, wind turbine, inverter, and a battery, was installed to supply energy to 24 W lamps, considering that the renewable energy resources of this site where the system was installed were 1700 Wh/m2/day solar radiation and 3.43 m/s yearly average wind speed. Using the measured variables, the inverter and charge regulator efficiencies were calculated as 90% and 98%, respectively, and the overall system’s electrical efficiency is calculated as 72%. Life cycle costs per kWh are found to be $0.89 and LLP = 0.0428.

Accelerating Climate and Weather Simulations through Hybrid Computing

Science.gov (United States)

Zhou, Shujia; Cruz, Carlos; Duffy, Daniel; Tucker, Robert; Purcell, Mark

2011-01-01

Unconventional multi- and many-core processors (e.g. IBM (R) Cell B.E.(TM) and NVIDIA (R) GPU) have emerged as effective accelerators in trial climate and weather simulations. Yet these climate and weather models typically run on parallel computers with conventional processors (e.g. Intel, AMD, and IBM) using Message Passing Interface. To address challenges involved in efficiently and easily connecting accelerators to parallel computers, we investigated using IBM's Dynamic Application Virtualization (TM) (IBM DAV) software in a prototype hybrid computing system with representative climate and weather model components. The hybrid system comprises two Intel blades and two IBM QS22 Cell B.E. blades, connected with both InfiniBand(R) (IB) and 1-Gigabit Ethernet. The system significantly accelerates a solar radiation model component by offloading compute-intensive calculations to the Cell blades. Systematic tests show that IBM DAV can seamlessly offload compute-intensive calculations from Intel blades to Cell B.E. blades in a scalable, load-balanced manner. However, noticeable communication overhead was observed, mainly due to IP over the IB protocol. Full utilization of IB Sockets Direct Protocol and the lower latency production version of IBM DAV will reduce this overhead.

Modeling Taylor series approximations for prompt neutron kinetics with lab view simulations

International Nuclear Information System (INIS)

Adzri, E. P.

2012-09-01

The reactor point kinetics equations have been subjected to intense research in an effort to find simple yet accurate numerical solutions methods. The equations are very stiff numerically, meaning that there is a wide variation in the decay constants, so that using a particular time step in the numerical solution may provide sufficient accuracy for the group, but not for another. Several solutions techniques have been presented on the point kinetics equations with varying degrees of complexity. These include Power Series Solutions, CORE, PCA, Genapol and Taylor series methods. In this research, algorithms were developed based on the first and second order Taylor series expansion and simulated in LabVIEW to solve the Reactor Point Kinetics equations using block diagram nodes implemented within stacked sequences. The algorithms developed were fast,accurate and simple to code. Several reactivity insertions were used to simulate the change in neutron population with time. The LabVIEW- Taylor series solutions were compared with other solution techniques such as Power Series Solutions, CORE, PCA, Genapol and McMahon and Pierson's Taylor series approximation. The results of LabVIEW-Taylor series technique used by McMahon and Pearson The LabVIEW-implemented techniques were found to agree very well with these other methods. At 1x10 -8 s the neutron population was 1.000220 neutrons / cm 3 , at 1 x 10 -2 s it was 2.007681 neutrons / cm 3 and at 1x10 -1 s it was 2.075317 neutrons / cm 3 ; same results reported by Genapol for a fast reactor, it produced good and accurate results and compared very favorably with other methods found in the literature. Using much smaller time steps to the order or 10 -8 s commensurate with fast reactor parameters also produced very satisfactory results, indicating that the LabVIEW-based Taylor series technique is suitable for simulating the kinetics of fast reactors as well as thermal reactors. Algorithms developed that included second order terms

Plasma pressure tensor effects on reconnection: Hybrid and Hall-magnetohydrodynamics simulations

International Nuclear Information System (INIS)

Yin Lin; Winske, Dan

2003-01-01

Collisionless reconnection is studied using two-dimensional (2-D) hybrid (particle ions, massless fluid electrons) and Hall-magnetohydrodynamics (Hall-MHD) simulations. Both use the full electron pressure tensor instead of a localized resistivity in Ohm's law to initiate reconnection; an initial perturbation or boundary driving to the equilibrium is used. The initial configurations include one-dimensional (1-D) and 2-D current sheets both with and without a guide field. Electron dynamics from the two calculations are compared, and overall agreement is found between the calculations in both reconnection rate and global configuration [L. Yin et al., J. Geophys. Res. 106, 10761 (2001)]. It is shown that the electron drifts in the small-transverse-scale fields near the X point cause the electron motion to decouple from the ion motion, and that reconnection occurs due to electron viscous effects contained in the off-diagonal terms of the electron pressure tensor. Comparing the hybrid and Hall-MHD simulations shows that effects of the off-diagonal terms in the ion pressure tensor, i.e., the ion gyro-radius effects, are necessary in order to model correctly the ion out-of-plane motion. It is shown that these effects can be modeled efficiently in a particle Hall-MHD simulation in which particle ions are used in a predictor/corrector manner to implement ion gyro-radius corrections [L. Yin et al., Phys. Plasmas 9, 2575 (2002)]. For modeling reconnection in large systems, a new integrated approach is examined in which Hall-MHD calculations using a full electron pressure tensor model is embedded inside a MHD simulation. The embedded simulation of current sheet thinning and reconnection dynamics in a realistic 2-D magnetotail equilibrium exhibits smooth transitions of plasma and field quantities between the two regions, with small-scale physics represented well in the compressed current sheet and in the near-X-point region

One dimensional neutron kinetics in the TRAC-BF1 code

International Nuclear Information System (INIS)

Weaver, W.L. III; Wagner, K.C.

1987-01-01

The TRAC-BWR code development program at the Idaho National Engineering Laboratory is developing a version of the TRAC code for the U.S. Nuclear Regulatory Commission (USNRC) to provide a best-estimate analysis capability for the simulation of postulated accidents in boiling water reactor (BWR) power systems and related experimental facilities. Recent development efforts in the TRAC-BWR program have focused on improving the computational efficiency through the incorporation of a hybrid Courant- limit-violating numerical solution scheme in the one-dimensional component models and on improving code accuracy through the development of a one-dimensional neutron kinetics model. Many other improvements have been incorporated into TRAC-BWR to improve code portability, accuracy, efficiency, and maintainability. This paper will describe the one- dimensional neutron kinetics model, the generation of the required input data for this model, and present results of the first calculations using the model

Analysis of actuator delay and its effect on uncertainty quantification for real-time hybrid simulation

Science.gov (United States)

Chen, Cheng; Xu, Weijie; Guo, Tong; Chen, Kai

2017-10-01

Uncertainties in structure properties can result in different responses in hybrid simulations. Quantification of the effect of these uncertainties would enable researchers to estimate the variances of structural responses observed from experiments. This poses challenges for real-time hybrid simulation (RTHS) due to the existence of actuator delay. Polynomial chaos expansion (PCE) projects the model outputs on a basis of orthogonal stochastic polynomials to account for influences of model uncertainties. In this paper, PCE is utilized to evaluate effect of actuator delay on the maximum displacement from real-time hybrid simulation of a single degree of freedom (SDOF) structure when accounting for uncertainties in structural properties. The PCE is first applied for RTHS without delay to determine the order of PCE, the number of sample points as well as the method for coefficients calculation. The PCE is then applied to RTHS with actuator delay. The mean, variance and Sobol indices are compared and discussed to evaluate the effects of actuator delay on uncertainty quantification for RTHS. Results show that the mean and the variance of the maximum displacement increase linearly and exponentially with respect to actuator delay, respectively. Sensitivity analysis through Sobol indices also indicates the influence of the single random variable decreases while the coupling effect increases with the increase of actuator delay.

Plane shear flows of frictionless spheres: Kinetic theory and 3D soft-sphere discrete element method simulations

Science.gov (United States)

Vescovi, D.; Berzi, D.; Richard, P.; Brodu, N.

2014-05-01

We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed average volume fraction and distance between the walls. The results of the numerical simulations are used to derive boundary conditions appropriated in the cases of large and small bumpiness. Those boundary conditions are, then, employed to numerically integrate the differential equations of Extended Kinetic Theory, where the breaking of the molecular chaos assumption at volume fraction larger than 0.49 is taken into account in the expression of the dissipation rate. We show that the Extended Kinetic Theory is in very good agreement with the numerical simulations, even for coefficients of restitution as low as 0.50. When the bumpiness is increased, we observe that some of the flowing particles are stuck in the gaps between the wall spheres. As a consequence, the walls are more dissipative than expected, and the flows resemble simple shear flows, i.e., flows of rather constant volume fraction and granular temperature.

Plane shear flows of frictionless spheres: Kinetic theory and 3D soft-sphere discrete element method simulations

International Nuclear Information System (INIS)

Vescovi, D.; Berzi, D.; Richard, P.; Brodu, N.

2014-01-01

We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed average volume fraction and distance between the walls. The results of the numerical simulations are used to derive boundary conditions appropriated in the cases of large and small bumpiness. Those boundary conditions are, then, employed to numerically integrate the differential equations of Extended Kinetic Theory, where the breaking of the molecular chaos assumption at volume fraction larger than 0.49 is taken into account in the expression of the dissipation rate. We show that the Extended Kinetic Theory is in very good agreement with the numerical simulations, even for coefficients of restitution as low as 0.50. When the bumpiness is increased, we observe that some of the flowing particles are stuck in the gaps between the wall spheres. As a consequence, the walls are more dissipative than expected, and the flows resemble simple shear flows, i.e., flows of rather constant volume fraction and granular temperature

Combined kinetic and transport modeling of radiofrequency current drive

International Nuclear Information System (INIS)

Dumont, R.; Giruzzi, G.; Barbato, E.

2000-07-01

A numerical model for predictive simulations of radiofrequency current drive in magnetically confined plasmas is developed. It includes the minimum requirements for a self consistent description of such regimes, i.e., a 3-D ,kinetic equation for the electron distribution function, 1-D heat and current transport equations, and resonant coupling between velocity space and configuration space dynamics, through suitable wave propagation equations. The model finds its full application in predictive studies of complex current profile control scenarios in tokamaks, aiming at the establishment of internal transport barriers by the simultaneous use of various radiofrequency current drive methods. The basic properties of this non-linear numerical system are investigated and illustrated by simulations applied to reversed magnetic shear regimes obtained by Lower Hybrid and Electron Cyclotron current drive for parameters typical of the Tore Supra tokamak. (authors)

G4-STORK: A Geant4-based Monte Carlo reactor kinetics simulation code

International Nuclear Information System (INIS)

Russell, Liam; Buijs, Adriaan; Jonkmans, Guy

2014-01-01

Highlights: • G4-STORK is a new, time-dependent, Monte Carlo code for reactor physics applications. • G4-STORK was built by adapting and expanding on the Geant4 Monte Carlo toolkit. • G4-STORK was designed to simulate short-term fluctuations in reactor cores. • G4-STORK is well suited for simulating sub- and supercritical assemblies. • G4-STORK was verified through comparisons with DRAGON and MCNP. - Abstract: In this paper we introduce G4-STORK (Geant4 STOchastic Reactor Kinetics), a new, time-dependent, Monte Carlo particle tracking code for reactor physics applications. G4-STORK was built by adapting and expanding on the Geant4 Monte Carlo toolkit. The toolkit provides the fundamental physics models and particle tracking algorithms that track each particle in space and time. It is a framework for further development (e.g. for projects such as G4-STORK). G4-STORK derives reactor physics parameters (e.g. k eff ) from the continuous evolution of a population of neutrons in space and time in the given simulation geometry. In this paper we detail the major additions to the Geant4 toolkit that were necessary to create G4-STORK. These include a renormalization process that maintains a manageable number of neutrons in the simulation even in very sub- or supercritical systems, scoring processes (e.g. recording fission locations, total neutrons produced and lost, etc.) that allow G4-STORK to calculate the reactor physics parameters, and dynamic simulation geometries that can change over the course of simulation to illicit reactor kinetics responses (e.g. fuel temperature reactivity feedback). The additions are verified through simple simulations and code-to-code comparisons with established reactor physics codes such as DRAGON and MCNP. Additionally, G4-STORK was developed to run a single simulation in parallel over many processors using MPI (Message Passing Interface) pipes

Hybrid computer simulation of the dynamics of the Hoger Onderwijs Reactor

International Nuclear Information System (INIS)

Moers, J.C.; Vries, J.W. de.

1976-01-01

A distributed parameter model for the dynamics of the Hoger Onderwijs Reactor (HOR) at Delft is presented. The neutronic and the thermodynamic part of this model have been separately implemented on the AD4-IBM1800 Hybrid Computer of the Delft University of Technology Computation Centre. A continuous Space/Discrete Time solution method has been employed. Some test results of the simulation are included

AMITIS: A 3D GPU-Based Hybrid-PIC Model for Space and Plasma Physics

Science.gov (United States)

Fatemi, Shahab; Poppe, Andrew R.; Delory, Gregory T.; Farrell, William M.

2017-05-01

We have developed, for the first time, an advanced modeling infrastructure in space simulations (AMITIS) with an embedded three-dimensional self-consistent grid-based hybrid model of plasma (kinetic ions and fluid electrons) that runs entirely on graphics processing units (GPUs). The model uses NVIDIA GPUs and their associated parallel computing platform, CUDA, developed for general purpose processing on GPUs. The model uses a single CPU-GPU pair, where the CPU transfers data between the system and GPU memory, executes CUDA kernels, and writes simulation outputs on the disk. All computations, including moving particles, calculating macroscopic properties of particles on a grid, and solving hybrid model equations are processed on a single GPU. We explain various computing kernels within AMITIS and compare their performance with an already existing well-tested hybrid model of plasma that runs in parallel using multi-CPU platforms. We show that AMITIS runs ∼10 times faster than the parallel CPU-based hybrid model. We also introduce an implicit solver for computation of Faraday’s Equation, resulting in an explicit-implicit scheme for the hybrid model equation. We show that the proposed scheme is stable and accurate. We examine the AMITIS energy conservation and show that the energy is conserved with an error < 0.2% after 500,000 timesteps, even when a very low number of particles per cell is used.

Effects of hot-air and hybrid hot air-microwave drying on drying kinetics and textural quality of nectarine slices

Science.gov (United States)

Miraei Ashtiani, Seyed-Hassan; Sturm, Barbara; Nasirahmadi, Abozar

2018-04-01

Drying and physicochemical characteristics of nectarine slices were investigated using hot-air and hybrid hot air-microwave drying methods under fixed air temperature and air speed (50 °C and 0.5 m/s, respectively). Microwave power levels for the combined hot air-microwave method were 80, 160, 240, and 320 W. Drying kinetics were analyzed and compared using six mathematical models. For both drying methods the model with the best fitness in explaining the drying behavior was the Midilli-Kucuk model. The coefficient of determination ( R 2), root mean square error (RMSE) and reduced chi square ( χ 2) for this model have been obtained greater than 0.999 and less than 0.006 and 0.0001 for hybrid hot air-microwave drying while those values for hot-air drying were more than 0.999 and less than 0.003 and 0.0001, respectively. Results showed that the hybrid method reduced the drying time considerably and produced products with higher quality. The range of effective moisture diffusivity ( D eff ) of hybrid and hot-air drying was between 8.15 × 10-8 and 2.83 × 10-7 m2/s and 1.27 × 10-8 m2/s, respectively. The total color difference (ΔE) has also been obtained from 36.68 to 44.27 for hybrid method; however this value for hot-air drying was found 49.64. Although reduced microwave power output led to a lower drying rate, it reduced changes in product parameters i.e. total color change, surface roughness, shrinkage and microstructural change and increased hardness and water uptake.

Microscopic distribution functions, structure, and kinetic energy of liquid and solid neon: Quantum Monte Carlo simulations

International Nuclear Information System (INIS)

Neumann, Martin; Zoppi, Marco

2002-01-01

We have performed extensive path integral Monte Carlo simulations of liquid and solid neon, in order to derive the kinetic energy as well as the single-particle and pair distribution functions of neon atoms in the condensed phases. From the single-particle distribution function n(r) one can derive the momentum distribution and thus obtain an independent estimate of the kinetic energy. The simulations have been carried out using mostly the semiempirical HFD-C2 pair potential by Aziz et al. [R. A. Aziz, W. J. Meath, and A. R. Allnatt, Chem. Phys. 79, 295 (1983)], but, in a few cases, we have also used the Lennard-Jones potential. The differences between the potentials, as measured by the properties investigated, are not very large, especially when compared with the actual precision of the experimental data. The simulation results have been compared with all the experimental information that is available from neutron scattering. The overall agreement with the experiments is very good

Microstructure in two- and three-dimensional hybrid simulations of perpendicular collisionless shocks

Czech Academy of Sciences Publication Activity Database

Burgess, D.; Hellinger, Petr; Gingell, I.; Trávníček, Pavel M.

2016-01-01

Roč. 82, č. 4 (2016), 905820401/1-905820401/23 ISSN 0022-3778 Institutional support: RVO:68378289 Keywords : ion-acceleration * numerical simulations * bow shock * electron acceleration * cluster observations * self-reformation * magnetic-field * whistler waves * injection * nonstationarity Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.160, year: 2016 https://www.cambridge.org/core/ journals /journal-of-plasma-physics/article/microstructure-in-two-and-three-dimensional-hybrid-simulations-of-perpendicular-collisionless-shocks/F964EF89FB14A6504A49CFAD54970E2B

Model validation of solar PV plant with hybrid data dynamic simulation based on fast-responding generator method

Directory of Open Access Journals (Sweden)

Zhao Dawei

2016-01-01

Full Text Available In recent years, a significant number of large-scale solar photovoltaic (PV plants have been put into operation or been under planning around the world. The model accuracy of solar PV plant is the key factor to investigate the mutual influences between solar PV plants and a power grid. However, this problem has not been well solved, especially in how to apply the real measurements to validate the models of the solar PV plants. Taking fast-responding generator method as an example, this paper presents a model validation methodology for solar PV plant via the hybrid data dynamic simulation. First, the implementation scheme of hybrid data dynamic simulation suitable for DIgSILENT PowerFactory software is proposed, and then an analysis model of solar PV plant integration based on IEEE 9 system is established. At last, model validation of solar PV plant is achieved by employing hybrid data dynamic simulation. The results illustrate the effectiveness of the proposed method in solar PV plant model validation.

Energy Efficiency Comparison between Hydraulic Hybrid and Hybrid Electric Vehicles

Directory of Open Access Journals (Sweden)

Jia-Shiun Chen

2015-05-01

Full Text Available Conventional vehicles tend to consume considerable amounts of fuel, which generates exhaust gases and environmental pollution during intermittent driving cycles. Therefore, prospective vehicle designs favor improved exhaust emissions and energy consumption without compromising vehicle performance. Although pure electric vehicles feature high performance and low pollution characteristics, their limitations are their short driving range and high battery costs. Hybrid electric vehicles (HEVs are comparatively environmentally friendly and energy efficient, but cost substantially more compared with conventional vehicles. Hydraulic hybrid vehicles (HHVs are mainly operated using engines, or using alternate combinations of engine and hydraulic power sources while vehicles accelerate. When the hydraulic system accumulator is depleted, the conventional engine reengages; concurrently, brake-regenerated power is recycled and reused by employing hydraulic motor–pump modules in circulation patterns to conserve fuel and recycle brake energy. This study adopted MATLAB Simulink to construct complete HHV and HEV models for backward simulations. New European Driving Cycles were used to determine the changes in fuel economy. The output of power components and the state-of-charge of energy could be retrieved. Varying power component models, energy storage component models, and series or parallel configurations were combined into seven different vehicle configurations: the conventional manual transmission vehicle, series hybrid electric vehicle, series hydraulic hybrid vehicle, parallel hybrid electric vehicle, parallel hydraulic hybrid vehicle, purely electric vehicle, and hydraulic-electric hybrid vehicle. The simulation results show that fuel consumption was 21.80% lower in the series hydraulic hybrid vehicle compared to the series hybrid electric vehicle; additionally, fuel consumption was 3.80% lower in the parallel hybrid electric vehicle compared to the

Parallel Hybrid Vehicle Optimal Storage System

Science.gov (United States)

Bloomfield, Aaron P.

2009-01-01

A paper reports the results of a Hybrid Diesel Vehicle Project focused on a parallel hybrid configuration suitable for diesel-powered, medium-sized, commercial vehicles commonly used for parcel delivery and shuttle buses, as the missions of these types of vehicles require frequent stops. During these stops, electric hybridization can effectively recover the vehicle's kinetic energy during the deceleration, store it onboard, and then use that energy to assist in the subsequent acceleration.

Numerical Simulation of the Kinetic Critical Nucleus

OpenAIRE

Sanada, Masaaki; Nishioka, Kazumi; Okada, Masahumi; Maksimov, Igor, L.

1997-01-01

Our main interest is to see whether the number density indicates a peak at the kinetically stable critical nucleus due to its kinetical stability. We have numerically calculated the time evolution of the number densities of clusters in the case of water vapor nucleation. We employ the condition in which the difference between the size of the thermodynamic crtitical nucleus and that of the kinetic one is appreciable. The results show that the peak does not appear in the number densities of clu...

On the use of reverse Brownian motion to accelerate hybrid simulations

Energy Technology Data Exchange (ETDEWEB)

Bakarji, Joseph; Tartakovsky, Daniel M., E-mail: tartakovsky@stanford.edu

2017-04-01

Multiscale and multiphysics simulations are two rapidly developing fields of scientific computing. Efficient coupling of continuum (deterministic or stochastic) constitutive solvers with their discrete (stochastic, particle-based) counterparts is a common challenge in both kinds of simulations. We focus on interfacial, tightly coupled simulations of diffusion that combine continuum and particle-based solvers. The latter employs the reverse Brownian motion (rBm), a Monte Carlo approach that allows one to enforce inhomogeneous Dirichlet, Neumann, or Robin boundary conditions and is trivially parallelizable. We discuss numerical approaches for improving the accuracy of rBm in the presence of inhomogeneous Neumann boundary conditions and alternative strategies for coupling the rBm solver with its continuum counterpart. Numerical experiments are used to investigate the convergence, stability, and computational efficiency of the proposed hybrid algorithm.

Time-domain hybrid method for simulating large amplitude motions of ships advancing in waves

Directory of Open Access Journals (Sweden)

Shukui Liu

2011-03-01

Full Text Available Typical results obtained by a newly developed, nonlinear time domain hybrid method for simulating large amplitude motions of ships advancing with constant forward speed in waves are presented. The method is hybrid in the way of combining a time-domain transient Green function method and a Rankine source method. The present approach employs a simple double integration algorithm with respect to time to simulate the free-surface boundary condition. During the simulation, the diffraction and radiation forces are computed by pressure integration over the mean wetted surface, whereas the incident wave and hydrostatic restoring forces/moments are calculated on the instantaneously wetted surface of the hull. Typical numerical results of application of the method to the seakeeping performance of a standard containership, namely the ITTC S175, are herein presented. Comparisons have been made between the results from the present method, the frequency domain 3D panel method (NEWDRIFT of NTUA-SDL and available experimental data and good agreement has been observed for all studied cases between the results of the present method and comparable other data.

Comparison of plasma data from ASPERA-3/Mars-Express with a 3-D hybrid simulation

Directory of Open Access Journals (Sweden)

A. Bößwetter

2007-08-01

Full Text Available The ELS and IMA sensors of the ASPERA-3 experiment onboard of Mars-Express (MEX can measure electron as well as ion moments. We compare these measurements for a specific orbit with the simulation results from a 3-D hybrid model. In the hybrid approximation the electrons are modeled as a massless charge-neutralizing fluid, whereas the ions are treated as individual particles. This approach allows gyroradius effects to be included in our model calculations of the Martian plasma environment because the gyroradii of the solar wind protons are in the range of several hundred kilometers and therefore comparable with the characteristic scales of the subsolar ionospheric interaction region. The position of both the bow shock and the Ion Composition Boundary (ICB manifest in the MEX data as well as in the results from the hybrid simulation nearly at the same location. The characteristic features of these boundaries, i.e. an increase of proton density and temperature at the Bow Shock and a transition from solar wind to ionospheric particles at the ICB, are clearly identifiable in the data.

Accelerating Climate Simulations Through Hybrid Computing

Science.gov (United States)

Zhou, Shujia; Sinno, Scott; Cruz, Carlos; Purcell, Mark

2009-01-01

Unconventional multi-core processors (e.g., IBM Cell B/E and NYIDIDA GPU) have emerged as accelerators in climate simulation. However, climate models typically run on parallel computers with conventional processors (e.g., Intel and AMD) using MPI. Connecting accelerators to this architecture efficiently and easily becomes a critical issue. When using MPI for connection, we identified two challenges: (1) identical MPI implementation is required in both systems, and; (2) existing MPI code must be modified to accommodate the accelerators. In response, we have extended and deployed IBM Dynamic Application Virtualization (DAV) in a hybrid computing prototype system (one blade with two Intel quad-core processors, two IBM QS22 Cell blades, connected with Infiniband), allowing for seamlessly offloading compute-intensive functions to remote, heterogeneous accelerators in a scalable, load-balanced manner. Currently, a climate solar radiation model running with multiple MPI processes has been offloaded to multiple Cell blades with approx.10% network overhead.

Simulating Growth Kinetics in a Data-Parallel 3D Lattice Photobioreactor

Directory of Open Access Journals (Sweden)

A. V. Husselmann

2013-01-01

Full Text Available Though there have been many attempts to address growth kinetics in algal photobioreactors, surprisingly little have attempted an agent-based modelling (ABM approach. ABM has been heralded as a method of practical scientific inquiry into systems of a complex nature and has been applied liberally in a range of disciplines including ecology, physics, social science, and microbiology with special emphasis on pathogenic bacterial growth. We bring together agent-based simulation with the Photosynthetic Factory (PSF model, as well as certain key bioreactor characteristics in a visual 3D, parallel computing fashion. Despite being at small scale, the simulation gives excellent visual cues on the dynamics of such a reactor, and we further investigate the model in a variety of ways. Our parallel implementation on graphical processing units of the simulation provides key advantages, which we also briefly discuss. We also provide some performance data, along with particular effort in visualisation, using volumetric and isosurface rendering.

New hybrid voxelized/analytical primitive in Monte Carlo simulations for medical applications

International Nuclear Information System (INIS)

Bert, Julien; Lemaréchal, Yannick; Visvikis, Dimitris

2016-01-01

Monte Carlo simulations (MCS) applied in particle physics play a key role in medical imaging and particle therapy. In such simulations, particles are transported through voxelized phantoms derived from predominantly patient CT images. However, such voxelized object representation limits the incorporation of fine elements, such as artificial implants from CAD modeling or anatomical and functional details extracted from other imaging modalities. In this work we propose a new hYbrid Voxelized/ANalytical primitive (YVAN) that combines both voxelized and analytical object descriptions within the same MCS, without the need to simultaneously run two parallel simulations, which is the current gold standard methodology. Given that YVAN is simply a new primitive object, it does not require any modifications on the underlying MC navigation code. The new proposed primitive was assessed through a first simple MCS. Results from the YVAN primitive were compared against an MCS using a pure analytical geometry and the layer mass geometry concept. A perfect agreement was found between these simulations, leading to the conclusion that the new hybrid primitive is able to accurately and efficiently handle phantoms defined by a mixture of voxelized and analytical objects. In addition, two application-based evaluation studies in coronary angiography and intra-operative radiotherapy showed that the use of YVAN was 6.5% and 12.2% faster than the layered mass geometry method, respectively, without any associated loss of accuracy. However, the simplification advantages and differences in computational time improvements obtained with YVAN depend on the relative proportion of the analytical and voxelized structures used in the simulation as well as the size and number of triangles used in the description of the analytical object meshes. (paper)

New hybrid voxelized/analytical primitive in Monte Carlo simulations for medical applications.

Science.gov (United States)

Bert, Julien; Lemaréchal, Yannick; Visvikis, Dimitris

2016-05-07

Monte Carlo simulations (MCS) applied in particle physics play a key role in medical imaging and particle therapy. In such simulations, particles are transported through voxelized phantoms derived from predominantly patient CT images. However, such voxelized object representation limits the incorporation of fine elements, such as artificial implants from CAD modeling or anatomical and functional details extracted from other imaging modalities. In this work we propose a new hYbrid Voxelized/ANalytical primitive (YVAN) that combines both voxelized and analytical object descriptions within the same MCS, without the need to simultaneously run two parallel simulations, which is the current gold standard methodology. Given that YVAN is simply a new primitive object, it does not require any modifications on the underlying MC navigation code. The new proposed primitive was assessed through a first simple MCS. Results from the YVAN primitive were compared against an MCS using a pure analytical geometry and the layer mass geometry concept. A perfect agreement was found between these simulations, leading to the conclusion that the new hybrid primitive is able to accurately and efficiently handle phantoms defined by a mixture of voxelized and analytical objects. In addition, two application-based evaluation studies in coronary angiography and intra-operative radiotherapy showed that the use of YVAN was 6.5% and 12.2% faster than the layered mass geometry method, respectively, without any associated loss of accuracy. However, the simplification advantages and differences in computational time improvements obtained with YVAN depend on the relative proportion of the analytical and voxelized structures used in the simulation as well as the size and number of triangles used in the description of the analytical object meshes.

Simulation of hybrid ground-coupled heat pump with domestic hot water heating systems using HVACSIM+

Energy Technology Data Exchange (ETDEWEB)

Cui, Ping; Yang, Hongxing [Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong (China); Spitler, Jeffrey D. [School of Mechanical Engineering, Oklahoma State University (United States); Fang, Zhaohong [Ground Source Heat Pump Research Center, Shandong University of Architecture and Engineering, Jinan (China)

2008-07-01

A hybrid ground-coupled heat pump (HGCHP) with domestic hot water (DHW) supply system has been proposed in this paper for space cooling/heating and DHW supply for residential buildings in hot-climate areas. A simulation model for this hybrid system is established within the HVACSIM+ environment. A sample system, applied for a small residential apartment located in Hong Kong, is hourly simulated in a typical meteorological year. The conventional GCHP system and an electric heater for DHW supply are also modeled and simulated on an hourly basis within the HVACSIM+ for comparison purpose. The results obtained from this case study show that the HGCHP system can effectively alleviate the imbalanced loads of the ground heat exchanger (GHE) and can offer almost 95% DHW demand. The energy saving for DHW heating is about 70% compared with an electric heater. This proposed scheme, i.e. the HGCHP with DHW supply, is suitable to residential buildings in hot-climate areas, such as in Hong Kong. (author)

Lower hybrid current drive: an overview of simulation models, benchmarking with experiment, and predictions for future devices

International Nuclear Information System (INIS)

Bonoli, P.T.; Barbato, E.; Imbeaux, F.

2003-01-01

This paper reviews the status of lower hybrid current drive (LHCD) simulation and modeling. We first discuss modules used for wave propagation, absorption, and current drive with particular emphasis placed on comparing exact numerical solutions of the Fokker Planck equation in 2-dimension with solution methods that employ 1-dimensional and adjoint approaches. We also survey model predictions for LHCD in past and present experiments showing detailed comparisons between simulated and observed current drive efficiencies and hard X-ray profiles. Finally we discuss several model predictions for lower hybrid current profile control in proposed next step reactor options. (authors)

Displacement cascades and defect annealing in tungsten, Part II: Object kinetic Monte Carlo simulation of tungsten cascade aging

Energy Technology Data Exchange (ETDEWEB)

Nandipati, Giridhar, E-mail: giridhar.nandipati@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA (United States); Setyawan, Wahyu; Heinisch, Howard L. [Pacific Northwest National Laboratory, Richland, WA (United States); Roche, Kenneth J. [Pacific Northwest National Laboratory, Richland, WA (United States); Department of Physics, University of Washington, Seattle, WA 98195 (United States); Kurtz, Richard J. [Pacific Northwest National Laboratory, Richland, WA (United States); Wirth, Brian D. [University of Tennessee, Knoxville, TN (United States)

2015-07-15

The results of object kinetic Monte Carlo (OKMC) simulations of the annealing of primary cascade damage in bulk tungsten using a comprehensive database of cascades obtained from molecular dynamics (Setyawan et al.) are described as a function of primary knock-on atom (PKA) energy at temperatures of 300, 1025 and 2050 K. An increase in SIA clustering coupled with a decrease in vacancy clustering with increasing temperature, in addition to the disparate mobilities of SIAs versus vacancies, causes an interesting effect of temperature on cascade annealing. The annealing efficiency (the ratio of the number of defects after and before annealing) exhibits an inverse U-shape curve as a function of temperature. The capabilities of the newly developed OKMC code KSOME (kinetic simulations of microstructure evolution) used to carry out these simulations are described.

Displacement cascades and defect annealing in tungsten, Part II: Object kinetic Monte Carlo Simulation of Tungsten Cascade Aging

Energy Technology Data Exchange (ETDEWEB)

Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

2015-07-01

The results of object kinetic Monte Carlo (OKMC) simulations of the annealing of primary cascade damage in bulk tungsten using a comprehensive database of cascades obtained from molecular dynamics (Setyawan et al.) are described as a function of primary knock-on atom (PKA) energy at temperatures of 300, 1025 and 2050 K. An increase in SIA clustering coupled with a decrease in vacancy clustering with increasing temperature, in addition to the disparate mobilities of SIAs versus vacancies, causes an interesting effect of temperature on cascade annealing. The annealing efficiency (the ratio of the number of defects after and before annealing) exhibits an inverse U-shape curve as a function of temperature. The capabilities of the newly developed OKMC code KSOME (kinetic simulations of microstructure evolution) used to carry out these simulations are described.

Numerical simulation of turbulent combustion: Scientific challenges

Science.gov (United States)

Ren, ZhuYin; Lu, Zhen; Hou, LingYun; Lu, LiuYan

2014-08-01

Predictive simulation of engine combustion is key to understanding the underlying complicated physicochemical processes, improving engine performance, and reducing pollutant emissions. Critical issues as turbulence modeling, turbulence-chemistry interaction, and accommodation of detailed chemical kinetics in complex flows remain challenging and essential for high-fidelity combustion simulation. This paper reviews the current status of the state-of-the-art large eddy simulation (LES)/prob-ability density function (PDF)/detailed chemistry approach that can address the three challenging modelling issues. PDF as a subgrid model for LES is formulated and the hybrid mesh-particle method for LES/PDF simulations is described. Then the development need in micro-mixing models for the PDF simulations of turbulent premixed combustion is identified. Finally the different acceleration methods for detailed chemistry are reviewed and a combined strategy is proposed for further development.

Hybrid fast Hankel transform implementation for optics simulation

Science.gov (United States)

Davis, Paul K.

2013-09-01

The most compute intensive part of a full optics simulation, especially including diffraction effects, is the Fourier transform between pupil and image spaces. This is typically performed as a two dimensional fast discrete transform. For a nearly radially symmetric system there are advantages to using polar coordinates, in which case the radial transform becomes a Hankel transform, using Bessel functions instead of circular functions. However, there are special difficulties in calculating and handling Bessel functions. Several solutions have been proposed. We present a hybrid Hankel transform which divides the domain, calculating a portion using Bessel function approximations but converting most of the domain into a one dimensional Fourier transform which can be handled by standard methods.

Hybrid Computational Simulation and Study of Terahertz Pulsed Photoconductive Antennas

Science.gov (United States)

Emadi, R.; Barani, N.; Safian, R.; Nezhad, A. Zeidaabadi

2016-11-01

A photoconductive antenna (PCA) has been numerically investigated in the terahertz (THz) frequency band based on a hybrid simulation method. This hybrid method utilizes an optoelectronic solver, Silvaco TCAD, and a full-wave electromagnetic solver, CST. The optoelectronic solver is used to find the accurate THz photocurrent by considering realistic material parameters. Performance of photoconductive antennas and temporal behavior of the excited photocurrent for various active region geometries such as bare-gap electrode, interdigitated electrodes, and tip-to-tip rectangular electrodes are investigated. Moreover, investigations have been done on the center of the laser illumination on the substrate, substrate carrier lifetime, and diffusion photocurrent associated with the carriers temperature, to achieve efficient and accurate photocurrent. Finally, using the full-wave electromagnetic solver and the calculated photocurrent obtained from the optoelectronic solver, electromagnetic radiation of the antenna and its associated detected THz signal are calculated and compared with a measurement reference for verification.

Coupling Chemical Kinetics and Flashes in Reactive, Thermal and Compositional Reservoir Simulation

DEFF Research Database (Denmark)

Kristensen, Morten Rode; Gerritsen, Margot G.; Thomsen, Per Grove

2007-01-01

of convergence and error test failures by more than 50% compared to direct integration without the new algorithm. To facilitate the algorithmic development we construct a virtual kinetic cell model. We use implicit one-step ESDIRK (Explicit Singly Diagonal Implicit Runge-Kutta) methods for integration......Phase changes are known to cause convergence problems for integration of stiff kinetics in thermal and compositional reservoir simulations. We propose an algorithm for detection and location of phase changes based on discrete event system theory. The algorithm provides a robust way for handling...... the switching of variables and equations required when the number of phases changes. We extend the method to handle full phase equilibrium described by an equation of state. Experiments show that the new algorithm improves the robustness of the integration process near phase boundaries by lowering the number...

Structure of Mercury's magnetosphere for different pressure of the solar wind: Three dimensional hybrid simulations

Czech Academy of Sciences Publication Activity Database

Trávníček, Pavel; Hellinger, Petr; Schriver, D.

2007-01-01

Roč. 34, č. 5 (2007), L05104/1-L05104/5 ISSN 0094-8276 R&D Projects: GA ČR GA205/05/1011 Institutional research plan: CEZ:AV0Z30420517 Keywords : Global simulations * Mercury's magnetosphere * solar wind * hybrid simulations * ion drift driven rings Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.744, year: 2007

Amine-oxide hybrid materials for acid gas separations

KAUST Repository

Bollini, Praveen

2011-01-01

Organic-inorganic hybrid materials based on porous silica materials functionalized with amine-containing organic species are emerging as an important class of materials for the adsorptive separation of acid gases from dilute gas streams. In particular, these materials are being extensively studied for the adsorption of CO 2 from simulated flue gas streams, with an eye towards utilizing these materials as part of a post-combustion carbon capture process at large flue gas producing installations, such as coal-fired electricity-generating power plants. In this Application Article, the utilization of amine-modified organic-inorganic hybrid materials is discussed, focusing on important attributes of the materials, such as (i) CO 2 adsorption capacities, (ii) adsorption and desorption kinetics, and (iii) material stability, that will determine if these materials may one day be useful adsorbents in practical CO 2 capture applications. Specific research needs and limitations associated with the current body of work are identified. © 2011 The Royal Society of Chemistry.

A critical look at the kinetic parameter values used in simulating the thermoluminescence glow-curve

Energy Technology Data Exchange (ETDEWEB)

Sadek, A.M., E-mail: dr_amrsadek@hotmail.com [Ionizing Radiation Metrology Department, National Institute for Standards, El-Haram, Giza (Egypt); Kitis, G. [Nuclear Physics and Elementary Particles Physics Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Makedonia (Greece)

2017-03-15

Objections against utilizing the peak fitting method in computing the kinetics parameters of thermoluminescence (TL) glow-peaks were discussed previously in the literature. These objections came through testing the accuracy of the peak fitting by applying on simulated peaks. The results showed that in some cases the simulated peaks may have unusual geometrical properties and do not reflect the real properties of TL peaks. Thereby, estimating the accuracy of the peak fitting by applying on such peaks would be misleading. Two main reasons may lead to unrealistic simulated peaks; the improper selection of the simulation inputs, and performing the TL simulation process via the heating stage only. It has been proved that considering the irradiation and the relaxation stages in the simulation process is crucial. However, there are other cases in which the analytical methods were not able to reveal the real values of the simulated peaks. These cases were successfully resolved using analytical expressions derived from the one trap-one recombination (OTOR) level model and the non-interactive multiple trap system (NMTS) model. A general conclusion can be drawn that the accuracy of the peak fitting method is critically dependent on the TL analytical expressions utilized in this method. The failure of this method in estimating the TL kinetic parameters should be attributed to the TL model equation utilized in fitting process. - Highlights: • Objections against using the TL peak fitting method are discussed. • Improper selection of simulation inputs may lead to non realistic TL peaks. • Considering the irradiation and the relaxation stages in simulation is crucial. • TL expressions could not describe TL peaks with unrealistic geometrical properties. • The accuracy of the peak fitting method depends on the model used in the fitting.

Hybrid simulations of radial transport driven by the Rayleigh-Taylor instability

Science.gov (United States)

Delamere, P. A.; Stauffer, B. H.; Ma, X.

2017-12-01

Plasma transport in the rapidly rotating giant magnetospheres is thought to involve a centrifugally-driven flux tube interchange instability, similar to the Rayleigh-Taylor (RT) instability. In three dimensions, the convective flow patterns associated with the RT instability can produce strong guide field reconnection, allowing plasma mass to move radially outward while conserving magnetic flux (Ma et al., 2016). We present a set of hybrid (kinetic ion / fluid electron) plasma simulations of the RT instability using high plasma beta conditions appropriate for Jupiter's inner and middle magnetosphere. A density gradient, combined with a centrifugal force, provide appropriate RT onset conditions. Pressure balance is achieved by initializing two ion populations: one with fixed temperature, but varying density, and the other with fixed density, but a temperature gradient that offsets the density gradient from the first population and the centrifugal force (effective gravity). We first analyze two-dimensional results for the plane perpendicular to the magnetic field by comparing growth rates as a function of wave vector following Huba et al. (1998). Prescribed perpendicular wave modes are seeded with an initial velocity perturbation. We then extend the model to three dimensions, introducing a stabilizing parallel wave vector. Boundary conditions in the parallel direction prohibit motion of the magnetic field line footprints to model the eigenmodes of the magnetodisc's resonant cavity. We again compare growth rates based on perpendicular wave number, but also on the parallel extent of the resonant cavity, which fixes the size of the largest parallel wavelength. Finally, we search for evidence of strong guide field magnetic reconnection within the domain by identifying areas with large parallel electric fields or changes in magnetic field topology.

Stochastic optimization-based study of dimerization kinetics

Indian Academy of Sciences (India)

To this end, we study dimerization kinetics of protein as a model system. We follow the dimerization kinetics using a stochastic simulation algorithm and ... optimization; dimerization kinetics; sensitivity analysis; stochastic simulation ... tion in large molecules and clusters, or the design ..... An unbiased strategy of allocating.

Contribution to the modelling and multi-scale numerical simulation of kinetic electron transport in hot plasma

International Nuclear Information System (INIS)

Mallet, J.

2012-01-01

This research thesis stands at the crossroad of plasma physics, numerical analysis and applied mathematics. After an introduction presenting the problematic and previous works, the author recalls some basis of classical kinetic models for plasma physics (collisionless kinetic theory and Vlasov equation, collisional kinetic theory with the non-relativistic Maxwell-Fokker-Plansk system) and describes the fundamental properties of the collision operators such as conservation laws, entropy dissipation, and so on. He reports the improvement of a deterministic numerical method to solve the non-relativistic Vlasov-Maxwell system coupled with Fokker-Planck-Landau type operators. The efficiency of each high order scheme is compared. The evolution of the hot spot is studied in the case of thermonuclear reactions in the centre of the pellet in a weakly collisional regime. The author focuses on the simulation of the kinetic electron collisional transport in inertial confinement fusion (ICF) between the laser absorption zone and the ablation front. A new approach is then introduced to reduce the huge computation time obtained with kinetic models. In a last chapter, the kinetic continuous equation in spherical domain is described and a new model is chosen for collisions in order to preserve collision properties

Modeling Coronal Mass Ejections with the Multi-Scale Fluid-Kinetic Simulation Suite

International Nuclear Information System (INIS)

Pogorelov, N. V.; Borovikov, S. N.; Wu, S. T.; Yalim, M. S.; Kryukov, I. A.; Colella, P. C.; Van Straalen, B.

2017-01-01

The solar eruptions and interacting solar wind streams are key drivers of geomagnetic storms and various related space weather disturbances that may have hazardous effects on the space-borne and ground-based technological systems as well as on human health. Coronal mass ejections (CMEs) and their interplanetary counterparts, interplanetary CMEs (ICMEs), belong to the strongest disturbances and therefore are of great importance for the space weather predictions. In this paper we show a few examples of how adaptive mesh refinement makes it possible to resolve the complex CME structure and its evolution in time while a CME propagates from the inner boundary to Earth. Simulations are performed with the Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS). (paper)

Simulation study of two-ion hybrid resonance heating

International Nuclear Information System (INIS)

Riyopoulos, S.; Tajima, T.

1986-02-01

A one-dimensional low-noise, low-frequency electromagnetic particle simulation code that is appropriate for investigation of ion cyclotron resonance heating (ICRH) is developed. Retaining the hyperbolicity of the electromagnetic waves and exploiting nearly one-dimensional characteristics (perpendicular to the external magnetic field) of the ICRH, we use the guiding center electron approximation for the transverse electronic current calculation. We observe mode conversion of the incoming magnetosonic wave into the electrostatic ion-ion hybrid mode accompanied by strong ion-heating. The dependence of this heating on the different plasma parameters is examined through a series of simulations, focusing mainly on wave incidence from the high field side. Because K/sub parallel/ = 0 in our runs, the conventional Landau damping cannot explain the ion heating. Non-linear mechanisms for energy transfer are discussed. Our numerical results demonstrate the importance of the non-linear wave particle interaction for energy transfer are discussed. Our numerical results demonstrate the importance of the non-linear wave particle interaction for energy absorption during radio frequency heating in the ion cyclotron regime. 32 refs., 17 figs

Crash simulation of hybrid structures considering the stress and strain rate dependent material behavior of thermoplastic materials

Science.gov (United States)

Hopmann, Ch.; Schöngart, M.; Weber, M.; Klein, J.

2015-05-01

Thermoplastic materials are more and more used as a light weight replacement for metal, especially in the automotive industry. Since these materials do not provide the mechanical properties, which are required to manufacture supporting elements like an auto body or a cross bearer, plastics are combined with metals in so called hybrid structures. Normally, the plastics components are joined to the metal structures using different technologies like welding or screwing. Very often, the hybrid structures are made of flat metal parts, which are stiffened by a reinforcement structure made of thermoplastic materials. The loads on these structures are very often impulsive, for example in the crash situation of an automobile. Due to the large stiffness variation of metal and thermoplastic materials, complex states of stress and very high local strain rates occur in the contact zone under impact conditions. Since the mechanical behavior of thermoplastic materials is highly dependent on these types of load, the crash failure of metal plastic hybrid parts is very complex. The problem is that the normally used strain rate dependent elastic/plastic material models are not capable to simulate the mechanical behavior of thermoplastic materials depended on the state of stress. As part of a research project, a method to simulate the mechanical behavior of hybrid structures under impact conditions is developed at the IKV. For this purpose, a specimen for the measurement of mechanical properties dependet on the state of stress and a method for the strain rate depended characterization of thermoplastic materials were developed. In the second step impact testing is performed. A hybrid structure made from a metal sheet and a reinforcement structure of a Polybutylenterephthalat Polycarbonate blend is tested under impact conditions. The measured stress and strain rate depended material data are used to simulate the mechanical behavior of the hybrid structure under highly dynamic load with

N-S/DSMC hybrid simulation of hypersonic flow over blunt body including wakes

Science.gov (United States)

Li, Zhonghua; Li, Zhihui; Li, Haiyan; Yang, Yanguang; Jiang, Xinyu

2014-12-01

A hybrid N-S/DSMC method is presented and applied to solve the three-dimensional hypersonic transitional flows by employing the MPC (modular Particle-Continuum) technique based on the N-S and the DSMC method. A sub-relax technique is adopted to deal with information transfer between the N-S and the DSMC. The hypersonic flows over a 70-deg spherically blunted cone under different Kn numbers are simulated using the CFD, DSMC and hybrid N-S/DSMC method. The present computations are found in good agreement with DSMC and experimental results. The present method provides an efficient way to predict the hypersonic aerodynamics in near-continuum transitional flow regime.

Evaluating the influence of goal setting on intravenous catheterization skill acquisition and transfer in a hybrid simulation training context.

Science.gov (United States)

Brydges, Ryan; Mallette, Claire; Pollex, Heather; Carnahan, Heather; Dubrowski, Adam

2012-08-01

Educators often simplify complex tasks by setting learning objectives that focus trainees on isolated skills rather than the holistic task. We designed 2 sets of learning objectives for intravenous catheterization using goal setting theory. We hypothesized that setting holistic goals related to technical, cognitive, and communication skills would result in superior holistic performance, whereas setting isolated goals related to technical skills would result in superior technical performance. We randomly assigned practicing health care professionals to set holistic (n = 14) or isolated (n = 15) goals. All watched an instructional video and studied a list of 9 goals specific to their group. Participants practiced independently in a hybrid simulation (standardized patient combined with an arm simulator). The first and the last practice trials were videotaped for analysis. One-week later, participants completed a transfer test in another hybrid simulation scenario. Blinded experts evaluated performance on all 3 trials using the Direct Observation of Procedural Skills tool. The holistic group scored higher than the isolated group on the holistic Direct Observation of Procedural Skills score for all 3 trials [mean (SD), 45.0 (9.16) vs. 38.4 (9.17); P = 0.01]. The isolated group did not perform better than the holistic group on the technical skills score [10.3 (2.73) vs. 11.6 (3.01); P = 0.11]. Our results suggest that asking learners to set holistic goals did not interfere with their attaining competent holistic and technical skills during hybrid simulation training. This exploratory trial provides preliminary evidence for how to consider integrating hybrid simulation into medical curricula and for the design of learning goals in simulation-based education.

Monte Carlo kinetics simulations of ice-mantle formation on interstellar grains

Science.gov (United States)

Garrod, Robin

2015-08-01

The majority of interstellar dust-grain chemical kinetics models use rate equations, or alternative population-based simulation methods, to trace the time-dependent formation of grain-surface molecules and ice mantles. Such methods are efficient, but are incapable of considering explicitly the morphologies of the dust grains, the structure of the ices formed thereon, or the influence of local surface composition on the chemistry.A new Monte Carlo chemical kinetics model, MIMICK, is presented here, whose prototype results were published recently (Garrod 2013, ApJ, 778, 158). The model calculates the strengths and positions of the potential mimima on the surface, on the fly, according to the individual pair-wise (van der Waals) bonds between surface species, allowing the structure of the ice to build up naturally as surface diffusion and chemistry occur. The prototype model considered contributions to a surface particle's potential only from contiguous (or "bonded") neighbors; the full model considers contributions from surface constituents from short to long range. Simulations are conducted on a fully 3-D user-generated dust-grain with amorphous surface characteristics. The chemical network has also been extended from the simple water system previously published, and now includes 33 chemical species and 55 reactions. This allows the major interstellar ice components to be simulated, such as water, methane, ammonia and methanol, as well as a small selection of more complex molecules, including methyl formate (HCOOCH3).The new model results indicate that the porosity of interstellar ices are dependent on multiple variables, including gas density, the dust temperature, and the relative accretion rates of key gas-phase species. The results presented also have implications for the formation of complex organic molecules on dust-grain surfaces at very low temperatures.

Self-learning kinetic Monte Carlo simulations of Al diffusion in Mg

International Nuclear Information System (INIS)

Nandipati, Giridhar; Govind, Niranjan; Andersen, Amity; Rohatgi, Aashish

2016-01-01

Vacancy-mediated diffusion of an Al atom in the pure Mg matrix is studied using the atomistic, on-lattice self-learning kinetic Monte Carlo (SLKMC) method. Activation barriers for vacancy-Mg and vacancy-Al atom exchange processes are calculated on the fly using the climbing image nudged-elastic-band method and binary Mg–Al modified embedded-atom method interatomic potential. Diffusivities of an Al atom obtained from SLKMC simulations show the same behavior as observed in experimental and theoretical studies available in the literature; that is, an Al atom diffuses faster within the basal plane than along the c-axis. Although the effective activation barriers for an Al atom diffusion from SLKMC simulations are close to experimental and theoretical values, the effective prefactors are lower than those obtained from experiments. We present all the possible vacancy-Mg and vacancy-Al atom exchange processes and their activation barriers identified in SLKMC simulations. A simple mapping scheme to map an HCP lattice onto a simple cubic lattice is described, which enables simulation of the HCP lattice using the on-lattice framework. We also present the pattern recognition scheme which is used in SLKMC simulations to identify the local Al atom configuration around a vacancy. (paper)

Numerical simulations of subcritical reactor kinetics in thermal hydraulic transient phases

Energy Technology Data Exchange (ETDEWEB)

Yoo, J; Park, W S [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1999-12-31

A subcritical reactor driven by a linear proton accelerator has been considered as a nuclear waste incinerator at Korea Atomic Energy Research Institute (KAERI). Since the multiplication factor of a subcritical reactor is less than unity, to compensate exponentially decreasing fission neutrons, external neutrons form spallation reactions are essentially required for operating the reactor in its steady state. Furthermore, the profile of accelerator beam currents is very important in controlling a subcritical reactor, because the reactor power varies in accordance to the profile of external neutrons. We have developed a code system to find numerical solutions of reactor kinetics equations, which are the simplest dynamic model for controlling reactors. In a due course of our previous numerical study of point kinetics equations for critical reactors, however, we learned that the same code system can be used in studying dynamic behavior of the subcritical reactor. Our major motivation of this paper is to investigate responses of subcritical reactors for small changes in thermal hydraulic parameters. Building a thermal hydraulic model for the subcritical reactor dynamics, we performed numerical simulations for dynamic responses of the reactor based on point kinetics equations with a source term. Linearizing a set of coupled differential equations for reactor responses, we focus our research interest on dynamic responses of the reactor to variations of the thermal hydraulic parameters in transient phases. 5 refs., 8 figs. (Author)

Numerical simulations of subcritical reactor kinetics in thermal hydraulic transient phases

Energy Technology Data Exchange (ETDEWEB)

Yoo, J.; Park, W. S. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1998-12-31

A subcritical reactor driven by a linear proton accelerator has been considered as a nuclear waste incinerator at Korea Atomic Energy Research Institute (KAERI). Since the multiplication factor of a subcritical reactor is less than unity, to compensate exponentially decreasing fission neutrons, external neutrons form spallation reactions are essentially required for operating the reactor in its steady state. Furthermore, the profile of accelerator beam currents is very important in controlling a subcritical reactor, because the reactor power varies in accordance to the profile of external neutrons. We have developed a code system to find numerical solutions of reactor kinetics equations, which are the simplest dynamic model for controlling reactors. In a due course of our previous numerical study of point kinetics equations for critical reactors, however, we learned that the same code system can be used in studying dynamic behavior of the subcritical reactor. Our major motivation of this paper is to investigate responses of subcritical reactors for small changes in thermal hydraulic parameters. Building a thermal hydraulic model for the subcritical reactor dynamics, we performed numerical simulations for dynamic responses of the reactor based on point kinetics equations with a source term. Linearizing a set of coupled differential equations for reactor responses, we focus our research interest on dynamic responses of the reactor to variations of the thermal hydraulic parameters in transient phases. 5 refs., 8 figs. (Author)

COED Transactions, Vol. X, No. 10, October 1978. Simulation of a Sampled-Data System on a Hybrid Computer.

Science.gov (United States)

Mitchell, Eugene E., Ed.

The simulation of a sampled-data system is described that uses a full parallel hybrid computer. The sampled data system simulated illustrates the proportional-integral-derivative (PID) discrete control of a continuous second-order process representing a stirred-tank. The stirred-tank is simulated using continuous analog components, while PID…

Development of a hydro kinetic river turbine with simulation and operational measurement results in comparison

International Nuclear Information System (INIS)

Ruopp, A; Ruprecht, A; Riedelbauch, S; Arnaud, G; Hamad, I

2014-01-01

The development of a hydro-kinetic prototype was shown including the compound structure, guide vanes, runner blades and a draft tube section with a steeply sloping, short spoiler. The design process of the hydrodynamic layout was split into three major steps. First the compound and the draft tube section was designed and the best operating point was identified using porous media as replacement for the guide vane and runner section (step one). The best operating point and the volume flux as well as the pressure drop was identified and used for the design of the guide vane section and the runner section. Both were designed and simulated independently (step two). In step three, all parts were merged in stationary simulation runs detecting peak power and operational bandwidth. In addition, the full scale demonstrator was installed in August 2010 and measured in the St. Lawrence River in Quebec supporting the average inflow velocity using ADCP (Acoustic Doppler Current Profiler) and the generator power output over the variable rotational speed. Simulation data and measurements are in good agreement. Thus, the presented approach is a suitable way in designing a hydro kinetic turbine

Velocity trajectory optimization in Hybrid Electric trucks

NARCIS (Netherlands)

Keulen, T. van; Jager, B. de; Foster, D.L.; Steinbuch, M.

2010-01-01

Hybrid Electric Vehicles (HEVs) enable fuel savings by re-using kinetic and potential energy that was recovered and stored in a battery during braking or driving down hill. Besides, the vehicle itself can be seen as a storage device, where kinetic energy can be stored and retrieved by changing the

Study of photo-oxidative reactivity of sunscreening agents based on photo-oxidation of uric acid by kinetic Monte Carlo simulation

International Nuclear Information System (INIS)

Moradmand Jalali, Hamed; Bashiri, Hadis; Rasa, Hossein

2015-01-01

In the present study, the mechanism of free radical production by light-reflective agents in sunscreens (TiO 2 , ZnO and ZrO 2 ) was obtained by applying kinetic Monte Carlo simulation. The values of the rate constants for each step of the suggested mechanism have been obtained by simulation. The effect of the initial concentration of mineral oxides and uric acid on the rate of uric acid photo-oxidation by irradiation of some sun care agents has been studied. The kinetic Monte Carlo simulation results agree qualitatively with the existing experimental data for the production of free radicals by sun care agents. - Highlights: • The mechanism and kinetics of uric acid photo-oxidation by irradiation of sun care agents has been obtained by simulation. • The mechanism has been used for free radical production of TiO 2 (rutile and anatase), ZnO and ZrO 2 . • The ratios of photo-activity of ZnO to anastase, rutile and ZrO have been obtained. • By doubling the initial concentrations of mineral oxide, the rate of reaction was doubled. • The optimum ratio of initial concentration of mineral oxides to uric acid has been obtained

FY2014 FES (Fusion Energy Sciences) Theory & Simulation Performance Target, Final Report

Energy Technology Data Exchange (ETDEWEB)

Fu, Guoyong [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Budny, Robert [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Gorelenkov, Nikolai [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Poli, Francesca [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Chen, Yang [Univ. of Colorado, Boulder, CO (United States); McClenaghan, Joseph [Univ. of California, Irvine, CA (United States); Lin, Zhihong [Univ. of California, Irvine, CA (United States); Spong, Don [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bass, Eric [Univ. of California, San Diego, CA (United States); Waltz, Ron [General Atomics, San Diego, CA (United States)

2014-10-14

We report here the work done for the FY14 OFES Theory Performance Target as given below: "Understanding alpha particle confinement in ITER, the world's first burning plasma experiment, is a key priority for the fusion program. In FY 2014, determine linear instability trends and thresholds of energetic particle-driven shear Alfven eigenmodes in ITER for a range of parameters and profiles using a set of complementary simulation models (gyrokinetic, hybrid, and gyrofluid). Carry out initial nonlinear simulations to assess the effects of the unstable modes on energetic particle transport". In the past year (FY14), a systematic study of the alpha-driven Alfven modes in ITER has been carried out jointly by researchers from six institutions involving seven codes including the transport simulation code TRANSP (R. Budny and F. Poli, PPPL), three gyrokinetic codes: GEM (Y. Chen, Univ. of Colorado), GTC (J. McClenaghan, Z. Lin, UCI), and GYRO (E. Bass, R. Waltz, UCSD/GA), the hybrid code M3D-K (G.Y. Fu, PPPL), the gyro-fluid code TAEFL (D. Spong, ORNL), and the linear kinetic stability code NOVA-K (N. Gorelenkov, PPPL). A range of ITER parameters and profiles are specified by TRANSP simulation of a hybrid scenario case and a steady-state scenario case. Based on the specified ITER equilibria linear stability calculations are done to determine the stability boundary of alpha-driven high-n TAEs using the five initial value codes (GEM, GTC, GYRO, M3D-K, and TAEFL) and the kinetic stability code (NOVA-K). Both the effects of alpha particles and beam ions have been considered. Finally, the effects of the unstable modes on energetic particle transport have been explored using GEM and M3D-K.

Numerical methodologies for investigation of moderate-velocity flow using a hybrid computational fluid dynamics - molecular dynamics simulation approach

International Nuclear Information System (INIS)

Ko, Soon Heum; Kim, Na Yong; Nikitopoulos, Dimitris E.; Moldovan, Dorel; Jha, Shantenu

2014-01-01

Numerical approaches are presented to minimize the statistical errors inherently present due to finite sampling and the presence of thermal fluctuations in the molecular region of a hybrid computational fluid dynamics (CFD) - molecular dynamics (MD) flow solution. Near the fluid-solid interface the hybrid CFD-MD simulation approach provides a more accurate solution, especially in the presence of significant molecular-level phenomena, than the traditional continuum-based simulation techniques. It also involves less computational cost than the pure particle-based MD. Despite these advantages the hybrid CFD-MD methodology has been applied mostly in flow studies at high velocities, mainly because of the higher statistical errors associated with low velocities. As an alternative to the costly increase of the size of the MD region to decrease statistical errors, we investigate a few numerical approaches that reduce sampling noise of the solution at moderate-velocities. These methods are based on sampling of multiple simulation replicas and linear regression of multiple spatial/temporal samples. We discuss the advantages and disadvantages of each technique in the perspective of solution accuracy and computational cost.

Research on Hybrid Vehicle Drivetrain

Science.gov (United States)

Xie, Zhongzhi

Hybrid cars as a solution to energy saving, emission reduction measures, have received widespread attention. Motor drive system as an important part of the hybrid vehicles as an important object of study. Based on the hybrid electric vehicle powertrain control system for permanent magnet synchronous motor as the object of study. Can be applied to hybrid car compares the characteristics of traction motors, chose permanent magnet synchronous Motors as drive motors for hybrid vehicles. Building applications in hybrid cars in MATLAB/Simulink simulation model of permanent-magnet synchronous motor speed control system and analysis of simulation results.

Molecular Dynamics Simulations and Kinetic Measurements to Estimate and Predict Protein-Ligand Residence Times.

Science.gov (United States)

Mollica, Luca; Theret, Isabelle; Antoine, Mathias; Perron-Sierra, Françoise; Charton, Yves; Fourquez, Jean-Marie; Wierzbicki, Michel; Boutin, Jean A; Ferry, Gilles; Decherchi, Sergio; Bottegoni, Giovanni; Ducrot, Pierre; Cavalli, Andrea

2016-08-11

Ligand-target residence time is emerging as a key drug discovery parameter because it can reliably predict drug efficacy in vivo. Experimental approaches to binding and unbinding kinetics are nowadays available, but we still lack reliable computational tools for predicting kinetics and residence time. Most attempts have been based on brute-force molecular dynamics (MD) simulations, which are CPU-demanding and not yet particularly accurate. We recently reported a new scaled-MD-based protocol, which showed potential for residence time prediction in drug discovery. Here, we further challenged our procedure's predictive ability by applying our methodology to a series of glucokinase activators that could be useful for treating type 2 diabetes mellitus. We combined scaled MD with experimental kinetics measurements and X-ray crystallography, promptly checking the protocol's reliability by directly comparing computational predictions and experimental measures. The good agreement highlights the potential of our scaled-MD-based approach as an innovative method for computationally estimating and predicting drug residence times.

Nonlinear simulation of tearing mode and m=1 kink mode based on kinetic RMHD model

International Nuclear Information System (INIS)

Yagi, M.; Yoshida, S.; Itoh, S.-I.; Naitou, H.; Nagahara, H.; Leboeuf, J.-N.; Itoh, K.; Matsumoto, T.; Tokuda, S.; Azumi, M.

2005-01-01

In this paper, we investigate dynamics of sawtooth oscillation and neoclassical tearing modes based on kinetic RMHD model, putting an emphasis on interaction with microscopic and transport processes. The simulation results show that the assumption in the conventional theory of neoclassical tearing mode is rather rude. (author)

Development of a Continuum Damage Mechanics Material Model of a Graphite-Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing

Science.gov (United States)

Jackson, Karen E.; Fasanella, Edwin L.; Littell, Justin D.

2017-01-01

This paper describes the development of input properties for a continuum damage mechanics based material model, Mat 58, within LS-DYNA(Registered Trademark) to simulate the response of a graphite-Kevlar(Registered Trademark) hybrid plain weave fabric. A limited set of material characterization tests were performed on the hybrid graphite-Kevlar(Registered Trademark) fabric. Simple finite element models were executed in LS-DYNA(Registered Trademark) to simulate the material characterization tests and to verify the Mat 58 material model. Once verified, the Mat 58 model was used in finite element models of two composite energy absorbers: a conical-shaped design, designated the "conusoid," fabricated of four layers of hybrid graphite-Kevlar(Registered Trademark) fabric; and, a sinusoidal-shaped foam sandwich design, designated the "sinusoid," fabricated of the same hybrid fabric face sheets with a foam core. Dynamic crush tests were performed on components of the two energy absorbers, which were designed to limit average vertical accelerations to 25- to 40-g, to minimize peak crush loads, and to generate relatively long crush stroke values under dynamic loading conditions. Finite element models of the two energy absorbers utilized the Mat 58 model that had been verified through material characterization testing. Excellent predictions of the dynamic crushing response were obtained.

Analysis of Hybrid-Integrated High-Speed Electro-Absorption Modulated Lasers Based on EM/Circuit Co-simulation

DEFF Research Database (Denmark)

Johansen, Tom Keinicke; Krozer, Viktor; Kazmierski, C.

2009-01-01

An improved electromagnetic simulation (EM) based approach has been developed for optimization of the electrical to optical (E/O) transmission properties of integrated electro-absorption modulated lasers (EMLs) aiming at 100 Gbit/s Ethernet applications. Our approach allows for an accurate analysis...... of the EML performance in a hybrid microstrip assembly. The established EM-based approach provides a design methodology for the future hybrid integration of the EML with its driving electronics....

Study of photo-oxidative reactivity of sunscreening agents based on photo-oxidation of uric acid by kinetic Monte Carlo simulation.

Science.gov (United States)

Moradmand Jalali, Hamed; Bashiri, Hadis; Rasa, Hossein

2015-05-01

In the present study, the mechanism of free radical production by light-reflective agents in sunscreens (TiO2, ZnO and ZrO2) was obtained by applying kinetic Monte Carlo simulation. The values of the rate constants for each step of the suggested mechanism have been obtained by simulation. The effect of the initial concentration of mineral oxides and uric acid on the rate of uric acid photo-oxidation by irradiation of some sun care agents has been studied. The kinetic Monte Carlo simulation results agree qualitatively with the existing experimental data for the production of free radicals by sun care agents. Copyright © 2015 Elsevier B.V. All rights reserved.

Design and simulation of a hybrid ventilation system with earth-air heat exchanger

Energy Technology Data Exchange (ETDEWEB)

Athienitis, A.K.; Zhao, M. [Concordia Univ., Centre for Building Studies, Montreal, PQ (Canada). Dept. of Building, Civil and Environmental Engineering; Roy, M. [Martin Roy and Associes Group Conseil Inc., Montreal, PQ (Canada)

2005-07-01

A simulation study was conducted during the design phase of a new circus building in Montreal which includes a hybrid ventilation system through which fresh air is supplied from an earth-air heat exchanger (EAHE). The EAHE has the potential to satisfy the cooling needs of the building and can also be used to preheat fresh air, thereby satisfying one-third or more of the building's heating needs. Another feature of the building is that it uses displacement ventilation by which the air is supplied at low velocities through large diffusers behind the top level seats or under the seats. In this study, computational fluid dynamics (CFD) simulations were carried out to help size the supply and return units of the heating, ventilating and air conditioning (HVAC) system, as well as the exhaust chimney. The primary objective of the CFD simulation was to determine the maximum velocity and temperature in the seated area to ensure thermal comfort. CFD simulation predictions were found to be in good agreement with preliminary measurements taken in the building. In order to monitor the operation of the system over the next year, the underground ducts were equipped with temperature sensors at several depths into the soil. The energy efficiency of the hybrid HVAC system will be assessed and the velocity and temperature distribution in the theatre will be examined under various operating and energy load conditions. 8 refs., 6 figs.

A hybrid classical-quantum approach for ultra-scaled confined nanostructures : modeling and simulation*

Directory of Open Access Journals (Sweden)

Pietra Paola

2012-04-01

Full Text Available We propose a hybrid classical-quantum model to study the motion of electrons in ultra-scaled confined nanostructures. The transport of charged particles, considered as one dimensional, is described by a quantum effective mass model in the active zone coupled directly to a drift-diffusion problem in the rest of the device. We explain how this hybrid model takes into account the peculiarities due to the strong confinement and we present numerical simulations for a simplified carbon nanotube. Nous proposons un modèle hybride classique-quantique pour décrire le mouvement des électrons dans des nanostructures très fortement confinées. Le transport des particules, consideré unidimensionel, est décrit par un modèle quantique avec masse effective dans la zone active couplé à un problème de dérive-diffusion dans le reste du domaine. Nous expliquons comment ce modèle hybride prend en compte les spécificités de ce très fort confinement et nous présentons des résultats numériques pour un nanotube de carbone simplifié.

Hybrid Reynolds-Averaged/Large Eddy Simulation of the Flow in a Model SCRamjet Cavity Flameholder

Science.gov (United States)

Baurle, R. A.

2016-01-01

Steady-state and scale-resolving simulations have been performed for flow in and around a model scramjet combustor flameholder. Experimental data available for this configuration include velocity statistics obtained from particle image velocimetry. Several turbulence models were used for the steady-state Reynolds-averaged simulations which included both linear and non-linear eddy viscosity models. The scale-resolving simulations used a hybrid Reynolds-averaged/large eddy simulation strategy that is designed to be a large eddy simulation everywhere except in the inner portion (log layer and below) of the boundary layer. Hence, this formulation can be regarded as a wall-modeled large eddy simulation. This e ort was undertaken to not only assess the performance of the hybrid Reynolds-averaged / large eddy simulation modeling approach in a flowfield of interest to the scramjet research community, but to also begin to understand how this capability can best be used to augment standard Reynolds-averaged simulations. The numerical errors were quantified for the steady-state simulations, and at least qualitatively assessed for the scale-resolving simulations prior to making any claims of predictive accuracy relative to the measurements. The steady-state Reynolds-averaged results displayed a high degree of variability when comparing the flameholder fuel distributions obtained from each turbulence model. This prompted the consideration of applying the higher-fidelity scale-resolving simulations as a surrogate "truth" model to calibrate the Reynolds-averaged closures in a non-reacting setting prior to their use for the combusting simulations. In general, the Reynolds-averaged velocity profile predictions at the lowest fueling level matched the particle imaging measurements almost as well as was observed for the non-reacting condition. However, the velocity field predictions proved to be more sensitive to the flameholder fueling rate than was indicated in the measurements.

Hybrid neural network bushing model for vehicle dynamics simulation

International Nuclear Information System (INIS)

Sohn, Jeong Hyun; Lee, Seung Kyu; Yoo, Wan Suk

2008-01-01

Although the linear model was widely used for the bushing model in vehicle suspension systems, it could not express the nonlinear characteristics of bushing in terms of the amplitude and the frequency. An artificial neural network model was suggested to consider the hysteretic responses of bushings. This model, however, often diverges due to the uncertainties of the neural network under the unexpected excitation inputs. In this paper, a hybrid neural network bushing model combining linear and neural network is suggested. A linear model was employed to represent linear stiffness and damping effects, and the artificial neural network algorithm was adopted to take into account the hysteretic responses. A rubber test was performed to capture bushing characteristics, where sine excitation with different frequencies and amplitudes is applied. Random test results were used to update the weighting factors of the neural network model. It is proven that the proposed model has more robust characteristics than a simple neural network model under step excitation input. A full car simulation was carried out to verify the proposed bushing models. It was shown that the hybrid model results are almost identical to the linear model under several maneuvers

Real-time hybrid simulation in a shaking table configuration for parametric studies of high-voltage equipment and IEEE693 development

Energy Technology Data Exchange (ETDEWEB)

Günay, Selim [nees@berkeley, UC Berkeley, Richmond, CA (United States); Mosalam, Khalid [Department of Civil and Environmental Engineering, UC Berkeley, Berkeley, CA (United States); Takhirov, Shakhzod, E-mail: takhirov@berkeley.edu [nees@berkeley, UC Berkeley, Richmond, CA (United States)

2015-12-15

Highlights: • A real-time hybrid simulation (RTHS) system for high-voltage (HV) equipment is developed. • The system is a cost effective and timely efficient approach for seismic testing and evaluation. • The coupled system of equipment and modeled support structure is tested/analyzed in real time. • The system is validated by comparing the RTHS test results with the shaking table results. • The effect of support structure on the equipment response is analyzed in a parametric study. - Abstract: This paper presents extensive discussion on seismic qualification of substation equipment in conventional shake table tests and its comparison to real-time hybrid simulation (RTHS). The hybrid simulation technique is based on a sub-structuring idea where a portion of a test specimen with well-predicted performance can be replaced by its finite element model. The rest of the test specimen is experimentally studied as part of the coupled system, where the test object and the mathematical model are interacting with each other in real time. The real-time hybrid simulation technique has a strong potential of complementing and in some cases replacing seismic qualification testing. In addition to that, it has a strong potential as a comprehensive and reliable tool for IEEE693 development, where code provisions can be developed from parametric hybrid simulation studies of actual pieces of substation equipment which are otherwise difficult to model. As a typical example of successful application of hybrid simulation, a comprehensive study related to RTHS of electrical disconnect switches is discussed in the paper. First, the RTHS system developed for this purpose is described and the results of a RTHS test are compared with a benchmark conventional shaking table test as a validation of the system. Second, effect of the support structures of the disconnect switches on the global and local responses of different insulator types is evaluated using the results of a series of

Real-time hybrid simulation in a shaking table configuration for parametric studies of high-voltage equipment and IEEE693 development

International Nuclear Information System (INIS)

Günay, Selim; Mosalam, Khalid; Takhirov, Shakhzod

2015-01-01

Highlights: • A real-time hybrid simulation (RTHS) system for high-voltage (HV) equipment is developed. • The system is a cost effective and timely efficient approach for seismic testing and evaluation. • The coupled system of equipment and modeled support structure is tested/analyzed in real time. • The system is validated by comparing the RTHS test results with the shaking table results. • The effect of support structure on the equipment response is analyzed in a parametric study. - Abstract: This paper presents extensive discussion on seismic qualification of substation equipment in conventional shake table tests and its comparison to real-time hybrid simulation (RTHS). The hybrid simulation technique is based on a sub-structuring idea where a portion of a test specimen with well-predicted performance can be replaced by its finite element model. The rest of the test specimen is experimentally studied as part of the coupled system, where the test object and the mathematical model are interacting with each other in real time. The real-time hybrid simulation technique has a strong potential of complementing and in some cases replacing seismic qualification testing. In addition to that, it has a strong potential as a comprehensive and reliable tool for IEEE693 development, where code provisions can be developed from parametric hybrid simulation studies of actual pieces of substation equipment which are otherwise difficult to model. As a typical example of successful application of hybrid simulation, a comprehensive study related to RTHS of electrical disconnect switches is discussed in the paper. First, the RTHS system developed for this purpose is described and the results of a RTHS test are compared with a benchmark conventional shaking table test as a validation of the system. Second, effect of the support structures of the disconnect switches on the global and local responses of different insulator types is evaluated using the results of a series of

Extended pattern recognition scheme for self-learning kinetic Monte Carlo simulations

International Nuclear Information System (INIS)

Shah, Syed Islamuddin; Nandipati, Giridhar; Kara, Abdelkader; Rahman, Talat S

2012-01-01

We report the development of a pattern recognition scheme that takes into account both fcc and hcp adsorption sites in performing self-learning kinetic Monte Carlo (SLKMC-II) simulations on the fcc(111) surface. In this scheme, the local environment of every under-coordinated atom in an island is uniquely identified by grouping fcc sites, hcp sites and top-layer substrate atoms around it into hexagonal rings. As the simulation progresses, all possible processes, including those such as shearing, reptation and concerted gliding, which may involve fcc-fcc, hcp-hcp and fcc-hcp moves are automatically found, and their energetics calculated on the fly. In this article we present the results of applying this new pattern recognition scheme to the self-diffusion of 9-atom islands (M 9 ) on M(111), where M = Cu, Ag or Ni.

Adaptive multi-rate interface: development and experimental verification for real-time hybrid simulation

DEFF Research Database (Denmark)

Maghareh, Amin; Waldbjørn, Jacob Paamand; Dyke, Shirley J.

2016-01-01

Real-time hybrid simulation (RTHS) is a powerful cyber-physical technique that is a relatively cost-effective method to perform global/local system evaluation of structural systems. A major factor that determines the ability of an RTHS to represent true system-level behavior is the fidelity...... of the numerical substructure. While the use of higher-order models increases fidelity of the simulation, it also increases the demand for computational resources. Because RTHS is executed at real-time, in a conventional RTHS configuration, this increase in computational resources may limit the achievable sampling...

Microwave imaging for conducting scatterers by hybrid particle swarm optimization with simulated annealing

International Nuclear Information System (INIS)

Mhamdi, B.; Grayaa, K.; Aguili, T.

2011-01-01

In this paper, a microwave imaging technique for reconstructing the shape of two-dimensional perfectly conducting scatterers by means of a stochastic optimization approach is investigated. Based on the boundary condition and the measured scattered field derived by transverse magnetic illuminations, a set of nonlinear integral equations is obtained and the imaging problem is reformulated in to an optimization problem. A hybrid approximation algorithm, called PSO-SA, is developed in this work to solve the scattering inverse problem. In the hybrid algorithm, particle swarm optimization (PSO) combines global search and local search for finding the optimal results assignment with reasonable time and simulated annealing (SA) uses certain probability to avoid being trapped in a local optimum. The hybrid approach elegantly combines the exploration ability of PSO with the exploitation ability of SA. Reconstruction results are compared with exact shapes of some conducting cylinders; and good agreements with the original shapes are observed.

Kinetic Monte Carlo simulation of nanoparticle film formation via nanocolloid drying

Science.gov (United States)

Kameya, Yuki

2017-06-01

A kinetic Monte Carlo simulation of nanoparticle film formation via nanocolloid drying is presented. The proposed two-dimensional model addresses the dynamics of nanoparticles in the vertical plane of a drying nanocolloid film. The gas-liquid interface movement due to solvent evaporation was controlled by a time-dependent chemical potential, and the resultant particle dynamics including Brownian diffusion and aggregate growth were calculated. Simulations were performed at various Peclet numbers defined based on the rate ratio of solvent evaporation and nanoparticle diffusion. At high Peclet numbers, nanoparticles accumulated at the top layer of the liquid film and eventually formed a skin layer, causing the formation of a particulate film with a densely packed structure. At low Peclet numbers, enhanced particle diffusion led to significant particle aggregation in the bulk colloid, and the resulting film structure became highly porous. The simulated results showed some typical characteristics of a drying nanocolloid that had been reported experimentally. Finally, the potential of the model as well as the remaining challenges are discussed.

Kinetic plasma simulation of ion beam extraction from an ECR ion source

International Nuclear Information System (INIS)

Elliott, S.M.; White, E.K.; Simkin, J.

2012-01-01

Designing optimized ECR (electron cyclotron resonance) ion beam sources can be streamlined by the accurate simulation of beam optical properties in order to predict ion extraction behavior. The complexity of these models, however, can make PIC-based simulations time-consuming. In this paper, we first describe a simple kinetic plasma finite element simulation of extraction of a proton beam from a permanent magnet hexapole ECR ion source. Second, we analyze the influence of secondary electrons generated by ion collisions in the residual gas on the space charge of a proton beam of a dual-solenoid ECR ion source. The finite element method (FEM) offers a fast modeling environment, allowing analysis of ion beam behavior under conditions of varying current density, electrode potential, and gas pressure. The new version of SCALA/TOSCA v14 permits the making of simulations in tens of minutes to a few hours on standard computer platforms without the need of particle-in-cell methods. The paper is followed by the slides of the presentation. (authors)

Numerical nodal simulation of the axial power distribution within nuclear reactors using a kinetics diffusion model. I

International Nuclear Information System (INIS)

Barros, R.C. de.

1992-05-01

Presented here is a new numerical nodal method for the simulation of the axial power distribution within nuclear reactors using the one-dimensional one speed kinetics diffusion model with one group of delayed neutron precursors. Our method is based on a spectral analysis of the nodal kinetics equations. These equations are obtained by integrating the original kinetics equations separately over a time step and over a spatial node, and then considering flat approximations for the forward difference terms. These flat approximations are the only approximations that are considered in the method. As a result, the spectral nodal method for space - time reactor kinetics generates numerical solutions for space independent problems or for time independent problems that are completely free from truncation errors. We show numerical results to illustrate the method's accuracy for coarse mesh calculations. (author)

Simulations of the Fuel Economy and Emissions of Hybrid Transit Buses over Planned Local Routes

Energy Technology Data Exchange (ETDEWEB)

Gao, Zhiming [ORNL; LaClair, Tim J [ORNL; Daw, C Stuart [ORNL; Smith, David E [ORNL; Franzese, Oscar [ORNL

2014-01-01

We present simulated fuel economy and emissions city transit buses powered by conventional diesel engines and diesel-hybrid electric powertrains of varying size. Six representative city drive cycles were included in the study. In addition, we included previously published aftertreatment device models for control of CO, HC, NOx, and particulate matter (PM) emissions. Our results reveal that bus hybridization can significantly enhance fuel economy by reducing engine idling time, reducing demands for accessory loads, exploiting regenerative braking, and shifting engine operation to speeds and loads with higher fuel efficiency. Increased hybridization also tends to monotonically reduce engine-out emissions, but trends in the tailpipe (post-aftertreatment) emissions involve more complex interactions that significantly depend on motor size and drive cycle details.

Sensitivity analysis of the titan hybrid deterministic transport code for SPECT simulation

International Nuclear Information System (INIS)

Royston, Katherine K.; Haghighat, Alireza

2011-01-01

Single photon emission computed tomography (SPECT) has been traditionally simulated using Monte Carlo methods. The TITAN code is a hybrid deterministic transport code that has recently been applied to the simulation of a SPECT myocardial perfusion study. For modeling SPECT, the TITAN code uses a discrete ordinates method in the phantom region and a combined simplified ray-tracing algorithm with a fictitious angular quadrature technique to simulate the collimator and generate projection images. In this paper, we compare the results of an experiment with a physical phantom with predictions from the MCNP5 and TITAN codes. While the results of the two codes are in good agreement, they differ from the experimental data by ∼ 21%. In order to understand these large differences, we conduct a sensitivity study by examining the effect of different parameters including heart size, collimator position, collimator simulation parameter, and number of energy groups. (author)

Optimal design of supply chain network under uncertainty environment using hybrid analytical and simulation modeling approach

Science.gov (United States)

Chiadamrong, N.; Piyathanavong, V.

2017-12-01

Models that aim to optimize the design of supply chain networks have gained more interest in the supply chain literature. Mixed-integer linear programming and discrete-event simulation are widely used for such an optimization problem. We present a hybrid approach to support decisions for supply chain network design using a combination of analytical and discrete-event simulation models. The proposed approach is based on iterative procedures until the difference between subsequent solutions satisfies the pre-determined termination criteria. The effectiveness of proposed approach is illustrated by an example, which shows closer to optimal results with much faster solving time than the results obtained from the conventional simulation-based optimization model. The efficacy of this proposed hybrid approach is promising and can be applied as a powerful tool in designing a real supply chain network. It also provides the possibility to model and solve more realistic problems, which incorporate dynamism and uncertainty.

Hybrid RANS/LES method for wind flow over complex terrain

DEFF Research Database (Denmark)

Bechmann, Andreas; Sørensen, Niels N.

2010-01-01

for flows at high Reynolds numbers. To reduce the computational cost of traditional LES, a hybrid method is proposed in which the near-wall eddies are modelled in a Reynolds-averaged sense. Close to walls, the flow is treated with the Reynolds-averaged Navier-Stokes (RANS) equations (unsteady RANS...... rough walls. Previous attempts of combining RANS and LES has resulted in unphysical transition regions between the two layers, but the present work improves this region by using a stochastic backscatter model. To demonstrate the ability of the proposed hybrid method, simulations are presented for wind...... the turbulent kinetic energy, whereas the new method captures the high turbulence levels well but underestimates the mean velocity. The presented results are for a relative mild configuration of complex terrain, but the proposed method can also be used for highly complex terrain where the benefits of the new...

Simulation methods with extended stability for stiff biochemical Kinetics

Directory of Open Access Journals (Sweden)

Rué Pau

2010-08-01

Full Text Available Abstract Background With increasing computer power, simulating the dynamics of complex systems in chemistry and biology is becoming increasingly routine. The modelling of individual reactions in (biochemical systems involves a large number of random events that can be simulated by the stochastic simulation algorithm (SSA. The key quantity is the step size, or waiting time, τ, whose value inversely depends on the size of the propensities of the different channel reactions and which needs to be re-evaluated after every firing event. Such a discrete event simulation may be extremely expensive, in particular for stiff systems where τ can be very short due to the fast kinetics of some of the channel reactions. Several alternative methods have been put forward to increase the integration step size. The so-called τ-leap approach takes a larger step size by allowing all the reactions to fire, from a Poisson or Binomial distribution, within that step. Although the expected value for the different species in the reactive system is maintained with respect to more precise methods, the variance at steady state can suffer from large errors as τ grows. Results In this paper we extend Poisson τ-leap methods to a general class of Runge-Kutta (RK τ-leap methods. We show that with the proper selection of the coefficients, the variance of the extended τ-leap can be well-behaved, leading to significantly larger step sizes. Conclusions The benefit of adapting the extended method to the use of RK frameworks is clear in terms of speed of calculation, as the number of evaluations of the Poisson distribution is still one set per time step, as in the original τ-leap method. The approach paves the way to explore new multiscale methods to simulate (biochemical systems.

Design, simulation, and prototype production of a through the road parallel hybrid electric motorcycle

International Nuclear Information System (INIS)

Asaei, Behzad; Habibidoost, Mahdi

2013-01-01

Highlights: • Design, simulation, and manufacturing of a hybrid electric motorcycle are explained. • The electric machine is mounted in the front wheel hub of an ordinary motorcycle. • Two different energy control strategy are implemented. • The simulation results show that the motorcycle performance is improved. • The acceleration is improved and the fuel consumption and pollutions are decreased. - Abstract: In this paper, design, simulation, and conversion of a normal motorcycle to a Hybrid Electric Motorcycle (HEM) is described. At first, a simple model designed and simulated using ADVISOR2002. Then, the controller schematic and its optimized control strategy are described. A 125 cc ICE motorcycle is selected and converted into a HEM. A brushless DC (BLDC) motor assembled in the front wheel and a normal internal combustion engine in the rear wheel propel the motorcycle. The nominal powers are 6.6 kW and 500 W for the ICE and BLDC respectively. The original motorcycle has a Continuous Variable Transmission (CVT) that is the best choice for a HEM power transmission because it can operate in the automatic handling mode and has high efficiency. Moreover, by using the CVT, the ICE can be started while motorcycle is running. Finally, three operating modes of HEM, two implemented energy control strategies, and HEM engine control system by servomotors, and LCD display are explained

Seismic performance evaluation of an MR elastomer-based smart base isolation system using real-time hybrid simulation

International Nuclear Information System (INIS)

Eem, S H; Jung, H J; Koo, J H

2013-01-01

Recently, magneto-rheological (MR) elastomer-based base isolation systems have been actively studied as alternative smart base isolation systems because MR elastomers are capable of adjusting their modulus or stiffness depending on the magnitude of the applied magnetic field. By taking advantage of the MR elastomers’ stiffness-tuning ability, MR elastomer-based smart base isolation systems strive to alleviate limitations of existing smart base isolation systems as well as passive-type base isolators. Until now, research on MR elastomer-based base isolation systems primarily focused on characterization, design, and numerical evaluations of MR elastomer-based isolators, as well as experimental tests with simple structure models. However, their applicability to large civil structures has not been properly studied yet because it is quite challenging to numerically emulate the complex behavior of MR elastomer-based isolators and to conduct experiments with large-size structures. To address these difficulties, this study employs the real-time hybrid simulation technique, which combines physical testing and computational modeling. The primary goal of the current hybrid simulation study is to evaluate seismic performances of an MR elastomer-based smart base isolation system, particularly its adaptability to distinctly different seismic excitations. In the hybrid simulation, a single-story building structure (non-physical, computational model) is coupled with a physical testing setup for a smart base isolation system with associated components (such as laminated MR elastomers and electromagnets) installed on a shaking table. A series of hybrid simulations is carried out under two seismic excitations having different dominant frequencies. The results show that the proposed smart base isolation system outperforms the passive base isolation system in reducing the responses of the structure for the excitations considered in this study. (paper)

A Hybrid Three Layer Architecture for Fire Agent Management in Rescue Simulation Environment

Directory of Open Access Journals (Sweden)

Alborz Geramifard

2005-06-01

Full Text Available This paper presents a new architecture called FAIS for implementing intelligent agents cooperating in a special Multi Agent environment, namely the RoboCup Rescue Simulation System. This is a layered architecture which is customized for solving fire extinguishing problem. Structural decision making algorithms are combined with heuristic ones in this model, so it's a hybrid architecture.

A hybrid FDTD-Rayleigh integral computational method for the simulation of the ultrasound measurement of proximal femur.

Science.gov (United States)

Cassereau, Didier; Nauleau, Pierre; Bendjoudi, Aniss; Minonzio, Jean-Gabriel; Laugier, Pascal; Bossy, Emmanuel; Grimal, Quentin

2014-07-01

The development of novel quantitative ultrasound (QUS) techniques to measure the hip is critically dependent on the possibility to simulate the ultrasound propagation. One specificity of hip QUS is that ultrasounds propagate through a large thickness of soft tissue, which can be modeled by a homogeneous fluid in a first approach. Finite difference time domain (FDTD) algorithms have been widely used to simulate QUS measurements but they are not adapted to simulate ultrasonic propagation over long distances in homogeneous media. In this paper, an hybrid numerical method is presented to simulate hip QUS measurements. A two-dimensional FDTD simulation in the vicinity of the bone is coupled to the semi-analytic calculation of the Rayleigh integral to compute the wave propagation between the probe and the bone. The method is used to simulate a setup dedicated to the measurement of circumferential guided waves in the cortical compartment of the femoral neck. The proposed approach is validated by comparison with a full FDTD simulation and with an experiment on a bone phantom. For a realistic QUS configuration, the computation time is estimated to be sixty times less with the hybrid method than with a full FDTD approach. Copyright © 2013 Elsevier B.V. All rights reserved.

Elbow helical axes of motion are not the same in physiologic and kinetic joint simulators.

Science.gov (United States)

Muriuki, Muturi G; Mohagheh-Motlagh, Amin; Smolinski, Patrick J; Miller, Mark Carl

2012-08-31

Physiologic and kinetic joint simulators have been widely used for investigations of joint mechanics. The two types of simulator differ in the way joint motion is achieved; through prescribed motions and/or forces in kinetic joint simulators and by tendon loads in physiologic joint simulators. These two testing modalities have produced important insights, as in elucidating the importance of soft tissue structures to joint stability. However, the equivalence of the modalities has not been tested. This study sequentially tested five cadaveric elbows using both a physiologic simulator and a robot/6DOF system. Using position data from markers on the humerus and ulna, we calculated and compared the helical axes of motion of the specimens as the elbows were flexed from full extension. Six step size increments were used in the helical axis calculation. Marker position data at each test's full extension and full flexion point were also used to calculate a datum (overall) helical axis. The angles between the datum axis and step-wise movements were computed and stored. Increasing step size monotonically decreased the variability and the average conical angle encompassing the helical axes; a repeated measures ANOVA using test type (robot or physiologic simulator) and step size found that both type and step caused statistically significant differences (p<0.001). The large changes in helical axis angle observed for small changes in elbow flexion angle, especially in the robot tests, are a caveat for investigators using similar control algorithms. Controllers may need to include increased joint compliance and/or C(1) continuity to reduce variability. Copyright © 2012 Elsevier Ltd. All rights reserved.

Kinetic Monte Carlo simulations compared with continuum models and experimental properties of pattern formation during ion beam sputtering

International Nuclear Information System (INIS)

Chason, E; Chan, W L

2009-01-01

Kinetic Monte Carlo simulations model the evolution of surfaces during low energy ion bombardment using atomic level mechanisms of defect formation, recombination and surface diffusion. Because the individual kinetic processes are completely determined, the resulting morphological evolution can be directly compared with continuum models based on the same mechanisms. We present results of simulations based on a curvature-dependent sputtering mechanism and diffusion of mobile surface defects. The results are compared with a continuum linear instability model based on the same physical processes. The model predictions are found to be in good agreement with the simulations for predicting the early-stage morphological evolution and the dependence on processing parameters such as the flux and temperature. This confirms that the continuum model provides a reasonable approximation of the surface evolution from multiple interacting surface defects using this model of sputtering. However, comparison with experiments indicates that there are many features of the surface evolution that do not agree with the continuum model or simulations, suggesting that additional mechanisms are required to explain the observed behavior.

Hybrid simulation of shock formation for super-Alfvénic expansion of laser ablated debris through an ambient, magnetized plasma

International Nuclear Information System (INIS)

Clark, S. E.; Schaeffer, D. B.; Everson, E. T.; Bondarenko, A. S.; Constantin, C. G.; Niemann, C.; Winske, D.

2013-01-01

Two-dimensional hybrid simulations of perpendicular collisionless shocks are modeled after potential laboratory conditions that are attainable in the LArge Plasma Device (LAPD) at the University of California, Los Angeles Basic Plasma Science Facility. The kJ class 1053 nm Nd:Glass Raptor laser will be used to ablate carbon targets in the LAPD with on-target energies of 100-500 J. The ablated debris ions will expand into ambient, partially ionized hydrogen or helium. A parameter study is performed via hybrid simulation to determine possible conditions that could lead to shock formation in future LAPD experiments. Simulation results are presented along with a comparison to an analytical coupling parameter

Kinetic Monte Carlo simulation of growth of Ge quantum dot multilayers with amorphous matrix

Energy Technology Data Exchange (ETDEWEB)

Endres, Jan, E-mail: endres.jan@gmail.com; Holý, Václav; Daniš, Stanislav [Charles University, Faculty of Mathematics and Physics (Czech Republic); Buljan, Maja [Ruđer Bošković Institute (Croatia)

2017-04-15

Kinetic Monte Carlo method is used to simulate the growth of germanium quantum dot multilayers with amorphous matrix. We modified a model for self-assembled growth of quantum dots in crystalline matrix for the case of the amorphous one. The surface morphology given as hills above the buried dots is the main driving force for the ordering of the quantum dots. In the simulations, we observed a short-range self-ordering in the lateral direction. The ordering in lateral and vertical direction depends strongly on the surface morphology, mostly on the strength how the deposited material replicates previous surfaces.

Study of photo-oxidative reactivity of sunscreening agents based on photo-oxidation of uric acid by kinetic Monte Carlo simulation

Energy Technology Data Exchange (ETDEWEB)

Moradmand Jalali, Hamed; Bashiri, Hadis, E-mail: hbashiri@kashanu.ac.ir; Rasa, Hossein

2015-05-01

In the present study, the mechanism of free radical production by light-reflective agents in sunscreens (TiO{sub 2}, ZnO and ZrO{sub 2}) was obtained by applying kinetic Monte Carlo simulation. The values of the rate constants for each step of the suggested mechanism have been obtained by simulation. The effect of the initial concentration of mineral oxides and uric acid on the rate of uric acid photo-oxidation by irradiation of some sun care agents has been studied. The kinetic Monte Carlo simulation results agree qualitatively with the existing experimental data for the production of free radicals by sun care agents. - Highlights: • The mechanism and kinetics of uric acid photo-oxidation by irradiation of sun care agents has been obtained by simulation. • The mechanism has been used for free radical production of TiO{sub 2} (rutile and anatase), ZnO and ZrO{sub 2}. • The ratios of photo-activity of ZnO to anastase, rutile and ZrO have been obtained. • By doubling the initial concentrations of mineral oxide, the rate of reaction was doubled. • The optimum ratio of initial concentration of mineral oxides to uric acid has been obtained.

Simulation of styrene polymerization reactors: kinetic and thermodynamic modeling

Directory of Open Access Journals (Sweden)

A. S. Almeida

2008-06-01

Full Text Available A mathematical model for the free radical polymerization of styrene is developed to predict the steady-state and dynamic behavior of a continuous process. Special emphasis is given for the kinetic and thermodynamic models, where the most sensitive parameters were estimated using data from an industrial plant. The thermodynamic model is based on a cubic equation of state and a mixing rule applied to the low-pressure vapor-liquid equilibrium of polymeric solutions, suitable for modeling the auto-refrigerated polymerization reactors, which use the vaporization rate to remove the reaction heat from the exothermic reactions. The simulation results show the high predictive capability of the proposed model when compared with plant data for conversion, average molecular weights, polydispersity, melt flow index, and thermal properties for different polymer grades.

Liquid phase electro epitaxy growth kinetics of GaAs-A three-dimensional numerical simulation study

International Nuclear Information System (INIS)

Mouleeswaran, D.; Dhanasekaran, R.

2006-01-01

A three-dimensional numerical simulation study for the liquid phase electro epitaxial growth kinetic of GaAs is presented. The kinetic model is constructed considering (i) the diffusive and convective mass transport, (ii) the heat transfer due to thermoelectric effects such as Peltier effect, Joule effect and Thomson effect, (iii) the electric current distribution with electromigration and (iv) the fluid flow coupled with concentration and temperature fields. The simulations are performed for two configurations namely (i) epitaxial growth from the arsenic saturated gallium rich growth solution, i.e., limited solution model and (ii) epitaxial growth from the arsenic saturated gallium rich growth solution with polycrystalline GaAs feed. The governing equations of liquid phase electro epitaxy are solved numerically with appropriate initial and boundary conditions using the central difference method. Simulations are performed to determine the following, a concentration profiles of solute atoms (As) in the Ga-rich growth solution, shape of the substrate evolution, the growth rate of the GaAs epitaxial film, the contributions of Peltier effect and electromigration of solute atoms to the growth with various experimental growth conditions. The growth rate is found to increase with increasing growth temperature and applied current density. The results are discussed in detail

Simulating Study on Drive System Performance for Hybrid Electric Bus Based on ADVISOR

Directory of Open Access Journals (Sweden)

Wang Xingxing

2017-01-01

Full Text Available Hybrid electric bus has a number of advantages when compared with ordinary passenger cars, but in the dynamic matching and the vehicle performance are difficult to detect, thus limits its development process. In this paper, combined with the actual models, the hybrid electric bus module parameters were modified in the software of ADVISOR (Advanced Vehicle Simulator, main including: module of the vehicle, the wheel module, motor module, a battery module and engine module, three kinds of bus models for A, B and C were established, and the related performance that need to be analyzed was set up, such as acceleration, gradability, emissions and energy utilization and so on, in order to ensure the vehicle running in the same environment and convenient for comparison, a fixed vehicle driving cycles was chose, then the simulation results was analyzed, and the various performance was compared with the dynamic indicators and economic indicators which determined by referencing of traditional city bus standard and each other, and finally, the performance optimal model of B was chose out which can meet the demand, its related performance parameters of the simulation results are as follows: the best gradability is 26%, maximum speed is 72.7km/h, maximum acceleration is 1.7m/s2, 0~50km/h acceleration time is 9.5s and fuel consumption is 25L/km.

Efficient kinetic method for fluid simulation beyond the Navier-Stokes equation.

Science.gov (United States)

Zhang, Raoyang; Shan, Xiaowen; Chen, Hudong

2006-10-01

We present a further theoretical extension to the kinetic-theory-based formulation of the lattice Boltzmann method of Shan [J. Fluid Mech. 550, 413 (2006)]. In addition to the higher-order projection of the equilibrium distribution function and a sufficiently accurate Gauss-Hermite quadrature in the original formulation, a regularization procedure is introduced in this paper. This procedure ensures a consistent order of accuracy control over the nonequilibrium contributions in the Galerkin sense. Using this formulation, we construct a specific lattice Boltzmann model that accurately incorporates up to third-order hydrodynamic moments. Numerical evidence demonstrates that the extended model overcomes some major defects existing in conventionally known lattice Boltzmann models, so that fluid flows at finite Knudsen number Kn can be more quantitatively simulated. Results from force-driven Poiseuille flow simulations predict the Knudsen's minimum and the asymptotic behavior of flow flux at large Kn.

Time-domain finite-difference/finite-element hybrid simulations of radio frequency coils in magnetic resonance imaging

International Nuclear Information System (INIS)

Wang Shumin; Duyn, Jeff H

2008-01-01

A hybrid method that combines the finite-difference time-domain (FDTD) method and the finite-element time-domain (FETD) method is presented for simulating radio-frequency (RF) coils in magnetic resonance imaging. This method applies a high-fidelity FETD method to RF coils, while the human body is modeled with a low-cost FDTD method. Since the FDTD and the FETD methods are applied simultaneously, the dynamic interaction between RF coils and the human body is fully accounted for. In order to simplify the treatment of the highly irregular FDTD/FETD interface, composite elements are proposed. Two examples are provided to demonstrate the validity and effectiveness of the hybrid method in high-field receive-and-transmit coil design. This approach is also applicable to general bio-electromagnetic simulations

Effect of backbone chemistry on hybridization thermodynamics of oligonucleic acids: a coarse-grained molecular dynamics simulation study.

Science.gov (United States)

Ghobadi, Ahmadreza F; Jayaraman, Arthi

2016-02-28

In this paper we study how varying oligonucleic acid backbone chemistry affects the hybridization/melting thermodynamics of oligonucleic acids. We first describe the coarse-grained (CG) model with tunable parameters that we developed to enable the study of both naturally occurring oligonucleic acids, such as DNA, and their chemically-modified analogues, such as peptide nucleic acids (PNAs) and locked nucleic acids (LNAs). The DNA melting curves obtained using such a CG model and molecular dynamics simulations in an implicit solvent and with explicit ions match with the melting curves obtained using the empirical nearest-neighbor models. We use these CG simulations to then elucidate the effect of backbone flexibility, charge, and nucleobase spacing along the backbone on the melting curves, potential energy and conformational entropy change upon hybridization and base-pair hydrogen bond residence time. We find that increasing backbone flexibility decreases duplex thermal stability and melting temperature mainly due to increased conformational entropy loss upon hybridization. Removing charges from the backbone enhances duplex thermal stability due to the elimination of electrostatic repulsion and as a result a larger energetic gain upon hybridization. Lastly, increasing nucleobase spacing decreases duplex thermal stability due to decreasing stacking interactions that are important for duplex stability.

Hybrid quantum and classical methods for computing kinetic isotope effects of chemical reactions in solutions and in enzymes.

Science.gov (United States)

Gao, Jiali; Major, Dan T; Fan, Yao; Lin, Yen-Lin; Ma, Shuhua; Wong, Kin-Yiu

2008-01-01

A method for incorporating quantum mechanics into enzyme kinetics modeling is presented. Three aspects are emphasized: 1) combined quantum mechanical and molecular mechanical methods are used to represent the potential energy surface for modeling bond forming and breaking processes, 2) instantaneous normal mode analyses are used to incorporate quantum vibrational free energies to the classical potential of mean force, and 3) multidimensional tunneling methods are used to estimate quantum effects on the reaction coordinate motion. Centroid path integral simulations are described to make quantum corrections to the classical potential of mean force. In this method, the nuclear quantum vibrational and tunneling contributions are not separable. An integrated centroid path integral-free energy perturbation and umbrella sampling (PI-FEP/UM) method along with a bisection sampling procedure was summarized, which provides an accurate, easily convergent method for computing kinetic isotope effects for chemical reactions in solution and in enzymes. In the ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT), these three aspects of quantum mechanical effects can be individually treated, providing useful insights into the mechanism of enzymatic reactions. These methods are illustrated by applications to a model process in the gas phase, the decarboxylation reaction of N-methyl picolinate in water, and the proton abstraction and reprotonation process catalyzed by alanine racemase. These examples show that the incorporation of quantum mechanical effects is essential for enzyme kinetics simulations.

Hybrid simulation methods to perform grid integration studies for large scale offshore wind power connected through VSC-HVDC

NARCIS (Netherlands)

Meer, van der A.A.; Hendriks, R.L.; Gibescu, M.; Ferreira, J.A.; Kling, W.L.

2011-01-01

This paper deals with the inclusion of VSC-HVdc transmission schemes into stability-type simulations by hybrid methods. These methods allow selected parts of the network to be simulated in detail by including electro-magnetic behaviour of devices and network elements whereas the remainder of the

Simulation of hybrid vehicle propulsion with an advanced battery model

Energy Technology Data Exchange (ETDEWEB)

Nallabolu, S.; Kostetzer, L.; Rudnyi, E. [CADFEM GmbH, Grafing (Germany); Geppert, M.; Quinger, D. [LION Smart GmbH, Frieding (Germany)

2011-07-01

In the recent years there has been observed an increasing concern about global warming and greenhouse gas emissions. In addition to the environmental issues the predicted scarcity of oil supplies and the dramatic increase in oil price puts new demands on vehicle design. As a result energy efficiency and reduced emission have become one of main selling point for automobiles. Hybrid electric vehicles (HEV) have therefore become an interesting technology for the governments and automotive industries. HEV are more complicated compared to conventional vehicles due to the fact that these vehicles contain more electrical components such as electric machines, power electronics, electronic continuously variable transmissions (CVT), and embedded powertrain controllers. Advanced energy storage devices and energy converters, such as Li-ion batteries, ultracapacitors, and fuel cells are also considered. A detailed vehicle model used for an energy flow analysis and vehicle performance simulation is necessary. Computer simulation is indispensible to facilitate the examination of the vast hybrid electric vehicle design space with the aim to predict the vehicle performance over driving profiles, estimate fuel consumption and the pollution emissions. There are various types of mathematical models and simulators available to perform system simulation of vehicle propulsion. One of the standard methods to model the complete vehicle powertrain is ''backward quasistatic modeling''. In this method vehicle subsystems are defined based on experiential models in the form of look-up tables and efficiency maps. The interaction between adjacent subsystems of the vehicle is defined through the amount of power flow. Modeling the vehicle subsystems like motor, engine, gearbox and battery is under this technique is based on block diagrams. The vehicle model is applied in two case studies to evaluate the vehicle performance and fuel consumption. In the first case study the affect

Physical time scale in kinetic Monte Carlo simulations of continuous-time Markov chains.

Science.gov (United States)

Serebrinsky, Santiago A

2011-03-01

We rigorously establish a physical time scale for a general class of kinetic Monte Carlo algorithms for the simulation of continuous-time Markov chains. This class of algorithms encompasses rejection-free (or BKL) and rejection (or "standard") algorithms. For rejection algorithms, it was formerly considered that the availability of a physical time scale (instead of Monte Carlo steps) was empirical, at best. Use of Monte Carlo steps as a time unit now becomes completely unnecessary.

A new approach to flow simulation using hybrid models

Science.gov (United States)

Solgi, Abazar; Zarei, Heidar; Nourani, Vahid; Bahmani, Ramin

2017-11-01

The necessity of flow prediction in rivers, for proper management of water resource, and the need for determining the inflow to the dam reservoir, designing efficient flood warning systems and so forth, have always led water researchers to think about models with high-speed response and low error. In the recent years, the development of Artificial Neural Networks and Wavelet theory and using the combination of models help researchers to estimate the river flow better and better. In this study, daily and monthly scales were used for simulating the flow of Gamasiyab River, Nahavand, Iran. The first simulation was done using two types of ANN and ANFIS models. Then, using wavelet theory and decomposing input signals of the used parameters, sub-signals were obtained and were fed into the ANN and ANFIS to obtain hybrid models of WANN and WANFIS. In this study, in addition to the parameters of precipitation and flow, parameters of temperature and evaporation were used to analyze their effects on the simulation. The results showed that using wavelet transform improved the performance of the models in both monthly and daily scale. However, it had a better effect on the monthly scale and the WANFIS was the best model.

Easy to use program “Simkine3” for simulating kinetic profiles of multi-step chemical Systems and optimisation of predictable rate coefficients therein

Directory of Open Access Journals (Sweden)

S.B. Jonnalagadda

2012-08-01

Full Text Available ‘Simkine3’, a Delphi based software is developed to simulate the kinetic schemes of complex reaction mechanisms involving multiple sequential and competitive elementary steps for homogeneous and heterogeneous chemical reactions. Simkine3 is designed to translate the user specified mechanism into chemical first-order differential equations (ODEs and optimise the estimated rate constants in such a way that simulated curves match the experimental kinetic profiles. TLSoda which uses backward differentiation method is utilised to solve resulting ODEs and Downhill Simplex method is used to optimise the estimated rate constants in a robotic way. An online help file is developed using HelpScrible Demo to guide the users of Simkine3. The versatility of the software is demonstrated by simulating the complex reaction between methylene violet and acidic bromate, a reaction which exhibits complex nonlinear kinetics. The new software is validated after testing it on a 19-step intricate mechanism involving 15 different species. The kinetic profiles of multiple simulated curves, illustrating the effect of initial concentrations of bromate, and bromide were matched with the corresponding experimental curves.DOI: http://dx.doi.org/10.4314/bcse.v26i2.10

Hybrid Smith predictor and phase lead based divergence compensation for hardware-in-the-loop contact simulation with measurement delay

Science.gov (United States)

Qi, Chenkun; Gao, Feng; Zhao, Xianchao; Wang, Qian; Ren, Anye

2018-06-01

On the ground the hardware-in-the-loop (HIL) simulation is a good approach to test the contact dynamics of spacecraft docking process in space. Unfortunately, due to the time delay in the system the HIL contact simulation becomes divergent. However, the traditional first-order phase lead compensation approach still result in a small divergence for the pure time delay. The serial Smith predictor and phase lead compensation approach proposed by the authors recently will lead to an over-compensation and an obvious convergence. In this study, a hybrid Smith predictor and phase lead compensation approach is proposed. The hybrid Smith predictor and phase lead compensation can achieve a higher simulation fidelity with a little convergence. The phase angle of the compensator is analyzed and the stability condition of the HIL simulation system is given. The effectiveness of the proposed compensation approach is tested by simulations on an undamped elastic contact process.

A survey of electric and hybrid vehicles simulation programs. Volume 2: Questionnaire responses

Science.gov (United States)

Bevan, J.; Heimburger, D. A.; Metcalfe, M. A.

1978-01-01

The data received in a survey conducted within the United States to determine the extent of development and capabilities of automotive performance simulation programs suitable for electric and hybrid vehicle studies are presented. The survey was conducted for the Department of Energy by NASA's Jet Propulsion Laboratory. Volume 1 of this report summarizes and discusses the results contained in Volume 2.

A Hybrid Three Layer Architecture for Fire Agent Management in Rescue Simulation Environment

Directory of Open Access Journals (Sweden)

Alborz Geramifard

2008-11-01

Full Text Available This paper presents a new architecture called FAIS for imple- menting intelligent agents cooperating in a special Multi Agent environ- ment, namely the RoboCup Rescue Simulation System. This is a layered architecture which is customized for solving fire extinguishing problem. Structural decision making algorithms are combined with heuristic ones in this model, so it's a hybrid architecture.

A hybrid Genetic and Simulated Annealing Algorithm for Chordal Ring implementation in large-scale networks

DEFF Research Database (Denmark)

Riaz, M. Tahir; Gutierrez Lopez, Jose Manuel; Pedersen, Jens Myrup

2011-01-01

The paper presents a hybrid Genetic and Simulated Annealing algorithm for implementing Chordal Ring structure in optical backbone network. In recent years, topologies based on regular graph structures gained a lot of interest due to their good communication properties for physical topology of the...

A kinetic model of trp-cage folding from multiple biased molecular dynamics simulations.

Directory of Open Access Journals (Sweden)

Fabrizio Marinelli

2009-08-01

Full Text Available Trp-cage is a designed 20-residue polypeptide that, in spite of its size, shares several features with larger globular proteins.Although the system has been intensively investigated experimentally and theoretically, its folding mechanism is not yet fully understood. Indeed, some experiments suggest a two-state behavior, while others point to the presence of intermediates. In this work we show that the results of a bias-exchange metadynamics simulation can be used for constructing a detailed thermodynamic and kinetic model of the system. The model, although constructed from a biased simulation, has a quality similar to those extracted from the analysis of long unbiased molecular dynamics trajectories. This is demonstrated by a careful benchmark of the approach on a smaller system, the solvated Ace-Ala3-Nme peptide. For theTrp-cage folding, the model predicts that the relaxation time of 3100 ns observed experimentally is due to the presence of a compact molten globule-like conformation. This state has an occupancy of only 3% at 300 K, but acts as a kinetic trap.Instead, non-compact structures relax to the folded state on the sub-microsecond timescale. The model also predicts the presence of a state at Calpha-RMSD of 4.4 A from the NMR structure in which the Trp strongly interacts with Pro12. This state can explain the abnormal temperature dependence of the Pro12-delta3 and Gly11-alpha3 chemical shifts. The structures of the two most stable misfolded intermediates are in agreement with NMR experiments on the unfolded protein. Our work shows that, using biased molecular dynamics trajectories, it is possible to construct a model describing in detail the Trp-cage folding kinetics and thermodynamics in agreement with experimental data.

Modeling, simulation, and concept studies of a fuel cell hybrid electric vehicle powertrain

Energy Technology Data Exchange (ETDEWEB)

Oezbek, Markus

2010-03-29

This thesis focuses on the development of a fuel cell-based hybrid electric powertrain for smaller (2 kW) hybrid electric vehicles (HEVs). A Hardware-in-the-Loop test rig is designed and built with the possibility to simulate any load profile for HEVs in a realistic environment, whereby the environment is modeled. Detailed simulation models of the test rig are developed and validated to real physical components and control algorithms are designed for the DC/DC-converters and the fuel cell system. A state-feedback controller is developed for the DC/DC-converters where the state-space averaging method is used for the development. For the fuel cells, a gain-scheduling controller based on state feedback is developed and compared to two conventional methods. The design process of an HEV with regard to a given load profile is introduced with comparison between SuperCaps and batteries. The HEV is also evaluated with an introduction to different power management concepts with regard to fuel consumption, dynamics, and fuel cell deterioration rate. The power management methods are implemented in the test rig and compared. (orig.)

Kinetic simulations of neoclassical and anomalous transport processes in helical systems

International Nuclear Information System (INIS)

Sugama, Hideo; Watanabe, Tomohiko; Nunami, Masanori; Satake, Shinsuke; Matsuoka, Seikichi; Tanaka, Kenji

2012-01-01

Drift kinetic and gyrokinetic theories and simulations are powerful means for quantitative predictions of neoclassical and anomalous transport fluxes in helical systems such as the Large Helical Device (LHD). The δf Monte Carlo particle simulation code, FORTEC-3D, is used to predict radial profiles of the neoclassical particle and heat transport fluxes and the radial electric field in helical systems. The radial electric field profiles in the LHD plasmas are calculated from the ambipolarity condition for the neoclassical particle fluxes obtained by the global simulations using the FORTEC-3D code, in which effects of ion or electron finite orbit widths are included. Gyrokinetic Vlasov simulations using the GKV code verify the theoretical prediction that the neoclassical optimization of helical magnetic configuration enhances the zonal flow generation which leads to the reduction of the turbulent heat diffusivity χ i due to the ion temperature gradient (ITG) turbulence. Comparisons between results for the high ion temperature LHD experiment and the gyrokinetic simulations using the GKV-X code show that the χ i profile and the poloidal wave number spectrum of the density fluctuation obtained from the simulations are in reasonable agreements with the experimental results. It is predicted theoretically and confirmed by the linear GKV simulations that the E × B rotation due to the background radial electric field E r can enhance the zonal-flow response to a given source. Thus, in helical systems, the turbulent transport is linked to the neoclassical transport through E r which is determined from the ambipolar condition for neoclassical particle fluxes and influences the zonal flow generation leading to reduction of the turbulent transport. In order to investigate the E r effect on the regulation of the turbulent transport by the zonal flow generation, the flux-tube bundle model is proposed as a new method for multiscale gyrokinetic simulations. (author)

Atomistic computer simulations of FePt nanoparticles. Thermodynamic and kinetic properties

Energy Technology Data Exchange (ETDEWEB)

Mueller, M.

2007-12-20

In the present dissertation, a hierarchical multiscale approach for modeling FePt nanoparticles by atomistic computer simulations is developed. By describing the interatomic interactions on different levels of sophistication, various time and length scales can be accessed. Methods range from static quantum-mechanic total-energy calculations of small periodic systems to simulations of whole particles over an extended time by using simple lattice Hamiltonians. By employing these methods, the energetic and thermodynamic stability of non-crystalline multiply twinned FePt nanoparticles is investigated. Subsequently, the thermodynamics of the order-disorder transition in FePt nanoparticles is analyzed, including the influence of particle size, composition and modified surface energies by different chemical surroundings. In order to identify processes that reduce or enhance the rate of transformation from the disordered to the ordered state, the kinetics of the ordering transition in FePt nanoparticles is finally investigated by assessing the contributions of surface and volume diffusion. (orig.)

Fate of bulk and trace organics during a simulated aquifer recharge and recovery (ARR)-ozone hybrid process

KAUST Repository

Yoon, Min

2013-11-01

The attenuation of bulk organic matter and trace organic contaminants (TOrCs) was evaluated for various aquifer recharge and recovery (ARR)-ozone (O3) hybrid treatment process combinations using soil-batch reactor and bench-scale ozonation experiments as a proof of concept prior to pilot and/or field studies. In water reclamation and especially potable reuse, refractory bulk organic matter and TOrCs are of potential health concern in recycled waters. In this study, the role of biotransformation of bulk organic matter and TOrCs was investigated considering different simulated treatment combinations, including soil passage (ARR) alone, ARR after ozonation (O3-ARR), and ARR prior to ozonation (ARR-O3). During oxic (aerobic) ARR simulations, soluble microbial-like substances (e.g., higher molecular weight polysaccharides and proteins) were easily removed while (lower molecular weight) humic substances and aromatic organic matter were not efficiently removed. During ARR-ozone treatment simulations, removals of bulk organic matter and TOrCs were rapid and effective compared to ARR alone. A higher reduction of effluent-derived organic matter, including aromatic organic matter and humic substances, was observed in the ARR-O3 hybrid followed by the O3-ARR hybrid. An enhanced attenuation of recalcitrant TOrCs was observed while increasing the ozone dose slightly (O3: DOC=1). TOrC removal efficiency also increased during the post-ozone treatment combination (i.e., ARR-O3). In addition, the carcinogenic wastewater disinfection byproduct N-nitrosodimethylamine (NDMA) was eliminated below the method reporting limit (<5ngL-1) both during ARR treatment alone and the ARR-ozone hybrid. © 2013 Elsevier Ltd.

The hybridized Discontinuous Galerkin method for Implicit Large-Eddy Simulation of transitional turbulent flows

Science.gov (United States)

Fernandez, P.; Nguyen, N. C.; Peraire, J.

2017-05-01

We present a high-order Implicit Large-Eddy Simulation (ILES) approach for transitional aerodynamic flows. The approach encompasses a hybridized Discontinuous Galerkin (DG) method for the discretization of the Navier-Stokes (NS) equations, and a parallel preconditioned Newton-GMRES solver for the resulting nonlinear system of equations. The combination of hybridized DG methods with an efficient solution procedure leads to a high-order accurate NS solver that is competitive to alternative approaches, such as finite volume and finite difference codes, in terms of computational cost. The proposed approach is applied to transitional flows over the NACA 65-(18)10 compressor cascade and the Eppler 387 wing at Reynolds numbers up to 460,000. Grid convergence studies are presented and the required resolution to capture transition at different Reynolds numbers is investigated. Numerical results show rapid convergence and excellent agreement with experimental data. In short, this work aims to demonstrate the potential of high-order ILES for simulating transitional aerodynamic flows. This is illustrated through numerical results and supported by theoretical considerations.

Test of Shi et al. Method to Infer the Magnetic Reconnection Geometry from Spacecraft Data: MHD Simulation with Guide Field and Antiparallel Kinetic Simulation

Science.gov (United States)

Denton, R.; Sonnerup, B. U. O.; Swisdak, M.; Birn, J.; Drake, J. F.; Heese, M.

2012-01-01

When analyzing data from an array of spacecraft (such as Cluster or MMS) crossing a site of magnetic reconnection, it is desirable to be able to accurately determine the orientation of the reconnection site. If the reconnection is quasi-two dimensional, there are three key directions, the direction of maximum inhomogeneity (the direction across the reconnection site), the direction of the reconnecting component of the magnetic field, and the direction of rough invariance (the "out of plane" direction). Using simulated spacecraft observations of magnetic reconnection in the geomagnetic tail, we extend our previous tests of the direction-finding method developed by Shi et al. (2005) and the method to determine the structure velocity relative to the spacecraft Vstr. These methods require data from four proximate spacecraft. We add artificial noise and calibration errors to the simulation fields, and then use the perturbed gradient of the magnetic field B and perturbed time derivative dB/dt, as described by Denton et al. (2010). Three new simulations are examined: a weakly three-dimensional, i.e., quasi-two-dimensional, MHD simulation without a guide field, a quasi-two-dimensional MHD simulation with a guide field, and a two-dimensional full dynamics kinetic simulation with inherent noise so that the apparent minimum gradient was not exactly zero, even without added artificial errors. We also examined variations of the spacecraft trajectory for the kinetic simulation. The accuracy of the directions found varied depending on the simulation and spacecraft trajectory, but all the directions could be found within about 10 for all cases. Various aspects of the method were examined, including how to choose averaging intervals and the best intervals for determining the directions and velocity. For the kinetic simulation, we also investigated in detail how the errors in the inferred gradient directions from the unmodified Shi et al. method (using the unperturbed gradient