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Sample records for atomistic-continuum hybrid simulation

  1. Atomistic-Continuum Hybrid Simulation of Heat Transfer between Argon Flow and Copper Plates

    CERN Document Server

    Mao, Yijin; Chen, C L

    2016-01-01

    A simulation work aiming to study heat transfer coefficient between argon fluid flow and copper plate is carried out based on atomistic-continuum hybrid method. Navier-Stokes equations for continuum domain are solved through the Pressure Implicit with Splitting of Operators (PISO) algorithm, and the atom evolution in molecular domain is solved through the Verlet algorithm. The solver is validated by solving Couette flow and heat conduction problems. With both momentum and energy coupling method applied, simulations on convection of argon flows between two parallel plates are performed. The top plate is kept as a constant velocity and has higher temperature, while the lower one, which is modeled with FCC copper lattices, is also fixed but has lower temperature. It is found that, heat transfer between argon fluid flow and copper plate in this situation is much higher than that at macroscopic when the flow is fully developed.

  2. A robust, coupled approach for atomistic-continuum simulation.

    Energy Technology Data Exchange (ETDEWEB)

    Aubry, Sylvie; Webb, Edmund Blackburn, III (Sandia National Laboratories, Albuquerque, NM); Wagner, Gregory John; Klein, Patrick A.; Jones, Reese E.; Zimmerman, Jonathan A.; Bammann, Douglas J.; Hoyt, Jeffrey John (Sandia National Laboratories, Albuquerque, NM); Kimmer, Christopher J.

    2004-09-01

    This report is a collection of documents written by the group members of the Engineering Sciences Research Foundation (ESRF), Laboratory Directed Research and Development (LDRD) project titled 'A Robust, Coupled Approach to Atomistic-Continuum Simulation'. Presented in this document is the development of a formulation for performing quasistatic, coupled, atomistic-continuum simulation that includes cross terms in the equilibrium equations that arise due to kinematic coupling and corrections used for the calculation of system potential energy to account for continuum elements that overlap regions containing atomic bonds, evaluations of thermo-mechanical continuum quantities calculated within atomistic simulations including measures of stress, temperature and heat flux, calculation used to determine the appropriate spatial and time averaging necessary to enable these atomistically-defined expressions to have the same physical meaning as their continuum counterparts, and a formulation to quantify a continuum 'temperature field', the first step towards constructing a coupled atomistic-continuum approach capable of finite temperature and dynamic analyses.

  3. Control of density fluctuations in atomistic-continuum simulations of dense liquids

    DEFF Research Database (Denmark)

    Kotsalis, E.M.; Walther, Jens Honore; Koumoutsakos, P.

    2007-01-01

    continuum solver for the simulation of the Navier-Stokes equations. The lack of periodic boundary conditions in the molecular dynamics simulations hinders the proper accounting for the virial pressure leading to spurious density fluctuations at the continuum-atomistic interface. An ad hoc boundary force is...... usually employed to remedy this situation.We propose the calculation of this boundary force using a control algorithm that explicitly cancels the density fluctuations. The results demonstrate that the present approach outperforms state-of-the-art algorithms. The conceptual and algorithmic simplicity of...

  4. Propriedades dinâmicas de fluidos por simulação computacional: métodos híbridos atomístico-contínuo Computer simulations of dynamical properties of fluids: atomistic-continuum hybrid methods

    Directory of Open Access Journals (Sweden)

    Luciano T. Costa

    2010-01-01

    Full Text Available Computational methods for the calculation of dynamical properties of fluids might consider the system as a continuum or as an assembly of molecules. Molecular dynamics (MD simulation includes molecular resolution, whereas computational fluid dynamics (CFD considers the fluid as a continuum. This work provides a review of hybrid methods MD/CFD recently proposed in the literature. Theoretical foundations, basic approaches of computational methods, and dynamical properties typically calculated by MD and CFD are first presented in order to appreciate the similarities and differences between these two methods. Then, methods for coupling MD and CFD, and applications of hybrid simulations MD/CFD, are presented.

  5. Investigation of the removing process of cathode material in micro-EDM using an atomistic-continuum model

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Jianwen; Zhang, Guojun; Huang, Yu; Ming, Wuyi; Liu, Min; Huang, Hao, E-mail: huanghaohust1990@gmail.com

    2014-10-01

    Highlights: • An atomistic-continuum computational simulation model for single-discharge micro-EDM process of Cu cathode is constructed. • Cathode material is removed mainly in the form of single atoms or small clusters in micro-EDM. • Electric action leads to the formation of peaks on the surface of crater. • Removing process of cathode material under the hybrid action combining the thermal action and the electric action is studied, and the strength of either action needed for material to remove is much reduced. - Abstract: In micro-electrical discharge machining (micro-EDM), the discharge duration is ultra-short, and both the electric action and the thermal action by the discharge channel play important roles in the removing process of cathode material. However, in most researches on the machining mechanism of micro-EDM, only the thermal action is concerned. In this article, a combined atomistic-continuum modeling method in which the two-temperature model and the molecular dynamics simulation model are integrated is used to construct the simulation model for cathode in single-discharge micro-EDM process. With this simulation model, removing processes of Cu cathode material in micro-EDM under pure thermal action, pure electric action and the combination of them are investigated in a simulative way. By analyzing evolutions of temperature, stress and micro-structure of material as well as the dynamical behaviors of material in the removing process, mechanisms of the cathode material removal and crater formation are revealed. In addition, the removing process of cathode material under the combination of pure thermal action and pure electric action is compared with those under the two pure actions respectively to analyze the interactive effect between the thermal action and the electric action.

  6. Investigation of the removing process of cathode material in micro-EDM using an atomistic-continuum model

    International Nuclear Information System (INIS)

    Highlights: • An atomistic-continuum computational simulation model for single-discharge micro-EDM process of Cu cathode is constructed. • Cathode material is removed mainly in the form of single atoms or small clusters in micro-EDM. • Electric action leads to the formation of peaks on the surface of crater. • Removing process of cathode material under the hybrid action combining the thermal action and the electric action is studied, and the strength of either action needed for material to remove is much reduced. - Abstract: In micro-electrical discharge machining (micro-EDM), the discharge duration is ultra-short, and both the electric action and the thermal action by the discharge channel play important roles in the removing process of cathode material. However, in most researches on the machining mechanism of micro-EDM, only the thermal action is concerned. In this article, a combined atomistic-continuum modeling method in which the two-temperature model and the molecular dynamics simulation model are integrated is used to construct the simulation model for cathode in single-discharge micro-EDM process. With this simulation model, removing processes of Cu cathode material in micro-EDM under pure thermal action, pure electric action and the combination of them are investigated in a simulative way. By analyzing evolutions of temperature, stress and micro-structure of material as well as the dynamical behaviors of material in the removing process, mechanisms of the cathode material removal and crater formation are revealed. In addition, the removing process of cathode material under the combination of pure thermal action and pure electric action is compared with those under the two pure actions respectively to analyze the interactive effect between the thermal action and the electric action

  7. Bridging Atomistic/Continuum Scales in Solids with Moving Dislocations

    Institute of Scientific and Technical Information of China (English)

    TANG Shao-Qiang; LIU Wing K.; KARPOV Eduard G.; HOU Thomas Y.

    2007-01-01

    @@ We propose a multiscale method for simulating solids with moving dislocations. Away from atomistic subdomains where the atomistic dynamics are fully resolved, a dislocation is represented by a localized jump profile, superposed on a defect-free field. We assign a thin relay zone around an atomistic subdomain to detect the dislocation profile and its propagation speed at a selected relay time. The detection technique utilizes a lattice time history integral treatment. After the relay, an atomistic computation is performed only for the defect-free field. The method allows one to effectively absorb the fine scale fluctuations and the dynamic dislocations at the interface between the atomistic and continuum domains. In the surrounding region, a coarse grid computation is adequate.

  8. Continuum simulations of water flow past fullerene molecules

    DEFF Research Database (Denmark)

    Popadic, A.; Praprotnik, M.; Koumoutsakos, P.;

    2015-01-01

    as computed by the present model are in good agreement with results from atomistic and atomistic-continuum simulations at a fraction of the cost. We simulate the flow past a single fullerene and an array of fullerenes and demonstrate that such nanoscale flows can be computed efficiently by continuum flow...

  9. Analysis of hybrid viscous damper by real time hybrid simulations

    DEFF Research Database (Denmark)

    Brodersen, Mark Laier; Ou, Ge; Høgsberg, Jan Becker;

    2016-01-01

    Results from real time hybrid simulations are compared to full numerical simulations for a hybrid viscous damper, composed of a viscous dashpot in series with an active actuator and a load cell. By controlling the actuator displacement via filtered integral force feedback the damping performance...... of the hybrid viscous damper is improved, while for pure integral force feedback the damper stroke is instead increased. In the real time hybrid simulations viscous damping is emulated by a bang-bang controlled Magneto-Rheological (MR) damper. The controller activates high-frequency modes and generates drift...... in the actuator displacement, and only a fraction of the measured damper force can therefore be used as input to the investigated integral force feedback in the real time hybrid simulations....

  10. Hybrid2 - The hybrid power system simulation model

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-31

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

  11. Simulation of a Hybrid Locomotion Robot Vehicle

    Science.gov (United States)

    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.

  12. Hybrid simulation models of production networks

    CERN Document Server

    Kouikoglou, Vassilis S

    2001-01-01

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

  13. Methane production in simulated hybrid bioreactor landfill.

    Science.gov (United States)

    Xu, Qiyong; Jin, Xiao; Ma, Zeyu; Tao, Huchun; Ko, Jae Hac

    2014-09-01

    The aim of this work was to study a hybrid bioreactor landfill technology for landfill methane production from municipal solid waste. Two laboratory-scale columns were operated for about ten months to simulate an anaerobic and a hybrid landfill bioreactor, respectively. Leachate was recirculated into each column but aeration was conducted in the hybrid bioreactor during the first stage. Results showed that leachate pH in the anaerobic bioreactor maintained below 6.5, while in the hybrid bioreactor quickly increased from 5.6 to 7.0 due to the aeration. The temporary aeration resulted in lowering COD and BOD5 in the leachate. The volume of methane collected from the hybrid bioreactor was 400 times greater than that of the anaerobic bioreactor. Also, the methane production rate of the hybrid bioreactor was improved within a short period of time. After about 10 months' operation, the total methane production in the hybrid bioreactor was 212 L (16 L/kgwaste).

  14. Simulated Annealing using Hybrid Monte Carlo

    OpenAIRE

    Salazar, Rafael; Toral, Raúl

    1997-01-01

    We propose a variant of the simulated annealing method for optimization in the multivariate analysis of differentiable functions. The method uses global actualizations via the hybrid Monte Carlo algorithm in their generalized version for the proposal of new configurations. We show how this choice can improve upon the performance of simulated annealing methods (mainly when the number of variables is large) by allowing a more effective searching scheme and a faster annealing schedule.

  15. TRNSYS HYBRID wind diesel PV simulator

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-31

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

  16. Hybrid Method Simulation of Slender Marine Structures

    DEFF Research Database (Denmark)

    Christiansen, Niels Hørbye

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

  17. Hybrid Monte Carlo simulation of polymer chains

    CERN Document Server

    Irbäck, A

    1993-01-01

    We develop the hybrid Monte Carlo method for simulations of single off-lattice polymer chains. We discuss implementation and choice of simulation parameters in some detail. The performance of the algorithm is tested on models for homopolymers with short- or long-range self-repulsion, using chains with $16\\le N\\le 512$ monomers. Without excessive fine tuning, we find that the computational cost grows as $N^{2+z^\\prime}$ with $0.64

  18. Hybrid Simulations of Particle Acceleration at Shocks

    Energy Technology Data Exchange (ETDEWEB)

    Caprioli, Damiano

    2014-11-15

    We present the results of large hybrid (kinetic ions – fluid electrons) simulations of particle acceleration at non-relativistic collisionless shocks. Ion acceleration efficiency and magnetic field amplification are investigated in detail as a function of shock inclination and strength, and compared with predictions of diffusive shock acceleration theory, for shocks with Mach number up to 100. Moreover, we discuss the relative importance of resonant and Bell's instability in the shock precursor, and show that diffusion in the self-generated turbulence can be effectively parametrized as Bohm diffusion in the amplified magnetic field.

  19. Multiscale simulation of blood flow in brain arteries with an aneurysm

    CERN Document Server

    Grinberg, Leopold; Fedosov, Dmitry A; Insley, Joseph A; Papka, Michael E; Kumaran, Kalyan; Karniadakis, George Em

    2011-01-01

    Interfacing atomistic-based with continuum-based simulation codes is now required in many multiscale physical and biological systems. We present the first results from coupled atomistic-continuum simulations on 190,000 processors. Platelet aggregation in the patient-specific model of an aneurysm has been modeled using a high-order spectral/hp element Navier-Stokes solver with a stochastic (coarse-grained) Molecular Dynamics solver based on Dissipative Particle Dynamics (DPD).

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

    Science.gov (United States)

    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

  1. Accelerating Climate Simulations Through Hybrid Computing

    Science.gov (United States)

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

    2009-01-01

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

  2. Modeling, Stability Analysis, and Testing of a Hybrid Docking Simulator

    OpenAIRE

    Zebenaya, M.; Boge, T.; Choukroun, D.

    2014-01-01

    A hybrid docking simulator is a hardware-in-the-loop (HIL) simulator that includes a hardware element within a numerical simulation loop. One of the goals of performing a HIL simulation at the European Proximity Operation Simulator (EPOS) is the verification and validation of the docking phase in an on-orbit servicing mission.....

  3. Hybrid simulation: an active power filter case study

    Directory of Open Access Journals (Sweden)

    Y. A. Garcés

    2011-10-01

    Full Text Available The hybrid simulation concept consisting of a combination of computer simulation and laboratory tests. This approach is a cost effective alternative to physically testing the whole system and allows better understanding of complex coupled systems.This paper describes implementing an active power filter (APF hybrid prototype where the source system and load are implemented as a real-time simulation and the system of static power converter acting as an active power filter is implemented in physical hardware. It also confirmed the hybrid simulation results by implementing the simulation in MATLAB-Simulink regarding the same system implemented during the active power filter analysis and design stage.

  4. Mirror instability near the threshold: Hybrid simulations

    Science.gov (United States)

    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.

  5. Numerical simulations of plasma brush behavior in hybrid armatures

    Science.gov (United States)

    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.

  6. Numerical simulations of plasma brush behavior in hybrid armatures

    Energy Technology Data Exchange (ETDEWEB)

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

    1992-04-01

    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 liquid 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 will be presented and discussed.

  7. Hybrid2: The hybrid system simulation model, Version 1.0, user manual

    Energy Technology Data Exchange (ETDEWEB)

    Baring-Gould, E.I.

    1996-06-01

    In light of the large scale desire for energy in remote communities, especially in the developing world, the need for a detailed long term performance prediction model for hybrid power systems was seen. To meet these ends, engineers from the National Renewable Energy Laboratory (NREL) and the University of Massachusetts (UMass) have spent the last three years developing the Hybrid2 software. The Hybrid2 code provides a means to conduct long term, detailed simulations of the performance of a large array of hybrid power systems. This work acts as an introduction and users manual to the Hybrid2 software. The manual describes the Hybrid2 code, what is included with the software and instructs the user on the structure of the code. The manual also describes some of the major features of the Hybrid2 code as well as how to create projects and run hybrid system simulations. The Hybrid2 code test program is also discussed. Although every attempt has been made to make the Hybrid2 code easy to understand and use, this manual will allow many organizations to consider the long term advantages of using hybrid power systems instead of conventional petroleum based systems for remote power generation.

  8. Hybrid and Electric Advanced Vehicle Systems Simulation

    Science.gov (United States)

    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.

  9. Development and implementation of advanced control methods for hybrid simulation

    OpenAIRE

    Kim, Hong

    2011-01-01

    Hybrid simulation is an effective way of testing structures that combines the benefits of a computational analysis and experimental testing techniques. Innovative structures consists of state-ofthe-art components and assemblages whose function as a system needs to be tested experimentally. Often times, these components and assemblages push the controller and other testing equipment to its limits. Performing hybrid simulation with the controller in displacement control mode does not always suf...

  10. Electric and plug-in hybrid vehicles advanced simulation methodologies

    CERN Document Server

    Varga, Bogdan Ovidiu; Moldovanu, Dan; Iclodean, Calin

    2015-01-01

    This book is designed as an interdisciplinary platform for specialists working in electric and plug-in hybrid electric vehicles powertrain design and development, and for scientists who want to get access to information related to electric and hybrid vehicle energy management, efficiency and control. The book presents the methodology of simulation that allows the specialist to evaluate electric and hybrid vehicle powertrain energy flow, efficiency, range and consumption. The mathematics behind each electric and hybrid vehicle component is explained and for each specific vehicle the powertrain

  11. Temperature field simulation of laser-TIG hybrid welding

    Institute of Scientific and Technical Information of China (English)

    陈彦宾; 李俐群; 方俊飞; 封小松; 吴林

    2003-01-01

    The three-dimensional transient temperature distribution of laser-TIG hybrid welding was analyzed and simulated numerically. Calculations were based on a finite element model, in which the physical process of hybrid welding was studied and the coupling effect of the laser and arc in the hybrid process was fully considered. The temperature fields and weld cross-sections of the typical welding parameters are obtained using present model. The calculation results show that the model can indicate the relationship of energy match between laser and arc to joints cross-sections objectively, and the simulation results are well agreed with the experimental results.

  12. The hall effect in magnetic reconnection: Hybrid versus Hall-less hybrid simulations

    Science.gov (United States)

    Malakit, K.; Cassak, P. A.; Shay, M. A.; Drake, J. F.

    2009-04-01

    To understand the role of the Hall effect during fast magnetic reconnection, hybrid simulations with and without the Hall term in the generalized Ohm's Law are compared, as done originally by Karimabadi et al. (2004). It is found that reconnection with the Hall term is fast, but reconnection in the so-called Hall-less hybrid simulations is Sweet-Parker like (slow) when the resistivity is constant and uniform. These results re-affirm the importance of the Hall term in allowing fast reconnection in the hybrid model.

  13. Towards Hybrid Overset Grid Simulations of the Launch Environment

    Science.gov (United States)

    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.

  14. Parallel multiscale simulations of a brain aneurysm

    Science.gov (United States)

    Grinberg, Leopold; Fedosov, Dmitry A.; Karniadakis, George Em

    2013-07-01

    Cardiovascular pathologies, such as a brain aneurysm, are affected by the global blood circulation as well as by the local microrheology. Hence, developing computational models for such cases requires the coupling of disparate spatial and temporal scales often governed by diverse mathematical descriptions, e.g., by partial differential equations (continuum) and ordinary differential equations for discrete particles (atomistic). However, interfacing atomistic-based with continuum-based domain discretizations is a challenging problem that requires both mathematical and computational advances. We present here a hybrid methodology that enabled us to perform the first multiscale simulations of platelet depositions on the wall of a brain aneurysm. The large scale flow features in the intracranial network are accurately resolved by using the high-order spectral element Navier-Stokes solver NɛκTαr. The blood rheology inside the aneurysm is modeled using a coarse-grained stochastic molecular dynamics approach (the dissipative particle dynamics method) implemented in the parallel code LAMMPS. The continuum and atomistic domains overlap with interface conditions provided by effective forces computed adaptively to ensure continuity of states across the interface boundary. A two-way interaction is allowed with the time-evolving boundary of the (deposited) platelet clusters tracked by an immersed boundary method. The corresponding heterogeneous solvers (NɛκTαr and LAMMPS) are linked together by a computational multilevel message passing interface that facilitates modularity and high parallel efficiency. Results of multiscale simulations of clot formation inside the aneurysm in a patient-specific arterial tree are presented. We also discuss the computational challenges involved and present scalability results of our coupled solver on up to 300 K computer processors. Validation of such coupled atomistic-continuum models is a main open issue that has to be addressed in future

  15. Parallel multiscale simulations of a brain aneurysm

    Energy Technology Data Exchange (ETDEWEB)

    Grinberg, Leopold [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States); Fedosov, Dmitry A. [Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, Jülich 52425 (Germany); Karniadakis, George Em, E-mail: george_karniadakis@brown.edu [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States)

    2013-07-01

    Cardiovascular pathologies, such as a brain aneurysm, are affected by the global blood circulation as well as by the local microrheology. Hence, developing computational models for such cases requires the coupling of disparate spatial and temporal scales often governed by diverse mathematical descriptions, e.g., by partial differential equations (continuum) and ordinary differential equations for discrete particles (atomistic). However, interfacing atomistic-based with continuum-based domain discretizations is a challenging problem that requires both mathematical and computational advances. We present here a hybrid methodology that enabled us to perform the first multiscale simulations of platelet depositions on the wall of a brain aneurysm. The large scale flow features in the intracranial network are accurately resolved by using the high-order spectral element Navier–Stokes solver NεκTαr. The blood rheology inside the aneurysm is modeled using a coarse-grained stochastic molecular dynamics approach (the dissipative particle dynamics method) implemented in the parallel code LAMMPS. The continuum and atomistic domains overlap with interface conditions provided by effective forces computed adaptively to ensure continuity of states across the interface boundary. A two-way interaction is allowed with the time-evolving boundary of the (deposited) platelet clusters tracked by an immersed boundary method. The corresponding heterogeneous solvers (NεκTαr and LAMMPS) are linked together by a computational multilevel message passing interface that facilitates modularity and high parallel efficiency. Results of multiscale simulations of clot formation inside the aneurysm in a patient-specific arterial tree are presented. We also discuss the computational challenges involved and present scalability results of our coupled solver on up to 300 K computer processors. Validation of such coupled atomistic-continuum models is a main open issue that has to be addressed in

  16. Autocorrelations in hybrid Monte Carlo simulations

    International Nuclear Information System (INIS)

    Simulations of QCD suffer from severe critical slowing down towards the continuum limit. This problem is known to be prominent in the topological charge, however, all observables are affected to various degree by these slow modes in the Monte Carlo evolution. We investigate the slowing down in high statistics simulations and propose a new error analysis method, which gives a realistic estimate of the contribution of the slow modes to the errors. (orig.)

  17. A Parallel Genetic Simulated Annealing Hybrid Algorithm for Task Scheduling

    Institute of Scientific and Technical Information of China (English)

    SHU Wanneng; ZHENG Shijue

    2006-01-01

    In this paper combined with the advantages of genetic algorithm and simulated annealing, brings forward a parallel genetic simulated annealing hybrid algorithm (PGSAHA) and applied to solve task scheduling problem in grid computing .It first generates a new group of individuals through genetic operation such as reproduction, crossover, mutation, etc, and than simulated anneals independently all the generated individuals respectively.When the temperature in the process of cooling no longer falls, the result is the optimal solution on the whole.From the analysis and experiment result, it is concluded that this algorithm is superior to genetic algorithm and simulated annealing.

  18. A hybrid society model for simulating residential electricity consumption

    International Nuclear Information System (INIS)

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

  19. Simulating Strongly Correlated Electron Systems with Hybrid Monte Carlo

    Institute of Scientific and Technical Information of China (English)

    LIU Chuan

    2000-01-01

    Using the path integral representation, the Hubbard and the periodic Anderson model on D-dimensional cubic lattice are transformed into field theories of fermions in D + 1 dimensions. These theories at half-filling possess a positive definite real symmetry fermion matrix and can be simulated using the hybrid Monte Carlo method.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-01-01

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

  1. Frequency Dependent Network Equivalent for Electromagnetic and Electromechanical Hybrid Simulation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi; WU Wenchuan; ZHANG Boming; Aniruddha M. Gole

    2012-01-01

    The frequency dependent network equivalent (FDNE) can represent not only the fundamental frequency response but also the high frequency response of the network. Thus, it can accommodate the waveform distortion at the interface located in electromagnetic and electromechanical transient hybrid simulation.

  2. Wind Solar Hybrid System Rectifier Stage Topology Simulation

    Directory of Open Access Journals (Sweden)

    Anup M. Gakare

    2014-06-01

    Full Text Available This paper presents power-control strategies of a grid-connected hybrid generation system with versatile power transfer. The hybrid system allows maximum utilization of freely available renewable sources like wind and photovoltaic energies. This paper presents a new system configuration of the multi input rectifier stage for a hybrid wind and photovoltaic energy system. This configuration allows the two sources to supply the load simultaneously depending on the availability of the energy sources maximum power from the sun when it is available. An adaptive MPPT algorithm with a standard perturbs and observed method will be used for the Photo Voltaic system. The main advantage of the hybrid system is to give continuous power supply to the load. The gating pulses to the inverter switches are implemented with conventional and fuzzy controller. This hybrid wind-photo voltaic system is modeled in MATLAB/ SIMULINK environment. Simulation circuit is analyzed and results are presented for this hybrid wind and solar energy system.

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

    Science.gov (United States)

    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

  4. Simulation and Test of a Fuel Cell Hybrid Golf Cart

    Directory of Open Access Journals (Sweden)

    Jingming Liang

    2014-01-01

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

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

    Science.gov (United States)

    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.

  6. A Matlab—Based Simulation for Hybrid Electric Motorcycle

    Institute of Scientific and Technical Information of China (English)

    邵定国; 李永斌; 汪信尧; 江建中

    2003-01-01

    This paper presents a simulation and modeling package based on Matlab for a parallel hybrid electric motorcycle (HEM).The package consists of several main detailed models: internal combustion engine (ICE), motor, continuously variable transmission(CVT), battery, energy management system (EMS) etc. Each component is built as a library, and can be connected together accord-ing to the parallel HEM's topology. Simulation results, such as ICE power demand, motor power demand, battery instantaneous state-of-charge (SOC), pollution emissions etc. Are given and discussed. Lastly experimental data verify our simulation results.

  7. A Hybrid Model for Smoke Simulation

    Institute of Scientific and Technical Information of China (English)

    童若锋; 董金祥

    2002-01-01

    A smoke simulation approach based on the integration of traditional particlesystems and density functions is presented in this paper. By attaching a density function toeach particle as its attribute, the diffusion of smoke can be described by the variation of parti-cles' density functions, along with the effect on airflow by controlling particles' movement andfragmentation. In addition, a continuous density field for realistic rendering can be generatedquickly through the look-up tables of particle's density functions. Compared with traditionalparticle systems, this approach can describe smoke diffusion, and provide a continuous densityfield for realistic rendering with much less computation. A quick rendering scheme is also pre-sented in this paper as a useful preview tool for tuning appropriate parameters in the smokemodel.

  8. Dynamic simulations of hybrid energy systems in load sharing application

    International Nuclear Information System (INIS)

    The paper analyzes the energy, environmental and economic performance of two hybrid micro-cogeneration systems in a load sharing application among residential and office buildings under Napoli (South Italy) weather conditions. The load sharing approach is investigated using dynamic simulations in comparison to a base case with separate conventional systems. Once the advantage of load sharing approach was demonstrated, the performance of two different hybrid systems in load sharing scenario were analyzed. The first one consists of a ground source heat pump (GSHP) and a fuel cell (FC); while the second one is based on a GSHP and a photovoltaic thermal (PVT) system. The performance of these two systems were also compared to a stand-alone GSHP system in order to analyze the advantages of hybrid systems to a single GSHP system. The energy analysis results show that in a load sharing case while using conventional technologies the primary energy savings are equal to 2.1% with respect to the reference case. The introduction of hybrid microcogeneration systems in load sharing application led to primary energy saving with respect to the reference case of 12.8% for the GSHP-FC system and 53.1% for the GSHP-PVT system. The environmental analysis shows a reduction of CO2 equivalent emissions equal to 15.8% and 52.0% for GSHP-FC and GSHP-PVT respectively. The better energy and environmental performance of GSHP-PVT system is due to the introduction of a significant amount of renewable energy source. The economic analysis focusses on operational cost and Simple Pay Back (SPB) index of the different cases and it is also based on an accurate study of the natural gas and electricity tariffs in Italy. This analysis highlights the advantages of the load sharing approach, because in some cases it allows the reduction of both the investment cost and the operational cost. The economic analysis for the two hybrid systems shows an operational costs reduction equal to 28.0% for GSHP-FC and

  9. Characteristic of Ion loss as determined by hybrid simulations

    Science.gov (United States)

    Brecht, Stephen H.; Ledvina, Stephen

    2016-10-01

    One of the major objectives of the MAVEN mission is to determine the loss rate of oxygen ions from the atmosphere of Mars. It is thought that the oxygen ion loss represents a conduit for the loss of water from Mars. However, the actual measurements and estimates of global loss rates are very difficult because one needs an average over many orbits and full coverage of the loss regions of Mars; something that MAVEN will only accomplish with an extended mission. In the meantime global kinetic simulations are an avenue to gain further insight into the loss process and perhaps offer insight into the data analysis that will be performed on the MAVEN data. Hybrid particle codes provide self-consistent simulations of the ion dynamics occurring when the solar wind interacts with Mars.This paper reports the results of HALFSHEL hybrid code simulations of the solar wind interaction with Mars and the subsequent loss of oxygen ions in the form of O+ and O2+. Four simulations were performed representing different orientations of the crustal magnetic fields with the subsolar regions using a solar EUV flux representative of the moderate solar activity experienced by MAVEN. Loss rates will be presented as will evaluations of the distribution functions of the various loss ion species as accumulated at roughly 2 Rm for each of the four simulations. The results will be presented as faces on a box surrounding Mars so that one can evaluate regions such as that of the measured plasma plume. The plume feature has now been measured and is often seen in simulations. Finally, the losses and the subsequent velocity distributions will be compared between the various crustal magnetic field orientations.In summary, results from the HALFSHEL hybrid code will be presented. These results will address characteristics of the oxygen ions lost from Mars as a function of crustal magnetic field orientation. Further, they will be compared with respect to the regions surrounding Mars and the associated

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

    Science.gov (United States)

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

    1981-01-01

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

  11. Multiscale Hy3S: Hybrid stochastic simulation for supercomputers

    Directory of Open Access Journals (Sweden)

    Kaznessis Yiannis N

    2006-02-01

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

  12. Vlasov Simulations of Ionospheric Heating Near Upper Hybrid Resonance

    Science.gov (United States)

    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. Hybrid Computational Simulation and Study of Terahertz Pulsed Photoconductive Antennas

    Science.gov (United States)

    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.

  14. A hybrid algorithm for parallel molecular dynamics simulations

    CERN Document Server

    Mangiardi, Chris M

    2016-01-01

    This article describes an algorithm for hybrid parallelization and SIMD vectorization of molecular dynamics simulations with short-ranged forces. The parallelization method combines domain decomposition with a thread-based parallelization approach. The goal of the work is to enable efficient simulations of very large (tens of millions of atoms) and inhomogeneous systems on many-core processors with hundreds or thousands of cores and SIMD units with large vector sizes. In order to test the efficiency of the method, simulations of a variety of configurations with up to 74 million atoms have been performed. Results are shown that were obtained on multi-core systems with AVX and AVX-2 processors as well as Xeon-Phi co-processors.

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

    Science.gov (United States)

    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.

  16. Sizing and Simulation of PV-Wind Hybrid Power System

    Directory of Open Access Journals (Sweden)

    Mustafa Engin

    2013-01-01

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

  17. Hybrid simulation of metal oxide surge-arrester thermal behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Huang, L.; Raghuveer, M.R. [Manitoba Univ., Winnipeg, MB (Canada). Dept. of Electrical and Computer Engineering

    1996-01-01

    A finite-difference-based technique for simulating the thermal behaviour of a metal oxide surge arrester (MOSA) was described. The improved hybrid thermal modelling technique was claimed to accurately represent heat-transfer modes. Fin theory was used to represent arrester sheds. The proposed model, which relies on simple measurements at the arrester terminals, yields the temporal variation of temperature in a MOSA in both the axial and radial direction. The thermal behaviour of a MOSA under steady-state and transient conditions can be simulated using such a model under different environmental conditions. The accuracy of the modelling technique was demonstrated experimentally by measurements conducted on an arrester. 15 refs., 7 figs.

  18. Hybrid neural network bushing model for vehicle dynamics simulation

    International Nuclear Information System (INIS)

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

  19. Accelerating Climate and Weather Simulations through Hybrid Computing

    Science.gov (United States)

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

    2011-01-01

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

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

    Science.gov (United States)

    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.

  1. A hybrid simulation model for a stable auroral arc

    Directory of Open Access Journals (Sweden)

    P. Janhunen

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

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

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

    Science.gov (United States)

    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

  3. A Fast Hybrid Approach to Air Shower Simulations and Applications

    CERN Document Server

    Drescher, H J; Bleicher, M; Reiter, M; Soff, S; Stöcker, H; Stoecker, Horst

    2003-01-01

    The SENECA model, a new hybrid approach to air shower simulations, is presented. It combines the use of efficient cascade equations in the energy range where a shower can be treated as one-dimensional, with a traditional Monte Carlo method which traces individual particles. This allows one to reproduce natural fluctuations of individual showers as well as the lateral spread of low energy particles. The model is quite efficient in computation time. As an application of the new approach, the influence of the low energy hadronic models on shower properties for AUGER energies is studied. We conclude that these models have a significant impact on the tails of lateral distribution functions, and deserve therefore more attention.

  4. Hybrid simulations of mini-magnetospheres in the laboratory

    International Nuclear Information System (INIS)

    Solar energetic ions are a known hazard to both spacecraft electronics and to manned space flights in interplanetary space missions that extend over a long period of time. A dipole-like magnetic field and a plasma source, forming a mini-magnetosphere, are being tested in the laboratory as means of protection against such hazards. We investigate, via particle-in-cell hybrid simulations, using kinetic ions and fluid electrons, the characteristics of the mini-magnetospheres. Our results, for parameters identical to the experimental conditions, reveal the formation of a mini-magnetosphere, whose features are scanned with respect to the plasma density, the plasma flow velocity and the intensity of the dipole field. Comparisons with a simplified theoretical model reveal a good qualitative agreement and excellent quantitative agreement for higher plasma dynamic pressures and lower B-fields

  5. A wind turbine hybrid simulation framework considering aeroelastic effects

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    S. Simon

    2006-05-01

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

  7. Simulation study of two-ion hybrid resonance heating

    International Nuclear Information System (INIS)

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

  8. Hybrid Simulation of the Shock Wave Trailing the Moon

    Science.gov (United States)

    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.

  9. Quantum Simulations of Solvated Biomolecules Using Hybrid Methods

    Science.gov (United States)

    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.

  10. Hybrid molecular simulation of methane storage inside pillared graphene

    Science.gov (United States)

    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.

  11. SIMULATION OF WIRELESS SENSOR NETWORK WITH HYBRID TOPOLOGY

    Directory of Open Access Journals (Sweden)

    J. Jaslin Deva Gifty

    2016-03-01

    Full Text Available The design of low rate Wireless Personal Area Network (WPAN by IEEE 802.15.4 standard has been developed to support lower data rates and low power consuming application. Zigbee Wireless Sensor Network (WSN works on the network and application layer in IEEE 802.15.4. Zigbee network can be configured in star, tree or mesh topology. The performance varies from topology to topology. The performance parameters such as network lifetime, energy consumption, throughput, delay in data delivery and sensor field coverage area varies depending on the network topology. In this paper, designing of hybrid topology by using two possible combinations such as star-tree and star-mesh is simulated to verify the communication reliability. This approach is to combine all the benefits of two network model. The parameters such as jitter, delay and throughput are measured for these scenarios. Further, MAC parameters impact such as beacon order (BO and super frame order (SO for low power consumption and high channel utilization, has been analysed for star, tree and mesh topology in beacon disable mode and beacon enable mode by varying CBR traffic loads.

  12. Dynamic simulation and optimal control strategy for a parallel hybrid hydraulic excavator

    Institute of Scientific and Technical Information of China (English)

    Xiao LIN; Shuang-xia PAN; Dong-yun WANG

    2008-01-01

    The primary focus of this study is to investigate the control strategies of a hybrid system used in hydraulic excavators. First, the structure and evaluation target of hybrid hydraulic excavators are analyzed. Then the dynamic system model including batteries, motor and engine is built as the simulation environment to obtain control results. A so-called multi-work-point dynamic control strategy, which has both closed-loop speed PI (proportion integral) control and direct torque control, is proposed and studied in the simulation model. Simulation results indicate that the hybrid system with this strategy can meet the power demand and achieve better system stability and higher fuel efficiency.

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

    Directory of Open Access Journals (Sweden)

    Hong-Wen He

    2010-11-01

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

  14. Generation of hybrid meshes for the simulation of petroleum reservoirs; Generation de maillages hybrides pour la simulation de reservoirs petroliers

    Energy Technology Data Exchange (ETDEWEB)

    Balaven-Clermidy, S.

    2001-12-01

    Oil reservoir simulations study multiphase flows in porous media. These flows are described and evaluated through numerical schemes on a discretization of the reservoir domain. In this thesis, we were interested in this spatial discretization and a new kind of hybrid mesh has been proposed where the radial nature of flows in the vicinity of wells is directly taken into account in the geometry. Our modular approach described wells and their drainage area through radial circular meshes. These well meshes are inserted in a structured reservoir mesh (a Corner Point Geometry mesh) made up with hexahedral cells. Finally, in order to generate a global conforming mesh, proper connections are realized between the different kinds of meshes through unstructured transition ones. To compute these transition meshes that we want acceptable in terms of finite volume methods, an automatic method based on power diagrams has been developed. Our approach can deal with a homogeneous anisotropic medium and allows the user to insert vertical or horizontal wells as well as secondary faults in the reservoir mesh. Our work has been implemented, tested and validated in 2D and 2D1/2. It can also be extended in 3D when the geometrical constraints are simplicial ones: points, segments and triangles. (author)

  15. Co-Simulation of Hybrid Systems with SpaceEx and Uppaal

    DEFF Research Database (Denmark)

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

    2015-01-01

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

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

    Science.gov (United States)

    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.

  17. Kinematics and Simulation of a Hybrid Mechanism: MATLAB/SimMechanics

    International Nuclear Information System (INIS)

    Kinematic analysis and simulation of hybrid drive system are addressed in this study. A seven link mechanism with two degrees of freedom is selected as the configuration of the system. Kinematic analysis is performed by loop closure equations and required inputs of servo motor are given to get desired ram motion scenario. MATLAB/SimMechanics platform is used to model the hybrid driven mechanical system mechanism characteristics. The simulation results are presented herein

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  20. Hybrid programming model for implicit PDE simulations on multicore architectures

    KAUST Repository

    Kaushik, Dinesh K.

    2011-01-01

    The complexity of programming modern multicore processor based clusters is rapidly rising, with GPUs adding further demand for fine-grained parallelism. This paper analyzes the performance of the hybrid (MPI+OpenMP) programming model in the context of an implicit unstructured mesh CFD code. At the implementation level, the effects of cache locality, update management, work division, and synchronization frequency are studied. The hybrid model presents interesting algorithmic opportunities as well: the convergence of linear system solver is quicker than the pure MPI case since the parallel preconditioner stays stronger when hybrid model is used. This implies significant savings in the cost of communication and synchronization (explicit and implicit). Even though OpenMP based parallelism is easier to implement (with in a subdomain assigned to one MPI process for simplicity), getting good performance needs attention to data partitioning issues similar to those in the message-passing case. © 2011 Springer-Verlag.

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

    Directory of Open Access Journals (Sweden)

    Siavash Sadeghi

    2010-04-01

    Full Text Available Dynamic behavior analysis of electric motors is required in order to accuratelyevaluate the performance, energy consumption and pollution level of hybrid electricvehicles. Simulation tools for hybrid electric vehicles are divided into steady state anddynamic models. Tools with steady-state models are useful for system-level analysiswhereas tools that utilize dynamic models give in-depth information about the behavior ofsublevel components. For the accurate prediction of hybrid electric vehicle performance,dynamic modeling of the motor and other components is necessary. Whereas the switchedreluctance machine is well suited for electric and hybrid electric vehicles, due to the simpleand rugged construction, low cost, and ability to operate over a wide speed range atconstant power, in this paper dynamic performance of the switched reluctance motor for eseries hybrid electric vehicles is investigated. For this purpose a switched reluctance motorwith its electrical drive is modeld and simulated first, and then the other components of aseries hybrid electric vehicle, such as battery, generator, internal combusion engine, andgearbox, are designed and linked with the electric motor. Finally a typical series hybridelectric vehicle is simulated for different drive cycles. The extensive simulation results showthe dynamic performance of SRM, battery, fuel consumption, and emissions.

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

    Directory of Open Access Journals (Sweden)

    Laurenzi Ian J

    2009-12-01

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

  3. CONEX and CORSIKA: a new 3D hybrid model for air shower simulation

    International Nuclear Information System (INIS)

    The hybrid air shower simulation code CONEX has been implemented as an option in the air shower Monte-Carlo model CORSIKA. In CONEX, Monte-Carlo simulation of high energy interactions is combined with a fast numerical solution of cascade equations. Low energy secondary particles can then be tracked within CORSIKA to obtain the lateral extension of the air shower. This allows the fast and realistic simulation of 3D showers at ultra-high energies.

  4. Hybrid simulation of whistler excitation by electron beams in two-dimensional non-periodic domains

    Energy Technology Data Exchange (ETDEWEB)

    Woodroffe, J.R., E-mail: woodrofj@erau.edu; Streltsov, A.V., E-mail: streltsa@erau.edu

    2014-11-01

    We present a two-dimensional hybrid fluid-PIC scheme for the simulation of whistler wave excitation by relativistic electron beams. This scheme includes a number of features which are novel to simulations of this type, including non-periodic boundary conditions and fresh particle injection. Results from our model suggest that non-periodicity of the simulation domain results in the development of fundamentally different wave characteristics than are observed in periodic domains.

  5. Instability in the Molecular Dynamics Step of Hybrid Monte Carlo in Dynamical Fermion Lattice QCD Simulations

    CERN Document Server

    Joó, B; Kennedy, A D; Irving, A C; Sexton, J C; Pickles, S M; Booth, S P; Joo, Balint; Pendleton, Brian; Kennedy, Anthony D.; Irving, Alan C.; Sexton, James C.; Pickles, Stephen M.; Booth, Stephen P.

    2000-01-01

    We investigate instability and reversibility within Hybrid Monte Carlo simulations using a non-perturbatively improved Wilson action. We demonstrate the onset of instability as tolerance parameters and molecular dynamics step sizes are varied. We compare these findings with theoretical expectations and present limits on simulation parameters within which a stable and reversible algorithm is obtained for physically relevant simulations. Results of optimisation experiments with respect to tolerance prarameters are also presented.

  6. Modeling and Simulation of Hybrid Solar Photovoltaic, Wind turbine and Hydraulic Power System

    OpenAIRE

    Sami, S.; D. Icaza

    2015-01-01

    This paper presents the modeling and simulation of the energy conversion equations describing the total power generated by a hybrid system of solar photovoltaic, wind turbine and hydraulic turbine. To validate this simulation model, the aforementioned equations were coded with MATLAB V13.2, compared to experimental data. The model is intended to be used as an optimization and design tool. A block diagram approach was used during the simulation with MATLAB. The model predicted results compared...

  7. Variable Bus Voltage Modeling for Series Hybrid Electric Vehicle Simulation

    OpenAIRE

    Merkle, Matthew Alan

    1997-01-01

    A growing dependence on foreign oil, along with a heightened concern over the environmental impact of personal transportation, had led the U. S. government to investigate and sponsor research into advanced transportation concepts. One of these future technologies is the hybrid electric vehicle (HEV), typically featuring both an internal combustion engine and an electric motor, with the goal of producing fewer emissions while obtaining superior fuel economy. While vehicles such as the Virg...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 .

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-01

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

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

    International Nuclear Information System (INIS)

    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 (E)quivalent Penetrameter Sensitivity for Radiography of Steel Plates [1]. Potential uses for the method include characterizing alternative radiological sources and simulating NDE radiographs

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

    Science.gov (United States)

    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.

  13. An introduction to the hybrid simulation – the conception of the simulation system

    Directory of Open Access Journals (Sweden)

    K. Foit

    2010-04-01

    Full Text Available Purpose: of this paper: The aim of this paper is to present a simple hybrid simulation system, which is composed of virtual reality software and a mathematically oriented application. From the engineer’s point of view, an important possibility is to link together the mathematical software programs with these for creating presentation graphics or virtual reality, in order to create a simulation system with the large customisability.Design/methodology/approach: The coupling of mathematical and virtual reality system can be done in several different ways, using mechanisms for the Interprocess Communication.Findings: It has been assumed that EonX control will be used in a program conceptually similar to the EON Viewer, but equipped with support of basic interprocess communication interfaces in order to maximize flexibility and possibility of data exchange with different applications.Research limitations/implications: The one of specific requirements is to create an appropriate virtual world in EON Studio with use of external events nodes.Practical implications: The simple application named SockED has been created for testing purposes. The SockED application, which is hosting EonX control, acts as DDE server. As an external application any mathematical program that supports the DDE communication can be used (eg. Microsoft Excel, Matlab. There is also theoretical possibility of use the Programmable Logic Controller in similar manner like in case of SCADA application, but this case was not tested yet.Originality/value: There is no program on the market that allows complicated mathematical computation along with high resolution, 3D presentation graphics. The creation of SockED application allowed combining a mathematical program with the powerful graphics engine from EON Reality.

  14. Hybrid TS fuzzy modelling and simulation for chaotic Lorenz system

    Institute of Scientific and Technical Information of China (English)

    Li De-Quan

    2006-01-01

    The projection of the chaotic attractor observed from the Lorenz system in the X-Z plane is like a butterfly, hence the classical Lorenz system is widely known as the butterfly attractor, and has served as a prototype model for studying chaotic behaviour since it was coined. In this work we take one step further to investigate some fundamental dynamic behaviours of a novel hybrid Takagi-Sugeno (TS) fuzzy Lorenz-type system, which is essentially derived from the delta-operator-based TS fuzzy modelling for complex nonlinear systems, and contains the original Lorenz system of continuous-time TS fuzzy form as a special case. By simply and appropriately tuning the additional parametric perturbations in the two-rule hybrid TS fuzzy Lorenz-type system, complex (two-wing) butterfly attractors observed from this system in the three dimensional (3D) X-Y-Z space are created, which have not yet been reported in the literature, and the forming mechanism of the compound structures have been numerically investigated.

  15. Hybrid hotspot detection using regression model and lithography simulation

    Science.gov (United States)

    Kimura, Taiki; Matsunawa, Tetsuaki; Nojima, Shigeki; Pan, David Z.

    2016-03-01

    As minimum feature sizes shrink, unexpected hotspots appear on wafers. Therefore, it is important to detect and fix these hotspots at design stage to reduce development time and manufacturing cost. Currently, as the most accurate approach, lithography simulation is widely used to detect such hotspots. However, it is known to be time-consuming. This paper proposes a novel aerial image synthesizing method using regression and minimum lithography simulation for only hotspot detection. Experimental results show hotspot detection on the proposed method is equivalent compared with the results on the conventional hotspot detection method which uses only lithography simulation with much less computational cost.

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

    Science.gov (United States)

    Bellos, Vasilis; Tsakiris, George

    2016-09-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-01-01

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

  18. Hybrid Modeling and Simulation of Automotive Supply Chain Network

    Directory of Open Access Journals (Sweden)

    Wen Wang

    2013-07-01

    Full Text Available According to the operation of automotive supply chain and the features of various simulation methods, we create and simulate a automotive supply chain network model with the core enterprise of two vehicle manufacturers, consisting of several parts suppliers, vehicle distributors and logistics service providers. On this basis of a conceptual model including the establishment of enterprise layer, business layer and operation layer, we establish a detailed model of the network system according to the network structure of automotive supply chain, the operation process and the internal business process of core enterprises; then we use System Dynamics (SD, Discrete Event Simulation (DES and Agent Based Modeling (ABM to describe the operating state of each node in the network model. We execute and analyze the simulation model of the whole network system described by Anylogic, using the results of the distributors’ inventory, inventory cost and customer’s satisfaction to prove the effectiveness of the model.

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

    Science.gov (United States)

    Goh, Yang Miang; Askar Ali, Mohamed Jawad

    2016-08-01

    One of the key challenges in improving construction safety and health is the management of safety behavior. From a system point of view, workers work unsafely due to system level issues such as poor safety culture, excessive production pressure, inadequate allocation of resources and time and lack of training. These systemic issues should be eradicated or minimized during planning. However, there is a lack of detailed planning tools to help managers assess the impact of their upstream decisions on worker safety behavior. Even though simulation had been used in construction planning, the review conducted in this study showed that construction safety management research had not been exploiting the potential of simulation techniques. Thus, a hybrid simulation framework is proposed to facilitate integration of safety management considerations into construction activity simulation. The hybrid framework consists of discrete event simulation (DES) as the core, but heterogeneous, interactive and intelligent (able to make decisions) agents replace traditional entities and resources. In addition, some of the cognitive processes and physiological aspects of agents are captured using system dynamics (SD) approach. The combination of DES, agent-based simulation (ABS) and SD allows a more "natural" representation of the complex dynamics in construction activities. The proposed hybrid framework was demonstrated using a hypothetical case study. In addition, due to the lack of application of factorial experiment approach in safety management simulation, the case study demonstrated sensitivity analysis and factorial experiment to guide future research. PMID:26456000

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

    Science.gov (United States)

    Goh, Yang Miang; Askar Ali, Mohamed Jawad

    2016-08-01

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

  1. Plasma simulation in a hybrid ion electric propulsion system

    Science.gov (United States)

    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.

  2. Thermodynamic Simulation of a Hybrid Pneumatic-Combustion Engine Concept

    Directory of Open Access Journals (Sweden)

    Yann Chamaillard

    2002-03-01

    Full Text Available Although internal combustion engines display high overall maximum global efficiencies, this potential cannot be fully exploited in automotive applications: in real conditions, the average engine load (and thus efficiency is quite low and the kinetic energy during a braking phase is lost. This work presents a new hybrid pneumatic-combustion engine and the associated thermodynamic cycles, which is able to store energy in the form of compressed air. This energy can be issued from a braking phase or from a combustion phase at low power. The potential energy from the air tank can then be restored to start the engine, or charge the engine at full load. The regenerative breaking and the suppression of the idling phases could provide an improvement in terms of fuel economy as high as 15% or more if combined with engine downsizing.

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

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, R.A. (U. of California, Irvine, CA); Brouwer, J. (U. of California, Irvine, CA); 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.

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

    International Nuclear Information System (INIS)

    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

  5. Hybrid-model transient stability simulation using dynamic phasors based HVDC system model

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Haojun; Cai, Zexiang [College of Electrical Engineering, South China University of Technology, Guangzhou 510640 (China); Liu, Haoming [Department of Electrical Engineering, Southeast University, Nanjing 210096 (China); Qi, Qingru [North China Power Engineering Co. Ltd., Beijing 100084 (China); Ni, Yixin [Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong (China)

    2006-04-15

    A novel hybrid-model transient stability simulation algorithm for ac/dc power systems is suggested in this paper, where dynamic phasors theory is applied for HVDC transmission system modeling, and traditional electromechanical transient models are used for ac system. A detailed dynamic-phasors-based HVDC system model is derived first, and the algorithm for interface of the dc dynamic phasors model to ac network is proposed next. Computer simulation results show that the HVDC dynamic phasors model has very good accuracy as compared with its electromagnetic transient model; the test results from a 2-area ac/dc power system and a multi-infeed HVDC power system show clearly that the suggested interface algorithm works effectively in system transient stability analysis. The proposed hybrid-model simulation algorithm provides a new approach for dynamic simulation of large-scale ac/dc power systems. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Strehl, Robert; Ilie, Silvana, E-mail: silvana@ryerson.ca [Department of Mathematics, Ryerson University, Toronto, Ontario M5B 2K3 (Canada)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Petsev, Nikolai D.; Leal, L. Gary; Shell, M. Scott [Department of Chemical Engineering, University of California at Santa Barbara, Santa Barbara, California 93106-5080 (United States)

    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.

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

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  9. A multi-scale code for flexible hybrid simulations

    CERN Document Server

    Leukkunen, L; Lopez-Acevedo, O

    2012-01-01

    Multi-scale computer simulations combine the computationally efficient classical algorithms with more expensive but also more accurate ab-initio quantum mechanical algorithms. This work describes one implementation of multi-scale computations using the Atomistic Simulation Environment (ASE). This implementation can mix classical codes like LAMMPS and the Density Functional Theory-based GPAW. Any combination of codes linked via the ASE interface however can be mixed. We also introduce a framework to easily add classical force fields calculators for ASE using LAMMPS, which also allows harnessing the full performance of classical-only molecular dynamics. Our work makes it possible to combine different simulation codes, quantum mechanical or classical, with great ease and minimal coding effort.

  10. Transient simulation of regression rate on thrust regulation process in hybrid rocket motor

    OpenAIRE

    Tian Hui; Li Yijie; Zeng Peng

    2014-01-01

    The main goal of this paper is to study the characteristics of regression rate of solid grain during thrust regulation process. For this purpose, an unsteady numerical model of regression rate is established. Gas–solid coupling is considered between the solid grain surface and combustion gas. Dynamic mesh is used to simulate the regression process of the solid fuel surface. Based on this model, numerical simulations on a H2O2/HTPB (hydroxyl-terminated polybutadiene) hybrid motor have been per...

  11. Simulation of external flows using a hybrid particle mesh vortex method

    DEFF Research Database (Denmark)

    Spietz, Henrik; Hejlesen, Mads Mølholm; Walther, Jens Honore

    The long-term goal of this project is to develop and apply state-of-the-art simulation software to enable accurate prediction of fluid structure interaction, specifically vortex-induced-vibration and flutter of long-span suspension bridges to avoid error-prone structural designs. In the following...... a hybrid particle mesh vortex method is applied for the simulation of uniform flow past stationary solid obstacles of arbitrary shapes....

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

    OpenAIRE

    Liukkonen, Matti; Hentunen, Ari; Suomela, Jussi; Kyyrä, Jorma

    2008-01-01

    This paper proposes method for rapid control prototyping of the series-hybrid transmission system. The rapid control prototyping needs simulation submodels from all system components in order to develop supervisory control software. The same simulation models can also be used to optimize the drive train. The target framework for the rapid control prototyping method is the original equipment manufacturer (OEM), where the objective is to build devices from subcontractor's components. The machin...

  13. Estimating Rare Event Probabilities in Large Scale Stochastic Hybrid Systems by Sequential Monte Carlo Simulation

    NARCIS (Netherlands)

    Blom, H.A.P.; Krystul, J.; Bakker, G.J.

    2006-01-01

    We study the problem of estimating small reachability probabilities for large scale stochastic hybrid processes through Sequential Monte Carlo (SMC) simulation. Recently, [Cerou et al., 2002, 2005] developed an SMC approach for diffusion processes, and referred to the resulting SMC algorithm as an I

  14. Multiple molecular dynamics time-scales in Hybrid Monte Carlo fermion simulations

    OpenAIRE

    PEARDON, MICHAEL JAMES; SEXTON, JAMES CHRISTOPHER

    2003-01-01

    PUBLISHED A scheme for separating the high- and low-frequency molecular dynamics modes in Hybrid Monte Carlo (HMC) simulations of gauge theories with dynamical fermions is presented. The algorithm is tested in the Schwinger model with Wilson fermions. MP is grateful to Enterprise-Ireland for support under grant SC/01/306.

  15. Hybrid simulations of intermediate shocks - Coplanar and noncoplanar solutions. [of space plasma flow

    Science.gov (United States)

    Karimabadi, H.; Omidi, N.

    1992-01-01

    A hybrid code is used to investigate the kinetic structure and stability of subfast intermediate shocks (IS) formed dynamically by the interaction between a flowing plasma and a stationary piston. Results of the kinetic simulation of noncoplanar ISs are compared with predictions of the MHD theory. The relevance of the results of the study to observations of the magnetopause is discussed.

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

    DEFF Research Database (Denmark)

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

    2016-01-01

    Real-time hybrid simulation (RTHS) is a powerful cyber-physical technique that is a relatively cost-effective method to perform global/local system evaluation of structural systems. A major factor that determines the ability of an RTHS to represent true system-level behavior is the fidelity...

  17. Hybrid Multiscale Simulation of Hydrologic and Biogeochemical Processes in the River-Groundwater Interaction Zone

    Science.gov (United States)

    Yang, X.; Scheibe, T. D.; Chen, X.; Hammond, G. E.; Song, X.

    2015-12-01

    The zone in which river water and groundwater mix plays an important role in natural ecosystems as it regulates the mixing of nutrients that control biogeochemical transformations. Subsurface heterogeneity leads to local hotspots of microbial activity that are important to system function yet difficult to resolve computationally. To address this challenge, we are testing a hybrid multiscale approach that couples models at two distinct scales, based on field research at the U. S. Department of Energy's Hanford Site. The region of interest is a 400 x 400 x 20 m macroscale domain that intersects the aquifer and the river and contains a contaminant plume. However, biogeochemical activity is high in a thin zone (mud layer, hybrid multiscale approach is used to efficiently and accurately predict flow and reactive transport at both scales. In our simulations, models at both scales are simulated using the PFLOTRAN code. Multiple microscale simulations in dynamically defined sub-domains (fine resolution, complex reaction network) are executed and coupled with a macroscale simulation over the entire domain (coarse resolution, simpler reaction network). The objectives of the research include: 1) comparing accuracy and computing cost of the hybrid multiscale simulation with a single-scale simulation; 2) identifying hot spots of microbial activity; and 3) defining macroscopic quantities such as fluxes, residence times and effective reaction rates.

  18. Modeling and Simulation for Hybrid of PV-Wind system

    Directory of Open Access Journals (Sweden)

    Maged N. F. Nashed

    2015-04-01

    Full Text Available The rising consumption rate of fossil fuels causes a significant pollution impact on the atmosphere, unwanted greenhouse gases has drawn worldwide attention towards renewable energy sources. Moreover, in recent year’s generation of electricity using the different types of renewable sources are specifically evaluated in the economical performance of the overall equipment. This paper focuses on the modeling and analysis of a Standalone Photovoltaic (PV- wind energy hybrid generation system under different conditions using MATLAB. The proposed system consists of two renewable sources i.e. wind and solar energy. Modeling of PV array and wind turbine is explained. The wind subsystem is equipped of an induction generator. In photovoltaic system, the variable DC output voltage is controlled using buck-boost converter for the MPPT. These two systems are combined to operate in parallel and the common bus collects the total energy from the wind and PV systems are uses it to the load and with change the load

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2015-07-01

    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 10months. 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 75d and 60d 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 133.4L/kgvs and 113.2L/kgvs. As for MSW with high content of food waste, leachate recirculation right after aeration stopped was not recommended due to VFA inhibition for methanogens. PMID:25857421

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

    Science.gov (United States)

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

    2015-07-01

    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 10months. 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 75d and 60d 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 133.4L/kgvs and 113.2L/kgvs. As for MSW with high content of food waste, leachate recirculation right after aeration stopped was not recommended due to VFA inhibition for methanogens.

  3. Nonlinear electromagnetic gyrokinetic particle simulations with the electron hybrid model

    Science.gov (United States)

    Nishimura, Y.; Lin, Z.; Chen, L.; Hahm, T.; Wang, W.; Lee, W.

    2006-10-01

    The electromagnetic model with fluid electrons is successfully implemented into the global gyrokinetic code GTC. In the ideal MHD limit, shear Alfven wave oscillation and continuum damping is demonstrated. Nonlinear electromagnetic simulation is further pursued in the presence of finite ηi. Turbulence transport in the AITG unstable β regime is studied. This work is supported by Department of Energy (DOE) Grant DE-FG02-03ER54724, Cooperative Agreement No. DE-FC02-04ER54796 (UCI), DOE Contract No. DE-AC02-76CH03073 (PPPL), and in part by SciDAC Center for Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasmas. Z. Lin, et al., Science 281, 1835 (1998). F. Zonca and L. Chen, Plasma Phys. Controlled Fusion 30, 2240 (1998); G. Zhao and L. Chen, Phys. Plasmas 9, 861 (2002).

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Qiyong; Tian, Ying; Wang, Shen; Ko, Jae Hac, E-mail: jaehacko@pkusz.edu.cn

    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.

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

    KAUST Repository

    Azdoud, Yan

    2014-01-01

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

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-08-15

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

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-29

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

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

    Science.gov (United States)

    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

  13. Development of a hybrid simulation course to reduce central line infections.

    Science.gov (United States)

    Clapper, Timothy

    2012-05-01

    Clinical educators are continually looking at ways to effectively deliver large amounts of information to their learners. Whether as a part of pre-course work or as a separate phase of training, there are numerous benefits to making information available to learners before conducting sessions that allow the learners to practice the skills. Hybrid courses consist of a mixture of online and on-site instruction and offer a viable option for clinical educators to consider, especially when their intended audience consists of thousands of learners. This article describes the experiences of a medical simulation center and the use of a hybrid curriculum technique to reduce central line infections.

  14. Modeling and Simulation of Hybrid Solar Photovoltaic, Wind turbine and Hydraulic Power System

    Directory of Open Access Journals (Sweden)

    S. Sami

    2015-09-01

    Full Text Available This paper presents the modeling and simulation of the energy conversion equations describing the total power generated by a hybrid system of solar photovoltaic, wind turbine and hydraulic turbine. To validate this simulation model, the aforementioned equations were coded with MATLAB V13.2, compared to experimental data. The model is intended to be used as an optimization and design tool. A block diagram approach was used during the simulation with MATLAB. The model predicted results compared fairly with experimental data under various conditions.

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

    CERN Document Server

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

    2015-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-01-01

    We present simulated fuel economy and emissions city transit buses powered by conventional diesel engines and diesel-hybrid electric powertrains of varying size. Six representative city drive cycles were included in the study. In addition, we included previously published aftertreatment device models for control of CO, HC, NOx, and particulate matter (PM) emissions. Our results reveal that bus hybridization can significantly enhance fuel economy by reducing engine idling time, reducing demands for accessory loads, exploiting regenerative braking, and shifting engine operation to speeds and loads with higher fuel efficiency. Increased hybridization also tends to monotonically reduce engine-out emissions, but trends in the tailpipe (post-aftertreatment) emissions involve more complex interactions that significantly depend on motor size and drive cycle details.

  17. Modelling and Simulation of System Dynamics of Hybrid-Driven Precision Press

    Institute of Scientific and Technical Information of China (English)

    LI Yonggang; ZHANG Ce; MENG Caifang; SONG Yimin

    2005-01-01

    Different from conventional mechanical systems with single degree of freedom (DOF), the main idea of the system of hybrid-driven precision press is to combine the motion of a constant speed motor with a servomotor via a two-DOF mechanism to provide flexible output. In order to make the feasibility clear, this paper studies theoretically the dynamic characteristics of this hybrid-driven mechanical system.Firstly,the dynamics model of the whole electromechanical system is set up by combining dynamic equations of DC motors with those of two-DOF nine-bar mechanism deduced by the Lagrange′s formula. Secondly through the numerical solution with the fourth Runge-Kutta, computer simulation about the dynamics is done, which shows that the designed and optimized hybrid-driven precision press is feasible in theory. These provide theoretical basis for later experimental research.

  18. Microwave imaging for conducting scatterers by hybrid particle swarm optimization with simulated annealing

    International Nuclear Information System (INIS)

    In this paper, a microwave imaging technique for reconstructing the shape of two-dimensional perfectly conducting scatterers by means of a stochastic optimization approach is investigated. Based on the boundary condition and the measured scattered field derived by transverse magnetic illuminations, a set of nonlinear integral equations is obtained and the imaging problem is reformulated in to an optimization problem. A hybrid approximation algorithm, called PSO-SA, is developed in this work to solve the scattering inverse problem. In the hybrid algorithm, particle swarm optimization (PSO) combines global search and local search for finding the optimal results assignment with reasonable time and simulated annealing (SA) uses certain probability to avoid being trapped in a local optimum. The hybrid approach elegantly combines the exploration ability of PSO with the exploitation ability of SA. Reconstruction results are compared with exact shapes of some conducting cylinders; and good agreements with the original shapes are observed.

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

    Science.gov (United States)

    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.

  20. Numerical simulations for the effiency improvement of hybrid dye-microcrystalline silicon pin-solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Burdorf, Sven; Bauer, Gottfried Heinrich; Brueggemann, Rudolf [Institut fuer Physik, Carl von Ossietzky Universitaet, Oldenburg (Germany)

    2011-07-01

    Hybrid solar cells consisting of dye sensitizers incorporated in the i-layer of microcrystalline silicon pin solar cell have been proposed and even recently processed. The dye sensitizer molecules are embedded in the matrix and enhance the overall absorption of the dye-matrix system due to their high absorption coefficient in the spectral range interesting for photovoltaic applications. However, the charge transport properties of dyes are quite poor. Microcrystalline silicon on the other hand has acceptable charge transport properties, while the absorption, given a layer thickness in the micron range, is relatively poor. This contribution investigates the effiency improvement of hybrid dye-microcrystalline solar cells compared to pure microcrystalline solar cells by simulation. The results indicate that, under optimal conditions, the effiency can be improved by more than 20 % compared to a pure microcrystalline silicon cell. The thickness reduction for the hybrid system can be as large as 50 % for the same effiency.

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

    Science.gov (United States)

    Karlis, Athanasios; 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.

  2. Fast garment simulation with aid of hybrid bones

    Institute of Scientific and Technical Information of China (English)

    吴博; 陈寅; 徐凯; 程志全; 熊岳山

    2015-01-01

    A data-driven method was proposed to realistically animate garments on human poses in reduced space. Firstly, a gradient based method was extended to generate motion sequences and garments were simulated on the sequences as our training data. Based on the examples, the proposed method can fast output realistic garments on new poses. Our framework can be mainly divided into offline phase and online phase. During the offline phase, based on linear blend skinning (LBS), rigid bones and flex bones were estimated for human bodies and garments, respectively. Then, rigid bone weight maps on garment vertices were learned from examples. In the online phase, new human poses were treated as input to estimate rigid bone transformations. Then, both rigid bones and flex bones were used to drive garments to fit the new poses. Finally, a novel formulation was also proposed to efficiently deal with garment-body penetration. Experiments manifest that our method is fast and accurate. The intersection artifacts are fast removed and final garment results are quite realistic.

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

    Science.gov (United States)

    Chehel Amirani, Morteza; Tang, Tian

    2015-12-14

    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. PMID:26542447

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

    Energy Technology Data Exchange (ETDEWEB)

    Tsai A, Banta L, Tucker D

    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.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Cappelli, Mark A., E-mail: cap@stanford.edu; Young, Christopher V.; Cha, Eunsun [Stanford Plasma Physics Laboratory, 452 Escondido Mall, Bldg. 520-118, Stanford, California 94305 (United States); Fernandez, Eduardo [Mathematics and Physics Department, Eckerd College, 4200 54th Avenue South, St. Petersburg, Florida 33711 (United States)

    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.

  7. Hybrid Decomposition Method in Parallel Molecular Dynamics Simulation Based on SMP Cluster Architecture

    Institute of Scientific and Technical Information of China (English)

    WANG Bing; SHU Jiwu; ZHENG Weimin; WANG Jinzhao; CHEN Min

    2005-01-01

    A hybrid decomposition method for molecular dynamics simulations was presented, using simultaneously spatial decomposition and force decomposition to fit the architecture of a cluster of symmetric multi-processor (SMP) nodes. The method distributes particles between nodes based on the spatial decomposition strategy to reduce inter-node communication costs. The method also partitions particle pairs within each node using the force decomposition strategy to improve the load balance for each node. Simulation results for a nucleation process with 4 000 000 particles show that the hybrid method achieves better parallel performance than either spatial or force decomposition alone, especially when applied to a large scale particle system with non-uniform spatial density.

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

    OpenAIRE

    Zhu, Sha; Degnan, James H; Eldon, Bjarki

    2013-01-01

    Hybrid-Lambda is a software package that simulates gene trees under Kingman or two Lambda-coalescent processes within species networks or species trees. It is written in C++, and re- leased under GNU General Public License (GPL) version 3. Users can modify and make new dis- tribution under the terms of this license. For details of this license, visit http://www.gnu.org/licenses/. Hybrid Lambda is available at https://code.google.com/p/hybrid-lambda.

  9. Full Wave Simulation of Integrated Circuits Using Hybrid Numerical Methods

    Science.gov (United States)

    Tan, Jilin

    Transmission lines play an important role in digital electronics, and in microwave and millimeter-wave circuits. Analysis, modeling, and design of transmission lines are critical to the development of the circuitry in the chip, subsystem, and system levels. In the past several decays, at the EM modeling level, the quasi-static approximation has been widely used due to its great simplicity. As the clock rates increase, the inter-connect effects such as signal delay, distortion, dispersion, reflection, and crosstalk, limit the performance of microwave systems. Meanwhile, the quasi-static approach loses its validity for some complex system structures. Since the successful system design of the PCB, MCM, and the chip packaging, rely very much on the computer aided EM level modeling and simulation, many new methods have been developed, such as the full wave approach, to guarantee the successful design. Many difficulties exist in the rigorous EM level analysis. Some of these include the difficulties in describing the behavior of the conductors with finite thickness and finite conductivity, the field singularity, and the arbitrary multilayered multi-transmission lines structures. This dissertation concentrates on the full wave study of the multi-conductor transmission lines with finite conductivity and finite thickness buried in an arbitrary lossy multilayered environment. Two general approaches have been developed. The first one is the integral equation method in which the dyadic Green's function for arbitrary layered media has been correctly formulated and has been tested both analytically and numerically. By applying this method, the double layered high dielectric permitivitty problem and the heavy dielectrical lossy problem in multilayered media in the CMOS circuit design have been solved. The second approach is the edge element method. In this study, the correct functional for the two dimensional propagation problem has been successfully constructed in a rigorous way

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

    Science.gov (United States)

    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

  11. NUMERICAL SIMULATION OF STRESS-INDUCED SECONDARY FLOWS WITH HYBRID FINITE ANALYTIC METHOD

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The algorithm of the Hybrid Finite Analytic Method (HFAM) was used to simulate fully developed trubulent flows in non-circular ducts and open channels. And the turbulent flow fields in a square duct and a rectangular open channels were calculated by Naot and Rodi's model, and that in a compound channel was calculated by Speaizle's non-linear eddy-viscosity model with this algorithm. The results show that the HFAM is suitable for calculating these complicated turbulent flows.

  12. Proposal for high-fidelity quantum simulation using a hybrid dressed state

    OpenAIRE

    Cai, Jianming; Cohen, Itsik; Retzker, Alex; Plenio, Martin B.

    2015-01-01

    A fundamental goal of quantum technologies concerns the exploitation of quantum coherent dynamics for the realisation of novel quantum applications such as quantum computing, quantum simulation, 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 hybrid dressed state from a pair of continuously driven systems. It allows sufficiently strong driving fields to suppress th...

  13. Efficient parabolic evaluation of coupling terms in hybrid quantum/classical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Bastida, Adolfo, E-mail: bastida@um.es [Departamento de Quimica Fisica, Facultad de Quimica, Universidad de Murcia, 30100 Murcia (Spain); Soler, Miguel Angel; Zuniga, Jose; Requena, Alberto [Departamento de Quimica Fisica, Facultad de Quimica, Universidad de Murcia, 30100 Murcia (Spain); Miguel, Beatriz [Departamento de Ingenieria Quimica y Ambiental, Universidad Politecnica de Cartagena, 30203 Cartagena (Spain)

    2009-03-30

    A parabolic interpolation function of time is proposed to evaluate the non-adiabatic coupling matrix elements and the adiabatic energies at intermediate times within the classical time integration interval in hybrid quantum/classical simulations. The accuracy and the computational efficiency of this parabolic approximation are illustrated by carrying out a numerical application to the well-studied vibrational relaxation of I{sub 2} in liquid xenon.

  14. Hybrid Simulation of the Seismic Response of Squat Reinforced Concrete Shear Walls

    OpenAIRE

    Whyte, Catherine Alexandra

    2012-01-01

    Most industrial and nuclear facilities rely on reinforced concrete structural walls as their primary seismic lateral-force-resisting components. These walls commonly have an aspect ratio smaller than 0.5 and have a very high stiffness and strength. There is a significant uncertainty regarding the behavior of these walls under earthquake loading, their failure modes, and their expected strengths and deformation capacities. Hybrid simulation is an effective experimental method to examine these...

  15. Optimized Mooring Line Simulation Using a Hybrid Method Time Domain Scheme

    DEFF Research Database (Denmark)

    Christiansen, Niels Hørbye; Voie, Per Erlend Torbergsen; Høgsberg, Jan;

    2014-01-01

    Dynamic analyses of slender marine structures are computationally expensive. Recently it has been shown how a hybrid method which combines FEM models and artificial neural networks (ANN) can be used to reduce the computation time spend on the time domain simulations associated with fatigue analysis...... installation. It is shown that it is possible to estimate the cost of ignoring one or more input variables in an analysis....

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

    Energy Technology Data Exchange (ETDEWEB)

    Amano, Takanobu, E-mail: amano@eps.s.u-tokyo.ac.jp; 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.

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

    Science.gov (United States)

    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.

  18. A hybrid Genetic and Simulated Annealing Algorithm for Chordal Ring implementation in large-scale networks

    DEFF Research Database (Denmark)

    Riaz, M. Tahir; Gutierrez Lopez, Jose Manuel; Pedersen, Jens Myrup;

    2011-01-01

    The paper presents a hybrid Genetic and Simulated Annealing algorithm for implementing Chordal Ring structure in optical backbone network. In recent years, topologies based on regular graph structures gained a lot of interest due to their good communication properties for physical topology...... of the networks. There have been many use of evolutionary algorithms to solve the problems which are in combinatory complexity nature, and extremely hard to solve by exact approaches. Both Genetic and Simulated annealing algorithms are similar in using controlled stochastic method to search the solution...

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

    Science.gov (United States)

    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.

  20. Corona plasma in tokamak: measures and numerical simulation; application to hybrid frequency heating of Wega plasma

    International Nuclear Information System (INIS)

    The tokamak edge plasma region begins beyond the middle plasma, limited by a diaphragm and spread to torus vacuum chamber wall. Parameters of edge plasma have been measured; several disgnostic type have been used. Numerical simulation code is used for result interpretarion and to display important phenomena in this region. Simulation results give a relation between the plasma parameters at the limiter radius; these parameters can be used as limit conditions for inner plasma transport codes. Edge plasma measurements have been examined with care during lower hybrid frequency heating. Study of plasma parameter modifications can help to a better comprehension of phenomena related to heating

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    Burgess, David; Gingell, Peter W; Trávníček, Pavel M

    2016-01-01

    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 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 tim...

  4. A novel technique for the numerical simulation of hot collision-free plasma; Vlasov Hybrid Simulation

    OpenAIRE

    D. Nunn

    1993-01-01

    This paper presents a highly efficient and stable algorithm for the numerical simulation of collision free plasma. This algorithm has been successfully used to numerically model non linear electron cyclotron resonance in VLF band radio waves in space, and has produced good simulations of radio emissions such as ‘dawn chorus’ and ‘triggered VLF emissions’. The algorithm fills the phase box with simulation particles which represent phase space trajectories. Particle trajectories are followed fo...

  5. Comparative hybrid and digital simulation studies of the behaviour of a wind generator equipped with a static frequency converter

    Science.gov (United States)

    Dube, B.; Lefebvre, S.; Perocheau, A.; Nakra, H. L.

    1988-01-01

    This paper describes the comparative results obtained from digital and hybrid simulation studies on a variable speed wind generator interconnected to the utility grid. The wind generator is a vertical-axis Darrieus type coupled to a synchronous machine by a gear-box; the synchronous machine is connected to the AC utility grid through a static frequency converter. Digital simulation results have been obtained using CSMP software; these results are compared with those obtained from a real-time hybrid simulator that in turn uses a part of the IREQ HVDC simulator. The agreement between hybrid and digital simulation results is generally good. The results demonstrate that the digital simulation reproduces the dynamic behavior of the system in a satisfactory manner and thus constitutes a valid tool for the design of the control systems of the wind generator.

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

    Directory of Open Access Journals (Sweden)

    Pietra Paola

    2012-04-01

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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

  9. Development and Simulation of a Type of Four-Shaft ECVT for a Hybrid Electric Vehicle

    Directory of Open Access Journals (Sweden)

    Yong Zhang

    2016-02-01

    Full Text Available In hybrid electric vehicles with power-split configurations, the engine can be decoupled from the wheel and operated with improved fuel economy, while the entire efficiency of the powertrain is affected by the circular electric power flow. Two planetary gear (2-PG sets with adding brakes/clutches, namely a type of four shaft elelctric continuously variable transmission (ECVT can provide multi-mode operation for the powertrain and extend the efficient area. First, a conventional 2-PG AT (Automatic Transmission architecture is investigated. By analyzing and comparing the connection and operating modes based on the kinematic relationship and lever analogy, a feasible four-shaft ECVT architecture with two brakes and two simplified versions are picked. To make a trade-off between fuel economy and configuration complexity, an instantaneous optimal control strategy based on the equivalent consumption minimization strategy (ECMS concept is then developed and employed as the unified optimization method in the simulations of three different configurations. Finally, the simulation results show that the simplified versions are suboptimal sets and the fuel economy is sacrificed by the limits of different modes. From the viewpoint of concept design, a multi-mode power-split configuration is more suitable for hybrid electric vehicles. This research applied a systematic methodology from concept design to energy management optimization, which can provide the guidelines for researchers to select a suitable multi-mode power-split hybrid powertrain.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Zheng, E-mail: 19994035@sina.com [College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101 (China); Wang, Jun; Zhou, Bihua [National Defense Key Laboratory on Lightning Protection and Electromagnetic Camouflage, PLA University of Science and Technology, Nanjing 210007 (China); Zhou, Shudao [College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101 (China); Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044 (China)

    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.

  14. A hybrid atomistic electrodynamics-quantum mechanical approach for simulating surface-enhanced Raman scattering.

    Science.gov (United States)

    Payton, John L; Morton, Seth M; Moore, Justin E; Jensen, Lasse

    2014-01-21

    Surface-enhanced Raman scattering (SERS) is a technique that has broad implications for biological and chemical sensing applications by providing the ability to simultaneously detect and identify a single molecule. The Raman scattering of molecules adsorbed on metal nanoparticles can be enhanced by many orders of magnitude. These enhancements stem from a twofold mechanism: an electromagnetic mechanism (EM), which is due to the enhanced local field near the metal surface, and a chemical mechanism (CM), which is due to the adsorbate specific interactions between the metal surface and the molecules. The local field near the metal surface can be significantly enhanced due to the plasmon excitation, and therefore chemists generally accept that the EM provides the majority of the enhancements. While classical electrodynamics simulations can accurately simulate the local electric field around metal nanoparticles, they offer few insights into the spectral changes that occur in SERS. First-principles simulations can directly predict the Raman spectrum but are limited to small metal clusters and therefore are often used for understanding the CM. Thus, there is a need for developing new methods that bridge the electrodynamics simulations of the metal nanoparticle and the first-principles simulations of the molecule to facilitate direct simulations of SERS spectra. In this Account, we discuss our recent work on developing a hybrid atomistic electrodynamics-quantum mechanical approach to simulate SERS. This hybrid method is called the discrete interaction model/quantum mechanics (DIM/QM) method and consists of an atomistic electrodynamics model of the metal nanoparticle and a time-dependent density functional theory (TDDFT) description of the molecule. In contrast to most previous work, the DIM/QM method enables us to retain a detailed atomistic structure of the nanoparticle and provides a natural bridge between the electronic structure methods and the macroscopic

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    Jingwei Song

    2014-01-01

    Full Text Available 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%.

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

    International Nuclear Information System (INIS)

    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

  19. Nonlinear electromagnetic formulation for particle simulation of lower hybrid waves in toroidal geometry

    CERN Document Server

    Bao, J; Kuley, A; Wang, Z X

    2016-01-01

    Electromagnetic particle simulation model has been formulated and verified for nonlinear processes of lower hybrid (LH) waves in fusion plasmas. Electron dynamics is described by the drift kinetic equation using either kinetic momentum or canonical momentum. Ion dynamics is treated as the fluid system or by the Vlasov equation. Compressible magnetic perturbation is retained to simulate both the fast and slow LH waves. Numerical properties are greatly improved by using electron continuity equation to enforce consistency between electrostatic potential and vector potential, and by using the importance sampling technique. The simulation model has been implemented in the gyrokinetic toroidal code (GTC), and verified for the dispersion relation and nonlinear particle trapping of the electromagnetic LH waves.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bao, J., E-mail: baojian@pku.edu.cn [Fusion Simulation Center and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China); Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Lin, Z. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Kuley, A. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Fusion Simulation Center and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China)

    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.

  1. On the Design, Characterization and Simulation of Hybrid Metal-Composite Interfaces

    Science.gov (United States)

    Kießling, R.; Ihlemann, J.; Pohl, M.; Stommel, M.; Dammann, C.; Mahnken, R.; Bobbert, M.; Meschut, G.; Hirsch, F.; Kästner, M.

    2016-09-01

    Multi-material lightweight designs are a key feature for the development of innovative and resource-efficient products. In the development of a hybrid composite, the interface between the joined components has to be considered in detail as it represents a typical location of the initialization of failure. This contribution gives an overview of the simulative engineering of metal-composite interfaces. To this end, several design aspects on the microscale and macroscale are explained and methods to model the mechanical behavior of the interface within finite element simulations. This comprises the utilization of cohesive elements with a continuum description of the interface. Likewise, traction-separation based cohesive elements, i.e. a zero-thickness idealization of the interface, are outlined and applied to a demonstration example. Within these finite element simulations, the constitutive behavior of the connected components has to be described by suitable material models. Therefore, inelastic material models at large strains are formulated based on rheological models.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    Justin S Hogg

    2014-04-01

    Full Text Available 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

  6. Hybrid simulations: combining atomistic and coarse-grained force fields using virtual sites.

    Science.gov (United States)

    Rzepiela, Andrzej J; Louhivuori, Martti; Peter, Christine; Marrink, Siewert J

    2011-06-14

    Hybrid simulations, in which part of the system is represented at atomic resolution and the remaining part at a reduced, coarse-grained, level offer a powerful way to combine the accuracy associated with the atomistic force fields to the sampling speed obtained with coarse-grained (CG) potentials. In this work we introduce a straightforward scheme to perform hybrid simulations, making use of virtual sites to couple the two levels of resolution. With the help of these virtual sites interactions between molecules at different levels of resolution, i.e. between CG and atomistic molecules, are treated the same way as the pure CG-CG interactions. To test our method, we combine the Gromos atomistic force field with a number of coarse-grained potentials, obtained through several approaches that are designed to obtain CG potentials based on an existing atomistic model, namely iterative Boltzmann inversion, force matching, and a potential of mean force subtraction procedure (SB). We also explore the use of the MARTINI force field for the CG potential. A simple system, consisting of atomistic butane molecules dissolved in CG butane, is used to study the performance of our hybrid scheme. Based on the potentials of mean force for atomistic butane in CG solvent, and the properties of 1:1 mixtures of atomistic and CG butane which should exhibit ideal mixing behavior, we conclude that the MARTINI and SB potentials are particularly suited to be combined with the atomistic force field. The MARTINI potential is subsequently used to perform hybrid simulations of atomistic dialanine peptides in both CG butane and water. Compared to a fully atomistic description of the system, the hybrid description gives similar results provided that the dielectric screening of water is accounted for. Within the field of biomolecules, our method appears ideally suited to study e.g. protein-ligand binding, where the active site and ligand are modeled in atomistic detail and the rest of the protein

  7. A Robust Method for Handling Low Density Regions in Hybrid Simulations for Collisionless Plasmas

    CERN Document Server

    Amano, Takanobu; Shirakawa, Keisuke

    2014-01-01

    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 velocit...

  8. Stochastic analysis and simulation of hydrometeorological processes for optimizing hybrid renewable energy systems

    Science.gov (United States)

    Tsekouras, Georgios; Ioannou, Christos; Efstratiadis, Andreas; Koutsoyiannis, Demetris

    2013-04-01

    The drawbacks of conventional energy sources including their negative environmental impacts emphasize the need to integrate renewable energy sources into energy balance. However, the renewable sources strongly depend on time varying and uncertain hydrometeorological processes, including wind speed, sunshine duration and solar radiation. To study the design and management of hybrid energy systems we investigate the stochastic properties of these natural processes, including possible long-term persistence. We use wind speed and sunshine duration time series retrieved from a European database of daily records and we estimate representative values of the Hurst coefficient for both variables. We conduct simultaneous generation of synthetic time series of wind speed and sunshine duration, on yearly, monthly and daily scale. To this we use the Castalia software system which performs multivariate stochastic simulation. Using these time series as input, we perform stochastic simulation of an autonomous hypothetical hybrid renewable energy system and optimize its performance using genetic algorithms. For the system design we optimize the sizing of the system in order to satisfy the energy demand with high reliability also minimizing the cost. While the simulation scale is the daily, a simple method allows utilizing the subdaily distribution of the produced wind power. Various scenarios are assumed in order to examine the influence of input parameters, such as the Hurst coefficient, and design parameters such as the photovoltaic panel angle.

  9. Modelization and Simulation of an Electric and Fuel Cell Hybrid Vehicle under Real Conditions

    Directory of Open Access Journals (Sweden)

    Victor Alfonsin

    2015-06-01

    Full Text Available This paper presents a toolbox for the simulation of a zero emission urban hybrid bus, which combines batteries and fuel cells. This type of vehicle performs predefined routes with a certain frequency, then they are an ideal option to the replacement of combustion engines with renewable energy systems. The simulation of these vehicles can be made for different standard driving cycles (ECE-15, EUDC, NEDC, SFUDS or for real routes from GPS device data. This will allow to consider the orography of the route, considering the slope that overcomes the vehicle at each time, generally this parameter is not included in other models, and it could become a determining factor for the applicability of these vehicles on certain specified routes. Moreover, this tool lets to study and to analyse other not easily quantifiable factors, such as the weather or peak-hour traffic. Finally, the performance of an urban hybrid bus was investigated to assess its theoretical range and the technical feasibility of zero-emission vehicles. Keywords: Electric vehicle; Battery; Fuel cell; Hydrogen; Simulation 

  10. Simulation of a Natural Convection by the Hybrid Thermal Lattice Boltzmann Equation

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Seungyeob; Kang, Hanok; Seo, Jaekwang; Yun, Juhyeon; Zee, Sung-Quun [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2006-07-01

    Recently, the lattice Boltzmann method(LBM) has gained much attention for its ability to simulate fluid flows, and for its potential advantages over conventional CFD method. The key advantages of LBM are, (1) suitability for parallel computations, (2) absence of the need to solve the time-consuming Poisson equation for a pressure, and (3) an ease with multiphase flows, complex geometries and interfacial dynamics may be treated. In spite of its success in solving various challenging problems involving athermal fluids, the LBM has not been able to handle realistic thermal fluids with a satisfaction. The difficulty encountered in the thermal LBM seems to be the numerical instabilities. The existing thermal lattice Boltzmann models may be classified into three categories based on their approach in solving the Boltzmann equation, namely, the multispeed, the passive scalar and the thermal energy distribution approach. For more details see Ref. In the present work, the hybrid thermal lattice Boltzmann scheme proposed by Lallemand and Luo is used for simulating a natural convection in a square cavity. They proposed a hybrid thermal lattice Boltzmann equation(HTLBE) in which the mass and momentum conservation equations are solved by using the multiple-relaxation-time(MRT) model, whereas the diffusion-advection equations for the temperature are solved separately by using finite-difference technique. The main objective of the present work is to establish the lattice Boltzmann method as a viable tool for the simulation of temperature fields at high Rayleigh numbers.

  11. Thermalization of Na+ Pickup Ions in Mercury's Magnetosheath and Magnetosphere via Hybrid Simulation

    Science.gov (United States)

    Boardsen, S. A.; Omidi, N.; Slavin, J. A.

    2007-12-01

    In previous studies it has been suggested that the incorporation of Na+ pickup ions into Mercury's magnetosphere could have a significant impact on various magnetospheric processes. Test particle simulations indicate that freshly created Na+ ions are rapidly energized and lost from the system. In order to incorporate these ions into the bulk magnetospheric plasma they must be thermalized. A recent study that used linear theory suggests that the wavelengths of electromagnetic ion cyclotron waves may be to large and may not grow to sufficient amplitudes to thermalize these ions and concluded that global thermalization of these ions is not possible. However, under certain solar wind and IMF conditions such thermalization might take place in limited regions of Mercury's magnetosphere, primarily in the sub-solar magnetosheath. Due the small scale size of Mercury's magnetosphere compared to the gyro-radii of these heavy ions and their associated wave modes, hybrid simulation with a kinetic treatment for the ions and a fluid treatment for the electrons may be the only way to study if thermalization of Na+ can occur. Preliminary results of a hybrid simulation that incorporates the Na+ pickup ions in its kinetic treatment will be presented.

  12. 2D-3D hybrid stabilized finite element method for tsunami runup simulations

    Science.gov (United States)

    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.

  13. Accelerated Degradation for Hardware in the Loop Simulation of Fuel Cell-Gas Turbine Hybrid System

    DEFF Research Database (Denmark)

    Abreu-Sepulveda, Maria A.; Harun, Nor Farida; Hackett, Gregory;

    2015-01-01

    The U.S. Department of Energy (DOE)-National Energy Technology Laboratory (NETL) in Morgantown, WV has developed the hybrid performance (HyPer) project in which a solid oxide fuel cell (SOFC) one-dimensional (1D), real-time operating model is coupled to a gas turbine hardware system by utilizing...... hardware-in-the-loop simulation. To assess the long-term stability of the SOFC part of the system, electrochemical degradation due to operating conditions such as current density and fuel utilization have been incorporated into the SOFC model and successfully recreated in real time. The mathematical...

  14. Plasma environment of magnetized asteroids: a 3-D hybrid simulation study

    Directory of Open Access Journals (Sweden)

    S. Simon

    2006-03-01

    Full Text Available The interaction of a magnetized asteroid with the solar wind is studied by using a three-dimensional hybrid simulation code (fluid electrons, kinetic ions. When the obstacle's intrinsic magnetic moment is sufficiently strong, the interaction region develops signs of magnetospheric structures. On the one hand, an area from which the solar wind is excluded forms downstream of the obstacle. On the other hand, the interaction region is surrounded by a boundary layer which indicates the presence of a bow shock. By analyzing the trajectories of individual ions, it is demonstrated that kinetic effects have global consequences for the structure of the interaction region.

  15. Simulation and experimental results of hybrid electric machine with a novel flux control strategy

    Directory of Open Access Journals (Sweden)

    Paplicki Piotr

    2015-03-01

    Full Text Available The paper presents selected simulation and experimental results of a hybrid ECPMS-machine (Electric Controlled Permanent Magnet Synchronous Machine. This permanent magnets (PMs excited machine offers an extended magnetic field control capability which makes it suitable for battery electric vehicle (BEV drives. Rotor, stator and the additional direct current control coil of the machine are analyzed in detail. The control system and strategy, the diagram of power supply system and an equivalent circuit model of the ECPMS-machine are presented. Influence of the additional excitation on the performance parameters of the machine, such as: torque, efficiency, speed limits and back-EMF have also been discussed.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  18. Self-consistent hybrid neoclassical-magnetohydrodynamic simulations of axisymmetric plasmas

    Science.gov (United States)

    Lyons, Brendan Carrick

    Neoclassical effects (e.g., conductivity reduction and bootstrap currents) have a profound impact on many magnetohydrodynamic (MHD) instabilities in toroidally-confined plasmas, including tearing modes, edge-localized modes, and resistive wall modes. High-fidelity simulations of such phenomena require a multiphysics code that self-consistently couples the kinetic and fluid models. We review a hybrid formulation from the recent literatureAB that is appropriate for such studies. In particular, the formulation uses a set of time-dependent drift-kinetic equations (DKEs) to advance the non-Maxwellian part of the electron and ion distribution functions (fNM) with linearized Fokker-Planck-Landau collision operators. The form of the DKEs used were derived in a Chapman-Enskog-like fashion, ensuring that fNM carries no density, momentum, or temperature. Rather, these quantities are contained within the background Maxwellian and are evolved by a set of MHD equations which are closed by moments of fNM . We then present two DKE solvers based upon this formulation in axisymmetric toroidal geometries. The Neoclassical Ion-Electron Solver (NIES) solves the steady-state DKEs in the low-collisionality limit. Convergence and benchmark studies are discussed, providing a proof-of-principle that this new formulation can accurately reproduce results from the literature in the limit considered. We then present the DK4D code which evolves the finite-collisionality DKEs time-dependently. Computational methods used and successful benchmarks to other neoclassical models and codes are discussed. Furthermore, we couple DK4D to a reduced, transport-timescale MHD code. The resulting hybrid code is used to simulate the evolution of the current density in a large-aspect-ratio plasma in the presence of several different time-dependent pressure profiles. These simulations demonstrate the self-consistent, dynamic formation of the ohmic and bootstrap currents. In the slowly-evolving plasmas considered

  19. Optimization of Hybrid Power Trains by Mechanistic System Simulations Optimisation de groupes motopropulseurs électriques hybrides par simulation du système mécanique

    Directory of Open Access Journals (Sweden)

    Katrašnik T.

    2013-05-01

    Full Text Available The paper presents a mechanistic system level simulation model for mode/big hybrid and conventional vehicle topologies. The paper addresses the Dynamic interaction between different domains: internal combustion engine. exhaust after treatment devices, electric components. mechanical drive train. cooling circuit system and corresponding control units. To achieve a good ratio between accuracy. predictability and computational speed of the model an innovative time domain decoupling is presented, which is based on applying domain specific integration steps to ditferent domains and subsequent consistent cross-domain coupling ol’thefluxes. In addition, a computationally efficient frunieveork for transporting active and passive gaseous species is introduced to combine computational efficiency with the need for modeling pollutant transport in the gas path. The applicability and versatility of the mechanistic system level simulations model is presented through analyses of transient phenomena caused by the high interdependency of the sub-systems, i.e. domains. Results of a hyt’hrid vehicle are compared to results of a conventional vehicle to highlight differences in operating regimes of partiular components that are inherent to particular poster train topology. L’article présente un modèle de simulation au niveau mécanique destiné à la modélisation de topologies de véhicules hydrides et conventionnels. L’article décrit l’interaction dynamique entre différents domaines : moteur à combustion interne, dispositifs de post-traitement d’échappement, composants électriques, chaîne cinématique mécanique, circuit de refroidissement et les unités de contrôle correspondantes. Afin d’obtenir un rapport correct entre précision, prévisibilité et vitesse de calculs du modèle, un découplage innovant du domaine temporel est présenté, lequel est basé sur l’application à différents domaines, d’étapes d’intégration sp

  20. Modeling And Simulation As The Basis For Hybridity In The Graphic Discipline Learning/Teaching Area

    Directory of Open Access Journals (Sweden)

    Jana Žiljak Vujić

    2009-01-01

    Full Text Available Only some fifteen years have passed since the scientific graphics discipline was established. In the transition period from the College of Graphics to «Integrated Graphic Technology Studies» to the contemporary Faculty of Graphics Arts with the University in Zagreb, three main periods of development can be noted: digital printing, computer prepress and automatic procedures in postpress packaging production. Computer technology has enabled a change in the methodology of teaching graphics technology and studying it on the level of secondary and higher education. The task has been set to create tools for simulating printing processes in order to master the program through a hybrid system consisting of methods that are separate in relation to one another: learning with the help of digital models and checking in the actual real system. We are setting a hybrid project for teaching because the overall acquired knowledge is the result of completely different methods. The first method is on the free programs level functioning without consequences. Everything remains as a record in the knowledge database that can be analyzed, statistically processed and repeated with new parameter values of the system being researched. The second method uses the actual real system where the results are in proving the value of new knowledge and this is something that encourages and stimulates new cycles of hybrid behavior in mastering programs. This is the area where individual learning incurs. The hybrid method allows the possibility of studying actual situations on a computer model, proving it on an actual real model and entering the area of learning envisaging future development.

  1. Modeling and Simulation as the Basis for Hybridity in the Graphic Discipline Learning/Teaching Area

    Directory of Open Access Journals (Sweden)

    Vilko Ziljak

    2009-11-01

    Full Text Available Only some fifteen years have passed since the scientific graphics discipline was established. In the transition period from the College of Graphics to «Integrated Graphic Technology Studies» to the contemporary Faculty of Graphics Arts with the University in Zagreb, three main periods of development can be noted: digital printing, computer prepress and automatic procedures in postpress packaging production. Computer technology has enabled a change in the methodology of teaching graphics technology and studying it on the level of secondary and higher education. The task has been set to create tools for simulating printing processes in order to master the program through a hybrid system consisting of methods that are separate in relation to one another: learning with the help of digital models and checking in the actual real system.  We are setting a hybrid project for teaching because the overall acquired knowledge is the result of completely different methods. The first method is on the free programs level functioning without consequences. Everything remains as a record in the knowledge database that can be analyzed, statistically processed and repeated with new parameter values of the system being researched. The second method uses the actual real system where the results are in proving the value of new knowledge and this is something that encourages and stimulates new cycles of hybrid behavior in mastering programs. This is the area where individual learning incurs. The hybrid method allows the possibility of studying actual situations on a computer model, proving it on an actual real model and entering the area of learning envisaging future development.

  2. A hybrid model for the computationally-efficient simulation of the cerebellar granular layer

    Directory of Open Access Journals (Sweden)

    Anna eCattani

    2016-04-01

    Full Text Available 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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  5. Gallbladder Removal Simulation for Laparoscopic Surgery Training:A Hybrid Modeling Method

    Institute of Scientific and Technical Information of China (English)

    Youngjun Kim; Dongjune Chang; Jungsik Kim; Sehyung Park

    2013-01-01

    Laparoscopic surgery has many advantages,but it is difficult for a surgeon to achieve the necessary surgical skills.Recently,virtual training simulations have been gaining interest because they can provide a safe and efficient learning environment for medical students and novice surgeons.In this paper,we present a hybrid modeling method for simulating gallbladder removal that uses both the boundary element method (BEM) and the finite element method (FEM).Each modeling method is applied according to the deformable properties of human organs:BEM for the liver and FEM for the gallbladder.Connective tissues between the liver and the gallbladder are also included in the surgical simulation.Deformations in the liver and the gallbladder models are transferred via connective tissue springs using a mass-spring method.Special effects and techniques are developed to achieve realistic simulations,and the software is integrated into a custom-designed haptic interface device.Various computer graphical techniques are also applied in the virtual gallbladder removal laparoscopic surgery training.The detailed techniques and the results of the simulations are described in this paper.

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

    Science.gov (United States)

    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.

  7. SOLAR WIND TURBULENCE FROM MHD TO SUB-ION SCALES: HIGH-RESOLUTION HYBRID SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Franci, Luca; Verdini, Andrea; Landi, Simone [Dipartimento di Fisica e Astronomia, Università di Firenze, Largo E. Fermi 2, I-50125 Firenze (Italy); Matteini, Lorenzo [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Hellinger, Petr [Astronomical Institute, AS CR, Bocni II/1401, CZ-14100 Prague (Czech Republic)

    2015-05-10

    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.

  8. Solar wind turbulence from MHD to sub-ion scales: high-resolution hybrid simulations

    CERN Document Server

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

    2015-01-01

    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 wave numbers. The simulation results exhibit simultaneously several properties of the observed solar wind fluctuations: spectral indices of the magnetic, kinetic, and residual energy spectra in the magneto-hydrodynamic (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.

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

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

  11. A conservative and a hybrid early rejection schemes for accelerating Monte Carlo molecular simulation

    KAUST Repository

    Kadoura, Ahmad Salim

    2014-03-17

    Molecular simulation could provide detailed description of fluid systems when compared to experimental techniques. They can also replace equations of state; however, molecular simulation usually costs considerable computational efforts. Several techniques have been developed to overcome such high computational costs. In this paper, two early rejection schemes, a conservative and a hybrid one, are introduced. In these two methods, undesired configurations generated by the Monte Carlo trials are rejected earlier than it would when using conventional algorithms. The methods are tested for structureless single-component Lennard-Jones particles in both canonical and NVT-Gibbs ensembles. The computational time reduction for both ensembles is observed at a wide range of thermodynamic conditions. Results show that computational time savings are directly proportional to the rejection rate of Monte Carlo trials. The proposed conservative scheme has shown to be successful in saving up to 40% of the computational time in the canonical ensemble and up to 30% in the NVT-Gibbs ensemble when compared to standard algorithms. In addition, it preserves the exact Markov chains produced by the Metropolis scheme. Further enhancement for NVT-Gibbs ensemble is achieved by combining this technique with the bond formation early rejection one. The hybrid method achieves more than 50% saving of the central processing unit (CPU) time.

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

    Science.gov (United States)

    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.

  13. Interaction of Enceladus's Water Plume with Saturnian Magnetosphere via Hybrid Numerical Simulations

    Science.gov (United States)

    Somr, J.; Travnicek, P. M.; Stverak, S.; Khurana, K. K.; Hellinger, P.; Dougherty, M. K.

    2008-12-01

    Several close Cassini flybys of the Santurnian moon Enceladus provided direct in situ measurements of neutral water molecules escaping from the surface showing their interaction with the ambient plasma environment. Cassini measurements indicate Enceladus to act as an obstacle to the magnetized Saturnian plasma flow resulting in an effect of field line draping. Ionization of escaping neutrals by way of charge exchange with the ambient plasma produces fresh ions which are picked up by the Saturnian magnetosphere. The Saturnian co-rotating plasma flow therefore slows down and the ambient magnetic field is affected. We study these local plasma interaction of Enceladus and its neutral water plume with the Saturnian magnetosphere by using a full 3D hybrid code numerical simulation. The results of our model are subsequently compared with Cassini observations. Since a complete and accurate description of Enceladus surroundings is still missing, the initialialization of our simulations is based on currently published estimations. However, by use the hybrid code we are able to recover very similar magnetic field signatures as some of those realy observed by Cassini spacecraft.

  14. Aspect of Dynamic Simulation and Experimental Research Studies on Hybrid Pneumatic Power System

    Directory of Open Access Journals (Sweden)

    K. David Huang

    2010-01-01

    Full Text Available A Hybrid Pneumatic Power System (HPPS has been developed for several years with the major aim of reducing the vehicle fuel consumption, environment pollution and enhancing the vehicle performance as well. Comparing with the conventional hybrid system, HPPS replaces the battery's electrochemical energy with a high-pressure air storage tank and enables the internal combustion engine (ICE to function at its sweet spot. Besides, the HPPS, which effectively merges both the high-pressure air flow from the storage tank and the recycled exhaust flow from the ICE, thereby increases the thermal efficiency of the ICE and transforms the merged flow energy into mechanical energy using a high-efficiency turbine. This paper focuses on the major research process into HPPSs, including overall dynamic simulation and experimental validation. By using the simulation tool ITI-Sim, this research demonstrates an experiment which can be operated precisely according to the requirements of various driving conditions under which a car actually runs on the road in accordance with the regulated running vehicle test mode. HPPS is expected to increase the performance of the entire system from 15% to 39%, and is likely to replace the traditional system in the coming years.

  15. Ion cyclotron instability at Io: Hybrid simulation results compared to in situ observations

    Science.gov (United States)

    Šebek, Ondřej; Trávníček, Pavel M.; Walker, Raymond J.; Hellinger, Petr

    2016-08-01

    We present analysis of global three-dimensional hybrid simulations of Io's interaction with Jovian magnetospheric plasma. We apply a single-species model with simplified neutral-plasma chemistry and downscale Io in order to resolve the ion kinetic scales. We consider charge exchange, electron impact ionization, and photoionization by using variable rates of these processes to investigate their impact. Our results are in a good qualitative agreement with the in situ magnetic field measurements for five Galileo flybys around Io. The hybrid model describes ion kinetics self-consistently. This allows us to assess the distribution of temperature anisotropies around Io and thereby determine the possible triggering mechanism for waves observed near Io. We compare simulated dynamic spectra of magnetic fluctuations with in situ observations made by Galileo. Our results are consistent with both the spatial distribution and local amplitude of magnetic fluctuations found in the observations. Cyclotron waves, triggered probably by the growth of ion cyclotron instability, are observed mainly downstream of Io and on the flanks in regions farther from Io where the ion pickup rate is relatively low. Growth of the ion cyclotron instability is governed mainly by the charge exchange rate.

  16. Modeling, simulation, and concept studies of a fuel cell hybrid electric vehicle powertrain

    Energy Technology Data Exchange (ETDEWEB)

    Oezbek, Markus

    2010-03-29

    This thesis focuses on the development of a fuel cell-based hybrid electric powertrain for smaller (2 kW) hybrid electric vehicles (HEVs). A Hardware-in-the-Loop test rig is designed and built with the possibility to simulate any load profile for HEVs in a realistic environment, whereby the environment is modeled. Detailed simulation models of the test rig are developed and validated to real physical components and control algorithms are designed for the DC/DC-converters and the fuel cell system. A state-feedback controller is developed for the DC/DC-converters where the state-space averaging method is used for the development. For the fuel cells, a gain-scheduling controller based on state feedback is developed and compared to two conventional methods. The design process of an HEV with regard to a given load profile is introduced with comparison between SuperCaps and batteries. The HEV is also evaluated with an introduction to different power management concepts with regard to fuel consumption, dynamics, and fuel cell deterioration rate. The power management methods are implemented in the test rig and compared. (orig.)

  17. Hybrid MPI-OpenMP Paradigm on SMP Clusters: MPEG-2 Encoder and N-Body Simulation

    OpenAIRE

    Duy, Truong Vinh Truong; Yamazaki, Katsuhiro; Ikegami, Kosai; Oyanagi, Shigeru

    2012-01-01

    Clusters of SMP nodes provide support for a wide diversity of parallel programming paradigms. Combining both shared memory and message passing parallelizations within the same application, the hybrid MPI-OpenMP paradigm is an emerging trend for parallel programming to fully exploit distributed shared-memory architecture. In this paper, we improve the performance of MPEG-2 encoder and n-body simulation by employing the hybrid MPI-OpenMP programming paradigm on SMP clusters. The hierarchical im...

  18. An extended hybrid magnetohydrodynamics gyrokinetic model for numerical simulation of shear Alfv\\'en waves in burning plasmas

    OpenAIRE

    Wang, X.; Briguglio, S.; Chen, L.; Di Troia, C; Fogaccia, G.; Vlad, G.; Zonca, F.

    2010-01-01

    Adopting the theoretical framework for the generalized fishbonelike dispersion relation, an extended hybrid magnetohydrodynamics gyrokinetic simulation model has been derived analytically by taking into account both thermal ion compressibility and diamagnetic effects in addition to energetic particle kinetic behaviors. The extended model has been used for implementing an eXtended version of Hybrid Magnetohydrodynamics Gyrokinetic Code (XHMGC) to study thermal ion kinetic effects on Alfv\\'enic...

  19. Simulation of a Pneumatic Hybrid Powertrain with VVT in GT-Power and Comparison with Experimental Data

    OpenAIRE

    Trajkovic, Sasa; Tunestål, Per; Johansson, Bengt

    2009-01-01

    In the study presented in this paper, experimental data from a pneumatic hybrid has been compared to the results from a simulation of the engine in GT-Power. The engine in question is a single-cylinder Scania D12 diesel engine, which has been converted to work as a pneumatic hybrid. The base engine model, provided by Scania, is made in GT-Power and it is based on the same engine configuration as the one used during real engine testing. During pneumatic hybrid operation the engine can be us...

  20. Analysis of Winske-Daughton 3D Electromagnetic Particle Simulation of Ion Ring Generated Lower Hybrid Turbulence

    CERN Document Server

    Rudakov, Leonid; Mithaiwala, Manish; Ganguli, Gurudas

    2012-01-01

    Using electromagnetic particle-in-cell simulations Winske and Daughton [Phys Plasmas, 19, 072109, 2012] have recently demonstrated that the nonlinear evolution of a wave turbulence initiated by cold ion ring beam is vastly different in three dimensions than in two dimensions. We further analyze the Winske-Daughton three dimensional simulation data and show that the nonlinear induced scattering by thermal plasma particles is crucial for understanding the evolution of lower hybrid/whistler wave turbulence as described in the simulation.

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

    Science.gov (United States)

    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.

  2. Simulation and Optimization of Air-Cooled PEMFC Stack for Lightweight Hybrid Vehicle Application

    Directory of Open Access Journals (Sweden)

    Jingming Liang

    2015-01-01

    Full Text Available A model of 2 kW air-cooled proton exchange membrane fuel cell (PEMFC stack has been built based upon the application of lightweight hybrid vehicle after analyzing the characteristics of heat transfer of the air-cooled stack. Different dissipating models of the air-cooled stack have been simulated and an optimal simulation model for air-cooled stack called convection heat transfer (CHT model has been figured out by applying the computational fluid dynamics (CFD software, based on which, the structure of the air-cooled stack has been optimized by adding irregular cooling fins at the end of the stack. According to the simulation result, the temperature of the stack has been equally distributed, reducing the cooling density and saving energy. Finally, the 2 kW hydrogen-air air-cooled PEMFC stack is manufactured and tested by comparing the simulation data which is to find out its operating regulations in order to further optimize its structure.

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

    Science.gov (United States)

    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.

  4. Transient simulation of regression rate on thrust regulation process in hybrid rocket motor

    Institute of Scientific and Technical Information of China (English)

    Tian Hui; Li Yijie; Zeng Peng

    2014-01-01

    The main goal of this paper is to study the characteristics of regression rate of solid grain during thrust regulation process. For this purpose, an unsteady numerical model of regression rate is established. Gas–solid coupling is considered between the solid grain surface and combustion gas. Dynamic mesh is used to simulate the regression process of the solid fuel surface. Based on this model, numerical simulations on a H2O2/HTPB (hydroxyl-terminated polybutadiene) hybrid motor have been performed in the flow control process. The simulation results show that under the step change of the oxidizer mass flow rate condition, the regression rate cannot reach a stable value instantly because the flow field requires a short time period to adjust. The regression rate increases with the linear gain of oxidizer mass flow rate, and has a higher slope than the relative inlet function of oxidizer flow rate. A shorter regulation time can cause a higher regression rate during regulation process. The results also show that transient calculation can better simulate the instantaneous regression rate in the operation process.

  5. Transient simulation of regression rate on thrust regulation process in hybrid rocket motor

    Directory of Open Access Journals (Sweden)

    Tian Hui

    2014-12-01

    Full Text Available The main goal of this paper is to study the characteristics of regression rate of solid grain during thrust regulation process. For this purpose, an unsteady numerical model of regression rate is established. Gas–solid coupling is considered between the solid grain surface and combustion gas. Dynamic mesh is used to simulate the regression process of the solid fuel surface. Based on this model, numerical simulations on a H2O2/HTPB (hydroxyl-terminated polybutadiene hybrid motor have been performed in the flow control process. The simulation results show that under the step change of the oxidizer mass flow rate condition, the regression rate cannot reach a stable value instantly because the flow field requires a short time period to adjust. The regression rate increases with the linear gain of oxidizer mass flow rate, and has a higher slope than the relative inlet function of oxidizer flow rate. A shorter regulation time can cause a higher regression rate during regulation process. The results also show that transient calculation can better simulate the instantaneous regression rate in the operation process.

  6. Hybridization of Genetic Algorithm with Parallel Implementation of Simulated Annealing for Job Shop Scheduling

    Directory of Open Access Journals (Sweden)

    Thamilselvan Rakkiannan

    2012-01-01

    Full Text Available Problem statement: The Job Shop Scheduling Problem (JSSP is observed as one of the most difficult NP-hard, combinatorial problem. The problem consists of determining the most efficient schedule for jobs that are processed on several machines. Approach: In this study Genetic Algorithm (GA is integrated with the parallel version of Simulated Annealing Algorithm (SA is applied to the job shop scheduling problem. The proposed algorithm is implemented in a distributed environment using Remote Method Invocation concept. The new genetic operator and a parallel simulated annealing algorithm are developed for solving job shop scheduling. Results: The implementation is done successfully to examine the convergence and effectiveness of the proposed hybrid algorithm. The JSS problems tested with very well-known benchmark problems, which are considered to measure the quality of proposed system. Conclusion/Recommendations: The empirical results show that the proposed genetic algorithm with simulated annealing is quite successful to achieve better solution than the individual genetic or simulated annealing algorithm."

  7. Molecular dynamics and Monte Carlo hybrid simulation for fuzzy tungsten nanostructure formation

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2012-01-01

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

  9. Benchmark Simulations of Gyro-Kinetic Electron and Fully-Kinetic Ion Model for Lower Hybrid Waves in Linear Region

    International Nuclear Information System (INIS)

    Particle-in-cell (PIC) simulation method has been proved to be a good candidate to study the interactions between plasmas and radio-frequency waves. However, for waves in the lower hybrid range of frequencies, a full PIC simulation is not efficient due to its high computational cost. In this work, a gyro-kinetic electron and fully-kinetic ion (GeFi) particle simulation model is applied to study the propagations and mode conversion processes of lower hybrid waves (LHWs) in plasmas. With this method, the computational efficiency of LHW simulations is greatly increased by using a larger grid size and time step. The simulation results in the linear regime are validated by comparison with the linear theory. (magnetically confined plasma)

  10. Simulations of hybrid system varying solar radiation and microturbine response time

    Energy Technology Data Exchange (ETDEWEB)

    Fernández Ribaya, Yolanda, E-mail: fernandezryolanda@uniovi.es; Álvarez, Eduardo; Paredes Sánchez, José Pablo; Xiberta Bernat, Jorge [Department of Energy E.I.M.E.M., University of Oviedo. 13 Independencia Street 2" n" d floor, 36004, Oviedo (Spain)

    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.

  11. Simulations of hybrid system varying solar radiation and microturbine response time

    Directory of Open Access Journals (Sweden)

    Yolanda Fernández Ribaya

    2015-07-01

    Full Text Available 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.

  12. Simulations of hybrid system varying solar radiation and microturbine response time

    International Nuclear Information System (INIS)

    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

  13. Simulations of hybrid system varying solar radiation and microturbine response time

    Science.gov (United States)

    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.

  14. A general hybrid radiation transport scheme for star formation simulations on an adaptive grid

    International Nuclear Information System (INIS)

    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.

  15. A general hybrid radiation transport scheme for star formation simulations on an adaptive grid

    Energy Technology Data Exchange (ETDEWEB)

    Klassen, Mikhail; Pudritz, Ralph E. [Department of Physics and Astronomy, McMaster University 1280 Main Street W, Hamilton, ON L8S 4M1 (Canada); Kuiper, Rolf [Max Planck Institute for Astronomy Königstuhl 17, D-69117 Heidelberg (Germany); Peters, Thomas [Institut für Computergestützte Wissenschaften, Universität Zürich Winterthurerstrasse 190, CH-8057 Zürich (Switzerland); Banerjee, Robi; Buntemeyer, Lars, E-mail: klassm@mcmaster.ca [Hamburger Sternwarte, Universität Hamburg Gojenbergsweg 112, D-21029 Hamburg (Germany)

    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.

  16. Hybrid-PIC Computer Simulation of the Plasma and Erosion Processes in Hall Thrusters

    Science.gov (United States)

    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.

  17. Recent Developments on Hybrid Time-Frequency Numerical Simulation Techniques for RF and Microwave Applications

    Directory of Open Access Journals (Sweden)

    Jorge F. Oliveira

    2013-01-01

    Full Text Available This paper reviews some of the promising doors that functional analysis techniques have recently opened in the field of electronic circuit simulation. Because of the modulated nature of radio frequency (RF signals, the corresponding electronic circuits seem to operate in a slow time scale for the aperiodic information and another, much faster, time scale for the periodic carrier. This apparent multirate behavior can be appropriately described using partial differential equations (PDEs within a bivariate framework, which can be solved in an efficient way using hybrid time-frequency techniques. With these techniques, the aperiodic information dimension is treated in the discrete time domain, while the periodic carrier dimension is processed in the frequency domain, in which the solution is evaluated within a space of harmonically related sinusoidal functions. The objective of this paper is thus to provide a general overview on the most important hybrid time-frequency techniques, as the ones found in commercial tools or the ones recently published in the literature.

  18. Dynamic Modeling and Motion Simulation for A Winged Hybrid-Driven Underwater Glider

    Institute of Scientific and Technical Information of China (English)

    WANG Shu-xin; SUN Xiu-jun; WANG Yan-hui; WU Jian-guo; WANG Xiao-ming

    2011-01-01

    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.

  19. Steady-state hydrodynamic instabilities of active liquid crystals: hybrid lattice Boltzmann simulations.

    Science.gov (United States)

    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. PMID:17930285

  20. Simulation of a sea ice ecosystem using a hybrid model for slush layer desalination

    Science.gov (United States)

    Saenz, Benjamin T.; Arrigo, Kevin R.

    2012-05-01

    Porous, slushy layers are a common feature of Antarctic sea ice and are often colonized by high concentrations of algae. Despite its potential importance to the physics and biogeochemistry of the sea ice ecosystem, current knowledge of the evolution of sea ice slush layers is limited. Here we present a model of sea ice that is capable of reproducing the vertical biophysical evolution of sea ice that contains slush layers. The model uses a novel hybrid desalination scheme to calculate salt fluxes and brine motion during freezing using one of two different methods depending on the brine fraction of the ice. Model runs using atmospheric and snow depth forcing from the Ice Station Weddell experiment show that model is able to simulate the magnitude and timing of sea ice temperature, salinity, and associated algal growth of observed slush layers, as well as the surrounding sea ice. The model was designed with regional-scale simulations in mind and we show that the model performs well at lower vertical resolutions, as long as the slush layer is resolved. Incorporation of our model of slush ice desalination into regional and global simulations has potential to improve model estimates of salt, heat, and biochemical fluxes in polar marine environments.

  1. Full-wave simulations of lower hybrid wave propagation in the EAST tokamak

    Science.gov (United States)

    Bonoli, P. T.; Lee, J. P.; Shiraiwa, S.; Wright, J. C.; Ding, B.; Yang, C.

    2015-11-01

    Studies of lower hybrid (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 simulations were performed for EAST using the TORLH field solver. These simulations 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 simulations will also be presented. Work supported by the US DOE under Contract No. DE-SC0010492 and DE-FC02-01ER54648.

  2. A new hybrid kinetic electron model for full-f gyrokinetic simulations

    Science.gov (United States)

    Idomura, Y.

    2016-05-01

    A new hybrid kinetic electron model is developed for electrostatic full-f gyrokinetic simulations 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 simulations of ITG-TEM turbulence with a reasonable computational cost. Comparisons between flux driven ITG turbulence simulations 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.

  3. Dynamic Simulation and Exergo-Economic Optimization of a Hybrid Solar–Geothermal Cogeneration Plant

    Directory of Open Access Journals (Sweden)

    Francesco Calise

    2015-04-01

    Full Text Available This paper presents a dynamic simulation model and a parametric analysis of a solar-geothermal hybrid cogeneration plant based on an Organic Rankine Cycle (ORC powered by a medium-enthalpy geothermal resource and a Parabolic Trough Collector solar field. The fluid temperature supplying heat to the ORC varies continuously as a function of the solar irradiation, affecting both the electrical and thermal energies produced by the system. Thus, a dynamic simulation was performed. The ORC model, developed in Engineering Equation Solver, is based on zero-dimensional energy and mass balances and includes specific algorithms to evaluate the off-design system performance. The overall simulation model of the solar-geothermal cogenerative plant was implemented in the TRNSYS environment. Here, the ORC model is imported, whereas the models of the other components of the system are developed on the basis of literature data. Results are analyzed on different time bases presenting energetic, economic and exergetic performance data. Finally, a rigorous optimization has been performed to determine the set of system design/control parameters minimizing simple payback period and exergy destruction rate. The system is profitable when a significant amount of the heat produced is consumed. The highest irreversibilities are due to the solar field and to the heat exchangers.

  4. Simulation of Thermal Flow Problems via a Hybrid Immersed Boundary-Lattice Boltzmann Method

    Directory of Open Access Journals (Sweden)

    J. Wu

    2012-01-01

    Full Text Available A hybrid immersed boundary-lattice Boltzmann method (IB-LBM is presented in this work to simulate the thermal flow problems. In current approach, the flow field is resolved by using our recently developed boundary condition-enforced IB-LBM (Wu and Shu, (2009. The nonslip boundary condition on the solid boundary is enforced in simulation. At the same time, to capture the temperature development, the conventional energy equation is resolved. To model the effect of immersed boundary on temperature field, the heat source term is introduced. Different from previous studies, the heat source term is set as unknown rather than predetermined. Inspired by the idea in (Wu and Shu, (2009, the unknown is calculated in such a way that the temperature at the boundary interpolated from the corrected temperature field accurately satisfies the thermal boundary condition. In addition, based on the resolved temperature correction, an efficient way to compute the local and average Nusselt numbers is also proposed in this work. As compared with traditional implementation, no approximation for temperature gradients is required. To validate the present method, the numerical simulations of forced convection are carried out. The obtained results show good agreement with data in the literature.

  5. Hybrid multiphase CFD simulation for liquid-liquid interfacial area prediction in annular centrifugal contactors

    International Nuclear Information System (INIS)

    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 hybrid 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. Simulations 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

  6. Proton temperature-anisotropy-driven instabilities in weakly collisional plasmas: Hybrid simulations

    CERN Document Server

    Hellinger, Petr

    2014-01-01

    Kinetic instabilities in weakly collisional, high beta plasmas are investigated using two-dimensional hybrid expanding box simulations with Coulomb collisions modeled through the Langevin equation (corresponding to the Fokker-Planck one). The expansion drives a parallel or perpendicular temperature anisotropy (depending on the orientation of the ambient magnetic field). For the chosen parameters the Coulomb collisions are important with respect to the driver but are not strong enough to keep the system stable with respect to instabilities driven by the proton temperature anisotropy. In the case of the parallel temperature anisotropy the dominant oblique fire hose instability efficiently reduces the anisotropy in a quasilinear manner. In the case of the perpendicular temperature anisotropy the dominant mirror instability generates coherent compressive structures which scatter protons and reduce the temperature anisotropy. For both the cases the instabilities generate temporarily enough wave energy so that the ...

  7. Hybrid multiphase CFD simulation for liquid-liquid interfacial area prediction in annular centrifugal contactors

    Energy Technology Data Exchange (ETDEWEB)

    Wardle, K.E. [Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2013-07-01

    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 hybrid 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. Simulations 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.

  8. Numerical Simulation for One Dimensional Steady Quasineutral Hybrid Model of Stationary Plasma Thruster

    Institute of Scientific and Technical Information of China (English)

    Yu Daren; Wu Zhiwen; Wu Xiaoling

    2005-01-01

    Based on the analysis of the physical mechanism of the Stationary Plasma Thruster (SPT), an integral equation describing the ion density of the steady SPT and the ion velocity distribution function at an arbitrary axial position of the steady SPT channel are derived. The integral equation is equivalent to the Vlasov equation, but the former is simpler than the latter. A one dimensional steady quasineutral hybrid model is established. In this model, ions are described by the above integral equation, and neutrals and electrons are described by hydrodynamic equations. The transferred equivalency to the differential equation and the integral equation, together with other equations, are solved by an ordinary differential equation (ODE) solver in the Matlab.The numerical simulation results show that under various circumstances, the ion average velocity would be different and needs to be deduced separately.

  9. Novel hybrid methods applied for the numerical simulation of three-phase biotechnological flows

    Energy Technology Data Exchange (ETDEWEB)

    Diez Robles, Lucia

    2009-07-01

    Granular Activated Sludge (GAS) is na novel biological secondary treatment of wastewater which presents multiple advantages with respect to Conventional Activated Sludge (CAS). For fluid mechanical analysis of the bioreactor in which GAS is cultivated, two strategies are adopted: numerical analysis which is carried out in the present thesis and optical in situ measurements which validate the numerical results. The Eulerian-Eulerian multi-fluid approach does not offer a satisfactory description of the three-phase flow as there is a lack of appropriate mathematical models and the solution of the equation systems is problematic. Hybrid methods are here developed in order to complement the classical numerical techniques. These improve the convergence of the numerical simulation, generate results more in accordance with the experimental results and reduce the CPU time required for the calculations. An additional momentum exchange between the dispersed phases is also proposed for the consideration of the four-way coupling case. (orig.)

  10. Simulation of generalized hybrid model for solar and wind power generation

    Directory of Open Access Journals (Sweden)

    Vankadara Sampath kumar

    2015-03-01

    Full Text Available Due to urbanization, globalization and industrialization the demand for energy is rapidly increasing allows the world and India is not an exception. Out of all energies electrical energy is playing a major role in developed as well as developing countries. The energy is mostly produced by fossil fuels which are developing day his is to by day .they also produce lot of pollutants which totally damage the environment the alternative to this is to encourage renewable energy source. Now days the energy production at domestic level is becoming popular with the help of solar and wind energies . These technologies are widely used now days in the present paper an attempt has been made to simulate a generalized hybrid model including solar and wind.

  11. Simulation of hydrogen bubble growth in tungsten by a hybrid model

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Chaofeng, E-mail: sang@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China); Sun, Jizhong [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China); Bonnin, Xavier [LSPM-CNRS, Université Paris 13, Sorbonne Paris Cité, Villetaneuse 93430 (France); Wang, L. [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Wang, Dezhen, E-mail: wangdez@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China)

    2015-08-15

    A two dimensional hybrid 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 simulation 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.

  12. Hybrid vehicle simulation for a turbogenerator-based power-train

    Energy Technology Data Exchange (ETDEWEB)

    Leontopoulos, C.; Etemad, M.R.; Pullen, K.R.; Lamperth, M.U. [Imperial Coll. of Science, Technology and Medicine, Dept. of Mechanical Engineering, London (United Kingdom)

    1998-10-01

    The potential of the turbogenerator-based power-train for hybrid vehicles is described. Data from a small gas turbine, a prototype high-speed generator and an advanced lead-acid battery pack show that the 'turboelectric' concept is feasible and can provide a viable road transport solution which will comply with the stringent environmental legislation. The simulation results show improved overall vehicle efficiencies due to the implementation of regenerative braking capability. Most importantly the lean combustion of the gas-turbine engine with a suitable energy control strategy can provide lower emissions than ultra-low-emission vehicle (ULEV) limits, while an acceptable zero-emissions vehicle (ZEV) driving range can be achieved for city centres. (Author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Tikare, Veena; Hernandez-Rivera, Efrain; Madison, Jonathan D.; Holm, Elizabeth Ann [Carnegie Mellon University, Pittsburgh, PA; Patterson, Burton R. [University of Florida, Gainesville, FL; Homer, Eric R. [Brigham Young University, Provo, UT

    2013-09-01

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

  14. A hybrid model for coupling kinetic corrections of fusion reactivity to hydrodynamic implosion simulations

    Science.gov (United States)

    Tang, Xian-Zhu; McDevitt, C. J.; Guo, Zehua; Berk, H. L.

    2014-03-01

    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 hybrid model that couples the kinetic correction of fusion reactivity to global hydrodynamic implosion simulations. 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.

  15. Business Scenario Evaluation Method Using Monte Carlo Simulation on Qualitative and Quantitative Hybrid Model

    Science.gov (United States)

    Samejima, Masaki; Akiyoshi, Masanori; Mitsukuni, Koshichiro; Komoda, Norihisa

    We propose a business scenario evaluation method using qualitative and quantitative hybrid 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 simulation. 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%.

  16. Simulation of hydrogen bubble growth in tungsten by a hybrid model

    International Nuclear Information System (INIS)

    A two dimensional hybrid 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 simulation 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

  17. Hybrid electrodynamics and kinetics simulation for electromagnetic wave propagation in weakly ionized hydrogen plasmas.

    Science.gov (United States)

    Chen, Qiang; Chen, Bin

    2012-10-01

    In this paper, a hybrid 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 simulations 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.

  18. Two-dimensional Hybrid Simulations of Kinetic Plasma Turbulence: Current and Vorticity vs Proton Temperature

    CERN Document Server

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

    2016-01-01

    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 hybrid particle-in-cell simulation 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.

  19. Simulation of hydrogen bubble growth in tungsten by a hybrid model

    Science.gov (United States)

    Sang, Chaofeng; Sun, Jizhong; Bonnin, Xavier; Wang, L.; Wang, Dezhen

    2015-08-01

    A two dimensional hybrid 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 simulation 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.

  20. Hybrid electrodynamics and kinetics simulation for electromagnetic wave propagation in weakly ionized hydrogen plasmas

    Science.gov (United States)

    Chen, Qiang; Chen, Bin

    2012-10-01

    In this paper, a hybrid 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 simulations 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.

  1. Hybrid Broadband Ground-Motion Simulation Using Scenario Earthquakes for the Istanbul Area

    KAUST Repository

    Reshi, Owais A.

    2016-04-13

    Seismic design, analysis and retrofitting of structures demand an intensive assessment of potential ground motions in seismically active regions. Peak ground motions and frequency content of seismic excitations effectively influence the behavior of structures. In regions of sparse ground motion records, ground-motion simulations provide the synthetic seismic records, which not only provide insight into the mechanisms of earthquakes but also help in improving some aspects of earthquake engineering. Broadband ground-motion simulation methods typically utilize physics-based modeling of source and path effects at low frequencies coupled with high frequency semi-stochastic methods. I apply the hybrid simulation method by Mai et al. (2010) to model several scenario earthquakes in the Marmara Sea, an area of high seismic hazard. Simulated ground motions were generated at 75 stations using systematically calibrated model parameters. The region-specific source, path and site model parameters were calibrated by simulating a w4.1 Marmara Sea earthquake that occurred on November 16, 2015 on the fault segment in the vicinity of Istanbul. The calibrated parameters were then used to simulate the scenario earthquakes with magnitudes w6.0, w6.25, w6.5 and w6.75 over the Marmara Sea fault. Effects of fault geometry, hypocenter location, slip distribution and rupture propagation were thoroughly studied to understand variability in ground motions. A rigorous analysis of waveforms reveal that these parameters are critical for determining the behavior of ground motions especially in the near-field. Comparison of simulated ground motion intensities with ground-motion prediction quations indicates the need of development of the region-specific ground-motion prediction equation for Istanbul area. Peak ground motion maps are presented to illustrate the shaking in the Istanbul area due to the scenario earthquakes. The southern part of Istanbul including Princes Islands show high amplitudes

  2. Modeling, control, and simulation of grid connected intelligent hybrid battery/photovoltaic system using new hybrid fuzzy-neural method.

    Science.gov (United States)

    Rezvani, Alireza; Khalili, Abbas; Mazareie, Alireza; Gandomkar, Majid

    2016-07-01

    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 hybrid 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 hybrid 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 hybrid 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 hybrid system have been proposed using Matlab/Simulink. PMID:26961319

  3. Modeling, control, and simulation of grid connected intelligent hybrid battery/photovoltaic system using new hybrid fuzzy-neural method.

    Science.gov (United States)

    Rezvani, Alireza; Khalili, Abbas; Mazareie, Alireza; Gandomkar, Majid

    2016-07-01

    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 hybrid 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 hybrid 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 hybrid 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 hybrid system have been proposed using Matlab/Simulink.

  4. Analysis tools for simulation of hybrid systems; Herramientas de analisis para simulacion de sistemas hibridos

    Energy Technology Data Exchange (ETDEWEB)

    Guillen S, Omar; Mejia N, Fortino [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)

    2005-07-01

    In order to facilitate and to simplify the development and analysis of a Hybrid System in reference to its design, construction, operation and maintenance, it turns out optimal to carry out the simulation of this one by means of software, with which a significant reduction in the investment costs is obtained. Given the mix of technology of electrical generation which is involved in a hybrid system, it is very important to have a tool integrated with specialized packages of calculation (software), that allow to carry out the simulation tasks of the operational functioning of these systems. Combined with the former, one must not fail to consider the operation characteristics, the facilities of the user, the clarity in the obtained results and the possibility of its validation with respect to prototypes orchestrated in field. Equally, it is necessary to consider the identification of tasks involved in relation to the place of installation of this electrification technology. At the moment, the hybrid systems technology still is in a stage of development in the international level, and exist important limitations as far as the methodology availability and engineering tools for the optimum design of these systems. With the development of this paper, it is intended to contribute to the advance of the technology and to count on own tools to solve the described series of problems. In this article are described the activities that more impact have in the design and development of hybrid systems, as well as the identification of variables, basic characteristics and form of validation of tools in the integration of a methodology for the simulation of these systems, facilitating their design and development. [Spanish] Para facilitar y simplificar el desarrollo y analisis de un Sistema Hibrido en lo que refiere a su diseno, construccion, operacion y mantenimiento, resulta optimo efectuar la simulacion de este por medio de un software, con lo que se obtiene una reduccien

  5. BCA-kMC Hybrid Simulation for Hydrogen and Helium Implantation in Material under Plasma Irradiation

    Science.gov (United States)

    Kato, Shuichi; Ito, Atsushi; Sasao, Mamiko; Nakamura, Hiroaki; Wada, Motoi

    2015-09-01

    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 simulated 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 hybrid simulation'' for the hydrogen and helium implantation under the plasma irradiation.

  6. Proposal for High-Fidelity Quantum Simulation Using a Hybrid Dressed State.

    Science.gov (United States)

    Cai, Jianming; Cohen, Itsik; Retzker, Alex; Plenio, Martin B

    2015-10-16

    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 simulation, 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 hybrid 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 simulation 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

  7. Hybrid Simulated Annealing and Nelder-Mead Algorithm for Solving Large-Scale Global Optimization Problems

    Directory of Open Access Journals (Sweden)

    Ahmed Fouad Ali

    2014-05-01

    Full Text Available This paper presents a new algorithm for solving large scale global optimization problems based on hybridization of simulated annealing and Nelder-Mead algorithm. The new algorithm is called simulated Nelder-Mead algorithm with random variables updating (SNMRVU. SNMRVU starts with an initial solution, which is generated randomly and then the solution is divided into partitions. The neighborhood zone is generated, random number of partitions are selected and variables updating process is starting in order to generate a trail neighbor solutions. This process helps the SNMRVU algorithm to explore the region around a current iterate solution. The Nelder- Mead algorithm is used in the final stage in order to improve the best solution found so far and accelerates the convergence in the final stage. The performance of the SNMRVU algorithm is evaluated using 27 scalable benchmark functions and compared with four algorithms. The results show that the SNMRVU algorithm is promising and produces high quality solutions with low computational costs.

  8. Hybrid (kinetic-fluid) simulation scheme based on method of characteristics

    CERN Document Server

    Javaheri, N; Abbasi, H

    2015-01-01

    Certain features of the method of characteristics are of considerable interest in relation with Vlasov simulation [H. Abbasi {\\it et al}, Phys. Rev. E \\textbf{84}, 036702 (2011)]. A Vlasov simulation scheme of this kind can be recurrence free providing initial phase points in velocity space are set randomly. Naturally, less filtering of fine-structures (arising from grid spacing) is possible as there is now a smaller scale than the grid spacing that is average distance between two phase points. Its interpolation scheme is very simple in form and carried out with less operations. In our previous report, the simplest model (immobile ions) was considered to merely demonstrate the important features. Now, a hybrid model is introduced that solves the coupled Vlasov-Fluid-Poisson system self-consistently. A possible application of the code is the study of ion-acoustic (IA) soliton attributes. To this end, a collisionless plasma with hot electrons and cold positive ions is considered. For electrons, the collisionles...

  9. Assessing the Impact of Policy Changes in the Icelandic Cod Fishery Using a Hybrid Simulation Model

    Directory of Open Access Journals (Sweden)

    Sigríður Sigurðardóttir

    2014-01-01

    Full Text Available 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 hybrid-simulation 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 simulating 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.

  10. Hybrid Molecular and Spin Dynamics Simulations for Ensembles of Magnetic Nanoparticles for Magnetoresistive Systems

    Directory of Open Access Journals (Sweden)

    Lisa Teich

    2015-11-01

    Full Text Available 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 simulations one can study the magnetic microstructure theoretically, although this requires performing classical spin dynamics and molecular dynamics simulations 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 hybrid approach, arbitrary sensor configurations can be investigated and their magnetoresistive properties can be optimized.

  11. Handling performance control for hybrid 8-wheel-drive vehicle and simulation verification

    Science.gov (United States)

    Ni, Jun; Hu, Jibin

    2016-08-01

    In order to improve handling performance of a hybrid 8-Wheel-Drive vehicle, the handling performance control strategy was proposed. For armoured vehicle, besides handling stability in high speed, the minimum steer radius in low speed is also a key tactical and technical index. Based on that, the proposed handling performance control strategy includes 'Handling Stability' and 'Radius Minimization' control modes. In 'Handling Stability' control mode, 'Neutralsteer Radio' is defined to adjust the steering characteristics to satisfy different demand in different speed range. In 'Radius Minimization' control mode, the independent motors are controlled to provide an additional yaw moment to decrease the minimum steer radius. In order to verify the strategy, a simulation platform was built including engine and continuously variable transmission systems, generator and battery systems, independent motors and controllers systems, vehicle dynamic and tyre mechanical systems. The simulation results show that the handling performance of the vehicle can be enhanced significantly, and the minimum steer radius can be decreased by 20% which is significant improvement compared to the common level of main battle armoured vehicle around the world.

  12. A New Hybrid Scheme for Simulations of Highly Collisional RF-Driven Plasmas

    CERN Document Server

    Eremin, Denis; Mussenbrock, Thomas

    2015-01-01

    This work describes a new 1D hybrid approach for modeling atmospheric pressure discharges featuring complex chemistry. In this approach electrons are described fully kinetically using Particle-In-Cell/Monte-Carlo (PIC/MCC) scheme, whereas the heavy species are modeled within a fluid description. Validity of the popular drift-diffusion approximation is verified against a "full" fluid model accounting for the ion inertia and a fully kinetic PIC/MCC code for ions as well as electrons. The fluid models require knowledge of the momentum exchange frequency and dependence of the ion mobilities on the electric field when the ions are in equilibrium with the latter. To this end an auxiliary Monte-Carlo scheme is constructed. It is demonstrated that the drift-diffusion approximation can overestimate ion transport in simulations of RF-driven discharges with heavy ion species operated in the $\\gamma$ mode at the atmospheric pressure or in all discharge simulations for lower pressures. This can lead to exaggerated plasma ...

  13. A hybrid formulation for the numerical simulation of condensed phase explosives

    Science.gov (United States)

    Michael, L.; Nikiforakis, N.

    2016-07-01

    In this article we present a new formulation and an associated numerical algorithm, for the simulation 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 hybrid (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 hybrid 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.

  14. Jovian plasma torus interaction with Europa. Plasma wake structure and effect of inductive magnetic field: 3D Hybrid kinetic simulation

    CERN Document Server

    Lipatov, A S; Paterson, W R; Sittler, E C; Hartle, R E; Simpson, D G

    2012-01-01

    The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect a 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 et al., 2007; Shematovich et al., 2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyroradius 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 backgr...

  15. Study on Forward-Facing Model and Real-Time Simulation for a Series Hybrid Electric Vehicle

    Directory of Open Access Journals (Sweden)

    Xudong Liu

    2011-10-01

    Full Text Available To shorten design period and reduce development costs, computer modeling and simulation is important for HEV design and development. In this paper, real-time simulation for a Series Hybrid Electric Vehicle (SHEV is made to verify its fuzzy logic control strategy based on dSPACE-DS1103 development kits. The whole real-time simulation schematic is designed and the vehicle forward-facing simulation model is set up. Modeling methods for the driver, controller and vehicle (includes engine, generator, motor, battery, etc. under MATLAB/Simulink environment are discussed in detail. Driver behavior is simulated by two potentiometers and introduced into the real-time system to realize close-loop control. A real-time monitoring interface is also developed to observe the experiment results. Experiment results show that the real-time simulation platform works well and the SHEV fuzzy logic control strategy is effective.

  16. 3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

    Science.gov (United States)

    Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu

    2016-07-01

    The eigenmode stability properties of three-dimensional lower-hybrid-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) simulation model with a realistic ion-to-electron mass ratio mi/me . In contrast to the fully kinetic PIC simulation 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 simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation 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 simulation 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 simulation results indicate that varying mi/me , the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.

  17. Hardware-Based Simulation of a Fuel Cell Turbine Hybrid Response to Imposed Fuel Cell Load Transients

    Energy Technology Data Exchange (ETDEWEB)

    Smith, T.P. (Georgia Inst. of Technology); Tucker, D.A.; Haynes, C.L. (Georgia Inst. of Technology); Liese, E.A.; Wepfer, W.J. (Georgia Inst. of Technology)

    2006-11-01

    Electrical load transients imposed on the cell stack of a solid oxide fuel cell/gas turbine hybrid power system are studied using the Hybrid Performance (HyPer) project. The hardware simulation facility is located at the U.S. Department of Energy, National Energy Technology Laboratory (NETL). A computational fuel cell model capable of operating in real time is integrated with operating gas turbine hardware. The thermal output of a modeled 350 kW solid oxide fuel cell stack is replicated in the facility by a natural gas fired burner in a direct fired hybrid configuration. Pressure vessels are used to represent a fuel cell stack's cathode flow and post combustion volume and flow impedance. This hardware is used to simulate the fuel cell stack and is incorporated with a modified turbine, compressor, and 120 kW generator on a single shaft. For this study, a simulation was started with a simulated current demand of 307 A on the fuel cell at approximately 0.75 V and an actual 45 kW electrical load on the gas turbine. An open loop response, allowing the turbine rotational speed to respond to thermal transients, was successfully evaluated for a 5% current reduction on the fuel cell followed by a 5% current increase. The impact of the fuel cell load change on system process variables is presented. The test results demonstrate the capabilities of the hardware-in-the-loop simulation approach in evaluating hybrid fuel cell turbine dynamics and performance.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ku, S. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Hager, R. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Chang, C. S. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Kwon, J. M. [National Fusion Research Institute, Republic of Korea; Parker, S. E. [University of Colorado Boulder, USA

    2016-06-01

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

  19. Mapping of coma anisotropies to plasma structures of weak comets: a 3-D hybrid simulation study

    Directory of Open Access Journals (Sweden)

    N. Gortsas

    2009-04-01

    Full Text Available The effects of coma anisotropies on the plasma environment of comets have been studied by means of a 3-D hybrid model which treats electrons as a massless, charge-neutralizing fluid, whereas ion dynamics are covered by a kinetic approach. From Earth-based observations as well as from in-situ spacecraft measurements the shape of the coma of many comets is ascertained to be anisotropic. However, most plasma simulation studies deploy a spherically symmetric activity pattern. In this paper anisotropy is studied by considering three different coma shape models. The first model is derived from the Haser model and is characterised by spherically symmetry. This reference model is then compared with two different neutral gas shape models: the dayside restricted model with no nightside activity and a cone shaped model with opening angle of π/2. In all models the integrated surface activity is kept constant. The simulations have been done for the Rosetta target comet 67P/Churyumov-Gerasimenko for two heliocentric distances, 1.30 AU and 3.25 AU. It is found that shock formation processes are modified as a result of increasing spatial confinement. Characteristic plasma structures of comets such as the bow shock, magnetic barrier region and the ion composition boundary exhibit a shift towards the sun. In addition, the cone shaped model leads to a strong increase of the mass-loaded region which in turn leads to a smooth deceleration of the solar wind flow and an increasing degree of mixture between the solar wind and cometary ion species. This creates an additional transport channel of the magnetic field from the magnetic barrier region away which in turn leads to a broadening of this region. In addition, it leads to an ion composition boundary which is only gradually developed.

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

    Science.gov (United States)

    Ku, S.; Hager, R.; Chang, C. S.; Kwon, J. M.; Parker, S. E.

    2016-06-01

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

  1. Particle-in-cell simulation study of a lower-hybrid shock

    CERN Document Server

    Dieckmann, Mark Eric; Doria, Domenico; Ynnerman, Anders; Borghesi, Marco

    2016-01-01

    The expansion of a magnetized high-pressure plasma into a low-pressure ambient medium is examined with particle-in-cell (PIC) simulations. The magnetic field points perpendicularly 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-hybrid (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...

  2. Subproton-scale Cascades in Solar Wind Turbulence: Driven Hybrid-kinetic Simulations

    Science.gov (United States)

    Cerri, S. S.; Califano, F.; Jenko, F.; Told, D.; Rincon, F.

    2016-05-01

    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 simulations of forced hybrid-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.

  3. Subproton-scale cascades in solar wind turbulence: driven hybrid-kinetic simulations

    CERN Document Server

    Cerri, S S; Jenko, F; Told, D; Rincon, F

    2016-01-01

    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 Alfv\\'en 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 simulations of forced hybrid-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 $\\beta\\gtrsim1$ and by magnetosonic/whistler fluctuations at lower $\\beta$. 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 va...

  4. Hybrid Potential Simulation of the Acylation of Enterococcus faecium l,d-Transpeptidase by Carbapenems.

    Science.gov (United States)

    Bhattacharjee, Nicholus; Field, Martin J; Simorre, Jean-Pierre; Arthur, Michel; Bougault, Catherine M

    2016-06-01

    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 simulations in conjunction with QC/MM hybrid 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

  5. Semi-active tuned liquid column damper implementation with real-time hybrid simulations

    Science.gov (United States)

    Riascos, Carlos; Marulanda Casas, Johannio; Thomson, Peter

    2016-04-01

    Real-time hybrid simulation (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.

  6. Hybrid Potential Simulation of the Acylation of Enterococcus faecium l,d-Transpeptidase by Carbapenems.

    Science.gov (United States)

    Bhattacharjee, Nicholus; Field, Martin J; Simorre, Jean-Pierre; Arthur, Michel; Bougault, Catherine M

    2016-06-01

    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 simulations in conjunction with QC/MM hybrid 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.

  7. Ion Dynamics at A Rippled Quasi-parallel Shock: 2-D Hybrid Simulations

    CERN Document Server

    Hao, Yufei; Gao, Xinliang; Wang, Shui

    2016-01-01

    In this paper, two-dimensional (2-D) hybrid simulations 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 reformation 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 easier to transmit through the upper part of a ripple, and the bulk velocity in the corresponding 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. For the reflected ions by the shock, they may suffer multiple stage acceleration when moving along the shock surface, or trapped between the upstream waves and the shock front. At last, these ions may escape to the further upstream or ent...

  8. Simulation and optimum design of hybrid solar-wind and solar-wind-diesel power generation systems

    Science.gov (United States)

    Zhou, Wei

    optimal sizing method was developed to find the system optimum configuration and settings that can achieve the custom-required Renewable Energy Fraction (fRE) of the system with minimum Annualized Cost of System (ACS). Du to the need for optimum design of the hybrid systems, an analysis of local weather conditions (solar radiation and wind speed) was carried out for the potential installation site, and mathematical simulation of the hybrid systems' components was also carried out including PV array, wind turbine and battery bank. By statistically analyzing the long-term hourly solar and wind speed data, Hong Kong area is found to have favorite solar and wind power resources compared with other areas, which validates the practical applications in Hong Kong and Guangdong area. Simulation of PV array performance includes three main parts: modeling of the maximum power output of the PV array, calculation of the total solar radiation on any tilted surface with any orientations, and PV module temperature predictions. Five parameters are introduced to account for the complex dependence of PV array performance upon solar radiation intensities and PV module temperatures. The developed simulation model was validated by using the field-measured data from one existing building-integrated photovoltaic system (BIPV) in Hong Kong, and good simulation performance of the model was achieved. Lead-acid batteries used in hybrid systems operate under very specific conditions, which often cause difficulties to predict when energy will be extracted from or supplied to the battery. In this thesis, the lead-acid battery performance is simulated by three different characteristics: battery state of charge (SOC), battery floating charge voltage and the expected battery lifetime. Good agreements were found between the predicted values and the field-measured data of a hybrid solar-wind project. At last, one 19.8kW hybrid solar-wind power generation project, designed by the optimal sizing method and

  9. Hybrid multi-grids simulations of Ganymede's magnetosphere : comparison with Galileo observations.

    Science.gov (United States)

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

    2015-12-01

    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 hybrid 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 hybrid 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 simulation 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

  10. Evolution of flux ropes in the magnetotail: A three-dimensional global hybrid simulation

    International Nuclear Information System (INIS)

    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 simulations 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 hybrid simulation 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=−30RE∼−15RE 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 RE, and the spatial scale of the flux ropes in the dawn-dusk direction is on the order of several RE and does not extend across the entire section of the magnetotail, contrary to previous models and MHD simulation 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 evolution of the

  11. A computational simulation of the effect of hybrid treatment for thoracoabdominal aortic aneurysm on the hemodynamics of abdominal aorta

    OpenAIRE

    Jun Wen; Ding Yuan; Qingyuan Wang; Yao Hu; Jichun Zhao; Tinghui Zheng; Yubo Fan

    2016-01-01

    Hybrid visceral-renal debranching procedures with endovascular repair have been proposed as an appealing technique to treat conventional thoracoabdominal aortic aneurysm (TAAA). This approach, however, still remained controversial because of the non-physiological blood flow direction of its retrograde visceral revascularization (RVR) which is generally constructed from the aortic bifurcation or common iliac artery. The current study carried out the numerical simulation to investigate the effe...

  12. Simulations of Plug-in Hybrid Vehicles Using Advanced Lithium Batteries and Ultracapacitors on Various Driving Cycles

    OpenAIRE

    Burke, Andy; Zhao, Hengbing

    2010-01-01

    The use of ultracapacitors in plug-in hybrid vehicles (PHEVs) with high energy density lithium-ion and zinc-air batteries is studied. Simulations were performed for various driving cycles with the PHEVs operating in the charge depleting and charge sustaining modes. The effects of the load leveling of the power demand from the batteries using the ultracapacitors are evident. The average and the peak currents from the batteries are lower by a factor of 2-3.

  13. A frequency response analysis approach for quantitative assessment of actuator tracking for real-time hybrid simulation

    International Nuclear Information System (INIS)

    Real-time hybrid simulation 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 hybrid simulations. 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 hybrid simulation. (paper)

  14. First Lunar Wake Passage of ARTEMIS: Discrimination of Wake Effects and Solar Wind Fluctuations by 3D Hybrid Simulations

    Science.gov (United States)

    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.

    2011-01-01

    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 hybrid simulations. As the solar wind magnetic field was highly dynamic during the passage, a simulation 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 simulation of the flyby has been performed. The input values of this simulation are taken from NASA OMNI data and adapted to the P1 data, resulting in a good agreement between simulation and measurements. Combined with the stationary simulation 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 simulations. The simulations 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 simulation 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.

  15. Simulation of transients in natural gas pipelines using hybrid TVD schemes

    Energy Technology Data Exchange (ETDEWEB)

    Junyang Zhou [Pennsylvania State Univ., Petroleum and Natural Gas Engineering, University Park, PA (United States); Adewumi, Michael A. [Pennsylvania State Univ., Petroleum and Natural Gas Section, University Park, PA (United States)

    2000-07-01

    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. Hybrid 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 simulate 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. (Author)

  16. Simulation of transients in natural gas pipelines using hybrid TVD schemes

    Science.gov (United States)

    Zhou, Junyang; Adewumi, Michael A.

    2000-02-01

    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. Hybrid 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 simulate 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

  17. Large eddy simulations and experiments of nonlinear flow interactions in hybrid rocket combustion

    Science.gov (United States)

    Na, Y.; Lee, C.

    2013-03-01

    Nonlinear combustion phenomenon was investigated through an experiment in a hybrid 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 simulation (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.

  18. Simulation of Potential Production and Optimum Population Quantitative Indices for the Second Hybrid Rice

    Institute of Scientific and Technical Information of China (English)

    YAN Li-jiao; YAO Zhong; ZHENG Zhi-ming; LI Hua-bin

    2006-01-01

    The article established the HDRICE model by modifying the structure of the ORYZA1 model and revising its parameters by field experiments. The HDRICE model consists of the modules of morphological development of rice, daily dry matter accumulation and partitioning, daily CO2 assimilation of the canopy, leaf area, and tiller development. The model preferably simulated the dynamic rice development because of the thorough integration of the effects of temperature and light on the rates of rice development, photosynthesis, respiration, and. other ecophysiological processes. In addition, this model has attainable grain yield in the test experiment that showed the potential yield of cultivar Xieyou 46 ranged from 11 to 13 tons ha-1. Besides, the model was used to optimize the combinations of the transplanting date, seedling age and density for cultivar Xieyou 46 at Jinhua area, and the population quantitative indices to attain the potential yield such as maximum stems, effective panicles, filled grain number/leaf area, and so on. The result showed that the combination of transplanting date on July 25, seedling age of 35 days and base seedling density of 1.33 × 106ha-1 is the optimum combination for the second hybrid rice production in Jinhua County, China. And the maximum stems, the effective panicles, the filled grain per panicle, the peak of optimum LAI, LAI in later filling stage, and the filled grain number/leaf were 6.03 × 106 ha, 3.99 × 106 ha,119.2, 8.59, 5-6, and 0.64, respectively.

  19. Dipolarization fronts as earthward propagating flux ropes: A three-dimensional global hybrid simulation

    Science.gov (United States)

    Lu, S.; Lu, Q.; Lin, Y.; Wang, X.; Ge, Y.; Wang, R.; Zhou, M.; Fu, H.; Huang, C.; Wu, M.; Wang, S.

    2015-12-01

    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 hybrid simulation for the first time. In the simulation, 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 anti-reconnection 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 anti-reconnection. 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 ~150km/s to ~1000km/s. The FR/DFs can be tilted in the GSM xy plane with respect to the y (dawn-dusk) axis and only extend several RE in this direction. Moreover, the structure and evolution of the FRs/DFs are non-uniform in the dawn-dusk direction, which indicates that the DFs are essentially 3-D.

  20. Fate of bulk and trace organics during a simulated aquifer recharge and recovery (ARR)-ozone hybrid process

    KAUST Repository

    Yoon, Min

    2013-11-01

    The attenuation of bulk organic matter and trace organic contaminants (TOrCs) was evaluated for various aquifer recharge and recovery (ARR)-ozone (O3) hybrid treatment process combinations using soil-batch reactor and bench-scale ozonation experiments as a proof of concept prior to pilot and/or field studies. In water reclamation and especially potable reuse, refractory bulk organic matter and TOrCs are of potential health concern in recycled waters. In this study, the role of biotransformation of bulk organic matter and TOrCs was investigated considering different simulated treatment combinations, including soil passage (ARR) alone, ARR after ozonation (O3-ARR), and ARR prior to ozonation (ARR-O3). During oxic (aerobic) ARR simulations, soluble microbial-like substances (e.g., higher molecular weight polysaccharides and proteins) were easily removed while (lower molecular weight) humic substances and aromatic organic matter were not efficiently removed. During ARR-ozone treatment simulations, removals of bulk organic matter and TOrCs were rapid and effective compared to ARR alone. A higher reduction of effluent-derived organic matter, including aromatic organic matter and humic substances, was observed in the ARR-O3 hybrid followed by the O3-ARR hybrid. An enhanced attenuation of recalcitrant TOrCs was observed while increasing the ozone dose slightly (O3: DOC=1). TOrC removal efficiency also increased during the post-ozone treatment combination (i.e., ARR-O3). In addition, the carcinogenic wastewater disinfection byproduct N-nitrosodimethylamine (NDMA) was eliminated below the method reporting limit (<5ngL-1) both during ARR treatment alone and the ARR-ozone hybrid. © 2013 Elsevier Ltd.

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

    Directory of Open Access Journals (Sweden)

    Bravo S.

    2004-01-01

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

  2. Applying new hybrid method of analytical hierarchy process, Monte Carlo Simulation and PROMETHEE to prioritize and selecting appropriate target market

    Directory of Open Access Journals (Sweden)

    Amir Kariznoee

    2015-06-01

    Full Text Available Making decision to choose the appropriate target market is one of the key decisions in the success of firms, which has direct effect in the amount of their profits. The aim of this paper is to introduce and use of new hybrid method of AHP, Monte Carlo simulation and PROMETHEE to prioritize cities to establish retailers, considering different indices. The problem of this study is related to a factory, constructing premade pieces of buildings, that to introduce and distribute its new products is searching the new retailers in different cities. To prioritize cities, with the interview with experts and the studying of the previous works the indices have been determined and the hierarchy pattern has been made. Then using the hybrid method of AHP and Monte Carlo simulation the weights of the indices have been determined and then using PROMETHEE method the best city has been chosen and the other ones have been prioritized. From the benefits of the new introduced hybrid method with respect to other ways of selecting target markets is decreasing the risk and increasing the power of decision making.

  3. Modeling and simulation of a series hybrid electric vehicle propulsion system

    OpenAIRE

    Muñoz Aguilar, Raúl Santiago

    2010-01-01

    Two problems related with hybrid electric vehicles have been analyzed in this dissertation. The first one consists in proposing a propulsion system scheme for the vehicle and the second one consist in modeling it. In order to set a propulsion system scheme, the standard configurations for the hybrid electric vehicles are presented as well as some variations of the series topologies. Then, a novel configuration which is composed by a synchronous machine and an induction machi...

  4. STRUCTURE DEVELOPMENT AND SIMULATION OF PLUG-IN HYBRID ELECTRIC VEHICLE

    OpenAIRE

    A. A. Marozka; Yu. N. Petrenko

    2013-01-01

    Electric-drive vehicles (EDVs) have gained attention, especially in the context of growing concerns about global warming and energy security aspects associated with road transport. The main characteristic of EDVs is that the torque is supplied to the wheels by an electric motor that is powered either solely by a battery or in combination with an internal combustion engine (ICE). This covers hybrid electric vehicles (HEVs), battery electric vehicles (BEVs), and plug-in hybrid electric vehicles...

  5. A hybrid simulated annealing approach to handle energy resource management considering an intensive use of electric vehicles

    DEFF Research Database (Denmark)

    Sousa, Tiago; Vale, Zita; Carvalho, Joao Paulo;

    2014-01-01

    The massification of electric vehicles (EVs) can have a significant impact on the power system, requiring a new approach for the energy resource management. The energy resource management has the objective to obtain the optimal scheduling of the available resources considering distributed...... to determine the best solution in a reasonable amount of time. This paper presents a hybrid artificial intelligence technique to solve a complex energy resource management problem with a large number of resources, including EVs, connected to the electric network. The hybrid approach combines simulated...... generators, storage units, demand response and EVs. The large number of resources causes more complexity in the energy resource management, taking several hours to reach the optimal solution which requires a quick solution for the next day. Therefore, it is necessary to use adequate optimization techniques...

  6. Monte Carlo simulations of biaxial structure in thin hybrid nematic film based upon spatially anisotropic pair potential

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhi-Dong; Chang Chun-Rui; Ma Dong-Lai

    2009-01-01

    Hybrid nematic films have been studied by Monte Carlo simulations using a lattice spin model,in which the pair potential is spatially anisotropic and dependent on elastic constants of liquid crystals.We confirm in the thin hybrid nematic film the existence of a biaxially nonbent structure and the structarc transition from the biaxial to the bent-director structure,which is similar to the result obtained using the Lebwohl-Lasher model.However,the step-like director's profile,characteristic for the biaxial structure,is spatially asymmetric in the film because the pair potential leads to K1≠K3.We estimate the upper cell thickness to be 69 spin layers,in which the biaxial structure can be found.

  7. Dynamic Modeling, Control and Simulation of a Wind and PV Hybrid System for Grid Connected Application Using MATLAB

    Directory of Open Access Journals (Sweden)

    D. Mahesh Naik

    2014-07-01

    Full Text Available This paper proposes a dynamic modeling and control strategy for a grid connected hybrid wind and photovoltaic (PV energy system inter-connected to electrical grid through power electronic interface. A gearless permanent magnet synchronous generator (PMSG is used to capture the maximum wind energy. The PV and wind systems are connected dc-side of the voltage source inverter through a boost converter individually and maintain a fixed dc output at dc link. A proper control scheme is required to operate power converters to match up the grid connection requirements. This study considered the performance of modeled hybrid system under different case scenarios. All simulation models are developed using MATLAB/Simulink.

  8. Modeling,Analysis and Simulation ofThree Phase Hybrid Power Filter forPower Quality Improvement

    Directory of Open Access Journals (Sweden)

    Prashanta Kumar Das

    2012-05-01

    Full Text Available A three-phase hybrid series power filter is constituted by a series active filter and a passive filter connected in parallel with the load. The control strategy is based on the “dual formulation of the electric power vectorial theory”. The proposed algorithm eliminates the current harmonics of supply. It also improves the power factor and harmonic compensation features of the associated passive filter even if there is a change in system parameters.A shunt hybrid power filter is constituted by a shunt active filter and a passive filter connected in parallel with the load, is proposed with same control strategy. Simulations have been carried out on the MATLAB-SIMULINK platform with different loads and with variation in the source impedance.

  9. Passive hybrid force-position control for tele-operation based on real-time simulation of a virtual mechanism

    International Nuclear Information System (INIS)

    Hybrid force-position control aims at controlling position and force in separate directions. It is particularly useful to perform certain robotic tasks. In tele-operation context, passivity is important because it ensures stability when the system interacts with any passive environment. In this paper, we propose an original approach to hybrid force-position control of a force reflecting tele-robot system. It is based on real-time simulation of a virtual mechanism corresponding to the task. the resulting control law is passive. Experiments on a 6 degrees of freedom tele-operation system consisting in following a bent pipe under several control modes validate the approach. (authors). 12 refs., 6 figs

  10. Passive hybrid force-position control for tele-operation based on real-time simulation of a virtual mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Joly, L.; Andriot, C.

    1995-12-31

    Hybrid force-position control aims at controlling position and force in separate directions. It is particularly useful to perform certain robotic tasks. In tele-operation context, passivity is important because it ensures stability when the system interacts with any passive environment. In this paper, we propose an original approach to hybrid force-position control of a force reflecting tele-robot system. It is based on real-time simulation of a virtual mechanism corresponding to the task. the resulting control law is passive. Experiments on a 6 degrees of freedom tele-operation system consisting in following a bent pipe under several control modes validate the approach. (authors). 12 refs., 6 figs.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-01

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

  12. Molecular dynamics simulation of joining process of Ag-Au nanowires and mechanical properties of the hybrid nanojoint

    Directory of Open Access Journals (Sweden)

    Su Ding

    2015-05-01

    Full Text Available The nanojoining process of Ag-Au hybrid nanowires at 800K was comprehensively studied by virtue of molecular dynamics (MD simulation. Three kinds of configurations including end-to-end, T-like and X-like were built in the simulation 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 simulation 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.

  13. Electromagnetic particle simulation of the effect of toroidicity on linear mode conversion and absorption of lower hybrid waves

    Science.gov (United States)

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

    2016-06-01

    Effects of toroidicity on linear mode conversion and absorption of lower hybrid (LH) waves in fusion plasmas have been studied using electromagnetic particle simulation. The simulation 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 simulation. 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.

  14. Dynamic modelling of an adsorption storage tank using a hybrid approach combining computational fluid dynamics and process simulation

    Science.gov (United States)

    Mota, J.P.B.; Esteves, I.A.A.C.; Rostam-Abadi, M.

    2004-01-01

    A computational fluid dynamics (CFD) software package has been coupled with the dynamic process simulator 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 hybrid computational tool has been successfully employed to accurately simulate the discharge of a new tank design and evaluate its performance. The case study presented here shows that CFD and process simulation 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.

  15. Hybrid cadaveric/surrogate model of thoracolumbar spine injury due to simulated fall from height.

    Science.gov (United States)

    Ivancic, Paul C

    2013-10-01

    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 hybrid cadaveric/surrogate model for producing thoracolumbar spine injury during simulated 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

  16. Investigation of storm time magnetotail and ion injection using three-dimensional global hybrid simulation

    Science.gov (United States)

    Lin, Y.; Wang, X. Y.; Lu, S.; Perez, J. D.; Lu, Q.

    2014-09-01

    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 hybrid simulation 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

  17. Monte Carlo simulation of simultaneous radiation detection in the hybrid tomography system ClearPET-XPAD3/CT

    Science.gov (United States)

    Dávila, H. Olaya; Sevilla, A. C.; Castro, H. F.; Martínez, S. A.

    2016-07-01

    Using the Geant4 based simulation framework SciFW1, a detailed simulation was performed for a detector array in the hybrid 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 hybrid 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 simulation proposed will improve distribution of detectors rings and interference values will be taken into account in the new versions of detectors.

  18. 3-D hybrid LES-RANS model for simulation of open-channel T-diversion flows

    Institute of Scientific and Technical Information of China (English)

    Jie ZHOU; Cheng ZENG

    2009-01-01

    The study of flow diversions in open channels plays an important practical role in the design and management of open-channel networks for irrigation or drainage.To accurately predict the mean flow and turbulence characteristics of open-channel dividing flows,a hybrid LES-RANS model,which combines the large eddy simulation (LES) model with the Reynolds-averaged Navier-Stokes (RANS) model,is proposed in the present study.The unsteady RANS model was used to simulate the upstream and downstream regions of a main channel,as well as the downstream region of a branch channel.The LES model was used to simulate the channel diversion region,where turbulent flow characteristics ate complicated.Isotropic velocity fluctuations were added at the inflow interface of the LES region to trigger the generation of resolved turbulence.A method based on the virtual body force is proposed to impose Reynolds-averaged velocity fields near the outlet of the LES region in order to take downstream flow effects computed by the RANS model into account and dissipate the excessive turbulent fluctuations.This hybrid approach saves computational effort and makes it easier to properly specify inlet and outlet boundary conditions.Comparison between computational results and experimental data indicates that this relatively new modeling approach can accurately predict open-channel T-diversion flows.

  19. A HYBRID MODEL FOR SIMULATING VELOCITY FIELD OF A RIVER WITH COMPLEX GEOMETRY PLUNGED BY MULTIPLE JETS

    Institute of Scientific and Technical Information of China (English)

    LI Lian-xia; LIAO Hua-sheng; LI Tian-xiang

    2006-01-01

    A hybrid model that combines both physical and numerical models was employed to simulate the velocity field in a river area in complex geometry with multiple plunging jets. The simulation was based on experiments concerning energy dissipation and scour prevention at the Xiluodu Hydropower Station on the Yangtze River. The calculated results indicate that the complex geometry of the river area has a significant influence on the velocity field, especially on the circulation flow pattern at upstream and downstream of the plunging area and on the asymmetric characteristics of the spiral flow near both banks. The scour characteristics of the downstream river bed caused by the multiple jets were also predicted and analyzed according to the characteristics of the calculated velocity field. The good agreement between the simulated and experimental results indicates that the hybrid model can be used to effectively solve complicated 3-D problems with complex geometric and inlet conditions. Such problems may not easily be solved by using either a physical or a numerical model alone, and therefore the method presented in this article is considered to be a practical and effective way of dealing with this kind of problems.

  20. 3-D hybrid LES-RANS model for simulation of open-channel T-diversion flows

    Directory of Open Access Journals (Sweden)

    Jie ZHOU

    2009-09-01

    Full Text Available The study of flow diversions in open channels plays an important practical role in the design and management of open-channel networks for irrigation or drainage. To accurately predict the mean flow and turbulence characteristics of open-channel dividing flows, a hybrid LES-RANS model, which combines the large eddy simulation (LES model with the Reynolds-averaged Navier-Stokes (RANS model, is proposed in the present study. The unsteady RANS model was used to simulate the upstream and downstream regions of a main channel, as well as the downstream region of a branch channel. The LES model was used to simulate the channel diversion region, where turbulent flow characteristics are complicated. Isotropic velocity fluctuations were added at the inflow interface of the LES region to trigger the generation of resolved turbulence. A method based on the virtual body force is proposed to impose Reynolds-averaged velocity fields near the outlet of the LES region in order to take downstream flow effects computed by the RANS model into account and dissipate the excessive turbulent fluctuations. This hybrid approach saves computational effort and makes it easier to properly specify inlet and outlet boundary conditions. Comparison between computational results and experimental data indicates that this relatively new modeling approach can accurately predict open-channel T-diversion flows.

  1. Vlasov Hybrid Simulation-an efficient and stable algorithm for the numerical simulation of collision-free plasma

    OpenAIRE

    D. Nunn

    2005-01-01

    This paper presents a highly efficient and stable algorithm for the numerical simulation of collision free plasma. The algorithm has been successfully used to numerically model non linear electron cyclotron resonance in VLF band radio waves in space, and has produced good simulations of radio emissions such as ‘dawn chorus’ and ‘triggered VLF emissions’. The algorithm fills the phase box with simulation particles which represent phase space trajectories. Particle trajectories are followed for...

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

    Science.gov (United States)

    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.

  3. Identifying bottlenecks in charging infrastructure of plug-in hybrid electric vehicles through agent-based traffic simulation

    OpenAIRE

    Lindgren, Juuso; Lund, Peter D.

    2015-01-01

    The effect of different charging infrastructure configurations on the electric-driven distance of plug-in hybrid electric vehicles (e-mileage) has been investigated, using an agent-based traffic simulation. Our findings suggest that the same e-mileage can be achieved with fewer charging poles if the poles support charging from several parking slots around them, and the charging cable is switched from one vehicle to the next. We also find that the charging power supported by most Finnish charg...

  4. Development and validation of a hybrid simulation technique for cone beam CT: application to an oral imaging system

    Science.gov (United States)

    Zhang, G.; Pauwels, R.; Marshall, N.; Shaheen, E.; Nuyts, J.; Jacobs, R.; Bosmans, H.

    2011-09-01

    This paper proposes a hybrid technique to simulate the complete chain of an oral cone beam computed tomography (CBCT) system for the study of both radiation dose and image quality. The model was developed around a 3D Accuitomo 170 unit (J Morita, Japan) with a tube potential range of 60-90 kV. The Monte Carlo technique was adopted to simulate the x-ray generation, filtration and collimation. Exact dimensions of the bow-tie filter were estimated iteratively using experimentally acquired flood images. Non-flat radiation fields for different exposure settings were mediated via 'phase spaces'. Primary projection images were obtained by ray tracing at discrete energies and were fused according to the two-dimensional energy modulation templates derived from the phase space. Coarse Monte Carlo simulations were performed for scatter projections and the resulting noisy images were smoothed by Richardson-Lucy fitting. Resolution and noise characteristics of the flat panel detector were included using the measured modulation transfer function (MTF) and the noise power spectrum (NPS), respectively. The Monte Carlo dose calculation was calibrated in terms of kerma free-in-air about the isocenter, using an ionization chamber, and was subsequently validated by comparison against the measured air kerma in water at various positions of a cylindrical water phantom. The resulting dose discrepancies were found artifact pattern in comparison to experimentally acquired images, with <5% difference for voxel values of the aluminum and air insert regions and <3% difference for voxel uniformity across the homogeneous PMMA region. The detector simulation by use of the MTF and NPS data exhibited a big influence on noise and the sharpness of the resulting images. The hybrid simulation technique is flexible and has wide applicability to CBCT systems.

  5. Investigation of interphase effects in silica-polystyrene nanocomposites based on a hybrid molecular-dynamics-finite-element simulation framework

    Science.gov (United States)

    Pfaller, Sebastian; Possart, Gunnar; Steinmann, Paul; Rahimi, Mohammad; Müller-Plathe, Florian; Böhm, Michael C.

    2016-05-01

    A recently developed hybrid method is employed to study the mechanical behavior of silica-polystyrene nanocomposites (NCs) under uniaxial elongation. The hybrid method couples a particle domain to a continuum domain. The region of physical interest, i.e., the interphase around a nanoparticle (NP), is treated at molecular resolution, while the surrounding elastic continuum is handled with a finite-element approach. In the present paper we analyze the polymer behavior in the neighborhood of one or two nanoparticle(s) at molecular resolution. The coarse-grained hybrid method allows us to simulate a large polymer matrix region surrounding the nanoparticles. We consider NCs with dilute concentration of NPs embedded in an atactic polystyrene matrix formed by 300 chains with 200 monomer beads. The overall orientation of polymer segments relative to the deformation direction is determined in the neighborhood of the nanoparticle to investigate the polymer response to this perturbation. Calculations of strainlike quantities give insight into the deformation behavior of a system with two NPs and show that the applied strain and the nanoparticle distance have significant influence on the deformation behavior. Finally, we investigate to what extent a continuum-based description may account for the specific effects occurring in the interphase between the polymer matrix and the NPs.

  6. Experimental evaluation of hybrid vehicle fuel economy and pollutant emissions over real-world simulation driving cycles

    Science.gov (United States)

    Fontaras, Georgios; Pistikopoulos, Panayotis; Samaras, Zissis

    2008-06-01

    The reduction of transport-generated CO2 emissions is currently a problem of global interest. Hybrid electric vehicles (HEVs) are considered as one promising technological solution for limiting transport-generated greenhouse gas emissions. Currently, the number of HEVs in the market remains limited, but this picture will change in the years to come as HEVs are expected to pave the way for cleaner technologies in transport. In this paper, results are presented regarding fuel economy and pollutant emissions measurements of two hybrid electric production vehicles. The measurements were conducted on a Prius II and a Honda Civic IMA using both the European legislated driving cycle (New European Driving Cycle, NEDC) and real-world simulation driving cycles (Artemis). In addition to the emissions measurements, other vehicle-operating parameters were studied in an effort to better quantify the maximum CO2 reduction potential. Data from real-world operation of a Prius II vehicle were also used in the evaluation. Results indicate that in most cases both vehicles present improved energy efficiency and pollutant emissions compared to conventional cars. The fuel economy benefit of the two HEVs peaked under urban driving conditions where reductions of 60% and 40% were observed, respectively. Over higher speeds the difference in fuel economy was lower, reaching that of conventional diesel at 95 km h-1. The effect of ambient temperature on fuel consumption was also quantified. It is concluded that urban operation benefits the most of hybrid technology, leading to important fuel savings and urban air quality improvement.

  7. A hybrid approach for simulating fluid loading effects on structures using experimental modal analysis and the boundary element method.

    Science.gov (United States)

    Shepherd, Micah R; Fahnline, John B; Dare, Tyler P; Hambric, Stephen A; Campbell, Robert L

    2015-11-01

    Many structural acoustics problems involve a vibrating structure in a heavy fluid. However, obtaining fluid-loaded natural frequencies and damping experimentally can be difficult and expensive. This paper presents a hybrid experimental-numerical approach to determine the heavy-fluid-loaded resonance frequencies and damping of a structure from in-air measurements. The approach combines in-air experimentally obtained mode shapes with simulated in-water acoustic resistance and reactance matrices computed using boundary element (BE) analysis. The procedure relies on accurate estimates of the mass-normalized, in vacuo mode shapes using singular value decomposition and rational fraction polynomial fitting, which are then used as basis modes for the in-water BE analysis. The method is validated on a 4.445 cm (1.75 in.) thick nickel-aluminum-bronze rectangular plate by comparing natural frequencies and damping obtained using the hybrid approach to equivalent data obtained from actual in-water measurements. Good agreement is shown for the fluid-loaded natural frequencies and one-third octave loss factors. Finally, the limitations of the hybrid approach are examined. PMID:26627781

  8. Control Strategies, Robustness Analysis, Digital Simulation and Practical Implementation for a Hybrid APF with a Resonant Ac-link

    Directory of Open Access Journals (Sweden)

    Chen Chen

    2010-12-01

    Full Text Available This paper proposes a novel hybrid active power filter (HAPF topology based onthe cascaded connection of the AC-side capacitor and the third-order LCL-filter, which hasthe advantage of the conventional hybrid filter and the LCL-filter in terms of reduced dclinkvoltage and better switching ripple attenuation. The robust deadbeat control law isderived for the current loop, with special emphasis on robustness analysis. The stabilityand robustness analysis under parameter variations are presented for the converter-sidecurrent tracking scheme and the grid-side current tracking scheme. It is found that thestability margins obtained from the converter-side current tracking control scheme aregenerally higher than those obtained from the grid-side current tracking scheme. However,the converter-side current tracking scheme is sensitive to the variation of the dampingresistance, and it would impose additional parameter uncertainty on the control system andcomplicate the problem. Hence the grid-side current tracking scheme is implemented. Thesimulation results obtained from Matlab/Simulink are presented for verification, where theinductance variation and grid disturbance scenarios are also taken into consideration. Theeffectiveness of the proposed hybrid APF is substantially confirmed by the simulation andexperimental results.

  9. Efficient Mooring Line Fatigue Analysis Using a Hybrid Method Time Domain Simulation Scheme

    DEFF Research Database (Denmark)

    Christiansen, Niels Hørbye; Voie, Per Erlend Torbergsen; Høgsberg, Jan Becker;

    2013-01-01

    Dynamic analyses of mooring line systems are computationally expensive. Over the last decades an extensive variety of methods to reduce this computational cost have been suggested. One method that has shown promising preliminary results is a hybrid method which combines finite element analysis...

  10. Energy management of power-split plug-in hybrid electric vehicles based on simulated annealing and Pontryagin's minimum principle

    Science.gov (United States)

    Chen, Zheng; Mi, Chunting Chris; Xia, Bing; You, Chenwen

    2014-12-01

    In this paper, an energy management method is proposed for a power-split plug-in hybrid electric vehicle (PHEV). Through analyzing the PHEV powertrain, a series of quadratic equations are employed to approximate the vehicle's fuel-rate, using battery current as the input. Pontryagin's Minimum Principle (PMP) is introduced to find the battery current commands by solving the Hamiltonian function. Simulated Annealing (SA) algorithm is applied to calculate the engine-on power and the maximum current coefficient. Moreover, the battery state of health (SOH) is introduced to extend the application of the proposed algorithm. Simulation results verified that the proposed algorithm can reduce fuel-consumption compared to charge-depleting (CD) and charge-sustaining (CS) mode.

  11. Molecular dynamics simulation of the formation of sp3 hybridized bonds in hydrogenated diamondlike carbon deposition processes.

    Science.gov (United States)

    Murakami, Yasuo; Horiguchi, Seishi; Hamaguchi, Satoshi

    2010-04-01

    The formation process of sp3 hybridized carbon networks (i.e., diamondlike structures) in hydrogenated diamondlike carbon (DLC) films has been studied with the use of molecular-dynamics simulations. The processes simulated in this study are injections of hydrocarbon (CH3 and CH) beams into amorphous carbon (a-C) substrates. It has been shown that diamondlike sp3 structures are formed predominantly at a subsurface level when the beam energy is relatively high, as in the "subplantation" process for hydrogen-free DLC deposition. However, for hydrogenated DLC deposition, the presence of abundant hydrogen at subsurface levels, together with thermal spikes caused by energetic ion injections, substantially enhances the formation of carbon-to-carbon sp3 bonds. Therefore, the sp3 bond formation process for hydrogenated DLC films essentially differs from that for hydrogen-free DLC films.

  12. Development of a hybrid particle-mesh method for two-phase flow simulations with phase change

    International Nuclear Information System (INIS)

    A hybrid particle-mesh method was developed for efficient and accurate simulations of two-phase flows with phase change. In this method, the CIP/MM (constrained interpolated profile/multi-moment finite volume) method is used to calculate the main part of two-phase flows, while the finite volume particle (FVP) method is applied to represent the interface between two phases based on a Lagrangian scheme. The conservation equations are first solved by CIP/MM, and then mass, velocity and energy on the mesh grid are interpolated to numerical particles, which are distributed only on the surface of liquid phase to capture the phase interface by the FVP method. The particles are also used to calculate heat and mass transfers due to phase change on the interface. The phase of each particle is determined according to its enthalpy value interpolated from mesh grids. The mesh and particle methods are combined tightly in a single numerical solution algorithm to improve numerical accuracy and stability. Two benchmark simulations of conventional 1D Stefan problem for a vapor-liquid system and horizontal film boiling behavior demonstrate that this hybrid method is potentially applicable to two-phase flow calculations with phase change occurring at moving interface. (author)

  13. Particle simulations of mode conversion between slow mode and fast mode in lower hybrid range of frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Guozhang; Xiang, Nong; Huang, Yueheng [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Center for Magnetic Fusion Theory, Chinese Academy of Sciences, Hefei 230031 (China); Wang, Xueyi [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Physics Department, 206 Allison Laboratory, Auburn University, Alabama 36849-5311 (United States); Lin, Yu [Physics Department, 206 Allison Laboratory, Auburn University, Alabama 36849-5311 (United States)

    2016-01-15

    The propagation and mode conversion of lower hybrid waves in an inhomogeneous plasma are investigated by using the nonlinear δf algorithm in a two-dimensional particle-in-cell simulation code based on the gyrokinetic electron and fully kinetic ion (GeFi) scheme [Lin et al., Plasma Phys. Controlled Fusion 47, 657 (2005)]. The characteristics of the simulated waves, such as wavelength, frequency, phase, and group velocities, agree well with the linear theoretical analysis. It is shown that a significant reflection component emerges in the conversion process between the slow mode and the fast mode when the scale length of the density variation is comparable to the local wavelength. The dependences of the reflection coefficient on the scale length of the density variation are compared with the results based on the linear full wave model for cold plasmas. It is indicated that the mode conversion for the waves with a frequency of 2.45 GHz (ω ∼ 3ω{sub LH}, where ω{sub LH} represents the lower hybrid resonance) and within Tokamak relevant amplitudes can be well described in the linear scheme. As the frequency decreases, the modification due to the nonlinear term becomes important. For the low-frequency waves (ω ∼ 1.3ω{sub LH}), the generations of the high harmonic modes and sidebands through nonlinear mode-mode coupling provide new power channels and thus could reduce the reflection significantly.

  14. Particle simulations of mode conversion between slow mode and fast mode in lower hybrid range of frequencies

    Science.gov (United States)

    Jia, Guozhang; Xiang, Nong; Wang, Xueyi; Huang, Yueheng; Lin, Yu

    2016-01-01

    The propagation and mode conversion of lower hybrid waves in an inhomogeneous plasma are investigated by using the nonlinear δf algorithm in a two-dimensional particle-in-cell simulation code based on the gyrokinetic electron and fully kinetic ion (GeFi) scheme [Lin et al., Plasma Phys. Controlled Fusion 47, 657 (2005)]. The characteristics of the simulated waves, such as wavelength, frequency, phase, and group velocities, agree well with the linear theoretical analysis. It is shown that a significant reflection component emerges in the conversion process between the slow mode and the fast mode when the scale length of the density variation is comparable to the local wavelength. The dependences of the reflection coefficient on the scale length of the density variation are compared with the results based on the linear full wave model for cold plasmas. It is indicated that the mode conversion for the waves with a frequency of 2.45 GHz (ω ˜ 3ωLH, where ωLH represents the lower hybrid resonance) and within Tokamak relevant amplitudes can be well described in the linear scheme. As the frequency decreases, the modification due to the nonlinear term becomes important. For the low-frequency waves (ω ˜ 1.3ωLH), the generations of the high harmonic modes and sidebands through nonlinear mode-mode coupling provide new power channels and thus could reduce the reflection significantly.

  15. Hybrid Strategy of Particle Swarm Optimization and Simulated Annealing for Optimizing Orthomorphisms

    Institute of Scientific and Technical Information of China (English)

    Tong Yan; Zhang Huanguo

    2012-01-01

    Orthomorphism on F2^n is a kind of elementary pemmtation with good cryptographic properties. This paper proposes a hybrid strategy of Particle Swarm Optimization (PSO) and Sirrmlated Annealing (SA) for finding orthomorphisrm with good cryptographic properties. By experiment based on this strategy, we get some orthorrorphisrm on F2^n = 5, 6, 7, 9, 10) with good cryptographic properties in the open document for the first time, and the optirml orthorrrphism on F found in this paper also does better than the one proposed by Feng Dengguo et al. in stream cipher Loiss in difference uniformity, algebraic degree, algebraic irrarnity and corresponding pernmtation polynomial degree. The PSOSA hybrid strategy for optimizing orthomerphism in this paper makes design of orthorrorphisrm with good cryptographic properties automated, efficient and convenient, which proposes a new approach to design orthornorphisrm.

  16. Hybrid (Vlasov-Fluid) simulation of ion-acoustic solitons chain formation including trapped electrons

    Energy Technology Data Exchange (ETDEWEB)

    Behjat, E.; Aminmansoor, F.; Abbasi, H. [Faculty of Energy Engineering and Physics, Amirkabir University of Technology, P. O. Box 15875-4413, Tehran (Iran, Islamic Republic of)

    2015-08-15

    Disintegration of a Gaussian profile into ion-acoustic solitons in the presence of trapped electrons [H. Hakimi Pajouh and H. Abbasi, Phys. Plasmas 15, 082105 (2008)] is revisited. Through a hybrid (Vlasov-Fluid) model, the restrictions associated with the simple modified Korteweg de-Vries (mKdV) model are studied. For instance, the lack of vital information in the phase space associated with the evolution of electron velocity distribution, the perturbative nature of mKdV model which limits it to the weak nonlinear cases, and the special spatio-temporal scaling based on which the mKdV is derived. Remarkable differences between the results of the two models lead us to conclude that the mKdV model can only monitor the general aspects of the dynamics, and the precise picture including the correct spatio-temporal scales and the properties of solitons should be studied within the framework of hybrid model.

  17. Development and validation of a hybrid simulation technique for cone beam CT: application to an oral imaging system

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, G; Marshall, N; Shaheen, E; Bosmans, H [Department of Radiology, University Hospitals Leuven, Herestraat 49, Leuven 3000 (Belgium); Pauwels, R; Jacobs, R [Oral Imaging Center, University Hospitals Leuven, Kapucijnenvoer 33, Leuven 3000 (Belgium); Nuyts, J, E-mail: guozhi.zhang@med.kuleuven.be [Department of Nuclear Medicine, University Hospitals Leuven, Herestraat 49, Leuven 3000 (Belgium)

    2011-09-21

    This paper proposes a hybrid technique to simulate the complete chain of an oral cone beam computed tomography (CBCT) system for the study of both radiation dose and image quality. The model was developed around a 3D Accuitomo 170 unit (J Morita, Japan) with a tube potential range of 60-90 kV. The Monte Carlo technique was adopted to simulate the x-ray generation, filtration and collimation. Exact dimensions of the bow-tie filter were estimated iteratively using experimentally acquired flood images. Non-flat radiation fields for different exposure settings were mediated via 'phase spaces'. Primary projection images were obtained by ray tracing at discrete energies and were fused according to the two-dimensional energy modulation templates derived from the phase space. Coarse Monte Carlo simulations were performed for scatter projections and the resulting noisy images were smoothed by Richardson-Lucy fitting. Resolution and noise characteristics of the flat panel detector were included using the measured modulation transfer function (MTF) and the noise power spectrum (NPS), respectively. The Monte Carlo dose calculation was calibrated in terms of kerma free-in-air about the isocenter, using an ionization chamber, and was subsequently validated by comparison against the measured air kerma in water at various positions of a cylindrical water phantom. The resulting dose discrepancies were found <10% for most cases. Intensity profiles of the experimentally acquired and simulated projection images of the water phantom showed comparable fractional increase over the common area as changing from a small to a large field of view, suggesting that the scatter was accurately accounted. Image validation was conducted using two small phantoms and the built-in quality assurance protocol of the system. The reconstructed simulated images showed high resemblance on contrast resolution, noise appearance and artifact pattern in comparison to experimentally acquired images

  18. Hybrid Simulations of the Broadband Ground Motions for the 2008 MS8.0 Wenchuan, China, Earthquake

    Science.gov (United States)

    Yu, X.; Zhang, W.

    2012-12-01

    The Ms8.0 Wenchuan earthquake occurred on 12 May 2008 at 14:28 Beijing Time. It is the largest event happened in the mainland of China since the 1976, Mw7.6, Tangshan earthquake. Due to occur in the mountainous area, this great earthquake and the following thousands aftershocks also caused many other geological disasters, such as landslide, mud-rock flow and "quake lakes" which formed by landslide-induced reservoirs. These resulted in tremendous losses of life and property. Casualties numbered more than 80,000 people, and there were major economic losses. However, this earthquake is the first Ms 8 intraplate earthquake with good close fault strong motion coverage. Over four hundred strong motion stations of the National Strong Motion Observation Network System (NSMONS) recorded the mainshock. Twelve of them located within 20 km of the fault traces and another 33 stations located within 100 km. These observations, accompanying with the hundreds of GPS vectors and multiple ALOS INSAR images, provide an unprecedented opportunity to study the rupture process of such a great intraplate earthquake. In this study, we calculate broadband near-field ground motion synthetic waveforms of this great earthquake using a hybrid broadband ground-motion simulation methodology, which combines a deterministic approach at low frequencies (f Green's function calculation approach at high frequency ( ~ 10.0 Hz). The fault rupture is represented kinematically and incorporates spatial heterogeneity in slip, rupture speed, and rise time that were obtained by an inversion kinematic source model. At the same time, based on the aftershock data, we analyze the site effects for the near-field stations. Frequency-dependent site-amplification values for each station are calculated using genetic algorithms. For the calculation of the synthetic waveforms, at first, we carry out simulations using the hybrid methodology for the frequency up to 10.0 Hz. Then, we consider for the soil site simulations

  19. A hybrid modelling approach to simulating foot-and-mouth disease outbreaks in Australian livestock

    Directory of Open Access Journals (Sweden)

    Richard A Bradhurst

    2015-03-01

    Full Text Available Foot-and-mouth disease (FMD is a highly contagious and economically important viral disease of cloven-hoofed animals. Australia's freedom from FMD underpins a valuable trade in live animals and animal products. An outbreak of FMD would result in the loss of export markets and cause severe disruption to domestic markets. The prevention of, and contingency planning for, FMD are of key importance to government, industry, producers and the community. The spread and control of FMD is complex and dynamic due to a highly contagious multi-host pathogen operating in a heterogeneous environment across multiple jurisdictions. Epidemiological modelling is increasingly being recognized as a valuable tool for investigating the spread of disease under different conditions and the effectiveness of control strategies. Models of infectious disease can be broadly classified as: population-based models that are formulated from the top-down and employ population-level relationships to describe individual-level behaviour, individual-based models that are formulated from the bottom-up and aggregate individual-level behaviour to reveal population-level relationships, or hybrid models which combine the two approaches into a single model.The Australian Animal Disease Spread (AADIS hybrid model employs a deterministic equation-based model (EBM to model within-herd spread of FMD, and a stochastic, spatially-explicit agent-based model (ABM to model between-herd spread and control. The EBM provides concise and computationally efficient predictions of herd prevalence and clinical signs over time. The ABM captures the complex, stochastic and heterogeneous environment in which an FMD epidemic operates. The AADIS event-driven hybrid EBM/ABM architecture is a flexible, efficient and extensible framework for modelling the spread and control of disease in livestock on a national scale. We present an overview of the AADIS hybrid approach and a description of the model

  20. Energy-based modelling and simulation of a series hybrid electric vehicle propulsion system

    OpenAIRE

    Muñoz Aguilar, Raúl Santiago; Dòria Cerezo, Arnau; Puleston, Paul

    2009-01-01

    This paper presents an energy-based model of a series hybrid electric vehicle. The proposed propulsion system has a new configuration using a wound-rotor synchronous generator (WRSM) and a doublyfed induction machine (DFIM). From the classic dq dynamical equations of the WRSM and DFIM the port-controlled Hamiltonian models of each machine is described. One of the abilities of the port-based models is that the complete model is easy to obtain by means of interconnection rules. Foll...

  1. Development and Simulation of a Type of Four-Shaft ECVT for a Hybrid Electric Vehicle

    OpenAIRE

    Yong Zhang; Xuerui Ma; Chengliang Yin; Shifei Yuan

    2016-01-01

    In hybrid electric vehicles with power-split configurations, the engine can be decoupled from the wheel and operated with improved fuel economy, while the entire efficiency of the powertrain is affected by the circular electric power flow. Two planetary gear (2-PG) sets with adding brakes/clutches, namely a type of four shaft elelctric continuously variable transmission (ECVT) can provide multi-mode operation for the powertrain and extend the efficient area. First, a conventional 2-PG AT (Aut...

  2. Issues regarding the modelling and simulation of hybrid micro grid systems

    Science.gov (United States)

    Szeidert, I.; Filip, I.; Prostean, O.

    2016-02-01

    The main followed objectives within control strategies dedicated to hybrid micro grid systems (wind/hydro/solar), that operate based on maximum power point tracking (MPPT) techniques are to improve the conversion systems efficiency and to maintain the quality of the produced electrical energy (the voltage and power factor control). One of the main goals of maximum power point tracking strategy is to achieve the harvesting of the maximal possible energy within a pre-set time period. In order to implement the control strategies for micro grid systems that operate at time variable parameter, there are usually required specific transducers (anemometer for wind speed measurement, optical rotational transducers, taco generators, etc.). In the technical literature there are presented several variants of the MPPT techniques, which are particularized at several applications (wind energy conversion systems, solar systems, hydro plants and micro grid hybrid systems). The maximum power point tracking implementations are mainly based on two-level architecture. The inferior level controls the primary variables, while the superior level represents the MPPT control structure. In the paper, authors present some micro grid structures proposed at Politehnica University Timisoara within the frame of a research grant. The paper is focused on the application of MPPT strategies on hybrid micro grid systems. There are presented several structures and control strategies and are highlighted their advantages and disadvantages, together with practical implementation guidelines.

  3. A hybrid CFD-DSMC model designed to simulate rapidly rarefying flow fields and its application to physical vapor deposition

    Science.gov (United States)

    Gott, Kevin

    This research endeavors to better understand the physical vapor deposition (PVD) vapor transport process by determining the most appropriate fluidic model to design PVD coating manufacturing. An initial analysis was completed based on the calculation of Knudsen number from titanium vapor properties. The results show a dense Navier-Stokes solver best describes flow near the evaporative source, but the material properties suggest expansion into the chamber may result in a strong drop in density and a rarefied flow close to the substrate. A hybrid CFD-DSMC solver is constructed in OpenFOAM for rapidly rarefying flow fields such as PVD vapor transport. The models are patched together combined using a new patching methodology designed to take advantage of the one-way motion of vapor from the CFD region to the DSMC region. Particles do not return to the dense CFD region, therefore the temperature and velocity can be solved independently in each domain. This novel technique allows a hybrid method to be applied to rapidly rarefying PVD flow fields in a stable manner. Parameter studies are performed on a CFD, Navier-Stokes continuum based compressible solver, a Direct Simulation Monte Carlo (DSMC) rarefied particle solver, a collisionless free molecular solver and the hybrid CFD-DSMC solver. The radial momentum at the inlet and radial diffusion characteristics in the flow field are shown to be the most important to achieve an accurate deposition profile. The hybrid model also shows sensitivity to the shape of the CFD region and rarefied regions shows sensitivity to the Knudsen number. The models are also compared to each other and appropriate experimental data to determine which model is most likely to accurately describe PVD coating deposition processes. The Navier-Stokes solvers are expected to yield backflow across the majority of realistic inlet conditions, making their physics unrealistic for PVD flow fields. A DSMC with improved collision model may yield an accurate

  4. Data of NODDI diffusion metrics in the brain and computer simulation of hybrid diffusion imaging (HYDI acquisition scheme

    Directory of Open Access Journals (Sweden)

    Chandana Kodiweera

    2016-06-01

    Full Text Available This article provides NODDI diffusion metrics in the brains of 52 healthy participants and computer simulation data to support compatibility of hybrid diffusion imaging (HYDI, “Hybrid diffusion imaging” [1] acquisition scheme in fitting neurite orientation dispersion and density imaging (NODDI model, “NODDI: practical in vivo neurite orientation dispersion and density imaging of the human brain” [2]. HYDI is an extremely versatile diffusion magnetic resonance imaging (dMRI technique that enables various analyzes methods using a single diffusion dataset. One of the diffusion data analysis methods is the NODDI computation, which models the brain tissue with three compartments: fast isotropic diffusion (e.g., cerebrospinal fluid, anisotropic hindered diffusion (e.g., extracellular space, and anisotropic restricted diffusion (e.g., intracellular space. The NODDI model produces microstructural metrics in the developing brain, aging brain or human brain with neurologic disorders. The first dataset provided here are the means and standard deviations of NODDI metrics in 48 white matter region-of-interest (ROI averaging across 52 healthy participants. The second dataset provided here is the computer simulation with initial conditions guided by the first dataset as inputs and gold standard for model fitting. The computer simulation data provide a direct comparison of NODDI indices computed from the HYDI acquisition [1] to the NODDI indices computed from the originally proposed acquisition [2]. These data are related to the accompanying research article “Age Effects and Sex Differences in Human Brain White Matter of Young to Middle-Aged Adults: A DTI, NODDI, and q-Space Study” [3].

  5. Simulation of Alfvén eigenmode bursts using a hybrid code for nonlinear magnetohydrodynamics and energetic particles

    Science.gov (United States)

    Todo, Y.; Berk, H. L.; Breizman, B. N.

    2012-03-01

    A hybrid simulation code for nonlinear magnetohydrodynamics (MHD) and energetic-particle dynamics has been extended to simulate recurrent bursts of Alfvén eigenmodes by implementing the energetic-particle source, collisions and losses. The Alfvén eigenmode bursts with synchronization of multiple modes and beam ion losses at each burst are successfully simulated with nonlinear MHD effects for the physics condition similar to a reduced simulation for a TFTR experiment (Wong et al 1991 Phys. Rev. Lett. 66 1874, Todo et al 2003 Phys. Plasmas 10 2888). It is demonstrated with a comparison between nonlinear MHD and linear MHD simulation results that the nonlinear MHD effects significantly reduce both the saturation amplitude of the Alfvén eigenmodes and the beam ion losses. Two types of time evolution are found depending on the MHD dissipation coefficients, namely viscosity, resistivity and diffusivity. The Alfvén eigenmode bursts take place for higher dissipation coefficients with roughly 10% drop in stored beam energy and the maximum amplitude of the dominant magnetic fluctuation harmonic δBm/n/B ~ 5 × 10-3 at the mode peak location inside the plasma. Quadratic dependence of beam ion loss rate on magnetic fluctuation amplitude is found for the bursting evolution in the nonlinear MHD simulation. For lower dissipation coefficients, the amplitude of the Alfvén eigenmodes is at steady levels δBm/n/B ~ 2 × 10-3 and the beam ion losses take place continuously. The beam ion pressure profiles are similar among the different dissipation coefficients, and the stored beam energy is higher for higher dissipation coefficients.

  6. Hybrid Electro-Mechanical Simulation Tool for Wind Turbine Generators: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Singh, M.; Muljadi, E.; Jonkman, J.

    2013-05-01

    This paper describes the use of MATLAB/Simulink to simulate the electrical and grid-related aspects of a WTG and the FAST aero-elastic wind turbine code to simulate the aerodynamic and mechanical aspects of the WTG. The combination of the two enables studies involving both electrical and mechanical aspects of the WTG.

  7. Experiments, modeling and simulation of the magnetic behavior of inhomogeneously coated nickel/aluminum hybrid foams

    Energy Technology Data Exchange (ETDEWEB)

    Jung, A., E-mail: anne.jung@mx.uni-saarland.de [Universität des Saarlandes, Institute of Applied Mechanics, Campus A4 2, 66123 Saarbrücken (Germany); Klis, D., E-mail: d.klis@lte.uni-saarland.de [Universität des Saarlandes, Laboratory for Electromagnetic Theory, Campus C6 3, 66123 Saarbrücken (Germany); Goldschmidt, F., E-mail: f.goldschmidt@mx.uni-saarland.de [Universität des Saarlandes, Institute of Applied Mechanics, Campus A4 2, 66123 Saarbrücken (Germany)

    2015-03-15

    Open-cell metal foams are used as lightweight construction elements, energy absorbers or as support for catalytic coatings. Coating of open-cell metal foams is not only used for catalytic applications, but it leads also to tremendous increase in stiffness and energy absorption capacity. A non-line of sight coating technique for complex 3D structures is electrodeposition. Unfortunately, due to the 3D porosity and the related problems in mass transport limitation during the deposition, it is not possible to produce homogeneously coated foams. In the present contribution, we present a semi-non-destructive technique applicable to determine the coating thickness distribution of magnetic coatings by measuring the remanent magnetic field of coated foams. In order to have a closer look at the mass transport mechanism, a numerical model was developed to predict the field scans for different coating thickness distributions in the foams. For long deposition times the deposition reaches a steady state whereas a Helmholtz equation is sufficient to predict the coating thickness distribution. The applied current density could be identified as the main influencing parameter. Based on the developed model, it is possible to improve the electrodeposition process and hence the homogeneity in the coating thickness of coated metal foams. This leads to enhanced mechanical properties of the hybrid foams and contributes to better and resource-efficient energy absorbers and lightweight materials. - Highlights: • Production of hybrid foams by electrodeposition of nickel on open-cell metal foams. • Magnetic field scans for visualization of spatial coating thickness distribution. • Modeling of magnetic fields of inhomogeneously coated hybrid foams. • Investigation of mass transport limitation during coating by a Helmholtz equation. • Increasing coating homogeneity by use of low current densities and deposition rates.

  8. Histological characterization of gell formation and lesion development on leaves of Phaseolus vulgaris and clones of hybrid poplar after exposure to simulated sulfate acid rain

    Energy Technology Data Exchange (ETDEWEB)

    Dacosta, F.

    1978-01-01

    Histological investigations with leaves of several hybrid poplar clones illustrate gall formations in response to simulated acid rain that result from hyperplasia and hypertrophy of mesophyll cells. Similar experiments with phaseolus vulgaris and clones of hybrid poplar show a sequence of events that follow a general pattern of adaxial epidermis destruction, injury to palisade parenchyma and eventual destruction of more interior tissues after continued exposure to one, six-minute, rain event daily. Results show that most (95%) lesions on Phaseolus vulgaris developed near trichomes and stomata after exposure to the simulated acid rain.

  9. Performance simulation and analysis of a fuel cell/battery hybrid forklift truck

    DEFF Research Database (Denmark)

    Hosseinzadeh, Elham; Rokni, Masoud; Advani, Suresh G.;

    2013-01-01

    The performance of a forklift truck powered by a hybrid system consisting of a PEM fuel cell and a lead acid battery is modeled and investigated by conducting a parametric study. Various combinations of fuel cell size and battery capacity are employed in conjunction with two distinct control...... strategies to study their effect on hydrogen consumption and battery state-of-charge for two drive cycles characterized by different operating speeds and forklift loads. The results show that for all case studies, the combination of a 110 cell stack with two strings of 55 Ah batteries is the most economical...

  10. Modeling and simulation of stand-alone hybrid power system with fuzzy MPPT for remote load application

    Directory of Open Access Journals (Sweden)

    Bogaraj T.

    2015-09-01

    Full Text Available Many parts of remote locations in the world are not electrified even in this Advanced Technology Era. To provide electricity in such remote places renewable hybrid energy systems are very much suitable. In this paper PV/Wind/Battery Hybrid Power System (HPS is considered to provide an economical and sustainable power to a remote load. HPS can supply the maximum power to the load at a particular operating point which is generally called as Maximum Power Point (MPP. Fuzzy Logic based MPPT (FLMPPT control method has been implemented for both Solar and Wind Power Systems. FLMPPT control technique is implemented to generate the optimal reference voltage for the first stage of DC-DC Boost converter in both the PV and Wind energy system. The HPS is tested with variable solar irradiation, temperature, and wind speed. The FLMPPT method is compared with P&O MPPT method. The proposed method provides a good maximum power operation of the hybrid system at all operating conditions. In order to combine both sources, the DC bus voltage is made constant by employing PI Controllers for the second stage of DC-DC Buck-Boost converter in both Solar and Wind Power Systems. Battery Bank is used to store excess power from Renewable Energy Sources (RES and to provide continuous power to load when the RES power is less than load power. A SPWM inverter is designed to convert DC power into AC to supply three phase load. An LC filter is also used at the output of inverter to get sinusoidal current from the PWM inverter. The entire system was modeled and simulated in Matlab/Simulink Environment. The results presented show the validation of the HPS design.

  11. Simulation study of proposed off-midplane lower hybrid current drive in KSTAR

    Science.gov (United States)

    Bae, Young-soon; Shiraiwa, S.; Bonoli, P.; Wallace, G.; Wright, J. C.; Parker, R.; Kim, J. H.; Namkung, W.; Cho, M. H.; Park, B. H.; Yoon, S. W.; Oh, Y. K.; Park, H.

    2016-07-01

    A new proposal of lower hybrid (LH) wave launching is studied for efficient current drive aiming for high performance H-mode operation in Korea Superconducting Tokamak Advanced Research (KSTAR). This new concept is the off-midplane launch which results in a rapid up-shift of the parallel component of refractive index and hence simultaneously maintains good wave accessibility and efficient single pass absorption via Landau damping. In order to locate an optimal position of the launcher in the poloidal direction, the ray-tracing and Fokker–Planck codes were used. Based on a survey of the LH wave launch parameters and operation conditions including the compatibility issues with the existing in-vessel components, the LH wave launch from the top position near the upper X-point of the plasma separatrix provides the possibility to eliminate the accessibility problem and reduce parasitic edge loss for the KSTAR high performance H-mode operation scenario using 5 GHz lower hybrid current drive.

  12. Full wave simulations of fast wave mode conversion and lower hybrid wave propagation in tokamaks

    DEFF Research Database (Denmark)

    Wright, J.C.; Bonoli, P.T.; Brambilla, M.;

    2004-01-01

    Fast wave (FW) studies of mode conversion (MC) processes at the ion-ion hybrid layer in toroidal plasmas must capture the disparate scales of the FW and mode converted ion Bernstein and ion cyclotron waves. Correct modeling of the MC layer requires resolving wavelengths on the order of k(perpendi......Fast wave (FW) studies of mode conversion (MC) processes at the ion-ion hybrid layer in toroidal plasmas must capture the disparate scales of the FW and mode converted ion Bernstein and ion cyclotron waves. Correct modeling of the MC layer requires resolving wavelengths on the order of k......(perpendicular to)rho(i)similar to1 which leads to a scaling of the maximum poloidal mode number, M-max, proportional to 1/rho(*) (rho(*)equivalent torho(i)/L). The computational resources needed scale with the number of radial (N-r), poloidal (N-theta), and toroidal (N-phi) elements as N-r * N-phi * N-theta(3...... time are capable of achieving the resolution and speed necessary to address mode conversion phenomena in full two-dimensional (2-D) toroidal geometry. These codes have been used in conjunction with theory and experimental data from the Alcator C-Mod [I. H. Hutchinson , Phys. Plasmas 1, 1511 (1994...

  13. Hybrid heating systems optimization of residential environment to have thermal comfort conditions by numerical simulation.

    Science.gov (United States)

    Jahantigh, Nabi; Keshavarz, Ali; Mirzaei, Masoud

    2015-01-01

    The aim of this study is to determine optimum hybrid heating systems parameters, such as temperature, surface area of a radiant heater and vent area to have thermal comfort conditions. DOE, Factorial design method is used to determine the optimum values for input parameters. A 3D model of a virtual standing thermal manikin with real dimensions is considered in this study. Continuity, momentum, energy, species equations for turbulent flow and physiological equation for thermal comfort are numerically solved to study heat, moisture and flow field. K - ɛRNG Model is used for turbulence modeling and DO method is used for radiation effects. Numerical results have a good agreement with the experimental data reported in the literature. The effect of various combinations of inlet parameters on thermal comfort is considered. According to Pareto graph, some of these combinations that have significant effect on the thermal comfort require no more energy can be used as useful tools. A better symmetrical velocity distribution around the manikin is also presented in the hybrid system.

  14. Molecular dynamics simulations on the relationship between the elastic parameters and the molecular structures of nano-hybrid POSS materials

    Institute of Scientific and Technical Information of China (English)

    ZENG Fan-lin; SUN Yi; HU Li-jiang

    2006-01-01

    To research the relationship between the elastic parameters and the molecular structures of nano hybrid polyhedral oligomeric silsesquioxanes (POSS) materials, the mechanical properties at different temperatures for three POSS polymers with different molecular architectures, polymerlized norbornene POSS homopolymer (PNPOSS, pedant architecture), γ - (2, 3 glycidoxy) propyl diaminoethane POSS polymer (GPDP, catena architecture) and trimethoxysilylcyclopentyl POSS polymer (TSCP, cage -cage network architecture) were obtained by molecular dynamics simulations based on the Compass force-field. Results indicate that the molecular architectures of the POSS polymers have great influence on the reinforced effects. The effect of the cage-cage network architecture is best, while that of the catena architecture takes second place and the pedant architecture has the least influence comparatively. The reinforced effects of the POSS monomers were examined. The influences of the temperatures on these effects were analyzed also. It may provide some basis for the reasonable applications of the excellent mechanical properties of the organic-inorganic nano-hybrid materials. It may also provide references for exploitation and design of the POSS materials.

  15. Computational modelling of six speed hybrid gear box and its simulation using Simulinkas an interactive tool of MATLAB

    Directory of Open Access Journals (Sweden)

    Devesh Ramphal Upadhyay

    2016-02-01

    Full Text Available The paper introduces an idea which adds itself into contribution of getting best fuel economy of a passenger car when it is running at high speed on a highway. A six speed (forward gear box is addressed in the paper which is controlled manually and automatically as well. The paper introduces an advancement in manual transmission gear box for passenger cars. Hydraulic circuit is designed with mechatronics point of view and resulting in making the shifting of gear automatically. A computational design is made of the Hybrid Gear Box (HGB using CATIA P3 V5 as a designing software. A new gear meshing in 5 speed manual transmission gear box which synchronizes with the output shaft of the transmission automatically after getting command by the automated system designed. Parameters are considered on the basis of practical model and is been simulated by using Simdriveline as the Simulink tool of MATLAB r2010a. The mechanical properties of the components of the hybrid gear box is calculated on the basis of the functional parameters and with help of the fundamental and dependent properties formulation. The final result is the graphical analysis of the model forobtaining at least 15% fuel efficient than any of the vehicle of same configurations.

  16. Determination of the Operating Envelope for a Direct Fired Fuel Cell Turbine Hybrid Using Hardware Based Simulation

    Energy Technology Data Exchange (ETDEWEB)

    David Tucker; Eric Liese; Randall Gemmen

    2009-02-10

    The operating range of a direct fired solid oxide fuel cell gas turbine (SOFC/GT) hybrid with bypass control of cathode airflow was determined using a hardware-based simulation facility designed and built by the U.S. Department of Energy, National Energy Technology Laboratory (NETL). Three methods of cathode airflow management using bypass valves in a hybrid power system were evaluated over the maximum range of operation. The cathode air flow was varied independently over the full range of operation of each bypass valve. Each operating point was taken at a steady state condition and was matched to the thermal, pressure and flow output of a corresponding fuel cell operation condition. Turbine electric load was also varied so that the maximum range of fuel cell operation could be studied, and a preliminary operating map could be made. Results are presented to show operating envelopes in terms of cathode air flow, fuel cell and turbine load, and compressor surge margin to be substantial.

  17. Experiment and CFD simulation of hybrid SNCR-SCR using urea solution in a pilot-scale reactor

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, T.D.B.; Lim, Y.I.; Eom, W.H.; Kim, S.J.; Yoo, K.S. [Hankyong National University, Gyonggi Do (Republic of Korea). Dept. of Chemical Engineering

    2010-10-12

    The urea-based selective non-catalytic reduction (SNCR) experiment and modeling previously presented by Nguyen, Lim, et al. (2008) was extended in this study to the hybrid SNCR-SCR process for nitrogen oxides (NOx) removal in a pilot-scale flow reactor. The 5 wt% urea-water solution was sprayed into the SNCR zone and a commercial V{sub 2}O{sub 5}-WO{sub 3}/TiO{sub 2} catalyst in the form of monolith honeycomb was applied in the SCR zone. The NOx reduction efficiency of 91% was obtained from hybrid SNCR-SCR experiments, while 81% of NOx was reduced from the SNCR zone at 940{sup o}C and a normalized stoichiometric ratio (NSR) of 2.0. The turbulent reacting flow computational fluid dynamics (CFD) model with a nonuniform droplet size distribution was used, incorporating with the reduced seven-step reactions of SNCR and one Arrhenius-type SCR kinetics. The CFD simulation results showed a reasonable agreement with the experimental data in the temperature range between 900 and 980{sup o}C.

  18. Modelling and Simulation of a Hybrid Solid Oxide Fuel Cell Coupled with a Gas Turbine Power Plant

    Directory of Open Access Journals (Sweden)

    Luca Andreassi

    2009-09-01

    Full Text Available

    The paper presents a simulation of a hybrid solid oxide fuel cell-gas turbine (SOFC-GT power generation system fueled by natural gas. In the system considered, the unreacted fuel from a topping solid oxide fuel cell is burnt in an afterburner to feed a bottoming gas turbine and produce additional power. Combustion gas expands in the gas turbine after having preheated the inlet air and fuel and it is used to generate steam required by the reforming reactions. A novel thermodynamic model has been developed for the fuel cell and implemented into the library of a modular object-oriented Process Simulator, CAMELPro™. The relevant plant performance indicators have been analyzed to evaluate the incremental increase in efficiency brought about by the introduction of the gas turbine and heat regeneration system. Simulations were performed for different values of the main plant parameters.

    • This paper is an updated version of a paper published in the ECOS'08 proceedings. 

  19. 2D hybrid simulations of super-diffusion at the magnetopause driven by Kelvin-Helmholtz instability

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-01-01

    This manuscript describes the self-consistent simulation of diffusion at the magnetopause driven by Kelvin-Helmholtz (KH) instability. Two-dimensional hybrid (kinetic ions, fluid electrons) simulations of the most KH-unstable configuration where the shear flow is oriented perpendicular to the uniform magnetic field are carried out. The motion of the simulation particles are tracked during the run and their mean-square displacement normal to the magnetopause is calculated from which diffusion coefficients are determined. The diffusion coefficients are found to be time dependent, with D{sub x} {proportional_to} t{sup {alpha}}, where {alpha} > 1. Additionally, the probability distribution functions (PDF) of the 'jump lengths' the particles make over time are found to be non-gaussian. Such time-dependent diffusion coefficients and non-gaussian PDF's have been associated with so-called 'super-diffusion', in which diffusive mixing of particles is enhanced over classical diffusion. The results indicate that while turbulence associated with the break-down of vortices contributes to this enhanced diffusion, it is the growth of large-scale, coherent vortices is the more important process in facilitating it.

  20. Hybrid (particle in cell-fluid) simulation of ion-acoustic soliton generation including super-thermal and trapped electrons

    Energy Technology Data Exchange (ETDEWEB)

    Nopoush, M.; Abbasi, H. [Faculty of Physics, Amirkabir University of Technology, P. O. Box 15875-4413, Tehran (Iran, Islamic Republic of)

    2011-08-15

    The present paper is devoted to the simulation of the nonlinear disintegration of a localized perturbation into an ion-acoustic soliton in a plasma. Recently, this problem was studied by a simple model [H. Abbasi et al., Plasma Phys. Controlled Fusion 50, 095007 (2008)]. The main assumptions were (i) in the electron velocity distribution function (DF), the ion-acoustic soliton velocity was neglected in comparison to the electron thermal velocity, (ii) on the ion-acoustic evolution time-scale, the electron velocity DF was assumed to be stationary, and (iii) the calculation was restricted to the small amplitude case. In order to generalize the model, one has to consider the evolution of the electron velocity DF for finite amplitudes. For this purpose, a one dimensional electrostatic hybrid code, particle in cell (PIC)-fluid, was designed. It simulates the electrons dynamics by the PIC method and the cold ions dynamics by the fluid equations. The plasma contains a population of super-thermal electrons and, therefore, a Lorentzian (kappa) velocity DF is used to model the high energy tail in the electron velocity DF. Electron trapping is included in the simulation in view of their nonlinear resonant interaction with the localized perturbation. A Gaussian initial perturbation is used to model the localized perturbation. The influence of both the trapped and the super-thermal electrons on this process is studied and compared with the previous model.

  1. Impact of velocity space distribution on hybrid kinetic-magnetohydrodynamic simulation of the (1,1) mode

    International Nuclear Information System (INIS)

    Numeric studies of the impact of the velocity space distribution on the stabilization of (1,1) internal kink mode and excitation of the fishbone mode are performed with a hybrid kinetic-magnetohydrodynamic model. These simulations demonstrate an extension of the physics capabilities of NIMROD[C. R. Sovinec et al., J. Comput. Phys. 195, 355 (2004)], a three-dimensional extended magnetohydrodynamic (MHD) code, to include the kinetic effects of an energetic minority ion species. Kinetic effects are captured by a modification of the usual MHD momentum equation to include a pressure tensor calculated from the δf particle-in-cell method [S. E. Parker and W. W. Lee, Phys. Fluids B 5, 77 (1993)]. The particles are advanced in the self-consistent NIMROD fields. We outline the implementation and present simulation results of energetic minority ion stabilization of the (1,1) internal kink mode and excitation of the fishbone mode. A benchmark of the linear growth rate and real frequency is shown to agree well with another code. The impact of the details of the velocity space distribution is examined; particularly extending the velocity space cutoff of the simulation particles. Modestly increasing the cutoff strongly impacts the (1,1) mode. Numeric experiments are performed to study the impact of passing versus trapped particles. Observations of these numeric experiments suggest that assumptions of energetic particle effects should be re-examined.

  2. Hybrid Finite-Discrete Element Simulation of the EDZ Formation and Mechanical Sealing Process Around a Microtunnel in Opalinus Clay

    Science.gov (United States)

    Lisjak, Andrea; Tatone, Bryan S. A.; Mahabadi, Omid K.; Grasselli, Giovanni; Marschall, Paul; Lanyon, George W.; Vaissière, Rémi de la; Shao, Hua; Leung, Helen; Nussbaum, Christophe

    2016-05-01

    The analysis and prediction of the rock mass disturbance around underground excavations are critical components of the performance and safety assessment of deep geological repositories for nuclear waste. In the short term, an excavation damaged zone (EDZ) tends to develop due to the redistribution of stresses around the underground openings. The EDZ is associated with an increase in hydraulic conductivity of several orders of magnitude. In argillaceous rocks, sealing mechanisms ultimately lead to a partial reduction in the effective hydraulic conductivity of the EDZ with time. The goal of this study is to strengthen the understanding of the phenomena involved in the EDZ formation and sealing in Opalinus Clay, an indurated claystone currently being assessed as a host rock for a geological repository in Switzerland. To achieve this goal, hybrid finite-discrete element method (FDEM) simulations are performed. With its explicit consideration of fracturing processes, FDEM modeling is applied to the HG-A experiment, an in situ test carried out at the Mont Terri underground rock laboratory to investigate the hydro-mechanical response of a backfilled and sealed microtunnel. A quantitative simulation of the EDZ formation process around the microtunnel is first carried out, and the numerical results are compared with field observations. Then, the re-compression of the EDZ under the effect of a purely mechanical loading, capturing the increase of swelling pressure from the backfill onto the rock, is considered. The simulation results highlight distinctive rock failure kinematics due to the bedded structure of the rock mass. Also, fracture termination is simulated at the intersection with a pre-existing discontinuity, representing a fault plane oblique to the bedding orientation. Simulation of the EDZ re-compression indicates an overall reduction of the total fracture area as a function of the applied pressure, with locations of ineffective sealing associated with self

  3. Hybrid Simulation Environment for Construction Projects: Identification of System Design Criteria

    Directory of Open Access Journals (Sweden)

    Mohamed Moussa

    2014-01-01

    Full Text Available Large construction projects are complex, dynamic, and unpredictable. They are subject to external and uncontrollable events that affect their schedule and financial outcomes. Project managers take decisions along the lifecycle of the projects to align with projects objectives. These decisions are data dependent where data change over time. Simulation-based modeling and experimentation of such dynamic environment are a challenge. Modeling of large projects or multiprojects is difficult and impractical for standalone computers. This paper presents the criteria required in a simulation environment suitable for modeling large and complex systems such as construction projects to support their lifecycle management. Also presented is a platform that encompasses the identified criteria. The objective of the platform is to facilitate and simplify the simulation and modeling process and enable the inclusion of complexity in simulation models.

  4. Simulations of compressible, diffusive, reactive flows with detailed chemistry using a high-order hybrid WENO-CD scheme

    Science.gov (United States)

    Ziegler, Jack L.

    A hybrid weighted essentially non-oscillatory (WENO)/centered-difference (CD) numerical method, with low numerical dissipation, high-order shock-capturing, and structured adaptive mesh refinement (SAMR), has been developed for the direct numerical simulation (DNS) of the multicomponent, compressive, reactive Navier-Stokes equations. The method enables accurate resolution of diffusive processes within reaction zones. This numerical method is verified with a series of one- and two-dimensional test problems, including a convergence test of a two-dimensional unsteady reactive double Mach reflection problem. Validation of the method is conducted with experimental comparisons of three applications all of which model multi-dimensional, unsteady reactive flow: an irregular propane detonation, shock and detonation bifurcations, and spark ignition deflagrations.

  5. Simulation of a Hybrid Optical/Radio/Acoustic Extension to IceCube for EeV Neutrino Detection

    CERN Document Server

    Besson, D; Ahrens, J; Atlee, D W; Bahcall, J N; Bai, X; Baret, B; Bartelt, M; Bay, R; Barwick, S W; Beattie, K; Becka, T; Becker, K H; Becker, J K; Berghaus, P; Berley, D; Bernardini, E; Bertrand, D; Besson, D Z; Blaufuss, E; Boersma, D J; Bohm, C; Boser, S; Botner, O; Bouchta, A; Braun, J; Burgess, C; Burgess, T; Castermans, T; Chirkin, D; Clem, J; Conrad, J; Cooley, J; Cowen, D F; D'Agostino, M V; Davour, A; Day, C T; De Clercq, C; Desiati, P; De Young, T R; Dreyer, J; Duvoort, M R; Edwards, W R; Ehrlich, R; Ekstrom, P; Ellsworth, R W; Evenson, P A; Fazely, A R; Feser, T; Filimonov, K; Gaisser, T K; Gallagher, J; Ganugapati, R; Geenen, H; Gerhardt, L; Greene, M G; Grullon, S; Goldschmidt, A; Goodman, J; Gro, A; Gunasingha, R M; Hallgren, A; Halzen, F; Hanson, K; Hardtke, D; Hardtke, R; Harenberg, T; Hart, J E; Hauschildt, T; Hays, D; Heise, J; Helbing, K; Hellwig, M; Herquet, P; Hill, G C; Hodges, J; Hoffman, K D; Hoshina, K; Hubert, D; Hughey, B; Hulth, P O; Hultqvist, K; Hundertmark, S; Ishihara, A; Jacobsen, J; Japaridze, G S; Jones, A; Joseph, J M; Kampert, K H; Karle, A; Kawai, H; Kelley, J L; Kestel, M; Kitamura, N; Klein, S R; Klepser, S; Kohnen, G; Kolanoski, H; Köpke, L; Krasberg, M; Kühn, K; Kujawski, E; Landsman, H; Lang, R; Leich, H; Liubarsky, I; Lundberg, J; Madsen, J; Marciniewski, P; Mase, K; Matis, H S; McCauley, T; McParland, C P; Meli, A; Messarius, T; Mészáros, P; Minor, R H; Miocinovic, P; Miyamoto, H; Mokhtarani, A; Montaruli, T; Morey, A; Morse, R; Movit, S M; Munich, K; Nahnhauer, R; Nam, J W; Niessen, P; Nygren, D R; Ogelman, H; Olbrechts, P; Olivas, A; Patton, S; Peña-Garay, C; Perez de los Heros, C; Pieloth, D; Pohl, A C; Porrata, R; Pretz, J; Price, P B; Przybylski, G T; Rawlins, K; Razzaque, S; Refflinghaus, F; Resconi, E; Rhode, W; Ribordy, M; Richter, S; Rizzo, A; Robbins, S; Rott, C; Rutledge, D; Sander, H G; Schlenstedt, S; Schneider, D; Schwarz, R; Seckel, D; Seo, S H; Silvestri, A; Smith, A J; Solarz, M; Song, C; Sopher, J E; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Steffen, P; Stezelberger, T; Stokstad, R G; Stoufer, M; Stoyanov, S; Sulanke, K H; Sullivan, G W; Sumner, T J; Taboada, I; Tarasova, O; Tepe, A; Thollander, L; Tilav, S; Toale, P A; Turcan, D; van Eijndhoven, N; Vandenbroucke, J; Voigt, B; Wagner, W; Walck, C; Waldmann, H; Walter, M; Wang, Y R; Wendt, C; Wiebusch, C; Wikström, G; Williams, D; Wischnewski, R; Wissing, H; Woschnagg, K; Xu, X W; Yoshida, S; Yodh, G; Böser, S; Vandenbroucke, J A

    2005-01-01

    Astrophysical neutrinos at $\\sim$EeV energies promise to be an interesting source for astrophysics and particle physics. Detecting the predicted cosmogenic ("GZK") neutrinos at 10$^{16}$ - 10$^{20}$ eV would test models of cosmic ray production at these energies and probe particle physics at $\\sim$100 TeV center-of-mass energy. While IceCube could detect $\\sim$1 GZK event per year, it is necessary to detect 10 or more events per year in order to study temporal, angular, and spectral distributions. The IceCube observatory may be able to achieve such event rates with an extension including optical, radio, and acoustic receivers. We present results from simulating such a hybrid detector.

  6. Simulation of Noise-Cancelling in the Cockpit of an Aircraft Using Two-Rate Hybrid Neural Network

    Directory of Open Access Journals (Sweden)

    ASTROV, I.

    2007-11-01

    Full Text Available This paper presents the two-rate hybrid neural network (TRHNN for processing of noisy signal. The received TRHNN consists of "fast" ADAptive LInear NEuron neural network (FADALINENN and "slow" radial basis neural network (SRBNN. The illustrative design example - noise-cancelling of noisy pilot's voice pattern - was carried out using the TRHNN. The received TRHNN has high speed of signal processing. This example demonstrates that the proposed TRHNN is capable not only to recognize the pilot's voice in the noisy voice pattern, but also to restore the pilot's voice. The simulation results with use the software package Simulink show the computing procedure and applicability of the TRHNNs for fast-acting signal processing and analysis in real-time flight conditions.

  7. Development of a hybrid PIC code for the simulation of plasma spacecraft interactions

    OpenAIRE

    Masselin, Matthieu

    2012-01-01

    Electric propulsion is gaining popularity in space industry. This type of propulsion is replacing chemical propulsion for different maneuvers. But it deeply modifies the ambient plasma that surrounds the satellites and can affect the operation of satellites. Modelling the interactions arising from electric propulsion is then critical. In the frame of SPIS, a simulation software designed to simulate plasma-spacecraft interactions, European Space Agency (ESA) started the AISEPS project which ai...

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

    OpenAIRE

    Danquah, Wiseborn Manfe; Altilar, Turgay 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...

  9. Potential production simulation and optimal nutrient management of two hybrid rice varieties in Jinhua, Zhejiang Province, China

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-xia; WANG Guang-huo; ZHANG Qi-chun

    2007-01-01

    Potential growth of two widely-grown hybrid rice varieties in the Jinhua district of Zhejiang Province, Shanyou63 for mid-rice and Xieyou46 for late rice, was simulated using a crop growth model of WOFOST. Parameters of the rice growth in WOFOST were calibrated through field experiments from 1999 to 2002 in Jinhua. The potential yield simulated with WOFOST was about 12 t/ha for Shanyou63 and 10 t/ha for Xieyou46, which are in good agreement with the highest recorded yield obtained in this area. Under farmers practice, current yield is about 7.5 t/ha for Shanyou63 and 6.5 t/ha for Xieyou46. There is a gap between the actual rice yield and the potential yield for these two hybrid rice varieties grown in this area. The attainable target yields were set to 70% to 75% of their potential yields for the two varieties. A recently developed software "Nutrient Decision Support System (NuDSS)" for irrigated rice was used to optimize nutrient management for these two rice varieties. According to NuDSS, the optimal fertilizer N requirement for the target yields was about 150 kg/ha for Shanyou63 and about 120 kg/ha for Xieyou46, which were only about 70% of the fertilizer N application under current farmers' practice. Comparing with farmers' practice, there is great potential to increase actual rice yields and to reduce fertilizer N use rates by improving rice crop management practice in Jinhua.

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

    Directory of Open Access Journals (Sweden)

    G. Grelle

    2015-06-01

    Full Text Available SiSeRHMap is a computerized methodology capable of drawing up prediction maps of seismic response. 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 metamodeling process confers a hybrid nature to the methodology. In this process, the one-dimensional linear equivalent analysis produces acceleration response spectra of shear wave velocity-thickness profiles, defined as trainers, which are randomly selected in each zone. Subsequently, a numerical adaptive simulation model (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 Spectra model. In addition, the spectra topographic amplification is also computed by means of a numerical prediction model. This latter is built to match the results of the numerical simulations related to isolate reliefs using GIS topographic attributes. In this way, different sets of seismic response maps are developed, on which, also maps of seismic design response spectra are defined by means of an enveloping technique.

  11. Reclaimed water quality during simulated ozone-managed aquifer recharge hybrid

    KAUST Repository

    Yoon, Min

    2014-06-17

    A synergistic hybrid of two treatment processes, managed aquifer recharge (MAR) combined with ozonation, was proposed for wastewater reclamation and water reuse applications. Batch reactor and soil-column experiments were performed to evaluate reclaimed water quality using various chemical and bacterial analyses. The ozone process was optimized at low ozone dose (0.5 mg O3/mg DOC) based on the control of N-nitrosodimethylamine (<5 ng L-1) and bromate (<10 μg L-1), and applied prior to (i.e., O3-MAR) and after MAR (i.e., MAR-O3). This work demonstrates that effluent organic matter (EfOM) and trace organic contaminants (TOrCs) are effectively removed during the hybrid process of MAR combined ozonation, compared to MAR only. Based on fluorescence excitation-emission matrices analyses, both MAR and ozonation reduce soluble microbial (protein-like) products while only ozonation contributes in reducing humic and fulvic substances. Even at low ozone dose of 0.5 mg O3/mg DOC, the O3-MAR hybrid significantly reduced UV absorbance by ≥2 m-1, BDOC by ≥64 %, and total (Σ) TOrC concentrations by ≥70 % in the effluent water quality. However, no significant improvement (<10 %) in the removal of Σ16 TOrC concentrations was observed for the increased ozone dose at 1.0 mg O3/mg DOC during MAR combined ozonation processes. Overall, O3-MAR was effective by 10-30 % in treating effluent water than MAR based on DOC, UV254 nm EfOM, TOrC and bacterial analyses. In addition, MAR-O3 was better than O3-MAR for the reduction of fluorescence (close MQ), TOrCs (≥74 %) and total bacteria cell concentrations (>3 log reduction). Therefore, implementing MAR prior to ozonation appears to remove the bio-amenable compounds that react rapidly with ozone, thereby reducing oxidant demand and treatment efficiency. © 2014 Springer-Verlag Berlin Heidelberg.

  12. MODELISATION, SIMULATION ET OPTIMISATION D’UN SYSTEME HYBRIDE EOLIEN-PHOTOVOLTAIQUE

    OpenAIRE

    BELGHITRI, HOUDA

    2010-01-01

    L’exploitation des ressources renouvelables connaît un grand essor dans les pays industrialisés et même dans quelques pays sous-développés. L’Algérie à fournit un grand effort pour l’électrification rurale et saharienne .En effet, le taux d’électrification national pour l’année 2001 est de 96%. Malgré le taux élevé, il existe toujours des foyers épars qui leurs électrifications par l’extension du réseau conventionnel est très coûteuse. Le système hybride de production d’électri...

  13. Hybrid simulations of whistler waves generation and current closure by a pulsed tether in the ionosphere

    Science.gov (United States)

    Chang, C. L.; Lipatov, A. S.; Drobot, A. T.; Papadopoulos, K.; Satya-Narayana, P.

    1994-01-01

    The dynamic response of a magnetized collisionless plasma to an externally driven, finite size, sudden switch-on current source across the magnetic field has been studied using a two dimensional hybrid code. It was found that the predominant plasma response was the excitation of whistler waves and the formation of current closure by induced currents in the plasma. The results show that the current closure path consists of: (a) two antiparallel field-aligned current channels at the end of the imposed current sheet; and (b) a cross-field current region connecting these channels. The formation of the current closure path occured in the whistler timescale much shorter than that of MHD and the closure region expanded continuously in time. The current closure process was accompanied by significant energy loss due to whistler radiation.

  14. An improving method for micro-G simulation with magnetism-buoyancy hybrid system

    Science.gov (United States)

    Zhu, Zhanxia; Yuan, Jianping; Song, Jiangzhou; Cui, Rongxin

    2016-06-01

    This paper presents a novel solution for the micro-G experiment with magnetism-buoyancy hybrid system. The improvement includes two parts, (i) proposing an innovative system called general balance test bed (GBTB), and (ii) designing a resistance effect compensation system. The GBTB, a special platform, can be used to realize the effect of neutral buoyancy, by using controllable electromagnetic force instead of conventional weight or foam module to eliminate the difference between gravity and liquid buoyancy. In this paper, principles, components, and functions of the GBTB are developed. Then, in order to improve test fidelity, a compensation system is designed to counteract the water resistance effect during maneuver, and a novel prediction law is proposed to make water resistance force prediction more coincident with the real value by introducing control errors and error rates. Finally, the feasibility and effectiveness of the proposed solution are demonstrated through micro-G experiments and tests.

  15. Simulation of borehole induction using the hybrid extended Born approximation and CG-FFHT method

    Science.gov (United States)

    Zhang, Zhong Qing; Liu, Qing Huo

    2000-07-01

    We propose the hybridization of the extended Born approximation (EBA) with the conjugate-gradient fast Fourier Hankel transform (CG-FFHT) method to improve the efficiency of numerical solution of borehole induction problems in axisymmetric media. First, we use the FFHT to accelerate the EBA as a nonlinear approximation to induction problems, resulting in an algorithm with O(N log2 N) arithmetic operations, where N is the number of unknowns in the problem. This improved EBA is accurate for most formations encountered. Then, for formations with extremely high contrasts, we utilize this improved EBA as a partial preconditioner in the CG-FFHT method to solve the problem accurately with few iterations. The seamless combination of these two approaches provides an automatic way toward the efficient and accurate modeling of induction measurements in axisymmetric media.

  16. An Event-Driven Hybrid Molecular Dynamics and Direct Simulation Monte Carlo Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Donev, A; Garcia, A L; Alder, B J

    2007-07-30

    A novel algorithm is developed for the simulation of polymer chains suspended in a solvent. The polymers are represented as chains of hard spheres tethered by square wells and interact with the solvent particles with hard core potentials. The algorithm uses event-driven molecular dynamics (MD) for the simulation of the polymer chain and the interactions between the chain beads and the surrounding solvent particles. The interactions between the solvent particles themselves are not treated deterministically as in event-driven algorithms, rather, the momentum and energy exchange in the solvent is determined stochastically using the Direct Simulation Monte Carlo (DSMC) method. The coupling between the solvent and the solute is consistently represented at the particle level, however, unlike full MD simulations of both the solvent and the solute, the spatial structure of the solvent is ignored. The algorithm is described in detail and applied to the study of the dynamics of a polymer chain tethered to a hard wall subjected to uniform shear. The algorithm closely reproduces full MD simulations with two orders of magnitude greater efficiency. Results do not confirm the existence of periodic (cycling) motion of the polymer chain.

  17. Hybrid Simulations and Scaling Laws for Shock Formation in the UCLA Collisionless Shock Experiment

    Science.gov (United States)

    Larson, David; Winske, Dan; Cowee, Misa; Clark, S. Eric; Niemann, Christoph; Brecht, Stephen

    2015-11-01

    Two- and three-dimensional simulations are used to compare and contrast the plasma expansion, formation of a magnetic cavity, and generation of an outgoing shock wave for conditions relevant to the laser experiment at UCLA, as a function of the background ion mass. A model of the shock formation process is constructed that yields an expression for the speed of the shock, which we show is in good agreement with the simulations. In addition, the criteria for generating strongly-coupled shocks are derived and simulations are used to examine the velocity scaling obtained via momentum conservation. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and supported by DTRA10027-6759.

  18. 并行遗传/模拟退火混合算法及其应用%Parallel Genetic Algorithm / Simulated Annealing Hybrid Algorithm and its Applications

    Institute of Scientific and Technical Information of China (English)

    温平川; 徐晓东; 何先刚

    2003-01-01

    This paper presents a highly hybrid Genetic Algorithm / Simulated Annealing algorithm. This algorithmhas been successfully implemented on Beowulf PCs Cluster and applied to a set of standard function optimization prob-lems. From experimental results, it is easily to see that this algorithm proposed by us is not only effective but also robust.

  19. Efficient magnetohydrodynamic simulations on distributed multi-GPU systems using a novel GPU Direct-MPI hybrid approach

    Science.gov (United States)

    Wong, Un-Hong; Aoki, Takayuki; Wong, Hon-Cheng

    2014-07-01

    Modern graphics processing units (GPUs) have been widely utilized in magnetohydrodynamic (MHD) simulations in recent years. Due to the limited memory of a single GPU, distributed multi-GPU systems are needed to be explored for large-scale MHD simulations. However, the data transfer between GPUs bottlenecks the efficiency of the simulations on such systems. In this paper we propose a novel GPU Direct-MPI hybrid approach to address this problem for overall performance enhancement. Our approach consists of two strategies: (1) We exploit GPU Direct 2.0 to speedup the data transfers between multiple GPUs in a single node and reduce the total number of message passing interface (MPI) communications; (2) We design Compute Unified Device Architecture (CUDA) kernels instead of using memory copy to speedup the fragmented data exchange in the three-dimensional (3D) decomposition. 3D decomposition is usually not preferable for distributed multi-GPU systems due to its low efficiency of the fragmented data exchange. Our approach has made a breakthrough to make 3D decomposition available on distributed multi-GPU systems. As a result, it can reduce the memory usage and computation time of each partition of the computational domain. Experiment results show twice the FLOPS comparing to common 2D decomposition MPI-only implementation method. The proposed approach has been developed in an efficient implementation for MHD simulations on distributed multi-GPU systems, called MGPU-MHD code. The code realizes the GPU parallelization of a total variation diminishing (TVD) algorithm for solving the multidimensional ideal MHD equations, extending our work from single GPU computation (Wong et al., 2011) to multiple GPUs. Numerical tests and performance measurements are conducted on the TSUBAME 2.0 supercomputer at the Tokyo Institute of Technology. Our code achieves 2 TFLOPS in double precision for the problem with 12003 grid points using 216 GPUs.

  20. Hybrid Simulation of Laser-Plasma Interactions and Fast Electron Transport in Inhomogeneous Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, B I; Kemp, A; Divol, L

    2009-05-27

    A new framework is introduced for kinetic simulation of laser-plasma interactions in an inhomogenous plasma motivated by the goal of performing integrated kinetic simulations of fast-ignition laser fusion. The algorithm addresses the propagation and absorption of an intense electromagnetic wave in an ionized plasma leading to the generation and transport of an energetic electron component. The energetic electrons propagate farther into the plasma to much higher densities where Coulomb collisions become important. The high-density plasma supports an energetic electron current, return currents, self-consistent electric fields associated with maintaining quasi-neutrality, and self-consistent magnetic fields due to the currents. Collisions of the electrons and ions are calculated accurately to track the energetic electrons and model their interactions with the background plasma. Up to a density well above critical density, where the laser electromagnetic field is evanescent, Maxwell's equations are solved with a conventional particle-based, finite-difference scheme. In the higher-density plasma, Maxwell's equations are solved using an Ohm's law neglecting the inertia of the background electrons with the option of omitting the displacement current in Ampere's law. Particle equations of motion with binary collisions are solved for all electrons and ions throughout the system using weighted particles to resolve the density gradient efficiently. The algorithm is analyzed and demonstrated in simulation examples. The simulation scheme introduced here achieves significantly improved efficiencies.

  1. F-16XL Hybrid Reynolds-Averaged Navier-Stokes/Large Eddy Simulation on Unstructured Grids

    Science.gov (United States)

    Park, Michael A.; Abdol-Hamid, Khaled S.; Elmiligui, Alaa

    2015-01-01

    This study continues the Cranked Arrow Wing Aerodynamics Program, International (CAWAPI) investigation with the FUN3D and USM3D flow solvers. CAWAPI was established to study the F-16XL, because it provides a unique opportunity to fuse fight test, wind tunnel test, and simulation to understand the aerodynamic features of swept wings. The high-lift performance of the cranked-arrow wing planform is critical for recent and past supersonic transport design concepts. Simulations of the low speed high angle of attack Flight Condition 25 are compared: Detached Eddy Simulation (DES), Modi ed Delayed Detached Eddy Simulation (MDDES), and the Spalart-Allmaras (SA) RANS model. Iso- surfaces of Q criterion show the development of coherent primary and secondary vortices on the upper surface of the wing that spiral, burst, and commingle. SA produces higher pressure peaks nearer to the leading-edge of the wing than flight test measurements. Mean DES and MDDES pressures better predict the flight test measurements, especially on the outer wing section. Vorticies and vortex-vortex interaction impact unsteady surface pressures. USM3D showed many sharp tones in volume points spectra near the wing apex with low broadband noise and FUN3D showed more broadband noise with weaker tones. Spectra of the volume points near the outer wing leading-edge was primarily broadband for both codes. Without unsteady flight measurements, the flight pressure environment can not be used to validate the simulations containing tonal or broadband spectra. Mean forces and moment are very similar between FUN3D models and between USM3D models. Spectra of the unsteady forces and moment are broadband with a few sharp peaks for USM3D.

  2. Feasibility study for SOFC-GT hybrid locomotive power part II. System packaging and operating route simulation

    Science.gov (United States)

    Martinez, Andrew S.; Brouwer, Jacob; Samuelsen, G. Scott

    2012-09-01

    This work assesses the feasibility of Solid Oxide Fuel Cell-Gas Turbine (SOFC-GT) hybrid power systems for use as the prime mover in freight locomotives. The available space in a diesel engine-powered locomotive is compared to that required for an SOFC-GT system, inclusive of fuel processing systems necessary for the SOFC-GT. The SOFC-GT space requirement is found to be similar to current diesel engines, without consideration of the electrical balance of plant. Preliminary design of the system layout within the locomotive is carried out for illustration. Recent advances in SOFC technology and implications of future improvements are discussed as well. A previously-developed FORTRAN model of an SOFC-GT system is then augmented to simulate the kinematics and power notching of a train and its locomotives. The operation of the SOFC-GT-powered train is investigated along a representative route in Southern California, with simulations presented for diesel reformate as well as natural gas reformate and hydrogen as fuels. Operational parameters and difficulties are explored as are comparisons of expected system performance to modern diesel engines. It is found that even in the diesel case, the SOFC-GT system provides significant savings in fuel and CO2 emissions, making it an attractive option for the rail industry.

  3. Three-dimensional needle-tip localization by electric field potential and camera hybridization for needle electromyography exam robotic simulator.

    Science.gov (United States)

    He, Siyu; Gomez-Tames, Jose; Yu, Wenwei

    2016-01-01

    As one of neurological tests, needle electromygraphy exam (NEE) plays an important role to evaluate the conditions of nerves and muscles. Neurology interns and novice medical staff need repetitive training to improve their skills in performing the exam. However, no training systems are able to reproduce multiple pathological conditions to simulate real needle electromyogram exam. For the development of a robotic simulator, three components need to be realized: physical modeling of upper limb morphological features, position-dependent electromyogram generation, and needle localization; the latter is the focus of this study. Our idea is to couple two types of sensing mechanism in order to acquire the needle-tip position with high accuracy. One is to segment the needle from camera images and calculate its insertion point on the skin surface by a top-hat transform algorithm. The other is voltage-based depth measurement, in which a conductive tissue-like phantom was used to realize both needle-tip localization and physical sense of needle insertion. For that, a pair of electrodes was designed to generate a near-linear voltage distribution along the depth direction of the tissue-like phantom. The accuracy of the needle-tip position was investigated by the electric field potential and camera hybridization. The results showed that the needle tip could be detected with an accuracy of 1.05±0.57 mm. PMID:27382339

  4. Enhanced Si-O Bond Breaking in Silica Glass by Water Dimer: A Hybrid Quantum-Classical Simulation Study

    Science.gov (United States)

    Kouno, Takahisa; Ogata, Shuji; Shimada, Takaaki; Tamura, Tomoyuki; Kobayashi, Ryo

    2016-05-01

    A hybrid quantum-classical simulation of a 4,608-atom silica glass is performed at a temperature of 400 K with either a water monomer or dimer inserted in a void. The quantum region that includes the water and the surrounding atoms is treated by the density-functional theory (DFT). During a simulation, the silica glass is gradually compressed or expanded. No Si-O bond breaking occurs with a water monomer until the silica glass collapses. With a water dimer, we find that Si-O bond breaking occurs through three steps in 3 out of 24 compression cases: (i) H-transfer as 2H2O → OH- + H3O+ accompanied by the adsorption of OH- at a strained Si to make it five-coordinated, (ii) breaking of a Si-O bond that originates from the five-coordinated Si, and (iii) H-transfer from H3O+ to the O of the broken Si-O bond. A separate DFT calculation confirms that the barrier energy of the bond breaking with a water dimer under compression is smaller than that with a water monomer and that the barrier energy decreases significantly when the silica glass is compressed further.

  5. Simulation of vortex shedding behind a bluff body flame stabilizer using a hybrid U-RANS/PDF method

    Institute of Scientific and Technical Information of China (English)

    Min-Ming Zhu; Ping-Hui Zhao; Hai-Wen Ge; Yi-Liang Chen

    2012-01-01

    The present study aims at the investigation of the effects of turbulence-chemistry interaction on combustion instabilities using a probability density function (PDF)method. The instantaneous quantities in the flow field were decomposed into the Favre-averaged variables and the stochastic fluctuations,which were calculated by unsteady Reynolds averaged Navier-Stokes (U-RANS) equations and the PDF model,respectively.A joint fluctuating velocityfrequency-composition PDF was used.The governing equations are solved by a consistent hybrid finite volume/MonteCarlo algorithm on triangular unstructured meshes.A nonreacting flow behind a triangular-shaped bluff body flame stabilizer in a rectilinear combustor was simulated by the present method.The results demonstrate the capability of the present method to capture the large-scale coherent structures.The triple decomposition was performed,by dividing the coherent Favre-averaged velocity into time-averaged value and periodical coherent part,to analyze the coherent and incoherent contributions to Reynolds stresses.A simple modification to the coefficients in the turbulent frequency model will help to improve the simulation results.Unsteady flow fields were depicted by streamlines and vorticity contours.Moreover,the association between turbulence production and vorticity saddle points is illustrated.

  6. Three-dimensional needle-tip localization by electric field potential and camera hybridization for needle electromyography exam robotic simulator

    Science.gov (United States)

    He, Siyu; Gomez-Tames, Jose; Yu, Wenwei

    2016-01-01

    As one of neurological tests, needle electromygraphy exam (NEE) plays an important role to evaluate the conditions of nerves and muscles. Neurology interns and novice medical staff need repetitive training to improve their skills in performing the exam. However, no training systems are able to reproduce multiple pathological conditions to simulate real needle electromyogram exam. For the development of a robotic simulator, three components need to be realized: physical modeling of upper limb morphological features, position-dependent electromyogram generation, and needle localization; the latter is the focus of this study. Our idea is to couple two types of sensing mechanism in order to acquire the needle-tip position with high accuracy. One is to segment the needle from camera images and calculate its insertion point on the skin surface by a top-hat transform algorithm. The other is voltage-based depth measurement, in which a conductive tissue-like phantom was used to realize both needle-tip localization and physical sense of needle insertion. For that, a pair of electrodes was designed to generate a near-linear voltage distribution along the depth direction of the tissue-like phantom. The accuracy of the needle-tip position was investigated by the electric field potential and camera hybridization. The results showed that the needle tip could be detected with an accuracy of 1.05±0.57 mm. PMID:27382339

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-08-15

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

  8. Design and simulation of C6+ hybrid single cavity linac for cancer therapy with direct plasma injection scheme

    Science.gov (United States)

    Lu, Liang; Hattori, Toshiyuki; Hayashizaki, Noriyosu

    2012-10-01

    A hybrid single cavity (HSC) linac, whose structure is formed by combining a radio frequency quadrupole (RFQ) structure and a drift tube (DT) structure into one interdigital-H (IH) cavity, has been developed over a span of a few years by our research team [1]. In the present work, several different structures of an HSC linac are analyzed in order to achieve an optimum cavity electric field distribution and to enhance beam transmission. The proposed HSC linac design is a direct injector linac for a heavy ion synchrotron for radiotherapy. This design also has potential as a neutron source in boron neutron capture therapy. According to our simulations, an HSC linac accelerated C6+ ions from 25 keV/u up to 2 MeV/u in 1800 mm for a 94 kW feeding power with a 100 MHz operation. The detailed HSC linac structure design and the results of the cavity electromagnetic field simulation are reported in this paper.

  9. Hybrid approach combining dissipative particle dynamics and finite-difference diffusion model: simulation of reactive polymer coupling and interfacial polymerization.

    Science.gov (United States)

    Berezkin, Anatoly V; Kudryavtsev, Yaroslav V

    2013-10-21

    A novel hybrid approach combining dissipative particle dynamics (DPD) and finite difference (FD) solution of partial differential equations is proposed to simulate complex reaction-diffusion phenomena in heterogeneous systems. DPD is used for the detailed molecular modeling of mass transfer, chemical reactions, and phase separation near the liquid∕liquid interface, while FD approach is applied to describe the large-scale diffusion of reactants outside the reaction zone. A smooth, self-consistent procedure of matching the solute concentration is performed in the buffer region between the DPD and FD domains. The new model is tested on a simple model system admitting an analytical solution for the diffusion controlled regime and then applied to simulate practically important heterogeneous processes of (i) reactive coupling between immiscible end-functionalized polymers and (ii) interfacial polymerization of two monomers dissolved in immiscible solvents. The results obtained due to extending the space and time scales accessible to modeling provide new insights into the kinetics and mechanism of those processes and demonstrate high robustness and accuracy of the novel technique.

  10. Simulations of cavity flow noise and turbulent jet noise using a hybrid method

    Directory of Open Access Journals (Sweden)

    Hai-Yan Bie

    2016-02-01

    Full Text Available A hybrid method was explored to investigate the generation and near-field radiation of aerodynamic sound from an unsteady turbulent flow over a two-dimensional open cavity and three-dimensional jet flow. A two-dimensional cavity model was established to study the unsteady flow and radiated jet sound. It was revealed that the radiated sound that generated by the boundary layer separation and vortex impact cavity wall intervened in the front of the cavity, and an obvious interference phenomenon appeared. The far-field radiated sound generated by the cavity presented obvious directivity, and the sound pressure in the area located at 45°–135° interval was much higher. Then, the unsteady turbulence jet noises of the elliptical and rectangular nozzles were analyzed. It was revealed that the scale and intensity of the vortexes generated by the elliptical nozzle were larger than those by the rectangular nozzle. The jet noise of the elliptical nozzle is lower than that of the rectangular nozzle. Besides, the sound pressure distributions of the two nozzles presented obvious directivity. The sound pressure in the short-axis direction of the nozzle section was higher than that in the long-axis direction.

  11. Kinetic cascade beyond MHD of solar wind turbulence in two-dimensional hybrid simulations

    CERN Document Server

    Verscharen, Daniel; Motschmann, Uwe; Müller, Joachim

    2012-01-01

    The nature of solar wind turbulence in the dissipation range at scales much smaller than the large MHD scales remains under debate. Here a two-dimensional model based on the hybrid code abbreviated as A.I.K.E.F. is presented, which treats massive ions as particles obeying the kinetic Vlasov equation and massless electrons as a neutralizing fluid. Up to a certain wavenumber in the MHD regime, the numerical system is initialized by assuming a superposition of isotropic Alfv\\'en waves with amplitudes that follow the empirically confirmed spectral law of Kolmogorov. Then turbulence develops and energy cascades into the dispersive spectral range, where also dissipative effects occur. Under typical solar wind conditions, weak turbulence develops as a superposition of normal modes in the kinetic regime. Spectral analysis in the direction parallel to the background magnetic field reveals a cascade of left-handed Alfv\\'en/ion-cyclotron waves up to wave vectors where their resonant absorption sets in, as well as a cont...

  12. Solar Trigeneration: a Transitory Simulation of HVAC Systems Using Different Typologies of Hybrid Panels

    Directory of Open Access Journals (Sweden)

    Alejandro del Amo Sancho

    2014-03-01

    Full Text Available The high energy demand on buildings requires efficient installations and the integration of renewable energy to achieve the goal of reducing energy consumption using traditional energy sources. Usually, solar energy generation and heating loads have different profiles along a day and their maximums take place at different moments. In addition, in months in which solar production is higher, the heating demands are the minimum (hot water is consumed only domestically in summer. Cooling machines (absorption and adsorption allow using thermal energy to chill a fluid. This heat flow rate could be recovered from solar collectors or any other heat source. The aim of this study is to integrate different typologies of solar hybrid (photovoltaic and thermal collectors with cooling machines getting solar trigeneration and concluding the optimal combination for building applications. The heat recovered from the photovoltaic module is used to provide energy to these cooling machines getting a double effect: to get a better efficiency on PV modules and to cool the building. In this document the authors analyse these installations, their operating conditions, dimensions and parameters, in order to get the optimal installation in three different European cities. This work suggests that in a family house in Madrid, the optimal combination is to use CPVT with azimuthally tracking and absorption machine. In this case, the solar trigeneration system using 55 m2 of collector area saves the cooling loads and 79% of the heating load in the house round the year.

  13. Using hybrid implicit Monte Carlo diffusion to simulate gray radiation hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Cleveland, Mathew A., E-mail: cleveland7@llnl.gov; Gentile, Nick

    2015-06-15

    This work describes how to couple a hybrid Implicit Monte Carlo Diffusion (HIMCD) method with a Lagrangian hydrodynamics code to evaluate the coupled radiation hydrodynamics equations. This HIMCD method dynamically applies Implicit Monte Carlo Diffusion (IMD) [1] to regions of a problem that are opaque and diffusive while applying standard Implicit Monte Carlo (IMC) [2] to regions where the diffusion approximation is invalid. We show that this method significantly improves the computational efficiency as compared to a standard IMC/Hydrodynamics solver, when optically thick diffusive material is present, while maintaining accuracy. Two test cases are used to demonstrate the accuracy and performance of HIMCD as compared to IMC and IMD. The first is the Lowrie semi-analytic diffusive shock [3]. The second is a simple test case where the source radiation streams through optically thin material and heats a thick diffusive region of material causing it to rapidly expand. We found that HIMCD proves to be accurate, robust, and computationally efficient for these test problems.

  14. Hybrid Rendering Architecture for Realtime and Photorealistic Simulation of Robot-Assisted Surgery.

    Science.gov (United States)

    Müller, Sebastijan; Bihlmaier, Andreas; Irgenfried, Stephan; Wörn, Heinz

    2016-01-01

    In this paper we present a method for combining realtime and non-realtime (photorealistic) rendering with open source software. Realtime rendering provides sufficient realism and is a good choice for most simulation and regression testing purposes in robot-assisted surgery. However, for proper end-to-end testing of the system, some computer vision algorithms require high fidelity images that capture more minute details of the real scene. One of the central practical obstacles to combining both worlds in a uniform way is creating models that are suitable for both kinds of rendering paradigms. We build a modeling pipeline using open source tools that builds on established, open standards for data exchange. The result is demonstrated through a unified model of the medical OpenHELP phantom used in the Gazebo robotics simulator, which can at the same time be rendered with more visual fidelity in the Cycles raytracer. PMID:27046586

  15. Particle transport simulation of lower-hybrid current drive experiments on the Versator II tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Chen, K.h.; Luckhardt, S.C.; Mayberry, M.J.; Porkolab, M.

    1987-09-01

    The one-dimensional particle transport equation has been solved numerically to simulate temporal and spatial evolutions of density behavior observed during 800MHz and 2.45GHz LHCD experiments. In order to fit the 800MHz profiles, the inward pinch velocity has to be increased several fold. However, for the 2.45GHz case, the reduction of the diffusive loss near the periphery seems to be needed.

  16. Hybrid Simulation Environment for Construction Projects: Identification of System Design Criteria

    OpenAIRE

    Mohamed Moussa; Ruwanpura, Janaka Y.; George Jergeas; Tamer Mohamed

    2014-01-01

    Large construction projects are complex, dynamic, and unpredictable. They are subject to external and uncontrollable events that affect their schedule and financial outcomes. Project managers take decisions along the lifecycle of the projects to align with projects objectives. These decisions are data dependent where data change over time. Simulation-based modeling and experimentation of such dynamic environment are a challenge. Modeling of large projects or multiprojects is difficult and imp...

  17. SAUNA: A system for grid generation and flow simulation using hybrid structured/unstructured grids

    Science.gov (United States)

    Childs, P. N.; Shaw, J. A.; Peace, A. J.; Georgala, J. M.

    1992-05-01

    The development of a flow simulation facility for predicting the aerodynamics of complex configurations wherein the grid is composed of both structured and unstructured regions is described. Issues relating to the generation and analysis of such grids and to the accurate and efficient computation of both inviscid and viscous flows thereon are considered. Further the development of a comprehensive post-processing and visualization facility is explored. Techniques are illustrated throughout by application to realistic aircraft geometries.

  18. Study of neutron response for two hybrid RPC setups using the GEANT4 MC simulation approach

    Institute of Scientific and Technical Information of China (English)

    M.Jamil; J.T.Rhee; Y.J.Jeon

    2009-01-01

    The present article describes a detailed neutron simulation study in the energy range 10~(-10) MeV to 1.0 GeV for two different RPC configurations.The simulation studies were taken by using the GEANT4 MC code.Aluminum was utilized on the GND and readout strips for the (a) Bakelite-based and (b) glass-based RPCs.For the former type of RPC setup the neutron sensitivity for the isotropic source was S_n=2.702×10~(-2) at E_n=1.0 GeV, while for the latter type of RPC, the neutron sensitivity for the same source was evaluated as S_n=4.049×10~(-2) at E_n=1.0 geV.These results were further compared with the previous RPC configuration in which copper was used for ground and pickup pads.Additionally A1 was employed at (GND+strips) of the phosphate glass RPC setup and compared with the copper-based phosphate glass RPC.Good agreement with sensitivity values was obtained with the current and previous simulation results.

  19. Status on the Development of a Modeling and Simulation Framework for the Economic Assessment of Nuclear Hybrid Energy Systems

    International Nuclear Information System (INIS)

    An effort to design and build a modeling and simulation framework to assess the economic viability of Nuclear Hybrid Energy Systems (NHES) was undertaken in fiscal year 2015 (FY15). The purpose of this report is to document the various tasks associated with the development of such a framework and to provide a status on its progress. Several tasks have been accomplished. First, starting from a simulation strategy, a rigorous mathematical formulation has been achieved in which the economic optimization of a Nuclear Hybrid Energy System is presented as a constrained robust (under uncertainty) optimization problem. Some possible algorithms for the solution of the optimization problem are presented. A variation of the Simultaneous Perturbation Stochastic Approximation algorithm has been implemented in RAVEN and preliminary tests have been performed. The development of the software infrastructure to support the simulation of the whole NHES has also moved forward. The coupling between RAVEN and an implementation of the Modelica language (OpenModelica) has been implemented, migrated under several operating systems and tested using an adapted model of a desalination plant. In particular, this exercise was focused on testing the coupling of the different code systems; testing parallel, computationally expensive simulations on the INL cluster; and providing a proof of concept for the possibility of using surrogate models to represent the different NHES subsystems. Another important step was the porting of the RAVEN code under the Windows™ operating system. This accomplishment makes RAVEN compatible with the development environment that is being used for dynamic simulation of NHES components. A very simplified model of a NHES on the electric market has been built in RAVEN to confirm expectations on the analysis capability of RAVEN to provide insight into system economics and to test the capability of RAVEN to identify limit surfaces even for stochastic constraints. This

  20. Status on the Development of a Modeling and Simulation Framework for the Economic Assessment of Nuclear Hybrid Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Bragg-Sitton, Shannon Michelle [Idaho National Lab. (INL), Idaho Falls, ID (United States); Rabiti, Cristian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kinoshita, Robert Arthur [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kim, Jong Suk [Idaho National Lab. (INL), Idaho Falls, ID (United States); Deason, Wesley Ray [Idaho National Lab. (INL), Idaho Falls, ID (United States); Boardman, Richard Doin [Idaho National Lab. (INL), Idaho Falls, ID (United States); Garcia, Humberto E. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-09-01

    An effort to design and build a modeling and simulation framework to assess the economic viability of Nuclear Hybrid Energy Systems (NHES) was undertaken in fiscal year 2015 (FY15). The purpose of this report is to document the various tasks associated with the development of such a framework and to provide a status on its progress. Several tasks have been accomplished. First, starting from a simulation strategy, a rigorous mathematical formulation has been achieved in which the economic optimization of a Nuclear Hybrid Energy System is presented as a constrained robust (under uncertainty) optimization problem. Some possible algorithms for the solution of the optimization problem are presented. A variation of the Simultaneous Perturbation Stochastic Approximation algorithm has been implemented in RAVEN and preliminary tests have been performed. The development of the software infrastructure to support the simulation of the whole NHES has also moved forward. The coupling between RAVEN and an implementation of the Modelica language (OpenModelica) has been implemented, migrated under several operating systems and tested using an adapted model of a desalination plant. In particular, this exercise was focused on testing the coupling of the different code systems; testing parallel, computationally expensive simulations on the INL cluster; and providing a proof of concept for the possibility of using surrogate models to represent the different NHES subsystems. Another important step was the porting of the RAVEN code under the Windows™ operating system. This accomplishment makes RAVEN compatible with the development environment that is being used for dynamic simulation of NHES components. A very simplified model of a NHES on the electric market has been built in RAVEN to confirm expectations on the analysis capability of RAVEN to provide insight into system economics and to test the capability of RAVEN to identify limit surfaces even for stochastic constraints. This

  1. Elucidating the Functional Roles of Spatial Organization in Cross-Membrane Signal Transduction by a Hybrid Simulation Method.

    Science.gov (United States)

    Chen, Jiawen; Xie, Zhong-Ru; Wu, Yinghao

    2016-07-01

    The ligand-binding of membrane receptors on cell surfaces initiates the dynamic process of cross-membrane signal transduction. It is an indispensable part of the signaling network for cells to communicate with external environments. Recent experiments revealed that molecular components in signal transduction are not randomly mixed, but spatially organized into distinctive patterns. These patterns, such as receptor clustering and ligand oligomerization, lead to very different gene expression profiles. However, little is understood about the molecular mechanisms and functional impacts of this spatial-temporal regulation in cross-membrane signal transduction. In order to tackle this problem, we developed a hybrid computational method that decomposes a model of signaling network into two simulation modules. The physical process of binding between receptors and ligands on cell surfaces are simulated by a diffusion-reaction algorithm, while the downstream biochemical reactions are modeled by stochastic simulation of Gillespie algorithm. These two processes are coupled together by a synchronization framework. Using this method, we tested the dynamics of a simple signaling network in which the ligand binding of cell surface receptors triggers the phosphorylation of protein kinases, and in turn regulates the expression of target genes. We found that spatial aggregation of membrane receptors at cellular interfaces is able to either amplify or inhibit downstream signaling outputs, depending on the details of clustering mechanism. Moreover, by providing higher binding avidity, the co-localization of ligands into multi-valence complex modulates signaling in very different ways that are closely related to the binding affinity between ligand and receptor. We also found that the temporal oscillation of the signaling pathway that is derived from genetic feedback loops can be modified by the spatial clustering of membrane receptors. In summary, our method demonstrates the functional

  2. Three-dimensional needle-tip localization by electric field potential and camera hybridization for needle electromyography exam robotic simulator

    Directory of Open Access Journals (Sweden)

    He SY

    2016-06-01

    Full Text Available Siyu He,1 Jose Gomez-Tames,1 Wenwei Yu1,2 1Medical System Engineering Department, Graduate School of Engineering, 2Center for Frontier Medical Engineering, Chiba University, Chiba, Japan Abstract: As one of neurological tests, needle electromygraphy exam (NEE plays an important role to evaluate the conditions of nerves and muscles. Neurology interns and novice medical staff need repetitive training to improve their skills in performing the exam. However, no training systems are able to reproduce multiple pathological conditions to simulate real needle electromyogram exam. For the development of a robotic simulator, three components need to be realized: physical modeling of upper limb morphological features, position-dependent electromyogram generation, and needle localization; the latter is the focus of this study. Our idea is to couple two types of sensing mechanism in order to acquire the needle-tip position with high accuracy. One is to segment the needle from camera images and calculate its insertion point on the skin surface by a top-hat transform algorithm. The other is voltage-based depth measurement, in which a conductive tissue-like phantom was used to realize both needle-tip localization and physical sense of needle insertion. For that, a pair of electrodes was designed to generate a near-linear voltage distribution along the depth direction of the tissue-like phantom. The accuracy of the needle-tip position was investigated by the electric field potential and camera hybridization. The results showed that the needle tip could be detected with an accuracy of 1.05±0.57 mm. Keywords: needle-tip localization, needle EMG exam, top-hat transform, tissue-like phantom, voltage distribution simulation

  3. Real-time 3-D hybrid simulation of Titan's plasma interaction during a solar wind excursion

    Directory of Open Access Journals (Sweden)

    S. Simon

    2009-09-01

    Full Text Available The plasma environment of Saturn's largest satellite Titan is known to be highly variable. Since Titan's orbit is located within the outer magnetosphere of Saturn, the moon can leave the region dominated by the magnetic field of its parent body in times of high solar wind dynamic pressure and interact with the thermalized magnetosheath plasma or even with the unshocked solar wind. By applying a three-dimensional hybrid simulation code (kinetic description of ions, fluid electrons, we study in real-time the transition that Titan's plasma environment undergoes when the moon leaves Saturn's magnetosphere and enters the supermagnetosonic solar wind. In the simulation, the transition between both plasma regimes is mimicked by a reversal of the magnetic field direction as well as a change in the composition and temperature of the impinging plasma flow. When the satellite enters the solar wind, the magnetic draping pattern in its vicinity is reconfigured due to reconnection, with the characteristic time scale of this process being determined by the convection of the field lines in the undisturbed plasma flow at the flanks of the interaction region. The build-up of a bow shock ahead of Titan takes place on a typical time scale of a few minutes as well. We also analyze the erosion of the newly formed shock front upstream of Titan that commences when the moon re-enters the submagnetosonic plasma regime of Saturn's magnetosphere. Although the model presented here is far from governing the full complexity of Titan's plasma interaction during a solar wind excursion, the simulation provides important insights into general plasma-physical processes associated with such a disruptive change of the upstream flow conditions.

  4. A hybrid anchored-ANOVA - POD/Kriging method for uncertainty quantification in unsteady high-fidelity CFD simulations

    Science.gov (United States)

    Margheri, Luca; Sagaut, Pierre

    2016-11-01

    To significantly increase the contribution of numerical computational fluid dynamics (CFD) simulation for risk assessment and decision making, it is important to quantitatively measure the impact of uncertainties to assess the reliability and robustness of the results. As unsteady high-fidelity CFD simulations are becoming the standard for industrial applications, reducing the number of required samples to perform sensitivity (SA) and uncertainty quantification (UQ) analysis is an actual engineering challenge. The novel approach presented in this paper is based on an efficient hybridization between the anchored-ANOVA and the POD/Kriging methods, which have already been used in CFD-UQ realistic applications, and the definition of best practices to achieve global accuracy. The anchored-ANOVA method is used to efficiently reduce the UQ dimension space, while the POD/Kriging is used to smooth and interpolate each anchored-ANOVA term. The main advantages of the proposed method are illustrated through four applications with increasing complexity, most of them based on Large-Eddy Simulation as a high-fidelity CFD tool: the turbulent channel flow, the flow around an isolated bluff-body, a pedestrian wind comfort study in a full scale urban area and an application to toxic gas dispersion in a full scale city area. The proposed c-APK method (anchored-ANOVA-POD/Kriging) inherits the advantages of each key element: interpolation through POD/Kriging precludes the use of quadrature schemes therefore allowing for a more flexible sampling strategy while the ANOVA decomposition allows for a better domain exploration. A comparison of the three methods is given for each application. In addition, the importance of adding flexibility to the control parameters and the choice of the quantity of interest (QoI) are discussed. As a result, global accuracy can be achieved with a reasonable number of samples allowing computationally expensive CFD-UQ analysis.

  5. Atomistic simulations of thiol-terminated modifiers for hybrid photovoltaic interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Malloci, G. [Istituto Officina dei Materiali (CNR-IOM), Unità di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Italy); Petrozza, A. [Center for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, I-20133 Milano (Italy); Mattoni, A., E-mail: mattoni@iom.cnr.it [Istituto Officina dei Materiali (CNR-IOM), Unità di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Italy)

    2014-06-02

    Small aromatic molecules such as benzene or pyridine derivatives are often used as interface modifiers (IMs) at polymer/metal oxide hybrid interfaces. We performed a theoretical investigation on prototypical thiol-terminated IMs aimed at improving the photovoltaic performances of poly(3-hexylthiophene)/TiO{sub 2} devices. By means of first-principles calculations in the framework of the density functional theory we investigate 3-furanthiol (3FT), 4-mercaptobenzoicacid (4MB), and 6-isoquinolinethiol (6QT) molecules. We discuss the role of these molecules as modifiers alternative to 4-mercaptopyridine (4MP) which has recently shown to induce a large improvement in the overall power conversion efficiency of mesoporous films of TiO{sub 2} infiltrated by poly(3-hexylthiophene). The IMs investigated are expected to keep the beneficial features of 4MP giving at the same time the possibility to further tune the interlayer properties (e.g., its thickness, stability, and density). Dense interlayers of 6QT turn out to be slightly unstable since the titania substrate induces a compressive strain in the molecular film. On the contrary, we predict very stable films for both 3FT and 4MB molecules, which makes them interesting candidates for future experimental investigations. - Highlights: • We performed a theoretical investigation on thiol-terminated interface modifiers. • We investigate 3-furanthiol (3FT), 4-mercaptobenzoicacid (4MB), and 6-isoquinolinethiol molecules. • We discuss the role of these molecules as modifiers alternative to 4-mercaptopyridine. • Dense interlayers of 6-isoquinolinethiol turn out to be slightly unstable. • We predict very stable self-assembled thin-films for both 3FT and 4MB molecules.

  6. A Finding Method of Business Risk Factors Using Characteristics of Probability Distributions of Effect Ratios on Qualitative and Quantitative Hybrid Simulation

    Science.gov (United States)

    Samejima, Masaki; Negoro, Keisuke; Mitsukuni, Koshichiro; Akiyoshi, Masanori

    We propose a finding method of business risk factors on qualitative and quantitative hybrid simulation in time series. Effect ratios of qualitative arcs in the hybrid simulation vary output values of the simulation, so we define effect ratios causing risk as business risk factors. Finding business risk factors in entire ranges of effect ratios is time-consuming. It is considered that probability distributions of effect ratios in present time step and ones in previous time step are similar, the probability distributions in present time step can be estimated. Our method finds business risk factors in only estimated ranges effectively. Experimental results show that a precision rate and a recall rate are 86%, and search time is decreased 20% at least.

  7. Hybrid Method for the Numerical Simulation of Three Dimensional Open Space Flows

    Institute of Scientific and Technical Information of China (English)

    ZhongminXIONG; GuoCanLING

    1996-01-01

    A new hydrid method combining the compact finite difference and Fourier spectral expansion in different spatial directions is developed in this paper to perform the numerical simulation of 3-D open space flows.The implicit fourth-order compact scheme for solving the Helmholtz equations satisfied by the velocities and pressure in spectral space is derived and its preconditioned conjugate gradient iteration method is studied.The treatment of pressure boundary conditions and the three dimensional non-reflecting outflow boundary conditions are presented.Application to the vortex dislocation evolution in a three dimensional wake is also reported.

  8. A Matlab-Based Simulation for Hybrid Electric Motorcycle%基于Matlab的混合动力摩托车仿真研究

    Institute of Scientific and Technical Information of China (English)

    邵定国; 李永斌; 汪信尧; 江建中

    2003-01-01

    This paper presents a simulation and modeling package based on Matlab for a parallel hybrid electric motorcycle (HEM).The package consists of several main detailed models: internal combustion engine (ICE), motor, continuously variable transmission(CVT), battery, energy management system (EMS) etc. Each component is built as a library, and can be connected together accord-ing to the parallel HEM's topology. Simulation results, such as ICE power demand, motor power demand, battery instantaneous state-of-charge (SOC), pollution emissions etc. are given and discussed. Lastly experimental data verify our simulation results.

  9. Monthly water balance modeling: Probabilistic, possibilistic and hybrid methods for model combination and ensemble simulation

    Science.gov (United States)

    Nasseri, M.; Zahraie, B.; Ajami, N. K.; Solomatine, D. P.

    2014-04-01

    Multi-model (ensemble, or committee) techniques have shown to be an effective way to improve hydrological prediction performance and provide uncertainty information. This paper presents two novel multi-model ensemble techniques, one probabilistic, Modified Bootstrap Ensemble Model (MBEM), and one possibilistic, FUzzy C-means Ensemble based on data Pattern (FUCEP). The paper also explores utilization of the Ordinary Kriging (OK) method as a multi-model combination scheme for hydrological simulation/prediction. These techniques are compared against Bayesian Model Averaging (BMA) and Weighted Average (WA) methods to demonstrate their effectiveness. The mentioned techniques are applied to the three monthly water balance models used to generate stream flow simulations for two mountainous basins in the South-West of Iran. For both basins, the results demonstrate that MBEM and FUCEP generate more skillful and reliable probabilistic predictions, outperforming all the other techniques. We have also found that OK did not demonstrate any improved skill as a simple combination method over WA scheme for neither of the basins.

  10. Cosmological SPH simulations A hybrid multi-phase model for star formation

    CERN Document Server

    Springel, V; Springel, Volker; Hernquist, Lars

    2003-01-01

    We present a model for star formation and supernova feedback that describes the multi-phase structure of star forming gas on scales that are typically not resolved in cosmological simulations. Our approach includes radiative heating and cooling, the growth of cold clouds embedded in an ambient hot medium, star formation in these clouds, feedback from supernovae in the form of thermal heating and cloud evaporation, galactic winds and outflows, and metal enrichment. Implemented using SPH, our scheme is a significantly modified and extended version of the grid-based method of Yepes et al. (1997), and enables us to achieve high dynamic range in simulations of structure formation. We discuss properties of the feedback model in detail and show that it predicts a self-regulated, quiescent mode of star formation, which, in particular, stabilises the star forming gaseous layers of disk galaxies. The parameterisation of this mode can be reduced to a single free quantity which determines the overall timescale for star f...

  11. Development of Computational Approaches for Simulation and Advanced Controls for Hybrid Combustion-Gasification Chemical Looping

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Abhinaya; Lou, Xinsheng; Neuschaefer, Carl; Chaudry, Majid; Quinn, Joseph

    2012-07-31

    This document provides the results of the project through September 2009. The Phase I project has recently been extended from September 2009 to March 2011. The project extension will begin work on Chemical Looping (CL) Prototype modeling and advanced control design exploration in preparation for a scale-up phase. The results to date include: successful development of dual loop chemical looping process models and dynamic simulation software tools, development and test of several advanced control concepts and applications for Chemical Looping transport control and investigation of several sensor concepts and establishment of two feasible sensor candidates recommended for further prototype development and controls integration. There are three sections in this summary and conclusions. Section 1 presents the project scope and objectives. Section 2 highlights the detailed accomplishments by project task area. Section 3 provides conclusions to date and recommendations for future work.

  12. A hybrid mortar virtual element method for discrete fracture network simulations

    Science.gov (United States)

    Benedetto, Matías Fernando; Berrone, Stefano; Borio, Andrea; Pieraccini, Sandra; Scialò, Stefano

    2016-02-01

    The most challenging issue in performing underground flow simulations in Discrete Fracture Networks (DFN) is to effectively tackle the geometrical difficulties of the problem. In this work we put forward a new application of the Virtual Element Method combined with the Mortar method for domain decomposition: we exploit the flexibility of the VEM in handling polygonal meshes in order to easily construct meshes conforming to the traces on each fracture, and we resort to the mortar approach in order to "weakly" impose continuity of the solution on intersecting fractures. The resulting method replaces the need for matching grids between fractures, so that the meshing process can be performed independently for each fracture. Numerical results show optimal convergence and robustness in handling very complex geometries.

  13. Excitable laser processing network node in hybrid silicon: analysis and simulation.

    Science.gov (United States)

    Nahmias, Mitchell A; Tait, Alexander N; Shastri, Bhavin J; de Lima, Thomas Ferreira; Prucnal, Paul R

    2015-10-01

    The combination of ultrafast laser dynamics and dense on-chip multiwavelength networking could potentially address new domains of real-time signal processing that require both speed and complexity. We present a physically realistic optoelectronic simulation model of a circuit for dynamical laser neural networks and verify its behavior. We describe the physics, dynamics, and parasitics of one network node, which includes a bank of filters, a photodetector, and excitable laser. This unconventional circuit exhibits both cascadability and fan-in, critical properties for the large-scale networking of information processors based on laser excitability. In addition, it can be instantiated on a photonic integrated circuit platform and requires no off-chip optical I/O. Our proposed processing system could find use in emerging applications, including cognitive radio and low-latency control. PMID:26480191

  14. Numerical simulation of Stokes flow around particles via a hybrid Finite Difference-Boundary Integral scheme

    Science.gov (United States)

    Bhattacharya, Amitabh

    2013-11-01

    An efficient algorithm for simulating Stokes flow around particles is presented here, in which a second order Finite Difference method (FDM) is coupled to a Boundary Integral method (BIM). This method utilizes the strong points of FDM (i.e. localized stencil) and BIM (i.e. accurate representation of particle surface). Specifically, in each iteration, the flow field away from the particles is solved on a Cartesian FDM grid, while the traction on the particle surface (given the the velocity of the particle) is solved using BIM. The two schemes are coupled by matching the solution in an intermediate region between the particle and surrounding fluid. We validate this method by solving for flow around an array of cylinders, and find good agreement with Hasimoto's (J. Fluid Mech. 1959) analytical results.

  15. Excitable laser processing network node in hybrid silicon: analysis and simulation.

    Science.gov (United States)

    Nahmias, Mitchell A; Tait, Alexander N; Shastri, Bhavin J; de Lima, Thomas Ferreira; Prucnal, Paul R

    2015-10-01

    The combination of ultrafast laser dynamics and dense on-chip multiwavelength networking could potentially address new domains of real-time signal processing that require both speed and complexity. We present a physically realistic optoelectronic simulation model of a circuit for dynamical laser neural networks and verify its behavior. We describe the physics, dynamics, and parasitics of one network node, which includes a bank of filters, a photodetector, and excitable laser. This unconventional circuit exhibits both cascadability and fan-in, critical properties for the large-scale networking of information processors based on laser excitability. In addition, it can be instantiated on a photonic integrated circuit platform and requires no off-chip optical I/O. Our proposed processing system could find use in emerging applications, including cognitive radio and low-latency control.

  16. Combining stated and revealed choice research to simulate the neighbor effect: The case of hybrid-electric vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Axsen, Jonn [Institute of Transportation Studies, Univ. of California at Davis, 2028 Academic Surge, One Shields Avenue, Davis, CA 95616 (United States); Mountain, Dean C. [DeGroote School of Business, McMaster Univ., 1280 Main Street West, Hamilton, ON L8S 4M4 (Canada); Jaccard, Mark [School of Resource and Environmental Management, Simon Fraser Univ., 8888 Univ. Drive, Burnaby, BC V5A 1S6 (Canada)

    2009-08-15

    According to intuition and theories of diffusion, consumer preferences develop along with technological change. However, most economic models designed for policy simulation unrealistically assume static preferences. To improve the behavioral realism of an energy-economy policy model, this study investigates the ''neighbor effect'', where a new technology becomes more desirable as its adoption becomes more widespread in the market. We measure this effect as a change in aggregated willingness to pay under different levels of technology penetration. Focusing on hybrid-electric vehicles (HEVs), an online survey experiment collected stated preference (SP) data from 535 Canadian and 408 Californian vehicle owners under different hypothetical market conditions. Revealed preference (RP) data was collected from the same respondents by eliciting the year, make and model of recent vehicle purchases from regions with different degrees of HEV popularity: Canada with 0.17% new market share, and California with 3.0% new market share. We compare choice models estimated from RP data only with three joint SP-RP estimation techniques, each assigning a different weight to the influence of SP and RP data in coefficient estimates. Statistically, models allowing more RP influence outperform SP influenced models. However, results suggest that because the RP data in this study is afflicted by multicollinearity, techniques that allow more SP influence in the beta estimates while maintaining RP data for calibrating vehicle class constraints produce more realistic estimates of willingness to pay. Furthermore, SP influenced coefficient estimates also translate to more realistic behavioral parameters for CIMS, allowing more sensitivity to policy simulations. (author)

  17. The IBEX Ribbon and the Pickup Ion Ring Stability in the Outer Heliosheath. I. Theory and Hybrid Simulations

    Science.gov (United States)

    Florinski, V.; Heerikhuisen, J.; Niemiec, J.; Ernst, A.

    2016-08-01

    The nearly circular band of energetic neutral atom emission dominating the field of view of the Interplanetary Boundary Explorer (IBEX ) satellite, is most commonly attributed to the effect of charge exchange of secondary pickup ions (PUIs) gyrating about the magnetic field in the outer heliosheath and the interstellar space beyond. Several models for the PUI dynamics of this mechanism have been proposed, each requiring either strong or weak scattering of the initial pitch angle. Conventional wisdom states that ring distributions tend to generate waves and scatter onto a shell on timescales too short for charge exchange to occur. We performed a careful study of ring and thin shell proton distribution stability using theoretical tools and hybrid plasma simulations. We show that the kinetic behavior of a freshly injected proton ring is a far more complicated process than previously thought. In the presence of a warm Maxwellian core, narrower rings could be more stable than broader toroidal distributions. The scattered rings possess a fine structure that can only be revealed using very large numbers of macroparticles in a simulation. It is demonstrated that a “stability gap” in ring temperature exists where the protons could retain large gyrating anisotropies for years, and the wave activity could remain below the level of the ambient magnetic fluctuations in interstellar space. In the directions away from the ribbon, however, a partial shell distribution is more likely to be unstable, leading to significant scattering into one hemisphere in velocity space. The process is accompanied by turbulence production, which is puzzling given the very low level of magnetic fluctuations measured in the outer heliosheath by Voyager 1.

  18. Plasma and fields in the wake of Rhea: 3-D hybrid simulation and comparison with Cassini data

    Directory of Open Access Journals (Sweden)

    E. Roussos

    2008-03-01

    Full Text Available Rhea's magnetospheric interaction is simulated using a three-dimensional, hybrid plasma simulation code, where ions are treated as particles and electrons as a massless, charge-neutralizing fluid. In consistency with Cassini observations, Rhea is modeled as a plasma absorbing obstacle. This leads to the formation of a plasma wake (cavity behind the moon. We find that this cavity expands with the ion sound speed along the magnetic field lines, resulting in an extended depletion region north and south of the moon, just a few Rhea radii (RRh downstream. This is a direct consequence of the comparable thermal and bulk plasma velocities at Rhea. Perpendicular to the magnetic field lines the wake's extension is constrained by the magnetic field. A magnetic field compression in the wake and the rarefaction in the wake sides is also observed in our results. This configuration reproduces well the signature in the Cassini magnetometer data, acquired during the close flyby to Rhea on November 2005. Almost all plasma and field parameters show an asymmetric distribution along the plane where the corotational electric field is contained. A diamagnetic current system is found running parallel to the wake boundaries. The presence of this current system shows a direct corelation with the magnetic field configuration downstream of Rhea, while the resulting j×B forces on the ions are responsible for the asymmetric structures seen in the velocity and electric field vector fields in the equatorial plane. As Rhea is one of the many plasma absorbing moons of Saturn, we expect that this case study should be relevant for most lunar-type interactions at Saturn.

  19. The IBEX Ribbon and the Pickup Ion Ring Stability in the Outer Heliosheath. I. Theory and Hybrid Simulations

    Science.gov (United States)

    Florinski, V.; Heerikhuisen, J.; Niemiec, J.; Ernst, A.

    2016-08-01

    The nearly circular band of energetic neutral atom emission dominating the field of view of the Interplanetary Boundary Explorer (IBEX ) satellite, is most commonly attributed to the effect of charge exchange of secondary pickup ions (PUIs) gyrating about the magnetic field in the outer heliosheath and the interstellar space beyond. Several models for the PUI dynamics of this mechanism have been proposed, each requiring either strong or weak scattering of the initial pitch angle. Conventional wisdom states that ring distributions tend to generate waves and scatter onto a shell on timescales too short for charge exchange to occur. We performed a careful study of ring and thin shell proton distribution stability using theoretical tools and hybrid plasma simulations. We show that the kinetic behavior of a freshly injected proton ring is a far more complicated process than previously thought. In the presence of a warm Maxwellian core, narrower rings could be more stable than broader toroidal distributions. The scattered rings possess a fine structure that can only be revealed using very large numbers of macroparticles in a simulation. It is demonstrated that a “stability gap” in ring temperature exists where the protons could retain large gyrating anisotropies for years, and the wave activity could remain below the level of the ambient magnetic fluctuations in interstellar space. In the directions away from the ribbon, however, a partial shell distribution is more likely to be unstable, leading to significant scattering into one hemisphere in velocity space. The process is accompanied by turbulence production, which is puzzling given the very low level of magnetic fluctuations measured in the outer heliosheath by Voyager 1.

  20. Generation of kinetic Alfven waves in the high-latitude near-Earth magnetotail: A global hybrid simulation

    Science.gov (United States)

    Guo, Zhifang; Hong, Minghua; Lin, Yu; Du, Aimin; Wang, Xueyi; Wu, Mingyu; Lu, Quanming

    2015-02-01

    In this paper, effects of a fast flow in the tail plasma sheet on the generation of kinetic Alfven waves (KAWs) in the high-latitude of the near-Earth magnetotail are investigated by performing a two-dimensional (2-D) global-scale hybrid simulation, where the plasma flow is initialized by the E ×B drift near the equatorial plane due to the existence of the dawn-dusk convection electric field. It is found that firstly, the plasma sheet becomes thinned and the dipolarization of magnetic field appears around (x ,z ) =(-10.5 RE,0.3 RE) , where RE is the radius of the Earth. Then, shear Alfven waves are excited in the plasma sheet, and the strong earthward flow is braked by the dipole-like magnetic field. These waves propagate along the magnetic field lines toward the polar regions later. Subsequently, KAWs with k⊥≫k∥ are generated in the high-latitude magnetotail due to the existence of the non-uniformity of the magnetic field and density in the polar regions. The ratio of the electric field to the magnetic field in these waves is found to obey the relation (δEz)/(δBy )˜ω/k∥ of KAWs. Our simulation provides a mechanism for the generation of the observed low-frequency shear Alfven waves in the plasma sheet and kinetic Alfven waves in the high-latitude near-Earth magnetotail, whose source is suggested to be the flow braking in the low-latitude plasma sheet.

  1. Investigation of Bubble-Slag Layer Behaviors with Hybrid Eulerian-Lagrangian Modeling and Large Eddy Simulation

    Science.gov (United States)

    Li, Linmin; Li, Baokuan

    2016-08-01

    In ladle metallurgy, bubble-liquid interaction leads to complex phase structures. Gas bubble behavior, as well as the induced slag layer behavior, plays a significant role in the refining process and the steel quality. In the present work, a mathematical model using the large eddy simulation (LES) is developed to investigate the bubble transport and slag layer behavior in a water model of an argon-stirred ladle. The Eulerian volume of fluid model is adopted to track the liquid steel-slag-air free surfaces while the Lagrangian discrete phase model is used for tracking and handling the dynamics of discrete bubbles. The bubble coalescence is considered using O'Rourke's algorithm to solve the bubble diameter redistribution and bubbles are removed after leaving the air-liquid interface. The turbulent liquid flow that is induced by bubble-liquid interaction is solved by LES. The slag layer fluactuation, slag droplet entrainment and spout eye open-close phenomenon are well revealed. The bubble diameter distribution and the spout eye size are compared with the experiment. The results show that the hybrid Eulerian-Lagrangian-LES model provides a valid modeling framework to predict the unsteady gas bubble-slag layer coupled behaviors.

  2. Optical data exchange of m-QAM signals using a silicon-organic hybrid slot waveguide: proposal and simulation.

    Science.gov (United States)

    Gui, Chengcheng; Wang, Jian

    2014-10-01

    We present modulation-format-transparent data exchange for m-ary quadrature amplitude modulation (m-QAM) signals using a single silicon-organic hybrid slot waveguide which offers tight light confinement and enhanced nonlinearity. By exploiting the parametric depletion effect of non-degenerate four-wave mixing (ND-FWM) process in the slot waveguide, we simulate low-power (waveguide length is studied, showing an optimized waveguide length of ~17 mm. For a given waveguide length of 17 mm, the SNR penalty of data exchange, at a BER of 2e-3, is kept below 4 dB when varying input pump power from 8.4 to 9.8 mW for 2.56 Tbit/s 16-QAM and from 8.9 to 9.2 mW for 3.84 Tbit/s 64-QAM. In addition, data exchange running at low speed (e.g. 20 Gbaud) and data exchange taking into account waveguide propagation loss are also analyzed with favorable operation performance.

  3. Real-time hybrid simulation of a complex bridge model with MR dampers using the convolution integral method

    International Nuclear Information System (INIS)

    Magneto-rheological (MR) fluid dampers can be used to reduce the traffic induced vibration in highway bridges and protect critical structural components from fatigue. Experimental verification is needed to verify the applicability of the MR dampers for this purpose. Real-time hybrid simulation (RTHS), where the MR dampers are physically tested and dynamically linked to a numerical model of the highway bridge and truck traffic, provides an efficient and effective means to experimentally examine the efficacy of MR dampers for fatigue protection of highway bridges. In this paper a complex highway bridge model with 263 178 degrees-of-freedom under truck loading is tested using the proposed convolution integral (CI) method of RTHS for a semiactive structural control strategy employing two large-scale 200 kN MR dampers. The formation of RTHS using the CI method is first presented, followed by details of the various components in the RTHS and a description of the implementation of the CI method for this particular test. The experimental results confirm the practicability of the CI method for conducting RTHS of complex systems. (paper)

  4. Response of SAOS-2 cells to simulated microgravity and effect of biocompatible sol-gel hybrid coatings

    Science.gov (United States)

    Catauro, M.; Bollino, F.; Papale, F.

    2016-05-01

    The health of astronauts, during space flight, is threatened by bone loss induced by microgravity, mainly attributed to an imbalance in the bone remodeling process. In the present work, the response to the microgravity of bone cells has been studied using the SAOS-2 cell line grown under the condition of weightlessness, simulated by means of a Random Positioning Machine (RPM). Cell viability after 72 h of rotation has been evaluated by means of WST-8 assay and compared to that of control cells. Although no significant difference between the two cell groups has been observed in terms of viability, F-actin staining showed that microgravity environment induces cell apoptosis and altered F-actin organization. To investigate the possibility of hindering the trend of the cells towards the death, after 72 h of rotation the cells have been seeded onto biocompatible ZrO2/PCL hybrid coatings, previously obtained using a sol-gel dip coating procedure. WST-8 assay, carried out after 24 h, showed that the materials are able to inhibit the pro-apoptotic effect of microgravity on cells.

  5. A computational simulation of the effect of hybrid treatment for thoracoabdominal aortic aneurysm on the hemodynamics of abdominal aorta.

    Science.gov (United States)

    Wen, Jun; Yuan, Ding; Wang, Qingyuan; Hu, Yao; Zhao, Jichun; Zheng, Tinghui; Fan, Yubo

    2016-01-01

    Hybrid visceral-renal debranching procedures with endovascular repair have been proposed as an appealing technique to treat conventional thoracoabdominal aortic aneurysm (TAAA). This approach, however, still remained controversial because of the non-physiological blood flow direction of its retrograde visceral revascularization (RVR) which is generally constructed from the aortic bifurcation or common iliac artery. The current study carried out the numerical simulation to investigate the effect of RVR on the hemodynamics of abdominal aorta. The results indicated that the inflow sites for the RVR have great impact on the hemodynamic performance. When RVR was from the distal aorta, the perfusion to visceral organs were adequate but the flow flux to the iliac artery significantly decreased and a complex disturbed flow field developed at the distal aorta, which endangered the aorta at high risk of aneurysm development. When RVR was from the right iliac artery, the abdominal aorta was not troubled with low WSS or disturbed flow, but the inadequate perfusion to the visceral organs reached up to 40% and low WSS and flow velocity predominated appeared at the right iliac artery and the grafts, which may result in the stenosis in grafts and aneurysm growth on the host iliac artery. PMID:27029949

  6. Receptor-mediated membrane adhesion of lipid-polymer hybrid (LPH) nanoparticles studied by dissipative particle dynamics simulations

    Science.gov (United States)

    Li, Zhenlong; Gorfe, Alemayehu A.

    2014-12-01

    Lipid-polymer hybrid (LPH) nanoparticles represent a novel class of targeted drug delivery platforms that combine the advantages of liposomes and biodegradable polymeric nanoparticles. However, the molecular details of the interaction between LPHs and their target cell membranes remain poorly understood. We have investigated the receptor-mediated membrane adhesion process of a ligand-tethered LPH nanoparticle using extensive dissipative particle dynamics (DPD) simulations. We found that the spontaneous adhesion process follows a first-order kinetics characterized by two distinct stages: a rapid nanoparticle-membrane engagement, followed by a slow growth in the number of ligand-receptor pairs coupled with structural re-organization of both the nanoparticle and the membrane. The number of ligand-receptor pairs increases with the dynamic segregation of ligands and receptors toward the adhesion zone causing an out-of-plane deformation of the membrane. Moreover, the fluidity of the lipid shell allows for strong nanoparticle-membrane interactions to occur even when the ligand density is low. The LPH-membrane avidity is enhanced by the increased stability of each receptor-ligand pair due to the geometric confinement and the cooperative effect arising from multiple binding events. Thus, our results reveal the unique advantages of LPH nanoparticles as active cell-targeting nanocarriers and provide some general principles governing nanoparticle-cell interactions that may aid future design of LPHs with improved affinity and specificity for a given target of interest.

  7. Hybrid CFD/FEM-BEM simulation of cabin aerodynamic noise for vehicles traveling at high speed

    Institute of Scientific and Technical Information of China (English)

    WANG; YiPing; ZHEN; Xin; WU; Jing; GU; ZhengQi; XIAO; ZhenYi; YANG; Xue

    2013-01-01

    Flow passing a vehicle may lead to the increase of the cabin interior noise level through a variety of mechanisms. These mechanisms include vibrations caused by aerodynamic excitations and reradiation from the glass panels, exterior noise trans-mitted and leaked through door seals including gaps and glass edge, and transmission of airborne noise generated by the interaction of flow with body panels. It is of vital importance to predict both the flow fields and the acoustic sources around the ve-hicle to accurately assess the impact of wind induced noise inside the cabin. In the present study, an unstructured segregated finite volume model was used to calculate the flow fields in which a hexahedron grid is used to simplify the vehicle geometry.A large eddy simulation coupled with a wall function model was applied to predict the exterior transient flow fields. The mean flow quantities were thus calculated along the symmetry plane and the vehicle’s side windows. A coupled FEM/BEM method was used to compute the vehicle’s interior noise level. The total contribution of the interior noise level due to the body panels of the vehicle was subsequently analyzed.

  8. Hybrid Models: Bridging Particle and Continuum Scales in Hydrodynamic Flow Simulations

    Science.gov (United States)

    Flekkoy, Eirik G.; McNamara, Sean; Maloy, Jorgen; Maloy, Knut; Feder, Jens; Wagner, Geri

    Different models for the coupling of field and particle descriptions are introduced and examined. For the purpose of establishing how a molecular description may be coupled to a continuum description of the same physical system, we study a molecular dynamics system coupled to a Navier-Stokes description within the same physical space. A simple toy model version of this system is studied as well, i.e., a system of random walkers coupled to the diffusion equation. These coupling schemes are shown to work in the sense that they provide a seamless coupling between the different representations. In order to establish a sufficiently computationally efficient method for the simulation of gas-grain flow, we introduce a model where the grains are described explicitly but where the gas is described only through its continuum pressure field. It is shown that this model easily produces macroscopic structures, such as the bubbles in fluidized beds. The model is also used to study a novel bubble instability observed experimentally in the flow of gas-grain systems in simple tubes.

  9. Ordered particles versus ordered pointers in the hybrid ordered plasma simulation (HOPS) code

    International Nuclear Information System (INIS)

    From a computational standpoint, particle simulation calculations for plasmas have not adapted well to the transitions from scalar to vector processing nor from serial to parallel environments. They have suffered from inordinate and excessive accessing of computer memory and have been hobbled by relatively inefficient gather-scatter constructs resulting from the use of indirect indexing. Lastly, the many-to-one mapping characteristic of the deposition phase has made it difficult to perform this in parallel. The authors' code sorts and reorders the particles in a spatial order. This allows them to greatly reduce the memory references, to run in directly indexed vector mode, and to employ domain decomposition to achieve parallelization. The field model solves pre-maxwell equations by interatively implicit methods. The OSOP (Ordered Storage Ordered Processing) version of HOPS keeps the particle tables ordered by rebuilding them after each particle pushing phase. Alternatively, the RSOP (Random Storage Ordered Processing) version keeps a table of pointers ordered by rebuilding them. Although OSOP is somewhat faster than RSOP in tests on vector-parallel machines, it is not clear this advantage will carry over to massively parallel computers

  10. Simulations of sooting turbulent jet flames using a hybrid flamelet/stochastic Eulerian field method

    Science.gov (United States)

    Consalvi, Jean-Louis; Nmira, Fatiha; Burot, Daria

    2016-03-01

    The stochastic Eulerian field method is applied to simulate 12 turbulent C1-C3 hydrocarbon jet diffusion flames covering a wide range of Reynolds numbers and fuel sooting propensities. The joint scalar probability density function (PDF) is a function of the mixture fraction, enthalpy defect, scalar dissipation rate and representative soot properties. Soot production is modelled by a semi-empirical acetylene/benzene-based soot model. Spectral gas and soot radiation is modelled using a wide-band correlated-k model. Emission turbulent radiation interactions (TRIs) are taken into account by means of the PDF method, whereas absorption TRIs are modelled using the optically thin fluctuation approximation. Model predictions are found to be in reasonable agreement with experimental data in terms of flame structure, soot quantities and radiative loss. Mean soot volume fractions are predicted within a factor of two of the experiments whereas radiant fractions and peaks of wall radiative fluxes are within 20%. The study also aims to assess approximate radiative models, namely the optically thin approximation (OTA) and grey medium approximation. These approximations affect significantly the radiative loss and should be avoided if accurate predictions of the radiative flux are desired. At atmospheric pressure, the relative errors that they produced on the peaks of temperature and soot volume fraction are within both experimental and model uncertainties. However, these discrepancies are found to increase with pressure, suggesting that spectral models describing properly the self-absorption should be considered at over-atmospheric pressure.

  11. Hybrid Systems Modeling in Non Standard Queue and Optimization with the Simulation Approach in CNG Stations

    Directory of Open Access Journals (Sweden)

    Meysam Haddadi

    2012-07-01

    Full Text Available Modeling line in non standard way occurs when layout constraints and inappropriate placing customer is limited for taking customer service by the servant. The aim of this study is providing a mixed model for analyzing the system of non-standard line with Considering the limitations of the layout with Using the concepts and principles of queuing theory So that the main parameters of the model for this type of system can be calculated and The basis of queuing systems with non-standard parameters may be considered. In these nonstandard systems, because of special arrangement of servants, there are some delay times for giving services and exit. The use of simulation tools to demonstrate the relatively low efficiency of CNG (Compressed Natural Gas stations in Iran, To provide an optimum combination of servers (Fuel nozzle Also more efficient layout for the CNG stations has Studied. Manufacturing firms and service managers can use this model and evaluate and analysis their own system and get a better recognition of their system. One of the most widely used queuing systems in the country are CNG stations, in consideration high investment cost and land value in large cities, so we decided to studied on this area as one of the servicing activities.

  12. Optimization Of Thermo-Electric Coolers Using Hybrid Genetic Algorithm And Simulated Annealing

    Directory of Open Access Journals (Sweden)

    Khanh Doan V.K.

    2014-06-01

    Full Text Available Thermo-electric Coolers (TECs nowadays are applied in a wide range of thermal energy systems. This is due to their superior features where no refrigerant and dynamic parts are needed. TECs generate no electrical or acoustical noise and are environmentally friendly. Over the past decades, many researches were employed to improve the efficiency of TECs by enhancing the material parameters and design parameters. The material parameters are restricted by currently available materials and module fabricating technologies. Therefore, the main objective of TECs design is to determine a set of design parameters such as leg area, leg length and the number of legs. Two elements that play an important role when considering the suitability of TECs in applications are rated of refrigeration (ROR and coefficient of performance (COP. In this paper, the review of some previous researches will be conducted to see the diversity of optimization in the design of TECs in enhancing the performance and efficiency. After that, single-objective optimization problems (SOP will be tested first by using Genetic Algorithm (GA and Simulated Annealing (SA to optimize geometry properties so that TECs will operate at near optimal conditions. Equality constraint and inequality constraint were taken into consideration.

  13. Modeling, control, and simulation of battery storage photovoltaic-wave energy hybrid renewable power generation systems for island electrification in Malaysia.

    Science.gov (United States)

    Samrat, Nahidul Hoque; Bin Ahmad, Norhafizan; Choudhury, Imtiaz Ahmed; Bin Taha, Zahari

    2014-01-01

    Today, the whole world faces a great challenge to overcome the environmental problems related to global energy production. Most of the islands throughout the world depend on fossil fuel importation with respect to energy production. Recent development and research on green energy sources can assure sustainable power supply for the islands. But unpredictable nature and high dependency on weather conditions are the main limitations of renewable energy sources. To overcome this drawback, different renewable sources and converters need to be integrated with each other. This paper proposes a standalone hybrid photovoltaic- (PV-) wave energy conversion system with energy storage. In the proposed hybrid system, control of the bidirectional buck-boost DC-DC converter (BBDC) is used to maintain the constant dc-link voltage. It also accumulates the excess hybrid power in the battery bank and supplies this power to the system load during the shortage of hybrid power. A three-phase complex vector control scheme voltage source inverter (VSI) is used to control the load side voltage in terms of the frequency and voltage amplitude. Based on the simulation results obtained from Matlab/Simulink, it has been found that the overall hybrid framework is capable of working under the variable weather and load conditions. PMID:24892049

  14. Modeling, control, and simulation of battery storage photovoltaic-wave energy hybrid renewable power generation systems for island electrification in Malaysia.

    Science.gov (United States)

    Samrat, Nahidul Hoque; Bin Ahmad, Norhafizan; Choudhury, Imtiaz Ahmed; Bin Taha, Zahari

    2014-01-01

    Today, the whole world faces a great challenge to overcome the environmental problems related to global energy production. Most of the islands throughout the world depend on fossil fuel importation with respect to energy production. Recent development and research on green energy sources can assure sustainable power supply for the islands. But unpredictable nature and high dependency on weather conditions are the main limitations of renewable energy sources. To overcome this drawback, different renewable sources and converters need to be integrated with each other. This paper proposes a standalone hybrid photovoltaic- (PV-) wave energy conversion system with energy storage. In the proposed hybrid system, control of the bidirectional buck-boost DC-DC converter (BBDC) is used to maintain the constant dc-link voltage. It also accumulates the excess hybrid power in the battery bank and supplies this power to the system load during the shortage of hybrid power. A three-phase complex vector control scheme voltage source inverter (VSI) is used to control the load side voltage in terms of the frequency and voltage amplitude. Based on the simulation results obtained from Matlab/Simulink, it has been found that the overall hybrid framework is capable of working under the variable weather and load conditions.

  15. Computer simulations for direct conversion of the HF electromagnetic wave into the upper hybrid wave in ionospheric heating experiments

    OpenAIRE

    Ueda, H. O.; Omura, Y.; Matsumoto, H

    1998-01-01

    Excitation of upper hybrid waves associated with the ionospheric heating experiments is assumed to be essential in explaining some of the features of stimulated electromagnetic emissions (SEE). A direct conversion process is proposed as an excitation mechanism of the upper hybrid waves where the energy of an obliquely propagating electromagnetic pump wave is converted into the electrostatic upper hybrid waves due to small-scale density irregularities. We performed electromagnetic particle-in-...

  16. Simulation Analysis on Driving Cycle of a Hybrid Electric Vehicle%混合动力汽车行驶工况的仿真分析

    Institute of Scientific and Technical Information of China (English)

    李东东; 程金瑞; 田源玉

    2012-01-01

    Vehicle performance is influenced by actual driving condition directly.For a hybrid electric vehicle,selection of its componemnts and formulation of control strategy are closely related to road driving cycle.Driving cycle of a vehicle is analyzed in this paper.modeling and simulation of a mini hybrid electric vehicle is comducted by using GT-DRIV.The simulation results show that the hybrid electric vehicle has obvious advantages than traditional vehicle in fuel economy.Better electric distribution will be the key point in hybrid electric vehicle design.%汽车的实际行驶条件对汽车性能具有直接影响。对于混合动力汽车,其部件的选型以及控制策略的制定都与道路行驶工况密切相关文章对汽车行驶工况做了相应的分析.利用GT—DRIVE软件对某微型混合动力汽车进行了建模与仿真仿真结果表明,在经济性方面混合动力汽车比传统汽车有明显的优势.如何更好地分配混合动力汽车功率将是混合动力汽车研究的重点.

  17. A Lithium-Ion Battery Simulator Based on a Diffusion and Switching Overpotential Hybrid Model for Dynamic Discharging Behavior and Runtime Predictions

    Directory of Open Access Journals (Sweden)

    Lan-Rong Dung

    2016-01-01

    Full Text Available A new battery simulator based on a hybrid model is proposed in this paper for dynamic discharging behavior and runtime predictions in existing electronic simulation environments, e.g., PSIM, so it can help power circuit designers to develop and optimize their battery-powered electronic systems. The hybrid battery model combines a diffusion model and a switching overpotential model, which automatically switches overpotential resistance mode or overpotential voltage mode to accurately describe the voltage difference between battery electro-motive force (EMF and terminal voltage. Therefore, this simulator can simply run in an electronic simulation software with less computational efforts and estimate battery performances by further considering nonlinear capacity effects. A linear extrapolation technique is adopted for extracting model parameters from constant current discharging tests, so the EMF hysteresis problem is avoided. For model validation, experiments and simulations in MATLAB and PSIM environments are conducted with six different profiles, including constant loads, an interrupted load, increasing and decreasing loads and a varying load. The results confirm the usefulness and accuracy of the proposed simulator. The behavior and runtime prediction errors can be as low as 3.1% and 1.2%, respectively.

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

    CERN Document Server

    Cook, J W S; Dendy, R O

    2010-01-01

    We present particle-in-cell (PIC) simulations of minority energetic protons in deuterium plasmas, which demonstrate a collective instability responsible for emission near the lower hybrid frequency and its harmonics. The simulations capture the lower hybrid drift instability in a regime relevant to tokamak fusion plasmas, and show further that the excited electromagnetic fields collectively and collisionlessly couple free energy from the protons to directed electron motion. This results in an asymmetric tail antiparallel to the magnetic field. We focus on obliquely propagating modes under conditions approximating the outer mid-plane edge in a large tokamak, through which there pass confined centrally born fusion products on banana orbits that have large radial excursions. A fully self-consistent electromagnetic relativistic PIC code representing all vector field quantities and particle velocities in three dimensions as functions of a single spatial dimension is used to model this situation, by evolving the in...

  19. Digital holography simulations and experiments to quantify the accuracy of 3D particle location and 2D sizing using a proposed hybrid method

    Energy Technology Data Exchange (ETDEWEB)

    Guildenbecher, Daniel R.; Gao, Jian; Reu, Phillip L.; Chen, Jun

    2013-01-01

    The accuracy of digital in-line holography to detect particle position and size within a 3D domain is evaluated with particular focus placed on detection of nonspherical particles. Dimensionless models are proposed for simulation of holograms from single particles, and these models are used to evaluate the uncertainty of existing particle detection methods. From the lessons learned, a new hybrid method is proposed. This method features automatic determination of optimum thresholds, and simulations indicate improved accuracy compared to alternative methods. To validate this, experiments are performed using quasi-stationary, 3D particle fields with imposed translations. For the spherical particles considered in experiments, the proposed hybrid method resolves mean particle concentration and size to within 4% of the actual value, while the standard deviation of particle depth is less than two particle diameters. Initial experimental results for nonspherical particles reveal similar performance.

  20. 着色Petri网的混杂系统仿真平台构架%Platform Framework of Complex Hybrid System Simulation Based on Colored Petri Nets

    Institute of Scientific and Technical Information of China (English)

    方哲梅; 王明哲; 杨翠蓉

    2011-01-01

    提出一种以Petri网为仿真进程控制,以着色Petri网与Matlab交互为主题的混杂仿真跨平台构架.该仿真构架通过运用和扩展着色Petri网中替代变迁的概念,结合融合库所和折叠功能,实现了混杂系统的复杂逻辑建模和连续系统内嵌.同时,着色Petri网的分析功能在一定程度上缓解了逻辑结构复杂的混杂系统检验困难的问题.最后通过一个混杂系统实例的建模与仿真分析,验证了该平台的可行性与逻辑检验的有效性,为复杂混杂系统的建模与仿真提供了一条新途径.%This paper proposes a cross-platform framework for hybrid simulation based on the interaction between colored Petri net (CPN) and Matlab, using Petri net as a tool for simulation process control. Utilizing and extending the concept of substitution transition, with the function of fusion place and folding, this framework can accomplish complex logical modeling and establishment of imbedded continuous process for hybrid systems. Besides, the analytical function of CPN reduces difficulty in logical verification for hybrid systems with complex logical behaviors. Finally, by modeling, simulation and analysis of a simple instance, feasibility of the platform and validity of the logic are shown. It provides a new method of modeling and simulation for large and complicated hybrid systems.

  1. Simulation of the PEM fuel cell hybrid power train of an automated guided vehicle and comparison with experimental results

    NARCIS (Netherlands)

    Veenhuizen, Bram; Bosma, J.C.N.

    2009-01-01

    At HAN University research has been started into the development of a PEM fuel cell hybrid power train to be used in an automated guided vehicle. For this purpose a test facility is used with the possibility to test all important functional aspects of a PEM fuel cell hybrid power train. In this pape

  2. Efficient design and simulation of an expandable hybrid (wind-photovoltaic) power system with MPPT and inverter input voltage regulation features in compliance with electric grid requirements

    Energy Technology Data Exchange (ETDEWEB)

    Skretas, Sotirios B.; Papadopoulos, Demetrios P. [Electrical Machines Laboratory, Department of Electrical and Computer Engineering, Democritos University of Thrace (DUTH), 12 V. Sofias, 67100 Xanthi (Greece)

    2009-09-15

    In this paper an efficient design along with modeling and simulation of a transformer-less small-scale centralized DC - bus Grid Connected Hybrid (Wind-PV) power system for supplying electric power to a single phase of a three phase low voltage (LV) strong distribution grid are proposed and presented. The main components of the hybrid system are: a PV generator (PVG); and an array of horizontal-axis, fixed-pitch, small-size, variable-speed wind turbines (WTs) with direct-driven permanent magnet synchronous generator (PMSG) having an embedded uncontrolled bridge rectifier. An overview of the basic theory of such systems along with their modeling and simulation via Simulink/MATLAB software package are presented. An intelligent control method is applied to the proposed configuration to simultaneously achieve three desired goals: to extract maximum power from each hybrid power system component (PVG and WTs); to guarantee DC voltage regulation/stabilization at the input of the inverter; to transfer the total produced electric power to the electric grid, while fulfilling all necessary interconnection requirements. Finally, a practical case study is conducted for the purpose of fully evaluating a possible installation in a city site of Xanthi/Greece, and the practical results of the simulations are presented. (author)

  3. Core loading pattern optimization of a typical two-loop 300 MWe PWR using Simulated Annealing (SA), novel crossover Genetic Algorithms (GA) and hybrid GA(SA) schemes

    International Nuclear Information System (INIS)

    Highlights: • SA and GA based optimization for loading pattern has been carried out. • The LEOPARD and MCRAC codes for a typical PWR have been used. • At high annealing rates, the SA shows premature convergence. • Then novel crossover and mutation operators are proposed in this work. • Genetic Algorithms exhibit stagnation for small population sizes. - Abstract: A comparative study of the Simulated Annealing and Genetic Algorithms based optimization of loading pattern with power profile flattening as the goal, has been carried out using the LEOPARD and MCRAC neutronic codes, for a typical 300 MWe PWR. At high annealing rates, Simulated Annealing exhibited tendency towards premature convergence while at low annealing rates, it failed to converge to global minimum. The new ‘batch composition preserving’ Genetic Algorithms with novel crossover and mutation operators are proposed in this work which, consistent with the earlier findings (Yamamoto, 1997), for small population size, require comparable computational effort to Simulated Annealing with medium annealing rates. However, Genetic Algorithms exhibit stagnation for small population size. A hybrid Genetic Algorithms (Simulated Annealing) scheme is proposed that utilizes inner Simulated Annealing layer for further evolution of population at stagnation point. The hybrid scheme has been found to escape stagnation in bcp Genetic Algorithms and converge to the global minima with about 51% more computational effort for small population sizes

  4. DEVELOPMENT AND APPLICATIONS OF HYBRID SIMULATION AND EXPERIMENTATION USING OPENSEES%OpenSees混合模拟试验技术发展与应用

    Institute of Scientific and Technical Information of China (English)

    何政; 蒋碧聪

    2012-01-01

    将现代结构地震性能模拟与试验分为整体结构模拟试验和子结构模拟试验两类.在此基础之上详细讨论了混合模拟试验的基本概念背景及其应用与发展现状.结合面相对象有限元程序OpenSees的高层程序架构和并行计算程序架构,详细论述了基于OpenSees的4种混合模拟试验系统,并简要介绍了多尺度一体化混合建模的概念与应用.证明基于商业或非商业有限元软件平台开展混合模拟试验是可行的;混合模拟试验所要处理的核心问题是如何将不同的有限元软件平台以及各个试验站点的设备联系起来,并实现相互之间的协同工作.混合模拟试验在强震作用下结构连续倒塌问题的研究中具有一定的优势.指出混合模拟试验这一新技术的实质性发展离不开目前所强调的多学科之间的无缝融合.%In this paper, modern structural performance simulation or experimentation systems can be clas- sified into global (i.e. structure) and local (substructure) categories. The background, some basic concepts, state-of-the-art development and applications of hybrid simulation (experimentation) are discussed in detail within this kind of classification. Based on the object-oriented finite element program Open System for Earth- quake Engineering Simulation (OpenSees) and its high-level software architecture as well as parallel computing program structure, four OpenSees-based hybrid simulation and hybrid experimentation systems are addressed. Further, a brief introduction of the concepts and applications of multi-scale integrated hybrid modeling is given herein. It has been proved to be feasible for developing hybrid simulations or hybrid experimentations based on some commercially and non-commercially available finite element (FE) software platforms. The key issue confronted is how to incorporate different FE software platforms with the testing apparatus locating at differ- ent

  5. Numerical Hybrid Simulation Modeling Verification for a Curved 3-Pier Bridge (Investigation of Combined Actions on Reinforced Concrete Bridge Piers (CABER Project

    Directory of Open Access Journals (Sweden)

    Adel Abdelnaby

    2013-06-01

    Full Text Available Reinforced concrete bridge piers are subjected to complex loading conditions under earthquake ground motions. Bridge geometric irregularities and asymmetries result in combined actions imposed on the piers as a combination of displacements and rotations in all six degrees of freedom at the pier-deck juncture. Existing analytical tools have proven their inadequacy in representing the actual behavior of piers under these combined actions, particularly in their inelastic range. The objective of this investigation is to develop a fundamental understanding of the effects of these combined actions on the performance of RC piers and the resulting system response. This paper describes a part of the CABER project that verifies the numerical hybrid simulation of the curved bridge. In this part two models were introduced, a whole model and a sub-structured hybrid model. The whole model was established using the Zeus-NL analysis platform, which is capable of performing inelastic nonlinear response history analysis of the whole curved bridge. The hybrid model was divided into three modules which comprised the deck, left and right piers, and the middle pier of the bridge. The three modules were modeled by Zeus-NL as a static analysis module interface. The simulation coordinator (SimCor software was utilized to communicate between these modules using a Pseudo-Dynamic time integration scheme. Results obtained from both models were compared and conclusions were drawn.

  6. Regenerative braking potencial and energy simulations for a plug-in hybrid electric vehicle under real driving conditions

    OpenAIRE

    Martins, Luís Barreiros; Brito, J. M. O.; Rocha, A. M. D.; Martins, Jorge

    2009-01-01

    There are several possible configurations and technologies for the powertrains of electric and hybrid vehicles, but most of them will include advanced energy storage systems comprising batteries and ultra-capacitors. Thus, it will be of capital importance to evaluate the power and energy involved in braking and the fraction that has the possibility of being regenerated. The Series type Plug-in Hybrid Electric Vehicle (SPHEV), with electric traction and a small Internal Co...

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

    Science.gov (United States)

    Kuniansky, Eve L.

    2016-09-22

    been developed that incorporate the submerged conduits as a one-dimensional pipe network within the aquifer rather than as discrete, extremely transmissive features in a porous-equivalent medium; these submerged conduit models are usually referred to as hybrid models and may include the capability to simulate both laminar and turbulent flow in the one-dimensional pipe network. Comparisons of the application of a porous-equivalent media model with and without turbulence (MODFLOW-Conduit Flow Process mode 2 and basic MODFLOW, respectively) and a hybrid (MODFLOW-Conduit Flow Process mode 1) model to the Woodville Karst Plain near Tallahassee, Florida, indicated that for annual, monthly, or seasonal average hydrologic conditions, all methods met calibration criteria (matched observed groundwater levels and average flows). Thus, the increased effort required, such as the collection of data on conduit location, to develop a hybrid model and its increased computational burden, is not necessary for simulation of average hydrologic conditions (non-laminar flow effects on simulated head and spring discharge were minimal). However, simulation of a large storm event in the Woodville Karst Plain with daily stress periods indicated that turbulence is important for matching daily springflow hydrographs. Thus, if matching streamflow hydrographs over a storm event is required, the simulation of non-laminar flow and the location of conduits are required. The main challenge in application of the methods and approaches for developing hybrid models relates to the difficulty of mapping conduit networks or having high-quality datasets to calibrate these models. Additionally, hybrid models have long simulation times, which can preclude the use of parameter estimation for calibration. Simulation of contaminant transport that does not account for preferential flow through conduits or extremely permeable zones in any approach is ill-advised. Simulation results in other karst aquifers or other

  8. Application of a hybrid breakup model for the spray simulation of a multi-hole injector used for a DISI gasoline engine

    International Nuclear Information System (INIS)

    A hybrid atomization and breakup model was developed for the simulation of the fuel injection processes of multi-hole injectors for direct injection spark ignition (DISI) gasoline engines. In modeling primary breakup, a competition between the Huh–Gosman and Kelvin–Helmholtz (KH) breakup mechanisms was adopted. In addition to the two breakup mechanisms above, the Rayleigh–Taylor (RT) model was selected as a third competing mechanism in simulating secondary breakup. The hybrid model was implemented in the Star-CD software to simulate the effect of the background and injection pressures on the breakup processes of gasoline jets in a constant volume vessel, and on the mixture stratification of a wall-guided DISI gasoline engine with a newly-designed cavity in the piston. Results indicate that a higher background pressure intensifies the aerodynamically induced breakup along the tip of spray although it tends to reduce the overall breakup of spray. The spray atomization enhanced by increasing injection pressures is more pronounced at elevated background pressures. With the retard of fuel injection timing, the inhomogeneity of mixture increases in the DISI gasoline engine. Double injection with elevated second injection pressure can reduce the overall inhomogeneity of the mixture and effectively direct the mixture towards the spark plug. - Highlights: •A hybrid breakup model was developed to simulate injection process in a DISI engine. •Higher fuel injection pressure enhances breakup and evaporation at the spray tip. •Single fuel injection leads to a narrow spark timing range. •Two-stage fuel injection improves the homogeneity of the mixture. •The second injection with higher fuel pressure decreases over-rich mixture

  9. Evaluation of the Gibbs Free Energy Changes and Melting Temperatures of DNA/DNA Duplexes Using Hybridization Enthalpy Calculated by Molecular Dynamics Simulation.

    Science.gov (United States)

    Lomzov, Alexander A; Vorobjev, Yury N; Pyshnyi, Dmitrii V

    2015-12-10

    A molecular dynamics simulation approach was applied for the prediction of the thermal stability of oligonucleotide duplexes. It was shown that the enthalpy of the DNA/DNA complex formation could be calculated using this approach. We have studied the influence of various simulation parameters on the secondary structure and the hybridization enthalpy value of Dickerson-Drew dodecamer. The optimal simulation parameters for the most reliable prediction of the enthalpy values were determined. The thermodynamic parameters (enthalpy and entropy changes) of a duplex formation were obtained experimentally for 305 oligonucleotides of various lengths and GC-content. The resulting database was studied with molecular dynamics (MD) simulation using the optimized simulation parameters. Gibbs free energy changes and the melting temperatures were evaluated using the experimental correlation between enthalpy and entropy changes of the duplex formation and the enthalpy values calculated by the MD simulation. The average errors in the predictions of enthalpy, the Gibbs free energy change, and the melting temperature of oligonucleotide complexes were 11%, 10%, and 4.4 °C, respectively. We have shown that the molecular dynamics simulation gives a possibility to calculate the thermal stability of native DNA/DNA complexes a priori with an unexpectedly high accuracy.

  10. Accuracy Evaluation Method for Electromechanical-electromagnetic Hybrid Simulation%机电-电磁混合仿真精度评估方法研究

    Institute of Scientific and Technical Information of China (English)

    房钊; 陶顺; 杨洋; 陈鹏伟; 肖湘宁

    2016-01-01

    Electromechanical-electromagnetic hybrid simulation can both do electromechanical transient simulation for the large-scale complex power grid and do electromagnetic transient simulation for a local network. It achieves harmonization on simulation scale and simulation accuracy. Whether the simulation results can accurately reflect the real situation will determine the reliability of the simulation results. This paper proposes a multiple time quantum, multiple locations and multiple variables three-level accuracy evaluation system, which can give quantitative value and qualitative interpretation for electromechanical-electromagnetic hybrid simulation. First of all, this paper introduces the basic principles and the relevant indicators of two typical feature extraction algorithms of power system simulation, which are prony method and feature selective validation. Then taking into account the properties of each object observations in electromechanical-electromagnetic hybrid simulation, the object observation is divided into three categories: electromagnetic system observables, the interface state observables and electromechanical system observables. By combining the two methods, a hierarchical accuracy evaluation system is set up. Finally, through evaluating the differences between the results of the two current sources hybrid simulation and full electromagnetic simulation, the applicability of the proposed accuracy evaluation system is verified.%机电-电磁混合仿真既能够对大规模复杂电网进行机电暂态仿真,也可对局部网络进行电磁暂态仿真,实现仿真规模和仿真精度的协调统一,其仿真结果反映真实情况的程度,决定仿真结果的可信度,通过一种多时间、多位置和多物理量的3 级精度评估体系,定量和定性描述机电-电磁混合仿真结果的精度.首先,介绍 Prony 分析法和特征选择验证这两种典型特征量提取算法的基本原理及相关指标;然后,根据机电-电

  11. Research on Hybrid Vehicle Drivetrain

    Science.gov (United States)

    Xie, Zhongzhi

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

  12. Modeling and Simulation of Parallel Plug-in Hybrid Electric Bus%插电式并联混合动力客车建模及仿真

    Institute of Scientific and Technical Information of China (English)

    范彪; 袁景敏; 李建鹏; 袁月会; 舒红

    2011-01-01

    基于Advisor软件中并联混合动力客车仿真模型,建立插电式并联双离合器混合动力客车仿真模型,并对发动机、电机、传动系和电池等进行参数匹配;分析电力辅助控制策略,利用正交设计对其控制参数进行优选研究。仿真结果表明,动力系统主要参数及整车控制策略设计合理,满足整车性能要求。%Based on the simulation model of a parallel plug-in hybrid electric bus in the Advisor software, a simulation model for a parallel plug-in hybrid electric bus which has two clutches is established. Main parameters of the engine, motor, transmission and batteries are matched. The electric-assistant control strategy is analyzed and its control parameters are optimized parameters of powertrain and the demands. by orthogonal design method. The simulation results show that the design PHEV's control strategy are reasonable and satisfy the vehicle's performance

  13. The solvent shell structure of aqueous iodide: X-ray absorption spectroscopy and classical, hybrid QM/MM and full quantum molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Pham, V.T. [Ecole Polytechnique Federale de Lausanne, Laboratoire de spectroscopie ultrarapide, ISIC, FSB-BSP, CH-1015 Lausanne (Switzerland); Tavernelli, I. [Ecole Polytechnique Federale de Lausanne, Laboratoire de chimie et biochimie computationnelles, ISIC, FSB-BSP, CH-1015 Lausanne (Switzerland); Milne, C.J.; van der Veen, R.M. [Ecole Polytechnique Federale de Lausanne, Laboratoire de spectroscopie ultrarapide, ISIC, FSB-BSP, CH-1015 Lausanne (Switzerland); D' Angelo, P. [Dipartimento di Chimica, Universita di Roma ' La Sapienza' , Ple A. Moro 5, 00185 Roma (Italy); Bressler, Ch. [Ecole Polytechnique Federale de Lausanne, Laboratoire de spectroscopie ultrarapide, ISIC, FSB-BSP, CH-1015 Lausanne (Switzerland); Chergui, M., E-mail: Majed.Chergui@epfl.ch [Ecole Polytechnique Federale de Lausanne, Laboratoire de spectroscopie ultrarapide, ISIC, FSB-BSP, CH-1015 Lausanne (Switzerland)

    2010-05-25

    Graphical abstract: The L{sub 3}-edge EXAFS spectra of aqueous iodide are compared to classical, QM/MM and DFT-based molecular dynamics simulations. The QM/MM simulations reproduce best the experimental data. An anisotropy of the solvation shell is also identified. - Abstract: The L{sub 3} X-ray absorption spectrum of aqueous iodide is reported, and its EXAFS is compared to theoretical spectra reconstructed from the radial distribution function of the iodide hydration obtained from classical, hybrid Quantum Mechanics Molecular Mechanics, (QM/MM) and full quantum (density functional theory, DFT) molecular dynamics simulations. Since EXAFS is mainly sensitive to short distances around the iodide ion, it is a direct probe of the local solvation structure. The comparison shows that QM/MM simulations deliver a satisfactory description of the EXAFS signal, while nonpolarizable classical simulations are somewhat less satisfactory and DFT-based simulations perform poorly. We also identify a weak anisotropy of the water solvation shell around iodide, which may be of importance in electron photoejection experiments.

  14. Simulated annealing: in mathematical global optimization computation, hybrid with local or global search, and practical applications in crystallography and molecular modelling

    CERN Document Server

    Zhang, Jiapu

    2013-01-01

    Simulated annealing (SA) was inspired from annealing in metallurgy, a technique involving heating and controlled cooling of a material to increase the size of its crystals and reduce their defects, both are attributes of the material that depend on its thermodynamic free energy. In this Paper, firstly we will study SA in details on its practical implementation. Then, hybrid pure SA with local (or global) search optimization methods allows us to be able to design several effective and efficient global search optimization methods. In order to keep the original sense of SA, we clarify our understandings of SA in crystallography and molecular modeling field through the studies of prion amyloid fibrils.

  15. Effect of piston shapes and fuel injection strategies on stoichiometric stratified flame ignition (SFI) hybrid combustion in a PFI/DI gasoline engine by numerical simulations

    International Nuclear Information System (INIS)

    Highlights: • SFI was proposed to enhance the control of combustion and moderate PRRmax. • Effect of pistons, SOI timings and DI ratios on SFI was studied using 3-D CFD. • Shallow bowl pistons can optimize mixture stratification and reduce PRRmax. • Later SOI timing and larger DI ratio can significantly reduce the PRRmax. • Spark timing is effective to control CA50, IMEP and PRRmax of SFI. - Abstract: In this research, the stratified flame ignition (SFI) hybrid combustion process was proposed to enhance the control of SI–CAI hybrid combustion and moderate the maximum pressure rise rate (PRRmax) by the combination of port fuel injection (PFI) and direct injection (DI). The effect of the stratified flame formed by different piston shapes, start of direct injection (SOI) timings and direct injection ratios (rDI) on the stoichiometric SFI hybrid combustion and heat release process was studied using the three-dimensional computational fluid dynamics (3-D CFD) simulations. The spark ignited flame propagation near the spark plug and the auto-ignition heat release process of the diluted mixture were modelled in the framework of 3-Zones Extended Coherent Flame Model (ECFM3Z) by the extended coherent flame model and tabulated auto-ignition chemistry of a 4-component gasoline surrogate, respectively. The operating load of indicated mean effective pressure (IMEP) 3.6 bar was selected to represent a typical part-load operation. The sweep of the spark timing (ST) was performed for different pistons, SOI timings and direct injection ratios. The SFI hybrid combustion process with the same combustion phasing was investigated in details. The optimal stratified mixture pattern, characterized with the central rich mixture around spark plug and stratified lean mixture at the peripheral region, formed by the newly designed Piston A and B effectively lowers the PRRmax with a slight deterioration of IMEP. The later SOI timing advances the crank angle of 50% total heat release

  16. Hybrid mesh generation for the new generation of oil reservoir simulators: 3D extension; Generation de maillage hybride pour les simulateurs de reservoir petrolier de nouvelle generation: extension 3D

    Energy Technology Data Exchange (ETDEWEB)

    Flandrin, N.

    2005-09-15

    During the exploitation of an oil reservoir, it is important to predict the recovery of hydrocarbons and to optimize its production. A better comprehension of the physical phenomena requires to simulate 3D multiphase flows in increasingly complex geological structures. In this thesis, we are interested in this spatial discretization and we propose to extend in 3D the 2D hybrid model proposed by IFP in 1998 that allows to take directly into account in the geometry the radial characteristics of the flows. In these hybrid meshes, the wells and their drainage areas are described by structured radial circular meshes and the reservoirs are represented by structured meshes that can be a non uniform Cartesian grid or a Corner Point Geometry grids. In order to generate a global conforming mesh, unstructured transition meshes based on power diagrams and satisfying finite volume properties are used to connect the structured meshes together. Two methods have been implemented to generate these transition meshes: the first one is based on a Delaunay triangulation, the other one uses a frontal approach. Finally, some criteria are introduced to measure the quality of the transition meshes and optimization procedures are proposed to increase this quality under finite volume properties constraints. (author)

  17. Study on Hybrid Simulation of Power System and Communication Network%电网和通信网综合仿真研究

    Institute of Scientific and Technical Information of China (English)

    童和钦; 倪明; 李悦岑; 余文杰

    2016-01-01

    在智能电网和能源互联网中,通信的可靠性和延时以及误码等因素对电网安全稳定的影响很大,有必要研究通信系统和电力系统的交互作用。首先综述了电网和通信网综合仿真研究的现状。在对支撑电网稳控业务的同步数字体系(synchronous digital hierarchy,SDH)通信网络的特点和动态特性进行分析的基础上,提出了电网和通信网综合仿真平台的整体框架和关键技术,并用电网仿真软件FASTEST和通信仿真软件SSFNET开发了电网和通信网综合仿真平台,以研究通信对电网稳控系统的影响。最后,以某省级电网为仿真算例,利用该平台检验了通信故障对稳控装置功能的影响。%In smart grid and energy internet,the security and stability control of power system are impacted seriously by factors such as the reliability of communication network and its latency and bits errors. This paper first gives a review of the current status of the re-search on hybrid simulation of power system and communication network. After analyzing the characteristics and the dynamic features of SDH (synchronous digital hierarchy)network which supports the power system protection and stability control functions,the frame-work and key technologies for power system and communication network hybrid simulation platform is proposed,and an interactive hy-brid simulation platform for power system and communication network is developed with FASTEST (a power system simulation soft-ware)and SSFNET (a communication simulation software)to study the impact of communication failures on the stability control de-vices. Finally,the impact is verified with the platform on a case of certain provincial power grid.

  18. Transfer impedance simulation and measurement methods to analyse shielding behaviour of HV cables used in Electric-Vehicles and Hybrid-Electric-Vehicles

    Science.gov (United States)

    Mushtaq, Abid; Frei, Stephan

    2016-09-01

    In the power drive system of the Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs), High Voltage (HV) cables play a major role in evaluating the EMI of the whole system. Transfer impedance (ZT) is the most commonly used performance parameter for the HV cable. To analyse and design HV cables and connectors with better shielding effectiveness (SE), appropriate measurement and simulation methods are required. In this paper, Ground Plate Method (GPM) with improvements has been proposed to measure ZT. Use of low-frequency ferrites to avoid ground-loop effects has also been investigated. Additionally, a combination of analytical model with a circuit model has been implemented to simulate limitations (frequency response) of the test setup. Also parametrical studies using the analytical model have been performed to analyse the shielding behaviour of HV cables.

  19. Design and Simulation of 2×2 MMI Coupler and Thermo-optic Switch Using Sol-Gel Derived Organic-Inorganic Hybrid Material

    Science.gov (United States)

    Samah, M. Firdaus A.; Nawabjan, Amirjan; Abdullah, Ahmad Sharmi; Ibrahim, Mohd Haniff; Kassim, Norazan Mohd; Mohamad, Abu Bakar

    2011-05-01

    A new design of Multimode Interference (MMI) thermo-optic switch with improved crosstalk figure is demonstrated in this paper. The device is designed and simulated using BeamProp 3D from Rsoft and 3D BPM CAD softwares. The devices are designed based on sol-gel derived organic-inorganic hybrid material, vinyltriethoxysilane (VTES), tetraethoxysilane (TEOS) and tetrabutoxytitanate (TTBu) or VTT with refractive index of 1.47 as a core and surrounded by silica with refractive index of 1.45 at 1550 nm wavelength. The switching power is 164mW and the simulation result show that the propagation loss of the MMI device is 1.8 dB and zero crosstalk.

  20. Simulation Analysis of Slewing System for Hybrid Hydraulic Excavator%油液混合动力挖掘机回转系统仿真分析

    Institute of Scientific and Technical Information of China (English)

    郑辉; 吴文海; 邓斌; 刘桓龙; 柯坚

    2012-01-01

    In order to recover the braking energy from braking process of slewing platform of hydraulic excavator, a hybrid hydraulic excavator energy recovery system was proposed in which accumulator was used to recover the braking energy. The differences of the principle of the slewing hydraulic system between the hybrid hydraulic excavator and the ordinary excavator were elaborated. The simulation model was built based on AMESim. Simulation results show that using the hybrid hydraulic excavator, the power loss of the hydraulic pumps and the pressure fluctuations of the hydraulic motors are reduced. In the energy saving aspect, the energy recovery efficiency of the accumulator can reach 70% , and the reuse efficiency of the hydraulic energy can reach 72. 8%. So the system has high recovery efficiency and the energy saving purpose is achieved.%为了回收挖掘机回转平台制动过程中的制动能量,设计了油液混合动力挖掘机回转系统,利用蓄能器回收回转平台的制动能量.阐述油液混合动力回转系统和普通回转系统液压原理的不同,建立AMESim模型并进行仿真分析.仿真结果表明:油液混合动力挖掘机回转系统在一定程度上降低了液压泵的功率损耗和液压马达的压力波动;在节能方面,蓄能器的能量回收效率达到70.0%,再利用效率达到72.8%,利用率较高,达到节能的目的.

  1. Particle-in-cell simulations of an alpha channeling scenario: electron current drive arising from lower hybrid drift instability of fusion-born ions

    Science.gov (United States)

    Cook, James; Chapman, Sandra; Dendy, Richard

    2010-11-01

    Particle-in-cell (PIC) simulations of fusion-born protons in deuterium plasmas demonstrate a key alpha channeling phenomenon for tokamak fusion plasmas. We focus on obliquely propagating modes at the plasma edge, excited by centrally born fusion products on banana orbits, known to be responsible for observations of ion cyclotron emission in JET and TFTR. A fully self-consistent electromagnetic 1D3V PIC code evolves a ring-beam distribution of 3MeV protons in a 10keV thermal deuterium-electron plasma with realistic mass ratio. A collective instability occurs, giving rise to electromagnetic field activity in the lower hybrid range of frequencies. Waves spontaneously excited by this lower hybrid drift instability undergo Landau damping on resonant electrons, drawing out an asymmetric tail in the distribution of electron parallel velocities, which constitutes a net current. These simulations demonstrate a key building block of some alpha channeling scenarios: the direct collisionless coupling of fusion product energy into a form which can help sustain the equilibrium of the tokamak.

  2. Hybrid Broadband Ground-Motion Simulations: Combining Long-Period Deterministic Synthetics with High-Frequency Multiple S-to-S Backscattering

    KAUST Repository

    Mai, Paul Martin

    2010-09-20

    We present a new approach for computing broadband (0-10 Hz) synthetic seismograms by combining high-frequency (HF) scattering with low-frequency (LF) deterministic seismograms, considering finite-fault earthquake rupture models embedded in 3D earth structure. Site-specific HF-scattering Green\\'s functions for a heterogeneous medium with uniformly distributed random isotropic scatterers are convolved with a source-time function that characterizes the temporal evolution of the rupture process. These scatterograms are then reconciled with the LF-deterministic waveforms using a frequency-domain optimization to match both amplitude and phase spectra around the target intersection frequency. The scattering parameters of the medium, scattering attenuation ηs, intrinsic attenuation ηi, and site-kappa, as well as frequency-dependent attenuation, determine waveform and spectral character of the HF-synthetics and thus affect the hybrid broadband seismograms. Applying our methodology to the 1994 Northridge earthquake and validating against near-field recordings at 24 sites, we find that our technique provides realistic broadband waveforms and consistently reproduces LF ground-motion intensities for two independent source descriptions. The least biased results, compared to recorded strong-motion data, are obtained after applying a frequency-dependent site-amplification factor to the broadband simulations. This innovative hybrid ground-motion simulation approach, applicable to any arbitrarily complex earthquake source model, is well suited for seismic hazard analysis and ground-motion estimation.

  3. Performance metrics in a hybrid MPI-OpenMP based molecular dynamics simulation with short-range interactions

    CERN Document Server

    Pal, Anirban; Raha, Soumyendu; Bhattacharya, Baidurya

    2015-01-01

    We discuss the computational bottlenecks in molecular dynamics (MD) and describe the challenges in parallelizing the computation intensive tasks. We present a hybrid algorithm using MPI (Message Passing Interface) with OpenMP threads for parallelizing a generalized MD computation scheme for systems with short range interatomic interactions. The algorithm is discussed in the context of nanoindentation of Chromium films with carbon indenters using the Embedded Atom Method potential for Cr Cr interaction and the Morse potential for Cr C interactions. We study the performance of our algorithm for a range of MPIthread combinations and find the performance to depend strongly on the computational task and load sharing in the multicore processor. The algorithm scaled poorly with MPI and our hybrid schemes were observed to outperform the pure message passing scheme, despite utilizing the same number of processors or cores in the cluster. Speed-up achieved by our algorithm compared favourably with that achieved by stan...

  4. Energy filtering transmission electron microscopy and atomistic simulations of tribo-induced hybridization change of nanocrystalline diamond coating

    OpenAIRE

    Bouchet, M.I.D.; Matta, C.; Vacher, B; Le-Mogne, T.; Martin, J. M.; Lautz, J. von; T. Ma; Pastewka, L.; Otschik, J.; Gumbsch, P.; Moseler, M.

    2015-01-01

    The tribofilm formed on nanocrystalline diamond coating during ultralow friction in presence of water and glycerol lubrication has been studied experimentally by energy filtering transmission electron microscopy (EF-TEM) and electron energy loss spectroscopy (EELS) on focus ion beam (FIB) cross sections. Surprisingly, even under mild tribological conditions, a tribo-induced hybridization change (sp(3) towards sp(2)) can be clearly detected at the top of the coating resulting in the formation ...

  5. Simulations

    CERN Document Server

    Ngada, N M

    2015-01-01

    The complexity and cost of building and running high-power electrical systems make the use of simulations unavoidable. The simulations available today provide great understanding about how systems really operate. This paper helps the reader to gain an insight into simulation in the field of power converters for particle accelerators. Starting with the definition and basic principles of simulation, two simulation types, as well as their leading tools, are presented: analog and numerical simulations. Some practical applications of each simulation type are also considered. The final conclusion then summarizes the main important items to keep in mind before opting for a simulation tool or before performing a simulation.

  6. A novel integrated thermal-/membrane-based solar energy-driven hybrid desalination system: Concept description and simulation results.

    Science.gov (United States)

    Kim, Young-Deuk; Thu, Kyaw; Ng, Kim Choon; Amy, Gary L; Ghaffour, Noreddine

    2016-09-01

    In this paper, a hybrid desalination system consisting of vacuum membrane distillation (VMD) and adsorption desalination (AD) units, designated as VMD-AD cycle, is proposed. The synergetic integration of the VMD and AD is demonstrated where a useful effect of the AD cycle is channelled to boost the operation of the VMD process, namely the low vacuum environment to maintain the high pressure gradient across the microporous hydrophobic membrane. A solar-assisted multi-stage VMD-AD hybrid desalination system with temperature modulating unit is first designed, and its performance is then examined with a mathematical model of each component in the system and compared with the VMD-only system with temperature modulating and heat recovery units. The total water production and water recovery ratio of a solar-assisted 24-stage VMD-AD hybrid system are found to be about 21% and 23% higher, respectively, as compared to the VMD-only system. For the solar-assisted 24-stage VMD-AD desalination system having 150 m(2) of evacuated-tube collectors and 10 m(3) seawater storage tanks, both annual collector efficiency and solar fraction are close to 60%.

  7. A novel integrated thermal-/membrane-based solar energy-driven hybrid desalination system: Concept description and simulation results

    KAUST Repository

    Kim, Young-Deuk

    2016-05-03

    In this paper, a hybrid desalination system consisting of vacuum membrane distillation (VMD) and adsorption desalination (AD) units, designated as VMD-AD cycle, is proposed. The synergetic integration of the VMD and AD is demonstrated where a useful effect of the AD cycle is channelled to boost the operation of the VMD process, namely the low vacuum environment to maintain the high pressure gradient across the microporous hydrophobic membrane. A solar-assisted multi-stage VMD-AD hybrid desalination system with temperature modulating unit is first designed, and its performance is then examined with a mathematical model of each component in the system and compared with the VMD-only system with temperature modulating and heat recovery units. The total water production and water recovery ratio of a solar-assisted 24-stage VMD-AD hybrid system are found to be about 21% and 23% higher, respectively, as compared to the VMD-only system. For the solar-assisted 24-stage VMD-AD desalination system having 150 m2 of evacuated-tube collectors and 10 m3 seawater storage tanks, both annual collector efficiency and solar fraction are close to 60%.

  8. A novel integrated thermal-/membrane-based solar energy-driven hybrid desalination system: Concept description and simulation results.

    Science.gov (United States)

    Kim, Young-Deuk; Thu, Kyaw; Ng, Kim Choon; Amy, Gary L; Ghaffour, Noreddine

    2016-09-01

    In this paper, a hybrid desalination system consisting of vacuum membrane distillation (VMD) and adsorption desalination (AD) units, designated as VMD-AD cycle, is proposed. The synergetic integration of the VMD and AD is demonstrated where a useful effect of the AD cycle is channelled to boost the operation of the VMD process, namely the low vacuum environment to maintain the high pressure gradient across the microporous hydrophobic membrane. A solar-assisted multi-stage VMD-AD hybrid desalination system with temperature modulating unit is first designed, and its performance is then examined with a mathematical model of each component in the system and compared with the VMD-only system with temperature modulating and heat recovery units. The total water production and water recovery ratio of a solar-assisted 24-stage VMD-AD hybrid system are found to be about 21% and 23% higher, respectively, as compared to the VMD-only system. For the solar-assisted 24-stage VMD-AD desalination system having 150 m(2) of evacuated-tube collectors and 10 m(3) seawater storage tanks, both annual collector efficiency and solar fraction are close to 60%. PMID:27176649

  9. GATE Monte Carlo simulations for variations of an integrated PET/MR hybrid imaging system based on the Biograph mMR model

    International Nuclear Information System (INIS)

    A simulation toolkit, GATE (Geant4 Application for Tomographic Emission), was used to develop an accurate Monte Carlo (MC) simulation of a fully integrated 3T PET/MR hybrid imaging system (Siemens Biograph mMR). The PET/MR components of the Biograph mMR were simulated in order to allow a detailed study of variations of the system design on the PET performance, which are not easy to access and measure on a real PET/MR system. The 3T static magnetic field of the MR system was taken into account in all Monte Carlo simulations. The validation of the MC model was carried out against actual measurements performed on the PET/MR system by following the NEMA (National Electrical Manufacturers Association) NU 2-2007 standard. The comparison of simulated and experimental performance measurements included spatial resolution, sensitivity, scatter fraction, and count rate capability. The validated system model was then used for two different applications. The first application focused on investigating the effect of an extension of the PET field-of-view on the PET performance of the PET/MR system. The second application deals with simulating a modified system timing resolution and coincidence time window of the PET detector electronics in order to simulate time-of-flight (TOF) PET detection. A dedicated phantom was modeled to investigate the impact of TOF on overall PET image quality. Simulation results showed that the overall divergence between simulated and measured data was found to be less than 10%. Varying the detector geometry showed that the system sensitivity and noise equivalent count rate of the PET/MR system increased progressively with an increasing number of axial detector block rings, as to be expected. TOF-based PET reconstructions of the modeled phantom showed an improvement in signal-to-noise ratio and image contrast to the conventional non-TOF PET reconstructions. In conclusion, the validated MC simulation model of an integrated PET/MR system with an overall

  10. Fluid-particle hybrid simulation on the transports of plasma, recycling neutrals, and carbon impurities in the Korea Superconducting Tokamak Advanced Research divertor region

    Science.gov (United States)

    Kim, Deok-Kyu; Hong, Sang Hee

    2005-06-01

    A two-dimensional simulation modeling that has been performed in a self-consistent way for analysis on the fully coupled transports of plasma, recycling neutrals, and intrinsic carbon impurities in the divertor domain of tokamaks is presented. The numerical model coupling the three major species transports in the tokamak edge is based on a fluid-particle hybrid approach where the plasma is described as a single magnetohydrodynamic fluid while the neutrals and impurities are treated as kinetic particles using the Monte Carlo technique. This simulation code is applied to the KSTAR (Korea Superconducting Tokamak Advanced Research) tokamak [G. S. Lee, J. Kim, S. M. Hwang et al., Nucl. Fusion 40, 575 (2000)] to calculate the peak heat flux on the divertor plate and to explore the divertor plasma behavior depending on the upstream conditions in its base line operation mode for various values of input heating power and separatrix plasma density. The numerical modeling for the KSTAR tokamak shows that its full-powered operation is subject to the peak heat loads on the divertor plate exceeding an engineering limit, and reveals that the recycling zone is formed in front of the divertor by increasing plasma density and by reducing power flow into the scrape-off layer. Compared with other researchers' work, the present hybrid simulation more rigorously reproduces severe electron pressure losses along field lines by the presence of recycling zone accounting for the transitions between the sheath limited and the detached divertor regimes. The substantial profile changes in carbon impurity population and ionic composition also represent the key features of this divertor regime transition.

  11. A Concept of a Hybrid WDM/TDM Topology Using the Fabry-Perot Laser in the Optiwave Simulation Environment

    Directory of Open Access Journals (Sweden)

    Jan Skapa

    2011-01-01

    Full Text Available The aim of this article is to point out the possibility of solving problems related to a concept of a flexible hybrid optical access network. The entire topology design was realized using the OPTIWAVE development environment in which particular test measurements were carried out as well. Therefore, in the following chapters, we will subsequently focus on individual parts of the proposed topology and will give reasons for their functions whilst the last part of the article consists of values measured in the topology and their overall evaluation.

  12. Density Functional Theory Simulations of Semiconductors for Photovoltaic Applications: Hybrid Organic-Inorganic Perovskites and III/V Heterostructures

    Directory of Open Access Journals (Sweden)

    Jacky Even

    2014-01-01

    Full Text Available Potentialities of density functional theory (DFT based methodologies are explored for photovoltaic materials through the modeling of the structural and optoelectronic properties of semiconductor hybrid organic-inorganic perovskites and GaAs/GaP heterostructures. They show how the properties of these bulk materials, as well as atomistic relaxations, interfaces, and electronic band-lineups in small heterostructures, can be thoroughly investigated. Some limitations of available standard DFT codes are discussed. Recent improvements able to treat many-body effects or based on density-functional perturbation theory are also reviewed in the context of issues relevant to photovoltaic technologies.

  13. Effects of Concentration and Temperature on DNA Hybridization by Two Closely Related Sequences via Large-Scale Coarse-Grained Simulations.

    Science.gov (United States)

    Markegard, Cade B; Gallivan, Cameron P; Cheng, Darrell D; Nguyen, Hung D

    2016-08-18

    A newly developed coarse-grained model called BioModi is utilized to elucidate the effects of temperature and concentration on DNA hybridization in self-assembly. Large-scale simulations demonstrate that complementary strands of either the tetrablock sequence or randomized sequence with equivalent number of cytosine or guanine nucleotides can form completely hybridized double helices. Even though the end states are the same for the two sequences, there exist multiple kinetic pathways that are populated with a wider range of transient aggregates of different sizes in the system of random sequences compared to that of the tetrablock sequence. The ability of these aggregates to undergo the strand displacement mechanism to form only double helices depends upon the temperature and DNA concentration. On one hand, low temperatures and high concentrations drive the formation and enhance stability of large aggregating species. On the other hand, high temperatures destabilize base-pair interactions and large aggregates. There exists an optimal range of moderate temperatures and low concentrations that allow minimization of large aggregate formation and maximization of fully hybridized dimers. Such investigation on structural dynamics of aggregating species by two closely related sequences during the self-assembly process demonstrates the importance of sequence design in avoiding the formation of metastable species. Finally, from kinetic modeling of self-assembly dynamics, the activation energy for the formation of double helices was found to be in agreement with experimental results. The framework developed in this work can be applied to the future design of DNA nanostructures in both fields of structural DNA nanotechnology and dynamic DNA nanotechnology wherein equilibrium end states and nonequilibrium dynamics are equally important requiring investigation in cooperation. PMID:27447850

  14. 混合增压柴油机增压系统参数模拟计算研究%Numerical Simulation on Parameters of Hybrid Turbocharging System in Hybrid Turbocharged Diesel Engine

    Institute of Scientific and Technical Information of China (English)

    赵付舟; 常思勤; 韩国强

    2009-01-01

    该文优化调整模拟计算时确定的混合增压系统的参数,扩大了增压系统涡轮的流量,减小了高速电机功率,电机功率下降直接带来发动机的轻量化和增压器转动惯量的大幅减小.同时,涡轮流量的增加还提高了车用发动机在常用工况下的经济性和低速高负荷工况下的潜在动力性.与原废气旁通增压柴油机相比,参数调整后的混合增压柴油机减小了排气提前角调整不当对发动机燃油经济性的扰动.%The parameters of the hybrid turbocharging system are adjusted and optimised after simulation. The method is to magnify the flow rate of a turbine and decrease the power of a high-speed motor. Downsizing the motor can directly make the engine lightweight and greatly reduce the moment of inertia for the turbocharging system. Magnifying the flow rate of a turbine can not only reduce the BSFC (Brake specific fuel consumption ) in the frequent engine conditions , but also boost the potential of engine drivability in the low-speed and high-load condition. Compared with the original wastegated diesel engine, the adjusted hybrid turbocharged engine can minish the BSFC disturbance from the inappropriate advanced exhaust angle.

  15. A robust hybrid fuzzy-simulated annealing-intelligent water drops approach for tuning a distribution static compensator nonlinear controller in a distribution system

    Science.gov (United States)

    Bagheri Tolabi, Hajar; Hosseini, Rahil; Shakarami, Mahmoud Reza

    2016-06-01

    This article presents a novel hybrid optimization approach for a nonlinear controller of a distribution static compensator (DSTATCOM). The DSTATCOM is connected to a distribution system with the distributed generation units. The nonlinear control is based on partial feedback linearization. Two proportional-integral-derivative (PID) controllers regulate the voltage and track the output in this control system. In the conventional scheme, the trial-and-error method is used to determine the PID controller coefficients. This article uses a combination of a fuzzy system, simulated annealing (SA) and intelligent water drops (IWD) algorithms to optimize the parameters of the controllers. The obtained results reveal that the response of the optimized controlled system is effectively improved by finding a high-quality solution. The results confirm that using the tuning method based on the fuzzy-SA-IWD can significantly decrease the settling and rising times, the maximum overshoot and the steady-state error of the voltage step response of the DSTATCOM. The proposed hybrid tuning method for the partial feedback linearizing (PFL) controller achieved better regulation of the direct current voltage for the capacitor within the DSTATCOM. Furthermore, in the event of a fault the proposed controller tuned by the fuzzy-SA-IWD method showed better performance than the conventional controller or the PFL controller without optimization by the fuzzy-SA-IWD method with regard to both fault duration and clearing times.

  16. Characterization of a Solid Oxide Fuel Cell Gas Turbine Hybrid System Based on a Factorial Design of Experiments Using Hardware Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Restrepo, Bernardo; Banta, Larry E; Tucker, David

    2012-10-01

    A full factorial experimental design and a replicated fractional factorial design were carried out using the Hybrid Performance (HyPer) project facility installed at the National Energy Technology Laboratory (NETL), U.S. Department of Energy to simulate gasifer/fuel cell/turbine hybrid power systems. The HyPer facility uses hardware in the loop (HIL) technology that couples a modified recuperated gas turbine cycle with hardware driven by a solid oxide fuel cell model. A 34 full factorial design (FFD) was selected to study the effects of four factors: cold-air, hot-air, bleed-air bypass valves, and the electric load on different parameters such as cathode and turbine inlet temperatures, pressure and mass flow. The results obtained, compared with former results where the experiments were made using one-factor-at-a-time (OFAT), show that no strong interactions between the factors are present in the different parameters of the system. This work also presents a fractional factorial design (ffd) 34-2 in order to analyze replication of the experiments. In addition, a new envelope is described based on the results of the design of experiments (DoE), compared with OFAT experiments, and analyzed in an off-design integrated fuel cell/gas turbine framework. This paper describes the methodology, strategy, and results of these experiments that bring new knowledge concerning the operating state space for this kind of power generation system.

  17. Plasma beta dependence of the ion-scale spectral break of solar wind turbulence: high-resolution 2D hybrid simulations

    CERN Document Server

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

    2016-01-01

    We investigate properties of the ion-scale spectral break of solar wind turbulence by means of two-dimensional high-resolution hybrid particle-in-cell simulations. We impose an initial ambient magnetic field perpendicular to the simulation box and add a spectrum of in-plane, large-scale, magnetic and kinetic fluctuations. We perform a set of simulations with different values of the plasma beta, distributed over three orders of magnitude, from 0.01 to 10. In all the cases, once turbulence is fully developed, we observe a power-law spectrum of the fluctuating magnetic field on large scales (in the inertial range) with a spectral index close to -5/3, while in the sub-ion range we observe another power-law spectrum with a spectral index systematically varying with $\\beta$ (from around -3.6 for small values to around -2.9 for large ones). The two ranges are separated by a spectral break around ion scales. The length scale at which this transition occurs is found to be proportional to the ion inertial length, $d_i$...

  18. Numerical Simulation of P-Wave Propagation in Rock Mass with Granular Material-Filled Fractures Using Hybrid Continuum-Discrete Element Method

    Science.gov (United States)

    Gui, Y. L.; Zhao, Z. Y.; Zhou, H. Y.; Wu, W.

    2016-10-01

    In this paper, a cohesive fracture model is applied to model P-wave propagation through fractured rock mass using hybrid continuum-discrete element method, i.e. Universal Distinct Element Code (UDEC). First, a cohesive fracture model together with the background of UDEC is presented. The cohesive fracture model considers progressive failure of rock fracture rather than an abrupt damage through simultaneously taking into account the elastic, plastic and damage mechanisms as well as a modified failure function. Then, a series of laboratory tests from the literature on P-wave propagation through rock mass containing single fracture and two parallel fractures are introduced and the numerical models used to simulate these laboratory tests are described. After that, all the laboratory tests are simulated and presented. The results show that the proposed model, particularly the cohesive fracture model, can capture very well the wave propagation characteristics in rock mass with non-welded and welded fractures with and without filling materials. In the meantime, in order to identify the significance of fracture on wave propagation, filling materials with different particle sizes and the fracture thickness are discussed. Both factors are found to be crucial for wave attenuation. The simulations also show that the frequency of transmission wave is lowered after propagating through fractures. In addition, the developed numerical scheme is applied to two-dimensional wave propagation in the rock mass.

  19. A Hybrid Genetic-Simulated Annealing Algorithm for the Location-Inventory-Routing Problem Considering Returns under E-Supply Chain Environment

    Directory of Open Access Journals (Sweden)

    Yanhui Li

    2013-01-01

    Full Text Available Facility location, inventory control, and vehicle routes scheduling are critical and highly related problems in the design of logistics system for e-business. Meanwhile, the return ratio in Internet sales was significantly higher than in the traditional business. Many of returned merchandise have no quality defects, which can reenter sales channels just after a simple repackaging process. Focusing on the existing problem in e-commerce logistics system, we formulate a location-inventory-routing problem model with no quality defects returns. To solve this NP-hard problem, an effective hybrid genetic simulated annealing algorithm (HGSAA is proposed. Results of numerical examples show that HGSAA outperforms GA on computing time, optimal solution, and computing stability. The proposed model is very useful to help managers make the right decisions under e-supply chain environment.

  20. A hybrid genetic-simulated annealing algorithm for the location-inventory-routing problem considering returns under e-supply chain environment.

    Science.gov (United States)

    Li, Yanhui; Guo, Hao; Wang, Lin; Fu, Jing

    2013-01-01

    Facility location, inventory control, and vehicle routes scheduling are critical and highly related problems in the design of logistics system for e-business. Meanwhile, the return ratio in Internet sales was significantly higher than in the traditional business. Many of returned merchandise have no quality defects, which can reenter sales channels just after a simple repackaging process. Focusing on the existing problem in e-commerce logistics system, we formulate a location-inventory-routing problem model with no quality defects returns. To solve this NP-hard problem, an effective hybrid genetic simulated annealing algorithm (HGSAA) is proposed. Results of numerical examples show that HGSAA outperforms GA on computing time, optimal solution, and computing stability. The proposed model is very useful to help managers make the right decisions under e-supply chain environment.

  1. Moderate Humidity Delays Electron-Hole Recombination in Hybrid Organic-Inorganic Perovskites: Time-Domain Ab Initio Simulations Rationalize Experiments.

    Science.gov (United States)

    Long, Run; Fang, Weihai; Prezhdo, Oleg V

    2016-08-18

    Experiments show both positive and negative changes in performance of hybrid organic-inorganic perovskite solar cells upon exposure to moisture. Ab initio nonadiabatic molecular dynamics reveals the influence of humidity on nonradiative electron-hole recombination. In small amounts, water molecules perturb perovskite surface and localize photoexcited electron close to the surface. Importantly, deep electron traps are avoided. The electron-hole overlap decreases, and the excited state lifetime increases. In large amounts, water forms stable hydrogen-bonded networks, has a higher barrier to enter perovskite, and produces little impact on charge localization. At the same time, by contributing high frequency polar vibrations, water molecules increase nonadiabatic coupling and accelerate recombination. In general, short coherence between electron and hole benefits photovoltaic response of the perovskites. The calculated recombination time scales show excellent agreement with experiment. The time-domain atomistic simulations reveal the microscopic effects of humidity on perovskite excited-state lifetimes and rationalize the conflicting experimental observations. PMID:27485025

  2. A hybrid genetic-simulated annealing algorithm for the location-inventory-routing problem considering returns under e-supply chain environment.

    Science.gov (United States)

    Li, Yanhui; Guo, Hao; Wang, Lin; Fu, Jing

    2013-01-01

    Facility location, inventory control, and vehicle routes scheduling are critical and highly related problems in the design of logistics system for e-business. Meanwhile, the return ratio in Internet sales was significantly higher than in the traditional business. Many of returned merchandise have no quality defects, which can reenter sales channels just after a simple repackaging process. Focusing on the existing problem in e-commerce logistics system, we formulate a location-inventory-routing problem model with no quality defects returns. To solve this NP-hard problem, an effective hybrid genetic simulated annealing algorithm (HGSAA) is proposed. Results of numerical examples show that HGSAA outperforms GA on computing time, optimal solution, and computing stability. The proposed model is very useful to help managers make the right decisions under e-supply chain environment. PMID:24489489

  3. Numerical simulations of nanodiamond nitrogen-vacancy centers coupled with tapered optical fibers as hybrid quantum nanophotonic devices.

    Science.gov (United States)

    Almokhtar, Mohamed; Fujiwara, Masazumi; Takashima, Hideaki; Takeuchi, Shigeki

    2014-08-25

    Tapered optical fibers are promising one-dimensional nanophotonic waveguides that can provide efficient coupling between their fundamental mode and quantum nanoemitters placed inside them. Here, we present numerical studies on the coupling of single nitrogen-vacancy (NV) centers (single point dipoles) in nanodiamonds with tapered fibers. Our results lead to two important conclusions: (1) A maximum coupling efficiency of 53.4% can be realized for the two fiber ends when the NV bare dipole is located at the center of the tapered fiber. (2) NV centers even in 100-nm-sized nanodiamonds where bulk-like optical properties were reported show a coupling efficiency of 22% at the taper surface, with the coupling efficiency monotonically decreasing as the nanodiamond size increases. These results will be helpful in guiding the development of hybrid quantum devices for applications in quantum information science. PMID:25321215

  4. Titan's plasma environment during a magnetosheath excursion: Real-time scenarios for Cassini's T32 flyby from a hybrid simulation

    Directory of Open Access Journals (Sweden)

    S. Simon

    2009-02-01

    Full Text Available With a Saturnian magnetopause average stand-off distance of about 21 planetary radii, Titan spends most of its time inside the rotating magnetosphere of its parent planet. However, when Saturn's magnetosphere is compressed due to high solar wind dynamic pressure, Titan can cross Saturn's magnetopause in the subsolar region of its orbit and therefore to interact with the shocked solar wind plasma in Saturn's magnetosheath. This situation has been observed during the T32 flyby of the Cassini spacecraft on 13 June 2007. Until a few minutes before closest approach, Titan had been located inside the Saturnian magnetosphere. During the flyby, Titan encountered a sudden change in the direction and magnitude of the ambient magnetic field. The density of the ambient plasma also increased dramatically during the pass. Thus, the moon's exosphere and ionosphere were exposed to a sudden change in the upstream plasma conditions. The resulting reconfiguration of Titan's plasma tail has been studied in real-time by using a three-dimensional, multi-species hybrid simulation model. The hybrid approximation treats the electrons of the plasma as a massless, charge-neutralizing fluid, while ion dynamics are described by a kinetic approach. In the simulations, the magnetopause crossing is modeled by a sudden change of the upstream magnetic field vector as well as a modification of the upstream plasma composition. We present real-time simulation results, illustrating how Titan's induced magnetotail is reconfigured due to magnetic reconnection. The simulations allow to determine a characteristic time scale for the erosion of the original magnetic draping pattern that commences after Titan has crossed Saturn's magnetopause. Besides, the influence of the plasma composition in the magnetosheath on the reconfiguration process is discussed in detail. The question of whether the magnetopause crossing is likely to yield a detachment of Titan

  5. Hybrid deterministic and stochastic x-ray transport simulation for transmission computed tomography with advanced detector noise model

    Science.gov (United States)

    Popescu, Lucretiu M.

    2016-03-01

    We present a model for simulation of noisy X-ray computed tomography data sets. The model is made of two main components, a photon transport simulation component that generates the noiseless photon field incident on the detector, and a detector response model that takes as input the incident photon field parameters and given the X-ray source intensity and exposure time can generate noisy data sets, accordingly. The photon transport simulation component combines direct ray-tracing of polychromatic X-rays for calculation of transmitted data, with Monte Carlo simulation for calculation of the scattered-photon data. The Monte Carlo scatter simulation is accelerated by implementing particle splitting and importance sampling variance reduction techniques. The detector-incident photon field data are stored as energy expansion coefficients on a refined grid that covers the detector area. From these data the detector response model is able to generate noisy detector data realizations, by reconstituting the main parameters that describe each detector element response in statistical terms, including spatial correlations. The model is able to generate very fast, on the fly, CT data sets corresponding to different radiation doses, as well as detector response characteristics, facilitating data management in extensive optimization studies by reducing the computation time and storage space demands.

  6. Simplifications of Simulation on Energy Balances and Estimations of a Hybrid Renewable Energy System for Use in Cold Climate Regions

    Science.gov (United States)

    Akpan, Itoro Etim; Sasaki, Masafumi; Endoh, Noboru

    A simplified double grade meteorological data model for the simulation of the annual performance of a domestic-size renewable energy system is proposed. With the model, only two representative days (clearest and cloudiest) during each season of the year are necessary to estimate annual energy balances, carbon emissions and the running costs. The model was chosen in preference to other simplified models based on the error distributions from the results of the continuous simulations in a test period. Detailed numerical simulation studies show that the carbon emissions from the renewable energy system are about 16%of a comparable conventional system. The thermal energy produced by a solar collector during the winter season, however, is insufficient to meet all the loads so that frequent heat pump operations and the auxiliary boiler are necessary in cold climate regions.

  7. A Phenomenological Heat Transfer Model of SI Engines – Application to the Simulation of a Full-Hybrid Vehicle Un modèle phénoménologique de transfert thermique au sein de moteurs à allumage commandé — Application à la simulation d’un véhicule full-hybride

    Directory of Open Access Journals (Sweden)

    Dubouil R.

    2013-02-01

    Full Text Available A hybrid thermal-electric vehicle allows some significant fuel economy due to its peculiar use of the Internal Combustion Engine (ICE that runs with better efficiency. However, this propulsion system impacts its thermal behaviour, especially during its warm-up after a cold start. The ICE can indeed be shut down when the vehicle is stopped (Stop&Start system and during full-electric propulsion mode (allowed at light speed and load if the battery state of charge is high enough resulting in a lack of heat source and a slow down of the warm-up. Moreover, the use of the ICE at higher loads while charging the batteries provides an increase of the heating power generated by the combustion. Control strategies in a hybrid vehicle (energy repartition between the two propulsions: thermal and electric have a significant effect on its final consumption. Therefore, the simulation of hybrid vehicles is then useful to evaluate the efficiency of these strategies. However, the consideration of the warm-up of the ICE in such a propulsion system was done in only few published studies. A simulation tool using the Amesim software has been developed in order to simulate the warm-up of an ICE used in a hybrid parallel propulsion system. The corresponding model is developed in order to take into account the thermal phenomena occurring between the different ICE components. Thus, a thermodynamic model is coupled with a thermal model of the metallic parts and the different fluid loops (water and oil. Their mean temperature dependence with different parameters like speed, the load, the cylinder geometry and the spark advance, is studied with the aim at reducing fuel consumption. The thermal model of the engine is finally integrated in a simulation of the whole vehicle. The thermal behaviour of a parallel electric full-hybrid vehicle using a spark ignition engine is then presented using this simulation tool. The simulation results show the impact of the peculiar use of the

  8. Simulation and Performance Analysis of Lithium Battery Bank Mounted on the Hybrid Power System for Mobile Public Health Center

    Science.gov (United States)

    Busono, Pratondo; Kartini, Evvy

    2013-07-01

    Mobile medical clinic has been proposed to serve homeless people, people in the disaster area or in the remote area where no health service exist. At that site, a number of essential services such as primary health care, general health screening, medical treatment and emergency/rescue operations are required. Such services usually requires on board electrical equipments such as refrigerators, komputer, power tools and medical equipments. To supply such electrical equipments, it needs extra auxiliary power sources, in addition of standard automotive power supply. The auxiliary power source specifically design to supply non automotive load which may have similar configuration, but usually uses high power alternator rated and larger deep cycle on board battery bank. This study covers the modeling and dynamic simulation of auxiliary power source/battery to supply the medical equipment and other electrical equipments on board. It consists a variable speed diesel generator set, photovoltaic (PV) generator mounted on the roof of the car, a rechargable battery bank. As an initial step in the system design, a simulation study was performed. The simulation is conducted in the system level. Simulation results shows that dynamical behaviour by means of current density, voltage and power plot over a chosen time range, and functional behaviour such as charging and discharging characteristic of the battery bank can be obtained.

  9. A hybrid simulated method for analyzing the optical efficiency of a head-mounted display with a quasi-crystal OLED panel.

    Science.gov (United States)

    Chang, Kao-Der; Li, Chang-Yi; Pan, Jui-Wen; Cheng, Kuei-Yuan

    2014-03-10

    Organic light emitting diodes (OLEDs) with a quasi-crystal (QC) structure are analyzed and applied in a head-mounted display (HMD) system in this study. We adopt a hybrid simulated method to evaluate the light extraction efficiency (LEE) and far-field pattern in the air, and study the relationship between them. The simulation results show that OLEDs implanted with the QC structure can provide a collimated far-field pattern to increase the brightness. Using this 10-fold QC arrangement the maxima LEE of the OLEDs can be increased by 1.20 times. Compared with conventional OLEDs, the viewing angle of the OLED panel decreases from 120 degrees to 26 degrees with an improvement in the optical efficiency of the HMD system by 2.66 times. Moreover, the normalized on-axis intensity in the pupil of the eyepiece can be enlarged up to 3.95 times which suggests that the OLED panel can save 74.68% energy while achieving the same on-axis intensity as conventional OLEDs. PMID:24922267

  10. Software Development of Kinematics Simulation for PRS- XY Hybrid Machining Tool%PRS-XY混联数控机床运动学仿真件开发

    Institute of Scientific and Technical Information of China (English)

    孙宏昌; 戴怡; 李丽娜; 张建民; 罗奕

    2011-01-01

    Based on the architectural charactefistics of the hybrid machine tool, the kinnemtics model of the machine is given as well as the forward and reverse mathematical solution process. Both the real-time nachine molel and rite kinematics simutlation are finished by OpenGL with Visual C ++ within thc Windows. By the simulation soft, the mechanism of the machine can be shoown and the manufacture progress can be simulated with the interference checkout. The safety and the rationality of the trace planning can be guaranteed for the practical cutting.%根据PRS-XY型混联机床结构特点构建机床运动学模型,介绍了其运动的逆解和正解过程.在Windows环境下,应用Visual C++6.0调用OpenGL实现了该机床的实体建模和运动学仿真.运动学仿真软件能够实时显示出机床机构形态、模拟出混联数控机床的加工运动过程,可实现并联机构干涉校验,进而保证加工轨迹规划的合理性、安全性,为混联机床的安全加工提供保障.

  11. Hybrid Particle-In-Cell (PIC) simulation of heat transfer and ionization balance in overdense plasmas irradiated by subpicosecond pulse lasers

    Energy Technology Data Exchange (ETDEWEB)

    Zhidkov, A.; Sasaki, Akira [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment

    1998-11-01

    A 1D hybrid electromagnetic particle-in-cell code with new methods to include particle collisions and atomic kinetics is developed and applied to ultra-short-pulse laser plasma interaction. Using the Langevin equation to calculate the Coulomb collision term, the present code is shown to be fast and stable in calculating the particle motion in the PIC simulation. Furthermore, by noting that the scale length of the change of atomic kinetics is much longer than the Debye radius, we calculate ionization and X-ray emission on kinetics cells, which are determined by averaging plasma parameters such as the electron density and energy over number of PIC cells. The absorption of short-pulse laser by overdense plasmas is calculated in self-consistent manner, including the effect of rapid change of density and temperature caused by instantaneous heating and successive fast ionization of the target material. The calculated results agree well with those obtained from the Fokker-Planck simulation as well as experiments, for non-local heat transport in plasmas with steep temperature gradient, and for the absorption of a short laser pulse by solid density targets. These results demonstrate usefulness of the code and the computational method therein for understanding of physics of short pulse laser plasma interaction experiments, and for application to the gain calculation of short-pulse laser excited X-ray laser as well. (author)

  12. HYBRID Simulations of Diffraction-Limited Focusing with Kirkpatrick-Baez Mirrors for a Next-Generation In Situ Hard X-ray Nanoprobe

    Science.gov (United States)

    Maser, Jörg; Shi, Xianbo; Reininger, Ruben; Lai, Barry; Vogt, Stefan

    2016-02-01

    Next-generation hard X-ray nanoprobe beamlines such as the In Situ Nanoprobe (ISN) beamline being planned at the Advanced Photon Source aim at providing very high spatial resolution while also enabling very high focused flux, to study complex materials and devices using fast, multidimensional imaging across many length scales. The ISN will use diffractive optics to focus X-rays with a bandpass of ∆E/E = 10-4 into a focal spot of 20 nm or below. Reflective optics in Kirkpatrick-Baez geometry will be used to focus X-rays with a bandpass as large as ∆E/E = 10-2 into a focal spot of 50 nm. Diffraction-limited focusing with reflective optics is achieved by spatial filtering and use of a very long, vertically focusing mirror. To quantify the performance of the ISN beamline, we have simulated the propagation of both partially and fully coherent wavefronts from the undulator source, through the ISN beamline and into the mirror-based focal spot. Simulations were carried out using the recently developed software "HYBRID."

  13. Proton heating by pick-up ion driven cyclotron waves in the outer heliosphere: Hybrid expanding box simulations

    CERN Document Server

    Hellinger, Petr

    2016-01-01

    Using one-dimensional hybrid expanding box model we investigate properties of the solar wind in the outer heliosphere. We assume a proton-electron plasma with a strictly transverse ambient magnetic field and, beside the expansion, we take into account influence of a continuous injection of cold pick-up protons through the charge-exchange process between the solar wind protons and hydrogen of interstellar origin. The injected cold pick-up protons form a ring distribution function that rapidly becomes unstable and generate Alfv\\'en cyclotron waves. The Alfv\\'en cyclotron waves scatter pick-up protons to a spherical shell distribution function that thickens over that time owing to the expansion-driven cooling. The Alf\\'ven cyclotron waves heat solar wind protons in the perpendicular direction (with respect to the ambient magnetic field) through the cyclotron resonance. At later times, the Alfv\\'en cyclotron waves become parametrically unstable and the generated ion acoustic waves heat protons in the parallel dir...

  14. Design and simulation of a fast-charging station for plug-in hybrid electric vehicle (PHEV) batteries

    Science.gov (United States)

    de Leon, Nathalie Pulmones

    2011-12-01

    With the increasing interest in green technologies in transportation, plug-in hybrid electric vehicles (PHEV) have proven to be the best short-term solution to minimize greenhouse gas emissions. Despite such interest, conventional vehicle drivers are still reluctant in using such a new technology, mainly because of the long duration (4-8 hours) required to charge PHEV batteries with the currently existing Level I and II chargers. For this reason, Level III fast-charging stations capable of reducing the charging duration to 10-15 minutes are being considered. The present thesis focuses on the design of a fast-charging station that uses, in addition to the electrical grid, two stationary energy storage devices: a flywheel energy storage and a supercapacitor. The power electronic converters used for the interface of the energy sources with the charging station are designed. The design also focuses on the energy management that will minimize the PHEV battery charging duration as well as the duration required to recharge the energy storage devices. For this reason, an algorithm that minimizes durations along with its mathematical formulation is proposed, and its application in fast charging environment will be illustrated by means of two scenarios.

  15. Hybrid Upwind Discretization for the Implicit Simulation of Three-Phase Coupled Flow and Transport with Gravity

    Science.gov (United States)

    Hamon, F. P.; Mallison, B.; Tchelepi, H.

    2015-12-01

    The systems of algebraic equations arising from implicit (backward-Euler) finite-volume discretization of the conservation laws governing multiphase flow in porous media are quite challenging for nonlinear solvers. In the presence of counter-current flow due to buoyancy, the coupling between flow (pressure) and transport (saturations) is often the cause of nonlinear problems when single-point Phase-Potential Upwinding (PPU) is used. To overcome such convergence problems in practice, the time step is reduced and Newton's method is restarted from the solution at the previous converged time step. Here, we generalize the work of Lee, Efendiev and Tchelepi [Advances in Water Resources, 2015] to propose an Implicit Hybrid Upwinding (IHU) scheme for coupled flow and transport. In the pure transport problem, we show that the numerical flux obtained with IHU is differentiable, monotone and consistent for two and three-phase flow. For coupled flow and transport, we prove saturation physical bounds as well as the existence of a solution to our scheme. Challenging two- and three-phase heterogeneous multi-dimensional numerical tests confirm that the new scheme is non-oscillatory and convergent, and illustrate the superior convergence rate of our IHU-based Newton solver for large time steps.

  16. Unsteady Three-Dimensional Simulation of a Shear Coaxial GO2/GH2 Rocket Injector with RANS and Hybrid-RAN-LES/DES Using Flamelet Models

    Science.gov (United States)

    Westra, Doug G.; West, Jeffrey S.; Richardson, Brian R.

    2015-01-01

    Hybrid RANSLES/ Detached Eddy simulations (DES). Computation costs will be reported, along with comparison of accuracy and cost to much less expensive two-dimensional RANS simulations of the same geometry.

  17. A Selective Review of Simulated Driving Studies: Combining Naturalistic and Hybrid Paradigms, Analysis Approaches, and Future Directions

    OpenAIRE

    Calhoun, V D; Pearlson, G.D.

    2011-01-01

    Naturalistic paradigms such as movie watching or simulated driving that mimic closely real-world complex activities are becoming more widely used in functional magnetic resonance imaging (fMRI) studies both because of their ability to robustly stimulate brain connectivity and the availability of analysis methods which are able to capitalize on connectivity within and among intrinsic brain networks identified both during a task and in resting fMRI data. In this paper we review over a decade of...

  18. Investigation of Francis Turbine Part Load Instabilities using Flow Simulations with a Hybrid RANS-LES Turbulence Model

    International Nuclear Information System (INIS)

    The operation of Francis turbines in part load condition causes high pressure fluctuations and dynamic loads in the turbine as well as high flow losses in the draft tube. Owing to the co-rotating velocity distribution at the runner blade trailing edge a low pressure zone arises in the hub region finally leading to a rotating vortex rope in the draft tube. A better understanding and a more accurate prediction of this phenomenon can help in the design process of a Francis turbine. The goal of this study is to reach a quantitatively better numerical prediction of the flow at part load and to evaluate the necessary numerical depth with respect to effort and benefit. As standard practice, simulation results are obtained for the steady state approach with SST turbulence modelling. Those results are contrasted with transient simulations applying a SST as well as a SAS (Scale Adaptive Simulation) turbulence model. The structure of the SAS model is such, that it is able to resolve the turbulent flow behaviour in more detail. The investigations contain a comparison of the flow losses in different turbine components. A detailed flow evaluation is done in the cone and the diffuser of the draft tube. The different numerical approaches show a different representation of the vortex rope phenomenon indicating differences in pressure pulsations at different geometric positions in the entire turbine. Finally, the turbulent flow structures in the draft tube are illustrated with several evaluation methods, such as turbulent eddy viscosity, velocity invariant and turbulent kinetic energy spectra

  19. Simple pair-wise interactions for hybrid Monte Carlo-molecular dynamics simulations of titania/yttria-doped iron.

    Science.gov (United States)

    Hammond, Karl D; Voigt, Hyon-Jee Lee; Marus, Lauren A; Juslin, Niklas; Wirth, Brian D

    2013-02-01

    We present pair-wise, charge-neutral model potentials for an iron-titanium-yttrium-oxygen system. These simple models are designed to provide a tractable method of simulating nanostructured ferritic alloys (NFAs) using off-lattice Monte Carlo and molecular dynamics techniques without deviating significantly from the formalism employed in existing Monte Carlo simulations. The model is fitted to diamagnetic density functional theory (DFT) calculations of the various species over a range of densities and concentrations. The resulting model potentials provide reasonable and in some cases even excellent mechanical and thermodynamic properties for the pure metals. The model replicates the qualitative trends in formation energy predicted by DFT, though the energies of formation do not agree as well for dilute systems as they do for more concentrated systems. We find that on-lattice models will consistently favor tetrahedral oxygen interstitial sites over octahedral interstitial sites, while relaxed systems typically favor octahedral sites. This emphasizes the need for the off-lattice simulations for which this potential was designed. PMID:23288578

  20. Investigation of Francis Turbine Part Load Instabilities using Flow Simulations with a Hybrid RANS-LES Turbulence Model

    Science.gov (United States)

    Krappel, Timo; Ruprecht, Albert; Riedelbauch, Stefan; Jester-Zuerker, Roland; Jung, Alexander

    2014-03-01

    The operation of Francis turbines in part load condition causes high pressure fluctuations and dynamic loads in the turbine as well as high flow losses in the draft tube. Owing to the co-rotating velocity distribution at the runner blade trailing edge a low pressure zone arises in the hub region finally leading to a rotating vortex rope in the draft tube. A better understanding and a more accurate prediction of this phenomenon can help in the design process of a Francis turbine. The goal of this study is to reach a quantitatively better numerical prediction of the flow at part load and to evaluate the necessary numerical depth with respect to effort and benefit. As standard practice, simulation results are obtained for the steady state approach with SST turbulence modelling. Those results are contrasted with transient simulations applying a SST as well as a SAS (Scale Adaptive Simulation) turbulence model. The structure of the SAS model is such, that it is able to resolve the turbulent flow behaviour in more detail. The investigations contain a comparison of the flow losses in different turbine components. A detailed flow evaluation is done in the cone and the diffuser of the draft tube. The different numerical approaches show a different representation of the vortex rope phenomenon indicating differences in pressure pulsations at different geometric positions in the entire turbine. Finally, the turbulent flow structures in the draft tube are illustrated with several evaluation methods, such as turbulent eddy viscosity, velocity invariant and turbulent kinetic energy spectra.