• 한국국방경영분석학회지
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• 제18권2호
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• pp.114-125
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• 1992

A policy of periodic replacement with minimal repair at failure is considered for a complex system. Under such a policy the system is replaced at periodic times. iT(i=1,2, $\ldots$), while minimal repair is performed at any intervening system failures. The cost of the j-th minimal repair to the component which fails at age t is g(C(t). $c_j$ (t)), where C(t) is the age-dependent random part, $c_j$(t) is the deterministic part which depends on the age and the number of the minimal repair to the component, and g is a positive nondecreasing continuous function. The cost of replacement is expensive when the number of failures occurring in (0. T) is greater than a threshold level. The problem of determining the optimal replacement period, $T^{\ast}$, which minimizes the total expected cost per unit time over an infinite time horizon is considered. Various special cases are considered.

• 산업경영시스템학회지
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• 제14권24호
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• pp.7-13
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• 1991

Recently, in FMS composing of various automatic equipments, the machines with lower operating costs, and with higher operating costs and replacement costs resulting from deterioration have been appearing successively as a result of rapidly advances in technology. "Control Limit Policy" [1] by using Markov decision policy, a kind of optimal economic replacement decision, well reflects and represents this environment. In this paper, it is reviewed that the decision method of the forecasted replacement alternatives in planning horizon under technological advances is derived. The proposed method is applied to a numerical example and some characteristics are examined by sensitivity. It is clarified that the method is relatively insensitive to changes of parameters at the present decision. decision.

• 품질경영학회지
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• 제21권2호
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• pp.109-120
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• 1993

Most systems are composed of components which have different failure chracteristics. Since the failure characteristics of components is different, it is rational and reasonable to establish a maintenance model to be considered repair and replacement policies which are proper to failure characteristics of these components. This paper proposes the age replacement time for a system composed of components which have different failure characteristics. In this model, it is assumed that a system is composed of a critical failure component, a major failure component, minor failure component. If any failure occurs to critical component before its age replacement time, the system should be replaced. If any failure does not occur until its age replacement time, preventive replacement should be performed at age replacement time T. Major component is minimal repaired if any failure occurs during operation. Minor component should be replaced as soon as failure is found. This paper determines the optimal replacement time of the system which minimize, total maintenance cost and initial stock Quantity of minor component within this optimal replacement time. Numerical example illustrates these results.

• 산업공학
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• 제12권1호
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• pp.114-120
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• 1999

A system consisting of two continuously and independently operating equipment subject to breakdown and repair, is considered. It is assumed that both equipment age only when in operation, and a group replacement policy is in effect, that is, both equipment are replaced simultaneously by new identical ones as soon as either of them reaches a specified replacement age. First, a system of partial differential equations based on enumerating the various probabilistic events, is derived. Then, solutions of such system of equations for a model considered in the steady-state are obtained. Finally, an economic analysis is performed to determine the optimal replacement ages of both equipment.

• 대한산업공학회지
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• 제11권1호
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• pp.3-10
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• 1985

Periodic replacement policies are proposed for a system whose repair cost, when it fails, can be estimated by inspection. The system is replaced when it reaches age T (Policy A), or when it fails for the first time after age T (Policy B). If it fails before reaching age T, the repair cost is estimated and minimal repair is then undertaken if the estimated cost is less than a predetermined limit L; otherwise, the system is replaced. The expected cost rate functions are obtained, their behaviors are examined, and ways of obtaining optimal T and L are explored.

• 품질경영학회지
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• 제28권1호
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• pp.57-77
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• 2000

A two-dimensional warranty policy, two types of warranty criteria, such as the age and mileage of an automobile, are employed simultaneously to determine the eligibility of a warranty claim. We deal with the analysis of a variety of combined two-dimensional free replacement warranty(FRW) and pro-rata replacement warranty(PRW). In this paper we also propose the analysis of policies with item failures modelled using the one-dimensional and two-dimensional approach, respectively. We obtain expressions for the expected warranty costs and illustrate through numerical examples.

• 품질경영학회지
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• 제12권2호
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• pp.33-36
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• 1984

This paper is concerned with the optimal replacement policy of auto-scale with increasing error-variance. This optimization model is to minimize the sum of the cost of defective and excess weight allowance for a target value. The numerical example for the proposed problem is solved by Golden-Section Search and Simpsons's rule.

• 한국국방경영분석학회지
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• 제7권2호
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• pp.100-113
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• 1981

A replacement policy for a finite time span is proposed for the cumulative process where an item can fail only when the total amount of deterioration exceeds a prespecified failure level. The optimal deterioration limit level is determined to minimize the total cost expected per unit for a given time span. An illustrative example in case of periodically inspected reformer tubes in ammonia plant is also presented.

• KDI Journal of Economic Policy
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• 제40권3호
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• pp.1-44
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• 2018

This paper studies the macroeconomic effects of an enhancement in unemployment benefits in Korea. In particular, I quantify the welfare effect of two specific policy chances which have been mainly discussed among policymakers in recent years: increasing wage replacement rates by 10%p and extending maximum benefit durations by one month. To this end, I build and calibrate an overlapping generation model which reflects the heterogeneity of the unemployed and the specificity of the unemployment insurance (UI) system in Korea. The quantitative analysis conducted here shows that extending maximum benefit durations by one month improves social welfare, whereas increasing wage replacement rates by 10%p deteriorates social welfare. Extending maximum benefit durations is applied to potentially all the UI recipients, including unemployed workers whose wage before job loss is relatively low and whose marginal utility is relatively high. However, increasing wage replacement rates is applied to only a small number of UI recipients whose wage before job loss is relatively high, while the increase in the UI premium is passed onto all of the employed. This study suggests that given the current UI system and economic environment in Korea, it is more desirable to extend maximum benefit durations rather than to increase wage replacement rates in terms of social welfare.

• 한국멀티미디어학회논문지
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• 제8권7호
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• pp.943-952
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• 2005

본 연구는 이동환경에서 연속 미디어 객체에 대한 사용자 요구들에 대하여 효율적으로 자원을 관리하기 위하여, 사용자의 이동성 정보를 반영하는 협력적 프록시 캐슁 정책을 제안한다. 제안된 정책은 담당영역 내에서 사용자의 요구들을 참조하여 캐슁하는 기존의 프록시 캐슁 정책과는 다르게 인접한 영역의 많은 사용자 요구 정보들을 이용하여 캐슁 객체를 선택함으로써 이동환경에서 발생하는 사용자들의 임의접근 요구들을 충분히 반영할 수 있도록 한다. 그리고 제안된 캐슁 정책을 위해서 각 프록시에서 발생한 요구정보의 가중치와 재생량을 기반으로 하는 재배치 기법을 제안한다. 그래서 객체단위와 세그먼트 단위로 재배치 기법을 수행하여 캐슁 정책의 성능을 평가하였다. 그 결과, 이동환경에서 적절한 세그먼트의 크기, 사용자의 이동성 비율 그리고 가중치가 협력적 캐슁의 성능에 영향을 미치는 중요한 요인이 된다는 것을 알았다.