• 한국신뢰성학회지:신뢰성응용연구
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• 제6권1호
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• pp.63-91
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• 2006

According to the rapid development of science technologies, a life and development cycle of products are getting shorter and structures and functions become more complex so that the reliability requirement of customers is getting greater for components in the products. However, most domestic mechanical components are manufactured by small and medium-sized companies, who are manufacturing in poor economic and technical condition. Because of this, assessment technologies and equipment to predict and guarantee the reliability are very weak. For this reason, it is the fact that many customers neglect the domestic mechanical components which fail to win the reliability. Korean government has been trying to eliminate the problem by establishing 18 reliability assessment centers in 2000 and performing R-Mark certification promotion and constructions of the foundation for reliability assessment to rebuild the reliability on the domestic components and materials. Korea Institute of Machinery and Materials has been designated as a supervising organization for reliability assessment in the machinery filed for 5 years. In this paper, we would like to introduce effective and systematized 12 steps of reliability substantiation test on mechanical components with know-how we achieved during the period.

• Journal of Magnetics
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• 제17권1호
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• pp.46-50
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• 2012

A reliability-based optimization method for electromagnetic design is presented to take uncertainties of design parameters into account. The method can provide an optimal design satisfying a specified confidence level in the presence of uncertain parameters. To achieve the goal, the reliability index approach based on the firstorder reliability method is adopted to deal with probabilistic constraint functions and a double-loop optimization algorithm is implemented to obtain an optimum. The proposed method is applied to the TEAM Workshop Problem 22 and its accuracy and efficiency is verified with reference of Monte Carlo simulation results.

• Journal of Electrical Engineering and Technology
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• 제7권1호
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• pp.46-50
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• 2012

The current paper presents an effective methodology for assessing the reliability of electromagnetic designs when considering uncertainties of design variables. To achieve this goal, the reliability index approach based on the first-order reliability method is adopted to deal with probabilistic constraint functions, which are expressed in terms of random design variables. The proposed method is applied to three different designs of a superconducting magnetic energy storage system that corresponds to initial, deterministic, and roust designs. The validity and efficiency of the method is investigated with reference values obtained from Monte Carlo simulation.

• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.331-338
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• 2013

A new reliability calculation method is proposed based on design sensitivity analysis by the finite element method for nonlinear performance constraints in the optimal design of electromagnetic devices. In the proposed method, the reliability of a given design is calculated by using the Monte Carlo simulation (MCS) method after approximating a constraint function to a linear one in the confidence interval with the help of its sensitivity information. The validity and numerical efficiency of the proposed sensitivity-assisted MCS method are investigated by comparing its numerical results with those obtained by using the conventional MCS method and the first-order reliability method for analytic functions and the TEAM Workshop Problem 22.

• International Journal of Reliability and Applications
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• 제2권4호
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• pp.253-262
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• 2001

A k-out-of-n standby system is considered where all of its components are s-independent and classified either working or cold standby connected with imperfect switches. The probability density function of the life length for this system is established in closed form, when the underlying components have constant failure rates. Also the reliability function of the system is derived. Finally, the reliability functions for one, two and three out of four systems are deduced for perfect or imperfect switches and identical or non-identical constant failure rates for working and standby components.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권3호
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• pp.305-318
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• 2011

In the statement of logistics reliability prediction methodology, all components should be managed as the analysis objectives. However, in some reliability prediction of weapon systems, fastening parts, e.g., screws, bolts and nuts, have been frequently ignored because some organizations related to weapon systems have emphasized that those parts are not significant in their failures rate and functions. In this paper, failure rates, modes, and distributions were presented to prove that fastening parts should be included in reliability prediction objectives. Also, failure rate prediction methods of fastening parts are presented and compared.

• International Journal of Reliability and Applications
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• 제14권1호
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• pp.27-39
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• 2013

In this article, a new model based on the Rayleigh distribution is introduced. This model is useful and practical in physics, reliability, and life testing. The statistical and reliability properties of this model are presented, including moments, the hazard rate, the reversed hazard rate, and mean residual life functions, among others. In addition, it is shown that the distributions of the new model are ordered regarding the strongest likelihood ratio ordering. Four estimating methods, namely, method of moment, maximum likelihood method, Bayes estimation, and uniformly minimum variance unbiased, are used to estimate the parameters of this model. Simulation is used to calculate the estimates and to study their properties. Finally, the appropriateness of this model for real data sets is shown by using the chi-square goodness of fit test and the Kolmogorov-Smirnov statistic.

• International Journal of Reliability and Applications
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• 제5권2호
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• pp.81-103
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• 2004

Improvements of a bridge network system are studied in this paper. Then equivalence between different improved designs of the bridge network system is discussed. Three different methods are used to get different better designs of the network in the sense of having higher reliability and mean time to failure. Then two different types of reliability equivalence factors of the system are derived. It is assumed here that the failure rates of the system's components are identical and constant. The reliability functions and mean time to failure of the original and improved designs of the network are derived. Comparison between the mean time to failures of the original system and improved designs of the system are presented. Numerical studies and conclusion are presented in order to explain how one can apply the the theoretical results obtained.

• 한국가스학회지
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• 제22권5호
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• pp.72-78
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• 2018

최근 가스안전기기의 동향은 무선 기술의 발전과 수요자의 요구에 따라 무선 가스안전기기에 대한 개발과 연구가 활발히 이루어지고 있다. 무선의 신뢰성에 대한 논란이 제기되고 있지만 무선의 편리성이란 강점으로 가스안전기기에 도입이 확대되고 있으므로 이러한 기기의 안전성과 신뢰성을 검증할 수 있는 합리적인 성능평가 방안이 필요하다. 본 논문은 무선 가스안전기기에 대한 안전성과 신뢰성을 확인하여 기기가 원활하게 확대 보급될 수 있도록 성능평가 장치 설계 제작과 성능평가 방안 제시를 목적으로 한다. 이를 위하여 국내 외 무선 가스안전기기 관련제도를 조사하여 신뢰성과 안전성을 확인하는 기능과 방법을 검토하고 주요기능에 대해 시험평가가 가능한 장치를 제작하며 무선가스안전기기의 신뢰성과 안전성 요구조건을 만족시키는 주요 성능평가 항목(안)과 시험방안을 제시한다.

• 대한물리의학회지
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• 제9권2호
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• pp.201-211
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• 2014

PURPOSE: The purpose of this study was to investigate the inter-rater absolute reliability and the concurrent validity of the Tinetti-gait scale that was translated into Korean for chronic stroke patients. METHODS: Fifty-two patients with post-stroke participated in this study. Inter-rater reliability was analyzed by Intraclass Correlation Coefficient ($ICC_{3,1}$) and Kappa coefficient, and absolute reliability was analyzed by the Standard Error of Measurement (SEM), and the Minimal Detectable Change (MDC). Concurrent validity was analyzed by correlating between the Tinetti-gait scale and physical functions. The physical functions were measured by using the Dynamic Gait Index(DGI), 10m walking test(10WT), One Leg Standing Test of affected/non-affected side(OLST), Sit to Stand test(STS), (Fugl Meyer assessment of Lower Extremity(FM-LE). RESULTS: The inter-rater reliability of the Tinetti-gait scale was high; $ICC_{(3,1)}=.91$ (95% CI=.85~.95) (very reliable), the range of Kappa coefficient were .73~.92 (substantial~good). The inter-rater agreement of the each item in Tinetti-gait scale ranged from .74 to .92 (95 % CI=.59~.95) (reliable~very reliable). The SEM and MDC were .56 and 1.55, respectively. In the results of concurrent validity, there were moderate positive correlation between Tinetti-gait scale and DGI (r=.78), 10WT (r=.74), OLST (r=.65~.73), FM-LE (r=67). And there was moderate negative correlation between Tinetti-gait scale and STS (r=-79) (p<.01). CONCLUSION: The Tinetti-gait scale(Korean version) was a reliable and valid tool to measure gait ability in patients with chronic stroke. Thus, it could be a useful tool for examining a gait ability of post-stroke patients. Further study should be conducted to investigate the usability to predict fall risk of post-stroke patients of the Tinetti-gait scale.