• International Journal of Reliability and Applications
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• 제9권2호
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• pp.153-165
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• 2008

This paper discusses the reliability equivalences of a series-parallel system. The system components are assumed to be independent and identical. The failure rates of the system components are functions of time and follow Weibull distribution. Three different methods are used to improve the given system reliability. The reliability equivalence factor is obtained using the reliability function. The fractiles of the original and improved systems are also obtained. Numerical example is presented to interpret how to utilize the obtained results.

• 한국신뢰성학회지:신뢰성응용연구
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• 제5권4호
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• pp.427-438
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• 2005

This paper is concerned with the problem in predicting the reliability of an LCD product, Product reliability calculation methods classify accelerated life test (ALT) and using the reliability standard as MIL-HDBK-217F and Telcordia SR-332. The reliability standard can calculate estimating value more quickly than accelerated life test. The system MTBF was calculated in accordance of Telcordia SR-332 standard which includes directions of part electronic measurement, temperature rise and environmental test data. This research is intended to obtain the useful information for each electric design step to save time and cost.

• Structural Engineering and Mechanics
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• 제52권6호
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• pp.1099-1120
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• 2014

In this paper, reliability-based design optimization (RBDO) of structures is addressed. For this purpose, the global search and optimization capabilities of genetic algorithm (GA) are combined with the efficiency and reasonable accuracy of an advanced moment-based finite element reliability method. For performing RBDO, three variants of GA including a real-coded, a binary-coded and an improved binary-coded GA are developed. In these methods, GA performs (finite element) reliability analyses to evaluate reliability constraints. For truss structures which include finite element modeling, reliability constraints are evaluated using finite element reliability analysis. Response sensitivity required for finite element reliability analysis is obtained by direct differentiation method (DDM) rather than finite difference method (FDM). The proposed methods are examined within four standard test examples and real-world design problems. The results illustrate the superiority and efficiency of the improved binary-coded GA. Results also illustrate that DDM significantly reduces the computational cost and improves the efficiency of the optimization procedure.

• 대한기계학회논문집A
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• 제35권10호
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• pp.1291-1298
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• 2011

본 논문은 탄약, 미사일, 우주발사체 등과 같은 일회성(one-shot) 시스템의 가부반응데이터를 이용하여 신뢰도를 추정하는 새로운 방법을 제안한다. 제안한 방법은 모수 추정법을 기반으로 한다. 제안한 방법은 가부반응 데이터의 시간에 따른 고장 비율 감소를 고려하였으며 모수 추정법의 문제점을 극복할 수 있다. 기존 문헌에 공개된 7 가지 추정방법들과 제안한 방법과의 정확성을 비교하여 제안한 방법을 검증하였다. 정확성 비교 시, 다양한 샘플 수 변화를 고려하여 신뢰도 추정결과에 대한 SSE를 이용하였다. 정확성 비교 결과, 제안한 방법은 다른 방법에 비해 정확성이 높은 신뢰도 추정결과를 제공하였다.

• The Journal of Korean Physical Therapy
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• 제22권4호
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• pp.57-64
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• 2010

Purpose: This study aimed to determine whether there are differences in subtalar joint range of motion (ROM) when using different measurement methods, and to determine inter- and intra-rater reliability of goniometry as used in clinical setting. Methods: Subjects were thirty-one healthy males and females (sixty-two ankles) living in Korea. Three raters with different clinical experiences measured inversion and eversion range of motion of the subtalar joint two times. Measurements were done with subjects prone (open kinetic chain) and standing (closed kinetic chain). Rater and measurement methods were based on analyzing differences in range of motion. Intra-class correlation coefficients (ICCs) were calculated to determine intra-rater and inter-rater reliability. Results: Mean subtalar jont range of motion for inversion ranged from $9.31^{\circ}$ to $11.94^{\circ}$ for eversion, it ranged from $6.73^{\circ}$ to $9.20^{\circ}$. The differences in ROM between raters and between measurement methods were significant (p<0.01). The ICCs for interrater reliability ranged from $0.02^{\circ}$ to $0.20^{\circ}$ for inversion and from $0.23^{\circ}$ to $0.39^{\circ}$ for eversion. Intrarater reliability ranged from $0.32^{\circ}$ to $0.78^{\circ}$ for inversion and from $0.45^{\circ}$ to $0.73^{\circ}$ for eversion. Conclusion: Subtalar joint inversion and eversion ROM show differences for measurement methods low reliability between different raters, and low to high intra-rater reliability within sessions.

• Structural Engineering and Mechanics
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• 제45권5호
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• pp.595-611
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• 2013

This paper aims to compare three collocation point methods associated with the odd order stochastic response surface method (SRSM) in a systematical and quantitative way. The SRSM with the Hermite polynomial chaos is briefly introduced first. Then, three collocation point methods, namely the point method, the root method and the without origin method underlying the odd order SRSMs are highlighted. Three examples are presented to demonstrate the accuracy and efficiency of the three methods. The results indicate that the condition that the Hermite polynomial information matrix evaluated at the collocation points has a full rank should be satisfied to yield reliability results with a sufficient accuracy. The point method and the without origin method are much more efficient than the root method, especially for the reliability problems involving a large number of random variables or requiring complex finite element analysis. The without origin method can also produce sufficiently accurate reliability results in comparison with the point and root methods. Therefore, the origin often used as a collocation point is not absolutely necessary. The odd order SRSMs with the point method and the without origin method are recommended for the reliability analysis due to their computational accuracy and efficiency. The order of SRSM has a significant influence on the results associated with the three collocation point methods. For normal random variables, the SRSM with an order equaling or exceeding the order of a performance function can produce reliability results with a sufficient accuracy. The order of SRSM should significantly exceed the order of the performance function involving strongly non-normal random variables.

• 한국지반공학회논문집
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• 제23권12호
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• pp.61-73
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• 2007

본 논문에서는 국내 하중저항계수설계법 개발의 일환으로 구조물기초설계기준에 적용된 항타강관말뚝의 두 정역학적 지지력공식에 대하여 대표적인 신뢰성분석기법인 일차신뢰도법(FORM)과 몬테카를로 시뮬레이션(MCS)을 이용한 강도 높은 신뢰성해석을 수행하고 그 신뢰성수준을 평가하였다. 두 정역학설계법에 대한 저항편향계수는 대표 측정지지력과 설계지지력을 비교함으로써 평가하였다. 국내 정재하시험 및 지반조사 자료를 수집하여 말뚝의 측정 극한지지력을 결정하였고, 정역학적 지지력공식과 Meyerhof 경험식을 이용하여 설계 극한지지력을 산정하였다. 정확하고 효율적인 신뢰성평가를 위해 일차신뢰도법 및 몬테카를로 시뮬레이션 기반의 컴퓨터 프로그램을 개발하였다. 저항편향계수의 통계치를 이용하여 명시적 형태의 간편법인 평균일계이차모멘트법(MVFOSM)과 개선된 방법인 일차신뢰도법 및 몬테카를로 시뮬레이션에 의한 신뢰성해석을 수행하여 그 결과를 비교하였다. 또한 신뢰성 분석에 대한 주요 확률변수의 영향정도와 민감도를 파악하기 위하여 매개변수연구를 수행하였다.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.242-249
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• 1999

Spot welding is very important and useful technology in fabrication of an automobile body structure. Because fatigue strength of the spot welding point is however considerably lower than parent metal due to stress concentration at the nugget edge, accurate stress analysis and fatigue stength evaluation of spot welded lap joint are very important to valuate the reliability and durability of automobile body structure and to establish a criterion of long life fatigue design. Many invetigators have studied so far onsystematic fatigue strength evaluation with various methods. It is however necessary to verify their reliability and abailability for practical application to fatigue design of spot welded structure, Thus,in this study, fatigue strength evaluation methods of spot welded lap joint. which are the maximum principal stress method. the fracture and availability with the Weibull probability distribution. From the results, it was found that reliability and availability withe the Weibull probaility distribution. From the results, it was found that reliability and availability of the suggest fatigue strength estimation methods methods were higher than $\Delta$P-$N_f$ relation. However, among them , reliability of the maximum pricipal stress method was the highest.

• 품질경영학회지
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• 제39권1호
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• pp.71-77
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• 2011

In the fields of reliability application, the most commonly used test methods for reliability qualification are zero failure tests since they require fewer test samples and less test time compared to other test methods that guarantee the same reliability with a given confidence level. An economic zero failure test plan is developed that minimizes the total cost related to perform a life test to guarantee a specified reliability of a product with a given confidence level and a numerical example is provided to illustrate the use of the proposed test method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.199-208
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• 1994

One of the main objectives of the study is to propose a practical but realistic limit state model considering combined effect of axial and bending load for reliability analysis and safety assessment of cable-stayed bridge under vehicle traffic loads. This paper is intended to propose a new approach for the evaluation of reserved load carrying capacity of cable-stayed bridge under vehicle traffic loads in terms of equivalent strength, which may be defined as a bridge strength corresponding to the reliability index of the bridge. This can be derived from an inverse process based on the concept of FOSM form of reliability index. AFOSM and IST methods are used for the reliability analysis of the proposed models. The proposed reliability model and methods are applied to the safety assessment of Jindo Bridge which is one of major two cable-stayed bridges in Korea.