• 한국신뢰성학회지:신뢰성응용연구
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• 제16권3호
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• pp.245-253
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• 2016

Purpose: The purpose of this study is to measure the reliability of complex equipment. Reliability of product is one of the most important factor to achieve competitiveness in the market. While there were many researches for assessing the reliability on components and modules, research on quantitative assessment tool for equipment with many component was little because of equipment's complexity. Methods: In this article, we developed index to assess reliability management system by using IEC 60300 and Reliability Management Tool-kit. With MIR and BARS, we developed reliability index clauses relevant to reliability activities and found weight factor for each clause by survey on experts. Results: The results of this study were as follows; reliability index that can assess both management side and technology side of the company was developed. Conclusion: Using this index, we assessed the reliability of a manufacturing equipment and found out the current reliability level of the manufacturing equipment, and derived improvement points.

• International Journal of Reliability and Applications
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• 제10권2호
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• pp.109-118
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• 2009

Crankshaft, the core element of the engine of a vehicle, transforms the translational motion generated by combustion to rotational motion. Its failure will cause serious damage to the engine so its reliability verification must be performed. In this study, the S-N data of the bending and torsion fatigue limits of a crankshaft are derived. To evaluate the reliability of the crankshaft, reliability verification and analysis are performed. For the purpose of further evaluation, the bending and torsion tests of the original crankshaft are carried out, and failure mode analysis is made. The appropriate number of samples, the applied load, and the test time are computed. On the basis of the test results, Weibull analysis for the shape and scale parameters of the crankshaft is estimated. Likewise, the $B_{10}$ life under 50% of the confidence level and the MTTF are exactly calculated, and the groundwork for improving the reliability of the crankshaft is laid.

• 대한기계학회논문집A
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• 제34권6호
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• pp.743-749
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• 2010

본 논문은 시스템 신뢰성 향상을 위한 확률적 접근을 이용한 부하경감설계방법을 제안한다. 제안하는 설계방법은 부품 수준이 아닌 시스템 수준에서 온도와 전류와 같은 스트레스의 경감 수준을 선정하는 것이다. 직렬 시스템의 신뢰도 모델을 이용하여, 스트레스와 시간의 함수로 주어진 부품들의 신뢰도값들을 이용하여 시스템 신뢰도를 평가한다. 기존의 부하경감설계에서는 고려되지 않았지만, 본 연구에서는 환경 및 동작 조건에서 시스템이 받게 되는 스트레스의 변량을 고려하였다. 시스템 신뢰도 향상을 위한 최적화 문제를 정의하고, FORM을 적용하여 해를 구함으로써 최적의 부하경감설계를 수행하였다. 전기 시스템에 대한 설계를 통하여 제안한 설계방법에 대한 자세한 설명과 응용가능성을 제시하였다.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2006년도 정기학술발표대회 논문집
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• pp.175-180
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• 2006

건축 프로젝트의 초기단계에서 실시하는 개산견적의 결과값인 예측된 공사비(개산견적 공사비)는 실제 시공한 후 정산한 공사비(실 공사비)와 차이가 발생할 수밖에 없는 리스크가 존재한다. 따라서 개산견적 공사비를 실 공사비와 비교했을 때 얼마나 정확하며 얼마나 신뢰할 수 있는지 평가하고, 개산견적의 신뢰도를 향상시킬 수 있으면 매우 유용하다. 본 연구는 건축 프로젝트 초기단계에서 실시하는 개산견적의 신뢰도를 견적전문가들의 지식을 활용하여 평가하고 이를 바탕으로 신뢰도 향상을 위한 대안을 제시할 수 있는 방안을 제안하고자 한다. 본 연구를 수행하기 위하여 실제 개산견적을 수행하고 공사를 실시한 83개의 건설 프로젝트 자료를 수집하였다. 본 연구에서 개발한 개산견적의 신뢰도를 평가하는 모델을 이용하게 되면 발주자 또는 의사결정자는 개산견적 공사비가 얼마나 신뢰할 수 있는 파악할 수 있게 된다. 또한 평가에 대한 검토와 피드백이 가능하여 개산견적 신뢰도 향상을 위한 방안을 모색할 수 있게 된다. 이러한 과정을 통해서 개산견적의 신뢰도에 좋지 않는 영향을 주는 요인의 상황(현황)윤 찾아내어 신뢰도 평가가 높게 되도록 상황을 개선시켜 다시 견적하면 개산견적의 신뢰도를 높일 수 있게 된다.

• International Journal of Reliability and Applications
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• 제17권2호
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• pp.149-158
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• 2016

We are enjoying a very comfortable life thanks to modern civilization, however, comfort is not guaranteed to us. Development of software system is a difficult and complex process. Therefore, the main focus of software development is on improving the reliability and stability of a software system. We have become aware of the importance of developing software reliability models and have begun to develop software reliability models. NHPP software reliability models have been developed through the fault intensity rate function and the mean value functions within a controlled testing environment to estimate reliability metrics such as the number of residual faults, failure rate, and reliability of the software. In this paper, we present a new NHPP software reliability model with Burr Type III fault detection rate, and present the goodness-of-fit of the fault detection rate software reliability model and other NHPP models based on two datasets of software testing data. The results show that the proposed model fits significantly better than other NHPP software reliability models.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 추계학술발표회요약집
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• pp.181.2-181
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• 1999

• International Journal of Reliability and Applications
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• 제12권2호
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• pp.123-129
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• 2011

Due to restriction of vehicle emissions and high demand for fossil fuels nowadays, car manufacturers around the world are looking into alternative ways in introducing new car model that would vastly captured the market. Thus, Electric Vehicle (EV) has been further developed to take the advantage of the current global issues on price of fossil fuels and impact on the environment. Since car battery plays the crucial role on the overall performance of EV, many researchers have been working on improving the component. This paper focused on the reliability of EV battery which involves recognizing failure types, testing method and life prediction method. By focusing on these elements, the reliability feature being identified and as a result the batteries life will be prolonged.

• International Journal of Reliability and Applications
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• 제12권2호
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• pp.79-94
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• 2011

Redundancy-reliability allocation problems in multi-stage series-parallel systems are addressed in this study. Fuzzy programming techniques are proposed for finding satisfactory solutions. First, a multi-objective programming model is formulated for simultaneously maximizing system reliability and minimizing system total cost. Due to the nature of uncertainty in the problem, the fuzzy set theory and technique are used to convert the deterministic multi-objective programming model into a fuzzy nonlinear programming problem. A heuristic method is developed to get satisfactory solutions for the fuzzy nonlinear programming problem. A Pareto optimal solution is found with maximal degree of satisfaction from the interception area of fuzzy sets. A case study that is related to the electronic control unit installed on aircraft engine over-speed protection system is used to implement the developed approach. Results suggest that the developed fuzzy multi-objective programming model can effectively resolve the fuzzy and uncertain problem when design goals and constraints are not clearly confirmed at the initial conceptual design phase.

• 산업경영시스템학회지
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• 제40권2호
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• pp.41-50
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• 2017

The purpose of this paper is to improve the service tree analysis introduced recently by Geum et al. [15]. Service tree analysis structures the service based on the customer participation perspective and provides a qualitative analysis method categorizing the service elements on the basis of its impact to top service. This paper attempts to apply the concept of reliability importance to the service tree analysis as a perspective of quantitative analysis, which is considered little in Geum et al. [15]. Reliability importance is a measure of the structural impact of the components that make up the system on the system lifetime in reliability engineering field and often used in fault tree analysis. We transform the reliability importance into service importance in accordance with service tree analysis, so that the influence of service elements on the service can be judged and compared. The service importance is defined as the amount of change of the service according to the change of the service element, therefore, it can be utilized as an index for determining a service element for service improvement. In addition, as an index for paired service elements, the relationship between the two service components can be measured by joint service importance. This paper introduces conceptual changes in the process of applying reliability importance to service analysis, and shows how to use the service importance for identifying the priority of service element for the final service and improving customer satisfaction through an example. By using the service importance and joint service importance in service tree analysis, it is possible to make efficient decision making in the process of determining the service elements for analyzing and improving the service.

• 항공우주기술
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• 제2권1호
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• pp.205-212
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• 2003

신뢰성이란 부품이나 시스템이 얼마나 오랫동안 안심하고 사용할 수 있는가를 정량적 수치로 표현하는 미래의 품질 개념으로 앞으로 제품의 국제적인 경쟁력을 갖추기 위하여 필수적으로 요구되는 기술이다. 국내에서도 제품의 신뢰성 향상에 대한 관심과 필요성이 더욱 고조됨에 따라, 정부에서도 세계적 수준의 신뢰성 평가 인프라를 구축하기 위해 “신뢰성 향상 기반 구축사업”을 적극적으로 추진하고 있으며, 대학, 연구기관 및 전자, 자동차, 중공업 등 수출업체에서 신뢰성에 관한 연구 및 시험평가센터를 설립하여 본격적으로 신뢰성 문제를 다루고 있다. 본 논문에서는 신뢰성 향상 사업에 대한 국내의 현황을 소개하고 항공우주분야에 대한 신뢰성 인증제도 도입의 필요성에 대하여 검토하였다.