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동적 시스템의 신뢰도 평가를 위한 마코프체인과 베이지안만의 적용에 관한 연구
Ahn, Suneung,KOO, Jungmo 한국경영과학회 2003 한국경영과학회 학술대회논문집 Vol.- No.2
This paper is intended to assess a system reliability that is changed as time passes. The proposed methodology consists of two steps: (1) predicting probabilities that each component fails at specific time by using a Markov Chain model and (2) calculating reliability of the whole system via Bayesian network. The proposed methodology includes extended Bayesian network model reflecting the case that components are mutually dependent.
An Interpretation of the Mixture of Poisson Distributions with a Gamma Distributed Parameter
Suneung Ahn 한국산업경영시스템학회 2003 한국산업경영시스템학회 학술대회 Vol.2003 No.춘계
Used as a mixing distribution for an unknown Poisson parameter, the gamma distribution leads to the negative binomial distribution. The hyperparameters of the gamma distribution have their own meanings according to what the Poisson parameter represents. Different sources in the randomness of the Poisson parameter give different interpretations of the negative binomial distribution.
Ahn, Suneung,Kim, Hyunmook 한국경영과학회 2003 한국경영과학회 학술대회논문집 Vol.- No.2
This paper is intended to compare between the Bayesian estimates of hazard rate and the hazard rates of nixed distributions. In estimating hazard rates, especially when the MLE method is used, such difficulties as a lack of data and the existence of censored data make it difficult to estimate the rates. For this reason, the estimates of hazard rate based on the Bayesian approach are introduced. For the simplicity, the exponential and gamma distributions are adopted as a sampling distribution and its natural conjugate prior distribution, respectively.
Deriving a Likelihood Model for Fatigue Lifetime Based on the Physics of Crack-Propagation
Suneung Ahn,Sun Hur 한국산업경영시스템학회 2002 한국산업경영시스템학회 학술대회 Vol.2002 No.추계
This paper presents an approach to derive likelihood models for use in engineering design problems. One main point is made. It is that incorporating engineering knowledge into a likelihood model is possible. The work is foundational in nature, but is developed with an explicit example taken from fatigue failure problem of a structural component, the Paris crack-propagation criterion, and a modified truncated Gaussian distribution.
Probability Models for Material Failure Based on the von Mises Criterion
Ahn, Suneung 漢陽大學校 工學技術硏究所 2002 工學技術論文集 Vol.11 No.-
This paper presents an approach to derive probability models for use in structural reliability studies. Two main points are made. First, that it is possible to translate engineering and physics knowledge into a requirement on the form of a probability model. And second, that making assumptions about a probability model for structural failure implies either explicit or hidden assumptions about material and structural properties. The work is foundational in nature, but is developed with explicit examples taken from planar and general stress problems, the von Mises failure criterion, and a modified Weibull distribution.
Comparing the Bayesian Estimate of a Failure Rate with the Failure Rate of a Mixed Distribution
Suneung Ahn 한국산업경영시스템학회 2003 한국산업경영시스템학회 학술대회 Vol.2003 No.춘계
This paper is intended to compare between the Bayesian estimate of a failure rate and the failure rate of a mixed distribution. For the sake of simplification, an exponential distribution and a gamma distribution are adopted as a sampling distribution and its natural conjugate prior distribution. The result shows that both the failure rates are being updated using data and they differ in whether they are functions of unobserved future data or not.
Developing Mathematical Methods for Project Risk Management Based on Reliability Functions
Seonha Han,Suneung Ahn 한국산업경영시스템학회 2013 한국산업경영시스템학회 학술대회 Vol.2013 No.춘계
In this paper, a mathematical model is developed for finding a degree of influence of risks affecting the project. At risk identification step, all risks are structured in forms of block diagrams after risks of project activities are identified. At risk analysis step, reliability functions are derived based on block diagrams of risks. Reliability function represents the probability of the project success. Based on the derived reliability functions, risks importance is defined as a criterion for expressing a degree of influence of each risk affecting the success of the project, which is. Risks importance includes the structural importance of risk, the probability of risk, and the impact of risk. It could be applied to determine the priorities of risks which should be controlled, and the use of such priorities could guarantee successful project activities. Finally, examples of the proposed mathematical models will be given.
자동차 구동축 소음 저감을 위한 신뢰성 개선프로세스의 개발
윤혁춘(Hyukchoon Yun),안선응(Suneung Ahn),배석주(Suk Joo Bae) 한국신뢰성학회 2020 신뢰성응용연구 Vol.20 No.4
Purpose: Securing reliability of the components in automobiles is a key issue. The purpose of this research is to develop a step-by step process for reliability improvement using accelerated tests to reduce the noises from the drive shafts in automobiles. Methods: The step-by-step reliability improvement process includes problem definition, reliability test planning, executing an accelerated test, reliability analysis, deriving an improvement scheme, and making a reliability qualification standard. Results: A real case study shows that the proposed process can reduce the noises from the drive shafts by identifying the failure causes and mechanisms through material tests and bench tests. Finally, intended reliability target is proved to be satisfied by quantitative reliability analysis. Conclusion: Reliability improvement can be realized by establishing the systematic reliability evaluation process. We expected that the proposed reliability improvement process can be widely applied to other components in automobiles or other industries to establish the reliability management policy.
이주현,안선응,Lee, Juhyun,Ahn, Suneung 한국신뢰성학회 2018 신뢰성응용연구 Vol.18 No.2
Purpose: This paper proposes the non-periodic preventive maintenance policy based on the level of cumulative hazard intensity. We aim to construct a cost-effectiveness on the proposed model with relaxing the constraint on reliability. Methods: We use the level of cumulative hazard intensity as a condition variable, instead of reliability. Such a level of cumulative hazard intensity can derive the reliability which decreases as the frequency of preventive maintenance action increases. We also model the imperfect preventive maintenance action using the proportional age setback model. Conclusion: We provide a numerical example to illustrate the proposed model. We also analyze how the parameters of our model affect the optimal preventive maintenance policy. The results show that as long as high reliability is guaranteed, the inefficient preventive maintenance action is performed reducing the system operation time. Moreover, the optimal value of the proposed model is sensitive to changes in preventive maintenance cost and replacement cost.
Juhyun Lee,Jihyun Park,Suneung Ahn 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.2
Maintenance activities are regarded as a key part of the repairable deteriorating system because they maintain the equipment in good condition. In practice, many maintenance policies are used in engineering fields to reduce unexpected failures and slow down the deterioration of the system. However, in traditional maintenance policies, maintenance activities have often been assumed to be performed at the same time interval, which may result in higher operational costs and more system failures. Thus, this study presents two non-periodic preventive maintenance (PM) policies for repairable deteriorating systems, employing the failure rate of the system as a conditional variable. In the proposed PM models, the failure rate of the system was restored via the failure rate reduction factors after imperfect PM activities. Operational costs were also considered, which increased along with the operating time of the system and the frequency of PM activities to reflect the deterioration process of the system. A numerical example was provided to illustrate the proposed PM policy. The results showed that PM activities performed at a low failure rate threshold slowed down the degradation of the system and thus extended the system lifetime. Moreover, when the operational cost was considered in the proposed maintenance scheme, the system replacement was more cost-effective than frequent PM activities in the severely degraded system.