• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2638-2651
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• 2020

Nozzle corner cracks present at the intersection of reactor pressure vessels (RPVs) and inlet or outlet nozzles have been a persistent problem for a number of years. The fracture analysis of such nozzle corner cracks is very important and critical for the efficient design and assessment of the structural integrity of RPVs. This paper aims to perform an engineering critical assessment of RPVs with nozzle corner cracks subjected to several transients accompanied by pressurized thermal shocks. The critical crack size of the RPV model with nozzle corner cracks under transient loading is evaluated on failure assessment curve. In particular, the influence of cladding on the crack initiation of nozzle corner crack under thermal transients is studied. The influence of primary internal pressure and secondary thermal stress on the stress field at nozzle corner and SIF at crack front is analyzed. Finally, the influence of different crack size and crack shape on the final critical crack size is analyzed.

• Journal of Electrical Engineering and Technology
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• 제2권3호
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• pp.386-390
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• 2007

At recent times, an essential issue in the replacement of the old analogue I&C to computer-based digital systems in nuclear power plants becomes the quantitative software reliability assessment. Software reliability models have been successfully applied to many industrial applications, but have the unfortunate drawback of requiring data from which one can formulate a model. Software that is developed for safety critical applications is frequently unable to produce such data for at least two reasons. First, the software is frequently one-of-a-kind, and second, it rarely fails. Safety critical software is normally expected to pass every unit test producing precious little failure data. The basic premise of the rare events approach is that well-tested software does not fail under normal routine and input signals, which means that failures must be triggered by unusual input data and computer states. The failure data found under the reasonable testing cases and testing time for these conditions should be considered for the quantitative reliability assessment. We presented the quantitative reliability assessment methodology of safety critical software for rare failure cases in this paper.

• 국제학술발표논문집
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• The 2th International Conference on Construction Engineering and Project Management
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• pp.9-18
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• 2007

The success of a building design team is achieved as a result of a combination of multiple events/factors and interactions, and has a great impact on the quality of the building construction process. While most of previous studies have focused on quality of the construction process, the success of a design team has not been completely investigated. This paper presents the critical factors that impact the success of a building design team and describes an assessment tool to measure the successful performance of the design team with respect to the critical factors. The development of the assessment tool employs the concept of quality function deployment (QFD), a technique to measure the service quality of an organization.

• 한국농공학회논문집
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• 제63권5호
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• pp.27-38
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• 2021

The physical condition assessment criteria of fill dam safety inspection are now weakly regulated and inappropriate for small agricultural reservoirs since these criteria have fundamental backgrounds suitable for large-scale dams. This study proposes the degree (critical values) of defects for the quantitative condition assessment of the embankment in order to prepare the condition assessment criteria for a small reservoir with a storage capacity of less than one (1) million cubic meters. The critical values of defects were calculated by applying the method that considers the size ratios based on the dimensional data of reservoirs, and the method of statistical analysis on the measured values of the defect degree which extracted from comprehensive annual reports on reservoir safety inspection. In comparison with the current criteria, the newly proposed critical values for each condition assessment item of the reservoir embankment are presented in paragraphs 4 and 6 of the conclusion. In addition, this study presents a method of displaying geometric figures to clarify the rating classification for condition assessment items with the two defect indicators.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.292-301
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• 2009

The employment of risk management theory in Urban Disaster Management System (UDMS) has become an important trend in recent years. The viewpoint of risk management is mainly a comprehensive risk assessment of various internal and external factors, and a subsequent handling of risks. Through continuous and systematic accumulation and analysis of risk information, disaster prevention and rescue system is established. Taking risk management theory as the foundation, Organization for Economic Cooperation and Development (OECD) has developed a series of UDMS in the mega-cities all over the world. With this system as a common platform, OECD cooperates with different cities to develop disaster prevention and rescue system consisting of vulnerability assessment methods, risk assessment and countermeasures. The paper refers to the urban disaster vulnerability assessment and risk management of OECD and the mega-cities of different advanced and developed countries in the world, and then constructs a preliminarily drafted structure for the vulnerability assessment methods and risk management mechanism in the metropolitan districts of Taiwan.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.138-145
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• 2019

With the application of digital technology to safety-critical infrastructures, cyber-attacks have emerged as one of the new dangerous threats. In safety-critical infrastructures such as a nuclear power plant (NPP), a cyber-attack could have serious consequences by initiating dangerous events or rendering important safety systems unavailable. Since a cyber-attack is conducted intentionally, numerous possible cases should be considered for developing a cyber security system, such as the attack paths, methods, and potential target systems. Therefore, prior to developing a risk-informed cyber security strategy, the importance of cyber-attacks and significant critical digital assets (CDAs) should be analyzed. In this work, an importance analysis method for cyber-attacks on an NPP was proposed using the probabilistic safety assessment (PSA) method. To develop an importance analysis framework for cyber-attacks, possible cyber-attacks were identified with failure modes, and a PSA model for cyber-attacks was developed. For case studies, the quantitative evaluations of cyber-attack scenarios were performed using the proposed method. By using quantitative importance of cyber-attacks and identifying significant CDAs that must be defended against cyber-attacks, it is possible to develop an efficient and reliable defense strategy against cyber-attacks on NPPs.

• 한국수자원학회논문집
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• 제51권12호
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• pp.1237-1245
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• 2018

본 연구에서는 주 단위 지하수자원 관리 취약시기 평가 방법을 개발하였다. 강수의 지하수위에 대한 영향을 고려하기 위하여 한계 침투량을 고려한 강우이동평균 방법을 통해 지하수위와의 상관계수를 산정하였다. 취약 시기 평가 기준을 개발하고 평가 기준에 대한 가중치를 엔트로피 방법을 이용하여 산정하였다. 강수와의 상관계수와 산정된 가중치를 이용한 주 단위 지하수자원 관리 취약시기 평가 방법을 개발하였으며, 개발한 방법을 통하여 소규모 행정구역을 대상으로 취약시기를 평가하였다. 본 연구에서 개발된 방법은 지역적일뿐만 아니라 계절적인 지하수자원의 효율적 관리 대책 수립의 근거가 될 수 있을 것이다.

• 항공우주시스템공학회지
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• 제6권3호
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• pp.7-12
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• 2012

The contents of aircraft system safety assessment vary depending on factors such as the complexity of the system, how critical the system is to flight safety, what volume of experience is available on the type of system and the novelty and complexity of the technologies being used. If the system safety assessment is to substantiate that the developed products are 'safe enough' to be taken into use, then the system safety assessment should be planned and managed to provide the necessary assurance that all relevant hazards and failure conditions have been identified and that all significant combinations of hazards and failures which could cause those conditions have been considered. The assessment must assist the designer and management in making decisions. It must make clear what the critical features of each system are and upon which special manufacturing techniques, inspection, testing, crew drills and maintenance practice they are critically dependent. This paper has prepared to study on promoting the efficiency of aircraft system safety assessment and to present how to compile system safety assessment strategy.

• 대한산업공학회지
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• 제41권2호
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• pp.144-149
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• 2015

In this study, the effective technology readiness assessment (TRA) method for system development project is suggested. We analyze the domestic and foreign TRA practice and derive the new idea to resolve the problems found from the analysis. Domestic and foreign organizations develop and use checklist for the precise TRA, but the checklist has some problems in type of questions and analysis of assessment. TRA method using the original TRL definition or the checklist should be selected depending on the project characteristic. Questions of the checklist should be classified into critical or non-critical according to their importance. Finally, Test and evaluation master plan (TEMP) in system engineering process can provide an obvious criteria to assess technology readiness level (TRL) of critical technology elements (CTE) composing the system.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.571-576
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• 2010

In this study, an application method of critical strains concept for tunnels' safety by using the values of measured displacements which are obtained in the field is discussed. The aim is to: (1) study on the engineering meanings of critical strains concept by reviewing the previous researches and application examples with measured displacement values; (2) study on the engineering reasonability of critical strains concept with the view point of a tunnel engineering and a geotechnical engineering; (3) study on the features of ground deformation due to tunneling and reciprocal relation between total displacement and measured displacement; (4) evaluate a tunnel safety by using domestic measurements collected in the field; and (5) re-evaluate the control criteria which were previously used in the field, with the view point of critical strains concept. Consequently, it was confirmed that critical strains in the ground has a reasonability and a possibility of unified or common concept with the view point of a tunnel engineering.