• Journal of the Korean Data and Information Science Society
• /
• 제18권3호
• /
• pp.689-696
• /
• 2007

This paper considers a Bayesian approach to determine an optimal PM policy with random maintenance quality. Thus, we assume that the quality of a PM action is a random variable following a probability distribution. 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 PM policy. Finally, the numerical examples are presented for illustrative purpose.

• 산업경영시스템학회지
• /
• 제19권39호
• /
• pp.285-292
• /
• 1996

In the case of existence of second-hand market, some methods for economic depreciation measurement have been developed. Among them, we consider two method. Those are Box -Cox model by Halten and Wykoff and Ratio method of T-factor by Iowa State University. Here, we suggest a new measurement method of economic depreciation based on the above two methods. According to the new method, we can get the failure rate of a equipment under the appropriate assumption. Then we can measure the economic depreciation more simply.

• 한국정보처리학회:학술대회논문집
• /
• 한국정보처리학회 2009년도 추계학술발표대회
• /
• pp.151-152
• /
• 2009

Grid 컴퓨팅 환경에서 Risk-resilient 한 Job 수행을 보장하기 위해 그 동안 Job migration 기법이 연구되어 왔으나, 자원 재선정 및 Job 이동/재할당에 따른 기준의 단순성으로 인해, Migration에 따른 Job 수행의 이득과 손실이 정확하게 판별되지 못한 경향이 있었다. 따라서 본고에서는 Job failure Rate을 바탕으로 특정 Job의 확률적 수행 지연 시간을 추정하고, 이를 이용하여 Migration gain을 평가하는 모델을 제안한다.

• 산업기술연구
• /
• 제20권A호
• /
• pp.229-238
• /
• 2000

Simulation analysis for an auto body manufacturing system has been performed in this study. The major goal is to figure out the condition yielding the production rate, 70 per hour. It is, however, very difficult to maintain this rate due to inherent system factors such as machine failure rates, machine repair rates, number of carriers between manufacturing lines(shops), carrier speed etc. We first carefully examined the system and developed a simulation model using ARENA. We then applied statistical experimental design concepts for performance analysis. Our results indicate that the buffer size of 30 and quick repair of failed robots are required for the desired production rate. Other factors, on the other hand, are seen to have minor effects on the throughput. The approach taken in this study and the results obtained may provide a practical guideline for performance analysis and thus be applied without trepidation for similar cases.

• 재무관리논총
• /
• 제6권1호
• /
• pp.313-334
• /
• 2000

In this paper, we obtained some supportive evidence for the long-run PPP relationship concerning the Korean Won currency. Previous tests of PPP in the bilateral exchange rates of the Korean Won rate vis-a-vis the U.S. Dollar have been exposed to the lack of power problem. We argue that their failure to find PPP relation in Korean Won rates was due to the low power of Augmented Dickey-Fuller tests or the Engle-Granger two-step tests applied to the Korean exchange rate data with short sample period. En attempting to alleviate this low power problem, we used the error-correction model test and the Johansen test for bilateral long-run equilibrium relationships between exchange rates and price indices from Korea's major trading partners. It is surprising that our evidence supporting for long-run PPP in Korean Won rate contrasts sharply with Bahmani-Oskooee, Moshen and Rhee, Hyun-Jae(1992)'s.

• 산업경영시스템학회지
• /
• 제23권55호
• /
• pp.25-31
• /
• 2000

To make a better decision about when to shutdown a nuclear power plant, we build a decision model using influence diagrams. We proceed the analysis adopting a bayesian approach. Firstly, an accident arrival rate is assumed to be known and this assumption is relaxed later. We perform our analysis on the cases of exponential time to accidents, and gamma distribution for the arrival rate. An optimal shutdown time is obtained considering the trade-off between the costs incurred by an accident due to late shutdown and the possible loss of revenues due to the early shutdown. We also derive the upper bound of the failure rate where we may operate the plant.

• 한국철도학회논문집
• /
• 제18권3호
• /
• pp.186-193
• /
• 2015

본 연구에서는 차세대 고속열차의 신뢰성 성장률 분석에 대한 연구를 수행하였다. 차세대 고속열차의 신뢰성 평가를 효과적으로 수행하기 위해서 6개의 서브시스템으로 분류를 하였으며, 이에 대한 기능블록선도와 신뢰성블록선도를 도출하였다. 또한 안정화 시험 중에 수행된 시험결과를 바탕으로 고장정보분석을 수행하였다. 그리고 Duane 모델에 기반한 신뢰성 성장률 분석을 차세대 고속열차의 실험 결과에 적용하였다. 본 연구를 통해서 지속적인 차량의 유지 보수 활동이 신뢰성 성장에 영향을 미치고 있음을 확인하였다.

• Nuclear Engineering and Technology
• /
• 제56권1호
• /
• pp.48-55
• /
• 2024

The safety-related raw water system's strong operational condition supports the radiation defense and biological shield of nuclear plant containment structures. Gaps and failures in maintaining proper working condition of main equipment like pump were among the most common causes of unavailability of safety related raw water systems. We integrated the advanced data analytics tools to evaluate the maintenance records of water systems and gave special consideration to deficiencies related to pump. We utilized maintenance data over a three-and-a-half-year period to produce metrics like MTBF, MTTF, MTTR, and failure rate. The visual analytic platform using tableau identified the efficacy of maintenance & deficiency in the safety raw water systems. When the number of water quality violation was compared to the other O&M deficiencies, it was discovered that water quality violations account for roughly 15% of the system's deficiencies. The pumps were substantial contributors to the deficit. Pump availability was predicted and optimized with real time data using response surface method. The prediction model was significant with r-squared value of 0.98. This prediction model can be used to predict forth coming pump failures in nuclear plant.

• Computers and Concrete
• /
• 제34권2호
• /
• pp.137-149
• /
• 2024

In order to study the triaxial mechanical behavior of steel fiber reinforced high performance concrete (SFRHPC), the standard triaxial compression tests with four different confining pressures are performed on the cylindrical specimens. Three different steel fiber volumes (0, 1% and 2%) are added in the specimens with diameter of 50 mm and height of 100 mm. Test results show that the triaxial compressive strength and peak strain increase with the increasing of fiber content at the same confining pressure. At the same steel fiber content, the triaxial compressive strength and peak strain increases with the confining pressure. The compressive strength growth rate declines as the confining pressure and steel fiber content increases. Longitudinal cracks are dominant in specimens with or without steel fiber under uniaxial compression loading. While with the confining pressure increases, diagonal crack due to shear is obvious. The Mohr-Coulomb criterion is illustrated can be used to describe the failure behavior, and the cohesive force increases as steel fiber content increases. Finally, the numerical model is built by using the PFC3D software. In the numerical model a index is introduced to reflect the effect of steel fiber content on the triaxial compressive behavior. The simulating stress-strain curve and failure mode of SFRHPC are agree well with the experimental results.

• Nuclear Engineering and Technology
• /
• 제13권3호
• /
• pp.121-129
• /
• 1981

많은 기존 공식중 세계의 가장 우수한 최대 유량공식을 찾아, 그 세개의 한계유량공식의 개요와, 냉각재상실사고시 격납용기격리에 실패하는 경우를 특정지을 수 있는 구멍의 크기와 격납용기의 압력 및 온도 등이 주어진 상태하에서 격납용기로부터 외부대기로 방출되는 개략적인 핵분열생성물의 양을 추정하기 위한 계산절차를 제시하였다. 이상기체의 임계유량공식과 이상유(two-phase flow)의 최대유량을 산출하기 위한 무디(Moody)의 도표를 이용하여 계산실예를 제시하였으며, 그 결과를 콘뎀프트-앨티(CONTEMPT-LT) 전산코드의 질량유출공식을 콘버징 노즐(converging nozzle)을 통과하는 음속류(sonic flow)의 경우에 적용하여 산출한 값과 비교하여 보았다. 이리하여 이상 기체의 임계유량공식은 무디(Moody)의 공식이 주는 값과 거의 비슷한 결과를 줌을 입증하였다. 또한 냉각재상실 사고시 격납용기로부터의 유출율을 추정하기 위해서는 콘템프트-앨티(CONTEMPT-LT)의 질량유출공식을 사용하는 것보다 이상 기체의 최대유량공식을 사용하는 것이 더 보수적인 방법임을 보여 주었다.