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ATM网络基于队列长度阀值的传输调度 总被引:5,自引:3,他引:5
本文提出了ATM网络的一种实时传输调度和信元丢失控制的综合方案.这种方案是基于队列长度阀值而设计的,它适应于ATM网络面向连接的特性.本文给出了这种方案的随机Petri网性能模型,并给出模型分解和迭代的近似求解方法. 相似文献
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Web服务器集群请求分配和选择的性能分析 总被引:31,自引:2,他引:29
讨论并提出了 Web服务器集群的请求分配和选择控制方案 ,而且提供了这些方案的随机高级 Petri网模型 ,并强调研究这些方案及性能模型和分析方法 .为解决模型状态空间爆炸问题 ,作者提出了一种近似性能分析技术 ,可以显著地简化模型求解的复杂性 .文中的 Web服务器集群模型、请求分配和选择控制方案及近似性能分析技术可以应用于这类复杂系统的性能评价 . 相似文献
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设计了一种基于折扣广义值迭代的智能算法, 用于解决一类复杂非线性系统的最优跟踪控制问题. 通过选取合适的初始值, 值迭代过程中的代价函数将以单调递减的形式收敛到最优代价函数. 基于单调递减的值迭代算法, 在不同折扣因子的作用下, 讨论了迭代跟踪控制律的可容许性和误差系统的渐近稳定性. 为了促进算法的实现, 建立一个数据驱动的模型网络用于学习系统动态信息, 同时构造评判网络和执行网络用于近似迭代代价函数和计算迭代跟踪控制律. 值得注意的是, 我们提出了新颖的停止准则来保证迭代跟踪控制律的有效性. 这种停止准则包含两个条件, 一个条件用来保证迭代跟踪控制律的可用性, 这有利于评估误差系统的渐近稳定性; 而另一个条件用来确保跟踪控制律的近似最优性. 最后, 通过包括污水处理在内的两个应用实例验证了本文提出的近似最优跟踪控制方法的可行性和有效性. 相似文献
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基于双线性模型的动态系统优化和参数估计集成方法 总被引:3,自引:1,他引:3
针对双线性模型与实际系统之间的差异,提出一种基于双线性模型求解非线性动态系统最优控制的迭代算法。该算法通过重复求解修正的基于双线性模型的优化控制问题和参数估计问题,获得实际系统的最优解。同时提出求解修正的基于双线性模型的优化控制问题的一种新的分解方法,克服了非线性和双线性两点边值问题求解的困难。仿真例子表明该算法的有效性和实用性。 相似文献
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IEC61499功能块逐渐被工业采纳。本文针对分布式功能块控制应用(DFBCA)缺乏性能分析方法的情况,提出了一种基于随机Petri网的DFBCA性能分析方法。该方法以DFBCA的运行状态为着手点,利用Petri网易于表示系统中可能发生的各种状态变化及其关系的特点,将DFBCA转换为随机Petri网模型。再利用随机Petri网模型与马尔可夫链(MC)同构的特征,将随机Petri网模型转换为MC。得到的MC为DFBCA的性能分析提供了数学基础。最后基于MC的状态转移矩阵和稳态概率,对在每个状态中的驻留时间、变迁的利用率、变迁的标记流速、子系统延时时间等性能指标进行了分析。通过具体的示例说明了这种性能分析方法的可行性。 相似文献
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In this paper, the fixed point iteration and Newton’s methods for iteratively solving nonlinear equations are studied in the control theoretical framework. This work is motivated by the ever increasing demands for integrating iterative solutions of nonlinear functions into embedded control systems. The use of the well-established control theoretical methods for our application purpose is inspired by the recent control-theoretical study on numerical analysis. Our study consists of two parts. In the first part, the existing fixed point iteration and Newton’s methods are analysed using the stability theory for the sector-bounded Lure’s systems. The second part is devoted to the modified iteration methods and the integration of sensor signals into the iterative computations. The major results achieved in our study are, besides some academic examples, applied to the iterative computation of the air path model embedded in the engine control systems. 相似文献
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《Computer Networks》2007,51(3):671-682
In this paper, we present studies of an optical switching (OS) node utilizing a limited number of WCs (wavelength converters) in order to reduce the implementation cost of an OS node. The study stems from practical observation that WCs are expensive. Consequently, each output wavelength may not necessarily have its own WC and has to share a limited pool of WCs with other output wavelengths. In order to improve the utilization of the limited number of WCs, a share per node (SPN) method is proposed for the OBS node. Subsequently, a multi-dimensional Markov chain model of SPN is presented to evaluate its performance. To reduce the complexity of the multi-dimension Markov analysis, we propose a suite of methods, called randomized states (RS) multi-plane Markov chain analysis, followed by self-constrained iteration (SCI) and eventually ending with the sliding window (SW) update method, to solve for the solution. Numerical results are presented to verify the accuracy of the analytical model. With SPN, about 50% and 80% of WCs can be saved in high load and low load scenarios respectively. 相似文献
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In this paper, we introduce and analyze a modification of the Hermitian and skew-Hermitian splitting iteration method for solving a broad class of complex symmetric linear systems. We show that the modified Hermitian and skew-Hermitian splitting (MHSS) iteration method is unconditionally convergent. Each iteration of this method requires the solution of two linear systems with real symmetric positive definite coefficient matrices. These two systems can be solved inexactly. We consider acceleration of the MHSS iteration by Krylov subspace methods. Numerical experiments on a few model problems are used to illustrate the performance of the new method. 相似文献
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强化学习(Reinforcement Learning)是学习环境状态到动作的一种映射,并且能够获得最大的奖赏信号。强化学习中有三种方法可以实现回报的最大化:值迭代、策略迭代、策略搜索。该文介绍了强化学习的原理、算法,并对有环境模型和无环境模型的离散空间值迭代算法进行研究,并且把该算法用于固定起点和随机起点的格子世界问题。实验结果表明,相比策略迭代算法,该算法收敛速度快,实验精度好。 相似文献
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《Computers & Mathematics with Applications》2007,53(6):972-976
In this paper we consider a geometric construction of iteration functions of order three to develop cubically convergent iterative methods for solving nonlinear equations. This construction can be applied to any iteration function of order two to develop an iteration function of order three. Some examples are given of deriving several third-order iteration methods, and several numerical results follow to illustrate the performance of the derived methods. 相似文献
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Web服务组合能够利用互联网上分布的Web服务构建出功能更加强大的服务,然而不同的组合方式,组合的系统的性能不一样,性能分析能帮助我们组合性能更好的系统,通过SPN计算系统的性能,并利用计算系统性能指标的公式找出性能优化的方案. 相似文献
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The World Wide Web has become the primary means for information dissemination. Due to the limited resources of the network bandwidth, users always suffer from long time waiting. Web prefetching and web caching are the primary approaches to reducing the user perceived access latency and improving the quality of services. In this paper, a Stochastic Petri Nets (SPN) based integrated web prefetching and caching model (IWPCM) is presented and the performance evaluation of IWPCM is made. The performance metrics, access latency, throughput, HR (hit ratio) and BHR (byte hit ratio) are analyzed and discussed. Simulations show that compared with caching only model (CM), IWPCM can further improve the throughput, HR and BHR efficiently and reduce the access latency. The performance evaluation based on the SPN model can provide a basis for implementation of web prefetching and caching and the combination of web prefetching and caching holds the promise of improving the QoS of web systems. 相似文献
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《IEEE transactions on pattern analysis and machine intelligence》1987,(12):1297-1310
We have developed a Generalized Timed Petri Net (GTPN) model for evaluating the performance of computer systems. Our model is a generalization of the TPN model proposed by Zuberek [1] and extended by Razouk and Phelps [2]. In this paper, we define the GTPN model and present how performance estimates are obtained from the GTPN. We demonstrate the use of our automated GTPN analysis techniques on the dining philosophers example. This example violates restrictions made in the earlier TPN models. Finally, we compare the GTPN to the stochastic Petri net (SPN) models. We show that the GTPN model has capabilities for modeling and analyzing parallel systems lacking in existing SPN models. The GTPN provides an efficient, easily used method of obtaining accurate performance estimates for models of computer systems which include both deterministic and geometric holding times. 相似文献