基于Petri网方法的红血球代谢系统研究

随着生物网络数据的迅速增长,对这些数据进行模拟分析的工具也随之发展。由于组合了图形化和数学化的特征,Petri网成为这一领域的重要模拟分析工具之一。但是,通过Petri网模拟分析的生物系统大多是一些孤立的生化途径。本文采用Petri网技术对红血球细胞的新陈代谢系统进行建模分析。首先介绍了基本的Petri网概念和分析方法,然后采用Petri网技术研究红血球的新陈代谢系统,建立了红血球新陈代谢系统的Petri网模型,最后计算了该模型中的P、T不变量,并讨论了它们的功能意义。     

基于Gillespie算法的生化随机Petri网演化分析

Petri网既有严格的数学表达方式,又有直观的图形描述形式,是当前生物化学系统模拟和定性分析的一个有力工具。作为标准Petri网的一个重要扩展,随机Petri网使得可以定量地分析生物化学系统。建立了两个典型的生物化学系统的随机Petri网模型：Schlogl系统和转录调控系统,并使用Gillespie随机仿真算法模拟了这些生化随机Petri网模型的状态演化。     

基于随机对象Petri网的柔性制造系统性能分析

为了增强传统对象Petri网的定量分析能力,提出随机对象Petri网模型。该模型具备随机性和层次特性,获得与随机Petri网的等价关系,从宏观和微观2个层面对系统进行性能分析,并将该模型应用到柔性制造系统中。实验结果表明,该系统保留了面向对象的建模能力,具有较强的定量分析能力。     

基于形式化方法的网络业务流Petri网模型的仿真分析

针对自相似业务流的影响,给出具有自相似特性的网络业务流传输过程的随机Petri网模型,使用Petri网分别建立了无限缓冲区的IP层网络模型和有限缓冲区的以太网模型,采用一种马尔可夫随机Petri网的方法对模型进行分析,然后通过实例证明了网络中确实存在着自相似现象,最后利用随机Petri网性能分析工具SPNP对所建立的模型进行了模拟和验证,研究了网络业务流的自相似特性对网络性能的影响.提出的模型在一定程度上能够很好地拟合不同网络的流量特性,为网络构建、网络特性分析和网络性能评估提供了重要的理论基础.     

随机Petri网可视化软件的设计与实现

针对随机Petri网建模设计与分析的复杂性问题,通过面向对象方法在VisualC++环境下利用MFC开发了可视化的随机Petri网建模和分析工具SPNSim。利用广度优先思想,设计了可达图的生成算法,给出了随机Petri网模型的编辑器,用户可以直观方便地进行随机Petri网编辑,同时还能进行模型分析,得到可达图、稳态概率等随机Petri网特性和系统性能指标。通过对一个实例的建模与分析,结果验证了软件工具SPNSim的正确性和可用性。     

基于XML的生物代谢Petri网模型的标准化

针对分析生物代谢网络的需要，构建了生物代谢Petri网模型建模环境，并采用基于XML的Petri网标记语言PNML为标准，利用DOM实现XML解析，完成Petri网模型的标准化，通过对代谢网络Petri网模型实例的仿真，验证了标准化模型的正确性。     

基于Petri网的工作流过程模型及资源分布分析

针对工作流系统的特点对时延Petri网模型进行扩展,提出了一种新的工作流建模方法,即扩展时延Petri网。给出了扩展时延Petri网的定义,并用该方法分析了工作流四种基本模型;给出了利用排队论和随机Petri网理论计算工作流模型时间性能指标的新方法,用这种方法可求得与实例到达率相关的工作流模型平均完成时间。最后应用上述方法讨论了工作流资源分布的几种模式,并与模拟结果加以对比,计算结果的最大误差在3%左右,说明基于扩展时延Petri网的方法是分析工作流系统时间性能的有效方法。     

基于Petri网的工作流建模在群体决策支持系统中的应用研究

Petri网作为一种图形化的建模工具,具有坚实的数学理论基础,是对工作流进行建模和分析的理想工具。通过对网络会商群体决策支持系统的描述,提出了一种基于Petri网的网络会商群体决策系统的工作流模型,并对该模型进行正确性验证,提高了决策支持系统的可靠性和高效性。     

模糊时间Petri网及扩展的模糊时间Petri网

网络实时系统对时间和QoS有严格要求,因此对设计、实现和测试的技术和工具都有很高的要求。模糊时间Petri网是将模糊集合理论用于不确定的或主观的时间信息的表示,在每个变迁上添加时间间隔约束对模糊时间Petri网进行扩展得到扩展的模糊时间Petri网,它是一种对网络实时系统进行建模和分析的形式化模型,Petri网数学理论基础能保证并发系统的可靠性和正确性。本文详细地介绍了模糊时间Petri网及可扩展的时间Petri网,可扩展的时间Petri网的网精简方法,使用design／CPN仿真,及使用EFTN对多媒体同步建模,并探讨了进一步研究的方向。     

计算机系统与计算机网络中的动态优化:模型、求解与应用

动态优化是计算机系统与计算机网络中进行资源分配与任务调度等方面研究所采用的主要理论工具之一.目前,国内外已开展大量研究,致力于深化动态优化的理论研究与工程应用.文中从模型、求解与应用3个角度,对马尔可夫决策过程动态优化理论模型进行了综述,并重点介绍了将动态优化理论与随机Petri网理论相结合的马尔可夫决策Petri网和随机博弈网模型,详细讨论了这些模型的建模方法、求解算法与一些应用实例.最后,对全文进行了总结,并对未来可能的研究方向进行了展望.     

着色Petri网应用研究

着色Petri网是在经典Petri网理论基础上增加了token类型和网的模块这两个功能,它现在已成为一种较完善的语言,可以用来对各种系统规范和协议等进行设计、规范描写、仿真和验证等。文章对着色Petri网的基本理论进行了简单介绍,并对一个简单的通信协议进行建模和分析,提出了今后着色Petri网发展的一个主要方向。     

神光III控制系统的故障建模与分析

应用混合随机Petri网对神光III控制系统的故障进行了建模,并应用Visobj Net对建立的故障模型进行了仿真分析。网络化控制系统是一个离散和连续相结合的混合动态系统,具有动态、并发及同步等特征;神光III控制系统就是网络化控制技术在武器装备上的一个典型应用;对于复杂系统的建模和分析,Petri网是一个非常有效的工具。Petri网已经被证明是离散事件或异步系统很好的建模和分析工具,混合随机Petri网是Petri网的一个扩展,具有强大的建模功能。仿真结果表明,所建立的模型是正确的。     

基于Petri网的工作流过程建模

业务过程建模是整个工作流管理系统的基础,选择一种高效的建模技术对复杂多变的实际业务流程进行形式化表示对构建一个灵活的工作流管理系统起着至关重要的作用。本文利用了Petri网技术给业务过程建模,构造了一个灵活可分析的过程模型：首先介绍了相关的基于Petri网的工作流建模技术,接着描述了Petri网到工作流过程模型执行的映 射,然后给出了一个具体的基于Petri网建模方式的实例,最后利用随机Petri网和概率论的一些知识对该模型进行了时间性能分析。     

Modeling and performance evaluation of supply chains using batch deterministic and stochastic Petri nets

Batch deterministic and stochastic Petri nets are introduced as a tool for modeling and performance evaluation of supply chains. The new model is developed by enhancing deterministic and stochastic Petri nets (DSPNs) with batch places and batch tokens. By incorporating stochastic Petri nets (SPNs) with the batch features, inhibitor arcs, and marking-dependent weights, operational policies of supply chains such as inventory policies can be easily described in the model. Methods for structural and performance analysis of the model are developed by extending existing ones for DSPNs. As applications, an inventory system and an industrial supply chain are modeled and their performances are evaluated analytically and by simulation, respectively, using this BSPN model. The applications demonstrate that our model and associated methods can solve some important supply chain modeling and analysis issues. Note to Practitioners-This paper was motivated by the problem of performance analysis and optimization of supply chains but it also applies to other discrete event systems where materials are processed in finite discrete quantities (batches) and operations are performed in a batch way because of batch inputs and/or in order to take advantages of the economies of scale. Existing Petri net modeling and analysis tools for such systems ignore their batch features, making their modeling complicated. This paper suggests a new model called batch deterministic and stochastic Petri nets (BDSPNs) by enhancing deterministic and stochastic Petri nets with batch places and batch tokens. Methods for structural and performance analysis of the model are developed. We then show how an inventory system and a real-life supply chain can be modeled and their performances can be evaluated analytically and by simulation respectively based on the model. The model and associated analysis methods therefore provide a promising tool for modeling and performance evaluation of supply chains.     

IDD-based model validation of biochemical networks

This paper presents efficient techniques for the qualitative and quantitative analysis of biochemical networks, which are modeled by means of qualitative and stochastic Petri nets, respectively. The analysis includes standard Petri net properties as well as model checking of the Computation Tree Logic and the Continuous Stochastic Logic. Efficiency is achieved by using Interval decision diagrams to alleviate the well-known problem of state space explosion, and by applying operations exploiting the Petri structure and the principle of locality. All presented techniques are implemented in our tool IDD-MC which is available on our website.     

基于粗糙集和Petri网的随机流网络可靠性评价方法

针对随机流网络可靠性建模难的问题,提出一种基于粗糙集和Petri网相结合的随机流网络可靠性评价方法.建立了随机流网络在确定网络状态下的Petri网模型,并利用粗糙集方法求得网络中各边状态对系统状态的重要度;然后以此作为随机流网络的Petri网模型中各变迁的优先因子来控制模型中变迁的激发;最后通过蒙特卡罗仿真求得随机流网络可靠度的估计值.仿真结果表明,该方法是一种计算随机流网络可靠性的有效方法.     

Software modeling and analysis using a hierarchical object-oriented Petri net

Petri net is used widely to analyze and model various systems formally. Recently, many Petri nets mania devote their efforts to enhancing and extending the expressive power of Petri nets. One such effort is to extend Petri nets with object-oriented concepts. An object-oriented paradigm provides excellent concepts to model real-world problems. Object-oriented concepts allow us to build software systems easily, intuitively, and naturally. Although several high-level Petri nets with the concept of objects are suggested, these nets do not fully support the object-oriented concepts. In this paper, we propose a hierarchical object-oriented Petri net (HOONet). The formal syntax and semantics of HOONet are explained in detail. HOONet supports a wide range of object-oriented features including abstract, encapsulated and modularized objects, object interaction by message passing, inheritance, and ploymorphism. HOONet also supports a variety of modeling and analysis mechanisms such as incremental modeling of evolving systems, unfolding the HOONet to lower level Petri net, and incremental reachability analysis for HOONet models. We demonstrate the usefulness of HOONet by applying it to modeling and analysis with an example.     

Fuzzy Petri net-based programmable logic controller

Programmable logic controllers (PLCs) are able to directly implement control sequences specified by means of standard languages such as Grafcet or formal models such as Petri nets. In the case of simple regulation problems between two steps it could be of great interest to introduce a notion of “fuzzy events” in order to denote a continuous evolution from one state to another. This could result from a linear interpolation between the commands attached to two control steps represented by two Petri net (PN) places. This paper is an attempt to develop fuzzy PN-based PLCs in a similar way as fuzzy controllers (regulators). Our approach is based on a combination of Petri nets with possibility theory (Petri nets with fuzzy markings)