• Journal of the Korean Data and Information Science Society
• /
• 제14권4호
• /
• pp.889-901
• /
• 2003

In this paper, we consider the optimal replacement policies following the expiration of the combination warranty. The combination warranty can be divided into the renewing combination warranty and the non-renewing combination warranty. The criterion used to determine the optimal replacement period is the overall value function based on the expected cost and the expected downtime. Thus, we obtain the expected cost rate per unit time and the expected downtime per unit time for our model. And then the overall value function suggested by Jiagn and Ji(2002) is applied to obtain the optimal replacement period. The numerical examples are presented for illustrative purpose.

• Journal of the Korean Data and Information Science Society
• /
• 제17권3호
• /
• pp.743-752
• /
• 2006

This paper considers a Bayesian approach to replacement policy model with minimal repair. We use the criterion based on the expected cost and the expected downtime to determine the optimal replacement period. To do so, we obtain the expected cost rate per unit time and the expected downtime per unit time, respectively. When the failure time is Weibull distribution with uncertain parameters, a Bayesian approach is established to formally express and update the uncertain parameters for determining an optimal maintenance policy. Especially, the overall value function suggested by Jiagn and Ji(2002) is applied to obtain the optimal replacement period. The numerical examples are presented for illustrative purpose.

• Journal of the Korean Data and Information Science Society
• /
• 제19권2호
• /
• pp.587-596
• /
• 2008

This paper develops the optimal periodic preventive maintenance policies following the expiration of warranty: renewing warranty and non-renewing warranty. After the warranty period is expired, the system undergoes the PM periodically and is minimally repaired at each failure between two successive PMs. Firstly, we determine the expected cost rate per unit time and the expected downtime per unit time for the periodic PM model. Then the overall value function suggested by Jiang and Ji(2002) is applied to obtain the optimal PM period and the optimal PM number. Finally, the numerical examples are presented for illustrative purpose.

• Journal of the Korean Data and Information Science Society
• /
• 제21권5호
• /
• pp.873-882
• /
• 2010

본 논문에서는 비재생혼합보증이 종료된 이후의 교체정책에 대한 베이지안 접근을 고려한다. 이때, 비재생혼합보증은 비재생무료교체보증과 비재생비례교체보증의 혼합된 형태가 된다. 최적의 교체주기를 결정하기 위하여 기대비용과 기대비가동시간에 근거한 기준이 사용되는데, 이를 위해서 단위시간당 기대비용과 단위시간당 기대비가동시간이 각각 구해진다. 시스템의 고장시간이 불확실한 모수를 갖는 와이블분포를 할 때, 베이지안 접근에 근거하여 최적의 교체정책이 제안된다. 이때, 최적의 교체주기를 결정하기 위해서 Jiang과 Ji (2002)에 의해서 제안된 총밸류함수가 사용된다. 끝으로, 본 논문에서 제안된 베이지안 교체정책을 설명하기 위해서 수치적 예를 살펴본다.

• Communications for Statistical Applications and Methods
• /
• 제15권6호
• /
• pp.909-923
• /
• 2008

본 논문에서는 수리가 가능한 시스템에 대하여 혼합보증이 종료된 이후의 교체모형과 예방보전모형을 고려하는데, 만약 보증기간이 종료된 이후에 시스템에 고장이 발생하면 최소수리를 수행한다. 최적의 교체정책과 최적의 예방보전정책을 결정하기 위한 기준으로는 기대비용과 기대비가동시간에 근거한 총밸류함수를 사용한다. 그리고 시스템의 고장시간이 와이블분포를 할 때 수치적 예를 통해서 제안된 최적의 교체정책 및 예방보전정책을 자세히 설명하고자 한다.

• International Journal of Reliability and Applications
• /
• 제2권2호
• /
• pp.99-105
• /
• 2001

Delay time analysis is a pragmatic mathematical concept readily embraced by engineers which has been developed as a means to model maintenance decision problem. This paper considers an inspection period using delay time analysis for fishing vessel equipment. We assume that delay time has a Weibull distribution. In this paper, we determine the optimal inspection period which minimize the expected downtime per unit time. Explicit solutions for the optimal inspection are presented for illustrative purposes.

• 산업경영시스템학회지
• /
• 제37권3호
• /
• pp.16-23
• /
• 2014

Most of metal cutting and processing companies are going through the difficulties such as frequent downtime and high failure rates by missing times to replace parts of CNC equipment. The reason is that the correct operation times of expensive CNC equipment can't be calculated. In this paper, to solve this problem, we try to construct the intelligent production information system for a case company and analyze its expected effects. The effects are as follows. First, it saves money about 3 million won each year during the useful life of three years by reducing downtime and failure rates, and increasing production rates etc. Second, it makes easily find and fix the cause of faulty through traceability of the production process, and enables to perform a systematic facility management through the calculation of reliable equipment's overall efficiency. This case can be easily applied in similar industries, and will contribute greatly to enhancing the competitiveness of related industries.

• International Journal of Quality Innovation
• /
• 제7권3호
• /
• pp.15-23
• /
• 2006

A spare ordering policy is considered for planned maintenance. Introducing the ordering, uptime, downtime, inventory costs and salvage value, we derive the expected cost effectiveness. The problem is to determine jointly the ordering time for a spare and the preventive replacement time for the operating unit which maximize the expected cost effectiveness. Some properties regarding the optimal policy are derived, and a numerical example is included to explain the proposed model.

• 한국신뢰성학회:학술대회논문집
• /
• 한국신뢰성학회 2000년도 추계학술대회
• /
• pp.329-333
• /
• 2000

Delay time analysis is a pragmatic mathematical concept readily embraced by engineers which has been developed as a means to model maintenance decision problem. This paper considers an inspection period using delay time analysis for fishing vessel equipment. We assume that delay time distribution is Weibull and inspections are perfect. In this paper, we determine the optimal inspection period which minimize the expected downtime per unit time.

• 터널과지하공간
• /
• 제29권6호
• /
• pp.394-406
• /
• 2019

도심지와 하·해저 터널에서는 연약지반 혹은 특수지반(단층대, 복합지반 등)을 조우할 가능성이 높으며, 이러한 조건에서는 TBM의 굴진율이 저하되고 다운타임이 증가하는 등의 문제점이 발생한다. 이러한 문제점들은 지반조사에서 발견되지 않은 불리한 지반조건에 기인하는 경우가 많으며, 굴진 중 수집된 굴진데이터를 근거로 향후 지층조건에 대한 최적의 운용조건을 결정하는 것이 최선이다. 본 연구는 향후 쉴드 TBM을 이용한 터널공사에서 단층대 및 복합지반에서의 효율적인 시공을 위하여 수행되었다. 외국의 사례를 통해 수집된 TBM의 굴진데이터를 활용하여 굴진율과 다운타임 발생 특성을 지층조건에 따라 분석하였다. 추력, 토크, RPM 등 주요 TBM의 기계데이터와 굴진율, 다운타임은 단층대와 복합지반의 특징에 따라 크게 영향을 받는 것을 확인하였고, 그 특징에 대하여 논하였다. 향후 국내외 유사한 지반에서의 TBM 시공 시 유용하게 활용될 수 있을 것으로 기대된다.