• Nuclear Engineering and Technology
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• 제40권5호
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• pp.365-374
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• 2008

Dependability-critical systems, such as digital instrumentation and control systems in nuclear power plants, necessitate engineering techniques and tools to provide assurances of their safety and reliability. Determining system reliability at the architectural design phase is important since it may guide design decisions and provide crucial information for trade-off analysis and estimating system cost. Despite this, reliability and system engineering remain separate disciplines and engineering processes by which the dependability analysis results may not represent the designed system. In this article we provide an overview and application of our approach to build architecture-based, dynamic system models for dependability-critical systems and then automatically generate dynamic fault trees (DFT) for comprehensive, tool-supported reliability analysis. Specifically, we use the Architectural Analysis and Design Language (AADL) to model the structural, behavioral and failure aspects of the system in a composite architecture model. From the AADL model, we seek to derive the DFT(s) and use Galileo's automated reliability analyses to estimate system reliability. This approach alleviates the dependability engineering - systems engineering knowledge expertise gap, integrates the dependability and system engineering design and development processes and enables a more formal, automated and consistent DFT construction. We illustrate this work using an example based on a dynamic digital feed-water control system for a nuclear reactor.

• 산업공학
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• 제25권4호
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• pp.382-392
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• 2012

Reactor protection system to keep nuclear safety and operational economy of plants requires high reliability. Such a high reliability of the system can be achieved through the redundant design of components. However, common cause failures of components reduce the benefits of redundant design. Thus, the common cause failure analysis, to accurately calculate the reliability of the reactor protection system, is carried out using alpha-factor model. Analysis results to 24 operating months are that 1) the system reliability satisfies the reliability goal of EPRI-URD and 2) the common cause failure contributes 90% of the system unreliability. The uncertainty analysis using alpha factor parameters of 0.05 and 0.95 quantile values shows significantly large difference in the system unreliability.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.105-112
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• 1996

A practical approach for the assessment of system reliability-based safety and load carring capacity under vehicle traffics is proposed for the realistic evaluation of safety and rating of cable-stayed bridges. A partial event tree analysis model incorporating major critical failure paths is suggested as a practical tool for the system reliability analysis and system reliability-based capacity rating. The proposed approach for the system reliability analysis and system reliability-based rating is applied to the safety assessment of the Jindo Bridge which is one of two existing cable-stayed bridges in Korea. The results of analyses at the system level based on the system reliability are compared with those at the element level.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1440-1443
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• 2004

In this paper, to assess and enhance the reliability of Korea High Speed Train, auxiliary power is selected and reliability analysis is carried out. The auxiliary power system is classified into subsystems and functional analysis is conducted. Reliability block diagrams are drawn. and reliability parametric analysis is performed. Analysis results show that the reliability of auxiliary power system depends on critical items. To grow the system reliability, activities have been concentrated on improvement of critical items and the results were successful.

• 산업기술연구
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• 제26권B호
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• pp.135-144
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• 2006

The significance of hydro-power plant is increasing in its public roles such as flood control and water supply as well as electric power production. Even if high level of reliability in facility operation is required, no specific reliability research has been made. This specifically stems from the lack of technology and research investments. The eventual goal of this study is to secure a methodology for reliability analysis of hydro-power plant so that an appropriate decision for operation and investment can be made. Specific effort was put to develop a reliability model for water supply system within hydro-power plant. For this study, we briefly examined the overview of the hydro-power plant including the electric power generation facility system. We then discussed the facility reliability analysis methodology for hydro-power plant. Based on rigorous examination of the water supply system and components roles, we drew major failure modes for each component and examined their effects.

• Structural Engineering and Mechanics
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• 제63권6호
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• pp.799-808
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• 2017

Failure of a redundant long-span bridge is often described by innumerable failure modes, which make the structural system reliability analysis become a computationally intractable work. In this paper, an innovative procedure is proposed to efficiently identify the dominant failure modes and quantify the structural reliability for a long-span bridge system. The procedure is programmed by ANSYS and MATLAB. Considering the correlation between failure paths, a new branch and bound operation criteria is applied to the traditional stage critical strength branch and bound algorithm. Computational effort can be saved by ignoring the redundant failure paths as early as possible. The reliability of dominant failure mode is computed by FORM, since the limit state function of failure mode can be expressed by the final stage critical strength. PNET method and FORM for system are suggested to be the suitable calculation method for the bridge system reliability. By applying the procedure to a CFST arch bridge, the proposed method is demonstrated suitable to the system reliability analysis for long-span bridge structure.

• 전기학회논문지
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• 제59권1호
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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.

• 한국안전학회지
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• 제31권5호
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• pp.95-101
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• 2016

This study proposes a multi-scale dynamic system reliability analysis of control system as a method of quantitative evaluation of its performance in probabilistic terms. In this second paper, we discuss the control effect of the viscous damper on the seismic performance of the structure-level failure. Since the failure of one structural member does not necessarily cause the collapse of the structural system, we need to consider a set of failure scenarios of the structural system and compute the sum of the failure probabilities of the failure scenarios where the statistical dependence between the failure scenarios should be taken into account. Therefore, this computation requires additional system reliability analysis. As a result, the proposed approach takes a hierarchial framework where the failure probability of a structural member is computed using a lower-scale system reliability with the union set of time-sequential member failures and their statistical dependence, and the failure probability of the structural system is again computed using a higher-scale system reliability with the member failure probabilities obtained by the lower-scale system reliability and their statistical dependence. Numerical results demonstrate that the proposed approach can provide an accurate and stable reliability assessment of the control performance of the viscous damper system on the system failure. Also, the parametric study of damper capacity on the seismic performance has been performed to demonstrate the applicability of the proposed approach through the probabilistic assessment of the seismic performance improvement of the damper system.

• 산업경영시스템학회지
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• 제39권4호
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• pp.49-59
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• 2016

Naval combat system developed in-country is progressing at an alarming rate since 2000. ROK navy will be achieved all vessels that have combat system in the near future. The importance of System Engineering and Integrated Logistics Support based on reliability analysis is increasing. However, reliability analysis that everyone trusted and recognized is not enough and applied practically for development of Defense Acquisition Program. In particular, Existing Reliability Analysis is focusing on reliability index (Mean Time Between Failure (MTBF) etc.) for policy decision of defense improvement project. Most of the weapon system acquisition process applying in the exponential distribution simply persist unreality due to memoryless property. Critical failures are more important than simple faults to ship's operator. There are no confirmed cases of reliability analysis involved with critical failure that naval ship scheduler and operator concerned sensitively. Therefore, this study is focusing on Mean Time To Critical Failure (MTTCF), reliability on specific time and Operational Readiness Float (ORF) requirements related to critical failure of Patrol Killer Guided missile (PKG) combat system that is beginning of naval combat system developed in-country. Methods of analysis is applied parametric and non-parametric statistical techniques. It is compared to the estimates and proposed applications. The result of study shows that parametric and non-parametric estimators should be applied differently depending on purpose of utilization based on test of normality. For the first time, this study is offering Reliability of ROK Naval combat system to stakeholders involved with defense improvement project. Decision makers of defense improvement project have to active support and effort in this area for improvement of System Engineering.

• 한국철도학회논문집
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• 제9권6호
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• pp.739-745
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• 2006

The role of maintenance in railway is going to be extended to improve the reliability of railway system in the aspect of Asset management gradually. In this paper, the meaning of reliability and safety in RCM which has been applied in order to improve the efficiency of maintenance is deduced. And the analysis task of reliability and safely which has been recommended in railway standards such as EN50126 and IEC62278 is reviewed in the aspect of RCM. Finally, the several ways are proposed to apply RCM to railway system through the comparison between the RCM procedure and the analysis procedure for the reliability and safety in railway standards. Hereafter, if the analysis of reliability and safety is performed with the concept of RCM in the beginning of railway business, it will be more efficient to improve the reliability and manage the railway asset.