• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.9
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• pp.1717-1722
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• 2016

Availability, one of the important metrics used to assess the performance of network system, is defined as the probability that a system is operational at a given point in time under a given set of environmental conditions. To improve the availability of the network service, the redundancy models and the rejuvenation schemes are the effective schemes to be typically used. In this paper, we analyse the effect of 2N redundancy model and/or rejuvenation scheme on the availability of network service. The 2N redundancy model consists of one active and one standby component and the performance of time-based rejuvenation scheme mainly depends on its rejuvenation period. We design stochastic reward net model for the 2N redundancy model with time-based rejuvenation scheme and analyse the service availability of the model using stochastic Petri net package. We provide some numerical examples of the service availability, which shows that the system with rejuvenation has higher availability than the system without rejuvenation.

• Journal of Korean Society for Quality Management
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• v.18 no.2
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• pp.54-68
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• 1990

Contingency response in a FMS system requires that the system be able to identify and evaluate a number of alternatives. This paper is outlined that DSS completes with a problem processor in corporating Timed Petri Nets model, and a data base system. DSS enables the FMS user to get the maximum benefit from a FMS. The structure of this DSS parallels the organizational activities involved in running the FMS. In designing a shop floor controller for FMS, interactions between the different real time, discrete event functions must be established. The specification of the machine tool and material handling system functions working as a concurrent and cooperative system is given in terms of Timed Petri Nets. In addition, the basic concepts and uses of Petri Nets are surveyed. The system to be studied is first modelled by a Timed Petri Nets and then procedure for evaluating the FMS system performance are presented. Numerical examples are studied to illustrate a session of the FMS used-DSS interaction.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.4
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• pp.292-298
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• 2002

We focus on the slicing off some sub-nets using the transitive matrix. Control flows in the Petri nets is done based on the token flows. One control f]ow explains the independent tokens status and if the token-in divides into several tokens after firing a transition then the control flow divides to several flows, as well. Accordingly, we define that the basic unit of concur-rency (short BUC) is a set of the executed control flows based on the behavioral properties in the net. The BUC is S-invariant which has one control flow. We show the usefulness of transitive matrix to slice off some subnets from the original net based on BUC-through on an example.

• Transactions on Control, Automation and Systems Engineering
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• v.2 no.2
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• pp.121-129
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• 2000

In this paper, an optimal group control for elevator systems is proposed with timed Petri net based approach. Elevator system is modeled by time Petri nets and hall call response times are estimated with moment generating functions (MGFs) methos, which is applicable to real traffic patterns. Two assignment policies are proposed to satisfy the demands of passengers(i.e. hall/car calls) and to handle exceptional situations. In addition, optimal algorithms are implementated to minimize cost functions. THe performances of the elevator system employing the proposed algorithms are compared with each others in ways of several performance measures by a computer simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.101-108
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• 1997

The initial token value required to the optimal performance of discrete event systems can be decided by Sum of Delay Time and Synchronic Time ratio, which are new synchronic variables in Timed Place Petri Nets. For the system consisting of two Live-and-Bounded circuits(LB-circuits) fused in common Transition-Transition-Path or common Place-Place-Path, we prove that the Synchronic Time Ratio is the initial token ratio between two LB-circuits to optimally perform system functions. These results are generalized and formulated as a theorem. The initial tokens of a specific place can imply shared resources. Using the theorem, we can decide the minimum number of the shared resources to obtain the optimal performance, and minimize the idling time of resources. As an example, an automated assembly system is modeled by Timed Place Petri Net, and the initial tokens to achieve the optimal system performance are identified. All the values are verified by simulation.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.975-978
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• 2002

A new conception of public-key cryptography MEPKC, Petri net based Multi-stage-Encryption Public-Key Cryptography, has been proposed in onder to guarantee stronger network communication security. Different from an ordinary public-key cryptography that opens only a single public key to the public, MEPKC opens a key-generator that can generate multiple encryption keys and uses these keys to encrypt a plain text to a cipher text stage by stage. In this paper, we propose the methods how to carry out the encryption operations. First, we describe how to design a hash function H that is used to conceal the encryption keys from attack. Then, given with a key-generator (a Petri net supposed to possess a large number of elementary T-invariants), we discuss how to randomly generate a series of encryption keys, the elementary T-invariants. Finally, we show how to use these encryption keys to encrypt a plain text to a cipher text by applying a private key cryptography, say DES.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1990.04a
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• pp.22-31
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• 1990

In this paper, we have studied modelling and simulation of computer communication protocols theoretically. After describing a definition and functions of communication protocols, we have classified models for protocol design. And, in those protocol models, by endowing Timed Petri Net (TPN) models with a time function .tau., we have proposed a structural definition of TPN models. Furthermore, in order to complement Petri Net Based models with some problems, we have introduced the Discrete EVent system Specification (DEVS) concept in system simulation field. As an important result of our study, we have presented a theorem, which says that a TPN model becomes a DEVS model, and proved it. According to the theorem, we can perform efficient simulation by using the DEVS model transformed from a TPN model when we intend the TPN model to be simulated, otherwise we design another simulation model for it.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.29B no.7
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• pp.30-41
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• 1992

As a general model of rule-based systems, we propose a model for a fuzzy production system having chaining rules and an inference engine associated with the model. The concept of so-called 'fuzzy petri nets' is used to model the fuzzy production system and the inference engine is designed to be capable of handling inexact knowledge. The fuzzy logic is adopted to represent vagueness in the rules and the certainty factor is used to express uncertainty of each rules given by a human expert. Parallel, inference schemes are devised by transforming Fuzzy Petri nets to matrix formula. Futher, the inference engine mechanism under the Mamdani's implication method can be desceribed by a simple algebraic formula, which makes real time inference possible.

• Journal of Korean Society for Quality Management
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• v.31 no.3
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• pp.114-125
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• 2003

In this paper, we deal with the problem of modeling of agent-based robot manufacturing cell. Its role is becoming increasingly important in automated manufacturing systems. For Object Oriented & Queueing Petri Nets (OO&QPNs), an extended formalism for the combined quantitative and qualitative analysis of different systems is used for structure and performance analysis of mobile robotic cell. In the case study, the OO&QPN model of a mobile robotic cell is represented and analyzed, considering multi-class parts, non-preemptive priority and alternative routing. Finally, the comparison of performance values between Shortest Process Time (SPT) rule and First Come First Serve (FCFS) rule is suggested. In general, SPT rule is most suitable for parts that have shorter processing time than others.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5512-5517
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• 2012

In this paper we suggest multimedia synchronization model that is based on the Petri-net and services desirable quality of service requirement. Proposed model applies variable buffer which can be allowed, and then it presents high quality of service and real time characteristics. This paper decreases the data loss resulted from variation of delay time and from loss time of media-data by means of applying delay jitter in order to deal with synchronization interval adjustment. Plus, the mechanism adaptively manages the waiting time of smoothing buffer, which leads to minimize the gap from the variation of delay time. The proposed paper is suitable to the system which requires the guarantee of high quality of service and mechanism improves quality of services such as decrease of loss rate, increase of playout rate.