• 전기학회논문지P
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• 제58권1호
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• pp.27-32
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• 2009

A technical system generally comprise a number of subsystems and components that are interconnected in such a way that the system is able to perform a set of required function. Because of the complex system structure with serial, parallel and bridged connections, some certain subsystems or components are more critical than the others. The main concern of a reliability engineer is to identify potential failures and to prevent these failures from occurring. In order to prevent fatal failures, proper inspections and maintenance actions for each component are required Considering above objectives of reliability engineers and characteristics of a practical system, several practical method for evaluating system and component reliabilities have developed namely Birnbaum's and Fussell & Vesely's measures. However there are several critical weaknesses in traditional calculation process as the target system gets larger. In this paper, a new technique for calculating component's structural importance is proposed and compared to Birnbaum's with representative system examples (serial, parallel. k out of n, and bridge type).

• 대한산업공학회지
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• 제33권1호
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• pp.61-69
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• 2007

In a large complex system, maintenance priorities for the failed components are important to maintain the sys-tern reliability at required level. Commonly used methods of determining maintenance priorities are based onranking the failed components by using reliability importance measures such as Birnbaum reliability importance,risk achievement worth and F-V importance, etc. In the preceding works, maintenance priorities for the failedcomponents are determined by using such existing measures, In this study, a new method of determining main-tenance priorities, which utilizes the joint reliability importance is proposed. By investigating the sign of thejoint reliability importance, maintenance priorities obtained by the existing methods are adjusted to yield new re-vised priorities. The revised maintenance priorities are shown to be more effective than the existing ones fromthe standpoint of the speed of system recovery, Effectiveness of the proposed method is illustrated by numericalexamples.

• 대한안전경영과학회지
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• 제14권1호
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• pp.225-233
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• 2012

The research discusses interrelationship of structural and reliability importance measures which used in the probabilistic safety assessment. The most frequently used component importance measures, such as Birnbaum's Importance (BI), Risk Reduction (RR), Risk Reduction Worth (RRW), RA (Risk Achievement), Risk Achievement Worth (RAW), Fussel Vesely (FV) and Critically Importance (CI) can be derived from two structure importance measures that are developed based on the size and the number of Minimal Path Set (MPS) and Minimal Cut Set (MCS). In order to show an effectiveness of importance measures which is developed in this paper, the three representative functional structures, such as series-parallel, k out of n and bridge are used to compare with Birnbaum's Importance measure. In addition, the study presents the implementation examples of Total Productive Maintenance (TPM) metrics and alternating renewal process models with exponential distribution to calculate the availability and unavailability of component facility for improving system performances. System state structure functions in terms of component states can be converted into the system availability (unavailability) functions by substituting the component reliabilities (unavailabilities) for the component states. The applicable examples are presented in order to help the understanding of practitioners.

• 정보보호학회논문지
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• 제23권4호
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• pp.639-653
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• 2013

스마트 그리드는 기존 전력망에 IT 기술을 접목하여 에너지 효율을 최적화하는 차세대 지능형 전력망으로 미국, 유럽, 일본 등 전 세계적으로 기술개발이 이루어지고 있으며 실증사업을 추진하고 있다. 최근 스마트 그리드에 대한 공격 사례가 증가되고 있으며 개인정보의 사용 및 유출의 피해가 높아지고 있다. 전력망이 더욱 복잡해지고 상호 연결됨에 따라 보안 분석과 평가에 대한 노력이 점차 중요해지고 있다. 본 논문에서는 스마트 그리드의 핵심 기술인 AMI(Advanced Metering Infrastructure)의 공격과 공격에 대한 대응책을 ACT(Attack Countermeasure Tree)를 이용하여 모델링 하였다. 보안 분석은 확률이 있는 경우와 확률이 없는 경우로 나누어서 수행하였다. 이러한 모델을 가지고 SHARPE(Symbolic Hierarchical Automated Reliability and Performance Evaluator)로 구현하여 다양한 경우의 확률과 ROA, ROI, Structure Importance, Birnbaum Importance에 대해 계산하였다.