• 전자공학회논문지CI
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• 제39권1호
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• pp.14-22
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• 2002

분산처리시스템에서 작업의 도착률과 서비스요구, 그리고 서버의 서비스률 등이 네트워크환경에 따라 모호성을 갖는 경우, 시스템의 성능을 평가할 수 있는 퍼지 BCMP 큐잉네트워크모델을 제안하였다. 이 모델은 시스템외부로부터 작업의 진입여부에 따라 개방형 및 폐쇄형으로 분류하고, 퍼지요소들을 처리할 수 있는 퍼지평균값 분석방법을 사용하여 작업평균소요시간, 시스템내 작업수 및 서버 활용률 등의 시스템성능을 평가할 수 있는 측도를 각각 유도하였다. 이들의 유효함을 검증하기 위하여 퍼지 BCMP 큐잉네트워크모델에 작업의 퍼지도착률. 클라이언트 수 및 퍼지서비스 요구에 따른 시스템의 성능분석을 개방형과 폐쇄형으로 각각 시뮬레이션하였다. 그 결과 예측된 시스템의 성능평가와 일치함을 보였다.

• 한국컴퓨터정보학회논문지
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• 제6권4호
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• pp.138-145
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• 2001

본 논문에서는 분산처리시스템에서 서버에 대한 작업의 서비스요구와 서버의 서비스율이 네트워크환경에 따라 모호성을 갖는 경우, 시스템의 성능을 평가할 수 있는 퍼지 폐쇄형 BCMP 큐잉네트워크모델을 제안하였다. 이 모델은 퍼지요소들을 처리할 수 있는 퍼지평균값분석방법을 사용하여 시스템성능을 평가할 수 있는 측도를 유도하였다. 이들의 유효함을 검증하기 위하여 제안한 모델에 작업의 서비스요구와 클라이언트의 수의 변화에 따른 성능평가를 시뮬레이션 하였고, 그 결과를 확인하였다.

• 한국경영과학회지
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• 제22권1호
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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.

• 한국경영과학회지
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• 제13권1호
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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.

• 한국경영과학회지
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• 제23권4호
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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.

• 산업경영시스템학회지
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• 제24권67호
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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.

• 산업경영시스템학회지
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• 제20권43호
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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.

• 한국국방경영분석학회지
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• 제15권1호
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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.

• 품질경영학회지
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• 제19권1호
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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.

• 대한산업공학회지
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• 제15권1호
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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.