• 전자공학회논문지B
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• 제31B권8호
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• pp.1-10
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• 1994

In this paper load redistribution algorithm to allow fault-tolerance by redistributing the workload of n failure nodes to the remaining good nodes in distributed systems are investigated. To evaluate the efficiency of the algorithms a simulation model of algorithms is developed using SLAM II simulation language. The job arrival rate service rate failure and repair rate of nodes and communication delay time due to load migraion are used as parameters. The result of the simulation shows that the job arrival rate failure and repair rate of nodes do not affected on the relative efficiency of algorithms. If the communication delay time is greater than average job processing time algorithm B is better. Otherwise algorithm C is superior to the others.

• International Journal of Reliability and Applications
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• 제5권2호
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• pp.81-103
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• 2004

Improvements of a bridge network system are studied in this paper. Then equivalence between different improved designs of the bridge network system is discussed. Three different methods are used to get different better designs of the network in the sense of having higher reliability and mean time to failure. Then two different types of reliability equivalence factors of the system are derived. It is assumed here that the failure rates of the system's components are identical and constant. The reliability functions and mean time to failure of the original and improved designs of the network are derived. Comparison between the mean time to failures of the original system and improved designs of the system are presented. Numerical studies and conclusion are presented in order to explain how one can apply the the theoretical results obtained.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2016년도 춘계학술발표대회
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• pp.124-126
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• 2016

Successful deployment of the Software Defined Network (SDN) depends on its ability to cope up with network failures. There are various types of failures that may occur in an SDN. The most common are switch and link failures. It is necessary to recover the network from failures for a continuous service availability. But for the real-time services fast recovery from the failure is required to minimize the service disruption time. In the proposed work, we focused on minimizing the recovery time after the failure is detected. Once the failure is detected, the controller involvement is needed to dynamically reroute the failure disrupted flows from the failed component to an alternate path. The aim of the proposed scheme is to provide a traffic management scheme which can react to the dynamic network events by rapidly modifying the forwarding behavior of the switches for faster in-band network adaptability. The proposed scheme (1) Considers the shared data and control path delay (2) Optimally utilize the network resources (3) Eliminates the need of constant monitoring overhead at the controller which results into faster detouring and ultimately rapid recovery.

• 정보처리학회논문지A
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• 제13A권5호
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• pp.421-428
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• 2006

본 논문에서는 복잡해져 가는 제어 컴퓨터의 높은 신뢰성 확보를 위해 시간 여분(time redundancy)의 일종인 재실행과 rollback 기법을 TMR 구조에 적절하게 혼용하는 방법을 제안한다 재실행과 rollback 기법은 약간의 추가 시간만으로 재구성(reconfiguration) 없이도 일시적인 결함(fault)에 의해 발생한 TMR 고장(failure)의 회복을 위해 상호 보완적으로 사용될 수 있다. 이를 위해 고장 검출시 가능한 모든 시스템의 고장상태 확률을 추정하였으며, 이를 바탕으로 전체 작업의 평균 실행시간이 최소가 되는 최적의 재실행과 rollback 횟수를 유도하였다. 또한 제안된 방법과 다른 고장회복 기법을 적용했을 때의 평균 실행 시간을 정량적으로 비교하여 그 우수성을 검증하였다.

• 전자공학회논문지CI
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• 제40권2호
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• pp.26-37
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• 2003

소프트웨어 배포 문제는 프로젝트관리에 매우 중요하다. 왜냐하면 다양한 운용 환경 하에서 개발비용 및 에러의 발견, 수정 등에 밀접한 관계에 있기 때문이다. 본 논문은 대형 교환시스템 소프트웨어의 Release 시점을 예측할 수 있는 최적배포 문제로서 시스템의 안정도를 평가해 볼 수 있는 측면에서 소프트웨어 최적 배포 문제를 다루었다. 또, 신뢰도 평가 기준을 제시하여 제품의 적기 공급 및 개발자원의 효율적 이용 측면을 분석하고 신뢰성 평가 척도와 개발비용 고려한 최적 배포 문제를 기술하였다. 그밖에 소프트웨어 신뢰도 성장 모델 중 지수형 모델을 근거로 한 초기 고장데이터를 활용하여 교환시스템의 소프트웨어 개발비용과 신뢰성 평가기준을 고려한 최적 배포시기를 결정하고 시험시 발생된 고장데이터에 대한 분석 및 관리기법 등을 소개한다.

• 한국해안·해양공학회논문집
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• 제32권4호
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• pp.223-229
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• 2020

시간차를 지닌 단층파괴 활동은 지진해일의 초기파형 생성에 영향을 끼치며, 이로 인해 해안에서의 처오름 높이에도 변화를 준다. 이러한 단층파괴 활동이 처오름 높이에 미치는 영향을 검토하기 위하여 일본 서해역에 다수의 가상 단층파괴를 가정하여 수치모의를 수행하였다. 소단층들이 해안선에 평행하게 위치한 경우에는 시간차를 지닌 단층파괴가 처오름 높이에 미치는 영향은 미미했으나, 해안선에 수직으로 위치해 있는 경우에는 초기파형의 중첩효과가 두드러지게 발생하여 해안선에서 처오름 높이가 증가하였다.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.957-963
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• 2014

Converter transformers play important roles in high-voltage direct current transmission systems. This paper presents experimental and analysis results of the combined electrical and thermal aging of oil-impregnated paper at pulsating DC voltages. Breakdown voltages and time-to-breakdown of oil-paper specimens were measured by using short-time and constant-stress tests. The breakdown characteristics of combined electrical and thermal aging on insulation system were discussed. According to the relationship between failure time and aging temperature, the two-parameter Weibull model was improved. On the basis of the competing risk algorithm and the improved Weibull model, the two factors failure model was calculated. And the influence of temperature in the insulation system has been analyzed. This model performs better than the two-parameter Weibull model when both time and temperature are considered as variables in estimating the lifetime of oil-paper insulation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.508-518
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• 2008

Reliability and sensitivity analysis of the design parameters for a section of caisson type quaywall which is the most applicable in Korea were performed. It was tried to estimate probabilities of failure for the system of the multiple failure modes and to analyze LCC in the quaywall structure. The reliability analysis was performed by FORM. Also, sensitivity indices were estimated using the reliability indices, which may be used inferring effects of each design parameter on the reliability indices. As a result, the coefficient of friction between caisson and rubble, the moment by self weight and the moment of resistance mostly affected on the reliability indices in the sliding, overturning and foundation failure, respectively. System reliability theorem was applied in order to estimate the probabilities of failure for the system of the multiple failure modes. As the results of estimation of the probabilities of failure for the system, all cases were more conservative than those for the elements, according to both failure mode and load combination applied to series system. It entirely exceeded the target reliability index, but it was consistent with the theorem. According to the optimum LCC with the width of the caisson, the probability of failure exceeded the target probability of failure at then time. Therefore, it was judged to be insufficient to the practical application.

• 전기학회논문지
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• 제62권8호
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• pp.1177-1183
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• 2013

In this paper, the analysis of inspection period bases on reliability is suggested in the field of traction power system. Even though there are several maintenance models, the most commonly used maintenance assessment has been focused on time based maintenance in real traction power systems. The maintenance intervals are selected on the basis of long-time experience. It ensures high availability and exact planning of staff. Reliability centered maintenance, which evaluates criticality and severity of each failure mode, achieves the operation, maintenance, and cost-effective improvement that will manage the risks of equipment. This paper deals with electrification in railway inspection frequency and applied reliability based inspection frequency instead of constant intervals. The distribution function of failure rate in traction power system belongs to Weibull function. Also, the fault data and the number of installed equipments for electrifications are collected. The failure history is investigated and classified in detail. Though these complicated procedures, it contribute to extend equipment lifetime and to reduce maintenance costs.

• 대한산업공학회지
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• 제22권4호
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• pp.651-662
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• 1996

This paper concerns with preventive replacement under periodic inspections for an item (system) which is in a state of preparedness. The item is subject to wear. The item fails randomly but the failure rate depends on the accumulated wear. The item is preventively replaced if it survives a certain wear limit at periodic inspections. The foiled item is, however, replaced at periodic inspections. Given the costs for replacements and inspections, and the penalty cost of the time elapsed between failure und its detection, the optimal wear limit according to the long-run expected cost per unit time criterion is derived. It has been proved that the optimal wear limit is unique if an item has increasing weer-dependent failure rate. A numerical example for a stationary gamma wear process with Weibull distributed failure is given to show its applicability.