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...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.展开更多
多工序加工系统中最终产品的尺寸误差是所有加工工序上尺寸误差累积、耦合与传递的结果。目前方法是建立数学模型对多工序加工系统尺寸误差传递进行分析,而缺乏逻辑层次上的建模理论和方法。为解决多工序加工系统中尺寸误差传递的逻辑...多工序加工系统中最终产品的尺寸误差是所有加工工序上尺寸误差累积、耦合与传递的结果。目前方法是建立数学模型对多工序加工系统尺寸误差传递进行分析,而缺乏逻辑层次上的建模理论和方法。为解决多工序加工系统中尺寸误差传递的逻辑分析问题,采用面向对象Petri网方法,在定义误差状态通用物理对象基础上,建立通用物理对象和加工系统的映射规则,对误差状态子类物理对象进行继承和封装,设计出误差状态消息传递关系网。建立的产品尺寸误差面向对象Petri网(Errors of product dimension-object oriented Petri net,EPD-OPN)模型可以作为多工序加工系统中尺寸误差传递动态分析和故障诊断依据。通过发动机缸盖的多工序加工过程为例证明该模型的有效性和可行性。该模型具有模块化、可重复使用性的特点和结构化的复杂逻辑关系描述能力,是目前数学模型很好的扩展。展开更多
The problem of constructing a Petri net feedback controller, which enforces the conjunction of a set of linear inequalities on the reachable marking of the place and transition modeled by Petri net, is discussed. A ne...The problem of constructing a Petri net feedback controller, which enforces the conjunction of a set of linear inequalities on the reachable marking of the place and transition modeled by Petri net, is discussed. A new method of controller design with mixed constraint is presented, and a net reduction technique of Petri net fuses all the constrained places into one place whose marking is equal to the sum of the markings of the constrained places, and then compared with the constrained transitions. The net reduction eases the design of controller and holds remarkable advantages especially for systems with large scale. The method is proved to be simpler and more efficient than the method presented by Yamalidou, et al, using an applied case used by Yamalidou, et al.展开更多
过程挖掘技术将观察到的行为(即事件日志)与建模的行为(如bpmn模型或petri网)联系起来.可以通过对日志进行挖掘,获得实际业务流程模型,再对其中关联严格结构检测,通过并行优化的方法优化实际业务流程模型.目前的业务流程优化主要是针对...过程挖掘技术将观察到的行为(即事件日志)与建模的行为(如bpmn模型或petri网)联系起来.可以通过对日志进行挖掘,获得实际业务流程模型,再对其中关联严格结构检测,通过并行优化的方法优化实际业务流程模型.目前的业务流程优化主要是针对管理者或开发者给出的业务流程模型,其与实际运行中的业务流程可能与之有些许偏差,从而影响了优化结果.在此提出一种新方法对业务流程进行优化.首先使用Prom框架中的Alpha Miner及Heuristic miner获得流程模型的PetriNet及C-net结构;然后使用最大分解的方法修复流程模型;针对修复后的模型提出其中高频简单网部分,并发现关联严格结构,使用Colored Petri nets对关联严格结构重新构造为关联并行结构,确定优化结果.该方法通过实际业务流程的研究案例及比较实验进行评估,其结果表明关联并行优化可明显缩短实际业务流程耗时.展开更多
Recently automotive nets are adopted to solve increasing problems in automotive electronic systems.Technologies of automotive local area network from CAN and LIN can solve the problems of the increasing of wire bunch ...Recently automotive nets are adopted to solve increasing problems in automotive electronic systems.Technologies of automotive local area network from CAN and LIN can solve the problems of the increasing of wire bunch weight and lack in module installation space.However,the multilayer automotive nets software becomes more and more complex,and the development expense is difficult to predict and to keep in check.In this paper,the modeling method of hierarchical automotive nets and the substitution operation based on object-oriented colored Petri net(OOCPN) are proposed.The OOCPN model which analyzes the software structure and validates the collision mechanism of CAN/LIN bus can speed the automobile system development.First,the subsystems are divided and modeled by object-oriented Petri net(OOPN).According to the sets of message sharing relations,the message ports among them are set and the communication gate transitions are defined.Second,the OOPN model is substituted step by step until the inner objects in the automotive body control modules(BCM) are indivisible and colored by colored Petri net(CPN).And the color subsets mark the node messages for the collision mechanism.Third,the OOCPN model of the automotive body CAN/LIN nets is assembled,which keeps the message sets and the system can be expanded.The proposed model is used to analyze features of information sharing among the objects,and it is also used to describe each subsystem real-time behavior of processing messages and implemental device controllers operating,and puts forward a reasonable software framework for the automotive body control subsystem.The research can help to design the communication model in the automotive body system effectively and provide a convenient and rapid way for developing the logical hierarchy software.展开更多
The command and control（C2） is a decision-making process based on human cognition,which contains operational,physical,and human characteristics,so it takes on uncertainty and complexity.As a decision support approac...The command and control（C2） is a decision-making process based on human cognition,which contains operational,physical,and human characteristics,so it takes on uncertainty and complexity.As a decision support approach,Bayesian networks（BNs） provide a framework in which a decision is made by combining the experts＇ knowledge and the specific data.In addition,an expert system represented by human cognitive framework is adopted to express the real-time decision-making process of the decision maker.The combination of the Bayesian decision support and human cognitive framework in the C2 of a specific application field is modeled and executed by colored Petri nets（CPNs）,and the consequences of execution manifest such combination can perfectly present the decision-making process in C2.展开更多
Sometimes historic information about workflow execution is needed to analyze business processes. Process mining aims at extracting information from event logs for capturing a business process in execution. In this pap...Sometimes historic information about workflow execution is needed to analyze business processes. Process mining aims at extracting information from event logs for capturing a business process in execution. In this paper a process mining algorithm is proposed based on Synchro-Net which is a synchronization-based model of workflow logic and workflow semantics. With this mining algorithm based on the model, problems such as invisible tasks and short-loops can be dealt with at ease. A process mining example is presented to illustrate the algorithm, and the evaluation is also given.展开更多
In response to the production capacity and functionality variations, a genetic algorithm （GA） embedded with deterministic timed Petri nets（DTPN） for reconfigurable production line（RPL） is proposed to solve its s...In response to the production capacity and functionality variations, a genetic algorithm （GA） embedded with deterministic timed Petri nets（DTPN） for reconfigurable production line（RPL） is proposed to solve its scheduling problem. The basic DTPN modules are presented to model the corresponding variable structures in RPL, and then the scheduling model of the whole RPL is constructed. And in the scheduling algorithm, firing sequences of the Petri nets model are used as chromosomes, thus the selection, crossover, and mutation operator do not deal with the elements in the problem space, but the elements of Petri nets model. Accordingly, all the algorithms for GA operations embedded with Petri nets model are proposed. Moreover, the new weighted single-objective optimization based on reconfiguration cost and E/T is used. The results of a DC motor RPL scheduling suggest that the presented DTPN-GA scheduling algorithm has a significant impact on RPL scheduling, and provide obvious improvements over the conventional scheduling method in practice that meets duedate, minimizes reconfiguration cost, and enhances cost effectivity.展开更多
A treelike hybrid multi-cluster tool is composed of both single-arm and dual-arm cluster tools with a treelike topology. Scheduling such a tool is challenging. For a hybrid treelike multi-cluster tool whose bottleneck...A treelike hybrid multi-cluster tool is composed of both single-arm and dual-arm cluster tools with a treelike topology. Scheduling such a tool is challenging. For a hybrid treelike multi-cluster tool whose bottleneck individual tool is process-bound, this work aims at finding its optimal one-wafer cyclic schedule. It is modeled with Petri nets such that a onewafer cyclic schedule is parameterized as its robots' waiting time.Based on the model, this work proves the existence of its onewafer cyclic schedule that features with the ease of industrial implementation. Then, computationally efficient algorithms are proposed to find the minimal cycle time and optimal onewafer cyclic schedule. Multi-cluster tool examples are given to illustrate the proposed approach. The use of the found schedules enables industrial multi-cluster tools to operate with their highest productivity.展开更多
Workflow management aims at the controlling, monitoring, optimizing and supporting of business processes. Well designed formal models will facilitate such management since they provide explicit representations of busi...Workflow management aims at the controlling, monitoring, optimizing and supporting of business processes. Well designed formal models will facilitate such management since they provide explicit representations of business processes as the basis for computerized analysis, verification and execution. Petri Nets have been recognized as the most suitable candidate for workflow modeling, and as such, formal models based on Petri Nets have been proposed, among them WF-net by Aalst is the most popular one. But WF-net has turned out to be conceptually chaotic as will be illustrated in this paper with an example from Aalst＇s book. This paper proposes a series of models for the description and analysis of business processes at conceptually different hierarchical layers. Analytic goals and methods at these layers are also discussed. The underlying structure, shared by all these models, is SYNCHRONIZER, which is designed with the guidance of synchrony theory of GNT （General Net Theory） and serves as the conceptual foundation of workflow formal models. Structurally, synchronizers connect tasks to form a whole while dynamically synchronizers control tasks to achieve synchronization.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No. 60472044. The authors would like to thank research fellow Dr. Yun Shi of China State Post Bureau and Professor Dr. Jun Zou of Tsinghua University for their helpful and constructive comments.
文摘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.
文摘多工序加工系统中最终产品的尺寸误差是所有加工工序上尺寸误差累积、耦合与传递的结果。目前方法是建立数学模型对多工序加工系统尺寸误差传递进行分析,而缺乏逻辑层次上的建模理论和方法。为解决多工序加工系统中尺寸误差传递的逻辑分析问题,采用面向对象Petri网方法,在定义误差状态通用物理对象基础上,建立通用物理对象和加工系统的映射规则,对误差状态子类物理对象进行继承和封装,设计出误差状态消息传递关系网。建立的产品尺寸误差面向对象Petri网(Errors of product dimension-object oriented Petri net,EPD-OPN)模型可以作为多工序加工系统中尺寸误差传递动态分析和故障诊断依据。通过发动机缸盖的多工序加工过程为例证明该模型的有效性和可行性。该模型具有模块化、可重复使用性的特点和结构化的复杂逻辑关系描述能力,是目前数学模型很好的扩展。
文摘The problem of constructing a Petri net feedback controller, which enforces the conjunction of a set of linear inequalities on the reachable marking of the place and transition modeled by Petri net, is discussed. A new method of controller design with mixed constraint is presented, and a net reduction technique of Petri net fuses all the constrained places into one place whose marking is equal to the sum of the markings of the constrained places, and then compared with the constrained transitions. The net reduction eases the design of controller and holds remarkable advantages especially for systems with large scale. The method is proved to be simpler and more efficient than the method presented by Yamalidou, et al, using an applied case used by Yamalidou, et al.
文摘过程挖掘技术将观察到的行为(即事件日志)与建模的行为(如bpmn模型或petri网)联系起来.可以通过对日志进行挖掘,获得实际业务流程模型,再对其中关联严格结构检测,通过并行优化的方法优化实际业务流程模型.目前的业务流程优化主要是针对管理者或开发者给出的业务流程模型,其与实际运行中的业务流程可能与之有些许偏差,从而影响了优化结果.在此提出一种新方法对业务流程进行优化.首先使用Prom框架中的Alpha Miner及Heuristic miner获得流程模型的PetriNet及C-net结构;然后使用最大分解的方法修复流程模型;针对修复后的模型提出其中高频简单网部分,并发现关联严格结构,使用Colored Petri nets对关联严格结构重新构造为关联并行结构,确定优化结果.该方法通过实际业务流程的研究案例及比较实验进行评估,其结果表明关联并行优化可明显缩短实际业务流程耗时.
基金supported by National Natural Science Foundation of China (Grant No. 60873003)
文摘Recently automotive nets are adopted to solve increasing problems in automotive electronic systems.Technologies of automotive local area network from CAN and LIN can solve the problems of the increasing of wire bunch weight and lack in module installation space.However,the multilayer automotive nets software becomes more and more complex,and the development expense is difficult to predict and to keep in check.In this paper,the modeling method of hierarchical automotive nets and the substitution operation based on object-oriented colored Petri net(OOCPN) are proposed.The OOCPN model which analyzes the software structure and validates the collision mechanism of CAN/LIN bus can speed the automobile system development.First,the subsystems are divided and modeled by object-oriented Petri net(OOPN).According to the sets of message sharing relations,the message ports among them are set and the communication gate transitions are defined.Second,the OOPN model is substituted step by step until the inner objects in the automotive body control modules(BCM) are indivisible and colored by colored Petri net(CPN).And the color subsets mark the node messages for the collision mechanism.Third,the OOCPN model of the automotive body CAN/LIN nets is assembled,which keeps the message sets and the system can be expanded.The proposed model is used to analyze features of information sharing among the objects,and it is also used to describe each subsystem real-time behavior of processing messages and implemental device controllers operating,and puts forward a reasonable software framework for the automotive body control subsystem.The research can help to design the communication model in the automotive body system effectively and provide a convenient and rapid way for developing the logical hierarchy software.
基金supported by the National Natural Science Foundation of China (60874068)
文摘The command and control（C2） is a decision-making process based on human cognition,which contains operational,physical,and human characteristics,so it takes on uncertainty and complexity.As a decision support approach,Bayesian networks（BNs） provide a framework in which a decision is made by combining the experts＇ knowledge and the specific data.In addition,an expert system represented by human cognitive framework is adopted to express the real-time decision-making process of the decision maker.The combination of the Bayesian decision support and human cognitive framework in the C2 of a specific application field is modeled and executed by colored Petri nets（CPNs）,and the consequences of execution manifest such combination can perfectly present the decision-making process in C2.
基金Supported by the National Natural Science Foundation of China under Grant No. 60473058.
文摘Sometimes historic information about workflow execution is needed to analyze business processes. Process mining aims at extracting information from event logs for capturing a business process in execution. In this paper a process mining algorithm is proposed based on Synchro-Net which is a synchronization-based model of workflow logic and workflow semantics. With this mining algorithm based on the model, problems such as invisible tasks and short-loops can be dealt with at ease. A process mining example is presented to illustrate the algorithm, and the evaluation is also given.
基金This project is supported by Key Science-Technology Project of Shanghai City Tenth Five-Year-Plan, China (No.031111002)Specialized Research Fund for the Doctoral Program of Higher Education, China (No.20040247033)Municipal Key Basic Research Program of Shanghai, China (No.05JC14060)
文摘In response to the production capacity and functionality variations, a genetic algorithm （GA） embedded with deterministic timed Petri nets（DTPN） for reconfigurable production line（RPL） is proposed to solve its scheduling problem. The basic DTPN modules are presented to model the corresponding variable structures in RPL, and then the scheduling model of the whole RPL is constructed. And in the scheduling algorithm, firing sequences of the Petri nets model are used as chromosomes, thus the selection, crossover, and mutation operator do not deal with the elements in the problem space, but the elements of Petri nets model. Accordingly, all the algorithms for GA operations embedded with Petri nets model are proposed. Moreover, the new weighted single-objective optimization based on reconfiguration cost and E/T is used. The results of a DC motor RPL scheduling suggest that the presented DTPN-GA scheduling algorithm has a significant impact on RPL scheduling, and provide obvious improvements over the conventional scheduling method in practice that meets duedate, minimizes reconfiguration cost, and enhances cost effectivity.
基金supported in part by Science and Technology Development Fund(FDCT)of Macao(106/2016/A3)the National Natural Science Foundation of China(U1401240)the Delta Electronics Inc and the National Research Foundation(NRF)Singapore under the Corp Lab@University Scheme
文摘A treelike hybrid multi-cluster tool is composed of both single-arm and dual-arm cluster tools with a treelike topology. Scheduling such a tool is challenging. For a hybrid treelike multi-cluster tool whose bottleneck individual tool is process-bound, this work aims at finding its optimal one-wafer cyclic schedule. It is modeled with Petri nets such that a onewafer cyclic schedule is parameterized as its robots' waiting time.Based on the model, this work proves the existence of its onewafer cyclic schedule that features with the ease of industrial implementation. Then, computationally efficient algorithms are proposed to find the minimal cycle time and optimal onewafer cyclic schedule. Multi-cluster tool examples are given to illustrate the proposed approach. The use of the found schedules enables industrial multi-cluster tools to operate with their highest productivity.
基金Supported by the National Natural Science Foundation of China nnder Grant No.60473058the National Grand Fundamental Research 973 Program of China under Graut Nos.2002CB312004,2002CB312006.
文摘Workflow management aims at the controlling, monitoring, optimizing and supporting of business processes. Well designed formal models will facilitate such management since they provide explicit representations of business processes as the basis for computerized analysis, verification and execution. Petri Nets have been recognized as the most suitable candidate for workflow modeling, and as such, formal models based on Petri Nets have been proposed, among them WF-net by Aalst is the most popular one. But WF-net has turned out to be conceptually chaotic as will be illustrated in this paper with an example from Aalst＇s book. This paper proposes a series of models for the description and analysis of business processes at conceptually different hierarchical layers. Analytic goals and methods at these layers are also discussed. The underlying structure, shared by all these models, is SYNCHRONIZER, which is designed with the guidance of synchrony theory of GNT （General Net Theory） and serves as the conceptual foundation of workflow formal models. Structurally, synchronizers connect tasks to form a whole while dynamically synchronizers control tasks to achieve synchronization.
