The design and calibration of a simulation model of a star computer network

A simulation model of the CERN (European Organization for Nuclear Research) SPS star computer network is described. The model concentrates on simulating the message handling computer, through which all messages in the network pass. The paper describes the main features of the model, the transfer time parameters in the model and how performance measurements were used to assist in the calibration of the model.     

Performance of supply chain collaboration – A simulation study

In the past few decades several supply chain management initiatives such as Vendor Managed Inventory, Continuous Replenishment and Collaborative Planning Forecasting and Replenishment (CPFR) have been proposed in literature to improve the performance of supply chains. But, identifying the benefits of collaboration is still a big challenge for many supply chains. Confusion around the optimum number of partners, investment in collaboration and duration of partnership are some of the barriers of healthy collaborative arrangements. To evolve competitive supply chain collaboration (SCC), all SC processes need to be assessed from time to time for evaluating the performance. In a growing field, performance measurement is highly indispensable in order to make continuous improvement; in a new field, it is equally important to check the performance to test conduciveness of SCC. In this research, collaborative performance measurement will act as a testing tool to identify conducive environment to collaborate, by the way of pinpointing areas requiring improvements before initializing collaboration. We use actual industrial data and simulation to help managerial decision-making on the number of collaborating partners, the level of investments and the involvement in supply chain processes. This approach will help the supply chains to obtain maximum benefit of collaborative relationships. The use of simulation for understanding the performance of SCC is relatively a new approach and this can be used by companies that are interested in collaboration without having to invest a huge sum of money in establishing the actual collaboration.     

基于声线跟踪法开发超声无损检测动态仿真软件

以“声线跟踪法”为基础，运用面向对象的编程语言VisualC＋＋和三维场景开发工具OpenGL，按照面向对象的程序设计思想开发了超声波无损检测仿真软件。该系统实现了超声检测过程的三维可视化并对超声波传播路径和A型显示进行了较为准确的模拟。该文对仿真过程中的三维介质建模和传播路径模拟计算等关键问题进行了详细的讨论，采用CSG／B-Rep混合模型表示法对三维介质模型进行快速建模，并且采用声线跟踪法对传播路径进行较为准确的模拟。最后通过仿真实例，验证了算法的有效性。     

通信网络随机模拟的快速方法研究

引入现代控制科学离散事件动态系统摄动分析思想，提出通信网络随机模拟的快速并行算法。在一台个人计算机上根据被模拟网络在一组参数下的仿真样本轨迹，同时构造一簇不同参数集合的网络系统样本轨迹。     

Performance of N-body codes on hybrid machines

N-body codes are routinely used for simulation studies of physical systems, e.g. in the fields of computational astrophysics and molecular dynamics. Typically, they require only a moderate amount of run-time memory, but are very demanding in computational power. A detailed analysis of an N-body code performance, in terms of the relative weight of each task of the code, and how this weight is influenced by software or hardware optimisations, is essential in improving such codes. The approach of developing a dedicated device, GRAPE [J. Makino, M. Taiji, Scientific Simulations with Special Purpose Computers, Wiley, New York, 1998], able to provide a very high performance for the most expensive computational task of this code, has resulted in a dramatic performance leap. We explore on the performance of different versions of parallel N-body codes, where both software and hardware improvements are introduced. The use of GRAPE as a ‘force computation accelerator’ in a parallel computer architecture, can be seen as an example of a hybrid architecture, where special purpose device boards help a general purpose (multi)computer to reach a very high performance.     

混合系统改进的仿真时钟等步长同步方法及性能评价研究

通过对一类混合系统仿真中的连续系统、离散事件系统及推理决策系统各自仿真时钟的分析,得出了推理决策系统仿真依赖于其两个系统的结果,继而提出了用其中的离散事件 系统仿真时钟云同步具有等步长策略的连续系统仿真时钟改进的等步长方法,并给出了相应的软件实现方法与性能评价准则,解决了该类混合记真时钟的同步问题,减少了仿真误差,从而为该类混合系统的仿真提供理论依据。     

一类混合系统稳态型仿真时间的确定方法

对于随机性混合系统稳态型仿真,其仿真时间的确定方法是一个值得研究的问题。该文以线性跳变系统为例,研究了一类混合系统稳态型仿真时间的优化准则与计算方法,并给出了应用实例。     

混合式组播--分布式仿真中一种新型信息传输方式

大规模分布式仿真的信息过滤机制要求使用组播方式传送信息犤1犦,但是当前网络硬件对IP组播的支持很有限,远不能满足实际系统的需要。为此,该文引入了在性能上介于“点对点传送”和组播之间的混合式组播,提出了混合式组播优先的组播组分配算法以解决可用组播组数量偏少的问题。     

基于Simulink模型的COM组件及其性能分析

MATLAB/Simulink提供了友好的可视化建模界面以及大量的通用模块,赢得广大用户的青睐,但其较低的执行效率及不支持分布式计算使其在复杂动力学问题中的应用受到了限制.为提高执行效率及方便系统集成,同时又尽量保持Simulink模型原有的灵活性,该文结合RTW（Real Time Workshop）工具探讨并演示了将Simulink模型快速转换为COM组件的技术途径,并结合卫星姿态动力学仿真实例,针对所生成的组件,分别就进程内服务器、本地进程外服务器和远程服务器三类进程模型以及连续/单步两种运行模式下的性能进行了分析,试验数据说明此方法可以大大提高执行效率.     

Simulation-based optimization of multiple-task GRID applications

This paper deals with the performance optimization of multiple-task applications in GRID environments. Typically such applications are launched by a Resource Manager, which only takes into account the application’s resource requirements and current availability on the GRID. Here a novel approach is presented, that performs resource management in user space, making it possible to exploit application modularity and flexibility and to take into account expected performance figures produced by GRID simulation. The objective is to make optimized choices that can lead to reduced application response times. After an introduction to the GRID simulation environment used, the structure of an application launcher able to optimize a number of application tasks and their mapping on the GRID is sketched, presenting the encouraging performance results obtained.     

基于NS2仿真平台的Ad hoc新路由协议的模拟

使用网络模拟软件NS2做网络模拟仿真成为研究Ad hoc网络的主流,在NS2平台上进行Ad hoc新路由协议模拟,包括新路由协议的设计、仿真和性能分析等过程,目前并没有一套系统的方法可以参照。在提出一种基于路径收集机制的AODV优化协议基础上,系统地分析和讨论了这一全过程,并研究总结出一套在NS2下进行路由协议设计、仿真和性能分析的方法。最后在大量的实验仿真基础上,详细讨论了不同的网络环境设置对仿真实验结果的影响;且仿真结果表明,优化的AODV路由协议综合性能更优。     

混合动力轿车的建模与仿真

该文介绍了应用电动汽车仿真软件ADVISOR 2 0 0 2对国内一汽车企业的混合动力轿车样车进行建模与仿真的研究工作。待仿真的轿车与日本本田公司的混合动力轿车Insight的动力系统结构相同 ,因此作者采用在ADVISOR中的Insight模型的基础上 ,修改其设备参数 ,重新设计其控制策略模块的模型的技术方案来进行仿真工作 ,最后给出了混合动力轿车的整车性能和工作过程的仿真结果。该研究可以帮助确定混合动力轿车动力系统的配置方案 ,为企业设计混合动力轿车提供参考。     

混合系统建模理论与混合系统模型

在现代工程仿真中,大部分仿真对象表现出同时具有连续和离散对象的特征,利用现有的离散或者连续建模理论不能全面的反应出对象特性,需要对混合系统的建模进行相应的理论研究.从系统理论出发,围绕着系统的连续属性和离散属性,以及他们对系统信息的响应,还有他们之间的相互作用为中心,建立混合系统模型的形式化表达和系统理论基础,并在此基础上建立了混合系统模型.以此模型为基础,在实践中为某大型仿真项目中的工程对象建立了混合模型,在仿真中得到有效的应用.     

基于Matlab状态流的混杂系统仿真设计

混杂系统是集连续动态和离散事件为一体的复杂系统,是近十余年来控制理论研究领域的热门课题,混杂动态系统的研究为解决一类复杂的、非线性的大系统提供了一个很好的理论框架,计算机仿真是分析和研究混杂系统的有效工具。该文在分析混杂系统仿真关键问题的基础上,提出如何应用MATLAB环境中的状态流工具箱,实现基于混杂自动机模型的混杂系统仿真,并就典型混杂系统给出仿真实例。结果表明,应用MATLAB状态流工具箱进行混杂系统仿真,具有很好的可视化,而且混杂系统的离散和连续两部分可以很好的同步协调,结构简单而明了,效果很好。     

基于混合编程的HPN仿真

混合Petri网（HPN）是离散事件和连续时间变量在同一层次的直接交互。其混合变迁规则较为复杂。既要考虑到离散部分与连续部分之间的相互影响，又要考虑到连续标识和离散标识之间的相互转化，所以如果选用单一语言来对混合Petri网进行仿真，难度高，编程量大，开发周期长，针对这一现象。该文提出混合编程的思想。即充分发挥不同编程语言的优势来仿真混合Petri网。该文采用了Matlab与Vc＋＋混合编程的方法来进行混合Petri网的仿真，此种方法可以很好的实现对混合Petri网的仿真，并通过混合变迁规则来验证所建HPN模型的正确性。而且由于混编的应用大大减少了编程工作量，缩短了开发周期。最后针对一个蒸发过程进行实例研究。     

Control of sampled-data systems with variable sampling rate

This paper addresses stability and performance of sampled-data systems with variable sampling rate, where the change between sampling rates is decided by a scheduler. A motivational example is presented, where a stable continuous time system is controlled with two sampling rates. It is shown that the resulting system could be unstable when the sampling changes between these two rates, although each individual closed-loop system is stable under the designed controller that minimizes the same continuous loss function. Two solutions are presented in this paper. The first solution is to impose restrictions on switching sequences such that only stable sequences are chosen. The second solution presented is more general, where a piecewise constant state feedback control law is designed which guarantees stability for all possible variations of sampling rate. Furthermore, the performance defined by a continuous time quadratic cost function for the sampled-data system with variable sampling rate can be optimized using the proposed synthesis method.