• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 추계학술대회 논문집
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• pp.325-329
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• 1992

The development of automatic production system have required intelligent diagnostic and monitoring function to repair system failure and reduce production loss by the failure. In order to perform accurate functions of intelligent system, inference about total system failure and fault analysis due to each mechanical component failures are required. Also the solution about repair and maintenance can be suggested from these analysis results. Generally, bearing is a essential mechanical component in the machinery. The bearing failure is caused by lubricant system failure, metallurgical defficiency, mechanical condition(vibration overloading misalignment), environmental effect. This study described roller bearing fault train due to stress variation and metallurgical defficiency from lubricant failure by using FTA.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1052-1059
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• 2018

This paper deals with commutation failure of the line-commutated converter high voltage direct current (LCC HVDC) system caused by a three phase fault in the ac power system. An analytic calculation method is proposed to estimate the maximum permissible voltage drop at the LCC HVDC station on various operating point and to assess the area of vulnerability for commutation failure (AOV-CF) in the power system based on the residual phase voltage equation. The concept is extended to multi-infeed HVDC power system as the area of severity for simultaneous commutation failure (AOS-CF). In addition, this paper presents the implementation of a shunt compensator applying to the proposed method. An analysis and simulation have been performed with the IEEE 57 bus sample power system and the Jeju island power system in Korea.

• 한국군사과학기술학회지
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• 제12권6호
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• pp.719-726
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• 2009

A delay system in fuze for high explosive shell is an important safety device, but failure in the delay system usually causes failure of the shell. Root-cause analysis of failure in the delay system is required since failure in over 10-years stored delay system recently occurs. In this paper, failure in the delay system was reproduced experimentally to examine aged characteristics of the delay system, and the failed delay system shows the same characteristics as ones of failed delay systems in field. Based on the reproduced experiments, accelerated life testings and the data analysis of failure times of delay systems were performed to predict the storage lifetime.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.647-650
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• 2000

For the failure diagnosis of industrial system like various manufacturing systems, power plants and etc, many failure diagnosis approaches are considered. Here we are focus on the DES approach for failure diagnosis. We treats of failure recovery problem that is euly not mentioned in DES approach. The procedure to design a recoverable diagnoser is presented. And the recoverability, necessary and sufficient condition fur recoverability are defined. Then we make the high-level diagnoser to reduce the state size of recoverable diagnsoer. Finally, a pump-valve system example is presented.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.410-417
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• 2018

현대의 시스템은 지속적으로 대형화, 복잡화되어 왔기 때문에 시스템의 오류 발생 가능성이 커졌다. 시스템의 고장은 안전 사고를 발생시키고, 인명과 재산상의 막대한 피해를 줄 수 있다. 이러한 이유로 미 국방성과 IEC 등의 국제표준기구에서는 시스템의 안전성을 확보하기 위한 안전 관련 국제표준을 제정하였고, 시스템 설계와 안전 활동이 통합적으로 수행되어야 함을 권고하였다. 이에 따라 최근의 연구들은 모델기반 시스템 설계를 진행함과 동시에 모델을 활용하여 시스템의 안전성 검증을 수행하였다. 하지만 시스템 설계를 위한 모델과 안전성 분석 및 검증을 위한 고장모델을 서로 다른 모델링 언어를 기반으로 생성하였기 때문에 시스템 설계와 안전 활동이 통합적으로 수행되지 못하였다. 또한, UML 또는 SysML 기반으로 고장모델을 활용하여 안전 요구사항을 도출한 연구들은 안전 분석 및 검증에 고장모델이 제한적으로 활용되었다. 이와 같은 문제점을 해결하기 위해서 기존의 고장모델 활용법을 확장 시킬 필요가 있다. 우선 시스템 설계와 안전성 검증 활동을 통합적으로 수행할 수 있는 개선된 SysML 기반의 고장모델을 생성해야 한다. 다음으로 이 고장모델을 활용하여 도출된 안전요구사항이 시스템 설계에 제대로 반영되었는지 검증할 수 있어야 한다. 따라서 본 논문에서는 개선된 SysML 기반 고장모델의 개념과 생성 절차를 제시하였고, 자동차 시스템에 대한 고장모델을 생성하였다. 또한, 자동차 시스템의 안전성을 검증하기 위해서 고장모델의 시뮬레이션을 수행하였다. 이를 통해서 개선된 SysML 기반 고장모델을 활용하여 시스템 설계와 안전성 검증 활동을 수행할 수 있음을 보였다.

• International Journal of Precision Engineering and Manufacturing
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• 제8권3호
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• pp.50-53
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• 2007

Improving the reliability or long-term dependability of a system requires a different approach from the previous emphasis on short-term concerns. The purpose of this paper is to present a reliability evaluation method for an oil cooler intended for high-precision machining centers. The oil cooler system in question is a cooling device that minimizes the deformation caused from the heat generated by driving devices. This system is used for machine tools and semiconductor equipment. We predicted the reliability of the system based on the failure rate database and conducted the reliability test using a test-bed to evaluate the life of the oil cooler. The results provided an indication of the reliability of the system in terms of the failure rate and the MTBF of the oil cooler system and its components, as well as a distribution of the failure mode. These results will help increase the reliability of oil cooler systems. The evaluation method can also be used to determine the reliability of other machinery products.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.244-250
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• 1997

The mean time to failure (MTTF) expressing the mean value of the system life is a measure of system effectiveness. To estimate the remaining life of component and/or system, the dynamic mean time to failure concept is suggested. It is the time-dependent Property depending on the status of components. The Kalman filter is used to estimate the reliability of components using the on-line information (directly measured sensor output or device-specific diagnostics in the intelligent sensor) in form of the numerical value (state factor). This factor considers the persistency of the fault condition and confidence level in measurement. If there is a complex system with many components, each calculated reliability's or components are combined, which results in the dynamic MTTF or system. The illustrative examples are discussed. The results show that the dynamic MTTF can well express the component and system failure behaviour whether any kinds of failure are occurred or not.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
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• pp.529-533
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• 2008

임무컴퓨터는 항공전자시스템에서 전체 시스템을 관리하고, 특정 임무를 처리하는 중요한 역할을 수행한다. 일반적으로 단일 시스템에서 SPOF(Single Point Of Failure) 요소의 고장은 전체 시스템의 고장으로 이어질 수 있으며, 이는 서비스의 중단으로 인한 임무의 실패뿐만 아니라 조종사의 생명까지도 위협할 수 있다. 이에 본 논문에서는 SPOF 요소를 제거하기 위해 단일 시스템을 이중화하여 고장발생에 유연하게 대처하도록 설계하였다. 또한 이를 효율적으로 운영하기 위한 방안으로 리눅스 기반의 Heartbeat, Fake, DRBD(Distributed Replicated Block Device), Bonding 등의 기법을 이용하여 시스템을 관리한다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제8권3호
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• pp.113-124
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• 2008

In reliability engineering, failure reporting, analysis, and corrective action system (FRACAS) is an useful tool for effective failure reporting and related operations. FRACAS is generally mainly focused on implementation of its closed-loop process, but also includes various related information which has to be effectively managed such as failure types, failure modes, failure mechanisms, and corrective actions. In this study, we adopt and utilize the concept of process knowledge, and create it through abstraction of FRACAS information. At each step of closed-loop process, the necessary type of knowledge, priority and usability are clearly defined. This study also suggests corresponding management tools such as business process management system, knowledge management system, and their key elements and functions to deal with process knowledge. A prototype system using simple closed-loop process with its process knowledge is presented to demonstrate the feasibility of the proposed work.

• 산업경영시스템학회지
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• 제45권3호
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• pp.78-89
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• 2022

The purpose of this study was to propose useful suggestion by analyzing preventive replacement policy under which there are minor and major failure. Here, major failure is defined as the failure of system which causes the system to stop working, however, the minor failure is defined as the situation in which the system is working but there exists inconvenience for the user to experience the degradation of performance. For this purpose, we formulated an expected cost rate as a function of periodic replacement time and the number of system update cycles. Then, using the probability and differentiation theory, we analyzed the cost rate function to find the optimal points for periodic replacement time and the number of system update cycles. Also, we present a numerical example to show how to apply our model to the real and practical situation in which even under the minor failure, the user of system is not willing to replace or repair the system immediately, instead he/she is willing to defer the repair or replacement until the periodic or preventive replacement time. Optimal preventive replacement timing using two variables, which are periodic replacement time and the number of system update cycles, is provided and the effects of those variables on the cost are analyzed.