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시험시간과 오류수정개수를 고려한 소프트웨어 출시 시점결정
유영관,Yoo, Young Kwan 한국벤처창업학회 2012 벤처창업연구 Vol.7 No.4
본 논문에서는 시험시간과 오류의 수정개수를 동시에 고려하는 소프트웨어 출시 모형을 제시한다. 소프트웨어의 시험기간은 정해진 시험시간이나 오류수정개수 중 먼저 도래하는 시간까지 지속된다. 고려되는 비용은 시험기간 중의 오류수정비용과 출시 지연비용, 그리고 시험기간 경과 후의 운용 중 발생하는 오류수정비용으로 구성된다. 생명주기는 특별한 제한이 없고, 오류의 검출과정은 비제차 포아송과정을 따른다고 가정한다. 총비용함수가 도출되며 이전의 출시방안들은 제시된 모형의 특별한 경우임을 보인다. In this paper, a software policy considering testing time and the number of errors corrected is presented. The software is tested until a specified testing time or the time to a specified number of errors are corrected, whichever comes first. The model includes the cost of error correction and software testing during the testing time, and the cost of error correction during operation. It is assumed that the length of software life cycle has no bounds, and the error correction follows an non-homogeneous Poisson process. An expression for the total cost under the policy is derived. It is shown that the model includes the previous models as special cases.
유영관,Yoo, Young-Kwan 대한안전경영과학회 2017 대한안전경영과학회지 Vol.19 No.3
This paper presents another maintenance policy for a group of units under finite operating horizon. A group of identical units are subject to random failures. Group maintenances are performed to all units together at specified intervals, and the failed units during operation are remained idle until the next group maintenance set-up. Unlike the traditional assumption of infinite operating horizon, we adopt the assumption of the finite operating horizon which reflect the rapid industrial advance and short life cycle of modern times. The units are under operation until the end of the operating horizon. Further, the operation of units are extended to the first group maintenance time after the end of the horizon. The total cost under the proposed maintenance policy is derived. The optimal group maintenance interval and the expected number of group maintenances during the horizon are found. It is shown that the proposed policy is better than the classical group maintenance policy in terms of total cost over the operating horizon. Numerical examples are presented for illustrations.
경제적인 그룹교체보전을 위한 최적 예비품 재고수준의 결정
유영관,박노국,Yoo, Young Kwan,Park, Roh Gook 한국벤처창업학회 2014 벤처창업연구 Vol.9 No.2
In this paper, a jointly optimal group replacement and spare provisioning policy is presented. Most maintenance policies assume that the spare inventory is always available, but in practice the maintenance schedule is affected by the availability of spare inventory. We present a maintenance-inventory model which jointly optimizes the group replacement interval and spare ordering quantity. Group replacement policy is used when a group of units are put in operation simultaneously. The operating fleet is replaced altogether at a predetermined number of units are failed. A sufficient level of spare inventory is carried to perform a number of group replacement. A cost rate expression which considers the group maintenance cost and inventory holding cost is derived and a heuristic method for searching the optimum value of decision variables is suggested. Numerical examples demonstrate the analytical results and the performance of the presented model. 본 논문에서는 그룹교체 정책과 예비품 재고정책을 동시에 고려하여 최적화하는 방안을 제시한다. 일반적으로 보전정책들은 예비품의 재고가 늘 가용하다고 가정하고 있으나 예비품의 재고 확보 여부에 의해 보전활동은 영향을 받을 수밖에 없다. 동일한 여러 유닛들이 동시에 운용될 때 이용되는 그룹교체정책을 바탕으로 이를 지원하기 위한 최적 재고수준을 결정한다. 일정한 개수의 유닛이 고장 나는 시점에서 그룹교체를 수행한다. 예비품의 재고는 일정 횟수의 그룹교체를 할 만큼 주문하여 유지한다. 보전비용과 재고비용 등 운용비용을 최소화할 수 있는 최적의 그룹교체 주기와 재고수준을 구한다.
랜덤한 시평 동안 운용되는 상황 하의 확장된 일제교체 모델
유영관 ( Yoo Young Kwan ) 한국경영공학회 2016 한국경영공학회지 Vol.21 No.4
This paper deals with the problem of determination of optimum block replacement interval under random time horizon. The operation horizon has been assumed as an infinite one, but the recent rapid technological development suggest that the random and finite time horizon is more suitable assumption. The total cost involved in an extended block replacement policy under random time horizon is derived. The optimum block replacement interval which minimizes the total cost is explored, and the results are illustrated by some numerical examples.
유영관 ( Young-kwan Yoo ) 대한설비관리학회 2017 대한설비관리학회지 Vol.22 No.3
In this paper, a group maintenance policy for a group of identical units operating over finite and random horizon is presented. Most previous researches usually assume the infinite operating horizon, but because of the recent rapid technological advances, it is resonable to assume that the operating horizon is finite. A modified group maintenance model for a group of identical units with the finite operating horizon is developed, and the total maintenance cost during the operating horizon is derived. The optimum group maintenance interval which minimizes the total cost is explored. Specifically, the optimum group maintenance interval is derived for units with exponential time-to-failure and exponential duration of operating horizon. Numerical examples are presented to demonstrate the results.
유영관 ( Young-kwan Yoo ) 대한설비관리학회 2016 대한설비관리학회지 Vol.21 No.4
In this paper, a replacement policy for an equipment operating over a random time horizon under minimal repair is studied. Most previous researches deals with the optimal replacement policies over an infinite time horizon which minimizes the operating cost rate per unit time. However, the recent rapid technological development suggest that the finite operating horizon is more practical assumption. This paper develops a cost model which represent the total operating cost for an equipment over a random time horizon, and explores the optimal replacement interval under minimal repair which minimizes the total cost. This study is different from the previous random horizon models in that the equipment continues its operation over the end of horizon for the remaining replacement interval. The condition that guaranties the existence of finite and unique replacement interval which minimizes the total cost is found, and it is demonstrated with some numerical examples.