Modeling and Analysis of Logistics System Based on Stochastic Petri Net under Supply Chain Circumstances

In order to describe the impacts of adjustment ability of logistics system on the profit and cost of logistics system, we constructed a model of logistics system based on stochastic Petri net （ SPN）, and proposed a theorem for the adjustment ability of logistics system under supply chain circumstances on condition that the payoff of supply chain is a steadily increasing process. Then we put forward that a sequence of MGF （ moment generating function ） of out-of-goods risk process for logistics system is a martingale. The model we proposed can overcome shortcomings of the previous ones that can not describe the characteristics of the adjustment ability of logistics system. The results of simulation experiments are consistent with theoretical analysis.

Generalized stochastic Petri nets based models for performance analysis of communication networks of IEC61850 system

In this paper, data streams are classified into four types conforming to a standardized infrastructure of communication networks for a substation automation system （SAS） based on IEC61850 system. The data exchanged on the net are demonstrated to be stochastic according to investigation on the Ethemet communication principles. Four generalized stochastic Petri nets （GSPN） based models for performance analysis of communication networks of IEC61850 system are developed based on the three-level structure of SAS, different time requirements of the four data streams and different networks topology for different voltage level. The GSPN-based model associated with immediate and exponential transitions is proven to be theoretically isomorphic with Markov chain; hence we apply the mathematic methods of performance evaluation contained in Markov chain to the GSPN models proposed. The computer simulation of the model including only sample value data streams shows that it can meet performance evaluation needs of communication networks of IEC61850 system. Further researches should be focused on the pe^ormance of the other three models to explain clear how those different data streams are interrelated to and interact on each other.

Stochastic Petri Net Based Modeling of Emergency Medical Rescue Processes During Earthquakes

The post-disaster emergency medical rescue(EMR) is critical for people’s lives. This paper presents a stochastic Petri net(SPN) model based on the process of the rescue structure and a Markov chain model(MC), which is applied to the optimization of the EMR process, with the aim of identifying the key activities of EMR. An isomorphic MC model is developed for measuring and evaluating the time performance of the EMR process during earthquakes with the data of the 2008 Wenchuan earthquake.This paper provides a mathematical approach to simulate the process and to evaluate the efficiency of EMR. Simultaneously, the expressions of the steady state probabilities of this system under various states are obtained based on the MC, and the variations of the probabilities are analyzed by changing the firing rates for every transition. Based on the concrete data of the event, the authors find the most time consuming and critical activities for EMR decisions. The model results show that the key activities can improve the efficiency of medical rescue, providing decision-makers with rescue strategies during the large scale earthquake.

Performability analysis of avionics system with multilayer HM/FM using stochastic Petri nets

The integrated modular avionics （IMA） architecture is an open standard in avionics industry, in which the number of functionalities implemented by software is greater than ever before. In the IMA architecture, the reliability of the avionics system is highly affected by the software applications. In order to enhance the fault tolerance feature with regard to software application failures, many industrial standards propose a layered health monitoring/fault management （HM/FM） scheme to periodically check the health status of software application processes and recover the malfunctioning software process whenever an error is located. In this paper, we make an analytical study of the HM/FM system for avionics application software. We use the stochastic Petri nets （SPN） to build a formal model of each component and present a method to combine the components together to form a complete system model with respect to three interlayer query strategies. We further investigate the effectiveness of these strategies in an illustrative system.

End-of-Life Decision making in circular economy using generalized colored stochastic Petri nets

Circular economy enables to restore product value at the end of life i.e.when no longer used or damaged.Thus,the product life cycle is extended and this economy permits to reduce waste increase and resources rarefaction.There are several revaluation options(reuse,remanufacturing,recycling,...).So,decisionmakers need to assess these options to determine which is the best decision.Thus,we will present a study about an End-Of-Life(EoL)decision making which aims to facilitate the industrialization of circular economy.For this,it is essential to consider all variables and parameters impacting the decision of the product trajectory.A first part of the work proposes to identify the variables and parameters impacting the decision making.A second part proposes an assessment approach based on a modeling by Generalized Colored Stochastic Petri Net(GCSPN)and on a Monte-Carlo simulation.The approach developed is tested on an industrial example from the literature to analyze the efficiency and effectiveness of the model.This first application showed the feasibility of the approach,and also the limits of the GCSPN modelling.

STOCHASTIC OBJECT-ORIENTED PETRI NETS (SOPNS) AND ITS APPLICATION IN MODELING OF MANUFACTURING SYSTEM RELIABILITY

Object-oriented Petri nets (OPNs) is extended into stochastic object-oriented Petri nets (SOPNs) by associating the OPN of an object with stochastic transitions and introducing stochastic places. The stochastic transition of the SOPNs of a production resources can be used to model its reliability, while the SOPN of a production resource can describe its performance with reliability considered. The SOPN model of a case production system is built to illustrate the relationship between the system's performances and the failures of individual production resources.

Survivability analysis of wireless Ad hoc network using stochastic reward nets

To provide services in presence of failures or attacks in a timely manner, the network survivability was analyzed. Based on stochastic Petri nets, we put forward an effective model for ad hoe network and adopt a two-phase approach consisting of the steady-state availability analysis and the system transient performance analysis, then provide a quantitative approach for analysis of the network survivability. The results show that the proposed model is useful for the design and evaluation of the wireless ad hoc network.

An SPN analysis method for parallel scheduling in Ad Hoc networks

In this paper, a new analytic method for modeling and evaluating mobile ad hoc networks (MANET) is proposed. Petri nets technique is introduced into MANET and a packet-flow parallel scheduling scheme is presented using Stochastic Petri Nets (SPN). The flowing of tokens is used in graphics mode to characterize dynamical features of sharing a single wireless channel. Through SPN reachability analysis and isomorphic continuous time Markov process equations, some network parameters, such as channel efficiency, one-hop transmission delay etc., can be obtained. Compared with conventional performance evaluation methods, the above parameters are mathematical expressions instead of test results from a simulator.

A multiserver multiqueue network: modeling and performance analysis

A new category of system model, multiserver multiqueuenetwork(MSMQN), is proposed for distributed systems such as thegeographically distributed Web-server clusters. A MSMQN comprisesmultiple multiserver multiqueue(MSMQ)nodes distributed over thenetwork, and every node consists of a number of servers that eachcontains multiple priority queues for waiting customers. An in-coming request can be distributed to a waiting queue of any server inany node, according to the routing policy integrated by the node-selection policy at network-level, request-dispatching policy atnode-level, and request-scheduling policy at server-level.

Analysis of response time probability distribution of workflows

An evaluation approach for the response time probability distribution of workflows based on the fluid stochastic Petri net formalism is presented. Firstly, some problems about stochastic workflow net modeling are discussed. Then how to convert a stochastic workflow net model into a fluid stochastic Petri net model is described. The response time distribution can be obtained directly upon the transient state solution of the fluid stochastic Petri net model. In the proposed approach, there are not any restrictions on the structure of workflow models, and the processing times of workflow tasks can be modeled by using arbitrary probability distributions. Large workflow models can be efficiently tackled by recursively using a net reduction technique.

Modelling and analysis of hybrid stochastic timed Petri net

In this paper,an interesting Hybrid Stochastic Timed Petri Net(HSTPN)is proposed for a class of hybrid systems.The proposed HSTPN can be adopted to represent hybrid systems with discrete,continuous,conflicting,time-delay and stochastic characteristics simultaneously.The proposed HSTPN outperforms conventional hybrid Petri net models in terms of describing the scalability and immediacy of hybrid systems.Advantages of the HSTPN on describing hybrid system are verified by establishing some equivalent models of HPN and its derived models.

Anti-Attacking Modeling and Analysis of Cyberspace Mimic DNS

With the rapid development of information technology,the cyberspace security problem is increasingly serious.Kinds of dynamic defense technology have emerged such as moving target defense and mimic defense.This paper aims to describe the architecture and analyze the performance of Cyberspace Mimic DNS based on generalized stochastic Petri net.We propose a general method of anti-attacking analysis.For general attack and special attack model,the available probability,escaped probability and nonspecial awareness probability are adopted to quantitatively analyze the system performance.And we expand the GSPN model to adjust to engineering practice by specifying randomness of different output vectors.The result shows that the proposed method is effective,and Mimic system has high anti-attacking performance.To deal with the special attack,we can integrate the traditional defense mechanism in engineering practice.Besides,we analyze the performance of mimic DNSframework based on multi-ruling proxy and input-output desperation,the results represent we can use multi ruling or high-speed cache servers to achieve the consistent cost of delay,throughput compared with single authorized DNS,it can effectively solve 10%to 20%performance loss caused by general ruling proxy.

Modeling and performance evaluation of QoS-aware job scheduling of computational grids

To achieve high quality of service （QoS） on computational grids, the QoS-aware job scheduling is investigated for a hierarchical decentralized grid architecture that consists of multilevel schedulers. An integrated QoS-aware job dispatching policy is proposed, which correlates priorities of incoming jobs used for job selecting at the local scheduler of the grid node with the job dispatching policies at the global scheduler for computational grids. The stochastic high-level Petri net （SHLPN） model of a two-level hierarchy computational grid architecture is presented, and a model refinement is made to reduce the complexity of the model solution. A performance analysis technique based on the SHLPN is proposed to investigate the QoS-aware job scheduling policy. Numerical results show that the QoS-aware job dispatching policy outperforms the QoS-unaware job dispatching policy in balancing the high-priority jobs, and thus enables priority-based QoS.

Stochastic individual predicate/transition nets

We analyze the drawbacks of generally distributed time transition stochastic Petri nets(GDTT_SPN) in evaluating the performance of parallel systems,and propose a more general model,stochastic individual predicate/transition nets(SIPTN). SIPTN has higher modeling power and could provide more realistic models compared to GDTT_SPN,because in SIPTN the sojourn time distribution is determined not only by the transition,but also by the individuals. It is further proved that GDTT_SPN is a subset of SIPTN. As SIPTN introduces folding techniques from predicate/transition nets,SIPTN models have simpler and more intuitive graphic notations and accordingly higher usability,and thus are suitable for constructing simulation models for parallel systems.

A LIMITED RESOURCE VECTOR LOAD-BALANCING ALGORITHM FOR SOFTSWITCH-BASED HETEROGENEOUS CLUSTERED MEDIA SERVER

Based on the system feature of softswitch-based heterogeneous clustered media server, this paper proposed a limited resource vector load-balancing algorithm. The purpose of the algorithm was to balance the load of clusters by utilizing all system resources effectively and to avoid violent shaking of the system per- formance. A lot of simulations on the Petri net model of load balance system are conducted and the algorithm is compared with some traditional algorithms on balancing ability for heterogeneity, system throughput, re- quest response time and performance stability. The results of simulations show that the algorithm achieves system higher performance and it has excellent ability to deal with the heterogeneity of clustered media server.

A NEW DYNAMIC QUOTA-BASED ADMISSION CONTROL WITH SUB-NEGOTIATION FOR SOFTSWITCH-BASED CLUSTERED MEDIA SERVER

Based on the demand of the admission control of softswitch-based clustered media server, this pa- per proposed a new dynamic quota-based admission control algorithm that has a sub-negotiation process. The strongpoint of quota-based algorithm had been inherited in the algorithm and at the same time some new ideas had also been introduced into it. Simulations of the algorithm had been conducted on the Petri net model and the results show that this algorithm has excellent performance. In order to find the optimal resource quota set- ting in real time, the paper proposed two approximation analysis methods. It can be seen from analysis results that these two methods can be used to get sub-optimal quota values quickly and effectively. These two ap- proximation analysis methods will play important roles in implementation of the algorithm in system.

Availability evaluation of controller area networks under the influence of intermittent connection faults

Controller area networks(CANs),as one of the widely used fieldbuses in the industry,have been extended to the automation field with strict standards for safety and reliability.In practice,factors such as fatigue and insulation wear of the cables can cause intermittent connection(IC)faults to occur frequently in the CAN,which will affect the dynamic behavior and the safety of the system.Hence,quantitatively evaluating the performance of the CAN under the influence of IC faults is crucial to real-time health monitoring of the system.In this paper,a novel methodology is proposed for real-time quantitative evaluation of CAN availability when considering IC faults,with the system availability parameter being calculated based on the network state transition model.First,the causal relationship between IC fault and network error response is constructed,based on which the IC fault arrival rate is estimated.Second,the states of the network considering IC faults are analyzed,and the deterministic and stochastic Petri net(DSPN)model is applied to describe the transition relationship of the states.Then,the parameters of the DSPN model are determined and the availability of the system is calculated based on the probability distribution and physical meaning of markings in the DSPN model.A testbed is constructed and case studies are conducted to verify the proposed methodology under various experimental setups.Experimental results show that the estimation results obtained using the proposed method agree well with the actual values.

Performance Modeling and Approximate Analysis of Multiserver Multiqueue Systems with Poisson and Self-similar Arrivals

The problem of state space explosion is still ran outstanding challenge in Markovian performance analysis for multiserver multiqueue (MSMQ) systems. The system behavior of a MSMQ system is described using stochastic high-level Petri net (SHLPN) models, and an approximate performance analysis technique is proposed based on decomposition and refinement methods as well as iteration technique. A real MSMQ system, Web-server cluster, is investigated. The performance of an integrated scheme of request dispatching and scheduling is analyzed with both Poisson and self-similar request arrivals. The study shows that the approximate analysis technique significantly reduces the complexity of the model solution and is also efficient for accuracy of numerical results.

Electricity Services Based Dependability Model of Power Grid Communication Networking

The technology of Ultra-High Voltage （UHV） transmission requires higher dependability for electric power grid. Power Grid Communication Networking （PGCN）, the fundamental information infrastructure, severs data transmission including control signal, protection signal, and common data services. Dependability is the necessary requirement to ensure services timely and accurately. Dependability analysis aims to predicate operation status and provide suitable strategies getting rid of the potential dangers. Due to the dependability of PGCN may be affected by external environment, devices quality, implementation strategies, and so on, the scale explosion and the structure complexity make the PGCN＇s dependability much challenging. In this paper, with the observation of interdependency between power grid and PGCN, we propose an electricity services based dependability analysis model of PGCN. The model includes methods of analyzing its dependability and procedures of designing the dependable strategies. We respectively discuss the deterministic analysis method based on matrix analysis and stochastic analysis model based on stochastic Petri nets.

An SPN-Based Integrated Model for Web Prefetching and Caching

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.