• 마이크로전자및패키징학회지
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• 제23권2호
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• pp.37-42
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• 2016

전력가격의 상승으로 데이터센터의 운영비 부담이 늘어나는 가운데, 슈퍼컴퓨터에 저전력 프로세서를 사용하여 데이터센터의 전력소모를 감소시키는 연구가 활발하다. 일반적으로 모바일 기기 등의 운용환경을 기준으로 신뢰성 평가가 이루어지는 저전력 프로세서를 슈퍼컴퓨터에 사용하는 경우 상대적으로 가혹한 운용환경으로 인해 물리적, 기계적 신뢰성 문제가 발생할 수 있다. 이 논문은 슈퍼컴퓨터 운용 환경을 바탕으로 저전력 프로세서 패키지의 수명을 평가하였다. 먼저 문헌조사, 고장모드 및 치명도 분석을 통해 저전력 프로세서 패키지의 주요 고장원인으로 온도 사이클을 선정하였다. 부하-온도 관계를 확인하기 위해 단계적인 부하를 가하며 프로세서의 온도를 측정하였다. 가장 보수적인 운용조건을 가정하고 온도 사이클에 관련된 고장물리 모델을 이용한 결과 저전력 프로세서 패키지의 기대수명은 약 3년 이하로 예측되었다. 실험 결과를 바탕으로 저전력 프로세서 패키지의 기대수명을 향상하는 방법을 제시하였다.

• Structural Engineering and Mechanics
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• 제64권3호
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• pp.347-352
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• 2017

The poor maintenance practice increases the possibility of system failure. Subsequently, the consequences of failure fall on the aspects of output, safety and healthy, environmental integrity, system quality, and customer satisfaction. Conditionbased maintenance is seen as a potential strategy to improve performance. Whereby, the key success factor of this maintenance strategy is identified as the system inspection. This study aims to investigate the association between system breakdown rate and frequency of inspection. A mixed method approach is implemented by distributing questionnaire and interviewing for data collection. Subsequently, descriptive analysis, correlation analysis and regression are adopted to analyse the collected data from 100 respondents and the results are validated with interview data of 10 interviewees. The research result establishes significant relationship between the system breakdown rate and the frequency of inspection. Additionally, the result of regression analysis confirms that the frequency of inspection is the significant predictor of system breakdown rate. Planning of accurate inspection frequency is crucial to secure the system performance. Hence, the research signifies the importance to carry out regular inspection towards the building systems and components. As a recommendation, the maintenance personnel should assess the risk criticality of the building systems. Then, continuously monitor the condition of critical building systems; regularly inspect the condition of non-critical building systems and randomly inspect all of them.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1991년도 가을 학술발표회 논문집
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• pp.29-32
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• 1991

It is well known that the fatigue damage process in composite materials is very complicated due to complex failure mechanisms that comprise debounding, matrix cracking, delamination and fiber splitting of laminates. Therefore, the residual strength, instead of a single dominant crack length, is chosen to describe the criticality of the damage accumulated in the sublaminate. In this study, two models for residual strength degradation established by Yang-Liu and Tanimoto-Ishikawa that are capable of predicting the statistical distribution of both fatigue life and residual strength have been investigated and compared. Statistical methodologies for fatigue life prediction of composite materials have frequently been adopted. However, these are usually based on a simplified probabilistic approach considering only the variation of fatigue test data. The main object of this work is to propose a fatigue reliability analysis model which accounts for the effect of all sources of variation such as fabrication and workmanship, error in the fatigue model, load itself, etc. The proposed model is examined using the previous experimental data of GFRP and it is shown that it can be practically applied for fatigue problems in composite materials.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.202-204
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• 2008

RCM(reliability Centered Maintenance) 적용 시 나타나는 장점으로 인해 이미 여러 산업 분야에 적용되고 있다. 설비의 안정성을 중요시하는 원자력발전 부문에서 처음으로 도입 후 전력산업분야 대부분에서 RCM을 적용하거나 적용연구가 진행되고 있다. 철도산업에서도 전력산업 분야와 같이 안정적 이면서 경제적인 전력을 공급하는 것이 중요하므로 정비업무의 중요성이 크다고 할 수 있다. 특히 철도 시스템 중 한전에서 154kV나 345kV를 수전 받아 철도 시스템에 전력을 공급하는 변전소의 역할은 매우 중요하다. 따라서 철도 변전소를 구성하고 있는 설비의 특성과 운영방식에 대한 연구를 통해 적절한 RCM적용 방안을 위한 고장모드 및 임계분석 (FMECA: Failure Mode, Effects and Criticality Analysis) 연구의 필요성이 대두된다. RCM과 FMECA는 적용 산업분야에 따라 적용 절차를 다르게 적용되어진다. 따라서 철도 변전소에 대한 고장데이터와 설비들의 특성 및 현재 운용방식 등을 종합적으로 고려하여 적절한 수립방법 연구가 필요하다.

• 대한안전경영과학회지
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• 제14권3호
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• pp.39-48
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• 2012

Risk Assessment to list possible safety disasters and their probability and severity is the starting point for effective safety management on construction project site. However, the safety managers in owners, construction supervisors, contractors, and sub-contractors still have difficulties in judging the priorities of safety activities and preparing responses to each potential safety disasters. Therefore, this study aimed to suggest a systematic method in assessing safety risk prior to commencement with the agreement of stakeholders. FMECA(failure mode effects and criticality analysis) was selected as a main assessment tool and it was modified according to the characteristics of construction projects and trades. Each risk is, firstly, evaluated with occurrence probability, possible loss and impacts to projects, and detections, and then risk priority number(RPN) is calculated. Subsequently, the managers of each stakeholder discuss the types, timing, and responsibilities of responses as a group decision-making process.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1481-1486
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• 2008

To apply more effective the RCM analysis for railway vehicle, the maintenance cost per equipment should be considered together with failure criticality per equipment considered in existing. This paper is described the systematic calculation of maintenance cost considering the RCM analysis of railway vehicle. To calculate the maintenance cost systematically, the cost breakdown structure was established, and basic cost information and calculated cost items were defined. In addition, the linking between calculated cost and RCM analysis was considered. In future, this proposal would be used to analysis of cost effectiveness through RCM analysis of railway vehicle.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2013년도 춘계학술발표대회
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• pp.964-967
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• 2013

현재에 시스템의 결함을 분석하는 안전성 분석 기법들이 여러 가지가 있다. 본 논문에서는 많은 결함 분석 기법 중에서 FTA(Fault Tree Analysis)와 FMECA(Failure Modes, Effect and Criticality Analysis)을 통하여 안전성 분석을 하고자 한다. 또한 이 두 가지 기법을 따로 사용하지 않고 전방에서 FTA 분석을 하고 후방에서 FMECA 분석을 수행하는 통합 기법을 제안한다. 이를 통해 각 기법의 단점을 최소화하고 장점을 최대화 하여 안전성 분석의 효율성을 제고하고자 한다.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1464-1478
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• 2021

Selective Production of Exotic Species is an innovative plant for advanced nuclear physic studies. A radioactive beam, generated by using an UCx target-ion source system, is ionized, selected and accelerated for experimental objects. Very high vacuum conditions and appropriate safety systems to storage exhaust gases are required to avoid radiological risk for operators and people. In this paper, Failure Mode, Effects, and Criticality Analysis of a preliminary design of high activity gas recovery system is performed by using a modified Fuzzy Risk Priority Number to rank the most critical components in terms of failures and human errors. Comparisons between fuzzy approach and classic application allow to show that Fuzzy Risk Priority Number is able to enhance the focus of risk assessments and to improve the safety of complex and innovative systems such as those under consideration.

• Nuclear Engineering and Technology
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• 제38권3호
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• pp.231-238
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• 2006

Whole-body exposure to high-dose radiation causes injury involving multiple organs that depends on their sensitivity to radiation. This acute radiation syndrome (ARS) is caused by a brief exposure of a major part of the body to radiation at a relatively high dose rate. ARS is characterized by an initial prodromal stage, a latent symptom-free period, a critical or manifestation phase that usually takes one of four forms (three forms): hematologic, gastrointestinal, or cardiovascular and neurological (neurovascular), depending upon the exposure dose, and a recovery phase or death. One of the most important factors in treating victims exposed to radiation is the estimation of the exposure dose. When high-dose exposure is considered, initial dose estimation must be performed in order to make strategy decisions for treatment as soon as possible. Dose estimation can be based on onset and severity of prodromal symptoms, decline in absolute lymphocyte count post exposure, and chromosomal analysis of peripheral blood lymphocytes. Moreover, dose assessment on the basis of calculation from reconstruction of the radiation event may be required. Experience of a criticality accident occurring in 1999 at Tokai-mura, Japan, showed that ARS led to multiple organ failure (MOF). This article will review ARS and discuss the possible mechanisms of MOF developing from ARS.

• Journal of Communications and Networks
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• 제14권4호
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• pp.451-460
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• 2012

Natural disasters often lead to regional failures that can cause network nodes and links co-located in a large geographical area to fail. Novel approaches are required to assess the network vulnerability under such regional failures. In this paper, we investigate the vulnerability of networks by considering the geometric properties of regional failures and network nodes. To evaluate the criticality of node locations and determine the critical areas in a network, we propose the concept of ${\alpha}$-critical-distance with a given failure impact ratio ${\alpha}$, and we formulate two optimization problems based on the concept. By analyzing the geometric properties of the problems, we show that although finding critical nodes or links in a pure graph is a NP-complete problem, the problem of finding critical areas has polynomial time complexity. We propose two algorithms to deal with these problems and analyze their time complexities. Using real city-level Internet topology data, we conducted experiments to compute the ${\alpha}$-critical-distances for different networks. The computational results demonstrate the differences in vulnerability of different networks. The results also indicate that the critical area of a network can be estimated by limiting failure centers on the locations of network nodes. Additionally, we find that with the same impact ratio ${\alpha}$, the topologies examined have larger ${\alpha}$-critical-distances when the network performance is measured using the giant component size instead of the other two metrics. Similar results are obtained when the network performance is measured using the average two terminal reliability and the network efficiency, although computation of the former entails less time complexity than that of the latter.