• Journal of Preventive Medicine and Public Health
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• 제19권1호
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• pp.56-64
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• 1986

This paper describes a GPSS-based, multi-server queueing model that was developed to simulate the patient flow, and to analyze the effectiveness of the patient scheduling system under various conditions. Unpredictable and unacceptably long waits to receive the service at the outpatient department of a general hospital necessitated the study. Arrival and service time distribution needed for the simulation model were generated from actual arrival and service patterns observed during the peak hours. The simulation results show that a change in patient scheduling system (i.e. time interval between appointments, starting time. and the number of physicians) from a current system would significantly reduce the patient wait time. This study provides the hospital administrator with an analysis of patient scheduling system under several conditions, and will be used to plan future scheduling system and staffing. Studies such as this can demonstrate the value of simulation in providing information for use in future planning.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1994년도 춘계공동학술대회논문집; 창원대학교; 08월 09일 Apr. 1994
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• pp.437-450
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• 1994

The problem of testing for a change in the parameter of a stochastic process is particularly important in simulation studies. In studies of the steady state characteristics of a simulation model, it is important to identify initialization bias and to evaluate efforts to control this problem. A simulation output have the characteristics of chaotic behavior because of sensitive dependence on initial conditions. For that reason, we will apply Lyapunov exponent for diagnosis of chaotic motion to simulation output analysis. This paper proposes two methods for diagnosis of steady state in simulation output. In order to evaluate the performance and effectiveness of these methods using chaos theory, M/M/I(.inf.) queueing model is used for testing point estimator, average bias.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2000년도 추계학술대회 및 정기총회
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• pp.59-62
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• 2000

Many of the previous researchers have been studied for the performance estimation of an AS/RS with a static model or computer simulation. Especially, they assumes that the storage/retrieval (S/R) machine performs either only single command (SC) or dual command (DC) and their requests are known in advance. However, the S/R machine performs a SC or a DC. or both or becomes idle according to the operating policy and the status of system at an arbitrary point of time. In this paper, we propose a stochastic model for the performance estimation of a unit-load AS/RS by using a M/G/1 queueing model with a single-server and two queues. Expected numbers of waiting storage and retrieval commands, and the waiting time in queues for the storage and retrieval commands are found

• 대한산업공학회지
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• 제27권1호
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• pp.111-117
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• 2001

Most of the techniques for the performance estimation of unit-load AS/RS are a static model or computer simulation. Especially, their models have been developed under the assumption that the Storage/Retrieval (S/R) machine performs either single command(SC) or dual command(DC) only. In reality, depending on the operating policy and the status of the system at a particular time, the S/R machine performs a SC or a DC, or becomes idle. In order to resolve this weak point, we propose a stochastic model for the performance estimation of unit-load ASIRS by using a M/G/1 queueing model with a single server and two queues. Server utilization, expected numbers of waiting storage and retrieval commands and mean time spent in queue and system are found.

• 한국통신학회논문지
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• 제17권8호
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• pp.779-788
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• 1992

일반적으로 높은 성능의 컴퓨터 시스템은 입력/출력 서브시스템에서 자주 병목현상이 나타난다. 일반적으로 시스템 성능평가 모델은 I/O 시스템의 영향을 포함하여 다루어진다. 본 논문에서는 컴퓨터 자원의 분배에 필수적인 장치인 터미널 서버를 모델링 하여 연구한다. 시스템 성능의 주요 요소를 찾아 보기 위해 M/M/I 큐잉 모델을 사용한다. 터미널 서버의 FIFO버퍼 크기는 시스템 설계에 중요 요소이며 전체 시스템 성능에 영향을 비칠 수 있다. 본 논문에서는 시스템 성능을 향상 시키기 위해 터미널 서버모델의 최적 버퍼 크기를 제시한다. 또한 큐잉 모델을 이용하여 터미널서버의 지연시간을 분석하고 시뮬레이션 결과에서 참조 모델을 찾는다.

• 대한산업공학회지
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• 제15권1호
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• pp.1-15
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• 1989

In the past few years, increasing numbers of automatic storage/retrieval system (AS/RS) using computer controlled storage/retrieval machine have been installed. This paper introduces two modeling approaches to determine the best operating policy for AS/RS : an M/G/1 queueing model and a computer simulation model. The operating policy consists of three elements. : the operation command cycle, the storage location method, and the operation dispatching rule. The analysis based on M/G/1 model is suitable for a quick and approximate evaluation, due to its inherent strict assumptions. The computer simulation can be used to perform a more realistic analysis. It is shown through the study that a significant improvement in the throughput and/or the space requirement can be expected by determining the best operating policy to a particular system. Most important, the computer simulation demonstrates its powerful capability in evaluating dynamic stochatic systems with imperfect information.

• 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.

• 한국국방경영분석학회지
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• 제16권1호
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• pp.113-129
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• 1990

This paper presents the simulation model to decide the mean size of cannibalization aircraft (MSCA) under steady state when an airbase makes use of cannibalization to support the spare parts of an airfleet. In this model, the essential factors such as mission requirements, mission time, failure time, repair time, repair capability, inventory policy, cannivalization rule are considered. The model is constructed with above factors and actual airbase operating rules for a basis. Because of the tangled interdependencies among the each factors, it is inevitable to construct the model by the simulation technique. The mission and support system of the airbase is considered as a closed queueing network with a finite number of unit The troubled aircrafts are repaired in accordance with the priorities that are determined by their repair times. The illustrative example of the model, using the actual data of xx-airbase, is presented. The model would be a useful tool not only to determine the MSCA and the size of scheduled maintenance aircraft but to evaluate the NORS (not operationally ready supply) rate and the availability of an airfleet.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.513-519
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• 1989

Modeling of the network interface for MAP and its performance analysis is investigated in this study. The parameters for the network interface are selected and a special interest is concentrated on the parameters related to the performance of the network interface itself. A queueing model of the network interface is proposed and simulation is performed to validate the proposed model of the network interface.

• 한국통신학회논문지
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• 제23권9A호
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• pp.2184-2196
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• 1998

Admission control is one of the most important congestion control mechanism to be executed at the call set up phase by regulating traffic into a network in a preventive way. An efficient QOS evaluation or bandwidth estimation method is required for call admission to be decided in real time. In this paper, we spropose a computtionally simple approximation method of estimating cell loss probability and mean cell delay for admission control of both delay sensitive and loss sensitive calls. Mixed input queueing system, where a new call combines with the existing traffic, is used as a queueing model for QOS estimation. Also traffic parameters are suggested to characterize both a new call and existing traffic. Aggregate traffic is approximated by a renewal process with these traffic parameters and then mean delay and cell loss probability are detemined using appropriate approximation formulas. The accuracy of this approximation approach is examined by comparing their results with exact analysis or simulation results of vrious mixed unput queueing systems. Based on this QOS estimation method, call admission control scheme which is traffic independent and computable in yeal time are proposed.