Science.gov

Sample records for 1d hybrid simulations

  1. Hybrid Simulator

    2005-10-15

    HybSim (short for Hybrid Simulator) is a flexible, easy to use screening tool that allows the user to quanti the technical and economic benefits of installing a village hybrid generating system and simulates systems with any combination of —Diesel generator sets —Photovoltaic arrays -Wind Turbines and -Battery energy storage systems Most village systems (or small population sites such as villages, remote military bases, small communities, independent or isolated buildings or centers) depend on diesel generationmore » systems for their source of energy. HybSim allows the user to determine other "sources" of energy that can greatly reduce the dollar to kilo-watt hour ratio. Supported by the DOE, Energy Storage Program, HybSim was initially developed to help analyze the benefits of energy storage systems in Alaskan villages. Soon after its development, other sources of energy were added providing the user with a greater range of analysis opportunities and providing the village with potentially added savings. In addition to village systems, HybSim has generated interest for use from military institutions in energy provisions and USAID for international village analysis.« less

  2. 1D-3D hybrid modeling—from multi-compartment models to full resolution models in space and time

    PubMed Central

    Grein, Stephan; Stepniewski, Martin; Reiter, Sebastian; Knodel, Markus M.; Queisser, Gillian

    2014-01-01

    Investigation of cellular and network dynamics in the brain by means of modeling and simulation has evolved into a highly interdisciplinary field, that uses sophisticated modeling and simulation approaches to understand distinct areas of brain function. Depending on the underlying complexity, these models vary in their level of detail, in order to cope with the attached computational cost. Hence for large network simulations, single neurons are typically reduced to time-dependent signal processors, dismissing the spatial aspect of each cell. For single cell or networks with relatively small numbers of neurons, general purpose simulators allow for space and time-dependent simulations of electrical signal processing, based on the cable equation theory. An emerging field in Computational Neuroscience encompasses a new level of detail by incorporating the full three-dimensional morphology of cells and organelles into three-dimensional, space and time-dependent, simulations. While every approach has its advantages and limitations, such as computational cost, integrated and methods-spanning simulation approaches, depending on the network size could establish new ways to investigate the brain. In this paper we present a hybrid simulation approach, that makes use of reduced 1D-models using e.g., the NEURON simulator—which couples to fully resolved models for simulating cellular and sub-cellular dynamics, including the detailed three-dimensional morphology of neurons and organelles. In order to couple 1D- and 3D-simulations, we present a geometry-, membrane potential- and intracellular concentration mapping framework, with which graph- based morphologies, e.g., in the swc- or hoc-format, are mapped to full surface and volume representations of the neuron and computational data from 1D-simulations can be used as boundary conditions for full 3D simulations and vice versa. Thus, established models and data, based on general purpose 1D-simulators, can be directly coupled to

  3. Numerical simulations of heavily polluted fine-grained sediment remobilization using 1D, 1D+, and 2D channel schematization.

    PubMed

    Kaiglová, Jana; Langhammer, Jakub; Jiřinec, Petr; Janský, Bohumír; Chalupová, Dagmar

    2015-03-01

    This article used various hydrodynamic and sediment transport models to analyze the potential and the limits of different channel schematizations. The main aim was to select and evaluate the most suitable simulation method for fine-grained sediment remobilization assessment. Three types of channel schematization were selected to study the flow potential for remobilizing fine-grained sediment in artificially modified channels. Schematization with a 1D cross-sectional horizontal plan, a 1D+ approach, splitting the riverbed into different functional zones, and full 2D mesh, adopted in MIKE by the DHI modeling suite, was applied to the study. For the case study, a 55-km stretch of the Bílina River, in the Czech Republic, Central Europe, which has been heavily polluted by the chemical and coal mining industry since the mid-twentieth century, was selected. Long-term exposure to direct emissions of toxic pollutants including heavy metals and persistent organic pollutants (POPs) resulted in deposits of pollutants in fine-grained sediments in the riverbed. Simulations, based on three hydrodynamic model schematizations, proved that for events not exceeding the extent of the riverbed profile, the 1D schematization can provide comparable results to a 2D model. The 1D+ schematization can improve accuracy while keeping the benefits of high-speed simulation and low requirements of input DEM data, but the method's suitability is limited by the channel properties. PMID:25687259

  4. Hyperbranched quasi-1D TiO2 nanostructure for hybrid organic-inorganic solar cells.

    PubMed

    Ghadirzadeh, Ali; Passoni, Luca; Grancini, Giulia; Terraneo, Giancarlo; Li Bassi, Andrea; Petrozza, Annamaria; Di Fonzo, Fabio

    2015-04-15

    The performance of hybrid solar cells is strongly affected by the device morphology. In this work, we demonstrate a poly(3-hexylthiophene-2,5-diyl)/TiO2 hybrid solar cell where the TiO2 photoanode comprises an array of tree-like hyperbranched quasi-1D nanostructures self-assembled from the gas phase. This advanced architecture enables us to increase the power conversion efficiency to over 1%, doubling the efficiency with respect to state of the art devices employing standard mesoporous titania photoanodes. This improvement is attributed to several peculiar features of this array of nanostructures: high interfacial area; increased optical density thanks to the enhanced light scattering; and enhanced crystallization of poly(3-hexylthiophene-2,5-diyl) inside the quasi-1D nanostructure. PMID:25822757

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    SciTech Connect

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

    2015-12-31

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

  7. Expansion effects on solar wind hybrid simulations

    SciTech Connect

    Parashar, Tulasi N.; Velli, Marco; Goldstein, Bruce E.

    2013-06-13

    Ion kinetic simulations of the solar wind using hybrid codes can model local wave input, heating and instabilities, but generally do not include long term evolution effects in the expanding solar wind. We further develop the expanding box model used in earlier studies to include the mirror force effects and study their role in the evolution of the proton distribution functions in the outer corona and inner heliosphere. The mirror force, significant in the acceleration region of the solar wind, is required for consistency with the conservation of magnetic moment of particles in the expanding wind. We present preliminary results from the modified 1D expanding box hybrid (EBHM) simulations.

  8. Hybrid Solar GHP Simulator

    2012-12-11

    This project provides an easy-to-use, menu-driven, software tool for designing hybrid solar-geothermal heat pump systems (GHP) for both heating- and cooling-dominated buildings. No such design tool currently exists. In heating-dominated buildings, the design approach takes advantage of glazed solar collectors to effectively balance the annual thermal loads on the ground with renewable solar energy. In cooling-dominated climates, the design approach takes advantage of relatively low-cost, unglazed solar collectors as the heat rejecting component. The primarymore » benefit of hybrid GHPs is the reduced initial cost of the ground heat exchanger (GHX). Furthermore, solar thermal collectors can be used to balance the ground loads over the annual cycle, thus making the GHX fully sustainable; in heating-dominated buildings, the hybrid energy source (i.e., solar) is renewable, in contrast to a typical fossil fuel boiler or electric resistance as the hybrid component; in cooling-dominated buildings, use of unglazed solar collectors as a heat rejecter allows for passive heat rejection, in contrast to a cooling tower that consumes a significant amount of energy to operate, and hybrid GHPs can expand the market by allowing reduced GHX footprint in both heating- and cooling-dominated climates. The design tool allows for the straight-forward design of innovative GHP systems that currently pose a significant design challenge. The project lays the foundations for proper and reliable design of hybrid GHP systems, overcoming a series of difficult and cumbersome steps without the use of a system simulation approach, and without an automated optimization scheme. As new technologies and design concepts emerge, sophisticated design tools and methodologies must accompany them and be made usable for practitioners. Lack of reliable design tools results in reluctance of practitioners to implement more complex systems. A menu-driven software tool for the design of hybrid solar GHP systems

  9. Particle simulation of bounded 1D plasma systems

    SciTech Connect

    Lawson, W.S.

    1989-02-01

    The physical and numerical problems of kinetic simulation of a bounded electrostatic plasma system in one planar dimension are examined, and solutions to them are presented. These problems include particle absorption, reflection and emission at boundaries, the solution of Poisson's equation under non-periodic boundary conditions, and the treatment of an external circuit connecting the boundaries. The methods which are described here are implemented in a code named PDW1, which is available from Professor C. K. Birdsall, Plasma Theory and Simulation Group, Cory Hall, University of California, Berkeley, CA 94720. copyright 1989 Academic Press, Inc.

  10. Partical Simulation of Bounded 1D Plasma Systems

    NASA Astrophysics Data System (ADS)

    Lawson, William S.

    1989-02-01

    The physical and numerical problems of kinetic simulation of a bounded electrostatic plasma system in one planar dimension are examined, and solutions to them are presented. These problems include particle absorption, reflection and emission at boundaries, the solution of Poisson's equation under non-periodic boundary conditions, and the treatment of an external circuit connecting the boundaries. The methods which are described here are immlemented in a code named PDW1, which is available from Professor C. K. Birdsall, Plasma Theory and Simulation Group, Cory Hall, University of California, Berkeley, CA 94720.

  11. 1D quantum simulation using a solid state platform

    NASA Astrophysics Data System (ADS)

    Kirkendall, Megan; Irvin, Patrick; Huang, Mengchen; Levy, Jeremy; Lee, Hyungwoo; Eom, Chang-Beom

    Understanding the properties of large quantum systems can be challenging both theoretically and numerically. One experimental approach-quantum simulation-involves mapping a quantum system of interest onto a physical system that is programmable and experimentally accessible. A tremendous amount of work has been performed with quantum simulators formed from optical lattices; by contrast, solid-state platforms have had only limited success. Our experimental approach to quantum simulation takes advantage of nanoscale control of a metal-insulator transition at the interface between two insulating complex oxide materials. This system naturally exhibits a wide variety of ground states (e.g., ferromagnetic, superconducting) and can be configured into a variety of complex geometries. We will describe initial experiments that explore the magnetotransport properties of one-dimensional superlattices with spatial periods as small as 4 nm, comparable to the Fermi wavelength. The results demonstrate the potential of this solid-state quantum simulation approach, and also provide empirical constraints for physical models that describe the underlying oxide material properties. We gratefully acknowledge financial support from AFOSR (FA9550-12-1- 0057 (JL), FA9550-10-1-0524 (JL) and FA9550-12-1-0342 (CBE)), ONR N00014-15-1-2847 (JL), and NSF DMR-1234096 (CBE).

  12. Parametric Simulations of Slanted 1D Photonic Crystal Sensors

    NASA Astrophysics Data System (ADS)

    Breuer-Weil, Aaron; Almasoud, Naif Nasser; Abbasi, Badaruddin; Yetisen, Ali K.; Yun, Seok-Hyun; Butt, Haider

    2016-03-01

    Photonic crystals and band gap materials act as manipulators of light and have a plethora of applications. They are made up of stacks of alternating dielectric constants. This article shows the simulations of an inclined, one dimensional and tuneble photonic crystal, using numerical finite element methods. The photonic crystal was made up of silver nanoparticles embedded in a hydrogel matrix and it has the ability to change and recover its periodicity. A series of factors concerning the geometry of the lattice were tested in order to analyze the efficiency, performance and optimize the properties of the optical sensor. These factors range from the size of the nanoparticles and their density within the stacks, to observing the effect of diffraction angle in readouts.

  13. Parametric Simulations of Slanted 1D Photonic Crystal Sensors.

    PubMed

    Breuer-Weil, Aaron; Almasoud, Naif Nasser; Abbasi, Badaruddin; Yetisen, Ali K; Yun, Seok-Hyun; Butt, Haider

    2016-12-01

    Photonic crystals and band gap materials act as manipulators of light and have a plethora of applications. They are made up of stacks of alternating dielectric constants. This article shows the simulations of an inclined, one dimensional and tuneble photonic crystal, using numerical finite element methods. The photonic crystal was made up of silver nanoparticles embedded in a hydrogel matrix and it has the ability to change and recover its periodicity. A series of factors concerning the geometry of the lattice were tested in order to analyze the efficiency, performance and optimize the properties of the optical sensor. These factors range from the size of the nanoparticles and their density within the stacks, to observing the effect of diffraction angle in readouts. PMID:27000025

  14. Apoferritin fibers: a new template for 1D fluorescent hybrid nanostructures.

    PubMed

    Jurado, Rocío; Castello, Fabio; Bondia, Patricia; Casado, Santiago; Flors, Cristina; Cuesta, Rafael; Domínguez-Vera, José M; Orte, Angel; Gálvez, Natividad

    2016-05-01

    Recently, research in the field of protein amyloid fibers has gained great attention due to the use of these materials as nanoscale templates for the construction of functional hybrid materials. The formation of apoferritin amyloid-like protein fibers is demonstrated herein for the first time. The morphology, size and stiffness of these one-dimensional structures are comparable to the fibers formed by β-lactoglobulin, a protein frequently used as a model in the study of amyloid-like fibrillar proteins. Nanometer-sized globular apoferritin is capable of self-assembling to form 1D micrometer-sized structures after being subjected to a heating process. Depending on the experimental conditions, fibers with different morphologies and sizes are obtained. The wire-like protein structure is rich in functional groups and allows chemical functionalization with diverse quantum dots (QD), as well as with different Alexa Fluor (AF) dyes, leading to hybrid fluorescent fibers with variable emission wavelengths, from green to near infrared, depending on the QD and AFs coupled. For fibers containing the pair AF488 and AF647, efficient fluorescence energy transfer from the covalently coupled donor (AF488) to acceptor tags (AF647) takes place. Apoferritin fibers are proposed here as a new promising template for obtaining hybrid functional materials. PMID:27103107

  15. Electric/Hybrid Vehicle Simulation

    NASA Technical Reports Server (NTRS)

    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.

  16. Apoferritin fibers: a new template for 1D fluorescent hybrid nanostructures

    NASA Astrophysics Data System (ADS)

    Jurado, Rocío; Castello, Fabio; Bondia, Patricia; Casado, Santiago; Flors, Cristina; Cuesta, Rafael; Domínguez-Vera, José M.; Orte, Angel; Gálvez, Natividad

    2016-05-01

    Recently, research in the field of protein amyloid fibers has gained great attention due to the use of these materials as nanoscale templates for the construction of functional hybrid materials. The formation of apoferritin amyloid-like protein fibers is demonstrated herein for the first time. The morphology, size and stiffness of these one-dimensional structures are comparable to the fibers formed by β-lactoglobulin, a protein frequently used as a model in the study of amyloid-like fibrillar proteins. Nanometer-sized globular apoferritin is capable of self-assembling to form 1D micrometer-sized structures after being subjected to a heating process. Depending on the experimental conditions, fibers with different morphologies and sizes are obtained. The wire-like protein structure is rich in functional groups and allows chemical functionalization with diverse quantum dots (QD), as well as with different Alexa Fluor (AF) dyes, leading to hybrid fluorescent fibers with variable emission wavelengths, from green to near infrared, depending on the QD and AFs coupled. For fibers containing the pair AF488 and AF647, efficient fluorescence energy transfer from the covalently coupled donor (AF488) to acceptor tags (AF647) takes place. Apoferritin fibers are proposed here as a new promising template for obtaining hybrid functional materials.Recently, research in the field of protein amyloid fibers has gained great attention due to the use of these materials as nanoscale templates for the construction of functional hybrid materials. The formation of apoferritin amyloid-like protein fibers is demonstrated herein for the first time. The morphology, size and stiffness of these one-dimensional structures are comparable to the fibers formed by β-lactoglobulin, a protein frequently used as a model in the study of amyloid-like fibrillar proteins. Nanometer-sized globular apoferritin is capable of self-assembling to form 1D micrometer-sized structures after being subjected to a

  17. Modeling blood flow circulation in intracranial arterial networks: a comparative 3D/1D simulation study.

    PubMed

    Grinberg, L; Cheever, E; Anor, T; Madsen, J R; Karniadakis, G E

    2011-01-01

    We compare results from numerical simulations of pulsatile blood flow in two patient-specific intracranial arterial networks using one-dimensional (1D) and three-dimensional (3D) models. Specifically, we focus on the pressure and flowrate distribution at different segments of the network computed by the two models. Results obtained with 1D and 3D models with rigid walls show good agreement in massflow distribution at tens of arterial junctions and also in pressure drop along the arteries. The 3D simulations with the rigid walls predict higher amplitude of the flowrate and pressure temporal oscillations than the 1D simulations with compliant walls at various segments even for small time-variations in the arterial cross-sectional areas. Sensitivity of the flow and pressure with respect to variation in the elasticity parameters is investigated with the 1D model. PMID:20661645

  18. Electric-hybrid-vehicle simulation

    NASA Astrophysics Data System (ADS)

    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.

  19. Numerical simulations of plasma brush behavior in hybrid armatures

    NASA Astrophysics Data System (ADS)

    Hawke, R. S.; Pincosy, P. A.

    1993-01-01

    Hybrid armatures used to accelerate projectiles in railguns are often the consequence of using a solid armature or in some cases the preferred armature type. Although hybrid armatures are often used, their design has been empirical and their performance sporadic. As a first step towards understanding hybrid design and performance, we have begun a combined numerical simulation and experimental verification effort. This paper will describe numerical simulations performed with a quasi 1-D MHD code (CONFUSE) which has been applied to simulate the behavior of plasma brushes used in hybrid armatures. The simulations have provided estimates of the plasma brush length, resistive voltage drop and temperatures corresponding to a range of; 1) brush gap size, 2) fuse thickness, and 3) magnetic pressure. The results of these simulations is presented and discussed.

  20. Build up An Operational Flood Simulation from Existing 1D Channel Flow Works

    NASA Astrophysics Data System (ADS)

    Chang, Che-Hao; Hsu, Chih-Tsung; Wu, Shiang-Jen; Lien, Ho-Cheng; Shen, Jhih-Cyuan; Chung, Ming-Ko

    2016-04-01

    Several 2D flood simulations will be developed for urban area in recent years in Taiwan. Original ideas focus on the static flood maps produced by the 2D flood simulation with respect to design events, which could be useful no matter for planning or disaster awareness. However, an extra bonus is expected to see if we can reuse the 2D flood simulation framework for operational use or not. Such a project goal inspire us to setup a standard operation procedure before any progress from existing 1D channel flow works. 3 key issues are taken into account in the SOP: 1. High Resolution Terrain: A 1m resolution digital terrain model (DTM) is considered as a reference. The Channels and structures should be setup in 1D channel flow works if we can identify under such high resolution. One should examine the existing 1D channel flow works consistent with the DTM or not. 2. Meteo Stations Referenced: Real time precipitation would be send to referenced location in RR models during an operational forecast. Existing 1D channels flow works are usually specifically for design events which are not necessarily equipped with such references. 3. Time Consuming: A full scale 2D flood simulation needs a lot of computation resources. A solution should be derived within practical time limits. Under the above consideration, some impacts and procedures will be analyzed and developed to setup the SOP for further model modification.

  1. Identification of the minimum pharmacophore of lipid-phosphatidylserine (PS) binding peptide-peptoid hybrid PPS1D1.

    PubMed

    Singh, Jaspal; Shukla, Satya Prakash; Desai, Tanvi J; Udugamasooriya, D Gomika

    2016-09-15

    We previously reported a unique peptide-peptoid hybrid, PPS1 that specifically recognizes lipid-phosphatidylserine (PS) and a few other negatively charged phospholipids, but not neutral phospholipids, on the cell membrane. The dimeric version of PPS1, i.e., PPS1D1 triggers strong cancer cell cytotoxicity and has been validated in lung cancer models both in vitro and in vivo. Given that PS and other negatively charged phospholipids are abundant in almost all tumor microenvironments, PPS1D1 is an attractive drug lead that can be developed into a globally applicable anti-cancer agent. Therefore, it is extremely important to identify the minimum pharmacophore of PPS1D1. In this study, we have synthesized alanine/sarcosine derivatives as well as truncated derivatives of PPS1D1. We performed ELISA-like competitive binding assay to evaluate the PS-recognition potential and standard MTS cell viability assay on HCC4017 lung cancer cells to validate the cell cytotoxicity effects of these derivatives. Our studies indicate that positively charged residues at the second and third positions, as well as four hydrophobic residues at the fifth through eighth positions, are imperative for the binding and activity of PPS1D1. Methionine at the first position was not essential, whereas the positively charged Nlys at the fourth position was minimally needed, as two derivatives that were synthesized replacing this residue were almost as active as PPS1D1. PMID:27485601

  2. 1D and 2D simulations of seismic wave propagation in fractured media

    NASA Astrophysics Data System (ADS)

    Möller, Thomas; Friederich, Wolfgang

    2016-04-01

    Fractures and cracks have a significant influence on the propagation of seismic waves. Their presence causes reflections and scattering and makes the medium effectively anisotropic. We present a numerical approach to simulation of seismic waves in fractured media that does not require direct modelling of the fracture itself, but uses the concept of linear slip interfaces developed by Schoenberg (1980). This condition states that at an interface between two imperfectly bonded elastic media, stress is continuous across the interface while displacement is discontinuous. It is assumed that the jump of displacement is proportional to stress which implies a jump in particle velocity at the interface. We use this condition as a boundary condition to the elastic wave equation and solve this equation in the framework of a Nodal Discontinuous Galerkin scheme using a velocity-stress formulation. We use meshes with tetrahedral elements to discretise the medium. Each individual element face may be declared as a slip interface. Numerical fluxes have been derived by solving the 1D Riemann problem for slip interfaces with elastic and viscoelastic rheology. Viscoelasticity is realised either by a Kelvin-Voigt body or a Standard Linear Solid. These fluxes are not limited to 1D and can - with little modification - be used for simulations in higher dimensions as well. The Nodal Discontinuous Galerkin code "neXd" developed by Lambrecht (2013) is used as a basis for the numerical implementation of this concept. We present examples of simulations in 1D and 2D that illustrate the influence of fractures on the seismic wavefield. We demonstrate the accuracy of the simulation through comparison to an analytical solution in 1D.

  3. Quantum simulation of 2D topological physics in a 1D array of optical cavities

    PubMed Central

    Luo, Xi-Wang; Zhou, Xingxiang; Li, Chuan-Feng; Xu, Jin-Shi; Guo, Guang-Can; Zhou, Zheng-Wei

    2015-01-01

    Orbital angular momentum of light is a fundamental optical degree of freedom characterized by unlimited number of available angular momentum states. Although this unique property has proved invaluable in diverse recent studies ranging from optical communication to quantum information, it has not been considered useful or even relevant for simulating nontrivial physics problems such as topological phenomena. Contrary to this misconception, we demonstrate the incredible value of orbital angular momentum of light for quantum simulation by showing theoretically how it allows to study a variety of important 2D topological physics in a 1D array of optical cavities. This application for orbital angular momentum of light not only reduces required physical resources but also increases feasible scale of simulation, and thus makes it possible to investigate important topics such as edge-state transport and topological phase transition in a small simulator ready for immediate experimental exploration. PMID:26145177

  4. Development of 1D Particle-in-Cell Code and Simulation of Plasma-Wall Interactions

    NASA Astrophysics Data System (ADS)

    Rose, Laura P.

    This thesis discusses the development of a 1D particle-in-cell (PIC) code and the analysis of plasma-wall interactions. The 1D code (Plasma and Wall Simulation -- PAWS) is a kinetic simulation of plasma done by treating both electrons and ions as particles. The goal of this thesis is to study near wall plasma interaction to better understand the mechanism that occurs in this region. The main focus of this investigation is the effects that secondary electrons have on the sheath profile. The 1D code is modeled using the PIC method. Treating both the electrons and ions as macroparticles the field is solved on each node and weighted to each macro particle. A pre-ionized plasma was loaded into the domain and the velocities of particles were sampled from the Maxwellian distribution. An important part of this code is the boundary conditions at the wall. If a particle hits the wall a secondary electron may be produced based on the incident energy. To study the sheath profile the simulations were run for various cases. Varying background neutral gas densities were run with the 2D code and compared to experimental values. Different wall materials were simulated to show their effects of SEE. In addition different SEE yields were run, including one study with very high SEE yields to show the presence of a space charge limited sheath. Wall roughness was also studied with the 1D code using random angles of incidence. In addition to the 1D code, an external 2D code was also used to investigate wall roughness without secondary electrons. The roughness profiles where created upon investigation of wall roughness inside Hall Thrusters based off of studies done on lifetime erosion of the inner and outer walls of these devices. The 2D code, Starfish[33], is a general 2D axisymmetric/Cartesian code for modeling a wide a range of plasma and rarefied gas problems. These results show that higher SEE yield produces a smaller sheath profile and that wall roughness produces a lower SEE yield

  5. Simultaneous potential and circuit solution for 1D bounded plasma particle simulation codes

    SciTech Connect

    Verboncoeur, J.P.; Vahedi, V.; Birdsall, C.K. ); Alves, M.V. , S.J. dos Campos )

    1993-02-01

    A general second-order accurate method for solving the combined potential and circuit equations in a one-dimensional electrostatic bounded plasma PIC simulation is presented. The boundary conditions include surface charge on the electrodes, which are connected to a series RLC circuit with driving terms V(t) or l(t). The solution is obtained for planar, cylindrical, and spherical electrodes. The result is a tridiagonal matrix which is readily solved using well-known methods. The method is implemented in the codes PDPL (plasma device planar 1 D), PDC1 (cylindrical), and PDS1 (spherical).

  6. Nanoelectronic Modeling (NEMO): Moving from commercial grade 1-D simulation to prototype 3-D simulation

    NASA Astrophysics Data System (ADS)

    Klimeck, Gerhard

    2001-03-01

    The quantum mechanical functionality of commercially pursued heterostructure devices such as resonant tunneling diodes (RTDs), quantum well infrared photodetectors, and quantum well lasers are enabled by material variations on an atomic scale. The creation of these heterostructure devices is realized in a vast design space of material compositions, layer thicknesses and doping profiles. The full experimental exploration of this design space is unfeasible and a reliable design tool is needed. The Nanoelectronic Modeling tool (NEMO) is one of the first commercial grade attempts for such a modeling tool. NEMO was developed as a general-purpose quantum mechanics-based 1-D device design and analysis tool from 1993-97 by the Central Research Laboratory of Texas Instruments (later Raytheon Systems). NEMO enables(R. Lake, G. Klimeck, R. C. Bowen, and D. Jovanovic, J. Appl. Phys. 81), 7845 (1997). the fundamentally sound inclusion of the required(G. Klimeck et al.), in the 1997 55th Annual Device Research Conference Digest, (IEEE, NJ, 1997), p. 92^,(R. C. Bowen et al.), J. Appl. Phys 81, 3207 (1997). physics: bandstructure, scattering, and charge self-consistency based on the non-equilibrium Green function approach. A new class of devices which require full 3-D quantum mechanics based models is starting to emerge: quantum dots, or in general semiconductor based deca-nano devices. We are currently building a 3-D modeling tool based on NEMO to include the important physics to understand electronic stated in such superscaled structures. This presentation will overview various facets of the NEMO 1-D tool such electron transport physics in RTDs, numerical technology, software engineering and graphical user interface. The lessons learned from that work are now entering the NEMO 3-D development and first results using the NEMO 3-D prototype will be shown. More information about

  7. Computing 1-D atomic densities in macromolecular simulations: The density profile tool for VMD

    NASA Astrophysics Data System (ADS)

    Giorgino, Toni

    2014-01-01

    Molecular dynamics simulations have a prominent role in biophysics and drug discovery due to the atomistic information they provide on the structure, energetics and dynamics of biomolecules. Specialized software packages are required to analyze simulated trajectories, either interactively or via scripts, to derive quantities of interest and provide insight for further experiments. This paper presents the Density Profile Tool, a package that enhances the Visual Molecular Dynamics environment with the ability to interactively compute and visualize 1-D projections of various density functions of molecular models. We describe how the plugin is used to perform computations both via a graphical interface and programmatically. Results are presented for realistic examples, all-atom bilayer models, showing how mass and electron densities readily provide measurements such as membrane thickness, location of structural elements, and how they compare to X-ray diffraction experiments.

  8. 1D GAS-DYNAMIC SIMULATION OF SHOCK-WAVE PROCESSES VIA INTERNET

    SciTech Connect

    Khishchenko, K. V.; Levashov, P. R.; Povarnitsyn, M. E.; Zakharenkov, A. S.

    2009-12-28

    We present a Web-interface for 1D simulation of different shock-wave experiments. The choosing of initial parameters, the modeling itself and output data treatment can be made directly via the Internet. The interface is based upon the expert system on shock-wave data and equations of state and contains both the Eulerian and Lagrangian Godunov hydrocodes. The availability of equations of state for a broad set of substances makes this system a useful tool for planning and interpretation of shock-wave experiments. As an example of simulation with the system, results of modeling of multistep shock loading of potassium between polytetrafluoroethylene and stainless steel plates are presented in comparison with experimental data from Shakhray et al.(2005).

  9. Simulation of cirrus clouds with a quasi 2-moment microphysical scheme: a 1D case study

    NASA Astrophysics Data System (ADS)

    Pinty, J.-P.

    2003-04-01

    Cirrus clouds are receiving a great scientific interest because of their importance on the climate system through their impact on the radiation budget and on the physico-chemical balance of the upper troposphere. In this presentation, we concentrate on the application of a mixed-phase 2-moment microphysical scheme to simulate cirrus cloud properties with various ice nucleation modes. The complete scheme is implemented in the multi-purpose mesoscale model MésoNH with several capabilities (3D real vs. academic flows, grid-nesting, etc.). The 1D FIRE and subvisible test cases of Jensen et al. (1994 and 1996 both in JGR) are selected in the present study. The simulations are performed with a similar a thermo-dynamical and dynamical framework and microphysical results are analysed. Additional variations of some critical input parameters (CCN and IN concentrations, vertical velocity and ice characteristics) are explored to test the sensitivity of the microphysical scheme.

  10. A hybrid metalloarsenate 3D framework-1D interrupted metal oxide.

    PubMed

    Hughes, Robert W; Gerrard, Lee A; Price, Daniel J; Weller, Mark T

    2003-06-30

    Complex metal arsenates of the stoichiometry M(1)(-)(x)()M'(6)(OH)(3)(AsO(4)H(2)(x)()(/3))(3)(HAsO(4)), M = M' = Co, Ni, have been synthesized under hydrothermal conditions. The two compounds display a very similar structural topology to that of the mineral dumortierite, an uncommon complex oxyborosilicate of aluminum. The hybrid structures consist of well separated, vacancy interrupted chains of face sharing MO(6) octahedra, with short M.M distances near 2.5 A, embedded in a metalloarsenate 3D framework having the topology of the aluminosilicate cancrinite. The framework also contains a quadruply bridging hydroxide ion. Magnetic susceptibility measurements reveal a strong antiferromagnetic interaction and magnetic transition to low temperature spin canted phases below 51 K (Co) and 42 K (Ni). The material may be considered as a zeotype framework structure templated by an interrupted one-dimensional metal oxide. PMID:12817976

  11. 1D simulation of polymer flooding including the viscoelastic effect of polymer solution

    SciTech Connect

    Masuda, Y.; Tang, K.C.; Miyazawa, M.; Tanaka, S. )

    1992-05-01

    This paper reports that simple simulation models are constructed to predict the performance of 1D polymer flooding. In the models, two phases of oil and polymer solution were assumed to be immiscible with each other. Because the displacing fluid was non-Newtonian, the Buckley-Leverett equation could be modified and a new approach developed to calculate fractional-flow curves. The rheological behavior of polymer solution was modeled with an Ellis type model and a viscoelastic model. To verify the models, two 1D flooding experiments were carried out on 2.8-cm-diameter, 47-cm-long, unconsolidated cores packed with glass beads (70/100 mesh). Porosities of the cores are about 37% and permeabilities are around 26{mu}m{sup 2}. Two white mineral oils of viscosities 25 and 60 mPa {center dot} s and a 200-ppm polyacrylamide solution were used. In each experiment, polymer flooding was done after waterflooding. Initial water saturation was controlled to be almost the same at the start of each flood. The calculated polymer-flooding performances were compared with experimental data. On the other hand, the viscoelastic model predicted fractional-flow curves, oil recovery performances, and breakthrough times of the experiments very well. The viscoelastic effect of polymer solution is thought to play an important role in the improvement of oil recovery.

  12. Mirror instability near the threshold: Hybrid simulations

    NASA Astrophysics Data System (ADS)

    Hellinger, P.; Trávníček, P.; Passot, T.; Sulem, P.; Kuznetsov, E. A.; Califano, F.

    2007-12-01

    Nonlinear behavior of the mirror instability near the threshold is investigated using 1-D hybrid simulations. The simulations demonstrate the presence of an early phase where quasi-linear effects dominate [ Shapiro and Shevchenko, 1964]. The quasi-linear diffusion is however not the main saturation mechanism. A second phase is observed where the mirror mode is linearly stable (the stability is evaluated using the instantaneous ion distribution function) but where the instability nevertheless continues to develop, leading to nonlinear coherent structures in the form of magnetic humps. This regime is well modeled by a nonlinear equation for the magnetic field evolution, derived from a reductive perturbative expansion of the Vlasov-Maxwell equations [ Kuznetsov et al., 2007] with a phenomenological term which represents local variations of the ion Larmor radius. In contrast with previous models where saturation is due to the cooling of a population of trapped particles, the resulting equation correctly reproduces the development of magnetic humps from an initial noise. References Kuznetsov, E., T. Passot and P. L. Sulem (2007), Dynamical model for nonlinear mirror modes near threshold, Phys. Rev. Lett., 98, 235003. Shapiro, V. D., and V. I. Shevchenko (1964), Sov. JETP, 18, 1109.

  13. Cenozoic ice volume and temperature simulations with a 1-D ice-sheet model

    NASA Astrophysics Data System (ADS)

    de Boer, B.; van de Wal, R. S. W.; Bintanja, R.; Lourens, L. J.; Tuenter, E.

    2009-04-01

    Ice volume and temperature for the past 35 Million years is investigated with a 1-D ice-sheet model, simulating ice-sheets on both hemispheres. The simulations include two continental Northern Hemisphere (NH) ice-sheets representative for glaciation on the two major continents, i.e. Eurasia (EAZ) and North America (NAM). Antarctic glaciation is simulated with two separate ice-sheets, respectively for West and East Antarctica. The surface air temperature is reconstructed with an inventive inverse procedure, forced with benthic δ18O data. The procedure linearly relates the temperature to the difference between the modelled and observed marine δ18O 100 years later. The derived temperature, representative for the NH, is used to run the ice-sheet model over 100 years, to obtain a mutually consistent record of marine δ18O, sea level and temperature for the last 35 Ma of the Cenozoic. For Northern Hemispheric glaciations results are good compared to similar simulations performed with a much more comprehensive 3-D ice-sheet model. On average, differences are only 1.9 ˚ C for temperature and 6.1 m for sea level. Results with ice-sheets on both hemispheres are very similar. Most notably, the reconstructed ice volume as function of temperature shows a transition from climate dominated by Antarctic ice volume variation towards NH ice-sheets controlled climate. The transition period falls within the range of interglacials (about -2 to +8 ˚ C with respect to present day) and is thus characterized by lower ice volume changes per ˚ C. The relationship between temperature, sea level and δ18O input is tested with an equilibrium experiment, which results in a linear and symmetric relationship for both temperature and total sea level, providing limited evidence for hysteresis, though transient behaviour is still important. Furthermore results show a rather good comparison with other simulations of Antarctic ice volume and observed sea level and deep-sea temperature.

  14. High-Performance Supercapacitor Electrode Based on Cobalt Oxide-Manganese Dioxide-Nickel Oxide Ternary 1D Hybrid Nanotubes.

    PubMed

    Singh, Ashutosh K; Sarkar, Debasish; Karmakar, Keshab; Mandal, Kalyan; Khan, Gobinda Gopal

    2016-08-17

    We report a facile method to design Co3O4-MnO2-NiO ternary hybrid 1D nanotube arrays for their application as active material for high-performance supercapacitor electrodes. This as-prepared novel supercapacitor electrode can store charge as high as ∼2020 C/g (equivalent specific capacitance ∼2525 F/g) for a potential window of 0.8 V and has long cycle stability (nearly 80% specific capacitance retains after successive 5700 charge/discharge cycles), significantly high Coulombic efficiency, and fast response time (∼0.17s). The remarkable electrochemical performance of this unique electrode material is the outcome of its enormous reaction platform provided by its special nanostructure morphology and conglomeration of the electrochemical properties of three highly redox active materials in a single unit. PMID:27430868

  15. Colliding Two Shocks: 1-D full Particle-in-Cell Simulation

    NASA Astrophysics Data System (ADS)

    Nakanotani, Masaru; Hada, T.; Matsukiyo, Shuichi; Mazelle, Christian

    2016-07-01

    Shock-shock interactions occur on various places in space and the interaction can produce high energy particles. A coronal mass ejection driven shock can collide with the Earth's bow shock [Hietala et al., 2011]. This study reported that ions are accelerated by the first Fermi acceleration between the two shocks before the collision. An electron acceleration through an interplanetary shock-Earth's bow shock interaction was also reported [Terasawa et al., 1997]. Shock-shock interactions can occur in astrophysical phenomena as well as in the heliosphere. For example, a young supernova shock can collide with the wind termination shock of a massive star if they are close to each other [Bykov et al., 2013]. Although hybrid simulations (ions and electrons treated as super-particles and mass-less fluid, respectively) were carried out to understand the kinetic nature of a shock-shock interaction [Cargill et al., 1986], hybrid simulations cannot resolve electron dynamics and non-thermal electrons. We, therefore, use one-dimensional full particle-in-cell (PIC) simulations to investigate a shock-shock interaction in which two shocks collide head-on. In a case of quasi-perpendicular shocks, electrons are accelerated by the mirror reflection between the two shocks before the collision (Fermi acceleration). On the other hand, because ions cannot go back upstream, the electron acceleration mechanism does not occur for ions. In a case of quasi-parallel shocks, ions can go back upstream and are accelerated at the shocks. The accelerated ions have great effect on the shock structure.

  16. Hybrid2 - The hybrid power system simulation model

    SciTech Connect

    Baring-Gould, E.I.; Green, H.J.; Dijk, V.A.P. van; Manwell, J.F.

    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.

  17. Specifications of ZnO growth for heterostructure solar cell and PC1D based simulations

    PubMed Central

    Hussain, Babar; Ebong, Abasifreke

    2015-01-01

    This data article is related to our recently published article (Hussain et al., in press [1]) where we have proposed a new solar cell model based on n-ZnO as front layer and p-Si as rear region. The ZnO layer will act as an active n-layer as well as antireflection (AR) coating saving considerable processing cost. There are several reports presenting use of ZnO as window/antireflection coating in solar cells (Mansoor et al., 2015; Haq et al., 2014; Hussain et al., 2014; Matsui et al., 2014; Ding et al., 2014 [2], [3], [4], [5], [6]) but, here, we provide data specifically related to simultaneous use of ZnO as n-layer and AR coating. Apart from the information we already published, we provide additional data related to growth of ZnO (with and without Ga incorporation) layers using MOCVD. The data related to PC1D based simulation of internal and external quantum efficiencies with and without antireflection effects of ZnO as well as the effects of doping level in p-Si on current–voltage characteristics have been provided. PMID:26587557

  18. 1D-Simulation of Thermonuclear Target Compression and Burning for Laser Facility NIF and LMJ

    SciTech Connect

    Valiev, R. Zh.; Chizhkov, M. N.; Karlyhanov, N. G.; Lusganova, O. V.; Lykov, V. A.; Netsvetayev, D. S.; Timakova, M. S.

    2006-08-03

    The high-power laser facilities NIF and LMJ with the pulse energy as high as 2 MJ are being created in the USA and France. The basic cryogenic indirect-drive targets for thermonuclear ignition on these facilities are a spherical shell from polystyrene doped with oxygen and bromine. (CH+5%O+0,25%Br), whose inner surface is covered with DT-ice layer. The central region of targets is filled with DT-gas. The targets for NIF and LMJ have different external radii (1,11 and 1,215 mm, correspondingly), masses of DT-fuel (210 icy 310 {mu}g), X-ray radiation temperature dependences in time. The thermonuclear yield from the NIF target calculated with LASNEX code is 15 MJ, the yield from the LMJ target calculated with FCI1 code is 25.4 MJ. In RFNC-VNIITF calculations of compression and burning of basic NIF and LMJ targets were performed by using of the 1D ERA code in the spectral diffusion approximation for radiation transfer. We used tabulated opacity calculated by the mean ion model. Thermonuclear yield calculated with ERA code is about 18 MJ for the NIF target and nearly 23 MJ for the LMJ target. Calculated yields are in good agreement with published results. Performed calculations justified the possibility to simulate ICF targets in RFNC-VNIITF. In paper are also presented analysis results of target sensitivity to opacity and X-ray temperature variations.

  19. Simulation of a Hybrid Locomotion Robot Vehicle

    NASA Astrophysics Data System (ADS)

    Aarnio, P.

    2002-10-01

    This study describes a simulation process of a mobile robot. The focus is in kinematic and dynamic behavior simulations of hybrid locomotion robot vehicles. This research is motivated by the development needs of the WorkPartner field service robot. The whole robot system consists of a mobile platform and a two-hand manipulator. The robot platform, called Hybtor, is a hybrid locomotion robot capable of walking and driving by wheels as well as combining these two locomotion modes. This study describes first the general problems and their solutions in the dynamic simulation of mobile robots. A kinematic and dynamic virtual model of the Hybtor robot was built and simulations were carried out using one commercial simulation tool. Walking, wheel driven and rolking mode locomotion, which is a special hybrid locomotion style, has been simulated and analyzed. Position and force control issues during obstacle overrun and climbing were also studied.

  20. Validation of a 3D/1D Simulation Tool for ICRF Antennas

    NASA Astrophysics Data System (ADS)

    Maggiora, R.; Lancellotti, V.; Milanesio, D.; Vecchi, G.; Kyrytsya, V.; Parisot, A.; Wukitch, S. J.

    2005-09-01

    TOPICA is an innovative tool for the simulation of the Ion Cyclotron Radio Frequency (ICRF) antenna systems that incorporates commercial-grade graphic interfaces into a fully 3D self-consistent description of the antenna geometry and an accurate description of the plasma; it can be considered as a "Virtual Prototyping Laboratory" to assist the detailed design phase of the antenna system. Recent theoretical and computational advances of the TOPICA code has allowed to incorporate a CAD drawing capability of the antenna geometry, with fully 3D geometrical modeling, and to combine it with a 1D accurate plasma description that takes into account density and temperature profiles, and FLR effects; the profiles are inserted directly from measured data (when available), or specified analytically by the user. The coaxial feeding line is modeled as such; computation and visualization of relevant parameters (input scattering parameters, current and field distributions, etc.) complete the suite. The approach to the problem is based on an integral-equation formulation for the self-consistent evaluation of the current distribution on the conductors. The environment has been subdivided in two coupled region: the plasma region and the vacuum region. The two problems are linked self-consistently by representing the field continuity in terms of equivalent (unknown) sources. In the vacuum region all the calculations are executed in the spatial (configuration) domain, and this allows triangular-facet description of the arbitrarily shaped conductors and associated currents; in the plasma region a spectral representation of the fields is used, which allows to enter the plasma effect via a surface impedance matrix; for this reason any plasma model can be used, and at present the FELICE code has been adopted; special techniques have been adopted to increase the numerical efficiency. The TOPICA suite has been previously tested against assessed codes and against measurements of mock-ups and

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  2. Spatially branched hierarchical ZnO nanorod-TiO2 nanotube array heterostructures for versatile photocatalytic and photoelectrocatalytic applications: towards intimate integration of 1D-1D hybrid nanostructures.

    PubMed

    Xiao, Fang-Xing; Hung, Sung-Fu; Tao, Hua Bing; Miao, Jianwei; Yang, Hong Bin; Liu, Bin

    2014-12-21

    Hierarchically ordered ZnO nanorods (NRs) decorated nanoporous-layer-covered TiO2 nanotube array (ZnO NRs/NP-TNTAs) nanocomposites have been prepared by an efficient, two-step anodization route combined with an electrochemical deposition strategy, by which monodispersed one-dimensional (1D) ZnO NRs were uniformly grown on the framework of NP-TNTAs. The crystal phases, morphologies, optical properties, photocatalytic as well as photoelectrocatalytic performances of the well-defined ZnO NRs/NP-TNTAs heterostructures were systematically explored to clarify the structure-property correlation. It was found that the ZnO NRs/NP-TNTAs heterostructure exhibits significantly enhanced photocatalytic and photoelectrocatalytic performances, along with favorable photostability toward degradation of organic pollutants under UV light irradiation, as compared to the single component counterparts. The remarkably enhanced photoactivity of ZnO NRs/NP-TNTAs heterostructure is ascribed to the intimate interfacial integration between ZnO NRs and NP-TNTAs substrate imparted by the unique spatially branched hierarchical structure, thereby contributing to the efficient transfer and separation of photogenerated electron-hole charge carriers. Moreover, the specific active species during the photocatalytic process was unambiguously determined and photocatalytic mechanism was tentatively presented. It is anticipated that our work could provide new insights for the construction of various hierarchical 1D-1D hybrid nanocomposites for extensive photocatalytic applications. PMID:25363649

  3. NASA One-Dimensional Combustor Simulation--User Manual for S1D_ML

    NASA Technical Reports Server (NTRS)

    Stueber, Thomas J.; Paxson, Daniel E.

    2014-01-01

    The work presented in this paper is to promote research leading to a closed-loop control system to actively suppress thermo-acoustic instabilities. To serve as a model for such a closed-loop control system, a one-dimensional combustor simulation composed using MATLAB software tools has been written. This MATLAB based process is similar to a precursor one-dimensional combustor simulation that was formatted as FORTRAN 77 source code. The previous simulation process requires modification to the FORTRAN 77 source code, compiling, and linking when creating a new combustor simulation executable file. The MATLAB based simulation does not require making changes to the source code, recompiling, or linking. Furthermore, the MATLAB based simulation can be run from script files within the MATLAB environment or with a compiled copy of the executable file running in the Command Prompt window without requiring a licensed copy of MATLAB. This report presents a general simulation overview. Details regarding how to setup and initiate a simulation are also presented. Finally, the post-processing section describes the two types of files created while running the simulation and it also includes simulation results for a default simulation included with the source code.

  4. Design and Simulation of Hybridization Experiments

    1995-11-28

    DB EXP DESIGN is a suite of three UNIX shell-like programs, DWC which computes oligomer composition of DNA texts using directed acyclic word data structures; DWO, which simulates hybridization experiments; and DMI, which calculates the information contenet of individual probes, their mutual information content, and their joint information content through estimation of Markov trees.

  5. TRNSYS HYBRID wind diesel PV simulator

    SciTech Connect

    Quinlan, P.J.A.; Mitchell, J.W.; Klein, S.A.; Beckman, W.A.; Blair, N.J.

    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.

  6. Comparison of 1D stagnation solutions to 3D wire-array Z pinch simulations in absence of radiation

    NASA Astrophysics Data System (ADS)

    Yu, Edmund; Velikovich, Alexander; Maron, Yitzhak

    2013-10-01

    In the idealized picture of a Z pinch, a cylindrically symmetric plasma shell implodes towards axis. In this 1D (radial) picture, the resulting stagnation is very efficient: all the kinetic energy of the shell converts to internal energy, as for instance in the Noh shock solution or the homogeneous stagnation flow. If we generalize the problem to 2D by deforming the shell from perfectly circular to oblate, the resulting stagnation will not be as efficient. As in the Hiemenz flow, in which a jet of fluid strikes a rigid flat boundary and squirts out to the sides, the more complicated flows allowed in 2D allow flow kinetic energy to redirect rather than stagnate. With this picture in mind, we might expect the stagnation of a wire-array Z pinch, which in actuality forms a highly distorted 3D imploding plasma, to dissipate its kinetic energy inefficiently due to the lack of symmetry, and be indescribable by means of the idealized 1D stagnation solutions. On the other hand, one might expect that if the imploding plasma is sufficiently messy, the non-uniformities might ``wash out,'' allowing a quasi-1D description of the averaged quantities of plasma. In this work we explore this idea, comparing predictions of 1D stagnation solutions with 3D simulation. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC0 4-94AL85000.

  7. Understanding the Rayleigh-Taylor instability through 1D and 3D simulations

    NASA Astrophysics Data System (ADS)

    Mikhaeil, Mark; Denissen, Nicholas; Ranjan, Devesh

    2015-11-01

    A series of Rayleigh-Taylor instability numerical simulations were completed using the Arbitrary Lagrangian-Eulerian hydrocode FLAG developed at Los Alamos National Laboratory. One-dimensional simulations employed a Reynolds-averaged Navier-Stokes approach with turbulence closure models selected from the Besnard-Harlow-Rauenzahn family of models. Growth rate parameters and turbulence statistics are derived from these simulations and compared between closure models. Variations from experimental results are explored and used to validate the models. The effect of density ratio on the bubble-spike growth rate asymmetry is also investigated. High resolution three-dimensional large eddy simulations (LES) are also completed and presented. LES were initialized using a multi-modal perturbation prescribed from experimental data collected at the Georgia Institute of Technology multi-layer Gas Tunnel facility. Turbulence statistics are gathered by averaging many simulations started with different initial conditions. Late time development is compared to Gas Tunnel experimental results and previous LES.

  8. Improved 1D model for calculating hydraulic properties in meandering rivers: Comparisons with measurements and 3D numerical simulations

    NASA Astrophysics Data System (ADS)

    Haji Mohammadi, M.; Kang, S.; Sotiropoulos, F.

    2011-12-01

    It is well-known that meander bends impose local losses of energy to the flow in rivers. These local losses should be added together with friction loss to get the total loss of energy. In this work, we strive to develop a framework that considers the effect of bends in meandering rivers for one-dimensional (1-D) homogenous equations of flow. Our objective is to develop a simple, yet physically sound, and efficient model for carrying out engineering computations of flow through meander bends. We consider several approaches for calculating 1-D hydraulic properties of meandering rivers such as friction factor and Manning coefficient. The method of Kasper et al. (2005), which is based on channel top width, aspect ratio and radius of curvature, is adopted for further calculations. In this method, a correction is implemented in terms of local energy loss, due to helical motion and secondary currents of fluid particles driven by centrifugal force, in meanders. To validate the model, several test cases are simulated and the computed results are compared with the reported data in the literature in terms of water surface elevation, shear velocity, etc. For all cases the computed results are in reasonable agreement with the experimental data. 3-D RANS turbulent flow simulations are also carried out, using the method of Kang et al. (Adv. In Water Res., vol. 34, 2011), for different geometrical parameters of Kinoshita Rivers to determine the spatial distribution of shear stress on river bed and banks, which is the key factor in scour/deposition patterns. The 3-D solutions are then cross-sectionally averaged and compared with the respective solutions from the 1-D model. The comparisons show that the improved 1D model, which incorporates the effect of local bend loss, captures key flow parameters with reasonable accuracy. Our results also underscore the range of validity and limitations of 1D models for meander bend simulations. This work was supported by NSF Grants (as part of

  9. Gen Purpose 1-D Finite Element Network Fluid Flow Heat Transfer System Simulator

    1993-08-02

    SAFSIM (System Analysis Flow Simulator) is a FORTRAN computer program to simulate the integrated performance of systems involving fluid mechanics, heat transfer, and reactor dynamics. SAFSIM provides sufficient versatility to allow the engineering simulation of almost any system, from a backyard sprinkler system to a clustered nuclear reactor propulsion system. In addition to versatility, speed and robustness are primary SAFSIM development goals. SAFSIM contains three basic physics modules: (1) a one-dimensional finite element fluid mechanicsmore » module with multiple flow network capability; (2) a one-dimensional finite element structure heat transfer module with multiple convection and radiation exchange capability; and (3) a point reactor dynamics module with reactivity feedback and decay heat capability. SAFSIM can be used for compressible and incompressible, single-phase, multicomponent flow systems.« less

  10. Analysis of instability growth and collisionless relaxation in thermionic converters using 1-D PIC simulations

    SciTech Connect

    Kreh, B.B.

    1994-12-01

    This work investigates the role that the beam-plasma instability may play in a thermionic converter. The traditional assumption of collisionally dominated relaxation is questioned, and the beam-plasma instability is proposed as a possible dominant relaxation mechanism. Theory is developed to describe the beam-plasma instability in the cold-plasma approximation, and the theory is tested with two common Particle-in-Cell (PIC) simulation codes. The theory is first confirmed using an unbounded plasma PIC simulation employing periodic boundary conditions, ES1. The theoretically predicted growth rates are on the order of the plasma frequencies, and ES1 simulations verify these predictions within the order of 1%. For typical conditions encountered in thermionic converters, the resulting growth period is on the order of 7 {times} 10{sup {minus}11} seconds. The bounded plasma simulation PDP1 was used to evaluate the influence of finite geometry and the electrode boundaries. For this bounded plasma, a two-stream interaction was supported and resulting in nearly complete thermalization in approximately 5 {times} 10{sup {minus}10} seconds. Since the electron-electron collision rate of 10{sup 9} Hz and the electron atom collision rate of 10{sup 7} Hz are significantly slower than the rate of development of these instabilities, the instabilities appear to be an important relaxation mechanism.

  11. Ion velocity distribution at the termination shock: 1-D PIC simulation

    SciTech Connect

    Lu Quanming; Yang Zhongwei; Lembege, Bertrand

    2012-11-20

    The Voyager 2 (V2) plasma observations of the proton temperature downstream of the quasi-perpendicular heliospheric termination shock (TS) showed that upstream thermal solar wind ions played little role in the shock dissipation mechanism and their downstream temperature is an order of magnitude smaller than predicted by MHD Rankine-Hugoniot conditions. While pickup ions (PUI) are generally expected to play an important role in energy dissipation at the shock, the details remain unclear. Here, one-dimensional (1-D) Particle-in-cell (PIC) code is used to examine kinetic properties and downstream velocity distribution functions of pickup ions (the hot supra-thermal component) and solar wind protons (SWs, the cold component) at the perpendicular heliospheric termination shock. The code treats the pickup ions self-consistently as a third component. Present results show that: (1) both of the incident SWs and PUIs can be separated into two parts: reflected (R) ions and directly transmitted (DT) ions, the energy gain of the R ions at the shock front is much larger than that of the DT ions; (2) the fraction of reflected SWs and their downstream temperature decrease with the relative percentage PUI%; (3) no matter how large the PUI% is, the downstream ion velocity distribution function always can be separated into three parts: 1. a high energy tail (i.e. the wings) dominated by the reflected PUIs, 2. a low energy core mainly contributed by the directly transmitted SWs, and 3. a middle energy part which is a complicated superposition of reflected SWs and directly transmitted PUIs. The significance of the presence of pickup ions on shock front micro-structure and nonstationarity is also discussed.

  12. Global Hybrid Simulations of the Bow Shock

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Blanco-Cano, X.; Russell, C. T.

    2005-08-01

    This paper summarizes recent results from global hybrid (kinetic ions, fluid electrons) simulations of bow shocks or waves associated with solar wind interaction with magnetic dipoles of various strength. By virtue of resolving ion temporal and spatial scales, global hybrid simulations account for collissionless dissipational processes at and upstream of the shock and their effects on the macrostructure of the bow shock, ion foreshock and the magnetosheath. The results demonstrate that as the level of magnetization increases and the dipole becomes a more effective obstacle, the quasi-perpendicular part of the bow shock forms first and that formation of quasi-parallel part of the bow shock is tied to the generation of oblique magnetosonic waves which steepen to form shocklets in the upstream region.

  13. A Mass Conservative Method for Integrating 1-D Vadose Zone Simulations Discretized in the Moisture Content Domain with 2-D Groundwater Interflow Simulations

    NASA Astrophysics Data System (ADS)

    Steinke, R. C.

    2015-12-01

    Discretizing 1-D vadose zone simulations in the moisture content domain, such as is done in the Talbot-Ogden method, provides some advantages over discretizing in depth, such as is done in Richards' Equation. These advantages include inherent mass conservation and lower computational cost. However, doing so presents a difficulty for integration with 2-D groundwater interflow simulations. The equations of motion of the bins of discrete moisture content take the depth of the water table as an input. They do not produce it as an output. Finding the correct water table depth so that the groundwater recharge from the 1-D vadose zone simulation mass balances with the lateral flows from the 2-D groundwater interflow simulation was a previously unsolved problem. In this paper we present a net-groundwater-recharge method to solve to this problem and compare it with the source-term method used with Richards' Equation.

  14. SPH_1D: Hierarchical gravity/SPH treecode for simulations of interacting galaxies

    NASA Astrophysics Data System (ADS)

    Olson, Kevin M.; Dorband, John E.

    1999-12-01

    We describe a fast tree algorithm for gravitational N-body simulation on SIMD parallel computers. The tree construction uses fast, parallel sorts. The sorted lists are recursively divided along their x, y and z coordinates. This data structure is a completely balanced tree (i.e., each particle is paired with exactly one other particle) and maintains good spatial locality. An implementation of this tree-building algorithm on a 16k processor Maspar MP-1 performs well and constitutes only a small fraction (approximately 15%) of the entire cycle of finding the accelerations. Each node in the tree is treated as a monopole. The tree search and the summation of accelerations also perform well. During the tree search, node data that is needed from another processor is simply fetched. Roughly 55% of the tree search time is spent in communications between processors. We apply the code to two problems of astrophysical interest. The first is a simulation of the close passage of two gravitationally, interacting, disk galaxies using 65,636 particles. We also simulate the formation of structure in an expanding, model universe using 1,048,576 particles. Our code attains speeds comparable to one head of a Cray Y-MP, so single instruction, multiple data (SIMD) type computers can be used for these simulations. The cost/performance ratio for SIMD machines like the Maspar MP-1 make them an extremely attractive alternative to either vector processors or large multiple instruction, multiple data (MIMD) type parallel computers. With further optimizations (e.g., more careful load balancing), speeds in excess of today's vector processing computers should be possible.

  15. On the parameterization of 1D vertical mixing in planetary atmospheres: insights from 2D and 3D simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Xi; Showman, Adam P.

    2015-11-01

    Most of the current atmospheric chemistry models for planets (e.g., Krasnopolsky & Parshev 1981; Yung & Demore 1982; Yung, Allen & Pinto 1984; Lavvas et al. 2008; Zhang et al. 2012) and exoplanets (e.g., Line, Liang & Yung 2010; Moses et al. 2011; Hu & Seager 2014) adopt a one-dimensional (1D) chemical-diffusion approach in the vertical coordinate. Although only a crude approximation, these 1D models have succeeded in explaining the global-averaged vertical profiles of many chemical species in observations. One of the important assumptions of these models is that all chemical species are transported via the same eddy diffusion profile--that is, the assumption is made that the eddy diffusivity is a fundamental property of the dynamics alone, and does not depend on the chemistry. Here we show that, as also noticed in the Earth community (e.g., Holton 1986), this “homogenous eddy diffusion” assumption generally breaks down. We first show analytically why the 1D eddy diffusivity must generally depend both on the horizontal eddy mixing and the chemical lifetime of the species. This implies that the long-lived species and short-lived chemical species will generally exhibit different eddy diffusion profiles, even in a given atmosphere with identical dynamics. Next, we present tracer-transport simulations in a 2D chemical-diffusion-advection model (Shia et al. 1989; Zhang, Shia & Yung 2013) and a 3D general circulation model (MITgcm, e.g., Liu & Showman 2013), for both rapid-rotating planets and tidally-locked exoplanets, to further explore the effect of chemical timescales on the eddy diffusivity. From the 2D and 3D simulation outputs, we derive effective 1D eddy diffusivity profiles for chemical tracers exhibiting a range of chemical timescales. We show that the derived eddy diffusivity can depend strongly on the horizontal eddy mixing and chemistry, although the dependences are more complex than the analytic model predicts. Overall, these results suggest that

  16. Hybrid simulations of rotational discontinuities. [Alfven wave propagation in astrophysics

    NASA Technical Reports Server (NTRS)

    Goodrich, C. C.; Cargill, P. J.

    1991-01-01

    1D hybrid simulations of rotational discontinuities (RDs) are presented. When the angle between the discontinuity normal and the magnetic field (theta-BN) is 30 deg, the RD broadens into a quasi-steady state of width 60-80 c/omega-i. The hodogram has a characteristic S-shape. When theta-BN = 60 deg, the RD is much narrower (10 c/omega-i). For right handed rotations, the results are similar to theta-BN = 30 deg. For left handed rotations, the RD does not evolve much from its initial conditions and the S-shape in the hodogram is much less visible. The results can be understood in terms of matching a fast mode wavelike structure upstream of the RD with an intermediate mode one downstream.

  17. Simulating the focusing of light onto 1D nanostructures with a B-spline modal method

    NASA Astrophysics Data System (ADS)

    Bouchon, P.; Chevalier, P.; Héron, S.; Pardo, F.; Pelouard, J.-L.; Haïdar, R.

    2015-03-01

    Focusing the light onto nanostructures thanks to spherical lenses is a first step to enhance the field, and is widely used in applications, in particular for enhancing non-linear effects like the second harmonic generation. Nonetheless, the electromagnetic response of such nanostructures, which have subwavelength patterns, to a focused beam can not be described by the simple ray tracing formalism. Here, we present a method to compute the response to a focused beam, based on the B-spline modal method. The simulation of a gaussian focused beam is obtained thanks to a truncated decomposition on plane waves computed on a single period, which limits the computation burden.

  18. Single-Layered Hybrid Materials Based on 1D Associated Metalorganic Nanoribbons for Controlled Release of Pheromones.

    PubMed

    Moreno, José María; Navarro, Ismael; Díaz, Urbano; Primo, Jaime; Corma, Avelino

    2016-09-01

    A new family of stable layered organic-inorganic materials has been prepared, in one-step solvothermal process. They are based on an ordered nickel cluster-type nanoribbons separated from each other by specific alkyl (heptyl- or dodecyl-) arylic mono-carboxylate moieties acting as molecular spacers, perpendicular to the 1D inorganic chains. These organic spacers contain hydrocarbon tails with different length which control the separation level between inorganic 1D sub-units, inhibiting the 3D growth of conventional DUT-8-type metal-organic frameworks (MOFs). The lamellar nature of the materials formed was studied and confirmed by different characterization techniques, showing the structural location of individual organic and inorganic building units. They have been successfully used as a long-lasting biodegradable and water-proof materials for controlled release of chemicals, such as pheromones for sustainable treatment of insect plagues. PMID:27444798

  19. The research of 1D / 3D coupling simulation on pump and pipe system

    NASA Astrophysics Data System (ADS)

    Wu, D. Z.; Liu, Q. L.; Wu, P.; Wang, L. Q.; Paulus, T.; Wang, B. G.; Oesterle, M.

    2012-11-01

    The research of performances of hydraulic mechanical depends on static complete characteristic curves, which have great difference compared with the actual work condition and have accidents potential. So we need a new way to compute the dynamic system, which is more reasonable. So the method to couple one dimensional simulation and three dimensional CFD analysis based on Flowmaster and Fluent is explored, and the dynamic characteristics and internal flow of the pumping system are analyzed. First, a pipe system model is created in Flowmaster and a pump model is created in Fluent; then VB code and scheme code are used to realize the automated operation for Flowmaster and Fluent; at last, the exchange of data between these two parts is realized by an interface program. In this paper, the interaction between pumps and pipe system are analyzed by coupling one-dimensional and three-dimensional simulations. This study would be helpful to identify the influences of the rapid adjustment process on stability of system and provide guides for design of pump system.

  20. Impact of Variations on 1-D Flow in Gas Turbine Engines via Monte Carlo Simulations

    NASA Technical Reports Server (NTRS)

    Ngo, Khiem Viet; Tumer, Irem

    2004-01-01

    The unsteady compressible inviscid flow is characterized by the conservations of mass, momentum, and energy; or simply the Euler equations. In this paper, a study of the subsonic one-dimensional Euler equations with local preconditioning is presented using a modal analysis approach. Specifically, this study investigates the behavior of airflow in a gas turbine engine using the specified conditions at the inflow and outflow boundaries of the compressor, combustion chamber, and turbine, to determine the impact of variations in pressure, velocity, temperature, and density at low Mach numbers. Two main questions motivate this research: 1) Is there any aerodynamic problem with the existing gas turbine engines that could impact aircraft performance? 2) If yes, what aspect of a gas turbine engine could be improved via design to alleviate that impact and to optimize aircraft performance? This paper presents an initial attempt to model the flow behavior in terms of their eigenfrequencies subject to the assumption of the uncertainty or variation (perturbation). The flow behavior is explored using simulation outputs from a customer-deck model obtained from Pratt & Whitney. Variations of the main variables (i.e., pressure, temperature, velocity, density) about their mean states at the inflow and outflow boundaries of the compressor, combustion chamber, and turbine are modeled. Flow behavior is analyzed for the high-pressure compressor and combustion chamber utilizing the conditions on their left and right boundaries. In the same fashion, similar analyses are carried out for the high-pressure and low-pressure turbines. In each case, the eigenfrequencies that are obtained for different boundary conditions are examined closely based on their probabilistic distributions, a result of a Monte Carlo 10,000 sample simulation. Furthermore, the characteristic waves and wave response are analyzed and contrasted among different cases, with and without preconditioners. The results reveal

  1. Linking 1D evolutionary to 3D hydrodynamical simulations of massive stars

    NASA Astrophysics Data System (ADS)

    Cristini, A.; Meakin, C.; Hirschi, R.; Arnett, D.; Georgy, C.; Viallet, M.

    2016-03-01

    Stellar evolution models of massive stars are important for many areas of astrophysics, for example nucleosynthesis yields, supernova progenitor models and understanding physics under extreme conditions. Turbulence occurs in stars primarily due to nuclear burning at different mass coordinates within the star. The understanding and correct treatment of turbulence and turbulent mixing at convective boundaries in stellar models has been studied for decades but still lacks a definitive solution. This paper presents initial results of a study on convective boundary mixing (CBM) in massive stars. The ‘stiffness’ of a convective boundary can be quantified using the bulk Richardson number ({{Ri}}{{B}}), the ratio of the potential energy for restoration of the boundary to the kinetic energy of turbulent eddies. A ‘stiff’ boundary ({{Ri}}{{B}}˜ {10}4) will suppress CBM, whereas in the opposite case a ‘soft’ boundary ({{Ri}}{{B}}˜ 10) will be more susceptible to CBM. One of the key results obtained so far is that lower convective boundaries (closer to the centre) of nuclear burning shells are ‘stiffer’ than the corresponding upper boundaries, implying limited CBM at lower shell boundaries. This is in agreement with 3D hydrodynamic simulations carried out by Meakin and Arnett (2007 Astrophys. J. 667 448-75). This result also has implications for new CBM prescriptions in massive stars as well as for nuclear burning flame front propagation in super-asymptotic giant branch stars and also the onset of novae.

  2. A PIC simulation study on the evolution of the real and imaginary frequencies of 1D plasma waves

    NASA Astrophysics Data System (ADS)

    Grismayer, Thomas; Fahlen, Jay; Winjum, Benjamin; Tsung, Frank; Morales, George; Mori, Warren

    2009-11-01

    We use electrostatic PIC simulations to study the evolution of both the real and complex frequency of 1D plasma waves. We are considering especially the linear regime where the asymptotic damping rate is much bigger than the bounce frequency. In this regime the waves are typically very small and below the thermal noise. These waves can be studied using a subtraction technique where two simulations where identical random number generation seeds are carried out. In the first, a small amplitude wave is excited. In the second simulation no wave is excited. The results from each simulation are subtracted providing a clean linear wave that can be studied. As previously predicted, the damping is divided in two stages, an initial transient and an asymptotic decay (Landau's formula). The time-dependent resonant width measured in the simulations is compared with the theoretical prediction. In typical ICF plasmas nld^3 <˜10^3. Therefore, the number of resonant electrons can be small for linear waves. We will consider the effects of small numbers of resonant particles and their consequences of the observed damping.

  3. 1-D DSMC simulation of Io's atmospheric collapse and reformation during and after eclipse

    NASA Astrophysics Data System (ADS)

    Moore, C. H.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.; Stewart, B.

    2009-06-01

    A one-dimensional Direct Simulation Monte Carlo (DSMC) model is used to examine the effects of a non-condensable species on Io's sulfur dioxide sublimation atmosphere during eclipse and just after egress. Since the vapor pressure of SO 2 is extremely sensitive to temperature, the frost-supported dayside sublimation atmosphere had generally been expected to collapse during eclipse as the surface temperature dropped. For a pure SO 2 atmosphere, however, it was found that during the first 10 min of eclipse, essentially no change in the atmospheric properties occurs at altitudes above ˜100 km due to the finite ballistic/acoustic time. Hence immediately after ingress the auroral emission morphology above 100 km should resemble that of the immediate pre-eclipse state. Furthermore, the collapse dynamics are found to be greatly altered by the presence of even a small amount of a non-condensable species which forms a diffusion layer near the surface that prevents rapid collapse. It is found that after 10 min essentially no collapse has occurred at altitudes above ˜20 km when a nominal mole fraction of non-condensable gas is present. Collapse near the surface occurs relatively quickly until a static diffusion layer many mean free paths thick of the non-condensable gas builds up which then retards further collapse of the SO 2 atmosphere. For example, for an initial surface temperature of 110 K and 35% non-condensable mole-fraction, the ratio of the SO 2 column density to the initial column density was found to be 0.73 after 10 min, 0.50 after 30 min, and 0.18 at the end of eclipse. However, real gas species (SO, O 2) may not be perfectly non-condensable at Io's surface temperatures. If the gas species was even weakly condensable (non-zero sticking/reaction coefficient) then the effect of the diffusion layer on the dynamics was dramatically reduced. In fact, if the sticking coefficient of the non-condensable exceeds ˜0.25, the collapse dynamics are effectively the same as

  4. Calibration of a 1D Crustal Velocity and Q Model for Ground Motion Simulations in Central and Eastern US

    NASA Astrophysics Data System (ADS)

    Graves, R. W.

    2012-12-01

    I have performed low frequency (f < 1 Hz) ground motion simulations for the 2008 Mw 5.23 Mt. Carmel, Illinois and 2011 Mw 5.74 Mineral, Virginia earthquakes to calibrate a rock-site 1D crustal velocity and Q structure model for central and eastern US (CEUS). For each earthquake, the observed ground motions were simulated at sites extending out to about 900 km from the epicenter. Sites within the Mississippi embayment are not included in the modeling. The initial 1D velocity model was developed by averaging profiles extracted from the CUS V1.3 3D velocity model (Ramirez-Guzman et al, 2012) at each of the recording sites, with the surface shear wave velocity set at 2200 m/s. The Mt. Carmel earthquake is represented as a point double couple (strike=25, dip=90, rake=-175) at a depth of 14 km and a slip-rate function having a Brune corner frequency of 0.89 Hz (Hartzell and Mendoza, 2011). The Mineral earthquake is represented as a point double couple (strike=26, dip=55, rake=108) at a depth of 6 km and a slip-rate function having a corner frequency of 0.50 Hz. Full waveform Green's functions were computed using the FK method of Zhu and Rivera (2002). The initial model does well at reproducing the median level of observed response spectral acceleration (Sa) for most sites out to 300 km at periods of 2 to 5 sec, including the observed flattening in distance attenuation between 70 and 150 km. However, this model under predicts the motions beyond about 400 km distance. Increasing Q in the mid- and lower crust from the original value of 700 to 5000 removes this under prediction of the larger distance motions. Modified Mercalli Intensity (MMI) estimates have been computed from the simulations using the ground motion-intensity conversion equations of Atkinson and Kaka (2007; AK2007) and Dangkua and Cramer (2011; DC2011-ENA) for comparison against the observed "Did You Feel It" intensity estimates. Given the bandwidth limitations of the simulations, I use the conversion

  5. Forcing continuous reconnection in hybrid simulations

    SciTech Connect

    Laitinen, T. V. Janhunen, P.; Jarvinen, R.; Kallio, E.

    2014-07-15

    We have performed hybrid simulations of driven continuous reconnection with open boundary conditions. Reconnection is started by a collision of two subsonic plasma fronts with opposite magnetic fields, without any specified magnetic field configuration as initial condition. Due to continued forced plasma inflow, a current sheet co-located with a dense and hot plasma sheet develops. The translational symmetry of the current sheet is broken by applying a spatial gradient in the inflow speed. We compare runs with and without localized resistivity: reconnection is initiated in both cases, but localized resistivity stabilizes it and enhances its efficiency. The outflow speed reaches about half of Alfvén speed. We quantify the conversion of magnetic energy to kinetic energy of protons and to Joule heating and show that with localized resistivity, kinetic energy of protons is increased on average five-fold in the reconnection in our simulation case.

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

    NASA Astrophysics Data System (ADS)

    Düben, Peter D.; Dolaptchiev, Stamen I.

    2015-08-01

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

  7. Hybrid Concurrent Constraint Simulation Models of Several Systems

    NASA Technical Reports Server (NTRS)

    Sweet, Adam

    2003-01-01

    This distribution contains several simulation models created for the hybrid simulation language, Hybrid Concurrent Constraint (HCC). An HCC model contains the information specified in the widely-accepted academic definition of a hybrid system: this includes expressions for the modes of the systems to be simulated and the differential equations that apply in each mode. These expressions are written in the HCC syntax. The models included here were created by either applying basic physical laws or implementing equations listed in previously published papers.

  8. A phased approach to enable hybrid simulation of complex structures

    NASA Astrophysics Data System (ADS)

    Spencer, Billie F.; Chang, Chia-Ming; Frankie, Thomas M.; Kuchma, Daniel A.; Silva, Pedro F.; Abdelnaby, Adel E.

    2014-08-01

    Hybrid simulation has been shown to be a cost-effective approach for assessing the seismic performance of structures. In hybrid simulation, critical parts of a structure are physically tested, while the remaining portions of the system are concurrently simulated computationally, typically using a finite element model. This combination is realized through a numerical time-integration scheme, which allows for investigation of full system-level responses of a structure in a cost-effective manner. However, conducting hybrid simulation of complex structures within large-scale testing facilities presents significant challenges. For example, the chosen modeling scheme may create numerical inaccuracies or even result in unstable simulations; the displacement and force capacity of the experimental system can be exceeded; and a hybrid test may be terminated due to poor communication between modules (e.g., loading controllers, data acquisition systems, simulation coordinator). These problems can cause the simulation to stop suddenly, and in some cases can even result in damage to the experimental specimens; the end result can be failure of the entire experiment. This study proposes a phased approach to hybrid simulation that can validate all of the hybrid simulation components and ensure the integrity large-scale hybrid simulation. In this approach, a series of hybrid simulations employing numerical components and small-scale experimental components are examined to establish this preparedness for the large-scale experiment. This validation program is incorporated into an existing, mature hybrid simulation framework, which is currently utilized in the Multi-Axial Full-Scale Sub-Structuring Testing and Simulation (MUST-SIM) facility of the George E. Brown Network for Earthquake Engineering Simulation (NEES) equipment site at the University of Illinois at Urbana-Champaign. A hybrid simulation of a four-span curved bridge is presented as an example, in which three piers are

  9. Hybrid Simulation of the Shock Wave Trailing the Moon

    NASA Technical Reports Server (NTRS)

    Israelevich, P.; Ofman, Leon

    2012-01-01

    A standing shock wave behind the Moon was predicted by Michel (1967) but never observed nor simulated. We use 1D hybrid code in order to simulate the collapse of the plasma-free cavity behind the Moon and for the first time to model the formation of this shock. Starting immediately downstream of the obstacle we consider the evolution of plasma expansion into the cavity in the frame of reference moving along with the solar wind. Well-known effects as electric charging of the cavity affecting the plasma flow and counterstreaming ion beams in the wake are reproduced. Near the apex of the inner Mach cone where the plasma flows from the opposite sides of the obstacle meet, a shock wave arises. We expect the shock to be produced at periods of high electron temperature solar wind streams (T(sub i) much less than T(sub e) approximately 100 eV). The shock is produced by the interaction of oppositely directed proton beams in the plane containing solar wind velocity and interplanetary magnetic field vectors. In the direction across the magnetic field and the solar wind velocity, the shock results from the interaction of the plasma flow with the region of the enhanced magnetic field inside the cavity that plays the role of the magnetic barrier. The appearance of the standing shock wave is expected at the distance of approximately 7R(sub M) downstream of the Moon.

  10. Pluto's atmosphere-plasma interaction: Hybrid simulations

    NASA Astrophysics Data System (ADS)

    Delamere, P. A.; Bagenal, F.; Strobel, D. F.; Barnes, N. P.; McComas, D. J.; Elliott, H. A.; Hill, M. E.; McNutt, R. L., Jr.

    2015-12-01

    Pluto's low gravity implies that the atmosphere is only weakly bound. The escaping neutrals are photoionized and the heavy ions (N2+) move away from Pluto in the direction perpendicular to the solar wind flow (i.e., nearly unmagnetized relative to the length scales of the plasma interaction region). The turning distance of the solar wind protons at the magnetic pileup boundary is large compared to the interaction region. As a result, large ion gyroradius effects determine Pluto's highly asymmetric interaction with the solar wind. We use a three-dimensional hybrid code (fluid electrons, kinetic ions) to investigate the geometry of the interaction region using recent atmospheric models for hybrid simulation input. We will present initial results, showing the sensitivity of bow shock location to variations in the model atmosphere as well as variations in the solar wind conditions. Synthetic energy spectrograms taken from the simluations could be directly compared with the New Horizons plasma data to further constrain model input parameters. Initial results indicate that a full bow shock could form with possible structuring in the wake region due to bi-ion waves and Kelvin-Helmholtz waves.

  11. Accelerating Climate Simulations Through Hybrid Computing

    NASA Technical Reports Server (NTRS)

    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.

  12. Hybrid reference metrology exploiting patterning simulation

    NASA Astrophysics Data System (ADS)

    Rana, Narender; Archie, Chas

    2010-03-01

    Workhorse metrology such as CD-SEM is used during process development, process control, and optical proximity correction model generation and verification. Such metrology needs to be calibrated to handle various types of profiles encountered during IC fabrication. Reference metrology is used for calibration of workhorse metrology. There is an astounding need for sub-half and sub-quarter nanometer measurement uncertainty in the near future technology nodes as envisaged in the International Technology Roadmap for Semiconductors. In this regime of desired measurement uncertainty all metrology techniques are deemed limited and hybrid metrology appears promising to offer a solution. Hybrid metrology is the use of multiple metrology techniques, each with particular strength, to reduce the overall measurement uncertainty. CD-AFM makes use of a flared probe in order to scan the sidewalls and bottom of the pattern on a wafer to provide 3D profile and CD measurements at desired location on the profile. As the CD shrinks with technology nodes especially the space, the size of the AFM probe also needs to shrink while maintaining the flared geometry specifications. Unfortunately the fabrication of such probes is a challenge and new techniques are required to extend reference metrology to the smallest space and hole of interest. This paper proposes a reference system combining CD-AFM and patterning simulation model. This hybrid metrology system enables CD metrology in a space not measurable directly by conventional CD-AFM probe. The key idea is to use the successfully measured profile and CD information from the CD-AFM to calibrate or train the patterning simulation optical and resist model. Ability of this model to predict profile and CD measurement is verified on a physically measured dataset including cross sections and additional CD-AFM measurements. It is hypothesized that this model will be able to predict profile and CD measurements in otherwise immeasurable geometries

  13. Digital simulation of hybrid loop operation in RFI backgrounds.

    NASA Technical Reports Server (NTRS)

    Ziemer, R. E.; Nelson, D. R.

    1972-01-01

    A digital computer model for Monte-Carlo simulation of an imperfect second-order hybrid phase-locked loop (PLL) operating in radio-frequency interference (RFI) and Gaussian noise backgrounds has been developed. Characterization of hybrid loop performance in terms of cycle slipping statistics and phase error variance, through computer simulation, indicates that the hybrid loop has desirable performance characteristics in RFI backgrounds over the conventional PLL or the costas loop.

  14. A 1D-ecosystem model for pelagic waters in the southern Baltic Sea. Numerical simulations (future decades)

    NASA Astrophysics Data System (ADS)

    Dzierzbicka-Glowacka, L.; Maciejewska, A.; Osiński, R.; Jakacki, J.; Jędrasik, J.

    2009-04-01

    This paper presents a one-dimensional Ecosystem Model. Mathematically, the pelagic variables in the model are described by a second-order partial differential equation of the diffusion type with biogeochemical sources and sinks. The temporal changes in the phytoplankton biomass are caused by primary production, respiration, mortality, grazing by zooplankton and sinking. The zooplankton biomass is affected by ingestion, excretion, respiration, fecal production, mortality, and carnivorous grazing. The changes in the pelagic detritus concentration are determined by input of: dead phytoplankton and zooplankton, natural mortality of predators, fecal pellets, and sinks: sedimentation, zooplankton grazing and decomposition. The nutrient concentration is caused by nutrient release, zooplankton excretion, predator excretion, detritus decomposition and benthic regeneration as sources and by nutrient uptake by phytoplankton as sinks. However, the benthic detritus is described by phytoplankton sedimentation, detritus sedimentation and remineralisation. The particulate organic carbon concentration is determined as the sum of phytoplankton, zooplankton and dead organic matter (detritus) concentrations. The 1D ecosystem model was used to simulate the seasonal dynamics of pelagic variables (phytoplankton, zooplankton, pelagic detritus and POC) in the southern Baltic Sea (Gdańsk Deep, Bornholm Deep and Gotland Deep). The calculations were made assuming: 1) increase in the water temperature in the upper layer - 0.008oC per year, 2) increase in the available light - 0.2% per year. Based on this trend, daily, monthly and seasonal and annual variability of phytoplankton, zooplankton, pelagic detritus and particulate organic carbon in different areas of the southern Baltic Sea (Gdańsk Deep, Borrnholm Deep and Gotland Deep) in the euphotic layer was calculated for the years: 2000, 2010, 2020, 2030, 2040 and 2050.

  15. Hybrid Simulations of Plasma Environment Around Enceladus

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Russell, C.; Leisner, J.; Tokar, R.; Kurth, W.

    2008-12-01

    The Cassini flybys of the moon Enceladus have established the presence of magnetic field perturbations and plasma deflections due to its interaction with the corotating plasma. These observations show that the nature of the interaction region changes from one flyby to another indicating a time dependent behavior. In general, the field and plasma perturbations can be caused by the body of the moon, its exosphere (if present) and the plumes associated with the escape of neutral gasses from its southern hemisphere. Thus, the time dependency of the interaction region is tied to the variabilities of the neutral densities associated with the exosphere or plumes and also the observed, planetary rotation synched variation of plasma density in the region around the orbit of Enceladus . To understand the nature of plasma interaction with Enceladus we have conducted an investigation using 3-D electromagnetic hybrid simulations in which ions are treated kinetically while the electrons form a massless fluid. In these simulations, charge exchange between corotating ions and neutrals around Enceladus and plasma absorption by the body of the moon are included. The results show that the body of Enceladus by itself leads to an interaction consisting of a density cavity behind the moon with little change in plasma flow velocity and weak magnetic field perturbations. On the other hand, the presence of a dense enough exosphere or a plasma plume modify the nature of the interaction region significantly leading to more complex density and flow structures and generation of Alfvenic and slow magnetosonic wings. In this presentation, we describe these results in detail and show how the body of Enceladus, its exosphere and plumes contribute to the overall interaction region in isolation and collectively. We also compare the results with Cassini flyby data to estimate the neutral densities associated with the plumes and whether they indicate the presence of an exosphere or not.

  16. Hybrid simulations of thin current sheets

    NASA Technical Reports Server (NTRS)

    Burkhart, G. R.; Dusenbery, P. B.; Speiser, T. W.

    1993-01-01

    A one-dimensional, hybrid simulation code is used to study current sheets with a nonzero normal magnetic field B(sub z) and a dawn-to-dusk electric field E(sub y). Such configurations are dependent upon only two parameters: we use the normalized normal magnetic field B-normalized (sub z) = B(sub z)/(4(pi)(n(sub b)) (v(exp 2 sub T))(exp 1/2) and normalized electric field V-normalized (sub D) = (1/V(sub T)(cE(sub y)/B(sub z)), where V(sub T) is the thermal velocity of ions prior to their interaction with the current sheet and n(sub b) is the number density outside the current sheet (at the simulation boundary). A third parameter that is relevant to the motion of particles in current sheets is kappa(sub A), the value of kappa = (R(sub min)/rho(sub max))(exp 1/2) for particles of average energy. We find that if either B-normalized (sub z) is close to or greater than 1, or if kappa(sub A) is close to 1, a rotational mode develops in which the z = 0 current rotates with the ion sense about the normal magnetic field, while for small values of both B-normalized (sub z) or kappa(sub A), the configuration is quasi-steady. To achieve values of kappa(sub A) of the order of or larger than 1, we decrease the value of V-normalized (sub D) uniformly. We find that the magnetic field fluctuations and particle distribution functions are similar in many respects to what was observed in the day 240, 1986, Active Magnetospheric Particle Tracer Explorer (AMPTE)/CCE current disruption event, an event that appears to be located at the site of initiation of current disruption and related particle energization.

  17. Hybrid Simulations of Plasma Interactions with Enceladus

    NASA Astrophysics Data System (ADS)

    Omidi, Nojan; Russell, Christopher; Tokar, Robert; Leisner, Jared; Cowee, Misa

    During Cassini flybys of the moon Enceladus plasma deflections and magnetic field perturbations were detected. The changes in plasma and magnetic field properties are associated with the interaction of the corotating plasma with Enceladus. In general, this interaction can be caused by the body of the moon, Enceladus' exosphere and the plumes associated with the escape of neutral gasses. Cassini observations also suggest that the nature of the interaction region changed from one flyby to another indicating a time dependent behavior. Such a time dependence is expected given the variabilities of the exosphere and plumes with time. To understand the nature of the interaction region we have conducted an investigation using 3-D electromagnetic hybrid (kinetic ions, fluid electrons) simulations including charge exchange between ions and neutrals. The results show that in the absence of an exosphere and plumes the absorption of plasma by Enceladus leads to a density cavity behind the moon with little change in plasma flow velocity and weak magnetic field perturbations. Addition of an exosphere modifies the nature of the interaction region significantly leading to more complex density and flow structures and generation of an Alfven wing. Similarly, the presence of a plume modifies the interaction region considerably leading to asymmetric flow and magnetic field patterns. In this presentation, we describe these results in detail and show how the body of Enceladus, its exosphere and plumes contribute to the overall interaction region in isolation and collectively.

  18. Simulation and Analysis of the Hybrid Operating Mode in ITER

    SciTech Connect

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

    2005-09-22

    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.

  19. Hybrid and Electric Advanced Vehicle Systems Simulation

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    Predefined components connected to represent wide variety of propulsion systems. Hybrid and Electric Advanced Vehicle System (HEAVY) computer program is flexible tool for evaluating performance and cost of electric and hybrid vehicle propulsion systems. Allows designer to quickly, conveniently, and economically predict performance of proposed drive train.

  20. Relationships between Th1 or Th2 iNKT Cell Activity and Structures of CD1d-Antigen Complexes: Meta-analysis of CD1d-Glycolipids Dynamics Simulations

    PubMed Central

    Laurent, Xavier; Renault, Nicolas; Farce, Amaury; Chavatte, Philippe; Hénon, Eric

    2014-01-01

    A number of potentially bioactive molecules can be found in nature. In particular, marine organisms are a valuable source of bioactive compounds. The activity of an α-galactosylceramide was first discovered in 1993 via screening of a Japanese marine sponge (Agelas mauritanius). Very rapidly, a synthetic glycololipid analogue of this natural molecule was discovered, called KRN7000. Associated with the CD1d protein, this α-galactosylceramide 1 (KRN7000) interacts with the T-cell antigen receptor to form a ternary complex that yields T helper (Th) 1 and Th2 responses with opposing effects. In our work, we carried out molecular dynamics simulations (11.5 µs in total) involving eight different ligands (conducted in triplicate) in an effort to find out correlation at the molecular level, if any, between chemical modulation of 1 and the orientation of the known biological response, Th1 or Th2. Comparative investigations of human versus mouse and Th1 versus Th2 data have been carried out. A large set of analysis tools was employed including free energy landscapes. One major result is the identification of a specific conformational state of the sugar polar head, which could be correlated, in the present study, to the biological Th2 biased response. These theoretical tools provide a structural basis for predicting the very different dynamical behaviors of α-glycosphingolipids in CD1d and might aid in the future design of new analogues of 1. PMID:25376021

  1. Integrating a 1D Thermal Lake Model into a Global and Regional Climate Model: Model Evaluation and Regional Climate Simulation

    NASA Astrophysics Data System (ADS)

    Subin, Z. M.; Riley, W. J.

    2009-12-01

    Compared to solid ground, lakes tend to have decreased albedo, increased ground heat conductance, and increased effective ground heat capacity. These features alter local surface fluxes compared to nearby vegetation, which in turn alter the climate of the nearby atmosphere and surrounding land areas. Interest in feedbacks between lake behavior and climate change provides motivation for including lakes in global climate models, as does the desire to do effective regional downscaling of climate model predictions over regions with large lake area fraction, like the Great Lakes region. Finally, the initiation, warming, and expansion of Arctic thermokarst lakes could provide an important geophysical and biogeochemical feedback to climate warming. The Community Land Model (CLM) 3.5 currently uses a 1D Hostetler lake scheme. We have updated this model to improve the characterization of surface fluxes, eddy diffusivity, and convective mixing. We also link the lake model with the full snow physics found over other land surface types (including 5 snow layers, aerosol deposition, partial transparency of snow layers, and snow aging), add phase change & ice physics to the lake model, and include soil layers beneath lakes. These soil layers will be an important component of future thermokarst lake modeling, as thermokarst lakes tend to form regions of unfrozen soil (talik) beneath them that become active sites for anaerobic decomposition of pre-modern peat. We have also integrated the updated lake model into a modified version of the Weather Research and Forecasting (WRF) Model 3.0. We will present comparisons between predicted and observed thermal conditions, snow and ice depths, and surface energy fluxes at several lake sites, using local meteorological forcing or integrated regional atmospheric coupling. The thermal predictions are generally reasonable and show a marked improvement from runs performed with the baseline CLM 3.5 version of the lake model. Over Sparkling Lake

  2. Simulation of unsteady state performance of a secondary air system by the 1D-3D-Structure coupled method

    NASA Astrophysics Data System (ADS)

    Wu, Hong; Li, Peng; Li, Yulong

    2016-02-01

    This paper describes the calculation method for unsteady state conditions in the secondary air systems in gas turbines. The 1D-3D-Structure coupled method was applied. A 1D code was used to model the standard components that have typical geometric characteristics. Their flow and heat transfer were described by empirical correlations based on experimental data or CFD calculations. A 3D code was used to model the non-standard components that cannot be described by typical geometric languages, while a finite element analysis was carried out to compute the structural deformation and heat conduction at certain important positions. These codes were coupled through their interfaces. Thus, the changes in heat transfer and structure and their interactions caused by exterior disturbances can be reflected. The results of the coupling method in an unsteady state showed an apparent deviation from the existing data, while the results in the steady state were highly consistent with the existing data. The difference in the results in the unsteady state was caused primarily by structural deformation that cannot be predicted by the 1D method. Thus, in order to obtain the unsteady state performance of a secondary air system more accurately and efficiently, the 1D-3D-Structure coupled method should be used.

  3. Hybrid functionals for simulating complex oxides

    NASA Astrophysics Data System (ADS)

    Franchini, Cesare

    Hybrid functionals are a class of exchange-correlation (XC) functionals in density functional theory (DFT) that are constructed by a suitable mixing of local/semi-local XC functionals (LDA/GGA) with a certain portion of the exact Hartree-Fock exchange. After being used for years in the chemistry community for studying molecular properties, hybrid functionals are being increasingly widely used for solid state problems, for which standard LDA/GGA approximations provide a defective description. In particular, hybrid functionals appear to account well for the complicated coupling between lattice, charge and spin degrees of freedom in transition metal oxides, a class of materials that has recently attracted a lot of interest due to its technological relevance (all-oxides electronics), the large spectrum of functionalities, and the many challenging issues related to strong electronic correlation. The purpose of this talk is to present the essential ideas and physical picture of hybrid functionals and to present a map of recent applications to complex oxides aiming to cover an ample spectra of cases (sp , 3 d, 4 d and 5 d compounds) and to discuss an extended array of physical phenomena including: metal-to-insulator transitions, electron localization, bandgap prediction, polarons, multiferroism, and spin-orbit coupling.

  4. Comprehensive analysis of photonic effects on up-conversion of β-NaYF4:Er3+ nanoparticles in an organic-inorganic hybrid 1D photonic crystal

    NASA Astrophysics Data System (ADS)

    Hofmann, C. L. M.; Fischer, S.; Reitz, C.; Richards, B. S.; Goldschmidt, J. C.

    2016-04-01

    Upconversion (UC) presents a possibility to exploit sub-bandgap photons for current generation in solar cells by creating one high-energy photon out of at least two lower-energy photons. Photonic structures can enhance UC by two effects: a locally increased irradiance and a modified local density of photon states (LDOS). Bragg stacks are promising photonic structures for this application, because they are straightforward to optimize and overall absorption can be increased by adding more layers. In this work, we present a comprehensive simulation-based analysis of the photonic effects of a Bragg stack on UC luminescence. The investigated organic-inorganic hybrid Bragg stack consists of alternating layers of Poly(methylmethacrylate) (PMMA), containing purpose-built β-NaYF4:25% Er3+ core-shell nanoparticles and titanium dioxide (TiO2). From optical characterization of single thin layers, input parameters for simulations of the photonic effects are generated. The local irradiance enhancement and modulated LDOS are first simulated separately. Subsequently they are coupled in a rate equation model of the upconversion dynamics. Using the integrated model, UC luminescence is maximized by adapting the Bragg stack design. For a Bragg stack of only 5 bilayers, UC luminescence is enhanced by a factor of 3.8 at an incident irradiance of 2000 W/m2. Our results identify the Bragg stack as promising for enhancing UC, especially in the low-irradiance regime, relevant for the application in photovoltaics. Therefore, we experimentally realized optimized Bragg stack designs. The PMMA layers, containing UC nanoparticles, are produced via spin-coating from a toluene based solution. The TiO2 layers are produced by atomic layer deposition from molecular precursors. The reflectance measurements show that the realized Bragg stacks are in good agreement with predictions from simulation.

  5. Towards Hybrid Overset Grid Simulations of the Launch Environment

    NASA Astrophysics Data System (ADS)

    Moini-Yekta, Shayan

    A hybrid overset grid approach has been developed for the design and analysis of launch vehicles and facilities in the launch environment. The motivation for the hybrid grid methodology is to reduce the turn-around time of computational fluid dynamic simulations and improve the ability to handle complex geometry and flow physics. The LAVA (Launch Ascent and Vehicle Aerodynamics) hybrid overset grid scheme consists of two components: an off-body immersed-boundary Cartesian solver with block-structured adaptive mesh refinement and a near-body unstructured body-fitted solver. Two-way coupling is achieved through overset connectivity between the off-body and near-body grids. This work highlights verification using code-to-code comparisons and validation using experimental data for the individual and hybrid solver. The hybrid overset grid methodology is applied to representative unsteady 2D trench and 3D generic rocket test cases.

  6. Ice Concentration Retrieval in Stratiform Mixed-phase Clouds Using Cloud Radar Reflectivity Measurements and 1D Ice Growth Model Simulations

    SciTech Connect

    Zhang, Damao; Wang, Zhien; Heymsfield, Andrew J.; Fan, Jiwen; Luo, Tao

    2014-10-01

    Measurement of ice number concentration in clouds is important but still challenging. Stratiform mixed-phase clouds (SMCs) provide a simple scenario for retrieving ice number concentration from remote sensing measurements. The simple ice generation and growth pattern in SMCs offers opportunities to use cloud radar reflectivity (Ze) measurements and other cloud properties to infer ice number concentration quantitatively. To understand the strong temperature dependency of ice habit and growth rate quantitatively, we develop a 1-D ice growth model to calculate the ice diffusional growth along its falling trajectory in SMCs. The radar reflectivity and fall velocity profiles of ice crystals calculated from the 1-D ice growth model are evaluated with the Atmospheric Radiation Measurements (ARM) Climate Research Facility (ACRF) ground-based high vertical resolution radar measurements. Combining Ze measurements and 1-D ice growth model simulations, we develop a method to retrieve the ice number concentrations in SMCs at given cloud top temperature (CTT) and liquid water path (LWP). The retrieved ice concentrations in SMCs are evaluated with in situ measurements and with a three-dimensional cloud-resolving model simulation with a bin microphysical scheme. These comparisons show that the retrieved ice number concentrations are within an uncertainty of a factor of 2, statistically.

  7. Molecular dynamics simulation of liquid water: Hybrid density functionals

    SciTech Connect

    Todorova, T; Seitsonen, A; Hutter, J; Kuo, W; Mundy, C

    2005-09-12

    The structure, dynamical and electronic properties of liquid water utilizing different hybrid density functionals were tested within the plane wave framework of first principles molecular dynamics simulations. The computational approach, which employs modified functionals with short-ranged Hartree-Fock exchange, was first tested in calculations of the structural and bonding properties of the water dimer and cyclic water trimer. Liquid water simulations were performed at the state point of 350 K at the experimental density. Simulations included three different hybrid functionals, a meta functional, four gradient corrected functionals, the local density and Hartree-Fock approximation. It is found that hybrid functionals are superior in reproducing the experimental structure and dynamical properties as measured by the radial distribution function and self diffusion constant when compared to the pure density functionals. The local density and Hartree-Fock approximations show strongly over- and under-structured liquids, respectively. Hydrogen bond analysis shows that the hybrid functionals give slightly smaller averaged numbers of hydrogen bonds and similar hydrogen bond populations as pure density functionals. The average molecular dipole moments in the liquid from the three hybrid functionals are lower than from the corresponding pure density functionals.

  8. Pressure calculation in hybrid particle-field simulations.

    PubMed

    Milano, Giuseppe; Kawakatsu, Toshihiro

    2010-12-01

    In the framework of a recently developed scheme for a hybrid particle-field simulation techniques where self-consistent field (SCF) theory and particle models (molecular dynamics) are combined [J. Chem. Phys. 130, 214106 (2009)], we developed a general formulation for the calculation of instantaneous pressure and stress tensor. The expressions have been derived from statistical mechanical definition of the pressure starting from the expression for the free energy functional in the SCF theory. An implementation of the derived formulation suitable for hybrid particle-field molecular dynamics-self-consistent field simulations is described. A series of test simulations on model systems are reported comparing the calculated pressure with those obtained from standard molecular dynamics simulations based on pair potentials. PMID:21142296

  9. STEM image simulation with hybrid CPU/GPU programming.

    PubMed

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

    2016-07-01

    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. PMID:27093687

  10. A hybrid parallel framework for the cellular Potts model simulations

    SciTech Connect

    Jiang, Yi; He, Kejing; Dong, Shoubin

    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}).

  11. HYBRID COSMOLOGICAL SIMULATIONS WITH STREAM VELOCITIES

    SciTech Connect

    Richardson, Mark L. A.; Scannapieco, Evan; Thacker, Robert J.

    2013-07-10

    In the early universe, substantial relative ''stream'' velocities between the gas and dark matter arise due to radiation pressure and persist after recombination. To assess the impact of these velocities on high-redshift structure formation, we carry out a suite of high-resolution adaptive mesh refinement (AMR) cosmological simulations, which use smoothed particle hydrodynamic data sets as initial conditions, converted using a new tool developed for this work. These simulations resolve structures with masses as small as a few 100 M{sub Sun }, and we focus on the 10{sup 6} M{sub Sun} ''mini-halos'' in which the first stars formed. At z Almost-Equal-To 17, the presence of stream velocities has only a minor effect on the number density of halos below 10{sup 6} M{sub Sun }, but it greatly suppresses gas accretion onto all halos and the dark matter structures around them. Stream velocities lead to significantly lower halo gas fractions, especially for Almost-Equal-To 10{sup 5} M{sub Sun} objects, an effect that is likely to depend on the orientation of a halo's accretion lanes. This reduction in gas density leads to colder, more compact radial profiles, and it substantially delays the redshift of collapse of the largest halos, leading to delayed star formation and possibly delayed reionization. These many differences suggest that future simulations of early cosmological structure formation should include stream velocities to properly predict gas evolution, star formation, and the epoch of reionization.

  12. A hybrid approach to simulating mechanical properties of polymer nanocomposites.

    PubMed

    Mccarron, Andy P; Raj, Sharad; Hyers, Robert; Kim, Moon K

    2009-12-01

    Empirical studies indicate that a polymer reinforced with nanoscale particles could enhance its mechanical properties such as stiffness and toughness. To give insight into how and why this nanoparticle reinforcement is effective, it is necessary to develop computational models that can accurately simulate the effects of nanoparticles on the fracture characteristics of polymer composites. Furthermore, a hybrid model that can account for both continuum and non-continuum effects will hasten the development of not only new hierarchical composite materials but also new theories to explain their behavior. This paper presents a hybrid modeling scheme for simulating fracture of polymer nanocomposites by utilizing an atomistic modeling approach called Elastic Network Model (ENM) in conjunction with a traditional Finite Element Analysis (FEA). The novelty of this hybrid ENM-FEA approach lies in its ability to model less interesting outer domains with FEA while still accounting for areas of interest such as crack tip reion and the interface between a nanoparticle and the polymer matrix at atomic scale with ENM. Various simulation conditions have been tested to determine the feasibility of the proposed hybrid model. For instance, an iterative result from a uniaxial loading with isotropic properties in an ENM-FEA model shows accuracy and convergence to the analytic solution. PMID:19908790

  13. A survey of electric and hybrid vehicle simulation programs

    NASA Technical Reports Server (NTRS)

    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.

  14. Pulse wave propagation in a model human arterial network: Assessment of 1-D visco-elastic simulations against in vitro measurements

    PubMed Central

    Alastruey, Jordi; Khir, Ashraf W.; Matthys, Koen S.; Segers, Patrick; Sherwin, Spencer J.; Verdonck, Pascal R.; Parker, Kim H.; Peiró, Joaquim

    2011-01-01

    The accuracy of the nonlinear one-dimensional (1-D) equations of pressure and flow wave propagation in Voigt-type visco-elastic arteries was tested against measurements in a well-defined experimental 1:1 replica of the 37 largest conduit arteries in the human systemic circulation. The parameters required by the numerical algorithm were directly measured in the in vitro setup and no data fitting was involved. The inclusion of wall visco-elasticity in the numerical model reduced the underdamped high-frequency oscillations obtained using a purely elastic tube law, especially in peripheral vessels, which was previously reported in this paper [Matthys et al., 2007. Pulse wave propagation in a model human arterial network: Assessment of 1-D numerical simulations against in vitro measurements. J. Biomech. 40, 3476–3486]. In comparison to the purely elastic model, visco-elasticity significantly reduced the average relative root-mean-square errors between numerical and experimental waveforms over the 70 locations measured in the in vitro model: from 3.0% to 2.5% (p<0.012) for pressure and from 15.7% to 10.8% (p<0.002) for the flow rate. In the frequency domain, average relative errors between numerical and experimental amplitudes from the 5th to the 20th harmonic decreased from 0.7% to 0.5% (p<0.107) for pressure and from 7.0% to 3.3% (p<10−6) for the flow rate. These results provide additional support for the use of 1-D reduced modelling to accurately simulate clinically relevant problems at a reasonable computational cost. PMID:21724188

  15. Simulation of decay heat removal by natural convection in a pool type fast reactor model-ramona-with coupled 1D/2D thermal hydraulic code system

    SciTech Connect

    Kasinathan, N.; Rajakumar, A.; Vaidyanathan, G.; Chetal, S.C.

    1995-09-01

    Post shutdown decay heat removal is an important safety requirement in any nuclear system. In order to improve the reliability of this function, Liquid metal (sodium) cooled fast breeder reactors (LMFBR) are equipped with redundant hot pool dipped immersion coolers connected to natural draught air cooled heat exchangers through intermediate sodium circuits. During decay heat removal, flow through the core, immersion cooler primary side and in the intermediate sodium circuits are also through natural convection. In order to establish the viability and validate computer codes used in making predictions, a 1:20 scale experimental model called RAMONA with water as coolant has been built and experimental simulation of decay heat removal situation has been performed at KfK Karlsruhe. Results of two such experiments have been compiled and published as benchmarks. This paper brings out the results of the numerical simulation of one of the benchmark case through a 1D/2D coupled code system, DHDYN-1D/THYC-2D and the salient features of the comparisons. Brief description of the formulations of the codes are also included.

  16. RFI in hybrid loops - Simulation and experimental results.

    NASA Technical Reports Server (NTRS)

    Ziemer, R. E.; Nelson, D. R.; Raghavan, H. R.

    1972-01-01

    A digital simulation of an imperfect second-order hybrid phase-locked loop (HPLL) operating in radio frequency interference (RFI) is described. Its performance is characterized in terms of phase error variance and phase error probability density function (PDF). Monte-Carlo simulation is used to show that the HPLL can be superior to the conventional phase-locked loops in RFI backgrounds when minimum phase error variance is the goodness criterion. Similar experimentally obtained data are given in support of the simulation data.

  17. Biochemical simulations: stochastic, approximate stochastic and hybrid approaches

    PubMed Central

    2009-01-01

    Computer simulations have become an invaluable tool to study the sometimes counterintuitive temporal dynamics of (bio-)chemical systems. In particular, stochastic simulation methods have attracted increasing interest recently. In contrast to the well-known deterministic approach based on ordinary differential equations, they can capture effects that occur due to the underlying discreteness of the systems and random fluctuations in molecular numbers. Numerous stochastic, approximate stochastic and hybrid simulation methods have been proposed in the literature. In this article, they are systematically reviewed in order to guide the researcher and help her find the appropriate method for a specific problem. PMID:19151097

  18. Direct Numerical Simulation of Acoustic Waves Interacting with a Shock Wave in a Quasi-1D Convergent-Divergent Nozzle Using an Unstructured Finite Volume Algorithm

    NASA Technical Reports Server (NTRS)

    Bui, Trong T.; Mankbadi, Reda R.

    1995-01-01

    Numerical simulation of a very small amplitude acoustic wave interacting with a shock wave in a quasi-1D convergent-divergent nozzle is performed using an unstructured finite volume algorithm with a piece-wise linear, least square reconstruction, Roe flux difference splitting, and second-order MacCormack time marching. First, the spatial accuracy of the algorithm is evaluated for steady flows with and without the normal shock by running the simulation with a sequence of successively finer meshes. Then the accuracy of the Roe flux difference splitting near the sonic transition point is examined for different reconstruction schemes. Finally, the unsteady numerical solutions with the acoustic perturbation are presented and compared with linear theory results.

  19. Battery thermal models for hybrid vehicle simulations

    NASA Astrophysics Data System (ADS)

    Pesaran, Ahmad A.

    This paper summarizes battery thermal modeling capabilities for: (1) an advanced vehicle simulator (ADVISOR); and (2) battery module and pack thermal design. The National Renewable Energy Laboratory's (NREL's) ADVISOR is developed in the Matlab/Simulink environment. There are several battery models in ADVISOR for various chemistry types. Each one of these models requires a thermal model to predict the temperature change that could affect battery performance parameters, such as resistance, capacity and state of charges. A lumped capacitance battery thermal model in the Matlab/Simulink environment was developed that included the ADVISOR battery performance models. For thermal evaluation and design of battery modules and packs, NREL has been using various computer aided engineering tools including commercial finite element analysis software. This paper will discuss the thermal ADVISOR battery model and its results, along with the results of finite element modeling that were presented at the workshop on "Development of Advanced Battery Engineering Models" in August 2001.

  20. Nonorthogonal generalized hybrid Wannier functions for large-scale DFT simulations

    NASA Astrophysics Data System (ADS)

    Greco, Andrea; Freeland, John W.; Mostofi, Arash A.

    Semiconductor-based thin-films have applications in microelectronics,from transistors to nanocapacitors. Many properties of such devices strongly depend on the details of the interface between a metallic electrode and the thin-film semiconductor/insulator. Hybrid Wannier Functions (WFs), extended in the surface plane, but localized along the direction normal to the surface/interface, have been successfully used to explore the properties of such heterostructures layered along a given direction, and are a natural way to study systems that are at the same time a 2D conductor (in plane) and a 1D insulator (out of plane). Current state-of-the art implementations of Hybrid WFs rely on first performing a traditional cubic-scaling density-functional theory (DFT) calculation. This unfavourable scaling precludes the applicability of this method to the large length scales typically associated with processes in realistic structures. To overcome this limitation we extend the concept of Hybrid WFs to nonorthogonal orbitals that are directly optimized in situ in the electronic structure calculation. We implement this method in the ONETEP large-scale DFT code and we apply it to realistic heterostructure systems, showing it is able to provide plane-wave accuracy but at reduced computational cost. The authors would like to acknowledge support from the EPSRC, the Centre for Doctoral Training in Theory and Simulation of Materials, and Argonne National Laboratory.

  1. Plasma Interaction at Io: Multi-species Hybrid Simulations

    NASA Astrophysics Data System (ADS)

    Sebek, O.; Travnicek, P. M.; Walker, R. J.; Hellinger, P.

    2015-12-01

    We present analysis of global 3-dimensional multi-species hybrid simulations of Io's interaction with Jovian magnetospheric plasma. In the multi-species simulations we assume five species, plasma torus is composed of O+, S+ and S++ ions and ions of SO+, SO2+ are created around Io by ionization of its neutral atmosphere. We consider several ionization processes, namely, charge exchange ionization and photoionization/electron impact ionization. We compare our results to data acquired in situ by the Galileo spacecraft. Our results are in a good qualitative agreement with the in situ magnetic field measurements for five Galileo's flybys around Io. The hybrid model enables to study ion kinetic effects, we investigate magnetic fluctuations triggered by growth of ion cyclotron and/or mirror instabilities of temperature anisotropic pick-up plasma. We also investigate structure of Alfvén wings under different conditions of the interaction.

  2. Ion foreshock and magnetosheath properties in global hybrid simulations

    NASA Astrophysics Data System (ADS)

    Hercik, D.; Travnicek, P. M.; Schriver, D.; Hellinger, P.

    2010-12-01

    Properties of the interaction between the solar wind and magnetized small bodies is investigated using 3-D global hybrid simulations (Travnicek et al., 2009, 2010). We investigate the ion foreshock, formation and properties of the back-streaming proton population and the corresponding wave activity. We also investigate properties of the quasi-parallel shock and the adjacent magnetosheath. The properties of the quasi-parallel magnetosheath are compared with the properties of the quasi-perpendicular one. References Travnicek, P. M., P. Hellinger, D. Schriver, D. Hercik, J.A. Slavin, and B. J. Anderson (2009), Kinetic instabilities in Mercury's magnetosphere: three-dimensional simulatin results, Geophys. Res. Lett., 36, L07104,2009 Travnicek,P. M., D. Schriver, P. Hellinger, D. Hercik, B.J. Anderson, M Sarantos, and J.A. Slavin (2010), Mercury's magnetosphere-solar wind interaction for northward and southward interplanetary magnetic field: Hybrid simulation results, Icarus,209,11-22

  3. Hybrid Simulations of Plasma-Neutral-Dust Interactions at Enceladus

    SciTech Connect

    Omidi, N.; Russell, C. T.; Jia, Y. D.; Tokar, R. L.; Farrell, W. M.

    2010-12-30

    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.

  4. Atomistic hybrid DSMC/NEMD method for nonequilibrium multiscale simulations

    SciTech Connect

    Gu Kai; Watkins, Charles B. Koplik, Joel

    2010-03-01

    A multiscale hybrid method for coupling the direct simulation Monte Carlo (DSMC) method to the nonequilibrium molecular dynamics (NEMD) method is introduced. The method addresses Knudsen layer type gas flows within a few mean free paths of an interface or about an object with dimensions of the order of a few mean free paths. It employs the NEMD method to resolve nanoscale phenomena closest to the interface along with coupled DSMC simulation of the remainder of the Knudsen layer. The hybrid DSMC/NEMD method is a particle based algorithm without a buffer zone. It incorporates a new, modified generalized soft sphere (MGSS) molecular collision model to improve the poor computational efficiency of the traditional generalized soft sphere GSS model and to achieve DSMC compatibility with Lennard-Jones NEMD molecular interactions. An equilibrium gas, a Fourier thermal flow, and an oscillatory Couette flow, are simulated to validate the method. The method shows good agreement with Maxwell-Boltzmann theory for the equilibrium system, Chapman-Enskog theory for Fourier flow, and pure DSMC simulations for oscillatory Couette flow. Speedup in CPU time of the hybrid solver is benchmarked against a pure NEMD solver baseline for different system sizes and solver domain partitions. Finally, the hybrid method is applied to investigate interaction of argon gas with solid surface molecules in a parametric study of the influence of wetting effects and solid molecular mass on energy transfer and thermal accommodation coefficients. It is determined that wetting effect strength and solid molecular mass have a significant impact on the energy transfer between gas and solid phases and thermal accommodation coefficient.

  5. Hybrid and electric advanced vehicle systems (heavy) simulation

    NASA Technical Reports Server (NTRS)

    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.

  6. Hybrid system modeling, simulation, and visualization: a crane system

    NASA Astrophysics Data System (ADS)

    Hiniduma Udugama Gamage, Sahan S.; Palmer, Patrick R.

    2003-08-01

    Modeling and visualization of a complex hybrid system with different domains of energy flow and signal flow are described in this paper. It is a crane system situated in a barge complete with the load, electrical power, drive and control systems. A dynamically and functionally accurate model of the crane was developed. The implementation is in the freely available software suit of Virtual Test Bed (VTB) for simulation and Visual Extension Engine (VXE) for visualization. The bidirectional interaction of simulator and visualizer is fully utilized in this application. The further challenges confronted in implementing this particular system and any other complex system are discussed and possible solutions are suggested.

  7. From 1D chain to 3D network: a new family of inorganic-organic hybrid semiconductors MO3(L)(x) (M = Mo, W; L = organic linker) built on perovskite-like structure modules.

    PubMed

    Zhang, Xiao; Hejazi, Mehdi; Thiagarajan, Suraj J; Woerner, William R; Banerjee, Debasis; Emge, Thomas J; Xu, Wenqian; Teat, Simon J; Gong, Qihan; Safari, Ahmad; Yang, Ronggui; Parise, John B; Li, Jing

    2013-11-20

    MO3 (M = Mo, W) or VI-VI binary compounds are important semiconducting oxides that show great promise for a variety of applications. In an effort to tune and enhance their properties in a systematic manner we have applied a designing strategy to deliberately introduce organic linker molecules in these perovskite-like crystal lattices. This approach has led to a wealth of new hybrid structures built on one-dimensional (1D) and two-dimensional (2D) VI-VI modules. The hybrid semiconductors exhibit a number of greatly improved properties and new functionality, including broad band gap tunability, negative thermal expansion, largely reduced thermal conductivity, and significantly enhanced dielectric constant compared to their MO3 parent phases. PMID:24152119

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

    NASA Astrophysics Data System (ADS)

    Eremin, Denis; Hemke, Torben; Mussenbrock, Thomas

    2016-02-01

    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.

  9. Development of a Numerical Method for Patient-Specific Cerebral Circulation Using 1D-0D Simulation of the Entire Cardiovascular System with SPECT Data.

    PubMed

    Zhang, Hao; Fujiwara, Naoya; Kobayashi, Masaharu; Yamada, Shigeki; Liang, Fuyou; Takagi, Shu; Oshima, Marie

    2016-08-01

    The detailed flow information in the circle of Willis (CoW) can facilitate a better understanding of disease progression, and provide useful references for disease treatment. We have been developing a one-dimensional-zero-dimensional (1D-0D) simulation method for the entire cardiovascular system to obtain hemodynamics information in the CoW. This paper presents a new method for applying 1D-0D simulation to an individual patient using patient-specific data. The key issue is how to adjust the deviation of physiological parameters, such as peripheral resistance, from literature data when patient-specific geometry is used. In order to overcome this problem, we utilized flow information from single photon emission computed tomography (SPECT) data. A numerical method was developed to optimize physiological parameters by adjusting peripheral cerebral resistance to minimize the difference between the resulting flow rate and the SPECT data in the efferent arteries of the CoW. The method was applied to three cases using different sets of patient-specific data in order to investigate the hemodynamics of the CoW. The resulting flow rates in the afferent arteries were compared to those of the phase-contrast magnetic resonance angiography (PC-MRA) data. Utilization of the SPECT data combined with the PC-MRA data showed a good agreement in flow rates in the afferent arteries of the CoW with those of PC-MRA data for all three cases. The results also demonstrated that application of SPECT data alone could provide the information on the ratios of flow distributions among arteries in the CoW. PMID:26721836

  10. Hybrid multiscale simulation of a mixing-controlled reaction

    NASA Astrophysics Data System (ADS)

    Scheibe, Timothy D.; Schuchardt, Karen; Agarwal, Khushbu; Chase, Jared; Yang, Xiaofan; Palmer, Bruce J.; Tartakovsky, Alexandre M.; Elsethagen, Todd; Redden, George

    2015-09-01

    Continuum-scale models, which employ a porous medium conceptualization to represent properties and processes averaged over a large number of solid grains and pore spaces, are widely used to study subsurface flow and reactive transport. Recently, pore-scale models, which explicitly resolve individual soil grains and pores, have been developed to more accurately model and study pore-scale phenomena, such as mineral precipitation and dissolution reactions, microbially-mediated surface reactions, and other complex processes. However, these highly-resolved models are prohibitively expensive for modeling domains of sizes relevant to practical problems. To broaden the utility of pore-scale models for larger domains, we developed a hybrid multiscale model that initially simulates the full domain at the continuum scale and applies a pore-scale model only to areas of high reactivity. Since the location and number of pore-scale model regions in the model varies as the reactions proceed, an adaptive script defines the number and location of pore regions within each continuum iteration and initializes pore-scale simulations from macroscale information. Another script communicates information from the pore-scale simulation results back to the continuum scale. These components provide loose coupling between the pore- and continuum-scale codes into a single hybrid multiscale model implemented within the SWIFT workflow environment. In this paper, we consider an irreversible homogeneous bimolecular reaction (two solutes reacting to form a third solute) in a 2D test problem. This paper is focused on the approach used for multiscale coupling between pore- and continuum-scale models, application to a realistic test problem, and implications of the results for predictive simulation of mixing-controlled reactions in porous media. Our results and analysis demonstrate that the hybrid multiscale method provides a feasible approach for increasing the accuracy of subsurface reactive transport

  11. Multiscale Hy3S: Hybrid stochastic simulation for supercomputers

    PubMed Central

    Salis, Howard; Sotiropoulos, Vassilios; Kaznessis, Yiannis N

    2006-01-01

    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 create biological systems

  12. Vlasov Simulations of Ionospheric Heating Near Upper Hybrid Resonance

    NASA Astrophysics Data System (ADS)

    Najmi, A. C.; Eliasson, B. E.; Shao, X.; Milikh, G. M.; Papadopoulos, K.

    2014-12-01

    It is well-known that high-frequency (HF) heating of the ionosphere can excite field- aligned density striations (FAS) in the ionospheric plasma. Furthermore, in the neighborhood of various resonances, the pump wave can undergo parametric instabilities to produce a variety of electrostatic and electromagnetic waves. We have used a Vlasov simulation with 1-spatial dimension, 2-velocity dimensions, and 2-components of fields, to study the effects of ionospheric heating when the pump frequency is in the vicinity of the upper hybrid resonance, employing parameters currently available at ionospheric heaters such as HAARP. We have found that by seeding theplasma with a FAS of width ~20% of the simulation domain, ~10% depletion, and by applying a spatially uniform HF dipole pump electric field, the pump wave gives rise to a broad spectrum of density fluctuations as well as to upper hybrid and lower hybrid oscillating electric fields. We also observe collisionless bulk-heating of the electrons that varies non-linearly with the amplitude of the pump field.

  13. HYPERS: A Unidimensional Asynchronous Framework for Multiscale Hybrid Simulations

    NASA Astrophysics Data System (ADS)

    Omelchenko, Y. A.; Karimabadi, H.; Vu, H. X.

    2011-12-01

    Kinetic ion-driven processes are crucial for understanding the complex dynamics of the closely coupled Earth magnetosphere-ionosphere system. Largely varying time and length scales impose severe numerical constraints on global simulations with hybrid (particle ions + fluid electrons) codes. To enable larger simulations we developed a unique, uni-dimensional multiscale hybrid code, HYPERS. Instead of stepping all simulation variables uniformly in time, HYPERS tracks physically meaningful changes to individual particles and cell-based electromagnetic fields via asynchronous discrete events. HYPERS has been parallelized with the Preemptive Event Processing (PEP) technique. The parallel algorithm enables arbitrary domain decompositions and processor configurations on restarts. This is a critical prerequisite for implementing a full load balancing functionality in the future. We validate HYPERS by simulating the interaction of streaming plasmas with dipole magnetospheres and show that our approach results in superior numerical metrics (stability, accuracy and speed) compared to conventional techniques. We also discuss further extensions to the HYPERS framework that would enable seemless integration of ion fluid and kinetic schemes.

  14. Hybrid Simulation of Linked Structural System With Shear Friction Damper

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-soo; Choi, Jae-hyouk

    2011-01-01

    Hybrid simulations were conducted to investigate effects of the friction damper on seismic behavior of a composite structure consisting of an old concrete structure and a new steel frame. The hybrid simulation results have indicated that the cyclical behavior of the friction damper made of steel plate and aluminum plate could be accurately simulated with the so-called perfect elastic-plastic model without degradation in stiffness. It has also been verified that the seismic performance of the composite structures could be accurately predicted if one use the perfect elastic-plastic model to simulate the behavior of the connecting friction damper. In addition, the tests have shown that the use of friction damper to connect an existing unfit concrete building and new steel building could effectively reduce their displacement response and acceleration response simultaneously. The mitigation degree due to the friction damper on the seismic response of the composite structures depends upon the relative stiffness of the two buildings, the natural periods, and the mass ratio of the two buildings.

  15. Hybrid Computational Simulation and Study of Terahertz Pulsed Photoconductive Antennas

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  16. Computational simulation of intermingled-fiber hybrid composite behavior

    NASA Technical Reports Server (NTRS)

    Mital, Subodh K.; Chamis, Christos C.

    1992-01-01

    Three-dimensional finite-element analysis and a micromechanics based computer code ICAN (Integrated Composite Analyzer) are used to predict the composite properties and microstresses of a unidirectional graphite/epoxy primary composite with varying percentages of S-glass fibers used as hydridizing fibers at a total fiber volume of 0.54. The three-dimensional finite-element model used in the analyses consists of a group of nine fibers, all unidirectional, in a three-by-three unit cell array. There is generally good agreement between the composite properties and microstresses obtained from both methods. The results indicate that the finite-element methods and the micromechanics equations embedded in the ICAN computer code can be used to obtain the properties of intermingled fiber hybrid composites needed for the analysis/design of hybrid composite structures. However, the finite-element model should be big enough to be able to simulate the conditions assumed in the micromechanics equations.

  17. A 1-D simulation analysis of the development and maintenance of the 2001 red tide of the ichthyotoxic dinoflagellate Karenia brevis on the West Florida shelf

    NASA Astrophysics Data System (ADS)

    Lenes, J. M.; Darrow, B. P.; Walsh, J. J.; Jolliff, J. K.; Chen, F. R.; Weisberg, R. H.; Zheng, L.

    2012-06-01

    A one-dimensional (1-D) ecological model, HABSIM, examined the initiation and maintenance of the 2001 red tide on the West Florida shelf (WFS). Phytoplankton competition among toxic dinoflagellates (Karenia brevis), nitrogen fixing cyanophytes (Trichodesmium erythraeum), large siliceous phytoplankton (diatoms), and small non-siliceous phytoplankton (microflagellates) explored the sequence of events required to support the observed red tide from August to December 2001. The ecological model contained 24 state variables within five submodels: circulation, atmospheric (iron deposition), bio-optics, pelagic (phytoplankton, nutrients, bacteria, zooplankton, and fish), and benthic (nutrient regeneration). The 2001 model results reaffirmed that diazotrophs are the basis for initiation of red tides of K. brevis on the WFS. A combination of selective grazing pressure, iron fertilization, low molar nitrogen to phosphorus ratios, and eventual silica limitation of fast-growing diatoms set the stage for dominance of nitrogen fixers. "New" nitrogen was made available for subsequent blooms of K. brevis through the release of ammonium and urea during nitrogen fixation, as well as during cell lysis, by the Trichodesmium population. Once K. brevis biomass reached ichthyotoxic levels, rapid decay of subsequent fish kills supplied additional organic nutrients for utilization by these opportunistic toxic algae. Both nutrient vectors represented organic non-siliceous sources of nitrogen and phosphorus, further exacerbating silica limitation of the diatom population. The model reproduced this spring transition from a simple estuarine-driven, diatom-based food chain to a complex summer-fall system of Trichodesmium and toxic dinoflagellates. While the model was able to replicate the initiation and maintenance of the 2001 red tide, bloom termination was not captured by this 1-D form on the WFS. Here, horizontal advection and perhaps cell lysis loss terms might play a significant role, to be

  18. Utilization of hybrid computational equipment for the simulation of parachute system flight

    SciTech Connect

    Curry, W.H.; Schatzle, P.R.

    1981-01-01

    Hybrid (analog/digital) computational equipment has been satisfactorily utilized for flight simulation of parachute retarded configurations. Implementation of specific mathematical models on a hybrid computer is described, and example results are presented.

  19. Hybrid stochastic simulations of intracellular reaction-diffusion systems

    PubMed Central

    Kalantzis, Georgios

    2009-01-01

    With the observation that stochasticity is important in biological systems, chemical kinetics have begun to receive wider interest. While the use of Monte Carlo discrete event simulations most accurately capture the variability of molecular species, they become computationally costly for complex reaction-diffusion systems with large populations of molecules. On the other hand, continuous time models are computationally efficient but they fail to capture any variability in the molecular species. In this study a novel hybrid stochastic approach is introduced for simulating reaction-diffusion systems. We developed a dynamic partitioning strategy using fractional propensities. In that way processes with high frequency are simulated mostly with deterministic rate-based equations, and those with low frequency mostly with the exact stochastic algorithm of Gillespie. In this way we preserve the stochastic behavior of cellular pathways while being able to apply it to large populations of molecules. In this article we describe this hybrid algorithmic approach, and we demonstrate its accuracy and efficiency compared with the Gillespie algorithm for two different systems. First, a model of intracellular viral kinetics with two steady states and second, a compartmental model of the postsynaptic spine head for studying the dynamics of Ca+2 and NMDA receptors. PMID:19414282

  20. Hybrid Multiscale Simulation of a Mixing-Controlled Reaction

    NASA Astrophysics Data System (ADS)

    Yang, X.; Scheibe, T. D.; Schuchardt, K.; Agarwal, K.; Chase, J.; Palmer, B. J.; Tartakovsky, A. M.; Elsethagen, T.

    2014-12-01

    Continuum scale models have been used to study subsurface flow, transport, and reactions for many years but lack the capability to resolve fine-grained processes. Recently, pore-scale models, which operate at scales of individual soil grains, have been developed to more accurately model and study pore-scale phenomena, such as mineral precipitation and dissolution reactions, microbially-mediated surface reactions, and other complex processes. However, these highly-resolved models are prohibitively expensive for modeling domains of sizes relevant to practical problems. To broaden the utility of pore-scale models for larger domains, we developed a hybrid multiscale model that initially simulates the full domain at the continuum scale and applies a pore-scale model only to areas of high reactivity. Python script components provide loose coupling between the pore- and continuum-scale codes into a single hybrid multiscale model implemented in the SWIFT parallel scripting language. We consider an irreversible homogenous bimolecular reaction (two solutes reacting to form a third solute) in a 2D test problem. This presentation is focused on the approach used for multiscale coupling between pore- and continuum-scale models, application to a realistic test problem, and implications of the results for predictive simulation of mixing-controlled reactions in porous media. Our results and analysis demonstrate that loose coupling provides a feasible, efficient and scalable approach for multiscale subsurface simulations.

  1. Simulation-Guided DNA Probe Design for Consistently Ultraspecific Hybridization

    PubMed Central

    Wang, J. Sherry; Zhang, David Yu

    2015-01-01

    Hybridization of complementary sequences is one of the central tenets of nucleic acid chemistry; however, the unintended binding of closely related sequences limits the accuracy of hybridization-based approaches for analyzing nucleic acids. Thermodynamics-guided probe design and empirical optimization of reaction conditions have been used to enable discrimination of single nucleotide variants, but typically these approaches provide only an approximate 25-fold difference in binding affinity. Here we show that simulations of the binding kinetics are both necessary and sufficient to design nucleic acid probe systems with consistently high specificity as they enable the discovery of an optimal combination of thermodynamic parameters. Simulation-guided probe systems designed against 44 different target single nucleotide variants sequences showed between 200- and 3000-fold (median 890) higher binding affinity than their corresponding wildtype sequences. As a demonstration of the usefulness of this simulation-guided design approach we developed probes which, in combination with PCR amplification, we use to detect low concentrations of variant alleles (1%) in human genomic DNA. PMID:26100802

  2. Lower Hybrid Drift in Simulations of Hypersonic Plasma

    NASA Astrophysics Data System (ADS)

    Niehoff, D.; Ashour-Abdalla, M.; Niemann, C.; Schriver, D.; Sotnikov, V. I.; Lapenta, G.

    2014-12-01

    It has been shown experimentally that hypersonic plasma (defined as moving with a bulk flow velocity of more than 5 to 10 times the Mach speed) traveling through a magnetic field will create a diamagnetic cavity, or bubble [1]. At the edge of the bubble, opposing field and density gradients can drive the lower hybrid drift instability [2]. We will explore two and a half dimensional (2 space and 3 velocity dimensions) simulations of hypersonic plasma within a parameter regime motivated by the aforementioned diamagnetic bubble experiments, wherein we find oscillations excited near the lower hybrid frequency propagating perpendicular to the bulk motion of the plasma and the background magnetic field. The simulations are run using the implicit PIC code iPIC3D so that we are able to capture dynamics of the plasma below ion scales, but not be forced to resolve all electron scales [3]. [1] Niemann et al, Phys. Plasmas 20, 012108 (2013) [2] Davidson et al, Phys. Fluids, Vol. 20, No. 2, February 1977 [3] S. Markidis et al, Math. Comput. Simul. (2009), doi 10.1016/j.matcom.2009.08.038

  3. Global hybrid simulations: foreshock and bow shock morphology

    NASA Astrophysics Data System (ADS)

    Blanco-Cano, Xochitl; Omidi, Nojan; Russell, Christopher

    The solar wind interaction with earth's magnetosphere is mediated by the formation of a bow shock. Ahead of this shock a foreshock forms. Global hybrid simulations have proven to be very useful to study these complex regions, where kinetic effects play a major role in dissipation process and largely affect the large scale dynamics of the foreshock-bow shock-magnetosheath system. In this work we use global hybrid simulations to study solar wind coupling with the magnetosphere for oblique (45° ) and radial IMF geometries. We find that the foreshock morphology changes drastically from one case to the other. We study ULF waves' properties, evolution, and their impact on the quasi-parallel shock. We also investigate differences in suprathermal ion distributions under the two geometries and relate this to wave origin. We find that under the radial geometry the foreshock is permeated also by density cavities that are not clear for the oblique interaction. We discuss the properties of these cavities and their impact on the quasi-parallel bow shock. We also relate simulation cavities to observations in earth's foreshock.

  4. Magnetohydrodynamic and hybrid simulations of broadband fluctuations near interplanetary shocks

    SciTech Connect

    Agim, Y.Z.; Vinas, A.F.; Goldstein, M.L.

    1995-09-01

    We present results of a theoretical study of evolution of a spectrum of finite amplitude right-hand elliptically polarized magnetohydrodynamic (MHD) waves. The analysis includes use of one-and-a-half-dimensional solutions of the equations that describe compressible MHD together with one-and-a-half-dimensional hybrid simulation of the phenomenon. The motivation of the study is to understand the origin and properties of finite amplitude waves often observed in the vicinity of collisionless shocks in the heliosphere. The solutions of the MHD equations are compared with both the results of the hybrid simulations and observations previously reported by Vinas et al. in the vicinity of a quasi-parallel interplanetary shock. The initial conditions of the MHD solutions were constructed to model the observed spectrum of magnetic and velocity fluctuations; plasma parameters were also chosen to replicate the observed parameters. For the typical parameters of {beta} = 0.5, {sigma}B/B{sub 0} = 0.25 and a spectrum of parallel propagating, circularly polarized dispersive waves, initially the density and magnetic energy density correlations grow due to the (nonlinear) ponderomotive effect. The spectral features below the ion cyclotron frequency are established quickly on the Alfvenic timescale but then persist and match closely the observed fluctuations. The parametric decay instabilities that subsequently appear further enhance the density fluctuations and produce a high-frequency magnetic power spectrum consistent with the spacecraft observation. The MHD and hybrid simulations extend the previous picture of wave generation by a beam-driven ion cyclotron instability to the fully nonlinear stage. 64 refs., 24 figs.

  5. Global Hybrid Simulations: Applications to Bow Shock and Dayside Magnetosphere

    NASA Astrophysics Data System (ADS)

    Omidi, Nojan; Sibeck, David; Phan, Tai; Eastwood, Jonathan

    With the advent of global hybrid (kinetic ions, fluid electrons) simulations it has become possible to examine magnetospheric processes and their interconnections on ion time and spatial scales. This capability combined with multi-spacecraft missions such as Cluster and THEMIS provide an unprecedented opportunity to perform detailed, quantitative comparisons between theory and observations to examine basic paradigms and build new ones. To illustrate this capability, this presentation focuses on a number of topics related to the bow shock and dayside magnetosphere. One topic concerns the formation of the ion foreshock boundary predicted by global hybrid simulations and their relationship to the observed phenomenon of foreshock cavities. Interaction of solar wind discontinuities with the bow shock lead to a variety of phenomena such as hot flow anomalies (HFAs) or initiation of magnetic reconnection in the magnetosheath. We show examples of both processes in hybrid simulations and comparisons with spacecraft observations. In regards to HFAs, recent THEMIS measurements provide detailed information on their magnetosheath signatures. Understanding of these signatures and impacts on the magnetosphere/ionosphere system remains an important topic of investigation. Magnetic reconnection in the magnetosheath provides an opportunity to examine this important process in relative isolation and symmetric plasma conditions. Here, we address the impact of discontinuity thickness and magnetic shear on the nature of the resulting reconnection and the implications for time dependency and geometry (anti-parallel vs component) of reconnection at the magnetopause. The final topic of the presentation is the formation of flux transfer events (FTEs) at the magnetopause and their subsequent motion and interaction with the cusps. This interaction involves secondary magnetic reconnection and acceleration of plasma into the cusp. As we illustrate, this process may account for the formation of

  6. Predicting System Accidents with Model Analysis During Hybrid Simulation

    NASA Technical Reports Server (NTRS)

    Malin, Jane T.; Fleming, Land D.; Throop, David R.

    2002-01-01

    Standard discrete event simulation is commonly used to identify system bottlenecks and starving and blocking conditions in resources and services. The CONFIG hybrid discrete/continuous simulation tool can simulate such conditions in combination with inputs external to the simulation. This provides a means for evaluating the vulnerability to system accidents of a system's design, operating procedures, and control software. System accidents are brought about by complex unexpected interactions among multiple system failures , faulty or misleading sensor data, and inappropriate responses of human operators or software. The flows of resource and product materials play a central role in the hazardous situations that may arise in fluid transport and processing systems. We describe the capabilities of CONFIG for simulation-time linear circuit analysis of fluid flows in the context of model-based hazard analysis. We focus on how CONFIG simulates the static stresses in systems of flow. Unlike other flow-related properties, static stresses (or static potentials) cannot be represented by a set of state equations. The distribution of static stresses is dependent on the specific history of operations performed on a system. We discuss the use of this type of information in hazard analysis of system designs.

  7. A hybrid simulation study of magnetic reconnection in anisotropic plasmas

    NASA Astrophysics Data System (ADS)

    Guo, Jun; Li, Yi; Lu, Quan-ming; Wang, Shui

    2003-10-01

    The process of magnetic reconnection in anisotropic plasmas is studied numerically using a 2-dimensional, 3-component hybrid simulation. The results of the calculation show that, when the plasma pressure in the direction perpendicular to magnetic field is larger than that in the parallel direction (e.g. P ⊥/P ‖ = 1.5 ), instability may greatly increase, speeding up the rate of reconnection. When P⊥ is smaller than P‖, (e.g., when P ⊥/P ‖ = 0.6 ), fire hose instability appears, which will restrain the tearing mode instability and the process of magnetic reconnection.

  8. Hybrid simulation codes with application to shocks and upstream waves

    NASA Technical Reports Server (NTRS)

    Winske, D.

    1985-01-01

    Hybrid codes in which part of the plasma is represented as particles and the rest as a fluid are discussed. In the past few years such codes with particle ions and massless, fluid electrons have been applied to space plasmas, especially to collisionless shocks. All of these simulation codes are one-dimensional and similar in structure, except for how the field equations are solved. The various approaches that are used (resistive Ohm's law, predictor-corrector, Hamiltonian) are described in detail and results from the various codes are compared with examples taken from collisionless shocks and low frequency wave phenomena upstream of shocks.

  9. Adaptive hybrid simulations for multiscale stochastic reaction networks

    NASA Astrophysics Data System (ADS)

    Hepp, Benjamin; Gupta, Ankit; Khammash, Mustafa

    2015-01-01

    The probability distribution describing the state of a Stochastic Reaction Network (SRN) evolves according to the Chemical Master Equation (CME). It is common to estimate its solution using Monte Carlo methods such as the Stochastic Simulation Algorithm (SSA). In many cases, these simulations can take an impractical amount of computational time. Therefore, many methods have been developed that approximate sample paths of the underlying stochastic process and estimate the solution of the CME. A prominent class of these methods include hybrid methods that partition the set of species and the set of reactions into discrete and continuous subsets. Such a partition separates the dynamics into a discrete and a continuous part. Simulating such a stochastic process can be computationally much easier than simulating the exact discrete stochastic process with SSA. Moreover, the quasi-stationary assumption to approximate the dynamics of fast subnetworks can be applied for certain classes of networks. However, as the dynamics of a SRN evolves, these partitions may have to be adapted during the simulation. We develop a hybrid method that approximates the solution of a CME by automatically partitioning the reactions and species sets into discrete and continuous components and applying the quasi-stationary assumption on identifiable fast subnetworks. Our method does not require any user intervention and it adapts to exploit the changing timescale separation between reactions and/or changing magnitudes of copy-numbers of constituent species. We demonstrate the efficiency of the proposed method by considering examples from systems biology and showing that very good approximations to the exact probability distributions can be achieved in significantly less computational time. This is especially the case for systems with oscillatory dynamics, where the system dynamics change considerably throughout the time-period of interest.

  10. Adaptive hybrid simulations for multiscale stochastic reaction networks

    SciTech Connect

    Hepp, Benjamin; Gupta, Ankit; Khammash, Mustafa

    2015-01-21

    The probability distribution describing the state of a Stochastic Reaction Network (SRN) evolves according to the Chemical Master Equation (CME). It is common to estimate its solution using Monte Carlo methods such as the Stochastic Simulation Algorithm (SSA). In many cases, these simulations can take an impractical amount of computational time. Therefore, many methods have been developed that approximate sample paths of the underlying stochastic process and estimate the solution of the CME. A prominent class of these methods include hybrid methods that partition the set of species and the set of reactions into discrete and continuous subsets. Such a partition separates the dynamics into a discrete and a continuous part. Simulating such a stochastic process can be computationally much easier than simulating the exact discrete stochastic process with SSA. Moreover, the quasi-stationary assumption to approximate the dynamics of fast subnetworks can be applied for certain classes of networks. However, as the dynamics of a SRN evolves, these partitions may have to be adapted during the simulation. We develop a hybrid method that approximates the solution of a CME by automatically partitioning the reactions and species sets into discrete and continuous components and applying the quasi-stationary assumption on identifiable fast subnetworks. Our method does not require any user intervention and it adapts to exploit the changing timescale separation between reactions and/or changing magnitudes of copy-numbers of constituent species. We demonstrate the efficiency of the proposed method by considering examples from systems biology and showing that very good approximations to the exact probability distributions can be achieved in significantly less computational time. This is especially the case for systems with oscillatory dynamics, where the system dynamics change considerably throughout the time-period of interest.

  11. Hybrid multiscale simulation of a mixing-controlled reaction

    SciTech Connect

    Scheibe, Timothy D.; Schuchardt, Karen L.; Agarwal, Khushbu; Chase, Jared M.; Yang, Xiaofan; Palmer, Bruce J.; Tartakovsky, Alexandre M.; Elsethagen, Todd O.; Redden, George D.

    2015-09-01

    Continuum-scale models have been used to study subsurface flow, transport, and reactions for many years but lack the capability to resolve fine-grained processes. Recently, pore-scale models, which operate at scales of individual soil grains, have been developed to more accurately model and study pore-scale phenomena, such as mineral precipitation and dissolution reactions, microbially-mediated surface reactions, and other complex processes. However, these highly-resolved models are prohibitively expensive for modeling domains of sizes relevant to practical problems. To broaden the utility of pore-scale models for larger domains, we developed a hybrid multiscale model that initially simulates the full domain at the continuum scale and applies a pore-scale model only to areas of high reactivity. Since the location and number of pore-scale model regions in the model varies as the reactions proceed, an adaptive script defines the number and location of pore regions within each continuum iteration and initializes pore-scale simulations from macroscale information. Another script communicates information from the pore-scale simulation results back to the continuum scale. These components provide loose coupling between the pore- and continuum-scale codes into a single hybrid multiscale model implemented within the SWIFT workflow environment. In this paper, we consider an irreversible homogenous bimolecular reaction (two solutes reacting to form a third solute) in a 2D test problem. This paper is focused on the approach used for multiscale coupling between pore- and continuum-scale models, application to a realistic test problem, and implications of the results for predictive simulation of mixing-controlled reactions in porous media. Our results and analysis demonstrate that loose coupling provides a feasible, efficient and scalable approach for multiscale subsurface simulations.

  12. Ganymede's interaction with the jovian plasma from hybrid simulation

    NASA Astrophysics Data System (ADS)

    Leclercq, L.; Modolo, R.; Hess, S.; Leblanc, F.

    2013-12-01

    Ganymede is a unique object: it is the biggest moon of our solar system, and the only satellite which has its own intrinsic magnetic field leading to the formation of a small magnetosphere. The magnetosphere of Ganymede being embedded in the Jovian magnetosphere, the environment of the Galilean moon presents the only known case of interaction between two magnetospheres (Kivelson et al. 1996). This peculiar interaction has been investigated by means of a 3D parallel multi-species hybrid model based on a CAM-CL algorithm (Mathews et al. 1994). This generic model has been largely used for other magnetized or unmagnetized bodies such as Mars (Modolo et al. 2005; 2006 and 2012), Titan (Modolo et al. 2007, Modolo and Chauteur 2008) or Mercury (Richer et al. 2012). IIn this formalism, ions have a kinetic description whereas electrons are considered as an inertialess fluid which ensure the neutrality of the plasma and contribute to the total current and electronic pressure. Maxwell's equations are solved to compute the temporal evolution of electromagnetic field. The hybrid simulation describes the dynamics of the magnetospheric plasma, composed of O+ and H+ ions, and Ganymede's ionospheric plasma (W+, H2+, H+). Similarly to Paty and Winglee (2004), a density profile with a scale height of 125km of the ionospheric plasma is loaded and feeded during the simulation. Charge exchange leading to H2+ and H+ are also computed. To represent Ganymede's magnetosphere a magnetic dipole is implemented at initialization with dipolar moments values taken from Kivelson et al, 2002. This dipole is progressively distorted and lead to the formal of the mini-magnetopshere. Simulation results also emphasize the presence of Alfvén wings and are in good agreement with other simulation results (Jia et al, 2008, Paty et al, 2008). Hybrid simulations are performed on a uniform cartesian grid with a spatial resolution of about 200 km. Simulations results are presented and compared to magnetometer

  13. Bioinspired, Highly Stretchable, and Conductive Dry Adhesives Based on 1D-2D Hybrid Carbon Nanocomposites for All-in-One ECG Electrodes.

    PubMed

    Kim, Taehoon; Park, Junyong; Sohn, Jongmoo; Cho, Donghwi; Jeon, Seokwoo

    2016-04-26

    Here we propose a concept of conductive dry adhesives (CDA) combining a gecko-inspired hierarchical structure and an elastomeric carbon nanocomposite. To complement the poor electrical percolation of 1D carbon nanotube (CNT) networks in an elastomeric matrix at a low filler content (∼1 wt %), a higher dimensional carbon material (i.e., carbon black, nanographite, and graphene nanopowder) is added into the mixture as an aid filler. The co-doped graphene and CNT in the composite show the lowest volume resistance (∼100 ohm·cm) at an optimized filler ratio (1:9, total filler content: 1 wt %) through a synergetic effect in electrical percolation. With an optimized conductive elastomer, gecko-inspired high-aspect-ratio (>3) microstructures over a large area (∼4 in.(2)) are successfully replicated from intaglio-patterned molds without collapse. The resultant CDA pad shows a high normal adhesion force (∼1.3 N/cm(2)) even on rough human skin and an excellent cycling property for repeatable use over 30 times without degradation of adhesion force, which cannot be achieved by commercial wet adhesives. The body-attachable CDA can be used as a metal-free, all-in-one component for measuring biosignals under daily activity conditions (i.e., underwater, movements) because of its superior conformality and water-repellent characteristic. PMID:26986477

  14. On the potential for CO2 mineral storage in continental flood basalts - PHREEQC batch- and 1D diffusion-reaction simulations.

    PubMed

    Van Pham, Thi Hai; Aagaard, Per; Hellevang, Helge

    2012-01-01

    Continental flood basalts (CFB) are considered as potential CO2 storage sites because of their high reactivity and abundant divalent metal ions that can potentially trap carbon for geological timescales. Moreover, laterally extensive CFB are found in many place in the world within reasonable distances from major CO2 point emission sources.Based on the mineral and glass composition of the Columbia River Basalt (CRB) we estimated the potential of CFB to store CO2 in secondary carbonates. We simulated the system using kinetic dependent dissolution of primary basalt-minerals (pyroxene, feldspar and glass) and the local equilibrium assumption for secondary phases (weathering products). The simulations were divided into closed-system batch simulations at a constant CO2 pressure of 100 bar with sensitivity studies of temperature and reactive surface area, an evaluation of the reactivity of H2O in scCO2, and finally 1D reactive diffusion simulations giving reactivity at CO2 pressures varying from 0 to 100 bar.Although the uncertainty in reactive surface area and corresponding reaction rates are large, we have estimated the potential for CO2 mineral storage and identified factors that control the maximum extent of carbonation. The simulations showed that formation of carbonates from basalt at 40 C may be limited to the formation of siderite and possibly FeMg carbonates. Calcium was largely consumed by zeolite and oxide instead of forming carbonates. At higher temperatures (60 - 100 C), magnesite is suggested to form together with siderite and ankerite. The maximum potential of CO2 stored as solid carbonates, if CO2 is supplied to the reactions unlimited, is shown to depend on the availability of pore space as the hydration and carbonation reactions increase the solid volume and clog the pore space. For systems such as in the scCO2 phase with limited amount of water, the total carbonation potential is limited by the amount of water present for hydration of basalt

  15. On the potential for CO2 mineral storage in continental flood basalts – PHREEQC batch- and 1D diffusion–reaction simulations

    PubMed Central

    2012-01-01

    Continental flood basalts (CFB) are considered as potential CO2 storage sites because of their high reactivity and abundant divalent metal ions that can potentially trap carbon for geological timescales. Moreover, laterally extensive CFB are found in many place in the world within reasonable distances from major CO2 point emission sources. Based on the mineral and glass composition of the Columbia River Basalt (CRB) we estimated the potential of CFB to store CO2 in secondary carbonates. We simulated the system using kinetic dependent dissolution of primary basalt-minerals (pyroxene, feldspar and glass) and the local equilibrium assumption for secondary phases (weathering products). The simulations were divided into closed-system batch simulations at a constant CO2 pressure of 100 bar with sensitivity studies of temperature and reactive surface area, an evaluation of the reactivity of H2O in scCO2, and finally 1D reactive diffusion simulations giving reactivity at CO2 pressures varying from 0 to 100 bar. Although the uncertainty in reactive surface area and corresponding reaction rates are large, we have estimated the potential for CO2 mineral storage and identified factors that control the maximum extent of carbonation. The simulations showed that formation of carbonates from basalt at 40 C may be limited to the formation of siderite and possibly FeMg carbonates. Calcium was largely consumed by zeolite and oxide instead of forming carbonates. At higher temperatures (60 – 100 C), magnesite is suggested to form together with siderite and ankerite. The maximum potential of CO2 stored as solid carbonates, if CO2 is supplied to the reactions unlimited, is shown to depend on the availability of pore space as the hydration and carbonation reactions increase the solid volume and clog the pore space. For systems such as in the scCO2 phase with limited amount of water, the total carbonation potential is limited by the amount of water present for hydration of basalt

  16. Flow Simulation of N2B Hybrid Wing Body Configuration

    NASA Technical Reports Server (NTRS)

    Kim, Hyoungjin; Liou, Meng-Sing

    2012-01-01

    The N2B hybrid wing body aircraft was conceptually designed to meet environmental and performance goals for the N+2 generation transport set by the subsonic fixed wing project. In this study, flow fields around the N2B configuration is simulated using a Reynolds-averaged Navier-Stokes flow solver using unstructured meshes. Boundary conditions at engine fan face and nozzle exhaust planes are provided by response surfaces of the NPSS thermodynamic engine cycle model. The present flow simulations reveal challenging design issues arising from boundary layer ingestion offset inlet and nacelle-airframe interference. The N2B configuration can be a good test bed for application of multidisciplinary design optimization technology.

  17. The 5-HT1D/1B receptor agonist sumatriptan enhances fear of simulated speaking and reduces plasma levels of prolactin.

    PubMed

    de Rezende, Marcos Gonçalves; Garcia-Leal, Cybele; Graeff, Frederico Guilherme; Del-Ben, Cristina Marta

    2013-12-01

    This study measured the effects of the preferential 5-HT1D/1B receptor agonist sumatriptan in healthy volunteers who performed the Simulated Public Speaking Test (SPST), which recruits the neural network involved in panic disorder and social anxiety disorder. In a double-blind, randomised experiment, 36 males received placebo (12), 50 mg (12) or 100 mg (12) of sumatriptan 2 h before the SPST. Subjective, physiological and hormonal measures were taken before, during and after the test. The dose of 100 mg of sumatriptan increased speech-induced fear more than either a 50mg dose of the drug or placebo. The largest dose of sumatriptan also enhanced vigilance more than placebo, without any change in blood pressure, heart rate or electrical skin conductance. Sumatriptan decreased plasma levels of prolactin. A significant but moderate increase in plasma cortisol after SPST occurred, independent of treatment. Because sumatriptan decreases 5-HT release into the extracellular space, the potentiation of SPST-induced fear caused by the drug supports the hypothesis that 5-HT attenuates this emotional state. As acute administration of antidepressants has also been shown to enhance speaking fear and increase plasma prolactin, in contrast to sumatriptan, the 5-HT regulation of stress-hormone release is likely to be different from that of emotion. PMID:23325368

  18. Hybrid Reactor Simulation of Boiling Water Reactor Power Oscillations

    SciTech Connect

    Huang Zhengyu; Edwards, Robert M.

    2003-08-15

    Hybrid reactor simulation (HRS) of boiling water reactor (BWR) instabilities, including in-phase and out-of-phase (OOP) oscillations, has been implemented on The Pennsylvania State University TRIGA reactor. The TRIGA reactor's power response is used to simulate reactor neutron dynamics for in-phase oscillation or the fundamental mode of the reactor modal kinetics for OOP oscillations. The reactor power signal drives a real-time boiling channel simulation, and the calculated reactivity feedback is in turn fed into the TRIGA reactor via an experimental changeable reactivity device. The thermal-hydraulic dynamics, together with first harmonic mode power dynamics, is digitally simulated in the real-time environment. The real-time digital simulation of boiling channel thermal hydraulics is performed by solving constitutive equations for different regions in the channel and is realized by a high-performance personal computer. The nonlinearity of the thermal-hydraulic model ensures the capability to simulate the oscillation phenomena, limit cycle and OOP oscillation, in BWR nuclear power plants. By adjusting reactivity feedback gains for both modes, various oscillation combinations can be realized in the experiment. The dynamics of axially lumped power distribution over the core is displayed in three-dimensional graphs. The HRS reactor power response mimics the BWR core-wide power stability phenomena. In the OOP oscillation HRS, the combination of reactor response and the simulated first harmonic power using shaping functions mimics BWR regional power oscillations. With this HRS testbed, a monitoring and/or control system designed for BWR power oscillations can be experimentally tested and verified.

  19. The Collisionless Shock in Hybrid-Vlasov Simulations

    NASA Astrophysics Data System (ADS)

    Pfau-Kempf, Y.; Vainio, R. O.; Palmroth, M.; Battarbee, M. C.; Hoilijoki, S.; Ganse, U.; von Alfthan, S.

    2015-12-01

    We will present an overview of the recent numerical results on collisionless shocks obtained from Vlasiator, a hybrid-Vlasov simulation designed to model the Earth's magnetosphere. We will present results on the Earth bow shock under different solar wind and interplanetary magnetic field conditions and compare them with results on planar shocks for similar Mach numbers. As the simulation treats only ions kinetically, we will limit our study to the ion scales and beyond, characterizing the nature of fluctuations and ion distribution functions under different conditions and numerical settings. We will also investigate the role of dimensionality of the system, i.e., compare simulations performed in 2D and 3D in ordinary space (with full 3D in velocity space in both cases). In particular, we will characterize the foreshock ULF waves reproduced by the simulations and compare them with quasi-linear theory and observations of ion foreshocks ahead of the quasi-parallel bow shock and interplanetary shocks. The reasons for the differences in the foreshock characteristics under different modeling approximations will be discussed, in particular concerning the oblique propagation and dispersion relations of the foreshock waves, which are markedly different from quasi-linear theory and in quantitative agreement with spacecraft observations.

  20. Neutral depletion in inductively coupled plasmas using hybrid-type direct simulation Monte Carlo

    SciTech Connect

    Shimada, Masashi; Tynan, George R.; Cattolica, Robert

    2008-02-01

    Neutral and ion transport phenomena were simulated by a hybrid-type direct simulation Monte Carlo (DSMC) method for a one-dimensional (1D) electrostatic plasma in Ar/N{sub 2} mixtures to identify the mechanism of neutral depletion. The results show that gas heating and pressure balance are the main mechanisms of neutral depletion in an inductively coupled plasma. When plasma pressure becomes comparable to neutral pressure in high density plasma sources (T{sub e}{approx}2-5 eV, n{sub e}{approx}10{sup 11}-10{sup 12} cm{sup -3}), the total pressure (neutral pressure and plasma pressure) is conserved. Therefore, the finite plasma pressure (mainly electron pressure) reduces the neutral pressure. Neutrals collide with ions that have been accelerated by the ambipolar electric field and with Franck-Condon dissociated atoms, resulting in gas heating. Significant neutral depletion (up to 90%) is found at the typical condition of inductively coupled plasma process reactors. The resulting neutral depletion enhances the plasma transport to the surrounding wall, increases the particle loss, and decreases the plasma density.

  1. Accelerating Climate and Weather Simulations through Hybrid Computing

    NASA Technical Reports Server (NTRS)

    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.

  2. Particle/Continuum Hybrid Simulation in a Parallel Computing Environment

    NASA Technical Reports Server (NTRS)

    Baganoff, Donald

    1996-01-01

    The objective of this study was to modify an existing parallel particle code based on the direct simulation Monte Carlo (DSMC) method to include a Navier-Stokes (NS) calculation so that a hybrid solution could be developed. In carrying out this work, it was determined that the following five issues had to be addressed before extensive program development of a three dimensional capability was pursued: (1) find a set of one-sided kinetic fluxes that are fully compatible with the DSMC method, (2) develop a finite volume scheme to make use of these one-sided kinetic fluxes, (3) make use of the one-sided kinetic fluxes together with DSMC type boundary conditions at a material surface so that velocity slip and temperature slip arise naturally for near-continuum conditions, (4) find a suitable sampling scheme so that the values of the one-sided fluxes predicted by the NS solution at an interface between the two domains can be converted into the correct distribution of particles to be introduced into the DSMC domain, (5) carry out a suitable number of tests to confirm that the developed concepts are valid, individually and in concert for a hybrid scheme.

  3. Real-time hybrid computer simulation of a small turboshaft engine and control system

    NASA Technical Reports Server (NTRS)

    Hart, C. E.; Wenzel, L. M.

    1984-01-01

    The development of an analytical model of a small turboshaft engine designed for helicopter propulsion systems is described. The model equations were implemented on a hybrid computer system to provide a real time nonlinear simulation of the engine performance over a wide operating range. The real time hybrid simulation of the engine was used to evaluate a microprocessor based digital control module. This digital control module was developed as part of an advanced rotorcraft control program. After tests with the hybrid engine simulation the digital control module was used to control a real engine in an experimental program. A hybrid simulation of the engine's electrical hydromechanical control system was developed. This allowed to vary the fuel flow and torque load inputs to the hybrid engine simulation for simulating transient operation. A steady-state data and the experimental tests are compared. Analytical model equations, analog computer diagrams, and a digital computer flow chart are included.

  4. Hybrid particle-field molecular dynamics simulation for polyelectrolyte systems.

    PubMed

    Zhu, You-Liang; Lu, Zhong-Yuan; Milano, Giuseppe; Shi, An-Chang; Sun, Zhao-Yan

    2016-04-14

    To achieve simulations on large spatial and temporal scales with high molecular chemical specificity, a hybrid particle-field method was proposed recently. This method is developed by combining molecular dynamics and self-consistent field theory (MD-SCF). The MD-SCF method has been validated by successfully predicting the experimentally observable properties of several systems. Here we propose an efficient scheme for the inclusion of electrostatic interactions in the MD-SCF framework. In this scheme, charged molecules are interacting with the external fields that are self-consistently determined from the charge densities. This method is validated by comparing the structural properties of polyelectrolytes in solution obtained from the MD-SCF and particle-based simulations. Moreover, taking PMMA-b-PEO and LiCF3SO3 as examples, the enhancement of immiscibility between the ion-dissolving block and the inert block by doping lithium salts into the copolymer is examined by using the MD-SCF method. By employing GPU-acceleration, the high performance of the MD-SCF method with explicit treatment of electrostatics facilitates the simulation study of many problems involving polyelectrolytes. PMID:27001709

  5. Hybrid simulation of wave propagation in the Io plasma torus

    NASA Astrophysics Data System (ADS)

    Stauffer, B. H.; Delamere, P. A.; Damiano, P. A.

    2015-12-01

    The transmission of waves between Jupiter and Io is an excellent case study of magnetosphere/ionosphere (MI) coupling because the power generated by the interaction at Io and the auroral power emitted at Jupiter can be reasonably estimated. Wave formation begins with mass loading as Io passes through the plasma torus. A ring beam distribution of pickup ions and perturbation of the local flow by the conducting satellite generate electromagnetic ion cyclotron waves and Alfven waves. We investigate wave propagation through the torus and to higher latitudes using a hybrid plasma simulation with a physically realistic density gradient, assessing the transmission of Poynting flux and wave dispersion. We also analyze the propagation of kinetic Alfven waves through a density gradient in two dimensions.

  6. Hybrid simulation techniques applied to the earth's bow shock

    NASA Technical Reports Server (NTRS)

    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.

  7. A Hybrid Multiscale Framework for Subsurface Flow and Transport Simulations

    SciTech Connect

    Scheibe, Timothy D.; Yang, Xiaofan; Chen, Xingyuan; Hammond, Glenn E.

    2015-06-01

    Extensive research efforts have been invested in reducing model errors to improve the predictive ability of biogeochemical earth and environmental system simulators, with applications ranging from contaminant transport and remediation to impacts of biogeochemical elemental cycling (e.g., carbon and nitrogen) on local ecosystems and regional to global climate. While the bulk of this research has focused on improving model parameterizations in the face of observational limitations, the more challenging type of model error/uncertainty to identify and quantify is model structural error which arises from incorrect mathematical representations of (or failure to consider) important physical, chemical, or biological processes, properties, or system states in model formulations. While improved process understanding can be achieved through scientific study, such understanding is usually developed at small scales. Process-based numerical models are typically designed for a particular characteristic length and time scale. For application-relevant scales, it is generally necessary to introduce approximations and empirical parameterizations to describe complex systems or processes. This single-scale approach has been the best available to date because of limited understanding of process coupling combined with practical limitations on system characterization and computation. While computational power is increasing significantly and our understanding of biological and environmental processes at fundamental scales is accelerating, using this information to advance our knowledge of the larger system behavior requires the development of multiscale simulators. Accordingly there has been much recent interest in novel multiscale methods in which microscale and macroscale models are explicitly coupled in a single hybrid multiscale simulation. A limited number of hybrid multiscale simulations have been developed for biogeochemical earth systems, but they mostly utilize application

  8. A Hybrid Multiscale Framework for Subsurface Flow and Transport Simulations

    DOE PAGESBeta

    Scheibe, Timothy D.; Yang, Xiaofan; Chen, Xingyuan; Hammond, Glenn E.

    2015-06-01

    Extensive research efforts have been invested in reducing model errors to improve the predictive ability of biogeochemical earth and environmental system simulators, with applications ranging from contaminant transport and remediation to impacts of biogeochemical elemental cycling (e.g., carbon and nitrogen) on local ecosystems and regional to global climate. While the bulk of this research has focused on improving model parameterizations in the face of observational limitations, the more challenging type of model error/uncertainty to identify and quantify is model structural error which arises from incorrect mathematical representations of (or failure to consider) important physical, chemical, or biological processes, properties, ormore » system states in model formulations. While improved process understanding can be achieved through scientific study, such understanding is usually developed at small scales. Process-based numerical models are typically designed for a particular characteristic length and time scale. For application-relevant scales, it is generally necessary to introduce approximations and empirical parameterizations to describe complex systems or processes. This single-scale approach has been the best available to date because of limited understanding of process coupling combined with practical limitations on system characterization and computation. While computational power is increasing significantly and our understanding of biological and environmental processes at fundamental scales is accelerating, using this information to advance our knowledge of the larger system behavior requires the development of multiscale simulators. Accordingly there has been much recent interest in novel multiscale methods in which microscale and macroscale models are explicitly coupled in a single hybrid multiscale simulation. A limited number of hybrid multiscale simulations have been developed for biogeochemical earth systems, but they mostly utilize application

  9. A hybrid model for simulation of secondary electron emission in plasma immersion ion implantation under different pulse rise time

    SciTech Connect

    Navab Safa, N. Ghomi, H.

    2015-02-15

    A hybrid fluid Particle in Cell–Monte Carlo Collision (PiC–MCC) model is presented to study the effect of secondary electron emission on the plasma immersion ion implantation process under different pulse rise time. The model describes the temporal evolution of various parameters of plasma such as ion density, ion velocity, secondary electron density, and secondary electron current for different rise times. A 3D–3 V PiC–MCC model is developed to simulate the secondary electrons which are emitted from the sample surface while the plasma ions and electrons are treated using a 1D fluid model. The simulation results indicate that the secondary electron density and secondary electron current increase as the rise time decreases. The main differences between the results for different rise times are found during the initial phase of the pulse. The results are explained through studying the fundamental parameters of plasma.

  10. A wind turbine hybrid simulation framework considering aeroelastic effects

    NASA Astrophysics Data System (ADS)

    Song, Wei; Su, Weihua

    2015-04-01

    In performing an effective structural analysis for wind turbine, the simulation of turbine aerodynamic loads is of great importance. The interaction between the wake flow and the blades may impact turbine blades loading condition, energy yield and operational behavior. Direct experimental measurement of wind flow field and wind profiles around wind turbines is very helpful to support the wind turbine design. However, with the growth of the size of wind turbines for higher energy output, it is not convenient to obtain all the desired data in wind-tunnel and field tests. In this paper, firstly the modeling of dynamic responses of large-span wind turbine blades will consider nonlinear aeroelastic effects. A strain-based geometrically nonlinear beam formulation will be used for the basic structural dynamic modeling, which will be coupled with unsteady aerodynamic equations and rigid-body rotations of the rotor. Full wind turbines can be modeled by using the multi-connected beams. Then, a hybrid simulation experimental framework is proposed to potentially address this issue. The aerodynamic-dominant components, such as the turbine blades and rotor, are simulated as numerical components using the nonlinear aeroelastic model; while the turbine tower, where the collapse of failure may occur under high level of wind load, is simulated separately as the physical component. With the proposed framework, dynamic behavior of NREL's 5MW wind turbine blades will be studied and correlated with available numerical data. The current work will be the basis of the authors' further studies on flow control and hazard mitigation on wind turbine blades and towers.

  11. Towards Microsecond Biological Molecular Dynamics Simulations on Hybrid Processors

    SciTech Connect

    Hampton, Scott S; Agarwal, Pratul K

    2010-01-01

    Biomolecular simulations continue to become an increasingly important component of molecular biochemistry and biophysics investigations. Performance improvements in the simulations based on molecular dynamics (MD) codes are widely desired. This is particularly driven by the rapid growth of biological data due to improvements in experimental techniques. Unfortunately, the factors, which allowed past performance improvements of MD simulations, particularly the increase in microprocessor clock frequencies, are no longer improving. Hence, novel software and hardware solutions are being explored for accelerating the performance of popular MD codes. In this paper, we describe our efforts to port and optimize LAMMPS, a popular MD framework, on hybrid processors: graphical processing units (GPUs) accelerated multi-core processors. Our implementation is based on porting the computationally expensive, non-bonded interaction terms on the GPUs, and overlapping the computation on the CPU and GPUs. This functionality is built on top of message passing interface (MPI) that allows multi-level parallelism to be extracted even at the workstation level with the multi-core CPUs as well as extend the implementation on GPU clusters. The results from a number of typically sized biomolecular systems are provided and analysis is performed on 3 generations of GPUs from NVIDIA. Our implementation allows up to 30-40 ns/day throughput on a single workstation as well as significant speedup over Cray XT5, a high-end supercomputing platform. Moreover, detailed analysis of the implementation indicates that further code optimization and improvements in GPUs will allow {approx}100 ns/day throughput on workstations and inexpensive GPU clusters, putting the widely-desired microsecond simulation time-scale within reach to a large user community.

  12. 3D Hybrid Simulation of the Titan's Plasma Environment

    NASA Astrophysics Data System (ADS)

    Lipatov, A. S.; Sittler, E. C.; Hartle, R. E.

    2007-05-01

    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 (see, e.g. [Lipatov, 2002]). 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 S Lipatov, The Hybrid Multiscale Simulation Technology. An Introduction with Application to Astrophysical and Laboratory Plasmas, Springer-Verlag, Berlin, Heidelberg, New York, 2002, p.p. 1-403.

  13. Simulation of electric vehicles with hybrid power systems

    SciTech Connect

    Burke, A.F.; Cole, G.H.

    1990-01-01

    Computer programs for the simulation of the operation of electric vehicles with hybrid power systems are described. These programs treat cases in which high energy density ultracapacitors or high power density pulse batteries are used to load level the main energy storage battery in the vehicle. A generalized control strategy for splitting the power between the main battery and the pulse power devices is implemented such that the user can specify the nominal battery power as a function of the state-of-charge of the ultracapacitor or pulse power battery. The programs display graphically on the screen, as they run, the power from both the main battery and the pulse power device and the state-of-charge of the pulse power device. After each run is completed, a summary is printed out from which the effect of load leveling the battery on vehicle range and energy consumption can be determined. Default input files are provided with the programs so various combinations of vehicles, driveline components, and batteries of special current interest to the EV community can be run with either type of pulse power device. Typical simulation results are shown including cases in which the pulse power devices are connected in parallel with the main battery without interface electronics. 2 refs., 7 figs., 14 tabs.

  14. Quantum Simulations of Solvated Biomolecules Using Hybrid Methods

    NASA Astrophysics Data System (ADS)

    Hodak, Miroslav

    2009-03-01

    One of the most important challenges in quantum simulations on biomolecules is efficient and accurate inclusion of the solvent, because the solvent atoms usually outnumber those in the biomolecule of interest. We have developed a hybrid method that allows for explicit quantum-mechanical treatment of the solvent at low computational cost. In this method, Kohn-Sham (KS) density functional theory (DFT) is combined with an orbital-free (OF) DFT. Kohn-Sham (KS) DFT is used to describe the biomolecule and its first solvation shells, while the orbital-free (OF) DFT is employed for the rest of the solvent. The OF part is fully O(N) and capable of handling 10^5 solvent molecules on current parallel supercomputers, while taking only ˜ 10 % of the total time. The compatibility between the KS and OF DFT methods enables seamless integration between the two. In particular, the flow of solvent molecules across the KS/OF interface is allowed and the total energy is conserved. As the first large-scale applications, the hybrid method has been used to investigate the binding of copper ions to proteins involved in prion (PrP) and Parkinson's diseases. Our results for the PrP, which causes mad cow disease when misfolded, resolve a contradiction found in experiments, in which a stronger binding mode is replaced by a weaker one when concentration of copper ions is increased, and show how it can act as a copper buffer. Furthermore, incorporation of copper stabilizes the structure of the full-length PrP, suggesting its protective role in prion diseases. For alpha-synuclein, a Parkinson's disease (PD) protein, we show that Cu binding modifies the protein structurally, making it more susceptible to misfolding -- an initial step in the onset of PD. In collaboration with W. Lu, F. Rose and J. Bernholc.

  15. Hybrid PIC Simulations of Particle Dynamics in Coaxial Plasma Jet Accelerators

    NASA Astrophysics Data System (ADS)

    Thoma, Carsten; Hughes, Thomas; Welch, Dale; Hakel, Peter

    2007-11-01

    We describe the results of 1D and 2D simulations of plasma jet accelerators using the particle-in-cell (PIC) code Lsp. Previous studies of 1D cartesian simulations have shown that ion particle dynamics at the plasma-vacuum interface depend critically on the local Hall parameter, which is strongly dependent on electron temperature. In a coaxial accelerator with finite transverse dimensions, large transverse ion motions, predicted at moderate Hall parameters in 1D, can lead to ion loss to the walls. The results of 2D r-z jet simulations are described and compared with the 1D cartesian results. The effects of particle loss and ablation at the wall are considered, as are electron heating mechanisms at the plasma-vacuum interface, including radiation losses. We will apply the results to the plasma jet experiments underway at HyperV Technologies Corp.

  16. Hybrid simulations of the plasma environment around Enceladus

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Russell, C. T.; Tokar, R. L.; Leisner, J. S.

    2010-05-01

    The plasma environment around Enceladus is governed by the interaction between the corotating plasma with the body of the moon and the neutral gas associated with Saturn's extended cloud and plumes ejected from its southern polar region. To understand the nature of this interaction, we use 3-D electromagnetic hybrid simulations that treat ions kinetically through particle-in-cell methods and treat the electrons as a charge-neutralizing fluid. In these simulations, plasma interaction with the neutrals takes place through charge exchange. The results show that plasma absorption by Enceladus forms a tail-like density cavity behind the moon and a depletion wake which is confined in the direction perpendicular to the magnetic field but extends many Enceladus radii along the magnetic field. Except in the cavity tail, the flow is not slowed by the interaction but is diverted toward the cavity in a symmetric fashion. Interaction of the corotating plasma with the extended neutrals results in the generation of ion cyclotron waves and plasma deceleration to velocities below the corotation speed. The results also show that the extent to which the presence of a plume in the southern pole affects the nature of the interaction depends on its density. For plumes with base densities of ˜106/cm3 (6.5 × 1029 molecules in the plume) or lower we find no significant impacts, while plumes with base densities of ˜107/cm3 and larger are found to greatly impact the interaction region. Specifically, the interaction is no longer symmetric with a density cavity tail in the Northern Hemisphere and a density enhancement tail in the Southern Hemisphere. At base densities of ˜108/cm3, a strong Alfven wing is also generated in the interaction. Preliminary comparisons of the simulations with the Cassini Plasma Spectrometer data during the 12 March 2008 encounter with Enceladus suggest plume base densities of ˜5 × 108/cm3 corresponding to production of ˜4 kg/s of new ions.

  17. Hybrid simulations of moon-magnetosphere interactions at Saturn (Invited)

    NASA Astrophysics Data System (ADS)

    Kriegel, H.

    2010-12-01

    Saturn's moons offer a huge variety of different types of plasma interactions of the planet's dipole field and magnetospheric plasma with the moon's solid body, its atmosphere in the case of Titan or plume in the case of Enceladus. These objects are embedded in rather different environments resulting e.g. in subalfvenic or superalfvenic interaction types with very different spatial and temporal scales. To all these diverse scenarios we successfully apply our hybrid simulation code A.I.K.E.F. (adaptive ion kinetic electron fluid) and investigate the underlying physical processes: The icy satellites Tethys and Rhea do not possess a significant atmosphere, leading to a direct absorption of the impinging magnetospheric plasma at the moons' surfaces. We analyze how the density void is refilled by counter-streaming ions as well as the weak magnetic perturbations measured by Cassini in the moons’ wakes. At Titan, the ion gyroradii are comparable to the radius of the moon, requiring a kinetic description of the asymmetric pick-up tail. We present real-time simulations of Titan's plasma interaction in a dynamical environment like the magnetopause crossing that was observed during Cassini's T32 flyby. The different field and plasma flow orientations in magnetosphere and -sheath result in fossil fields in Titan's lower ionosphere as well as in a large-scale reconfiguration of the pick-up tail, which can only be resolved simultaneously by using an adaptive mesh. Enceladus represents a unique combination of both, the icy-satellite-type-interaction and the interaction with a spatially displaced dense atmosphere, i.e. its plume. Our model is the first one to connect a realistic model of the multiple jets forming the neutral plume with a self-consistent description of the momentum loading process due to charge exchange. By comparing our latest simulation results with Cassini magnetometer data (MAG), we investigate the highly twisted structure of the Alfven wing system triggered

  18. Hybrid Simulation Modeling to Estimate U.S. Energy Elasticities

    NASA Astrophysics Data System (ADS)

    Baylin-Stern, Adam C.

    This paper demonstrates how an U.S. application of CIMS, a technologically explicit and behaviourally realistic energy-economy simulation model which includes macro-economic feedbacks, can be used to derive estimates of elasticity of substitution (ESUB) and autonomous energy efficiency index (AEEI) parameters. The ability of economies to reduce greenhouse gas emissions depends on the potential for households and industry to decrease overall energy usage, and move from higher to lower emissions fuels. Energy economists commonly refer to ESUB estimates to understand the degree of responsiveness of various sectors of an economy, and use estimates to inform computable general equilibrium models used to study climate policies. Using CIMS, I have generated a set of future, 'pseudo-data' based on a series of simulations in which I vary energy and capital input prices over a wide range. I then used this data set to estimate the parameters for transcendental logarithmic production functions using regression techniques. From the production function parameter estimates, I calculated an array of elasticity of substitution values between input pairs. Additionally, this paper demonstrates how CIMS can be used to calculate price-independent changes in energy-efficiency in the form of the AEEI, by comparing energy consumption between technologically frozen and 'business as usual' simulations. The paper concludes with some ideas for model and methodological improvement, and how these might figure into future work in the estimation of ESUBs from CIMS. Keywords: Elasticity of substitution; hybrid energy-economy model; translog; autonomous energy efficiency index; rebound effect; fuel switching.

  19. Cost Effective Simulation of the Hybrid Solar/wind and Diesel Energy System in Rural Area

    NASA Astrophysics Data System (ADS)

    Sim, Ee. Y.; Barsoum, Nader

    2008-10-01

    This paper describes the optimization of a hybrid energy system model. Currently in Sarawak, people living in the rural areas still depend on diesel generators to generate electricity. This increases the demand for fossil fuel, creates noise pollution and toxic gas is emitted to the environment. Hence, hybrid energy systems were introduced to replace this conventional energy system as well as improving the living standard in the villages. In this paper, several hybrid energy system configurations were investigated in order to find out the most cost effective hybrid system through Hybrid Optimization Model for Electric Renewability (Homer) software. Homer simulates, optimizes, and analyzes the sensitivity variables for each of the system configurations.

  20. An automated procedure for developing hybrid computer simulations of turbofan engines

    NASA Technical Reports Server (NTRS)

    Szuch, J. R.; Krosel, S. M.; Bruton, W. M.

    1981-01-01

    This paper offers a systematic, computer-aided, self-documenting methodology for developing hybrid computer simulations of turbofan engines. The methodology that is presented makes use of a host program that can run on a large digital computer and a machine-dependent target (hybrid) program. The host program performs all of the calculations and data manipulations that are needed to transform user-supplied engine design information to a form suitable for the hybrid computer. The host program also trims the self-contained engine model to match specified design point information. A test case is described and comparisons between hybrid simulation and specified engine performance data are presented.

  1. An automated procedure for developing hybrid computer simulations of turbofan engines

    NASA Technical Reports Server (NTRS)

    Szuch, J. R.; Krosel, S. M.

    1980-01-01

    A systematic, computer-aided, self-documenting methodology for developing hybrid computer simulations of turbofan engines is presented. The methodology makes use of a host program that can run on a large digital computer and a machine-dependent target (hybrid) program. The host program performs all of the calculations and date manipulations needed to transform user-supplied engine design information to a form suitable for the hybrid computer. The host program also trims the self contained engine model to match specified design point information. A test case is described and comparisons between hybrid simulation and specified engine performance data are presented.

  2. Real-time simulation of an automotive gas turbine using the hybrid computer

    NASA Technical Reports Server (NTRS)

    Costakis, W.; Merrill, W. C.

    1984-01-01

    A hybrid computer simulation of an Advanced Automotive Gas Turbine Powertrain System is reported. The system consists of a gas turbine engine, an automotive drivetrain with four speed automatic transmission, and a control system. Generally, dynamic performance is simulated on the analog portion of the hybrid computer while most of the steady state performance characteristics are calculated to run faster than real time and makes this simulation a useful tool for a variety of analytical studies.

  3. Hybrid molecular simulation of methane storage inside pillared graphene

    NASA Astrophysics Data System (ADS)

    Hassani, Atieh; Hamed Mosavian, Mohammad Taghi; Ahmadpour, Ali; Farhadian, Nafiseh

    2015-06-01

    In this study, a hybrid molecular dynamics—grand canonical Monte Carlo simulation is carried out to investigate the storage capacity of methane in a new nanostructure adsorbent called pillared graphene. This new nanostructure is composed of graphene sheets in parallel with vertical carbon nanotubes (CNTs), which act as their holders. The adsorption ability of this new structure is compared to graphene sheets to evaluate its potential for methane storage. The results show that in a specific adsorbent volume, applying pillared graphene increases the number of adsorbed methane up to 22% in comparison to graphene sheets. Given the application of various isotherm models such as Langmuir, Freundlich, Sips, and Toth and calculation of their parameters, it is predicted that methane adsorption on pillared graphene displays a heterogeneous behavior. Furthermore, the effects of geometry parameters such as CNTs diameter, the number of CNTs, and graphene sheets layer spacing on the methane uptake are investigated. The results show that the pillared graphene containing 1 CNT per 30 nm2 graphene sheet areas provides the best configuration for methane adsorption. This optimum structure is characterized by a small diameter of about 0.938 nm and an optimal layer spacing of about 1.2 nm. Finally, our results show that this kind of pillared structure can be suitable for methane storage.

  4. Hybrid molecular simulation of methane storage inside pillared graphene.

    PubMed

    Hassani, Atieh; Hamed Mosavian, Mohammad Taghi; Ahmadpour, Ali; Farhadian, Nafiseh

    2015-06-21

    In this study, a hybrid molecular dynamics--grand canonical Monte Carlo simulation is carried out to investigate the storage capacity of methane in a new nanostructure adsorbent called pillared graphene. This new nanostructure is composed of graphene sheets in parallel with vertical carbon nanotubes (CNTs), which act as their holders. The adsorption ability of this new structure is compared to graphene sheets to evaluate its potential for methane storage. The results show that in a specific adsorbent volume, applying pillared graphene increases the number of adsorbed methane up to 22% in comparison to graphene sheets. Given the application of various isotherm models such as Langmuir, Freundlich, Sips, and Toth and calculation of their parameters, it is predicted that methane adsorption on pillared graphene displays a heterogeneous behavior. Furthermore, the effects of geometry parameters such as CNTs diameter, the number of CNTs, and graphene sheets layer spacing on the methane uptake are investigated. The results show that the pillared graphene containing 1 CNT per 30 nm(2) graphene sheet areas provides the best configuration for methane adsorption. This optimum structure is characterized by a small diameter of about 0.938 nm and an optimal layer spacing of about 1.2 nm. Finally, our results show that this kind of pillared structure can be suitable for methane storage. PMID:26093570

  5. Broadband ground-motion simulation using a hybrid approach

    USGS Publications Warehouse

    Graves, R.W.; Pitarka, A.

    2010-01-01

    This paper describes refinements to the hybrid broadband ground-motion simulation methodology of Graves and Pitarka (2004), which combines a deterministic approach at low frequencies (f 1 Hz). In our approach, fault rupture is represented kinematically and incorporates spatial heterogeneity in slip, rupture speed, and rise time. The prescribed slip distribution is constrained to follow an inverse wavenumber-squared fall-off and the average rupture speed is set at 80% of the local shear-wave velocity, which is then adjusted such that the rupture propagates faster in regions of high slip and slower in regions of low slip. We use a Kostrov-like slip-rate function having a rise time proportional to the square root of slip, with the average rise time across the entire fault constrained empirically. Recent observations from large surface rupturing earthquakes indicate a reduction of rupture propagation speed and lengthening of rise time in the near surface, which we model by applying a 70% reduction of the rupture speed and increasing the rise time by a factor of 2 in a zone extending from the surface to a depth of 5 km. We demonstrate the fidelity of the technique by modeling the strong-motion recordings from the Imperial Valley, Loma Prieta, Landers, and Northridge earthquakes.

  6. Modeling and simulation of a hybrid ship power system

    NASA Astrophysics Data System (ADS)

    Doktorcik, Christopher J.

    2011-12-01

    Optimizing the performance of naval ship power systems requires integrated design and coordination of the respective subsystems (sources, converters, and loads). A significant challenge in the system-level integration is solving the Power Management Control Problem (PMCP). The PMCP entails deciding on subsystem power usages for achieving a trade-off between the error in tracking a desired position/velocity profile, minimizing fuel consumption, and ensuring stable system operation, while at the same time meeting performance limitations of each subsystem. As such, the PMCP naturally arises at a supervisory level of a ship's operation. In this research, several critical steps toward the solution of the PMCP for surface ships have been undertaken. First, new behavioral models have been developed for gas turbine engines, wound rotor synchronous machines, DC super-capacitors, induction machines, and ship propulsion systems. Conventional models describe system inputs and outputs in terms of physical variables such as voltage, current, torque, and force. In contrast, the behavioral models developed herein express system inputs and outputs in terms of power whenever possible. Additionally, the models have been configured to form a hybrid system-level power model (HSPM) of a proposed ship electrical architecture. Lastly, several simulation studies have been completed to expose the capabilities and limitations of the HSPM.

  7. A novel technique for the numerical simulation of hot collision-free plasma; Vlasov hybrid simulation

    SciTech Connect

    Nunn, D. )

    1993-09-01

    This paper reports a simple novel technique for the numerical simulation of hot collision-free plasmas. The method is termed Vlasov hybrid simulation (VHS). A time varying phase space simulation box and grid are defined, and the phase fluid within the box is filled with simulation particles. The distribution function F (or [sigma]F) is defined on the phase trajectory of each particle. At each timestep F (or [sigma]F) is interpolated from the simulation particles onto the phase space grid. Particles are followed continuously until exiting from the phase box and are not constantly recreated at phase space grid points. The algorithm is very efficient, stable, and has low noise levels. Distribution function fine structure is tolerated and the formalism does not require diffusion of the distribution function. The VHS method is particularly valuable when the flux of phase fluid across the phase box boundary is significant. In this case VHS codes have a dynamic population of particles-giving great efficiency gains over PIC codes with fixed particle populations. The VHS method has been applied to the numerical simulation of triggered VLF emissions in the magnetosphere and gives results in close agreement with observations. 27 refs., 13 figs., 1 tab.

  8. Breaking through 1D layout limitations and regaining 2D design freedom Part I: 2D layout decomposition and stitching techniques for hybrid optical and self-aligned multiple patterning

    NASA Astrophysics Data System (ADS)

    Liu, Hongyi; Zhou, Jun; Chen, Yijian

    2015-03-01

    To break through 1-D IC layout limitations, we develop computationally efficient 2-D layout decomposition and stitching techniques which combine the optical and self-aligned multiple patterning (SAMP) processes. A polynomial time algorithm is developed to decompose the target layout into two components, each containing one or multiple sets of unidirectional features that can be formed by a SAMP+cut/block process. With no need of connecting vias, the final 2-D features are formed by directly stitching two components together. This novel patterning scheme is considered as a hybrid approach as the SAMP processes offer the capability of density scaling while the stitching process creates 2-D design freedom as well as the multiple-CD/pitch capability. Its technical advantages include significant reduction of via steps and avoiding the interdigitating types of multiple patterning (for density multiplication) to improve the processing yield. The developed decomposition and synthesis algorithms are tested using 2-D layouts from NCSU open cell library. Statistical and computational characteristics of these public layout data are investigated and discussed.

  9. Integrating models to simulate emergent behaviour: effects of organic matter on soil hydraulics in the ICZ-1D soil-vegetation model

    NASA Astrophysics Data System (ADS)

    Valstar, Johan; Rowe, Ed; Konstantina, Moirogiorgou; Giannakis, Giorgos; Nikolaidis, Nikolaos

    2014-05-01

    explore the complex interactions involved in soil development and change. We were unable to identify appropriately-detailed existing models for plant productivity and for the dynamics of soil aggregation and porosity, and so developed the PROSUM and CAST models, respectively, to simulate these subsystems. Moreover, we applied the BRNS generator to obtain a chemical equilibrium model. These were combined with HYDRUS-1D (water and solute transport), a weathering model (derived from the SAFE model) and a simple bioturbation model. The model includes several feedbacks, such as the effect of soil organic matter on water retention and hydraulic conductivity. We encountered several important challenges when building the integrated model. First, a mechanism was developed that initiates the execution of a single time step for an individual sub-model and accounts for the relevant mass transfers between sub-models. This allows for different and sometimes variable time step duration in the submodels. Secondly, we removed duplicated processes and identified and included relevant solute production terms that had been neglected. The model is being tested against datasets obtained from several Soil Critical Zone Observatories in Europe. This contribution focuses on the design strategy for the model.

  10. A hybrid model to simulate the annual runoff of the Kaidu River in northwest China

    NASA Astrophysics Data System (ADS)

    Xu, Jianhua; Chen, Yaning; Bai, Ling; Xu, Yiwen

    2016-04-01

    Fluctuant and complicated hydrological processes can result in the uncertainty of runoff forecasting. Thus, it is necessary to apply the multi-method integrated modeling approaches to simulate runoff. Integrating the ensemble empirical mode decomposition (EEMD), the back-propagation artificial neural network (BPANN) and the nonlinear regression equation, we put forward a hybrid model to simulate the annual runoff (AR) of the Kaidu River in northwest China. We also validate the simulated effects by using the coefficient of determination (R2) and the Akaike information criterion (AIC) based on the observed data from 1960 to 2012 at the Dashankou hydrological station. The average absolute and relative errors show the high simulation accuracy of the hybrid model. R2 and AIC both illustrate that the hybrid model has a much better performance than the single BPANN. The hybrid model and integrated approach elicited by this study can be applied to simulate the annual runoff of similar rivers in northwest China.

  11. Simulating the Household Plug-in Hybrid Electric Vehicle Distribution and its Electric Distribution Network Impacts

    SciTech Connect

    Cui, Xiaohui; Kim, Hoe Kyoung; Liu, Cheng; Kao, Shih-Chieh; Bhaduri, Budhendra L

    2012-01-01

    This paper presents a multi agent-based simulation framework for modeling spatial distribution of plug-in hybrid electric vehicle ownership at local residential level, discovering plug-in hybrid electric vehicle hot zones where ownership may quickly increase in the near future, and estimating the impacts of the increasing plug-in hybrid electric vehicle ownership on the local electric distribution network with different charging strategies. We use Knox County, Tennessee as a case study to highlight the simulation results of the agent-based simulation framework.

  12. One-dimensional hybrid-direct kinetic simulation of the discharge plasma in a Hall thruster

    SciTech Connect

    Hara, Kentaro; Boyd, Iain D.; Kolobov, Vladimir I.

    2012-11-15

    In order to model the non-equilibrium plasma within the discharge region of a Hall thruster, the velocity distribution functions (VDFs) must be obtained accurately. A direct kinetic (DK) simulation method that directly solves the plasma Boltzmann equation can achieve better resolution of VDFs in comparison to particle simulations, such as the particle-in-cell (PIC) method that inherently include statistical noise. In this paper, a one-dimensional hybrid-DK simulation, which uses a DK simulation for heavy species and a fluid model for electrons, is developed and compared to a hybrid-PIC simulation. Time-averaged results obtained from the hybrid-DK simulation are in good agreement with hybrid-PIC results and experimental data. It is shown from a comparison of using a kinetic simulation and solving the continuity equation that modeling of the neutral atoms plays an important role for simulations of the Hall thruster discharge plasma. In addition, low and high frequency plasma oscillations are observed. Although the kinetic nature of electrons is not resolved due to the use of a fluid model, the hybrid-DK model provides spatially and temporally well-resolved plasma properties and an improved resolution of VDFs for heavy species with less statistical noise in comparison to the hybrid-PIC method.

  13. Simulation-optimization framework for multi-season hybrid stochastic models

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    SummaryA novel simulation-optimization framework is proposed that enables the automation of the hybrid stochastic modeling process for synthetic generation of multi-season streamflows. This framework aims to minimize the drudgery, judgment and subjectivity involved in the selection of the most appropriate hybrid stochastic model. It consists of a multi-objective optimization model as the driver and the hybrid multi-season stochastic streamflow generation model, hybrid matched block boostrap (HMABB) as the simulation engine. For the estimation of the hybrid model parameters, the proposed framework employs objective functions that aim to minimize the overall errors in the preservation of storage capacities at various demand levels, unlike the traditional approaches that are simulation based. Moreover this framework yields a number of competent hybrid stochastic models in a single run of the simulation-optimization framework. The efficacy of the proposed simulation-optimization framework is brought out through application to two monthly streamflow data sets from USA of varying sample sizes that exhibit multi-modality and a complex dependence structure. The results show that the hybrid models obtained from the proposed framework are able to preserve the statistical characteristics as well as the storage characteristics better than the simulation based HMABB model, while minimizing the manual effort and the subjectivity involved in the modeling process. The proposed framework can be easily extended to model multi-site multi-season streamflow data.

  14. Design and simulation of a hybrid dielectric waveguide

    NASA Astrophysics Data System (ADS)

    Aryal, Krishna Prasad

    Waveguides, in general are used as a means to route photons. Traditional dielectric waveguides, composed of a high index core surrounded by a low index cladding, produce maximum field intensities far from dielectric interfaces. This thesis presents the design of a plasmonic enhanced waveguide, which relocates the maximum optical field intensity from the center of the waveguide to an interfacial region defined by a dielectric and a negative index material. This is accomplished through the use of a metal film, positioned on top of a traditional ridge waveguide in those places where one wishes to excite a plasmon mode as opposed to the more traditional dielectric mode. Plasmon modes have their highest field intensity at the interface located between the metal and the dielectric. In this thesis, the waveguide dimensions of a hybrid dielectric waveguide are determined with the intent of producing single mode operation for a ridge waveguide with and without metal on top. A commercial Eigen mode solver (MODE Lumerical) is used to obtain all field profiles, waveguide effective index and waveguide loss. Multiple simulations were used to design a waveguide, which supports a single plasmonic mode when the metal film is in place and a single dielectric mode when the metal film is absent. Such a waveguide is expected to find use in the field of integrated quantum optics where quantum dots, defined by near surface confining potentials, require high interfacial fields for maximum dot/field interactions. Further, based on the final waveguide design height of ( 5microm ) and width of ( 7.9microm ), an effective index of ( 3.687 ) results when operated in the plasmon mode and (3.619) when operated in dielectric mode. This change in refractive index suggests such hybrid dielectric/plasmon waveguides can be used for the design of Bragg reflectors leading to plasmonic cavities, which, when coupled to the proposed near surface located quantum dots, can be used for the production and

  15. Modeling and Simulation of Water Allocation System Based on Simulated Annealing Hybrid Genetic Algorithm

    NASA Astrophysics Data System (ADS)

    Zhu, Jiulong; Wang, Shijun

    Presently water resource in most watersheds in China is distributed in terms of administrative instructions. This kind of allocation method has many disadvantages and hampers the instructional effect of market mechanism on water allocation. The paper studies South-to-North Water Transfer Project and discusses water allocation of the node lakes along the Project. Firstly, it advanced four assumptions. Secondly, it analyzed constraint conditions of water allocation in terms of present state of water allocation in China. Thirdly, it established a goal model of water allocation and set up a systematic model from the angle of comprehensive profits of water utilization and profits of the node lakes. Fourthly, it discussed calculation method of the model by means of Simulated Annealing Hybrid Genetic Algorithm (SHGA). Finally, it validated the rationality and validity of the model by a simulation testing.

  16. Hybrid Numerical Methods for Multiscale Simulations of Subsurface Biogeochemical Processes

    SciTech Connect

    Scheibe, Timothy D.; Tartakovsky, Alexandre M.; Tartakovsky, Daniel M.; Redden, George D.; Meakin, Paul

    2007-08-01

    Many subsurface flow and transport problems of importance today involve coupled non-linear flow, transport, and reaction in media exhibiting complex heterogeneity. In particular, problems involving biological mediation of reactions fall into this class of problems. Recent experimental research has revealed important details about the physical, chemical, and biological mechanisms involved in these processes at a variety of scales ranging from molecular to laboratory scales. However, it has not been practical or possible to translate detailed knowledge at small scales into reliable predictions of field-scale phenomena important for environmental management applications. A large assortment of numerical simulation tools have been developed, each with its own characteristic scale including molecular (e.g., molecular dynamics), microbial (e.g., cellular automata or particle individual-based models), pore (e.g., lattice-Boltzmann, pore network models, and discrete particle methods such as smoothed particle hydrodynamics) and continuum scales (e.g., traditional partial differential equations solved by finite difference or finite element methods). While many problems can be effectively addressed by one of these models at a single scale, some problems may require explicit integration of models across multiple scales. We are developing a hybrid multi-scale subsurface reactive transport modeling framework that integrates models with diverse representations of physics, chemistry and biology at different scales (sub-pore, pore and continuum). The modeling framework is being designed to take advantage of advanced computational technologies including parallel code components using the Common Component Architecture, parallel solvers, gridding, data and workflow management, and visualization. This paper describes the specific methods/codes being used at each scale, techniques used to directly and adaptively couple across model scales, and preliminary results of application to a

  17. SiSeRHMap v1.0: a simulator for mapped seismic response using a hybrid model

    NASA Astrophysics Data System (ADS)

    Grelle, Gerardo; Bonito, Laura; Lampasi, Alessandro; Revellino, Paola; Guerriero, Luigi; Sappa, Giuseppe; Guadagno, Francesco Maria

    2016-04-01

    The SiSeRHMap (simulator for mapped seismic response using a hybrid model) is a computerized methodology capable of elaborating prediction maps of seismic response in terms of acceleration spectra. It was realized on the basis of a hybrid model which combines different approaches and models in a new and non-conventional way. These approaches and models are organized in a code architecture composed of five interdependent modules. A GIS (geographic information system) cubic model (GCM), which is a layered computational structure based on the concept of lithodynamic units and zones, aims at reproducing a parameterized layered subsoil model. A meta-modelling process confers a hybrid nature to the methodology. In this process, the one-dimensional (1-D) linear equivalent analysis produces acceleration response spectra for a specified number of site profiles using one or more input motions. The shear wave velocity-thickness profiles, defined as trainers, are randomly selected in each zone. Subsequently, a numerical adaptive simulation model (Emul-spectra) is optimized on the above trainer acceleration response spectra by means of a dedicated evolutionary algorithm (EA) and the Levenberg-Marquardt algorithm (LMA) as the final optimizer. In the final step, the GCM maps executor module produces a serial map set of a stratigraphic seismic response at different periods, grid solving the calibrated Emul-spectra model. In addition, the spectra topographic amplification is also computed by means of a 3-D validated numerical prediction model. This model is built to match the results of the numerical simulations related to isolate reliefs using GIS morphometric data. In this way, different sets of seismic response maps are developed on which maps of design acceleration response spectra are also defined by means of an enveloping technique.

  18. Near-infrared spectro-interferometry of Mira variables and comparisons to 1D dynamic model atmospheres and 3D convection simulations

    NASA Astrophysics Data System (ADS)

    Wittkowski, M.; Chiavassa, A.; Freytag, B.; Scholz, M.; Höfner, S.; Karovicova, I.; Whitelock, P. A.

    2016-03-01

    Aims: We aim at comparing spectro-interferometric observations of Mira variable asymptotic giant branch (AGB) stars with the latest 1D dynamic model atmospheres based on self-excited pulsation models (CODEX models) and with 3D dynamic model atmospheres including pulsation and convection (CO5BOLD models) to better understand the processes that extend the molecular atmosphere to radii where dust can form. Methods: We obtained a total of 20 near-infrared K-band spectro-interferometric snapshot observations of the Mira variables o Cet, R Leo, R Aqr, X Hya, W Vel, and R Cnc with a spectral resolution of about 1500. We compared observed flux and visibility spectra with predictions by CODEX 1D dynamic model atmospheres and with azimuthally averaged intensities based on CO5BOLD 3D dynamic model atmospheres. Results: Our visibility data confirm the presence of spatially extended molecular atmospheres located above the continuum radii with large-scale inhomogeneities or clumps that contribute a few percent of the total flux. The detailed structure of the inhomogeneities or clumps show a variability on time scales of 3 months and above. Both modeling attempts provided satisfactory fits to our data. In particular, they are both consistent with the observed decrease in the visibility function at molecular bands of water vapor and CO, indicating a spatially extended molecular atmosphere. Observational variability phases are mostly consistent with those of the best-fit CODEX models, except for near-maximum phases, where data are better described by near-minimum models. Rosseland angular diameters derived from the model fits are broadly consistent between those based on the 1D and the 3D models and with earlier observations. We derived fundamental parameters including absolute radii, effective temperatures, and luminosities for our sources. Conclusions: Our results provide a first observational support for theoretical results that shocks induced by convection and pulsation in the

  19. Filamented ion tail structures at Titan: A hybrid simulation study

    NASA Astrophysics Data System (ADS)

    Feyerabend, Moritz; Simon, Sven; Motschmann, Uwe; Liuzzo, Lucas

    2015-11-01

    This study investigates the processes that lead to the detection of split signatures in ion density during several crossings of the Cassini spacecraft through Titan's mid-range plasma tail (T9, T63, and T75). During each of these flybys, the Cassini Plasma Spectrometer detected Titan's ionospheric ion population twice; i.e., the spacecraft passed through two spatially separated regions where cold ions were detected, with the regions also being dominated by ions of different masses in the case of T9. Whether this filamented tail structure is an omnipresent feature of Titan's plasma interaction or a result of non-stationary upstream conditions during specific flybys is still unclear. To explain these features, we apply the hybrid simulation code AIKEF (kinetic ions and fluid electrons). Our model includes chemical reactions as well as a realistic photoionization model for a sophisticated description of the ionospheric composition of Titan. Our simulations show that the filamentation of Titan's tail is indeed a common feature of the moon's plasma interaction. Light ionospheric species escape along draped magnetic field lines to form a parabolically shaped filament structure, which is mainly seen in planes that contain the upstream magnetospheric magnetic field and the upstream flow direction. In addition, transport of ions of all species from the ramside towards downstream produces a cone structure behind Titan, with a region of decreased density inside and filaments of 1-2 RT (RT=2575 km) thickness and enhanced density at the surface of the cone. Spacecraft trajectories that penetrate these structures allow for the detection of split signatures in the tail. The orientation of the upstream magnetic field and plasma flow as well as local time effects (i.e., Titan's orbital position) influence the location of the filaments in the tail and can also cause asymmetries in their sizes and densities. The detection of the split signatures along a spacecraft trajectory may

  20. HRSSA - Efficient hybrid stochastic simulation for spatially homogeneous biochemical reaction networks

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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.

  1. Real-time simulation of F100-PW-100 turbofan engine using the hybrid computer

    NASA Technical Reports Server (NTRS)

    Szuch, J. R.; Seldner, K.

    1975-01-01

    A real-time hybrid computer simulation of the F100-PW-100 augmented turbofan is presented. The digital portion of the hybrid computer is used to perform the bivariate function generation associated with modeling the performance of the engine's rotating components. The remaining calculations are performed on the analog computer. Steady state simulation data along with sea level, static, transient data are presented to show that the real-time simulation matches baseline digital simulation results over a wide range of power settings and flight conditions. Steady state simulation data are compared with sea level, experimental data to show that the real-time hybrid and baseline digital simulations do adequately predict the performance of the actual engine. FORTRAN listings and analog patching diagrams are provided.

  2. 1-D EQUILIBRIUM DISCRETE DIFFUSION MONTE CARLO

    SciTech Connect

    T. EVANS; ET AL

    2000-08-01

    We present a new hybrid Monte Carlo method for 1-D equilibrium diffusion problems in which the radiation field coexists with matter in local thermodynamic equilibrium. This method, the Equilibrium Discrete Diffusion Monte Carlo (EqDDMC) method, combines Monte Carlo particles with spatially discrete diffusion solutions. We verify the EqDDMC method with computational results from three slab problems. The EqDDMC method represents an incremental step toward applying this hybrid methodology to non-equilibrium diffusion, where it could be simultaneously coupled to Monte Carlo transport.

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

    NASA Astrophysics Data System (ADS)

    Same, Adam; Stipe, Alex; Grossman, David; Park, Jae Wan

    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.

  4. HYBRIST Mobility Model - A Novel Hybrid Mobility Model for VANET Simulations

    NASA Astrophysics Data System (ADS)

    ManfeDanquah, Wiseborn; Turgay Altilar, D.

    2014-01-01

    Simulations play a vital role in implementing, testing and validating proposed algorithms and protocols in VANET. Mobility model, defined as the movement pattern of vehicles, is one of the main factors that contribute towards the efficient implementation of VANET algorithms and protocols. Using near reality mobility models ensure that accurate results are obtained from simulations. Mobility models that have been proposed and used to implement and test VANET protocols and algorithms are either the urban mobility model or highway mobility model. Algorithms and protocols implemented using urban or highway mobility models may not produce accurate results in hybrid mobility models without enhancement due to the vast differences in mobility patterns. It is on this score the Hybrist, a novel hybrid mobility model is proposed. The realistic mobility pattern trace file of the proposed Hybrist hybrid mobility model can be imported to VANET simulators such as Veins and network simulators such as ns2 and Qualnet to simulate VANET algorithms and protocols.

  5. Visual Analytics for Complex Engineering Systems: Hybrid Visual Steering of Simulation Ensembles.

    PubMed

    Matković, Krešimir; Gračanin, Denis; Splechtna, Rainer; Jelović, Mario; Stehno, Benedikt; Hauser, Helwig; Purgathofer, Werner

    2014-12-01

    In this paper we propose a novel approach to hybrid visual steering of simulation ensembles. A simulation ensemble is a collection of simulation runs of the same simulation model using different sets of control parameters. Complex engineering systems have very large parameter spaces so a naïve sampling can result in prohibitively large simulation ensembles. Interactive steering of simulation ensembles provides the means to select relevant points in a multi-dimensional parameter space (design of experiment). Interactive steering efficiently reduces the number of simulation runs needed by coupling simulation and visualization and allowing a user to request new simulations on the fly. As system complexity grows, a pure interactive solution is not always sufficient. The new approach of hybrid steering combines interactive visual steering with automatic optimization. Hybrid steering allows a domain expert to interactively (in a visualization) select data points in an iterative manner, approximate the values in a continuous region of the simulation space (by regression) and automatically find the "best" points in this continuous region based on the specified constraints and objectives (by optimization). We argue that with the full spectrum of optimization options, the steering process can be improved substantially. We describe an integrated system consisting of a simulation, a visualization, and an optimization component. We also describe typical tasks and propose an interactive analysis workflow for complex engineering systems. We demonstrate our approach on a case study from automotive industry, the optimization of a hydraulic circuit in a high pressure common rail Diesel injection system. PMID:26356894

  6. Automated procedure for developing hybrid computer simulations of turbofan engines. Part 1: General description

    NASA Technical Reports Server (NTRS)

    Szuch, J. R.; Krosel, S. M.; Bruton, W. M.

    1982-01-01

    A systematic, computer-aided, self-documenting methodology for developing hybrid computer simulations of turbofan engines is presented. The methodology that is pesented makes use of a host program that can run on a large digital computer and a machine-dependent target (hybrid) program. The host program performs all the calculations and data manipulations that are needed to transform user-supplied engine design information to a form suitable for the hybrid computer. The host program also trims the self-contained engine model to match specified design-point information. Part I contains a general discussion of the methodology, describes a test case, and presents comparisons between hybrid simulation and specified engine performance data. Part II, a companion document, contains documentation, in the form of computer printouts, for the test case.

  7. Development of a Hybrid RANS/LES Method for Compressible Mixing Layer Simulations

    NASA Technical Reports Server (NTRS)

    Georgiadis, Nicholas J.; Alexander, J. Iwan D.; Reshotko, Eli

    2001-01-01

    A hybrid method has been developed for simulations of compressible turbulent mixing layers. Such mixing layers dominate the flows in exhaust systems of modem day aircraft and also those of hypersonic vehicles currently under development. The hybrid method uses a Reynolds-averaged Navier-Stokes (RANS) procedure to calculate wall bounded regions entering a mixing section, and a Large Eddy Simulation (LES) procedure to calculate the mixing dominated regions. A numerical technique was developed to enable the use of the hybrid RANS/LES method on stretched, non-Cartesian grids. The hybrid RANS/LES method is applied to a benchmark compressible mixing layer experiment. Preliminary two-dimensional calculations are used to investigate the effects of axial grid density and boundary conditions. Actual LES calculations, performed in three spatial directions, indicated an initial vortex shedding followed by rapid transition to turbulence, which is in agreement with experimental observations.

  8. Hybrid Global Model Simulations of He/N2 and He/H2O Atmospheric Pressure Capacitive Discharges

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.; Kawamura, E.; Ke, Ding; Lichtenberg, A. J.; Chabert, P.; Lazzaroni, C.

    2014-10-01

    We used 1D particle-in-cell (PIC) simulations of an atmospheric He/0.1%N2 discharge with simplified chemistry to guide the development of a hybrid analytical/numerical global model that includes electron multiplication and two classes of electrons: ``hot'' electrons associated with the sheaths, and ``warm'' electrons associated with the bulk. The model and PIC results show reasonable agreement and indicate a transition from a low power α-mode with a relatively high bulk electron temperature Te to a high power γ-mode with a low Te. The transition is accompanied by an increase in density and a decrease in sheath widths. Water is a trace gas of bio-medical interest since it may arise from contact with skin. We use the hybrid global model to simulate a chemically complex, bounded He/H2O atmospheric pressure discharge, including 148 volume reactions among 43 species, and including clusters up to H19O9+.For a planar discharge with a 1 cm electrode radius and a 0.5 mm gap driven at 13.56 MHz, we determine the depletion and diffusion effects and the α to γ transition for secondary emission γse = 0.25 over a range of rf currents and external H2O concentrations. Each simulation takes about 2 minutes on a moderate laptop. This work was partially supported by the Department of Energy Office of Fusion Energy Science Contract DE-SC000193 and by the Natural Science Foundation of China Contract 11375042.

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

    PubMed Central

    2009-01-01

    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. PMID:20003312

  10. Emergency birth hybrid simulation with standardized patients in midwifery education: implementation and evaluation.

    PubMed

    Lindsay Miller, Jane; Avery, Melissa D; Larson, Karin; Woll, Anne; VonAchen, Alison; Mortenson, Angela

    2015-01-01

    Structured simulations have become a critical part of health professions education at every level, particularly for high-risk, low-incidence scenarios. This article describes the implementation and evaluation of a hybrid simulation of emergency birth situations in a graduate midwifery program. In the fall of 2011 and spring of 2012, nurse-midwifery students twice participated in 2 simulated emergencies-shoulder dystocia and postpartum hemorrhage-using hybrid simulation (a standardized patient paired with a birth task trainer). Students found the simulations to be realistic. The use of best practices (ie, repetitive practice, team learning, small group debriefing, and large group debriefing) enhanced the quality of the simulation experience and the learners' reflection about their professional skills, strengths, weaknesses, and confidence in managing these 2 obstetric emergencies. This article is part of a special series of articles that address midwifery innovations in clinical practice, education, interprofessional collaboration, health policy, and global health. PMID:25963413

  11. Dynamics of ozone and nitrogen oxides at Summit, Greenland. II. Simulating snowpack chemistry during a spring high ozone event with a 1-D process-scale model

    NASA Astrophysics Data System (ADS)

    Murray, Keenan A.; Kramer, Louisa J.; Doskey, Paul V.; Ganzeveld, Laurens; Seok, Brian; Van Dam, Brie; Helmig, Detlev

    2015-09-01

    Observed depth profiles of nitric oxide (NO), nitrogen dioxide (NO2), and ozone (O3) in snowpack interstitial air at Summit, Greenland were best replicated by a 1-D process-scale model, which included (1) geometrical representation of snow grains as spheres, (2) aqueous-phase chemistry confined to a quasi-liquid layer (QLL) on the surface of snow grains, and (3) initialization of the species concentrations in the QLL through equilibrium partitioning with mixing ratios in snowpack interstitial air. A comprehensive suite of measurements in and above snowpack during a high O3 event facilitated analysis of the relationship between the chemistry of snowpack and the overlying atmosphere. The model successfully reproduced 2 maxima (i.e., a peak near the surface of the snowpack at solar noon and a larger peak occurring in the evening that extended down from 0.5 to 2 m) in the diurnal profile of NO2 within snowpack interstitial air. The maximum production rate of NO2 by photolysis of nitrate (NO3-) was approximately 108 molec cm-3 s-1, which explained daily observations of maxima in NO2 mixing ratios near solar noon. Mixing ratios of NO2 in snowpack interstitial air were greatest in the deepest layers of the snowpack at night and were attributed to thermal decomposition of peroxynitric acid, which produced up to 106 molec NO2 cm-3 s-1. Highest levels of NO in snowpack interstitial air were confined to upper layers of the snowpack and observed profiles were consistent with photolysis of NO2. Production of nitrogen oxides (NOx) from NO3- photolysis was estimated to be two orders of magnitude larger than NO production and supports the hypothesis that NO3- photolysis is the primary source of NOx within sunlit snowpack in the Arctic. Aqueous-phase oxidation of formic acid by O3 resulted in a maximum consumption rate of ∼106-107 molec cm-3 s-1 and was the primary removal mechanism for O3.

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

    NASA Astrophysics Data System (ADS)

    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

  13. A hybrid non-reflective boundary technique for efficient simulation of guided waves using local interaction simulation approach

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Cesnik, Carlos E. S.

    2016-04-01

    Local interaction simulation approach (LISA) is a highly parallelizable numerical scheme for guided wave simulation in structural health monitoring (SHM). This paper addresses the issue of simulating wave propagation in unbounded domain through the implementation of non-reflective boundary (NRB) in LISA. In this study, two different categories of NRB, i.e., the non-reflective boundary condition (NRBC) and the absorbing boundary layer (ABL), have been investigated in the parallelized LISA scheme. For the implementation of NRBC, a set of general LISA equations considering the effect from boundary stress is obtained first. As a simple example, the Lysmer and Kuhlemeyer (L-K) model is applied here to demonstrate the easiness of NRBC implementation in LISA. As a representative of ABL implementation, the LISA scheme incorporating the absorbing layers with increasing damping (ALID) is also proposed, based on elasto-dynamic equations considering damping effect. Finally, an effective hybrid model combining L-K and ALID methods in LISA is developed, and guidelines for implementing the hybrid model is presented. Case studies on a three-dimensional plate model compares the performance of hybrid method to that of L-K and ALID acting independently. The simulation results demonstrate that best absorbing efficiency is achieved with the hybrid method.

  14. Charaterizing the O+ ion plume from Hybrid simulations: comparison to MAVEN observations

    NASA Astrophysics Data System (ADS)

    Modolo, R.; Leblanc, F.; Chaufray, J. Y.; Leclercq, L.; Esteban-Hernandez, R.; Curry, S.; Dong, Y.; Brain, D. A.; Bowers, C.; Luhmann, J. G.; McFadden, J. P.; Halekas, J. S.; Espley, J. R.; Connerney, J. E. P.; Jakosky, B. M.

    2015-12-01

    MAVEN observations show a substantial plume-like distribution of escaping ions from the Martian atmosphere. It represents an important ion escape channel with large fluxes (Brain et al, 2015; Dong et al, 2015, Curry et al, 2015). Such structure is organized by the solar wind convection electric field and it is located in the MSE northward hemisphere. Global hybrid models (eg Modolo et al, 2005, 2012; Kallio et al, 2006; Brecht et al, 2006) reproduce nicely this plume. To further characterize this population, hybrid simulations have been performed with upstream solar wind conditions observed by MAVEN. Simulation results along the spacecraft track present signatures of high energetic O+ ions similar to MAVEN measurements. Comparison of simulated 3D distribution functions of this population are compared to STATIC and SWIA observations. Moreover a comparison of hybrid results with statistical ion fluxes maps derived from MAVEN (Dong et al, 2015; Brain et al, 2015) have been conducted and a reasonable agreement is found .

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

    SciTech Connect

    Rabiti, Cristian; Garcia, Humberto E.; Hovsapian, Rob; Kinoshita, Robert; Mesina, George L.; Bragg-Sitton, Shannon M.; Boardman, Richard D.

    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

  16. Mixing MARTINI: electrostatic coupling in hybrid atomistic-coarse-grained biomolecular simulations.

    PubMed

    Wassenaar, Tsjerk A; Ingólfsson, Helgi I; Priess, Marten; Marrink, Siewert J; Schäfer, Lars V

    2013-04-01

    Hybrid molecular dynamics simulations of atomistic (AA) solutes embedded in coarse-grained (CG) environment can substantially reduce the computational cost with respect to fully atomistic simulations. However, interfacing both levels of resolution is a major challenge that includes a balanced description of the relevant interactions. This is especially the case for polar solvents such as water, which screen the electrostatic interactions and thus require explicit electrostatic coupling between AA and CG subsystems. Here, we present and critically test computationally efficient hybrid AA/CG models. We combined the Gromos atomistic force field with the MARTINI coarse-grained force field. To enact electrostatic coupling, two recently developed CG water models with explicit electrostatic interactions were used: the polarizable MARTINI water model and the BMW model. The hybrid model was found to be sensitive to the strength of the AA-CG electrostatic coupling, which was adjusted through the relative dielectric permittivity εr(AA-CG). Potentials of mean force (PMFs) between pairs of amino acid side chain analogues in water and partitioning free enthalpies of uncharged amino acid side chain analogues between apolar solvent and water show significant differences between the hybrid simulations and the fully AA or CG simulations, in particular for charged and polar molecules. For apolar molecules, the results obtained with the hybrid AA/CG models are in better agreement with the fully atomistic results. The structures of atomistic ubiquitin solvated in CG water and of a single atomistic transmembrane α-helix and the transmembrane portion of an atomistic mechanosensitive channel in CG lipid bilayers were largely maintained during 50-100 ns of AA/CG simulations, partly due to an overstabilization of intramolecular interactions. This work highlights some key challenges on the way toward hybrid AA/CG models that are both computationally efficient and sufficiently accurate for

  17. Hybrid Monte-Carlo method for simulating neutron and photon radiography

    NASA Astrophysics Data System (ADS)

    Wang, Han; Tang, Vincent

    2013-11-01

    We present a Hybrid Monte-Carlo method (HMCM) for simulating neutron and photon radiographs. HMCM utilizes the combination of a Monte-Carlo particle simulation for calculating incident film radiation and a statistical post-processing routine to simulate film noise. Since the method relies on MCNP for transport calculations, it is easily generalized to most non-destructive evaluation (NDE) simulations. We verify the method's accuracy through ASTM International's E592-99 publication, Standard Guide to Obtainable Equivalent Penetrameter Sensitivity for Radiography of Steel Plates [1]. Potential uses for the method include characterizing alternative radiological sources and simulating NDE radiographs.

  18. GPU Accelerated Implementation of Density Functional Theory for Hybrid QM/MM Simulations.

    PubMed

    Nitsche, Matías A; Ferreria, Manuel; Mocskos, Esteban E; González Lebrero, Mariano C

    2014-03-11

    The hybrid simulation tools (QM/MM) evolved into a fundamental methodology for studying chemical reactivity in complex environments. This paper presents an implementation of electronic structure calculations based on density functional theory. This development is optimized for performing hybrid molecular dynamics simulations by making use of graphic processors (GPU) for the most computationally demanding parts (exchange-correlation terms). The proposed implementation is able to take advantage of modern GPUs achieving acceleration in relevant portions between 20 to 30 times faster than the CPU version. The presented code was extensively tested, both in terms of numerical quality and performance over systems of different size and composition. PMID:26580175

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

    SciTech Connect

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

    2004-12-14

    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.

  20. Effectiveness of Simulation in a Hybrid and Online Networking Course.

    ERIC Educational Resources Information Center

    Cameron, Brian H.

    2003-01-01

    Reports on a study that compares the performance of students enrolled in two sections of a Web-based computer networking course: one utilizing a simulation package and the second utilizing a static, graphical software package. Analysis shows statistically significant improvements in performance in the simulation group compared to the…

  1. Air-snowpack exchange of bromine, ozone and mercury in the springtime Arctic simulated by the 1-D model PHANTAS - Part 2: Mercury and its speciation

    NASA Astrophysics Data System (ADS)

    Toyota, K.; Dastoor, A. P.; Ryzhkov, A.

    2013-08-01

    Atmospheric mercury depletion events (AMDEs) refer to a recurring depletion of mercury in the springtime Arctic (and Antarctic) boundary layer, occurring, in general, concurrently with ozone depletion events (ODEs). To close some of the knowledge gaps in the physical and chemical mechanisms of AMDEs and ODEs, we have developed a one-dimensional model that simulates multiphase chemistry and transport of trace constituents throughout porous snowpack and in the overlying atmospheric boundary layer (ABL). Building on the model reported in a companion paper (Part 1: In-snow bromine activation and its impact on ozone), we have expanded the chemical mechanism to include the reactions of mercury in the gas- and aqueous-phases with temperature dependence of rate and equilibrium constants accounted for wherever possible. Thus the model allows us to study the chemical and physical processes taking place during ODEs and AMDEs within a single framework where two-way interactions between the snowpack and the atmosphere are simulated in a detailed, process-oriented manner. Model runs are conducted for meteorological and chemical conditions representing the springtime Arctic ABL loaded with "haze" sulfate aerosols and the underlying saline snowpack laid on sea ice. Using recent updates for the Hg + Br \\rightleftarrows HgBr reaction kinetics, we show that the rate and magnitude of photochemical loss of gaseous elemental mercury (GEM) during AMDEs exhibit a strong dependence on the choice of reaction(s) of HgBr subsequent to its formation. At 253 K, the temperature that is presumably low enough for bromine radical chemistry to cause prominent AMDEs as indicated from field observations, the parallel occurrence of AMDEs and ODEs is simulated if the reaction HgBr + BrO is assumed to produce a thermally stable intermediate, Hg(OBr)Br, at the same rate constant as the reaction HgBr + Br. On the contrary, the simulated depletion of atmospheric mercury is notably diminished by not

  2. Air-snowpack exchange of bromine, ozone and mercury in the springtime Arctic simulated by the 1-D model PHANTAS - Part 2: Mercury and its speciation

    NASA Astrophysics Data System (ADS)

    Toyota, K.; Dastoor, A. P.; Ryzhkov, A.

    2014-04-01

    Atmospheric mercury depletion events (AMDEs) refer to a recurring depletion of mercury occurring in the springtime Arctic (and Antarctic) boundary layer, in general, concurrently with ozone depletion events (ODEs). To close some of the knowledge gaps in the physical and chemical mechanisms of AMDEs and ODEs, we have developed a one-dimensional model that simulates multiphase chemistry and transport of trace constituents throughout porous snowpack and in the overlying atmospheric boundary layer (ABL). This paper constitutes Part 2 of the study, describing the mercury component of the model and its application to the simulation of AMDEs. Building on model components reported in Part 1 ("In-snow bromine activation and its impact on ozone"), we have developed a chemical mechanism for the redox reactions of mercury in the gas and aqueous phases with temperature dependent reaction rates and equilibrium constants accounted for wherever possible. Thus the model allows us to study the chemical and physical processes taking place during ODEs and AMDEs within a single framework where two-way interactions between the snowpack and the atmosphere are simulated in a detailed, process-oriented manner. Model runs are conducted for meteorological and chemical conditions that represent the springtime Arctic ABL characterized by the presence of "haze" (sulfate aerosols) and the saline snowpack on sea ice. The oxidation of gaseous elemental mercury (GEM) is initiated via reaction with Br-atom to form HgBr, followed by competitions between its thermal decomposition and further reactions to give thermally stable Hg(II) products. To shed light on uncertain kinetics and mechanisms of this multi-step oxidation process, we have tested different combinations of their rate constants based on published laboratory and quantum mechanical studies. For some combinations of the rate constants, the model simulates roughly linear relationships between the gaseous mercury and ozone concentrations as

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Reactor Subsystem Simulation for Nuclear Hybrid Energy Systems

    SciTech Connect

    Shannon Bragg-Sitton; J. Michael Doster; Alan Rominger

    2012-09-01

    Preliminary system models have been developed by Idaho National Laboratory researchers and are currently being enhanced to assess integrated system performance given multiple sources (e.g., nuclear + wind) and multiple applications (i.e., electricity + process heat). Initial efforts to integrate a Fortran-based simulation of a small modular reactor (SMR) with the balance of plant model have been completed in FY12. This initial effort takes advantage of an existing SMR model developed at North Carolina State University to provide initial integrated system simulation for a relatively low cost. The SMR subsystem simulation details are discussed in this report.

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

    NASA Technical Reports Server (NTRS)

    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

  6. Solar-wind turbulence at kinetic wavelengths: hybrid-Vlasov simulations

    NASA Astrophysics Data System (ADS)

    Valentini, F.; Califano, F.; Veltri, P.

    2010-12-01

    The cooling of the expanding solar wind is less efficient than expected. Scientists pointed out that the reason of this empirical evidence is related to the turbulent character of the solar wind plasma. The identification of the physical mechanism replacing "energy dissipation" in a collisionless magnetized plasma and establishing the link between macroscopic and microscopic scales would open a new scenario of broad importance in the field of turbulence and would have far-reaching implications in the problem of space plasma heating. Turbulent heating consists both in a progressive energy degradation and disorder increasing, going from large to small scales. The increase of disorder results into the production, through nonlinear interaction, of small-scale fluctuations involving not only the kinetic energy, as in the case of heat, but also the potential energy associated with electric and magnetic field fluctuations. To numerically analyze the kinetic effects on the evolution of the turbulent spectra in the solar wind, we make use of a recently developed numerical hybrid-Vlasov code [1], where the Vlasov equation is solved for the proton distribution function, while the electron response is taken into account through a generalized Ohm law that retains Hall effects and electron inertia terms. By performing multi-dimensional phase space simulations (1D or 2D in space and 3D in velocity) [2-5] on the last generation of supercomputers, we show that newly identified electrostatic (acoustic-like) modes, in longitudinal propagation with respect to the average magnetic field and driven by particle distribution functions far from local thermodynamic equilibrium, represent a privileged channel for turbulence to carry the energy towards small disordered scales. The system dynamics is analyzed for different electron to ion temperature ratios. Our numerical results provide a qualitative interpretation of a complex phenomenology ubiquitously recovered in many solar

  7. Hybrid simulations of magnetic reconnection with kinetic ions and fluid electron pressure anisotropy

    DOE PAGESBeta

    Le, A.; Daughton, W.; Karimabadi, H.; Egedal, J.

    2016-03-16

    We present the first hybrid simulations with kinetic ions and recently developed equations of state for the electron fluid appropriate for reconnection with a guide field. The equations of state account for the main anisotropy of the electron pressure tensor.Magnetic reconnection is studied in two systems, an initially force-free current sheet and a Harris sheet. The hybrid model with the equations of state is compared to two other models, hybrid simulations with isothermal electrons and fully kinetic simulations. Including the anisotropicequations of state in the hybrid model provides a better match to the fully kinetic model. In agreement with fullymore » kinetic results, the main feature captured is the formation of an electron current sheet that extends several ion inertial lengths. This electron current sheet modifies the Hall magnetic field structure near the X-line, and it is not observed in the standard hybrid model with isotropic electrons. The saturated reconnection rate in this regime nevertheless remains similar in all three models. Here, implications for global modeling are discussed.« less

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

    PubMed

    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. PMID:26456000

  9. Plasma simulation in a hybrid ion electric propulsion system

    NASA Astrophysics Data System (ADS)

    Jugroot, Manish; Christou, Alex

    2015-04-01

    An exciting possibility for the next generation of satellite technology is the microsatellite. These satellites, ranging from 10-500 kg, can offer advantages in cost, reduced risk, and increased functionality for a variety of missions. For station keeping and control of these satellites, a suitable compact and high efficiency thruster is required. Electrostatic propulsion provides a promising solution for microsatellite thrust due to their high specific impulse. The rare gas propellant is ionized into plasma and generates a beam of high speed ions by electrostatic processes. A concept explored in this work is a hybrid combination of dc ion engines and hall thrusters to overcome space-charge and lifetime limitations of current ion thruster technologies. A multiphysics space and time-dependent formulation was used to investigate and understand the underlying physical phenomena. Several regions and time scales of the plasma have been observed and will be discussed.

  10. VFSARES-a very fast simulated annealing FORTRAN program for interpretation of 1-D DC resistivity sounding data from various electrode arrays

    NASA Astrophysics Data System (ADS)

    Sharma, Shashi Prakash

    2012-05-01

    Employing the very fast simulated annealing (VFSA) global optimization technique, a FORTRAN program is developed for the interpretation of one-dimensional direct current resistivity sounding data from various electrode arrays. The VFSA optimization depicts various good fitting solutions (models) after analyzing a large number of models within a predefined model space. Various models that yield reasonably well fitting responses with the observed response lie along a narrow elongated region of the model space. Therefore, instead of selecting the global model on the basis of the lowest misfit error, it is better to analyze histograms and probability density functions (PDFs) of such models for depicting the global model. In a multidimensional model space, the most appropriate region to select suitable models to compute the mean model is the one in which the PDF is larger in comparison to the other regions of the model space. Initially, accepted models with misfit errors less than the predefined threshold value are selected and lognormal PDFs for each model parameter are computed. Subsequently, mean model and uncertainties are computed using the models in which each model parameter has a PDF more than the defined threshold value (>68.2%). The mean model computed from such models is very close to the actual subsurface structure (global model). It is observed that the mean model computed using models with a PDF more than 95% for each model parameters yields the actual model. Moreover uncertainty computed using models with such a high PDF and lying in a small model space will be small and it will not be considered as the actual global uncertainty. Resistivity sounding (synthetic and field) data over different subsurface structures are optimized using the VFSA program developed in the present study. Optimization results reveal that the actual model always locates within the estimated uncertainty in the mean model. Since the approach requires much less computing time (a few

  11. Dynamic Simulation of Carbonate Fuel Cell-Gas Turbine Hybrid Systems

    SciTech Connect

    Roberts, R.A.; Brouwer, J.; Liese, E.A.; Gemmen, R.S.

    2006-04-01

    Hybrid fuel cell/gas turbine systems provide an efficient means of producing electricity from fossil fuels with ultra low emissions. However, there are many significant challenges involved in integrating the fuel cell with the gas turbine and other components of this type of system. The fuel cell and the gas turbine must maintain efficient operation and electricity production while protecting equipment during perturbations that may occur when the system is connected to the utility grid or in stand-alone mode. This paper presents recent dynamic simulation results from two laboratories focused on developing tools to aid in the design and dynamic analyses of hybrid fuel cell systems. The simulation results present the response of a carbonate fuel cell/gas turbine, or molten carbonate fuel cell/gas turbine, (MCFC/GT) hybrid system to a load demand perturbation. Initial results suggest that creative control strategies will be needed to ensure a flexible system with wide turndown and robust dynamic operation.

  12. Power and energy computational models for the design and simulation of hybrid-electric combat vehicles

    NASA Astrophysics Data System (ADS)

    Smith, Wilford; Nunez, Patrick

    2005-05-01

    This paper describes the work being performed under the RDECOM Power and Energy (P&E) program (formerly the Combat Hybrid Power System (CHPS) program) developing hybrid power system models and integrating them into larger simulations, such as OneSAF, that can be used to find duty cycles to feed designers of hybrid power systems. This paper also describes efforts underway to link the TARDEC P&E System Integration Lab (SIL) in San Jose CA to the TARDEC Ground Vehicle Simulation Lab (GVSL) in Warren, MI. This linkage is being performed to provide a methodology for generating detailed driver profiles for use in the development of vignettes and mission profiles for system design excursions.

  13. Hybrid stochastic simulation of reaction-diffusion systems with slow and fast dynamics

    SciTech Connect

    Strehl, Robert; Ilie, Silvana

    2015-12-21

    In this paper, we present a novel hybrid method to simulate discrete stochastic reaction-diffusion models arising in biochemical signaling pathways. We study moderately stiff systems, for which we can partition each reaction or diffusion channel into either a slow or fast subset, based on its propensity. Numerical approaches missing this distinction are often limited with respect to computational run time or approximation quality. We design an approximate scheme that remedies these pitfalls by using a new blending strategy of the well-established inhomogeneous stochastic simulation algorithm and the tau-leaping simulation method. The advantages of our hybrid simulation algorithm are demonstrated on three benchmarking systems, with special focus on approximation accuracy and efficiency.

  14. On the simulation of trailing edge noise with a hybrid LES/APE method

    NASA Astrophysics Data System (ADS)

    Ewert, R.; Schröder, W.

    2004-02-01

    A hybrid method is applied to predict trailing edge noise based on a large eddy simulation (LES) of the compressible flow problem and acoustic perturbation equations (APE) for the time-dependent simulation of the acoustic field. The acoustic simulation in general considers the mean flow convection and refraction effects such that the computational domain of the flow simulation has to comprise only the significant acoustic source region. Using a modified rescaling method for the prediction of the unsteady turbulent inflow boundary layer, the LES just resolves the flow field in the immediate vicinity of the trailing edge. The linearized APE completely prevent the unbounded growth of hydrodynamic instabilities in critical mean flows.

  15. Hybrid molecular-continuum simulations using smoothed dissipative particle dynamics

    SciTech Connect

    Petsev, Nikolai D.; Leal, L. Gary; Shell, M. Scott

    2015-01-28

    We present a new multiscale simulation methodology for coupling a region with atomistic detail simulated via molecular dynamics (MD) to a numerical solution of the fluctuating Navier-Stokes equations obtained from smoothed dissipative particle dynamics (SDPD). In this approach, chemical potential gradients emerge due to differences in resolution within the total system and are reduced by introducing a pairwise thermodynamic force inside the buffer region between the two domains where particles change from MD to SDPD types. When combined with a multi-resolution SDPD approach, such as the one proposed by Kulkarni et al. [J. Chem. Phys. 138, 234105 (2013)], this method makes it possible to systematically couple atomistic models to arbitrarily coarse continuum domains modeled as SDPD fluids with varying resolution. We test this technique by showing that it correctly reproduces thermodynamic properties across the entire simulation domain for a simple Lennard-Jones fluid. Furthermore, we demonstrate that this approach is also suitable for non-equilibrium problems by applying it to simulations of the start up of shear flow. The robustness of the method is illustrated with two different flow scenarios in which shear forces act in directions parallel and perpendicular to the interface separating the continuum and atomistic domains. In both cases, we obtain the correct transient velocity profile. We also perform a triple-scale shear flow simulation where we include two SDPD regions with different resolutions in addition to a MD domain, illustrating the feasibility of a three-scale coupling.

  16. Hybrid molecular-continuum simulations using smoothed dissipative particle dynamics

    NASA Astrophysics Data System (ADS)

    Petsev, Nikolai D.; Leal, L. Gary; Shell, M. Scott

    2015-01-01

    We present a new multiscale simulation methodology for coupling a region with atomistic detail simulated via molecular dynamics (MD) to a numerical solution of the fluctuating Navier-Stokes equations obtained from smoothed dissipative particle dynamics (SDPD). In this approach, chemical potential gradients emerge due to differences in resolution within the total system and are reduced by introducing a pairwise thermodynamic force inside the buffer region between the two domains where particles change from MD to SDPD types. When combined with a multi-resolution SDPD approach, such as the one proposed by Kulkarni et al. [J. Chem. Phys. 138, 234105 (2013)], this method makes it possible to systematically couple atomistic models to arbitrarily coarse continuum domains modeled as SDPD fluids with varying resolution. We test this technique by showing that it correctly reproduces thermodynamic properties across the entire simulation domain for a simple Lennard-Jones fluid. Furthermore, we demonstrate that this approach is also suitable for non-equilibrium problems by applying it to simulations of the start up of shear flow. The robustness of the method is illustrated with two different flow scenarios in which shear forces act in directions parallel and perpendicular to the interface separating the continuum and atomistic domains. In both cases, we obtain the correct transient velocity profile. We also perform a triple-scale shear flow simulation where we include two SDPD regions with different resolutions in addition to a MD domain, illustrating the feasibility of a three-scale coupling.

  17. Nanoscale stabilization of zintl compounds: 1D ionic Li-P double helix confined inside a carbon nanotube

    NASA Astrophysics Data System (ADS)

    Ivanov, Alexander S.; Kar, Tapas; Boldyrev, Alexander I.

    2016-02-01

    One-dimensional (1D) ionic nanowires are extremely rare materials due to the difficulty in stabilizing 1D chains of ions under ambient conditions. We demonstrate here a theoretical prediction of a novel hybrid material, a nanotube encapsulated 1D ionic lithium monophosphide (LiP) chain, featuring a unique double-helix structure, which is very unusual in inorganic chemistry. This nanocomposite has been investigated with density functional theory, including molecular dynamics simulations and electronic structure calculations. We find that the formation of the LiP double-helical nanowire is facilitated by strong interactions between LiP and CNTs resulting in a charge transfer. This work suggests that nanostructured confinement may be used to stabilize other polyphosphide 1D chains, thus opening new ways to study the chemistry of zintl compounds at the nanoscale.One-dimensional (1D) ionic nanowires are extremely rare materials due to the difficulty in stabilizing 1D chains of ions under ambient conditions. We demonstrate here a theoretical prediction of a novel hybrid material, a nanotube encapsulated 1D ionic lithium monophosphide (LiP) chain, featuring a unique double-helix structure, which is very unusual in inorganic chemistry. This nanocomposite has been investigated with density functional theory, including molecular dynamics simulations and electronic structure calculations. We find that the formation of the LiP double-helical nanowire is facilitated by strong interactions between LiP and CNTs resulting in a charge transfer. This work suggests that nanostructured confinement may be used to stabilize other polyphosphide 1D chains, thus opening new ways to study the chemistry of zintl compounds at the nanoscale. Electronic supplementary information (ESI) available: Additional DOS, band structures, and Bader charges for LiP@SWCNTs. See DOI: 10.1039/c5nr07713c

  18. A Hybrid Computer Simulation to Generate the DNA Distribution of a Cell Population.

    ERIC Educational Resources Information Center

    Griebling, John L.; Adams, William S.

    1981-01-01

    Described is a method of simulating the formation of a DNA distribution, on which statistical results and experimentally measured parameters from DNA distribution and percent-labeled mitosis studies are combined. An EAI-680 and DECSystem-10 Hybrid Computer configuration are used. (Author/CS)

  19. A survey of electric and hybrid vehicles simulation programs. Volume 2: Questionnaire responses

    NASA Technical Reports Server (NTRS)

    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.

  20. Modeling of Nonacoustic Combustion Instability in Simulations of Hybrid Motor Tests

    NASA Technical Reports Server (NTRS)

    Rocker, M.

    2000-01-01

    A transient model of a hybrid motor was formulated to study the cause and elimination of nonacoustic combustion instability. The transient model was used to simulate four key tests out of a series of seventeen hybrid motor tests conducted by Thiokol, Rocketdyne, and Martin Marietta at NASA Marshall Space Flight Center (MSFC). These tests were performed under the Hybrid Propulsion Technology for Launch Vehicle Boosters (HPTLVB) program. The first test resulted in stable combustion. The second test resulted in large-amplitude, 6.5-Hz chamber pressure oscillations that gradually damped away by the end of the test. The third test resulted in large-amplitude, 7.5-Hz chamber pressure oscillations that were sustained throughout the test. The seventh test resulted in elimination of combustion instability with the installation of an orifice immediately upstream of the injector. Formulation and implementation of the model are the scope of this presentation. The current model is an independent continuation of modeling presented previously by joint Thiokol-Rocketdyne collaborators Boardman, Hawkins, Wassom. and Claflin. The previous model simulated an unstable independent research and development (IR&D) hybrid motor test performed by Thiokol. There was very good agreement between the model and test data. Like the previous model, the current model was developed using Matrix-x simulation software. However, tests performed at MSFC under the HPTLVB program were actually simulated. ln the current model, the hybrid motor, consisting of the liquid oxygen (lox) injector, the multiport solid fuel grain, and nozzle, was simulated. The lox feedsystem, consisting of the tank, venturi. valve, and feed lines, was also simulated in the model. All components of the hybrid motor and lox feedsystem are treated by a lumped-parameter approach. Agreement between the results of the transient model and actual test data was very good. This agreement between simulated and actual test data indicated

  1. Simulation of Non-Acoustic Combustion Instability in a Hybrid Rocket Motor

    NASA Technical Reports Server (NTRS)

    Rocker, Marvin

    1999-01-01

    A transient model of a hybrid motor was formulated to study the cause and elimination of non-acoustic combustion instability. The transient model was used to simulate four key tests out of a series of seventeen hybrid motor tests conducted by Thiokol, Rocketdyne and Martin Marietta at NASA/Marshall Space Flight Center (NASAIMSFC). These tests were performed under the Hybrid Propulsion Technology for Launch Vehicle Boosters (HPTLVB) program. The first test resulted in stable combustion. The second test resulted in large-amplitude, 6.5 Hz chamber pressure oscillations that gradually damped away by the end of the test. The third test resulted in large-amplitude, 7.5 Hz chamber pressure oscillations that were sustained throughout the test. The seventh test resulted in the elimination of combustion instability with the installation of an orifice immediately upstream of the injector. The formulation and implementation of the model are the scope of this presentation. The current model is an independent continuation of modeling presented previously by joint Thiokol-Rocketdyne collaborators Boardman, Hawkins, Wassom, and Claflin. The previous model simulated an unstable IR&D hybrid motor test performed by Thiokol. There was very good agreement between the model and the test data. Like the previous model, the current model was developed using Matrix-x simulation software. However, the tests performed at NASA/MSFC under the HPTLVB program were actually simulated. In the current model, the hybrid motor consisting of the liquid oxygen (LOX) injector, the multi-port solid fuel grain and the nozzle was simulated. Also, simulated in the model was the LOX feed system consisting of the tank, venturi, valve and feed lines. All components of the hybrid motor and LOX feed system are treated by a lumped-parameter approach. Agreement between the results of the transient model and the actual test data was very good. This agreement between simulated and actual test data indicated that the

  2. Simulation of Non-Acoustic Combustion Instability in a Hybrid Rocket Motor

    NASA Technical Reports Server (NTRS)

    Rocker, Marvin

    1999-01-01

    A transient model of a hybrid motor was formulated to study the cause and elimination of non-acoustic combustion instability. The transient model was used to simulate four key tests out of a series of seventeen hybrid motor tests conducted by Thiokol, Rocketdyne and Martin Marietta at NASA/Marshall Space Flight Center (NASA/MSFC). These tests were performed under the Hybrid Propulsion Technology for Launch Vehicle Boosters (HPTLVB) program. The first test resulted in stable combustion. The second test resulted in large-amplitude, 6.5 Hz chamber pressure oscillations that gradually damped away by the end of the test. The third test resulted in large-amplitude, 7.5 Hz chamber pressure oscillations that were sustained throughout the test. The seventh test resulted in the elimination of combustion instability with the installation of an orifice immediately upstream of the injector. The formulation and implementation of the model are the scope of this presentation. The current model is an independent continuation of modeling presented previously by joint Thiokol-Rocketdyne collaborators Boardman, Hawkins, Wassom, and Claflin. The previous model simulated an unstable IR&D hybrid motor test performed by Thiokol. There was very good agreement between the model and the test data. Like the previous model, the current model was developed using Matrix-x simulation software. However, the tests performed at NASA/MSFC under the HPTLVB program were actually simulated. In the current model, the hybrid motor consisting of the liquid oxygen (LOX) injector, the multi-port solid fuel grain and the nozzle was simulated. Also, simulated in the model was the LOX feed system consisting of the tank, venturi, valve and feed lines. All components of the hybrid motor and LOX feed system are treated by a lumped-parameter approach. Agreement between the results of the transient model and the actual test data was very good. This agreement between simulated and actual test data indicated that the

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

    NASA Technical Reports Server (NTRS)

    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.

  4. Hybrid (Kinetic Ion/Fluid Electron) Simulations of Reconnection Including Electron Pressure Anisotropy

    NASA Astrophysics Data System (ADS)

    Le, A.; Daughton, W. S.

    2015-12-01

    Fully kinetic simulations have shown that the structure of the thin current sheets that form during collisionless reconnection can fall into a variety of regimes depending on the electron pressure anisotropy [1]. Furthermore, recent two-fluid simulations with anisotropic electron equations of state appropriate for reconnection confirm that the electron pressure anisotropy may drive highly elongated current sheets in the reconnection exhaust [2]. While fully kinetic simulations are useful to model small regions of the Earth's magnetosphere, they are still far too expensive for global modeling. Thus, we have implemented the electron equations of state in the hybrid (kinetic ions and fluid electrons) code H3D [3], and initial 2D hybrid simulations of reconnection agree well with fully kinetic simulations. The updated hybrid code is a first step towards including electron anisotropy and full ion kinetics in global simulations of Earth's magnetosphere and laboratory experiments. [1] Le et al., Phys. Rev. Lett. 110, 135004 (2013)[2] Ohia et al., Phys. Rev. Lett. 109, 115004 (2012) [3] Karimabadi et al., Phys. Plasmas 21, 062308 (2014)

  5. Bluff-body flow simulations using hybrid RANS/LES.

    SciTech Connect

    Roy, Christopher John; DeChant, Lawrence Justin.; Payne, Jeffrey L.; Blottner, Frederick G.

    2003-06-01

    The Detached Eddy Simulation (DES) and steady-state Reynolds-Averaged Navier-Stokes (RANS) turbulence modeling approaches are examined for the incompressible flow over a square cross-section cylinder at a Reynolds number of 21,400. A compressible flow code is used which employes a second-order Roe upwind spatial discretization. Efforts are made to assess the numerical accuracy of the DES predictions with regards to statistical convergence, iterative convergence, and temporal and spatial discretization error. Three-dimensional DES simulations compared well with two-dimensional DES simulations, suggesting that the dominant vortex shedding mechanism is effectively two-dimensional. The two-dimensional simulations are validated via comparison to experimental data for mean and RMS velocities as well as Reynolds stress in the cylinder wake. The steady-state RANS models significantly overpredict the size of the recirculation zone, thus underpredicting the drag coefficient relative to the experimental value. The DES model is found to give good agreement with the experimental velocity data in the wake, drag coefficient, and recirculation zone length.

  6. Hybrid airfoil design methods for full-scale ice accretion simulation

    NASA Astrophysics Data System (ADS)

    Saeed, Farooq

    The objective of this thesis is to develop a design method together with a design philosophy that allows the design of "subscale" or "hybrid" airfoils that simulate fullscale ice accretions. These subscale or hybrid airfoils have full-scale leading edges and redesigned aft-sections. A preliminary study to help develop a design philosophy for the design of hybrid airfoils showed that hybrid airfoils could be designed to simulate full-scale airfoil droplet-impingement characteristics and, therefore, ice accretion. The study showed that the primary objective in such a design should be to determine the aft section profile that provides the circulation necessary for simulating full-scale airfoil droplet-impingement characteristics. The outcome of the study, therefore, reveals circulation control as the main design variable. To best utilize this fact, this thesis describes two innovative airfoil design methods for the design of hybrid airfoils. Of the two design methods, one uses a conventional flap system while the other only suggests the use of boundary-layer control through slot-suction on the airfoil upper surface as a possible alternative for circulation control. The formulation of each of the two design methods is described in detail, and the results from each method are validated using wind-tunnel test data. The thesis demonstrates the capabilities of each method with the help of specific design examples highlighting their application potential. In particular, the flap-system based hybrid airfoil design method is used to demonstrate the design of a half-scale hybrid model of a full-scale airfoil that simulates full-scale ice accretion at both the design and off-design conditions. The full-scale airfoil used is representative of a scaled modern business-jet main wing section. The study suggests some useful advantages of using hybrid airfoils as opposed to full-scale airfoils for a better understanding of the ice accretion process and the related issues. Results

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

    NASA Astrophysics Data System (ADS)

    Whitford, Paul C.; Sanbonmatsu, Karissa Y.

    2013-09-01

    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

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

    PubMed

    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

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

    PubMed Central

    Yang, Kecheng; Różycki, Bartosz; Cui, Fengchao; Shi, Ce; Chen, Wenduo; Li, Yunqi

    2016-01-01

    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. PMID:27227775

  10. Integrated Plasma Simulation of Lower Hybrid Current Drive in Tokamaks

    NASA Astrophysics Data System (ADS)

    Bonoli, P. T.; Wright, J. C.; Harvey, R. W.; Batchelor, D. B.; Berry, L. A.; Kessel, C. E.; Jardin, S. C.

    2012-03-01

    It has been shown in Alcator C-Mod that the onset time for sawteeth can be delayed significantly (up to 0.5 s) relative to ohmically heated plasmas, through the injection of off-axis LH current drive power [1]. We are simulating these experiments using the Integrated Plasma Simulator (IPS) [2], where the driven LH current density profiles are computed using a ray tracing component (GENRAY) and Fokker Planck code (CQL3D) [3] that are run in a tightly coupled time advance. The background plasma is evolved using the TSC transport code with the Porcelli sawtooth model [4]. Predictions of the driven LH current profiles will be compared with simpler ``reduced'' models for LHCD such as the LSC code which is implemented in TSC and which is also invoked within the IPS. [4pt] [1] C. E. Kessel et al, Bull. of the Am. Phys. Soc. 53, Poster PP6.00074 (2008). [0pt] [2] D. Batchelor et al, Journal of Physics: Conf. Series 125, 012039 (2008). [0pt] [3] R. W. Harvey and M. G. McCoy, Proc. of the IAEA Tech. Comm. Meeting on Simulation and Modeling of Therm. Plasmas, Montreal, Canada (1992). [0pt] [4] S. C. Jardin et al, J. Comp. Phys. 66, 481 (1986).

  11. A comparative study of leachate quality and biogas generation in simulated anaerobic and hybrid bioreactors

    SciTech Connect

    Xu, Qiyong; Tian, Ying; Wang, Shen; Ko, Jae Hac

    2015-07-15

    Highlights: • Temporary aeration shortened the initial acid inhibition phase for methanogens. • COD decreased faster in the hybrid bioreactor than that in the anaerobic control. • Methane generations from hybrid bioreactors were 133.4 L/kg{sub vs} and 113.2 L/kg{sub vs}. • MSW settlement increased with increasing the frequency of intermittent aeration. - Abstract: Research has been conducted to compare leachate characterization and biogas generation in simulated anaerobic and hybrid bioreactor landfills with typical Chinese municipal solid waste (MSW). Three laboratory-scale reactors, an anaerobic (A1) and two hybrid bioreactors (C1 and C2), were constructed and operated for about 10 months. The hybrid bioreactors were operated in an aerobic–anaerobic mode with different aeration frequencies by providing air into the upper layer of waste. Results showed that the temporary aeration into the upper layer aided methane generation by shortening the initial acidogenic phase because of volatile fatty acids (VFAs) reduction and pH increase. Chemical oxygen demand (COD) decreased faster in the hybrid bioreactors, but the concentrations of ammonia–nitrogen in the hybrid bioreactors were greater than those in the anaerobic control. Methanogenic conditions were established within 75 d and 60 d in C1 and C2, respectively. However, high aeration frequency led to the consumption of organic matters by aerobic degradation and resulted in reducing accumulative methane volume. The temporary aeration enhanced waste settlement and the settlement increased with increasing the frequency of aeration. Methane production was inhibited in the anaerobic control; however, the total methane generations from hybrid bioreactors were 133.4 L/kg{sub vs} and 113.2 L/kg{sub vs}. As for MSW with high content of food waste, leachate recirculation right after aeration stopped was not recommended due to VFA inhibition for methanogens.

  12. Hybrid Simulations of the Plasma Interaction with Europa's Atmosphere

    NASA Astrophysics Data System (ADS)

    Dols, V. J.; Delamere, P. A.; Wilson, R. J.; Weber, T. D.; Crary, F. J.; Bagenal, F.; Cassidy, T. A.

    2013-12-01

    Europa's atmosphere is about 100 times more tenuous than Io. The weaker ambient magnetic field and lower density of incident plasma means that the electrodynamic interaction is also weaker. Consequently, substantial fluxes of torus ions might reach the icy surface and produce radiolytic reactions. 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 consistent with an atmosphere that is composed predominately of O2 with a small amount (2%) 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 model the interaction between the plasma torus and Europa's atmosphere with a hybrid code, where ions are treated as kinetic particles moving under the Lorentz force and electrons as a fluid leading to a generalized formulation of Ohm's law. 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 observations, PLS electron density observations and a new re-analysis of the PLS plasma measurements (ion density, temperature and bulk flow velocity).

  13. Multivariable Robust Control of a Simulated Hybrid Solid Oxide Fuel Cell Gas Turbine Plant

    SciTech Connect

    Tsai, Alex; Banta, Larry; Tucker, D.A.; Gemmen, R.S.

    2008-06-01

    This paper presents a systematic approach to the multivariable robust control of a hybrid fuel cell gas turbine plant. The hybrid configuration under investigation comprises a physical simulation of a 300kW fuel cell coupled to a 120kW auxiliary power unit single spool gas turbine. The facility provides for the testing and simulation of different fuel cell models that in turn help identify the key issues encountered in the transient operation of such systems. An empirical model of the facility consisting of a simulated fuel cell cathode volume and balance of plant components is derived via frequency response data. Through the modulation of various airflow bypass valves within the hybrid configuration, Bode plots are used to derive key input/output interactions in Transfer Function format. A multivariate system is then built from individual transfer functions, creating a matrix that serves as the nominal plant in an H-Infinity robust control algorithm. The controller’s main objective is to track and maintain hybrid operational constraints in the fuel cell’s cathode airflow, and the turbo machinery states of temperature and speed, under transient disturbances. This algorithm is then tested on a Simulink/MatLab platform for various perturbations of load and fuel cell heat effluence.

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

    SciTech Connect

    Wang, Shaojie; Ellis, Dan

    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.

  15. Lower-hybrid drift instability saturation mechanisms in one-dimensional simulations

    SciTech Connect

    Chen, Y.J.; Birdsall, C.K.

    1980-09-19

    The linear properties and saturation mechanisms of the lower-hybrid drift instability have been investigated using a one-dimensional particle-hybrid simulation. For low drift velocities (V sub d much less than V sub ti), ion trapping and current relaxation (V sub d approaches limit of 0) are competing processes for stabilization. If the relative electron-ion drift velocity is kept constant in time, ion trapping causes the end of instability growth; if this drift is allowed to decrease consistent with momentum balance, then saturation is due to current relaxation.

  16. Lower-hybrid drift instability saturation mechanisms in one-dimensional simulations

    SciTech Connect

    Chen, Y.; Birdsall, C.K.

    1983-01-01

    The linear properties and saturation mechanisms of the lower-hybrid drift instability have been investigated using a one-dimensional particle-hybrid simulation. For low drift velocities (v/sub d/<..0) are competing processes for stabilization. If the relative electron--ion drift velocity is kept constant in time, ion trapping causes the end of instability growth; if this drift is allowed to decrease consistent with momentum balance, then saturation is due to current relaxation.

  17. Comparison of Hybrid-III and postmortem human surrogate response to simulated underbody blast loading.

    PubMed

    Bailey, Ann Marie; Christopher, John J; Salzar, Robert S; Brozoski, Frederick

    2015-05-01

    Response of the human body to high-rate vertical loading, such as military vehicle underbody blast (UBB), is not well understood because of the chaotic nature of such events. The purpose of this research was to compare the response of postmortem human surrogates (PMHS) and the Hybrid-III anthropomorphic test device (ATD) to simulated UBB loading ranging from 100 to 860 g seat and floor acceleration. Data from 13 whole body PMHS tests were used to create response corridors for vertical loading conditions for the pelvis, T1, head, femur, and tibia; these responses were compared to Hybrid-III responses under matched loading conditions. PMID:25751733

  18. Flow Simulation of N3-X Hybrid Wing-Body Configuration

    NASA Technical Reports Server (NTRS)

    Kim, Hyoungjin; Liou, Meng-Sing

    2013-01-01

    System studies show that a N3-X hybrid wing-body aircraft with a turboelectric distributed propulsion system using a mail-slot inlet/nozzle nacelle can meet the environmental and performance goals for N+3 generation transports (three generations beyond the current air transport technology level) set by NASA s Subsonic Fixed Wing Project. In this study, a Navier-Stokes flow simulation of N3-X on hybrid unstructured meshes was conducted, including the mail-slot propulsor. The geometry of the mail-slot propulsor was generated by a CAD (Computer-Aided Design)-free shape parameterization. A body force approach was used for a more realistic and efficient simulation of the turning and loss effects of the fan blades and the inlet-fan interactions. Flow simulation results of the N3-X demonstrates the validity of the present approach.

  19. Hybrid General Pattern Search and Simulated Annealing for Industrail Production Planning Problems

    NASA Astrophysics Data System (ADS)

    Vasant, P.; Barsoum, N.

    2010-06-01

    In this paper, the hybridization of GPS (General Pattern Search) method and SA (Simulated Annealing) incorporated in the optimization process in order to look for the global optimal solution for the fitness function and decision variables as well as minimum computational CPU time. The real strength of SA approach been tested in this case study problem of industrial production planning. This is due to the great advantage of SA for being easily escaping from trapped in local minima by accepting up-hill move through a probabilistic procedure in the final stages of optimization process. Vasant [1] in his Ph. D thesis has provided 16 different techniques of heuristic and meta-heuristic in solving industrial production problems with non-linear cubic objective functions, eight decision variables and 29 constraints. In this paper, fuzzy technological problems have been solved using hybrid techniques of general pattern search and simulated annealing. The simulated and computational results are compared to other various evolutionary techniques.

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

    NASA Astrophysics Data System (ADS)

    Ito, Atsushi M.; Takayama, Arimichi; Oda, Yasuhiro; Tamura, Tomoyuki; Kobayashi, Ryo; Hattori, Tatsunori; Ogata, Shuji; Ohno, Noriyasu; Kajita, Shin; Yajima, Miyuki; Noiri, Yasuyuki; Yoshimoto, Yoshihide; Saito, Seiki; Takamura, Shuichi; Murashima, Takahiro; Miyamoto, Mitsutaka; Nakamura, Hiroaki

    2015-08-01

    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.

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

    NASA Technical Reports Server (NTRS)

    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

  2. High order hybrid numerical simulations of two dimensional detonation waves

    NASA Technical Reports Server (NTRS)

    Cai, Wei

    1993-01-01

    In order to study multi-dimensional unstable detonation waves, a high order numerical scheme suitable for calculating the detailed transverse wave structures of multidimensional detonation waves was developed. The numerical algorithm uses a multi-domain approach so different numerical techniques can be applied for different components of detonation waves. The detonation waves are assumed to undergo an irreversible, unimolecular reaction A yields B. Several cases of unstable two dimensional detonation waves are simulated and detailed transverse wave interactions are documented. The numerical results show the importance of resolving the detonation front without excessive numerical viscosity in order to obtain the correct cellular patterns.

  3. Effects of alpha beam on the parametric decay of a parallel propagating circularly polarized Alfven wave: Hybrid simulations

    SciTech Connect

    Gao, Xinliang; Lu, Quanming; Tao, Xin; Hao, Yufei; Wang, Shui

    2013-09-15

    Alfven waves with a finite amplitude are found to be unstable to a parametric decay in low beta plasmas. In this paper, the parametric decay of a circularly polarized Alfven wave in a proton-electron-alpha plasma system is investigated with one-dimensional (1-D) hybrid simulations. In cases without alpha particles, with the increase of the wave number of the pump Alfven wave, the growth rate of the decay instability increases and the saturation amplitude of the density fluctuations slightly decrease. However, when alpha particles with a sufficiently large bulk velocity along the ambient magnetic field are included, at a definite range of the wave numbers of the pump wave, both the growth rate and the saturation amplitude of the parametric decay become much smaller and the parametric decay is heavily suppressed. At these wave numbers, the resonant condition between the alpha particles and the daughter Alfven waves is satisfied, therefore, their resonant interactions might play an important role in the suppression of the parametric decay instability.

  4. Effects of alpha beam on the parametric decay of a parallel propagating circularly polarized Alfven wave: Hybrid simulations

    NASA Astrophysics Data System (ADS)

    Gao, Xinliang; Lu, Quanming; Tao, Xin; Hao, Yufei; Wang, Shui

    2013-09-01

    Alfven waves with a finite amplitude are found to be unstable to a parametric decay in low beta plasmas. In this paper, the parametric decay of a circularly polarized Alfven wave in a proton-electron-alpha plasma system is investigated with one-dimensional (1-D) hybrid simulations. In cases without alpha particles, with the increase of the wave number of the pump Alfven wave, the growth rate of the decay instability increases and the saturation amplitude of the density fluctuations slightly decrease. However, when alpha particles with a sufficiently large bulk velocity along the ambient magnetic field are included, at a definite range of the wave numbers of the pump wave, both the growth rate and the saturation amplitude of the parametric decay become much smaller and the parametric decay is heavily suppressed. At these wave numbers, the resonant condition between the alpha particles and the daughter Alfven waves is satisfied, therefore, their resonant interactions might play an important role in the suppression of the parametric decay instability.

  5. Formation of compact clusters from high resolution hybrid cosmological simulations

    SciTech Connect

    Richardson, Mark L. A.; Scannapieco, Evan; Gray, William J.

    2013-11-20

    The early universe hosted a large population of small dark matter 'minihalos' that were too small to cool and form stars on their own. These existed as static objects around larger galaxies until acted upon by some outside influence. Outflows, which have been observed around a variety of galaxies, can provide this influence in such a way as to collapse, rather than disperse, the minihalo gas. Gray and Scannapieco performed an investigation in which idealized spherically symmetric minihalos were struck by enriched outflows. Here we perform high-resolution cosmological simulations that form realistic minihalos, which we then extract to perform a large suite of simulations of outflow-minihalo interactions including non-equilibrium chemical reactions. In all models, the shocked minihalo forms molecules through non-equilibrium reaction, and then cools to form dense, chemically homogenous clumps of star-forming gas. The formation of these high-redshift clusters may be observable with the next generation of telescopes and the largest of them should survive to the present-day, having properties similar to halo globular clusters.

  6. Full color hybrid display for aircraft simulators. [landing aids

    NASA Technical Reports Server (NTRS)

    Chase, W. D. (Inventor)

    1977-01-01

    A full spectrum color monitor, connected to the camera and lens system of a television camera supported by a gantry frame over a terrain model simulating an aircraft landing zone, projects the monitor image onto a lens or screen visually accessible to a trainee in the simulator. A digital computer produces a pattern corresponding to the lights associated with the landing strip onto a monochromatic display, and an optical system projects the calligraphic image onto the same lens so that it is superposed on the video representation of the landing field. The optical system includes a four-color wheel which is rotated between the calligraphic display and the lens, and an apparatus for synchronizing the generation of a calligraphic pattern with the color segments on the color wheel. A servo feedback system responsive to the servo motors on the gantry frame produces an input to the computer so that the calligraphically generated signal corresponds in shape, size and location to the video signal.

  7. Hybrid magneto-hydrodynamic simulation of a driven FRC

    SciTech Connect

    Rahman, H. U. Wessel, F. J.; Binderbauer, M. W.; Qerushi, A.; Rostoker, N.; Conti, F.; Ney, P.

    2014-03-15

    We simulate a field-reversed configuration (FRC), produced by an “inductively driven” FRC experiment; comprised of a central-flux coil and exterior-limiter coil. To account for the plasma kinetic behavior, a standard 2-dimensional magneto-hydrodynamic code is modified to preserve the azimuthal, two-fluid behavior. Simulations are run for the FRC's full-time history, sufficient to include: acceleration, formation, current neutralization, compression, and decay. At start-up, a net ion current develops that modifies the applied-magnetic field forming closed-field lines and a region of null-magnetic field (i.e., a FRC). After closed-field lines form, ion-electron drag increases the electron current, canceling a portion of the ion current. The equilibrium is lost as the total current eventually dissipates. The time evolution and magnitudes of the computed current, ion-rotation velocity, and plasma temperature agree with the experiments, as do the rigid-rotor-like, radial-profiles for the density and axial-magnetic field [cf. Conti et al. Phys. Plasmas 21, 022511 (2014)].

  8. Simulations of ionospheric turbulence produced by HF heating near the upper hybrid layer

    NASA Astrophysics Data System (ADS)

    Najmi, A.; Eliasson, B.; Shao, X.; Milikh, G. M.; Papadopoulos, K.

    2016-06-01

    Heating of the ionosphere by high-frequency (HF), ordinary (O) mode electromagnetic waves can excite magnetic field-aligned density striations, associated with upper and lower hybrid turbulence and electron heating. We have used Vlasov simulations in one spatial and two velocity dimensions to study the induced turbulence in the presence of striations when the O-mode pump is mode converted to large-amplitude upper hybrid oscillations trapped in a striation. Parametric processes give rise to upper and lower hybrid turbulence, as well as to large amplitude, short wavelength electron Bernstein waves. The latter excite stochastic electron heating when their amplitudes exceed a threshold for stochasticity, leading to a rapid increase of the electron temperature by several thousands of kelvin. The results have relevance for high-latitude heating experiments.

  9. Electric and hybrid electric vehicle study utilizing a time-stepping simulation

    NASA Technical Reports Server (NTRS)

    Schreiber, Jeffrey G.; Shaltens, Richard K.; Beremand, Donald G.

    1992-01-01

    The applicability of NASA's advanced power technologies to electric and hybrid vehicles was assessed using a time-stepping computer simulation to model electric and hybrid vehicles operating over the Federal Urban Driving Schedule (FUDS). Both the energy and power demands of the FUDS were taken into account and vehicle economy, range, and performance were addressed simultaneously. Results indicate that a hybrid electric vehicle (HEV) configured with a flywheel buffer energy storage device and a free-piston Stirling convertor fulfills the emissions, fuel economy, range, and performance requirements that would make it acceptable to the consumer. It is noted that an assessment to determine which of the candidate technologies are suited for the HEV application has yet to be made. A proper assessment should take into account the fuel economy and range, along with the driveability and total emissions produced.

  10. Simulations of the Fuel Economy and Emissions of Hybrid Transit Buses over Planned Local Routes

    SciTech Connect

    Gao, Zhiming; LaClair, Tim J; Daw, C Stuart; Smith, David E; Franzese, Oscar

    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.

  11. Simulation of catalytic oxidation and selective catalytic NOx reduction in lean-exhaust hybrid vehicles

    SciTech Connect

    Gao, Zhiming; Daw, C Stuart; Chakravarthy, Veerathu K

    2012-01-01

    We utilize physically-based models for diesel exhaust catalytic oxidation and urea-based selective catalytic NOx reduction to study their impact on drive cycle performance of hypothetical light-duty diesel powered hybrid vehicles. The models have been implemented as highly flexible SIMULINK block modules that can be used to study multiple engine-aftertreatment system configurations. The parameters of the NOx reduction model have been adjusted to reflect the characteristics of Cu-zeolite catalysts, which are of widespread current interest. We demonstrate application of these models using the Powertrain System Analysis Toolkit (PSAT) software for vehicle simulations, along with a previously published methodology that accounts for emissions and temperature transients in the engine exhaust. Our results illustrate the potential impact of DOC and SCR interactions for lean hybrid electric and plug-in hybrid electric vehicles.

  12. Simulated comparisons of emissions and fuel efficiency of diesel and gasoline hybrid electric vehicles

    SciTech Connect

    Gao, Zhiming; Chakravarthy, Veerathu K; Daw, C Stuart

    2011-01-01

    This paper presents details and results of hybrid and plug-in hybrid electric passenger vehicle (HEV and PHEV) simulations that account for the interaction of thermal transients from drive cycle demands and engine start/stop events with aftertreatment devices and their associated fuel penalties. The simulations were conducted using the Powertrain Systems Analysis Toolkit (PSAT) software developed by Argonne National Laboratory (ANL) combined with aftertreatment component models developed at Oak Ridge National Lab (ORNL). A three-way catalyst model is used in simulations of gasoline powered vehicles while a lean NOx trap model in used to simulated NOx reduction in diesel powered vehicles. Both cases also use a previously reported methodology for simulating the temperature and species transients associated with the intermittent engine operation and typical drive cycle transients which are a significant departure from the usual experimental steady-state engine-map based approach adopted often in vehicle system simulations. Comparative simulations indicate a higher efficiency for diesel powered vehicles but the advantage is lowered by about a third (for both HEVs and PHEVs) when the fuel penalty associated with operating a lean NOx trap is included and may be reduced even more when fuel penalty associated with a particulate filter is included in diesel vehicle simulations. Through these preliminary studies, it is clearly demonstrated how accurate engine and exhaust systems models that can account for highly intermittent and transient engine operation in hybrid vehicles can be used to account for impact of emissions in comparative vehicle systems studies. Future plans with models for other devices such as particulate filters, diesel oxidation and selective reduction catalysts are also discussed.

  13. Plasma Simulation Using Gyrokinetic-Gyrofluid Hybrid Models

    SciTech Connect

    Scott Parker

    2009-04-09

    We are developing kinetic ion models for the simulation of extended MHD phenomena. The model they have developed uses full Lorentz force ions, and either drift-kinetic or gyro-kinetic electrons. Quasi-neutrality is assumed and the displacement current is neglected. They are also studying alpha particle driven Toroidal Alfven Eigenmodes (TAE) in the GEM gyrokinetic code [Chen 07]. The basic kinetic ion MHD model was recently reported in an invited talk given by Dan Barnes at the 2007 American Physical Society - Division of Plasma Physics (APS-DPP) and it has been published [Jones 04, Barnes 08]. The model uses an Ohm's law that includes the Hall term, pressure term and the electron inertia [Jones 04]. These results focused on the ion physics and assumed an isothermal electron closure. It is found in conventional gyrokinetic turbulence simulations that the timestep cannot be made much greater than the ion cyclotron period. However, the kinetic ion MHD model has the compressional mode, which further limits the timestep. They have developed an implicit scheme to avoid this timestep constraint. They have also added drift kinetic electrons. This model has been benchmarked linearly. Waves investigated where shear and compressional Alfven, whisterl, ion acoustic, and drift waves, including the kinetic damping rates. This work is ongoing and was first reported at the 2008 Sherwood Fusion Theory Conference [Chen 08] and they are working on a publication. They have also formulated an integrated gyrokinetic electron model, which is of interest for studying electron gradient instabilities and weak guide-field magnetic reconnection.

  14. A Hybrid Navier-Stokes/Particle Method for Simulating Rarefied Flow

    NASA Astrophysics Data System (ADS)

    Duttweiler, Craig R.; Baganoff, Donald; Feiereisen, William J.

    1997-11-01

    A particle method such as the Direct Simulation Monte Carlo method (DSMC) simulates a gas flow by statistically modeling the behavior of a large number of virtual particles and is necessary for the simulation of rarefied flows for which the Navier-Stokes (NS) equations become invalid due to failure of the constituent relations upon which they are based. Unfortunately, while more versatile than NS, DSMC is also computationally much more intensive. Even on a parallel computer, simulation times can become large, and so a less computationally intensive method is desirable. Luckily, in a high-enthalpy flow, most of the particles, and hence computational intensity, are contained in a relatively small, dense region of the domain in which NS is often viable. A logical approach, then, is to hybridize NS and DSMC, allowing the former to handle regions of higher density and the latter to handle regions of greater rarefaction. A robust hybrid method has been developed and successfully applied to several problems, including a blunt body in Mach 10 flow and a lid-driven cavity. In these and other cases, the hybrid method takes less time to produce solutions whose quality is equal to or greater than that of solutions produced by DSMC alone.

  15. Development of a software platform for a plug-in hybrid electric vehicle simulator

    NASA Astrophysics Data System (ADS)

    Karlis, Athanasios D.; Bibeau, Eric; Zanetel, Paul; Lye, Zelon

    2012-03-01

    Electricity use for transportation has had limited applications because of battery storage range issues, although many recent successful demonstrations of electric vehicles have been achieved. Renewable biofuels such as biodiesel and bioethanol also contribute only a small percentage of the overall energy mix for mobility. Recent advances in hybrid technologies have significantly increased vehicle efficiencies. More importantly, hybridization now allows a significant reduction in battery capacity requirements compared to pure electric vehicles, allowing electricity to be used in the overall energy mix in the transportation sector. This paper presents an effort made to develop a Plug-in Hybrid Electric Vehicle (PHEV) platform that can act as a comprehensive alternative energy vehicle simulator. Its goal is to help in solving the pressing needs of the transportation sector, both in terms of contributing data to aid policy decisions for reducing fossil fuel use, and to support research in this important area. The Simulator will allow analysing different vehicle configurations, and control strategies with regards to renewable and non-renewable fuel and electricity sources. The simulation platform models the fundamental aspects of PHEV components, that is, process control, heat transfer, chemical reactions, thermodynamics and fluid properties. The outcomes of the Simulator are: (i) determining the optimal combination of fuels and grid electricity use, (ii) performing greenhouse gas calculations based on emerging protocols being developed, and (iii) optimizing the efficient and proper use of renewable energy sources in a carbon constrained world.

  16. Multivariable Robust Control of a Simulated Hybrid Solid Oxide Fuel Cell Gas Turbine Plant

    SciTech Connect

    Tsai, Alex; Banta, Larry; Tucker, David; Gemmen, Randall

    2010-08-01

    This work presents a systematic approach to the multivariable robust control of a hybrid fuel cell gas turbine plant. The hybrid configuration under investigation built by the National Energy Technology Laboratory comprises a physical simulation of a 300kW fuel cell coupled to a 120kW auxiliary power unit single spool gas turbine. The public facility provides for the testing and simulation of different fuel cell models that in turn help identify the key difficulties encountered in the transient operation of such systems. An empirical model of the built facility comprising a simulated fuel cell cathode volume and balance of plant components is derived via frequency response data. Through the modulation of various airflow bypass valves within the hybrid configuration, Bode plots are used to derive key input/output interactions in transfer function format. A multivariate system is then built from individual transfer functions, creating a matrix that serves as the nominal plant in an H{sub {infinity}} robust control algorithm. The controller’s main objective is to track and maintain hybrid operational constraints in the fuel cell’s cathode airflow, and the turbo machinery states of temperature and speed, under transient disturbances. This algorithm is then tested on a Simulink/MatLab platform for various perturbations of load and fuel cell heat effluence. As a complementary tool to the aforementioned empirical plant, a nonlinear analytical model faithful to the existing process and instrumentation arrangement is evaluated and designed in the Simulink environment. This parallel task intends to serve as a building block to scalable hybrid configurations that might require a more detailed nonlinear representation for a wide variety of controller schemes and hardware implementations.

  17. RAD sequencing and genomic simulations resolve hybrid origins within North American Canis.

    PubMed

    Rutledge, L Y; Devillard, S; Boone, J Q; Hohenlohe, P A; White, B N

    2015-07-01

    Top predators are disappearing worldwide, significantly changing ecosystems that depend on top-down regulation. Conflict with humans remains the primary roadblock for large carnivore conservation, but for the eastern wolf (Canis lycaon), disagreement over its evolutionary origins presents a significant barrier to conservation in Canada and has impeded protection for grey wolves (Canis lupus) in the USA. Here, we use 127,235 single-nucleotide polymorphisms (SNPs) identified from restriction-site associated DNA sequencing (RAD-seq) of wolves and coyotes, in combination with genomic simulations, to test hypotheses of hybrid origins of Canis types in eastern North America. A principal components analysis revealed no evidence to support eastern wolves, or any other Canis type, as the product of grey wolf × western coyote hybridization. In contrast, simulations that included eastern wolves as a distinct taxon clarified the hybrid origins of Great Lakes-boreal wolves and eastern coyotes. Our results support the eastern wolf as a distinct genomic cluster in North America and help resolve hybrid origins of Great Lakes wolves and eastern coyotes. The data provide timely information that will shed new light on the debate over wolf conservation in eastern North America. PMID:26156129

  18. RAD sequencing and genomic simulations resolve hybrid origins within North American Canis

    PubMed Central

    Rutledge, L. Y.; Devillard, S.; Boone, J. Q.; Hohenlohe, P. A.; White, B. N.

    2015-01-01

    Top predators are disappearing worldwide, significantly changing ecosystems that depend on top-down regulation. Conflict with humans remains the primary roadblock for large carnivore conservation, but for the eastern wolf (Canis lycaon), disagreement over its evolutionary origins presents a significant barrier to conservation in Canada and has impeded protection for grey wolves (Canis lupus) in the USA. Here, we use 127 235 single-nucleotide polymorphisms (SNPs) identified from restriction-site associated DNA sequencing (RAD-seq) of wolves and coyotes, in combination with genomic simulations, to test hypotheses of hybrid origins of Canis types in eastern North America. A principal components analysis revealed no evidence to support eastern wolves, or any other Canis type, as the product of grey wolf × western coyote hybridization. In contrast, simulations that included eastern wolves as a distinct taxon clarified the hybrid origins of Great Lakes-boreal wolves and eastern coyotes. Our results support the eastern wolf as a distinct genomic cluster in North America and help resolve hybrid origins of Great Lakes wolves and eastern coyotes. The data provide timely information that will shed new light on the debate over wolf conservation in eastern North America. PMID:26156129

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

    PubMed Central

    Whitford, Paul C.; Sanbonmatsu, Karissa Y.

    2013-01-01

    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

  20. A hybrid simulation-optimization approach for solving the areal groundwater pollution source identification problems

    NASA Astrophysics Data System (ADS)

    Ayvaz, M. Tamer

    2016-07-01

    In this study, a new simulation-optimization approach is proposed for solving the areal groundwater pollution source identification problems which is an ill-posed inverse problem. In the simulation part of the proposed approach, groundwater flow and pollution transport processes are simulated by modeling the given aquifer system on MODFLOW and MT3DMS models. The developed simulation model is then integrated to a newly proposed hybrid optimization model where a binary genetic algorithm and a generalized reduced gradient method are mutually used. This is a novel approach and it is employed for the first time in the areal pollution source identification problems. The objective of the proposed hybrid optimization approach is to simultaneously identify the spatial distributions and input concentrations of the unknown areal groundwater pollution sources by using the limited number of pollution concentration time series at the monitoring well locations. The applicability of the proposed simulation-optimization approach is evaluated on a hypothetical aquifer model for different pollution source distributions. Furthermore, model performance is evaluated for measurement error conditions, different genetic algorithm parameter combinations, different numbers and locations of the monitoring wells, and different heterogeneous hydraulic conductivity fields. Identified results indicated that the proposed simulation-optimization approach may be an effective way to solve the areal groundwater pollution source identification problems.

  1. A zero-equation turbulence model for two-dimensional hybrid Hall thruster simulations

    SciTech Connect

    Cappelli, Mark A. Young, Christopher V.; Cha, Eunsun; Fernandez, Eduardo

    2015-11-15

    We present a model for electron transport across the magnetic field of a Hall thruster and integrate this model into 2-D hybrid particle-in-cell simulations. The model is based on a simple scaling of the turbulent electron energy dissipation rate and the assumption that this dissipation results in Ohmic heating. Implementing the model into 2-D hybrid simulations is straightforward and leverages the existing framework for solving the electron fluid equations. The model recovers the axial variation in the mobility seen in experiments, predicting the generation of a transport barrier which anchors the region of plasma acceleration. The predicted xenon neutral and ion velocities are found to be in good agreement with laser-induced fluorescence measurements.

  2. A zero-equation turbulence model for two-dimensional hybrid Hall thruster simulations

    NASA Astrophysics Data System (ADS)

    Cappelli, Mark A.; Young, Christopher V.; Cha, Eunsun; Fernandez, Eduardo

    2015-11-01

    We present a model for electron transport across the magnetic field of a Hall thruster and integrate this model into 2-D hybrid particle-in-cell simulations. The model is based on a simple scaling of the turbulent electron energy dissipation rate and the assumption that this dissipation results in Ohmic heating. Implementing the model into 2-D hybrid simulations is straightforward and leverages the existing framework for solving the electron fluid equations. The model recovers the axial variation in the mobility seen in experiments, predicting the generation of a transport barrier which anchors the region of plasma acceleration. The predicted xenon neutral and ion velocities are found to be in good agreement with laser-induced fluorescence measurements.

  3. 3-D Hybrid Simulation of Interaction Between Solar Wind Discontinuity and Magnetosphere

    NASA Astrophysics Data System (ADS)

    Pang, Y.; Lin, Y.; Deng, X.; Wang, X.

    2008-12-01

    Previous simulations and observations indicate that interaction of interplanetary directional tangential discontinuities (TD), across which only the direction of magnetic field changes,with the bow shock may initiate magnetic reconnection as the TD is transmitted into the magnetosheath. We employ a 3-D electromagnetic, hybrid simulation to study such interaction between the TD and the bow shock-magnetosheath-magnetopause system, while the hybrid model treats the ions kinetically via particle-in-cell methods and the electrons as a massless fluid. We present results corresponding to different orientations of the initial IMF, TDs with various thicknesses ranging from 10 to 30 ion skin depths, and polarizations of magnetic field and senses of field rotation across the TD. Our results indicate that the reconnection rate and structure can be influenced by the width and the structure of the TD. The kinetic structure and evolution of FTEs produced by the magnetosheath reconnection, as they propagate to the magnetopause, will be studied.

  4. Simulation and Technology of Hybrid Welding of Thick Steel Parts with High Power Fiber Laser

    NASA Astrophysics Data System (ADS)

    Turichin, Gleb; Valdaytseva, Ekaterina; Tzibulsky, Igor; Lopota, Alexander; Velichko, Olga

    The article devoted to steady state and dynamic simulation of melt pool behavior during hybrid laser-arc welding of pipes and shipbuilding sections. The quasi-stationary process-model was used to determine an appropriate welding mode. The dynamical model of laser welding was used for investigation of keyhole depth and width oscillations. The experiments of pipe steel and stainless steel hybrid laser-MAG welding have been made with 15-kW fiber laser in wide range of welding mode parameters. Comparison of experimentally measured and simulated behavior of penetration depth as well as their oscillation spectra approved the self-oscillation nature of melt pool behavior. The welding mode influence of melt pool stability has also been observed. The technological peculiarities, which allow provide high quality weld seam, has been discussed also.

  5. Numerical simulations of turbulent thermal, bubble and hybrid plumes

    NASA Astrophysics Data System (ADS)

    Fabregat, Alexandre; Dewar, William K.; Özgökmen, Tamay M.; Poje, Andrew C.; Wienders, Nicolas

    2015-06-01

    To understand the near-field dynamics of blowout plumes such as the one produced by the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, the effects of gas bubbles on turbulent mixing and entrainment are studied via turbulence resolving simulations. We compare the evolution of three plumes where extremely large buoyancy anomalies are produced either thermally (single phase), solely by an imposed gas phase volume fraction, or by a combination of both buoyancy forcings. The plumes, with identical volume, momentum and buoyancy fluxes at the inlet, are released into an environment stratified with a constant temperature gradient. To clarify the first-order effects of dynamically active, dispersed bubbles, we employ a simple model which neglects the momentum of the gas phase while retaining bubble induced buoyancy in the seawater momentum equation. The gas phase is then distinguished by a single, measurable parameter, the slip velocity relative to that of the liquid phase. We find that bubbles, parameterized simply by a constant slip velocity, without any explicit assumptions of direct bubble induced turbulent production, significantly increase turbulent mixing in the plume in agreement with previous experimental results. Examination of mean momenta and turbulent kinetic energy budgets shows that the increased turbulence is due to direct modification of the mean profiles of both the momentum and the active scalar fields by the slipping gas phase. The narrowing of the active scalar field in the two-phase flow results in larger direct buoyancy production of turbulent energy at all vertical levels. The turbulence production is, however, primarily mechanical. At modest values of z/D, where the slip velocity is only a small fraction of the liquid phase velocity, slip stretches the mean vertical velocity field producing larger radial gradients and increased conversion of mean to turbulent energy. This first order effect, acting on the mean vertical velocity component

  6. Verification of electromagnetic fluid-kinetic hybrid electron model in global gyrokinetic particle simulation

    SciTech Connect

    Holod, I.; Lin, Z.

    2013-03-15

    The fluid-kinetic hybrid electron model is verified in global gyrokinetic particle simulation of linear electromagnetic drift-Alfvenic instabilities in tokamak. In particular, we have recovered the {beta}-stabilization of the ion temperature gradient mode, transition to collisionless trapped electron mode, and the onset of kinetic ballooning mode as {beta}{sub e} (ratio of electron kinetic pressure to magnetic pressure) increases.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. A robust method for handling low density regions in hybrid simulations for collisionless plasmas

    SciTech Connect

    Amano, Takanobu Higashimori, Katsuaki; Shirakawa, Keisuke

    2014-10-15

    A robust method to handle vacuum and near vacuum regions in hybrid simulations for space and astrophysical plasmas is presented. The conventional hybrid simulation model dealing with kinetic ions and a massless charge-neutralizing electron fluid is known to be susceptible to numerical instability due to divergence of the whistler-mode wave dispersion, as well as division-by-density operation in regions of low density. Consequently, a pure vacuum region is not allowed to exist in the simulation domain unless some ad hoc technique is used. To resolve this difficulty, an alternative way to introduce finite electron inertia effect is proposed. Contrary to the conventional method, the proposed one introduces a correction to the electric field rather than the magnetic field. It is shown that the generalized Ohm's law correctly reduces to Laplace's equation in a vacuum which therefore does not involve any numerical problems. In addition, a variable ion-to-electron mass ratio is introduced to reduce the phase velocity of high frequency whistler waves at low density regions so that the stability condition is always satisfied. It is demonstrated that the proposed model is able to handle near vacuum regions generated as a result of nonlinear self-consistent development of the system, as well as pure vacuum regions set up at the initial condition, without losing the advantages of the standard hybrid code.

  9. Coalescence phenomena in 1D silver nanostructures

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Wing, C.; Pérez-Alvarez, M.; Mondragón-Galicia, G.; Arenas-Alatorre, J.; Gutiérrez-Wing, M. T.; Henk, M. C.; Negulescu, I. I.; Rusch, K. A.

    2009-07-01

    Different coalescence processes on 1D silver nanostructures synthesized by a PVP assisted reaction in ethylene glycol at 160 °C were studied experimentally and theoretically. Analysis by TEM and HRTEM shows different defects found on the body of these materials, suggesting that they were induced by previous coalescence processes in the synthesis stage. TEM observations showed that irradiation with the electron beam eliminates the boundaries formed near the edges of the structures, suggesting that this process can be carried out by the application of other means of energy (i.e. thermal). These results were also confirmed by theoretical calculations by Monte Carlo simulations using a Sutton-Chen potential. A theoretical study by molecular dynamics simulation of the different coalescence processes on 1D silver nanostructures is presented, showing a surface energy driven sequence followed to form the final coalesced structure. Calculations were made at 1000-1300 K, which is near the melting temperature of silver (1234 K). Based on these results, it is proposed that 1D nanostructures can grow through a secondary mechanism based on coalescence, without losing their dimensionality.

  10. Io's Interaction with the Plasma Torus: Multi-Species Hybrid Simulations

    NASA Astrophysics Data System (ADS)

    Šebek, Ondřej; Trávníček, Pavel; Walker, Raymond; Hellinger, Petr

    2016-04-01

    We present analysis of global 3-dimensional multi-species hybrid simulations of Io's interaction with Jovian magnetospheric plasma. In the multi-species simulations we assume five species, plasma torus is composed of O+, S+ and S++ ions and ions of SO+, SO2+ are created around Io by ionization of its neutral atmosphere. We consider several ionization processes, namely, charge exchange ionization and photoionization/electron impact ionization. We compare our results to data acquired in situ by the Galileo spacecraft. Our results are in a good qualitative agreement with the in situ magnetic field measurements made during Galileo's flybys around Io.

  11. Hybrid simulations of Z-Pinches in support of wire array implosion experiments at NTF.

    SciTech Connect

    Sotnikov, Vladimir Isaakovich; Oliver, Bryan Velten; Ivanov, Vladimir V.; LePell, Paul David; Fedin, Dmitry; Kantsyrev, Victor Leonidovich; Coverdale, Christine Anne; Travnicek, P.; Deeney, Christopher; Hellinger, P.; Jones, B.; Leboeuf, J. N.; Cowan, Thomas E.; Safronova, Alla S.

    2005-07-01

    Three-dimensional hybrid simulation of a plasma current-carrying column reveal two different regimes of sausage and kink instability development. In the first regime, with small Hall parameter, development of instabilities leads to the appearance of large-scale axial perturbations and eventually to bending of the plasma column. In the second regime, with a four-times-larger Hall parameter, small-scale perturbations dominate and no bending of the plasma column is observed. Simulation results are compared with laser probing experimental data obtained during wire array implosions on the Zebra pulse power generator at the Nevada Terawatt Facility.

  12. Global hybrid simulation of unmagnetized planets - Comparison of Venus and Mars

    NASA Technical Reports Server (NTRS)

    Brecht, Stephen H.; Ferrante, John R.

    1991-01-01

    Results from three-dimensional hybrid particle simulations of the solar wind interaction with the planets Mars and Venus are presented. The simulations produce shocks and magnetic barriers which are asymmetric. These results are qualitatively in agreement with data. In the absence of an ionosphere the subsolar shock standoff distance was found to agree with the observations if the Hall current is limited. It was also found that the solar wind interaction with Mars and Venus was substantially different. The interaction with Venus can be generally viewed as a magnetized interaction. The Mars interaction is very kinetic in nature and appears not to have a shock in the classic sense.

  13. Architectural and operational considerations emerging from hybrid RF-optical network loading simulations

    NASA Astrophysics Data System (ADS)

    Chen, Yijiang; Abraham, Douglas S.; Heckman, David P.; Kwok, Andrew; MacNeal, Bruce E.; Tran, Kristy; Wu, Janet P.

    2016-03-01

    A technology demonstration of free space optical communication at interplanetary distances is planned via one or more future NASA deep-space missions. Such demonstrations will "pave the way" for operational use of optical communications on future robotic/potential Human missions. Hence, the Deep Space Network architecture will need to evolve. Preliminary attempts to model the anticipated future mission set and simulate how well it loads onto assumed architectures with combinations of RF and optical apertures have been evaluated. This paper discusses the results of preliminary loading simulations for hybrid RF-optical network architectures and highlights key mission and ground infrastructure considerations that emerge.

  14. Turbine Powered Simulator Calibration and Testing for Hybrid Wing Body Powered Airframe Integration

    NASA Technical Reports Server (NTRS)

    Shea, Patrick R.; Flamm, Jeffrey D.; Long, Kurtis R.; James, Kevin D.; Tompkins, Daniel M.; Beyar, Michael D.

    2016-01-01

    Propulsion airframe integration testing on a 5.75% scale hybrid wing body model us- ing turbine powered simulators was completed at the National Full-Scale Aerodynamics Complex 40- by 80-foot test section. Four rear control surface con gurations including a no control surface de ection con guration were tested with the turbine powered simulator units to investigate how the jet exhaust in uenced the control surface performance as re- lated to the resultant forces and moments on the model. Compared to ow-through nacelle testing on the same hybrid wing body model, the control surface e ectiveness was found to increase with the turbine powered simulator units operating. This was true for pitching moment, lift, and drag although pitching moment was the parameter of greatest interest for this project. With the turbine powered simulator units operating, the model pitching moment was seen to increase when compared to the ow-through nacelle con guration indicating that the center elevon and vertical tail control authority increased with the jet exhaust from the turbine powered simulator units.

  15. Hybrid two-chain simulation and integral equation theory : application to polyethylene liquids.

    SciTech Connect

    Huimin Li, David T. Wu; Curro, John G.; McCoy, John Dwane

    2006-02-01

    We present results from a hybrid simulation and integral equation approach to the calculation of polymer melt properties. The simulation consists of explicit Monte Carlo (MC) sampling of two polymer molecules, where the effect of the surrounding chains is accounted for by an HNC solvation potential. The solvation potential is determined from the Polymer Reference Interaction Site Model (PRISM) as a functional of the pair correlation function from simulation. This hybrid two-chain MC-PRISM approach was carried out on liquids of polyethylene chains of 24 and 66 CH{sub 2} units. The results are compared with MD simulation and self-consistent PRISM-PY theory under the same conditions, revealing that the two-chain calculation is close to MD, and able to overcome the defects of the PRISM-PY closure and predict more accurate structures of the liquid at both short and long range. The direct correlation function, for instance, has a tail at longer range which is consistent with MD simulation and avoids the short-range assumptions in PRISM-PY theory. As a result, the self-consistent two-chain MC-PRISM calculation predicts an isothermal compressibility closer to the MD results.

  16. HYBRID AND HALL-MHD SIMULATIONS OF COLLISIONLESS RECONNECTION: EFFECTS OF PLASMA PRESSURE TENSOR

    SciTech Connect

    L. YIN; D. WINSKE; ET AL

    2001-05-01

    In this study we performed two-dimensional hybrid (particle ions, massless fluid electrons) and Hall-MHD simulations of collisionless reconnection in a thin current sheet. Both calculations include the full electron pressure tensor (instead of a localized resistivity) in the generalized Ohm's law to initiate reconnection, and in both an initial perturbation to the Harris equilibrium is applied. First, electron dynamics from the two calculations are compared, and we find overall agreement between the two calculations in both the reconnection rate and the global configuration. To address the issue of how kinetic treatment for the ions affects the reconnection dynamics, we compared the fluid-ion dynamics from the Hall-MHD calculation to the particle-ion dynamics obtained from the hybrid simulation. The comparison demonstrates that off-diagonal elements of the ion pressure tensor are important in correctly modeling the ion out-of-plane momentum transport from the X point. It is that these effects can be modeled efficiently using a particle Hall-MHD simulation method in which particle ions used in a predictor/corrector to implement the ion gyro-radius corrections. We also investigate the micro- macro-scale coupling in the magnetotail dynamics by using a new integrated approach in which particle Hall-MHD calculations are embedded inside a MHD simulation. Initial results of the simulation concerning current sheet thinning and reconnection dynamics are discussed.

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

    ERIC Educational Resources Information Center

    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…

  18. A Hybrid URANS/LES Approach Used for Simulations of Turbulent Flows

    NASA Astrophysics Data System (ADS)

    Fraňa, Karel; Stiller, Jörg

    A hybrid model based on the unsteady Reynolds averaged Navier-Stokes approach represented by the one-equation Spalart-Allmaras model and the Large Eddy Simulation called Detached Eddy Simulation (DES) was applied for turbulent flow simulations. This turbulent approach was implemented into the flow solver based on the Finite-Element Method with pressure stabilized and streamlines upwind Petrov-Galerkin stabilization techniques. The effectiveness and robustness of this updated solver is successfully demonstrated at benchmark calculation represented by an unsteady turbulent flow past a cylinder at Reynolds number 3900. Results such as velocity fields and the flow periodicity, Reynolds stress tensor and eddy viscosity and pressure coefficient distributions are discussed and relatively good agreement was found to direct numerical simulations and experiments.

  19. Hybrid Reactor Simulation and 3-D Information Display of BWR Out-of-Phase Oscillation

    SciTech Connect

    Edwards, Robert; Huang, Zhengyu

    2001-06-17

    The real-time hybrid reactor simulation (HRS) capability of the Penn State TRIGA reactor has been expanded for boiling water reactor (BWR) out-of-phase behavior. During BWR out-of-phase oscillation half of the core can significantly oscillate out of phase with the other half, while the average power reported by the neutronic instrumentation may show a much lower amplitude for the oscillations. A description of the new HRS is given; three computers are employed to handle all the computations required, including real-time data processing and graph generation. BWR out-of-phase oscillation was successfully simulated. By adjusting the reactivity feedback gains from boiling channels to the TRIGA reactor and to the first harmonic mode power simulation, limit cycle can be generated with both reactor power and the simulated first harmonic power. A 3-D display of spatial power distributions of fundamental mode, first harmonic, and total powers over the reactor cross section is shown.

  20. A Hybrid Model for the Computationally-Efficient Simulation of the Cerebellar Granular Layer.

    PubMed

    Cattani, Anna; Solinas, Sergio; Canuto, Claudio

    2016-01-01

    The aim of the present paper is to efficiently describe the membrane potential dynamics of neural populations formed by species having a high density difference in specific brain areas. We propose a hybrid model whose main ingredients are a conductance-based model (ODE system) and its continuous counterpart (PDE system) obtained through a limit process in which the number of neurons confined in a bounded region of the brain tissue is sent to infinity. Specifically, in the discrete model, each cell is described by a set of time-dependent variables, whereas in the continuum model, cells are grouped into populations that are described by a set of continuous variables. Communications between populations, which translate into interactions among the discrete and the continuous models, are the essence of the hybrid model we present here. The cerebellum and cerebellum-like structures show in their granular layer a large difference in the relative density of neuronal species making them a natural testing ground for our hybrid model. By reconstructing the ensemble activity of the cerebellar granular layer network and by comparing our results to a more realistic computational network, we demonstrate that our description of the network activity, even though it is not biophysically detailed, is still capable of reproducing salient features of neural network dynamics. Our modeling approach yields a significant computational cost reduction by increasing the simulation speed at least 270 times. The hybrid model reproduces interesting dynamics such as local microcircuit synchronization, traveling waves, center-surround, and time-windowing. PMID:27148027

  1. Coalescent Simulations Reveal Hybridization and Incomplete Lineage Sorting in Mediterranean Linaria

    PubMed Central

    Blanco-Pastor, José Luis; Vargas, Pablo; Pfeil, Bernard E.

    2012-01-01

    We examined the phylogenetic history of Linaria with special emphasis on the Mediterranean sect. Supinae (44 species). We revealed extensive highly supported incongruence among two nuclear (ITS, AGT1) and two plastid regions (rpl32-trnLUAG, trnS-trnG). Coalescent simulations, a hybrid detection test and species tree inference in *BEAST revealed that incomplete lineage sorting and hybridization may both be responsible for the incongruent pattern observed. Additionally, we present a multilabelled *BEAST species tree as an alternative approach that allows the possibility of observing multiple placements in the species tree for the same taxa. That permitted the incorporation of processes such as hybridization within the tree while not violating the assumptions of the *BEAST model. This methodology is presented as a functional tool to disclose the evolutionary history of species complexes that have experienced both hybridization and incomplete lineage sorting. The drastic climatic events that have occurred in the Mediterranean since the late Miocene, including the Quaternary-type climatic oscillations, may have made both processes highly recurrent in the Mediterranean flora. PMID:22768061

  2. Proposal of tunneling- and diffusion-current hybrid MOSFET: A device simulation study

    NASA Astrophysics Data System (ADS)

    Furukawa, Kiichi; Teramoto, Akinobu; Kuroda, Rihito; Suwa, Tomoyuki; Hashimoto, Keiichi; Kojiri, Takashi; Sugawa, Shigetoshi

    2016-04-01

    Transistors with low-power operation and sufficient signal processing speed have been widely required especially for mobile applications. To meet these requirements, we propose a novel tunneling- and diffusion-current hybrid MOSFETs which utilize both a small S-factor of tunneling-current and a high current drivability of diffusion-current. On the basis of the device concept and the working principle that we propose, device structures and parameters of the hybrid MOSFET were examined in detail with device simulation. We investigated the optimum structure of the tunneling and diffusion parts, and the effects of various structural parameters. In particular, we found that the threshold voltage adjustment of each current and the suppression of leakage current were the most important to maximize the characteristics of the hybrid MOSFET. From the result of structural parameter optimization, a minimum S-factor of 20 mV/decade and a high current drivability of 500 µA/µm were obtained simultaneously. In addition, a process flow idea to fabricate three-dimensional structure hybrid MOSFETs with tunneling-current side channels and diffusion-current top channel is presented.

  3. A Hybrid Model for the Computationally-Efficient Simulation of the Cerebellar Granular Layer

    PubMed Central

    Cattani, Anna; Solinas, Sergio; Canuto, Claudio

    2016-01-01

    The aim of the present paper is to efficiently describe the membrane potential dynamics of neural populations formed by species having a high density difference in specific brain areas. We propose a hybrid model whose main ingredients are a conductance-based model (ODE system) and its continuous counterpart (PDE system) obtained through a limit process in which the number of neurons confined in a bounded region of the brain tissue is sent to infinity. Specifically, in the discrete model, each cell is described by a set of time-dependent variables, whereas in the continuum model, cells are grouped into populations that are described by a set of continuous variables. Communications between populations, which translate into interactions among the discrete and the continuous models, are the essence of the hybrid model we present here. The cerebellum and cerebellum-like structures show in their granular layer a large difference in the relative density of neuronal species making them a natural testing ground for our hybrid model. By reconstructing the ensemble activity of the cerebellar granular layer network and by comparing our results to a more realistic computational network, we demonstrate that our description of the network activity, even though it is not biophysically detailed, is still capable of reproducing salient features of neural network dynamics. Our modeling approach yields a significant computational cost reduction by increasing the simulation speed at least 270 times. The hybrid model reproduces interesting dynamics such as local microcircuit synchronization, traveling waves, center-surround, and time-windowing. PMID:27148027

  4. Performance of hybrid programming models for multiscale cardiac simulations: preparing for petascale computation.

    PubMed

    Pope, Bernard J; Fitch, Blake G; Pitman, Michael C; Rice, John J; Reumann, Matthias

    2011-10-01

    Future multiscale and multiphysics models that support research into human disease, translational medical science, and treatment can utilize the power of high-performance computing (HPC) systems. We anticipate that computationally efficient multiscale models will require the use of sophisticated hybrid programming models, mixing distributed message-passing processes [e.g., the message-passing interface (MPI)] with multithreading (e.g., OpenMP, Pthreads). The objective of this study is to compare the performance of such hybrid programming models when applied to the simulation of a realistic physiological multiscale model of the heart. Our results show that the hybrid models perform favorably when compared to an implementation using only the MPI and, furthermore, that OpenMP in combination with the MPI provides a satisfactory compromise between performance and code complexity. Having the ability to use threads within MPI processes enables the sophisticated use of all processor cores for both computation and communication phases. Considering that HPC systems in 2012 will have two orders of magnitude more cores than what was used in this study, we believe that faster than real-time multiscale cardiac simulations can be achieved on these systems. PMID:21768044

  5. Investigations of Subsonic Compressible Boundary Layer Flows using Hybrid Large Eddy Simulations

    NASA Astrophysics Data System (ADS)

    Taylor, Sara Jo

    The objective of this thesis is to investigate the spatially developing turbulent compressible boundary layer on a flat plate using the Spalart-Allmaras Detached Eddy Simulation (SA-DES) model [22] and the Nichols-Nelson hybrid Reynolds-Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) model [13] which have been implemented into the Wind-US 3.0 computational fluid dynamics code [30]; both of the hybrid approaches involve RANS modeling in the near-wall region and LES treatment in the outer region. Generation of unsteady turbulent inflow data is achieved via the prescribed energy spectrum method. The studies illustrated dependence on Reynolds number based on momentum thickness, Reθ, ranging from 3018 to 19430, and dependence on Mach number, M = 0.5 and M = 0.9. The SA-DES model predicted mean flow profiles to a satisfactory degree, and the Nichols-Nelson hybrid RANS/LES model adequately predicted density field fluctuations; the aero-thermal effects captured by the Nichols-Nelson model can be useful for near-field aero optics applications.

  6. Parameter estimation for chaotic systems using a hybrid adaptive cuckoo search with simulated annealing algorithm.

    PubMed

    Sheng, Zheng; Wang, Jun; Zhou, Shudao; Zhou, Bihua

    2014-03-01

    This paper introduces a novel hybrid optimization algorithm to establish the parameters of chaotic systems. In order to deal with the weaknesses of the traditional cuckoo search algorithm, the proposed adaptive cuckoo search with simulated annealing algorithm is presented, which incorporates the adaptive parameters adjusting operation and the simulated annealing operation in the cuckoo search algorithm. Normally, the parameters of the cuckoo search algorithm are kept constant that may result in decreasing the efficiency of the algorithm. For the purpose of balancing and enhancing the accuracy and convergence rate of the cuckoo search algorithm, the adaptive operation is presented to tune the parameters properly. Besides, the local search capability of cuckoo search algorithm is relatively weak that may decrease the quality of optimization. So the simulated annealing operation is merged into the cuckoo search algorithm to enhance the local search ability and improve the accuracy and reliability of the results. The functionality of the proposed hybrid algorithm is investigated through the Lorenz chaotic system under the noiseless and noise condition, respectively. The numerical results demonstrate that the method can estimate parameters efficiently and accurately in the noiseless and noise condition. Finally, the results are compared with the traditional cuckoo search algorithm, genetic algorithm, and particle swarm optimization algorithm. Simulation results demonstrate the effectiveness and superior performance of the proposed algorithm. PMID:24697395

  7. Parameter estimation for chaotic systems using a hybrid adaptive cuckoo search with simulated annealing algorithm

    SciTech Connect

    Sheng, Zheng; Wang, Jun; Zhou, Bihua; Zhou, Shudao

    2014-03-15

    This paper introduces a novel hybrid optimization algorithm to establish the parameters of chaotic systems. In order to deal with the weaknesses of the traditional cuckoo search algorithm, the proposed adaptive cuckoo search with simulated annealing algorithm is presented, which incorporates the adaptive parameters adjusting operation and the simulated annealing operation in the cuckoo search algorithm. Normally, the parameters of the cuckoo search algorithm are kept constant that may result in decreasing the efficiency of the algorithm. For the purpose of balancing and enhancing the accuracy and convergence rate of the cuckoo search algorithm, the adaptive operation is presented to tune the parameters properly. Besides, the local search capability of cuckoo search algorithm is relatively weak that may decrease the quality of optimization. So the simulated annealing operation is merged into the cuckoo search algorithm to enhance the local search ability and improve the accuracy and reliability of the results. The functionality of the proposed hybrid algorithm is investigated through the Lorenz chaotic system under the noiseless and noise condition, respectively. The numerical results demonstrate that the method can estimate parameters efficiently and accurately in the noiseless and noise condition. Finally, the results are compared with the traditional cuckoo search algorithm, genetic algorithm, and particle swarm optimization algorithm. Simulation results demonstrate the effectiveness and superior performance of the proposed algorithm.

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

    SciTech Connect

    Shen, Wei; Sheng, Zheng-Mao; Fu, G. Y.; Tobias, Benjamin; Zeeland, Michael Van; Wang, Feng

    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.

  9. Jovian Plasma Torus Interaction with Europa: 3D Hybrid Kinetic Simulation. First results

    NASA Technical Reports Server (NTRS)

    Lipatov, A. S.; Cooper, J. F.; Paterson, W. R.; Sittler, E. C.; Hartle, R. E.; Simpson, D. G.

    2010-01-01

    The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa-moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo orbiter mission, and for planning flyby and orbital measurements, (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy etal.,2007;Shematovichetal.,2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyro radius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream background ions).Non-thermal distributions of upstream plasma will be addressed in future work. Photoionization,electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider two models for background plasma:(a) with O(++) ions; (b) with O(++) and S(++) ions. The majority of O2 atmosphere is thermal with an extended cold population (Cassidyetal.,2007). A few first simulations already include an induced magnetic dipole; however, several important effects of induced magnetic fields arising from oceanic shell conductivity will be addressed in later work.

  10. A hybrid method for efficient and accurate simulations of diffusion compartment imaging signals

    NASA Astrophysics Data System (ADS)

    Rensonnet, Gaëtan; Jacobs, Damien; Macq, Benoît; Taquet, Maxime

    2015-12-01

    Diffusion-weighted imaging is sensitive to the movement of water molecules through the tissue microstructure and can therefore be used to gain insight into the tissue cellular architecture. While the diffusion signal arising from simple geometrical microstructure is known analytically, it remains unclear what diffusion signal arises from complex microstructural configurations. Such knowledge is important to design optimal acquisition sequences, to understand the limitations of diffusion-weighted imaging and to validate novel models of the brain microstructure. We present a novel framework for the efficient simulation of high-quality DW-MRI signals based on the hybrid combination of exact analytic expressions in simple geometric compartments such as cylinders and spheres and Monte Carlo simulations in more complex geometries. We validate our approach on synthetic arrangements of parallel cylinders representing the geometry of white matter fascicles, by comparing it to complete, all-out Monte Carlo simulations commonly used in the literature. For typical configurations, equal levels of accuracy are obtained with our hybrid method in less than one fifth of the computational time required for Monte Carlo simulations.

  11. Parameter estimation for chaotic systems using a hybrid adaptive cuckoo search with simulated annealing algorithm

    NASA Astrophysics Data System (ADS)

    Sheng, Zheng; Wang, Jun; Zhou, Shudao; Zhou, Bihua

    2014-03-01

    This paper introduces a novel hybrid optimization algorithm to establish the parameters of chaotic systems. In order to deal with the weaknesses of the traditional cuckoo search algorithm, the proposed adaptive cuckoo search with simulated annealing algorithm is presented, which incorporates the adaptive parameters adjusting operation and the simulated annealing operation in the cuckoo search algorithm. Normally, the parameters of the cuckoo search algorithm are kept constant that may result in decreasing the efficiency of the algorithm. For the purpose of balancing and enhancing the accuracy and convergence rate of the cuckoo search algorithm, the adaptive operation is presented to tune the parameters properly. Besides, the local search capability of cuckoo search algorithm is relatively weak that may decrease the quality of optimization. So the simulated annealing operation is merged into the cuckoo search algorithm to enhance the local search ability and improve the accuracy and reliability of the results. The functionality of the proposed hybrid algorithm is investigated through the Lorenz chaotic system under the noiseless and noise condition, respectively. The numerical results demonstrate that the method can estimate parameters efficiently and accurately in the noiseless and noise condition. Finally, the results are compared with the traditional cuckoo search algorithm, genetic algorithm, and particle swarm optimization algorithm. Simulation results demonstrate the effectiveness and superior performance of the proposed algorithm.

  12. Electrostatics of DNA nucleotide-carbon nanotube hybrids evaluated from QM:MM simulations

    NASA Astrophysics Data System (ADS)

    Chehel Amirani, Morteza; Tang, Tian

    2015-11-01

    Biomolecule-functionalized carbon nanotubes (CNTs) have been studied vastly in recent years due to their potential applications for instance in cancer detection, purification and separation of CNTs, and nanoelectronics. Studying the electrostatic potential generated by a biomolecule-CNT hybrid is important in predicting its interactions with the surrounding environment such as charged particles and surfaces. In this paper, we performed atomistic simulations using a QM:MM approach to evaluate the electrostatic potential and charge transfer for a hybrid structure formed by a DNA nucleotide and a CNT in solution. Four types of DNA nucleotides and two CNTs with chiralities of (4,4) and (7,0) were considered. The types of nucleotides and CNTs were both found to play important roles in the electrostatic potential and charge transfer of the hybrid. At the same distance from the CNT axis, the electrostatic potential for the nucleotide-(4,4) CNT hybrids was found to be stronger compared with that for the nucleotide-(7,0) CNT hybrids. Higher electric charge was also shown to be transferred from the DNA nucleotides to the (7,0) CNT compared with the (4,4) CNT. These results correlate with the previous finding that the nucleotides bound more tightly to the (7,0) CNT compared with the (4,4) CNT.Biomolecule-functionalized carbon nanotubes (CNTs) have been studied vastly in recent years due to their potential applications for instance in cancer detection, purification and separation of CNTs, and nanoelectronics. Studying the electrostatic potential generated by a biomolecule-CNT hybrid is important in predicting its interactions with the surrounding environment such as charged particles and surfaces. In this paper, we performed atomistic simulations using a QM:MM approach to evaluate the electrostatic potential and charge transfer for a hybrid structure formed by a DNA nucleotide and a CNT in solution. Four types of DNA nucleotides and two CNTs with chiralities of (4,4) and (7

  13. Improving Efficiency in SMD Simulations Through a Hybrid Differential Relaxation Algorithm.

    PubMed

    Ramírez, Claudia L; Zeida, Ari; Jara, Gabriel E; Roitberg, Adrián E; Martí, Marcelo A

    2014-10-14

    The fundamental object for studying a (bio)chemical reaction obtained from simulations is the free energy profile, which can be directly related to experimentally determined properties. Although quite accurate hybrid quantum (DFT based)-classical methods are available, achieving statistically accurate and well converged results at a moderate computational cost is still an open challenge. Here, we present and thoroughly test a hybrid differential relaxation algorithm (HyDRA), which allows faster equilibration of the classical environment during the nonequilibrium steering of a (bio)chemical reaction. We show and discuss why (in the context of Jarzynski's Relationship) this method allows obtaining accurate free energy profiles with smaller number of independent trajectories and/or faster pulling speeds, thus reducing the overall computational cost. Moreover, due to the availability and straightforward implementation of the method, we expect that it will foster theoretical studies of key enzymatic processes. PMID:26588154

  14. Simulated Annealing Based Hybrid Forecast for Improving Daily Municipal Solid Waste Generation Prediction

    PubMed Central

    Song, Jingwei; He, Jiaying; Zhu, Menghua; Tan, Debao; Zhang, Yu; Ye, Song; Shen, Dingtao; Zou, Pengfei

    2014-01-01

    A simulated annealing (SA) based variable weighted forecast model is proposed to combine and weigh local chaotic model, artificial neural network (ANN), and partial least square support vector machine (PLS-SVM) to build a more accurate forecast model. The hybrid model was built and multistep ahead prediction ability was tested based on daily MSW generation data from Seattle, Washington, the United States. The hybrid forecast model was proved to produce more accurate and reliable results and to degrade less in longer predictions than three individual models. The average one-week step ahead prediction has been raised from 11.21% (chaotic model), 12.93% (ANN), and 12.94% (PLS-SVM) to 9.38%. Five-week average has been raised from 13.02% (chaotic model), 15.69% (ANN), and 15.92% (PLS-SVM) to 11.27%. PMID:25301508

  15. Simulation of electromagnetic scattering by random discrete particles using a hybrid FE-BI-CBFM technique

    NASA Astrophysics Data System (ADS)

    Cui, Z.-W.; Han, Y.-P.; Li, C.-Y.

    2012-05-01

    A hybrid finite element-boundary integral-characteristic basis function method (FE-BI-CBFM) is proposed for an efficient simulation of electromagnetic scattering by random discrete particles. Specifically, the finite element method (FEM) is used to obtain the solution of the vector wave equation inside each particle and the boundary integral equation (BIE) using Green's functions is applied on the surfaces of all the particles as a global boundary condition. The coupling system of equations is solved by employing the characteristic basis function method (CBFM) based on the use of macro-basis functions constructed according to the Foldy-Lax multiple scattering equations. Due to the flexibility of FEM, the proposed hybrid technique can easily deal with the problems of multiple scattering by randomly distributed inhomogeneous particles that are often beyond the scope of traditional numerical methods. Some numerical examples are presented to demonstrate the validity and capability of the proposed method.

  16. Hybrid-PIC Algorithms for Simulation of Large-Scale Plasma Jet Accelerators

    NASA Astrophysics Data System (ADS)

    Thoma, Carsten; Welch, Dale

    2009-11-01

    Merging coaxial plasma jets are envisioned for use in magneto-inertial fusion schemes as the source of an imploding plasma liner. An experimental program at HyperV is considering the generation of large plasma jets (length scales on the order of centimeters) at high densities (10^16-10^17 cm-3) in long coaxial accelerators. We describe the Hybrid particle-in-cell (PIC) methods implemented in the code LSP for this parameter regime and present simulation results of the HyperV accelerator. A radiation transport algorithm has also been implemented into LSP so that the effect of radiation cooling on the jet mach number can be included self-consistently into the Hybrid PIC formalism.

  17. Laboratory simulation of ion acceleration in the presence of lower hybrid waves

    NASA Astrophysics Data System (ADS)

    McWilliams, R.; Koslover, R.; Boehmer, H.; Rynn, N.

    Ion acceleration perpendicular to the geomagnetic field has been observed by satellites and rockets in the suprauroral region. Also found are broadband lower-hybrid waves, and, at higher altitudes, conical upward-flowing ion distributions. The UCI Q-machine has been used to simulate the effect of lower hybrid waves on ion acceleration. Laser induced fluorescence was used for high resolution, non-perturbing measurements of the ion velocity distribution function. The plasma consisted of a 1 m long, 5 cm diameter barium plasma of densities on the order of 1010 per cm3 contained by a 3 kG magnetic field. Substantial changes in the perpendicular ion distribution were found. Main-body ion heating occurred along with non-maxwellian tail production. Over a 10 dB change in input wave power we observed up to a factor of 3 enhancement in main-body ion temperature.

  18. Simulated annealing based hybrid forecast for improving daily municipal solid waste generation prediction.

    PubMed

    Song, Jingwei; He, Jiaying; Zhu, Menghua; Tan, Debao; Zhang, Yu; Ye, Song; Shen, Dingtao; Zou, Pengfei

    2014-01-01

    A simulated annealing (SA) based variable weighted forecast model is proposed to combine and weigh local chaotic model, artificial neural network (ANN), and partial least square support vector machine (PLS-SVM) to build a more accurate forecast model. The hybrid model was built and multistep ahead prediction ability was tested based on daily MSW generation data from Seattle, Washington, the United States. The hybrid forecast model was proved to produce more accurate and reliable results and to degrade less in longer predictions than three individual models. The average one-week step ahead prediction has been raised from 11.21% (chaotic model), 12.93% (ANN), and 12.94% (PLS-SVM) to 9.38%. Five-week average has been raised from 13.02% (chaotic model), 15.69% (ANN), and 15.92% (PLS-SVM) to 11.27%. PMID:25301508

  19. Solid rocket combustion simulator technology using the hybrid rocket for simulation

    NASA Technical Reports Server (NTRS)

    Ramohalli, Kumar

    1994-01-01

    The hybrid rocket is reexamined in light of several important unanswered questions regarding its performance. The well-known heat transfer limited burning rate equation is quoted, and its limitations are pointed out. Several inconsistencies in the burning rate determination through fuel depolymerization are explicitly discussed. The resolution appears to be through the postulate of (surface) oxidative degradation of the fuel. Experiments are initiated to study the fuel degradation in mixtures of nitrogen/oxygen in the 99.9 percent/0.1 percent to 98 percent/2 percent range. The overall hybrid combustion behavior is studied in a 2 in-diameter rocket motor, where a PMMA tube is used as the fuel. The results include detailed, real-time infrared video images of the combustion zone. Space- and time-averaged images give a broad indication of the temperature reached in the gases. A brief outline is shown of future work, which will specifically concentrate on the exploration of the role of the oxidizer transport to the fuel surface, and the role of the unburned fuel that is reported to escape below the classical time-averaged boundary layer flame.

  20. CAVE2: a hybrid reality environment for immersive simulation and information analysis

    NASA Astrophysics Data System (ADS)

    Febretti, Alessandro; Nishimoto, Arthur; Thigpen, Terrance; Talandis, Jonas; Long, Lance; Pirtle, J. D.; Peterka, Tom; Verlo, Alan; Brown, Maxine; Plepys, Dana; Sandin, Dan; Renambot, Luc; Johnson, Andrew; Leigh, Jason

    2013-03-01

    Hybrid Reality Environments represent a new kind of visualization spaces that blur the line between virtual environments and high resolution tiled display walls. This paper outlines the design and implementation of the CAVE2TM Hybrid Reality Environment. CAVE2 is the world's first near-seamless flat-panel-based, surround-screen immersive system. Unique to CAVE2 is that it will enable users to simultaneously view both 2D and 3D information, providing more flexibility for mixed media applications. CAVE2 is a cylindrical system of 24 feet in diameter and 8 feet tall, and consists of 72 near-seamless, off-axisoptimized passive stereo LCD panels, creating an approximately 320 degree panoramic environment for displaying information at 37 Megapixels (in stereoscopic 3D) or 74 Megapixels in 2D and at a horizontal visual acuity of 20/20. Custom LCD panels with shifted polarizers were built so the images in the top and bottom rows of LCDs are optimized for vertical off-center viewing- allowing viewers to come closer to the displays while minimizing ghosting. CAVE2 is designed to support multiple operating modes. In the Fully Immersive mode, the entire room can be dedicated to one virtual simulation. In 2D model, the room can operate like a traditional tiled display wall enabling users to work with large numbers of documents at the same time. In the Hybrid mode, a mixture of both 2D and 3D applications can be simultaneously supported. The ability to treat immersive work spaces in this Hybrid way has never been achieved before, and leverages the special abilities of CAVE2 to enable researchers to seamlessly interact with large collections of 2D and 3D data. To realize this hybrid ability, we merged the Scalable Adaptive Graphics Environment (SAGE) - a system for supporting 2D tiled displays, with Omegalib - a virtual reality middleware supporting OpenGL, OpenSceneGraph and Vtk applications.

  1. A Hybrid Parachute Simulation Environment for the Orion Parachute Development Project

    NASA Technical Reports Server (NTRS)

    Moore, James W.

    2011-01-01

    A parachute simulation environment (PSE) has been developed that aims to take advantage of legacy parachute simulation codes and modern object-oriented programming techniques. This hybrid simulation environment provides the parachute analyst with a natural and intuitive way to construct simulation tasks while preserving the pedigree and authority of established parachute simulations. NASA currently employs four simulation tools for developing and analyzing air-drop tests performed by the CEV Parachute Assembly System (CPAS) Project. These tools were developed at different times, in different languages, and with different capabilities in mind. As a result, each tool has a distinct interface and set of inputs and outputs. However, regardless of the simulation code that is most appropriate for the type of test, engineers typically perform similar tasks for each drop test such as prediction of loads, assessment of altitude, and sequencing of disreefs or cut-aways. An object-oriented approach to simulation configuration allows the analyst to choose models of real physical test articles (parachutes, vehicles, etc.) and sequence them to achieve the desired test conditions. Once configured, these objects are translated into traditional input lists and processed by the legacy simulation codes. This approach minimizes the number of sim inputs that the engineer must track while configuring an input file. An object oriented approach to simulation output allows a common set of post-processing functions to perform routine tasks such as plotting and timeline generation with minimal sensitivity to the simulation that generated the data. Flight test data may also be translated into the common output class to simplify test reconstruction and analysis.

  2. Theory and simulation of lower-hybrid drift instability for current sheet with guide field

    SciTech Connect

    Yoon, P. H.; Lin, Y.; Wang, X. Y.; Lui, A. T. Y.

    2008-11-15

    The stability of a thin current sheet with a finite guide field is investigated in the weak guide-field limit by means of linear theory and simulation. The emphasis is placed on the lower-hybrid drift instability (LHDI) propagating along the current flow direction. Linear theory is compared against the two-dimensional linear simulation based on the gyrokinetic electron/fully kinetic ion code. LHDI is a flute mode characterized by k{center_dot}B{sub total}=0; hence, it is stabilized by a finite guide field if one is confined to k vector strictly parallel to the cross-field current. Comparison of the theory and simulation shows qualitatively good agreement.

  3. Global particle simulation of lower hybrid wave propagation and mode conversion in tokamaks

    NASA Astrophysics Data System (ADS)

    Bao, J.; Lin, Z.; Kuley, A.

    2015-12-01

    Particle-in-cell simulation of lower hybrid (LH) waves in core plasmas is presented with a realistic electron-to-ion mass ratio in toroidal geometry. Due to the fact that LH waves mainly interact with electrons to drive the current, ion dynamic is described by cold fluid equations for simplicity, while electron dynamic is described by drift kinetic equations. This model could be considered as a new method to study LH waves in tokamak plasmas, which has advantages in nonlinear simulations. The mode conversion between slow and fast waves is observed in the simulation when the accessibility condition is not satisfied, which is consistent with the theory. The poloidal spectrum upshift and broadening effects are observed during LH wave propagation in the toroidal geometry.

  4. An Investigation of a Hybrid Mixing Model for PDF Simulations of Turbulent Premixed Flames

    NASA Astrophysics Data System (ADS)

    Zhou, Hua; Li, Shan; Wang, Hu; Ren, Zhuyin

    2015-11-01

    Predictive simulations of turbulent premixed flames over a wide range of Damköhler numbers in the framework of Probability Density Function (PDF) method still remain challenging due to the deficiency in current micro-mixing models. In this work, a hybrid micro-mixing model, valid in both the flamelet regime and broken reaction zone regime, is proposed. A priori testing of this model is first performed by examining the conditional scalar dissipation rate and conditional scalar diffusion in a 3-D direct numerical simulation dataset of a temporally evolving turbulent slot jet flame of lean premixed H2-air in the thin reaction zone regime. Then, this new model is applied to PDF simulations of the Piloted Premixed Jet Burner (PPJB) flames, which are a set of highly shear turbulent premixed flames and feature strong turbulence-chemistry interaction at high Reynolds and Karlovitz numbers. Supported by NSFC 51476087 and NSFC 91441202.

  5. Global particle simulation of lower hybrid wave propagation and mode conversion in tokamaks

    SciTech Connect

    Bao, J.; Lin, Z.; Kuley, A.

    2015-12-10

    Particle-in-cell simulation of lower hybrid (LH) waves in core plasmas is presented with a realistic electron-to-ion mass ratio in toroidal geometry. Due to the fact that LH waves mainly interact with electrons to drive the current, ion dynamic is described by cold fluid equations for simplicity, while electron dynamic is described by drift kinetic equations. This model could be considered as a new method to study LH waves in tokamak plasmas, which has advantages in nonlinear simulations. The mode conversion between slow and fast waves is observed in the simulation when the accessibility condition is not satisfied, which is consistent with the theory. The poloidal spectrum upshift and broadening effects are observed during LH wave propagation in the toroidal geometry.

  6. Simulation of lithium-ion battery performance in hybrid electric vehicles.

    SciTech Connect

    Nelson, P.; Bloom, I.; Amine, K.; Henriksen, G.; Chemical Engineering

    2002-01-01

    n this study, three batteries were designed and these designs were evaluated in a hybrid vehicle simulation program. The battery designs were based on laboratory tests of 18650 cells for which a Lumped Parameter Battery Model was employed to correlate the cell impedance data. The three battery designs were each tested on three driving cycles, the Federal Urban Driving Schedule, the Highway Fuel Economy Test, and a special cycle developed to test the full power of the vehicle. The results of these simulation tests showed that the battery impedances were low for much of the time because the discharging and charging currents are not maintained at high levels for long periods of time on these cycles. For these conditions, the rates of heat generation in the batteries that were calculated by the simulation programs were low and may not be a serious problem.

  7. GTKDynamo: a PyMOL plug-in for QC/MM hybrid potential simulations.

    PubMed

    Bachega, José Fernando R; Timmers, Luís Fernando S M; Assirati, Lucas; Bachega, Leonardo R; Field, Martin J; Wymore, Troy

    2013-09-30

    Hybrid quantum chemical/molecular mechanical (QCMM) potentials are very powerful tools for molecular simulation. They are especially useful for studying processes in condensed phase systems, such as chemical reactions that involve a relatively localized change in electronic structure and where the surrounding environment contributes to these changes but can be represented with more computationally efficient functional forms. Despite their utility, however, these potentials are not always straightforward to apply since the extent of significant electronic structure changes occurring in the condensed phase process may not be intuitively obvious. To facilitate their use, we have developed an open-source graphical plug-in, GTKDynamo that links the PyMOL visualization program and the pDynamo QC/MM simulation library. This article describes the implementation of GTKDynamo and its capabilities and illustrates its application to QC/MM simulations. PMID:24137667

  8. Hybrid Model for Plasma Thruster Plume Simulation Including PIC-MCC Electrons Treatment

    SciTech Connect

    Alexandrov, A. L.; Bondar, Ye. A.; Schweigert, I. V.

    2008-12-31

    The simulation of stationary plasma thruster plume is important for spacecraft design due to possible interaction plume with spacecraft surface. Such simulations are successfully performed using the particle-in-cell technique for describing the motion of charged particles, namely the propellant ions. In conventional plume models the electrons are treated using various fluid approaches. In this work, we suggest an alternative approach, where the electron kinetics is considered 'ab initio', using the particle-in-cell--Monte Carlo collision method. To avoid the large computational expenses due to small time steps, the relaxation of simulated plume plasma is split into the fast relaxation of the electrons distribution function and the slow one of the ions. The model is self-consistent but hybrid, since the simultaneous electron and ion motion is not really modeled. The obtained electron temperature profile is in good agreement with experiment.

  9. Simulated fuel economy and emissions performance during city and interstate driving for a heavy-duty hybrid truck

    SciTech Connect

    Daw, C Stuart; Gao, Zhiming; Smith, David E; LaClair, Tim J; Pihl, Josh A; Edwards, Kevin Dean

    2013-01-01

    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.

  10. Exact hybrid particle/population simulation of rule-based models of biochemical systems.

    PubMed

    Hogg, Justin S; Harris, Leonard A; Stover, Lori J; Nair, Niketh S; Faeder, James R

    2014-04-01

    Detailed modeling and simulation of biochemical systems is complicated by the problem of combinatorial complexity, an explosion in the number of species and reactions due to myriad protein-protein interactions and post-translational modifications. Rule-based modeling overcomes this problem by representing molecules as structured objects and encoding their interactions as pattern-based rules. This greatly simplifies the process of model specification, avoiding the tedious and error prone task of manually enumerating all species and reactions that can potentially exist in a system. From a simulation perspective, rule-based models can be expanded algorithmically into fully-enumerated reaction networks and simulated using a variety of network-based simulation methods, such as ordinary differential equations or Gillespie's algorithm, provided that the network is not exceedingly large. Alternatively, rule-based models can be simulated directly using particle-based kinetic Monte Carlo methods. This "network-free" approach produces exact stochastic trajectories with a computational cost that is independent of network size. However, memory and run time costs increase with the number of particles, limiting the size of system that can be feasibly simulated. Here, we present a hybrid particle/population simulation method that combines the best attributes of both the network-based and network-free approaches. The method takes as input a rule-based model and a user-specified subset of species to treat as population variables rather than as particles. The model is then transformed by a process of "partial network expansion" into a dynamically equivalent form that can be simulated using a population-adapted network-free simulator. The transformation method has been implemented within the open-source rule-based modeling platform BioNetGen, and resulting hybrid models can be simulated using the particle-based simulator NFsim. Performance tests show that significant memory savings

  11. Exact Hybrid Particle/Population Simulation of Rule-Based Models of Biochemical Systems

    PubMed Central

    Stover, Lori J.; Nair, Niketh S.; Faeder, James R.

    2014-01-01

    Detailed modeling and simulation of biochemical systems is complicated by the problem of combinatorial complexity, an explosion in the number of species and reactions due to myriad protein-protein interactions and post-translational modifications. Rule-based modeling overcomes this problem by representing molecules as structured objects and encoding their interactions as pattern-based rules. This greatly simplifies the process of model specification, avoiding the tedious and error prone task of manually enumerating all species and reactions that can potentially exist in a system. From a simulation perspective, rule-based models can be expanded algorithmically into fully-enumerated reaction networks and simulated using a variety of network-based simulation methods, such as ordinary differential equations or Gillespie's algorithm, provided that the network is not exceedingly large. Alternatively, rule-based models can be simulated directly using particle-based kinetic Monte Carlo methods. This “network-free” approach produces exact stochastic trajectories with a computational cost that is independent of network size. However, memory and run time costs increase with the number of particles, limiting the size of system that can be feasibly simulated. Here, we present a hybrid particle/population simulation method that combines the best attributes of both the network-based and network-free approaches. The method takes as input a rule-based model and a user-specified subset of species to treat as population variables rather than as particles. The model is then transformed by a process of “partial network expansion” into a dynamically equivalent form that can be simulated using a population-adapted network-free simulator. The transformation method has been implemented within the open-source rule-based modeling platform BioNetGen, and resulting hybrid models can be simulated using the particle-based simulator NFsim. Performance tests show that significant memory

  12. Do4Models: Performance of current climate model dust emission schemes from a 1D box model perspective using field campaign data to constrain the simulated dust emission flux

    NASA Astrophysics Data System (ADS)

    Haustein, Karsten; King, James; Wiggs, Giles; Washington, Richard

    2013-04-01

    Dust emission schemes in climate models are relatively simple and are often tuned to represent observed background aerosol concentrations many of which are thousands of kilometres from source regions. Parameterisations of dust emission in numerical models were developed from idealised experiments such as those conducted in wind tunnels. Improvement of current model dust emission schemes has been difficult to achieve because of the paucity of observations from key dust sources. The Dust Observations for Models project (DO4Models) aims to gather data from source regions at a scale appropriate to climate model grid box resolution. Here we present the results of 1D box model simulations in which three commonly used parameterisations for the horizontal and vertical dust emission flux (Marticorena and Bergametti 1995, Alfaro and Gomez 2001, Shao et al. 2004) are applied and compared with Do4Models field campaign data retrieved over a typical salt pan dust source (Sua Pan, Botswana). The sensitivity of the schemes to input parameters such as soil moisture content, aerodynamic surface roughness length, shear velocity, soil texture class, and particle size is tested with particular regard to the representation of horizontal-to-vertical-mass-flux ratio. The effects of spatial averaging over 11 field sites is evaluated as is the average dust emission flux of a typical 12x12km model grid box. It is analysed whether the full range of surface processes (temporal changes in roughness, moisture, and soil conditions) is represented sufficiently well after averaging yet. Furthermore, the application of the dispersed soil size distribution on the performance of the emission schemes compared to the typically used undisturbed soil size distribution provided from soil databases is examined. Preliminary results suggest that the current schemes do not describe the observed emission process well. The scheme after Shao et al. (2004) provides the most accurate horizontal flux estimate so far

  13. The Hermean Bow Shock and Ion Foreshock as Seen by Three-Dimensional Global Hybrid Simulations

    NASA Astrophysics Data System (ADS)

    Chanteur, G. M.; Modolo, R.; Leblanc, F.

    2015-12-01

    The thinness of the Hermean magnetosheath evidenced by Mariner 10 and MESSENGER observations results from the small average standoff distance of the Bow Shock equal to 1.45RM and has important consequences especially in the region of the parallel shock. The magnetopause is clearly identified in front of the perpendicular shock meanwhile it is hardly recognized in front of the parallel shock due to a strong interaction between the shock and the magnetospheric boundary mediated by the magnetosheath flow. This interaction is investigated by means of three-dimensional global hybrid simulations for different IMF orientations and by varying the spatial resolution of the simulations between 120 and 40km. Accordingly to MESSENGER observations (Anderson et al, 2012) the planetary magnetic field implemented in the simulations combines a dipole and a quadrupole axisymmetric sources (Richer et al, 2012). References Anderson, B. J., C. L. Johnson, H. Korth, R. M. Winslow, J. E. Borovsky, M. E. Purucker, J. A. Slavin, S. C. Solomon, M.T. Zuber, and R. L. McNutt Jr. (2012), Low-degree structure in Mercury's planetary magnetic field, J. Geophys. Res.,117, E00L12, doi:10.1029/2012JE004159. Richer, E., R. Modolo, G. M. Chanteur, S. Hess, and F. Leblanc (2012), A global hybrid model for Mercury's interaction with the solar wind: Case study of the dipole representation, J. Geophys. Res., 117, A10228, doi:10.1029/2012JA017898.

  14. 2D-3D hybrid stabilized finite element method for tsunami runup simulations

    NASA Astrophysics Data System (ADS)

    Takase, S.; Moriguchi, S.; Terada, K.; Kato, J.; Kyoya, T.; Kashiyama, K.; Kotani, T.

    2016-09-01

    This paper presents a two-dimensional (2D)-three-dimensional (3D) hybrid stabilized finite element method that enables us to predict a propagation process of tsunami generated in a hypocentral region, which ranges from offshore propagation to runup to urban areas, with high accuracy and relatively low computational costs. To be more specific, the 2D shallow water equation is employed to simulate the propagation of offshore waves, while the 3D Navier-Stokes equation is employed for the runup in urban areas. The stabilized finite element method is utilized for numerical simulations for both of the 2D and 3D domains that are independently discretized with unstructured meshes. The multi-point constraint and transmission methods are applied to satisfy the continuity of flow velocities and pressures at the interface between the resulting 2D and 3D meshes, since neither their spatial dimensions nor node arrangements are consistent. Numerical examples are presented to demonstrate the performance of the proposed hybrid method to simulate tsunami behavior, including offshore propagation and runup to urban areas, with substantially lower computation costs in comparison with full 3D computations.

  15. 2D-3D hybrid stabilized finite element method for tsunami runup simulations

    NASA Astrophysics Data System (ADS)

    Takase, S.; Moriguchi, S.; Terada, K.; Kato, J.; Kyoya, T.; Kashiyama, K.; Kotani, T.

    2016-05-01

    This paper presents a two-dimensional (2D)-three-dimensional (3D) hybrid stabilized finite element method that enables us to predict a propagation process of tsunami generated in a hypocentral region, which ranges from offshore propagation to runup to urban areas, with high accuracy and relatively low computational costs. To be more specific, the 2D shallow water equation is employed to simulate the propagation of offshore waves, while the 3D Navier-Stokes equation is employed for the runup in urban areas. The stabilized finite element method is utilized for numerical simulations for both of the 2D and 3D domains that are independently discretized with unstructured meshes. The multi-point constraint and transmission methods are applied to satisfy the continuity of flow velocities and pressures at the interface between the resulting 2D and 3D meshes, since neither their spatial dimensions nor node arrangements are consistent. Numerical examples are presented to demonstrate the performance of the proposed hybrid method to simulate tsunami behavior, including offshore propagation and runup to urban areas, with substantially lower computation costs in comparison with full 3D computations.

  16. A macro finite element formulation for cardiac electrophysiology simulations using hybrid unstructured grids

    PubMed Central

    Rocha, Bernardo M.; Kickinger, Ferdinand; Prassl, Anton J.; Haase, Gundolf; Vigmond, Edward J.; dos Santos, Rodrigo Weber; Zaglmayr, Sabine; Plank, Gernot

    2011-01-01

    Electrical activity in cardiac tissue can be described by the bidomain equations whose solution for large scale simulations still remains a computational challenge. Therefore, improvements in the discrete formulation of the problem which decrease computational and/or memory demands are highly desirable. In this study, we propose a novel technique for computing shape functions of finite elements. The technique generates macro finite elements (MFEs) based on the local decomposition of elements into tetrahedral sub-elements with linear shape functions. Such an approach necessitates the direct use of hybrid meshes composed of different types of elements. MFEs are compared to classic standard finite elements with respect to accuracy and RAM memory usage under different scenarios of cardiac modeling including bidomain and monodomain simulations in 2D and 3D for simple and complex tissue geometries. In problems with analytical solutions, MFEs displayed the same numerical accuracy of standard linear triangular and tetrahedral elements. In propagation simulations, conduction velocity and activation times agreed very well with those computed with standard finite elements. However, MFEs offer a significant decrease in memory requirements. We conclude that hybrid meshes composed of MFEs are well suited for solving problems in cardiac computational electrophysiology. PMID:20699206

  17. Hybrid matched-block bootstrap for stochastic simulation of multiseason streamflows

    NASA Astrophysics Data System (ADS)

    Srinivas, V. V.; Srinivasan, K.

    2006-09-01

    SummaryA new hybrid model is proposed for stochastic simulation of multiseason streamflows, as an improvement over the hybrid moving block bootstrap (HMBB) model introduced by the authors in an earlier work. In the proposed model, periodic streamflows are partially pre-whitened using a parsimonious linear periodic autoregressive/autoregressive moving average model and residuals are extracted. The nonoverlapping within-year blocks formed from the residuals are conditionally resampled using the matched-block bootstrap (MABB) to obtain innovations, which are then post-blackened to generate synthetic replicates. The use of MABB for resampling the residuals, in lieu of moving block bootstrap (that was used in the HMBB model), has resulted in improved simulation of streamflows. The effectiveness of the proposed model in reproducing a wide variety of statistical attributes (including strong dependence structure) is demonstrated through Monte-Carlo simulations on both hypothetical and real data sets. Through application to streamflows of the Weber river, USA, the proposed model is shown to be more efficient in predicting reservoir storage capacity and in preserving storage based performance statistics and critical run characteristics compared to low-order linear periodic parametric models (Box-Jenkins type) and the HMBB model. This model offers enough flexibility and is a viable alternative to the conventional models when hydrologic sequence exhibits strong dependence and if the presence of nonlinearity and/or multimodality is suspected in the underlying hydrologic process. However, the proposed hybrid model may not be appropriate, if long-term dependence is significant in the hydrologic data.

  18. Synthesis of 1D-glyconanomaterials by a hybrid noncovalent-covalent functionalization of single wall carbon nanotubes: a study of their selective interactions with lectins and with live cells.

    PubMed

    Pernía Leal, M; Assali, M; Cid, J J; Valdivia, V; Franco, J M; Fernández, I; Pozo, D; Khiar, N

    2015-12-01

    To take full advantage of the remarkable applications of carbon nanotubes in different fields, there is a need to develop effective methods to improve their water dispersion and biocompatibility while maintaining their physical properties. In this sense, current approaches suffer from serious drawbacks such as loss of electronic structure together with low surface coverage in the case of covalent functionalizations, or instability of the dynamic hybrids obtained by non-covalent functionalizations. In the present work, we examined the molecular basis of an original strategy that combines the advantages of both functionalizations without their main drawbacks. The hierarchical self-assembly of diacetylenic-based neoglycolipids into highly organized and compacted rings around the nanotubes, followed by photopolymerization leads to the formation of nanotubes covered with glyconanorings with a shish kebab-type topology exposing the carbohydrate ligands to the water phase in a multivalent fashion. The glyconanotubes obtained are fully functional, and able to establish specific interactions with their cognate receptors. In fact, by taking advantage of this selective binding, an easy method to sense lectins as a working model of toxin detection was developed based on a simple analysis of TEM images. Remarkably, different experimental settings to assess cell membrane integrity, cell growth kinetics and cell cycle demonstrated the cellular biocompatibility of the sugar-coated carbon nanotubes compared to pristine single-walled carbon nanotubes. PMID:26531801

  19. Laboratory simulation of ion acceleration in the presence of lower hybrid waves

    NASA Astrophysics Data System (ADS)

    McWilliams, R.; Koslover, R.; Boehmer, H.; Rynn, N.

    The UCI Q-machine has been used to simulate the effect of lower hybrid waves on ion acceleration. Laser induced fluorescence was used for high resolution, nonperturbing measurements of the ion velocity distribution function. The plasma consisted of a 1 m long, 5 cm diameter barium plasma of densities on the order of 10 to the 10th per cu cm contained by a 3 kG magnetic field. Substantial changes in the perpendicular ion distribution were found. Main-body ion heating occurred along with non-Maxwellian tail production.

  20. Polar discontinuities and 1D interfaces in monolayered materials

    NASA Astrophysics Data System (ADS)

    Martinez-Gordillo, Rafael; Pruneda, Miguel

    2015-12-01

    Interfaces are the birthplace of a multitude of fascinating discoveries in fundamental science, and have enabled modern electronic devices, from transistors, to lasers, capacitors or solar cells. These interfaces between bulk materials are always bi-dimensional (2D) 'surfaces'. However the advent of graphene and other 2D crystals opened up a world of possibilities, as in this case the interfaces become one-dimensional (1D) lines. Although the properties of 1D nanoribbons have been extensively discussed in the last few years, 1D interfaces within infinite 2D systems had remained mostly unexplored until very recently. These include grain boundaries in polycrystalline samples, or interfaces in hybrid 2D sheets composed by segregated domains of different materials (as for example graphene/BN hybrids, or chemically different transition metal dichalcogenides). As for their 2D counterparts, some of these 1D interfaces exhibit polar characteristics, and can give rise to fascinating new physical properties. Here, recent experimental discoveries and theoretical predictions on the polar discontinuities that arise at these 1D interfaces will be reviewed, and the perspectives of this new research topic, discussed.

  1. On Using Atomistic Solvent Layers in Hybrid All-Atom/Coarse-Grained Molecular Dynamics Simulations.

    PubMed

    Kuhn, Alexander B; Gopal, Srinivasa M; Schäfer, Lars V

    2015-09-01

    Hybrid all-atom/coarse-grained (AA-CG) simulations in which AA solutes are embedded in a CG environment can provide a significant computational speed-up over conventional fully atomistic simulations and thus alleviate the current length and time scale limitations of molecular dynamics (MD) simulations of large biomolecular systems. On one hand, coarse graining the solvent is particularly appealing, since it typically constitutes the largest part of the simulation system and thus dominates computational cost. On the other hand, retaining atomic-level solvent layers around the solute is desirable for a realistic description of hydrogen bonds and other local solvation effects. Here, we devise and systematically validate fixed resolution AA-CG schemes, both with and without atomistic water layers. To quantify the accuracy and diagnose possible pitfalls, Gibbs free energies of solvation of amino acid side chain analogues were calculated, and the influence of the nature of the CG solvent surrounding (polarizable vs nonpolarizable CG water) and the size of the AA solvent region was investigated. We show that distance restraints to keep the AA solvent around the solute lead to too high of a density in the inner shell. Together with a long-ranged effect due to orientational ordering of water molecules at the AA-CG boundary, this affects solvation free energies. Shifting the onset of the distance restraints slightly away from the central solute significantly improves solvation free energies, down to mean unsigned errors with respect to experiment of 2.3 and 2.6 kJ/mol for the polarizable and nonpolarizable CG water surrounding, respectively. The speed-up of the nonpolarizable model renders it computationally more attractive. The present work thus highlights challenges, and outlines possible solutions, involved with modeling the boundary between different levels of resolution in hybrid AA-CG simulations. PMID:26575936

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

    PubMed

    Bert, Julien; Lemaréchal, Yannick; Visvikis, Dimitris

    2016-05-01

    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. PMID:27032813

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

    NASA Astrophysics Data System (ADS)

    Bert, Julien; Lemaréchal, Yannick; Visvikis, Dimitris

    2016-05-01

    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.

  4. Generalized Metropolis acceptance criterion for hybrid non-equilibrium molecular dynamics—Monte Carlo simulations

    SciTech Connect

    Chen, Yunjie; Roux, Benoît

    2015-01-14

    A family of hybrid simulation methods that combines the advantages of Monte Carlo (MC) with the strengths of classical molecular dynamics (MD) consists in carrying out short non-equilibrium MD (neMD) trajectories to generate new configurations that are subsequently accepted or rejected via an MC process. In the simplest case where a deterministic dynamic propagator is used to generate the neMD trajectories, the familiar Metropolis acceptance criterion based on the change in the total energy ΔE, min[1,  exp( − βΔE)], guarantees that the hybrid algorithm will yield the equilibrium Boltzmann distribution. However, the functional form of the acceptance probability is more complex when the non-equilibrium switching process is generated via a non-deterministic stochastic dissipative propagator coupled to a heat bath. Here, we clarify the conditions under which the Metropolis criterion remains valid to rigorously yield a proper equilibrium Boltzmann distribution within hybrid neMD-MC algorithm.

  5. Experimental and molecular simulation investigation of enhanced CO2 solubility in hybrid adsorbents.

    PubMed

    Ho, Ngoc Linh; Porcheron, Fabien; Pellenq, Roland J-M

    2010-08-17

    Hybrid adsorbents are prepared by confining physical solvents (propylene carbonate, N-methyl-2-pyrrolidone) within the porosity of a solid support (alumina) using both wet and dry impregnation methods. The resulting hybrid solids are analyzed using characterization methods (N(2) adsorption isotherm, TGA) to ensure that a proper confinement of the solvent has been achieved. The hybrid adsorbents are then subsequently assessed for CO(2) capture by performing solubility measurements. An enhanced CO(2) solubility is observed with regard to the ones in the bulk solvent and in the raw solid. In a next step, grand canonical Monte Carlo simulations have been performed on a slit pore model to understand the microscopic mechanisms yielding the apparition of enhanced solubility. The presence of solvent molecules favors the layering of CO(2) within the pore, and the resulting local density profile is then markedly increased compared to one found in the raw adsorbent as more carbon dioxide molecules can be accommodated into the pore volume. PMID:20695570

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

    SciTech Connect

    Yu, Yuqi; Wang, Jinan; Shao, Qiang E-mail: Jiye.Shi@ucb.com Zhu, Weiliang E-mail: Jiye.Shi@ucb.com; Shi, Jiye E-mail: Jiye.Shi@ucb.com

    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.

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

    NASA Astrophysics Data System (ADS)

    Yu, Yuqi; Wang, Jinan; Shao, Qiang; Shi, Jiye; Zhu, Weiliang

    2015-03-01

    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.

  8. Synthesis of 1D-glyconanomaterials by a hybrid noncovalent-covalent functionalization of single wall carbon nanotubes: a study of their selective interactions with lectins and with live cells

    NASA Astrophysics Data System (ADS)

    Pernía Leal, M.; Assali, M.; Cid, J. J.; Valdivia, V.; Franco, J. M.; Fernández, I.; Pozo, D.; Khiar, N.

    2015-11-01

    To take full advantage of the remarkable applications of carbon nanotubes in different fields, there is a need to develop effective methods to improve their water dispersion and biocompatibility while maintaining their physical properties. In this sense, current approaches suffer from serious drawbacks such as loss of electronic structure together with low surface coverage in the case of covalent functionalizations, or instability of the dynamic hybrids obtained by non-covalent functionalizations. In the present work, we examined the molecular basis of an original strategy that combines the advantages of both functionalizations without their main drawbacks. The hierarchical self-assembly of diacetylenic-based neoglycolipids into highly organized and compacted rings around the nanotubes, followed by photopolymerization leads to the formation of nanotubes covered with glyconanorings with a shish kebab-type topology exposing the carbohydrate ligands to the water phase in a multivalent fashion. The glyconanotubes obtained are fully functional, and able to establish specific interactions with their cognate receptors. In fact, by taking advantage of this selective binding, an easy method to sense lectins as a working model of toxin detection was developed based on a simple analysis of TEM images. Remarkably, different experimental settings to assess cell membrane integrity, cell growth kinetics and cell cycle demonstrated the cellular biocompatibility of the sugar-coated carbon nanotubes compared to pristine single-walled carbon nanotubes.To take full advantage of the remarkable applications of carbon nanotubes in different fields, there is a need to develop effective methods to improve their water dispersion and biocompatibility while maintaining their physical properties. In this sense, current approaches suffer from serious drawbacks such as loss of electronic structure together with low surface coverage in the case of covalent functionalizations, or instability of

  9. Comparative urban drive cycle simulations of light-duty hybrid vehicles with gasoline or diesel engines and emissions controls

    SciTech Connect

    Gao, Zhiming; Daw, C Stuart; Smith, David E

    2013-01-01

    Electric hybridization is a very effective approach for reducing fuel consumption in light-duty vehicles. Lean combustion engines (including diesels) have also been shown to be significantly more fuel efficient than stoichiometric gasoline engines. Ideally, the combination of these two technologies would result in even more fuel efficient vehicles. However, one major barrier to achieving this goal is the implementation of lean-exhaust aftertreatment that can meet increasingly stringent emissions regulations without heavily penalizing fuel efficiency. We summarize results from comparative simulations of hybrid electric vehicles with either stoichiometric gasoline or diesel engines that include state-of-the-art aftertreatment emissions controls for both stoichiometric and lean exhaust. Fuel consumption and emissions for comparable gasoline and diesel light-duty hybrid electric vehicles were compared over a standard urban drive cycle and potential benefits for utilizing diesel hybrids were identified. Technical barriers and opportunities for improving the efficiency of diesel hybrids were identified.

  10. Registration of range data using a hybrid simulated annealing and iterative closest point algorithm

    SciTech Connect

    LUCK,JASON; LITTLE,CHARLES Q.; HOFF,WILLIAM

    2000-04-17

    The need to register data is abundant in applications such as: world modeling, part inspection and manufacturing, object recognition, pose estimation, robotic navigation, and reverse engineering. Registration occurs by aligning the regions that are common to multiple images. The largest difficulty in performing this registration is dealing with outliers and local minima while remaining efficient. A commonly used technique, iterative closest point, is efficient but is unable to deal with outliers or avoid local minima. Another commonly used optimization algorithm, simulated annealing, is effective at dealing with local minima but is very slow. Therefore, the algorithm developed in this paper is a hybrid algorithm that combines the speed of iterative closest point with the robustness of simulated annealing. Additionally, a robust error function is incorporated to deal with outliers. This algorithm is incorporated into a complete modeling system that inputs two sets of range data, registers the sets, and outputs a composite model.

  11. Enhancing medical device training with hybrid physical-virtual simulators: smart peripherals for virtual devices.

    PubMed

    Samosky, Joseph T; Thornburg, Andrew; Karkhanis, Tushar; Petraglia, Frank; Strickler, Elise; Nelson, Douglas A; Weaver, Robert A; Robinson, Evan

    2013-01-01

    We introduce a novel platform for medical device training: hybrid physical-virtual simulators of medical devices, combining touchscreen-enabled virtual emulations of real devices with sensorized physical peripherals to enable tactile, hands-on interaction between the trainee, simulated device and standardized patients or mannequins. The system enables objective measurement and recording of trainee performance, including interactions with both the virtual device elements and the physical components, and can include metrics and feedback not available in the real device. The system also includes an integrated wireless signaling device for use with standardized patients. We present the implementation of an example system, a virtual defibrillator with sensorized paddles and wireless signaling of successful defibrillator operation. PMID:23400187

  12. Hybrid simulations of the effects of interstellar pickup hydrogen on the solar wind termination shock

    NASA Technical Reports Server (NTRS)

    Liewer, P. C.; Goldstein, B. E.; Omidi, N.

    1993-01-01

    Hybrid (kinetic ions/fluid electrons) plasma simulations are used to study the effects of a population of energetic interstellar pickup hydrogen ions on the solar wind termination shock. The pickup hydrogen is treated as a second ion species in the simulations, and thus the effects of the pick-ups on the shock, as well as the effects of the shock on the pickups, are treated in a fully self-consistent manner. For quasi-perpendicular shocks with 10-20 percent pickup hydrogen the pickup ions manifest themselves in a small foot ahead of the shock ramp caused by pickup ion reflection. For oblique shocks with smaller angles between the field and the shock normal, a large fraction of the pickup ions are reflected and move back upstream where they excite large amplitude magnetosonic waves which steepen into shocklets. These backstreaming pickup ions may provide advance warning of a spacecraft encounter with the termination shock.

  13. A hybrid transport-diffusion Monte Carlo method for frequency-dependent radiative-transfer simulations

    SciTech Connect

    Densmore, Jeffery D.; Thompson, Kelly G.; Urbatsch, Todd J.

    2012-08-15

    Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Implicit Monte Carlo radiative-transfer simulations in optically thick media. In DDMC, particles take discrete steps between spatial cells according to a discretized diffusion equation. Each discrete step replaces many smaller Monte Carlo steps, thus improving the efficiency of the simulation. In this paper, we present an extension of DDMC for frequency-dependent radiative transfer. We base our new DDMC method on a frequency-integrated diffusion equation for frequencies below a specified threshold, as optical thickness is typically a decreasing function of frequency. Above this threshold we employ standard Monte Carlo, which results in a hybrid transport-diffusion scheme. With a set of frequency-dependent test problems, we confirm the accuracy and increased efficiency of our new DDMC method.

  14. Fast surrogate-assisted simulation-driven optimization of compact microwave hybrid couplers

    NASA Astrophysics Data System (ADS)

    Kurgan, Piotr; Koziel, Slawomir

    2016-07-01

    This work presents a robust methodology for expedited simulation-driven design optimization of compact microwave hybrid couplers. The technique relies on problem decomposition, and a bottom-up design strategy, starting from the level of basic building blocks of the coupler, and finishing with a tuning procedure that exploits a fast surrogate model of the entire structure. The latter is constructed by cascading local response surface approximations of coupler elementary elements. The cross-coupling effects within the structure are neglected in the first stage of the design process; however, they are accounted for in the tuning phase by means of space-mapping correction of the surrogate. The proposed approach is demonstrated through the design of a compact rat-race and two branch-line couplers. In all cases, the computational cost of the optimization process is very low and corresponds to just a few high-fidelity electromagnetic simulations of respective structures. Experimental validation is also provided.

  15. A New Hybrid Viscoelastic Soft Tissue Model based on Meshless Method for Haptic Surgical Simulation

    PubMed Central

    Bao, Yidong; Wu, Dongmei; Yan, Zhiyuan; Du, Zhijiang

    2013-01-01

    This paper proposes a hybrid soft tissue model that consists of a multilayer structure and many spheres for surgical simulation system based on meshless. To improve accuracy of the model, tension is added to the three-parameter viscoelastic structure that connects the two spheres. By using haptic device, the three-parameter viscoelastic model (TPM) produces accurate deformationand also has better stress-strain, stress relaxation and creep properties. Stress relaxation and creep formulas have been obtained by mathematical formula derivation. Comparing with the experimental results of the real pig liver which were reported by Evren et al. and Amy et al., the curve lines of stress-strain, stress relaxation and creep of TPM are close to the experimental data of the real liver. Simulated results show that TPM has better real-time, stability and accuracy. PMID:24339837

  16. Solar Wind Turbulence from MHD to Sub-ion Scales: High-resolution Hybrid Simulations

    NASA Astrophysics Data System (ADS)

    Franci, Luca; Verdini, Andrea; Matteini, Lorenzo; Landi, Simone; Hellinger, Petr

    2015-05-01

    We present results from a high-resolution and large-scale hybrid (fluid electrons and particle-in-cell protons) two-dimensional numerical simulation of decaying turbulence. Two distinct spectral regions (separated by a smooth break at proton scales) develop with clear power-law scaling, each one occupying about a decade in wavenumbers. The simulation results simultaneously exhibit several properties of the observed solar wind fluctuations: spectral indices of the magnetic, kinetic, and residual energy spectra in the magnetohydrodynamic (MHD) inertial range along with a flattening of the electric field spectrum, an increase in magnetic compressibility, and a strong coupling of the cascade with the density and the parallel component of the magnetic fluctuations at sub-proton scales. Our findings support the interpretation that in the solar wind, large-scale MHD fluctuations naturally evolve beyond proton scales into a turbulent regime that is governed by the generalized Ohm’s law.

  17. Numerical Simulation of Cavitation Phenomena for Hybrid Contra-Rotating Shaft Propellers

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Hoon; Choo, Sung-Han; Park, Jeong-Yong; Choi, Gil-Hwan

    2015-12-01

    This paper deals with a numerical simulation of cavitation flow around a hybrid contra-rotating shaft propeller operating in wake field. The simulation for the cavitating flow is performed for straight operating and turning condition of podded propeller located behind the main propeller using unsteady Reynolds-Averaged Navier-Stokes. The behavior of the main propeller is almost similar regardless of the turning angle. In contrast, the cavitation behavior of the podded propeller depending on the turning angle appears to be entirely different due to the change of the load distribution on the podded propeller. At the large angle of the turning condition, the unstable cavity flow due to the large amount of cavitation and the hub vortex separated from the forward propeller as well as face cavitation is observed. Thus, a great caution on the cavitation phenomena is needed when designing and operating the HCRSP.

  18. Towards Reconfigurable, Separable and Hard Real-Time Hybrid Simulation and Test Systems

    NASA Astrophysics Data System (ADS)

    Quartier, F.; Delatte, B.; Joubert, M.

    2009-05-01

    Formation flight needs several new technologies, new disciplines, new approaches and above all, more concurrent engineering by more players. One of the problems to be addressed are more complex simulation and test systems that are easy to re-configure to include parts of the target hardware and that can provide sufficient power to handle simulation cores that are requiring one to two orders of magnitude more processing power than the current technology provides. Critical technologies that are already addressed by CNES and Spacebel are study model reuse and simulator reconfigurability (Basiles), model portability (SMP2) and the federation of several simulators using HLA. Two more critical issues are addressed in ongoing R&D work by CNES and Spacebel and are covered by this paper and concern the time engineering and management. The first issue concerns separability (characterisation, identification and handling of separable subsystems) and the consequences on practical systems. Experiments on the Pleiades operational simulator have shown that adding precise simulation of instruments such as Doris and the Star Tracker can be added without significantly impacting overall performance. Improved time analysis leads to better system understanding and testability. The second issue concerns architectures for distributed hybrid simulators systems that provide hard real-time capabilities and can react with a relative time precision and jitter that is in the 10 to 50 µsecond range using mainstream PC's and mainstream Operating Systems. This opens a way to make smaller economic hardware test systems that can be reconfigured to make large hardware test systems without restarting development. Although such systems were considered next to impossible till now, distributed hard real-time systems are getting in reach when modern but mainstream electronics are used and when processor cores can be isolated and reserved for real-time cores. This requires a complete rethinking of the

  19. Investigation of intrinsic variability in one-dimensional parallel shocks using steady state hybrid simulations

    NASA Technical Reports Server (NTRS)

    Bennett, Lee; Ellison, Donald C.

    1995-01-01

    We have developed a means of producing a steady state hybrid simulation of a collisionless shock. The shock is stopped in the simulation box by transforming into the shock frame and by modifying the downstream boundary conditions to allow the plasma to flow through the simulation box. Once the shock is stationary in the box frame, the simulation can be run for an arbitrary time with a fixed box size and a fixed number of simulation particles. Using this technique, we have shown that certain gross properties associated with the shock, such as the particle distribution function (including energetic particles produced by Fermi acceleration) and the flow speed profile, are constant (except for statistical variations) over hundreds of gyroperiods when averaged over times short compared to the average residence time of energetic particles. Our results imply that any microphysical processes responsible for particle heating and/or injection into the Fermi mechanism can be viewed as smooth and continuous on timescales longer than a few gyroperiods.

  20. Digital quantum simulators in a scalable architecture of hybrid spin-photon qubits.

    PubMed

    Chiesa, Alessandro; Santini, Paolo; Gerace, Dario; Raftery, James; Houck, Andrew A; Carretta, Stefano

    2015-01-01

    Resolving quantum many-body problems represents one of the greatest challenges in physics and physical chemistry, due to the prohibitively large computational resources that would be required by using classical computers. A solution has been foreseen by directly simulating the time evolution through sequences of quantum gates applied to arrays of qubits, i.e. by implementing a digital quantum simulator. Superconducting circuits and resonators are emerging as an extremely promising platform for quantum computation architectures, but a digital quantum simulator proposal that is straightforwardly scalable, universal, and realizable with state-of-the-art technology is presently lacking. Here we propose a viable scheme to implement a universal quantum simulator with hybrid spin-photon qubits in an array of superconducting resonators, which is intrinsically scalable and allows for local control. As representative examples we consider the transverse-field Ising model, a spin-1 Hamiltonian, and the two-dimensional Hubbard model and we numerically simulate the scheme by including the main sources of decoherence. PMID:26563516

  1. Digital quantum simulators in a scalable architecture of hybrid spin-photon qubits

    PubMed Central

    Chiesa, Alessandro; Santini, Paolo; Gerace, Dario; Raftery, James; Houck, Andrew A.; Carretta, Stefano

    2015-01-01

    Resolving quantum many-body problems represents one of the greatest challenges in physics and physical chemistry, due to the prohibitively large computational resources that would be required by using classical computers. A solution has been foreseen by directly simulating the time evolution through sequences of quantum gates applied to arrays of qubits, i.e. by implementing a digital quantum simulator. Superconducting circuits and resonators are emerging as an extremely promising platform for quantum computation architectures, but a digital quantum simulator proposal that is straightforwardly scalable, universal, and realizable with state-of-the-art technology is presently lacking. Here we propose a viable scheme to implement a universal quantum simulator with hybrid spin-photon qubits in an array of superconducting resonators, which is intrinsically scalable and allows for local control. As representative examples we consider the transverse-field Ising model, a spin-1 Hamiltonian, and the two-dimensional Hubbard model and we numerically simulate the scheme by including the main sources of decoherence. PMID:26563516

  2. Digital quantum simulators in a scalable architecture of hybrid spin-photon qubits

    NASA Astrophysics Data System (ADS)

    Chiesa, Alessandro; Santini, Paolo; Gerace, Dario; Raftery, James; Houck, Andrew A.; Carretta, Stefano

    2015-11-01

    Resolving quantum many-body problems represents one of the greatest challenges in physics and physical chemistry, due to the prohibitively large computational resources that would be required by using classical computers. A solution has been foreseen by directly simulating the time evolution through sequences of quantum gates applied to arrays of qubits, i.e. by implementing a digital quantum simulator. Superconducting circuits and resonators are emerging as an extremely promising platform for quantum computation architectures, but a digital quantum simulator proposal that is straightforwardly scalable, universal, and realizable with state-of-the-art technology is presently lacking. Here we propose a viable scheme to implement a universal quantum simulator with hybrid spin-photon qubits in an array of superconducting resonators, which is intrinsically scalable and allows for local control. As representative examples we consider the transverse-field Ising model, a spin-1 Hamiltonian, and the two-dimensional Hubbard model and we numerically simulate the scheme by including the main sources of decoherence.

  3. Global 3-D Hybrid Simulations of Mars and the Effect of Crustal Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Brecht, S. H.; Ledvina, S. A.; Luhmann, J. G.

    2001-12-01

    Mars is not protected from the solar wind by a strong intrinsic magnetic field. Further, Mars is a very small planet. These two aspects of Mars mean that the solar wind interaction with the planet is both direct and kinetic in behavior. The large gyroradius of the incoming solar wind and the large gyroradius of the pick up ions make the solar wind interaction with Mars very unique. Over the years the authors using a 3-D kinetic hybrid particle code have studied this planet. Mars Global Surveyor has produced many exciting discoveries. Probably the most significant and unexpected was the presence of the crustal magnetic fields on the surface of the planet. The presence of these strong crustal fields suggests that the solar wind interaction with Mars will be altered. In fact, it suggests that the loss rate of pick up ions and the shape of the Martian magnetosphere will be substantially changed. Results will be presented from our latest 3-D hybrid particle code simulations of Mars where models for the crustal magnetic field have been inserted into the simulations. Particular emphasis will be placed on changes to the magnetic field topology and the change in the rate of pick up ions.

  4. Jovian's plasma torus interaction with Europa: 3D hybrid kinetic simulation

    NASA Astrophysics Data System (ADS)

    Lipatov, A. S.; Cooper, J. F.; Paterson, W. R.

    2009-12-01

    The hybrid kinetic model approach supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical to improved interpretation of the existing measurements for surface and atmospheric composition from previous missions and to planning of future missions. The simulations are based on recent models of the atmosphere of Europa [1,2]. The hybrid model allows us to take into account the finite gyroradius effect and to estimate correctly the ions velocity distribution and the fluxes along the magnetic field in opposite the MHD simulation with the Maxwellian velocity distribution for background and pickup ions. The hybrid model also allows us to investigate the effects of the electron pressure on plasma wake structure that was already done for Jovian torus Io interaction [3]. Photoionization, electron-impact ionization and charge exchange are included in our model. The temperature of the background electrons and pickup electrons was also included into the generalized Ohm's law. We also take into account the collisions between the ions and neutrals. The background plasma contains only the ions with SO++ (Model A) [4] and O++ and S++ (Model B) [5]. The pickup ions were created from the atmosphere. The majority of O2 atmosphere is thermal with an extended non-thermal population [1]. The moon is modeled in this initial work as a weakly conducting body. Important effects of induced magnetic fields arising from oceanic shell conductivity will be addressed in later work. In this report we discuss the first results of the hybrid kinetic simulation of Europa's environment, namely, the global plasma structures, e.g., the formation of the magnetic barrier, Alfvén wing, pickup ion tail etc., and the computed map for the ion flux on the

  5. Extension and Validation of a Hybrid Particle-Finite Element Method for Hypervelocity Impact Simulation. Chapter 2

    NASA Technical Reports Server (NTRS)

    Fahrenthold, Eric P.; Shivarama, Ravishankar

    2004-01-01

    The hybrid particle-finite element method of Fahrenthold and Horban, developed for the simulation of hypervelocity impact problems, has been extended to include new formulations of the particle-element kinematics, additional constitutive models, and an improved numerical implementation. The extended formulation has been validated in three dimensional simulations of published impact experiments. The test cases demonstrate good agreement with experiment, good parallel speedup, and numerical convergence of the simulation results.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Liu, D.; Fu, G. Y.; Podestà, M.; Breslau, J. A.; Fredrickson, E. D.; Crocker, N. A.; Kubota, S.

    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.

  8. PHOTO: A computer simulation program for photovoltaic and hybrid energy systems. Document and user's guide

    NASA Astrophysics Data System (ADS)

    Manninen, L. M.; Lund, P. D.; Virkkula, A.

    1990-11-01

    The version 3.0 is described of the program package PHOTO for the simulation and sizing of hybrid power systems (photovoltaic and wind power plants) on IBM PC, XT, AT, PS/2 and compatibles. The minimum memory requirement is 260 kB. Graphical output is created with HALO'88 graphics subroutine library. In the simulation model, special attention is given to the battery storage unit. A backup generator can also be included in the system configuration. The dynamic method developed uses accurate system component models accounting for component interactions and losses in e.g. wiring and diodes. The photovoltaic array can operate in a maximum power mode or in a clamped voltage mode together with the other subsystems. Various control strategies can also be considered. Individual subsystem models were verified against real measurements. Illustrative simulation example is also discussed. The presented model can be used to simulate various system configurations accurately and evaluate system performance, such as energy flows and power losses in photovoltaic array, wind generator, backup generator, wiring, diodes, maximum power point tracking device, inverter and battery. Energy cost is also an important consideration.

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

    NASA Astrophysics Data System (ADS)

    Burgess, David; Hellinger, Petr; Gingell, Imogen; Trávníček, Pavel M.

    2016-08-01

    > Supercritical collisionless perpendicular shocks have an average macrostructure determined primarily by the dynamics of ions specularly reflected at the magnetic ramp. Within the overall macrostructure, instabilities, both linear and nonlinear, generate fluctuations and microstructure. To identify the sources of such microstructure, high-resolution two- and three-dimensional simulations have been carried out using the hybrid method, wherein the ions are treated as particles and the electron response is modelled as a massless fluid. We confirm the results of earlier two-dimensional (2-D) simulations showing both field-parallel aligned propagating fluctuations and fluctuations carried by the reflected-gyrating ions. In addition, it is shown that, for 2-D simulations of the shock coplanarity plane, the presence of short-wavelength fluctuations in all magnetic components is associated with the ion Weibel instability driven at the upstream edge of the foot by the reflected-gyrating ions. In 3-D simulations we show for the first time that the dominant microstructure is due to a coupling between field-parallel propagating fluctuations in the ramp and the motion of the reflected ions. This results in a pattern of fluctuations counter-propagating across the surface of the shock at an angle inclined to the magnetic field direction, due to a combination of field-parallel motion at the Alfvén speed of the ramp and motion in the sense of gyration of the reflected ions.

  10. Incorporating a Turbulence Transport Model into 2-D Hybrid Hall Thruster Simulations

    NASA Astrophysics Data System (ADS)

    Cha, Eunsun; Cappelli, Mark A.; Fernandez, Eduardo

    2014-10-01

    2-D hybrid simulations of Hall plasma thrusters that do not resolve cross-field transport-generating fluctuations require a model to capture how electrons migrate across the magnetic field. We describe the results of integrating a turbulent electron transport model into simulations of plasma behavior in a plane spanned by the E and B field vectors. The simulations treat the electrons as a fluid and the heavy species (ions/neutrals) as discrete particles. The transport model assumes that the turbulent eddy cascade in the electron fluid to smaller scales is the primary means of electron energy dissipation. Using this model, we compare simulations to experimental measurements made on a laboratory Hall discharge over a range of discharge voltage. Both the current-voltage trends as well as the plasma properties such as plasma temperature, electron density, and ion velocities seem agree favorably with experiments, where a simple Bohm transport model tends to perform poorly in capturing much of the discharge behavior.

  11. Molecular dynamics and Monte Carlo hybrid simulation for fuzzy tungsten nanostructure formation

    NASA Astrophysics Data System (ADS)

    Ito, A. M.; Takayama, A.; Oda, Y.; Tamura, T.; Kobayashi, R.; Hattori, T.; Ogata, S.; Ohno, N.; Kajita, S.; Yajima, M.; Noiri, Y.; Yoshimoto, Y.; Saito, S.; Takamura, S.; Murashima, T.; Miyamoto, M.; Nakamura, H.

    2015-07-01

    For the purposes of long-term use of tungsten divertor walls, the formation process of the fuzzy tungsten nanostructure induced by exposure to the helium plasma was studied. In the present paper, the fuzzy nanostructure's formation has been successfully reproduced by the new hybrid simulation method in which the deformation of the tungsten material due to pressure of the helium bubbles was simulated by the molecular dynamics and the diffusion of the helium atoms was simulated by the random walk based on the Monte Carlo method. By the simulation results, the surface height of the fuzzy nanostructure increased only when helium retention was under the steady state. It was proven that the growth of the fuzzy nanostructure was brought about by bursting of the helium bubbles. Moreover, we suggest the following key formation mechanisms of the fuzzy nanostructure: (1) lifting in which the surface lifted up by the helium bubble changes into a convexity, (2) bursting by which the region of the helium bubble changes into a concavity, and (3) the difference of the probability of helium retention by which the helium bubbles tend to appear under the concavity. Consequently, the convex-concave surface structure was enhanced and grew to create the fuzzy nanostructure.

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

    NASA Technical Reports Server (NTRS)

    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.

  13. Resonant indirect exchange in 1D semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Rozhansky, I. V.; Krainov, I. V.; Averkiev, N. S.; Lähderanta, E.

    2015-06-01

    We consider resonant indirect exchange interaction between magnetic centers in 1D nanostructures. The magnetic centers are assumed to be coupled to the 1D conducting channel by the quantum tunneling which can be of resonant character. The indirect exchange between the centers is mediated by the free carriers of the channel. The two cases of quadratic and linear energy dispersion of the 1D free carriers are considered. The former case is attributed to conventional semiconductor (InGaAs based to be concrete) nanowires or nanowhiskers, while the latter case is associated with carbon nanotubes with magnetic adatoms. We demonstrate that whenever the energy of a bound state at the magnetic center lies within the continuum energy spectra of the delocalized carriers in the channel the indirect exchange is strongly enhanced due to effective tunnel hybridization of the bound states with the continuum.

  14. High-resolution hybrid simulations of turbulence from inertial to sub-proton scales

    NASA Astrophysics Data System (ADS)

    Franci, Luca; Hellinger, Petr; Landi, Simone; Matteini, Lorenzo; Verdini, Andrea

    2015-04-01

    We investigate properties of turbulence from MHD scales to ion scales by means of two-dimensional, large-scale, high-resolution hybrid particle-in-cell simulations, which to our knowledge constitute the most accurate hybrid simulations of ion scale turbulence ever presented so far. We impose an initial ambient magnetic field perpendicular to the simulation box, and we add a spectrum of large-scale, linearly polarized Alfvén waves, balanced and Alfvénically equipartitioned, on average. When turbulence is fully developed, we observe an inertial range which is characterized by the power spectrum of perpendicular magnetic field fluctuations following a Kolmogorov law with spectral index close to -5/3, while the proton bulk velocity fluctuations exhibit a less steeper slope with index close to -3/2. Both these trends hold over a full decade. A definite transition is observed at a scale of the order of the proton inertial length, above which both spectra steepen, with the perpendicular magnetic field still exhibiting a power law with spectral index about -3 over another full decade. The spectrum of perpendicular electric fluctuations follows the one of the proton bulk velocity at MHD scales and reaches a sort of plateau at small scales. The turbulent nature of our data is also supported by the presence of intermittency. This is revealed by the non-Gaussianity of the probability distribution functions of MHD primitive variables increasing as approaching kinetic scales. All these features are in good agreement with solar wind observations.

  15. Constant-pH Hybrid Nonequilibrium Molecular Dynamics-Monte Carlo Simulation Method.

    PubMed

    Chen, Yunjie; Roux, Benoît

    2015-08-11

    A computational method is developed to carry out explicit solvent simulations of complex molecular systems under conditions of constant pH. In constant-pH simulations, preidentified ionizable sites are allowed to spontaneously protonate and deprotonate as a function of time in response to the environment and the imposed pH. The method, based on a hybrid scheme originally proposed by H. A. Stern (J. Chem. Phys. 2007, 126, 164112), consists of carrying out short nonequilibrium molecular dynamics (neMD) switching trajectories to generate physically plausible configurations with changed protonation states that are subsequently accepted or rejected according to a Metropolis Monte Carlo (MC) criterion. To ensure microscopic detailed balance arising from such nonequilibrium switches, the atomic momenta are altered according to the symmetric two-ends momentum reversal prescription. To achieve higher efficiency, the original neMD-MC scheme is separated into two steps, reducing the need for generating a large number of unproductive and costly nonequilibrium trajectories. In the first step, the protonation state of a site is randomly attributed via a Metropolis MC process on the basis of an intrinsic pKa; an attempted nonequilibrium switch is generated only if this change in protonation state is accepted. This hybrid two-step inherent pKa neMD-MC simulation method is tested with single amino acids in solution (Asp, Glu, and His) and then applied to turkey ovomucoid third domain and hen egg-white lysozyme. Because of the simple linear increase in the computational cost relative to the number of titratable sites, the present method is naturally able to treat extremely large systems. PMID:26300709

  16. Ion heating and energy partition at the heliospheric termination shock: hybrid simulations and analytical model

    SciTech Connect

    Gary, S Peter; Winske, Dan; Wu, Pin; Schwadron, N A; Lee, M

    2009-01-01

    The Los Alamos hybrid simulation code is used to examine heating and the partition of dissipation energy at the perpendicular heliospheric termination shock in the presence of pickup ions. The simulations are one-dimensional in space but three-dimensional in field and velocity components, and are carried out for a range of values of pickup ion relative density. Results from the simulations show that because the solar wind ions are relatively cold upstream, the temperature of these ions is raised by a relatively larger factor than the temperature of the pickup ions. An analytic model for energy partition is developed on the basis of the Rankine-Hugoniot relations and a polytropic energy equation. The polytropic index {gamma} used in the Rankine-Hugoniot relations is varied to improve agreement between the model and the simulations concerning the fraction of downstream heating in the pickup ions as well as the compression ratio at the shock. When the pickup ion density is less than 20%, the polytropic index is about 5/3, whereas for pickup ion densities greater than 20%, the polytropic index tends toward 2.2, suggesting a fundamental change in the character of the shock, as seen in the simulations, when the pickup ion density is large. The model and the simulations both indicate for the upstream parameters chosen for Voyager 2 conditions that the pickup ion density is about 25% and the pickup ions gain the larger share (approximately 90%) of the downstream thermal pressure, consistent with Voyager 2 observations near the shock.

  17. Sentaurus® based modeling and simulation for GFET's characteristic for ssDNA immobilization and hybridization

    NASA Astrophysics Data System (ADS)

    Yunfang, Jia; Cheng, Ju

    2016-01-01

    The graphene field effect transistor (GFET) has been widely studied and developed as sensors and functional devices. The first report about GFET sensing simulation on the device level is proposed. The GFET's characteristics, its responding for single strand DNA (ssDNA) and hybridization with the complimentary DNA (cDNA) are simulated based on Sentaurus, a popular CAD tool for electronic devices. The agreement between the simulated blank GFET feature and the reported experimental data suggests the feasibility of the presented simulation method. Then the simulations of ssDNA immobilization on GFET and hybridization with its cDNA are performed, the results are discussed based on the electron transfer (ET) mechanism between DNA and graphene. Project supported by the National Natural Science Foundation of China (No. 61371028) and the Tianjin Natural Science Foundation (No. 12JCZDJC22400).

  18. Characterization through global hybrid simulations of solar wind ions impacting the dayside of Mercury

    NASA Astrophysics Data System (ADS)

    Chanteur, Gérard M.; Modolo, Ronan; Hess, Sébastien; Leblanc, François; Richer, Emilie

    2014-05-01

    It has long been suspected since Mariner-10 observations that solar wind ions could reach the surface of Mercury: Kallio & Janhunen (2003) and Travnicek et al (2010) have presented simulated maps of precipitating proton fluxes. Attempts to refine estimations of precipitating fluxes of solar wind ions are important as these precipitations create additional sources of exospheric and possibly magnetospheric populations, and as their space-weathering effects modify the properties of the regolith. We run the global hybrid model used by Richer et al. (2012) which takes self-consistently into account the alpha particles of the solar wind to estimate fluxes of solar wind protons and alphas impacting the surface of Mercury under different IMF conditions. The internal source of the Hermean magnetic field is axisymmetric and is the superposition of a dipole and a quadrupole consistent with MESSENGER observations (Anderson et al., 2011) as in Richer et al. (2012). Results are briefly compared to predictions made with the offset dipole model of the planetary field. New simulations, made with an improved spatial resolution of 40km, reveal important differences between proton and alpha fluxes and show large variations with interplanetary conditions. In a first step we investigate the properties of solar wind ions impacting the dayside of the planet, precipitations on the night side will be examined later in a second step. References Anderson et al., Science, 333 , 1859, (2011) Kallio, E., and P. Janhunen, Solar wind and magnetospheric ion impact on Mercury's surface, Geophys. Res. Lett., 30(17), 1877, doi:10.1029/2003GL017842, 2003. Travnicek, P.M., D. Schriver, P. Hellinger, D. Hercik, B.J. Anderson, M. Sarantos, and J.A.Slavin, Mercury's magnetosphere-solar wind interaction for northward and southward interplanetary magnetic field: Hybrid simulation results, Icarus, doi:10.1016/j.icarus.2010.01.008, 2010 Richer, E., R. Modolo, G. M. Chanteur, S. Hess, and F. Leblanc (2012), A

  19. Fluid simulations with atomistic resolution: a hybrid multiscale method with field-wise coupling

    SciTech Connect

    Borg, Matthew K.; Lockerby, Duncan A.; Reese, Jason M.

    2013-12-15

    We present a new hybrid method for simulating dense fluid systems that exhibit multiscale behaviour, in particular, systems in which a Navier–Stokes model may not be valid in parts of the computational domain. We apply molecular dynamics as a local microscopic refinement for correcting the Navier–Stokes constitutive approximation in the bulk of the domain, as well as providing a direct measurement of velocity slip at bounding surfaces. Our hybrid approach differs from existing techniques, such as the heterogeneous multiscale method (HMM), in some fundamental respects. In our method, the individual molecular solvers, which provide information to the macro model, are not coupled with the continuum grid at nodes (i.e. point-wise coupling), instead coupling occurs over distributed heterogeneous fields (here referred to as field-wise coupling). This affords two major advantages. Whereas point-wise coupled HMM is limited to regions of flow that are highly scale-separated in all spatial directions (i.e. where the state of non-equilibrium in the fluid can be adequately described by a single strain tensor and temperature gradient vector), our field-wise coupled HMM has no such limitations and so can be applied to flows with arbitrarily-varying degrees of scale separation (e.g. flow from a large reservoir into a nano-channel). The second major advantage is that the position of molecular elements does not need to be collocated with nodes of the continuum grid, which means that the resolution of the microscopic correction can be adjusted independently of the resolution of the continuum model. This in turn means the computational cost and accuracy of the molecular correction can be independently controlled and optimised. The macroscopic constraints on the individual molecular solvers are artificial body-force distributions, used in conjunction with standard periodicity. We test our hybrid method on the Poiseuille flow problem for both Newtonian (Lennard-Jones) and non

  20. Simulations of hybrid system varying solar radiation and microturbine response time

    NASA Astrophysics Data System (ADS)

    Fernández Ribaya, Yolanda; Álvarez, Eduardo; Paredes Sánchez, José Pablo; Xiberta Bernat, Jorge

    2015-07-01

    Hybrid power systems, such as combinations of renewable power sources with intermittent power production and non-renewable power sources, theoretically increase the reliability and thus integration of renewable sources in the electrical system. However, a recent increase in the number of hybrid installations has sparked interest in the effects of their connection to the grid, especially in remote areas. This paper analyses a photovoltaic-gas microturbine hybrid system dimensioned to be installed in La Paz (Mexico).The research presented in this paper studies and quantifies the effects on the total electric power produced, varying both the solar radiation and the gas microturbine response time. The gas microturbine and the photovoltaic panels are modelled using Matlab/Simulink software, obtaining a platform where different tests to simulate real conditions have been executed. They consist of diverse ramps of irradiance that replicate solar radiation variations, and different microturbine response times reproduced by the time constants of a first order transfer function that models the microturbine dynamic response. The results obtained show that when radiation varies quickly it does not produce significant differences in the power guarantee or the microturbine gas consumption, to any microturbine response time. However, these two parameters are highly variable with smooth radiance variations. The maximum total power variation decreases greatly as the radiation variation gets lower. In addition, by decreasing the microturbine response time, it is possible to appreciably increase the power guarantee although the maximum power variation and gas consumption increase. Only in cases of low radiation variation is there no appreciable difference in the maximum power variation obtained by the different turbine response times.

  1. Simulations of hybrid system varying solar radiation and microturbine response time

    SciTech Connect

    Fernández Ribaya, Yolanda Álvarez, Eduardo; Paredes Sánchez, José Pablo; Xiberta Bernat, Jorge

    2015-07-15

    Hybrid power systems, such as combinations of renewable power sources with intermittent power production and non-renewable power sources, theoretically increase the reliability and thus integration of renewable sources in the electrical system. However, a recent increase in the number of hybrid installations has sparked interest in the effects of their connection to the grid, especially in remote areas. This paper analyses a photovoltaic-gas microturbine hybrid system dimensioned to be installed in La Paz (Mexico).The research presented in this paper studies and quantifies the effects on the total electric power produced, varying both the solar radiation and the gas microturbine response time. The gas microturbine and the photovoltaic panels are modelled using Matlab/Simulink software, obtaining a platform where different tests to simulate real conditions have been executed. They consist of diverse ramps of irradiance that replicate solar radiation variations, and different microturbine response times reproduced by the time constants of a first order transfer function that models the microturbine dynamic response. The results obtained show that when radiation varies quickly it does not produce significant differences in the power guarantee or the microturbine gas consumption, to any microturbine response time. However, these two parameters are highly variable with smooth radiance variations. The maximum total power variation decreases greatly as the radiation variation gets lower. In addition, by decreasing the microturbine response time, it is possible to appreciably increase the power guarantee although the maximum power variation and gas consumption increase. Only in cases of low radiation variation is there no appreciable difference in the maximum power variation obtained by the different turbine response times.

  2. A General Hybrid Radiation Transport Scheme for Star Formation Simulations on an Adaptive Grid

    NASA Astrophysics Data System (ADS)

    Klassen, Mikhail; Kuiper, Rolf; Pudritz, Ralph E.; Peters, Thomas; Banerjee, Robi; Buntemeyer, Lars

    2014-12-01

    Radiation feedback plays a crucial role in the process of star formation. In order to simulate the thermodynamic evolution of disks, filaments, and the molecular gas surrounding clusters of young stars, we require an efficient and accurate method for solving the radiation transfer problem. We describe the implementation of a hybrid radiation transport scheme in the adaptive grid-based FLASH general magnetohydrodyanmics code. The hybrid scheme splits the radiative transport problem into a raytracing step and a diffusion step. The raytracer captures the first absorption event, as stars irradiate their environments, while the evolution of the diffuse component of the radiation field is handled by a flux-limited diffusion solver. We demonstrate the accuracy of our method through a variety of benchmark tests including the irradiation of a static disk, subcritical and supercritical radiative shocks, and thermal energy equilibration. We also demonstrate the capability of our method for casting shadows and calculating gas and dust temperatures in the presence of multiple stellar sources. Our method enables radiation-hydrodynamic studies of young stellar objects, protostellar disks, and clustered star formation in magnetized, filamentary environments.

  3. Dynamic modeling and motion simulation for a winged hybrid-driven underwater glider

    NASA Astrophysics Data System (ADS)

    Wang, Shu-Xin; Sun, Xiu-Jun; Wang, Yan-Hui; Wu, Jian-Guo; Wang, Xiao-Ming

    2011-03-01

    PETREL, a winged hybrid-driven underwater glider is a novel and practical marine survey platform which combines the features of legacy underwater glider and conventional AUV (autonomous underwater vehicle). It can be treated as a multi-rigid-body system with a floating base and a particular hydrodynamic profile. In this paper, theorems on linear and angular momentum are used to establish the dynamic equations of motion of each rigid body and the effect of translational and rotational motion of internal masses on the attitude control are taken into consideration. In addition, due to the unique external shape with fixed wings and deflectable rudders and the dual-drive operation in thrust and glide modes, the approaches of building dynamic model of conventional AUV and hydrodynamic model of submarine are introduced, and the tailored dynamic equations of the hybrid glider are formulated. Moreover, the behaviors of motion in glide and thrust operation are analyzed based on the simulation and the feasibility of the dynamic model is validated by data from lake field trials.

  4. Hybrid LES/RANS Simulation of Transverse Sonic Injection into a Mach 2 Flow

    NASA Technical Reports Server (NTRS)

    Boles, John A.; Edwards, Jack R.; Baurle, Robert A.

    2008-01-01

    A computational study of transverse sonic injection of air and helium into a Mach 1.98 cross-flow is presented. A hybrid large-eddy simulation / Reynolds-averaged Navier-Stokes (LES/RANS) turbulence model is used, with the two-equation Menter baseline (Menter-BSL) closure for the RANS part of the flow and a Smagorinsky-type model for the LES part of the flow. A time-dependent blending function, dependent on modeled turbulence variables, is used to shift the closure from RANS to LES. Turbulent structures are initiated and sustained through the use of a recycling / rescaling technique. Two higher-order discretizations, the Piecewise Parabolic Method (PPM) of Colella and Woodward, and the SONIC-A ENO scheme of Suresh and Huyhn are used in the study. The results using the hybrid model show reasonably good agreement with time-averaged Mie scattering data and with experimental surface pressure distributions, even though the penetration of the jet into the cross-flow is slightly over-predicted. The LES/RANS results are used to examine the validity of commonly-used assumptions of constant Schmidt and Prandtl numbers in the intense mixing zone downstream of the injection location.

  5. A general hybrid radiation transport scheme for star formation simulations on an adaptive grid

    SciTech Connect

    Klassen, Mikhail; Pudritz, Ralph E.; Kuiper, Rolf; Peters, Thomas; Banerjee, Robi; Buntemeyer, Lars

    2014-12-10

    Radiation feedback plays a crucial role in the process of star formation. In order to simulate the thermodynamic evolution of disks, filaments, and the molecular gas surrounding clusters of young stars, we require an efficient and accurate method for solving the radiation transfer problem. We describe the implementation of a hybrid radiation transport scheme in the adaptive grid-based FLASH general magnetohydrodyanmics code. The hybrid scheme splits the radiative transport problem into a raytracing step and a diffusion step. The raytracer captures the first absorption event, as stars irradiate their environments, while the evolution of the diffuse component of the radiation field is handled by a flux-limited diffusion solver. We demonstrate the accuracy of our method through a variety of benchmark tests including the irradiation of a static disk, subcritical and supercritical radiative shocks, and thermal energy equilibration. We also demonstrate the capability of our method for casting shadows and calculating gas and dust temperatures in the presence of multiple stellar sources. Our method enables radiation-hydrodynamic studies of young stellar objects, protostellar disks, and clustered star formation in magnetized, filamentary environments.

  6. Simulating Gyrokinetic/fluid hybrid electromagnetic modes in the total-f gyrokinetic code XGC1

    NASA Astrophysics Data System (ADS)

    Lang, Jianying; Hager, Robert; Ku, Seung-Hoe; Chang, Choong-Seock

    2015-11-01

    XGC1 code has been extended to include the electronmagnetic capability using the hybrid model with gyrokinetic ions and fluid electrons. This feature will enable a more complete description of the MHD/fluid type mode activities including ELMs and low-n tearing modes. Their interaction with the kinetic neoclassical and microturbulence dynamics needs to be simulated together. Evolution of the background profile should also be captured self-consistently. We report recent development and verification of this hybrid model in the limit of small delta-B. The code has been verified for Alfven waves and ITG/KBM transition, and low-n resistive tearing modes. The KBM capability of XGC1 has been verified against the published results from Gyro, GEM, GS2, Gene, and GTC. Detailed verification of resistive tearing modes and kink modes in the toroidal geometry will be also presented. An implicit method is implemented in XGC1 to bypass the Courant condition caused by fast Alfven oscillations. Work supported by US DOE OFES and OASCR.

  7. Hybrid RANS/LES simulations of bluff-body flows on unstructured grids

    NASA Astrophysics Data System (ADS)

    Salvetti, Maria Vittoria; Camarri, Simone; Koobus, Bruno; Dervieux, Alain

    2004-11-01

    A hybrid RANS/LES model is set up by blending a k-\\varepsilon model and the Smagorinsky model according to the LNS idea [1], i.e. using the minimum value among the eddy viscosities given by the RANS and the LES closures. The Navier-Stokes equations are discretized by a mixed finite-volume/finite-element formulation applicable to unstrucured grid. A low diffusion MUSCL scheme, designed for LES, is adopted [2]. Both explicit (Runge-Kutta) and implicit (second-order accurate) time advancing can be used. The hybrid model is applied to the simulation of the flows around a square cylinder and around a sphere. Results are compared with those obtained with RANS and LES and with experimental data. REFERENCES: [1] P.Batten.LNS-An approach towards embedded LES. In phAIAA Paper 2002-0427. American Institute of Aeronautics and Astronautics, 2002. [2] S.Camarri,M.V.Salvetti,B.Koobus and A.Dervieux. A low-diffusion MUSCL scheme for LES on unstructured grids. phComputers and Fluids 2003; 33:1101-1129.

  8. Combustion performance and scale effect from N2O/HTPB hybrid rocket motor simulations

    NASA Astrophysics Data System (ADS)

    Shan, Fanli; Hou, Lingyun; Piao, Ying

    2013-04-01

    HRM code for the simulation of N2O/HTPB hybrid rocket motor operation and scale effect analysis has been developed. This code can be used to calculate motor thrust and distributions of physical properties inside the combustion chamber and nozzle during the operational phase by solving the unsteady Navier-Stokes equations using a corrected compressible difference scheme and a two-step, five species combustion model. A dynamic fuel surface regression technique and a two-step calculation method together with the gas-solid coupling are applied in the calculation of fuel regression and the determination of combustion chamber wall profile as fuel regresses. Both the calculated motor thrust from start-up to shut-down mode and the combustion chamber wall profile after motor operation are in good agreements with experimental data. The fuel regression rate equation and the relation between fuel regression rate and axial distance have been derived. Analysis of results suggests improvements in combustion performance to the current hybrid rocket motor design and explains scale effects in the variation of fuel regression rate with combustion chamber diameter.

  9. Hybrid-PIC Computer Simulation of the Plasma and Erosion Processes in Hall Thrusters

    NASA Technical Reports Server (NTRS)

    Hofer, Richard R.; Katz, Ira; Mikellides, Ioannis G.; Gamero-Castano, Manuel

    2010-01-01

    HPHall software simulates and tracks the time-dependent evolution of the plasma and erosion processes in the discharge chamber and near-field plume of Hall thrusters. HPHall is an axisymmetric solver that employs a hybrid fluid/particle-in-cell (Hybrid-PIC) numerical approach. HPHall, originally developed by MIT in 1998, was upgraded to HPHall-2 by the Polytechnic University of Madrid in 2006. The Jet Propulsion Laboratory has continued the development of HPHall-2 through upgrades to the physical models employed in the code, and the addition of entirely new ones. Primary among these are the inclusion of a three-region electron mobility model that more accurately depicts the cross-field electron transport, and the development of an erosion sub-model that allows for the tracking of the erosion of the discharge chamber wall. The code is being developed to provide NASA science missions with a predictive tool of Hall thruster performance and lifetime that can be used to validate Hall thrusters for missions.

  10. Numerical simulation of HTPB combustion in a 2D hybrid slab combustor

    NASA Astrophysics Data System (ADS)

    Gariani, Gabriela; Maggi, Filippo; Galfetti, Luciano

    2011-09-01

    A code for the numerical simulation of combustion processes in hybrid rockets, developed at the Space Propulsion Laboratory of Politecnico di Milano (SPLab), is presented. The code deals with Navier-Stokes equations solved with RANS approach, blowing effect, combustion kinetics and radiation. The equations are closed with k-epsilon turbulence model and well stirred reactor model. The P1 model, a simplification of the PN radiation model, is adopted. Specific simulation tools were developed using OpenFOAM®open source technology. The computational domain is 2D and split in two subdomains, simulating the reacting gas mixture on one side and the solid fuel grain on the other. The interface between the two regions plays a key role as the solid grain pyrolysis comes from a straight solution of the model without shortcuts. A propellant combination with polybutadiene and gaseous oxygen has been chosen and a reduced kinetic model for combustion of butadiene, considered as the major gaseous constituent coming from polybutadiene pyrolysis, has been developed for reactions occurring in oxygen atmosphere. The computational domain tries to replicate the real experimental setup and is split into three areas: pre-chamber, slab zone and post-chamber. High speed camera visualizations of the combustion processes allow to compare the flame height, obtained by the code and by experimental tests, along the grain for given boundary conditions.

  11. Steady-state hydrodynamic instabilities of active liquid crystals: Hybrid lattice Boltzmann simulations

    NASA Astrophysics Data System (ADS)

    Marenduzzo, D.; Orlandini, E.; Cates, M. E.; Yeomans, J. M.

    2007-09-01

    We report hybrid lattice Boltzmann (HLB) simulations of the hydrodynamics of an active nematic liquid crystal sandwiched between confining walls with various anchoring conditions. We confirm the existence of a transition between a passive phase and an active phase, in which there is spontaneous flow in the steady state. This transition is attained for sufficiently “extensile” rods, in the case of flow-aligning liquid crystals, and for sufficiently “contractile” ones for flow-tumbling materials. In a quasi-one-dimensional geometry, deep in the active phase of flow-aligning materials, our simulations give evidence of hysteresis and history-dependent steady states, as well as of spontaneous banded flow. Flow-tumbling materials, in contrast, rearrange themselves so that only the two boundary layers flow in steady state. Two-dimensional simulations, with periodic boundary conditions, show additional instabilities, with the spontaneous flow appearing as patterns made up of “convection rolls.” These results demonstrate a remarkable richness (including dependence on anchoring conditions) in the steady-state phase behavior of active materials, even in the absence of external forcing; they have no counterpart for passive nematics. Our HLB methodology, which combines lattice Boltzmann for momentum transport with a finite difference scheme for the order parameter dynamics, offers a robust and efficient method for probing the complex hydrodynamic behavior of active nematics.

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

    SciTech Connect

    Cowee, Misa M; Winske, Dan; Gary, S Peter

    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.

  13. Modeling, simulation, and concept design for hybrid-electric medium-size military trucks

    NASA Astrophysics Data System (ADS)

    Rizzoni, Giorgio; Josephson, John R.; Soliman, Ahmed; Hubert, Christopher; Cantemir, Codrin-Gruie; Dembski, Nicholas; Pisu, Pierluigi; Mikesell, David; Serrao, Lorenzo; Russell, James; Carroll, Mark

    2005-05-01

    A large scale design space exploration can provide valuable insight into vehicle design tradeoffs being considered for the U.S. Army"s FMTV (Family of Medium Tactical Vehicles). Through a grant from TACOM (Tank-automotive and Armaments Command), researchers have generated detailed road, surface, and grade conditions representative of the performance criteria of this medium-sized truck and constructed a virtual powertrain simulator for both conventional and hybrid variants. The simulator incorporates the latest technology among vehicle design options, including scalable ultracapacitor and NiMH battery packs as well as a variety of generator and traction motor configurations. An energy management control strategy has also been developed to provide efficiency and performance. A design space exploration for the family of vehicles involves running a large number of simulations with systematically varied vehicle design parameters, where each variant is paced through several different mission profiles and multiple attributes of performance are measured. The resulting designs are filtered to remove dominated designs, exposing the multi-criterial surface of optimality (Pareto optimal designs), and revealing the design tradeoffs as they impact vehicle performance and economy. The results are not yet definitive because ride and drivability measures were not included, and work is not finished on fine-tuning the modeled dynamics of some powertrain components. However, the work so far completed demonstrates the effectiveness of the approach to design space exploration, and the results to date suggest the powertrain configuration best suited to the FMTV mission.

  14. Spontaneous Hot Flow Anomalies at Quasi-Parallel Shocks: 2. Hybrid Simulations

    NASA Technical Reports Server (NTRS)

    Omidi, N.; Zhang, H.; Sibeck, D.; Turner, D.

    2013-01-01

    Motivated by recent THEMIS observations, this paper uses 2.5-D electromagnetic hybrid simulations to investigate the formation of Spontaneous Hot Flow Anomalies (SHFA) upstream of quasi-parallel bow shocks during steady solar wind conditions and in the absence of discontinuities. The results show the formation of a large number of structures along and upstream of the quasi-parallel bow shock. Their outer edges exhibit density and magnetic field enhancements, while their cores exhibit drops in density, magnetic field, solar wind velocity and enhancements in ion temperature. Using virtual spacecraft in the simulation, we show that the signatures of these structures in the time series data are very similar to those of SHFAs seen in THEMIS data and conclude that they correspond to SHFAs. Examination of the simulation data shows that SHFAs form as the result of foreshock cavitons interacting with the bow shock. Foreshock cavitons in turn form due to the nonlinear evolution of ULF waves generated by the interaction of the solar wind with the backstreaming ions. Because foreshock cavitons are an inherent part of the shock dissipation process, the formation of SHFAs is also an inherent part of the dissipation process leading to a highly non-uniform plasma in the quasi-parallel magnetosheath including large scale density and magnetic field cavities.

  15. Parametric identification of a servo-hydraulic actuator for real-time hybrid simulation

    NASA Astrophysics Data System (ADS)

    Qian, Yili; Ou, Ge; Maghareh, Amin; Dyke, Shirley J.

    2014-10-01

    In a typical Real-time Hybrid Simulation (RTHS) setup, servo-hydraulic actuators serve as interfaces between the computational and physical substructures. Time delay introduced by actuator dynamics and complex interaction between the actuators and the specimen has detrimental effects on the stability and accuracy of RTHS. Therefore, a good understanding of servo-hydraulic actuator dynamics is a prerequisite for controller design and computational simulation of RTHS. This paper presents an easy-to-use parametric identification procedure for RTHS users to obtain re-useable actuator parameters for a range of payloads. The critical parameters in a linearized servo-hydraulic actuator model are optimally obtained from genetic algorithms (GA) based on experimental data collected from various specimen mass/stiffness combinations loaded to the target actuator. The actuator parameters demonstrate convincing convergence trend in GA. A key feature of this parametric modeling procedure is its re-usability under different testing scenarios, including different specimen mechanical properties and actuator inner-loop control gains. The models match well with experimental results. The benefit of the proposed parametric identification procedure has been demonstrated by (1) designing an H∞ controller with the identified system parameters that significantly improves RTHS performance; and (2) establishing an analysis and computational simulation of a servo-hydraulic system that help researchers interpret system instability and improve design of experiments.

  16. Spontaneous hot flow anomalies at quasi-parallel shocks: 2. Hybrid simulations

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Zhang, H.; Sibeck, D.; Turner, D.

    2013-01-01

    Abstract<p label="1">Motivated by recent THEMIS observations, this paper uses 2.5-D electromagnetic <span class="hlt">hybrid</span> <span class="hlt">simulations</span> to investigate the formation of Spontaneous Hot Flow Anomalies (SHFAs) upstream of quasi-parallel bow shocks during steady solar wind conditions and in the absence of discontinuities. The results show the formation of a large number of structures along and upstream of the quasi-parallel bow shock. Their outer edges exhibit density and magnetic field enhancements, while their cores exhibit drops in density, magnetic field, solar wind velocity, and enhancements in ion temperature. Using virtual spacecraft in the <span class="hlt">simulation</span>, we show that the signatures of these structures in the time series data are very similar to those of SHFAs seen in THEMIS data and conclude that they correspond to SHFAs. Examination of the <span class="hlt">simulation</span> data shows that SHFAs form as the result of foreshock cavitons interacting with the bow shock. Foreshock cavitons in turn form due to the nonlinear evolution of ULF waves generated by the interaction of the solar wind with the backstreaming ions. Because foreshock cavitons are an inherent part of the shock dissipation process, the formation of SHFAs is also an inherent part of the dissipation process leading to a highly nonuniform plasma in the quasi-parallel magnetosheath including large-scale density and magnetic field cavities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17930285','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17930285"><span id="translatedtitle">Steady-state hydrodynamic instabilities of active liquid crystals: <span class="hlt">hybrid</span> lattice Boltzmann <span class="hlt">simulations</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Marenduzzo, D; Orlandini, E; Cates, M E; Yeomans, J M</p> <p>2007-09-01</p> <p>We report <span class="hlt">hybrid</span> lattice Boltzmann (HLB) <span class="hlt">simulations</span> of the hydrodynamics of an active nematic liquid crystal sandwiched between confining walls with various anchoring conditions. We confirm the existence of a transition between a passive phase and an active phase, in which there is spontaneous flow in the steady state. This transition is attained for sufficiently "extensile" rods, in the case of flow-aligning liquid crystals, and for sufficiently "contractile" ones for flow-tumbling materials. In a quasi-one-dimensional geometry, deep in the active phase of flow-aligning materials, our <span class="hlt">simulations</span> give evidence of hysteresis and history-dependent steady states, as well as of spontaneous banded flow. Flow-tumbling materials, in contrast, rearrange themselves so that only the two boundary layers flow in steady state. Two-dimensional <span class="hlt">simulations</span>, with periodic boundary conditions, show additional instabilities, with the spontaneous flow appearing as patterns made up of "convection rolls." These results demonstrate a remarkable richness (including dependence on anchoring conditions) in the steady-state phase behavior of active materials, even in the absence of external forcing; they have no counterpart for passive nematics. Our HLB methodology, which combines lattice Boltzmann for momentum transport with a finite difference scheme for the order parameter dynamics, offers a robust and efficient method for probing the complex hydrodynamic behavior of active nematics. PMID:17930285</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21282085','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21282085"><span id="translatedtitle">Full wave <span class="hlt">simulation</span> of lower <span class="hlt">hybrid</span> waves in Maxwellian plasma based on the finite element method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Meneghini, O.; Shiraiwa, S.; Parker, R.</p> <p>2009-09-15</p> <p>A full wave <span class="hlt">simulation</span> of the lower-<span class="hlt">hybrid</span> (LH) wave based on the finite element method is presented. For the LH wave, the most important terms of the dielectric tensor are the cold plasma contribution and the electron Landau damping (ELD) term, which depends only on the component of the wave vector parallel to the background magnetic field. The nonlocal hot plasma ELD effect was expressed as a convolution integral along the magnetic field lines and the resultant integro-differential Helmholtz equation was solved iteratively. The LH wave propagation in a Maxwellian tokamak plasma based on the Alcator C experiment was <span class="hlt">simulated</span> for electron temperatures in the range of 2.5-10 keV. Comparison with ray tracing <span class="hlt">simulations</span> showed good agreement when the single pass damping is strong. The advantages of the new approach include a significant reduction of computational requirements compared to full wave spectral methods and seamless treatment of the core, the scrape off layer and the launcher regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JCoPh.313..511I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JCoPh.313..511I"><span id="translatedtitle">A new <span class="hlt">hybrid</span> kinetic electron model for full-f gyrokinetic <span class="hlt">simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Idomura, Y.</p> <p>2016-05-01</p> <p>A new <span class="hlt">hybrid</span> kinetic electron model is developed for electrostatic full-f gyrokinetic <span class="hlt">simulations</span> of the ion temperature gradient driven trapped electron mode (ITG-TEM) turbulence at the ion scale. In the model, a full kinetic electron model is applied to the full-f gyrokinetic equation, the multi-species linear Fokker-Planck collision operator, and an axisymmetric part of the gyrokinetic Poisson equation, while in a non-axisymmetric part of the gyrokinetic Poisson equation, turbulent fluctuations are determined only by kinetic trapped electrons responses. By using this approach, the so-called ωH mode is avoided with keeping important physics such as the ITG-TEM, the neoclassical transport, the ambipolar condition, and particle trapping and detrapping processes. The model enables full-f gyrokinetic <span class="hlt">simulations</span> of ITG-TEM turbulence with a reasonable computational cost. Comparisons between flux driven ITG turbulence <span class="hlt">simulations</span> with kinetic and adiabatic electrons are presented. Although the similar ion temperature gradients with nonlinear upshift from linear critical gradients are sustained in quasi-steady states, parallel flows and radial electric fields are qualitatively different with kinetic electrons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DPPN12050B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DPPN12050B"><span id="translatedtitle">Full-wave <span class="hlt">simulations</span> of lower <span class="hlt">hybrid</span> wave propagation in the EAST tokamak</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonoli, P. T.; Lee, J. P.; Shiraiwa, S.; Wright, J. C.; Ding, B.; Yang, C.</p> <p>2015-11-01</p> <p>Studies of lower <span class="hlt">hybrid</span> (LH) wave propagation have been conducted in the EAST tokamak where electron Landau damping (ELD) of the wave is typically weak, resulting in multiple passes of the wave front prior to its being absorbed in the plasma core. Under these conditions it is interesting to investigate full-wave effects that can become important at the plasma cut-off where the wave is reflected at the edge, as well as full-wave effects such as caustic formation in the core. High fidelity LH full-wave <span class="hlt">simulations</span> were performed for EAST using the TORLH field solver. These <span class="hlt">simulations</span> used sufficient poloidal mode resolution to resolve the perpendicular wavelengths associated with electron Landau damping of the LH wave at the plasma periphery, thus achieving fully converged electric field solutions at all radii of the plasma. Comparison of these results with ray tracing <span class="hlt">simulations</span> will also be presented. Work supported by the US DOE under Contract No. DE-SC0010492 and DE-FC02-01ER54648.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25581253','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25581253"><span id="translatedtitle">Coarse-grained <span class="hlt">simulation</span> study of sequence effects on DNA <span class="hlt">hybridization</span> in a concentrated environment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Markegard, Cade B; Fu, Iris W; Reddy, K Anki; Nguyen, Hung D</p> <p>2015-02-01</p> <p>A novel coarse-grained model is developed to elucidate thermodynamics and kinetic mechanisms of DNA self-assembly. It accounts for sequence and solvent conditions to capture key experimental results such as sequence-dependent thermal property and salt-dependent persistence length of ssDNA and dsDNA. Moreover, constant-temperature <span class="hlt">simulations</span> on two single strands of a homogeneous sequence show two main mechanisms of <span class="hlt">hybridization</span>: a slow slithering mechanism and a one-order faster zippering mechanism. Furthermore, large-scale <span class="hlt">simulations</span> at a high DNA strand concentration demonstrate that DNA self-assembly is a robust and enthalpically driven process in which the formation of double helices is deciphered to occur via multiple self-assembly pathways including the strand displacement mechanism. However, sequence plays an important role in shifting the majority of one pathway over the others and controlling size distribution of self-assembled aggregates. This study yields a complex picture on the role of sequence on programmable self-assembly and demonstrates a promising <span class="hlt">simulation</span> tool that is suitable for studies in DNA nanotechnology. PMID:25581253</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22257161','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22257161"><span id="translatedtitle">A <span class="hlt">hybrid</span> stochastic-deconvolution model for large-eddy <span class="hlt">simulation</span> of particle-laden flow</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Michałek, W. R.; Kuerten, J. G. M.; Zeegers, J. C. H.; Liew, R.; Pozorski, J.; Geurts, B. J.</p> <p>2013-12-15</p> <p>We develop a <span class="hlt">hybrid</span> model for large-eddy <span class="hlt">simulation</span> of particle-laden turbulent flow, which is a combination of the approximate deconvolution model for the resolved scales and a stochastic model for the sub-grid scales. The stochastic model incorporates a priori results of direct numerical <span class="hlt">simulation</span> of turbulent channel flow, which showed that the parameters in the stochastic model are quite independent of Reynolds and Stokes number. In order to correctly predict the flux of particles towards the walls an extra term should be included in the stochastic model, which corresponds to the term related to the well-mixed condition in Langevin models for particle dispersion in inhomogeneous turbulent flow. The model predictions are compared with results of direct numerical <span class="hlt">simulation</span> of channel flow at a frictional Reynolds number of 950. The inclusion of the stochastic forcing is shown to yield a significant improvement over the approximate deconvolution model for the particles alone when combined with a Stokes dependent weight-factor for the well-mixed term.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DFD.F1013G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DFD.F1013G"><span id="translatedtitle"><span class="hlt">Simulation</span> of flow in the microcirculation using a <span class="hlt">hybrid</span> Lattice-Boltzman and Finite Element algorithm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gonzalez-Mancera, Andres; Gonzalez Cardenas, Diego</p> <p>2014-11-01</p> <p>Flow in the microcirculation is highly dependent on the mechanical properties of the cells suspended in the plasma. Red blood cells have to deform in order to pass through the smaller sections in the microcirculation. Certain deceases change the mechanical properties of red blood cells affecting its ability to deform and the rheological behaviour of blood. We developed a <span class="hlt">hybrid</span> algorithm based on the Lattice-Boltzmann and Finite Element methods to <span class="hlt">simulate</span> blood flow in small capillaries. Plasma was modeled as a Newtonian fluid and the red blood cells' membrane as a hyperelastic solid. The fluid-structure interaction was handled using the immersed boundary method. We <span class="hlt">simulated</span> the flow of plasma with suspended red blood cells through cylindrical capillaries and measured the pressure drop as a function of the membrane's rigidity. We also <span class="hlt">simulated</span> the flow through capillaries with a restriction and identify critical properties for which the suspended particles are unable to flow. The algorithm output was verified by reproducing certain common features of flow int he microcirculation such as the Fahraeus-Lindqvist effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM31B2484S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM31B2484S"><span id="translatedtitle">Titan's Interaction With the Supersonic Solar Wind During T96: A <span class="hlt">Hybrid</span> <span class="hlt">Simulation</span> Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simon, S.; Feyerabend, M.; Neubauer, F. M.; Motschmann, U. M.; Bertucci, C.; Edberg, N. J. T.; Hospodarsky, G. B.; Kurth, W. S.</p> <p>2015-12-01</p> <p>We apply a <span class="hlt">hybrid</span> <span class="hlt">simulation</span> code (kinetic ions, fluid electrons) to study the structure of Titan's plasma environment during the T96 flyby on 01 December 2013. The T96 encounter constitutes the only event of the Cassini era during which Titan was exposed to the supersonic solar wind upstream of Saturn's bow shock. Cassini plasma and magnetic field observations revealed a Venus/Mars-like plasma interaction, including the formation of a bow shock and a magnetic barrier upstream of Titan. However, it has also been suggested that the ambient solar wind conditions were not stationary at the time of the T96 encounter: around closest approach Cassini probably passed through a region of fossilized magnetic fields, arising from Titan's interaction with a previously encountered, high-pressure solar wind regime. To substantiate this hypothesis, we carry out <span class="hlt">simulation</span> runs for different ram pressures of the incident solar wind. The model reveals the interaction region to be dominated by kinetic effects, such as a splitting of the bow shock due to large ion gyroradii (shocklets). The <span class="hlt">simulation</span> results are compared against Cassini magnetic field data from T96.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26610134','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26610134"><span id="translatedtitle">First Principles <span class="hlt">Simulations</span> of the Infrared Spectrum of Liquid Water Using <span class="hlt">Hybrid</span> Density Functionals.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Cui; Donadio, Davide; Gygi, François; Galli, Giulia</p> <p>2011-05-10</p> <p>We show that first principles <span class="hlt">hybrid</span> functional (PBE0) <span class="hlt">simulations</span> of the infrared spectrum of liquid water yields a much better agreement with experimental results than a semilocal functional description; in particular, the quantitative accord with measured stretching and bending bands is very good. Such an improved description stems from two effects: a more accurate account, at the PBE0 level of theory, of the vibrational properties of the monomer and dimer and an underlying structural model for the liquid with a smaller number of hydrogen bonds and oxygen coordination than those obtained with semilocal functionals. The average electronic gap of the liquid is increased by 60% with respect to the PBE value, when computed at the PBE0 level of theory, and is in fair agreement with experimental results. PMID:26610134</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JNuM..463..367S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JNuM..463..367S"><span id="translatedtitle"><span class="hlt">Simulation</span> of hydrogen bubble growth in tungsten by a <span class="hlt">hybrid</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sang, Chaofeng; Sun, Jizhong; Bonnin, Xavier; Wang, L.; Wang, Dezhen</p> <p>2015-08-01</p> <p>A two dimensional <span class="hlt">hybrid</span> code (HIIPC-MC) joining rate-theory and Monte Carlo (MC) methods is developed in this work. We evaluate the cascade-coalescence mechanism contribution to the bubble growth by MC. First, effects of the starting radius and solute deuterium concentration on the bubble growth are studied; then the impacts of the wall temperature and implantation ion flux on the bubble growth are assessed. The <span class="hlt">simulation</span> indicates that the migration-coalescence of the bubbles and the high pressure inside the bubbles are the main driving forces for the bubble growth, and that neglect of the migration and coalescence would lead to an underestimation of the bubble growth or blistering.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014ESASP.724E.128Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014ESASP.724E.128Y&link_type=ABSTRACT"><span id="translatedtitle">Spaceborne <span class="hlt">Hybrid</span> Quad-Pol SAR Range Ambiguity Analysis and <span class="hlt">Simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Shilin; Li, Yang; Zhang, Jingjing; Hong, Wen</p> <p>2014-11-01</p> <p>The higher levels of range ambiguities in the cross-polarized measurement channels are the primary limitations for the matched quad-pol (e.g., HH, VV, VH, and HV) spaceborne synthetic aperture radar (SAR) systems. These ambiguities severely constrain the useful range of incident angles and the swath widths particularly at larger incidence. Adopting hybridpolarimetric architecture can remarkably reduce these ambiguities. In this paper, we analyse and develop the expression of range ambiguity to signal ratio (RASR) in the <span class="hlt">hybrid</span>-polarimetric architecture. <span class="hlt">Simulations</span> are made to testify this novel architecture’s advantage in the improvement of range ambiguities. The system operating parameters are derived from NASA’s DESDynl mission. In addition, we used the second order moments of polarimetric covariance matrices to depict target or the environment which are more precisely.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008ITEIS.128..656S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008ITEIS.128..656S"><span id="translatedtitle">Business Scenario Evaluation Method Using Monte Carlo <span class="hlt">Simulation</span> on Qualitative and Quantitative <span class="hlt">Hybrid</span> Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Samejima, Masaki; Akiyoshi, Masanori; Mitsukuni, Koshichiro; Komoda, Norihisa</p> <p></p> <p>We propose a business scenario evaluation method using qualitative and quantitative <span class="hlt">hybrid</span> model. In order to evaluate business factors with qualitative causal relations, we introduce statistical values based on propagation and combination of effects of business factors by Monte Carlo <span class="hlt">simulation</span>. In propagating an effect, we divide a range of each factor by landmarks and decide an effect to a destination node based on the divided ranges. In combining effects, we decide an effect of each arc using contribution degree and sum all effects. Through applied results to practical models, it is confirmed that there are no differences between results obtained by quantitative relations and results obtained by the proposed method at the risk rate of 5%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhRvE..86d6704C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhRvE..86d6704C"><span id="translatedtitle"><span class="hlt">Hybrid</span> electrodynamics and kinetics <span class="hlt">simulation</span> for electromagnetic wave propagation in weakly ionized hydrogen plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Qiang; Chen, Bin</p> <p>2012-10-01</p> <p>In this paper, a <span class="hlt">hybrid</span> electrodynamics and kinetics numerical model based on the finite-difference time-domain method and lattice Boltzmann method is presented for electromagnetic wave propagation in weakly ionized hydrogen plasmas. In this framework, the multicomponent Bhatnagar-Gross-Krook collision model considering both elastic and Coulomb collisions and the multicomponent force model based on the Guo model are introduced, which supply a hyperfine description on the interaction between electromagnetic wave and weakly ionized plasma. Cubic spline interpolation and mean filtering technique are separately introduced to solve the multiscalar problem and enhance the physical quantities, which are polluted by numerical noise. Several <span class="hlt">simulations</span> have been implemented to validate our model. The numerical results are consistent with a simplified analytical model, which demonstrates that this model can obtain satisfying numerical solutions successfully.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014snam.conf04304F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014snam.conf04304F"><span id="translatedtitle"><span class="hlt">Hybrid</span> parallel strategy for the <span class="hlt">simulation</span> of fast transient accidental situations at reactor scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faucher, V.; Galon, P.; Beccantini, A.; Crouzet, F.; Debaud, F.; Gautier, T.</p> <p>2014-06-01</p> <p>This contribution is dedicated to the latest methodological developments implemented in the fast transient dynamics software EUROPLEXUS (EPX) to <span class="hlt">simulate</span> the mechanical response of fully coupled fluid-structure systems to accidental situations to be considered at reactor scale, among which the Loss of Coolant Accident, the Core Disruptive Accident and the Hydrogen Explosion. Time integration is explicit and the search for reference solutions within the safety framework prevents any simplification and approximations in the coupled algorithm: for instance, all kinematic constraints are dealt with using Lagrange Multipliers, yielding a complex flow chart when non-permanent constraints such as unilateral contact or immersed fluid-structure boundaries are considered. The parallel acceleration of the solution process is then achieved through a <span class="hlt">hybrid</span> approach, based on a weighted domain decomposition for distributed memory computing and the use of the KAAPI library for self-balanced shared memory processing inside subdomains.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1720d0003F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1720d0003F"><span id="translatedtitle">Two-dimensional <span class="hlt">hybrid</span> <span class="hlt">simulations</span> of kinetic plasma turbulence: Current and vorticity vs proton temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Franci, Luca; Hellinger, Petr; Matteini, Lorenzo; Verdini, Andrea; Landi, Simone</p> <p>2016-03-01</p> <p>Proton temperature anisotropies between the directions parallel and perpendicular to the mean magnetic field are usually observed in the solar wind plasma. Here, we employ a high-resolution <span class="hlt">hybrid</span> particle-in-cell <span class="hlt">simulation</span> in order to investigate the relation between spatial properties of the proton temperature and the peaks in the current density and in the flow vorticity. Our results indicate that, although regions where the proton temperature is enhanced and temperature anisotropies are larger correspond approximately to regions where many thin current sheets form, no firm quantitative evidence supports the idea of a direct causality between the two phenomena. On the other hand, quite a clear correlation between the behavior of the proton temperature and the out-of-plane vorticity is obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22264175','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22264175"><span id="translatedtitle"><span class="hlt">Hybrid</span> multiphase CFD <span class="hlt">simulation</span> for liquid-liquid interfacial area prediction in annular centrifugal contactors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wardle, K.E.</p> <p>2013-07-01</p> <p>Liquid-liquid contacting equipment used in solvent extraction processes has the dual purpose of mixing and separating two immiscible fluids. Consequently, such devices inherently encompass a wide variety of multiphase flow regimes. A <span class="hlt">hybrid</span> multiphase computational fluid dynamics (CFD) solver which combines the Eulerian multi-fluid method with VOF (volume of fluid) sharp interface capturing has been developed for application to annular centrifugal contactors. This solver has been extended to enable prediction of mean droplet size and liquid-liquid interfacial area through a single moment population balance method. <span class="hlt">Simulations</span> of liquid-liquid mixing in a simplified geometry and a model annular centrifugal contactor are reported with droplet breakup/coalescence models being calibrated versus available experimental data. Quantitative comparison is made for two different housing vane geometries and it is found that the predicted droplet size is significantly smaller for vane geometries which result in higher annular liquid holdup.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1115320','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1115320"><span id="translatedtitle"><span class="hlt">Hybrid</span> models for the <span class="hlt">simulation</span> of microstructural evolution influenced by coupled, multiple physical processes.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tikare, Veena; Hernandez-Rivera, Efrain; Madison, Jonathan D.; Holm, Elizabeth Ann; Patterson, Burton R.; Homer, Eric R.</p> <p>2013-09-01</p> <p>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. <span class="hlt">Hybrid</span> 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 <span class="hlt">simulation</span> at the mesoscale of microstructural evolution processes by kinetic Monte Carlo methods. This makes these codes readily accessible and adaptable for future applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhPl...21c2706T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhPl...21c2706T"><span id="translatedtitle">A <span class="hlt">hybrid</span> model for coupling kinetic corrections of fusion reactivity to hydrodynamic implosion <span class="hlt">simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, Xian-Zhu; McDevitt, C. J.; Guo, Zehua; Berk, H. L.</p> <p>2014-03-01</p> <p>Inertial confinement fusion requires an imploded target in which a central hot spot is surrounded by a cold and dense pusher. The hot spot/pusher interface can take complicated shape in three dimensions due to hydrodynamic mix. It is also a transition region where the Knudsen and inverse Knudsen layer effect can significantly modify the fusion reactivity in comparison with the commonly used value evaluated with background Maxwellians. Here, we describe a <span class="hlt">hybrid</span> model that couples the kinetic correction of fusion reactivity to global hydrodynamic implosion <span class="hlt">simulations</span>. The key ingredient is a non-perturbative treatment of the tail ions in the interface region where the Gamow ion Knudsen number approaches or surpasses order unity. The accuracy of the coupling scheme is controlled by the precise criteria for matching the non-perturbative kinetic model to perturbative solutions in both configuration space and velocity space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PThPS.178..149O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PThPS.178..149O"><span id="translatedtitle">A Suite of <span class="hlt">Hybrid</span> <span class="hlt">Simulation</span> Schemes for Nano-to-Micrometer Scale Processes at Solid-Fluid Interfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ogata, S.; Kobayashi, R.; Gotoh, T.</p> <p></p> <p>Computer <span class="hlt">simulation</span> of a variety of solid-fluid interfaces in nano-to-micrometer scales has attracted much attention in recent years. We have been developing the <span class="hlt">hybrid</span> <span class="hlt">simulation</span> schemes to apply them to the interfaces at realistic settings without losing physical accuracies, by concurrently coupling the electronic density-functional theory (DFT), the molecular dynamics (MD), the recursive coarse-grained particle (RCGP) method, and the lattice Boltzmann equation (LBE) method. In the <span class="hlt">hybrid</span> DFT-MD <span class="hlt">simulation</span> scheme, multiple DFT regions each of which is composed of a relatively small number of atoms are embedded in a system of classical MD atoms. For robust coupling of the DFT and MD regions with reasonable mechanical accuracies the buffered-cluster method is adopted, which requires no link-atoms and is applicable to a wide range of materials and settings. The sizes and number of the DFT regions change adaptively to trace the chemical reactions during the <span class="hlt">simulation</span> run. T he <span class="hlt">hybrid</span> DFT-MD <span class="hlt">simulation</span> scheme is successfully applied to various interesting processes including the atomic-scale friction between nano-scale objects. Useful MD <span class="hlt">simulation</span> requires realistic, dynamic boundary conditions to the atoms. We develop the RCGP method to coarse-grain the atomic system in the solid phase, in which each particle represents a group of the atoms and the inter-particle interaction is constructed by renormalizing the inter-atomic interaction in a recursive manner under the assumption of the local statistical equilibrium. The RCGP method has attractive features such as its natural incorporation of the atomic phonons in the thermal equilibrium and its potential suitableness to connection to the atomistic system. In the <span class="hlt">hybrid</span> RCGP-MD <span class="hlt">simulation</span> scheme, the overall shape of the total system calculated with the RCGP method gives the dynamics boundary conditions to the MD regions. A nano-thrusting <span class="hlt">simulation</span> of a structured Al system that demonstrates rea sonable coupling of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26701343','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26701343"><span id="translatedtitle"><span class="hlt">Hybrid</span> Seminumerical <span class="hlt">Simulation</span> Scheme to Predict Transducer Outputs of Acoustic Microscopes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nierla, Michael; Rupitsch, Stefan J</p> <p>2016-02-01</p> <p>We present a seminumerical <span class="hlt">simulation</span> method called SIRFEM, which enables the efficient prediction of high-frequency transducer outputs. In particular, this is important for acoustic microscopy where the specimen under investigation is immersed in a coupling fluid. Conventional finite-element (FE) <span class="hlt">simulations</span> for such applications would consume too much computational power due to the required spatial and temporal discretization, especially for the coupling fluid between ultrasonic transducer and specimen. However, FE <span class="hlt">simulations</span> are in most cases essential to consider the mode conversion at and inside the solid specimen as well as the wave propagation in its interior. SIRFEM reduces the computational effort of pure FE <span class="hlt">simulations</span> by treating only the solid specimen and a small part of the fluid layer with FE. The propagation in the coupling fluid from transducer to specimen and back is processed by the so-called spatial impulse response (SIR). Through this <span class="hlt">hybrid</span> approach, the number of elements as well as the number of time steps for the FE <span class="hlt">simulation</span> can be reduced significantly, as it is presented for an axis-symmetric setup. Three B-mode images of a plane 2-D setup-computed at a transducer center frequency of 20 MHz-show that SIRFEM is, furthermore, able to predict reflections at inner structures as well as multiple reflections between those structures and the specimen's surface. For the purpose of a pure 2-D setup, the SIR of a curved-line transducer is derived and compared to the response function of a cylindrically focused aperture of negligible extend in the third spatial dimension. PMID:26701343</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhPl...20f2107Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhPl...20f2107Q"><span id="translatedtitle"><span class="hlt">Simulation</span> of linear and nonlinear Landau damping of lower <span class="hlt">hybrid</span> waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qi, Lei; Wang, X. Y.; Lin, Y.</p> <p>2013-06-01</p> <p>The linear physics of lower <span class="hlt">hybrid</span> waves (LHWs) and their nonlinear interaction with particles through Landau damping are studied with the gyrokinetic electron and fully kinetic ion (GeFi) particle <span class="hlt">simulation</span> model in the electrostatic limit. Unlike most other wave modes, the LHWs can resonantly interact with both electrons and ions, with the former being highly magnetized and latter nearly unmagnetized around the lower <span class="hlt">hybrid</span> frequency. Direct interactions of LHWs with electrons and/or ions are investigated for cases with various k∥/k ,Ti/Te, and wave amplitudes. In the linear electron Landau damping (ELD), the dispersion relation and the linear damping rate obtained from our <span class="hlt">simulation</span> agree well with the analytical linear theory. As the wave amplitude increases, the nonlinear Landau effects are present, and a transition from strong decay at smaller amplitudes to weak decay at larger amplitudes is observed. In the nonlinear stage, the LHWs in the long time evolution finally exhibit a steady Bernstein-Greene-Kruskal mode, in which the wave amplitude is saturated above the noise level. While the resonant electrons are trapped in the wave field in the nonlinear ELD, the resonant ions are untrapped in the LHW time scales. The ion Landau damping is thus predominantly in a linear fashion, leading to a wave saturation level significantly lower than that in the ELD. On the long time scales, however, the ions are still weakly trapped. The results show a coupling between the LHW frequency and the ion cyclotron frequency during the long-time LHW evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1000755','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1000755"><span id="translatedtitle">GIS-BASED <span class="hlt">1</span>-<span class="hlt">D</span> DIFFUSIVE WAVE OVERLAND FLOW MODEL</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>KALYANAPU, ALFRED; MCPHERSON, TIMOTHY N.; BURIAN, STEVEN J.</p> <p>2007-01-17</p> <p>This paper presents a GIS-based <span class="hlt">1</span>-<span class="hlt">d</span> distributed overland flow model and summarizes an application to <span class="hlt">simulate</span> a flood event. The model estimates infiltration using the Green-Ampt approach and routes excess rainfall using the <span class="hlt">1</span>-<span class="hlt">d</span> diffusive wave approximation. The model was designed to use readily available topographic, soils, and land use/land cover data and rainfall predictions from a meteorological model. An assessment of model performance was performed for a small catchment and a large watershed, both in urban environments. <span class="hlt">Simulated</span> runoff hydrographs were compared to observations for a selected set of validation events. Results confirmed the model provides reasonable predictions in a short period of time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26961319','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26961319"><span id="translatedtitle">Modeling, control, and <span class="hlt">simulation</span> of grid connected intelligent <span class="hlt">hybrid</span> battery/photovoltaic system using new <span class="hlt">hybrid</span> fuzzy-neural method.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rezvani, Alireza; Khalili, Abbas; Mazareie, Alireza; Gandomkar, Majid</p> <p>2016-07-01</p> <p>Nowadays, photovoltaic (PV) generation is growing increasingly fast as a renewable energy source. Nevertheless, the drawback of the PV system is its dependence on weather conditions. Therefore, battery energy storage (BES) can be considered to assist for a stable and reliable output from PV generation system for loads and improve the dynamic performance of the whole generation system in grid connected mode. In this paper, a novel topology of intelligent <span class="hlt">hybrid</span> generation systems with PV and BES in a DC-coupled structure is presented. Each photovoltaic cell has a specific point named maximum power point on its operational curve (i.e. current-voltage or power-voltage curve) in which it can generate maximum power. Irradiance and temperature changes affect these operational curves. Therefore, the nonlinear characteristic of maximum power point to environment has caused to development of different maximum power point tracking techniques. In order to capture the maximum power point (MPP), a <span class="hlt">hybrid</span> fuzzy-neural maximum power point tracking (MPPT) method is applied in the PV system. Obtained results represent the effectiveness and superiority of the proposed method, and the average tracking efficiency of the <span class="hlt">hybrid</span> fuzzy-neural is incremented by approximately two percentage points in comparison to the conventional methods. It has the advantages of robustness, fast response and good performance. A detailed mathematical model and a control approach of a three-phase grid-connected intelligent <span class="hlt">hybrid</span> system have been proposed using Matlab/Simulink. PMID:26961319</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JCoPh.313..279W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JCoPh.313..279W"><span id="translatedtitle">A <span class="hlt">hybrid</span> model for <span class="hlt">simulating</span> rogue waves in random seas on a large temporal and spatial scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Jinghua; Ma, Q. W.; Yan, S.</p> <p>2016-05-01</p> <p>A <span class="hlt">hybrid</span> model for <span class="hlt">simulating</span> rogue waves in random seas on a large temporal and spatial scale is proposed in this paper. It is formed by combining the derived fifth order Enhanced Nonlinear Schrödinger Equation based on Fourier transform, the Enhanced Spectral Boundary Integral (ESBI) method and its simplified version. The numerical techniques and algorithm for coupling three models on time scale are suggested. Using the algorithm, the switch between the three models during the computation is triggered automatically according to wave nonlinearities. Numerical tests are carried out and the results indicate that this <span class="hlt">hybrid</span> model could <span class="hlt">simulate</span> rogue waves both accurately and efficiently. In some cases discussed, the <span class="hlt">hybrid</span> model is more than 10 times faster than just using the ESBI method, and it is also much faster than other methods reported in the literature.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CoPhC.186...71K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CoPhC.186...71K"><span id="translatedtitle">AstroPhi: A code for complex <span class="hlt">simulation</span> of the dynamics of astrophysical objects using <span class="hlt">hybrid</span> supercomputers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kulikov, I. M.; Chernykh, I. G.; Snytnikov, A. V.; Glinskiy, B. M.; Tutukov, A. V.</p> <p>2015-01-01</p> <p>We propose a new code named AstroPhi for <span class="hlt">simulation</span> of the dynamics of astrophysical objects on <span class="hlt">hybrid</span> supercomputers equipped with Intel Xenon Phi computation accelerators. The details of parallel implementation are described, as well as changes to the computational algorithm that facilitate efficient parallel implementation. A single Xeon Phi accelerator yielded 27-fold acceleration. The use of 32 Xeon Phi accelerators resulted in 94% parallel efficiency. Several collapse problems are <span class="hlt">simulated</span> using the AstroPhi code.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24403412','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24403412"><span id="translatedtitle">Ultra-fast <span class="hlt">hybrid</span> CPU-GPU multiple scatter <span class="hlt">simulation</span> for 3-D PET.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Kyung Sang; Son, Young Don; Cho, Zang Hee; Ra, Jong Beom; Ye, Jong Chul</p> <p>2014-01-01</p> <p>Scatter correction is very important in 3-D PET reconstruction due to a large scatter contribution in measurements. Currently, one of the most popular methods is the so-called single scatter <span class="hlt">simulation</span> (SSS), which considers single Compton scattering contributions from many randomly distributed scatter points. The SSS enables a fast calculation of scattering with a relatively high accuracy; however, the accuracy of SSS is dependent on the accuracy of tail fitting to find a correct scaling factor, which is often difficult in low photon count measurements. To overcome this drawback as well as to improve accuracy of scatter estimation by incorporating multiple scattering contribution, we propose a multiple scatter <span class="hlt">simulation</span> (MSS) based on a simplified Monte Carlo (MC) <span class="hlt">simulation</span> that considers photon migration and interactions due to photoelectric absorption and Compton scattering. Unlike the SSS, the MSS calculates a scaling factor by comparing <span class="hlt">simulated</span> prompt data with the measured data in the whole volume, which enables a more robust estimation of a scaling factor. Even though the proposed MSS is based on MC, a significant acceleration of the computational time is possible by using a virtual detector array with a larger pitch by exploiting that the scatter distribution varies slowly in spatial domain. Furthermore, our MSS implementation is nicely fit to a parallel implementation using graphic processor unit (GPU). In particular, we exploit a <span class="hlt">hybrid</span> CPU-GPU technique using the open multiprocessing and the compute unified device architecture, which results in 128.3 times faster than using a single CPU. Overall, the computational time of MSS is 9.4 s for a high-resolution research tomograph (HRRT) system. The performance of the proposed MSS is validated through actual experiments using an HRRT. PMID:24403412</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2072063','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2072063"><span id="translatedtitle"><span class="hlt">Hybrid</span> Quantum Mechanical/Molecular Mechanical Molecular Dynamics <span class="hlt">Simulations</span> of HIV-1 Integrase/Inhibitor Complexes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Nunthaboot, Nadtanet; Pianwanit, Somsak; Parasuk, Vudhichai; Ebalunode, Jerry O.; Briggs, James M.; Kokpol, Sirirat</p> <p>2007-01-01</p> <p>Human immunodeficiency virus (HIV)-1 integrase (IN) is an attractive target for development of acquired immunodeficiency syndrome chemotherapy. In this study, conventional and coupled quantum mechanical and molecular mechanical (QM/MM) molecular dynamics (MD) <span class="hlt">simulations</span> of HIV-1 IN complexed with 5CITEP (IN-5CITEP) were carried out. In addition to differences in the bound position of 5CITEP, significant differences at the two levels of theory were observed in the metal coordination geometry and the areas involving residues 116–119 and 140–166. In the conventional MD <span class="hlt">simulation</span>, the coordination of Mg2+ was found to be a near-perfect octahedral geometry whereas a distorted octahedral complex was observed in QM/MM. All of the above reasons lead to a different pattern of protein-ligand salt link formation that was not observed in the classical MD <span class="hlt">simulation</span>. Furthermore to provide a theoretical understanding of inhibition mechanisms of 5CITEP and its derivative (DKA), <span class="hlt">hybrid</span> QM/MM MD <span class="hlt">simulations</span> of the two complexes (IN-5CITEP and IN-DKA) have been performed. The results reveal that areas involving residues 60–68, 116–119, and 140–149 were substantially different among the two systems. The two systems show similar pattern of metal coordination geometry, i.e., a distorted octahedron. In IN-DKA, both OD1 and OD2 of Asp-64 coordinate the Mg2+ in a monodentate fashion whereas only OD1 is chelated to the metal as observed in IN-5CITEP. The high potency of DKA as compared to 5CITEP is supported by a strong salt link formed between its carboxylate moiety and the ammonium group of Lys-159. Detailed comparisons between HIV-1 IN complexed with DKA and with 5CITEP provide information about ligand structure effects on protein-ligand interactions in particular with the Lys-159. This is useful for the design of new selective HIV-1 IN inhibitors. PMID:17693479</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvL.115p0504C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvL.115p0504C"><span id="translatedtitle">Proposal for High-Fidelity Quantum <span class="hlt">Simulation</span> Using a <span class="hlt">Hybrid</span> Dressed State</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Jianming; Cohen, Itsik; Retzker, Alex; Plenio, Martin B.</p> <p>2015-10-01</p> <p>A fundamental goal of quantum technologies concerns the exploitation of quantum coherent dynamics for the realization of novel quantum applications such as quantum computing, quantum <span class="hlt">simulation</span>, and quantum metrology. A key challenge on the way towards these goals remains the protection of quantum coherent dynamics from environmental noise. Here, we propose a concept of a <span class="hlt">hybrid</span> dressed state from a pair of continuously driven systems. It allows sufficiently strong driving fields to suppress the effect of environmental noise while at the same time being insusceptible to both the amplitude and phase noise in the continuous driving fields. This combination of robust features significantly enhances coherence times under realistic conditions and at the same time provides new flexibility in Hamiltonian engineering that otherwise is not achievable. We demonstrate theoretically applications of our scheme for a noise-resistant analog quantum <span class="hlt">simulation</span> in the well-studied physical systems of nitrogen-vacancy centers in diamond and of trapped ions. The scheme may also be exploited for quantum computation and quantum metrology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009P%26SS...57.2113K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009P%26SS...57.2113K"><span id="translatedtitle">The plasma interaction of Enceladus: 3D <span class="hlt">hybrid</span> <span class="hlt">simulations</span> and comparison with Cassini MAG data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kriegel, H.; Simon, S.; Müller, J.; Motschmann, U.; Saur, J.; Glassmeier, K.-H.; Dougherty, M. K.</p> <p>2009-12-01</p> <p>We study the interaction of Saturn's small, icy moon Enceladus and its plume with the corotating magnetospheric plasma by means of a 3D <span class="hlt">hybrid</span> <span class="hlt">simulation</span> model, which treats the ions as individual particles and the electrons as a massless, charge-neutralizing fluid. We analyze systematically how Enceladus' internal conductivity and plasma absorption at the surface as well as charge exchange and pick-up in the plume contribute to the overall structure of the interaction region. Furthermore, we provide a comparison of our <span class="hlt">simulation</span> results to data obtained by the Cassini magnetometer instrument. The major findings of this study are: (1) the magnetic field diffuses through the solid body of Enceladus almost unaffected, whereas plasma absorption gives rise to a symmetric depletion wake downstream of the moon; (2) due to the small gyroradii of the newly generated plume ions, the pick-up tail possesses a 2D structure; (3) the magnetic field lines drape around the plume, which triggers an Alfvén wing system that dominates the structure of Enceladus' plasma environment. Inside the plume itself, a magnetic cavity is formed; (4) besides the reproduction of the key features of the observed magnetic field signatures, evidence for variability in the locations of the active jets and in the total gas content of the plume are shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4701310','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4701310"><span id="translatedtitle"><span class="hlt">Hybrid</span> Molecular and Spin Dynamics <span class="hlt">Simulations</span> for Ensembles of Magnetic Nanoparticles for Magnetoresistive Systems</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Teich, Lisa; Schröder, Christian</p> <p>2015-01-01</p> <p>The development of magnetoresistive sensors based on magnetic nanoparticles which are immersed in conductive gel matrices requires detailed information about the corresponding magnetoresistive properties in order to obtain optimal sensor sensitivities. Here, crucial parameters are the particle concentration, the viscosity of the gel matrix and the particle structure. Experimentally, it is not possible to obtain detailed information about the magnetic microstructure, i.e., orientations of the magnetic moments of the particles that define the magnetoresistive properties, however, by using numerical <span class="hlt">simulations</span> one can study the magnetic microstructure theoretically, although this requires performing classical spin dynamics and molecular dynamics <span class="hlt">simulations</span> simultaneously. Here, we present such an approach which allows us to calculate the orientation and the trajectory of every single magnetic nanoparticle. This enables us to study not only the static magnetic microstructure, but also the dynamics of the structuring process in the gel matrix itself. With our <span class="hlt">hybrid</span> approach, arbitrary sensor configurations can be investigated and their magnetoresistive properties can be optimized. PMID:26580623</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/489408','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/489408"><span id="translatedtitle">A <span class="hlt">hybrid</span> symplectic PIC/spectral scheme for one-dimensional electrostatic <span class="hlt">simulations</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Doxas, I.; Cary, J.R.</p> <p>1996-12-31</p> <p>We develop a <span class="hlt">hybrid</span> PIC/spectral integration scheme based on the explicit symplectic integrator of reference. We find that for low-accuracy short-term integration (5% accuracy over {omega}{sub p}t = 500) the second-order symplectic method is most efficient, outperforming the fourth-order method by 65% and non-symplectic methods such as Runge-Kutta, Bulirsch-Stoer and {open_quote}naive{close_quote} leap-frog by a factor of 3-10. For high-accuracy short-term integration (10{sup -4} over w{sub p}t = 500) the second-order symplectic method is 20% more efficient than both the fourth-order method and Bulirsch-Stoer, and a factor of 8-20 more efficient than Runge-Kutta and {open_quote}naive{close_quote} leap-frog. For long-term integration (w{sub p}t = 10{sup 5}) the second order symplectic method outperforms all non-symplectic methods by a factor of 8-20. We also show that the symplectic method is more robust to roundoff error than all other methods we tested, and that for <span class="hlt">simulations</span> with a small number of particles per wavelength (usuall in plasma <span class="hlt">simulations</span>) cubic spline interpolation is more efficient that linear interpolation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PlST...18..394W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PlST...18..394W&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Hybrid</span> <span class="hlt">Simulation</span> of Duty Cycle Influences on Pulse Modulated RF SiH4/Ar Discharge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Xifeng; Song, Yuanhong; Zhao, Shuxia; Dai, Zhongling; Wang, Younian</p> <p>2016-04-01</p> <p>A one-dimensional fluid/Monte-Carlo (MC) <span class="hlt">hybrid</span> model is developed to describe capacitively coupled SiH4/Ar discharge, in which the lower electrode is applied by a RF source and pulse modulated by a square-wave, to investigate the modulation effects of the pulse duty cycle on the discharge mechanism. An electron Monte Carlo <span class="hlt">simulation</span> is used to calculate the electron energy distribution as a function of position and time phase. Rate coefficients in chemical reactions can then be obtained and transferred to the fluid model for the calculation of electron temperature and densities of different species, such as electrons, ions, and radicals. The <span class="hlt">simulation</span> results show that, the electron energy distribution f(ɛ) is modulated evidently within a pulse cycle, with its tail extending to higher energies during the power-on period, while shrinking back promptly in the afterglow period. Thus, the rate coefficients could be controlled during the discharge, resulting in modulation of the species composition on the substrate compared with continuous excitation. Meanwhile, more negative ions, like SiH‑3 and SiH‑2, may escape to the electrodes owing to the collapse of ambipolar electric fields, which is beneficial to films deposition. Pulse modulation is thus expected to provide additional methods to customize the plasma densities and components. supported by National Natural Science Foundation of China (No. 11275038)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020079884','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020079884"><span id="translatedtitle">Wave-Particle Interactions Associated with Nongyrotropic Distribution Functions: A <span class="hlt">Hybrid</span> <span class="hlt">Simulation</span> Study</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Convery, P. D.; Schriver, D.; Ashour-Abdalla, M.; Richard, R. L.</p> <p>2002-01-01</p> <p>Nongyrotropic plasma distribution functions can be formed in regions of space where guiding center motion breaks down as a result of strongly curved and weak ambient magnetic fields. Such are the conditions near the current sheet in the Earth's middle and distant magnetotail, where observations of nongyrotropic ion distributions have been made. Here a systematic parameter study of nongyrotropic proton distributions using electromagnetic <span class="hlt">hybrid</span> <span class="hlt">simulations</span> is made. We model the observed nongyrotropic distributions by removing a number of arc length segments from a cold ring distribution and find significant differences with the results of <span class="hlt">simulations</span> that initially have a gyrotropic ring distribution. Model nongyrotropic distributions with initially small perpendicular thermalization produce growing fluctuations that diffuse the ions into a stable Maxwellian-like distribution within a few proton gyro periods. The growing waves produced by nongyrotropic distributions are similar to the electromagnetic proton cyclotron waves produced by a gyrotropic proton ring distribution in that they propagate parallel to the background magnetic field and occur at frequencies on the order of the proton gyrofrequency, The maximum energy of the fluctuating magnetic field increases as the initial proton distribution is made more nongyrotropic, that is, more highly bunched in perpendicular velocity space. This increase can be as much as twice the energy produced in the gyrotropic case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26550857','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26550857"><span id="translatedtitle">Proposal for High-Fidelity Quantum <span class="hlt">Simulation</span> Using a <span class="hlt">Hybrid</span> Dressed State.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cai, Jianming; Cohen, Itsik; Retzker, Alex; Plenio, Martin B</p> <p>2015-10-16</p> <p>A fundamental goal of quantum technologies concerns the exploitation of quantum coherent dynamics for the realization of novel quantum applications such as quantum computing, quantum <span class="hlt">simulation</span>, and quantum metrology. A key challenge on the way towards these goals remains the protection of quantum coherent dynamics from environmental noise. Here, we propose a concept of a <span class="hlt">hybrid</span> dressed state from a pair of continuously driven systems. It allows sufficiently strong driving fields to suppress the effect of environmental noise while at the same time being insusceptible to both the amplitude and phase noise in the continuous driving fields. This combination of robust features significantly enhances coherence times under realistic conditions and at the same time provides new flexibility in Hamiltonian engineering that otherwise is not achievable. We demonstrate theoretically applications of our scheme for a noise-resistant analog quantum <span class="hlt">simulation</span> in the well-studied physical systems of nitrogen-vacancy centers in diamond and of trapped ions. The scheme may also be exploited for quantum computation and quantum metrology. PMID:26550857</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JCoPh.291..177G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JCoPh.291..177G"><span id="translatedtitle"><span class="hlt">Hybrid</span> Lattice Boltzmann/Finite Difference <span class="hlt">simulations</span> of viscoelastic multicomponent flows in confined geometries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gupta, A.; Sbragaglia, M.; Scagliarini, A.</p> <p>2015-06-01</p> <p>We propose numerical <span class="hlt">simulations</span> of viscoelastic fluids based on a <span class="hlt">hybrid</span> algorithm combining Lattice-Boltzmann models (LBM) and Finite Differences (FD) schemes, the former used to model the macroscopic hydrodynamic equations, and the latter used to model the polymer dynamics. The kinetics of the polymers is introduced using constitutive equations for viscoelastic fluids with finitely extensible non-linear elastic dumbbells with Peterlin's closure (FENE-P). The numerical model is first benchmarked by characterizing the rheological behavior of dilute homogeneous solutions in various configurations, including steady shear, elongational flows, transient shear and oscillatory flows. As an upgrade of complexity, we study the model in presence of non-ideal multicomponent interfaces, where immiscibility is introduced in the LBM description using the "Shan-Chen" interaction model. The problem of a confined viscoelastic (Newtonian) droplet in a Newtonian (viscoelastic) matrix under simple shear is investigated and numerical results are compared with the predictions of various theoretical models. The proposed numerical <span class="hlt">simulations</span> explore problems where the capabilities of LBM were never quantified before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008cosp...37.1275H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008cosp...37.1275H"><span id="translatedtitle">Shock Injection Problem and Beyond in <span class="hlt">Hybrid</span>/Particle-in-Cell <span class="hlt">Simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoshino, Masahiro</p> <p></p> <p>Collisionless shocks are a rich repository of nonlinear plasma instabilities and the self-regulated system of plasma waves, and provide not only quick thermalization but also nonthermal particle acceleration. One of the most widely accepted models of the nonthermal particle acceleration is the diffusive shock acceleration (DSA), which was established in the late seventies. In order that DSA operates effectively, however, the pre-acceleration of particles - the acceleration from the thermal into the suprathermal energies - is needed, namely, the so-called "shock injection problem" remains elusive. The transition from the thermal energies, the suprathermal energies, and the high energy nothermal particles are not well understood yet. With the recent advance of supper computer technology, kinetic plasma modeling by <span class="hlt">hybrid</span>/particle-in-cell <span class="hlt">simulations</span> are widely used for understanding the shock dynamics and the particle acceleration mechanisms etc. The modern computer capability is not enough to demonstrate DAS or other strong particle acceleration processes yet, but a great progress is now obtained. In this review talk, we discuss several important progresses: the pre-acceleration at the shock front as the particle injection problem, the turbulent wave generation in the shock transition/upstream as the particle scatterers of DAS, and the magnetic field amplification and so on. We will also give a perspective of the shock acceleration in the future <span class="hlt">simulation</span> study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24778597','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24778597"><span id="translatedtitle">Assessing the impact of policy changes in the Icelandic cod fishery using a <span class="hlt">hybrid</span> <span class="hlt">simulation</span> model.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sigurðardóttir, Sigríður; Johansson, Björn; Margeirsson, Sveinn; Viðarsson, Jónas R</p> <p>2014-01-01</p> <p>Most of the Icelandic cod is caught in bottom trawlers or longliners. These two fishing methods are fundamentally different and have different economic, environmental, and even social effects. In this paper we present a <span class="hlt">hybrid-simulation</span> framework to assess the impact of changing the ratio between cod quota allocated to vessels with longlines and vessels with bottom trawls. It makes use of conventional bioeconomic models and discrete event modelling and provides a framework for <span class="hlt">simulating</span> life cycle assessment (LCA) for a cod fishery. The model consists of two submodels, a system dynamics model describing the biological aspect of the fishery and a discrete event model for fishing activities. The model was run multiple times for different quota allocation scenarios and results are presented where different scenarios are presented in the three dimensions of sustainability: environmental, social, and economic. The optimal allocation strategy depends on weighing the three different factors. The results were encouraging first-steps towards a useful modelling method but the study would benefit greatly from better data on fishing activities. PMID:24778597</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..GECGT1048K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..GECGT1048K"><span id="translatedtitle">BCA-kMC <span class="hlt">Hybrid</span> <span class="hlt">Simulation</span> for Hydrogen and Helium Implantation in Material under Plasma Irradiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kato, Shuichi; Ito, Atsushi; Sasao, Mamiko; Nakamura, Hiroaki; Wada, Motoi</p> <p>2015-09-01</p> <p>Ion implantation by plasma irradiation into materials achieves the very high concentration of impurity. The high concentration of impurity causes the deformation and the destruction of the material. This is the peculiar phenomena in the plasma-material interaction (PMI). The injection process of plasma particles are generally <span class="hlt">simulated</span> by using the binary collision approximation (BCA) and the molecular dynamics (MD), while the diffusion of implanted atoms have been traditionally solved by the diffusion equation, in which the implanted atoms is replaced by the continuous concentration field. However, the diffusion equation has insufficient accuracy in the case of low concentration, and in the case of local high concentration such as the hydrogen blistering and the helium bubble. The above problem is overcome by kinetic Monte Carlo (kMC) which represents the diffusion of the implanted atoms as jumps on interstitial sites in a material. In this paper, we propose the new approach ``BCA-kMC <span class="hlt">hybrid</span> <span class="hlt">simulation</span>'' for the hydrogen and helium implantation under the plasma irradiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3977218','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3977218"><span id="translatedtitle">Assessing the Impact of Policy Changes in the Icelandic Cod Fishery Using a <span class="hlt">Hybrid</span> <span class="hlt">Simulation</span> Model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sigurðardóttir, Sigríður; Johansson, Björn; Margeirsson, Sveinn; Viðarsson, Jónas R.</p> <p>2014-01-01</p> <p>Most of the Icelandic cod is caught in bottom trawlers or longliners. These two fishing methods are fundamentally different and have different economic, environmental, and even social effects. In this paper we present a <span class="hlt">hybrid-simulation</span> framework to assess the impact of changing the ratio between cod quota allocated to vessels with longlines and vessels with bottom trawls. It makes use of conventional bioeconomic models and discrete event modelling and provides a framework for <span class="hlt">simulating</span> life cycle assessment (LCA) for a cod fishery. The model consists of two submodels, a system dynamics model describing the biological aspect of the fishery and a discrete event model for fishing activities. The model was run multiple times for different quota allocation scenarios and results are presented where different scenarios are presented in the three dimensions of sustainability: environmental, social, and economic. The optimal allocation strategy depends on weighing the three different factors. The results were encouraging first-steps towards a useful modelling method but the study would benefit greatly from better data on fishing activities. PMID:24778597</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARP34007G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARP34007G"><span id="translatedtitle">Effect of Backbone Design on <span class="hlt">Hybridization</span> Thermodynamics of Oligo-nucleic Acids: A Coarse-Grained Molecular Dynamics <span class="hlt">Simulation</span> Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghobadi, Ahmadreza F.; Jayaraman, Arthi</p> <p></p> <p>DNA <span class="hlt">hybridization</span> is the basis of various bio-nano technologies, such as DNA origami and assembly of DNA-functionalized nanoparticles. A <span class="hlt">hybridized</span> double stranded (ds) DNA is formed when complementary nucleobases on <span class="hlt">hybridizing</span> strands exhibit specific and directional hydrogen bonds through canonical Watson-Crick base-pairing interactions. In recent years, the need for cheaper alternatives and significant synthetic advances have driven design of DNA mimics with new backbone chemistries. However, a fundamental understanding of how these backbone modifications in the oligo-nucleic acids impact the <span class="hlt">hybridization</span> and melting behavior of the duplex is still lacking. In this talk, we present our recent findings on impact of varying backbone chemistry on <span class="hlt">hybridization</span> of oligo-nucleic acid duplexes. We use coarse-grained molecular dynamics <span class="hlt">simulations</span> to isolate the effect of strand flexibility, electrostatic interactions and nucleobase spacing on the melting curves for duplexes with various strand sequences and concentrations. Since conjugation of oligo-nucleic acids with polymers serve as building blocks for thermo-responsive polymer networks and gels, we also present the effect of such conjugation on <span class="hlt">hybridization</span> thermodynamics and polymer conformation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JCoPh.316..193M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JCoPh.316..193M&link_type=ABSTRACT"><span id="translatedtitle">A <span class="hlt">hybrid</span> formulation for the numerical <span class="hlt">simulation</span> of condensed phase explosives</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Michael, L.; Nikiforakis, N.</p> <p>2016-07-01</p> <p>In this article we present a new formulation and an associated numerical algorithm, for the <span class="hlt">simulation</span> of combustion and transition to detonation of condensed-phase commercial- and military-grade explosives, which are confined by (or in general interacting with one or more) compliant inert materials. Examples include confined rate-stick problems and interaction of shock waves with gas cavities or solid particles in explosives. This formulation is based on an augmented Euler approach to account for the mixture of the explosive and its products, and a multi-phase diffuse interface approach to solve for the immiscible interaction between the mixture and the inert materials, so it is in essence a <span class="hlt">hybrid</span> (augmented Euler and multi-phase) model. As such, it has many of the desirable features of the two approaches and, critically for our applications of interest, it provides the accurate recovery of temperature fields across all components. Moreover, it conveys a lot more physical information than augmented Euler, without the complexity of full multi-phase Baer-Nunziato-type models or the lack of robustness of augmented Euler models in the presence of more than two components. The model can sustain large density differences across material interfaces without the presence of spurious oscillations in velocity and pressure, and it can accommodate realistic equations of state and arbitrary (pressure- or temperature-based) reaction-rate laws. Under certain conditions, we show that the formulation reduces to well-known augmented Euler or multi-phase models, which have been extensively validated and used in practice. The full <span class="hlt">hybrid</span> model and its reduced forms are validated against problems with exact (or independently-verified numerical) solutions and evaluated for robustness for rate-stick and shock-induced cavity collapse case-studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1650.1047R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1650.1047R"><span id="translatedtitle"><span class="hlt">Simulation</span> of ultrasonic inspection of curved composites using a <span class="hlt">hybrid</span> semi-analytical/numerical code</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reverdy, Frédéric; Mahaut, Steve; Dominguez, Nicolas; Dubois, Philippe</p> <p>2015-03-01</p> <p>Carbon Fiber reinforced composites are increasingly used in structural parts in the aeronautics industry, as they allow to reduce the weight of aircrafts while maintaining high mechanical performances. However, such structures can be complicated to inspect due to their complex geometries and complex composite properties, leading to highly heterogeneous and anisotropic materials. Different potential damages and manufacturing flaws related to these parts are to be detected: porosities, ply waviness, delaminations after impact. Ultrasonic inspection, which is commonly used to test the full volume of composite panels, thus has to cope with both complex wave propagation (within anisotropic parts whose crystallographic orientation varies according to the layers structure) and flaw interaction (local distortion of plies such as ply waviness, small pores, structural noise due to periodicity patterns…). Developing NDT procedures for those parts therefore requires <span class="hlt">simulation</span> tools to help for understanding those phenomena, and to optimize probes and techniques. Within the CIVA multi-techniques platform, CEA-LIST has developed semi-analytical tools for ultrasonic techniques, which have the advantages of high computational efficiency (fast calculations), but with limited range of application due to some hypothesis (for instance, homogenization approaches which don't allow to take account of structural noise). On the other hand, numerical methods such as finite element (FEM) or finite difference in time domain (FDTD) are more suitable to compute ultrasonic wave propagation and defect scattering in complex materials such as composite but require more computational efforts. <span class="hlt">Hybrid</span> methods couple semi-analytical solutions and numerical computations in limited spatial domains to handle complex cases with high computation performances. In CIVA we have integrated a <span class="hlt">hybrid</span> model that combines the semi-analytical methods developed at CEA to FDTD codes developed at Airbus Group</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.P21C3925C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.P21C3925C"><span id="translatedtitle">Magnetic Reconnection Controls Impacts of Solar Wind Ions at Mercury's Surface : Investigation By Global <span class="hlt">Hybrid</span> <span class="hlt">Simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chanteur, G. M.; Modolo, R.; Leblanc, F.</p> <p>2014-12-01</p> <p>MESSENGER has revealed the complexity of the Hermean magnetic field which is dominated by dipolar and quadrupolar components (Anderson et al., 2012 and references therein). By contrast to other magnetized planets having large scale dynamo driven magnetic fields Mercury has a quadrupolar field large enough to reinforce the dipolar field at high northern latitudes and to shape the topology of the planetary field in the equatorial region and the southern hemisphere. Magnetic reconnection at Mercury is extremely effective for all IMF orientations [DiBraccio et al., JGR, 2013]. Global <span class="hlt">hybrid</span> <span class="hlt">simulations</span> by Richer et al. (2012) have demonstrated the dramatic influence of the quadrupolar field of Mercury on the topology of the Hermean magnetosphere. Then Chanteur et al. (AOGS 2014) have investigated the impacts of solar wind protons and alphas on Mercury's surface with the same <span class="hlt">hybrid</span> code and have presented a case study to demonstrate the importance of magnetic reconnection between the IMF and the planetary field in this process. We will present a set of different results corresponding to different configurations depending upon the IMF orientation and solar wind parameters. References Anderson, B. J., C. L. Johnson, H. Korth, R. M. Winslow, J. E. Borovsky, M. E. Purucker, J. A. Slavin, S. C. Solomon, M. T. Zuber, and R. L. McNutt Jr. (2012), Low-degree structure in Mercury's planetary magnetic field, J. Geophys. Res., 117, E00L12, doi:10.1029/2012JE004159. DiBraccio, G. A., J. A. Slavin, S. A. Boardsen, B. J. Anderson, H. Korth, T. H. Zurbuchen, J. M. Raines, D. N. Baker, R. L. McNutt Jr., and S. C. Solomon (2013), MESSENGER observations of magnetopause structure and dynamics at Mercury, J. Geophys. Res. Space Phys., 118, 997-1008, doi:10.1002/jgra50123. Richer, E., R. Modolo, G. M. Chanteur, S. Hess, and F. Leblanc (2012), A global <span class="hlt">hybrid</span> model for Mercury's interaction with the solar wind: Case study of the dipole representation, J. Geophys. Res., 117, A10228, doi:10</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16878583','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16878583"><span id="translatedtitle">Further validation of artificial neural network-based emissions <span class="hlt">simulation</span> models for conventional and <span class="hlt">hybrid</span> electric vehicles.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tóth-Nagy, Csaba; Conley, John J; Jarrett, Ronald P; Clark, Nigel N</p> <p>2006-07-01</p> <p>With the advent of <span class="hlt">hybrid</span> electric vehicles, computer-based vehicle <span class="hlt">simulation</span> becomes more useful to the engineer and designer trying to optimize the complex combination of control strategy, power plant, drive train, vehicle, and driving conditions. With the desire to incorporate emissions as a design criterion, researchers at West Virginia University have developed artificial neural network (ANN) models for predicting emissions from heavy-duty vehicles. The ANN models were trained on engine and exhaust emissions data collected from transient dynamometer tests of heavy-duty diesel engines then used to predict emissions based on engine speed and torque data from <span class="hlt">simulated</span> operation of a tractor truck and <span class="hlt">hybrid</span> electric bus. <span class="hlt">Simulated</span> vehicle operation was performed with the ADVISOR software package. Predicted emissions (carbon dioxide [CO2] and oxides of nitrogen [NO(x)]) were then compared with actual emissions data collected from chassis dynamometer tests of similar vehicles. This paper expands on previous research to include different driving cycles for the <span class="hlt">hybrid</span> electric bus and varying weights of the conventional truck. Results showed that different <span class="hlt">hybrid</span> control strategies had a significant effect on engine behavior (and, thus, emissions) and may affect emissions during different driving cycles. The ANN models underpredicted emissions of CO2 and NO(x) in the case of a class-8 truck but were more accurate as the truck weight increased. PMID:16878583</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014ISPAr.XL8..799K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014ISPAr.XL8..799K&link_type=ABSTRACT"><span id="translatedtitle">Comparative analysis of RISAT-1 and <span class="hlt">simulated</span> RADARSAT-2 <span class="hlt">hybrid</span> polarimetric SAR data for different land features</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumar, V.; Rao, Y. S.</p> <p>2014-11-01</p> <p>The purpose of this study is to compare the performance of first <span class="hlt">hybrid</span> polarimetric spaceborne satellite RISAT-1 data and <span class="hlt">simulated</span> <span class="hlt">hybrid</span> polarimetric data from quad-pol RADARSAT-2 data for different land use land cover (LULC) classes. The present study compares Stokes (g0, g1, g2 and g3) and its decomposed parameters (m, chi, delta and CPR) for satellite data acquired from RISAT- 1 and RADARSAT-2 over Vijayawada, Andhra Pradesh, India. Further, backscattering coefficients are also compared for different LULC types. The results indicate that both the satellites are following approximately the same trend for different classes except for settlements in RISAT-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JChPh.123x6101Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JChPh.123x6101Y"><span id="translatedtitle">A <span class="hlt">hybrid</span> model for molecular-dynamics <span class="hlt">simulations</span> of semiflexible main-chain liquid-crystalline polymer melts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yung, K. L.; He, Lan; Xu, Yan; Shen, Y. W.</p> <p>2005-12-01</p> <p>This Note proposes a new <span class="hlt">hybrid</span> model that combines the Gay-Berne/Lennard-Jones (GB/LJ) and bead-spring models to <span class="hlt">simulate</span> semiflexible main-chain liquid-crystalline polymers (LCPs) for improving <span class="hlt">simulation</span> efficiency without compromising accuracy. In the new model, one bead and two nonlinear springs are used to describe the flexible spacers between two adjacent rigid units described by ellipsoidal particles. The model is found to be able to describe, with accuracy, detailed structural properties of semiflexible main-chain LCPs, such as the odd-even effects of their thermodynamic properties, where the bead-spring model cannot depict. In our experiments, the speed of <span class="hlt">simulation</span> for the <span class="hlt">hybrid</span> model was shown to be up to ten times faster than that for the GB/LJ model when the number of molecular chains exceeded 150.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=190015','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=190015"><span id="translatedtitle">NEW FEATURES OF HYDRUS-<span class="hlt">1</span><span class="hlt">D</span>, VERSION 3.0</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>This paper briefly summarizes new features in version 3.0 of HYDRUS-<span class="hlt">1</span><span class="hlt">D</span>, released in May 2005, as compared to version 2.1. The new features are a) new approaches to <span class="hlt">simulate</span> preferential and nonequilibrium water flow and solute transport, b) a new hysteresis module that avoids the effects of pumpin...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090007678','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090007678"><span id="translatedtitle"><span class="hlt">Hybrid</span> Reynolds-Averaged/Large-Eddy <span class="hlt">Simulations</span> of a Co-Axial Supersonic Free-Jet Experiment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baurle, R. A.; Edwards, J. R.</p> <p>2009-01-01</p> <p>Reynolds-averaged and <span class="hlt">hybrid</span> Reynolds-averaged/large-eddy <span class="hlt">simulations</span> 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 <span class="hlt">hybrid</span> Reynolds-averaged/large-eddy <span class="hlt">simulations</span> to gather insight into the deficiencies of the Reynolds-averaged closure models. The Reynolds-averaged <span class="hlt">simulations</span> 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 <span class="hlt">simulations</span>, but variations in the Schmidt number did not improve the argon comparisons. The <span class="hlt">hybrid</span> <span class="hlt">simulation</span> results showed the same trends as the baseline Reynolds-averaged predictions. The primary reason conjectured for the discrepancy between the <span class="hlt">hybrid</span> <span class="hlt">simulation</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S34B..06H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S34B..06H"><span id="translatedtitle">Analysis of Laboratory <span class="hlt">Simulations</span> of Volcanic <span class="hlt">Hybrid</span> Earthquakes using Empirical Green's Functions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harrington, R. M.; Benson, P. M.</p> <p>2010-12-01</p> <p>Volcanic <span class="hlt">hybrid</span> earthquakes often precede explosive volcanic eruptions by hours to days, and are therefore frequently used for short term eruption forecasting. In spite of their predictive capabilities, their high-frequency onsets which transition to protracted low-frequency ringing make inferring a source mechanism a perplexing task. Complex models involving some combination of elastic shear, fluid, fluid shear, and their interactions are commonly invoked to explain their mechanism. However, some field observations suggest that the highly attenuating, complex travel path in a volcanic edifice may be responsible for some portion of the low-frequency part of the waveform. Resolving the ambiguity in the role of fluids in <span class="hlt">hybrid</span> generation is an important factor in understanding eruption dynamics, as it would better facilitate our ability to provide accurate forecasts of how explosive a given eruption may be. Here we present a new analysis of experimental <span class="hlt">simulations</span> of volcanic <span class="hlt">hybrid</span> signals, in efforts to better understand their origin. We examine the waveforms of laboratory microseismic events generated during two rock deformation experiments performed on samples of Mt. Etna basalt to determine their source characteristics and establish evidence for a mode of failure. Events were recorded during deformation under (a), unsaturated (dry) conditions, and (b), samples saturated with water. We employ an empirical Green's function approach to isolate the acoustic emission source spectra from attenuation and travel path effects, and estimate the spectral corner frequency using a least-squares fit to a Brune spectral model. Spectral fits indicate that the acoustic emission events occurring under dry conditions follow the expected scaling of moment and corner frequency for standard brittle-failure in an elastic medium with constant stress drop, namely M0 ∝ fc-3. Events occurring during the decompression phase of the saturated experiment have estimated corner frequencies</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1305900-electrostatic-gyrokinetic-electron-fully-kinetic-ion-simulation-lower-hybrid-drift-instability-harris-current-sheet','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1305900-electrostatic-gyrokinetic-electron-fully-kinetic-ion-simulation-lower-hybrid-drift-instability-harris-current-sheet"><span id="translatedtitle">3D electrostatic gyrokinetic electron and fully kinetic ion <span class="hlt">simulation</span> of lower-<span class="hlt">hybrid</span> drift instability of Harris current sheet</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu</p> <p>2016-07-07</p> <p>The eigenmode stability properties of three-dimensional lower-<span class="hlt">hybrid</span>-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) <span class="hlt">simulation</span> model with a realistic ion-to-electron mass ratio mi/me. In contrast to the fully kinetic PIC <span class="hlt">simulation</span> scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me. The GeFi <span class="hlt">simulations</span> are benchmarked against and show excellent agreement with both the fully kinetic PIC <span class="hlt">simulation</span> and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location wheremore » $$\\vec{k}$$• $$\\vec{B}$$ =0, consistent with previous analytical and <span class="hlt">simulation</span> studies. Here, $$\\vec{B}$$ is the equilibrium magnetic field and $$\\vec{k}$$ is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at $$\\vec{k}$$ •$$\\vec{B}$$ ≠0. Additionally, the <span class="hlt">simulation</span> results indicate that varying mi/me, the current sheet width, and the guide magnetic field can affect the stability of LHDI. <span class="hlt">Simulations</span> with the varying mass ratio confirm the lower <span class="hlt">hybrid</span> frequency and wave number scalings.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhPl...23g2104W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhPl...23g2104W&link_type=ABSTRACT"><span id="translatedtitle">3D electrostatic gyrokinetic electron and fully kinetic ion <span class="hlt">simulation</span> of lower-<span class="hlt">hybrid</span> drift instability of Harris current sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu</p> <p>2016-07-01</p> <p>The eigenmode stability properties of three-dimensional lower-<span class="hlt">hybrid</span>-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) <span class="hlt">simulation</span> model with a realistic ion-to-electron mass ratio mi/me . In contrast to the fully kinetic PIC <span class="hlt">simulation</span> scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me . The GeFi <span class="hlt">simulations</span> are benchmarked against and show excellent agreement with both the fully kinetic PIC <span class="hlt">simulation</span> and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location where k →.B → =0 , consistent with previous analytical and <span class="hlt">simulation</span> studies. Here, B → is the equilibrium magnetic field and k → is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at k →.B → ≠0 . In addition, the <span class="hlt">simulation</span> results indicate that varying mi/me , the current sheet width, and the guide magnetic field can affect the stability of LHDI. <span class="hlt">Simulations</span> with the varying mass ratio confirm the lower <span class="hlt">hybrid</span> frequency and wave number scalings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23849752','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23849752"><span id="translatedtitle">A <span class="hlt">hybrid</span> FDTD-Rayleigh integral computational method for the <span class="hlt">simulation</span> of the ultrasound measurement of proximal femur.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cassereau, Didier; Nauleau, Pierre; Bendjoudi, Aniss; Minonzio, Jean-Gabriel; Laugier, Pascal; Bossy, Emmanuel; Grimal, Quentin</p> <p>2014-07-01</p> <p>The development of novel quantitative ultrasound (QUS) techniques to measure the hip is critically dependent on the possibility to <span class="hlt">simulate</span> 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 <span class="hlt">simulate</span> QUS measurements but they are not adapted to <span class="hlt">simulate</span> ultrasonic propagation over long distances in homogeneous media. In this paper, an <span class="hlt">hybrid</span> numerical method is presented to <span class="hlt">simulate</span> hip QUS measurements. A two-dimensional FDTD <span class="hlt">simulation</span> 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 <span class="hlt">simulate</span> 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 <span class="hlt">simulation</span> 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 <span class="hlt">hybrid</span> method than with a full FDTD approach. PMID:23849752</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009PhDT.......133H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009PhDT.......133H&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Hybrid</span> hierarchical bio-based materials: Development and characterization through experimentation and computational <span class="hlt">simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haq, Mahmoodul</p> <p></p> <p>Environmentally friendly bio-based composites with improved properties can be obtained by harnessing the synergy offered by <span class="hlt">hybrid</span> constituents such as multiscale (nano- and micro-scale) reinforcement in bio-based resins composed of blends of synthetic and natural resins. Bio-based composites have recently gained much attention due to their low cost, environmental appeal and their potential to compete with synthetic composites. The advantage of multiscale reinforcement is that it offers synergy at various length scales, and when combined with bio-based resins provide stiffness-toughness balance, improved thermal and barrier properties, and increased environmental appeal to the resulting composites. Moreover, these <span class="hlt">hybrid</span> materials are tailorable in performance and in environmental impact. While the use of different concepts of multiscale reinforcement has been studied for synthetic composites, the study of mukiphase/multiscale reinforcements for developing new types of sustainable materials is limited. The research summarized in this dissertation focused on development of multiscale reinforced bio-based composites and the effort to understand and exploit the synergy of its constituents through experimental characterization and computational <span class="hlt">simulations</span>. Bio-based composites consisting of petroleum-based resin (unsaturated polyester), natural or bio-resin (epoxidized soybean and linseed oils), natural fibers (industrial hemp), and nanosilicate (nanoclay) inclusions were developed. The work followed the "materials by Mahmoodul Haq design" philosophy by incorporating an integrated experimental and computational approach to strategically explore the design possibilities and limits. Experiments demonstrated that the drawbacks of bio-resin addition, which lowers stiffness, strength and increases permeability, can be counter-balanced through nanoclay reinforcement. Bio-resin addition yields benefits in impact strength and ductility. Conversely, nanoclay enhances stiffness</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20991565','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20991565"><span id="translatedtitle">A <span class="hlt">hybrid</span> transport-diffusion method for Monte Carlo radiative-transfer <span class="hlt">simulations</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Densmore, Jeffery D. . E-mail: jdd@lanl.gov; Urbatsch, Todd J. . E-mail: tmonster@lanl.gov; Evans, Thomas M. . E-mail: tme@lanl.gov; Buksas, Michael W. . E-mail: mwbuksas@lanl.gov</p> <p>2007-03-20</p> <p>Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Monte Carlo particle-transport <span class="hlt">simulations</span> in diffusive media. If standard Monte Carlo is used in such media, particle histories will consist of many small steps, resulting in a computationally expensive calculation. In DDMC, particles take discrete steps between spatial cells according to a discretized diffusion equation. Each discrete step replaces many small Monte Carlo steps, thus increasing the efficiency of the <span class="hlt">simulation</span>. In addition, given that DDMC is based on a diffusion equation, it should produce accurate solutions if used judiciously. In practice, DDMC is combined with standard Monte Carlo to form a <span class="hlt">hybrid</span> transport-diffusion method that can accurately <span class="hlt">simulate</span> problems with both diffusive and non-diffusive regions. In this paper, we extend previously developed DDMC techniques in several ways that improve the accuracy and utility of DDMC for nonlinear, time-dependent, radiative-transfer calculations. The use of DDMC in these types of problems is advantageous since, due to the underlying linearizations, optically thick regions appear to be diffusive. First, we employ a diffusion equation that is discretized in space but is continuous in time. Not only is this methodology theoretically more accurate than temporally discretized DDMC techniques, but it also has the benefit that a particle's time is always known. Thus, there is no ambiguity regarding what time to assign a particle that leaves an optically thick region (where DDMC is used) and begins transporting by standard Monte Carlo in an optically thin region. Also, we treat the interface between optically thick and optically thin regions with an improved method, based on the asymptotic diffusion-limit boundary condition, that can produce accurate results regardless of the angular distribution of the incident Monte Carlo particles. Finally, we develop a technique for estimating radiation momentum deposition during the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..120.6133T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..120.6133T"><span id="translatedtitle">3D <span class="hlt">hybrid</span> <span class="hlt">simulations</span> of the interaction of a magnetic cloud with a bow shock</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turc, L.; Fontaine, D.; Savoini, P.; Modolo, R.</p> <p>2015-08-01</p> <p>In this paper, we investigate the interaction of a magnetic cloud (MC) with a planetary bow shock using <span class="hlt">hybrid</span> <span class="hlt">simulations</span>. It is the first time to our knowledge that this interaction is studied using kinetic <span class="hlt">simulations</span> which include self-consistently both the ion foreshock and the shock wave dynamics. We show that when the shock is in a quasi-perpendicular configuration, the MC's magnetic structure in the magnetosheath remains similar to that in the solar wind, whereas it is strongly altered downstream of a quasi-parallel shock. The latter can result in a reversal of the magnetic field north-south component in some parts of the magnetosheath. We also investigate how the MC affects in turn the outer parts of the planetary environment, i.e., from the foreshock to the magnetopause. We find the following: (i) The decrease of the Alfvén Mach number at the MC's arrival causes an attenuation of the foreshock region because of the weakening of the bow shock. (ii) The foreshock moves along the bow shock's surface, following the rotation of the MC's magnetic field. (iii) Owing to the low plasma beta, asymmetric flows arise inside the magnetosheath, due to the magnetic tension force which accelerates the particles in some parts of the magnetosheath and slows them down in others. (iv) The quasi-parallel region forms a depression in the shock's surface. Other deformations of the magnetopause and the bow shock are also highlighted. All these effects can contribute to significantly modify the solar wind/magnetosphere coupling during MC events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JCoPh.315..467K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JCoPh.315..467K"><span id="translatedtitle">A new <span class="hlt">hybrid</span>-Lagrangian numerical scheme for gyrokinetic <span class="hlt">simulation</span> of tokamak edge plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ku, S.; Hager, R.; Chang, C. S.; Kwon, J. M.; Parker, S. E.</p> <p>2016-06-01</p> <p>In order to enable kinetic <span class="hlt">simulation</span> of non-thermal edge plasmas at a reduced computational cost, a new <span class="hlt">hybrid</span>-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 <span class="hlt">simulating</span> the tokamak edge plasma that crosses the magnetic separatrix and is in contact with the material wall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011FlDyR..43b5501M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011FlDyR..43b5501M"><span id="translatedtitle"><span class="hlt">Hybrid</span> lattice-Boltzmann and finite-difference <span class="hlt">simulation</span> of electroosmotic flow in a microchannel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masilamani, Kannan; Ganguly, Suvankar; Feichtinger, Christian; Rüde, Ulrich</p> <p>2011-04-01</p> <p>A three-dimensional (3D) transient mathematical model is developed to <span class="hlt">simulate</span> electroosmotic flows (EOFs) in a homogeneous, square cross-section microchannel, with and without considering the effects of axial pressure gradients. The general governing equations for electroosmotic transport are incompressible Navier-Stokes equations for fluid flow and the nonlinear Poisson-Boltzmann (PB) equation for electric potential distribution within the channel. In the present numerical approach, the hydrodynamic equations are solved using a lattice-Boltzmann (LB) algorithm and the PB equation is solved using a finite-difference (FD) method. The <span class="hlt">hybrid</span> LB-FD numerical scheme is implemented on an iterative framework solving the system of coupled time-dependent partial differential equations subjected to the pertinent boundary conditions. Transient behavior of the EOF and effects due to the variations of different physicochemical parameters on the electroosmotic velocity profile are investigated. Transport characteristics for the case of combined electroosmotic- and pressure-driven microflows are also examined with the present model. For the sake of comparison, the cases of both favorable and adverse pressure gradients are considered. EOF behaviors of the non-Newtonian fluid are studied through implementation of the power-law model in the 3D LB algorithm devised for the fluid flow analysis. Numerical <span class="hlt">simulations</span> reveal that the rheological characteristic of the fluid changes the EOF pattern to a considerable extent and can have significant consequences in the design of electroosmotically actuated bio-microfluidic systems. To improve the performance of the numerical solver, the proposed algorithm is implemented for parallel computing architectures and the overall parallel performance is found to improve with the number of processors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...812...21F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...812...21F"><span id="translatedtitle">High-resolution <span class="hlt">Hybrid</span> <span class="hlt">Simulations</span> of Kinetic Plasma Turbulence at Proton Scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Franci, Luca; Landi, Simone; Matteini, Lorenzo; Verdini, Andrea; Hellinger, Petr</p> <p>2015-10-01</p> <p>We investigate properties of plasma turbulence from magnetohydrodynamic (MHD) to sub-ion scales by means of two-dimensional, high-resolution <span class="hlt">hybrid</span> particle-in-cell <span class="hlt">simulations</span>. We impose an initial ambient magnetic field perpendicular to the <span class="hlt">simulation</span> box, and we add a spectrum of large-scale magnetic and kinetic fluctuations with energy equipartition and vanishing correlation. Once the turbulence is fully developed, we observe an MHD inertial range, where the spectra of the perpendicular magnetic field and the perpendicular proton bulk velocity fluctuations exhibit power-law scaling with spectral indices of -5/3 and -3/2, respectively. This behavior is extended over a full decade in wavevectors and is very stable in time. A transition is observed around proton scales. At sub-ion scales, both spectra steepen, with the former still following a power law with a spectral index of ∼ -3. A -2.8 slope is observed in the density and parallel magnetic fluctuations, highlighting the presence of compressive effects at kinetic scales. The spectrum of the perpendicular electric fluctuations follows that of the proton bulk velocity at MHD scales, and flattens at small scales. All these features, which we carefully tested against variations of many parameters, are in good agreement with solar wind observations. The turbulent cascade leads to on overall proton energization with similar heating rates in the parallel and perpendicular directions. While the parallel proton heating is found to be independent on the resistivity, the number of particles per cell, and the resolution employed, the perpendicular proton temperature strongly depends on these parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1972C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1972C"><span id="translatedtitle">Theory and <span class="hlt">hybrid</span> <span class="hlt">simulations</span> of the radial evolution of the solar wind turbulence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Comisel, Horia; Narita, Yasuhito; Motschmann, Uwe</p> <p>2016-04-01</p> <p>Solar wind turbulence in the inner heliosphere is believed to evolve in the radial direction away from the Sun driven by various nonlinear processes. When a perturbative treatment is applicable, plasma fluctuations evolve along the dispersion relations while the frequencies deviate from the normal-mode frequency by exciting non-normal modes or sideband waves. Direct numerical <span class="hlt">simulations</span> of magnetized plasma at the scale of ion gyro-radius or smaller using the <span class="hlt">hybrid</span> code AIKEF show smooth transitions and evolutions into nonlinear stage with sideband wave excitations. The evolution profile of linear and nonlinear modes as well as the intrinsic nature of wave vector anisotropy can be unambiguously classified according to the values of ion plasma beta. By using a mapping based on a one-dimensional solar wind expansion model, the resulting ion kinetic scale turbulence is related to the solar distance from the Sun. We find that the relevant normal modes such as ion cyclotron and Bernstein mode will occur first at radial distance of about 0.2-0.3 AU, i.e., near the Mercury orbit. Furthermore, a radial dependence of the wave-vector anisotropy is obtained. The predominance of the filament structures highlights the strong impact of Alfvénic waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...823....7H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...823....7H"><span id="translatedtitle">Ion Dynamics at a Rippled Quasi-parallel Shock: 2D <span class="hlt">Hybrid</span> <span class="hlt">Simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hao, Yufei; Lu, Quanming; Gao, Xinliang; Wang, Shui</p> <p>2016-05-01</p> <p>In this paper, two-dimensional <span class="hlt">hybrid</span> <span class="hlt">simulations</span> are performed to investigate ion dynamics at a rippled quasi-parallel shock. The results show that the ripples around the shock front are inherent structures of a quasi-parallel shock, and the re-formation of the shock is not synchronous along the surface of the shock front. By following the trajectories of the upstream ions, we find that these ions behave differently when they interact with the shock front at different positions along the shock surface. The upstream particles are transmitted more easily through the upper part of a ripple, and the corresponding bulk velocity downstream is larger, where a high-speed jet is formed. In the lower part of the ripple, the upstream particles tend to be reflected by the shock. Ions reflected by the shock may suffer multiple-stage acceleration when moving along the shock surface or trapped between the upstream waves and the shock front. Finally, these ions may escape further upstream or move downstream; therefore, superthermal ions can be found both upstream and downstream.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhPl...23f2111D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhPl...23f2111D"><span id="translatedtitle">Particle-in-cell <span class="hlt">simulation</span> study of a lower-<span class="hlt">hybrid</span> shock</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dieckmann, M. E.; Sarri, G.; Doria, D.; Ynnerman, A.; Borghesi, M.</p> <p>2016-06-01</p> <p>The expansion of a magnetized high-pressure plasma into a low-pressure ambient medium is examined with particle-in-cell <span class="hlt">simulations</span>. The magnetic field points perpendicular to the plasma's expansion direction and binary collisions between particles are absent. The expanding plasma steepens into a quasi-electrostatic shock that is sustained by the lower-<span class="hlt">hybrid</span> (LH) wave. The ambipolar electric field points in the expansion direction and it induces together with the background magnetic field a fast E cross B drift of electrons. The drifting electrons modify the background magnetic field, resulting in its pile-up by the LH shock. The magnetic pressure gradient force accelerates the ambient ions ahead of the LH shock, reducing the relative velocity between the ambient plasma and the LH shock to about the phase speed of the shocked LH wave, transforming the LH shock into a nonlinear LH wave. The oscillations of the electrostatic potential have a larger amplitude and wavelength in the magnetized plasma than in an unmagnetized one with otherwise identical conditions. The energy loss to the drifting electrons leads to a noticeable slowdown of the LH shock compared to that in an unmagnetized plasma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22072569','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22072569"><span id="translatedtitle"><span class="hlt">Hybrid</span> <span class="hlt">simulation</span> of energetic particle effects on tearing modes in tokamak plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cai Huishan; Fu Guoyong</p> <p>2012-07-15</p> <p>The effects of energetic ions on stability of tearing mode are investigated by global kinetic/MHD <span class="hlt">hybrid</span> <span class="hlt">simulations</span> in a low beta tokamak plasma. The kinetic effects of counter circulating energetic ions from the non-adiabatic response are found to be strongly destabilizing while the effects from the adiabatic response are stabilizing. The net effect with both adiabatic and non-adiabatic contributions is destabilizing. On the other hand, the kinetic effects of co-circulating energetic ions from the non-adiabatic response are calculated to be weakly stabilizing while the corresponding adiabatic contribution is destabilizing for small energetic ion beta. The net effect is weakly stabilizing. The dependence of kinetic effects on energetic ion beta, gyroradius, and speed is studied systematically and the results agree in large part with the previous analytic results for the kinetic effects of circulating particles. For trapped energetic ions, their effects on tearing mode stability are dominated by the adiabatic response due to large banana orbit width and strong poloidal variation of particle pressure. The net effect of trapped energetic particles on tearing modes is much more destabilizing as compared to that of counter circulating particles at the same beta value.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25055303','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25055303"><span id="translatedtitle">Terahertz spectra of biotin based on first principle, molecular mechanical, and <span class="hlt">hybrid</span> <span class="hlt">simulations</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bykhovski, Alexei; Woolard, Dwight</p> <p>2013-07-01</p> <p>Terahertz (THz) absorption of biotin was <span class="hlt">simulated</span> using the first principle and the density functional theory (DFT) both in the harmonic approximation and with corrections for the anharmonicity. Anharmonicity corrections were calculated using two different approaches. First, the perturbation theory-based first principle calculations were performed to include third- and fourth-order anharmonicity corrections in atomic displacements to harmonic vibrational states. Second, the atom-centered density matrix propagation molecular dynamics model that provides a good energy conservation was used to calculate the atomic trajectories, velocities, and a dipole moment time history of biotin at low and room temperatures. Predicted low-THz lines agree well with the experimental spectra. The influence of the polyethylene (PE) matrix embedment on the THz spectra of biotin at the nanoscale was studied using the developed <span class="hlt">hybrid</span> DFT/molecular mechanical approach. While PE is almost transparent at THz frequencies, additional low-THz lines are predicted in the biotin/PE system, which reflects a dynamic interaction between biotin and a surrounding PE cavity. PMID:25055303</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27196382','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27196382"><span id="translatedtitle"><span class="hlt">Hybrid</span> Potential <span class="hlt">Simulation</span> of the Acylation of Enterococcus faecium l,d-Transpeptidase by Carbapenems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bhattacharjee, Nicholus; Field, Martin J; Simorre, Jean-Pierre; Arthur, Michel; Bougault, Catherine M</p> <p>2016-06-01</p> <p>The l,d-transpeptidases, Ldts, catalyze peptidoglycan cross-linking in β-lactam-resistant mutant strains of several bacteria, including Enterococcus faecium and Mycobacterium tuberculosis. Although unrelated to the essential d,d-transpeptidases, which are inactivated by the β-lactam antibiotics, they are nevertheless inhibited by the carbapenem antibiotics, making them potentially useful targets in the treatment of some important diseases. In this work, we have investigated the acylation mechanism of the Ldt from E. faecium by the carbapenem, ertapenem, using computational techniques. We have employed molecular dynamics <span class="hlt">simulations</span> in conjunction with QC/MM <span class="hlt">hybrid</span> potential calculations to map out possible reaction paths. We have focused on determining the following: (i) the protonation state of the nucleophilic cysteine of the enzyme when it attacks; (ii) whether nucleophilic attack and β-lactam ring-opening are concerted or stepwise, the latter occurring via an oxyanion intermediate; and (iii) the identities of the proton acceptors at the beginning and end of the reaction. Overall, we note that there is considerable plasticity in the mechanisms, owing to the significant flexibility of the enzyme, but find that the preferred pathways are ones in which nucleophilic attack of cysteine thiolate is concerted with β-lactam ring-opening. PMID:27196382</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRA..118.5421H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRA..118.5421H"><span id="translatedtitle">Protons and alpha particles in the expanding solar wind: <span class="hlt">Hybrid</span> <span class="hlt">simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hellinger, Petr; Trávníček, Pavel M.</p> <p>2013-09-01</p> <p>We present results of a two‒dimensional <span class="hlt">hybrid</span> expanding box <span class="hlt">simulation</span> of a plasma system with three ion populations, beam and core protons, and alpha particles (and fluid electrons), drifting with respect to each other. The expansion with a strictly radial magnetic field leads to a decrease of the ion perpendicular to parallel temperature ratios as well as to an increase of the ratio between the ion relative velocities and the local Alfvén velocity creating a free energy for many different instabilities. The system is most of the time marginally stable with respect to kinetic instabilities mainly due to the ion relative velocities; these instabilities determine the system evolution counteracting some effects of the expansion. Nonlinear evolution of these instabilities leads to large modifications of the ion velocity distribution functions. The beam protons and alpha particles are decelerated with respect to the core protons and all the populations are cooled in the parallel direction and heated in the perpendicular one. On the macroscopic level, the kinetic instabilities cause large departures of the system evolution from the double adiabatic prediction and lead to perpendicular heating and parallel cooling rates which are comparable to the heating rates estimated from the Helios observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9799E..19R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9799E..19R"><span id="translatedtitle">Semi-active tuned liquid column damper implementation with real-time <span class="hlt">hybrid</span> <span class="hlt">simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riascos, Carlos; Marulanda Casas, Johannio; Thomson, Peter</p> <p>2016-04-01</p> <p>Real-time <span class="hlt">hybrid</span> <span class="hlt">simulation</span> (RTHS) is a modern cyber-physical technique used for the experimental evaluation of complex systems, that treats the system components with predictable behavior as a numerical substructure and the components that are difficult to model as an experimental substructure. Therefore it is an attractive method for evaluation of the response of civil structures under earthquake, wind and anthropic loads. In this paper, the response of three-story shear frame controlled by a tuned liquid column damper (TLCD) and subject to base excitation is considered. Both passive and semi-active control strategies were implemented and are compared. While the passive TLCD achieved a reduction of 50% in the acceleration response of the main structure in comparison with the structure without control, the semi-active TLCD achieved a reduction of 70%, and was robust to variations in the dynamic properties of the main structure. In addition, a RTHS was implemented with the main structure modeled as a linear, time-invariant (LTI) system through a state space representation and the TLCD, with both control strategies, was evaluated on a shake table that reproduced the displacement of the virtual structure. Current assessment measures for RTHS were used to quantify the performance with parameters such as generalized amplitude, equivalent time delay between the target and measured displacement of the shake table, and energy error using the measured force, and prove that the RTHS described in this paper is an accurate method for the experimental evaluation of structural control systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15014093','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15014093"><span id="translatedtitle">Three-dimensional <span class="hlt">Hybrid</span> Continuum-Atomistic <span class="hlt">Simulations</span> for Multiscale Hydrodynamics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wijesinghe, S; Hornung, R; Garcia, A; Hadjiconstantinou, N</p> <p>2004-04-15</p> <p>We present an adaptive mesh and algorithmic refinement (AMAR) scheme for modeling multi-scale hydrodynamics. The AMAR approach extends standard conservative adaptive mesh refinement (AMR) algorithms by providing a robust flux-based method for coupling an atomistic fluid representation to a continuum model. The atomistic model is applied locally in regions where the continuum description is invalid or inaccurate, such as near strong flow gradients and at fluid interfaces, or when the continuum grid is refined to the molecular scale. The need for such ''<span class="hlt">hybrid</span>'' methods arises from the fact that hydrodynamics modeled by continuum representations are often under-resolved or inaccurate while solutions generated using molecular resolution globally are not feasible. In the implementation described herein, Direct <span class="hlt">Simulation</span> Monte Carlo (DSMC) provides an atomistic description of the flow and the compressible two-fluid Euler equations serve as our continuum-scale model. The AMR methodology provides local grid refinement while the algorithm refinement feature allows the transition to DSMC where needed. The continuum and atomistic representations are coupled by matching fluxes at the continuum-atomistic interfaces and by proper averaging and interpolation of data between scales. Our AMAR application code is implemented in C++ and is built upon the SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) framework developed at Lawrence Livermore National Laboratory. SAMRAI provides the parallel adaptive gridding algorithm and enables the coupling between the continuum and atomistic methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JPhCS.632a2040K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JPhCS.632a2040K&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Simulation</span> of the <span class="hlt">hybrid</span> Tunka Advanced International Gamma-ray and Cosmic ray Astrophysics (TAIGA)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kunnas, M.; Astapov, I.; Barbashina, N.; Beregnev, S.; Bogdanov, A.; Bogorodskii, D.; Boreyko, V.; Brückner, M.; Budnev, N.; Chiavassa, A.; Chvalaev, O.; Dyachok, A.; Epimakhov, S.; Eremin, T.; Gafarov, A.; Gorbunov, N.; Grebenyuk, V.; Gress, O.; Gress, T.; Grinyuk, A.; Grishin, O.; Horns, D.; Ivanova, A.; Karpov, N.; Kalmykov, N.; Kazarina, Y.; Kindin, V.; Kirichkov, N.; Kiryuhin, S.; Kokoulin, R.; Kompaniets, K.; Konstantinov, E.; Korobchenko, A.; Korosteleva, E.; Kozhin, V.; Kuzmichev, L.; Lenok, V.; Lubsandorzhiev, B.; Lubsandorzhiev, N.; Mirgazov, R.; Mirzoyan, R.; Monkhoev, R.; Nachtigall, R.; Pakhorukov, A.; Panasyuk, M.; Pankov, L.; Perevalov, A.; Petrukhin, A.; Platonov, V.; Poleschuk, V.; Popescu, M.; Popova, E.; Porelli, A.; Porokhovoy, S.; Prosin, V.; Ptuskin, V.; Romanov, V.; Rubtsov, G. I.; Müger; Rybov, E.; Samoliga, V.; Satunin, P.; Saunkin, A.; Savinov, V.; Semeney, Yu; Shaibonov (junior, B.; Silaev, A.; Silaev (junior, A.; Skurikhin, A.; Slunecka, M.; Spiering, C.; Sveshnikova, L.; Tabolenko, V.; Tkachenko, A.; Tkachev, L.; Tluczykont, M.; Veslopopov, A.; Veslopopova, E.; Voronov, D.; Wischnewski, R.; Yashin, I.; Yurin, K.; Zagorodnikov, A.; Zirakashvili, V.; Zurbanov, V.</p> <p>2015-08-01</p> <p>Up to several 10s of TeV, Imaging Air Cherenkov Telescopes (IACTs) have proven to be the instruments of choice for GeV/TeV gamma-ray astronomy due to their good reconstrucion quality and gamma-hadron separation power. However, sensitive observations at and above 100 TeV require very large effective areas (10 km2 and more), which is difficult and expensive to achieve. The alternative to IACTs are shower front sampling arrays (non-imaging technique or timing-arrays) with a large area and a wide field of view. Such experiments provide good core position, energy and angular resolution, but only poor gamma-hadron separation. Combining both experimental approaches, using the strengths of both techniques, could optimize the sensitivity to the highest energies. The TAIGA project plans to combine the non-imaging HiSCORE [8] array with small (∼10m2) imaging telescopes. This paper covers <span class="hlt">simulation</span> results of this <span class="hlt">hybrid</span> approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...822L..12C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...822L..12C"><span id="translatedtitle">Subproton-scale Cascades in Solar Wind Turbulence: Driven <span class="hlt">Hybrid</span>-kinetic <span class="hlt">Simulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cerri, S. S.; Califano, F.; Jenko, F.; Told, D.; Rincon, F.</p> <p>2016-05-01</p> <p>A long-lasting debate in space plasma physics concerns the nature of subproton-scale fluctuations in solar wind (SW) turbulence. Over the past decade, a series of theoretical and observational studies were presented in favor of either kinetic Alfvén wave (KAW) or whistler turbulence. Here, we investigate numerically the nature of the subproton-scale turbulent cascade for typical SW parameters by means of unprecedented high-resolution <span class="hlt">simulations</span> of forced <span class="hlt">hybrid</span>-kinetic turbulence in two real-space and three velocity-space dimensions. Our analysis suggests that small-scale turbulence in this model is dominated by KAWs at β ≳ 1 and by magnetosonic/whistler fluctuations at lower β. The spectral properties of the turbulence appear to be in good agreement with theoretical predictions. A tentative interpretation of this result in terms of relative changes in the damping rates of the different waves is also presented. Overall, the results raise interesting new questions about the properties and variability of subproton-scale turbulence in the SW, including its possible dependence on the plasma β, and call for detailed and extensive parametric explorations of driven kinetic turbulence in three dimensions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25808513','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25808513"><span id="translatedtitle">Molecular docking and dynamics <span class="hlt">simulations</span> on the interaction of cationic porphyrin-anthraquinone <span class="hlt">hybrids</span> with DNA G-quadruplexes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Arba, Muhammad; Kartasasmita, Rahmana E; Tjahjono, Daryono H</p> <p>2016-01-01</p> <p>A series of cationic porphyrin-anthraquinone <span class="hlt">hybrids</span> bearing either pyridine, imidazole, or pyrazole rings at the meso-positions have been investigated for their interaction with DNA G-quadruplexes by employing molecular docking and molecular dynamics <span class="hlt">simulations</span>. Three types of DNA G-quadruplexes were utilized, which comprise parallel, antiparallel, and mixed <span class="hlt">hybrid</span> topologies. The porphyrin <span class="hlt">hybrids</span> have a preference to bind with parallel and mixed <span class="hlt">hybrid</span> structures compared to the antiparallel structure. This preference arises from the end stacking of porphyrin moiety following G-stem and loop binding of anthraquinone tail, which is not found in the antiparallel due to the presence of diagonal and lateral loops that crowd the G-quartet. The binding to the antiparallel, instead, occurred with poorer affinity through both the loop and wide groove. All sites of porphyrin binding were confirmed by 6 ns molecular dynamics <span class="hlt">simulation</span>, as well as by the negative value of the total binding free energies that were calculated using the MMPBSA method. Free energy analysis shows that the favorable contribution came from the electrostatic term, which supposedly originated from the interaction of either cationic pyridinium, pyrazole, or imidazole groups and the anionic phosphate backbone, and also from the van der Waals energy, which primarily contributed through end stacking interaction. PMID:25808513</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=EL-2003-00311&hterms=Vought&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DVought','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=EL-2003-00311&hterms=Vought&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DVought"><span id="translatedtitle">Vought F4U-<span class="hlt">1</span><span class="hlt">D</span> Corsair</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1945-01-01</p> <p>Vought F4U-<span class="hlt">1</span><span class="hlt">D</span> Corsair: In February and March of 1945 this Corsair was examined in the NACA's 30 x 60 Full Scale Tunnel at Langley Field. The F4U-<span class="hlt">1</span><span class="hlt">D</span> has rockets mounted on its wings for this test. After installation and during testing, the wings would be lowered to their flight position.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM31B2492L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM31B2492L"><span id="translatedtitle"><span class="hlt">Hybrid</span> multi-grids <span class="hlt">simulations</span> of Ganymede's magnetosphere : comparison with Galileo observations.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leclercq, L.; Modolo, R.; Leblanc, F.</p> <p>2015-12-01</p> <p>The Jovian satellite Ganymede is the biggest moon of our solar system. One of the main motivation of our interest for this moon is its own intrinsic magnetic field, which has been discovered during the Galileo mission (Kivelson et al. 1996). The magnetic field of Ganymede directly interacts with the corotating jovian plasma, leading to the formation of a mini-magnetosphere which is embedded in the giant magnetosphere of Jupiter. This is the only known case of interaction between two planetary magnetospheres.In the frame of the European space mission JUICE (Jupiter Icy moon Exploration), we investigate this unique interaction with a 3D parallel multi-species <span class="hlt">hybrid</span> model. This model is based on the CAM-CL algorithm (Matthews 1994) and has been used to study the ionized environments of Titan, Mars and Mercury. In the <span class="hlt">hybrid</span> formalism, ions are kinetically treated whereas electrons are considered as a zero-inertial fluid to ensure the quasi-neutrality of the plasma. The temporal evolution of the electromagnetic fields is calculated solving Maxwell's equations. The jovian magnetospheric plasma is described as being composed of oxygen and proton ions. The magnetic field of Ganymede, which includes dipolar and induced components (Kivelson et al, 2002), is distorted by its interaction with the Jovian plasma and formed the Alfvén wings. The planetary plasma is described as being composed of O+, with a scale height equal to 125 km. The description of the exosphere is provided by the 3D multi-species collisional exospheric/atmospheric model of Leblanc et al, (2015) and Turc et al. (2014). The ionization of this neutral exosphere by charge exchanges, by electronic impacts, and by reaction with solar photons contributes to the production of planetary plasma. In this model, calculations are performed on a cartesian <span class="hlt">simulation</span> grid which is refined (down to ~120 km of spatial resolution) at Ganymede, using a multi-grids approach (Leclercq et al., submitted, 2015). Results are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/963431','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/963431"><span id="translatedtitle">Modeling, <span class="hlt">Simulation</span> Design and Control of <span class="hlt">Hybrid</span>-Electric Vehicle Drives</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Giorgio Rizzoni</p> <p>2005-09-30</p> <p>Ohio State University (OSU) is uniquely poised to establish such a center, with interdisciplinary emphasis on modeling, <span class="hlt">simulation</span>, design and control of <span class="hlt">hybrid</span>-electric drives for a number of reasons, some of which are: (1) The OSU Center for Automotive Research (CAR) already provides an infrastructure for interdisciplinary automotive research and graduate education; the facilities available at OSU-CAR in the area of vehicle and powertrain research are among the best in the country. CAR facilities include 31,000 sq. feet of space, multiple chassis and engine dynamometers, an anechoic chamber, and a high bay area. (2) OSU has in excess of 10 graduate level courses related to automotive systems. A graduate level sequence has already been initiated with GM. In addition, an Automotive Systems Engineering (ASE) program cosponsored by the mechanical and electrical engineering programs, had been formulated earlier at OSU, independent of the GATE program proposal. The main objective of the ASE is to provide multidisciplinary graduate education and training in the field of automotive systems to Masters level students. This graduate program can be easily adapted to fulfill the spirit of the GATE Center of Excellence. (3) A program in Mechatronic Systems Engineering has been in place at OSU since 1994; this program has a strong emphasis on automotive system integration issues, and has emphasized <span class="hlt">hybrid</span>-electric vehicles as one of its application areas. (4) OSU researchers affiliated with CAR have been directly involved in the development and study of: HEV modeling and <span class="hlt">simulation</span>; electric drives; transmission design and control; combustion engines; and energy storage systems. These activities have been conducted in collaboration with government and automotive industry sponsors; further, the same researchers have been actively involved in continuing education programs in these areas with the automotive industry. The proposed effort will include: (1) The development of a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhPl...22e2901L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhPl...22e2901L&link_type=ABSTRACT"><span id="translatedtitle">Evolution of flux ropes in the magnetotail: A three-dimensional global <span class="hlt">hybrid</span> <span class="hlt">simulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, S.; Lin, Y.; Lu, Q. M.; Wang, X. Y.; Wang, R. S.; Huang, C.; Wu, M. Y.; Wang, S.</p> <p>2015-05-01</p> <p>Flux ropes in the Earth's magnetotail are widely believed to play a crucial role in energy transport during substorms and the generation of energetic particles. Previous kinetic <span class="hlt">simulations</span> are limited to the local-scale regime, and thus cannot be used to study the structure associated with the geomagnetic field and the global-scale evolution of the flux ropes. Here, the evolution of flux ropes in the magnetotail under a steady southward interplanetary magnetic field are studied with a newly developed three-dimensional global <span class="hlt">hybrid</span> <span class="hlt">simulation</span> model for dynamics ranging from the ion Larmor radius to the global convection time scales. Magnetic reconnection with multiple X-lines is found to take place in the near-tail current sheet at geocentric solar magnetospheric distances x = - 30 R E ˜ - 15 R E around the equatorial plane ( z = 0 ). The magnetotail reconnection layer is turbulent, with a nonuniform structure and unsteady evolution, and exhibits properties of typical collisionless fast reconnection with the Hall effect. A number of small-scale flux ropes are generated through the multiple X-line reconnection. The diameter of the flux ropes is several R E , and the spatial scale of the flux ropes in the dawn-dusk direction is on the order of several R E and does not extend across the entire section of the magnetotail, contrary to previous models and MHD <span class="hlt">simulation</span> results and showing the importance of the three-dimensional effects. The nonuniform and unsteady multiple X-line reconnection with particle kinetic effects leads to various kinds of flux rope evolution: The small-scale flux ropes propagate earthward or tailward after formation, and eventually merge into the near-Earth region or the mid-/distant-tail plasmoid, respectively. During the propagation, some of the flux ropes can be tilted in the geocentric solar magnetospheric ( x , y ) plane with respect to the y (dawn-dusk) axis. Coalescence between flux ropes is also observed. At the same time, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22410327','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22410327"><span id="translatedtitle">Evolution of flux ropes in the magnetotail: A three-dimensional global <span class="hlt">hybrid</span> <span class="hlt">simulation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lu, S.; Lin, Y.; Wang, X. Y.; Lu, Q. M. Huang, C.; Wu, M. Y.; Wang, S.; Wang, R. S.</p> <p>2015-05-15</p> <p>Flux ropes in the Earth's magnetotail are widely believed to play a crucial role in energy transport during substorms and the generation of energetic particles. Previous kinetic <span class="hlt">simulations</span> are limited to the local-scale regime, and thus cannot be used to study the structure associated with the geomagnetic field and the global-scale evolution of the flux ropes. Here, the evolution of flux ropes in the magnetotail under a steady southward interplanetary magnetic field are studied with a newly developed three-dimensional global <span class="hlt">hybrid</span> <span class="hlt">simulation</span> model for dynamics ranging from the ion Larmor radius to the global convection time scales. Magnetic reconnection with multiple X-lines is found to take place in the near-tail current sheet at geocentric solar magnetospheric distances x=−30R{sub E}∼−15R{sub E} around the equatorial plane (z=0). The magnetotail reconnection layer is turbulent, with a nonuniform structure and unsteady evolution, and exhibits properties of typical collisionless fast reconnection with the Hall effect. A number of small-scale flux ropes are generated through the multiple X-line reconnection. The diameter of the flux ropes is several R{sub E}, and the spatial scale of the flux ropes in the dawn-dusk direction is on the order of several R{sub E} and does not extend across the entire section of the magnetotail, contrary to previous models and MHD <span class="hlt">simulation</span> results and showing the importance of the three-dimensional effects. The nonuniform and unsteady multiple X-line reconnection with particle kinetic effects leads to various kinds of flux rope evolution: The small-scale flux ropes propagate earthward or tailward after formation, and eventually merge into the near-Earth region or the mid-/distant-tail plasmoid, respectively. During the propagation, some of the flux ropes can be tilted in the geocentric solar magnetospheric (x,y) plane with respect to the y (dawn-dusk) axis. Coalescence between flux ropes is also observed. At the same time, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21396174','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21396174"><span id="translatedtitle"><span class="hlt">Hybrid</span> photovoltaic/thermal (PV/T) solar systems <span class="hlt">simulation</span> with Simulink/Matlab</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>da Silva, R.M.; Fernandes, J.L.M.</p> <p>2010-12-15</p> <p>The purpose of this work consists in thermodynamic modeling of <span class="hlt">hybrid</span> photovoltaic-thermal (PV/T) solar systems, pursuing a modular strategy approach provided by Simulink/Matlab. PV/T solar systems are a recently emerging solar technology that allows for the simultaneous conversion of solar energy into both electricity and heat. This type of technology present some interesting advantages over the conventional ''side-by-side'' thermal and PV solar systems, such as higher combined electrical/thermal energy outputs per unit area, and a more uniform and aesthetical pleasant roof area. Despite the fact that early research on PV/T systems can be traced back to the seventies, only recently it has gained a renewed impetus. In this work, parametric studies and annual transient <span class="hlt">simulations</span> of PV/T systems are undertaken in Simulink/Matlab. The obtained results show an average annual solar fraction of 67%, and a global overall efficiency of 24% (i.e. 15% thermal and 9% electrical), for a typical four-person single-family residence in Lisbon, with p-Si cells, and a collector area of 6 m{sup 2}. A sensitivity analysis performed on the PV/T collector suggests that the most important variable that should be addressed to improve thermal performance is the photovoltaic (PV) module emittance. Based on those results, some additional improvements are proposed, such as the use of vacuum, or a noble gas at low-pressure, to allow for the removal of PV cells encapsulation without air oxidation and degradation, and thus reducing the PV module emittance. Preliminary results show that this option allows for an 8% increase on optical thermal efficiency, and a substantial reduction of thermal losses, suggesting the possibility of working at higher fluid temperatures. The higher working temperatures negative effect in electrical efficiency was negligible, due to compensation by improved optical properties. The <span class="hlt">simulation</span> results are compared with experimental data obtained from other authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SMaS...23d5042G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SMaS...23d5042G"><span id="translatedtitle">A frequency response analysis approach for quantitative assessment of actuator tracking for real-time <span class="hlt">hybrid</span> <span class="hlt">simulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guo, Tong; Chen, Cheng; Xu, WeiJie; Sanchez, Frank</p> <p>2014-04-01</p> <p>Real-time <span class="hlt">hybrid</span> <span class="hlt">simulation</span> is a viable and economical technique that allows researchers to observe the behavior of critical elements at full scale when an entire structure is subjected to dynamic loading. To ensure reliable experimental results, it is necessary to evaluate the actuator tracking after the test, even when sophisticated compensation methods are used to negate the detrimental effect of servo-hydraulic dynamics. Existing methods for assessment of actuator tracking are often based on time-domain analysis. This paper proposes a frequency-domain-based approach to the assessment of actuator tracking for real-time <span class="hlt">hybrid</span> <span class="hlt">simulations</span>. To ensure the accuracy of the proposed frequency response approach, the effects of spectrum leakage are investigated as well as the length and sampling frequency requirements of the signals. Two signal pre-processing techniques (data segmentation and window transform) are also discussed and compared to improve the accuracy of the proposed approach. Finally the effectiveness of the proposed frequency-domain-based approach is demonstrated through both computational analyses and laboratory tests, including real-time tests with predefined displacement and real-time <span class="hlt">hybrid</span> <span class="hlt">simulation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC22A..06H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC22A..06H"><span id="translatedtitle">Development of a <span class="hlt">hybrid</span> 3-D hydrological model to <span class="hlt">simulate</span> hillslopes and the regional unconfined aquifer system in Earth system models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hazenberg, P.; Broxton, P. D.; Brunke, M.; Gochis, D.; Niu, G. Y.; Pelletier, J. D.; Troch, P. A. A.; Zeng, X.</p> <p>2015-12-01</p> <p>The terrestrial hydrological system, including surface and subsurface water, is an essential component of the Earth's climate system. Over the past few decades, land surface modelers have built one-dimensional (<span class="hlt">1</span><span class="hlt">D</span>) models resolving the vertical flow of water through the soil column for use in Earth system models (ESMs). These models generally have a relatively coarse model grid size (~25-100 km) and only account for sub-grid lateral hydrological variations using simple parameterization schemes. At the same time, hydrologists have developed detailed high-resolution (~0.1-10 km grid size) three dimensional (3D) models and showed the importance of accounting for the vertical and lateral redistribution of surface and subsurface water on soil moisture, the surface energy balance and ecosystem dynamics on these smaller scales. However, computational constraints have limited the implementation of the high-resolution models for continental and global scale applications. The current work presents a <span class="hlt">hybrid</span>-3D hydrological approach is presented, where the <span class="hlt">1</span><span class="hlt">D</span> vertical soil column model (available in many ESMs) is coupled with a high-resolution lateral flow model (h2D) to <span class="hlt">simulate</span> subsurface flow and overland flow. H2D accounts for both local-scale hillslope and regional-scale unconfined aquifer responses (i.e. riparian zone and wetlands). This approach was shown to give comparable results as those obtained by an explicit 3D Richards model for the subsurface, but improves runtime efficiency considerably. The h3D approach is implemented for the Delaware river basin, where Noah-MP land surface model (LSM) is used to calculated vertical energy and water exchanges with the atmosphere using a 10km grid resolution. Noah-MP was coupled within the WRF-Hydro infrastructure with the lateral 1km grid resolution h2D model, for which the average depth-to-bedrock, hillslope width function and soil parameters were estimated from digital datasets. The ability of this h3D approach to <span class="hlt">simulate</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1664e0007H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1664e0007H"><span id="translatedtitle">Crash <span class="hlt">simulation</span> of <span class="hlt">hybrid</span> structures considering the stress and strain rate dependent material behavior of thermoplastic materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hopmann, Ch.; Schöngart, M.; Weber, M.; Klein, J.</p> <p>2015-05-01</p> <p>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 <span class="hlt">hybrid</span> structures. Normally, the plastics components are joined to the metal structures using different technologies like welding or screwing. Very often, the <span class="hlt">hybrid</span> 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 <span class="hlt">hybrid</span> parts is very complex. The problem is that the normally used strain rate dependent elastic/plastic material models are not capable to <span class="hlt">simulate</span> the mechanical behavior of thermoplastic materials depended on the state of stress. As part of a research project, a method to <span class="hlt">simulate</span> the mechanical behavior of <span class="hlt">hybrid</span> 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 <span class="hlt">hybrid</span> 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 <span class="hlt">simulate</span> the mechanical behavior of the <span class="hlt">hybrid</span> structure under highly dynamic load with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015OptSp.119.1015I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015OptSp.119.1015I"><span id="translatedtitle"><span class="hlt">Simulation</span> of a symmetric optical response from a <span class="hlt">hybrid</span>-aligned structure of a dual-frequency nematic liquid crystal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivanov, A. V.; Vakulin, D. A.</p> <p>2015-12-01</p> <p>To create a <span class="hlt">hybrid</span>-aligned structure of a dual-frequency nematic liquid crystal (LC), we have obtained an approximate analytical solution of the system of equations that describes the dynamics of reorientations of the director under the action of a control electric signal of an arbitrary shape. Formulas obtained have been used to <span class="hlt">simulate</span> a symmetric optical response of the LC structure for a sinusoidal electric pulse. It has been shown that, in terms of the used approximations, the results of the analytical calculation agree well with results of computer <span class="hlt">simulation</span> and with experiment in the case of small deformations of the LC layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/842537','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/842537"><span id="translatedtitle">Global <span class="hlt">Hybrid</span> <span class="hlt">Simulations</span> of Energetic Particle Effects on the n=1 Mode in Tokamaks: Internal Kink and Fishbone Instability</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>G.Y. Fu; W. Park; H.R. Strauss; J. Breslau; J. Chen; S. Jardin; L.E. Sugiyama</p> <p>2005-08-09</p> <p>Global <span class="hlt">hybrid</span> <span class="hlt">simulations</span> of energetic particle effects on the n=1 internal kink mode have been carried out for tokamaks. For the International Thermonuclear Experimental Reactor (ITER) [ITER Physics Basis Editors et al., Nucl. Fusion 39:2137 (1999)], it is shown that alpha particle effects are stabilizing for the internal kink mode. However, the elongation of ITER reduces the stabilization effects significantly. Nonlinear <span class="hlt">simulations</span> of the precessional drift fishbone instability for circular tokamak plasmas show that the mode saturates due to flattening of the particle distribution function near the resonance region. The mode frequency chirps down rapidly as the flattening region expands radially outward. Fluid nonlinearity reduces the saturation level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhPl...23d2902G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhPl...23d2902G"><span id="translatedtitle">Generation of electromagnetic ion cyclotron waves in the near-Earth magnetotail during dipolarization: Two-dimensional global <span class="hlt">hybrid</span> <span class="hlt">simulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guo, Zhifang; Wu, Mingyu; Du, Aimin</p> <p>2016-04-01</p> <p>We employ two-dimensional global <span class="hlt">hybrid</span> <span class="hlt">simulations</span> to study the generation, propagation, and polarization of electromagnetic ion cyclotron (EMIC) waves in the near-Earth magnetotail (around x = - 10 R E ) during dipolarization. In our <span class="hlt">simulation</span>, EMIC waves with left-hand polarized signals originate in the low-latitude magnetotail as a result of the ion temperature anisotropy which is due to ion heating by Alfvén waves. Subsequently, EMIC waves can propagate along the ambient magnetic field toward high-latitudes. Our work provides one possible mechanism for the generation of EMIC waves observed in the near-Earth magnetotail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM13A2476L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM13A2476L"><span id="translatedtitle">Global Effects of the Interplanetary Shock Propagation through the Earth's Inner Magnetosphere: 3D <span class="hlt">Hybrid</span> Kinetic ModelingA.S. Lipatov {<span class="hlt">1</span>}, <span class="hlt">D</span>.G. Sibeck {2}{1} GPHI UMBC/NASA GSFC, Greenbelt, MD 20771, USA {2} NASA GSFC, Greenbelt, MD 20771, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lipatov, A. S.; Sibeck, D. G.</p> <p>2015-12-01</p> <p>We use a new <span class="hlt">hybrid</span> kinetic model to <span class="hlt">simulate</span> the response of ring current, outer radiation belt, and plasmasphere particle populations to impulsive interplanetary shocks. Since particle distributions attending the interplanetary shock waves and in the ring current and radiation belts are non-Maxwellian, wave-particle interactions play a crucial role in energy transport within the inner magnetosphere. Finite gyroradius effects become important in mass loading the shock waves with the background plasma in the presence of higher energy ring current and radiation belt ions and electrons. Initial results show that the shock causes strong deformations in the global structure of the ring current, radiation belt, and plasmasphere. The ion velocity distribution functions at the shock front, in the ring current, and in the radiation belt help us to determine energy transport through the Earth's inner magnetosphere. We compare our predictions with THEMIS and Van Allen Probes spacecraft observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012Tectp.541...43G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012Tectp.541...43G"><span id="translatedtitle">3D <span class="hlt">hybrid</span> tectono-stochastic modeling of naturally fractured reservoir: Application of finite element method and stochastic <span class="hlt">simulation</span> technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gholizadeh Doonechaly, N.; Rahman, S. S.</p> <p>2012-05-01</p> <p><span class="hlt">Simulation</span> of naturally fractured reservoirs offers significant challenges due to the lack of a methodology that can utilize field data. To date several methods have been proposed by authors to characterize naturally fractured reservoirs. Among them is the unfolding/folding method which offers some degree of accuracy in estimating the probability of the existence of fractures in a reservoir. Also there are statistical approaches which integrate all levels of field data to <span class="hlt">simulate</span> the fracture network. This approach, however, is dependent on the availability of data sources, such as seismic attributes, core descriptions, well logs, etc. which often make it difficult to obtain field wide. In this study a <span class="hlt">hybrid</span> tectono-stochastic <span class="hlt">simulation</span> is proposed to characterize a naturally fractured reservoir. A finite element based model is used to <span class="hlt">simulate</span> the tectonic event of folding and unfolding of a geological structure. A nested neuro-stochastic technique is used to develop the inter-relationship between the data and at the same time it utilizes the sequential Gaussian approach to analyze field data along with fracture probability data. This approach has the ability to overcome commonly experienced discontinuity of the data in both horizontal and vertical directions. This <span class="hlt">hybrid</span> technique is used to generate a discrete fracture network of a specific Australian gas reservoir, Palm Valley in the Northern Territory. Results of this study have significant benefit in accurately describing fluid flow <span class="hlt">simulation</span> and well placement for maximal hydrocarbon recovery.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20110015605&hterms=solar+wind&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3D%2528solar%2Bwind%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20110015605&hterms=solar+wind&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3D%2528solar%2Bwind%2529"><span id="translatedtitle">First Lunar Wake Passage of ARTEMIS: Discrimination of Wake Effects and Solar Wind Fluctuations by 3D <span class="hlt">Hybrid</span> <span class="hlt">Simulations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wiehle, S.; Plaschke, F.; Motschmann, U.; Glassmeier, K. H.; Auster, H. U.; Angelopoulos, V.; Mueller, J.; Kriegel, H.; Georgescu, E.; Halekas, J.; Sibeck, D. G.; McFadden, J. P.</p> <p>2011-01-01</p> <p>The spacecraft P1 of the new ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun) mission passed the lunar wake for the first time on February 13, 2010. We present magnetic field and plasma data of this event and results of 3D <span class="hlt">hybrid</span> <span class="hlt">simulations</span>. As the solar wind magnetic field was highly dynamic during the passage, a <span class="hlt">simulation</span> with stationary solar wind input cannot distinguish whether distortions were caused by these solar wind variations or by the lunar wake; therefore, a dynamic real-time <span class="hlt">simulation</span> of the flyby has been performed. The input values of this <span class="hlt">simulation</span> are taken from NASA OMNI data and adapted to the P1 data, resulting in a good agreement between <span class="hlt">simulation</span> and measurements. Combined with the stationary <span class="hlt">simulation</span> showing non-transient lunar wake structures, a separation of solar wind and wake effects is achieved. An anisotropy in the magnitude of the plasma bulk flow velocity caused by a non-vanishing magnetic field component parallel to the solar wind flow and perturbations created by counterstreaming ions in the lunar wake are observed in data and <span class="hlt">simulations</span>. The <span class="hlt">simulations</span> help to interpret the data granting us the opportunity to examine the entire lunar plasma environment and, thus, extending the possibilities of measurements alone: A comparison of a <span class="hlt">simulation</span> cross section to theoretical predictions of MHD wave propagation shows that all three basic MHD modes are present in the lunar wake and that their expansion governs the lunar wake refilling process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9556E..1AH','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9556E..1AH"><span id="translatedtitle">Optical properties of LEDs with patterned <span class="hlt">1</span><span class="hlt">D</span> photonic crystal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hronec, P.; Kuzma, A.; Å kriniarová, J.; Kováč, J.; Benčurová, A.; Haščík, Å.; Nemec, P.</p> <p>2015-08-01</p> <p>In this paper we focus on the application of the one-dimensional photonic crystal (<span class="hlt">1</span><span class="hlt">D</span> PhC) structures on the top of Al0.295Ga0.705As/GaAs multi-quantum well light emitting diode (MQW LED). <span class="hlt">1</span><span class="hlt">D</span> PhC structures with periods of 600 nm, 700 nm, 800 nm, and 900 nm were fabricated by the E-Beam Direct Write (EBDW) Lithography. Effect of <span class="hlt">1</span><span class="hlt">D</span> PhC period on the light extraction enhancement was studied. <span class="hlt">1</span><span class="hlt">D</span> PhC LED radiation profiles were obtained from Near Surface Light Emission Images (NSLEI). Measurements showed the strongest light extraction enhancement using 800 nm period of PhC. Investigation of PhC LED radiation profiles showed strong light decoupling when light reaches PhC structure. Achieved LEE was from 22.6% for 600 nm PhC LED to 47.0% for 800 nm PhC LED. LED with PhC structure at its surface was <span class="hlt">simulated</span> by FDTD <span class="hlt">simulation</span> method under excitation of appropriate launch field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SPIE.7629E..07D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SPIE.7629E..07D"><span id="translatedtitle">A <span class="hlt">1</span><span class="hlt">D</span> wavelet filtering for ultrasound images despeckling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dahdouh, Sonia; Dubois, Mathieu; Frenoux, Emmanuelle; Osorio, Angel</p> <p>2010-03-01</p> <p>Ultrasound images appearance is characterized by speckle, shadows, signal dropout and low contrast which make them really difficult to process and leads to a very poor signal to noise ratio. Therefore, for main imaging applications, a denoising step is necessary to apply successfully medical imaging algorithms on such images. However, due to speckle statistics, denoising and enhancing edges on these images without inducing additional blurring is a real challenging problem on which usual filters often fail. To deal with such problems, a large number of papers are working on B-mode images considering that the noise is purely multiplicative. Making such an assertion could be misleading, because of internal pre-processing such as log compression which are done in the ultrasound device. To address those questions, we designed a novel filtering method based on <span class="hlt">1</span><span class="hlt">D</span> Radiofrequency signal. Indeed, since B-mode images are initially composed of <span class="hlt">1</span><span class="hlt">D</span> signals and since the log compression made by ultrasound devices modifies noise statistics, we decided to filter directly the <span class="hlt">1</span><span class="hlt">D</span> Radiofrequency signal envelope before log compression and image reconstitution, in order to conserve as much information as possible. A bi-orthogonal wavelet transform is applied to the log transform of each signal and an adaptive <span class="hlt">1</span><span class="hlt">D</span> split and merge like algorithm is used to denoise wavelet coefficients. Experiments were carried out on synthetic data sets <span class="hlt">simulated</span> with Field II <span class="hlt">simulator</span> and results show that our filter outperforms classical speckle filtering methods like Lee, non-linear means or SRAD filters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EUCAS...4..113N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EUCAS...4..113N"><span id="translatedtitle">Large eddy <span class="hlt">simulations</span> and experiments of nonlinear flow interactions in <span class="hlt">hybrid</span> rocket combustion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Na, Y.; Lee, C.</p> <p>2013-03-01</p> <p>Nonlinear combustion phenomenon was investigated through an experiment in a <span class="hlt">hybrid</span> rocket motor. A poly(methyl methacrylate) (PMMA) / gaseous oxygen (GOx) combination was used with several types of disks equipped in a prechamber with the aim of modifying the local turbulent flow. By allowing this disturbance generated in a prechamber to interact with the shedding vortex inherently produced in the main chamber, a possibility of commonly observed nonlinear combustion feature such as DC-shift was analyzed. In a baseline test, a vortex shedding occurs due to the interaction of a main oxidizer flow with the evaporated fuel stream coming out of the surface during the regression process. Among the several types of disks, it turned out that only the disk4 produced the excitation which subsequently suppressed the vortex shedding phenomenon in the main chamber. This descent interaction was reflected in a sudden pressure drop (which may be described as direct current (DC) shift) of about 10 psi in the time history of the pressure during the nominal combustion. The present result with the disk4 suggests the possibility of phase cancellation between the excitation induced by the disk4 and the shedding vortex but much more work should be conducted to extract more accurate correlation of the phase information. In order to understand the baseline flow physics, a compressible large eddy <span class="hlt">simulation</span> (LES) was conducted with the prescribed wall blowing boundary condition. The result clearly exhibited the existence of vortex shedding phenomenon with a specified frequency. The fact that important flow features of the present computation are quite similar to those obtained with an incompressible assumption in a flat channel suggests that both compressibility and curvature effects do not dominate in the present flow configuration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/117672','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/117672"><span id="translatedtitle">Structure of the magnetopause inferred from one-dimensional <span class="hlt">hybrid</span> <span class="hlt">simulations</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Omidi, N.; Winske, D. |</p> <p>1995-07-01</p> <p>The structure of the magnetopause is investigated by studying the interaction between two plasmas with solar wind and magnetospheric properties. Both Hall-MHD and <span class="hlt">hybrid</span> (particle ions and fluid electrons) <span class="hlt">simulations</span> are performed to compare and contrast the nature of the solutions in the fluid and the kinetic limits. It is shown that, in accordance with previous studies, the fluid solutions consist of multiple discontinuities and waves such as slow shocks and waves, as well as contact and rotational discontinuities. In contrast, the kinetic solutions consist of fewer discontinuities and include non-MHD boundaries. The difference between the two types of solutions are attributed to the absence of contact surfaces in collisionless plasmas and the possible Landau damping of slow waves. The kinetic solutions are found to be in a much better agreement with magnetopause observations, which have shown little evidence for the presence of slow shocks or contact discontinuities. The results of kinetic calculations suggest that the presence of a small but finite normal component of the magnetic field allows for the mixing of magnetosheath and magnetospheric plasmas and may, in part, be responsible for the formation of the boundary layer even during the periods of northward interplanetary magnetic field. These results also show that the necessary changes in the fields and the plasma parameters across the magnetopause do not occur simultaneously (i.e., in the same spatial location). As such, the magnetopause cannot be viewed as a single boundary but instead is a region which includes both abrupt and gradual changes in the fields and plasma parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000IJNMF..32..407Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000IJNMF..32..407Z"><span id="translatedtitle"><span class="hlt">Simulation</span> of transients in natural gas pipelines using <span class="hlt">hybrid</span> TVD schemes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Junyang; Adewumi, Michael A.</p> <p>2000-02-01</p> <p>The mathematical model describing transients in natural gas pipelines constitutes a non-homogeneous system of non-linear hyperbolic conservation laws. The time splitting approach is adopted to solve this non-homogeneous hyperbolic model. At each time step, the non-homogeneous hyperbolic model is split into a homogeneous hyperbolic model and an ODE operator. An explicit 5-point, second-order-accurate total variation diminishing (TVD) scheme is formulated to solve the homogeneous system of non-linear hyperbolic conservation laws. Special attention is given to the treatment of boundary conditions at the inlet and the outlet of the pipeline. <span class="hlt">Hybrid</span> methods involving the Godunov scheme (TVD/Godunov scheme) or the Roe scheme (TVD/Roe scheme) or the Lax-Wendroff scheme (TVD/LW scheme) are used to achieve appropriate boundary handling strategy. A severe condition involving instantaneous closure of a downstream valve is used to test the efficacy of the new schemes. The results produced by the TVD/Roe and TVD/Godunov schemes are excellent and comparable with each other, while the TVD/LW scheme performs reasonably well. The TVD/Roe scheme is applied to <span class="hlt">simulate</span> the transport of a fast transient in a short pipe and the propagation of a slow transient in a long transmission pipeline. For the first example, the scheme produces excellent results, which capture and maintain the integrity of the wave fronts even after a long time. For the second example, comparisons of computational results are made using different discretizing parameters. Copyright</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..120.6286L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..120.6286L"><span id="translatedtitle">Dipolarization fronts as earthward propagating flux ropes: A three-dimensional global <span class="hlt">hybrid</span> <span class="hlt">simulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, San; Lu, Quanming; Lin, Yu; Wang, Xueyi; Ge, Yasong; Wang, Rongsheng; Zhou, Meng; Fu, Huishan; Huang, Can; Wu, Mingyu; Wang, Shui</p> <p>2015-08-01</p> <p>Dipolarization fronts (DFs) as earthward propagating flux ropes (FRs) in the Earth's magnetotail are presented and investigated with a three-dimensional (3-D) global <span class="hlt">hybrid</span> <span class="hlt">simulation</span> for the first time. In the <span class="hlt">simulation</span>, several small-scale earthward propagating FRs are found to be formed by multiple X line reconnection in the near tail. During their earthward propagation, the magnetic field Bz of the FRs becomes highly asymmetric due to the imbalance of the reconnection rates between the multiple X lines. At the later stage, when the FRs approach the near-Earth dipole-like region, the antireconnection between the southward/negative Bz of the FRs and the northward geomagnetic field leads to the erosion of the southward magnetic flux of the FRs, which further aggravates the Bz asymmetry. Eventually, the FRs merge into the near-Earth region through the antireconnection. These earthward propagating FRs can fully reproduce the observational features of the DFs, e.g., a sharp enhancement of Bz preceded by a smaller amplitude Bz dip, an earthward flow enhancement, the presence of the electric field components in the normal and dawn-dusk directions, and ion energization. Our results show that the earthward propagating FRs can be used to explain the DFs observed in the magnetotail. The thickness of the DFs is on the order of several ion inertial lengths, and the electric field normal to the front is found to be dominated by the Hall physics. During the earthward propagation from the near-tail to the near-Earth region, the speed of the FR/DFs increases from ~150 km/s to ~1000 km/s. The FR/DFs can be tilted in the GSM (x, y) plane with respect to the y (dawn-dusk) axis and only extend several Earth radii in this direction. Moreover, the structure and evolution of the FRs/DFs are nonuniform in the dawn-dusk direction, which indicates that the DFs are essentially 3-D.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23942016','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23942016"><span id="translatedtitle">Fate of bulk and trace organics during a <span class="hlt">simulated</span> aquifer recharge and recovery (ARR)-ozone <span class="hlt">hybrid</span> process.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yoon, Min K; Drewes, Jörg E; Amy, Gary L</p> <p>2013-11-01</p> <p>The attenuation of bulk organic matter and trace organic contaminants (TOrCs) was evaluated for various aquifer recharge and recovery (ARR)-ozone (O3) <span class="hlt">hybrid</span> 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 <span class="hlt">simulated</span> treatment combinations, including soil passage (ARR) alone, ARR after ozonation (O3-ARR), and ARR prior to ozonation (ARR-O3). During oxic (aerobic) ARR <span class="hlt">simulations</span>, 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 <span class="hlt">simulations</span>, 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 <span class="hlt">hybrid</span> followed by the O3-ARR <span class="hlt">hybrid</span>. 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 (<5 ng L(-1)) both during ARR treatment alone and the ARR-ozone <span class="hlt">hybrid</span>. PMID:23942016</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013CTM....17..142W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013CTM....17..142W"><span id="translatedtitle">Numerical <span class="hlt">simulation</span> and validation of SI-CAI <span class="hlt">hybrid</span> combustion in a CAI/HCCI gasoline engine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Xinyan; Xie, Hui; Xie, Liyan; Zhang, Lianfang; Li, Le; Chen, Tao; Zhao, Hua</p> <p>2013-02-01</p> <p>SI-CAI <span class="hlt">hybrid</span> 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 <span class="hlt">hybrid</span> 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 <span class="hlt">hybrid</span> combustion model (HCM) is then applied in the three-dimensional computational fluid dynamics (3-D CFD) engine <span class="hlt">simulation</span>. The <span class="hlt">simulation</span> results are compared with the experimental data obtained from a single cylinder VVA engine. The detailed analysis of the <span class="hlt">simulations</span> demonstrates that the SI-CAI <span class="hlt">hybrid</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.P41C1636H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.P41C1636H"><span id="translatedtitle">Understanding <span class="hlt">1</span><span class="hlt">D</span> Electrostatic Dust Levitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hartzell, C. M.; Scheeres, D. J.</p> <p>2011-12-01</p> <p>Electrostatically-dominated dust motion has been hypothesized since the Lunar Horizon Glow was observed by the Surveyor spacecraft. The hypothesized occurence of this phenomenon was naturally extended to asteroids due to their small gravities. Additionally, it has been suggested that the dust ponds observed on Eros by the NEAR mission may be created by electrostatically-dominated dust transport. Previous attempts to numerically model dust motion on the Moon and Eros have been stymied by poorly understood dust launching mechanisms. As a result, the initial velocity and charge of dust particles used in numerical <span class="hlt">simulations</span> may or may not have any relevance to the actual conditions occurring in situ. It has been seen that properly tuned initial states (velocity and charge) result in dust particles levitating above the surface in both <span class="hlt">1</span><span class="hlt">D</span> and 2D <span class="hlt">simulations</span>. Levitation is of interest to planetary scientists since it provides a way to quickly redistribute the surface dust particles over a body. However, there is currently no method to predict whether or not a certain initial state will result in levitation. We have developed a method to provide constraints on the initial states that result in levitation as a function of dust particle size and central body gravity. Additionally, our method can be applied to several models of the plasma sheath. Thus, we limit the guesswork involved in determining which initial conditions result in levitation. We provide a more detailed understanding of levitation phenomena couched in terms of the commonly recognized spring-mass system. This method of understanding dust motion removes the dependency on the launching mechanism, which remains fraught with controversy. Once a feasible dust launching mechanism is identified (be it micrometeoroid bombardment or electrostatic lofting), our method will allow the community to quickly ascertain if dust levitation will occur in situ or if it is simply a numerical artifact. In addition to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/957995','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/957995"><span id="translatedtitle">Fuel Economy and Performance of Mild <span class="hlt">Hybrids</span> with Ultracapacitors: <span class="hlt">Simulations</span> and Vehicle Test Results (Presentation)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gonder, J.; Pesaran, A.; Lustbader, J.; Tataria, H.</p> <p>2009-06-01</p> <p>NREL worked with GM and demonstrated equivalent performance in the Saturn Vue Belt Alternator Starter (BAS) <span class="hlt">hybrid</span> vehicle whether running with its stock batteries or a retrofit ultracapacitor system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AtmEn..80..408S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AtmEn..80..408S"><span id="translatedtitle"><span class="hlt">Hybrid</span> modelling approach for effective <span class="hlt">simulation</span> of reactive pollutants like Ozone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharma, Sumit; Sharma, Prateek; Khare, Mukesh</p> <p>2013-12-01</p> <p>Prediction of air quality is an important component of any air quality management programme. Broadly, two approaches are used to predict the ambient air quality - the deterministic and the statistical approach, with each approach having its own merits and demerits. While the models based on the deterministic approach accurately predict the concentrations of air pollutants in the middle percentile range, the statistical models provide a better estimate of concentrations in the extreme percentile ranges. However, the statistical models are site specific and are not able generate ‘what-if' scenarios; the deterministic models on the other hand are general in character and useful in creating alternative scenarios. An alternative approach - <span class="hlt">hybrid</span> modelling is a technique which aggregates the benefits of the two techniques and predicts the ‘entire range' of the distribution. While in the past there were attempts to predict the concentrations of inert pollutants using <span class="hlt">hybrid</span> modelling approach, this paper shows the <span class="hlt">hybrid</span> model applications for reactive secondary pollutants like ground level Ozone (GLO). This study presents the development of a <span class="hlt">hybrid</span> model that concatenates the results of CMAQ (community multi-scale air quality model) as its deterministic component with statistical distribution model (based on the specific area category and timeframe) to predict the entire range of GLO concentrations. Predictions have been made using both purely deterministic and <span class="hlt">hybrid</span> approaches at a receptor location near a major traffic intersection. The performance of the model has been found to improve from an index of agreement from 0.77 (deterministic model) to 0.91 (<span class="hlt">hybrid</span> model). In order to assess the predictive capability of the <span class="hlt">hybrid</span> approach, the model has been tested at an entirely different location for different set of temporal data. The results show an improvement in the predictions using the <span class="hlt">hybrid</span> model over the deterministic model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MS%26E...93a2001B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MS%26E...93a2001B"><span id="translatedtitle">Application of <span class="hlt">Hybrid</span> Real-Time Power System <span class="hlt">Simulator</span> for Designing and Researching of Relay Protection and Automation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Borovikov, Yu S.; Sulaymanov, A. O.; Andreev, M. V.</p> <p>2015-10-01</p> <p>Development, research and operation of smart grids (SG) with active-adaptive networks (AAS) are actual tasks for today. Planned integration of high-speed FACTS devices greatly complicates complex dynamic properties of power systems. As a result the operating conditions of equipment of power systems are significantly changing. Such situation creates the new actual problem of development and research of relay protection and automation (RPA) which will be able to adequately operate in the SGs and adapt to its regimes. Effectiveness of solution of the problem depends on using tools - different <span class="hlt">simulators</span> of electric power systems. Analysis of the most famous and widely exploited <span class="hlt">simulators</span> led to the conclusion about the impossibility of using them for solution of the mentioned problem. In Tomsk Polytechnic University developed the prototype of <span class="hlt">hybrid</span> multiprocessor software and hardware system - <span class="hlt">Hybrid</span> Real-Time Power System <span class="hlt">Simulator</span> (HRTSim). Because of its unique features this <span class="hlt">simulator</span> can be used for solution of mentioned tasks. This article introduces the concept of development and research of relay protection and automation with usage of HRTSim.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010SPIE.7719E..0EA&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010SPIE.7719E..0EA&link_type=ABSTRACT"><span id="translatedtitle">Design, <span class="hlt">simulation</span>, and fabrication of a 90° SOI optical <span class="hlt">hybrid</span> based on the self-imaging principle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abdul-Majid, Sawsan; Hasan, Imad I.; Bock, Przemek J.; Hall, Trevor J.</p> <p>2010-05-01</p> <p>This paper introduces a compact 90º optical <span class="hlt">hybrid</span>, built on small size SOI waveguide technology .This optical <span class="hlt">hybrid</span> is a critical component of a potentially low-cost coherent optical receiver design developed within the frame of our Optical Coherent Transmission for Access Network Extensions (OCTANE) project. In previous recent work, 90º optical <span class="hlt">hybrids</span> were realized in SOI rib waveguide technology with 4 μm top silicon and a rib height of approximately 2 μm. In this paper, we introduce a compact 90º optical <span class="hlt">hybrid</span>, built on small size SOI waveguide technology (1.5 μm SOI -based rib waveguide, with 0.8μm rib height). The proposed device consists of multimode interferometers (MMIs) connected in such a way that four different vector additions of a reference signal (local oscillator) and the signal to be detected are obtained. At the outputs, the <span class="hlt">hybrid</span> provides four linear combination of the signal with the reference which differs by a relative phase shift of the reference of 90º. The four output signals are detected by a pair of balanced receivers to provide in-phase and quadrature (I&Q) channels. The phase differences arise naturally from the self imaging property of a MMI. The key elements of the 90º optical <span class="hlt">hybrid</span>, including a 2×2 MMI, a 4×4 MMI, and polarization diversity configuration have been designed and <span class="hlt">simulated</span>, using the numerical mode solving tool FIMMPROB. The 2×2 and 4×4 MMI had overall lengths of 701μm and 3712.5μm lengths respectively. Tapers are used to couple adiabatically single mode waveguides to the entrance and exit ports of the MMI to assure correct operation by avoiding coupling to the higher order transverse modes allowed at the entrance and exit ports of the MMI. The <span class="hlt">simulation</span> results at 1550nm show polarization independence and phase errors between the ports of less than 0.03 degrees. Currently the design is in fabrication at the Canadian Photonics Fabrication Center with the support of CMC Microsystems and experimental</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NucFu..56f6007B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NucFu..56f6007B"><span id="translatedtitle">Electromagnetic particle <span class="hlt">simulation</span> of the effect of toroidicity on linear mode conversion and absorption of lower <span class="hlt">hybrid</span> waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bao, J.; Lin, Z.; Kuley, A.; Wang, Z. X.</p> <p>2016-06-01</p> <p>Effects of toroidicity on linear mode conversion and absorption of lower <span class="hlt">hybrid</span> (LH) waves in fusion plasmas have been studied using electromagnetic particle <span class="hlt">simulation</span>. The <span class="hlt">simulation</span> confirms that the toroidicity induces an upshift of parallel refractive index when LH waves propagate from the tokamak edge toward the core, which affects the radial position for the mode conversion between slow and fast LH waves. Furthermore, moving LH antenna launch position from low field side toward high field side leads to a larger upshift of the parallel refractive index, which helps the slow LH wave penetration into the tokamak core. The broadening of the poloidal spectrum of the wave-packet due to wave diffraction is also verified in the <span class="hlt">simulation</span>. Both the upshift and broadening effects of the parallel spectrum of the wave-packet modify the parallel phase velocity and thus the linear absorption of LH waves by electron Landau resonance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22488577','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22488577"><span id="translatedtitle">Molecular dynamics <span class="hlt">simulation</span> of joining process of Ag-Au nanowires and mechanical properties of the <span class="hlt">hybrid</span> nanojoint</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ding, Su; Tian, Yanhong Jiang, Zhi; He, Xiaobin</p> <p>2015-05-15</p> <p>The nanojoining process of Ag-Au <span class="hlt">hybrid</span> nanowires at 800K was comprehensively studied by virtue of molecular dynamics (MD) <span class="hlt">simulation</span>. Three kinds of configurations including end-to-end, T-like and X-like were built in the <span class="hlt">simulation</span> aiming to understand the nanojoining mechanism. The detailed dynamic evolution of atoms, crystal structure transformation and defects development during the nanojoining processes were performed. The results indicate that there are two stages in the nanojoining process of Ag-Au nanowires which are atom diffusion and new bonds formation. Temperature is a key parameter affecting both stages ascribed to the energy supply and the optimum temperature for Ag-Au nanojoint with diameter of 4.08 nm has been discussed. The mechanical properties of the nanojoint were examined with <span class="hlt">simulation</span> of tensile test on the end-to-end joint. It was revealed that the nanojoint was strong enough to resist fracture at the joining area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026463','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026463"><span id="translatedtitle">Dynamic modelling of an adsorption storage tank using a <span class="hlt">hybrid</span> approach combining computational fluid dynamics and process <span class="hlt">simulation</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Mota, J.P.B.; Esteves, I.A.A.C.; Rostam-Abadi, M.</p> <p>2004-01-01</p> <p>A computational fluid dynamics (CFD) software package has been coupled with the dynamic process <span class="hlt">simulator</span> of an adsorption storage tank for methane fuelled vehicles. The two solvers run as independent processes and handle non-overlapping portions of the computational domain. The codes exchange data on the boundary interface of the two domains to ensure continuity of the solution and of its gradient. A software interface was developed to dynamically suspend and activate each process as necessary, and be responsible for data exchange and process synchronization. This <span class="hlt">hybrid</span> computational tool has been successfully employed to accurately <span class="hlt">simulate</span> the discharge of a new tank design and evaluate its performance. The case study presented here shows that CFD and process <span class="hlt">simulation</span> are highly complementary computational tools, and that there are clear benefits to be gained from a close integration of the two. ?? 2004 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23792617','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23792617"><span id="translatedtitle"><span class="hlt">Hybrid</span> cadaveric/surrogate model of thoracolumbar spine injury due to <span class="hlt">simulated</span> fall from height.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ivancic, Paul C</p> <p>2013-10-01</p> <p>A fall from high height can cause thoracolumbar spine fracture with retropulsion of endplate fragments into the canal leading to neurological deficit. Our objectives were to develop a <span class="hlt">hybrid</span> cadaveric/surrogate model for producing thoracolumbar spine injury during <span class="hlt">simulated</span> fall from height, evaluate the feasibility and performance of the model, and compare injuries with those observed clinically. Our model consisted of a 3-vertebra human lumbar specimen (L3-L4-L5) stabilized with muscle force replication and mounted within an impact dummy. The model was subjected to a fall from height of 2.2 m with impact velocity of 6.6 m/s. Kinetic and kinematic time-history responses were determined using spinal and pelvis load cell data and analyses of high-speed video. Injuries to the L4 vertebra were evaluated by fluoroscopy, radiography, and detailed anatomical dissection. Peak compression forces during the fall from height occurred at 7 ms and reached 44.7 kN at the ground, 9.1 kN at the pelvis, and 4.5 kN at the spine. Pelvis acceleration peaks reached 209.9 g at 8 ms for vertical and 62.8 g at 12 ms for rearward. Tensile load peaks were then observed (spine: 657.0 N at 47 ms; pelvis: 569.4 N at 61 ms). T1/pelvis peak flexion of 68.3° occurred at 38 ms as the upper torso translated forward while the pelvis translated rearward. Complete axial burst fracture of the L4 vertebra was observed including endplate comminution, retropulsion of bony fragments into the canal, loss of vertebral body height, and increased interpedicular distance due to fractures anterior to the pedicles and a vertical split fracture of the left lamina. Our dynamic injury model closely replicated the biomechanics of real-life fall from height and produced realistic, clinically relevant burst fracture of the lumbar spine. Our model may be used for further study of thoracolumbar spine injury mechanisms and injury prevention strategies. PMID:23792617</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.7413L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.7413L"><span id="translatedtitle">Investigation of storm time magnetotail and ion injection using three-dimensional global <span class="hlt">hybrid</span> <span class="hlt">simulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Y.; Wang, X. Y.; Lu, S.; Perez, J. D.; Lu, Q.</p> <p>2014-09-01</p> <p>Dynamics of the near-Earth magnetotail associated with substorms during a period of extended southward interplanetary magnetic field is studied using a three-dimensional (3-D) global <span class="hlt">hybrid</span> <span class="hlt">simulation</span> model that includes both the dayside and nightside magnetosphere, for the first time, with physics from the ion kinetic to the global Alfvénic convection scales. It is found that the dayside reconnection leads to the penetration of the dawn-dusk electric field through the magnetopause and thus a thinning of the plasma sheet, followed by the magnetotail reconnection with 3-D, multiple flux ropes. Ion kinetic physics is found to play important roles in the magnetotail dynamics, which leads to the following results: (1) Hall electric fields in the thin current layer cause a systematic dawnward ion drift motion and thus a dawn-dusk asymmetry of the plasma sheet with a higher (lower) density on the dawnside (duskside). Correspondingly, more reconnection occurs on the duskside. Bidirectional fast ions are generated due to acceleration in reconnection, and more high-speed earthward flow injections are found on the duskside than the dawnside. Such finding of the dawn-dusk asymmetry is consistent with recent satellite observations. (2) The injected ions undergo the magnetic gradient and curvature drift in the dipole-like field, forming a ring current. (3) Ion particle distributions reveal multiple populations/beams at various distances in the tail. (4) Dipolarization of the tail magnetic field takes place due to the pileup of the injected magnetic fluxes and thermal pressure of injected ions, where the fast earthward flow is stopped. Oscillation of the dipolarization front is developed at the fast-flow braking, predominantly on the dawnside. (5) Kinetic compressional wave turbulence is present around the dipolarization front. The cross-tail currents break into small-scale structures with k⟂ρi˜1, where k⟂ is the perpendicular wave number. A sharp dip of magnetic field</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.B13A0209L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.B13A0209L"><span id="translatedtitle">Numerical <span class="hlt">Simulations</span> of <span class="hlt">1</span>-<span class="hlt">D</span> Two-Phase Flow with Non-Zero Mass Fluxes: Application to Phase Separation at 9° N (EPR) and the Main Endeavour Vent Field (JDF)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lewis, K.; Lowell, R. P.</p> <p>2004-12-01</p> <p>Numerical <span class="hlt">simulations</span> of vertical one-dimensional two-phase flow with non-zero mass fluxes can help to enumerate and describe the different parameter space regimes at which phase separation can occur in submarine hydrothermal systems. Our <span class="hlt">simulations</span> suggest that there are at least two such quasi-steady state regimes, corresponding to low and high mass fluxes imposed at the bottom of the system. For relatively low mass fluxes (10-5 - 10-4 kg/m2-s), a low salinity vapor-rich region forms near the top of the system, and high-salinity brine flows downward, raising the salinity in the lower half of the system. For high mass fluxes (&\\sim 10^{-3} kg/m^{2}-s), both vapor and brine flow upward, with the vapor moving more quickly than the brine. In this case, phase separation results in higher salinities near the top of the system, corresponding to a mixture of brine and vapor, and salinities approaching that of normal seawater lower in the system. Bulk surface salinities in the high-flux regime are qualitatively consistent with vent fluid salinities at hydrothermal systems such as 9\\deg$N on the East Pacific Rise and some of the vents of the Main Endeavour Field on the Juan de Fuca Ridge. Our future work will further test this preliminary analysis.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ACPD...1320341T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ACPD...1320341T"><span id="translatedtitle">Air-snowpack exchange of bromine, ozone and mercury in the springtime Arctic <span class="hlt">simulated</span> by the <span class="hlt">1</span>-<span class="hlt">D</span> model PHANTAS - Part 1: In-snow bromine activation and its impact on ozone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toyota, K.; McConnell, J. C.; Staebler, R. M.; Dastoor, A. P.</p> <p>2013-08-01</p> <p>To provide a theoretical framework towards better understanding of ozone depletion events (ODEs) and atmospheric mercury depletion events (AMDEs) in the polar boundary layer, we have developed a one-dimensional model that <span class="hlt">simulates</span> multiphase chemistry and transport of trace constituents from porous snowpack and through the atmospheric boundary layer (ABL) as a unified system. In this paper, we describe a general configuration of the model and the results of <span class="hlt">simulations</span> related to reactive bromine release from the snowpack and ODEs during the Arctic spring. The model employs a chemical mechanism adapted from the one previously used for the <span class="hlt">simulation</span> of multiphase halogen chemistry involving deliquesced sea-salt aerosols in the marine boundary layer. A common set of aqueous-phase reactions describe chemistry both in the liquid-like (or brine) layer on the grain surface of the snowpack and in "haze" aerosols mainly composed of sulfate in the atmosphere. The process of highly soluble/reactive trace gases, whether entering the snowpack from the atmosphere or formed via gas-phase chemistry in the snowpack interstitial air (SIA), is <span class="hlt">simulated</span> by the uptake on brine-covered snow grains and subsequent reactions in the aqueous phase while being traveled vertically within the SIA. A "bromine explosion", by which, in a conventional definition, HOBr formed in the ambient air is deposited and then converted heterogeneously to Br2, is a dominant process of reactive bromine formation in the top 1 mm (or less) layer of the snowpack. Deeper in the snowpack, HOBr formed within the SIA leads to an in-snow bromine explosion, but a significant fraction of Br2 is also produced via aqueous radical chemistry in the brine on the surface of the snow grains. These top- and deeper-layer productions of Br2 both contribute to the Br2 release into the atmosphere, but the deeper-layer production is found to be more important for the net outflux of reactive bromine. Although ozone is removed via</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AIPC.1753h0024D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AIPC.1753h0024D&link_type=ABSTRACT"><span id="translatedtitle">Monte Carlo <span class="hlt">simulation</span> of simultaneous radiation detection in the <span class="hlt">hybrid</span> tomography system ClearPET-XPAD3/CT</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dávila, H. Olaya; Sevilla, A. C.; Castro, H. F.; Martínez, S. A.</p> <p>2016-07-01</p> <p>Using the Geant4 based <span class="hlt">simulation</span> framework SciFW1, a detailed <span class="hlt">simulation</span> was performed for a detector array in the <span class="hlt">hybrid</span> tomography prototype for small animals called ClearPET / XPAD, which was built in the Centre de Physique des Particules de Marseille. The detector system consists of an array of phoswich scintillation detectors: LSO (Lutetium Oxy-ortosilicate doped with cerium Lu2SiO5:Ce) and LuYAP (Lutetium Ortoaluminate of Yttrium doped with cerium Lu0.7Y0.3AlO3:Ce) for Positron Emission Tomography (PET) and <span class="hlt">hybrid</span> pixel detector XPAD for Computed Tomography (CT). Simultaneous acquisition of deposited energy and the corresponding time - position for each recorded event were analyzed, independently, for both detectors. interference between detection modules for PET and CT. Information about amount of radiation reaching each phoswich crystal and XPAD detector using a phantom in order to study the effectiveness by radiation attenuation and influence the positioning of the radioactive source 22Na was obtained. The <span class="hlt">simulation</span> proposed will improve distribution of detectors rings and interference values will be taken into account in the new versions of detectors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/127946','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/127946"><span id="translatedtitle">A two-dimensional <span class="hlt">simulation</span> of the GEC RF reference cell using a <span class="hlt">hybrid</span> fluid-Monte Carlo method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pak, H.; Riley, M.E.</p> <p>1992-12-01</p> <p>A two-dimensional fluid-Monte Carlo <span class="hlt">hybrid</span> model is used to <span class="hlt">simulate</span> the GEC reference cell. The 2-D model assumes azimuthal symmetry and accounts for the ground shield about the electrodes as well as the grounded chamber walls. The <span class="hlt">hybrid</span> model consists of a Monte Carlo method for generating rates and a fluid model for transporting electrons and ions. In the fluid model, the electrons are transported using the continuity equation; and the electric fields are solved self-consistently using Poisson`s equation. The Monte Carlo model transports electrons using the fluid-generated periodic electric field. The ionization rates are then obtained using the electron energy distribution function. An averaging method is used to speed the solution by transporting the ions in a time-averaged electric field with a corrected ambipolar-type diffusion. The <span class="hlt">simulation</span> switches between the conventional and the averaging fluid model. Typically, the <span class="hlt">simulation</span> runs from 10`s to 100`s of averaging fluid cycles before reentering the conventional fluid model for 10`s of cycles. Speed increases of a factor of 100 are possible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2875837','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2875837"><span id="translatedtitle">Photochemical Reaction Dynamics of the Primary Event of Vision Studied by Means of a <span class="hlt">Hybrid</span> Molecular <span class="hlt">Simulation</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hayashi, Shigehiko; Tajkhorshid, Emad; Schulten, Klaus</p> <p>2009-01-01</p> <p>Abstract The photoisomerization reaction dynamics of a retinal chromophore in the visual receptor rhodopsin was investigated by means of <span class="hlt">hybrid</span> quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) <span class="hlt">simulations</span>. The photoisomerization reaction of retinal constitutes the primary step of vision and is known as one of the fastest reactions in nature. To elucidate the molecular mechanism of the high efficiency of the reaction, we carried out <span class="hlt">hybrid</span> ab initio QM/MM MD <span class="hlt">simulations</span> of the complete reaction process from the vertically excited state to the photoproduct via electronic transition in the entire chromophore-protein complex. An ensemble of reaction trajectories reveal that the excited-state dynamics is dynamically homogeneous and synchronous even in the presence of thermal fluctuation of the protein, giving rise to the very fast formation of the photoproduct. The synchronous nature of the reaction dynamics in rhodopsin is found to originate from weak perturbation of the protein surroundings and from dynamic regulation of volume-conserving motions of the chromophore. The <span class="hlt">simulations</span> also provide a detailed view of time-dependent modulations of hydrogen-out-of-plane vibrations during the reaction process, and identify molecular motions underlying the experimentally observed dynamic spectral modulations. PMID:19167292</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060013418','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060013418"><span id="translatedtitle">A Sub-filter Scale Noise Equation far <span class="hlt">Hybrid</span> LES <span class="hlt">Simulations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldstein, Marvin E.</p> <p>2006-01-01</p> <p><span class="hlt">Hybrid</span> LES/subscale modeling approaches have an important advantage over the current noise prediction methods in that they only involve modeling of the relatively universal subscale motion and not the configuration dependent larger scale turbulence . Previous <span class="hlt">hybrid</span> approaches use approximate statistical techniques or extrapolation methods to obtain the requisite information about the sub-filter scale motion. An alternative approach would be to adopt the modeling techniques used in the current noise prediction methods and determine the unknown stresses from experimental data. The present paper derives an equation for predicting the sub scale sound from information that can be obtained with currently available experimental procedures. The resulting prediction method would then be intermediate between the current noise prediction codes and previously proposed <span class="hlt">hybrid</span> techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PhDT........23Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PhDT........23Z"><span id="translatedtitle"><span class="hlt">Simulation</span> and optimum design of <span class="hlt">hybrid</span> solar-wind and solar-wind-diesel power generation systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysic