• Title, Summary, Keyword: Event Tree

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Reliability Assessment of Railway Power System by using Tree Architecture (Tree 구조를 이용한 전철급전시스템의 신뢰도 평가)

  • Cha, Jun-Min;Ku, Bon-Hui
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.1
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    • pp.9-15
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    • 2010
  • As catenary supply electric power directly to the railway system, it is very important to prevent an accident of a catenary for appropriate train operation. This paper proposed the assessment the outage data for "British Catenary Safety Analysis Report" and Korean data to compare the reliability of the railway system. The analyzed data were applied to Event Tree and Fault Tree algorithm to calculate the reliability indices of railway system. Event tree is created and gate results of fault tree analysis are used as the source of event tree probabilities. Fault tree represents the interaction of failures and basic events within a system. Event Tree and Fault Tree analysis result is helpful to assess the reliability to interpreted. The reliability indices can be used to determine the equipment to be replaced for the entire system reliability improvement.

Simulation-Based Risk Analysis of Integrated Power System (시뮬레이션을 이용한 통합전력시스템의 위험도 분석)

  • Lee, Ji Young;Han, Young Jin;Yun, Won Young;Bin, Jae Goo
    • Journal of Korean Institute of Industrial Engineers
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    • v.42 no.2
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    • pp.151-164
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    • 2016
  • In this paper, we deal with a risk analysis for an IPS (Integrated power system) and propose a simulation model combining the fault tree and event tree in order to estimate the system availability and risk level, together. Firstly, the basic information such as operational scenarios, physical structure, safety systems is explained in order to make the fault tree and event tree of the IPS. Next, we propose a discrete-event simulation model using a next-event time advance technique to advance the simulation time. Also the state transition and activity diagrams are explained to represent the relationship between the objects. By numerical examples, the redundancy allocation is considered in order to decrease the risk level of the IPS.

Vital Area Identification Rule Development and Its Application for the Physical Protection of Nuclear Power Plants (원자력발전소의 물리적방호를 위한 핵심구역파악 규칙 개발 및 적용)

  • Jung, Woo Sik;Hwang, Mee-Jeong;Kang, Minho
    • Journal of the Korean Society of Safety
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    • v.32 no.3
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    • pp.160-171
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    • 2017
  • US national research laboratories developed the first Vital Area Identification (VAI) method for the physical protection of nuclear power plants that is based on Event Tree Analysis (ETA) and Fault Tree Analysis (FTA) techniques in 1970s. Then, Korea Atomic Energy Research Institute proposed advanced VAI method that takes advantage of fire and flooding Probabilistic Safety Assessment (PSA) results. In this study, in order to minimize the burden and difficulty of VAI, (1) a set of streamlined VAI rules were developed, and (2) this set of rules was applied to PSA fault tree and event tree at the initial stage of VAI process. This new rule-based VAI method is explained, and its efficiency and correctness are demonstrated throughout this paper. This new rule-based VAI method drastically reduces problem size by (1) performing PSA event tree simplification by applying VAI rules to the PSA event tree, (2) calculating preliminary prevention sets with event tree headings, (3) converting the shortest preliminary prevention set into a sabotage fault tree, and (4) performing usual VAI procedure. Since this new rule-based VAI method drastically reduces VAI problem size, it provides very quick and economical VAI procedure. In spite of an extremely reduced sabotage fault tree, this method generates identical vital areas to those by traditional VAI method. It is strongly recommended that this new rule-based VAI method be applied to the physical protection of nuclear power plants and other complex safety-critical systems such as chemical and military systems.

Bayesian reliability prediction under event tree (Event tree하에서 베이지안 기법을 이용한 신뢰도 예측)

  • 박철순;전치혁;양희중;장수영
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • pp.24-30
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    • 1993
  • When modeling a complex system we use an event tree to analyze propagation of failure. An event tree cannot represent the statistical interrelationships among parameters, but it can be represented as a statistically identical influence diagram so that parameter updating can be easily performed. After updating parameters we can calculate posterior distribution of the failure rate for each path. But exact distribution requires considerably complex numerical integration. We propose an approximation method to calculate the posterior and derive the predictive distribution of the time to next failure. Finally we introduce the system which implements our methodology.

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Application of ETA(Event Tree Analysis) to the Performance-Based Design of fire protection (성능위주설계를 위한 ETA 기법 활용 고찰)

  • Kim, H.B.;Lee, S.K.;Song, D.W.;Kim, K.S.;Kim, J.H.
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
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    • pp.454-457
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    • 2011
  • 본 연구에서는 소방시설의 성능위주의설계를 수행하기 위하여 ETA(Event Tree Analysis) 기법을 적용하는 방안을 고찰하였다. ETA기법에서는 화재시나리오를 사건(Event)의 인과관계로 된 각 단계의 사건으로 구성한다. 본 연구에서는 ETA에서 구성된 시나리오에 따른 심각도를 화재시뮬레이션과 피난 시뮬레이션을 통한 수행으로 사망자수를 도출하는 방안을 적용하였고, 각 시나리오의 빈도(확률)은 FTA(Fault Tree Analysis) 기법을 적용하여 분기 확률을 도출하도록 하였다. ETA에서 도출한 사망자수와 빈도를 이용하여 F-N 커브를 작성하여 위험도를 평가하여 소방설계의 보완 및 대책을 수립하는 방안을 제시하였다.

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Construction of Event Tree & Fault Tree for Train Fire Risk Assessment (철도화재사고 위험도평가를 위한 Event Tree 및 Fault Tree 구성)

  • Kwak, Sang-Log;Wang, Jong-Bae;Lee, Bong-Seob;Park, Chan-Woo
    • Journal of the Korean Society for Railway
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    • v.11 no.6
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    • pp.530-535
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    • 2008
  • After train fire accident in Daegue, many research on train fire safety improvement have been carrying out. Since many alternative fire safety measures can be applied in our railway system, the effect of the each safety measure must be quantified prior to the safety investment. In order to estimate the effects of each safety measure quantitatively, fault trees and event trees are constructed in this study. Results can be applied for cost-benefit analysis or sensitivity analysis for safety measures in risk assessment process.

Feasibility Study on the Fault Tree Analysis Approach for the Management of the Faults in Running PCR Analysis (PCR 과정의 오류 관리를 위한 Fault Tree Analysis 적용에 관한 시범적 연구)

  • Lim, Ji-Su;Park, Ae-Ri;Lee, Seung-Ju;Hong, Kwang-Won
    • Applied Biological Chemistry
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    • v.50 no.4
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    • pp.245-252
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    • 2007
  • FTA (fault tree analysis), an analytical method for system failure management, was employed in the management of faults in running PCR analysis. PCR is executed through several processes, in which the process of PCR machine operation was selected for the analysis by FTA. The reason for choosing the simplest process in the PCR analysis was to adopt it as a first trial to test a feasibility of the FTA approach. First, fault events-top event, intermediate event, basic events-were identified by survey on expert knowledge of PCR. Then those events were correlated deductively to build a fault tree in hierarchical structure. The fault tree was evaluated qualitatively and quantitatively, yielding minimal cut sets, structural importance, common cause vulnerability, simulation of probability of occurrence of top event, cut set importance, item importance and sensitivity. The top event was 'errors in the step of PCR machine operation in running PCR analysis'. The major intermediate events were 'failures in instrument' and 'errors in actions in experiment'. The basic events were four events, one event and one event based on human errors, instrument failure and energy source failure, respectively. Those events were combined with Boolean logic gates-AND or OR, constructing a fault tree. In the qualitative evaluation of the tree, the basic events-'errors in preparing the reaction mixture', 'errors in setting temperature and time of PCR machine', 'failure of electrical power during running PCR machine', 'errors in selecting adequate PCR machine'-proved the most critical in the occurrence of the fault of the top event. In the quantitative evaluation, the list of the critical events were not the same as that from the qualitative evaluation. It was because the probability value of PCR machine failure, not on the list above though, increased with used time, and the probability of the events of electricity failure and defective of PCR machine were given zero due to rare likelihood of the events in general. It was concluded that this feasibility study is worth being a means to introduce the novel technique, FTA, to the management of faults in running PCR analysis.

A Study on the Structures for Efficient Event Queues (효율적인 이벤트 큐의 구조에 관한 연구)

  • 김상욱
    • Journal of the Korea Society for Simulation
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    • v.4 no.2
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    • pp.61-68
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    • 1995
  • The performance of event-driven logic simulation frequently used for VLSI design verification depends on the data structures for event queues. This paper improves the existing Timing Wheel as a data structure for an event queue. In case of the use of B+ tree, an efficient node degree is also presented based on the experiment results. A new Timing Wheel index structure, which eliminates the insertion and deletion overhead of B+ tree, is proposed and analyzed.

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Safety Analysis on the Tritium Release Accidents

  • Yang, Hee joong
    • Journal of the Korean Society for Quality Management
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    • v.19 no.2
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    • pp.96-107
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    • 1991
  • At the design stage of a plant, the plausible causes and pathways of release of hazardous materials are not clearly known. Thus there exist large amount of uncertainties on the consequences resulting from the operation of a fusion plant. In order to better handle such uncertain circumstances, we utilize the Probabilistic Risk Assessment(PRA) for the safety analyses on fusion power plant. In this paper, we concentrate on the tritium release accident. We develop a simple model that describes the process and flow of tritium, by which we figure out the locations of tritium inventory and their vulnerability. We construct event tree models that lead to various levels of tritium release from abnormal initiating events. Branch parameters on the event tree are assessed from the fault tree analysis. Based on the event tree models we construct influence diagram models which are more useful for the parameter updating and analysis. We briefly discuss the parameter updating scheme, and finally develop the methodology to obtain the predictive distribution of consequences resulting from the operating a fusion power plant. We also discuss the way to utilize the results of testing on sub-systems to reduce the uncertain ties on over all system.

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Application Cases of Risk Assessment for British Railtrack System (영국철도시스템에 적용된 리스크평가 사례)

  • Lee, Dong-Ha;Jeong, Gwang-Tae
    • Journal of the Ergonomics Society of Korea
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    • v.22 no.1
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    • pp.81-94
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    • 2003
  • The British railway safety research group has developed a risk assessment model for the railway infrastructure and major railway accidents. The major hazardous factors of the railway infrastructure were identified and classified in the model. The frequency rates of critical top events were predicted by the fault tree analysis method using failure data of the railway system components and ratings of railway maintenance experts, The consequences of critical top events were predicted by the event tree analysis method. They classified the Joss of accident due to railway system into personal. commercial and environmental damages. They also classified 110 hazardous event due to railway system into three categories. train accident. movement accident and non-movement accident. The risk assessment model of the British railway system has been designed to take full account of both the high frequency low consequence type events (events occurring routinely for which there is significant quantity of recorded data) and the low frequency high consequence events (events occurring rarely for which there is little recorded data). The results for each hazardous event were presented in terms of the frequency of occurrence (number of events/year) and the risk (number of equivalent fatalities per year).