• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.1
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• pp.14-22
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• 2002

We propose the fuzzy BCMP queueing network model for the performance evaluation of distributed processing system with the ambiguous arrival rates of job, service requirements, and service rates of server by the network environments. This model is classified as the open and closed type whether or not the network accepts jobs from the system outside. We derived the measures for system performances such as the job average spending time, average job number in the system and server utilizations using fuzzy mean value analysis which can process the fuzzy factors for both types. Computer simulation was performed for verifying the effectiveness of derived equations of performance evaluation. The fuzzy BCMP queueing network model was evaluated according to the fuzzy arrival rates of job, the number of clients, and the fuzzy service requirements of job for each the open and closed type. The results were agreed with the predicted performance evaluations of the system.

• Journal of the Korea Society of Computer and Information
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• v.6 no.4
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• pp.138-145
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• 2001

In this paper, we propose fuzzy closed BCMP queueing network model for the performance evaluation of distributed processing system. Which has the ambiguous service requirements of job to servers and service rates of server according to network environments. This model can derive the measures for system Performances using fuzzy mean value analysis which can process the fuzzy factors. Computer simulation has been performed for verifying the effectiveness of derived equations of performance evaluation according to service requirements of job and the numbers of clients.

• Journal of the Korean Operations Research and Management Science Society
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• v.22 no.1
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• pp.101-121
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• 1997

Consider a Jackson type closed queueing network in which each queue has a single exponential server. Assume that N customers are moving among .kappa. queues. We propose a candidata procedure which yields a lower bound of the network throughput which is sharper than those which are currently available : Let (.rho.$_{1}$, ... .rho.$_{\kappa}$) be the loading vector, let x be a real number with 0 .leq. x .leq. N, and let y(x) denote that y is a function of x and be the unique positive solution of the equation. .sum.$_{i = 1}$$^{\kappa}$y(x) .rho.$_{i}$ (N - y(x) x $p_{i}$ ) = 1 Whitt [17] has shown that y(N) is a lower bound for the throughput. In this paper, we present evidence that y(N -1) is also a lower bound. In dosing so, we are led to formulate a rather general conjecture on 'quot;Migrating Critical Points'quot; (MCP). The .MCP. conjecture asserts that zeros of successive derivatives of certain rational functions migrate at an accelerating rate. We provide a proof of MCP in the polynomial case and some other special cases, including that in which the rational function has exactly two real poles and fewer than three real zeros.tion has exactly two real poles and fewer than three real zeros.

• Journal of the Korean Operations Research and Management Science Society
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• v.13 no.1
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• pp.24-30
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• 1988

We study the optimal allocation of machines and pallets in a class of manufacturing systems. The FMS is modeled as a closed queueing network with balanced loading of the stations. An Algorithm is developed, which exploits the properties of the throughput function and solves the allocation problem for increasing concave profit and convex cost. We also study the more general case of allocating machines and pallets among a set of FMSs. A dynamic programming approach is developed, which solves the problem with O(M$^{3}$N$^{2}$) operations.

• Journal of the Korean Operations Research and Management Science Society
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• v.23 no.4
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• pp.75-86
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• 1998

We address the problem of determining the optimal processing times and pallet/fixture allocation in Flexible Manufacturing systems in order to minimize tool cost while meeting throughput targets of multiple part types. The problem is formulated as a nonlinear program superimposed on a closed queueing network of the FMSs under consideration. A numerical example reveals the potential of our approach for significant cost saving. We argue that our model can be Integrated Into the process planning system of an FMS to generate efficient process plans quickly.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.67
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• pp.19-26
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• 2001

A design issue for a flexible manufacturing system is to find the number of each resource type which assures a given production ratio with a minimal cost. The FMS is modeled as a closed queueing network with a local buffer of limited capacity. An efficient method to determine this optical configuration is presented. The proposed method consists of three steps : 1) determine a lower configuration, 2) derive a heuristic solution, 3) find the optimal solution. The derived heuristic solutions are close to the optical solution.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.43
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• pp.99-107
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• 1997

We consider a multiechelon repairable-item inventory system where several bases are supported by a central depot and the external repair facilities. Unlike METRIC- based models, there are only a finite number of repair channels at each base, central depot and the external repair facilities. It is desired to find repair capacities and spares level which together guarantee a specified service level at minimum cost. Closed queueing network theory is used to model the stochastic process. The purpose of this paper is to derive the steady-state distributions of this system.

• Journal of the military operations research society of Korea
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• v.15 no.1
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• pp.14-27
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• 1989

This paper deals with the mission effectiveness of an airfleet, Airfleet operating system consists of a finite number of units performing the several mission types. Earlier works for the mission effectiveness of a fleet is limited to only one mission type and computer simulation approaches. The mission effectiveness. model of a fleet is constructed by three attributes - the mission readiness of the units, the mission reliability and capability of units. The environmental conditions and human factors affecting the mission success are considered together. The solution of the model is obtained by analytical technique. Especially, AOS is considered a closed queueing network with a finite number of units and a single job class. And then, the mission readiness of the units is found by the mean value analysis. The model would be a useful tool to readily evaluate mission effectiveness of a airfleet as it is and provide a criterion for determining the optimal operating policy.

• Journal of Korean Society for Quality Management
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• v.19 no.1
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• pp.129-140
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• 1991

This paper deals with on (S-1, S) spare-part inventory model for multi-stage machine repair problem with attrition. The steady-state availability of the system is maximized under some constraints such as total cost, available space etc.. The problem is formulated as a closed queueing network and the system availability is calculated by Buzen's computational algorithm. In order to find the optimal numbers of spare units and repair channels for each operating stage, the problem is formulated as a non-linear integer programming(NLIP) problem and an efficient algorithm. which is a natural extension of the new Lawler-Bell algorithm of Sasaki et el., is used to solve the NLIP problem. A numerical example is given to illustrate the algorithm.

• Journal of Korean Institute of Industrial Engineers
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• v.15 no.1
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• pp.105-116
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• 1989

This study presents an algorithm that determines the optimal configuration of the FMSs with limited local buffers. The algorithm finds the lowest cost configuration, i.e. the number of tools, the number of pallets as well as the number of buffers to be installed in front of each machine in the system. Thus it assures a given production ratio with a minimum cost. In the algorithm, FMSs are considered as the closed queueing network with limited queue length. System performance evaluation is performed using the Block-&-Recirculation model developed by Yao and Buzacott. The algorithm is composed with three steps. The steps are namely i) determination of a lower configuration, ii) derivation of an heuristic solution, and iii) obtaining the optimal solution. The computational efforts required in the algorithm usually lies within the capability of personal computers.