High performance computer (HPC) is a complex huge system, of which the architecture design meets increasing difficulties and risks. Traditional methods, such as theoretical analysis, component-level simulation and s...High performance computer (HPC) is a complex huge system, of which the architecture design meets increasing difficulties and risks. Traditional methods, such as theoretical analysis, component-level simulation and sequential simulation, are not applicable to system-level simulations of HPC systems. Even the parallel simulation using large-scale parallel machines also have many difficulties in scalability, reliability, generality, as well as efficiency. According to the current needs of HPC architecture design, this paper proposes a system-level parallel simulation platform: ArchSim. We first introduce the architecture of ArchSim simulation platform which is composed of a global server (GS), local server agents (LSA) and entities. Secondly, we emphasize some key techniques of ArchSim, including the synchronization protocol, the communication mechanism and the distributed checkpointingestart mechanism. We then make a synthesized test of some main performance indices of ArchSim with the phold benchmark and analyze the extra overhead generated by ArchSim. Finally, based on ArchSim, we construct a parallel event-driven interconnection network simulator and a system-level simulator for a small scale HPC system with 256 processors. The results of the performance test and HPC system simulations demonstrate that ArchSim can achieve high speedup ratio and high scalability on parallel host machine and support system-level simulations for the architecture design of HPC systems.展开更多
Reasonable use of mathematical modeling and numerical simulation of regional earthquake activities has attracted more and more attentions in realistic seismicity studies in recent years.The inherent nature of their at...Reasonable use of mathematical modeling and numerical simulation of regional earthquake activities has attracted more and more attentions in realistic seismicity studies in recent years.The inherent nature of their attendant multi-scale properties,from either the temporal or the spatial direction,necessitates the use of the cutting-edge massive parallel data processing techniques.Our study here is focused on the model construction and numerical simulation of the regional stress evolution after large earthquake sequences along the fault zones in Sichuan and Yunnan areas,using large-scale parallel finite element approximations with tens of millions of unstructured meshes on the distributed systems.The objective of our study is to provide a state-of-the-art model and a large-scale numerical simulation platform,on which estimation of the risk of large earthquake triggering sequences can be carried out in a middle or long-term time scale with realistic data and constrains inputted from field observation and geological survey.展开更多
Parallel calculational methods were used to analyze incompressible turbulent flow through hydraulic machinery. Two parallel methods were used to simulate the complex flow field. The space decomposition method divides ...Parallel calculational methods were used to analyze incompressible turbulent flow through hydraulic machinery. Two parallel methods were used to simulate the complex flow field. The space decomposition method divides the computational domain into several sub-ranges. Parallel discrete event simulation divides the whole task into several parts according to their functions. The simulation results were compared with the serial simulation results and particle image velocimetry (PIV) experimental results. The results give the distribution and configuration of the complex vortices and illustrate the effectiveness of the parallel algorithms for numerical simulation of turbulent flows.展开更多
Large-scale artificial societies with millions or billions of agents call for high-performance parallel simulation.Prevailing supercomputers with thousands of CPUs and GPUs make it possible to carry out such simulatio...Large-scale artificial societies with millions or billions of agents call for high-performance parallel simulation.Prevailing supercomputers with thousands of CPUs and GPUs make it possible to carry out such simulation.The key is to distribute large-scale agents to massive cores of CPUs and GPUs properly for parallel computing with efficient communication and synchronization.For simplicity and efficiency,a modified discrete event system specification(DEVS)is proposed for large-scale artificial society modeling and parallelism is exploited in agent models because similar agents usually share similar behaviors.Through phased synchronization,a two-tier parallel simulation engine is designed with support of MPI and OpenCL where GPU is used as coprocessor.One-sided communication is used for reflection of remote simulation objects and message passing between processes.A general kernel function prototype is elaborately designed and conditionally compiled for execution on both CPU and GPU.An artificial society for epidemic study is used to test the performance on a supercomputer with 1024 CPU cores and 1792 GPU cores.The speedup reaches 3512 for even 2 billion agents with GPU acceleration which is far over 701 when only CPUs are used.It turns out feasible for parallel simulation of large-scale artificial society with GPU as coprocessor.展开更多
In this paper, a parallel simulation algorithm for the control problem in differential algebraic system is presented. The error of the algorithm is estimated. The stability analysis is made for a model problem and the...In this paper, a parallel simulation algorithm for the control problem in differential algebraic system is presented. The error of the algorithm is estimated. The stability analysis is made for a model problem and the stability region is given. The numerical example demonstrates that the method is efficient.展开更多
This paper is concerned with three-dimensional numerical simulation of a plunging liquid jet. The transient processes of forming an air cavity around the jet, capturing an initially large air bubble, and the break-up ...This paper is concerned with three-dimensional numerical simulation of a plunging liquid jet. The transient processes of forming an air cavity around the jet, capturing an initially large air bubble, and the break-up of this large toroidal-shaped bubble into smaller bubbles were analyzed. A stabilized finite element method (FEM) was employed under parallel numerical simulations based on adaptive, unstructured grid and coupled with a level-set method to track the interface between air and liquid. These simulations show that the inertia of the liquid jet initially depresses the pool's surface, forming an annular air cavity which surrounds the liquid jet. A toroidal liquid eddy which is subse- quently formed in the liquid pool results in air cavity collapse, and in turn entrains air into the liquid pool from the unstable annular air gap region around the liquid jet.展开更多
Low-Earth-Orbit satellite constellation networks(LEO-SCN)can provide low-cost,largescale,flexible coverage wireless communication services.High dynamics and large topological sizes characterize LEO-SCN.Protocol develo...Low-Earth-Orbit satellite constellation networks(LEO-SCN)can provide low-cost,largescale,flexible coverage wireless communication services.High dynamics and large topological sizes characterize LEO-SCN.Protocol development and application testing of LEO-SCN are challenging to carry out in a natural environment.Simulation platforms are a more effective means of technology demonstration.Currently available simulators have a single function and limited simulation scale.There needs to be a simulator for full-featured simulation.In this paper,we apply the parallel discrete-event simulation technique to the simulation of LEO-SCN to support large-scale complex system simulation at the packet level.To solve the problem that single-process programs cannot cope with complex simulations containing numerous entities,we propose a parallel mechanism and algorithms LP-NM and LP-YAWNS for synchronization.In the experiment,we use ns-3 to verify the acceleration ratio and efficiency of the above algorithms.The results show that our proposed mechanism can provide parallel simulation engine support for the LEO-SCN.展开更多
In this paper, a homogenous parallel simulation system is presented in detail for continuous--system simulation. The system is collstructed by a host computer and I I transputers connected into a topologyof 'Super...In this paper, a homogenous parallel simulation system is presented in detail for continuous--system simulation. The system is collstructed by a host computer and I I transputers connected into a topologyof 'Super--Node' which is very suitable for simulation of stiff systems. An automatic software interface runin the host is developed to partition simulation model, either equations or block diagrams, into several equitable segments and then pack them into parallel simulation program to be executed in the parallel system.This interface frees simulation users from parallel programming to focus on their simulation experiments.展开更多
By performing one-dimensional (l-D) hybrid simulations, we analyze in detail the parametric instabilities of the Alfv^n waves with a spectrum in a low beta plasma. The parametric instabilities experience two stages....By performing one-dimensional (l-D) hybrid simulations, we analyze in detail the parametric instabilities of the Alfv^n waves with a spectrum in a low beta plasma. The parametric instabilities experience two stages. In the first stage, the density modes are excited and immediately couple with the pump Alfv6n waves. In the second stage, each pump Alfv^n wave decays into a density mode and a daughter Alfv6n mode similar to the monochromatic cases. Ftlrthermore, the proton velocity beam will also be formed after the saturation of the parametric instabilities. When the plasma beta is high, the parametric decay in the second stage will be strongly suppressed.展开更多
The authors developed a 3-D numerical injection model on parallel TOUGH2-FLAC3 D based on the site-specific stratigraphic information in Ordos Basin to simulate the Shenhua CO_2 geological storage( CGS)demonstration p...The authors developed a 3-D numerical injection model on parallel TOUGH2-FLAC3 D based on the site-specific stratigraphic information in Ordos Basin to simulate the Shenhua CO_2 geological storage( CGS)demonstration project injection process for three years and forecast CO_2 migration and layers displacement after injection for seven years. The results suggested that CO_2 migration did not stop after three years of consecutive injection,but migration rate was slowing down with time. As a result,displacement near injection well increased with injection and decreased slowly after injection. The maximum displacement of surface center occurred near the end of injection,which was only 1. 24 cm. According to the displacement result,it is safe to continue injecting for this project.展开更多
This paper first provides a brief introduction to a numerical reservoir simulation and a parallel numerical reservoir integrated simulation platform developed by RDCPS (Research & Development Center for Parallel Sof...This paper first provides a brief introduction to a numerical reservoir simulation and a parallel numerical reservoir integrated simulation platform developed by RDCPS (Research & Development Center for Parallel Software, Institute of Software, Chinese Academy of Sciences), which includes Pre-Processing, Simulator (for a Three-Dimensional & Three-Phase Black-Oil models), Post Processing, seamlessly integrated with parallel computers. We then present key technologies of the simulator, such as nonlinear and linear solvers, communications among processors, parallel I/O, etc., and corresponding content. Finally, some results of the platform to solve one million grid blocks cases from Chinese oil fields are given in the paper, which can show that the simulator has a very robust portability, high-speed for deadline and good scalability for the tested cases. As one of the application softwares, its objective is always focusing on satisfying deadlines of oil industry. Now, for one million grid blocks' case with 20 - 30 year-production, its elapsed time with 16 processors is less than 12 hours on parallel computers based on Myrinet or QsNet, namely 'to submit a case just before off-duty and get its result just before on-duty'. A decreasing line of elapsed time is given for a case with one million grid blocks. The developing trace of the simulator along with parallel computers can be also inferred from the line.展开更多
The distribution and amount of ground ice on Mars is an important issue to be addressed for the future exploration of the planet.The occurrence of interstitial ice in Martian frozen ground is indicated by landforms,su...The distribution and amount of ground ice on Mars is an important issue to be addressed for the future exploration of the planet.The occurrence of interstitial ice in Martian frozen ground is indicated by landforms,such as fluidized ejecta craters,softened terrain,and fretted channels.How-ever,experimental data on the rheology of ice-rock mixture under Martian physical conditions are sparse,and the amount of ground ice that is required to produce the viscous deformation observed in Martian ice-related landforms is still unknown.In our study,we put forward a three-dimensional non-Newtonian viscous finite element model to investigate the behavior of ice-rock mixtures numeri-cally.The randomly distributed tetrahedral elements are generated in regular domain to represent the natural distribution of ice-rock materials.Numerical simulation results show that when the volume of rock is less than 40%,the rheology of the mixture is dominated by ice,and there is occurrence of a brittle-ductile transition when ice fraction reaches a certain value.Our preliminary results contribute to the knowledge of the determination of the rheology and ice content in Martian ice-rock mixture.The presented model can also be utilized to evaluate the amount of ground ice on Mars.展开更多
Mega-constellation networks have recently gained significant research attention because of their potential for providing ubiquitous and high-capacity connectivity in future sixth-generation(6G)wireless communication s...Mega-constellation networks have recently gained significant research attention because of their potential for providing ubiquitous and high-capacity connectivity in future sixth-generation(6G)wireless communication systems.However,the high dynamics of network topology and large scale of a megaconstellation pose new challenges to constellation simulation and performance evaluation.To address these issues,we introduce Ultra Star,a high-fidelity and high-efficiency computer simulator to support the development of 6G wireless communication systems with low-Earth-orbit mega-constellation satellites.The simulator facilitates the design and performance analysis of various algorithms and protocols for network operation and deployment.We propose a systematic,scalable,and comprehensive simulation architecture for the high-fidelity modeling of network configurations and for performing highefficiency simulations of network operations and management capabilities,while providing users with intuitive visualizations.We capture heterogeneous topology characteristics by establishing an environment update algorithm that incorporates real ephemeris data for satellite orbit prediction,sun outages,and link handovers.For a realistic simulation of software and hardware configurations,we develop a Network Simulator 3 based network model to support networking protocol extensions.We propose a message passing interface-based parallel and distributed approach with multiple cores or machines to achieve high simulation efficiency in large and complex network scenarios.Experimental results demonstrate the high fidelity and efficiency of Ultra Star can help pave the way for 6G integrated space-ground networks.展开更多
Liquid argon flow along a nanochannel is studied using molecular dynamics (MD) simulation in this work.Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) is used as the MD simulator.The effects of redu...Liquid argon flow along a nanochannel is studied using molecular dynamics (MD) simulation in this work.Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) is used as the MD simulator.The effects of reduced forces at 0.5,1.0 and 2.0 on argon flow on system energy in the form of system potential energy,pressure and velocity profile are described.Output in the form of three-dimensional visualization of the system at steady-state condition using Visual Molecular Dynamics (VMD) is provided to describe the dynamics of the argon atoms.The equilibrium state is reached after 16000 time steps.The effects on system energy,pressure and velocity profile due to reduced force of 2.0 (F2) are clearly distinguishable from the other two lower forces where sufficiently high net force along the direction of the nanochannel for F2 renders the attractive and repulsive forces between the argon atoms virtually non-existent.A reduced force of 0.5 (F0.5) provides liquid argon flow that approaches Poiseuille (laminar) flow as clearly shown by the n-shaped average velocity profile.The extension of the present MD model to a more practical application affords scientists and engineers a good option for simulation of other nanofluidic dynamics processes.展开更多
This paper studies the numerical simulation for semiconductor devices and discusses the software design of the simulation system. Our focus is on the deep submicron device simulation for BJT, MOSFET, heterojunction bi...This paper studies the numerical simulation for semiconductor devices and discusses the software design of the simulation system. Our focus is on the deep submicron device simulation for BJT, MOSFET, heterojunction bipolar transistors (HBT), etc. So the object oriented technology for software design and its realization is used to make the system easy to implement, maintain and extend. Besides the discussion of simulation and software system design, this paper introduces a device simulator SMDS and its parallel extension under local network environment using CORBA technology.展开更多
The traditional network simulator has function and performance limitation when simulating Internet worms,so we designed the grid-based Internet worm behavior simulator (IWBS Grid).IWBS Grid makes use of the real Inter...The traditional network simulator has function and performance limitation when simulating Internet worms,so we designed the grid-based Internet worm behavior simulator (IWBS Grid).IWBS Grid makes use of the real Internet topology,link and routing information,and simulates the worm behavior at the packet event-driven level;and proposes a high-performance Internet worms behavior simulation platform by right of the grid computing capability,resource and task management,and so on.The experimental results show that IWBS grid surpasses the traditional simulator in simulating capability,and the technology to track the worm propagation in packet level can propose the valuable information for the further study on worms.展开更多
Remarks on a benchmark nonlinear constrained optimization problem are made. Due to a citation error, two absolutely different results for the benchmark problem are obtained by independent researchers. Parallel simulat...Remarks on a benchmark nonlinear constrained optimization problem are made. Due to a citation error, two absolutely different results for the benchmark problem are obtained by independent researchers. Parallel simulated annealing using simplex method is employed in our study to solve the benchmark nonlinear constrained problem with mistaken formula and the best-known solution is obtained, whose optimality is testified by the Kuhn Tucker conditions.展开更多
The proliferation of ultra-high voltage direct current(UHVDC)transmission technology has heightened regulatory oversight of electromagnetic fields around buildings.In conventional direct current(DC)line design,the pre...The proliferation of ultra-high voltage direct current(UHVDC)transmission technology has heightened regulatory oversight of electromagnetic fields around buildings.In conventional direct current(DC)line design,the presence of residential areas was typically not taken into account.GB 39220-2020 now requires environmental assessments for residential balconies and platforms.The impact of nearby residential buildings has to be taken into account during the design of DC lines,necessitating the calculation of the three-dimensional total electric field.This study introduces a parallel charge simulation method-flux tracing method to quickly calculate the 3D total electric field near buildings in proximity to UHVDC lines,which is crucial for engineering design and environmental assessment.The method significantly speeds up calculations,with a 4-15 times faster ratio using 16-32 threads.It also analyses how UHVDC line dimensions,distances to buildings and parameters of residential buildings affect the maximum electric field on platforms.By using regression analysis,the formula for predicting the maximum electric field is obtained,and the traditional calculation time is improved.This advancement provides efficient predictions and detailed 3D electric field distributions for engineering and environmental assessments.展开更多
Hybrid systems such as Cyber Physical System(CPS)are becoming increasingly popular,mainly due to the involvement of information technology in different aspects of life.For analysis and verification of hybrid system mo...Hybrid systems such as Cyber Physical System(CPS)are becoming increasingly popular,mainly due to the involvement of information technology in different aspects of life.For analysis and verification of hybrid system models,simulation is used extensively.As parts of a common hybrid system may belong to different domains of study,it is sometimes beneficial to use specialized simulation packages(SPs)for each domain.In this case,parts of a system are simulated in different SPs.The idea may seem simple,but coupling more than one simulation component presents challenges related to numerical stability.The presented article suggests an implicit solver coupling technique enhanced to facilitate simulation of hybrid models using multiple simulation components.The technique is developed using two of the most popular simulation interoperability standards,namely,the High Level Architecture and the Functional Mock-up Interface.By using these standards,the developed algorithm will be useful for a large number of practitioners and researchers.The developed algorithm is described using a generic distributed computation model,which makes it reproducible even without using the standards.For the verification of results,the algorithm is tested on two case studies.The results are compared to a monolithic simulator and the proximity of results initiates the validity of the developed algorithm.展开更多
Presents information on a study which discussed the theory of parallel multi-stage and multi-step method, which is a form of combining Runge-Kutta method with linear multi-step method. Basic theory and equations; Appl...Presents information on a study which discussed the theory of parallel multi-stage and multi-step method, which is a form of combining Runge-Kutta method with linear multi-step method. Basic theory and equations; Applications of the method; Discussion and conclusions.展开更多
基金supported by the National High Technology Research and Development 863 Program of China under Grant No. 2007AA01Z117the National Basic Research 973 Program of China under Grant No.2007CB310900
摘要High performance computer (HPC) is a complex huge system, of which the architecture design meets increasing difficulties and risks. Traditional methods, such as theoretical analysis, component-level simulation and sequential simulation, are not applicable to system-level simulations of HPC systems. Even the parallel simulation using large-scale parallel machines also have many difficulties in scalability, reliability, generality, as well as efficiency. According to the current needs of HPC architecture design, this paper proposes a system-level parallel simulation platform: ArchSim. We first introduce the architecture of ArchSim simulation platform which is composed of a global server (GS), local server agents (LSA) and entities. Secondly, we emphasize some key techniques of ArchSim, including the synchronization protocol, the communication mechanism and the distributed checkpointingestart mechanism. We then make a synthesized test of some main performance indices of ArchSim with the phold benchmark and analyze the extra overhead generated by ArchSim. Finally, based on ArchSim, we construct a parallel event-driven interconnection network simulator and a system-level simulator for a small scale HPC system with 256 processors. The results of the performance test and HPC system simulations demonstrate that ArchSim can achieve high speedup ratio and high scalability on parallel host machine and support system-level simulations for the architecture design of HPC systems.
基金Supported by National Basic Research Program of China(Grant No.2008CB425701)National Natrual Science Foundation of China(Grant Nos.40774049,40474038)
摘要Reasonable use of mathematical modeling and numerical simulation of regional earthquake activities has attracted more and more attentions in realistic seismicity studies in recent years.The inherent nature of their attendant multi-scale properties,from either the temporal or the spatial direction,necessitates the use of the cutting-edge massive parallel data processing techniques.Our study here is focused on the model construction and numerical simulation of the regional stress evolution after large earthquake sequences along the fault zones in Sichuan and Yunnan areas,using large-scale parallel finite element approximations with tens of millions of unstructured meshes on the distributed systems.The objective of our study is to provide a state-of-the-art model and a large-scale numerical simulation platform,on which estimation of the risk of large earthquake triggering sequences can be carried out in a middle or long-term time scale with realistic data and constrains inputted from field observation and geological survey.
摘要Parallel calculational methods were used to analyze incompressible turbulent flow through hydraulic machinery. Two parallel methods were used to simulate the complex flow field. The space decomposition method divides the computational domain into several sub-ranges. Parallel discrete event simulation divides the whole task into several parts according to their functions. The simulation results were compared with the serial simulation results and particle image velocimetry (PIV) experimental results. The results give the distribution and configuration of the complex vortices and illustrate the effectiveness of the parallel algorithms for numerical simulation of turbulent flows.
基金supported by the National Natural Science Foundation of China under grant 91024030.
摘要Large-scale artificial societies with millions or billions of agents call for high-performance parallel simulation.Prevailing supercomputers with thousands of CPUs and GPUs make it possible to carry out such simulation.The key is to distribute large-scale agents to massive cores of CPUs and GPUs properly for parallel computing with efficient communication and synchronization.For simplicity and efficiency,a modified discrete event system specification(DEVS)is proposed for large-scale artificial society modeling and parallelism is exploited in agent models because similar agents usually share similar behaviors.Through phased synchronization,a two-tier parallel simulation engine is designed with support of MPI and OpenCL where GPU is used as coprocessor.One-sided communication is used for reflection of remote simulation objects and message passing between processes.A general kernel function prototype is elaborately designed and conditionally compiled for execution on both CPU and GPU.An artificial society for epidemic study is used to test the performance on a supercomputer with 1024 CPU cores and 1792 GPU cores.The speedup reaches 3512 for even 2 billion agents with GPU acceleration which is far over 701 when only CPUs are used.It turns out feasible for parallel simulation of large-scale artificial society with GPU as coprocessor.
摘要In this paper, a parallel simulation algorithm for the control problem in differential algebraic system is presented. The error of the algorithm is estimated. The stability analysis is made for a model problem and the stability region is given. The numerical example demonstrates that the method is efficient.
基金supported by the Office of Naval Research(Grant ONRDC14292111)
摘要This paper is concerned with three-dimensional numerical simulation of a plunging liquid jet. The transient processes of forming an air cavity around the jet, capturing an initially large air bubble, and the break-up of this large toroidal-shaped bubble into smaller bubbles were analyzed. A stabilized finite element method (FEM) was employed under parallel numerical simulations based on adaptive, unstructured grid and coupled with a level-set method to track the interface between air and liquid. These simulations show that the inertia of the liquid jet initially depresses the pool's surface, forming an annular air cavity which surrounds the liquid jet. A toroidal liquid eddy which is subse- quently formed in the liquid pool results in air cavity collapse, and in turn entrains air into the liquid pool from the unstable annular air gap region around the liquid jet.
基金supported by Jiangsu Provincial Key Research and Development Program (No.BE20210132)the Zhejiang Provincial Key Research and Development Program (No.2021C01040)the team of S-SET
摘要Low-Earth-Orbit satellite constellation networks(LEO-SCN)can provide low-cost,largescale,flexible coverage wireless communication services.High dynamics and large topological sizes characterize LEO-SCN.Protocol development and application testing of LEO-SCN are challenging to carry out in a natural environment.Simulation platforms are a more effective means of technology demonstration.Currently available simulators have a single function and limited simulation scale.There needs to be a simulator for full-featured simulation.In this paper,we apply the parallel discrete-event simulation technique to the simulation of LEO-SCN to support large-scale complex system simulation at the packet level.To solve the problem that single-process programs cannot cope with complex simulations containing numerous entities,we propose a parallel mechanism and algorithms LP-NM and LP-YAWNS for synchronization.In the experiment,we use ns-3 to verify the acceleration ratio and efficiency of the above algorithms.The results show that our proposed mechanism can provide parallel simulation engine support for the LEO-SCN.
摘要In this paper, a homogenous parallel simulation system is presented in detail for continuous--system simulation. The system is collstructed by a host computer and I I transputers connected into a topologyof 'Super--Node' which is very suitable for simulation of stiff systems. An automatic software interface runin the host is developed to partition simulation model, either equations or block diagrams, into several equitable segments and then pack them into parallel simulation program to be executed in the parallel system.This interface frees simulation users from parallel programming to focus on their simulation experiments.
基金Supported by the National Natural Science Foundation of China under Grant Nos 41331067,41474125,41274144,41174124 and 41121003the National Basic Research Program of China under Grant Nos 2013CBA01503 and 2012CB825602the Key Research Program of Chinese Academy of Sciences under Grant No KZZD-EW-01-4
摘要By performing one-dimensional (l-D) hybrid simulations, we analyze in detail the parametric instabilities of the Alfv^n waves with a spectrum in a low beta plasma. The parametric instabilities experience two stages. In the first stage, the density modes are excited and immediately couple with the pump Alfv6n waves. In the second stage, each pump Alfv^n wave decays into a density mode and a daughter Alfv6n mode similar to the monochromatic cases. Ftlrthermore, the proton velocity beam will also be formed after the saturation of the parametric instabilities. When the plasma beta is high, the parametric decay in the second stage will be strongly suppressed.
基金Supported by projects of National Natural Science Foundation of China(Nos.41372239,41772238,41602243)
摘要The authors developed a 3-D numerical injection model on parallel TOUGH2-FLAC3 D based on the site-specific stratigraphic information in Ordos Basin to simulate the Shenhua CO_2 geological storage( CGS)demonstration project injection process for three years and forecast CO_2 migration and layers displacement after injection for seven years. The results suggested that CO_2 migration did not stop after three years of consecutive injection,but migration rate was slowing down with time. As a result,displacement near injection well increased with injection and decreased slowly after injection. The maximum displacement of surface center occurred near the end of injection,which was only 1. 24 cm. According to the displacement result,it is safe to continue injecting for this project.
基金This work is supported in partial by Major State Basic Research Project (No. G19990328, Parallel Computations of the Large-Scale Reservoir Simulation (2003-2004) (Cooperated with China National 0ffshore 0il Corporation), and National Natural Science Foundation Project (No. 60303020, 2004.1-2006.12).
摘要This paper first provides a brief introduction to a numerical reservoir simulation and a parallel numerical reservoir integrated simulation platform developed by RDCPS (Research & Development Center for Parallel Software, Institute of Software, Chinese Academy of Sciences), which includes Pre-Processing, Simulator (for a Three-Dimensional & Three-Phase Black-Oil models), Post Processing, seamlessly integrated with parallel computers. We then present key technologies of the simulator, such as nonlinear and linear solvers, communications among processors, parallel I/O, etc., and corresponding content. Finally, some results of the platform to solve one million grid blocks cases from Chinese oil fields are given in the paper, which can show that the simulator has a very robust portability, high-speed for deadline and good scalability for the tested cases. As one of the application softwares, its objective is always focusing on satisfying deadlines of oil industry. Now, for one million grid blocks' case with 20 - 30 year-production, its elapsed time with 16 processors is less than 12 hours on parallel computers based on Myrinet or QsNet, namely 'to submit a case just before off-duty and get its result just before on-duty'. A decreasing line of elapsed time is given for a case with one million grid blocks. The developing trace of the simulator along with parallel computers can be also inferred from the line.
基金supported by the National Basic Research Pro-gram of China (No. 2008CB425701)the National Natural Science Foundation of China (No. 40774049)+2 种基金the National Science and Technology Project (No. SinoProbe-07)Institute of Earthquake Science,China Earthquake Administration,and Senior Visiting Professorship of Chinese Academy of SciencesCMG Program of the U.S. National Science Foundation
摘要The distribution and amount of ground ice on Mars is an important issue to be addressed for the future exploration of the planet.The occurrence of interstitial ice in Martian frozen ground is indicated by landforms,such as fluidized ejecta craters,softened terrain,and fretted channels.How-ever,experimental data on the rheology of ice-rock mixture under Martian physical conditions are sparse,and the amount of ground ice that is required to produce the viscous deformation observed in Martian ice-related landforms is still unknown.In our study,we put forward a three-dimensional non-Newtonian viscous finite element model to investigate the behavior of ice-rock mixtures numeri-cally.The randomly distributed tetrahedral elements are generated in regular domain to represent the natural distribution of ice-rock materials.Numerical simulation results show that when the volume of rock is less than 40%,the rheology of the mixture is dominated by ice,and there is occurrence of a brittle-ductile transition when ice fraction reaches a certain value.Our preliminary results contribute to the knowledge of the determination of the rheology and ice content in Martian ice-rock mixture.The presented model can also be utilized to evaluate the amount of ground ice on Mars.
基金supported in part by the Major Program of the National Natural Science Foundation of China(62495021 and 62495020)in part by the Natural Sciences and Engineering Research Council of Canada(NSERC)。
摘要Mega-constellation networks have recently gained significant research attention because of their potential for providing ubiquitous and high-capacity connectivity in future sixth-generation(6G)wireless communication systems.However,the high dynamics of network topology and large scale of a megaconstellation pose new challenges to constellation simulation and performance evaluation.To address these issues,we introduce Ultra Star,a high-fidelity and high-efficiency computer simulator to support the development of 6G wireless communication systems with low-Earth-orbit mega-constellation satellites.The simulator facilitates the design and performance analysis of various algorithms and protocols for network operation and deployment.We propose a systematic,scalable,and comprehensive simulation architecture for the high-fidelity modeling of network configurations and for performing highefficiency simulations of network operations and management capabilities,while providing users with intuitive visualizations.We capture heterogeneous topology characteristics by establishing an environment update algorithm that incorporates real ephemeris data for satellite orbit prediction,sun outages,and link handovers.For a realistic simulation of software and hardware configurations,we develop a Network Simulator 3 based network model to support networking protocol extensions.We propose a message passing interface-based parallel and distributed approach with multiple cores or machines to achieve high simulation efficiency in large and complex network scenarios.Experimental results demonstrate the high fidelity and efficiency of Ultra Star can help pave the way for 6G integrated space-ground networks.
基金Supported by the Academy of Sciences,Malaysia and Ministry of Science and Technology & Innovation
摘要Liquid argon flow along a nanochannel is studied using molecular dynamics (MD) simulation in this work.Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) is used as the MD simulator.The effects of reduced forces at 0.5,1.0 and 2.0 on argon flow on system energy in the form of system potential energy,pressure and velocity profile are described.Output in the form of three-dimensional visualization of the system at steady-state condition using Visual Molecular Dynamics (VMD) is provided to describe the dynamics of the argon atoms.The equilibrium state is reached after 16000 time steps.The effects on system energy,pressure and velocity profile due to reduced force of 2.0 (F2) are clearly distinguishable from the other two lower forces where sufficiently high net force along the direction of the nanochannel for F2 renders the attractive and repulsive forces between the argon atoms virtually non-existent.A reduced force of 0.5 (F0.5) provides liquid argon flow that approaches Poiseuille (laminar) flow as clearly shown by the n-shaped average velocity profile.The extension of the present MD model to a more practical application affords scientists and engineers a good option for simulation of other nanofluidic dynamics processes.
摘要This paper studies the numerical simulation for semiconductor devices and discusses the software design of the simulation system. Our focus is on the deep submicron device simulation for BJT, MOSFET, heterojunction bipolar transistors (HBT), etc. So the object oriented technology for software design and its realization is used to make the system easy to implement, maintain and extend. Besides the discussion of simulation and software system design, this paper introduces a device simulator SMDS and its parallel extension under local network environment using CORBA technology.
基金Sponsored by the National High Technology Research and Development Program of China (Grant No. 2007AA010503)the Science and Technology Development Program of Weihai (Grant No. 2007-96)the Science Foundation of HIT at Weihai (Grant No. HITWH 200702)
摘要The traditional network simulator has function and performance limitation when simulating Internet worms,so we designed the grid-based Internet worm behavior simulator (IWBS Grid).IWBS Grid makes use of the real Internet topology,link and routing information,and simulates the worm behavior at the packet event-driven level;and proposes a high-performance Internet worms behavior simulation platform by right of the grid computing capability,resource and task management,and so on.The experimental results show that IWBS grid surpasses the traditional simulator in simulating capability,and the technology to track the worm propagation in packet level can propose the valuable information for the further study on worms.
摘要Remarks on a benchmark nonlinear constrained optimization problem are made. Due to a citation error, two absolutely different results for the benchmark problem are obtained by independent researchers. Parallel simulated annealing using simplex method is employed in our study to solve the benchmark nonlinear constrained problem with mistaken formula and the best-known solution is obtained, whose optimality is testified by the Kuhn Tucker conditions.
基金Supported by State Grid Corporation of China(5200-202355390A-2-4-KJ).
摘要The proliferation of ultra-high voltage direct current(UHVDC)transmission technology has heightened regulatory oversight of electromagnetic fields around buildings.In conventional direct current(DC)line design,the presence of residential areas was typically not taken into account.GB 39220-2020 now requires environmental assessments for residential balconies and platforms.The impact of nearby residential buildings has to be taken into account during the design of DC lines,necessitating the calculation of the three-dimensional total electric field.This study introduces a parallel charge simulation method-flux tracing method to quickly calculate the 3D total electric field near buildings in proximity to UHVDC lines,which is crucial for engineering design and environmental assessment.The method significantly speeds up calculations,with a 4-15 times faster ratio using 16-32 threads.It also analyses how UHVDC line dimensions,distances to buildings and parameters of residential buildings affect the maximum electric field on platforms.By using regression analysis,the formula for predicting the maximum electric field is obtained,and the traditional calculation time is improved.This advancement provides efficient predictions and detailed 3D electric field distributions for engineering and environmental assessments.
摘要Hybrid systems such as Cyber Physical System(CPS)are becoming increasingly popular,mainly due to the involvement of information technology in different aspects of life.For analysis and verification of hybrid system models,simulation is used extensively.As parts of a common hybrid system may belong to different domains of study,it is sometimes beneficial to use specialized simulation packages(SPs)for each domain.In this case,parts of a system are simulated in different SPs.The idea may seem simple,but coupling more than one simulation component presents challenges related to numerical stability.The presented article suggests an implicit solver coupling technique enhanced to facilitate simulation of hybrid models using multiple simulation components.The technique is developed using two of the most popular simulation interoperability standards,namely,the High Level Architecture and the Functional Mock-up Interface.By using these standards,the developed algorithm will be useful for a large number of practitioners and researchers.The developed algorithm is described using a generic distributed computation model,which makes it reproducible even without using the standards.For the verification of results,the algorithm is tested on two case studies.The results are compared to a monolithic simulator and the proximity of results initiates the validity of the developed algorithm.
摘要Presents information on a study which discussed the theory of parallel multi-stage and multi-step method, which is a form of combining Runge-Kutta method with linear multi-step method. Basic theory and equations; Applications of the method; Discussion and conclusions.