Modelling digital circuits with delays by Stochastic Petri Nets

The analysis of the behaviour of digital circuits, with special reference to signal propagation delays, is performed by means of the Petri Nets (PN) formal model. In particular, concurrent signal changes in the circuit which may give rise to possible functional errors such as races or hazards, are represented by this model. Moreover, the delays, assumed to be random variables with assigned probability distributions and Stochastic Petri Nets (SPN), which are an extension of classical PN's, are employed. By the resulting model, a great flexibility of representation is achieved, matching also the requisites of the particular technology employed.It is also possible to account for time varying inputs both in combinational and sequential circuits, reconvergent fanouts and conflicting events.The algorithm derived from this model allows to obtain a static logic verification of the circuit and exhibits shorter simulation times as compared to those of classical simulators.     

工作流挖掘与Petri网表示的对偶交换

将对偶交换的观点引入工作流挖掘的研究可以获得新的认识。其在工作流结构验证中并行和选择互换后仍保持结构的正确性。工作流挖掘α算法先挖掘选择结构,余下并行结构,通过对偶交换得到算法,先挖掘并行结构,余下选择结构,算法能够减少非自由选择结构。不同情况下两种算法结果比较取优,能够使工作流挖掘的并行和选择的嵌套关系更为简练。以任务为变迁的Petri网能够最简洁地表示α算法挖掘结果,以任务为库所的Petri网能够最简洁地表示算法的挖掘结果。这两种Petri网表示也体现出对偶性。     

随机Petri网非乘积解系统的判定与界限求解

本文基于随机Petri网(SPN)提出了一种利用站平衡来判断非乘积解系统模型的方法,发现了可能导致站不平衡的三种Petri网结构,对这三种结构进行了分析,得出了产生非乘积解的系统原因,并给出了一种利用乘积解求解非乘积解系统模型性能界限的方法,这种方法可广泛应用于多种实际系统的性能界限求解.     

基于直觉模糊Petri网的知识表示和推理

针对模糊Petri网存在隶属度单一的问题,将直觉模糊集理论与Petri网理论相结合,构建直觉模糊Petri网(Intuitionistic Fuzzy Petri Nets,IFPN)模型,用于知识的表示和推理.首先构建了IFPN模型,并将其应用于知识的表示,通过在模型中引入抑止转移弧,解决了否命题的表示问题.其次提出了基于矩阵运算的IFPN推理算法,通过修改变迁触发后token值的传递规则,解决了推理过程中的事实的保留问题;通过修改变迁的触发规则,抑制了变迁的重复触发.最后对推理算法进行了分析,并举例验证了提出的IFPN模型及其推理算法的可行性,结果表明IFPN是对FPN的有效扩充和发展,其对推理结果的描述更加细腻、全面.     

Petri网理论及其在自动制造系统中的应用

文中详细综述了Ｐｅｔｒｉ网理论的发展、应用领域、基本定义以及分析方法和建模方法。重点介绍了Ｐｅｔｒｉ网在自动制造系统控制中的应用、发展方向，指出了Ｐｅｔｒｉ网在自动制造系统中的应用前景和作者的看法     

主体计划的Petri网方法及正确性验证

主体计划的生成问题是多主体系统实现的一个关键问题.为了实现多主体系统中的计划自动生成以及对生成的计划进行验证,以任务有效分解的Petri网模型为基础,提出了计划提取的方法并对相关的正确性运用同步器进行验证.首先,通过对网系统的可达性分析得到所有计划的集合,组成多主体系统的计划库.其次,根据同步网的相关思想,对计划库中的每一个计划的正确性进行了形式化的验证,从而为多主体系统的实现提供了保证.     

一种随机Petri网性能等价化简与分析方法

随机Petri网模型是系统性能评价的有力工具,但其状态空间随模型规模的增长而指数性增长的问题限制了其对复杂和大规模系统模型的性能数量分析能力.因此,在对模型进行分析之前,先对其进行适当的性能等价化简,是一种更为可行的分析方法.本文首先讨论了一类随机Petri网-基本随机Petri网(ESPN)的性能等价分析方法,这类随机Petri网由顺序、并行、选择和循环等四种基本结构及其组合构成.作者推导出这四种基本结构的性能等价公式,并运用自底向上逐步综合替代的分层分析方法,给出这类随机Petri网模型的性能等价化简分析方法,该方法的复杂性随模型增长而线性增长,有效解决了其性能数量分析问题.然后,讨论了两种非基本结构到基本结构的转换规则,使得复杂的随机Petri网模型也可能转换为ESPN模型,从而使性能等价算法可应用于一般随机Petri网.     

基于模型构件和Petri网的企业整体建模方法

模型复用是提高建模质量和效率的主要手段，而模型构件是复用的核心和基础。在对构成企业这一社会技术系统的各种要素进行分析的基础上，首先将组成系统的要素分为功能构件、资源构件和人力构件等三类模型构件。然后以Petri网作为建模工具，给出一种以模型构件作为变迁和库所的企业整体建模方法。由此方法建立的企业模型具有良好的整体性和可复用性，能够全面反映构成企业的技术实体、资源和人等要素的配置和相互关系。最后给出一个企业建模实例。     

随机Petri网模型中变迁的串、并联性能等价化简技术

随机Petri网的状态空间爆炸问题的研究始终是Petri网研究的主要问题之一.在随机Petri网模型中,变迁的串、并联是Petri网模型的主要基本形式,对它的化简不仅有助于解决随机Petri网状态空间的爆炸问题,而且也为其他随机Petri网的化简技术提供一个坚实的基础.另外在诸如工作流、多媒体等重要的随机Petri网模型中也存在大量的变迁的串、并联结构,所以对随机Petri网模型变迁的串、并联的化简,特别是能够推导出它的性能等价的数学公式就显得很有必要.本文详细阐述了随机Petri网变迁的串并联的模型化简技术,推导出了变迁的串、并联化简的性能等价公式,并给出一个化简的例子,最后对结果的相关问题进行了分析.     

Modeling and Verification of a Sentiment Analysis System Using Aspect-Oriented Petri Nets

An increasing number of social media and networking platforms have been widely used. People usually post the online comments to share their own opinions on the networking platforms with social media. Business companies are increasingly seeking effective ways to mine what people think and feel regarding their products and services. How to correctly understand the online customers’ reviews becomes an important issue. This study aims to propose a method with the aspect-oriented Petri nets (AOPN) to improve the examination correctness without changing any process and program. We collect those comments from the online reviews with Scrapy tools, perform sentiment analysis using SnowNLP, and examine the analysis results to improve the correctness. In this paper, we apply our method for a case of the online movie comments. The experimental results have shown that AOPN is helpful for the sentiment analysis and verifying its correctness.     

基于Petri网的工作流过程建模和时间性能分析

介绍了基于Petri网的工作流建模技术,并针对一个复杂的企业生产经营活动的流程构建了一个简化灵活的模型,利用随机Petri网的性能分析方法对建立的模型进行了时间性能分析。结果表明,文中的性能分析方法可对复杂的模型进行有效地简化分析。     

基于Petri网的SET双重签名建模与分析

双重签名是安全电子交易协议的一个重要技术,它将摘要和数字签名结合起来,使得交易中的各方仅得到部分消息即可完成验证从而达成多方协议。论文利用Petri网对双重签名进行建模和形式化描述,并就安全性对此模型进行了分析。     

一种基于Petri网的多目标无死锁蚁群调度算法

蚁群算法已被广泛应用于解决调度问题,针对资源受限的项目调度问题,死锁和多目标问题是重要的课题研究。文中针对具有死锁资源受限的多目标调度问题,采用Petri网模型,研究其蚁群调度算法,以紧急项目的完成时间和所有项目的完成时间最短为优化目标,并通过仿真实验验证了文中算法的有效性和实用性。     

即时消息业务中SIMPLE和IMPS的Petri网互通模型

该文提出新的Petri网耦合规则对即时消息在SIMPLE和IMPS之间的映射建立了互通Petri网模型,通过对该模型进行严格的数学分析验证,该模型满足正确的Petri网模型所应具备的所有特性,证明了该互通映射的合理性以及可行性。     

随机高级Petri网用于计算机网络传输协议的模型与性能评价

本文讨论了具有标记变量的随机高级Ｐｅｔｒｉ网（ＳＨＬＰＮ）以及标识类型，标记变量和等价标记变量的概念，给出了具有等价标记变量可达树构造算法，并证明了等价标记变量可达集与合并状态的马尔可夫链状态空间之间的同构。本文着重描述了ＳＨＬＰＮ在计算机网络传输协议的模型与性能评价中扩，通过这个例子充分显示了这些概念和算法的有效性。     

Implementation of a Remote Hierarchical Supervision System Using Petri Nets and Agent Technology

For remote control systems, certain human operations may violate desired requirements and result in catastrophic failure. For such human-in-the-loop systems, this paper implements a hierarchical supervision system to guarantee that remote human-issued commands meet required specifications. In the presented scheme, Petri nets are applied to model, design, and verify both the local controller and the remote supervisor. Then, the agent technology is adopted to implement the supervisor as an intelligent agent for an online supervision of the remote control system. Hence, undesired resource conflicts and deadlock states can be avoided. An application to a flexible manufacturing system controlled over the Internet is provided to illustrate the developed approach. Implementation results show that by applying the presented hierarchical scheme, the supervisor has a more compact model with fewer states. Moreover, fewer request/response transmissions are consumed so that the effects of time delays and packet losses across the Internet could be moderated     

Modeling and Performance Evaluation of Inventory Systems Using Batch Deterministic and Stochastic Petri Nets

This paper presents our work on modeling and performance analysis of inventory systems using batch deterministic and stochastic Petri nets (BDSPNs). It addresses issues frequently raised by industrial companies, but did not receive enough attention by the Petri nets (PNs) community in spite of its important role in the study of discrete event systems. The BDSPN is a new class of PNs capable of describing the synchronization of discrete and batch token flows in discrete batch processes. Such processes appear in inventory systems or more general supply chains where materials are purchased in finite discrete quantities (batches of different sizes), and many operations such as inventory replenishment and customer order fulfillment are usually performed in a batch way because of the batch nature of customer orders and/or in order to take advantages of the economies of scale. In this paper, the BDSPN model is formally introduced, and its conflict resolutions of transitions and batch firing indexes are addressed. The model is then applied to the modeling and performance evaluation of various inventory systems. Analytic performance evaluation techniques are developed for the model with illustrative applications to the inventory systems. Our study shows that the model is powerful for both modeling and performance evaluation of the systems.     

SDH系统E1接口定时的高质量恢复

SDH传输网中由指针调整带来的低频抖动和漂移已经成为SDH传输网与其它传输网互通的障碍.这一问题可以通过在SDH系统的边界支路输出口处采用极低带宽的锁相环对SDH网络指针调整带来的抖动和漂移进行平滑来得到改善和解决.本文介绍了一种捕捉速度快、带宽窄、适合于多支路大规模集成的用于SDH系统E1支路接口的二阶全数字锁相环路.     

Modeling and Performance Analysis of Cognitive Radio Networks Using Stochastic Timed Colored Petri Nets

Cognitive radio (CR) is currently one of the most promising information transmission technologies to deal with the problem of spectrum scarcity and spectrum underutilization in wireless communications. CR networks aim to enhance spectrum efficiency to meet the ever-increasing demands of end users. The principle is to provide the opportunity for unlicensed users (secondary users, SUs) to temporarily and dynamically access the unused or sparsely used bandwidth while ensuring that it never interferes or degrades the performance of the incumbent license holders, commonly called primary users (PUs). This raises several challenges to be addressed in CR networks and performance of secondary users is one of the critical issues tackled in this paper. That is, we propose to devise CR networks as a retrial queueing system where PUs have preemptive priority over SUs. To calculate performance measures of the devised model under quite general assumptions about the model parameters, analytical methods are known to require hard calculations and the obtained results are generally not exploitable. For this reason, simulation modeling becomes the last resort to assess the dependability indicators. To this extend, we build the simulation model of the queueing system using Timed Stochastic Colored Petri Nets. Various useful results will be hence drawn while varying network conditions. Both exponential and Erlang distributions are considered for modeling service time of SUs. The obtained results with restrictive assumptions fit the analytical outcomes experienced for quite similar queuing models, which demonstrate the effectiveness of the proposed STCPN simulation model.

     

门户网自助系统的扩展有色Petri网建模与分析

文章探讨了一种基于扩展有色Petri网的门户网自动生成系统,详细论述了有色Petri网与面向对象技术的融合方式,给出了面向对象的扩展有色Petri网的映射规则和形式化定义,并构建了门户网自动生成系统的ECPN模型,最后利用状态空间法和系统在实际生产中的效率统计,证明了模型的可用性、高效性。