• Journal of applied mathematics & informatics
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• 제25권1_2호
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• pp.183-199
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• 2007

In this paper we research the problem in which the objective is to minimize the sum of squared deviations of job expected completion times from the due date, and the job processing times are stochastic. In the problem the machine is subject to stochastic breakdowns and all jobs are preempt-repeat. In order to show that the replacing ESSD by SSDE is reasonable, we discuss difference between ESSD function and SSDE function. We first give an express of the expected completion times for both cases without resampling and with resampling. Then we show that the optimal sequence of the problem V-shaped with respect to expected occupying time. A dynamic programming algorithm based on the V-shape property of the optimal sequence is suggested. The time complexity of the algorithm is pseudopolynomial.

• Journal of applied mathematics & informatics
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• 제26권5_6호
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• pp.889-900
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• 2008

The problem of scheduling n jobs on a single machine is considered when the machine is subject to stochastic breakdowns. The objective is to minimize the weighted squared deviation of job completion times from a common due date. Two versions of the problem are addressed. In the first one the common due date is a given constant, whereas in the second one the common due date is a decision variable. In each case, a general form of deterministic equivalent of the stochastic scheduling problem is obtained when the counting process N(t) related to the machine uptimes is a Poisson process. It is proved that an optimal schedule must be V-shaped in terms of weighted processing time when the agreeable weight condition is satisfied. Based on the V-shape property, two dynamic programming algorithms are proposed to solve both versions of the problem.

• 한국경영과학회지
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• 제22권4호
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• pp.93-113
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• 1997

In studying an EOQ-like inventory model for a manufacturing process, a number of findings were made. The system can "go out of control" resulting in a relatively minor problem state or "break-down". When the production system is in the minor problem statei produces a number of defective items. It is assumed that each defective piece requires rework cost and related operations. Once the machine breakdown takes place, the production system produces severely defective items that are completely unusable. Each completely unusuable item is immediately discarded and incurs handling cost, scrapped raw material cost and related operations. Two investment options in improving the production process are introduced : (1) reducing the probability of machine breakdown, breakdowns, and (2) simultaneously reducing the probability of machine breakdowns and setup costs. By assuming specific forms of investment cost function, the optimal investment policies are obtained explicitly. Finally, to better understand the model in this paper, the sensitivity of these solutions to changes in parameter values and numerical examples are provided.amples are provided.

• 한국컴퓨터정보학회논문지
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• 제15권8호
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• pp.181-192
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• 2010

본 논문에서는 연속제조 생산방식을 취하는 제조업에서 기계고장이 발생하여 생산 일정이 실시간으로 변경되어 야 하는 환경에서도 적용 가능한 dispatching 방법을 개발한다. 개발된 dispatching 방법은 생산지연으로 인한 재료의 재가열 비용과 설치비용, 잔여납기일을 고려하여 지표를 개발하고, 지표의 값이 가장 작은 재료에 우선순위를 부여하여 기계에 할당하는 방식을 취하고 있다. 개발된 dispatching방법의 우수성 입증하기 위해 SPT와 선입선출 방법을 비교대상으로 선출하고, 이들 방법을 통계적 시뮬레이션을 통해 도출된 손실비용을 비교분석한다. 통계적으로 유효성을 입증하기 위해 각 방법별로 200개의 데이터와 20번의 반복을 통해 실험을 실시하며, 실험결과 본 연구에서 제시한 방법이 비교대상 방법에 비해 유효한 손실비용의 감소효과를 보였다. 또한 본 논문에서 개발된 통계적 시뮬레이터는 대기시간에 발생 가능한 비용을 추가하거나 변경이 용이하여 불확실성을 고려한 생산일정계획부문에 유용하게 사용될 것으로 기대한다.

• 경영과학
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• 제10권2호
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• pp.61-77
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• 1993

This paper involves a study of developing the production scheduling system in a general job shop type mechanical factory. We consider realistic situations in the job-shop environments, such as alternative machines for operation, the new kinds of processes, the machining center with the plural pallet, the operational situation of each machine during the scheduling period, occurings of urgent orders and machine breakdowns. We also propose the methodology of re-schedule. It is very fast and acceptable for real time production control system. These all functions are implemented on IBM PC and program source is written in PASCAL language.

• Journal of Biosystems Engineering
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• 제8권1호
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• pp.30-37
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• 1983

Frequent breakdowns of power tiller, particularly in the peak labor constraints, have been a cause of decreasing machine productivity and its efficient utilization. To keep power tiller always ready to work, it may be necessary to identify the failure characteristics of some major parts of power tiller, and to have those parts replaced accordingly before they show the symptom of mulfunction. This study was conducted to identify the failure characteristics of some major parts of power tiller and to estimate their lives (MTBF) using a Weibull distribution function. The result showed that about half of breakdowns currently being occurred may be reduced through timely replacement of those part having wearout failure characteristics.

• 한국전자통신학회논문지
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• 제10권2호
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• pp.195-202
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• 2015

회전기계에서는 예후 신호 없이 고장되는 경우는 거의 없으며, 따라서 설비고장은 신호를 감시함으로서 고장을 예측, 회피할 수 있다. 본 연구에서는 회전기계에서 발생할 수 있는 고장에 대한 안전진단에 대한 사례연구이다. 각각의 회전기계에 대하여 진동분석을 통한 고장발생유무를 각종의 측정 데이터를 이용하여 분석하여 향후에 발생할 수 있는 고장에 대한 안전진단에 대한 방법을 연구하였다. 결과에서 보는 바와 같이 제안된 측정방법으로 안정한 상태 감시 및 진단 결과를 보여준다.

• 경영과학
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• 제17권1호
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• pp.17-30
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• 2000

This paper addresses the effect of protective capacity on the lead time and throughput of a re-entrant line where statistical fluctuations exist in the form of variation in processing times and machine breakdowns. The specific framework employed in the paper is a five station re-entrant line structured as a closed network mode. This paper argues that protective capacity can be used in conjunction with WIP inventory in order to reduce the lead time and to increase the increase the throughput of a line. Simulation analyses are included to give insight into the effectiveness of protective capacity.

• 한국경영과학회지
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• 제24권2호
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• pp.1-15
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• 1999

This research involves the development and evaluation of a work flow control model for a type of flexible manufacturing system(FMS) called a flexible flow line(FFL). The control model can be considered as a kind of hybrid intelligent model in that it utilizes both computer simulation and neural network technique. Training data sets were obtained using computer simulation of typical FFL states. And these data sets were used to train the neural network model. The model can easily incorporate particular aspects of a specific FFL such as limited buffer capacity and dispatching rules used. It also dynamically adapts to system uncertainty caused by such factors as machine breakdowns. Performance of the control model is shown to be superior to the random releasing method and the Minimal Part Set(MPS) heuristic in terms of machine utilization and work-in-process inventory level.

• Management Science and Financial Engineering
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• 제3권1호
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• pp.57-74
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• 1997

An EOQ-like inventory model for a manufacturing process is studied. The system is assumed to deteriorate during the production process. The results are either the production of a number of defective items, or the breakdown of the production machine. The optimal production lot size is derived. The model is extended to the case in which the probabilities of making defective items and machine breakdowns are a function of both the quantity (amount) and quality (performance) of the consumed setup cost (including the preventive maintenance cost). We further assume that the setup performance can be improved by investing in the performance improvement program. Hence, the same or a better setup outcome can be achieved with a lower setup cost. We then investigate the optimal setup cost and investment policy simultaneously, thereby achieving a better process quality and setup cost reduction concurrently.